Topology Deduction and Analysis of Voltage Balancers for DC Microgrid

A voltage balancer that transfers unipolar dc bus configuration to bipolar dc bus configuration has been widely employed in dc microgrid. Fortunately, unbalanced power flow between positive and negative dc buses can be eliminated through a well-designed voltage balancer. Based on the analysis of a Buck/Boost-type voltage balancer, a deduction method for a series of voltage balancers is proposed in this paper, and is further investigated by applying to other existing voltage balancers. Consequently, several new topologies are proposed for various purpose of improvement with respect to the characters of existing topologies. Furthermore, four new topologies, i.e., Cuk-type, Super-Sepic/Zeta-type, and interleaved Buck/Boost-type voltage balancers have been proposed, which are compared with existing ones in terms of key characters. Finally, the interleaved Buck/Boost topology has been selected as an example for verification and a laboratory prototype is therefore built. The experimental results show a promising effect of current sharing and a good dynamic characteristic of the proposed interleaved average current control strategy based on interleaved sampling while maintaining a balanced power flow between the two dc buses.