An Isolated SEPIC DC-DC Converter for EV Charging Systems: Design, Simulation, and Feasibility Studies
Abstract
This paper presents the design and simulation-based performance assessment of an isolated single-ended primary-inductor converter (SEPIC) for electric vehicle (EV) battery-charging applications. The proposed topology allows adjustable step-up/step-down voltage conversion with galvanic isolation to ensure excellent operational safety and grid-to-vehicle system reliability. The detailed design procedures are established for the passive elements, crucial coupling capacitors, and the high-frequency isolation transformer working at 50kHz to maintain tight output voltage regulation under wide input voltage changes. The performance of the converter is extensively assessed in open-loop and closed-loop proportional-integral (PI) control schemes using MATLAB/Simulink. Additionally, a passive input filter is incorporated to improve the power quality and to decrease the grid current’s total harmonic distortion (THD) successfully to 6.89%. In closed-loop operation, the architecture can achieve a highly stabilized output voltage with a low ripple of 2.14% and a peak simulated efficiency of 95.49%. A CC-CV battery-charging profile and supply-voltage variation analysis are also presented to evaluate the simulated charging and regulation performance. Experimental verification is performed only on a scaled conventional SEPIC prototype rated at 168 W (56 V, 3 A), serving as a proof of concept for the component-sizing approach and SEPIC energy-transfer principle. The conventional SEPIC experimental results do not constitute experimental validation of the proposed isolated SEPIC converter. Future work will include experimental validation of the complete isolated converter. The proposed isolated SEPIC converter is verified by MATLAB/Simulink simulations. The simulation results reveal that the isolated SEPIC arrangement offers minimal output ripple, increased power quality, and high efficiency, proving its appropriateness for medium power on-board EV charging systems.