Diagnosis of Open Circuit Faults for Three-Phase Three-Level Converters Based on the Change Rate of Current Residual

To realize the diagnosis for IGBT open-circuit faults in a three-phase three-level rectifier, a fault diagnosis based on the change rate of current residual is proposed. Firstly, a mixed logic dynamic(MLD) model of the rectifier was established to generate the residual of the grid current. And then, combining the theoretical calculation with the simulation results, the change rate of current residual and the residual characteristics for different IGBT faults were analyzed. Then, the normalized diagnostic variables and the threshold were defined to accomplish fault detection for the single IGBT open-circuit faults in different situations. Finally, the validity of the diagnostic method was verified through MATLAB/Simulink simulation.