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CPSS TPEA Vol.8 No.1 (March 30, 2023)

Editorial

Editorial for the Special Issue on Safety and Reliability of Power Electronics Components and Systems

F. Blaabjerg, W. Chen, and H. Luo

Efficiency and power density have been widely concerned with the development of power electronics, while the safety and reliability issues are attracting more and more attention in a few years due to the increasingly stringent safety requirements, e.g., in electric vehicle, consumer electronics, and aerospace industries. To understand the failure mechanisms and the safe operation area of components/systems in practical applications, comprehensive testing methods considering the operating conditions are becoming essential. Besides accelerated aging tests, multi-physics modeling, physics-of-failure analyses, degradation modeling, electro-thermal simulation, and lifetime assessment contribute to a better understanding of the failure roots in components and systems and the design of a safer system. Moreover, designing condition monitoring and health status estimation tools, fault diagnosis, fault tolerance, and active thermal management techniques help to realize the predictive maintenance of power electronic components and systems. Finally, emerging artificial intelligence (AI) and machine learning (ML) techniques are getting a lot of attention in aging data processing, remaining useful life estimation, etc. Correspondingly, we organized this Special Issue on Safety and Reliability of Power Electronics Components and Systems to collect emerging research achievements within the scope of safety and reliability of power electronics components and systems and circuits.

Special Issue Papers

Synthetical Thermal Modeling and Optimization Design for High Power Density Inverter Heat Dissipation       

K. Dai, J. Gong, W. Lin, S. Pan, and X. Zha

Abstract Demanding accuracy and reliability of thermal design for high efficiency and high-power density inverter devices. Integrating heat conduction, convection heat transfer and fluid dynamics theories, a synthetical thermal model based on the characteristic length as the square root of the cross-sectional area and a multi-objective optimization method based on entropy yield minimization theory and electrothermal coupling are proposed for a typical forced air-cooling heatsink system to improve the efficiency of design optimizations in the structure and cost. The fin thickness, fin length, number of fins, and air velocity of the heat-sink are used as design variables, and the NSGA-III algorithm applying a prophet population is used to obtain the pareto fronts with minimum thermal resistance, cost and pressure loss as optimization objectives. Enhanced airflow through the heatsink by arranging the columns in a phyllotactic pattern. A temperature rise test by a 100 V/10 kW prototype was designed to prove the accuracy of the model proposed and heatsink optimized. At rated power, the surface temperature of power devices and heatsink has 10 °C reduction.

Parameter Shift Prediction of Planar Transformer Based on Bi-LSTM Algorithm  

Y. Chen, Z. Shen, Z. Xu, L. Jin, and W. Chen

Abstract The reliability issues of magnetic elements become more and more prominent with the wide-range application of high-power-density power electronics. Normally, high-frequency planar transformers take up above 30% of the weight and volume of the converter. They suffer various reliability stresses, such as high operating temperature and high-frequency voltages, which can lead to parameter degradations and even failure during operation. To achieve a reliability-oriented design and minimal lifetime maintenance cost of the high-power-density converter, the lifetime prediction of planar magnetics is essential. This paper proposes a method to predict the parameter of planar transformers under thermal reliability stress using a deep learning algorithm. A deep learning neural network is established using the existing parameter shift data in the accelerated aging test. Then, based on the Bi-LSTM model, the future parameter shift of the planar transformer is predicted. Finally, multiple methods are compared to show the advantage of the proposed method. Compared with the conventional curve fitting method, the deep learning algorithm is more suitable for lifetime prediction in terms of filtering data, considering the weight factor, and predicting future change trends.

An Online On-State Voltage Measurement Circuit With Series Diode Clamp for SiC MOSFETs   

Y. Duan, J. Kang, Y. Shi, and Z. Xin

Abstract The condition monitoring of SiC MOSFETs is significant for the reliability of the power electronic system. The on-state drain-source voltage (V_DS-on) of SiC MOSFETs contains the temperature information and reflects the health state. It is essential information for the junction temperature monitoring, loss calculation, and health state evaluation of SiC MOSFETs. A measurement circuit with a voltage clamp branch is proposed in this paper to solve the problems of large errors, complex structure, and low reliability of traditional V_DS-on measurement circuits. The proposed circuit uses several series diodes as the clamp branch, and the voltage peak of the input circuit is suppressed by setting a reverse parallel fast recovery diode. Simulation and experimental results show that the proposed circuit has high accuracy and reliability. Combined with the offline calibration of the linear relationship between V_DS-on and junction temperature, the proposed circuit can be used for the online monitoring of the junction temperature of SiC MOSFETs. Lastly, the optical fiber temperature sensor is used to verify the measurement results of the proposed circuit for junction temperature monitoring, which shows that the proposed circuit is highly accurate and feasible for junction temperature monitoring.

Research on the Influence of Signal Sampling Frequency on Soft Fault Diagnosis Accuracy of DC/DC Converters  

J. Miao, Y. Liu, Q. Yin, G. Zhang, and Y. Yuan

Abstract As a key component of power system, DC/DC converter needs to operate normally. Related DC/DC converter fault diagnosis technology has been widely proposed, among which the output voltage is often used to indicate the health status of the converter system. This paper mainly studies the influence of various sampling frequencies of output voltage on soft fault diagnosis accuracy of DC/DC converters. A buck converter is used as an example, and its output voltage signal is collected at different frequencies. Based on the obtained output voltage samples, various machine learning models are applied to diagnose converter soft faults. The diagnosis accuracy of these models under different output voltage sampling frequencies is studied. The appropriate sampling frequency of the models is investigated. This research provides a reference for the selection of signal sampling frequency for soft fault diagnosis of DC/DC converters in practical engineering applications, because the implementation cost of high-frequency sampling circuits may be high.

Implementation of an Electro-Thermal Model for Junction Temperature Estimation in a SiC MOSFET Based DC/DC Converter

D. Nayak and S. Pramanick

Abstract The junction temperature T_j is an essential indicator for evaluating the thermal stress and the health of the power semiconductor devices. However, direct measurement of T_j is not practical, and indirect non-invasive methods require substantial effort in building the sensing circuits which measure the T_j from the temperature-sensitive electrical parameters (TSEP) of the power devices. Hence, this paper proposes a simulation-based electro-thermal junction temperature T_j assessment method for the SiC MOSFETs in a half-bridge configuration based on the datasheet parameters. The proposed method estimates the MOS-FETs’ instantaneous power loss, including the gate driver parameters, impact of circuit parasitics and temperature-dependent reverse-recovery loss for different operating conditions. The power loss is then incorporated into a simple Foster-based thermal model to estimate the T_j. The effectiveness of the proposed method has been validated by comparing its results with the conventional and TSEP estimation techniques on a 10 kW three-phase interleaved boost converter (IBC) laboratory prototype.

A Novel Calculation Method for IGBT Junction Temperature Based on Fourier Transform

Z. Xu, Y. Zhang, H. Wang, X. Ge, Y. Liao, and B. Yao

Abstract Fast and accurate calculation of junction temperature is attractive for reliability evaluation of insulated gate bipolar transistor (IGBT) module. However, in most of existing methods, a trade-off between calculation accuracy and computational burden should be made. Considering this, a fast junction temperature calculation method based on the Fourier transform is proposed in this paper, which has the ability of maintaining an acceptable accuracy. In this method, the Fourier transform is applied in the instantaneous phase current, and the current is expressed by continuous Fourier components. Then, the power loss of the IGBT module is quantified with a description of temporal and continuous. With the assistance of the thermal network model, the dynamics of junction temperature within a fundamental period are expressed analytically. Finally, the effectiveness of the proposed junction temperature calculation method is verified through extensive simulations and experimental tests.

Regular Papers

An Enhanced Rotating Vector-Based Direct Torque Control for Matrix Converter-Fed PMSM Drives Using Virtual Pulsating Vectors  

W. Deng, J. Tang, and W. Cheng

Abstract Matrix converter (MC) rotating vectors (RVs) have the natural advantage for common-mode voltage (CMV) minimization, but it is rather complicated to establish the switching table with RVs in a direct torque control (DTC) strategy for motor drive systems. Moreover, the conventional RV-based MC-DTC has limited practical application, as it suffers from increased torque ripple and current distortion. A novel MC-DTC method using RVs is proposed in this paper, which breaks down the compromise between minimization of CMV and performance of torque and current. Two RVs that rotate in opposite directions are employed to synthesize a virtual vector. These virtual vectors are pulsating in a fixed line and are evenly distributed in the vector plane. Therefore, the switching table with virtual pulsating vectors can be established conveniently. The proposed method can not only eliminate common-mode voltage, but also improvethe torque and current steady state performances evidently compared with the existing rotating vector-based method. Experiments are carried out and the advantage of the proposed method is verified.

Small Signal Modeling and Interaction Analysis of Multi-VSCs System Connected to Weak Grid  

Y. Huang, F. Chen, D. Wang, S. Zhang, G. Zhu, and K. Zhou

Abstract This paper studies the modeling and interaction of the multi-VSCs (VSC, voltage source converter) system connected to the weak grid. To start with, the small-signal model of the multi-VSCs in DC voltage timescale in the weak grid is established based on the dynamic characteristics analysis method. Self-impact components and interaction-impact components are proposed to define the interaction between multi-VSCs. Furthermore, by studying the self-impact and interaction-impact components of each VSC with varied grid strengths, phase-locked loop bandwidths and terminal voltage control bandwidths, the influence mechanism of control systems on the interaction among VSCs is revealed out. Finally, detailed time-domain simulation and semi-physical models are built in Matlab/Simulink and Starsim respectively to verify the results of the multi-VSCs interaction analysis.

Random PWM Selective Harmonic Elimination Method With Master-Slave Mode for Seven-Level MPUC Inverter

G. Li, Z. Wu, D. Cao, and J. Li

Abstract A random pulse width modulation (PWM) selective harmonic elimination method with master-slave mode for seven-level modified packed U-cells (MPUC) inverter based on cell division is proposed. In this method, a U-cell in the multilevel MPUC inverter is regarded as a basic cell. And then the multilevel MPUC inverter is regarded as the result of series connection of several basic cells. Firstly, the random pulse width modulation (RPWM) selective harmonic elimination is realized in one basic cell, and the coordinated control among the cells is realized by using the carrier stacking strategy. If the specific harmonic does not appear in the output voltage of each cell, it will not appear in the total voltage after addition. The master-slave mode in RPWM selective harmonic elimination method is proposed in the process of coordinated control of series connected cells. That is, the main cell is mainly used to selectively eliminate specific sub harmonics, and the slave cell is mainly used to control the output of fundamental power, so as to solve the problem that the inverter output level is unnecessary to flip in the traditional method, and reduce the out-put harmonic distortion.

Quantitative Analysis Method Based on Frequency Domain RGA for Coupling Degree of Parallel Converters

Z. Zhao, B. Zhang, Z. Sun, L. Zhang, Y. Wang, and Y. Li

Abstract When LCL-type converters operate in parallel to increase system transmission capacity, the coupling will be generated by the difference of parameters, synchronization control and the change of grid impedance, which will reduce the cohesiveness of a single converter. The coupling analysis method based on the relative gain array (RGA) in the frequency domain is proposed in this paper to reveal the coupling mechanism of parallel converters. The transfer function model of the LCL-type converter with an active damping control loop is established. A high-order network matrix under multi-machine operating conditions is constructed based on the analysis of the impedance characteristics of a single converter. Combined with the principle of relative gain, the RGA model of parallel converters is established. And the main risk factors affecting the coupling characteristics of the parallel converter are quantitatively analyzed. Finally, the proposed analysis method is validated by simulation and experimental analysis. The proposed analytical method that can quantitatively analyze the coupling degree and reveal the coupling mechanism of parallel converters, which provides a theoretical basis for the optimization of the software and hardware parameters.

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