Coil Positioning Based on DC Pre-excitation and Magnetic Sensing for Wireless Electric Vehicle Charging

Abstract

This article proposes an accurate coil positioning method for the wireless charging system by sharing the primary coil to generate a dc magnetic field. Based on the research of the magnetic field and the discussion of the arrangement of magnetic sensors, the position equations containing core-placement coefficient G , which represents the effect of magnetic core on the field, are presented. An automatic identification of G is then proposed by judging the zero point of magnetic field, which can adapt to different charging pads. Furthermore, this article gives the flowchart of the positioning algorithm, comprising partitioning and noise suppression to improve the positioning accuracy. A large amount of samples distributed throughout the range of 20 × 16 cm are tested. The experimental results demonstrate that >97% of those samples have positioning errors of <2 cm. Besides, the proposed positioning system has been used in a 1-kW prototype for automatic changing of the compensation capacitance resulting in an improved misalignment tolerance.