Reducing Common-mode voltage and power dissipation in cascaded multilevel inverters with flexible dc sources

dc sources in cascaded multilevel inverters have constant and non-flexible values. Flexibility in the proposed values increases the system degrees of freedom in mitigating more harmonics leading to an improved THD. In this paper, a novel SHM control strategy has been proposed for cascaded multilevel inverters with flexible dc sources. Minimizing the objective function in the proposed strategy, the optimized dc sources values are found besides the switching angles. These optimized sources have lower values compared to the conventional ones. This is a major advantage of this proposed strategy as it leads to a lower common-mode voltage and power dissipation along with a significant improvement in the THD. Software implementation of the conventional and proposed SHM control strategies has been applied to five and seven-level inverters. Results show the superiority of the proposed strategy from the THD point of view along with the reduction in Common-mode voltage and power dissipation.