Lateral Misalignment and Foreign Object Detection in Resonant Capacitive Power Transfer

This paper proposes a method of detecting lateral misalignment and foreign objects in a resonant capacitive power transfer (RCPT) system. Foreign object detection (FOD) under misalignment is also considered. The method considers the admittance matrices associated with a practical RCPT link and leverages voltage measurements on the transmit-side for detection. To support this work, a 13.56 MHz RCPT link incorporating a six-plate structure was designed and built for electric vehicle charging applications. A matching simulation model was created and, when evaluating FOD, metallic and tissue-simulating foreign objects were added. Simulations, validated by measurements, show that a lateral misalignment of up to 170 mm can be identified, including the direction of misalignment. FOD simulations indicate a detection range of up to 380 mm, also including direction. Further simulations indicate that the detection range surpasses the distance at which the basic restrictions for electromagnetic field exposure would be exceeded. Additionally, simulation results show that foreign objects can be detected under misalignment. Thus, both lateral misalignment detection and FOD can be achieved without the use of external sensors. This work can help to advance the safety features of RCPT at minimal cost for important applications such as electric vehicle charging and electrified roadways.