Analysis and protection strategy based on Modular Multilevel Converter Direct Current faults

This paper conducts in-depth research on the topology structure, working principle, and modulation methods of Modular Multilevel Converter (MMC), providing theoretical support to examine the fault traits on the Direct Current (DC) side. The paper focuses on analyzing the typical DC side faults within the modular multilevel converter-based high-voltage direct current (MMC-HVDC) system and validates the analysis results of DC side faults through simulation using the PSCAD/EMTDC simulation platform. It also proposes a Full-Bridge Modular Multilevel Converter (FBMMC) topology structure that effectively controls the energy exchange during the DC side fault by introducing a submodule capacitor in the bridge arm.