Coupling coefficient of a magnetic coupler is a key factor that affects the efficiency of wireless charging system. DD-type couplers have the most common topology in the literature. However, they have low coupling coefficients. In order to obtain high coupling coefficient of magnetic coupler, firstly, the magnetic circuit models of DD-type and solenoid-type magnetic couplers commonly adopted in electric vehicles are built in this paper. Secondly, a hybrid DD-solenoid type coil winding is proposed based on the analytical model, and the optimized design of the magnetic core and shielding structure are also introduced in this paper. Thirdly, an optimization design method for magnetic coupler is proposed. 3-D finite-element analysis (FEA) and experimental results verify the theoretical analysis. It is shown that the performance of the hybrid winding method proposed in this paper is significantly improved compared to the traditional DD winding method, and it can also keep the high offset tolerance characteristics of DD winding. In the meantime, the proposed method can increase the coupling coefficient and decrease the cost through optimization of magnetic core, and the shielding structure can effectively reduce the electromagnetic interference.
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