An NPC‐type fault‐tolerant MLI with symmetrical and asymmetrical voltage modes

Abstract

SummaryCurrent studies have been challenging in reducing the number of devices and ensuring fault tolerance features of the multilevel inverters (MLIs). This article proposes a new fault‐tolerant neutral point clamped (NPC)‐type MLI using two three‐level NPC legs, which can work in symmetric and asymmetric modes to generate nine and 17‐level output voltage, respectively. The proposed converter has less device count and low total blocking voltage (TBV); further, the converter has different redundant switching states for tolerating different categories of faults. This article also implements a modified pulse width modulation (PWM) control strategy to ensure the zero‐dc offset at the output when asymmetrical voltage levels appear with the occurrence of switch faults. A detailed operation of the proposed converter under symmetric and asymmetric modes is presented for healthy and different categories of faults. The converter's feasibility is verified by its current and voltage characteristics obtained from the MATLAB‐SIMULINK software and the experimental prototype. Further, the efficiency of the converter is verified with the PLECS software. Finally, a comparison with recently proposed topologies is performed to emphasize converter performance.