Symmetrical switching strategy based on reduced switching state in a three‐phase multilevel converter with a single faulty cell.

Due to the possibility of the occurrence of a fault in converters, performance improvement of a converter under faulty conditions is important. In this paper, for improving the performance of the three‐phase cascaded H‐bridge multilevel converters (CHB‐MLCs) with a single faulty cell, the quarter‐and half‐wave symmetry selective harmonic mitigation (SHM) modulation method as well as reducing the number of switching angles (NSA) has been used. Consequently, it helps to reduce the switching frequency (fs) and the number of sentences of the Fourier series thus simplifies the objective function. In addition, the proposed method enables the switching angles of a faulty cell to be transferred to other normal cells per phase. For this purpose, the switching angles of the cells are optimized so that at least one of the cells does not overlap with the other cells in the same phase. By employing the maximum modulation index under the faulty condition, the maximum capacities of the remaining DC sources are used and consequently, the line voltage drop in the output voltage is prevented. To produce a balanced line voltage, the fundamental phase‐shift Compensation (FPSC) method is employed. Simulation and experimental results are presented to confirm the efficiency of the proposed strategy. [ABSTRACT FROM AUTHOR]