Open Circuit Fault Detection and Diagnosis for Seven-Level Hybrid Active Neutral Point Clamped (ANPC) Multilevel Inverter

In the recent decade, active neutral point clamped (ANPC) multilevel inverters have achieved remarkable attention in medium voltage motor drives. Several active switches in a multilevel converter augment the switch fault probability. A switch failure leads to malfunctioning of the whole system and needs to be diagnosed as fast as possible. In this paper, an open-circuit (OC) fault diagnosis method is suggested for a 7-level hybrid active neutral point clamped (7L-ANPC) multilevel inverter for the first time. The fault occurrence is identified based on the magnitude of output current and discrepancies between the measured output voltage and its desired value. In this regard, some up-counters are defined in the diagnosis scheme where each inconsistency leads to a change in the value of a specific up-counter. Therefore, by examination of the up-counters outputs, the faulty switch can be identified. The suggested method does not utilize any extra sensors, and the existing sensors on the load side are adequate to guarantee the proper functioning of the proposed fault diagnosis method. Moreover, the performance and effectiveness of the proposed detection method are investigated through the simulation in the MATLAB/Simulink environment.