Development and analysis of three‐coil wireless charging system for electric vehicles

Summary Wireless charger has become a potential solution for charging electric vehicles (EVs) due to its intrinsic convenience and further scope of countering range anxiety issue. However, ground clearance of the EVs varies with the vehicle type, manufacturer, and so on, which reduces the power transfer efficiency (PTE) and power delivered to load (PDL) by the wireless charger. To overcome these limitations, this paper focused to revamp the design of a three‐coil wireless charging system through optimized size and position of intermediate coil (InC). Further, the system is tested for different loads at different input voltages, misalignment conditions, and distances for 100‐kHz frequency and compared with a two‐coil system under the same conditions. Angular misalignment of InC near the transmitter coil (TxC) (50‐mm gap) showed increased efficiency compared to other misalignment conditions. Three‐coil system results at different distances of InC from TxC showed that the maximum efficiency region shifted to different loads. Maximum efficiency for designed three‐coil was achieved when the InC was placed in the center between the TxC and RxC. Maximum efficiency for power transfer distance (D) of 150 and 200 mm obtained are 76% and 70% for 25Ω and 35Ω. In this paper, a comparison of a two‐coil and a three‐coil wireless charger with a moving arm scenario is analyzed. Comparison for different power transfer distances, currents, voltages, frequencies, misalignments, and current stresses is discussed with computation and hardware results. The algorithm for the selection of optimal turns of Intermediate Coil (InC) and particular position of InC for a specific load is designed using mutual inductance and three‐coil circuit equations. Comparison of proposed analysis with literature is also discussed.