Charge balance control methods for asymmetrical cascade multilevel converters

Modulation strategies for multilevel converters have typically focused on synthesizing a desired set of sinusoidal voltage waveforms using a fixed number of DC voltage levels. This results in the average current injection and hence the net power drawn from the multiple DC voltages to be unmatched and time varying. Therefore, the DC voltage sources are unregulated, requiring corrective control action to incorporated. In this paper, first a new method is proposed for determination of DC voltage source levels of asymmetric cascade multilevel converters. Then four modulation strategies are proposed for DC power balance realization for asymmetrical multilevel converters expectation of the first unit. All of the expressed theoretical results are confirmed by simulation and experimental results.