Coupled-Inductor Bidirectional DC-DC Converter for EV Charging Applications with Wide Voltage Conversion Ratio and Low Parts Count

This paper proposes a new bidirectional dc-dc converter and presents its application for electric-vehicle (EV) charging applications. Using the benefits of a coupled-inductor, the proposed converter exhibits a wide voltage conversion ratio in both buck and boost modes, while using lesser number of components compared to other unidirectional and bidirectional converter counterparts. The steady-state analysis of the converter is presented and the steady-state waveforms are derived. The expressions for the dc voltage and current transfer functions, current and voltage stresses of the semiconductor components, and the design expressions for the converter passive components are derived. Design of a 3.2 kW, 380 V at Low-Voltage (LV) side and 48 V at High-Voltage (HV) side bidirectional converter is shown and verified by simulations. Simulation show efficiencies greater than 95% for both operating modes. A laboratory prototype of a small-scale 300 W bidirectional dc-dc converter with 40 V at LV-side and 300 V at HV-side is considered. The experimental results to support the theoretical predictions are given.