Dual-Active-Bridge Based Self-Balancing DC–DC Converter With Coupled Inductor for Bipolar DC Microgrids

Although bipolar dc microgrids exhibit enhanced reliability and transmission efficiency compared to unipolar dc microgrids, they are prone to voltage imbalance issues. This article proposes a dual active bridge (DAB) based bipolar dc–dc converter with coupled inductors to automatically balance bipolar output voltages under any load conditions. The proposed converter can operate with a simple single phase-shift modulation. Moreover, the coupled inductor is the key to realize self-balancing and roles as the power transfer inductor as well. The zero-voltage-switching can also be achieved for all switches under different load conditions. The operation and self-balancing principles are analyzed in detail. The characteristics of the proposed converter are well verified by a 1 kW prototypes under different load conditions.