Design of a DDQ Coil Structure for Electric Vehicle Wireless Power Transfer Systems

Achieving robust misalignment tolerance is a critical challenge in electric vehicle (EV) wireless power transfer (WPT) systems. To overcome this challenge, this paper proposes an optimised Double-D (DD) transmitter and a series-connected Double-D and Quadrature (DDQ) receiver architecture. By integrating a quadrature (Q) coil, the system effectively compensates for magnetic flux drops during lateral x-axis shifts, ensuring highly robust operation and uniform efficiency across the entire SAE J2954 spatial tolerance zone. Designed for WPT1 power class and Z1 air gap specifications, the system’s safety and performance were evaluated through the ANSYS 2017 (Electromagnetic Suite 18.0) Maxwell 3D finite element method (FEM) and physical prototyping. A 110-piece ferrite core structure successfully limits electromagnetic exposure to the 27 µT safety threshold. Validated via experimental measurements, the system achieves a measured peak efficiency of 96.61% under perfect alignment. Furthermore, to evaluate the structural limits of the topology, extreme misalignment stress tests were conducted. The results demonstrate that the system maintains over 93% measured efficiency across a broad lateral offset range up to 50 cm. This exceptional tolerance highlights the magnetic stability of the DDQ structure and its strong potential for future dynamic charging applications. The strong correlation between numerical models and experimental data confirms a highly reliable and electromagnetically compatible solution for EV charging.