Open-circuit fault diagnosis for cascaded H-bridge multilevel inverter based on LS-PWM technique

Multilevel inverters have been widely used in high voltage and high-power applications on account of their remarkable performance in recent years. The multilevel inverters have an increased chance of switch fault due to a considerably large number of semiconductor switches associated with the power conversion. Therefore it is crucial to detect and locate faults quickly. In this context, an open-circuit fault diagnosis method for cascaded H-bridge multilevel inverter (CHBMI) based on the level-shifted pulse width modulation (LS-PWM) technique is proposed. Unlike the fault diagnosis based on the algorithm, the proposed method only needs a certain logical judgment to diagnose the fault based on subtle fault characteristics. The output voltage of the H-bridge and load current are used for fault diagnosis.