A Special Magnetic Coupler Structure for Three-Coil Wireless Power Transfer: Analysis, Design, and Experimental Verification

In this article, a special magnetic coupler for three-coil wireless power transfer (WPT) is proposed to eliminate the mutual inductance between the source coil and the receiver coil, which can significantly improve the design freedom. Specifically, unipolar Q coil, mixed QDD coil, and bipolar DD coil are designed for the source coil, the transmitter coil ( $\text{T}_{\mathrm {X}}$ ), and the receiver coil ( $\text{R}_{\mathrm {X}}$ ), respectively. By making use of unipolar coils and bipolar coils, this structure magnetically decouples the receiver coil from the source coil. Meanwhile, under different lateral misalignment conditions, this new coupler facilitates maintaining high efficiency. A laboratory prototype has been constructed to validate the proposed structure, demonstrating that the proposed structure can realize inherent characteristics, enhance misalignment tolerance, and energy transfer. The potential applications are EV systems, but this design can be generalizable to other three-coil systems.