A Complete Impedance-Based Characterization of a High-Frequency Transformer in Triple Active Bridge Converters for EV Onboard Chargers

This paper proposes an experimental methodology for the systematic determination of the equivalent circuit parameters of three winding high frequency transformers (3W-HFTs) for modeling the electrical behavior and the power losses of triple active bridge (TAB) power converters intended for onboard electric vehicle charging applications. For modeling the 3W-HFTs, a comprehensive lumped element equivalent circuit is adopted, and its electrical and electromagnetic parameters are determined through a structured sequence of open-circuit and short-circuit measurements performed over a wide frequency range from 20 Hz to 13 MHz using a precision impedance analyzer to thoroughly investigate impedance resonance behavior, while wide-bandgap power electronic devices are employed. The comparison between the lumped element impedance model and the measured impedance responses demonstrates strong agreement in terms of both magnitude and phase across the frequency range under study. Furthermore, the comparison of simulation results and experimental measurements performed on a TAB prototype under both open-circuit and load operating conditions validates the 3W-HFT electrical characteristics and the estimation of TAB’s power losses distribution. The close consistency between experimental results and simulation outcomes confirms the effectiveness of the proposed characterization approach.