A fault detection method in cascaded H-bridge multilevel inverter

This paper presents the switch-fault detection method in a cascaded H-bridge multilevel inverter (CHBMI). When the open-fault occurred on the H-bridge inverter switch of single-phase CHBMI, the body diode of fault switch can provide a freewheeling current path. However, the output current distortion of short-fault is different from that of the open-fault because disconnection of fuse cannot provide a freewheeling current path. The fault detection method is based on the zero current time analysis according to zero-voltage switching states. The proposed method is available in the rotating level-shifted pulse width modulation (RLS-PWM) method. Using the proposed method, it is possible to detect not only the fault location of cell but the fault location of switch accurately. The PSIM simulation results show the effectiveness of proposed fault detection method.