Stacked-bridge-based three-level DAB converter in 800V dc micro-grids

800V dc micro-grid systems bring new challenges to the design of power electronic interfaces. In this paper, a stacked-bridge-based dual-active-bridge (DAB) converter is proposed to achieve bidirectional power transfer between the storage battery and 800V dc micro-grid. With the stacked bridge structure, the voltage stresses of MOSFETs on the high-voltage side are halved. Therefore, MOSFETs with lower voltage ratings can be applied to high-voltage applications. Moreover, an asymmetric pulse-width modulation (APWM) plus phase-shift modulation (PSM) hybrid modulation scheme is proposed to realize voltage match over a wide voltage range. A wide zero-voltage-switching (ZVS) range can be achieved over a wide battery voltage range. To verify the concept, a 1-kW rated prototype linking an 800V dc bus and a 100V-200V energy storage unit is designed and tested. The experimental results well validate the proposed concept.