Reliability comparison of multi-level inverters for motor drive

Due to the unique interconnecting nature of hexagram inverter, it can tolerate one leg failure without adding major power component. In the event of one leg failure, the whole power module is disabled and new control method will be initiated for hexagram inverter. Another widely used multi-level topology is Cascaded H-bridge Inverter, which proves to have extremely high reliability when contactors are added to the topology. This paper gives the control method of hexagram inverter under faulty condition, and is compared to Cascaded H-bridge inverter in this regards. Reliability analysis shows that without adding any major power components, the hexagram inverter has higher reliability than cascaded H-bridge inverter due to its simple structure and less components. Considering N+1 redundancy, Hexagram inverter proves to have higher reliability than Cascaded H-bridge inverter, in which additional contactors are required for fault tolerant control design.