Technical analysis of frequency tracking possibilities for contactless electric vehicle charging

A particular challenge in wireless power transfer (WPT) systems is energy transfer among distance d_s, displacement y_s, and change of the angle α of the two coils, which can vary depending on the vehicle payload. Hence extensive efficiency reduction can occur, especially with use of field-conducting materials, such as ferrites. This has an impact on the frequencies of the sending and the receiving resonant circuit according to the calibration condition. Based on measurement and simulations of the inductance of the coils analyses to investigate the performance of the resonant system are done. It ends with the depiction of possible solutions. As a first step to set up the equivalent circuit diagram (ECD) all components must be defined. Therefore the compensation strategies are presented and analyzed in detail. This has a great influence on the adjusting resonance frequencies at different positional tolerances. All simulations and calculations are done with Simplorer (Ansys)¹, respectively Maple² (Maplesoft) to get a qualitative indication for system performance.