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已有的模块化多电平换流器(modular multilevel converter,MMC)可靠性分析方法多数未考虑大量子模块之间(submodule,SM)的相关性,在一定程度上会导致最优冗余配置方案的选取缺乏合理性,因此重点解决考虑子模块相关性的MMC可靠性分析方法问题.首先,建立单个子模块的可靠性模型;其次,考虑同一个MMC桥臂中子模块电压纹波和相间环流等因素对各子模块使用寿命的影响,选取符合这一特殊应用场景的Copula函数,建立MMC各桥臂的可靠性函数.再次,分析考虑子模块相关性前提下不同的子模块冗余配置方案对MMC可靠性的影响.最后,利用Matlab软件编程验证了所提出的MMC可靠性分析方法的正确性和有效性.将Copula函数与数理统计领域的分析方法相结合,所得到的桥臂联合概率分布函数便于后续拓展与改进,为用于直流输电的多电平换流器的可靠性分析方法提供了较强的理论支撑.“,”The majority of the existing reliability analysis methods on modular multilevel converter (MMC) did not consider the submodule (SM) correlations,which may lead to unreasonable optimal SM redundancy configuration.Therefore,there is a need to investigate the SM correlation based on MMC reliability analysis method.Firstly,the reliability model of the individual SM was provided.Secondly,considering the impact of rippling capacitor voltage and circulating currents among three phases on the service life of each SM,we selected a Copula function which fits for this specific application scenario to establish the reliability functions for all the bridge arms.Thirdly,analyzed the impact of different SM redundancy configurations on MMC reliability when considering the SM correlations.Finally,the correctness and effectiveness of all the proposed approaches were validated by calculations using Matlab.The proposed joint distribution function for each bridge arm of MMC combines the Copula function and the classic mathematical statistics methods,hence it is open for later improvements and can be seen as a theoretical support on the reliability analysis of multilevel converters used in HVDC applications.