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This article proposes an integrated on-board charger (IOBC) for electric vehicles (EVs) based on an isolated three-port dc–dc converter. The proposed architecture integrates the on-board charger (OBC) and the auxiliary power module (APM) in a single multiport converter, offering a low component count. The proposed converter is capable of charging high-voltage (HV) and low-voltage (LV) batteries simultaneously, over the entire battery voltage ranges. A three-winding transformer is used to provide galvanic isolation between the converter ports and consequently, power flow is coupled among the three ports. In this article, a boundary condition is derived for the first time and a novel modulation scheme is proposed to regulate the power flow at the HV and LV ports independently, utilizing the converter’s 3-degrees-of-freedom (3-DOF). Hence, charging of the HV and LV batteries can be realized similar to dual-active-bridge (DAB) and phase-shifted full-bridge (PSFB) converter, respectively. Results show that all converter semiconductor devices operate with zero-voltage-switching (ZVS) over wide power and voltage range without the need for additional resonant components, due to the proposed 3-DOF selection scheme. A 3.5-kW hardware prototype of the proposed converter is built and tested and key experimental results are presented to verify the converter’s theoretical analysis and ZVS operation.
Kougioulis et al. (Mon,) studied this question.