基于广义电容电压不平衡度的MMC子模块开路故障诊断策略  

Open Circuit Fault Diagnosis Strategy of MMC Sub-Module Based on Generalized Capacitor Voltage Unbalance

作　　者：武鸿 王跃[1] 刘熠 李鹏坤 李润田 Wu Hong;Wang Yue;Liu Yi;Li Pengkun;Li Runtian(State Key Laboratory of Electrical Insulation and Power Equipment Xi’an Jiaotong University,Xi’an,710049 China)

机构地区：[1]电力设备电气绝缘国家重点实验室(西安交通大学),西安710049

出　　处：《电工技术学报》2023年第14期3909-3922,共14页Transactions of China Electrotechnical Society

基　　金：国家电网公司科技资助项目(5100-202156434A-0-0-00)。

摘　　要：模块化多电平换流器(MMC)广泛应用于高压大功率场合。MMC拓扑由大量的子模块(SM)组成,为了提高其运行可靠性,在其SM发生开路故障后,需要快速检测到故障并定位故障SM。现有研究基于经验的阈值设置在不同运行功率间难以推广。针对此,该文提出基于广义电容电压不平衡度的MMC子模块开路故障诊断策略。通过判断桥臂中电容电压最大SM的广义电容电压不平衡度是否超出设定阈值来检测故障,故障定位过程同样是基于该标志。通过理论分析,给出诊断阈值在不同运行功率下的设置方法。所提出的方法可以在不同功率点准确、快速地诊断出MMC子模块开路故障,并降低不同运行功率下阈值设置难度。最后通过硬件在环(HIL)平台验证了该方法的可行性。Modular multilevel converters(MMC)have features of modular construction,redundancy configuration,and power scalability.The MMC topology is composed of a large number of series-connected submodules(SMs),and reliability is one of its important issues.The faults of the insulated gate bipolar transistor(IGBT)can generally be divided into short-circuit faults and open-circuit faults.The short-circuit fault is destructive,but now the gate driver is always integrated with short-circuit protection.In contrast,the open-circuit fault will not immediately damage the SM and may remain undetected for a long time.MMC’s SM open-circuit diagnosis strategy can be divided into hardware-based and software-based categories.The software-based strategies have the advantages of no additional hardware and fast diagnosis time.However,it often requires an empirical threshold,which is difficult to set when the MMC operates at different power.Therefore,an open-circuit fault diagnosis strategy for MMC sub-modules based on generalized capacitor voltage unbalance degree(GCVUD)is proposed.The fault is detected by judging whether the GCVUD of the SM with the largest capacitor voltage in the arm exceeds the threshold.The remaining faulty SMs are located until the GCVUD of one SM is within the threshold according to the capacitor voltage sorting results.Moreover,to further eliminate the effects of errors and prevent fault misdiagnosis situations,a counting flag is used in the detection process and location process.In this strategy,the threshold setting determines the accuracy and rapidity directly.The threshold shall be greater than the GCVUD to ensure no misdiagnosis during normal operation.On the other hand,the threshold shall be less than the minimum of the corresponding GCVUD in the case of two types of open-circuit faults.The type II fault of SM in rectifier mode is selected for setting the diagnostic threshold.The quantitative relationship between the diagnostic threshold and the operating power is given by calculation and deduction.A deta

关 键 词：模块化多电平换流器 广义电容电压不平衡度 故障诊断 运行功率 

分 类 号：TM46[电气工程—电器]