Fault diagnosis of flexible DC modular multilevel converter based on consistency test

Aiming at the problem of fault diagnosis of modular multilevel converter, using the special feature of three-phase symmetry of converter, this paper proposes a method of modular multilevel converter fault diagnosis based on the redundancy of equipment itself. This method is a hardware redundancy method, which can avoid the problems of software redundancy method such as the effect of model deviation, the difficulty of simulating the actual operating environment, etc. It can also avoid the problems of equipment investment, land occupation, operating cost and so on, which are caused by the conventional hardware redundancy method that needs to rebuild redundant physical equipment. This method can realize the fault detection of converter and the faulty bridge arm location of converter. Simulation results show the effectiveness of the method.