A detection method for an open-switch fault in cascaded H-bridge multilevel inverters

This paper presents a detecting method for an open-switch fault in cascaded H-bridge multilevel inverters. Recently, cascaded multilevel inverters are widely used in high voltage and power systems. Therefore, the reliability of this topology has become an important factor. To improve the reliability, detecting methods for an open-switch fault are required. The proposed method is based on the current path analysis according to zero voltage switching states when the open-switch fault occurs. The location of both faulty cells and switches can be detected by the current waveform and zero voltage switching states. This method is applicable when using the level-shifted PWM that is commonly used for a modulation method in cascaded H-bridge multilevel inverters. The performance of proposed fault detecting method is verified by simulation results.