Estimation of Optimal Operating Frequency for Wireless EV Charging System under Misalignment

Wireless charging of electric vehicles is achieved by a resonance-enhanced inductive power transfer technique. In this paper, a new method is proposed for the estimation of the operating frequency under the contingency of misalignment of the pickup coil. Analytically, the mutual inductance between the primary and secondary coils is represented in terms of their vertical and horizontal displacements, using Neumann's approximation formula. The operating frequency of the high-frequency inverter corresponds to the resonance condition, a function of the mutual inductance, which is decided by the coil misalignment. The obtained relations are corroborated with studies of simulations. The proposed method is validated by numerical simulation. A 1 kW experimental prototype is designed and tested. Experimental results corroborate the notion about the analytical expression.