A General Four-Port Converter With Series LC Voltage Balancer for Bipolar DC Microgrid

To construct the bipolar DC microgrid and maintain poles voltage balanced, usually a dedicated voltage balancer (VB) is needed. In this article, a general four-port converter with series LC voltage balancer (LCVB) is proposed to replace the voltage balancer. The proposed converter is composed of two partial power processing dual-active-bridges (PDAB) and a series LC branch. The LC branch is added between the outputs of two PDABs, which is combined with half bridge circuits to form LCVB. Two PDAB inputs can realize independent bi-directional power flow according to the requirements of the connected equipment. At the same time, LCVB can also balance the bipolar voltage levels. In addition, compared with the traditional two module DAB converter, the proposed converter has no additional active switching device. Partial power processing structure improves the converter efficiency. And last, all the switches of PDAB turn on with zero-voltage switching (ZVS). Simulations and experiments are carried out to verify the validity of the converter.