Identification of Base Failure Rate of Submodules in Modular Multilevel Converters for MVDC Applications

In the application of modular multilevel converter (MMC) in medium-voltage DC (MVDC) systems, the reduced number of sub-modules (SMs) lead to reliability issues in the overall converter. For the multiple SM topologies that have been developed in MMC, this paper proposes a novel methodology for evaluating the failure rate in SMs. Considering the failure mode of components, structure redundancy, and classification of SM faults, this approach provides a comprehensive comparison between different SMs. With the identification of SM failure rate, the utilization of different IGBT modules in SMs and arm reliability in MMC are also analyzed.