Special Issue on Safety and Reliability of Power Electronics Components and Systems, 2023

Deadline for Submission of Manuscripts: December 15, 2022 (December 30, 2022)
Guest Editor-in-Chief:          Frede Blaabjerg, Aalborg University, Denmark
Guest Co-Editor-in-Chief:    Wu Chen, Southeast University, China
                                             Haoze Luo, Zhejiang University, China

CPSS TPEA Vol.7 No.4 (December 30, 2022)

An Improved Virtual Impedance Control Based Oscillation Suppression Method for MMC DC System

Lei GAO, Huiyuan ZHANG, and Jun XU

Abstract The oscillation phenomenon has detrimental effects on the stable operation of the module multilevel converter (MMC)-based high voltage DC (MMC-HVDC) transmission system. The virtual inductance or resistance control can be used as the oscillation suppression method to limit the system instability. To improve the oscillation suppression effectiveness based on the existing virtual impedance control methods. This paper first analyzes the DC output impedance of the MMC-HVDC system and verify the correctness of the DC output impedance. Then an improved virtual impedance control (IVIC) method is presented based on the traditional virtual resistance control (TVRC) and the phase lag compensation control (PLCC) method. Under the same conditions, the Nyquist stability analysis is presented to verify the MMC system stability can be more improved by using the IVIC method compared with the TVRC and PLCC. In PSCAD/EMTDC, the simulation results verify that the IVIC can suppress the MMC DC system oscillation and can improve the oscillation suppression effectiveness compared with the TVRC and PLCC. The stability analysis and simulation results verify that the proposed IVIC method can help to mitigate the detri-mental effects caused by system instabilities and oscillations.

A Review of Magnetic Core Materials, Core Loss Modeling and Measurements in High-Power High-Frequency Transformers

Zenong LI, Weijian HAN, Zhen XIN, Qing LIU, Jianliang CHEN, and Poh Chiang LOH

Abstract High-frequency transformers (HFTs) are the indispensable component in isolated high-power dc-dc converters which have been the basic building blocks for solid-state transformers. To ensure high efficiency, high power density and high reliability, careful selection, design, modeling and evaluation are necessary for the magnetic core of an HFT. However, due to the nonlinear characteristics and the complex physical mechanism, magnetic cores have always been regarded as the focus and difficulty. This paper systematically reviews magnetic core materials commonly used in HFTs, core loss modeling methods based on classical Steinmetz equation (SE), and advanced core loss measurement techniques. Pros and cons for the magnetic materials, modeling and measurement methods are comprehensively analyzed and summarized to provide a sufficient application insight.

Multiport AC-AC-DC Converter for SNOP With One Medium-Frequency Transformer

Dajun MA, Wu CHEN, Liangcai SHU, Kai HOU, Ruihuang LIU, and Chenyu ZHANG

Abstract With the access of increased renewable energy sources, the conventional AC distribution network is hard to flexibly adjust the line voltage and power flow. Therefore, the soft normally open point (SNOP) is applied to increase the flexibility of AC distribution network. The existing converters for SNOP use many submodules (SMs) and passive components, which have the poor economy. On this basis, a multiport AC-AC-DC converter for SNOP with one medium-frequency transformer (MFT) is proposed in this paper. The proposed multiport AC-AC-DC converter is based on the back-to-back (BTB) cascaded H-bridge (CHB) converter structure, and uses several LC resonant circuits and one MFT to replace the multiple DC-DC converters in the existing BTB CHB converters. Therefore, many SMs and passive components can be saved. Moreover, the voltages at multiple AC and DC ports of proposed multiport AC-AC-DC converter are completely decoupled, and the multiple AC and DC systems can be adjusted independently. The detailed circuit structure, control principle and design procedure of multiport AC-AC-DC converter are introduced in this paper. Finally, the simulation and experimental results verify the effectiveness of multiport AC-AC-DC converter.

High Voltage Gain Bidirectional DC-DC Converters for Supercapacitor Assisted Electric Vehicles: A Review

Ankit Kumar SINGH, Anjanee Kumar MISHRA, Krishna Kumar GUPTA, and Yam P. SIWAKOTI

Abstract Integration of supercapacitor alongwith battery in electric vehicles (EVs) improves the life cycle of the battery. Additionally, supercapacitor supplies or absorbs a large amount of instantaneous power during sudden demand such as acceleration or regenerative braking operation, hence also improve the dynamics of the internal power system. However, a major challenge with supercapacitor is that its terminal voltage is low and varies in a wide range during charging and discharging operation. Thus, a high voltage conversion ratio based bidirectional DC-DC converters are required to connect the lower supercapacitor voltage to higher DC-link voltage. The steep voltage conversion ratio with continuous gain based bidirectional DC-DC converters are an integral part of such applications. Various high gain converters exist in the literature such as isolated, non-isolated, cascaded, switched, flying capacitor, and coupled inductor based DC-DC converters, however all these converters have some limitations in context to high gain/high power applications. Therefore, to understand the development of next-generation high voltage gain bidirectional DC-DC converter, this paper focus to comprehensively review and classify various bidirectional step-up DC-DC converters based on their characteristics and voltage-boosting techniques. Further, practical suitability of the reviewed converters and future research directions in switched capacitor converters in context to EVs are also discussed in detail.

Nonlinear Function Integral Sliding Mode-Based Model Predictive Current Control for PMSM Drives With DC-Bus Voltage Observer

Qingfang TENG, Hongying YANG, and Jie TIAN

Abstract As for permanent magnet synchronous motor (PMSM) drive systems with dc-bus voltage sensor failure, a nonlinear function integral sliding mode (NFISM)-based finite-control-set model predictive current control (FCS MPCC) strategy with sensorless is put forward. In principle, measuring dc-bus voltage of voltage source inverter is vital for PMSM drives to perform FCS MPCC. Aiming at dc-bus voltage sensor unavailable, a new nonlinear extended state observer (ESO) is developed to estimate dc-bus voltage. In the light of load torque disturbance, a modified isokinetic reaching law is proposed and then outer loop NFISM speed regulator is brought forward to heighten the system robustness against load variation and attenuate the chatting level. What’s more, for the sake of decreasing the stator current ripple and improve dynamic response, an inner-loop FCS MPCC scheme is adopted. The proposed NFISM-based FCS MPCC with nonlinear ESO can make PMSM drives have satisfactory speed and torque performance. Compared with PI-based and ISM-based speed regulator, respectively, the proposed NFISM-based one enables FCS MPCC PMSM drive system to have stronger anti-load variation ability and weaker fluctuation. StarSim/Hardware experiments validate the feasibility and effectiveness of the proposed strategy.

The Structure and Its Leakage Inductance Model of Integrated LLC Transformer With Wide Range Value Variation

Qingbin CHEN, Xujia LONG, Yaodong CHEN, Shaohui XU, and Wei CHEN

Abstract The integrated magnetics technology is famous in academic and industrial applications to achieve low profile and high power density of switch-mode power supply (SMPS). The integrated LLC transformer is widely used in LLC converter, where the transformer and resonant inductor are integrated into a magnetic component. However, the value Variation range of leakage inductance of conventional integrated transformer structures is limited due to the low profile and small volume in some planar applications. In this paper, a new integrated LLC transformer structure and its leakage inductance adjustment method are proposed. Based on the two-dimensional equivalent model of the structure, the distribution of the leakage magnetic field and the leakage inductance calculation model of the proposed transformer structure are established. The proposed structure can improve the value variation range of leakage inductance in some special applications and is easily achieved in the planner structure. Finally, the design guideline of the proposed integrated LLC transformer is obtained. Simulation results and prototype experiment results verify the correctness and flexibility of the theoretical analysis.

Multi-resonant DC-DC Converter Based on Switched Capacitor Pre-voltage Reduction

Qi GUO, Xiangjun ZHANG, Yueshi GUAN, Yuhao SUN, Yijie WANG, and Dianguo XU

Abstract This paper proposes a multi-resonant DC-DC converter based on switched capacitor pre-buck. The converter can realize soft switching in the full load range and has good voltage gain characteristics. In order to effectively reduce the voltage stress on the device, the front stage of the converter adopts a stacked structure of switched capacitors. This structure realizes the function of high step-down ratio by pre-stepping the bus voltage. After reasonable parameter design and frequency matching, the third harmonic is superimposed on the high-order resonant link of the latter stage during the energy transmission process. This will significantly reduce the loss of the secondary side rectifier diode and increase the efficiency. This paper introduces the working principle of the converter, proposes a five-element parameter design scheme, and analyzes the parameter dispersion to assist the parameter design scheme to make it more reasonable, and finally conducts experimental verification. A 100 W prototype with 400 V input and 12 V output was built in the laboratory to verify the correctness of the theoretical analysis.

Accurate, Fast and Power Efficient PV Emulator Based on Hybrid Passive and Active Circuits

Habes Ali KHAWALDEH, Mohammad AL-SOEIDAT, Dylan Dah-Chuan LU, and Li LI

Abstract A photovoltaic emulator (PVE) has been proposed based on a physical equivalent photovoltaic cell model. It has fast dynamic performance that is compatible with a real PV system. The PV emulator can analyze and assess PV systems, including maximum power point tracking (MPPT). It is power efficient at the maximum power point. However, it has higher power loss at an open-circuit voltage (OCV). This paper, therefore, presents a hybrid solution using a switching circuit (SC) paralleled with the diode string (DS) to minimize the power loss. The SC consists of a two-switch non-inverting buck-boost dc/dc converter. The DS operates with a low power loss region, i.e., the current source region (CSR) of the I-V curve, in which the SC switches in to replace the DS in the voltage source region (VSR) to minimize power loss of the DS while maintaining the emulator’s circuit operation. The SC handles only a fraction of the rated emulator power and has a much narrower control bandwidth than a pure switching converter-based solution. Experimental results show that in the worst-case scenario, i.e., OCV condition, the efficiency and temperature of the PVE based on DS alone configuration reach 2.8% and 94.2 °C, respectively, as compared to 85.98% and 26.5 °C for the proposed hybrid solution. Under the 30% to 60% insolation change test, the suggested PV emulator lags the actual PV panel by only 3.2 ms, compared to 120 ms lagging for a commercial emulator. Furthermore, the control strategy is implemented to handle the trade-off between thermal and dynamic performances of the proposed solution.

Imbalanced Samples Fault Detection Using GANCNN for Power Inverters

Quan SUN, Fei PENG, Hongsheng LI, Xianghai YU, and Guodong SUN

Abstract Aiming at the problem of incomplete fault types existing in power switches fault detection for three phase inverters, a novel diagnosis method based on generative adversarial network (GAN) and convolutional neural network (CNN) is proposed. Firstly, the phase current is used as the fault-sensitive signal, and the fast Fourier transform (FFT) is performed to obtain the frequency domain features, and the normalization preprocessing is performed. Then, the GAN model is used for confrontation training to generate virtual samples by few real sample characteristics, in order to get balanced samples with different fault modes. Finally, convolutional neural network model is built to complete the power inverter fault diagnosis. The experimental results show that GAN-CNN can effectively improve the diagnosis accuracy and stability in the case of sample imbalance.

An Improved Constant Power Generation Algorithm for Photovoltaic Systems

Tangwu YANG, Xingshuo LI, and Shuye DING

Abstract High penetration of photovoltaic power generation will bring some new challenges to the grid, such as overvoltage and overload. To address these problems, a constant power generation (CPG) algorithm is proposed. However, the conventional CPG algorithm cannot balance tracking speed and accuracy. Therefore, an improved CPG algorithm with rapid tracking speed and high accuracy is proposed in this paper. Finally, the superiority of the algorithm is verified in simulation and experiments.

15 kV SiC MOSFET: An enabling technology for medium voltage solid state transformers

Alex Q. Huang, Qianlai Zhu, Li Wang, and Liqi Zhang

Review of GaN totem-pole bridgeless PFC

Qingyun Huang and Alex Q. Huang

Design for reliability of power electronics for grid-connected photovoltaic systems

Yongheng Yang, Ariya Sangwongwanich, Frede Blaabjerg

The past, present, and future of power electronics integration technology in motor drives

Thomas M. Jahns and Hang Dai

Bidirectional isolated dual-active-bridge (DAB) DC-DC converters using 1.2-kV 400-A SiC-MOSFET dual modules

Hirofumi Akagi, Shin-ichi Kinouchi, and Yuji Miyazaki

Application of GaN devices for 1 kW server power supply with integrated magnetics

Fred C. Lee, Qiang Li, Zhengyang Liu, Yuchen Yang, Chao Fei, and Mingkai Mu

Data center challenges and their power electronics

Philip T. Krein

Review of power semiconductor device reliability for power converters

Bo Wang, Jie Cai, Xiong Du, and Luowei Zhou

Opening the box: Survey of high power density inverter techniques from the little box challenge

Katherine A. Kim, Yu-Chen Liu, Ming-Cheng Chen, and Huang-Jen Chiu

Analysis and cell-level experimental verification of a 25 kW all-SiC isolated front end 6.6 kV/400 V AC-DC solid-state transformer

Jonas E. Huber, Julian Böhler, Daniel Rothmund, and Johann W. Kolar