Reliable Multilevel Inverter Topology using two DC Sources.

The proposed reliable multi-level inverter with the fault tolerant operation. The topology is with an asymmetrical source combination and the source ratio is 3:1. Under normal conditions, the topology develops a nine-level output voltage waveform with eight switches in which seven switches are unidirectional and one switch is bidirectional. The open-circuit fault is the most common fault which occurs due to the fault in the gate drive circuit. The magnitude of output voltage and level fall from nine to the five level when the fault occurs in the unidirectional switches and output voltage falls to three level when the fault is in the bi-directional switch. To maintain rated output voltage, the tap-changing transformer is placed between the inverter output and load. The presented multilevel inverter topology is simulated in MATLAB Simulink.