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Multilevel converter topologies are widely used in many applications. The cascaded Hbridge multilevel inverter (CHBMI), which is

one of many multilevel converter topologies, has been introduced as a useful topology in high and medium power. However, it

has a drawback to require a lot of switches. Therefore, the reliability of CHBMI is important factor for analyzing the performance.

This paper presents a simple switch fault diagnosis method for single-phase CHBMI. There are two types of switch faults: open-

fault and short-fault. In the open-fault, the body diode of faulty switch provides a freewheeling current path. However, when the

short-fault occurs, the distortion of output current is different from that of the open-fault because it has an unavailable freewheeling

current flow path due to a disconnection of fuse. The fault diagnosis method is based on the zero current time analysis according

to zero-voltage switching states. Using the proposed method, it is possible to detect the location of faulty switch accurately. The

PSIM simulation and experimental results show the effectiveness of proposed switch fault diagnosis method.