Fourier Analysis and Optimization of Inductive Wireless Power Transfer for Electric Vehicle Charging

With the growth of electric vehicle (EV) popularity, different charging options to increase user convenience and reduce charging time such as high power wireless charging are increasingly being developed and researched. Inductive wireless power transfer (WPT) systems for EVs must meet specifications such as stray field, battery power and voltage operating range, efficiency, and ground clearance. The coil geometry and design have a large impact in meeting these constraints. Typical design approaches include iterative analysis of predetermined coil geometries to identify candidates that meet these constraints.

This work instead directly generates WPT coil shapes and magnetic fields to meet specifications and constraints through the optimization of Fourier basis function coefficients and that can be used to predict system efficiency and performance.

The proposed Fourier Analysis Method (FAM) applies to arbitrary planar coil geometries and does not rely on iterative finite-element analysis (FEA) simulations. This flexibility allows for rapid design evaluation across a larger range of coil geometries and specifications. The method is used to consider the trade-off of coil current and stray field for given power levels to illustrate the flexibility and generality of the method. A 6.6 kW proof-of-concept demonstrator WPT system is built from the optimization result to compare model efficiency, stray fields, and performance to experimental measurements. The methodology is then used in the optimization, design, analysis, and testing of two 120 kW demonstrators, including thermal modeling and integration.