Comprehensive Analyses and Comparison of 1 kW Isolated DC–DC Converters for Bidirectional EV Charging Systems

Abstract

Isolated dc–dc converters with galvanic isolation are commonly used in electric vehicle (EV) battery chargers. These converters interface between a dc voltage link, which is usually the output of a power factor correction stage, and an energy storage unit. CLLC and dual active bridge (DAB) dc–dc converters can achieve high power density, high-energy efficiency, wide gain range, galvanic isolation, and bidirectional power flow, and therefore, have potential applications as dc–dc converters for bidirectional EV charging systems. In this paper, full-bridge CLLC, half-bridge CLLC, full-bridge DAB, and half-bridge DAB dc–dc converters are evaluated and compared for their suitability for EV chargers. All the converters are designed with optimal soft-switching features. The operating principles, design methodologies, and design considerations are presented. Prototypes of the converters with power rating of 1 kW are designed and developed. The prototypes interface a 500 V dc link and a 200–420 V load, which is common for EV applications. The performances of the circuits are analyzed and a comprehensive comparison is conducted.