Voltage balancing technique with low switching frequency for cascade multilevel active front-end

Recently cascade multilevel converters have attracted the attention of researchers for medium voltage applications such as FACTs devices and motor drives. This topology consists of several H-bridge cells in series, which has the advantages of modular structure and reduced number of components. The main challenges in these applications are limitation of switching frequency of semiconductor devices, low harmonic distortion requirement of grid current and balancing problems of the isolated DC-links. In this paper a new modulation method is proposed which produces low current distortion with low switching frequency. The balancing of the capacitors is well established, and the system has fast dynamic response. The method is simple and effective. Simulation results show the feasibility and superiority of the proposed method.