Open-Switch Fault Detection in Three-Phase Symmetrical Cascaded Multilevel Inverter Using Conducted Disturbances

This paper proposes a fault detection approach for open-circuit faults in a seven-level cascaded H-bridge (CHB) multilevel inverter. This method utilizes a simple three-phase electromagnetic interferences (EMI) filter placed at the inverter's output, to measure the conducted emissions. The measured voltages across the EMI filter resistors are compared to those expected in healthy case, and distortions are explored to locate open-switch fault. Time domain signals, Teager energy operator, and multi-scale wavelet were combined to make robust and effective fault detection method. Simulation results under different faulty cases demonstrate that an open-circuit fault in a CHB multilevel inverter can be detected in less than 20 ms.