Wensong Yu - Academia.edu (original) (raw)

Papers by Wensong Yu

2022 IEEE Energy Conversion Congress and Exposition (ECCE), Oct 9, 2022

This paper presents an adaptive Zero-Voltage-Switching control (ZVS) method and a hybrid current ... more This paper presents an adaptive Zero-Voltage-Switching control (ZVS) method and a hybrid current control strategy for the GaN-based MHz Totem-pole PFC rectifier. This novel ZVS control achieves the minimum ZVS time margin and maximum switching frequency clamping by adaptively controlling the synchronous rectifier (SR) turn off current. This adaptive SR turn off current control is a unified control strategy based on a proposed unified analytical converter model. The analytical model and the control strategy are applicable for full-range of input voltage and full-range of load for ZVS Totem-pole PFC. In addition, a dual-loop current control strategy is also proposed in this paper. This dual-loop current controller uses the outer average current control loop to directly regulates the inductor average current. The inner current control loop combines the peak current controller and the time based SR turn off current controller. The proposed SR turn off current control for ZVS is adaptively controlled by this time based controller. To verify the proposed ZVS control method and the hybrid current controller, a 1.5kW GaN-based MHz Totem-pole PFC prototype is demonstrated with full-range ZVS, 99% peak efficiency and high quality AC current.

2022 IEEE Applied Power Electronics Conference and Exposition (APEC), Mar 20, 2022

IEEE Journal of Emerging and Selected Topics in Power Electronics, Aug 1, 2022

A three-level bidirectional AC-DC converter with H8 topology is proposed to combine the advantage... more A three-level bidirectional AC-DC converter with H8 topology is proposed to combine the advantages of both neutral-point clamped and flying-capacitor three-level converters for medium voltage AC-DC solid-state transformer applications. The innovative H8 converter features self-balanced capacitor voltage, common-mode voltage elimination, and small capacitance of the flying capacitors. The proposed carrier-based modulation enables the H8 converter to operate under both active and reactive power conditions. A 10 kVA AC-DC converter prototype with 1.7 kV SiC MOSFETs and 3.3 kV SiC diodes verifies the feasibility and advantages of the proposed topology and the modulation method. The capacitance of the flying capacitors in the H8 converter is reduced by 45 times compared to that of the flying-capacitor converters. The H8 converter efficiency is tested up to 99% at 2 kV DC voltage. The proposed H8 converter is suitable for the next-generation PV inverter, grid-forming inverter, MV fast charger, and SST applications.

Energies, Jan 11, 2018

A flexible group battery energy storage system (FGBESS) based on cascaded multilevel converters i... more A flexible group battery energy storage system (FGBESS) based on cascaded multilevel converters is attractive for renewable power generation applications because of its high modularity and high power quality. However, reliability is one of the most important issues and the system may suffer from great financial loss after fault occurs. In this paper, based on conventional fundamental phase shift compensation and third harmonic injection, a hybrid compensation fault-tolerant method is proposed to improve the post-fault performance in the FGBESS. By adjusting initial phase offset and amplitude of injected component, the optimal third harmonic injection is generated in an asymmetric system under each faulty operation. Meanwhile, the optimal redundancy solution under each fault condition is also elaborated comprehensively with a comparison of the presented three fault-tolerant strategies. This takes full advantage of battery utilization and minimizes the loss of energy capacity. Finally, the effectiveness and feasibility of the proposed methods are verified by results obtained from simulations and a 10 kW experimental platform.

IEEE open journal of industry applications, 2023

This work was supported by Texas Instruments Inc.

2022 IEEE Energy Conversion Congress and Exposition (ECCE), Oct 9, 2022

IEEE Conference Proceedings, 2016

Regarded as one of the most successful wide bandgap (WBG) devices, Silicon Carbide (SiC) metal-ox... more Regarded as one of the most successful wide bandgap (WBG) devices, Silicon Carbide (SiC) metal-oxide-semiconductor field-transistors (MOSFETs) are being considered in an increasing number of power electronics applications. One of those applications is the hybrid and electric vehicle (HEV/EV) traction inverters where high-efficiency and high-power density is essential. From the system-level perspective, the gate driver circuit design for such device is challenging considering the device's fast switching speed and compact system structure. This paper presents a low profile (6 mm) isolated bias supply design using commercially available components for the SiC MOSFET modules targeting an HEV/EV traction inverter application. A single chip MAX 13256 (3 mm∗3 mm) is adopted to form the high-frequency link for entire power module gate drive supply. Distributed transformer strategy is highlighted to provide multiple isolated output and compact structure with minimized parasitic capacitance between all the isolation barriers. The featured low profile optimization reduces the parasitic parameters that might deteriorate the system performance for the fast switching WBG devices. Moreover, the open-loop high-frequency link architecture allows easy configuration for customized output voltage level, polarity and higher reliability. A prototype gate driver has been built for 1.2 kV, 50 A SiC six-pack MOSFET power module, and experimental results are presented.

A novel variable frequency variable duty cycle (VFVD) control scheme using off-line digital contr... more A novel variable frequency variable duty cycle (VFVD) control scheme using off-line digital control by only sensing the output voltage is proposed. Designed for a 6 kV 40 kHz series resonant DC-DC converter in solid state transformer application, it realizes cycle-by-cycle resonant current limiting and zero voltage switching (ZVS) at any load condition. According to the state plane analysis, with a certain output voltage, the resonant current can be well controlled by modifying the on-time, and ZVS of the medium voltage (MV) SiC devices can be ensured by adjusting the switching frequency. By sensing the output voltage, a digital controller with off-line lookup table can be easily implemented. Full ZVS together with fast current limiting greatly improves the reliability of the MV medium frequency converter.

2016 IEEE Energy Conversion Congress and Exposition (ECCE), 2016

Regarded as one of the most successful wide bandgap (WBG) devices, Silicon Carbide (SiC) metal-ox... more Regarded as one of the most successful wide bandgap (WBG) devices, Silicon Carbide (SiC) metal-oxide-semiconductor field-transistors (MOSFETs) are being considered in an increasing number of power electronics applications. One of those applications is the hybrid and electric vehicle (HEV/EV) traction inverters where high-efficiency and high-power density is essential. From the system-level perspective, the gate driver circuit design for such device is challenging considering the device's fast switching speed and compact system structure. This paper presents a low profile (6 mm) isolated bias supply design using commercially available components for the SiC MOSFET modules targeting an HEV/EV traction inverter application. A single chip MAX 13256 (3 mm∗3 mm) is adopted to form the high-frequency link for entire power module gate drive supply. Distributed transformer strategy is highlighted to provide multiple isolated output and compact structure with minimized parasitic capacitance between all the isolation barriers. The featured low profile optimization reduces the parasitic parameters that might deteriorate the system performance for the fast switching WBG devices. Moreover, the open-loop high-frequency link architecture allows easy configuration for customized output voltage level, polarity and higher reliability. A prototype gate driver has been built for 1.2 kV, 50 A SiC six-pack MOSFET power module, and experimental results are presented.

2019 IEEE Energy Conversion Congress and Exposition (ECCE), 2019

This paper presents a single-phase five-level AC-DC converter with hybrid three-level and two-lev... more This paper presents a single-phase five-level AC-DC converter with hybrid three-level and two-level legs using space vector modulation for medium-voltage SST application. The hybrid topology combines the low-loss Silicon Carbide (SiC) MOSFET and low-cost IGBT to solve the issues of severe switching-loss of semiconductors, unavailable medium-voltage SiC MOSFET, bulky volume of the inductor and high system cost under medium voltage. The converter reduces the number of active switches and transformers compared to the existing solutions. Moreover, a simple space vector modulation scheme which solves the zero-crossing distortion of presented topology is proposed and verified to realize the smooth transition between switch states for the hybrid topology using a digital signal processor (DSP) instead of FPGA. A 10 kW prototype has been built and verified the topology and modulation scheme.

2019 IEEE 7th Workshop on Wide Bandgap Power Devices and Applications (WiPDA), 2019

Layout strategies focused on commutation loop inductance minimization and decoupling capacitors c... more Layout strategies focused on commutation loop inductance minimization and decoupling capacitors current balancing for high power SiC circuit are investigated in this paper for high power SiC PCB busbar. At the same time, the normal operating current rating of ceramic capacitors have also been considered for fast switching applications. The discussion is based on PCB busbar board, ceramic capacitors, and CREE's 1.2kV/325A SiC power module. The FEA model for the PCB busbar, ceramic capacitors, and the module are built in ANSYS Q3D, so current distribution on capacitors and the loop inductance can be evaluated under different PCB layout strategies. The principle of flux cancelation is implemented to optimize the loop inductance. Meanwhile, the current density through the ceramic capacitors is minimized by increasing the number of capacitors and equally distributing the commutation current on ceramic capacitors that led to normal operating current rating of each ceramic capacitor for a practical 900V and 50kW application. The capacitance between each PCB busbar layer is considered as well to increase the high frequency response capability. Based on the results of simulations and double pulse test, the techniques of minimizing loop inductance and balancing current distribution are verified.

Proceedings of the IEEE, 2021

The transition to electric road transport technologies requires electric traction drive systems t... more The transition to electric road transport technologies requires electric traction drive systems to offer improved performances and capabilities, such as fuel efficiency (in terms of MPGe, i.e., miles per gallon of gasoline-equivalent), extended range, and fast-charging options. The enhanced electrification and transformed mobility are translating to a demand for higher power and more efficient electric traction drive systems that lead to better fuel economy for a given battery charge. To accelerate the mass-market adoption of electrified transportation, the U.S. Department of Energy (DOE), in collaboration with the automotive industry, has announced the technical targets for light-duty electric vehicles (EVs) for 2025. This article discusses the electric drive technology trends for passenger electric and hybrid EVs with commercially available solutions in terms of materials, electric machine and inverter designs, maximum speed, component cooling, power density, and performance. The emerging materials and technologies for power electronics and electric motors are presented, identifying the challenges and opportunities for even more aggressive designs to meet the need for next-generation EVs. Some innovative drive and motor designs with the potential to meet the DOE 2025 targets are also discussed.

IEEE Journal of Emerging and Selected Topics in Power Electronics, 2021

A three-level bidirectional AC-DC converter with H8 topology is proposed to combine the advantage... more A three-level bidirectional AC-DC converter with H8 topology is proposed to combine the advantages of both neutral-point clamped and flying-capacitor three-level converters for medium voltage AC-DC solid-state transformer applications. The innovative H8 converter features self-balanced capacitor voltage, common-mode voltage elimination, and small capacitance of the flying capacitors. The proposed carrier-based modulation enables the H8 converter to operate under both active and reactive power conditions. A 10 kVA AC-DC converter prototype with 1.7 kV SiC MOSFETs and 3.3 kV SiC diodes verifies the feasibility and advantages of the proposed topology and the modulation method. The capacitance of the flying capacitors in the H8 converter is reduced by 45 times compared to that of the flying-capacitor converters. The H8 converter efficiency is tested up to 99% at 2 kV DC voltage. The proposed H8 converter is suitable for the next-generation PV inverter, grid-forming inverter, MV fast charger, and SST applications.

2022 IEEE Energy Conversion Congress and Exposition (ECCE)

IECON 2016 - 42nd Annual Conference of the IEEE Industrial Electronics Society, 2016

This paper discusses the advancements in the development of the medium voltage solid state transf... more This paper discusses the advancements in the development of the medium voltage solid state transformer (SST) based on 15 kV SiC MOSFET and JBS diode. Designed for 7.2 kV single phase distribution grid applications, the medium voltage SST converts high voltage AC to low voltage 240/120V ac. The use of ultra-high voltage SiC devices allows the simplification of the power conversion circuit topology. This paper presents the characteristics of the high voltage SiC MOSFET devices as well as the topology innovations to achieve ultra-efficient SST design. Specifically, three different designs are discussed which utilize three-stage, two-stage and single stage power conversion topologies to achieve the AC to AC conversion.

2022 IEEE Applied Power Electronics Conference and Exposition (APEC)

2020 IEEE Energy Conversion Congress and Exposition (ECCE), 2020

A multi-port converter (MPC) consisting of a grid-forming port, a DC port, and a split-phase-AC p... more A multi-port converter (MPC) consisting of a grid-forming port, a DC port, and a split-phase-AC port is proposed which can be used as building blocks in hybrid AC-DC systems such as community microgrids enabling intra-community and inter-community energy sharing. Commercially available off-the-shelf SiC power modules are used to achieve a modular hardware design for ease of assembly and maintenance. Unified virtual oscillator control (uVOC) is used to enable grid-forming operation. uVOC enables enhanced fault ride-through with fast over-current limiting; furthermore, operation in grid-connected and islanded modes and seamless transition between the two are achieved. Supervisory control and data acquisition (SCADA) with secondary and tertiary level reference dispatch capability is obtained through an integrated cyber node enabled by open-source hardware and software. Experimental results using a full-scale prototype is provided to validate the design. Using a battery energy storage system (BESS) connected at the DC port of the MPC, black-start, islanded and grid-tied operation, unintentional islanding, and grid re-synchronization capabilities are demonstrated.

IEEE Transactions on Industry Applications, 2019

We propose a frequency domain passivity based damping controller combined with predictive current... more We propose a frequency domain passivity based damping controller combined with predictive current control for LCL-filter equipped voltage source converters (VSCs) connected to an arbitrary AC network to achieve passive VSC input admittance almost up to the Nyquist frequency. The controller guarantees resonance damping in the corresponding frequency range irrespective of the network impedance seen by the VSC. Resonant current compensation is added to eliminate the steadystate tracking error and to achieve superior disturbance rejection. We have used impedance based method for the analysis of harmonic resonance instabilities caused by current controllers. The developed passivity based predictive-resonant current controller is analytically shown to stabilize interactions among multi-paralleled VSCs. Resonance damping capability of the proposed method is validated through simulation and hardware experiments.

IEEE Transactions on Power Electronics, 2017

A novel carrier-based unipolar-SPWM-oriented modulation technique with synchronous rectification ... more A novel carrier-based unipolar-SPWM-oriented modulation technique with synchronous rectification for isolated bi-directional single-stage high-frequency-AC (HFAC) link DC-AC converters using SiC MOSFET is presented in this paper. The DC-AC converter is composed of a full-bridge (FB) inverter cascaded with a cycloconverter through a high-frequency transformer. A carrier-based unipolar-SPWM-oriented modulation technique with synchronous rectification is proposed to realize zero-voltage-switching (ZVS) for the FB inverter and zero-current or zero-voltage-switching (ZVS/ZCS) for the cycloconverter in all load ranges, and to suppress the voltage spikes introduced by the transformer leakage inductance as well. In order to increase the switching frequency, efficiency and power density, this paper proposes to utilize SiC MOSFETs for the converter. Synchronous rectification is implemented to further increase the converter efficiency. With the novel modulation technique, there are two switches in the cycloconverter that are continuously on at each interval, which eliminates 1/4 of the switching loss. A simulation model and a 400 VDC to 240 VAC, 1.2 kW prototype have been developed to validate the effectiveness and performance of the proposed unipolar soft-switching modulation technique and SiC converter.

2022 IEEE Energy Conversion Congress and Exposition (ECCE), Oct 9, 2022

This paper presents an adaptive Zero-Voltage-Switching control (ZVS) method and a hybrid current ... more This paper presents an adaptive Zero-Voltage-Switching control (ZVS) method and a hybrid current control strategy for the GaN-based MHz Totem-pole PFC rectifier. This novel ZVS control achieves the minimum ZVS time margin and maximum switching frequency clamping by adaptively controlling the synchronous rectifier (SR) turn off current. This adaptive SR turn off current control is a unified control strategy based on a proposed unified analytical converter model. The analytical model and the control strategy are applicable for full-range of input voltage and full-range of load for ZVS Totem-pole PFC. In addition, a dual-loop current control strategy is also proposed in this paper. This dual-loop current controller uses the outer average current control loop to directly regulates the inductor average current. The inner current control loop combines the peak current controller and the time based SR turn off current controller. The proposed SR turn off current control for ZVS is adaptively controlled by this time based controller. To verify the proposed ZVS control method and the hybrid current controller, a 1.5kW GaN-based MHz Totem-pole PFC prototype is demonstrated with full-range ZVS, 99% peak efficiency and high quality AC current.

2022 IEEE Applied Power Electronics Conference and Exposition (APEC), Mar 20, 2022

IEEE Journal of Emerging and Selected Topics in Power Electronics, Aug 1, 2022

A three-level bidirectional AC-DC converter with H8 topology is proposed to combine the advantage... more A three-level bidirectional AC-DC converter with H8 topology is proposed to combine the advantages of both neutral-point clamped and flying-capacitor three-level converters for medium voltage AC-DC solid-state transformer applications. The innovative H8 converter features self-balanced capacitor voltage, common-mode voltage elimination, and small capacitance of the flying capacitors. The proposed carrier-based modulation enables the H8 converter to operate under both active and reactive power conditions. A 10 kVA AC-DC converter prototype with 1.7 kV SiC MOSFETs and 3.3 kV SiC diodes verifies the feasibility and advantages of the proposed topology and the modulation method. The capacitance of the flying capacitors in the H8 converter is reduced by 45 times compared to that of the flying-capacitor converters. The H8 converter efficiency is tested up to 99% at 2 kV DC voltage. The proposed H8 converter is suitable for the next-generation PV inverter, grid-forming inverter, MV fast charger, and SST applications.

Energies, Jan 11, 2018

A flexible group battery energy storage system (FGBESS) based on cascaded multilevel converters i... more A flexible group battery energy storage system (FGBESS) based on cascaded multilevel converters is attractive for renewable power generation applications because of its high modularity and high power quality. However, reliability is one of the most important issues and the system may suffer from great financial loss after fault occurs. In this paper, based on conventional fundamental phase shift compensation and third harmonic injection, a hybrid compensation fault-tolerant method is proposed to improve the post-fault performance in the FGBESS. By adjusting initial phase offset and amplitude of injected component, the optimal third harmonic injection is generated in an asymmetric system under each faulty operation. Meanwhile, the optimal redundancy solution under each fault condition is also elaborated comprehensively with a comparison of the presented three fault-tolerant strategies. This takes full advantage of battery utilization and minimizes the loss of energy capacity. Finally, the effectiveness and feasibility of the proposed methods are verified by results obtained from simulations and a 10 kW experimental platform.

IEEE open journal of industry applications, 2023

This work was supported by Texas Instruments Inc.

2022 IEEE Energy Conversion Congress and Exposition (ECCE), Oct 9, 2022

IEEE Conference Proceedings, 2016

Regarded as one of the most successful wide bandgap (WBG) devices, Silicon Carbide (SiC) metal-ox... more Regarded as one of the most successful wide bandgap (WBG) devices, Silicon Carbide (SiC) metal-oxide-semiconductor field-transistors (MOSFETs) are being considered in an increasing number of power electronics applications. One of those applications is the hybrid and electric vehicle (HEV/EV) traction inverters where high-efficiency and high-power density is essential. From the system-level perspective, the gate driver circuit design for such device is challenging considering the device's fast switching speed and compact system structure. This paper presents a low profile (6 mm) isolated bias supply design using commercially available components for the SiC MOSFET modules targeting an HEV/EV traction inverter application. A single chip MAX 13256 (3 mm∗3 mm) is adopted to form the high-frequency link for entire power module gate drive supply. Distributed transformer strategy is highlighted to provide multiple isolated output and compact structure with minimized parasitic capacitance between all the isolation barriers. The featured low profile optimization reduces the parasitic parameters that might deteriorate the system performance for the fast switching WBG devices. Moreover, the open-loop high-frequency link architecture allows easy configuration for customized output voltage level, polarity and higher reliability. A prototype gate driver has been built for 1.2 kV, 50 A SiC six-pack MOSFET power module, and experimental results are presented.

A novel variable frequency variable duty cycle (VFVD) control scheme using off-line digital contr... more A novel variable frequency variable duty cycle (VFVD) control scheme using off-line digital control by only sensing the output voltage is proposed. Designed for a 6 kV 40 kHz series resonant DC-DC converter in solid state transformer application, it realizes cycle-by-cycle resonant current limiting and zero voltage switching (ZVS) at any load condition. According to the state plane analysis, with a certain output voltage, the resonant current can be well controlled by modifying the on-time, and ZVS of the medium voltage (MV) SiC devices can be ensured by adjusting the switching frequency. By sensing the output voltage, a digital controller with off-line lookup table can be easily implemented. Full ZVS together with fast current limiting greatly improves the reliability of the MV medium frequency converter.

2016 IEEE Energy Conversion Congress and Exposition (ECCE), 2016

Regarded as one of the most successful wide bandgap (WBG) devices, Silicon Carbide (SiC) metal-ox... more Regarded as one of the most successful wide bandgap (WBG) devices, Silicon Carbide (SiC) metal-oxide-semiconductor field-transistors (MOSFETs) are being considered in an increasing number of power electronics applications. One of those applications is the hybrid and electric vehicle (HEV/EV) traction inverters where high-efficiency and high-power density is essential. From the system-level perspective, the gate driver circuit design for such device is challenging considering the device's fast switching speed and compact system structure. This paper presents a low profile (6 mm) isolated bias supply design using commercially available components for the SiC MOSFET modules targeting an HEV/EV traction inverter application. A single chip MAX 13256 (3 mm∗3 mm) is adopted to form the high-frequency link for entire power module gate drive supply. Distributed transformer strategy is highlighted to provide multiple isolated output and compact structure with minimized parasitic capacitance between all the isolation barriers. The featured low profile optimization reduces the parasitic parameters that might deteriorate the system performance for the fast switching WBG devices. Moreover, the open-loop high-frequency link architecture allows easy configuration for customized output voltage level, polarity and higher reliability. A prototype gate driver has been built for 1.2 kV, 50 A SiC six-pack MOSFET power module, and experimental results are presented.

2019 IEEE Energy Conversion Congress and Exposition (ECCE), 2019

This paper presents a single-phase five-level AC-DC converter with hybrid three-level and two-lev... more This paper presents a single-phase five-level AC-DC converter with hybrid three-level and two-level legs using space vector modulation for medium-voltage SST application. The hybrid topology combines the low-loss Silicon Carbide (SiC) MOSFET and low-cost IGBT to solve the issues of severe switching-loss of semiconductors, unavailable medium-voltage SiC MOSFET, bulky volume of the inductor and high system cost under medium voltage. The converter reduces the number of active switches and transformers compared to the existing solutions. Moreover, a simple space vector modulation scheme which solves the zero-crossing distortion of presented topology is proposed and verified to realize the smooth transition between switch states for the hybrid topology using a digital signal processor (DSP) instead of FPGA. A 10 kW prototype has been built and verified the topology and modulation scheme.

2019 IEEE 7th Workshop on Wide Bandgap Power Devices and Applications (WiPDA), 2019

Layout strategies focused on commutation loop inductance minimization and decoupling capacitors c... more Layout strategies focused on commutation loop inductance minimization and decoupling capacitors current balancing for high power SiC circuit are investigated in this paper for high power SiC PCB busbar. At the same time, the normal operating current rating of ceramic capacitors have also been considered for fast switching applications. The discussion is based on PCB busbar board, ceramic capacitors, and CREE's 1.2kV/325A SiC power module. The FEA model for the PCB busbar, ceramic capacitors, and the module are built in ANSYS Q3D, so current distribution on capacitors and the loop inductance can be evaluated under different PCB layout strategies. The principle of flux cancelation is implemented to optimize the loop inductance. Meanwhile, the current density through the ceramic capacitors is minimized by increasing the number of capacitors and equally distributing the commutation current on ceramic capacitors that led to normal operating current rating of each ceramic capacitor for a practical 900V and 50kW application. The capacitance between each PCB busbar layer is considered as well to increase the high frequency response capability. Based on the results of simulations and double pulse test, the techniques of minimizing loop inductance and balancing current distribution are verified.

Proceedings of the IEEE, 2021

The transition to electric road transport technologies requires electric traction drive systems t... more The transition to electric road transport technologies requires electric traction drive systems to offer improved performances and capabilities, such as fuel efficiency (in terms of MPGe, i.e., miles per gallon of gasoline-equivalent), extended range, and fast-charging options. The enhanced electrification and transformed mobility are translating to a demand for higher power and more efficient electric traction drive systems that lead to better fuel economy for a given battery charge. To accelerate the mass-market adoption of electrified transportation, the U.S. Department of Energy (DOE), in collaboration with the automotive industry, has announced the technical targets for light-duty electric vehicles (EVs) for 2025. This article discusses the electric drive technology trends for passenger electric and hybrid EVs with commercially available solutions in terms of materials, electric machine and inverter designs, maximum speed, component cooling, power density, and performance. The emerging materials and technologies for power electronics and electric motors are presented, identifying the challenges and opportunities for even more aggressive designs to meet the need for next-generation EVs. Some innovative drive and motor designs with the potential to meet the DOE 2025 targets are also discussed.

IEEE Journal of Emerging and Selected Topics in Power Electronics, 2021

A three-level bidirectional AC-DC converter with H8 topology is proposed to combine the advantage... more A three-level bidirectional AC-DC converter with H8 topology is proposed to combine the advantages of both neutral-point clamped and flying-capacitor three-level converters for medium voltage AC-DC solid-state transformer applications. The innovative H8 converter features self-balanced capacitor voltage, common-mode voltage elimination, and small capacitance of the flying capacitors. The proposed carrier-based modulation enables the H8 converter to operate under both active and reactive power conditions. A 10 kVA AC-DC converter prototype with 1.7 kV SiC MOSFETs and 3.3 kV SiC diodes verifies the feasibility and advantages of the proposed topology and the modulation method. The capacitance of the flying capacitors in the H8 converter is reduced by 45 times compared to that of the flying-capacitor converters. The H8 converter efficiency is tested up to 99% at 2 kV DC voltage. The proposed H8 converter is suitable for the next-generation PV inverter, grid-forming inverter, MV fast charger, and SST applications.

2022 IEEE Energy Conversion Congress and Exposition (ECCE)

IECON 2016 - 42nd Annual Conference of the IEEE Industrial Electronics Society, 2016

This paper discusses the advancements in the development of the medium voltage solid state transf... more This paper discusses the advancements in the development of the medium voltage solid state transformer (SST) based on 15 kV SiC MOSFET and JBS diode. Designed for 7.2 kV single phase distribution grid applications, the medium voltage SST converts high voltage AC to low voltage 240/120V ac. The use of ultra-high voltage SiC devices allows the simplification of the power conversion circuit topology. This paper presents the characteristics of the high voltage SiC MOSFET devices as well as the topology innovations to achieve ultra-efficient SST design. Specifically, three different designs are discussed which utilize three-stage, two-stage and single stage power conversion topologies to achieve the AC to AC conversion.

2022 IEEE Applied Power Electronics Conference and Exposition (APEC)

2020 IEEE Energy Conversion Congress and Exposition (ECCE), 2020

A multi-port converter (MPC) consisting of a grid-forming port, a DC port, and a split-phase-AC p... more A multi-port converter (MPC) consisting of a grid-forming port, a DC port, and a split-phase-AC port is proposed which can be used as building blocks in hybrid AC-DC systems such as community microgrids enabling intra-community and inter-community energy sharing. Commercially available off-the-shelf SiC power modules are used to achieve a modular hardware design for ease of assembly and maintenance. Unified virtual oscillator control (uVOC) is used to enable grid-forming operation. uVOC enables enhanced fault ride-through with fast over-current limiting; furthermore, operation in grid-connected and islanded modes and seamless transition between the two are achieved. Supervisory control and data acquisition (SCADA) with secondary and tertiary level reference dispatch capability is obtained through an integrated cyber node enabled by open-source hardware and software. Experimental results using a full-scale prototype is provided to validate the design. Using a battery energy storage system (BESS) connected at the DC port of the MPC, black-start, islanded and grid-tied operation, unintentional islanding, and grid re-synchronization capabilities are demonstrated.

IEEE Transactions on Industry Applications, 2019

We propose a frequency domain passivity based damping controller combined with predictive current... more We propose a frequency domain passivity based damping controller combined with predictive current control for LCL-filter equipped voltage source converters (VSCs) connected to an arbitrary AC network to achieve passive VSC input admittance almost up to the Nyquist frequency. The controller guarantees resonance damping in the corresponding frequency range irrespective of the network impedance seen by the VSC. Resonant current compensation is added to eliminate the steadystate tracking error and to achieve superior disturbance rejection. We have used impedance based method for the analysis of harmonic resonance instabilities caused by current controllers. The developed passivity based predictive-resonant current controller is analytically shown to stabilize interactions among multi-paralleled VSCs. Resonance damping capability of the proposed method is validated through simulation and hardware experiments.

IEEE Transactions on Power Electronics, 2017

A novel carrier-based unipolar-SPWM-oriented modulation technique with synchronous rectification ... more A novel carrier-based unipolar-SPWM-oriented modulation technique with synchronous rectification for isolated bi-directional single-stage high-frequency-AC (HFAC) link DC-AC converters using SiC MOSFET is presented in this paper. The DC-AC converter is composed of a full-bridge (FB) inverter cascaded with a cycloconverter through a high-frequency transformer. A carrier-based unipolar-SPWM-oriented modulation technique with synchronous rectification is proposed to realize zero-voltage-switching (ZVS) for the FB inverter and zero-current or zero-voltage-switching (ZVS/ZCS) for the cycloconverter in all load ranges, and to suppress the voltage spikes introduced by the transformer leakage inductance as well. In order to increase the switching frequency, efficiency and power density, this paper proposes to utilize SiC MOSFETs for the converter. Synchronous rectification is implemented to further increase the converter efficiency. With the novel modulation technique, there are two switches in the cycloconverter that are continuously on at each interval, which eliminates 1/4 of the switching loss. A simulation model and a 400 VDC to 240 VAC, 1.2 kW prototype have been developed to validate the effectiveness and performance of the proposed unipolar soft-switching modulation technique and SiC converter.