A CLCLC-Type Immittance Resonant DAB Converter With Dual Unbalanced Modulation for Electric Vehicle Charger

The dc-dc converter is a crucial component of an electric vehicle (EV) charger, and its performance is essential for the charging speed and driving range of EVs. Despite recent advancements in converter topology and modulation techniques, enhancing both switching and conduction losses in dual-active-bridge (DAB) converters continues to be challenging. This article introduces a novel dual unbalanced modulation (DUM) for EV chargers. The DUM strategy, when combined with a CLCLC-type immittance resonant DAB (IRDAB) converter, can simultaneously reduce the switching and conduction losses. When the rated output power exceeds 25%, the DUM strategy operates in full-bridge mode, achieving zero-voltage switching (ZVS) operation of all switches, minimizing backflow power on both sides, and maintaining near-minimum root-mean-square (rms) currents. For output power rated below 25%, the DUM strategy shifts to half-bridge mode. This mode slightly increases the rms currents, yet it still ensures ZVS operation of all switches and minimum backflow power on both sides. Theoretical analysis and experimental results demonstrate that, when compared with conventional modulation strategies, DUM strategy maintains the highest efficiency across the entire load range.