A Ripple-Free DC Output Current Fast Charger for Electric Vehicles Based on Grid-Tied Modular Three-Phase Interleaved Converters

This paper presents an off-board DC fast battery charger for electric vehicles (EVs) based on modular three-phase interleaved converters supplied by the low-voltage AC grid. The charger rectifies the grid voltage to a common DC-bus voltage having a slightly adjustable level by means of AC/DC interleaved three-phase active rectifier, composed of three standard commercial two-level three-phase converter modules. Three identical three-phase modules connected in parallel form a modular interleaved DC/DC converter to supply the battery. This structure offers a use of low-cost, unified and industry-recognized three-phase power modules for high- power fast EV charging stations that will reduce capital and maintenance costs of the charging facilities, enhancing further expansion of the eco-friendly transport. An original control strategy has been proposed to provide ripple-free output current in the typical EV batteries voltage range. The effect of coupling on the individual input/output inductors and total input/output current ripples has been investigated, considering both possible coupling implementations, i.e. inverse and direct coupling. Simulation results, carried out in MATLAB/Simulink environment, are reported in to confirm the feasibility and the effectiveness of the proposed EV fast charging configuration.