Assessment of Reduced Switch Count based Multistring Multilevel Inverter with Fault Tolerance for Distributed Energy Sources

Multilevel inverters (MLIs) play a vital role in the renewable energy sources and power drive applications. In this paper a reduced switch count based single-phase Multistring-Multilevel Inverter (M-MLI) fed R-Load with fault-tolerance has been proposed. For m-level, the suggested M-MLI uses ‘(m+1)’ power switches and ‘(m-1)/2’ DC sources. Because of the substantial number of power semiconductors used, MLIs are prone to failure. Often, MLI switches are damaged; they enter an unfavorable operating mode. The Open Circuit (OC) fault that occurs on the individual switch in the M-MLI has been discussed through simulation study. During a fault, voltage levels are maintained but at a reduced scale by updating the Modulation Index (MI) and by using redundant switching states in the event of a fault. Redundant switching states ensure the inverter's fault-tolerant operation. To control the output voltage, Phase Disposition (PD) based sine modulation is analyzed for the presented M-MLI. The voltage levels and its THD for M-MLI using PD based sine modulation technique has been analyzed for various levels i.e., 3-level, 5-level, 7-level, 9-level and 11-levels using the MATLAB/SIMULINK tool.