Design and Implementation of Estimating Algorithm for Foreign Object Location in Wireless Charging EV Systems

Foreign object detection(FOD) is crucial in wireless power transfer architectures. The impact level of the foreign object(FO) is dependent on its location within the charging area. Therefore, location estimation of foreign objects on the transmitter and receiver pads is of great importance due firstly to the inaccessibility of the buried transmitter pad, and secondly to invisibility of the receiver pad attached underneath the car. This paper presents a theoretical formulation for location estimation of foreign object inside an inductive power transfer (IPT) system using resonant frequency and current deviation. An experimental set up of a self-tuning IPT system with a foreign object located on the primary coil as well as the ferrite bars is presented. The results show that for the same resonance frequency deviation caused by two foreign objects with different size, the one located on the primary coil surface relatively affects primary resonant current more than the one placed on ferrite bars. This difference in current can be used to characterize a current deviation profile which will enable the location of the FO to be accurately pin pointed within the IPT system.