A High Gain Multiport DC-DC Converter for Integrating Energy Storage Devices to DC Microgrid

Interfacing multiple low-voltage energy storage devices with a high-voltage dc bus efficiently has always been a challenge. In this article, a high gain multiport dc-dc converter is proposed for low voltage battery-supercapacitor based hybrid energy storage systems. The proposed topology utilizes a current-fed dual active bridge structure, thus providing galvanic isolation of the battery from the dc bus, wide zero voltage switching (ZVS) range of all the switches, and bidirectional power flow between any two ports. The dc bus side bridge uses voltage multiplier cells to achieve a high voltage conversion ratio between the supercapacitor (SC) and the dc bus. Moreover, as the proposed topology employs only one two-winding transformer to achieve a three-port interface, the number of control variables are reduced, which decreases control complexities. The operation of the proposed converter is analyzed in detail, including the derivation of ZVS conditions for the switches and transformer power flow equations. A decoupled closed-loop control strategy is implemented for the dc bus voltage control and energy management of the storage devices under different operating conditions. A 1-kW laboratory prototype is built to verify the effectiveness of the proposed converter, along with the control scheme.