Method to diagnose open-circuit faults in active power switches and clamp-diodes of three-level neutral-point clamped inverters

A new real-time method able to diagnose multiple semiconductor open-circuit (OC) faults in a three-level neutral-point clamped inverter is introduced in this paper. The proposed diagnostic method is based on the evaluation of the output pole voltages and output currents of the inverter. The proposed method allows a real-time detection and localisation of multiple OC faults in all active power switches and clamp-diodes within one modulation period. Experimental results obtained for different operating conditions of the inverter demonstrate the applicability and performance of the proposed diagnostic approach.