A Simple Diagnosis Approach for Multiple IGBT Faults in Cascaded H-Bridge Multilevel Converters

Cascaded H-bridge multilevel converters (CHBMCs) have been applied in various high-power topologies. Due to the multiple modular structures, each switch in every module is a potential source of failure. In order to quickly identify faulty switches of CHBMCs for improving maintenance efficiency, a simpler diagnosis approach is proposed by only extracting the change rate of DC-link voltages. Combined with switching states of the bridge arms and H-bridges, the specific current paths under different switch faults are analyzed to summarize the change of DC-link voltage. And then, the individual diagnosis variables are established to detect single or multiple faulty switches for single or multiple modules. The proposed diagnostic method can complete the different fault identification process in less than 3/4 current cycle, which only needs a fault counter to avoid the false alarm without the other detection thresholds. The proposed method is confirmed by the hardware-in-the-loop (HIL) test.