Fast Open-circuit Fault Detection Method for Defective Switches in Nested Neutral Point Clamped (NNPC) Converter

Recently, the nested neutral point clamped (NNPC) converter has been developed for medium voltage applications. This converter has been considered for its desirable properties, such as application in a wide range of voltages, the low voltage stress on the switches, and excellent output waveform quality. This study presents a fast open-circuit fault detection method in semiconductor switches. The proposed method only requires the measurement of output voltage. The output voltage of the converter is investigated in different switching states. If there is a discrepancy in the converter output in normal mode and after the fault, the defective switch is identifiable. The proposed method has been investigated in the MATLAB Simulink environment under different scenarios. The simulation results confirm the desired performance of the proposed method.