Power Decoupling Strategy of QAB Converters for DC Microgrids with Islanding Operations

Multiport DC-DC converters based on a dualactive-bridge (DAB) structure have attracted attention due to their high-power density and bidirectional power transfer in DC microgrid systems. Reliability is also high in connecting to various distributed resources (DRs). However, power coupling among ports magnetically connected by a single transformer induces poor power control and voltage regulation performance. To solve those problems, an enhanced power decoupling method for a quadraple-active-bridge (QAB) converter is proposed, which does not have supplementary decoupling components and control algorithms under both grid-connected and islanding mode operations of the DC microgrid system. In addition, a modular structure can be applied to individually connect with various loads. Finally, a 3-kW prototype QAB converter is implemented to verify the validity and performance of the proposed method.