Fault Diagnosis and Fault-tolerant Operation of Current Source Inverter for Safety-Critical Applications

This paper presents the fault-tolerant current source inverter based motor-drive system, which can diagnose the open-circuit failure of the switches and restructure the topology of the inverter to keep the inverter operating in the post-fault condition. The proposed diagnostic method is able to detect the open-circuit fault both in the main switches and those of the redundant switches. During fault-tolerant operation, the identified faulty switch is fully replaced by one of the switches from the fourth leg to ensure full rating operation of the inverter without any extra overrating requirements for switches. In addition, wide bandgap (WBG) devices are employed to configure the redundant fourth leg. During normal operation, soft switching is enabled across all the silicon IGBTs, while just WBG devices in the fourth leg undertake hard switching. Thus, the inverter efficiency is improved and the thermal stress in the IGBTs is relieved.