Open Circuit Fault Localization in NPC Inverter Fed Induction Motor Drives Using Cost Function and Estimated Voltages

Multi-level inverters (MLIs) are widely employed in numerous power conversion applications due to reduced (dv/dt) voltage stresses on the switching devices. The operational performance of MLI decreases due to frequent switch faults that may lead to system degradation and failure. Hence, reliable fault identification with an efficient fault switch localization method is mandatory. Deriving unique fault signatures for the individual switch in MLI is significantly complex. This brief proposes a rapid fault identification method using estimated phase voltages and average cost function for an NPC based induction motor (IM) drive system. The proposed approach has the advantages of a simplified structure and robustness against false alarms. The proposed techniques are implemented using MATLAB/Simulink software, and their efficacy is validated with a 3.7 kW IM drive in real time. The results indicate that effective fault diagnostics is taken from 4.2 ms to 15.2 msec.