Open-circuit diagnosis method based on dual-mode voltage residual model for T-type three-level inverter

This study proposes a rapid online diagnostic method based on a dual-mode line voltage residual model for diagnosing IGBT open-circuit faults in a T-type three-level inverter. The method is based on the voltage residual method and is integrated with a three-level fault-tolerant algorithm. Firstly, by analyzing the line voltage residuals after an open-circuit fault in the T-type inverter under normal operating conditions, 12 types of single-switch open-circuit faults are divided into 6 groups. Next, the breakdown of the spatial voltage vectors following the fault are analyzed, and the remaining vectors are reconfigured to enable the inverter's operation under three-level fault-tolerant control. In the fault-tolerant control, the residual voltage returns to its normal value, aiding in precise fault localization. Simulation and experimental results validate the method's robustness against load variations. This method significantly increases diagnostic speed and reduces harmonic interference in the diagnosis procedure. These findings are of paramount importance for fault diagnosis and the reliable operation of the T-type three-level inverter.