High power Li-Ion battery charger for electric vehicle

The manuscript presents a 50KW vehicle battery fast charger prototype design. The charger is basically a two-stage controlled rectifier with power factor correction. The input stage consists of a three phase full bridge rectifier combined with a shunt active power filter. The input stage creates an uncontrolled pulsating DC bus while complying with the grid codes by regulating the THD and power factor according to the permissible limits. The output stage is formed by six interleaved parallel groups of two DC-DC converters, fed by the uncontrolled DC bus and performing the charging process. Two independent control boards are employed: active filter control circuitry and the DC-DC control circuitry. The former is operated according to the predetermined grid interfacing behavior, while the operation of the latter is dictated by the requests from the Battery Management System (BMS). The charger is capable of operating in any of the two typical charging modes: Constant Current and Constant Voltage. Control loops are briefly explained throughout the paper and extended simulation/experimental results are presented.