Diagnosis of open-circuit switch faults in multilevel active-NPC (ANPC) inverters

Multilevel converters have been widely used in traction drive systems due to their attractive output performance. However, one major disadvantage of multilevel converters is the large number of switching devices employed, which could increase the failure probability of drive systems. Thus, an effective diagnosis method for switch faults in multilevel converters is of high importance for the fault-tolerant operation of such drive systems. This paper introduces an on-line diagnosis method for open-circuit switch faults that could happen in one of the most promising multilevel converters: Active Neutral-Point-Clamped (ANPC) converter. This diagnostic method is implemented based on the comprehensive information of pole voltages, phase currents, and switching states of ANPC inverters. Compared with the existing diagnostic methods in the literature, the presented method in this paper has lower cost and shorter detection time (less than one fundamental cycle). Simulation results verified the effectiveness and robustness of the introduced fault diagnosis method.