Fault diagnosis method for sub-module in modular multi-level converters

The open-circuit fault of sub-module is the most common type of fault in modular multi-level converters(MMC). It is very important to improve the reliability of the system and ensure the safe and stable operation of the MMC. In this paper, aiming at the open-circuit fault characteristics of MMC sub-module, a fault detection method based on Park's vector of three-phase AC average current is proposed. Park's vector mode value is used to detect the fault. Park's vector phase angle is employed to locate open-circuit fault sub-module. In the environment of Matlab / Simulink, a 9-level MMC simulation model is built. The simulation results show that the proposed method can diagnose sub-module faults accurately and quickly.