电工技术学报  2023, Vol. 38 Issue (6): 1608-1619    DOI: 10.19595/j.cnki.1000-6753.tces.211734
电力电子 |
级联H桥变换器IGBT开路故障分析与冗余方法研究
赵楠, 郑泽东, 刘建伟, 李驰, 李永东
电力系统及大型发电设备安全控制和仿真国家重点实验室(清华大学电机工程与应用电子技术系)北京 100084
IGBT Open-Circuit Fault Analysis and Fault-Tolerant Method for Cascaded H-Bridge Converter
Zhao Nan, Zheng Zedong, Liu Jianwei, Li Chi, Li Yongdong
State Key Laboratory of Power System and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing 100084 China
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摘要 级联H桥变换器包含了大量的开关器件,往往面临严峻的可靠性问题。该文从电路特性和调制过程两方面对级联H桥变换器IGBT开路故障的影响规律进行分析,并提出一种基于调制重构的级联H桥变换器IGBT故障冗余方法。该故障冗余方法通过重构变换器调制过程,使H桥从故障中恢复运行,且发生开路故障的单元依然具有部分功率传输能力,提高了级联H桥变换器开路故障的处理能力。
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关键词 级联H桥变换器开路故障分析冗余方法调制重构    
Abstract:Cascaded H-bridge (CHB) converters are a type of common topology for high-voltage high-power power conversion and reliability, especially fault tolerant control, is a key issue because a CHB converter consists of many converter submodules and power devices. There are two levels of fault tolerant control for CHB converters, namely system level, which makes use of redundant or hot standby converter submodules, and converter level, that enhances the fault-tolerant performances for a converter submodule. The system level control usually bypasses faulty submodules completely and needs extra components which introduce increased costs and decreased efficiency, and thus the converter level control is also important to enhance the fault tolerant performance of one submodule before being bypassed. This paper focuses on the converter level and proposes a modulation reconstruction method to output reduced power for H-bridge submodules with open-circuited power switches, which requires no additional redundant switches or changes in topology.
For open-circuit faults in a H-bridge, it is found and analyzed that one open-circuit switches only affects its corresponding output voltage in half of a line cycle, either positive or negative, depending on whether upper or lower switches are open-circuited and on the polarity of its current. In the affected half line cycle, the faulty H-bridge can only output half of its nominal voltage with a dc offset of half of its dc bus voltage, which will result in distortion in the output current. In the other half of a line cycle, the faulty H-bridge can operate like normal H-bridges. It is possible to modulate the faulty H-bridge to work in the unaffected half line cycle and to be bypassed in the other half, instead of bypassing the H-bridge at all times. Thus, a modulation method is proposed to enhance the power transfer capability of a CHB converter with faulty H-bridge submodules, based on which switch is open-circuited and the polarity of the current, and the modulation waveforms for the faulty and other healthy H-bridges are updated every half of the line cycle accordingly. In the unaffected half of the line cycle, every H-bridge submodule acts like normal conditions, and then in the other half of the line cycle, the faulty H-bridge submodule output zero voltage and the healthy H-bridge submodules output an increased voltage to compensate the voltage loss of the faulty H-bridge with adjusted phase shifts. As such, the faulty H-bridge submodule can still transfer power half of the time, and the power transfer capability for the CHB converter is increased from (n-1)P to 2(n-1)/(2n-1)P, if only one submodule is faulty, where n is the total number of submodules and P is the nominal power of one submodule.
The proposed method was validated in both simulation and experiment, using a 5-level CHB converter. After making one of the power switches in one H-bridge submodule faulty on purpose, the output voltage and current of the CHB converter were distorted and the dc bus voltages of each H-bridge submodule showed abnormal fluctuations. When applying the proposed modulation method, the CHB converter could output sinusoidal current again, although less than normal conditions, and the dc bus voltages were regulated stably. As such, the faulty module can still transfer certain power and the stable operation of cascaded H-bridge converter can be effectively maintained.
Key wordsCascaded H-bridge converter    open-circuit fault analysis    fault-tolerant method    modulation reconstruction   
收稿日期: 2021-10-29     
PACS: TM461  
基金资助:广东省重点领域研发计划资助项目(2020B0909030003)
通讯作者: 郑泽东 男,1980年生,教授,博士生导师,研究方向为交流电机控制、电力电子变压器、多电平电力电子变换器、机车牵引与船舶推进。E-mail:zzd@tsinghua.edu.cn   
作者简介: 赵 楠 男,1991年生,博士,研究方向为电力电子变压器、储能变换器、V2G双向充电桩。E-mail:zhaon_2020@tsinghua.org.cn
引用本文:   
赵楠, 郑泽东, 刘建伟, 李驰, 李永东. 级联H桥变换器IGBT开路故障分析与冗余方法研究[J]. 电工技术学报, 2023, 38(6): 1608-1619. Zhao Nan, Zheng Zedong, Liu Jianwei, Li Chi, Li Yongdong. IGBT Open-Circuit Fault Analysis and Fault-Tolerant Method for Cascaded H-Bridge Converter. Transactions of China Electrotechnical Society, 2023, 38(6): 1608-1619.
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