柔直配电系统混合型MMC可靠性评估

模块化多电平换流器(Modular Multilevel Converter,MMC) 作为柔性直流配电系统中的关键设备直接关系到整个配电系统的安全可靠,因此有必要对其可靠性的进行评估。本文首先对半、全桥以及混合型MMC进行比较分析,对比得出混合型MMC更适合运用柔直配电系统。然后通过对MMC工作原理、直流阻断能力、冗余配置的阐述计算出了全、半桥模块数及比例；建立元件可靠性模型并运用故障树法对混合型MMC进行了可靠性建模。最后利用Matlab针对冗余配置、全、半桥子模块比例、IGBT结温及损耗进行算例分析,得出结论：合理的冗余配置以及全、半桥比例是设计混合型MMC的关键所在。并指出IGBT的运行工况会导致混合型MMC的故障率提升。

Reliability evaluation of hybrid MMC for flexible dc distribution system

As a key device in flexible dc power distribution system, Modular Multilevel Converter (MMC) is directly related to the security and reliability of the whole power distribution system, so it is necessary to evaluate its reliability. In this paper, half, full bridge and mixed MMC are compared and analyzed, and the mixed MMC is more suitable for flexible direct distribution system. Then through the MMC working principle, dc blocking capacity, redundant configuration of the calculation of the full and half bridge module number and proportion; The component reliability model is established and the fault tree method is used to analyze the reliability of hybrid MMC. Finally, Matlab is used to analyze the redundancy configuration, full and half bridge sub-module ratio, IGBT junction temperature and loss, and the conclusion is drawn that reasonable redundancy configuration and full and half bridge ratio are the key to the design of hybrid MMC. It is also pointed out that the junction temperature and loss of IGBT will lead to the increase of the failure rate of mixed MMC.