Because of the global trends of energy demand increase and decarbonization, developing green energy sources and increasing energy conversion efficiency are recently two of the most urgent topics in energy fields. The requirements for power level and performance of converter systems are continuously growing for the fast development of modern technologies such as the Internet of things (IoT) and Industry 4.0. In this regard, power switching devices based on wide-bandgap (WBG) materials such as silicon carbide (SiC) and gallium nitride (GaN) are fast maturing and expected to greatly benefit power converters with complex switching schemes. In low- and medium-voltage applications, GaN-based high-electron-mobility transistors (HEMTs) are superior to conventional silicon (Si)-based devices in terms of switching frequency, power rating, thermal capability, and efficiency, which are crucial factors to enhance the performance of advanced power converters. Previously published review papers on GaN HEMT technology mainly focused on fabrication, device characteristics, and general applications. To realize the future development trend and potential of applying GaN technology in various converter designs, this paper reviews a total of 162 research papers focusing on GaN HEMT applications in mid- to high-power (over 500 W) converters. Different types of converters including direct current (DC)–DC, alternating current (AC)–DC, and DC–AC conversions with various configurations, switching frequencies, power densities, and system efficiencies are reviewed.

Review of GaN HEMT Applications in Power Converters over 500 W

Because of the time-sharing sampling logic, the three-phase currents reconstructed by single dc-link shunt present significant errors in the permanent magnet synchronous motor drives. A traceback-prediction current correction method for sampled currents is proposed in this article to eliminate the reconstruction errors. According to the analysis of time-sharing sampling errors, the concept of equivalent current change rate during one pulsewidth modulation (PWM) period is introduced, and the phase current characteristic model based on state observer is established. Both the equivalent and instantaneous current change rates can be obtained by the observer-based calculation method. In order to improve the current reconstruction precision, the ultimate values of three-phase currents can be predicted by adopting the proposed traceback-prediction current correction method, which does not require major computation and is easy to implement with no restrictions on the PWM strategy. The effectiveness of the proposed method is verified by experimental results.

Current Reconstruction Considering Time-Sharing Sampling Errors change throughout the running heads

Permanent magnet synchronous motor (PMSM) drives equipped with slim film capacitors have many advantages, including longer lifetime, smaller volume, and lower cost. However, improving the dc-link voltage utilization rate by the typical overmodulation strategy will cause the distortion of the stator voltage and current due to the dc-link voltage fluctuation. In this article, the influence of the dual-mode overmodulation strategy used in the small dc-link capacitor PMSM drive, including the stator voltage distortion and uncontrollable time for entering the six-step operation, is analyzed. A novel overmodulation strategy named as the optimized voltage boundary-based overmodulation strategy is proposed to reduce the distortion of the stator voltage and current. By switching between the actual dc-link voltage and the fixed dc-link voltage used for space vector pulse width modulation (SVPWM), the performance can be improved in the overmodulation region if the value of the dc-link voltage for SVPWM is selected appropriately. Experimental results on a PMSM drive platform are provided to verify the effectiveness of the proposed strategy.

Overmodulation Strategy for Electrolytic Capacitorless PMSM Drives: Voltage Distortion Analysis and Boundary Optimization

Power Factor Correction (PFC) single-phase AC/DC converters are used in several power electronics applications as full wave control rectifiers improving power quality and providing high standards of efficiency. Many papers dealing with the description or use of such topologies have been published in recent years; however, a review that describes and organizes their specific details has not been reported in the technical literature. Therefore, this paper presents an extensive review of PFC single-phase AC/DC converters operating with the Boost converter topology for low and medium voltage as well as and power appliances. A categorization of bridge, semi-bridgeless, and bridgeless, in accordance with the construction characteristics, was carried out in order to unify the technical terminology. Benefits and disadvantages are described and analyzed in detail. Furthermore, a comparison performance in terms of PFC, Total Harmonic Distortion (THD), power capacity, electromagnetic compatibility (EMC), number of elements, and efficiency is included.

PFC Single-Phase AC/DC Boost Converters: Bridge, Semi-Bridgeless, and Bridgeless Topologies

Gallium nitride (GaN) high electron mobility transistor (HEMT) is a promising candidate for the high-density power converter applications. Due to the low switching loss, the GaN HEMT may lead to a new horizon in the applications, such as fast charger, wireless charging, and 5G power amplifier. However, the fast switching speed of GaN HEMT makes it extremely sensitive to parasitic parameters, especially for the low-voltage GaN devices with small packages. Conventional switching loss estimation methods, which are normally based on the calibration fixture or modification of test circuit, cannot be effectively utilized for GaN HEMT. This article presents an accurate switching loss estimation method using the postprocessing technique. The proposed switching loss technique consists of three parts of signal processing, which are the wavelet denoising process to minimize the influence of background noise, the voltage–current ( $ V-I$ ) alignment process to reduce errors from probe propagation delay, and the linear interpolation process for further improvement of alignment accuracy. In addition, a modified SPICE model is proposed to investigate the influence of parasitic parameters on switching losses by the circuit simulation. Based on the theoretical switching characteristics, the switching loss estimation method is finally validated experimentally on a commercial 40-V/10-A GaN HEMT in a double-pulse test.

A Postprocessing-Technique-Based Switching Loss Estimation Method for GaN Devices

The LC resonance between the line inductor and the dc-link film capacitor is an important concern in the reduced dc-link capacitance interior permanent magnet synchronous motor drive system. In this paper, an active damping method based on the virtual damping resistor is applied to suppress the LC resonance and improve the drive system stability. The performance of the damping resistor is analyzed in a systematic level, and possible configurations have been analyzed to obtain the optimal solution, which is proved to be the inductor current feedback (ICF) damping method. In order to realize the equivalent damping effect, the dc-link voltage feedback is applied to emulate the ICF-based active damping method by a step-by-step approach. Meanwhile, the grid voltage distortion will stimulate additional harmonics of the grid current in the reduced dc-link capacitance motor drives. Hence a feedforward compensation method is applied to suppress the grid current distortion arising from the distorted grid voltage, which has not been investigated in the previous related researches. Harmonics of the grid current are reduced and requirements of EN61000-3-2 can be satisfied by applying the proposed method. Experiments on a compressor drive platform equipped with the reduced dc-link capacitance are performed to verify the effectiveness of the proposed method.

Inductor Current Feedback Active Damping Method for Reduced DC-Link Capacitance IPMSM Drives

This paper presents a GaN-based totem-pole bridgeless boost Power-Factor-Correction (PFC) converter for air conditioning applications. Based on the small signal modeling, the power level transfer function of totem-pole bridgeless boost PFC converter is derived by the state-space averaging method. The control strategy of the voltage and the current loops is proposed to meet the design requirement, and the Bode diagram is given to verify the performance of the control strategy. Finally, an 800W GaN-based totem-pole bridgeless boost PFC converter prototype is developed with 98% efficiency and 0.99 input power factor. The effectiveness of the control strategy has been verified.

Totem-Pole Bridgeless Boost PFC Converter Based on GaN HEMT for Air Conditioning Applications

Beat phenomenon is an important concern in the reduced dc-link capacitance motor drive system. In previous research works, the topic is mainly concentrated on the beat phenomenon caused by the interaction of the fluctuated dc-link voltage and the motor phase voltage. In this paper, another form of the beat phenomenon generated by the fluctuated dc-link voltage and the severely fluctuated load torque is investigated. The effect of the beat phenomenon on the grid current and the motor speed is analyzed, which fluctuate with the low-frequency oscillation. In order to improve the drive system performance, a power balancing controller is proposed to suppress the grid current fluctuation, and a resonant controller is utilized to regulate the periodic power signals. Meanwhile, the applied fluctuated torque suppression method could improve the performance of the motor speed, which is only sensitive to the frequency of the fluctuated load torque. Experimental results are provided to verify the effectiveness of the proposed method.

Beat Phenomenon Suppression for Reduced DC-Link Capacitance IPMSM Drives With Fluctuated Load Torque

The invention discloses a damping control method in a non-electrolytic capacitance permanent-magnet synchronous-motor air conditioning drive system and relates to a method for inhibiting resonance inthe built-in permanent-magnet synchronous-motor air conditioning drive system with an aim to solve the problem about resonance generated from interaction of an input side filter and a direct-current bus capacitor of the air conditioning drive system. The damping control method includes: 1), when the permanent-magnet synchronous motor runs, processing direct-current bus voltage by using a band-passfilter and multiplying the direct-current bus voltage by a coefficient K to obtain damping current; 2), performing processing according to the obtained damping current to obtain equivalent damping power and controlling the damping current by controlling the damping power, wherein the expression of the damping power is the damping current multiplied by the direct-current bus voltage; 3), changingoutput power of an inverter to achieve the damping power, generating an extra voltage reference value to have the output power of the inverter changed, and finally, generating an extra voltage commandsignal to have resonance in the system inhibited. The damping control method is applicable to the technical field of motor control.

Damping control method in non-electrolytic capacitance permanent-magnet synchronous-motor air conditioning drive system

Due to the excellent reverse recovery characteristics, gallium nitride high electron mobility transistor (GaN HEMT) is the ideal device for totem-pole bridgeless PFC circuits. However, the driving technology of GaN HEMT deserves to be concerned when working in a complementary conduction mode in a half-bridge circuit. Because of the parasitic parameters, the driving signal may oscillate and even malfunction may occur, hence the device may be damaged. In this paper, the influence of the impedance of the driving circuit and Miller capacitance on the drive circuit is analyzed. Meanwhile, the corresponding solution is given and a feasible drive scheme is proposed. An experiment platform of the totem-pole bridgeless PFC converter is built and experimental results could verify the effectiveness of the proposed drive scheme.

Rongchi Zhang

Papers

Inductor Current Feedback Active Damping Method for Reduced DC-Link Capacitance IPMSM Drives

Totem-Pole Bridgeless Boost PFC Converter Based on GaN HEMT for Air Conditioning Applications

Beat Phenomenon Suppression for Reduced DC-Link Capacitance IPMSM Drives With Fluctuated Load Torque

Damping control method in non-electrolytic capacitance permanent-magnet synchronous-motor air conditioning drive system

GaN HEMT Driving Scheme of Totem-Pole Bridgeless PFC Converter