Optimal Control of Semi-Dual Active Bridge DC/DC Converter With Wide Voltage Gain in a Fast-Charging Station With Battery Energy Storage

Abstract

Ultrawide voltage regulation is required in dc/dc converters interfacing battery energy storage systems (BESSs) and electric vehicle (EV) batteries in dc fast-charging stations with energy storage. Attaining high efficiency of this converter can be challenging due to the wide variation of input and output voltage yet is important due to the high power transfer. This article proposes a novel control strategy for the semi-dual active bridge (DAB) converter to achieve wide voltage gain while increasing the efficiency at operational points with high input voltage and low output voltage, which is a commonly occurring scenario when the BESS is fully charged, and the EV battery is at low charge. Furthermore, this article also provides an algorithm to determine the required phase shift in real time for any operating point, eliminating the need to devise the control trajectory offline. A 550-V, 10-kW experimental prototype is built and tested to validate the proposed control strategy. With a 25-A constant charging current, the prototype shows that the proposed control strategy can improve efficiency by up to 3.5% compared to the well-known dual phase shift control at operating points with high input voltage (450–550 V) and low output voltage (150–275 V), with a peak efficiency of 97.6%.