Design and Optimization of an 11 kW Integrated OBC-LDC EV Battery Charging System

초록

This article proposes a new integrated battery charging system (IBCS) for electric vehicles, combining a dual-active bridge (DAB) converter for the on-board charger (OBC) and a phase-shift full-bridge (PSFB) converter for the low-voltage dc-dc converter (LDC). Unlike conventional IBCSs, which employ the output inductors and transformer separately, the proposed IBCS integrates them using a two-transformer structure, thereby reducing the overall volume and the number of conducting components on the LDC secondary side. In addition, synchronous rectifiers (SRs) with an optimal driving scheme are introduced to minimize conduction losses. Furthermore, the transformers are designed to optimize the efficiency of the proposed IBCS in both grid-to-vehicle (G2V) and vehicle-to-grid (V2G) modes. These optimizations are based on a detailed analysis, including the coupling effects between the OBC and LDC and the impact of leakage inductances on the OBC primary and secondary sides, which have not been thoroughly addressed in previous studies. As a result, the proposed IBCS can achieve high power density and efficiency. Finally, to validate its performance, a prototype integrating an 11 kW OBC with a 2 kW LDC is built and tested, demonstrating a peak efficiency of 97.1% in both the G2V and V2G modes.

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