@article{xue_yu_huang_2021, title={A Family of Ultrahigh Efficiency Fractional dc-dc Topologies for High Power Energy Storage Device}, volume={9}, ISSN={["2168-6785"]}, DOI={10.1109/JESTPE.2020.2966177}, abstractNote={The application of a nonisolated bidirectional fractional dc–dc topology is proposed for high power energy storage device in this article. The proposed topology has the benefits of ultrahigh efficiency, simple structure, and low cost because it processes only a fractional of the total power. With the existence of an extra-low voltage (LV) power source, the converter voltage stress is only the difference between the dc bus and high voltage (HV) power source, therefore, low-cost LV transistors can be used in HV high power applications. Since a majority of the power is transferred directly between the energy storage device and dc bus, ultrahigh system efficiency can be achieved. Converter operating principle and design considerations such as battery capacity calculation methodologies and over voltage protection (OVP) are presented. A GaN transistor-based prototype is fabricated. Experimental results of a 1.2-kW battery energy storage prototype are presented to validate the analysis. The system efficiency is higher than 99% when a wide input–output voltage range is achieved. The fractional converter is convincing in achieving high efficiency and high conversion power with reduced cost for energy storage devices.}, number={2}, journal={IEEE JOURNAL OF EMERGING AND SELECTED TOPICS IN POWER ELECTRONICS}, author={Xue, Fei and Yu, Ruiyang and Huang, Alex}, year={2021}, month={Apr}, pages={1420–1427} }
 @article{huang_huang_yu_liu_yu_2019, title={High-Efficiency and High-Density Single-Phase Dual-Mode Cascaded Buck-Boost Multilevel Transformerless PV Inverter With GaN AC Switches}, volume={34}, ISSN={["1941-0107"]}, DOI={10.1109/TPEL.2018.2878586}, abstractNote={This paper introduces a high-efficiency and high-density single-phase dual-mode cascaded buck–boost multilevel transformerless photovoltaic (PV) inverter for residential application. This inverter topology combines a regulated cascaded H-bridge multilevel inverter stage with an unregulated GaN-based ac boost converter. The cascaded H-bridge inverter and the ac boost share a common inductor. Compared with the traditional cascaded H-bridge PV inverter, this topology significantly enlarges the input voltage range due to the additional ac boost. And, a flexible number of PV panels can be used. To control the multiple dc-link PV voltages and to reduce the switching loss of the ac boost, this paper further introduces a dual-mode operation. The two modes are buck mode and buck–boost mode. To maximize the utilizations of the dc-link voltages, this paper presents a minimized ac boost duty-cycle generation strategy with feedforward. Then, a dual-mode modulation based on the boost feedforward duty-cycle generation is introduced. This paper also uses an indirect current control for this inverter, since the ac boost is an unregulated stage. The ac boost stage is implemented with two interleaved phases and the ac switches based on the 650-V E-mode GaN FETs. Finally, an 8-port 2-kW prototype based on this topology is developed and demonstrated. Compared with the state-of-the-art microinverter-based 2-kW PV inverter system, the developed inverter prototype achieves 40% reduction of the total power loss, 25% improvement of the power density, 37.5% reduction of the power connectors, 50% reduction of the device count, and 87.5% reduction of the main magnetic count. Operating with natural convection cooling, this PV inverter achieves 98.0% efficiency at 60% of load and 97.8% efficiency at full load. The power density of the packaged PV inverter is 5.8 W/in3.}, number={8}, journal={IEEE TRANSACTIONS ON POWER ELECTRONICS}, author={Huang, Qingyun and Huang, Alex Q. and Yu, Ruiyang and Liu, Pengkun and Yu, Wensong}, year={2019}, month={Aug}, pages={7474–7488} }
 @article{xue_yu_huang_2017, title={A 98.3% Efficient GaN Isolated Bidirectional DC-DC Converter for DC Microgrid Energy Storage System Applications}, volume={64}, ISSN={["1557-9948"]}, DOI={10.1109/tie.2017.2686307}, abstractNote={This paper presents a novel 400 to 12 V isolated bidirectional dc–dc converter based on a phase-shift-controlled-modified dual-active-bridge power stage. The proposed converter consists of a half-bridge and center tap with active clamp circuit, which has promising performance for low-voltage high-current applications. 650 V gallium-nitride high electron mobility transistors are used on the high voltage side to avoid issues encountered using Si superjunction MOSFETs in phase-shift-controlled-bidirectional power conversions. The operation principle and power transfer characteristic are obtained based on a time-domain analysis of the inductor current. Design methodology and criteria and converter's efficiency analysis are discussed. Both the analysis and experiments verify that the proposed converter is capable of achieving low power loss and high power density in soft-switching and hard-switching modes. Experimental results are presented for a 1-kW, 400 V-to-12 V dc–dc prototype converter operating at 100 kHz switching frequency. A power density of 30 W/in3  and a peak efficiency of 98.3% in a wide input/output voltage range are achieved.}, number={11}, journal={IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS}, author={Xue, Fei and Yu, Ruiyang and Huang, Alex Q.}, year={2017}, month={Nov}, pages={9094–9103} }
 @inproceedings{huang_yu_huang_yu_2017, title={Adaptive zero-voltage-switching control and hybrid current control for high efficiency GaN-based MHz totem-pole PFC rectifier}, DOI={10.1109/apec.2017.7930937}, abstractNote={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.}, booktitle={2017 thirty second annual ieee applied power electronics conference and exposition (apec)}, author={Huang, Q. Y. and Yu, R. Y. and Huang, A. Q. and Yu, Wensong}, year={2017}, pages={1763–1770} }
 @inproceedings{guo_liu_yu_zhang_huang_2016, title={Analysis and loss comparison of megahertz high voltage isolated dc/dc converters utilizing integrated sic mosfet module}, DOI={10.1109/wipda.2016.7799955}, abstractNote={Silicon Carbide (SiC) MOSFETs are being increasingly utilized in medium and high power electronics converters (>1 kW) because of the significantly lower switching and conduction losses when compared with conventional power switches such as the Si IGBT. SiC MOSFET based converters operating at high frequency can achieve high efficiency and high power density at the same time. Minimum switching loss can be achieved in the SiC MOSFET with carefully designed gate driving condition and DC link layout, such as the integrated SiC MOSFET module discussed in this paper. Multi-megahertz switching frequency could be realized by the proposed SiC MOSFET module with proper soft switching topology. This paper analyzes three isolated DC/DC converters, namely the asymmetrical half bridge converter, phase shift full bridge converter, and LLC resonant converter. The loss model of the SiC MOSFET is developed and utilized in the analysis. Comparisons are carried out from the device loss and soft switching requirement point of view. The LLC resonant converter is deemed more suitable for multi-megahertz application. A 4.5 kW 1.2 MHz LLC resonant converter prototype is developed and it demonstrates a peak efficiency of 97% at 4 kW.}, booktitle={2016 IEEE 4th Workshop on Wide Bandgap Power Devices and Applications (wipda)}, author={Guo, S. X. and Liu, P. K. and Yu, R. Y. and Zhang, L. Q. and Huang, A. Q.}, year={2016}, pages={291–296} }
 @inproceedings{xue_yu_huang_2016, title={Design considerations of an isolated GaN bidirectional DC-DC converter}, DOI={10.1109/ecce.2016.7855016}, abstractNote={This paper investigates three design considerations of a novel bidirectional dc-dc converter for distributed energy storage device. They are the layout for minimum loop inductance and heat dissipation, gate drive power supply for high side Gallium-Nitride (GaN) device and high resolution digital PWM control methodology. The special package of the available GaN devices requires a PCB layout method that takes into account the thermal design as well as the switching loop inductance. Besides, the high dv/dt will introduce a circulating current in the high-side gate drivers and power supplies. This current should be minimized. Furthermore, conventional digital PWM modules is not precise enough for high frequency (usually >50kHz) converter modulation and will cause limited cycle oscillation. A high resolution digital phase-shift modulation scheme is utilized to improve the resolution of the phase-shift control for the 150 kHz converter. In the end, an optimized engineering design method is proposed. The experimental results are analyzed on a 1kW bidirectional dc-dc converter to verify the concepts.}, booktitle={2016 ieee energy conversion congress and exposition (ecce)}, author={Xue, F. and Yu, R. Y. and Huang, A. Q.}, year={2016} }
 @inproceedings{xue_yu_huang_2016, title={Loss analysis of a high efficiency GaN and Si device mixed isolated bidirectional DC-DC converter}, DOI={10.1109/apec.2016.7468399}, abstractNote={High conversion efficiency is always desired in energy storage device (ESD). In this work a high efficiency GaN and Si device mixed isolated bidirectional dc-dc converter is proposed in the distributed ESD application. To optimize the efficiency of the bidirectional half-bridge push-pull active clamp converter over a wide input/output voltage and load range, it is necessary to accurately predict the dissipated power for each power component so as to identify and properly design the heavily loaded components. This paper describes a universal method to predict the power losses of the converter. Loss models are provided to calculate total component losses using the current and voltage information derived from the steady state inductor current calculator. Details of loss breakdown are given. With the presented converter prototype, a top efficiency of 98.3% and an output power of 1 kW in a wide input/output voltage range is achieved. The loss analysis provides valuable information for designing an efficiency optimized converters in the application.}, booktitle={Apec 2016 31st annual ieee applied power electronics conference and exposition}, author={Xue, F. and Yu, R. Y. and Huang, A. Q.}, year={2016}, pages={3677–3683} }
 @inproceedings{xue_yu_yu_huang_du_2015, title={A novel bi-directional DC-DC converter for distributed energy storage device}, DOI={10.1109/apec.2015.7104489}, abstractNote={This paper presents a high efficiency, low-cost bidirectional isolated dc-dc converter for distributed energy storage device (DESD). Derived from dual active bridge (DAB), the proposed converter consists of a half-bridge circuit at high voltage side and a push-pull circuit with active clamp at low voltage side. The proposed topology is attractive in low voltage and high current applications and it also reduces the number of switching transistors such that the cost and complexity are considerably reduced. With single phase-shift control strategy, all the switches operate in zero-voltage switching (ZVS) condition without increasing circuit complexity. Besides, planar transformer is implemented where the low voltage windings consist of PCB trace and external copper foils. A 380V to 12V DC, 500W DESD hardware prototype has been designed, fabricated, and tested. Experimental results verify the validity of the proposed bi-directional converter, which has 97.3% peak efficiency and maintains greater than 92% efficiency over a load range between 100W and 600W.}, booktitle={2015 thirtieth annual ieee applied power electronics conference and exposition (apec 2015)}, author={Xue, F. and Yu, R. Y. and Yu, Wensong and Huang, A. Q. and Du, Y.}, year={2015}, pages={1126–1130} }
 @inproceedings{xue_yu_yu_huang_2015, title={Distributed energy storage device based on a novel bidirectional DC-DC converter with 650V GaN transistors}, DOI={10.1109/pedg.2015.7223038}, abstractNote={This paper presents a distributed energy storage device (DESD) based on a novel isolated bidirectional DC-DC converter with 650V GaN transistors. The device integrates a low-voltage (13.2V) Li-ion battery pack, an embedded bidirectional DC-DC converter and wireless communication system. The three parts are packaged together, thus it can be directly connected to high-voltage (380V) DC grid, enabling a modular approach for battery energy storage systems. Two 650V enhancement mode GaN transistors are used at the high voltage side. Compared with Si device, three improvements can be achieved in the application: expanding the operation range to light load, reducing switching loss and EMI, increasing the total efficiency of charging and discharging operation. The power stage design as well as a loss analysis of GaN is based on a steady state analysis and PSpice simulation. A 400V to 12V DC, 1kW converter for 1kWh DESD prototype is designed, fabricated, and tested. Experimental results verify the validity of the proposed DESD and the performance improved by using GaN transistors.}, booktitle={Ieee international symposium on power electronics for distributed}, author={Xue, F. and Yu, R. Y. and Yu, Wensong and Huang, A. Q.}, year={2015}, pages={369–374} }
 @inproceedings{xue_yu_yu_huang_2015, title={GaN transistor based Bi-directional DC-DC converter for stationary energy storage device for 400V DC microgrid}, DOI={10.1109/icdcm.2015.7152029}, abstractNote={This paper presents a novel GaN transistor based bidirectional isolated DC-DC converter for stationary energy storage device (SESD) for 400V DC microgrid. The improvements achieved in the application includes: first, benefitting from the internal ultra-fast free-wheeling diode, the converter's operation range can be expended to light load conditions (switches operate in hard switching). The light load efficiency can be greatly increased. Second, because of its low switching loss and on state resistance, the heavy load efficiency is increased. Third, the snubber inductor which is indispensable in Si device based converter can now be omitted in the GaN version. The power stage design as well as a loss analysis of GaN is based on a steady state analysis and PSpice simulation. Experimental results are presented for a 500 W bidirectional dc-dc converter prototype.}, booktitle={2015 IEEE First International Conference on DC microgrids (ICDCM)}, author={Xue, F. and Yu, R. Y. and Yu, Wensong and Huang, A. Q.}, year={2015} }
 @inproceedings{xue_yu_guo_yu_huang_2015, title={Loss analysis of GaN Devices in an isolated bidirectional DC-DC converter}, DOI={10.1109/wipda.2015.7369261}, abstractNote={GaN devices have emerged as a possible replacement for silicon devices in various power conversion applications and as an enabler of new applications not previously possible. This paper presents a 600V Gallium-Nitride (GaN) device based isolated bidirectional DC-DC converter applied in battery energy storage systems. Apart from the features of low turn-off loss, low output capacitance and low drain-source on-state resistance, the most salient one in our bidirectional DC-DC converter application is the ultra-fast freewheeling "body diode" that GaN devices have when compared with Si devices. To distinguish the above mentioned performances of GaN from those of the comparable Si devices, a figure of merit for power devices operating in synchronous rectifying mode is proposed. The converter's operating principle is analyzed in steady state. Switching losses of high voltage and low voltage side switches are simulated based on detailed PSpice models. The converter's safe operation area is extended by using GaN device is explained by calculating the loss in hard switching mode. A thermal simulation is conducted to predict its temperature. Experimental results are presented for a 1 kW, 380-to-12 V prototype DC-DC converter, which demonstrate the validity of the analysis and simulation.}, booktitle={WiPDA 2015 3rd IEEE Workshop on Wide Bandgap Power Devices and Applications}, author={Xue, F. and Yu, R. Y. and Guo, S. X. and Yu, Wensong and Huang, A. Q.}, year={2015}, pages={201–205} }
 @inproceedings{hambridge_huang_yu_2015, title={Solid state transformer (SST) as an energy router: Economic dispatch based energy routing strategy}, DOI={10.1109/ecce.2015.7309991}, abstractNote={The Solid State Transformer (SST) is a revolutionary technology being developed by the authors. It has a tremendous number of features, which include power management, fault management and energy management. Its autonomous and distributed power management capability enables large-scale integration of distributed energy resources (DER) into the power grid. Specifically, it supports AC or DC connected Energy Cells: a combination of DERs, energy storage devices and loads. The SST can achieve real-time power flow regulation via the Energy Cell, therefore forming the foundation of its capability to become a real-time Energy Router. This paper introduces an economic based energy routing strategy that utilizes energy storage to reduce consumption of grid power. Predictive photovoltaic and load forecasting are used to optimize charging and discharging of energy storage. This rule-based algorithm is implemented and demonstrated in a SST enabled 380 V DC Energy Cell.}, booktitle={2015 ieee energy conversion congress and exposition (ecce)}, author={Hambridge, S. and Huang, A. Q. and Yu, R. Y.}, year={2015}, pages={2355–2360} }
 @inproceedings{xue_zhao_yu_yu_huang_2015, title={Stationary energy storage system based on modular high voltage battery modules}, DOI={10.1109/icdcm.2015.7152028}, abstractNote={This paper focuses on the design and control of a stationary energy storage system based on multiple modular high voltage battery modules. The system achieves bi-directional power flow directly from 400V dc grid to the 12V battery modules via a bi-directional dc-dc converter with high conversion ratio as an interface. One merit of such a system is its extensibility and scalability for higher power rating for future use by dispatching more battery modules together. A 2kWh energy storage system prototype which is made up by one grid-connected solid state transformer (SST) emulator and two bi-directional dc-dc converters are designed, fabricated and tested. Based on the modified droop control, a double-loop digital control system for the SST emulator and a single-loop digital control system for the dc-dc converter are implemented respectively. At last, experimental results are presented to verify the proposed distributed control strategy.}, booktitle={2015 IEEE First International Conference on DC microgrids (ICDCM)}, author={Xue, F. and Zhao, Y. L. and Yu, R. Y. and Yu, Wensong and Huang, A. Q.}, year={2015} }
 @inproceedings{du_huang_xue_yu_2014, title={A modular integrated Li-ion battery pack with a multi-core based transformer isolated bidirectional DC-DC converter}, DOI={10.1109/epe.2014.6910785}, abstractNote={The paper presented a new energy storage device based on low-voltage (12.8V) Li-ion battery pack with an embedded DC-DC converter. The batteries and converter are packaged together. The integrated battery pack can be directly connected to high-voltage (400V) DC grid, enabling a modular approach for battery energy storage systems.}, booktitle={2014 16th european conference on power electronics and applications (epe'14-ecce europe)}, author={Du, Y. and Huang, A. Q. and Xue, F. and Yu, R. Y.}, year={2014} }