3-D Coil Positioning Based on Magnetic Sensing for Wireless EV Charging

Wireless power transfer (WPT) via magnetic resonance coupling is considered a promising outlet for electric vehicle (EV) charging due to the noncontact method. Unlike a traditional transformer, with WPT, the relative spacing and lateral distance between the primary and secondary coils are highly variable, which can affect the wireless power delivery and lower the efficiency. A magnetic positioning approach that shares the wireless charging structure is proposed to solve the misalignment issue associated with wireless EV charging. The proposed alignment sensing system employs multiple auxiliary minor coils on the secondary side to position the charging pad. The positioning principle and equivalent circuit were analyzed. The 108 samples were tested and they were distributed throughout the detection range of 70 cm. The experimental results demonstrate that > 92% of those samples have positioning errors of < 2 cm and 98% of them have positioning errors of < 3 cm.