Novel SVPWM based Switching Sequences for Modular Multilevel DC to AC Converter

Abstract

The switching sequences for modular multilevel converters (MMCs) should also maintain sub-module voltage balance, achieve low circulation currents and low common mode voltage in addition to the general requirements such as low total harmonic distortion (THD) and ease of implementation. Space vector pulse width modulation (SVPWM) algorithm gives more flexibility in designing switching sequences compared to conventional sine–triangle pulse width modulation (SPWM). This paper proposes two novel switching sequences based on SVPWM for the complete linear modulation region of MMC. The performance of these two new sequences are compared with that of the conventional SVPWM sequences and evaluated in terms of the circulation current, sub-module voltage imbalance and common mode voltage for the complete linear modulation region. The proposed switching sequences are verified through simulation and simulation results are presented.