The Journal of Engineering (2019-01-01)

Proportion and failure analysis of full-bridge sub-modules in a hybrid MMC

  • Yonghui Song,
  • Yongjie Luo,
  • Xiaofu Xiong,
  • Rui Lian

DOI
https://doi.org/10.1049/joe.2018.8445

Abstract

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Isolating DC bipolar short-circuit fault is one of the difficulties faced by the flexible DC distribution system. This study aims to the hybrid modular multi-level converter (MMC). Firstly, the fault-blocking mechanism of a hybrid MMC is analysed. Through theoretical calculation, the influence of the proportion of full-bridge sub-modules η on the fault isolation capability is obtained in the process of bipolar short-circuiting of the hybrid MMC-isolated DC side. Finally, the hybrid MMC DC-side bipolar short-circuit fault is simulated and analysed by the simulation model built in PSCAD/EMTDC software. The fault blocking capability of hybrid MMC and the relationship between η and the full-bridge sub-module capacitance voltage after the fault isolation phase are verified, which provides a theoretical basis for the design of the withstand voltage of hybrid MMC full-bridge sub-module capacitors.

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