A New Voltage Balancer With DC-DC Converter Function

In dc microgrid, a bipolar dc bus configuration has more merits than an unipolar one, due to higher reliability, easy grounding, and having more voltage levels. However, tight voltage balancing control is necessary to handle unbalanced power between positive and negative buses. To solve this issue effectively, this paper proposes a new voltage balancer with dc-dc converter function. The proposed balancer can serve as both a voltage balancer and a bidirectional dc-dc converter. Thus, it can be applied to battery management system or fast charger in electric vehicles (EVs) charging station while balancing the bipolar dc bus voltages. Unlike the conventional voltage balancing control using a three-level dc-dc converter, the voltage balancing range of the proposed system is not limited. To confirm this superiority, a comparison of the voltage balancing range between the proposed and conventional scheme is explored. Simulation and experimental results are provided in order to validate the effectiveness of the proposed system.