This paper presents a novel static synchronous compensator (STATCOM) topology based on modular multilevel converter (MMC). The model has a high degree of modularity and good reliability, and is convenient for maintenance and capacity extension, which is a typological structure with high development potential. Considering quite large amount of sub-modules (SMs) used in MMC topology, attention is drawn on the reliability of operation. Based on the analysis of existed fault-tolerant design for H-bridge converters, a novel fault-tolerant control strategy suitable for MMC-based STATCOM is proposed. According to the proposed strategy, all redundant SMs are set in hot stand-by state, once fault occurs, redundant SMs will rapidly take place of the faulted SMs, thus ensures the STATCOM under normal condition. Furthermore, according to the number of faulted SMs, multi-objective control strategy is adopted, which greatly expends the operating range of STATCOM. At the end of this paper, the validation of proposed strategy is evaluated in Matlab/Simulink environment. The reported results confirm the feasibility of the proposed fault-tolerant design.%提出了一种基于模块化多电平(MMC)技术的新型静止无功补偿器(STATCOM)的拓扑结构,指出该拓扑结构具有模块化程度高、可靠性好、便于维护及容量拓展等特点,是一种极具发展潜力的拓扑结构.考虑到模块化多电平换流器各桥臂由大量子模块级联而成,容易出现可靠性问题,在对已有级联H桥多电平换流器容错保护方案分析的基础上,提出了适合基于模块化多电平结构的静止无功补偿器的故障容错策略.该方法通过将冗余子模块设置在热备用状态,可以在子模块发生故障时迅速投入冗余模块,从而保证静止无功补偿器的正常工作.在此基础上,进一步根据发生故障模块数,采取多目标控制策略,最大化地提高了静止无功补偿器的工作范围.时域仿真的结果表明,所提出的故障容错控制策略可有效地提高了静止无功补偿器的运行可靠性,具有一定的工程意义.
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