Optimized DSSq Transmitter Coil-based Charging Pad Scheme to Mitigate Misalignment Issues for Wireless EV Chargers

The charging coils or pads are key components in inductive Wireless Power Transfer (WPT) technology. The offset between the transmitter and receiver pad positions causes a shift from the point of maximum flux linkage. This misalignment condition leads to a reduced coupling coefficient, thereby decreasing the power transferred to the battery load. To mitigate this issue, this paper proposes an optimised Double Set Square (DSSq) charging pad scheme for the transmitter. It is a combination of four right-angled triangular coils placed adjacent to one another. The first coil is connected to the third coil, and the second coil is connected to the fourth. The current excitation for the coils needs to be in quadrature to achieve an improved and wider flux profile around the charging pad, leading to enhanced tolerance for misalignment. An analytical formula to estimate mutual inductance and induced output voltage is derived for this design. Validation is performed using Finite Element Analysis (FEA) simulations on the Ansys Maxwell-3D platform. The proposed DSSq transmitter coil experimental design has been done and verified with simulated data. The coil has been designed for 80-90kHz operation and as per SAE-J2954 standards.