Evaluation of DC-DC buck-boost partial power converters for EV fast charging application

Abstract

This paper presents a comparison of buck-boost partial power converters (PPC) for the DC-DC conversion stage of an electrical vehicle (EV) fast charging station. By using a DC-DC buck-boost structure, the proposed fast charger can operate with wide output voltage range. The proposed topology can be used to charge either 400V or 800V batteries. Since the PCC only processes a fraction of the total power, high efficiency is obtained. Two different buck-boost PPC topologies are compared. First structure consider two-quadrant switches in order to obtain bipolar voltage, while the second structure uses an unfolding bridge to change the voltage polarity. Results show that the first solution with two-quadrant switches allows better efficiency. The proposed converter operation is then evaluated for fast charging applications for both 400V and 800V batteries, showing high efficiency up to 99%, making the proposed solution very attractive for fast charging application.