Impact of Fixed vs. Variable DC-Link Voltages on Maximizing Efficiency of EVs Fast-Charging Systems

In this study, the effect of the DC-link voltage on the efficiency of a two-stage converter system used in an electric vehicle (EV) fast-charging systems is presented. The rectification is performed in the first stage by means of an AC/DC three-phase three-level T-type converter (3P3L-T-type), and the second stage consists of a two-stage DC/DC converter that charges the EV battery. A comprehensive analysis of the efficiency is performed for various levels of DC-link voltage and EV battery voltages to find the impact of both variables on the efficiency of the rectifier and DC/DC converter stages. The analysis is established with different DC-link voltages, and the results lead toward the optimum condition of DC-link voltage for achieving maximum EV fast-charging efficiency. This study also provides valuable insights into the optimization of the design and operation of the EV fast-charging system, with the aim of effectively balancing performance and efficiency.