Coil Design for High Misalignment Tolerant Inductive Power Transfer System for EV Charging

The inductive power transfer (IPT) system for electric vehicle (EV) charging has acquired more research interest in its different facets. However, the misalignment tolerance between the charging coil (installed in the ground) and pick-up coil (mounted on the car chassis), has been a challenge and fundamental interest in the future market of EVs. This paper proposes a new coil design QDQ (Quad D Quadrature) that maintains the high coupling coefficient and efficient power transfer during reasonable misalignment. The QDQ design makes the use of four adjacent circular coils and one square coil, for both charging and pick-up side, to capture the maximum flux at any position. The coil design has been modeled in JMAG software for calculation of inductive parameters using the finite element method (FEM), and its hardware has been tested experimentally at various misaligned positions. The QDQ coils are shown to be capable of achieving good coupling coefficient and high efficiency of the system until the misalignment displacement reaches 50% of the employed coil size.