Fault-tolerant strategy using neutral-shift method for cascaded multilevel inverters based on level-shifted PWM

Most proposed methods for a fault-tolerant operation in many of studies are based on a phase-shifted PWM (PS-PWM) method. However these methods are not applied directly to multilevel inverter systems using a level-shifted PWM (LS-PWM). This paper focuses on fault-tolerant operation for a cascaded multilevel inverter based on LS-PWM. During the occurrence of a single-inverter-cell fault, reconfiguration of the carrier bands scheme is implemented and modulation assignment of inverter cells is modified in this proposed fault-tolerant operation. It is possible to generate balanced three-phase line-to-line voltages and line currents with the proposed strategy when a device failure occurs in cascaded multilevel inverters using LS-PWM. The feasibility of the proposed method is proved by simulation results.