High-Power Three-Port Converter for Efficient EV Fast Charging Using Partial Power Processing

This paper presents a high-power, isolated three-port converter designed for electric vehicle (EV) fast-charging applications. The proposed topology integrates the electrical grid and a BESS utilizing partial power processing (PPP) to enhance efficiency and minimize system cost, size, and power converter rating. A key feature of the design is the direct power path from the Battery Energy Storage System (BESS) to the EV, which reduces losses while maintaining galvanic isolation between the grid and EV, in compliance with IEC 61851-23:2014 standard. The converter features two active full-bridge input ports (for the grid and BESS) and a unidirectional series resonant converter (SRC) at the EV output, all of which are connected through a three-winding transformer. Power flow is analyzed using Fundamental Harmonic Approximation (FHA), introducing direct and indirect power flow ratios (k_dir, k_indir). A dual control strategy is implemented: switching frequency is used to manage EV charging, while phase shift controls BESS operation. A 1 kW prototype has been developed to validate the proposed converter, enabling uninterrupted BESS-powered charging during grid outages and thereby enhancing grid stability while reducing infrastructure demands.