Operation of Inductive Charging Systems Under Misalignment Conditions: A Review for Electric Vehicles

Inductive power transfer (IPT) for electric vehicles (EVs) is an emerging technology that can transfer power wirelessly over certain distances, thus offering some remarkable characteristics in terms of flexibility, position, and movability. The output power of an IPT system depends on the coupling factor of the magnetic couplers, which can deviate from the nominal operating conditions due to the occurrence of misalignment. Nevertheless, misalignment of the magnetic couplers in inductive charging is inevitable, and it usually results in the variation of the mutual inductance and output power of the system with a corresponding decrease in the system’s overall efficiency. So far, the literature has reported various techniques for achieving designs with higher misalignment tolerance. The reported techniques can be mainly classified into three categories, as viewed from the following aspects: magnetic couplers layouts, compensation networks, and control strategy. Each of these techniques has its pros and cons in terms of implementation cost, system layout, efficiency, power density, and reliability depending on the application. With the increased investigation of more applications of IPT, new modified techniques for improving the misalignment tolerance in the IPT system are continuously being proposed based on permutations and combinations of the existing ones; thus causing some confusion and difficulties for researchers and system vendors to follow. This article, therefore, aims to provide a comprehensive review of the existing methods for IPT systems that address the misalignment issue in EVs’ wireless charging. The background of the inductive charging systems for EVs is presented and an investigation of the numerous factors affecting the output power and other performances is conducted. In addition, the advantages and disadvantages of each technique on the IPT system’s performance are analyzed in detail.