Reliability Assessment of Fault-Tolerant Multilevel Inverter Topologies with Reduced Switch Count

Multilevel inverters (MLIs) are becoming increasingly popular in medium and high-power applications due to benefits of low total harmonic distortion (THD) and lower voltage stress across switches. The proper operation of these multilevel inverter topologies is heavily dependent on the reliable operation of semiconductor devices. The role of the inverter is very crucial and in case of failure of the switches, the output voltage of the MLI is significantly affected which leads to degraded performance or in some cases complete shutdown of the overall system. Recently, several fault-tolerant (FT) MLI topologies have been proposed, however, in most of cases, the design has been accomplished for the open circuit faults (OCF) only. The switches of any topology can suffer from another type of fault namely short-circuit fault (SCF). In this paper, a reliability assessment of the different FT-MLI has been carried out by considering OCF and SCF in single as well as double switches. A comparison has been provided to assess the reliability of the FT-MLI topologies with the scope for improvement in a more robust design. Finally, a 5-level FTT-type converter has been simulated and results have been analyzed for different types of faults.