Using auxiliary signals as a simple method for balancing DC bus voltages in cascaded H- bridge converters

Cascaded H-bridge (CHB) multilevel converters with capacitive sources need a voltage balancing algorithm to control their DC voltages. In this paper, a new method is proposed to achieve this goal in a simple manner. The proposed method adds auxiliary signals to the main reference of modulating signals to attain voltage balancing goal. This approach not only is simple and easy to implement, but also is independent of the main control strategy and the modulation technique. The validity of the proposed method is verified by simulations and experimental studies on a 7-level CHB based dynamic voltage restorer (DVR).