Generalized Charge Balancing Scheme for Symmetrical CHB Multilevel Inverters

Cascaded H-bridge (CHB) multilevel inverters (MLIs) are widely used in medium-voltage, high-power applications, mainly due to their modularity and reliability. One of the major challenges in CHB inverter (CHBI) topology is the charge balancing issue, which leads to uneven voltage levels of the individual H-bridge source voltages, resulting in increased maintenance cost. In this paper, a new charge balancing scheme is proposed based on a switch matrix, which is generalized for any n-level symmetrical CHB MLI. The validity of the proposed scheme is verified experimentally for single-phase five-level and seven-level inverters. A comparison of the proposed scheme with conventional and existing methods is also provided in order to emphasize the advantages of the novel system. The proposed scheme takes the least number of fundamental cycles for charge balancing, while the power drawn from each source voltage is found to be uniform.