Open Circuit Fault-Diagnosis and Fault-Tolerant Operation of ANPC

This paper introduces a real-time fault diagnosis and fault-tolerant method for detecting open-circuit (OC) faults in insulated-gate bipolar transistors (IGBTs) for a three-phase active neutral point clamp (3L-ANPC) converter. The strategy utilizes pole voltage as an input, and based on the deviation between the output pole voltage and the applied switching state, identifies any faulty switches. This approach is load-independent and does not require additional current information. Practical implementation of the strategy only necessitates three additional pole voltage sensors. This diagnostic method enables faster fault detection, typically within one switching cycle under favourable conditions, and can also detect multiple OC failures using the same strategy. Experimental and simulation results validate the effectiveness of the proposed method.