Fei Xue | North Carolina State University (original) (raw)

Papers by Fei Xue

2015 IEEE 3rd Workshop on Wide Bandgap Power Devices and Applications (WiPDA), 2015

High conversion efficiency is always desired in energy storage device (ESD). In this work a high ... more 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.

—This paper presents a distributed energy storage device (DESD) based on a novel isolated bidirec... more —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.

This paper focuses on the design and control of a stationary energy storage system based on multi... more 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.

This paper presents a distributed energy storage device (DESD) based on a novel isolated bidirect... more 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.

This paper focuses on the design and control of a stationary energy storage system based on multi... more 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.

The paper presented a new energy storage device based on low-voltage (12.8V) Li-ion battery pack ... more 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.

This paper presents a high efficiency, low-cost bidirectional isolated dc–dc converter for distri... more 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.

2015 IEEE 3rd Workshop on Wide Bandgap Power Devices and Applications (WiPDA), 2015

High conversion efficiency is always desired in energy storage device (ESD). In this work a high ... more 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.

—This paper presents a distributed energy storage device (DESD) based on a novel isolated bidirec... more —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.

This paper focuses on the design and control of a stationary energy storage system based on multi... more 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.

This paper presents a distributed energy storage device (DESD) based on a novel isolated bidirect... more 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.

This paper focuses on the design and control of a stationary energy storage system based on multi... more 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.

The paper presented a new energy storage device based on low-voltage (12.8V) Li-ion battery pack ... more 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.

This paper presents a high efficiency, low-cost bidirectional isolated dc–dc converter for distri... more 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.