IGBT Open-Circuit Fault Diagnosis in a Quasi-Z-Source Inverter

In this paper, a fast and practical method is proposed for open-circuit (OC) fault diagnosis (FD) in a three-phase quasi-Z-source inverter (q-ZSI). Compared with the existing fast OC FD techniques in three-phase voltage source inverters, this method is more cost-effective since no ultrafast processor or high-speed measurement is required. Additionally, the method is independent of the load condition. The proposed method is only applicable to Z-source family inverters and is based on observing the effect of shoot-through intervals on the system variables during switching periods. The proposed algorithm includes two consecutive stages: OC detection and fault location identification. When both stages of the OC FD algorithm are done, a redundant leg is activated and utilized instead of the failed leg. The accuracy of the proposed method is confirmed by the experimental results from a low-voltage q-ZSI prototype.