A carrier-based PWM method with optimal switching sequence for a multi-level four-leg VSI

This paper suggests a multi-level four-leg PWM voltage source inverter (VSI) as a topology for the high power applications where a function is required to control a zero sequence component as well as dq components. It proposes a carrier-based PWM method for a multi-level four-leg PWM VSI along with introducing a new offset voltage. The proposed offset voltage makes it possible for the switching sequence of all the legs to be optimized for the minimization of the harmonic distortion of the output voltage independently of the number of inverter levels. The feasibility of the proposed PWM method is verified throughout the spectral analysis, simulation and experimental results.