A hybrid cascaded multi-level converter for power storage system

Power storage system using battery and super-capacitor are more and more popular in renewable energy, smart grid and electrical vehicles. But the voltage and current of the basic battery cells and super-capacitor are limited. So in practical applications, a large number of cells are connected in seriously or parallel to improve the output voltage and current ability. Due to the differences between the cells, voltage and current equalizations are necessary to prevent overcharge or over-discharge on some cells. In this paper, a novel hybrid cascaded multi-level converter is proposed to solve the voltage equalization problems. The battery cells are connected by the cascaded half-bridges instead of being connected directly. The charge and discharge of the battery cells can be controlled separately and then the voltage equalization can be realized. Some experimental results will be given to verify the effects of the proposed converter.