IGBT Open-Circuit Fault Diagnosis and Location of MMC Sub-module

Modular multilevel converter (MMC) has a high probability of IGBT open-circuit fault, while reliability is one of the main challenges facing MMC. The sub-module fault is one type of common faults of MMC; the timely diagnosis and location is a great concern for the operational stability of MMC-HVDC. In this paper, in view of the single-tube open-circuit fault of MMC, a method for fault diagnosis and location is proposed. The method is based on sampling the output voltage of single arm which reduced computation complexity. With the purpose of fault diagnosis and location, the sub-module fault characteristics were analyzed, then according to the diagnosis rules to achieve the fault status identification of a bridge arm. A simple sequential process was applied to realize fault location. Based on PSCAD/EMTDC, a high-voltage DC simulation system with an 11-level modular multilevel converter was built. The final simulation confirms that the proposed schemes can achieve the timely sub-module fault diagnosis and location so that the stable operation of MMC-HVDC can be guaranteed.