Performance improvement of neutral-point voltage balancing for energy storage system using DC/DC converter

This paper presents an performance improvement of neutral-point balancing using DC/DC converter. The proposed energy storage system (ESS) is composed of AC/DC three-level converter and DC/DC three-level converter. The conventional neutral-point control method is balanced by adding a duty-offset to the duty of the switches. But this paper is proposed adding additional neutral-point controller using the DC/DC converter. The proposed improvement of neutral-point voltage balancing method is very simple. And this method is implemented without complex calculations or analysis. The effectiveness of the proposed method is verified by simulation.