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Proceedings | Materials
2020 CONFERENCE MATERIAL

Welcome to the 2020 CPES & PEC Conferences Proceedings page. With honored contributions from Tsinghua. Please select any sessions, organizations, and keywords to filter the results.

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Power Electronics
Power Systems
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# of Conference Materials with current filters (including presentation duplicates): 183

Dialogue Sessions

T1: Characterization, Packaging, and Applications of WBG Devices

T1.1: Commutation Loop Analysis and Optimization for a SiC-Based 25 kW, 380:460 V Three-Phase Matrix Converter
Authors: Victoria Baker, Louelson Costa, Boran Fan, Rolando Burgos, Blasko Vladimir, Warren Chen, Dushan Boroyevich
Victoria Baker picture
Representing Author: Victoria Baker - CPES
Keywords:silicon carbide (sic)
Abstract:

Wide bandgap devices like SiC and GaN MOSFETs features fast switching speed, low switching losses, and higher operating temperature. However, with the high di/dt, and dv/dts even small stray inductances can lead to greater overvoltages, and ringing during switching transients. Therefore, commutation loop parasitics are critical to consider in the design of a Printed Circuit Board (PCB) for SiC, and GaN implementations. This paper details the theoretical analysis, and simulation comparisons of different 3D layout strategies based on introduced parasitic inductance, capacitance and loop symmetries. A discussion, and evaluation of device cooling methods to increase the power density of the converter was also included, which inform certain constraints on the layout of the PCB. The results of this analysis are applied on a matrix converter phase leg, and evaluated. The layout parasitics were extracted with Finite Element Analysis (FEA) and switching transient/thermal performance were verified by experiments.

T1.2: Surge Current Capability of Ga2O3 Schottky Diodes
Authors: Cyril Buttay, Hiu-Yung Wong, Boyan Wang, Yuhao Zhang
Cyril Buttay picture
Representing Author: Cyril Buttay - CPES
Keywords:device characterization; device and system reliability; high temperature
Abstract:

Β-Ga2O3 is an attractive material to build power electronic semiconductor devices, because because of its ultra-wide bandgap and the availability of large-diameter wafers growing from its own melt. However, device performance may be limited by the relatively poor thermal conductivity of the material.

T1.3: PCB-Based Gate Driver and Bus Bar for a 10 kV SiC MOSFET Power Module
Authors: Mark Cairnie, Jacob Gersh, Christina DiMarino
Mark Cairnie picture
Representing Author: Mark Cairnie - CPES
Keywords:device characterization; high power density; insulation design and assessment; packaging; silicon carbide (sic)
Abstract:

Medium- and high-voltage Silicon Carbide (SiC) power modules have the potential to drastically improve the size, reliability, and operating temperature of existing power systems due to faster switching times and reduced loss when compared to conventional silicon IGBTs [1]. The proposed wirebond-less module seeks to reduce parasitics, enabling record switching speeds (>250V/ns), while employing an innovative common-mode screen to reduce conducted noise emissions [2]. The module housing and encapsulant is carefully designed to fully insulate the spring-loaded interconnects to the bus bar, eliminating the need for standard clearance requirements between the pins, and reducing the overall footprint of the module. Due to the close proximity of the interconnects, careful design of the gate driver and laminated bus bar is required to ensure low electric field strength and a safe partial discharge inception voltage (PDIV). The gate driver and bus bar are fully integrated into a single six-layer PCB and utilize various field grating techniques to ensure a PDIV >150% of the DC bus voltage. The design is optimized for electric field strength, as well as parasitic loop inductance, using a finite element analysis (FEA) method. From the design process, useful conclusions are drawn on the relationships and trade offs of various field grating techniques in high-density, high-voltage PCB design.

T1.4: Characterization of 4.5 kV SiC Charge-Balanced MOSFETs
Authors: Ibrahim M. Eshera, Christina M. DiMarino
Ibrahim Eshera picture
Representing Author: Ibrahim Eshera - CPES
Keywords:device characterization; high temperature; silicon carbide (sic)
Abstract:

Existing silicon carbide (SiC) unipolar power transistors for medium-voltage (>3 kV) applications suffer from high conduction loss at elevated temperatures, reducing the benefit compared to the incumbent silicon IGBTs [1]-[3]. SiC super-junction (SJ) technology can overcome this on-state loss limitation of unipolar devices, but requires challenging fabrication processes. General Electric has proposed an alternative solution that implements a novel drift layer architecture for 3 kV SiC charge-balanced (CB) JBS diodes that outperform the 1-D specific on-resistance versus breakdown voltage limit through buried Ρ-doped regions inside drift layer [1]. More recently, this proposed process has been used to create 4.5 kV SiC CB MOSFETs. This work will report the static and dynamic characterization of these 4.5 kV SiC CB MOSFETs up to 175 °C.

T1.5: Reliability Evaluation of High-Speed 10 kV SiC MOSFET Power Modules
Authors: Jacob Gersh, Christina DiMarino, Paul Paret (NREL), Douglas Devoto (NREL)
Jacob Gersh picture
Representing Author: Jacob Gersh - CPES
Keywords:device and system reliability; high temperature; packaging
Abstract:

Wide bandgap (WBG) devices represent enormous improvements in performance over conventional Silicon devices in power modules due to their high voltage blocking capability and fast switching speeds. To fully harness the benefits of WBG devices, power modules must be designed using materials and techniques that are just as reliable as conventional semiconductor packaging techniques but can handle the increased voltages and high electric fields. Existing literature is fairly detailed on individual ceramic substrates used in state-of-the-art power modules [2], [3], [4], [7]; however little work is done on stacked-substrate module packages. The module discussed in this work used Direct-Bonded Aluminum (DBA) substrates bonded together with a pressure-assisted sintering process [8]. Pressure-sintered substrate stacks may represent a reliability weakness, and as such this work will examine the reliability of these discussed components used in a high power density 10kV SiC MOSFET module.

T1.6: The Optimal Design of A High-Temperature PCB-Embedded Transformer GaN-Based Gate-Drive Power Supply with A Wide-Input Range
Authors: Jiewen Hu, Bo Wen, Rolando Burgos, Dushan Boroyevich
Jiewen Hu picture
Representing Author: Jiewen Hu - CPES
Keywords:gallium nitride (gan); high power density; high temperature; magnetic materials and integration
Abstract:

This paper presents the optimal design of a wide-input range, dual-output 10 W isolated active-clamp flyback (ACF) gate-drive power supply (GDPS) for high-temperature automotive applications. Detailed analysis and comparison between Critical Conduction Mode (CRM) and Continuous Conduction Mode (CCM) are provided to select the operating mode. A printed-circuit-board-embedded (PCB-embedded) transformer is carefully designed and it significantly improves the power density of the power supply. A 10 W, GaN-based converter prototype switching at 1MHz has been developed to demonstrate the attained power density (53.2 W/in3), peak efficiency (89.7%), input voltage range (8.5 V to 28 V), maximum operating ambient temperature (105 ?C at 8.5 V and 115°C at 28 V), and transformer input-output capacitance (9.7 pF).

T1.7: Practical Implementation and Efficiency Evaluation of a Phase Shifted Full Bridge DC-DC Converter Using Radiation Hardened GaN FETs for Space Applications
Authors: Victor Turriate, J. Witcher, Dushan Boroyevich, Rolando Burgos
Jiewen Hu picture
Representing Author: Jiewen Hu - CPES
Keywords:emi; gallium nitride (gan)
Abstract:

The practical implementation and efficiency evaluation of a Phase Shifted Full Bridge DC-DC converter for space applications using 200 V, 18 A, radiation hardened Gallium Nitride *GaN) Field Effect Transistors (FETs) are presented in this paper. Design considerations for topology selection and auxiliary circuitry resulting from constraints currently encountered in power electronics for space applications are briefly described. In addition, the process followed to design the power stage, as well as the effects of resonant inductance and transformer design on converter performance are presented. Furthermore, a hard-switched Full Bridge DC-DC converter was implemented to study the performance differences with the phase shift modulated converter. Both DC-DC converters deliver 500 W at a 20 V regulated output from a 100 V nominal DC bus. The Phase Shifted Full Bridge DC-DC converter presented in this paper achieves more than 95% peak efficiency at its nominal operating point, with an initial prototype power density of 79 W/inch3 obtained.

T1.8: Degradation of SiC MOSFETs Provoked by a Switching Based Ruggedness Test
Authors: Joseph Kozak, Ruizhe Zhang, Jingcun Liu, Khai Ngo, Yuhao Zhang
Joseph Kozak picture
Representing Author: Joseph Kozak - CPES
Keywords:device characterization; device and system reliability; silicon carbide (sic)
Abstract:

Evaluation of the robustness of SiC power MOSFETs outside the safe-operating-area (SOA) conditions is key for their integration into many power electronics applications. Traditional test methods, such as static accelerated lifetime tests, repetitive pulse tests and power cycling, stress devices in ways to excite particular failure mechanisms that do not resemble the device operation in industrial switching applications. This work presents a robustness test methodology for SiC MOSFETs, Switching Cycling, which is based on repetitive hard-switching cycles where switched stimuli (voltage and current) are set to exceed their rated values in each cycle. With the aid of device TCAD simulation and failure analysis, this work, for the first time, reveals the degradation and failure mechanisms of SIC MOSFETs under the out-of-SOA switching cycling tests. Two independent degradation and failure mechanisms have been identified. While the gate-oxide degradation emerges with the increased switching cycles, bulk-semiconductor degradation appears simultaneously and drives the device into a partially failed yet functional state before failure. Changes in electrical parameters over time, including threshold voltage, on-resistance, gate-leakage and drain-leakage currents are all monitored and precursors for two degradation and failure mechanisms have been identified.

T1.9: Physics of Degradation in SiC MOSFETs Stressed by Over-voltage and Over-current Switching
Authors: Joseph Kozak, Ruizhe Zhang, Jingcun Liu, Khai Ngo, Yuhao Zhang
Joseph Kozak picture
Representing Author: Joseph Kozak - CPES
Keywords:device characterization; device and system reliability; high temperature; silicon carbide (sic)
Abstract:

This work presents the ruggedness of SiC power MOSFETs outside the safe-operating-area (SOA) conditions based on a hard-switching cycling test. The device was stressed to withstand overvoltage and overcurrent beyond their voltage and current ratings in each switching cycle. This switching cycling test was performed at an ambient temperature of 25 oC and 100 oC. Two independent degradations, one at the gate-oxide and the other at the semiconductor junction region, were observed. The second degradation has not been previously reported in the literature. Both degradations were found to accelerate at the high ambient temperature. The physics of these two device degradations were unveiled: the hot-electron induced gate-oxide degradation accounts for the first device degradation; the electron hopping through the defect states created in the stress tests accounts for the second device degradation.

T1.10: Analysis of Parastic Capacitors Impact on Voltage Sharing of Series-Connected SiC MOSFETs and Body-Diodes
Authors: Xiang Lin, Lakshmi Ravi, Yuhao Zhang, Dong Dong, Rolando Burgos
Xiang Lin picture
Representing Author: Xiang Lin - CPES
Keywords:control; passive components; silicon carbide (sic)
Abstract:

The voltage sharing among series-connected SiC MOSFETs is more sensitive to the surrounding parasitic capacitors than Si IGBTs due to much higher dv⁄dt switching speed. To this end, this paper presents a detailed study of parasitic capacitors' impact on the voltage sharing of series-connected SiC MOSFETs and body-diodes. The impact of different heatsink connection schemes and the corresponding change of the parasitic capacitors are also analyzed. The study reveals that, for series-connected SiC MOSFETs, the parasitic capacitor differences affect the gate miller plateau voltage and ultimately the dv⁄dt during turn-off and the voltage sharing is more sensitive to gate-to-heatsink parasitic capacitor. For series-connected body-diodes, the voltage sharing is more sensitive to drain⁄source-to-heatsink capacitors which results in different dv⁄dt turn-off voltages across the body-diodes under different heatsink connections. The voltage sharing between two series-connected 10 kV SiC MOSFETs is tested in a multi-pulse test setup under different parasitic capacitors conditions.

T1.11: PCB-Interposer-on-DBC Packaging of 650 V, 120 A GaN HEMTs
Authors: Shengchang Lu, Tianyu Zhao, Rolando P. Burgos, Guoquan Lu, Sandeep Bala, Jing Xu
Shengchang Lu picture
Representing Author: Shengchang Lu - CPES
Keywords:gallium nitride (gan); high power density; packaging
Abstract:

Packaging of gallium nitride (GaN) HEMTs is challenging due to their high heat-flux density and small bonding pads. And, having a lateral device structure and being able to switch fast, these devices push the limit of packaging by demanding extremely low parasitic inductances. In this work, we developed a packaging approach based on embedding the GaN device chip between a printed-circuit board (PCB) interposer structure for terminal interconnection and a direct-bond-copper (DBC) substrate for heat extraction. The approach was demonstrated by packaging 650 V, 120 A GaN HEMT bare die. We also used silver sintering for bonding all of the device terminals to increase heat extraction from the device's thermal pad and avoid relying on multiple, different melting-point solders in the construction. FEA simulations showed that the package had a gate inductance (LG+LSS) of 3.1 nH, a drain-to-source inductance LD+LS of 1.2 nH, and a junction-to-case thermal resistance, RJC, of 0.14°C⁄W. Static characteristics of the PCB-on-DBC packages were measured by a curve tracer.

T1.12: Superjunction Power Transistors with Interface Charges: A Case Study for GaN
Authors: Yunwei Ma, Ming Xiao, Ruizhe Zhang, Han Wang, Yuhao Zhang
Yunwei Ma picture
Representing Author: Yunwei Ma - CPES
Keywords:gallium nitride (gan); optimization
Abstract:

Recent progress in p-GaN trench-filling epitaxy has shown promise for the demonstration of GaN superjunction (SJ) devices[1]. However, the presence of n-type interface charges at the regrowth interfaces has been widely observed[2]. These interface charges pose great challenges to the design and performance evaluation of SJ devices. This work presents an analytical model for SJ devices with interface charges for the first time. In our model, two approaches are proposed to compensate interface charges, by the modulation of the SJ doping or the SJ geometry. Based on our model, an analytical study is conducted for GaN SJ transistors, revealing the design windows and optimal values of doping concentration and pillar width as a function of interface charge density. Finally, TCAD simulation is performed for vertical GaN SJ transistors, which validated our analytical model. Our results show that, with optimal designs, interface charges would only induce small degradation in the performance of GaN SJ devices. However, with the increased interface charge density, the design windows for pillar width and doping concentration become increasingly narrow and the upper limit in the pillar width window reduces quickly. When the interface charge density exceeds 3×1012 cm2, the design window of pillar width completely falls into the sub-micron range, indicating significant difficulties in fabrication. Vertical GaN SJ transistors with interface charges retain great advantages over conventional GaN power transistors, but have narrower design windows and require different design rules compared to ideal GaN SJ devices.

T1.13: Gate-driver Integrated, Junction Temperature Estimation of SiC MOSFET Half-bridge Modules
Authors: Slavko Mocevic, Jun Wang, Rolando Burgos, Dushan Boroyevich, Marko Jaksic, Mehrdad Teimor
Slavko Mocevic picture
Representing Author: Slavko Mocevic - CPES
Keywords:device characterization; silicon carbide (sic)
Abstract:

SiC MOSFET power modules are becoming global solution in environment harsh systems due to the benefits of higher power density and efficiency. Achieving high reliability of such systems is of upmost importance due to large economic implications. Intelligence on the gate driver can lead to significant improvement of both short-term and long-term reliability of the SiC MOSFET devices by providing insight on real-time behavior of relevant switch information. Device switch-current Id can be used for shortcircuit detection under various fault impedances assessing the short-term reliability. In combination with Vds,on, the on-state resistance Rds,on and thus online junction temperature Tj estimation is possible. This enables to monitor status of the SiC MOSFET device such as state-of-health, remaining useful life, maintenance scheduling, etc. tackling the long-term reliability aspect. Focus of this paper is directed in choosing and designing proper Vds,on measurement method. Its performance is evaluated in the harsh switching environment of SiC MOSFET converters. This measurement method will be integrated on the enhanced gate driver with already developed Rogowski switch-current measurement and with help of FPGA, possibility of junction temperature monitoring arises. Furthermore, sensitivity and impact of the wire-bond degradation on measured Vds,on will be discussed and experimentally verified.

T1.14: Characterization, Reliability and Packaging for a 300 0C SiC MOSFET
Authors: David Nam, Lanbing Liu, Rolando Burgos, Guo Quan Lu
David Nam picture
Representing Author: David Nam - CPES
Keywords:device characterization; device and system reliability; high temperature; packaging; silicon carbide (sic)
Abstract:

Recent advancements in manufacturing for SiC transistors have opened a wide range of applications from high temperature to high power, high density environments. Although options are now available for high temperature application power devices, the variety is limited for several reasons. Specifically, for high temperature applications, the bottleneck is centered on the packaging for the device as well as the device reliability. Manufacturer methods, though vastly improved within the past half-decade, are still imperfect and can result in an undesirably short lifetime for transistors such as the MOSFET. Current temperature limitations of the newest generation MOSFETs are investigated in the process of developing a 300°C junction temperature operation and reliability power module. To overcome the limitations in packaging for commercially available devices, we develop and investigate a custom package. To study the limitations in current generation MOSFETs, we use high temperature accelerated lifetime bias testing to determine the reliability of our selected MOSFETs at 300°C junction temperature. Results of the lifetime tests are analyzed and discussed.

T1.15: Design of Navy Integrated Power Electronics Building Block (iPEBB)
Authors: Narayan Rajagopal, Christina DiMarino
Narayan Rajagopal picture
Representing Author: Narayan Rajagopal - CPES
Keywords:high power density; modular converters; packaging
Abstract:

The capabilities of 1.7 kV Silicon-Carbide (SiC) devices and modules have been successfully demonstrated in the development of the PEBB 1000 at the Center for Power Electronics Systems (CPES) [1]. Building on the success of the PEBB 1000, the development of a 1 kV, 250 A high-density integrated PEBB (Navy iPEBB) with galvanic isolation and high manufacturability is currently being explored for future electric ships. The development of the Navy iPEBB currently employs electromagnetic and thermal finite element analysis (FEA) to optimize the layout of the unit. By designing a unique integrated power stage, instead of employing discrete modules, the Navy iPEBB seeks to achieve low power- and gate-loop inductance (<3nH), uniform current distribution, and good thermal performance (Tj <175°C), while also minimizing conducted electromagnetic interference (EMI). The Navy iPEBB is exploring the use of flexible PCBs [2] and a multilayer substrate to achieve improved electrical and thermal performance [3]. FEA simulations are also being completed on organic insulated metal substrate (IMS) technology for reduced thermal resistance (<0.5 K⁄W) and improved heat spreading. The higher fracture toughness of organic IMS compared to ceramic-based substrates enables larger areas (>150 x 400 mm), allowing a common substrate for the Navy iPEBB power stage. This work also includes a literature review and analysis of state-of-the-art ancillary circuitry and planar magnetics that could be used in the Navy iPEBB [4] [5]. The next stage of development will be the building, testing, and packaging of a 1.7 kV H-bridge module to verify the power stage design and simulations.

T1.16: 16kV Input 200kW Rated SiC Based Three Phase Inverter
Authors: Lakshmi Ravi, Xiang Lin, Dong Dong, Rolando Burgos
Lakshmi Ravi picture
Representing Author: Lakshmi Ravi - CPES
Keywords:silicon carbide (sic); three-phase converters
Abstract:

This paper presents the design of a three phase direct-to-line central PV inverter using 10 kV SiC MOSFET power modules. The inverter rated for 200 kW, 11 kV ac output fed by a 16 kV dc input is realized using a simple two level topology with two series 10 kV MOSFETs per switch position allowing a low device count for the system. The power stage design including the power module arrangement, a gate driver with active voltage balancing control capability and Rogowski sensor based shortcircuit protection (<1μs response time), medium voltage PCB based modular bus for system integration (dc capacitors, ac output conductors and device static balancing resistors) and forced air thermal management system have been optimized for high power density with required high voltage insulation coordination. Additionally, a power quality filter is designed for the inverter output stage to meet IEEE 519 harmonic standards. Critical aspects of the design are highlighted for each component. The inverter hardware is validated through continuous three phase operation at 16 kV dc bus, 10.5 A rms output current at 10 kHz switching frequency exhibiting dv⁄dt up to 50 V⁄ns.

T1.17: Electric Field Control by Nonlinear Field Dependent Conductivity Dielectrics Characterization for High Voltage Power Module Packaging
Authors: Maryam Tousi, Mona Ghassemi
Maryam Tousi picture
Representing Author: Maryam Tousi - CPES
Keywords:high power density; insulation design and assessment; modeling and control; protection
Abstract:

Accelerated aging in next-generation insulation systems for wide bandgap (WBG) power electronic modules is the most significant barrier to realizing high-voltage, high-powerdensity conversion devices and systems. Accelerated aging in these systems is the result of two factors: 1) voltage pulses faster (with a ????????? up to 100 kV/?s) and more repetitive (with a frequency up to 500 kHz), and 2) electric field stress higher than that found in existing state-of-the-art technologies. Current geometrical techniques for electric field control in power modules cannot address this issue alone. Our goal in this paper is to characterize nonlinear field-dependent conductivity (FDC) materials applied to high electric stress regions that, in combination with geometrical techniques, can well address high electric field stress issue. Studies are carried out in COMSOL Multiphysics. The influence of applied voltage type, AC and DC, is investigated. It is shown that a bridging FDC coating layer can lead to more electric field reduction than non-bridging one.

T1.18: High-voltage vertical Ga2O3 power rectifiers operational at high temperatures up to 600 K
Authors: Boyan Wang, Ming Xiao, Xiaodong Yan, Hiu Yung Wong, Jiahui Ma, Kohei Sasaki, Han Wang, Yuhao Zhang
Boyan Wang picture
Representing Author: Boyan Wang - CPES
Keywords:high power density; high temperature
Abstract:

This work presents the temperature-dependent forward conduction and reverse blocking characteristics of a high-voltage vertical Ga2O3 power rectifier from 300 K to 600 K. Vertical ?-Ga2O3 Schottky barrier diodes (SBDs) were fabricated with a bevel-field-plated edge termination, where a bevel sidewall was implemented in both the mesa and the field oxide. The Schottky barrier height was found to increase from 1.2 eV to 1.3 eV as the temperature increases from 300 K to 600 K, indicating the existence of barrier height inhomogeneity. The net donor concentration in the drift region shows little dependence on the temperature. At 300-500 K, two competing leakage mechanisms have been identified from the reverse current-voltage characteristics measured up to 500 V. The first mechanism is the thermionic field emission limited by the Schottky contact, which dominates the device leakage current at relative low voltages. The second mechanism is the electron hopping via the defect states in the depletion region, which dominates the device leakage current at high voltages. At temperatures above 500 K, the thermionic field emission dominates the device leakage over the entire voltage range up to 500 V. Compared to the state-of-the-art SiC and GaN SBDs when blocking a similar voltage, our vertical Ga2O3 SBDs are capable of operating at significantly higher temperatures and shows a smaller leakage current increase with temperature. This shows the great potential of Ga2O3 SBDs for high-temperature and high-voltage power applications.

T1.19: Current Sharing Behavior and Characterization of a 1200 V, 6.5 mΩ SiC Half-Bridge Power Module with Flexible PCB Gate Loop Connection
Authors: Grace Watt, Slavko Mocevic, Rolando Burgos, Amy Romero, Marko Jaksic, Mehrdad Teimor
Grace Watt picture
Representing Author: Grace Watt - CPES
Keywords:device characterization; high power density; high temperature; packaging; silicon carbide (sic)
Abstract:

This paper describes 1.2 kV, 6.5 m?, half-bridge SiC MOSFET power module design, fabrication and initial testing exploring the benefits of flexible PCB gate loop connection and symmetrically patterned direct bonded copper (DBC). Paralleling power devices in modules increases current handling capability for the same bus voltage. Although simple, paralleling is challenging due to inherent parametric differences between dies and can lead to unbalanced current sharing causing overstress and thermal issues. Novel packaging techniques include use of the flexible PCB as the gate-source connection further reducing the possibility of external loop mismatches by using symmetric design for both switches keeping minimized loop connections. Furthermore, the DBC is patterned with symmetrical current pathways for both switches, thereby mitigating possible differences in the power loops. Therefore, all the variation in switching behavior can be attributed to the differences in the selected dies. Two power modules are designed to test current sharing behavior; the balanced module consists of carefully selected dies with matched threshold voltages (dies turn on at the same time), while the unbalanced module has dies with mismatched threshold voltages. Static and dynamic characterization demonstrate efficacy of the techniques utilized for this power module. Continuous testing in a boost converter demonstrates thermal performance of the modules.

T1.20: Design of a Compact, Low Inductance 1200 V, 6.5 mΩ SiC Half-Bridge Power Module with Flexible PCB Gate Loop Connection
Authors: Grace Watt, Amy Romero, Rolando Burgos, Marko Jaksic
Grace Watt picture
Representing Author: Grace Watt - CPES
Keywords:device characterization; high power density; high temperature; packaging; silicon carbide (sic)
Abstract:

This paper describes the design, packaging and test setup of a compact, low inductance, 1200 V, 6.5 m? half-bridge power module. In the design of this power module, the use of new techniques advances the properties of a SiC power module. The design has a power loop inductance of 3.9 nH and a gate loop inductance of 0.3 nH determined by Ansys Q3D. The low gate loop inductance is achieved with the use of a flexible gate circuit to connect to the gate and source of the die as well as a desaturation test point. Lastly, the use of the MOSFET body diode is place of antiparallel external diode allows for a compact layout. The design of a symmetrical layout and the fabrication of the power module is described. Two power modules are designed to compare current sharing behavior, the control sample with balanced die, the other sample with imbalanced die. A clamped inductive load tester set-up is designed to interface uniquely with the flexible PCB pins and the leads of the module. Use of Rogowski coils can allow for analysis of the individual die currents to determine the effects of imbalanced die on the power module performance.

T1.21: Evaluation of an Automated Modeling Tool Applied to New 600 V, 2 A Vertical GaN Transistors
Authors: Grace Watt, Alan Courtay, Amy Romero, Rolando Burgos, Rongming Chu, Dushan Boroyevich
Grace Watt picture
Representing Author: Grace Watt - CPES
Keywords:device characterization; gallium nitride (gan); modeling and control
Abstract:

The Power MOSFET Tool through Synopsys Saber can estimate static and dynamic behaviors of devices given measured static and dynamic characteristic curves. Model parameters are made accessible for behavior simulation and design optimization even if a datasheet is unavailable or more advanced device properties are in developmental stages. This functionality makes the tool ideal for predicting the behavior of a new GaN semiconductor in a circuit. Therefore, this paper first demonstrates a SiC model with accurate static and dynamic waveforms confirming the efficacy of the tool beyond Si. Second, this paper presents a model of a vertical GaN transistor using the Power MOSFET Tool which is compared against experimental static and dynamic measurements. The vertical GaN subcircuit model matches the experimental static results within 8.42% error. The model predicts the 8.48 ns turn-on and 30.2 turn-off time within a couple nanoseconds. With optimization of the parasitic elements in the circuit, the model matches the rise and fall rates as well as the frequency and magnitude of the ringing. Therefore, the model would simulate reliable switching times and losses critical for predicting devices’ behavior in prospective applications.

T1.22: Withstand Physics and Failure Mechanisms of p-Gate GaN HEMTs under Transient Surge Energy
Authors: Ruizhe Zhang, Joseph P. Kozak, Ming Xiao, Yuhao Zhang
Ruizhe Zhang picture
Representing Author: Ruizhe Zhang - CPES
Keywords:device characterization; device and system reliability; gallium nitride (gan)
Abstract:

An essential robustness of power devices is the capability to safely withstand the surge energy in unclamped inductive switching (UIS) conditions. The surge-energy robustness of GaN high electron mobility transistors (HEMTs) has not been fully understood, as GaN HEMTs has no or very little avalanche capability. This work, for the first time, unveils the comprehensive physics associated with the surge-energy withstand process and failure mechanisms of p-gate GaN HEMTs in UIS tests. Two commercial p-gate GaN HEMTs with Ohmic- and Schottky-type gate contacts are studied and they show similar withstand and failure physics. The withstand process comprises an LC-resonance between the load inductor and the device capacitance, followed by the device reverse conduction. The device failure occurs at the transient of peak resonant voltage and is directly limited by the peak overvoltage rather than the surge energy or the duration of overvoltage. Almost no energy is dissipated in the device during the withstand process. This suggests that, the avalanche energy, a widely used JEDEC robustness standard for MOSFETs, may not be a physically meaningful standard for p-gate GaN HEMTs. These results provide critical understandings on the robustness of GaN HEMTs and useful references for their qualifications and applications. We also demonstrate that the UIS test could be used as a new technique to study the transient overvoltage breakdown mechanism for GaN HEMTs. It can generate the short overvoltage period (<10 ns) that best resembles the resonant ringing in power converters. Using this technique, the surge-voltage breakdown mechanism of two p-gate GaN HEMTs has been clarified; the breakdown location of gate-injection-transistors has been experimentally identified for the first time.

T1.23: Third Quadrant Behavior of 10 kV SiC Planar MOSFET: New Device Findings and Circuit Implications
Authors: Ruizhe Zhang, Xiang Lin, Jingcun Liu, Slavko Mocevic, Yuhao Zhang
Ruizhe Zhang picture
Representing Author: Ruizhe Zhang - CPES
Keywords:device characterization; high temperature; silicon carbide (sic)
Abstract:

This work presents the comparative study on the third quadrant behaviors of 1.2-10 kV SiC planar MOSFETs, by combining the static characterization, simulation, modeling, and power circuit tests. New findings were presented on the competing current sharing between the MOS channel and the body diode. At zero or positive gate bias, the body-diode turn-on voltage increases with the increased device voltage rating and is much larger than the built-in potential of PN junction in high-voltage devices. Theoretical explanations were proposed based on the clamping effect by the MOS channel, and were validated by physics-based simulation and datasheet-driven models. A buck converter test was built up using 10 kV SiC MOSFET power module. The test results indicate that, for 10 kV SiC MOSFET, a negative gate bias is optimal to drive the device in 3rd quadrant conduction at high temperature, which is different from the gate driving strategy of lower voltage rating devices.

T1.24: Dynamic RDS(on) Evaluation of 650 V GaN e-HEMT Devices in Forward and Reverse Conduction Mode
Authors: Tianyu Zhao, Rolando Burgos, Jing Xu, Sandeep Bala
Tianyu Zhao picture
Representing Author: Tianyu Zhao - CPES
Keywords:device characterization; gallium nitride (gan)
Abstract:

Gallium nitride(GaN) high-electron-mobility transistors(HEMTs) have been widely applied in power converters due to small size, high switching frequency operation and low on-resistance with a given breakdown voltage. However, the increase of on-resistance following an off-state voltage stress and high power switching transition still represents a challenge of GaN based converter design which may lead to lower loss estimation. One type of commercial GaN e-HEMT device is tested in this work under double-pulse test in both forward and reverse conduction modes. Similarly to previous findings the following trends were found. Dynamic RDS(on) increases with higher off-state voltage stress. Near 30% increase has been found under the worst condition. While higher temperature and soft switching operation can reduce this degradation. Furthermore, continuous switching tests under soft-switching condition were also conducted to investigate the accumulation effect of dynamic RDS(on) increasing. These measurement results are able to provide effective instructions for converter design based on this device.

T1.25: Current Control with RSCS for Motor Drive
Authors: Sang Min Kim, Rolando Burgos
Sang Min Kim picture
Representing Author: Sang Min Kim - CPES
Keywords:control; silicon carbide (sic)
Abstract:

In this dialogue session, there will be presented a closed-loop current control with PCB-based switching current sensor. To reduce the cost, the unipolar power is applied for the sensor circuitry and the reset and SC protection circuit is built based on analog signal processing. A test bench will be built using 1.2kV SiC power modules and RL loads (or a 3-phase electric machine) to show the effectiveness of the switching current sensor for inverter applications at low and high frequency operating ranges.

T2: Magnetic Components and EMI Mitigation

T2.1: Transmitter Coils Design for Free Positioning Omnidirectional Wireless Power Transfer System
Authors: Junjie Feng, Qiang Li, Fred Lee
Junjie Feng picture
Representing Author: Junjie Feng - CPES
Keywords:wireless power transfer
Abstract:

Recently, omnidirectional wireless power transfer systems have been studied intensely due to their improved flexibility when compared with their planar counterparts. In this paper, a novel wireless charging bowl with multiple transmitter coils is proposed to power portable devices. The bowl-shaped transmitter coil is optimized to provide sufficiently strong and nearly uniform omnidirectional field distribution. Inside the bowl, a planar receiver coil can be charged with free-positioning and arbitrary orientation. This unique benefit is particularly attractive for low-power portable devices. In the experiment, the proposed transmitter coils are built and operated at 6.78 MHz. The magnetic field is measured to verify the uniform and omnidirectional magnetic field distribution. The coil to coil efficiency is 85 % to 95 %. A complete system including the inverter and rectifier stage is implemented. When charging a 5W smart phone receiver, the overall efficiency varies within a range from 68 % to 80 % for any possible position.

T2.2: A Square-Shaped Omnidirectional Wireless Charing Bowl with a Double Layer Electromagnetic Shield for Portable Device Applications
Authors: Junjie Feng, Qiang Li, Fred Lee
Junjie Feng picture
Representing Author: Junjie Feng - CPES
Keywords:emi; wireless power transfer
Abstract:

This paper presents a square-shaped omnidirectional wireless charging bowl with a double layer electromagnetic shield. The proposed transmitter coils structure achieves spatially uniform coupling coefficient with a receiver coil. Hence, it can uniformly charge a receiver device efficiently. A double layer shield structure, including a magnetic layer and a conductive layer, is first applied in a three dimensional charging setup to reduce the stray magnetic field. A comprehensive parametric analysis of this shield structure is conducted by a Finite Element Analysis software. The impact of the thickness and permeability/conductivity of each layer on the field distribution is evaluated respectively. A wireless charging bowl with the double layer shield is built successfully and the effectiveness of the shield is verified by measurement results. The system efficiency of charging a 5 W smart phone receiver is 78 % at 6.78 MHz.

T2.3: Balance Technique for CM Noise Reduction in Critical-Mode-Based Three-Phase Soft Switching Bidirectional AC-DC Converters
Authors: Zhengrong Huang, Qiang Li, Fred C. Lee
Zhengrong Huang picture
Representing Author: Zhengrong Huang - CPES
Keywords:emi; high power density; silicon carbide (sic); soft switching; three-phase converters
Abstract:

In this paper, balance technique is applied into three-phase bidirectional ac-dc converters with critical conduction mode based soft switching modulation. By adding additional inductors and making them coupled with the original ones, the realization of the balance becomes possible with proper design in order to reduce the CM noise. The balance condition is derived in order to provide the design guideline. Under discontinuous pulse width modulation, low frequency transient oscillation occurs every 60 degree when the clamping mode changes, which increases the distortion of grid current. The solution is proposed in order to suppress the oscillation to reduce the distortion. The effect of balance technique and the suppression of the low frequency transient oscillation are validated by experiments on a SiC-based three-phase bidirectional ac-dc converter prototype.

T2.4: PCB Winding Coupled Inductor Design for Critical-Mode-Based Three-Phase Bidirectional AC-DC Converters with Balance Technique
Authors: Zhengrong Huang, Qiang Li, Fred C. Lee
Zhengrong Huang picture
Representing Author: Zhengrong Huang - CPES
Keywords:high power density; magnetic materials and integration; silicon carbide (sic); soft switching; three-phase converters
Abstract:

In this paper, PCB winding coupled inductor is designed for a critical conduction mode based three-phase bidirectional ac-dc converter with balance technique to reduce CM noise. The design process is presented and the design trade-off is made between the inductor loss and the inductor footprint. The inductor winding arrangement is also optimized in order to further improve the effect of balance technique. The system efficiency and the effect of CM noise reduction are validated on a SiC-based three-phase bidirectional ac-dc converter prototype.

T2.5: High-Frequency PCB Winding Transformer With Integrated Inductors for a Bi-Directional Resonant Converter
Authors: Bin Li, Qiang Li, Fred C. Lee
Feng Jin picture
Representing Author: Feng Jin - CPES
Keywords:high power density; magnetic materials and integration; resonant converters; silicon carbide (sic)
Abstract:

The momentum toward high power density high efficiency power converters continues unabated. The key to reducing the size of power converters is high-frequency operation and the bottleneck is the magnetic components.With the emerging widebandgap devices, the switching frequency of power converters increases significantly, to hundreds of kilohertz, which provides us the opportunity to adopt printed circuit board (PCB) winding planar magnetics. Compared with the conventional litz-wire-based magnetics, planar magnetics can not only effectively reduce the converter size, but also offer improved reliability through automated manufacturing process with repeatable parasitics. Another way to reduce the number of magnetic components and shrink the size of power converters is through the magnetic integration. In this paper, a novel PCB winding based magnetic structure is proposed to integrate both inductor and transformer into one component. In this structure, the inductor value can be easily controlled by changing the cross-sectional area of the core or the length of the air gap. A 6.6-kW 500-kHz CLLC resonant converter prototype with 98% efficiency and 130W/in3 (8 kW/L) power density is built to verify the feasibility of the proposed PCB winding based magnetic structure.

T2.6: Design and Analysis of High-Temperature GaN-Based Active Filter for EMI Suppression in Electric Drive Applications
Authors: Daniel Knapp, Tam Nguyen, Rolando Burgos
Daniel Knapp picture
Representing Author: Daniel Knapp - CPES
Keywords:emi; gallium nitride (gan); high temperature
Abstract:

This paper presents the design of a gallium nitride (GaN) based active filter for electromagnetic interference (EMI) suppression for electric drive applications operating at a target temperature of 200 degrees Celsius. Previous solutions for EMI suppression used a hybrid EMI composed of an active filter to handle low frequency noise and a passive filter for high frequency noise. This hybrid filter implementation was used due to the limitation of the active filter's bandwidth and speed. GaN devices offer fast switching speeds and higher bandwidth which overcome the previous active filter's limitations. Using a wide bandgap active filter design will decrease the filter's size, operate at high temperatures, and will greatly reduce noise up to high frequencies. Experiments will be conducted on the GaN based active filter to evaluate the effectiveness and reliability of EMI noise suppression up to temperatures of 200 degrees Celsius.

T2.7: Magnetic Integration of Matrix Transformer with High Controllable Leakage Inductance
Authors: Ahmed Nabih, Qiang Li, Fred C. Lee
Ahmed Nabih picture
Representing Author: Ahmed Nabih - CPES
Keywords:gallium nitride (gan); high power density; magnetic materials and integration; resonant converters; soft switching
Abstract:

This invention proposes a novel approach to integrate high controllable leakage inductance with a matrix of four transformers using one magnetic core. The invention proposes a five-leg magnetic core where four legs are utilized for four transformer and and a fifth leg (center leg) is placed at the center among the four transformer legs to create controllable leakage inductance without sacrificing the power density of the magnetic structure. The secondary windings of the original matrix transformers are relocated to create leakage flux in the center leg. Different winding arrangements can also be used to create different leakage inductances on the secondary or primary sides. The leakage inductance can be controlled by controlling the cross section area and air gap of the center leg.

T2.8: A High-Density Single-Turn Inductor for a 6 kV SiC-based Power Electronics Building Block
Authors: He Song, Jun Wang, Yue Xu, Rolando Burgos, Dushan Boroyevich
He Song picture
Representing Author: He Song - CPES
Keywords:insulation design and assessment; magnetic materials and integration; optimization; passive components
Abstract:

This paper presents the design and optimization of a single-turn magnetic-core inductor for a 6 kV, 40 Hz power electronics building block (PEBB) using 10 kV SiC MOSFET modules. The inductor design begins with a comprehensive comparison between air-core, single-turn and multi-turn magnetic core structures, and the single-turn magnetic core structure is concluded to be the most suitable solution for the given specifications. The design process is then followed by an optimization of geometric dimensions and magnetics by a trade-off among power loss, volume, and parasitic capacitance. To achieve high compactness by minimizing the electric field stress in the air, a grounded shielding layer is applied to surround the winding, and the high-electric-field space is filled with void-free solid insulators. Major issues resulting from the shielded winding structure include extra loss on the shield, concentrated electric field at fringes, and induced grounding current. These problems have been addressed by shield conductivity selection, a proposed field-grading termination, and a well-designed damping circuit, respectively. Finally, the fabrication process of a prototype and the experimental performance are demonstrated.

T2.9: Common-Mode EMI Noise Reduction for Interleaved Multichannel GaN-Based PFC Converter
Authors: Shuo Wang, Fred C. Lee, Qiang Li
Shuo Wang picture
Representing Author: Shuo Wang - CPES
Keywords:emi; gallium nitride (gan); high power density; magnetic materials and integration; passive components
Abstract:

Adopting Gallium Nitride (GaN) device in power factor correction (PFC) converters, switching frequency can be increased up to the MHz range, with dramatic improvement in power density and not at the detriment of efficiency. Furthermore, the inductor value is reduced dramatically with more opportunities to integrate PCB windings into magnetics. With PCB based winding structure, opportunities for high frequency EMI common-mode (CM) noise reduction, previously inconceivable due to uncontrollable equivalent parallel capacitor (EPC) and equivalent parallel resistor (EPR), is possible to be realized in balance technique. To enhance the high frequency balance, a novel PCB winding structure with coupled inductor is proposed. CM noise model and balance condition for minimizing CM noise is derived. Moreover, ground loop impacts for high frequency noise is studied. A two phase interleaved totem-pole PFC converter with GaN device is built up to verify the proposed balance technique. Experimental results show that balance condition is independent to self-resonant frequency of inductor with proposed PCB inductor structure, and CM noise can be reduced uniformly up to 20 dB from 150 kHz to 30 MHz.

T2.10: Optimal Design of Planar Magnetic Components for a Two-Stage GaN-Based DC/DC Converter
Authors: Shuo Wang, Minfan Fu, Chao Fei, Yuchen Yang, Qiang Li, Fred C. Lee
Xingyu Chen picture
Representing Author: Xingyu Chen - CPES
Keywords:gallium nitride (gan); high power density; magnetic materials and integration; passive components
Abstract:

This paper develops a 200-W wide-input-range (64–160-to-24-V) rail grade dc–dc converter based on gallium nitride devices. A two-stage configuration is proposed. The first regulated stage is a two-phase interleaved buck converter (>400 kHz), and the second unregulated stage is an LLC (2-MHz) dc transformer. In order to achieve high frequency and high efficiency, the critical-mode operation is applied for the buck converter, and the negative coupled inductors are used to reduce the frequency and the conduction losses. Then, a systematical methodology is proposed to optimize the planar-coupled inductors. For the unregulated LLC converter, it can always work at its most efficient point, and an analytical model is used to optimize the planar transformer. Finally, the proposed dc–dc converter, built in a quarter brick form factor, is demonstrated with a peak efficiency of 95.8% and a power density of 195 W/in3.

T2.11: Common Mode Voltage Reduction Method for a Back-to-Back Three-Level NPC Converter
Authors: Xiaona Xu, Kui Wang, Zedong Zheng, Bo Yang, Yongdong Li
Representing Author: Xiaona Xu - Tsinghua
Keywords:control; emi; three phase converter
Abstract:

Common mode voltage (CMV) is a common problem in multi-level converter. It will hurt the bearing of the AC motor. This paper proposes a new CMV reduction method for a back-to-back three-level (3L) NPC converter. Based on phase-disposition PWM (PDPWM), a zero-sequence voltage (ZSV) injection method is adopted, which is injected to the selected phase of the inverter side to make its reference voltage equal to that of the corresponding phase of the rectifier side when the CMV is equal to 1/3 of the DC bus voltage. The specific selection method is discussed in detail in this paper. After using the proposed ZSV injection method, the CMV can be reduced to 1/6 of the DC bus voltage. Experimental results verify the effectiveness of the proposed method.

T2.12: Three-Terminal Common-Mode EMI Model for EMI Generation, Propagation, and Mitigation in a Full-SiC Three-Phase UPS Module
Authors: Sungjae Ohn, Jianghui Yu, Paul Rankin, Bingyao Sun, Rolando Burgos, Dushan Boroyevich, Harish Suryanarayana, Christopher Belcastro
Jianghui Yu picture
Representing Author: Jianghui Yu - CPES
Keywords:emi; modeling and control; silicon carbide (sic); three-phase converters
Abstract:

With superior loss characteristics, wide bandgap devices such as silicon carbide (SiC) MOSFETs are expected to replace Si-IGBTs in grid-connected applications. Uninterruptible power supply (UPS) is an application in which low conduction-loss and switching-loss from SiC devices can largely improve the system efficiency. However, fast switching of a SiC MOSFET worsens the electromagnetic interference (EMI). In addition, the UPS is comprised of multiple converters wherein different combinations of the converters take part in power-transfer depending on the mode of operation. This complicates the prediction and strategies for noise, especially the common-mode (CM) part. Such complexity calls for deliberate strategies to be set before prototyping to contain and mitigate the CM noise. In this paper, a three-terminal CM circuit model is presented for a three-phase UPS with an active battery charger and a battery rack. The significance of a dc-dc converter on CM EMI generation and propagation has been analyzed based on the model. In a mode of operation where the dc-dc converter is active, a considerable amount of the CM noise is generated from the dc-dc converter. Also, the multiple resonances on the propagation path associated with dc inductors and the battery rack highly deteriorates CM EMI. As a mitigation strategy in the design phase, different topologies and PWM schemes for the ac-ac stage and the dc-dc stage have been compared based on the model. A 20 kW full-SiC UPS has been built and tested to experimentally verify the impact of the dc-dc converter operation on the noise and to validate the mitigation strategy.

T2.13: Ultra High Frequency Integrated Coupled Inductor Design For IVR in Smartphone Application
Authors: Feiyang Zhu, Qiang Li, Fred C. Lee
Feiyang Zhu picture
Representing Author: Feiyang Zhu - CPES
Keywords:magnetic materials and integration; passive components
Abstract:

In order to provide a compact and efficient power solution for high-performance processors in smartphone application, three-dimensional integrated voltage regulator operating at ultra-high frequency (> 10MHz) becomes a promising solution. One of the most challenging parts is ultra-low profile magnetic design with small footprint, loss and large current handling capability. In this paper, a novel, two phase negative coupled inductor structure with TKOIN metal-flake composite magnetic material is proposed. The structure exploration and design process are illustrated with the help of finite element tool. The new inductor structure features very small inductor loss(<0.15W per phase) and footprint(<4mm2 per phase), large inductance density and current handling ability(> 3A dc current per phase) operating at 20MHz switching frequency. Three different inductor samples are fabricated and experimentally tested to verify the design and to evaluate thermal performance.

T2.14: Improved PCB Winding Structure for 11kW CRM PFC Converter
Authors: Phu Hieu Pham, Shuo Wang, Ahmed Nabih, Qiang Li, Fred. C. Lee
Phu Hieu Pham picture
Representing Author: Phu Hieu Pham - CPES
Keywords:emi; high power density; magnetic materials and integration; soft switching
Abstract:

The PCB based coupled inductor with balancing technique has been successfully applied to CRM PFC converter in various applications, such as data center and on-board charger. The power rating of such prototypes is rating from hundreds watt to 6 kilo watts [1-2]. However, the thermal issue, the coupling coefficient and the parasitic impact of PCB based coupled inductor on EMI performance have not been studied in detail. This paper will go deep into these issues and the proposed PCB winding structure is presented. The FEA simulated results shows the total inductor loss reduction of proposed structure over the conventional one. The 11kW prototype is built to verify the thermal performance as well as the EMI reduction of the proposed structure.

T3: Resonant Converters

T3.1: 18 kW Bidirectional SiC/GaN Charger with Partial Energy Processing
Authors: Yuliang Cao, Dong Dong
Yuliang Cao picture
Representing Author: Yuliang Cao - CPES
Keywords:control; high power density; resonant converters; silicon carbide (sic); soft switching
Abstract:

In this paper, we investigate the behavior of Β-Ga2O3 Schottky diodes in the condition of forward current surge. An analytical electro-thermal device model is calibrated with experimental devices and TCAD simulations. Then this device model is incorporated into a SPICE electro-thermal network model, which is used to simulate the device temperature rise during the surge transient, considering various device and packaging configurations (i.e. various chip thicknesses, single-side or double-sidecooling).

T3.2: LCCL-LC Resonant Converter and Its Soft Switching Realization for Omnidirectional Wireless Power Transfer Systems
Authors: Junjie Feng, Qiang Li, Fred Lee
Junjie Feng picture
Representing Author: Junjie Feng - CPES
Keywords:resonant converters; wireless power transfer
Abstract:

Recently, omnidirectional wireless power transfer systems have been studied intensely due to their improved flexibility as compared with their planar counterparts. A LCCL-LC resonant converter is derived to satisfy all of the five requirements. The design methodology of the circuit parameter is proposed. An analytical model of the LCCL-LC circuit is built to ensure zero voltage switching (ZVS) of the switching devices for one transmitter coil and one receiver coil case. The ZVS analysis is extended to the scenario of multiple transmitter coils and one receiver coil. A 6.78 MHz wireless charging system is built to verify the advantage of the LCCL-LC circuit and the accuracy of the ZVS analysis. The peak system efficiency of 78% at 5 W output power is achieved.

T3.3: Three-Phase Interleaved LLC Resonant Converter with Integrated Planar Magnetics
Authors: Rimon Gadelrab, Fred C. Lee, Qiang Li
Rimon Gadelrab picture
Representing Author: Rimon Gadelrab - CPES
Keywords:gallium nitride (gan); high power density; optimization; resonant converters; soft switching
Abstract:

The LLC converter is considered the most efficient topology in server and telecom applications. And, it has been demonstrated that three interleaved LLC converters can achieve further efficiency improvement at the 3KW power level. However, the magnetic components for multiphase LLC are complex, bulky, and difficult to manufacture in a cost-effective manner. In this paper, a high-frequency GaN based three-phase LLC converter is utilized to attempt to address these challenges. With GaN operating at 1 megahertz, all magnetic components, namely three inductors and three transformers, can be integrated in one common structure while all magnetic windings are contained in a compact 4-layer PCB with 3 oz. copper. The proposed structure can be easily and cost effectively manufactured in high quantities. Furthermore, up to a 20db reduction of common-mode noise, from 150KHz up to 30MHz, can be realized if 2 additional PCB layers are employed for proposed CM noise shielding. A 3kW 400V/48V 3-phase prototype is demonstrated, with an expected peak efficiency of 97.4% and a power density of 450W/in3 (28 kW/L).

T3.4: A High-Eficiency High-Density Wide-Bandgap Device-Based Bidirectional On-Board Charger
Authors: Bin Li, Qiang Li, Fred Lee, Zhengyang Liu, Yuchen Yang
Rimon Gadelrab picture
Representing Author: Rimon Gadelrab - CPES
Keywords:gallium nitride (gan); high power density; resonant converters; silicon carbide (sic); soft switching
Abstract:

This paper proposes a novel two-stage topology for a 6.6-kW on-board charger. The first stage, employing an interleaved bridgeless totem-pole ac/dc in critical conduction mode to realize zero-voltage switching, is operated at over 300 kHz. A bidirectional CLLC resonant converter operating at 500 kHz is chosen for the second stage. A variable dc-link voltage is adopted to track the wide battery voltage range, so that the CLLC resonant converter can always operate at its most efficient point. The 1.2-kV SiC devices are adopted for the ac/dc stage and the primary side of dc/dc stage, while 650-V GaN devices are used for the secondary side of dc/dc stage. In addition, PCB winding coupled inductors and integrated transformer are implemented in ac/dc stage and dc/dc stage, respectively, for the purpose of high density and manufacture automation. The proposed structure is demonstrated to have 37-W/in3 power density and above 96% efficiency over the entire battery voltage range, which far exceeds the current practice.

T3.5: Design-Oriented Equivalent Circuit Model for Resonant Converters
Authors: Yi-Hsun Hsieh, Fred C. Lee
Yi-Hsun Hsieh picture
Representing Author: Yi-Hsun Hsieh - CPES
Keywords:modeling and control; resonant converters
Abstract:

For high frequency power conversion, resonant converters are gaining increasing popularity. However, the lacking of an accurate small-signal model becomes an impediment for performance optimization. Recently, a simple equivalent circuit model was proposed based on the fundamental approximation where the resonant tank is deemed as a good band-pass filter. The model works well for series resonant converter (SRC) with high quality factor. The model is inadequate for LLC converter whose resonant tank doesn’t behave like a band-pass filter when it operates below the resonant frequency even under high quality factor. The harmonics, when passing through the rectifier, are intertwined. The model fidelity suffers if these complicated nonlinear effects are not accounted for. The recent modeling breakthrough is based on the extended describing function method when all harmonics are taken into consideration. This paper proposes a simplified which predicts accurately the small signal behavior up to 1/2 switching frequency. Furthermore, the simplified model provides significant physical insights on the small-signal dynamics of resonant converters.

T3.6: High-Efficiency High-Density DC/DC Converter for Battery Charger Applications
Authors: Feng Jin, Qiang Li, Fred C. Lee
Feng Jin picture
Representing Author: Feng Jin - CPES
Keywords:high power density; magnetic materials and integration; modular converters; resonant converters; silicon carbide (sic)
Abstract:

Due to the concerns regarding increasing fuel cost and air pollution, plug-in electric vehicles (PEVs) are drawing more and more attention. Range is the major drawback for electric cars, and the easiest way to increase it is to cram more storage capacity into a vehicle. Taking Tesla Inc’s Model X P100D as an example, it is equipped with a 100kWh battery to provide a 295 miles range. However, it will take 11 hours for the 100kWh battery to be full charged with its own on-board-charger which make long distance travel infeasible. Fast charging technique is the most promising method to short this charging period. In Tesla’s supercharger station, a Model X P100D can be fully charged within 75 minutes based on its 135kW charging capacity. Porsche, a German high-performance sports cars automobile manufacturer, developed a 350kW DC fast-charger for its 800V battery pack of Mission E. Electric vehicle infrastructures, such as ChargePoint, electrify America, etc., have launched their investment on 350kW or higher power fast charging stations. However, these fast chargers have low power density. In order to charge the battery faster, our developed single-phase on-board charger concept is extended to a higher power level. By utilizing the three-phase interleaved CLLC resonant converter as DC/DC stage, the charging power for one module is pushed to 12.5 kW. It can operate bi-directionally and achieve soft-switching with proper control. As a result, we will push the switching frequency to over 500kHz to help reduce converter size and weight. With the help of high-frequency operation, the transformers and inductors and be integrated together and build with PCB winding. Therefore, the proposed DC/DC converter will have not only very high density, but also very suitable for manufacture automation. In order to achieve wide output voltage range for battery charger applications, typically from 250V to 800V, to cover both state-of-the-art 400V battery pack and 800V battery pack in the near future, interleaved buck converter is adopted, and1.2kV SiC MOSFET will be used to build this module. This DC/DC module has very wide applications. It could be the second stage for an on-board charger with three-phase AC input. It also could be the final stage of an off-board charger with 800V DC link as its distribution bus. Basically, it is a general building block For EV battery charger application.

T3.7: Design of IPT Transformer under Space Constraint
Authors: Bo Li, Khai Ngo
Bo Li picture
Representing Author: Bo Li - CPES
Keywords:magnetic materials and integration
Abstract:

Inductive power transfer(IPT) has always suffered from large volume and weight. For IPT applied to small electric vehicles and drones, smaller receiver size and weight are always preferred. This paper presents a way to design IPT transformer under space constraint for receiver coil. The methodology of designing an IPT transformer with reduced receiver size but the same power level is first demonstrated. Maximizing power with fixed receiver size by varying transmitter is then introduced with the constraint of thermal and leakage field. The design method is finally verified by experiment.

T3.8: Design Optimization of Unregulated LLC Converter with Integrated Magnetics for Two-Stage 48V VRM
Authors: Mohamed H. Ahmed, Fred C. Lee, Qiang Li
Xin Lou picture
Representing Author: Xin Lou - CPES
Keywords:gallium nitride (gan); high power density; magnetic materials and integration; optimization; soft switching
Abstract:

In this paper, a high-efficiency and power-density unregulated LLC converter (DCX) is proposed for a first-stage converter in two-stages 48V voltage regulator module (VRM) for data center applications. An optimized matrix transformer structure including an enhanced termination method for both primary and secondary side winding, in addition, a PCB winding structure for equal current sharing among all transformer parallel layers is proposed, by which a significant reduction in the total conduction loss for the high frequency transformer is achieved. The proposed optimized design is applied for designing two LLC-DCX converters with different fixed transformation ratios of (4:1) and (8:1) to study and evaluate the impact of the intermediate bus voltage variation on the overall two-stage 48V VRM performance. The designed LLC-DCX with GaN devices can provide a continuous output power of 900W with maximum efficiencies of 98.4% for the (4:1) conversion and 98.0% for the (8:1) conversion with high-power-densities of 1600 W⁄in3 and 1200W⁄in3 respectively.

T3.9: Wide Voltage Range High-Efficiency Sigma Converter 48V VRM With Integrated Magnetics
Authors: Mohamed H. Ahmed, Fred C. Lee, Qiang Li
Xin Lou picture
Representing Author: Xin Lou - CPES
Keywords:gallium nitride (gan); high power density; magnetic materials and integration; resonant converters; soft switching
Abstract:

In this paper, a high-efficiency and power-density single-stage 48V voltage regulator module (VRM) based on a Sigma converter power architecture is proposed for CPU in data center applications. The proposed converter overcomes the limitation of wide voltage range operation in the Sigma converter architecture by utilizing a variable gain LLC converter by which the voltage distribution among the buck converter and the LLC converter in the quasi-parallel structure is maintained in the ranges that allow the highest possible conversion efficiency. A magnetic integration method is proposed for the variable gain LLC converter by which a PCB winding matrix transformer structure and resonant inductor are integrated with a single core structure and minimum winding requirement to achieve the required gain characteristics. A wide voltage range Sigma converter prototype is built that can operate with input voltage range of (40-60V) and output voltage range of (1.3-1.8V) while providing a maximum output current of 120A, the designed converter can achieve a maximum efficiency of 95.2% and a power-density of 700W⁄in3.

T3.10: Low Loss Integrated Inductor and Transformer Structure and Application in Regulated LLC Converter for 48V Bus Converter
Authors: Mohamed Ahmed, Ahmed Nabih, Fred C. Lee, Qiang Li
Ahmed Nabih picture
Representing Author: Ahmed Nabih - CPES
Keywords:gallium nitride (gan); high power density; magnetic materials and integration; resonant converters; soft switching
Abstract:

In this paper, an LLC converter utilizing gallium nitride (GaN) transistors is proposed for a 48V regulated and isolated bus converter. Compared to pulse width modulation (PWM) based topologies, the soft switching capability of an LLC allows operation at very high frequencies. In addition, the magnetic components size is reduced without sacrificing efficiency. In this work, a novel magnetic structure that integrates a matrix transformer and inductor with minimum winding and a single magnetic core is proposed, to allow a high-density and high-efficiency LLC converter design for a bus converter. A 40V-60V input and regulated 12V output converter is developed to deliver a 1 KW output power in a quarter brick form factor. The designed converter can achieve a power density of 700 W⁄in3 with a maximum efficiency of 97.82% at half load, dropping to 97.7% at full load operation.

T3.11: A Series-Series-CL Resonant Converter for Wireless Power Transfer in Auxiliary Power Network
Authors: Keyao Sun, Jun Wang, Rolando Burgos, Dushan Boroyevich
Keyao Sun picture
Representing Author: Keyao Sun - CPES
Keywords:optimization; resonant converters; wireless power transfer
Abstract:

This paper proposes a series-series-CL resonant converter for wireless power transfer (WPT) in auxiliary power network for 10 kV SiC MOSFET based power electronics building block. The topology of the converter can compensate reactive power thus increase system efficiency, generate a constant output voltage which can be tuned by changing one pair of LC parameters (or distance between coils), and keep a symmetrical coil structure which facilitates the design and optimization. A WPT converter prototype is built that features in 48 V to 48 V, 100 W, 92% efficiency, 4 pF isolation capacitance, and 24 kV insulation voltage.

T3.12: Design and Multi-Objective Optimization of Coil and Magnetic for Wireless Power Transfer in Auxiliary Power Network
Authors: Keyao Sun, Jun Wang, Rolando Burgos, Dushan Boroyevich
Keyao Sun picture
Representing Author: Keyao Sun - CPES
Keywords:gallium nitride (gan); magnetic materials and integration; optimization; resonant converters; wireless power transfer
Abstract:

This paper proposes a coil and magnetic design and multi-objective optimization method for wireless power transfer in auxiliary power network for 10 kV SiC MOSFET based power electronics building block. This paper summarizes basic parameters extraction methods for coil to avoid time-consuming 3D FEA simulations during the optimization process. In addition, effect of magnetic shielding layer is also analyzed. Self- and mutual-inductance calculation using mirror method when magnetic shielding is applied are also given. Coil optimization process considering efficiency, isolation capacitance and insulation capability is given. A wireless power transfer converter prototype is built that features in 48 V to 48 V, 100 W, 92% efficiency, 4 pF isolation capacitance, and 24 kV insulation voltage.

T3.13: Series-Capacitor Buck Converter with Soft Turn-On for Datacenters
Authors: Cong Tu, Khai Ngo, Rengang Chen
Cong Tu picture
Representing Author: Cong Tu - CPES
Keywords:gallium nitride (gan); optimization; resonant converters; soft switching
Abstract:

The Series-Capacitor Buck (SCB) converter lowers the switching loss, doubles the duty ratio, and equalizes the current between two phases. A Resonant Series-Capacitor Buck (RSCB) converter is realized by adding a parallel resonant tank next to the series-capacitor Cs. All switches turn on into zero-voltage (ZVOn) and the low-side switches turn off from zero-current (ZCOff). The voltage gain remains proportional to the off-time of the low-side switches. The resonant tank generates additional loss and increases the voltage stress of the low-side switches. A 2-MHz prototype with a full load efficiency of 97.3%, 48 V at the input, and 7 V, 20 A at the output, was built to verify the design.

T3.14: Analysis and Comparison of DC and AC Output Inductors in Tunable Piezoelectric Transformer Based DC/DC Converters
Authors: Le Wang, Rolando P. Burgos, Alfredo Vazquez Carazo
Le Wang picture
Representing Author: Le Wang - CPES
Keywords:passive components; resonant converters; soft switching
Abstract:

Tunable piezoelectric transformer (TPT) is a recently developed piezoelectric transformer with three ports: input, output and control ports. It can be treated as the integration of a resonant tank and a transformer, where the series resonant capacitance can be tuned by the control port. There are two methods to design the output filter in TPT based converters. The traditional method is to place the output inductor after the rectifier. Such inductor is denoted by DC output inductor since it has a non-zero average current. The proposed method in this paper is to place output inductor before the rectifier. Such output inductor operates with zero average current and is denoted by AC output inductor. In this work, the regulation limitation caused by the DC output inductor is analyzed. Benefits of the AC output inductor are explained from two points of view. The benefits of the input inductor, which is commonly utilized in piezoelectric transformer based converters, are also explained. The performance of TPT based converters with these two types of output inductors are compared. Experimental results show that with the help of the AC output inductor, the converter can achieve better efficiency and regulation compared to the one with DC output inductor.

T3.15: Design Analysis for Current-transformer Based High-frequency Auxiliary Power Supply for SiC-based Medium Voltage Converter Systems
Authors: Ning Yan, Jiewen Hu, Jun Wang, Dong Dong, Rolando Burgos
Ning Yan picture
Representing Author: Ning Yan - CPES
Keywords:gallium nitride (gan); passive components; resonant converters; soft switching
Abstract:

This paper presents a design of 1 MHz isolated auxiliary power supply system using gallium nitride (GaN) devices with medium voltage insulation reinforcement. The designed power supply is capable to simultaneously supply multiple gate drivers and auxiliary components for 10 kV silicon carbide (SiC) MOSFETs based converter systems with a strong high dv/dt common-mode nose immunit. In the system, a high-frequency soft-switched resonant topology and current-fed switching voltage regulator are applied to the power supplies sending and receiving sides respectively. To achieve medium voltage insulation (PD free) as well as low coupling capacitor (< 2 pF) of the system, a current based transformer with single turn on the sending side is designed. This complete auxiliary power supply design is capable of driving more than 6 distributed loads with total power of 120 W under different conditions and it is immune to load failures.

T4: Modeling and Control of Power Converters

T4.1: Damping Selection Strategy Considering Reliability for Maximum Energy on the Wave Energy Power Converters
Authors: Chien-An Chen, Lei Zuo, Khai Ngo
Chien-An Chen picture
Representing Author: Chien-An Chen - CPES
Keywords:device and system reliability; modeling and control; optimization
Abstract:

An optimal damping selection strategy on the power electronics in wave energy application is introduced to increase the total energy produced from the power converter in a wave energy converter (WEC) system. A damping map for maximum energy is built for the selection. The map is based on an irregular wave-to-wire simulation and reliability analysis on the IGBT module. From the yearly wave mission profile, the damping selection strategy is proved to provide 40% more energy than the conventional optimal power with passive damping selection in the WEC power converter.

T4.2: A Two-Stage Rail Grade DC/DC Converter Based on GaN Device
Authors: Minfan Fu, Chao Fei, Yuchen Yang, Qiang Li, Fred C. Lee
Tianlong Yuan picture
Representing Author: Tianlong Yuan - CPES
Keywords:gallium nitride (gan); modeling and control; soft switching
Abstract:

It is found that providing heat is removed through both sides of the die, a Β-Ga2O3 Schottky diode offers a robustness to surge current comparable to that of a SiC Schottky diode. The low thermal conductivity of Β-Ga2O3 is found to be balanced by the enhanced heat extraction from top-side cooling as well as the intrinsic low on-resistance (and conduction loss) increase with temperature in Β-Ga2O3 devices.

T4.3: Imbalance Mechanism and Balancing Control of DC Voltages in a Transformerless Series Injector Based on Paralleled H-Bridge Converters for AC Impedance Measurement
Authors: Zeng Liu, Igor Cvetkovic, Zhiyu Shen, Dushan Boroyevich, Rolando Burgos, Jinjun Liu
Igor Cvetkovic picture
Representing Author: Igor Cvetkovic - CPES
Keywords:control; modeling and control; modular converters; stability
Abstract:

Small-signal stability of ac power systems is able to be assessed by measuring their terminal impedance, and a trans- formerless series injector is very attractive for wideband mea-surement of load impedances. A typical implementation of the transformerless series injector is paralleled H-bridge (PHB) con-verters, where dc voltage imbalance will occur when system current magnitude is larger than a critical point, and thus the operation region of the series injector is seriously restricted. To address this issue, this paper presents a deep analysis on the mechanism be-hind dc voltage imbalance for PHB-based series injector, and it is revealed that a positive feedback exists in the dc voltage balanc-ing loop under high system current magnitude. Then an enhanced control scheme is proposed to balance dc voltages in full system current range, where a reactive component is injected in the output voltage while reactive circuiting current is introduced among H-bridge converters for redistributing active power. Furthermore, the system behavior with the proposed scheme is comprehensively analyzed and the reference design for the injected reactive component magnitude in the output voltage is offered. Finally, the imbalance mechanism and the proposed scheme are validated by simulation and experimental results.

T4.4: Modeling and Control of Modular Multilevel Converter
Authors: Yugal Gupta, Yi-Hsun Hsieh, Fred C. Lee, Qiang Li
Yugal Gupta picture
Representing Author: Yugal Gupta - CPES
Keywords:control; modeling and control; modular converters; three-phase converters
Abstract:

Because of simple modular structure and easy voltage scaling, the modular multilevel converter (MMC) is deemed the most suitable for high-voltage power conversion using relatively low-voltage devices. In most practices, the volume of the capacitors is more than 50% of the total module size. Hence, methods of reducing circulating energy and the size of the capacitor bank have been widely pursued. Recently, a new modeling approach based on state trajectory analysis for MMCs has been developed. It offers graphical visualization of the power throughput and circulating energy, enabling a more systematic approach to address control strategies for system optimization. Furthermore, it provides a simple equivalent circuit model which leads to establishment of the two control laws that enable maximum power throughput with minimum circulating energy. This study aims towards reviewing this new modeling approach in detail and, based on this, examine the effectiveness of existing control techniques and their further scope of improvement for capacitor size reduction.

T4.5: Neural Network-based Power Control Method for Direct-Drive Wave Energy Converters in Irregular Waves
Authors: Xuanrui Huang, Kai Sun, Xi Xiao
Representing Author: Xuanrui Huang - Tsinghua
Keywords:modeling and control; optimization; three phase converters
Abstract:

In this study, the maximum power extraction condition for a direct-drive wave energy converter in irregular waves in the time domain was proven and described using the variational method. Thus, a real-time optimal power control law was proposed, which contained a noncausal part. A classical controller requires information about the future wave excitation force to address the noncausal issue. To avoid the prediction, this study presents an optimal power control method based on a back propagation (BP) neural network. The network was used to learn the input-output mapping relationships of the noncausal part. The simulation and experiment demonstrated that the proposed method was valid, effective, and superior to some existing methods.

T4.6: A Distributed Hierarchical Digital Control System for Medium-Voltage Modular Converters Enabling Peak Current Mode Control for Parallel Operation
Authors: Qian Li, Jun Wang, Igor CvetKovic, Rolando Burgos, Dushan Boroyevich
Qian Li picture
Representing Author: Qian Li - CPES
Keywords:control; modeling and control; modular converters; silicon carbide (sic)
Abstract:

One of the key characteristics of modular converters is scalability. Therefore, precise parallel operation of multiple modular converters with current mode control is required. Furthermore, a well-structured digital control scheme allows for the programmability of the modular converter to achieve different functions and thus needs to be carefully defined. This digest introduces a distributed hierarchical digital control system for medium-voltage modular converters which uses gate drivers for PWM modulations. The gate driver, which features a PCB-embedded Rogowski current sensor and local FPGA with peripherals, is capable of directly sensing the switching currents of SiC devices and locally implementing PWM modulations. As an application example in this digest, a modular converter system is constructed and operated as paralleled-synchronous buck converters with peak current mode control. Each modular converter employs a hierarchical control structure where the local controller is responsible for the arithmetic calculation of control references and the gate drivers conduct peak current loop modulation. Data transmission between the local controller and the gate drivers occurs digitally through fiber optic cables which further increase the noise immunity of the modular converter. Good load current sharing between the paralleled modular converters is achieved and test results are demonstrated in this digest.

T4.7: Optimization Design of Medium-Voltage Modular Converter System with Terminal Constraints
Authors: Qian Li, Jun Wang, Igor CvetKovic, Rolando Burgos, Dushan Boroyevich
Qian Li picture
Representing Author: Qian Li - CPES
Keywords:control; modeling and control; modular converters; optimization; silicon carbide (sic)
Abstract:

In the medium-voltage power distribution system of a microgrid, power electronics converters are widely used in power source/load center connection, current limiting and power distribution system protection. In lieu of designing power converters separately for each application, Navy proposed a universal power processing unit concept, which is known as power electronics building blocks (PEBB), to be used for constructions of power electronics system of various functionalities and with different voltage and power ratings for the purpose of overall cost, losses, size and weight reduction. Consequently, it is desired to apply optimization techniques in the design of PEBB-based power electronics systems regarding weight, size and efficiency. As a commonly encountered load type, a step load is connected to the distribution bus through power electronics system and will cause negative effect on the bus if its power processing stage is not carefully dealt with. In order to meet the interface standards, optimization process of PEBB-based power processing stage needs to take into account of the terminal transient response performances (e.g. overshoot and rising time) as optimization design constraints. In this paper, a multi-objective optimization design of PEBB-based modular converter system in the presence of a step load is presented. Internal DC bus interface standards are added to the optimization process as extra design constraints.

T4.8: Improved V2 Constant On-Time Control with State-Trajectory Functions
Authors: Virginia Li, Qiang Li, Fred C. Lee
Virginia Li picture
Representing Author: Virginia Li - CPES
Keywords:control; modeling and control; optimization
Abstract:

Voltage regulator (VR) for smartphone CPU and GPU applications need to meet fast dynamic voltage scaling (DVS) and load transient requirements. Constant On-Time Control (COT) is a popular variable-frequency control in VR applications due to high light-load efficiency and high-bandwidth design to achieve fast transient. In addition, the V2 variation of COT is able to achieve fast DVS tracking capability and simple to implement. For fast load transient, it is possible for COT to lose control for a period of time. As a result, the output voltage not only have a large undershoot but also a ring-back before control is regained. The best transient response is a single-cycle response. Prior arts to realize single-cycle response involves complicated algorithm which need to be digitally implemented. In this paper, an improved method to improve V2 COT using state-trajectory control is proposed with analog implementation.

T4.9: Small-signal Stability Impact of Grid-connected Virtual Synchronous Machine with Grid-support Functions
Authors: Qing Lin, Ye Tang, Wen Bo, Rolando Burgos, Dushan Boroyevich
Qing Lin picture
Representing Author: Qing Lin - CPES
Keywords:modeling and control; stability; three-phase converters
Abstract:

This paper analyses the small signal stability impact of a virtual synchronous machine (VSM) based photovoltaic (PV) inverter. VSM is a power electronics-based approach which makes grid-integrated renewable generators appear to be electromechanical synchronous machines. In this paper, prototypes of VSM based and conventional phase-locked loop (PLL) based PV inverters are introduced. To support grid voltage, different local reactive power control modes are implemented in the control design. Small signal stability test results of PV inverter models with VSM and PLL in Simulink are compared and analyzed using Generalized Nyquist Criterion (GNC) based on impedance measurements.

T4.10: Frequency-coupling Admittance Modeling of Converter-Based Wind Turbine Generators and the Control-Hardware-in-the-Loop Validation
Authors: Wei Liu, Xiaorong Xie, Xu Zhang, Xuan Li
Representing Author: Wei Liu - Tsinghua
Keywords:control; stability; modeling and control; system reliability and stability
Abstract:

Recently, sub- and super-synchronous oscillation (SSO) associated with converter-based wind turbine generators (WTGs) has been attracting wide attentions. To investigate such SSO incidents, impedance or admittance-based modeling and analysis were widely used. It was discovered that coupling effects exist between impedances or admittances at complementary (i.e., sub and super-synchronous) frequencies. However, there is a lack of experimental validation on the coupling effects of different WTGs. In this paper, the frequency-coupling admittance models (FCAMs) of two types of widely adopted WTGs, i.e., direct-drive and doubly-fed WTGs, are presented at first. Secondly, a perturbation-based identification method is proposed to obtain the FCAMs. Next, the method is implemented in a control-hardware-in-the-loop (CHIL) platform based on RTDS. Then with extensive CHIL tests, the FCAMs of both types of WTGs are obtained, and the impacts of frequency-coupling effects on SSO are validated. Finally, the characteristics of frequency-coupling effects and the root causes are further examined. This study is of important reference value to select appropriate models for oscillatory stability analysis.

T4.11: Modeling and Control for 48V/1V Sigma Converter for Very Fast Transient Response
Authors: Xin Lou, Mohamed H. Ahmed, Fred C. Lee, Qiang Li, Virginia Li
Xin Lou picture
Representing Author: Xin Lou - CPES
Keywords:control; high power density; modeling and control; resonant converters
Abstract:

48V voltage regulator modules (VRMs) are critical for telecom power supplies, and is becoming popular for future data centers. By using a novel sigma converter topology, an outstanding performance in terms of efficiency (95.2%) and power density (700 W⁄in3) have been demonstrated in [1]. Both the efficiency and power density are much higher than state-of-art solutions. The sigma converter is a quasi-parallel converter comprises an LLC converter and a regulated buck converter connected in series from the input side and in parallel from the output side. However, the modeling and control of Sigma converter is challenging due to the quasi-parallel structure and have not been solved properly yet. Basically, there are three control methods, voltage mode, current mode and V2 control. In [2], a voltage mode control design is provided with the small-signal model. However, the voltage mode control is not suitable for high-bandwidth design due to the low frequency double-pole. In this paper, the small-signal model of current mode and V2 control are provided and compared with voltage mode control. The V2 control with active droop control is chosen for high-bandwidth and constant load line design. Additionally, the transient performance is performed and verified to meet the VR14 requirements.

T4.12: Evaluation and control of active capacitor banks for a floating power modules based converter
Authors: Tam Nguyen, Bo Wen, Rolando Burgos, Dushan Boroyevich, Jacob Verhulst, David L. Vrtachnik, Mohamed Belkhayat
Tam Nguyen picture
Representing Author: Tam Nguyen - CPES
Keywords:control; high power density
Abstract:

The Perturbation Injection Unit (PIU) is a core in an Impedance Measurement Unit (IMU), which evaluates the stability of the system based on the impedances obtained from the current injections to the grid. Due to a wide frequency range of the current injections, the DC-side floating capacitors in the floating power modules of the PIU are highly distorted by multiple current harmonics, which results in a large DC-bus ripple. Utilizing passive capacitors as in traditional methods helps reduce the DC-bus voltage ripple but makes the system bulky. In this paper, active capacitors are integrated with the floating H-bridge power modules to remove the effect of the ripple powers on the DC bus. The auxiliary circuits, which are much smaller in size compared to equivalent passive capacitors, helps increase the power density of the system. The work focuses on the analysis of power components and the extension of the active capacitor to the PIU. A control scheme is also proposed to compensate these multiple harmonics and balance the DC-link voltage in the active capacitor. Effectiveness of the active capacitor solution has been verified by simulation studies.

T4.13: A Power Hardware-in-the-Loop Testbench for Aerospace Applications
Authors: John Noon, He Song, Bo Wen, Rolando Burgos, Igor Cvetkovic, Dushan Boroyevich, Srdjan Srdic, Gernot Pammer
John Noon picture
Representing Author: John Noon - CPES
Keywords:control; device and system reliability; modeling and control; three-phase converters
Abstract:

As the aerospace industry moves towards the More Electric Aircraft (MEA), there is a growing need to model the increasingly complex electrical systems. Real-time modeling and simulation allows standalone simulations to be completed much faster than traditional simulation methods, and allows for Power Hardware-in-the-Loop (P-HIL) emulation and testing. The P-HIL testbench demonstrated in this paper can be run back-to-back where both the source and the load are emulated systems with real power transferred between them. This paper demonstrates the development and execution of machine and power converter emulation on the EGSTON Power Electronics' COMPISO System Unit CSU200-1GAMP6 P-HIL platform. The advantages and capabilities of P-HIL for the MEA are presented in this paper.

T4.14: Control Technique for CRM-Based High Frequency Soft Switching Three-Phase Inverter Under Grid Fault Condition
Authors: Gibong Son, Zhengrong Huang, Qiang Li, Fred C. Lee
Gibong Son picture
Representing Author: Gibong Son - CPES
Keywords:control; modeling and control; silicon carbide (sic); soft switching; three-phase converters
Abstract:

This paper presents a control technique for critical conduction mode (CRM) based high frequency soft switching three-phase inverter under grid fault condition. CRM-based soft switching modulation (DPWM +CRM+ DCM) enables three-phase inverter to operate at hundreds of kHz by reducing switching losses. For practicality of the modulation scheme, three-phase inverter with the soft switching modulation under grid fault condition, especially voltage sag, is investigated. To deliver constant active power to load during voltage sag, current references for the inverter become unbalanced. With unbalanced grid voltage and current reference, undesired CCM operation occurs where DCM operation is intended causing high turn-on loss. To avoid CCM operation and reduce the turn-on loss, a new control technique using pulse skipping concept in DCM phase is proposed. In this paper, review of the soft switching modulation, how CCM operation appears during voltage sag, and details of the new control technique under grid fault condition are discussed.

T4.15: Critical Conduction Mode Based High Frequency Single-Phase Transformerless PV Inverter
Authors: Gibong Son, Zhengrong Huang, Qiang Li, Fred C. Lee
Gibong Son picture
Representing Author: Gibong Son - CPES
Keywords:control; gallium nitride (gan); high power density; soft switching
Abstract:

This paper presents critical conduction mode (CRM) single-phase transformerless full-bridge inverter in residential photovoltaic (PV) system. CRM full-bridge inverter with bipolar pulse width modulation (PWM) features inherent zero voltage switching (ZVS) capability for the whole line cycle. This enables the inverter to push switching frequency up to hundreds kHz and achieve high power density with high efficiency. However, CRM operation incurs non-constant common mode (CM) voltage during resonant period causing high frequency leakage current. To minimize the leakage current, a new switching modulation strategy is introduced combining CRM and triangular current mode (TCM). The switching modulation scheme alleviates CM voltage by shortening the resonant period and consequently reduces the leakage current. In this paper, the basic operation principle of CRM full-bridge inverter, impacts of CRM operation on the leakage current, and details of the switching modulation method are discussed. Experimental results with laboratory prototype built with E-mode GaN device validate its performance.

T4.16: Stability Analysis of Power Systems With Multiple STATCOMs in Close Proximity
Authors: Chi Li, Rolando Burgos, Bo Wen, Ye Tang, Dushan Boroyevich
Ye Tang picture
Representing Author: Ye Tang - CPES
Keywords:control; modeling and control; stability; three-phase converters
Abstract:

Recently, multiple static synchronous compensator (STATCOM) units have been adopted in power transmission systems in order to obtain a better voltage regulation and to share loads. However, they could possibly interact in a negative way instead of helping each other, due to the improper design of the STATCOM controllers. To analyze this problem, a d–q frame impedance-based stability analysis was used to explore the instability with the presence of STATCOMs, where previous stability related ?ndings are not applicable directly because of some unique features of STATCOMs. This paper identi?ed the frequency range of interactions in a viewpoint of d–q frame impedances and pinpointed that the ac voltage regulation was the main reason of instability, masking the effects of phase-locked loop on power transmission systems. In addition, due to the high impedance of STATCOMs around the frequency range of interactions, the number of connected STATCOMs was the main contributor to stability instead of the topology of power systems or the locations of STATCOMs. A scaled-down 2-STATCOM power grid was built to verify the conclusions experimentally. This paper is accompanied by a video showing instability between STATCOMs in the experiment.

T4.17: Analysis of STATCOM Small-Signal Impedance in the Synchronous D-Q Frame
Authors: Chi Li, Rolando Burgos, Bo Wen, Ye Tang, Dushan Boroyevich
Ye Tang picture
Representing Author: Ye Tang - CPES
Keywords:control; modeling and control; stability; three-phase converters
Abstract:

Small-signal model impedances of grid-tied converters have recently attracted researchers' attention and have shown great importance in stability analysis. This paper proposes an impedance model in d-q frame for STATCOMs, including dynamics from synchronization, current, voltage loops and QV droop and reveals the significant features compared to other types of grid-tied converters that 1) impedance matrix strongly coupled in d and q channel due to nearly zero power factor, 2) different behaviors of impedances at low frequency due to inversed direction of reactive power and 3) coupled small-signal propagation paths on the voltage at point of common coupling from synchronization and ac voltage regulation. All these characteristics render difficulty in identifying instability patterns using existing knowledge and pinpointing the main contributor to instability among control loops, which was discussed and solved in this paper. To better understand the frequency coupling effects of STATCOMs, the d-q frame impedance model was further transformed in its complex matrix form. An example of possible instability with STATCOMs was presented and analyzed using the proposed model. The impedance model was verified experimentally with a scaled-down STATCOM prototype.

T4.18: Operation and Control of Converters Having Integrated Capacitor Blocked Transistor Cells
Authors: Jianghui Yu, Rolando Burgos
Jianghui Yu picture
Representing Author: Jianghui Yu - CPES
Keywords:control; modeling and control; modular converters; silicon carbide (sic)
Abstract:

Converters having Integrated Capacitor Blocked Transistor (ICBT) cells provide a new method to transfer high power in medium voltage or high voltage systems. Each ICBT cell operates as a single switching device, series-connected ICBT cells operate as a single high-voltage device without suffering from large additional losses or the requirement of fast balancing control. ICBT cells enable direct power flow from input to output and can operate in both dc and ac modes. Converters with ICBT cells have the scalability like Modular Multilevel Converters but require much lower cell capacitances. Voltage differences may accumulate among the cell capacitors because of components parameters mismatch and parasitic capacitors. The cell capacitor voltages are controlled by delaying the turn on or the turn off of ICBT cells.

T4.19: Control and Hardware Design of Matrix Converters Operating in Step-up Mode
Authors: Boran Fan, Rolando Burgos, Vicky Baker, Dushan Boroyevich
Boran Fan picture
Representing Author: Boran Fan - CPES
Keywords:control; high power density; modeling and control; silicon carbide (sic); three-phase converters
Abstract:

The paper developed a highly integrated SiC-based single stage, 15 kW direct AC-to-AC power converter (Matrix Converter (MxC) ) which avoids the need for an intermediate conversion to DC or energy storage circuit elements. The power structure of MxC is operated in Current Control Mode (CCM) to enable voltage boost above 86.6% of input voltage which was the limitation of the traditional MxC operating in Voltage Control Mode (VCM). The Model Predictive Control (MPC) is implemented to achieve high efficiency and meeting multiple objectives for reference tracking, minimize switching losses, eliminate selected harmonics etc. In the hardware design, low loss SiC-based bidirectional switches are adopted to enable efficiency of single stage conversion above 99% at nominal load conditions.

T4.20: Adaptive Hysteresis Current Based ZVS Modulation and Voltage Gain Compensation for High-Frequency Three-Phase Converters
Authors: Boran Fan, Qiong Wang, Rolando Burgos, Agirman Ismail, Dushan Boroyevich
Boran Fan picture
Representing Author: Boran Fan - CPES
Keywords:high power density; modeling and control; silicon carbide (sic); soft switching; three-phase converters
Abstract:

This paper proposed a systematic approach for the control of 3-phase bi-directional zero-voltage switching (ZVS) converters. Combining the adaptive hysteresis-band current control and turn-on delay modifications, ZVS conditions are realized in full line cycle in all loading conditions like active power, reactive power, light load and heavy load. The soft-switching resonant period is carefully analyzed, and the current band is designed accordingly which minimized the additional conduction loss. Meanwhile, a zero-sequence voltage injection control is included in the approach which compensates the voltage gain by 15% and narrows down the switching frequency variation range. The hardware design approach is also provided including the LCL filter design and a low-cost high-bandwidth high-accuracy current sensor design. A highly integrated 5kW SiC-implemented 3-phase ZVS converter prototype with printed circuit board (PCB) integrated inductors and customized current sensors are designed. All the control is implemented in a single microcontroller unit (MCU) which achieves a high EMC compatibility. The designed prototype achieves a total power density of 5.5kW/L and a peak efficiency of 98.5%. All the analysis and the proposed control approach are experimentally verified on the designed prototype.

T5: Medium-Voltage, High-Power Converters and Systems

T5.1: Figures-of-Merit and current metric for the comparison of IGCTs and IGBTs in Modular Multilevel Converters
Authors: Arthur Boutry, Cyril Buttay, Florent Morel, Bruno Lefebvre, Colin Davidson, Dong Dong, Rolando Burgos
Arthur Boutry picture
Representing Author: Arthur Boutry - CPES
Keywords:modular converters
Abstract:

IGCTs and IGBTs are compared in the case of a HVDC MMC. Specific figures of merit and a current metric providing simple means to compare them, are introduced and discussed. Simulation is used to validate the figures of merit. This analysis supports the growing interest in IGCTs for MMCs.

T5.2: Critical-Conduction-Mode-Based Soft-Switching Modulation for Three-Phase PV Inverters with Reactive Power Transfer Capability
Authors: Zhengrong Huang, Qiang Li, Fred C. Lee
Zhengrong Huang picture
Representing Author: Zhengrong Huang - CPES
Keywords:control; high power density; silicon carbide (sic); soft switching; three-phase converters
Abstract:

In this paper, an improved critical-conduction-mode (CRM)-based soft-switching modulation technique is proposed for three-phase photovoltaic (PV) inverter applications under not only the unity power factor operating condition but also nonunity power factor operating conditions in order to reduce switching loss. With the proposed improvements, for the typical power factor range from the 0.8 lagging condition to the 0.8 leading condition in PV applications, zero-voltage-switch (ZVS) turn-on or valley drain-source voltage turn-on is achieved, which is especially beneficial for silicon carbide (SiC)-based systems at high switching frequency operation to achieve not only high power density but also high efficiency. The proposed modulation technique is digitally implemented with one low-cost microcontroller (MCU). The capability of reactive power transfer and benefits of the improved modulation for achieving soft switching under nonunity power factor conditions are experimentally verified on a SiC-based three-phase bidirectional ac-dc converter prototype. The tested peak efficiency is 98.9% under the unity power factor operation, and above 98.0% within the aforementioned typical power factor range in PV applications, at above 300 kHz switching frequency operation.

T5.3: Improved Three-Phase Critical-Mode-Based Soft-Switching Modulation Technique with Low Leakage Current for PV Inverter Application
Authors: Zhengrong Huang, Qiang Li, Fred C. Lee
Zhengrong Huang picture
Representing Author: Zhengrong Huang - CPES
Keywords:control; high power density; silicon carbide (sic); soft switching; three-phase converters
Abstract:

In this paper, an improved three-phase critical-conduction-mode (CRM)-based soft-switching modulation technique is proposed in order to reduce the leakage current for photovoltaic (PV) inverter applications. Soft-switching turn-on is achievable, which is especially beneficial for silicon carbide (SiC)-based systems at high switching frequency operation to achieve both high power density and high efficiency. The proposed modulation technique is digitally implemented with one low-cost microcontroller (MCU). The modulation concept is verified in simulations and also experimentally implemented on a SiC-based three-phase bidirectional ac–dc converter prototype. Soft-switching turn-on during CRM and DCM operations is verified. In addition, the experiment results show that at least 89% reduction in the leakage current is achieved with the improved modulation technique.

T5.4: Medium Voltage Dual Active Bridge Using 3.3 kV SiC MOSFETs for EV Charging Application
Authors: Lee Gill, Takayuki Ikari, Toshihiro Kai, Bo Li, Khai Ngo, Dong Dong
Bo Li picture
Representing Author: Bo Li - CPES
Keywords:silicon carbide (sic)
Abstract:

Electric vehicle charging technology has come a long way and seen progressive outcomes toward a wide adoption of EVs. To further accelerate the EV evolution, though, the recharging time of electric vehicles will require much improvement. In order to address such a challenge, it is critical to develop a technology that would enable faster, more efficient, and more effective ways of charging an electric vehicle. In order to address such a challenge, it is critical to develop a technology that would enable faster, more efficient, and more effective ways of charging an electric vehicle. The current fast-charging solution involves a heavy and bulky MV-LV transformer, which adds installation complexity for EV charging stations. Therefore, this paper presents an alternative power-delivery solution utilizing a medium-voltage (MV) dual-active-bridge (DAB) converter. The proposed architecture is designed to directly interface the MV grid for high-power, fast-charging capability while eliminating the need for the installation of the MV-LV transformer. The MV DAB converter utilizes 3.3 kV SiC MOSFETs to realize the next 800 V EV charging system. This paper also provides an extended zero-voltage-switching (ZVS) scheme for the MV DAB converter by varying the input (DC-Link) voltage and the switching frequency of the converter. With the system specifications and requirements, a scaled-down 12 kW MV DAB prototype was developed, and its charging operation along with the extended ZVS scheme was simulated and verified by experiments.

T5.5: High-Frequency Transformer Design with High-Voltage Insulation for Modular Power Conversion from Medium-Voltage AC to 400-V DC
Authors: Zheqing Li, Qiang Li, Fred C. Lee, Yi-Hsun Hsieh, Orion Chen
Zheqing Li picture
Representing Author: Zheqing Li - CPES
Keywords:gallium nitride (gan); insulation design and assessment; magnetic materials and integration; resonant converters; silicon carbide (sic)
Abstract:

Due to the increasing use of cloud computing and big data, the power consumption of the datacenter alone will reach 10% of the total electrical power consumption in the world by 2020. In the conventional AC data center power architectures, a line frequency transformer is employed to step down a medium voltage(MV) AC to 480VAC which leads to a very bulky and costly transmission bus and large conduction losses. This line frequency transformer is cascaded by 480V UPS and rectified into 400V DC. In this work, a SiC and GaN based rectifier with high frequency MV solid-state transformer(SST) is proposed to directly step down MV AC to 400 V DC. The DC-DC stage is the key point for this work because of its MV insulation capability. A CLLC resonant converter is utilized with SiC and GaN device to achieve high efficiency, high power density and bi-direction operation. High frequency transformer in the CLLC converter is well designed for 30kV insulation capability for a 4.16kV input voltage referring to IEEE standard. A shielding layer is implemented to reduce the electric field stress in the air. In addition, magnetizing inductance and two resonant inductances are integrated in the transformer in order to subtract volume.

T5.6: A DC Access Solution for Offshore Wind Power Based on UCH-MMC
Authors: Zhengxuan Li, Qiang Song, Jingwei Meng
Representing Author: Zhengxuan Li - Tsinghua
Keywords:control; modular converters; high power density
Abstract:

With the offshore wind farm planned increasingly far from the onshore, the high voltage direct current (HVDC) transmission ought to be utilized. Although modular multilevel converter (MMC) has self-commutation capability and modular design, the huge volume and high cost of capacitors in submodules restrict its application. A unidirectional current H-bridge MMC was proposed and its energy storage reduction effects were verified in the existing paper. This paper proposed a new HVDC solution denoted as UCH-HVDC. To ensure safe operation, a variable dc voltage control method is also provided. The cost and volume evaluation are given.

T5.7: Active Voltage Balancing Embedded Digital Gate Driver for Series-Connected 10 kV SiC MOSFETs
Authors: Xiang Lin, Lakshmi Ravi, Slavko Mocevic, Dong Dong, Rolando Burgos
Xiang Lin picture
Representing Author: Xiang Lin - CPES
Keywords:control; protection; silicon carbide (sic)
Abstract:

This paper focuses on series connection of 10 kV SiC MOSFETs which enables higher operation voltage of devices for medium voltage application. To minimize switching losses, active voltage balancing for series-connected 10 kV SiC MOSFETs is implemented instead of passive snubbers. For this purpose, a new gate driver is designed for active voltage balancing of two series-connected 10 kV SiC MOSFETs with the following features: 1) miniaturized 10 kV drain-source voltage measurement unit and its interconnection to gate-driver; 2) Tunable gate signal delay time adjustment unit with 0.25 ns resolution; 3) Rogowski current sensing unit for fault current detection. Based on the developed gate driver, the FPGA-based closed-loop gate signal timing control for active voltage balancing and fault protection of series-connected 10 kV SiC MOSFETs are designed in this paper. The proposed gate driver and active voltage balancing method are validated in a phase-leg test achieving 16 kV total blocking voltage.

T5.8: Control of Modular Embedded Multilevel Converter and its Capacitor Voltage Balancing
Authors: Jian Liu, Dong Dong, Di Zhang
Jian Liu picture
Representing Author: Jian Liu - CPES
Keywords:control; modular converters
Abstract:

Modular Embedded Multilevel Converter (MEMC) is a hybrid converter combined by MMC and classic three-level PWM voltage source converter (VSC). Only half number of sub-module is required for MEMC compared to MMC, which leads to lower system volume and weight. However, the control strategy of its capacitor voltage balance was not studied in detail. In this paper, the control strategy of MEMC based on arm current is illustrated in detail. In addition, the optimal circulating current injection to minimize capacitor voltage deviation was proposed to guarantee DC-link voltage balancing.

T5.9: Ultra-Low Conduction Loss IGCT for Cross Connected modules in Modular Multilevel Converters
Authors: Jiapeng Liu, Biao Zhao, Wenpeng Zhou, Zhengyu Chen, Chunpin Ren, Zhanqing Yu, Rong Zeng
Representing Author: Jiapeng Liu - Tsinghua
Keywords:protection; device and system reliability; modular converters
Abstract:

In this paper, an optimized integrated gate commutated Thyristor (IGCT) for cross connected modules in modular multilevel converters is analyzed, developed and tested. The test result shows the optimized 4.5kV/2.4kA ultra-low conduction loss IGCT achieve a conduction voltage of approximately 1.4V at 3000A. Compared with commercial IGBTs and IGCTs with similar ratings, the ultra-low conduction loss IGCT inhibits great potential in long-term conduction applications.

T5.10: FutureHAUS nanogrid system and energy management algorithm
Authors: Vladimir Mitrovic, Igor Cvetkovic, Dushan Boroyevich, Joe Wheeler, Bobby Vance
Vladimir Mitrovic picture
Representing Author: Vladimir Mitrovic - CPES
Keywords:control; optimization
Abstract:

Technology advancements that happened in the last two decades have changed the way how people live, interact, and work more than any technology did in the past 100 years or so. Not only little "gadgets" enabled this enormous paradigm shift, the new innovative concepts have been well integrated into the design and manufacturing of computers, appliances, automobiles, airplanes, and ships, and it was about time to start seeing these concepts applied to the homes where building practices, by contrast, experienced a very slow, if not resistant effort to advance. At least they did before Virginia Tech demonstrated the use of advanced manufacturing concepts, prefabricated structures, and a great number of power electronics to redefine the conventional practice of modern home design. Its FutureHAUS won first place at the international competition in Dubai, UAE, validating an enormous societal desire to see this change happening finally. And, CPES hugely contributed to this gratifying victory. FutureHAUS featured a CPES-designed advanced power electronics system – a nanogrid, built to achieve a net-positive energy balance in the FutureHAUS utterly minimizing, if not eliminating, utility grid dependence. It comprised five solar arrays, aggregately contributing close to 14 kW of peak power. Each solar array featured its dedicated charge controller for increased reliability as well as for independent, per string, maximum power point tracking. Installed 14 kWh battery was the safest and least polluting rechargeable battery that could be found on the market, built with very high environmental standards, and safe to be stored indoors with no need for venting or cooling. Furthermore, the efficient and contemporary 8 kW power inverter interfaced photovoltaics and batteries with the utility grid and served as a main generator of the FutureHAUS clean energy. This inverter has been controlled with an advanced energy management algorithm that goes beyond the traditional residential system control. This presentation will give an overview of the whole project with a focus on the technical description of the FutureHAUS nanogrid system and energy management algorithm.

T5.11: Software System for Impedance Measurement Unit
Authors: Vladimir Mitrovic, Bo Wen, Dushan Boroyevich, Rolando Burgos, Sizhan Zhou, Zhiyu Shen
Vladimir Mitrovic picture
Representing Author: Vladimir Mitrovic - CPES
Keywords:stability
Abstract:

Small-signal impedances of components in an electronic power system can be used to judge the stability of the system. Measuring impedances of the system needs a sophisticated control and software system. The system consists of a state of the art data acquisition tools, several high precision sensors, and PC with the software for control and user interface. The main purpose of data acquisition tools is to sample the signal and improve it by removing the noise, addressing possible aliasing issues, and remove small DC offset issues due to imprecise components in the signal conditioner. The digitally conditioned signal is used for PLL and then sent to PC for off-line impedance calculation and system stability estimation. Different software techniques are used to ensure that acquired digital signal won't be lost on its way to storage. The software solutions applied to this system will be discussed in this paper.

T5.12: Design and Assessment of a Medium-Voltage Power Cell based on High-Current, 10 kV SiC MOSFET Half-Bridge Modules
Authors: Slavko Mocevic, Jianghui Yu, Yue Xu, Joshua Stewart, Jun Wang, Igor Cvetkovic, Dong Dong, Rolando Burgos
Slavko Mocevic picture
Representing Author: Slavko Mocevic - CPES
Keywords:high power density; insulation design and assessment; modular converters; silicon carbide (sic)
Abstract:

Rapid technology improvement of silicon-carbide (SiC) MOSFET transistors combined with their extraordinary characteristics are key drivers for their utilization in medium-voltage (MV) applications. For typical MV modular converter applications, power cell is a critical piece. Power cell systematic design and assessment methodology are crucial to prevent destruction and to fully test exploring its capabilities prior to implementation at the converter level. Thereby, this paper presents design and assessment methodology of an MV half-bridge power cell based on XHV-6 10 kV, high current, SiC MOSFET module with dc bus rated voltage of 6 kV. Critical design considerations, challenges and solutions are presented as well as the detailed assessment workflow and limitations of the power cell. The power cell design is validated through continuous operation at 6 kV, 84 A rms, 10 kHz exhibiting over 99% efficiency, switching with dv⁄dt up to 100 V⁄ns.

T5.13: 18 kW 500 kHz Transformer for Bidirectional Charging Application with PCB Termination
Authors: Minh Ngo, Yuliang Cao, Ning Yan, Dong, Burgos
Minh Ngo picture
Representing Author: Minh Ngo - CPES
Keywords:gallium nitride (gan); high power density; resonant converters; silicon carbide (sic); soft switching
Abstract:

Hybrid electric propulsion (H.E.P) is an exciting research area to improve fuel efficiency, lower emissions, and reduce noise levels in aircraft. Solid state transformers are necessary to achieve high efficiency in the bidirectional charging circuit in H.E.P systems. This paper discusses the design of an 18 kW, 500 kHz transformer for H.E.P. A comprehensive optimization procedure that discusses core selection, winding topology, and thermal management is shown. The design of a passive thermal management system is key to the success of the transformer in order to prevent thermal runaway and achieve higher power density. The transformer is designed with the goal of low leakage inductance to allow for a small resonant capacitor on the primary side of the transformer. Low leakage inductance is achieved through the usage of a PCB termination board which lowers loop inductance and allows for maximum interleaving of the transformer windings. Measurements of transformer core loss, winding loss, and leakage inductance are shown to verify the validity of the design.

T5.14: Development of a Power Hardware-in-the-Loop Induction Machine Emulator
Authors: John Noon, He Song, Bo Wen, Igor Cvetkovic, Rolando Burgos, Dushan Boroyevich
John Noon picture
Representing Author: John Noon - CPES
Keywords:control; device and system reliability; modeling and control; three-phase converters
Abstract:

Power Hardware-in-the-Loop (P-HIL) allows for increased flexibility when performing tests on motor drives. P-HIL allows for close-to-reality testing to be performed in the production stages between simulation and full hardware testing. The control scheme of the drive is able to be more faithfully tested under realistic conditions than in simulation or with a simple RL load. In this work, the design and implementation of an induction machine emulator is explained. A testbench consisting of a 30 kW PowerFlex 753 drive and the EGSTON Power Electronics COMPISO System Unit CSU200-1GAMP6 emulating an induction machine is compared with the same drive powering a Yasakawa induction machine.

T5.15: Evaluation of Alternative AC Filter Building Blocks (FBB) for Modular Three-Level Grid-Tied Inverters
Authors: Ripun Phukan, Sungjae Ohn, Rolando Burgos, Dong Dong, Dushan Boroyevich
Ripun Phukan picture
Representing Author: Ripun Phukan - CPES
Keywords:emi; magnetic materials and integration; modeling and control; silicon carbide (sic); three-phase converters
Abstract:

EMI filters in three phase converters occupy about 40% of total converter volume. With interleaved operation, this volume requirement can be reduced on the grid side filters due to the absence of switching frequency harmonics. However, due to the presence of circulating current between channels, there is an additional requirement for filter components which outweigh the benefit from interleaving. This affects overall system power density and increases filter volume contribution. In addition, the existing filter topologies do not address modularity i.e. they cannot be used with a any number of channels without affecting attenuation or performance. In this paper, a comprehensive study of existing and new modular filter topologies is performed to fully utilize the benefit from interleaving. The proposed modular filter structures are compared in frequency domain according to groups of harmonics. These modular filter topologies are further evaluated for power density and efficiency. The trade-off between different topologies is discussed and scalability to high power levels and higher channel count is addressed. In the end, a prospective candidate(s) is chosen for future evaluation.

T5.16: Insulation Design and Assessment of a 16 kV Rated PCB Based Planar DC Bus with Distributed Capacitors
Authors: Lakshmi Ravi, Xiang Lin, Dong Dong, Rolando Burgos
Lakshmi Ravi picture
Representing Author: Lakshmi Ravi - CPES
Keywords:high power density; insulation design and assessment; silicon carbide (sic); three-phase converters
Abstract:

This paper presents the insulation design and assessment of a medium voltage (MV), printed circuit board (PCB) based dc bus with distributed capacitors. A generalized insulation design process is described with considerations for insulator material stress as well as surface discharge on external interconnections. A 16 kV rated dc bus is designed for a three phase inverter application using the design procedure to achieve partial discharge (PD) free operation up to 18 kV. Finite-element analysis (FEA) simulation studies of the multilayer PCB bus are presented to analyze different approaches to control electric field distribution in the design layout. The designed dc bus also features a modular PCB design to improve the power density and specific power of the MV system. Partial discharge experimental test results are presented for insulation design validation. High speed switching performance of the inverter phase leg is verified using a standard clamped inductive load test.

T5.17: Optimal Capacity and Placement of Microgrids for Resiliency Enhancement of Distribution Networks Under Extreme Weather Events
Authors: Moein Borghei, Mona Ghassemi
Moein Razavi picture
Representing Author: Moein Razavi - CPES
Keywords:control; optimization
Abstract:

When a fault or a series of faults occur in a distribution network, it is of considerable significance to feeding loads, most importantly critical loads. Although network reconfiguration by switching operations has been usually considered as a relatively low-cost method for load restoration, it alone may not able to restore critical loads under extreme weather events such as hurricanes where multiple faults can happen within the network. Under such severe circumstances, one of the complementary methods for service restoration is benefiting from existing installed microgrids. In this paper, the idea of planning future microgrids -in terms of optimal location and capacity- in combination with switching operations to restore critical loads, for the first time, is considered. To this planning-operation concept end, a graph-theoretic method is developed to find optimal switching operations coupled with a heuristic optimization method developed to determine future microgrids' location and capacity to maximize the resiliency of the network while keeping the associated cost with distributed generations (DGs) in microgrids as low as possible. Simulations results on the modified IEEE 37-node distribution network show the effectiveness of the proposed idea. Moreover, using appropriate reduction techniques, the computational efficacy of the method has also been greatly improved.

T5.18: A Synchronous Distributed Control and Communication Network for SiC-Based Modular Power Converters
Authors: Yu Rong, Jun Wang, Zhiyu Shen, Sizhan Zhou, Bo Wen, Rolando Burgos, Dushan Boroyevich
Yu Rong picture
Representing Author: Yu Rong - CPES
Keywords:control; modular converters; silicon carbide (sic)
Abstract:

Numerous power electronics building blocks (PEBB) based power conversion systems have been developed to explore modular design, scalable voltage and current ratings, low-cost operations, etc. This paper further extends the modular concept from the power stage to the control system. The communication network in SiC-based modular power converters is becoming significant for distributed control architecture, with the requirement of tight synchronization. A synchronous distributed control and communication protocol with well-performed synchronization of 25 ns accuracy is proposed and verified for a 120 kHz SiC-based impedance measurement unit (IMU) with cascaded H-bridge PEBBs.

T5.19: Design of a PCB-based Laminated Bus for 10 kV SiC MOSFET-based Converters
Authors: Joshua Stewart, Rolando Burgos, Mona Ghassemi
Joshua Stewart picture
Representing Author: Joshua Stewart - CPES
Keywords:device and system reliability; high power density; insulation design and assessment; modular converters; passive components
Abstract:

Due to fast switching transients and the desire for a high power density, the laminated bus of medium voltage (MV) SiC-based converters needs to be designed with strict requirements to ensure insulation reliability. Due to generalized design procedures and defects within the insulation layers during fabrication, a traditional laminated bus requires relatively thick insulation layers to avoid internal partial discharge (PD). These thicker insulation layers increase the size and weight of the bus, while reducing the cooling performance and increasing stray inductance. By comparison, a PCB-based laminated bus can achieve reliable insulation with much less thickness by precisely implementing electric field management methods and controlling internal defects in the fabrication process. Therefore, the PCB-based planar laminated bus is promising for SiC-based MV converter applications. With the design targets of high power density, lower parasitic inductance, and PD free operation, this paper presents a systematic design methodology for the PCB-based laminated bus. In addition to benefits of electric field (E-field) control, radiated electromagnetic interference (EMI) is also shown to be reduced, through simulation, by utilizing the prescribed layer stackup. Thermal analysis and short circuit tests were preformed to ensure insulation reliability during expected operating conditions.

T5.20: Auxiliary Power Network Architecture for 10 kV SiC-based Power Electronics Building Blocks
Authors: Keyao Sun, Ning Yan, Jun Wang, Dong Dong, Rolando Burgos, Dushan Boroyevich
Keyao Sun picture
Representing Author: Keyao Sun - CPES
Keywords:gallium nitride (gan); insulation design and assessment; resonant converters; soft switching; wireless power transfer
Abstract:

This paper proposes a two-stage auxiliary power network architecture for 10 kV SiC-based power electronics building blocks after comparing advantages and disadvantages of different auxiliary power supplies. Standalone introduction of the wireless power transfer converter and the current-transformer based gate-driver power supply serving as the first- and second-stage are given. Combination test results of the two-stage system is shown including normal operation, fault response, and operation in the high voltage, high dv/dt system.

T5.21: Voltage Balancing of Four Series-Connected SiC MOSFETs under 2 kV Bus Voltage using Active dv/dt Control
Authors: Emma Raszmann, Keyao Sun, Rolando Burgos, Igor Cvetkovic, Jun Wang, Dushan Boroyevich
Keyao Sun picture
Representing Author: Keyao Sun - CPES
Keywords:control; device characterization; high power density
Abstract:

This paper demonstrates the voltage balancing performance and switching behavior of four series-connected SiC MOSFET devices. Both multilevel and two-level topologies are capable of achieving higher blocking voltages in high-power converter applications. Compared to multilevel topologies, two-level switching topologies are of interest due to less complex circuitry, higher density, and simpler control techniques. In order to balance the voltage between series-connected MOSFETs, device turn-off speeds are dynamically controlled on each gate-driver with active gate control. The implementation of the active gate control technique is described in this paper. Experimental results of the voltage balancing behavior across four non-commercial 1.7 kV SiC MOSFET devices in series (2 kV total dc bus voltage) with the selected active dv/dt control scheme are shown.

T5.22: Design and Test of a 6 kV Phase-Leg using Four Stacked 1.7 kV SiC MOSFET High-Current Modules
Authors: Emma Raszmann, Keyao Sun, Rolando Burgos, Igor Cvetkovic, Jun Wang, Dong Dong, Dushan Boroyevich
Keyao Sun picture
Representing Author: Keyao Sun - CPES
Keywords:control; device characterization; high power density
Abstract:

The stacking or series-connection of Silicon Carbide (SiC) MOSFETs is an attractive solution for achieving higher blocking voltage using lower voltage power semiconductors in medium- and high-voltage converter applications. However, when connecting MOSFETs in series, device voltages can be unbalanced due to tolerance in device parameters, package and layout parasitic components, and gate-signal timing delays. A modular gate-driver design with active gate control is implemented in this work in order to balance voltages between series-connected devices. The design of an online 6 kV bus measurement board is also described in this paper. This work demonstrates balancing performance of four stacked high-current power modules totaling eight 1.7 kV SiC MOSFETs in series under 6 kV bus voltage using an active dv/dt balancing method. Switching losses are evaluated for both turn-on and turn-off transitions across all eight MOSFETs under a load current of 240 A.

T5.23: A Novel DQ Impedance Measurement Method in Three-Phase Balanced Systems
Authors: Ye Tang, Rolando Burgos, Bo Wen, Dushan Boroyevich
Ye Tang picture
Representing Author: Ye Tang - CPES
Keywords:control; modeling and control; stability; three-phase converters
Abstract:

The stability of electronic power systems is essential to the safety and reliability of the system designs. Optimum stability analysis and measurement techniques are being discussed more frequently in the literature. One approach of assessing system stability is the Generalized Nyquist Criterion (GNC), which is based on d-q frame impedances. An impedance measurement unit (IMU) can be used to acquire d-q frame impedances for a three-phase balanced system. A novel d-q frame impedance measurement method, namely the single-phase impedance measurement approach, is applied to a three-phase balanced passive circuit and a voltage source inverter (VSI) separately. In this approach only single-phase data are needed. A comparison of measured results proves the capability of the single-phase impedance measurement method to obtain three-phase d-q frame impedances. In the passive circuit, both measurement methods only demand single-phase perturbation. In the converter circuit, the three-phase impedance measurement method still only needs a single-phase perturbation while the single-phase impedance measurement method requires three separate balanced single-phase perturbations.

T5.24: Insulation Online Monitoring for Critical Components inside SiC based Medium Voltage Converter Prototype
Authors: Yue Xu, Chongxing Zhang, Chaofei Gao, Jun Wang, Rolando Burgos, Dushan Boroyevich, Ming Ren
Yue Xu picture
Representing Author: Yue Xu - CPES
Keywords:insulation design and assessment; modular converters; silicon carbide (sic)
Abstract:

Comparing with Si based ones, SiC based converters can achieve much higher voltage rating and power density. Therefore, electric field intensity inside SiC based converters can become significant and initial surface discharges, which usually occur along the exposed metal or insulator to air interfaces. Although converters should be surface discharge free by design, it is hard to guarantee discharge free throughout the entire converter lifecycle, mainly due to the air properties change and insulation degradation. Since surface discharges should be prevented before any catastrophic failure occurs, insulation online monitoring, especially for critical components, can have great value for converter system operation and maintenance. In this paper, novel fiber-optic acoustic sensor and silicon photomultiplier based sensor are developed to realize surface discharge online monitoring inside converters. Both sensors are compact in size with high isolation level, thus they can be integrated into the SiC based medium voltage converter prototype easily. Based on experimental results, it demonstrates that the proposed sensors have good sensitivity, high immunity to the Electromagnetic Interference and can be applied inside converters for insulation online monitoring along multiple regions. This paper could provide some useful exploration about insulation online monitoring for future SiC based medium and high voltage converters.

T5.25: Shipboard PEBB Cooling Strategies
Authors: S. Yang, J. S. Chalfant, J. C. Ordonez, J. A. Khan, C. Li, I. Cvetkovic, J. V. C. Vargas, M. B. Chagas, Y. Xu, R. P. Burgos, D. Boroyevich
Yue Xu picture
Representing Author: Yue Xu - CPES
Keywords:high power density; modular converters; silicon carbide (sic)
Abstract:

We discuss herein several cooling strategies applicable to shipboard Power Electronics Building Blocks (PEBBs), namely the PEBB 1000 and a notional PEBB 6000 currently under development, subject to the following design goals and constraints: (1) small and lightweight package (i.e., high power density); (2) easy swap ability achieved by minimizing any connections requiring sailor intervention for connecting or disconnecting; and (3) any thermal solution must be able to cool not only a single PEBB unit, but also multiple units placed in close proximity to one another when combined to make up a converter. For the PEBB 1000 application, air cooling is most likely sufficient to meet the needs, and several arrangements of fin structures were investigated. On the other hand, air cooling, water cooling, and water cooling with a dry interface all have potential for meeting the cooling demand of an envisioned PEBB 6000 and warrant further investigation. In any case, the localized heat generated within the PEBB will require significant spreading to a larger surface area for subsequent transfer out of the PEBB.

T5.26: External Insulation Design and Assessment for Critical Components in Medium Voltage SiC based Converter via Optical Method
Authors: Chongxing Zhang, Yue Xu, Ming Dong, Rolando Burgos, Ming Ren, Dushan Boroyevich
Yue Xu picture
Representing Author: Yue Xu - CPES
Keywords:high power density; insulation design and assessment; modular converters; silicon carbide (sic)
Abstract:

Exposed metal or insulator to air interfaces are widely existing in medium voltage SiC based converters. To address external insulation along such interfaces properly, large insulation distance in air is applied. However, much overdesigned distance impairs converter power density and performance significantly. Targeting on the external discharge free design, guidelines which can reflect the relationship between insulation structures and PWM excitation parameters, are highly demanded. Moreover, due to possible fabrication issues, insulation properties change and degradation, massive external discharges may still occur, even that they should be eliminated by design. Therefore, insulation assessment along the entire system, or at least for critical components, is necessary. In this paper, novel silicon photomultiplier (SiPM) based external discharge sensors are proposed. Then, for a self-designed SiC based medium voltage converter, SiPM sensors help both its external insulation design and assessment. By using SiPM sensors, two types of external discharges are characterized under PWM excitation and thus general design suggestions are summarized. Moreover, as shown by two examples, SiPM sensors can achieve external insulation assessment for converter application. Based on the experimental data and real examples, this paper opens an access to external insulation design and assessment, for future medium voltage, high power density, SiC based converters.

T5.27: Insulation Design and Assessment Considerations to Eliminate Partial Discharge in SiC based Medium Voltage Converters
Authors: Yue Xu, Rolando Burgos, Dushan Boroyevich
Yue Xu picture
Representing Author: Yue Xu - CPES
Keywords:high power density; insulation design and assessment; modular converters; silicon carbide (sic)
Abstract:

During the development of the new generation SiC based Medium Voltage (MV) modular converters, compact and reliable insulation are highly demanded. Because of the high power density requirement and the fast switching transient, much overdesigned insulation size, which is a common practice for Si based MV converters, cannot be applied for SiC based ones. Therefore, insulation design for individual components and their coordination inside a single power cell, as well as among multiple converters in a Modular Multilevel Converter (MMC) structure, can be one of the major design aspects for future SiC based MV converters. In this paper, focusing on eliminating Partial Discharge (PD), two typical insulation design structures are introduced. Then, representative coupons are made and tested under different type of excitations, in order to establish general insulation design and assessment guidelines for converter application. Finally, several design examples are discussed in detail, for further demonstrating how to use the design and assessment methodology in real practice. Hopefully, this paper can provide some useful information for two major problems which are commonly found in SiC based MV converter development. The two problems are as below: First, what are the critical components or regions for insulation design in SiC based MV converter system? Second, what is the insulation design methodology that should be applied and how to do the proper insulation assessment for the prototype?

T5.28: SST Based 400kW Fast Charger
Authors: Chunyang Zhao, Yi-Hsun Hsieh, Zheqing Li, Orion Chen, Fred C. Lee, Qiang Li
Chunyang Zhao picture
Representing Author: Chunyang Zhao - CPES
Keywords:insulation design and assessment; magnetic materials and integration; resonant converters; silicon carbide (sic); soft switching
Abstract:

To shorten the charging time, increase the efficiency, and reduce the volume of an electric vehicle charger, the key research is to replace the bulky line-frequency medium-voltage (MV) transformer cascaded by a low-voltage rectifier with a high-frequency MV AC-DC solid-state transformer (SST). A 3.5% efficiency improvement is expected with such replacement. Besides, the modular feature of the SST is easier for a system power upgrade. Utilizing multi-level topology reduces the number of modules in series to handle the MV, which simplifies the system. The DC-DC stage is the critical component of a module since it is responsible for the MV insulation. This work utilizes the CLLC resonant converter with SiC devices to achieve high efficiency, high power-density, and bi-directional power flow. The impact of the switching frequency for loss and size trade-off is evaluated as well. The proposed design procedure minimizes the total device loss by optimizing the dead-time for zero-voltage switching (ZVS). The transformer in the CLLC converter is designed to meet insulation requirements up to 60 kV for a 13.2-kV AC input voltage according to IEC 60076-11 standard. Besides, the magnetizing inductance and two leakage inductances are all integrated into the transformer. The latest ferrite material is selected for the integrated magnetic component and an optimization is performed to achieve the best trade-off between loss and size.

T5.29: Development of Impedance Measurement Unit for 1 kV DC and 800 V AC Systems
Authors: Sizhan Zhou, Bo Wen, Yu Rong, Vladimir Mitrovic, Rolando Burgos, Dushan Boroyevich
Sizhan Zhou picture
Representing Author: Sizhan Zhou - CPES
Keywords:control; modular converters; silicon carbide (sic); stability
Abstract:

This poster describes the design and implementation of a impedance measurement unit (IMU) capable of characterizing in situ source and load impedances of 1 kV DC and 800 V AC networks in the frequency range of 10 Hz–1 kHz. The IMU comprises three power electronics building blocks (PEBBs) each built using 1.7-kV SiC MOSFET H-bridges with 200 A current capability and a modular and reconfigurable structure. The IMU can work in shunt current and series voltage perturbation injection mode, as both injection modes are needed to accurately predict the stability of the electrical system. These three PEBBs can be configured as a five-level cascaded H-bridge converter for source impedance characterization in shunt mode, or as an interleaved converter for load impedance characterization in series mode. Experimental tests are implemented to demonstrate the effectiveness of the proposed impedance identification approach.

T5.30: Finite Element Analysis of HF Pulsed Plasma Streamer Discharge in Flue Gaseous Dielectric
Authors: Matthew Kallicharran, Mona Ghassemi
Matthew Kallicharran picture
Representing Author: Matthew Kallicharran - CPES
Keywords:device characterization; gallium nitride (gan); high power density; insulation design and assessment; wireless power transfer
Abstract:

With the advancement of wideband gap devices including those provided by Gallium Nitride (GaN) semiconductor manufacturers, the importance of insulation capable of withstanding high frequency, repetitive pulses continues to increase given the power density available in most printed circuit boards and devices. Furthermore, implementation of active power modules used in electronics which continue to expand their market and become readily available for commercial use may be exposed to a plethora of high voltage environmental conditions, including those of lightening. In such environments, the potential for the development of corona and streamers, as a result of partial discharge or avalanche breakdown, insulation may serve as 1st order protection for such devices. In this study, we will attempt to analyze the propagation and development of positive coronal streamers in a generalized gaseous-mixtures dielectric when subject to voltage pulses of different orders of magnitude and their impact on GaN films. This analysis will be conducted using both experimentally validified data and theoretical predicted data using novel finite element mesh analysis methodology using COMSOL Multiphysics simulation software.
The case shown depicts a cathode-anode pair in a standard for high voltage modelling, needle-to-plane geometry, where the charge medium is a dielectric of variable permittivity, whose value depends not only on the electrical properties of the electrons/ionic species, but fluid, thermal, and material as well. The simulation was developed using AC analysis of this case where the ejection, and subsequent collisions, of a primary electron causes a chain-reaction, electron avalanche from the neutral gas molecules resulting in ionization. In this study, there are several well studied scenarios for demonstrating the effect of this ionization results in breakdown and subsequently, the development of a streamer as a function of electric field distribution and partial pressure.
Streamer propagation, A.K.A. “Kanal Discharge”, is believed to result from electron avalanches that occur in the presence of a growth in locally available charge carries. This however, is only validified when the electric fields present are solely provided by the source anode or cathode in either positive/ negative streamers respectively. This does not include the effect due to secondary electrons or space charges as they become negligible relative to the applied external field in most environments. This oversight, may be consequential to certain geometries where the field intensity is expected to become undesirably high in regions where insulation is expected to withstand, such as those of triple-points. In this study, we will discuss the theoretical framework for plasma models developed to describe vigorous ionization processes as well as the various effects due to secondary ionization; namely the positive ion, photonic, and metastable effect. The consequence is studied extensively for uniform, using either primary ignition or Townsend mechanism, contained fields with ideal geometry given well-defined boundary conditions. However, the use of analytical methods, including those given by the solution to Poisson’s Equations, become numerical difficult and may contain stochastic, time-dependent information when dealing with more sophisticated geometries where solutions remain iteratively indeterminate using standard numerical methods. In this study, we attempt to predict the consequence of streamers and analyze their propagation when weakly uniform fields are applied under different control and geometric circumstances.

T5.31: Techniques and Methodology to Provide Resiliency for Micro-grids Distribution Networks
Authors: Matthew Kallicharran, Mona Ghassemi
Matthew Kallicharran picture
Representing Author: Matthew Kallicharran - CPES
Keywords:device and system reliability; modeling and control; optimization; protection; wireless power transfer
Abstract:

Resiliency” as defined for future distribution systems as “the ability to prepare for and adapt to changing conditions and withstand and recover rapidly from disruptions; includes the ability to withstand and recover from deliberate attacks, accidents, or naturally occurring threats or incidents” pursuant by both the National Infrastructure Protection Plan and the Presidential Policy Directive 21 (2013) in response to Superstorm Sandy [1]. For power distribution networks, this serves as a rule and was developed to consider for a systems ability to prepare for and adapt to changing conditions and withstand and recover rapidly from disruptions includes the ability to withstand and recover from accidents, impacts, or natural disasters [2] as well as operating as intended under extreme circumstances. Most distribution systems which utilize Load Flow provide solutions with relatively fast convergence times with minimal memory usage. However, when attempting to resolve a system with the standard power flow methodology, the following properties tend to result in an ill-defined analysis, especially while representing ideally balanced 3-phase networks as single-phase networks:
Weakly meshed/Radial networds, Relatively low impedance networks, Unbalanced multi-phase networks, unbalanced distributed load, distributed generators (photovoltaics).
Most studies using microgrids to solve critical load restoration (CLR) are based on corrective actions and in power system operation step. In this study, several methods were discussed and evaluated from a graphical theoretic reference while also presents a critical review on benefitting from microgrids for resiliency enhancement of distribution networks under extreme weather events. Regarding the properties of each system, approaches include: semidefinite relaxation, spanning tree algorithm, Dijkstra’s algorithm, convex optimization, objective function parameterization, power flow injection, and more. In our study, one potential approach to improving this quality within high power infrastructure will be the adaptation of independently operating power storage and transfer units, also defined as microgrids, to consolidate power to critical load groups using methods of optimization within distribution networks. Particularly we aim to survey, model, improve, test and prototype several techniques used to achieve this with respect to the smart grid and transmission line applications in addition to general distribution network infrastructure. One of our objectives will be to develop a comprehensive methodology to handline unbalance power flow for the purposes of enhancing pre-existing network resiliency. Several of these methods may include photovoltaics, multivariable synchronous generators, reactive power control, semidefinite and linear programming, and wireless power transfer mutually between distinct storage elements and their load groups.

T5.32: Optimized Stage Turn-off strategy of Hybrid Circuit Breaker
Authors: Jian Liu, Lakshmi Ravi, Rolando Burgos, Dong Dong
Jian Liu picture
Representing Author: Jian Liu - CPES
Keywords:optimization; protection
Abstract:

As the key equipment in Medium voltage DC system, the hybrid circuit breaker (HCB) is responsible for DC system protection. Compared to Solid-state circuit breaker, hybrid circuit has higher efficiency due to lower conduction loss. But it suffers from longer fault current clearing time, which is caused by the time required for the vacuum switch to achieve sufficient dielectric strength across the contacts. In order to solve this problem, the stage turn-off strategy is employed to make full use of the dielectric strength between contacts of vacuum switch, which can reduce the peak current and absorbed energy. In this paper, two optimized turn-off strategy is proposed to balance the MOV energy. One is rotational scheme to balance in long term, another is per-cycle balance during each interrupt event. Experiment results are provided to verify the feasibility of proposed turn-off strategy.

T6: Cyber Security of the Power Grid and Instrumentation and Measurements

T6.1: Instrusion Detection for Distribution Systems and Substations
Authors: Jennifer Appiah-Kubi, Ruoxi Zhu, Chen-Ching Liu
Jennifer Appiah-Kubi picture
Representing Author: Jennifer Appiah-Kubi - PEC
Keywords:cyber physical system security power grid
Abstract:

The electric power grid is a complex cyber-physical system that forms the lifeline of a modern society. Its reliable and secure operation is of paramount importance to national security and economic well-being. The power grid today is a highly automated network, wherein a variety of communication networks and information systems are interconnected to the physical grid for the purpose of monitoring, protection, control, and market functions. The increased reliance on information and communications technology in the smart gird will significantly increase the vulnerabilities, which further underscores the importance of cyber security. As a result, cyber security of the power grid encompassing vulnerability assessment, anomaly detection, and mitigation of the substations and Supervisory Control and Data Acquisition systems are among the important priorities. The purpose of this research is to provide new concepts and testbed-based methodologies for the integrated cyber-power systems.
We have developed new technologies for anomaly detection/mitigation to secure the integrated cyber-physical system. The software testbed provides a comprehensive demo of cyber intrusions and anomaly detection/mitigation for SCADA, substation automation, and distribution automation systems. The quest to secure the power systems is the essence of our project. The goals are: (1) Detect cyber threats on the power system: we developed a scalable and realistic cyber model of the grid as well as of various cyberattacks and subsequently formulate intrusion detection algorithms to respond to the modeled attacks. (2) Mitigation of and response to cyber threats: A key question is: what actions to take when attacks are detected? The next goal is to develop a resilient mitigation framework that allows us to present the most appropriate response in the event that an attack is launched, thus preventing cyber anomalies from propagating to the physical system.

T6.2: DeVLearn: A Deep Visual Learning Framework for Localizing Temporary Faults in Power Systems
Authors: Shuchismita Biswas, Rounak Meyur, Virgilio Centeno
Shuchismita Biswas picture
Representing Author: Shuchismita Biswas - PEC
Keywords:fault identification; machine learning applications; power system operation and control
Abstract:

Frequently recurring transient faults in a transmission network may be indicative of impending permanent failures. Hence, determining their location is a critical task. This paper proposes a novel image embedding aided deep learning framework called DeVLearn for faulted line location using PMU measurements at generator buses. Inspired by breakthroughs in computer vision, DeVLearn represents measurements (one-dimensional time series data) as two-dimensional unthresholded Recurrent Plot (RP) images. These RP images preserve the temporal relationships present in the original time series and are used to train a deep Variational Auto-Encoder (VAE). The VAE learns the distribution of latent features in the images. Our results show that for faults on two different lines in the IEEE 68-bus network, DeVLearn is able to project PMU measurements into a two-dimensional space such that data for faults at different locations separate into well-defined clusters. This compressed representation may then be used with off-the-shelf classifiers for determining fault location. The efficacy of the proposed framework is demonstrated using local voltage magnitude measurements at two generator buses.

T6.3: Optimal Real-Time Coordination of Energy Storage Units As a Voltage-Constrained Game
Authors: Sarthak Gupta, Vassilis Kekatos, Walid Saad
Sarthak Gupta picture
Representing Author: Sarthak Gupta - PEC
Keywords:electricity markets; optimization; power system operation and control; voltage regularion
Abstract:

With increasingly favorable economics and bundling of different grid services, energy storage systems (ESSs) are expected to play a key role in integrating renewable generation. This paper considers the coordination of ESS owned by customers located at different buses of a distribution grid. Customers participate in frequency regulation and experience energy prices that increase with the total demand. Charging decisions are coupled across time due to battery dynamics, as well as across network nodes due to competitive pricing and voltage regulation constraints. Maximizing the per-user economic benefit while maintaining voltage magnitudes within allowable limits is posed here as a network-constrained game. It is analytically shown that a generalized Nash equilibrium exists and can be expressed as the minimizer of a convex yet infinite-time horizon aggregate optimization problem. To obtain a practical solution, a Lyapunov optimization approach is adopted to design a real-time scheme offering feasible charging decisions with performance guarantees. The proposed method improves over the standard Lyapunov technique via a novel weighting of user costs. By judiciously exploiting the physical grid response, a distributed implementation of the real-time solver is also designed. The features of the novel algorithmic designs are validated using numerical tests on realistic datasets.

T6.4: Phasor Measurement Unit (PMU) Based Real Time Controlled Islanding for Renewable Integration
Authors: Rahul Iyer, Prathamesh Tilekar, Aditya Parhad, Neel Gada, Sanal Almeida
Representing Author: Rahul Iyer - PEC
Keywords:measurements/instrumentation; power system operation and control; resiliency; system reliability and stability
Abstract:

Integration of distributed energy resources (DERs) in the power grid has made grid operation challenging from stability perspective. This is mainly due to intermittent and low inertia renewable sources like wind and solar. Utility-scale wind and solar farms are supplying an increasing proportion of our power in integration of the traditional power grid. But with this integration, many problems occur which adversely affect the system. In the event, a small portion of the system gets isolated from the main grid, an island is formed, which is usually not capable of functioning on its own and may send the system parameters beyond safe and acceptable limits, thus a situation occurs where complete isolation of DERs becomes necessary. Phasor Measurement Unit (PMU) plays a crucial role in the modern electrical grid as it can provide complete real time observability of system conditions and parameters. This paper attempts to illustrate a Real Time-Hardware in Loop (RT-HIL) model which uses PMUs to detect islands and perform anti-islanding operations based on this observation.

T6.5: Machine Learning for Inferring Power System Oscillations from Synchrophasor Data
Authors: Mana Jalali, Vassilis Kekatos, Siddharth Bhela, Hao Zhu
Mana Jalali picture
Representing Author: Mana Jalali - PEC
Keywords:machine learning applications; optimization
Abstract:

This work proposes a data-driven frequency estimation method for dynamic power systems. Leveraging the machine learning tool of Gaussian processes, a flexible and general frequency estimation method is developed. The inference scheme can be used under different setups of batch or online implementation and for various applications. The Bayesian estimation allows using different types of measurements (smart meters or phasor measurement units) and is robust to missing data across time. It is shown that the GP estimation method requires less number of measurements compared to other frequency estimation setups such as dynamic state estimation. Using the method of moments for parameter selection resulted in considerable computational advantages.

T6.6: Multi-setting Adaptive Distribution Protection Scheme for Directional Overcurrent Relays
Authors: Tapas Kumar Barik, Virgilio A. Centeno
Tapas Kumar Barik picture
Representing Author: Tapas Kumar Barik - PEC
Keywords:fault identification; measurements/instrumentation; power system operation and control; power system protection
Abstract:

Large-scale integration of Distributed Energy Resources (DERs) in power distribution systems has raised concerns for distribution protection coordination. Although prior works have addressed the issue of adaptive protection using extensive communication-based methods (centralized or peer-to-peer), the actual implementation of these methods is economically less viable in the near future considering the present infrastructure. However, with the advent of modern digital relays, protection schemes can be made adaptive yet keeping them somewhat decentralized and hence, easily implementable and deployable. Due to the bi-directional flow of power, Directional Overcurrent Relays (DOCRs) are being widely used in distribution systems. The pickup settings and time dial settings of these DOCRs needs to be modified with changing topologies and added DERs, to ensure reliability of protection schemes. However, the setting groups that can be stored in DOCRs to accommodate these numerous topologies are limited. The work in this paper discusses the implementation of K-Medoids clustering technique to cluster the numerous grid-connected and islanded topologies of a distribution system based upon the various pickup currents and operating time indexes. The work proposed in this paper also aspires to achieve enhanced primary and backup protection schemes by advocating storage of versatile setting groups in the DOCRs enabling better observability towards fault identification and isolation in the absence of extensive communication links. The testing results generated on a modified IEEE 13 node test feeder system demonstrate the effectiveness of the methodology over traditional schemes.

T6.7: Dynamics and Stability of a Microgrid as a Networked Control System
Authors: Lung-An Lee, Chen-Ching Liu
Lung-An Lee picture
Representing Author: Lung-An Lee - PEC
Keywords:microgrids; power system operation and control; resiliency
Abstract:

An islanded microgrid is used to serve critical load as a resiliency source when a severe outage occurs. In an islanded mode, the control of a microgrid relies on the communication system significantly. Hence, microgrids are cyber-physical systems and, therefore, the quality of the cyber system is crucial for the performance of the physical power system. A microgrid control scheme is proposed for regulation and power dispatch based on the droop and feedback controls. The proposed control strategy is validated for transient stability with respect to dynamic events. To evaluate the impact of a networked control system on the control scheme, a cyber model is developed to represent data reporting periods and communication delays. An analytical method is applied to determinate the critical data reporting periods and communication delays. Simulation results show that long data reporting periods and significant communication delays can cause a collapse of the system.

T6.8: Aggregate Model of Massive Distributed Energy Storage for Power System Operation
Authors: Hai Li, Yi Wang, Ning Zhang, Genghe Zhang, Xu Tian
Representing Author: Hai Li - Tsinghua
Keywords:power system operation and control; microgrid; power system analysis
Abstract:

Distributed energy storage (DES) has been expanding rapidly in recent years. Since the amount of DES is large while the capacity of single DES is small and the parameters of DES vary considerably, it is hard to consider the detailed model for each DES in power system operation such as unit commitment and economic dispatch. This paper proposes an equivalent aggregate model for massive DESs. The concepts of extreme charging and discharging curves are first proposed to describe the key operational characteristics of DES. On this basis, the aggregation methodology is proposed. Case studies of 1000 DESs show that the proposed method is an effective and conservative approximation of massive DESs.

T6.9: A Single-Input-Multiple-Output DC/DC Converter for Distributed Power Management in Many-Core Systems
Authors: Xingye Liu, Paul Ampadu
Representing Author: Xingye Liu - PEC
Keywords:voltage regularion
Abstract:

We propose a novel single-input-multiple-output DC-DC converter as a distributed power management solution for large-scale many-core systems. As power consumptions of cores vary significantly based on applications, dynamically voltage frequency scaling (DVFS) is necessary to optimize performance. Compared to centralized powering solutions that rely on dynamically reconfiguring the power delivery network, the proposed converter provides three local independent output channels that can respond to various workloads during runtime fast and reliably. From 1V input, output voltages range from 0.33V to 0.94V and supports up 60V/µs transitions. Maximum voltage ripple is limited within 50mV and three output voltages remain stable with a worst-case voltage droop of 30mV during load transitions. Cross regulation is minimized and only 28mV shift is observed at low-power Channel-3. Simulated in 32nm SOI CMOS technology with three customized in-package air-core inductors, peak efficiency achieved at Channel-1 is 92% and peak overall efficiency is 87.6% when all channels are delivering full power.

T6.10: Creating Realistic Synthetic Power Distribution Networks based on Interdependent Road Infrastructure
Authors: Rounak Meyur, Madhav Marathe, Anil Vullikanti, Virgilio Centeno
Rounak Meyur picture
Representing Author: Rounak Meyur - PEC
Keywords:machine learning applications; optimization; power system planning; resiliency; synthetic networks
Abstract:

Physical inter-dependencies between networked civil infrastructures such as transportation and power system network are well known. In order to analyze complex non-linear co-relations between such networks, datasets pertaining to such real infrastructures are required. Such data are not readily available due to their sensitive nature. This work proposes a methodology to generate realistic synthetic distribution network for a given geographical region. The generated network is not the actual distribution system but is very similar to the real distribution network. The synthetic network connects high voltage substations to individual residential consumers through primary and secondary distribution networks. The distribution network is generated by solving an optimization problem which minimizes the overall length of network and is subject to the usual structural and power flow constraints. The work also incorporates identification of long high voltage feeders originating from substations and connecting remotely situated customers in rural geographical locations. The proposed methodology is applied to create synthetic distribution networks in Montgomery county of south-west Virginia, USA. The created networks are validated for their structural feasibility and ability to operate within acceptable voltage limits under average load demand scenario.

T6.11: A Fault Tolerant Selective Harmonic Elimination Method for Modular Multilevel Converters
Authors: Ardavan Mohammadhassani, Ali Mehrizi-Sani
Ardavan Mohammadhassani picture
Representing Author: Ardavan Mohammadhassani - PEC
Keywords:fault identification; microgrids; optimization
Abstract:

A selective harmonic elimination pulse-width modulation (SHE-PWM) is proposed in this paper for adding fault tolerant capabilities to the operation of modular multilevel converters (MMC). This method maintains the fundamental harmonic of the faulty phase voltage during single submodule failures in order to keep the line-to-line voltages balanced. A circulating current controller is also designed to mitigate the ac component of the circulating currents while keeping the predefined shape of the output voltage. A 9-level MMC model is built in PSCAD/EMTDC to verify the advantages of the proposed method.

T6.12: Distributed Energy Resources (DERs) Enhancing Outage Management and Feeder Restoration of Distribution Systems
Authors: Chensen Qi, Chen-Ching Liu
Chensen Qi picture
Representing Author: Chensen Qi - PEC
Keywords:fault identification; microgrids; optimization; resiliency; system restoration
Abstract:

The increasing installation of DERs and Microgrids benefits the power grids by enhancing system resiliency. However, the new distributed energy resources also bring challenges to operation and protection of the power system. In this research, new computational methods are proposed to quickly locate faults and determine actions to restore service to the outage areas using data from smart meters. The proposed system includes Outage Management and Feeder Restoration Modules. The Outage Management module uses a hierarchical method based on hypotheses. By solving integer programming problems with two-level hypotheses, Outage Management provides accurate results of the fault locations and operation of protective devices. The Feeder Restoration module is based on a hierarchical optimization method. By solving a mixed integer programming in the first level, the critical load will be served with DERs and Microgrids by forming electrical islands. Based on the availability of utility sources, the restoration path will be determined at the second level to reconnect the islands to the substation. The proposed system has been tested on the modified IEEE 123-Node Test Feeder. The simulation results validate the capability of the proposed outage management and service restoration functions.

T6.13: Testbed Development for Real-Time Hardware-in-the-Loop Demonstration for Flexible Combined Heat and Power Systems
Authors: Sangeetha Rajasekeran
Representing Author: Sangeetha Rajasekeran - PEC
Keywords:microgrids; optimization
Abstract:

The increased penetration of renewable energy into the electric grid, combined with their intermittent nature, has introduced additional fluctuation and stress on the system and increased the need for reliable generation sources. Industrial Combined Heat and Power (CHP) plants located at Medium Voltage (MV) to Low Voltage (LV) levels are a lucrative choice for providing the much-needed grid support services in a highly efficient, environmentally friendly fashion. With some added generation capacity, such flexible CHP (F-CHP) systems aid the grid in times of deficit renewable energy production whilst benefiting from providing such services to the grid. In this regard, a multi-level modular converter (MMC) interfaced F-CHP is proposed and will be deployed as a Distributed Energy Resource (DER) to provide critical services to the power system. This work deals with the development of a microgrid system testbed for verifying the converter functionalities using real time simulation and a Power Hardware-in-the-Loop (PHIL) setup. Additionally, a microgrid controller was implemented according to the IEEE 2030.7 Standard for the secondary level control of the microgrid DER and loads.

T6.14: On the effect of Line Dynamics in Multi-Inverter Systems with Generalized Droop Control
Authors: Gurupraanesh Raman, Sidhaarth Venkatachari, Jimmy Peng
Representing Author: Gurupraanesh Raman - PEC
Keywords:power system analysis; power system operation and control; system reliability and stability
Abstract:

Generalized droop control has been proposed in literature as a solution to guarantee the stability of multi-inverter distribution systems by decoupling the real and reactive power flows in the interconnecting lines. This work demonstrates that even with generalized droop, the system experiences stability issues for some values of droop coefficients due to the effect of electromagnetic line dynamics. Further, it is established that true decoupling is not achievable due to the coupled dynamics of the lines. This cross-coupling, along with the lagging nature of the line dynamics are found to significantly decrease the damping of the critical eigenvalues. Both effects become insignificant at higher R/X ratios and consequently, the need to employ the computationally expensive fifth-order model is obviated, with the conventional third-order model being sufficient to describe the interactive dynamics between the various sources. A low-voltage case study is used to demonstrate the coherence between the fifth and third-order models for higher R/X ratios, and that, for such cases, global stability is truly guaranteed for all values of droop gains.

T6.15: Moving horizon-based optimal scheduling of EV charging: A power system-cognizant approach
Authors: Nitasha Sahani, Manish kumar Singh, Chen-Ching Liu
Nitasha Sahani picture
Representing Author: Nitasha Sahani - PEC
Keywords:electrification of transportation; optimization; voltage regularion
Abstract:

The rapid escalation in plug-in electric vehicles (PEVs) and their uncoordinated charging patterns pose several challenges in distribution system operation. Some of the undesirable effects include overloading of transformers, rapid voltage fluctuations, and over/under voltages. While this compromises the consumer power quality, it also puts on extra stress on the local voltage control devices. These challenges demand for a well-coordinated and power network-aware charging approach for PEVs in a community. This paper formulates a real-time electric vehicle charging scheduling problem as a mixed-integer linear program (MILP). The problem is to be solved by an aggregator, that provides charging service in a residential community. The proposed formulation maximizes the profit of the aggregator, enhancing the utilization of available infrastructure. With a prior knowledge of load demand and hourly electricity prices, the algorithm uses a moving time horizon optimization approach, allowing the number of vehicles arriving unknown. In this realistic setting, the proposed framework ensures that power system constraints are satisfied and guarantees desired PEV charging level within stipulated time. Numerical tests on an IEEE 13-node feeder system demonstrate the computational and performance superiority of the proposed MILP technique.

T6.16: Advanced optimal power distribution system restoration and reconfiguration formulations incorporating modern smart grid components
Authors: Manish K Singh, Sina Taheri, Vassilis Kekatos, Kevin Schneider, Chen-Ching Liu
Manish Singh picture
Representing Author: Manish Singh - PEC
Keywords:microgrids; optimization; resiliency; system restoration; voltage regularion
Abstract:

Power distribution system restoration and reconfiguration are classical problems of interest to utilities and researchers alike. However, the efficacy of existing solution approaches is oftentimes limited in exploiting the modern smart grid components such as distributed generators, smart inverters, voltage regulators, controllable switches etc. This work presents a suite of computationally efficient techniques that enable accurate modeling of these components in a practical setting. The proposed techniques are useful for various power distribution system operation, planning and design problems. This work demonstrates the superior performance of optimal restoration and reconfiguration solvers with the proposed techniques via extensive numerical tests on IEEE 37-node test feeder.

T6.17: Performance Validation of Sampled Values-Based Protection in an IEC 61850 Process Bus Network
Authors: Nicholas Skoff, Jaime De La Ree
Representing Author: Nicholas Skoff - PEC
Keywords:fault identification; measurements/instrumentation; power system protection
Abstract:

This research presents analysis of a distance-based protection algorithm that makes use of sampled voltages and currents sent over a switched ethernet network. A set of three phase voltage and current signals are input to an MSP432E microcontroller where they are converted from analog to digital quantities. Then, they are published in the form of unicast ethernet packets to a subscriber protection device. Test cases are carried out for a single line to ground (SLG) fault including standard operation, packet loss, and network traffic. Reliability and latency characteristics are evaluated, then compared to the same SLG fault applied to a SEL-421 distance relay.

T6.18: Fast Probabilistic Hosting Capacity Analysis of Feeders with Distributed Energy Resources
Authors: Sina Taheri, Mana Jalali, Vassilis Kekatos
Representing Author: Sayedsina Taheri Hosseinabadi - PEC
Keywords:optimization; power system analysis; power system operation and control; power system planning; voltage regularion
Abstract:

With increasing deployment of distributed energy resources (DERs), analyzing the hosting capacity of such resources is of great importance. This analysis involves solving a large number of optimal power flow (OPF) instances that are computationally challenging due to the sheer scale of distribution systems and often times may get infeasible. In this work, an exact penalty method is devised to handle infeasibility of OPF. To overcome the computational complexity of large scale multi-scenario OPFs, a multiparametric programing (MPP) approach is tailored specifically for OPF. Our numerical results show the effectiveness of MPP for solving OPF for a year of data.

T6.19: Stochastic Multi-Agent-Based Model to Measure Community Resilience
Authors: Jaber Valinejad, Lamine Mili
Jaber Valinejad picture
Representing Author: Jaber Valinejad - PEC
Keywords:power system analysis; power system operation and control; power system planning; resiliency
Abstract:

We propose a new stochastic multi-agent-based model to measure the resilience of a community facing a disaster. The social well-being of a social community during a disaster, which is recognized as a key characteristic of the community resilience, is investigated in terms of both mental and physical social health. Both types of health influence each other and are affected by emotional health, which in turn is influenced by the availability of the services provided by critical infrastructures such as food and agriculture, water, transportation, electric power and communications systems, and emergency services, to name a few. During a disaster, the mental characteristics of humans such as emotion, risk perception, information-seeking behavior, empathy, cooperation, experience, and flexibility are considered as vital. In this paper, we model the collective behavior of a society during a disaster to study community resilience. Due to their importance, we also model the electric power system and the emergency services that serve a society. In the proposed model, a society consists of a set of communities with different features, which are supposed to be Gaussian random variables. Assuming a mean and a standard deviation for each community feature and its population, a stochastic multi-agent-based algorithm to carry out Monte Carlo simulations is proposed. We investigate the effect of the level of empathy, cooperation, coordination, flexibility, and experience of individuals on their mental well-being. Furthermore, we explore the impact of the information that is provided by emergency services and the impact of the availability of electric energy on the physical, mental, and social well-being of individuals. For our simulations, we use a stochastic, multi-agent-based numerical framework that is reported in the companion paper for estimating the social well-being of a community when facing natural disasters such as hurricanes, floods, earthquakes, and tsunamis. The performance of the proposed method is assessed by measuring community resilience for a multitude of effects in the context of two case studies. The results show that a high level of cooperation can positively change individual behavior. In addition, the relationship among the individuals of a community is so vital that the society with less population and more empathy may be more resilient than the community with more population and less empathy.

T6.20: Wireless Power Transmission
Authors: Somayeh Yarahmadi, Lamine Mili
Representing Author: Somayeh Yarahmadi - PEC
Keywords:longitudinal waves; scalar field; tesla tower; wireless power transmission
Abstract:

The common electricity transfer is based on the use of wires between power source and load. But the wiring power transmission system has many drawbacks such as huge losses, high cost, transmission distance limitation, frequent power interruption, etc. Today, there is an urgent need for wireless power transmission (WPT) because it does not have the disadvantages of the wiring system, is very flexible, and of the advent of electric vehicles. WPT dates back to about one and a half centuries ago. In 1899, Nikola Tesla conducted experiments into the transmission of electrical energy without wires in Colorado Springs, USA. However, there is no significant advancement and strong research in the WPT system for high voltages and long distances so far. This is expected to change in the near future in view of the growing literature on that subject.

Presentation Sessions

P1: Presentation Session 1 - Impact of WBG Devices on High-Frequency Passive Components

Session Chair: Yuhao Zhang
P1.1: Analysis of Parastic Capacitors Impact on Voltage Sharing of Series-Connected SiC MOSFETs and Body-Diodes
Authors: Xiang Lin, Lakshmi Ravi, Yuhao Zhang, Dong Dong, Rolando Burgos
Xiang Lin picture
Representing Author: Xiang Lin - CPES
Keywords:control; passive components; silicon carbide (sic)
Abstract:

The voltage sharing among series-connected SiC MOSFETs is more sensitive to the surrounding parasitic capacitors than Si IGBTs due to much higher dv⁄dt switching speed. To this end, this paper presents a detailed study of parasitic capacitors' impact on the voltage sharing of series-connected SiC MOSFETs and body-diodes. The impact of different heatsink connection schemes and the corresponding change of the parasitic capacitors are also analyzed. The study reveals that, for series-connected SiC MOSFETs, the parasitic capacitor differences affect the gate miller plateau voltage and ultimately the dv⁄dt during turn-off and the voltage sharing is more sensitive to gate-to-heatsink parasitic capacitor. For series-connected body-diodes, the voltage sharing is more sensitive to drain⁄source-to-heatsink capacitors which results in different dv⁄dt turn-off voltages across the body-diodes under different heatsink connections. The voltage sharing between two series-connected 10 kV SiC MOSFETs is tested in a multi-pulse test setup under different parasitic capacitors conditions.

P1.2: The Optimal Design of A High-Temperature PCB-Embedded Transformer GaN-Based Gate-Drive Power Supply with A Wide-Input Range
Authors: Jiewen Hu, Bo Wen, Rolando Burgos, Dushan Boroyevich
Jiewen Hu picture
Representing Author: Jiewen Hu - CPES
Keywords:gallium nitride (gan); high power density; high temperature; magnetic materials and integration
Abstract:

This paper presents the optimal design of a wide-input range, dual-output 10 W isolated active-clamp flyback (ACF) gate-drive power supply (GDPS) for high-temperature automotive applications. Detailed analysis and comparison between Critical Conduction Mode (CRM) and Continuous Conduction Mode (CCM) are provided to select the operating mode. A printed-circuit-board-embedded (PCB-embedded) transformer is carefully designed and it significantly improves the power density of the power supply. A 10 W, GaN-based converter prototype switching at 1MHz has been developed to demonstrate the attained power density (53.2 W/in3), peak efficiency (89.7%), input voltage range (8.5 V to 28 V), maximum operating ambient temperature (105 ?C at 8.5 V and 115°C at 28 V), and transformer input-output capacitance (9.7 pF).

P1.3: Withstand Physics and Failure Mechanisms of p-Gate GaN HEMTs under Transient Surge Energy
Authors: Ruizhe Zhang, Joseph P. Kozak, Ming Xiao, Yuhao Zhang
Ruizhe Zhang picture
Representing Author: Ruizhe Zhang - CPES
Keywords:device characterization; device and system reliability; gallium nitride (gan)
Abstract:

An essential robustness of power devices is the capability to safely withstand the surge energy in unclamped inductive switching (UIS) conditions. The surge-energy robustness of GaN high electron mobility transistors (HEMTs) has not been fully understood, as GaN HEMTs has no or very little avalanche capability. This work, for the first time, unveils the comprehensive physics associated with the surge-energy withstand process and failure mechanisms of p-gate GaN HEMTs in UIS tests. Two commercial p-gate GaN HEMTs with Ohmic- and Schottky-type gate contacts are studied and they show similar withstand and failure physics. The withstand process comprises an LC-resonance between the load inductor and the device capacitance, followed by the device reverse conduction. The device failure occurs at the transient of peak resonant voltage and is directly limited by the peak overvoltage rather than the surge energy or the duration of overvoltage. Almost no energy is dissipated in the device during the withstand process. This suggests that, the avalanche energy, a widely used JEDEC robustness standard for MOSFETs, may not be a physically meaningful standard for p-gate GaN HEMTs. These results provide critical understandings on the robustness of GaN HEMTs and useful references for their qualifications and applications. We also demonstrate that the UIS test could be used as a new technique to study the transient overvoltage breakdown mechanism for GaN HEMTs. It can generate the short overvoltage period (<10 ns) that best resembles the resonant ringing in power converters. Using this technique, the surge-voltage breakdown mechanism of two p-gate GaN HEMTs has been clarified; the breakdown location of gate-injection-transistors has been experimentally identified for the first time.

P1.4: Ultra High Frequency Integrated Coupled Inductor Design For IVR in Smartphone Application
Authors: Feiyang Zhu, Qiang Li, Fred C. Lee
Feiyang Zhu picture
Representing Author: Feiyang Zhu - CPES
Keywords:magnetic materials and integration; passive components
Abstract:

In order to provide a compact and efficient power solution for high-performance processors in smartphone application, three-dimensional integrated voltage regulator operating at ultra-high frequency (> 10MHz) becomes a promising solution. One of the most challenging parts is ultra-low profile magnetic design with small footprint, loss and large current handling capability. In this paper, a novel, two phase negative coupled inductor structure with TKOIN metal-flake composite magnetic material is proposed. The structure exploration and design process are illustrated with the help of finite element tool. The new inductor structure features very small inductor loss(<0.15W per phase) and footprint(<4mm2 per phase), large inductance density and current handling ability(> 3A dc current per phase) operating at 20MHz switching frequency. Three different inductor samples are fabricated and experimentally tested to verify the design and to evaluate thermal performance.

P1.5: Common-Mode EMI Noise Reduction for Interleaved Multichannel GaN-Based PFC Converter
Authors: Shuo Wang, Fred C. Lee, Qiang Li
Shuo Wang picture
Representing Author: Shuo Wang - CPES
Keywords:emi; gallium nitride (gan); high power density; magnetic materials and integration; passive components
Abstract:

Adopting Gallium Nitride (GaN) device in power factor correction (PFC) converters, switching frequency can be increased up to the MHz range, with dramatic improvement in power density and not at the detriment of efficiency. Furthermore, the inductor value is reduced dramatically with more opportunities to integrate PCB windings into magnetics. With PCB based winding structure, opportunities for high frequency EMI common-mode (CM) noise reduction, previously inconceivable due to uncontrollable equivalent parallel capacitor (EPC) and equivalent parallel resistor (EPR), is possible to be realized in balance technique. To enhance the high frequency balance, a novel PCB winding structure with coupled inductor is proposed. CM noise model and balance condition for minimizing CM noise is derived. Moreover, ground loop impacts for high frequency noise is studied. A two phase interleaved totem-pole PFC converter with GaN device is built up to verify the proposed balance technique. Experimental results show that balance condition is independent to self-resonant frequency of inductor with proposed PCB inductor structure, and CM noise can be reduced uniformly up to 20 dB from 150 kHz to 30 MHz.

P2: Presentation Session 2 - High-Frequency Power Converter Modeling, Design and Analysis

Session Chair: Dong Dong
P2.1: A Series-Series-CL Resonant Converter for Wireless Power Transfer in Auxiliary Power Network
Authors: Keyao Sun, Jun Wang, Rolando Burgos, Dushan Boroyevich
Keyao Sun picture
Representing Author: Keyao Sun - CPES
Keywords:optimization; resonant converters; wireless power transfer
Abstract:

This paper proposes a series-series-CL resonant converter for wireless power transfer (WPT) in auxiliary power network for 10 kV SiC MOSFET based power electronics building block. The topology of the converter can compensate reactive power thus increase system efficiency, generate a constant output voltage which can be tuned by changing one pair of LC parameters (or distance between coils), and keep a symmetrical coil structure which facilitates the design and optimization. A WPT converter prototype is built that features in 48 V to 48 V, 100 W, 92% efficiency, 4 pF isolation capacitance, and 24 kV insulation voltage.

P2.2: Series-Capacitor Buck Converter with Soft Turn-On for Datacenters
Authors: Cong Tu, Khai Ngo, Rengang Chen
Cong Tu picture
Representing Author: Cong Tu - CPES
Keywords:gallium nitride (gan); optimization; resonant converters; soft switching
Abstract:

The Series-Capacitor Buck (SCB) converter lowers the switching loss, doubles the duty ratio, and equalizes the current between two phases. A Resonant Series-Capacitor Buck (RSCB) converter is realized by adding a parallel resonant tank next to the series-capacitor Cs. All switches turn on into zero-voltage (ZVOn) and the low-side switches turn off from zero-current (ZCOff). The voltage gain remains proportional to the off-time of the low-side switches. The resonant tank generates additional loss and increases the voltage stress of the low-side switches. A 2-MHz prototype with a full load efficiency of 97.3%, 48 V at the input, and 7 V, 20 A at the output, was built to verify the design.

P2.3: High-Efficiency High-Density DC/DC Converter for Battery Charger Applications
Authors: Feng Jin, Qiang Li, Fred C. Lee
Feng Jin picture
Representing Author: Feng Jin - CPES
Keywords:high power density; magnetic materials and integration; modular converters; resonant converters; silicon carbide (sic)
Abstract:

Due to the concerns regarding increasing fuel cost and air pollution, plug-in electric vehicles (PEVs) are drawing more and more attention. Range is the major drawback for electric cars, and the easiest way to increase it is to cram more storage capacity into a vehicle. Taking Tesla Inc’s Model X P100D as an example, it is equipped with a 100kWh battery to provide a 295 miles range. However, it will take 11 hours for the 100kWh battery to be full charged with its own on-board-charger which make long distance travel infeasible. Fast charging technique is the most promising method to short this charging period. In Tesla’s supercharger station, a Model X P100D can be fully charged within 75 minutes based on its 135kW charging capacity. Porsche, a German high-performance sports cars automobile manufacturer, developed a 350kW DC fast-charger for its 800V battery pack of Mission E. Electric vehicle infrastructures, such as ChargePoint, electrify America, etc., have launched their investment on 350kW or higher power fast charging stations. However, these fast chargers have low power density. In order to charge the battery faster, our developed single-phase on-board charger concept is extended to a higher power level. By utilizing the three-phase interleaved CLLC resonant converter as DC/DC stage, the charging power for one module is pushed to 12.5 kW. It can operate bi-directionally and achieve soft-switching with proper control. As a result, we will push the switching frequency to over 500kHz to help reduce converter size and weight. With the help of high-frequency operation, the transformers and inductors and be integrated together and build with PCB winding. Therefore, the proposed DC/DC converter will have not only very high density, but also very suitable for manufacture automation. In order to achieve wide output voltage range for battery charger applications, typically from 250V to 800V, to cover both state-of-the-art 400V battery pack and 800V battery pack in the near future, interleaved buck converter is adopted, and1.2kV SiC MOSFET will be used to build this module. This DC/DC module has very wide applications. It could be the second stage for an on-board charger with three-phase AC input. It also could be the final stage of an off-board charger with 800V DC link as its distribution bus. Basically, it is a general building block For EV battery charger application.

P2.4: Modeling and Control for 48V/1V Sigma Converter for Very Fast Transient Response
Authors: Xin Lou, Mohamed H. Ahmed, Fred C. Lee, Qiang Li, Virginia Li
Xin Lou picture
Representing Author: Xin Lou - CPES
Keywords:control; high power density; modeling and control; resonant converters
Abstract:

48V voltage regulator modules (VRMs) are critical for telecom power supplies, and is becoming popular for future data centers. By using a novel sigma converter topology, an outstanding performance in terms of efficiency (95.2%) and power density (700 W⁄in3) have been demonstrated in [1]. Both the efficiency and power density are much higher than state-of-art solutions. The sigma converter is a quasi-parallel converter comprises an LLC converter and a regulated buck converter connected in series from the input side and in parallel from the output side. However, the modeling and control of Sigma converter is challenging due to the quasi-parallel structure and have not been solved properly yet. Basically, there are three control methods, voltage mode, current mode and V2 control. In [2], a voltage mode control design is provided with the small-signal model. However, the voltage mode control is not suitable for high-bandwidth design due to the low frequency double-pole. In this paper, the small-signal model of current mode and V2 control are provided and compared with voltage mode control. The V2 control with active droop control is chosen for high-bandwidth and constant load line design. Additionally, the transient performance is performed and verified to meet the VR14 requirements.

P2.5: A Power Hardware-in-the-Loop Testbench for Aerospace Applications
Authors: John Noon, He Song, Bo Wen, Rolando Burgos, Igor Cvetkovic, Dushan Boroyevich, Srdjan Srdic, Gernot Pammer
John Noon picture
Representing Author: John Noon - CPES
Keywords:control; device and system reliability; modeling and control; three-phase converters
Abstract:

As the aerospace industry moves towards the More Electric Aircraft (MEA), there is a growing need to model the increasingly complex electrical systems. Real-time modeling and simulation allows standalone simulations to be completed much faster than traditional simulation methods, and allows for Power Hardware-in-the-Loop (P-HIL) emulation and testing. The P-HIL testbench demonstrated in this paper can be run back-to-back where both the source and the load are emulated systems with real power transferred between them. This paper demonstrates the development and execution of machine and power converter emulation on the EGSTON Power Electronics' COMPISO System Unit CSU200-1GAMP6 P-HIL platform. The advantages and capabilities of P-HIL for the MEA are presented in this paper.

P2.6: Discrete State Event-Driven Approach for Power Electronic Simulation
Authors: Bochen Shi, Zhengming Zhao, Yicheng Zhu, Zhujun Yu, Jiahe Ju
Representing Author: Bochen Shi - Tsinghua
Keywords:control; modeling and control; modular converters
Abstract:

Demands for high-power converters are increasing rapidly. Nevertheless, due to their complex structures and multi-time-scale features, accurate and efficient simulation of such systems has long been a huge obstacle. Aiming at improving the unacceptably slow simulation speed of high-power converters, this paper presents Discrete State Event-Driven (DSED) approach dedicated for power electronic simulations. Taking a 10kV 1MW electric energy router as an example, this paper evaluates the effectiveness of DSED in high-power applications. In the studied case, compared with other commercial simulator, DSED can achieve an up to 1000-fold improvement in simulation speed under the same accuracy: commercial tool takes 6 hours while DSED only takes 18 seconds. DSED provides a powerful simulation tool for analysis, design and control of high-power converters.

P3: Presentation Session 3 - Medium-Voltage, High-Power Converters and Systems

Session Chair: Christina DiMarino
P3.1: Insulation Design and Assessment of a 16 kV Rated PCB Based Planar DC Bus with Distributed Capacitors
Authors: Lakshmi Ravi, Xiang Lin, Dong Dong, Rolando Burgos
Lakshmi Ravi picture
Representing Author: Lakshmi Ravi - CPES
Keywords:high power density; insulation design and assessment; silicon carbide (sic); three-phase converters
Abstract:

This paper presents the insulation design and assessment of a medium voltage (MV), printed circuit board (PCB) based dc bus with distributed capacitors. A generalized insulation design process is described with considerations for insulator material stress as well as surface discharge on external interconnections. A 16 kV rated dc bus is designed for a three phase inverter application using the design procedure to achieve partial discharge (PD) free operation up to 18 kV. Finite-element analysis (FEA) simulation studies of the multilayer PCB bus are presented to analyze different approaches to control electric field distribution in the design layout. The designed dc bus also features a modular PCB design to improve the power density and specific power of the MV system. Partial discharge experimental test results are presented for insulation design validation. High speed switching performance of the inverter phase leg is verified using a standard clamped inductive load test.

P3.2: Design and Assessment of a Medium-Voltage Power Cell based on High-Current, 10 kV SiC MOSFET Half-Bridge Modules
Authors: Slavko Mocevic, Jianghui Yu, Yue Xu, Joshua Stewart, Jun Wang, Igor Cvetkovic, Dong Dong, Rolando Burgos
Slavko Mocevic picture
Representing Author: Slavko Mocevic - CPES
Keywords:high power density; insulation design and assessment; modular converters; silicon carbide (sic)
Abstract:

Rapid technology improvement of silicon-carbide (SiC) MOSFET transistors combined with their extraordinary characteristics are key drivers for their utilization in medium-voltage (MV) applications. For typical MV modular converter applications, power cell is a critical piece. Power cell systematic design and assessment methodology are crucial to prevent destruction and to fully test exploring its capabilities prior to implementation at the converter level. Thereby, this paper presents design and assessment methodology of an MV half-bridge power cell based on XHV-6 10 kV, high current, SiC MOSFET module with dc bus rated voltage of 6 kV. Critical design considerations, challenges and solutions are presented as well as the detailed assessment workflow and limitations of the power cell. The power cell design is validated through continuous operation at 6 kV, 84 A rms, 10 kHz exhibiting over 99% efficiency, switching with dv⁄dt up to 100 V⁄ns.

P3.3: High-Frequency Transformer Design with High-Voltage Insulation for Modular Power Conversion from Medium-Voltage AC to 400-V DC
Authors: Zheqing Li, Qiang Li, Fred C. Lee, Yi-Hsun Hsieh, Orion Chen
Zheqing Li picture
Representing Author: Zheqing Li - CPES
Keywords:gallium nitride (gan); insulation design and assessment; magnetic materials and integration; resonant converters; silicon carbide (sic)
Abstract:

Due to the increasing use of cloud computing and big data, the power consumption of the datacenter alone will reach 10% of the total electrical power consumption in the world by 2020. In the conventional AC data center power architectures, a line frequency transformer is employed to step down a medium voltage(MV) AC to 480VAC which leads to a very bulky and costly transmission bus and large conduction losses. This line frequency transformer is cascaded by 480V UPS and rectified into 400V DC. In this work, a SiC and GaN based rectifier with high frequency MV solid-state transformer(SST) is proposed to directly step down MV AC to 400 V DC. The DC-DC stage is the key point for this work because of its MV insulation capability. A CLLC resonant converter is utilized with SiC and GaN device to achieve high efficiency, high power density and bi-direction operation. High frequency transformer in the CLLC converter is well designed for 30kV insulation capability for a 4.16kV input voltage referring to IEEE standard. A shielding layer is implemented to reduce the electric field stress in the air. In addition, magnetizing inductance and two resonant inductances are integrated in the transformer in order to subtract volume.

P3.4: Evaluation of Alternative AC Filter Building Blocks (FBB) for Modular Three-Level Grid-Tied Inverters
Authors: Ripun Phukan, Sungjae Ohn, Rolando Burgos, Dong Dong, Dushan Boroyevich
Ripun Phukan picture
Representing Author: Ripun Phukan - CPES
Keywords:emi; magnetic materials and integration; modeling and control; silicon carbide (sic); three-phase converters
Abstract:

EMI filters in three phase converters occupy about 40% of total converter volume. With interleaved operation, this volume requirement can be reduced on the grid side filters due to the absence of switching frequency harmonics. However, due to the presence of circulating current between channels, there is an additional requirement for filter components which outweigh the benefit from interleaving. This affects overall system power density and increases filter volume contribution. In addition, the existing filter topologies do not address modularity i.e. they cannot be used with a any number of channels without affecting attenuation or performance. In this paper, a comprehensive study of existing and new modular filter topologies is performed to fully utilize the benefit from interleaving. The proposed modular filter structures are compared in frequency domain according to groups of harmonics. These modular filter topologies are further evaluated for power density and efficiency. The trade-off between different topologies is discussed and scalability to high power levels and higher channel count is addressed. In the end, a prospective candidate(s) is chosen for future evaluation.

P3.5: A Novel DQ Impedance Measurement Method in Three-Phase Balanced Systems
Authors: Ye Tang, Rolando Burgos, Bo Wen, Dushan Boroyevich
Ye Tang picture
Representing Author: Ye Tang - CPES
Keywords:control; modeling and control; stability; three-phase converters
Abstract:

The stability of electronic power systems is essential to the safety and reliability of the system designs. Optimum stability analysis and measurement techniques are being discussed more frequently in the literature. One approach of assessing system stability is the Generalized Nyquist Criterion (GNC), which is based on d-q frame impedances. An impedance measurement unit (IMU) can be used to acquire d-q frame impedances for a three-phase balanced system. A novel d-q frame impedance measurement method, namely the single-phase impedance measurement approach, is applied to a three-phase balanced passive circuit and a voltage source inverter (VSI) separately. In this approach only single-phase data are needed. A comparison of measured results proves the capability of the single-phase impedance measurement method to obtain three-phase d-q frame impedances. In the passive circuit, both measurement methods only demand single-phase perturbation. In the converter circuit, the three-phase impedance measurement method still only needs a single-phase perturbation while the single-phase impedance measurement method requires three separate balanced single-phase perturbations.

P4: Presentation Session 4 - Enhancing Reliability and Resiliency of Power Grids

Session Chair: Jaime De La Ree
P4.1: Advanced optimal power distribution system restoration and reconfiguration formulations incorporating modern smart grid components
Authors: Manish K Singh, Sina Taheri, Vassilis Kekatos, Kevin Schneider, Chen-Ching Liu
Manish Singh picture
Representing Author: Manish Singh - PEC
Keywords:microgrids; optimization; resiliency; system restoration; voltage regularion
Abstract:

Power distribution system restoration and reconfiguration are classical problems of interest to utilities and researchers alike. However, the efficacy of existing solution approaches is oftentimes limited in exploiting the modern smart grid components such as distributed generators, smart inverters, voltage regulators, controllable switches etc. This work presents a suite of computationally efficient techniques that enable accurate modeling of these components in a practical setting. The proposed techniques are useful for various power distribution system operation, planning and design problems. This work demonstrates the superior performance of optimal restoration and reconfiguration solvers with the proposed techniques via extensive numerical tests on IEEE 37-node test feeder.

P4.2: Resiliency of Distribution Systems Incorporating Asynchronous Information for System Restoration
Authors: Juan C. Bedoya, Jing Xie, Yubo Wang, Xi Zhang, Chen-Ching Liu
Juan Bedoya picture
Representing Author: Juan Bedoya - PEC
Keywords:optimization; resiliency; system restoration
Abstract:

Resiliency of distribution systems under extreme operating conditions is critical, especially when the utility is not available. With the large-scale deployment of distributed resources, it becomes possible to restore critical loads with local non-utility resources. Distribution system operators (DSOs) need to determine the critical loads to be restored, considering limited resources and distribution facilities. Several studies on resiliency have been conducted for the restoration of distribution systems. However, the inherent asynchronous characteristic on the information availability has not been incorporated. With incomplete and asynchronous information, decisions may be made that result in underutilization of generation resources. In this paper, a new distribution system restoration approach is proposed, considering uncertain devices and associated asynchronous information. It uses a two-module architecture that efficiently optimizes restoration actions using a binary linear programming model and evaluates their feasibility with unbalanced optimal power flow. Networked microgrids are included in the model. The IEEE 123-node test feeder is used for validation. Results show that asynchronous messages may affect the restoration actions significantly and the impacts can be mitigated by the proposed decision support tool for the DSOs.

P4.3: Creating Realistic Synthetic Power Distribution Networks based on Interdependent Road Infrastructure
Authors: Rounak Meyur, Madhav Marathe, Anil Vullikanti, Virgilio Centeno
Rounak Meyur picture
Representing Author: Rounak Meyur - PEC
Keywords:machine learning applications; optimization; power system planning; resiliency; synthetic networks
Abstract:

Physical inter-dependencies between networked civil infrastructures such as transportation and power system network are well known. In order to analyze complex non-linear co-relations between such networks, datasets pertaining to such real infrastructures are required. Such data are not readily available due to their sensitive nature. This work proposes a methodology to generate realistic synthetic distribution network for a given geographical region. The generated network is not the actual distribution system but is very similar to the real distribution network. The synthetic network connects high voltage substations to individual residential consumers through primary and secondary distribution networks. The distribution network is generated by solving an optimization problem which minimizes the overall length of network and is subject to the usual structural and power flow constraints. The work also incorporates identification of long high voltage feeders originating from substations and connecting remotely situated customers in rural geographical locations. The proposed methodology is applied to create synthetic distribution networks in Montgomery county of south-west Virginia, USA. The created networks are validated for their structural feasibility and ability to operate within acceptable voltage limits under average load demand scenario.

P4.4: Optimal Capacity and Placement of Microgrids for Resiliency Enhancement of Distribution Networks Under Extreme Weather Events
Authors: Moein Borghei, Mona Ghassemi
Moein Razavi picture
Representing Author: Moein Razavi - CPES
Keywords:control; optimization
Abstract:

When a fault or a series of faults occur in a distribution network, it is of considerable significance to feeding loads, most importantly critical loads. Although network reconfiguration by switching operations has been usually considered as a relatively low-cost method for load restoration, it alone may not able to restore critical loads under extreme weather events such as hurricanes where multiple faults can happen within the network. Under such severe circumstances, one of the complementary methods for service restoration is benefiting from existing installed microgrids. In this paper, the idea of planning future microgrids -in terms of optimal location and capacity- in combination with switching operations to restore critical loads, for the first time, is considered. To this planning-operation concept end, a graph-theoretic method is developed to find optimal switching operations coupled with a heuristic optimization method developed to determine future microgrids' location and capacity to maximize the resiliency of the network while keeping the associated cost with distributed generations (DGs) in microgrids as low as possible. Simulations results on the modified IEEE 37-node distribution network show the effectiveness of the proposed idea. Moreover, using appropriate reduction techniques, the computational efficacy of the method has also been greatly improved.

P4.5: A Novel Integrated DC/DC Converter for Distributed Power Management in Emerging Heterogeneous IoT System in Package Applications
Authors: Xingye Liu, Paul Ampadu
Representing Author: Xingye Liu - PEC
Keywords:voltage regularion
Abstract:

In this paper we present a novel integrated DC/DC converter for emerging IoT System-in-Package (SiP) applications. Considering more functions are required in one system, splitting a large System?on?Chip (SoC) into multiple dies using heterogeneous SiP integration will be the key technology enabling better performance and reliability. How to provide clean, efficient and dynamically scalable voltages and currents to multiple workloads remains to be challenging. Our proposed DC/DC converter is dedicated to solve this issue as providing multiple outputs simultaneously and can be used as a distributed power management unit in the entire package. The proposed converter features a scalable two-stage modular architecture which greatly reduces design complexity to support more outputs. We demonstrate the converter by designing a 3-output version chip. Each output channel supports 0.3V to 0.9V with up to 150 mA and worst-case ripple is 68 mV. With the simplified digital voltage?based feedback loop, the converter reaches a peak single-channel efficiency of 85.5 % and is able to track reference voltage by maximum 19.5 V/μ s. When multiple load transient responses occur simultaneously, there is no observable voltage spikes/droops or cross regulations. The 3?output version chip consumes about 1.4 mm2 area and extension to 6-output version only requires 0.56 mm2 additional area and same transient response performance can be maintained.

P4.6: Outlier Issues in Harmonic Source Location Based on Parameter Identification Method
Authors: Kexuan Tang, Chen Shen, Shuo Liang, Xiuqiong Huang
Representing Author: Kexuan Tang - Tsinghua
Keywords:power system analysis; system reliability and stability; power system operation and control
Abstract:

In this paper, the outlier issues in harmonic source location using parameter identification method are introduced and discussed. The theoretical models and outlier issues in parameter identification method are firstly introduced. Zero-crossing criteria of denominators in parameter solving processes are then obtained through theoretical derivations. Finally, the applicability of equivalent impedance models is discussed on the basis of theoretical and simulation results.

Tutorial Sessions

Tutorial Session 1 - Modular High-Frequency SiC Power Conversion Systems for High-Power Applications

Session Chair: Khai Ngo
Modular High-frequency SiC Power Conversion Systems for High-Power Applications
Authors: Dong Dong
Dong Dong picture
Representing Author: Dong Dong - CPES
Professional Title: CPES Faculty
Abstract:

Traditional high power conversation systems, running at moderate switching frequency, are dominated by silicon power semiconductor devices based solutions. Many emerging applications, e.g., high-speed drive, energy storage system, and solid-state transformers, crave power conversion solutions with higher density, better efficiency, and advanced performances. SiC has multiple advantages over its silicon (Si) counterpart including lower losses, higher switching frequencies, higher voltage operation, and improved thermal performance. However, faster SiC switching transitions and high-frequency switching operation lead to challenges like electromagnetic emission problems, susceptibility difficulties, and insulation degradation.

Bio/Information:

Dong Dong received his B.S. degree from Tsinghua University, Beijing, in 2007; M.S. and Ph.D degrees from Virginia Tech, Blacksburg, in 2009 and 2012, all in Electrical Engineering. From 2007 to 2012, he was a research assistant at Center for Power Electronics Systems (CPES). From 2012 to 2018, he was with Electric Power (EP) Organization at GE Global Research Center in Niskayuna, NY, developing power conversion and electric system technology for renewable energy system integration, electric grid, offshore and marine, oil and gas, aviation, navy, and industrial applications. In 2018, Dr. Dong returned to Virginia Tech, where he is currently assistant professor in The Bradley Department of Electrical and Computer Engineering. His research interests include modeling, design, and digital control of power electronic system, low-voltage to medium-voltage SiC high-frequency power electronics, high-power resonant converter and high-frequency transformer, power conversion systems for grid, renewable energy integration, and transportation applications, and real-time hardware-in-loop simulation.

Tutorial Session 2 - Battery Power Management Fundamentals

Session Chair: Khai Ngo
Battery Power Management Fundamentals
Authors: Jinrong Qian
Jinrong Qian picture
Representing Author: Jinrong Qian
Professional Title: Texas Instruments - General Manager, Battery Management Solutions
Abstract:

Battery power management plays a critical role in battery-powered devices. “How can I charge the battery faster and safer, extend battery run-time and use battery energy more efficiently?” These questions continue to plague battery system designers and end users. This session will first cover rechargeable battery chemistries, reviewing their charging and discharging characteristics, safety concerns and associated protections. Then, we will look at various battery-charging topologies and fast charging architecture, where high-efficiency battery charger examples will be introduced. Battery fuel gauge his another important topic. Too early shutdown the system will not fully use every drop of juice from the battery, making high-accuracy fuel gauges just as important as power conversion efficiency. Different fuel gauges will be discussed with their pros and cons. Finally, we will address overall trends in battery management for electric vehicles.

Bio/Information:

Jinrong Qian is a general manager of battery management business unit, and vice president at Texas Instruments. His main responsibilities include Profit & Loss, business investment strategy, new technologies and differentiated product roadmap in battery power management.

Invited Sessions

Invited Session 1

Session Chair: Fred C. Lee
Advances in Power Electronics Enabled by Converter Architectures, Soft Switching Techniques, and Wide Bandgap Semiconductors
Authors: Dragan Maksimovic
Dragan Maksimovic picture
Representing Author: Dragan Maksimovic
Professional Title: UC Boulder Professor - Director, Colorado Power Electronics Center
Abstract:

This seminar starts with an introduction to direct and indirect power concepts in switched-mode power converters, with insights leading to efficiency improvement approaches based on converter topologies, soft-switching techniques, and the use of wide bandgap (SiC or GaN) power semiconductor devices. It is shown how more complex converter architectures allow for more efficient indirect power processing, leading to efficiency and power density gains, as well as application-specific system-level benefits. Challenges around complex converter configurations include more complex controls, and reliability concerns associated with increased numbers of power semiconductor components. Addressing these challenges requires innovations in modeling and control, circuit integration, and packaging techniques. Examples discussed include digitally controlled high-density, high efficiency SiC-based composite dc-dc converters for electric vehicles, modular grid-tied dc-ac systems, hybrid dc-dc converters, and very high frequency converters based on custom GaN power integrated circuits.

Bio/Information:

Dragan Maksimovic received B.S. and M.S. degrees from the University of Belgrade in Serbia in 1984 and 1986, respectively, and his Ph.D. degree from the California Institute of Technology in 1989. Since 1992, he has been with the University of Colorado at Boulder, where he is currently a Professor and Director of the Colorado Power Electronics Center (CoPEC). He has co-authored over 300 papers, and textbooks Fundamentals of Power Electronics (2nd edition), and Digital Control of High-Frequency Switched-Mode Power Converters. Prof. Maksimovic is a Fellow of the IEEE, and a recipient of the IEEE PELS Modeling and Control Technical Achievement Award. His current research interests include power electronics for renewable energy sources and energy efficiency, high frequency power conversion using wide bandgap semiconductors, digital control of high-frequency switched-mode power converters, as well as integrated circuits for power management applications.

Power Devices Now and Future Direction
Authors: Hiromichi Ohashi
Hiromichi Ohashi picture
Representing Author: Hiromichi Ohashi
Professional Title: NPERC-J - President
Abstract:

Power devices have developed as technology basis of power electronics. However, power devices are now standing on a turning point for next step of development. As the efficiency of power convertor has been gradually approaching to full percentage, role of power devices is becoming to be more system and network oriented to realize ubiquitous power electronics in the more efficient and electrified society. For next generation power electronics and power devices, following technical issues would become important.

  1. Silicon power device technology with more than Si, including WBG devices
  2. Gate electronics creation by CMOS digital technology
  3. Network connected PE
  4. Integration of reliability science and engineering
Standing on this point of view, power device trend and future direction will be mentioned in the presentation.

Bio/Information:

Hiromichi Ohashi joined the Corporate Research and Development Center, Toshiba Corporation in1969 and retired in 2002. He was a full professor of Tokyo Institute of Technology, Tokyo, from 2003 to 2004. In 2005, he joined the Energy Technology Research Institute, in AIST (the National Institute of Advanced Industrial Science and technology), Tsukuba, Japan. Since 2014, he is president of NPERC-J (New-generation Power Electronics Research Consortium Japan).
He received Ph.D. degree in electronics from Tohoku?National University in 1990.He is the author of more than 100 papers and the holder of more than 100 patents. He is a Fellow member of the IEEJ and a life member of IEEE. He was the General Chairman of ISPSD’95. He is a recipient of the Medal with Purple Ribbon from the Japan government for his contribution to high power light triggered thyristors for power transmission network of Japan.

Power Electronics for Future Power Grids: Drivers and Challenges
Authors: Jan Svensson
Jan Svensson picture
Representing Author: Jan Svensson
Professional Title: ABB - Senior Principal Scientist and Adj. Professor
Abstract:

Currently, electric power systems start to shift toward more environment friendly energy productions to limit the climate change and reduce pollutions. The major focus is the variability of the new energy sources, and reliability of the supply. The challenge for the future electric power grids is how to integrate a widespread addition of renewable sources with intermittent nature in both transmission and distribution grids without compromising reliability, stability and cost of the service to the consumers. A system that can handle a generation mix with a high percentage of renewables will become a necessity which requires solutions as increased transmission capacity through AC and DC solutions, and/or a larger energy storage capacity in the grids.
Grid-connected converter technologies have had a truly revolutionary impact on the way that electrical energy is delivered to consumers all over the world and has become an indispensable part of the electric power systems today. It is anticipated that by 2030 all electric power generated utilizes power electronics somewhere between the point of generation and its end. Power electronics contribute in many ways to more efficient use of energy, which allows for energy savings, which in turn leads to reduced environmental impact. The R&D in this field aims at optimizing complex decisions and solutions that are required for the design of these power electronic converters to deliver innovation for the future conversion, processing, transmission, distribution as well as storage of energy across a wide range of applications.
This presentation will start with an overview of the main drivers for the future grids. Then the historical, the present and the future power grid will be discussed including the developments of power electronics in grid-connected applications such as HVDC and FACTS together with more futuristic applications. Moreover, the key design parameters of power electronics and its functionalities will be described in the context of megatrends and grand challenges of the electric power system evolution. Finally, the current state of the art and topics for the future research will be presented.

Bio/Information:

Jan Svensson received the Ph.D. degrees from Chalmers University of Technology, Göteborg, Sweden, in 1998. From 1998 to 2002, he was an Assistant Professor in power electronics at Chalmers, where he also received the D.Sc. degree (Docent) 2002. Up to 2009, he was with different business units at ABB involved in R&D of energy storage concepts, FACTS and HVDC transmission, especially design and control of Light-concept devices.
From 2009 to 2014, he was Program Manager for the global R&D program “Active grid infrastructure” at ABB Corporate Research. Currently, he is a Senior Principal Scientist on power electronics systems at ABB Power Grids Research and since 2018 he is an adjunct professor at Chalmers. His interests include design and control of power electronics in power systems, power quality, storage technologies and renewable energy.

Invited Session 2

Session Chair: Arun G. Phadke
Grid Modernization Trends and Federal Investments
Authors: Carl Imhoff
Carl Imhoff picture
Representing Author: Carl Imhoff
Professional Title: PNNL - Manager, Electricity Infrastructurre and Chair, Grid Modernization
Abstract:

Mr. Imhoff will present an overview of the DOE Grid Modernization Initiative strategy and research agenda launched in 2015. He will highlight the DOE view, informed by industry, of critical national challenges in modernizing the energy and the power system, and he will explore recent and newly launched research in the DOE $330m research portfolio led by a consortium of 14 National Labs in the Grid Modernization Laboratory Consortium. He will also highlight recent research outcomes emerging from the grid program at the Pacific Northwest National Lab, including new grid data repositories and open source platforms for advanced analytics designed to support the innovation community spanning Labs, industry and academia in support of the nation’s grid modernization agenda.

Bio/Information:

Mr. Imhoff manages the Electric Infrastructure research program at the Pacific Northwest National Laboratory. PNNL conducts fundamental and applied research as well as product development with the U.S. Department of Energy, other federal agencies, state governments, vendors, and energy firms. In this role he is responsible for PNNL's research and development programs on innovations in the areas of advanced power transmission and distribution reliability concepts, demand response, integration concepts for distributed energy resources, all scales of clean energy supply, physical and cyber security of electric systems, policy and strategy for smart grid concepts, and cross-cutting grid analytic tools in visualization and high performance computing.

Integrating High Levels of Variable Renewable Energy into Chinese Power System
Authors: Chongqing Kang
Chongqing Kang picture
Representing Author: Chongqing Kang - Tsinghua
Professional Title: Tsinghua - Professor and Dean of Electrical Engineering
Abstract:

Countries around the world set aggressive goal for the very high share of renewables in future power systems. However, uncertainty and variability of the high penetration renewables need more flexibility to balance the generation and load. There are significant challenges in Chinese power systems in terms of developing renewables. This presentation will introduce the situation which Chinese power system has been facing, and give some technologies that have been developed in Chinese power system to meet the requirements of high penetrated renewable energy integration. Furthermore, A few new measures which can provide power system with flexibility will be introduced, including concentrating solar power (CSP), cloud energy storage (CES), and multiple energy systems (MES).

Bio/Information:

Chongqing Kang is professor & Dean at the Department of Electrical Engineering, Tsinghua University. His research interest focused on power system planning, and operation, renewable energy and multiple energy systems. He is Fellow of IEEE and IET. He has been on the editorial board of many international journals including IEEE Transactions on Power Systems and Electric Power Systems Research. Currently he is the Editor-in-Chief of International Transactions on Electrical Energy Systems(Wiley). He has published 5 monographs. He published over 300 academic papers, including about 100 IEEE Transactions papers. He has been a member of IEEE PES Long Range Planning Committee and IEEE PES Fellows Nomination Resource Committee.

Panel Sessions

Exploring Collaboration Opportunities: Power Electronics and Power Systems

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FS: Faculty Panel Session - New Developments of the Cyber-Grid

Session Chair: Anthony Kuh
FS.1: Machine Learning for Power System Optimization and Monitoring
Authors: Vassilis Kekatos
Vassilis Kekatos picture
Representing Author: Vassilis Kekatos - PEC
Professional Title: PEC Faculty
Abstract:

When complexity can hinder real-time operation, learning from big data can be a viable alternative or aid to accelerate power system operation tools. This talk discusses how kernel-based learning and support vector machines (SVM) can be leveraged in the aforesaid direction. The first application is drawn from smart inverter control in power distribution grids. We explain how the reactive power control curves implemented by inverters can be learned from the anticipated load and solar data. Each inverter is modeled by an SVM and all SVMs are jointly trained under an optimal power flow formulation. The second application relates to monitoring dynamics in power transmission systems. Given synchrophasor angle and/or frequency data collected at a subset of buses, we demonstrate how one can postulate and train Gaussian processes to infer frequency oscillations at the remaining buses. Both applications showcase novel and exciting directions where machine learning could help towards enhancing power system monitoring and control.

Bio/Information:

Vassilis Kekatos is an Assistant Professor with the power systems group in the Bradley Dept. of ECE at Virginia Tech. He obtained his Ph.D. from the Univ. of Patras, Greece. He is a recipient of the NSF CAREER Award in 2018 and the Marie Curie Fellowship during 2009-2012. He has been a postdoctoral research associate with the ECE Dept. at the Univ. of Minnesota, and a visiting researcher with the Univ. of Texas at Austin and the Ohio State Univ. His research focus is on optimization and machine learning for power systems and smart grids. He is currently serving on the editorial board of the IEEE Trans. On Smart Grid.

FS.2: Learning in a Highly Variable Power System: Transition to Inverter-Dominated Resources
Authors: Ali Mehrizi-Sani
Ali Mehrizi-Sani picture
Representing Author: Ali Mehrizi-Sani - PEC
Professional Title: PEC Faculty
Abstract:

This short talk will begin by discussing the challenges in operation, control, and resiliency of a low-inertia power system, in which many generation and load resources are interfaced through inverters. The talk then discusses how (i) data revolution through availability of sensors and fast communications (5G) as well as (ii) powerful learning methods enabled by recent advances in computational power can be utilized to solve both traditional and modern problems in control, protection, resiliency, and security of the power system. A few examples will also be provided.

Bio/Information:

Ali Mehrizi-Sani received the B.Sc. degrees in electrical engineering and petroleum engineering from Sharif University of Technology, Tehran, Iran, both in 2005. He received the M.Sc. degree from the University of Manitoba, Winnipeg, MB, Canada, and the Ph.D. degree from the University of Toronto, Toronto, ON, Canada, both in electrical engineering, in 2007 and 2011.
He is currently an Associate Professor at Virginia Tech, Blacksburg, VA, USA, where he is Director of the Resilient Renewable Energy Grid Adaptation Laboratory (REGAL). From 2012 to 2019, he was an Associate Professor and Assistant Professor at Washington State University, Pullman, WA. He has held Visiting Professor appointments at TU Graz, Graz, Austria, in 2014, 2016, and 2018. He was a Research Engineer with CanmetENERGY, Montreal, QC, in 2019 and a Visiting Scientist with Manitoba Hydro International, Winnipeg, MB, in 2018. His areas of interest include power system applications of power electronics, integration of renewable energy resources, and low-inertia systems.
Dr. Mehrizi-Sani is an editor of IEEE Transactions on Power Systems, IEEE Transactions on Energy Conversion, and IEEE Power Engineering Letters. He is a past editor of IEEE Transactions on Power Delivery (2012--2019) and Wiley International Transactions on Electrical Energy Systems (ITEES) (2017--2019). He was the Chair of IEEE Task Force on Dynamic System Equivalents and the Secretary of CIGRE Working Group C4.34 on Application of PMUs for Monitoring Power System Dynamic Performance. He is the recipient of 2018 IEEE PES Outstanding Young Engineer Award, 2018 ASEE PNW Outstanding Teaching Award, 2017 IEEE Mac E. Van Valkenburg Early Career Teaching Award, 2017 WSU EECS Early Career Excellence in Research, 2016 WSU VCEA Reid Miller Excellence in Teaching Award, 2011 NSERC Postdoctoral Fellowship, and 2007 Dennis Woodford prize for his M.Sc. thesis. From 2007 to 2011, he was a Connaught Scholar at the University of Toronto.

FS.3: Time synchronized measurement for distribution systems
Authors: Virgilio Centeno
Virgilio Centeno picture
Representing Author: Virgilio Centeno - PEC
Professional Title: PEC Faculty
Abstract:

Time-synchronized devices have the potential to enhance the existing distribution monitoring system (DMS) to observe the dynamic behavior of the system, a requirement for the seamless integration of DER into existing DS. In high voltage transmission system, GPS clocks and PMUs have become standard equipment in substations. Couple with fiber optic these devices have enhance existing state estimators and enabled the implementation of linear state estimated that monitor the dynamics of the system at rates up to 60 frames per second (fps). Can we implement large number of time synchronized devices in distribution systems? And if we do, do we need the 60 fps, nanosecond synchronization, and 1% total vector error of the transmission system? Most modern distribution IEDs are suited with Ethernet ports allowing them to send information through wired or wireless networks implemented by utilities from proprietary and commercial channels. In addition, existing standard like the IEEE 1588 define protocols for network-connected devices that under optimal conditions supports time synchronization in the sub-microsecond range with minimal network bandwidth and local clock with various precision levels. To implement feasible time synchronized measurement in distribution systems we need to: a) determine the minimum acceptable time synchronization requirements by metering parameter at distribution levels; b) design, implement and test IED prototypes with the minimum hardware/software requirement to achieve the minimum network-synchronization requirements and; c) develop procedures to determine the optimal placements (by time synchronization requirements) of metering devices with diverse degree of time synchronization.

Bio/Information:

Dr. Centeno has more than 33 years of experience on the design, development, implementation, testing and applications of time synchronized measurement devices for electric utility applications. As a project engineering for Macrodyne, Dr. Centeno was a key member of the team that designed and implemented the first commercial PMUs. At Virginia Tech he was a faculty member of the research team that developed a Frequency Monitoring Network (FNET). He participated in the development of Dominion PMU-only Linear State Estimator, the development of PMU applications to enhance the reliability of the California Transmission Grid and the development of application to test Grid Protection Alliance open platform for Extensible Control and Analytics (OpenECA). In addition, he has participated in PMU related projects with Macrodyne, Inc., CFE, ONS, TVA, NIST, SCE, Dominion, PG&E, and PJM.

FS.4: Optimal Capacity and Placement of Microgrids for Resiliency Enhancement of Distribution Networks Under Extreme Weather Events
Authors: Mona Ghassemi
Mona Ghassemi picture
Representing Author: Mona Ghassemi - PEC
Professional Title: PEC Faculty
Abstract:

When a fault or a series of faults occur in a distribution network, it is of considerable significance to feeding loads, most importantly critical loads. Although network reconfiguration by switching operations has been usually considered as a relatively low-cost method for load restoration, it alone may not able to restore critical loads under extreme weather events such as hurricanes where multiple faults can happen within the network. Under such severe circumstances, one of the complementary methods for service restoration is benefiting from existing installed microgrids. Here, the idea of planning future microgrids -in terms of optimal location and capacity- in combination with switching operations to restore critical loads, for the first time, is discussed. To this planning-operation concept end, a graph-theoretic method is discussed to find optimal switching operations coupled with a heuristic optimization method developed to determine future microgrids? location and capacity to maximize the resiliency of the network while keeping the associated cost with distributed generations (DGs) in microgrids as low as possible.

Bio/Information:

Mona Ghassemi received her M.S. and Ph.D. degrees both with the first honor in electrical engineering from the University of Tehran, Iran in 2007 and 2012, respectively. She spent two years researching as Postdoctoral Fellow at high voltage laboratory of NSERC/Hydro-Quebec/UQAC Industrial Chair on Atmospheric Icing of Power Network Equipment (CIGELE) and Canada Research Chair on Power Network Atmospheric Icing Engineering (INGIVRE), University of Quebec at Chicoutimi (UQAC), QC, Canada from 2013 to 2015. She also was Postdoctoral Fellow at the Electrical Insulation Research Center (EIRC) of Institute of Materials Science (IMS) at the University of Connecticut from 2015-2017. In 2017, Dr. Ghassemi joined the Bradley Department of Electrical and Computer Engineering at Virginia Tech as assistant professor and as a member of the Center for Power Electronics Systems (CPES). Dr. Ghassemi is a Senior Member of the Institute of Electrical and Electronics Engineers (IEEE), a registered Professional Engineer, Associate Editor of Journal of High Voltage (IET) and Associate Editor of International Journal of Electrical Engineering Education. Her research interests include dielectrics and electrical insulation materials and systems containing those in power electronics modules and systems, high voltage technology, multiphysics modeling, plasma science, electromagnetic transients in power systems and power system modeling.

FS.5: Anomaly Detection for Electricity Trading
Authors: Paul Ampadu
Paul Ampadu picture
Representing Author: Paul Ampadu - PEC
Professional Title: PEC Faculty
Abstract:

With the growing installation of photovoltaics, building energy management platforms, and demand response enabled smart devices, the traditional energy trading is transforming from a linear utility-to-consumer into a more distributed peer-to-peer model. Photovoltaic and demand response energy trading are two major types of peer-to-peer electricity trading. Although blockchain as an emerging technology facilitates the deployment of distributed peer-to-peer electricity trading, through encrypted processes and records, it cannot detect malicious inputs (e.g. fake energy generation quantities or extremely high or low electricity bid prices). Consequentially, end-user anomaly detection is critical to ensure trust in peer-to-peer electricity trading. We summarize anomaly detection methods and identify gaps in current research. Case studies based on the hyperledger blockchain platform are implemented and analyzed to demonstrate the potential benefits of anomaly detection methods in blockchain-enabled electricity trading.

Bio/Information:

Dr. Paul K Ampadu is a professor of electrical and computer engineering and the associate director of the Advanced Research Institute (ARI) at Virginia Tech. He performs research in computer systems reliability, security, and energy efficiency. He is also exploring how techniques used in these areas can be exploited for power and energy systems. Paul teaches courses on Digital Systems, VLSI, Computers, Circuits & Systems, AC Circuits, and Digital Communications. Previously, he served for 13 years on the faculty of the University of Rochester NY, and was for two years the Dr. Martin Luther King Jr. Visiting Professor of Electrical Engineering & Computer Science at MIT in Cambridge, MA
Dr. Ampadu is the author of three books and over 100 articles on computer systems reliability, security, and energy-efficiency. He was twice elected to serve on the IEEE Circuits & Systems Board of Governors, where he also chaired its Young Professionals Program. He has served on the international program and technical committees and editorial boards of several conferences and journals. He is an African Diaspora Carnegie Foundation Fellow, an African Scientific Institute Fellow, and a senior member of the Institute of Electrical and Electronics Engineers. He is the recipient of numerous awards, including an IBM PhD Fellowship, a Semiconductor Research Corporation Scholarship, US Black Engineer of the Year Special Recognition Award, NASA Summer Faculty Fellowship, Charles Drew Professor's Choice Award, and the National Science Foundation CAREER award.
Dr. Ampadu earned a bachelor’s degree in electrical engineering from Tuskegee University, a master’s in electrical engineering from the University of Washington, and the doctorate in electrical and computer engineering from Cornell University. Prior to the Ph.D., he worked at the IBM Research Center in Yorktown Heights, New York and at Microsoft Corporation in Redmond, WA, where he helped ship the world's first 32-bit version of Microsoft Word Japanese, Korean, and Chinese versions. Dr. Ampadu has supervised over a dozen doctoral and master’s research thesis and projects and is considered a world leader in reliable, energy-efficient many-core embedded systems-on-chip.

IS: Industry Panel Session - Technology Needs for the Future Power Grid

Session Chair: Zhenyu (Henry) Huang
IS.1: New Technology to ensure a Reliable and Resilient Electric Grid
Authors: Kyle Thomas
Kyle Thomas picture
Representing Author: Kyle Thomas
Professional Title: Dominion - Manager-Electric Transmission System Protection
Abstract:

Dominion Energy is one of the nation’s largest producers and transporters of energy, with a portfolio of approximately 29,000 megawatts of generation, 16,000 miles of natural gas transmission, gathering and storage pipeline, and more than 10,000 miles of electric transmission lines and 85,000 miles of electric distribution circuits. Dominion Energy Virginia is the electric utility responsible for managing an electric grid that spans across Virginia and North Carolina. This presentation will focus on Dominion's mission of ensuring a robust, reliable, and resilient grid among all the existing and new challenges facing the industry, and how Dominion utilizes core fundamentals with the latest technology, tools, and disciplines to address these challenges. The rapid pace of changes in generation (both in location and type), physical and cyber security, consumer/industrial load makeup, and societal/regulatory demands require new tools, new solutions, and new strategies to ensure the reliability and resiliency is maintained and improved further.

Bio/Information:

Kyle Thomas is Manager of Electric Transmission System Protection Engineering at Dominion Energy Virginia. Kyle joined Dominion in 2009, and has worked in various roles within Electric Transmission, including System Protection Engineering, Fault Analysis, and Operations Engineering. His areas of focus and responsibility are system protection and control, the integration of renewable energy systems, and the resiliency of transmission and distribution electric grids. Kyle received his B.S. and M.S. degrees in Electrical Engineering from Virginia Tech, in 2009 and 2011 respectively, and is a licensed Professional Engineer in the Commonwealth of Virginia. He is currently pursuing his Ph.D. in Electrical Engineering at the University of Tennessee Knoxville.

IS.2: AEP Challenges, Responses, and Opportunities for Growth
Authors: Jay Ingram
Jay Ingram picture
Representing Author: Jay Ingram
Professional Title: AEP Protection and Control Technical Services - Director
Abstract:

American Electric Power is an exceptionally large utility headquartered in Columbus, Ohio, but serving eleven states. AEP has historically been known for innovation in the Transmission and Distribution fields, and examples will be provided. In a changing energy landscape, AEP faces many challenges to remain an innovation leader, and react to and comply with evolving NERC standards. Examples in microcosm from AEP’s Protection and Control discipline will be used to exemplify these, including challenges in fault analysis, data and measurement, considerations of NERC compliance versus system reliability, and attracting and retaining top engineering talent. There are many conceivable interactions between AEP and academia, such as in the potential development of automated fault analysis in limited form, development of algorithms that provide better distance to fault data, and innovation opportunities in protective relaying. These possibilities will also be discussed.

Bio/Information:

Jay Ingram is from Virginia Beach, Virginia, and attended both the College of William and Mary (B.A., History), and Virginia Tech. Jay graduated from Virginia Tech in December 1999 with a BSEE, and began full-time employment with American Electric Power the following month, starting his career in Fort Wayne, Indiana. Over a twenty-year career with AEP, Jay has served in both Field and Engineering capacities, both the Station Department and the Protection and Control Department, and in three different states. In 2012, Jay returned to Columbus, Ohio, to accept a Supervisory position in the Protection and Control Engineering department, and currently serves as the Director of P&C Technical Services for AEP’s Field organization.

IS.3: As Distributed Energy Resources and Utility Distribution Systems Evolve into Micro-grids, Solving the Complex Challenges of Integration May Be a Key to Improved Service Reliability and Lower Costs
Authors: Robert E. Bisson
Robert E. Bisson picture
Representing Author: Robert E. Bisson
Professional Title: NOVEC - Vice President Electric System Development
Abstract:

Northern Virginia Electric Cooperative (“NOVEC”) is an electric distribution cooperative serving approximately 173,000 customers in parts of six counties located in Northern Virginia. These counties include Fairfax County, Prince William County, Stafford County, Fauquier County and Clarke County which are all considered to be part of the greater metropolitan Washington DC area. NOVEC serves a customer base which include government defense contractors, data centers, offices buildings, federal, state and local governments and government agencies, businesses and homeowners. NOVEC serves customers who are generally affluent and highly educated. This customer base has communicated to NOVEC its desire for NOVEC to provide more renewable energy and more renewable energy related products while at the same time demanding NOVEC continue to maintain highly reliable electric service that is competitively priced. NOVEC believes that renewable distributed energy resources (“DER”) must play a prominent role in meeting these stated customer requirements and believes that the government will ultimately mandate similar requirements. The time is now to begin developing and implementing a strategy to meet much higher levels of DERs than are already in service. Any strategy will require engineers to create new ways and overcome many technical challenges in order to achieve successful integration of additional DERs into the electric distribution system. The challenges to be overcome are numerous. Some of these challenges need to be addressed and solved immediately while others may solve over a longer period.

Bio/Information:

Vice President of Electric System Development in NOVEC, in charge of executive oversight and responsibility in the areas of system engineering and planning, electric transmission and distribution line design and construction management and business Systems. These responsibilities include designing, planning, protecting, and specifying criteria for the electric system. Develop the capital budget and manage capital and operation expenditures for all transmission and distribution lines. Responsible for electric system customer growth forecasts and customer load forecasts and responsible for compliance with NERC reliability standards. Furthermore, he is an Adjunct Faculty at Electric and Computer Engineering Department, George Mason University and Director of operations at Fitchburg Gas and Electric responsible for all gas and electric operations including budget development and oversight in an investor owned utility, and for all activities associated with the design, construction, operation and service restoration of the electric system.

IS.4: Challenges in the Future Electrification Infrastructure
Authors: Zhenyuan Wang
Zhenyuan Wang picture
Representing Author: Zhenyuan Wang
Professional Title: ABB - Department Manager
Abstract:

Electric vehicles (EV) charging infrastructure and data center load is expected to grow significantly in the future grid. How to effectively manage its design and operation is very important to reduce its potentially adverse impact to the grid. This talk will discuss the requirements and challenges, as well as ongoing research in ABB to address them.

Bio/Information:

Dr. Wang graduated from the ECE department of Virginia Tech with a PhD degree in power systems in 2020, and joined ABB. In the past 20 years he has been involved in many research projects, including distribution automation, microgrid, LVDC distribution in buildings and datacenters, MVDC distribution in data centers and ships, cyber-physical security in transmission and distribution systems, charging stations, etc. He is the department manager for Electrical Systems in ABB’s research in Raleigh, NC.

IS.5: Improving the electric distribution network by using Optimal Power Flow
Authors: Keishi Matsuda
Keishi Matsuda picture
Representing Author: Keishi Matsuda
Professional Title: Mitsubishi - Developer and Designer for distribution network systems
Abstract:

There has been a rapid increase in the adoption of photovoltaic power generation systems in Japan. In addition, EVs and Battery are focused to solve energy problems (distribution voltage and current problem). for solving this distribution problems, we developed OPF (Optimal Power Flow) to determine the optimal operational state of the control equipment installed in the power system. By using this OPF calculation method, the voltage/current can be optimized efficiently by controlling the voltage regulating equipment and DERs in combination.

IS.6: SCADA and PMU analytics in power systems
Authors: Yubo Wang
Yubo Wang picture
Representing Author: Yubo Wang
Professional Title: Siemens - Research Scientist
Abstract:

With increasing number of measurement device installed and operating in the fields, we are collecting much more data compared with a decade ago. The question lies in how we utilize the collected data. Unlike many of the data analytics applications popular for internets, power systems are critical infrastructures that tolerate little faulty controls. This presentation tries to answer this question by introducing related cutting-edge researches at Siemens Corporate Technology

Bio/Information:

YUBO WANG received his B.S. in Electrical Engineering from Southeast University, Nanjing, China, in 2011. He received his M.S. in Electrical Engineering and Ph.D. in Mechanical Engineering from University of California, Los Angeles, USA, in 2012 and 2017, respectively. He is a research scientist at Siemens Corporation, Corporate Technology. His research interests include decentralized optimizations and data analytics with applications in power systems and Internet of Things.

IS.7: Autonomous Quantification of Distributed Energy Resource Inverter on Local Electric Power System Characteristics
Authors: Paul Duncan
Paul Duncan picture
Representing Author: Paul Duncan
Professional Title: MPR - Practice Leader, Energy Storage and Grid Modernization
Abstract:

The transformative shift away from centralized generation to localized distributed generation using inverter-interconnected resources has had a profound impact on local electric power system (EPS) characteristics. For low-penetration inverter-based distributed energy resource (DER) systems the impact is often negligible, but as high penetration solar, energy storage, and other types of DER increase, the (often undesirable) ability to influence secondary and primary voltage increase. A new type of functionality, as well as new type of analysis tools are required that are an intrinsic component of inverter-based systems so that the efficacy of the DER can be determined in a standardized manner, e.g. at the time of interconnection and commissioning as well as periodically during normal maturation, so that its influence on dynamic operation of the interconnection can be assessed.

Bio/Information:

Paul Duncan graduated in 1993 from Virginia Polytechnic Institute and State University, Blacksburg, VA, with a bachelor’s degree in Electrical and Computer Engineering, with concentrations in optics and power electronics. He is currently employed by MPR Associates, Inc., Alexandria, VA, where he leads the Grid Modernization practice, and is focused on all aspects of reliably integrating renewables and energy storage into utility operations. His functional expertise includes substation- and behind-the-meter-scale energy storage, distributed energy resource (DER) assets and their management systems (DERMS), development of microgrid resiliency criteria, and thought leadership surrounding all aspects of electric utility distribution operations. Recent focal points of work include providing leadership to utilities on smart inverters and associated functions, interconnection requirements and how they must evolve in context of energy storage and microgrid requirements, financial quantification of energy storage applications within the utility environment, development and execution of a substation microgrid program, and development of U.S. Dept. of Defense microgrid resiliency requirements. He is currently a contributing member to the U.S. Dept. of Energy’s Advanced Distribution Management System (ADMS) Steering Team, where he provides leadership on the integration of DER into ADMS research. He currently co-leads the New York Joint Utilities Smart Inverter Working Group, facilitating the establishment of updated interconnection standards and smart inverter requirements for interconnected DER. Mr. Duncan was appointed in July 2018 by Governor Ralph Northam to serve on Virginia’s Solar Energy Development and Energy Storage Authority, where he currently advises the Commonwealth on renewable energy and energy storage integration. Mr. Duncan is a contributing member to various IEEE standards groups including IEEE P1547.x, ICAP for IEEE 2030.5, and IEEE P1679. He currently holds 9 patents and is a recipient of a R&D 100 award.

IF: Industry Student Forum

Industry Member - Egston Power
Industry Member - Electronics Concepts, Inc.
Industry Member - GE Aviatian
Industry Member - Hitachi Metals
Industry Member - Moog, Inc.
Industry Member - Plexim
Industry Member - Simplis
Industry Member - Synopsis
Industry Member - TMEIC
Industry Member - VPT, Inc.
Industry Member - Cummins
Industry Member - ANSYS, Inc.
Industry Member - OPAL-RT Technologies
Industry Member - Fuji Electric
Industry Member - NexGen
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