Optimal Design of Grid-Side LCL Filters for Electric Vehicle Ultra-Fast Battery Chargers

This paper proposes a complete design procedure for LCL filters intended for electric vehicle (EV) ultra-fast battery chargers. The basic modeling of LCL filters is reported and the optimal ratio between grid-side and converter-side inductance is discussed. The design methodology is based on the identification of all parameter constraints, which allow to graphically determine the filter design space. Once the available space is identified, the feasible design which minimizes the total required inductance is selected, since inductors dominate the overall LCL filter volume, loss and cost. The proposed design procedure is directly applied to a 50 kW, 20 kHz 3-level unidirectional rectifier for a modular EV ultra-fast charger. The performances of the selected design, in terms of harmonic filtering and current control dynamics, are verified by means of simulation in PLECS environment, proving the validity of the proposed design methodology.