Design of Edge-Enhanced Coil Structure to Obtain Constant Mutual Inductance With Horizontal Misalignment in Wireless Power Transfer Systems of Electric Vehicles

Abstract

Horizontal misalignment to the $Y$ and X-axes can be as much as half the side length of a transmitting resonant coil or 10 cm for both dynamic and static wireless power transfer (DSWPT) systems. Misalignment to the Y-axis and X-axis may cause DSWPT systems to malfunction due to fluctuations in mutual inductance. In this paper, a structure of edge-enhanced coil (EEC) is proposed. The mutual inductance expression of the EEC structure is then established. Moreover, the variation of the mutual inductance of the EEC structure is obtained based on the mutual inductance expression. The study demonstrates that the mutual inductance of the EEC structure can be increased while reducing its fluctuation. The problem that quasi-constant mutual inductance is obtained at the expense of mutual inductance value is solved. Therefore, the high transmission efficiency of DSWPT systems can be obtained, and the transmission efficiency and output power can be maintained almost constant with the misalignment to the Y-axis or X-axis. The calculated, simulated, and measured results validating the effectiveness of the EEC structure are shown.