Detecting Open-Switch Faults: Using Asymmetric Zero-Voltage Switching States

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