A Multi-Level Power Converter Interface for a Battery Energy Storage System

This study proposes a multi-level power converter for a battery energy storage system (BESS) with bidirectional power flow. The multi-level power converter includes a DC-DC power converter, a selection switch set and a full-bridge inverter. The DC-DC power converter performs bidirectional power conversion and provides a DC voltage that is greater than the peak voltage of the utility. Integrating the selection switch set and the full-bridge inverter produces a five-level AC voltage that controls the real power flow and the reactive power flow between the battery set, the DC-DC power converter and the grid. Because partial power is directly processed using only the selection switch set and the full-bridge inverter, the DC-DC power converter is operated only when the grid voltage is greater than the voltage of the battery set. Therefore, the power conversion efficiency for the proposed BESS is improved. The proposed BESS uses only eight power electronic switches, so the power circuit is simplified. A hardware prototype with a digital signal processor controller is used to verify the performance of the proposed BESS. The experimental results are as expected.