Charge balance control of a seven-level asymmetric cascade multilevel inverter

Abstract

Among the topologies of multilevel inverters, the cascade multilevel inverters have received more attention due to easier control and variety in the structure. Although the cascade multilevel inverters have several advantages, they also suffer from some drawbacks. In the fundamental frequency control method, different value of power is drawn from different dc voltage sources and therefore they have different charge/discharge. Another problem considering the cascade multilevel inverters is the unequal power loss in the switches of different bridges. In this paper, the charge balance control method is proposed for the asymmetric cascade multilevel inverter. Applying this control method leads to equal charge of the dc voltage sources and equal loss on the power switches. Consequently, the lifetime of the dc voltage sources will be equal reducing the maintenance costs.