Field orientation based three-coil decoupled wireless transmitter for electric vehicle charging with large lateral receiver misalignment tolerance

Abstract

A three-coil decoupled transmitter is developed for the inductive power transfer system of electric vehicle charging. The three-coil decoupled transmitter consists of three overlapping rectangular coils with magnetic mutual decoupling and is capable of overcoming large receiver lateral misalignment up to 20 cm. A current optimization method is advanced to derive transmitter coil currents for the multi-phase system that minimizes the coil loss through optimizing the current distribution among transmitter coils. The optimized current distribution reduces the maximum leakage flux by around 40% compared to the best alternative excitation method. The compensation strategy provides unity power factor for high-power transfer phases and allows a single set of compensation capacitors to be used regardless of receiver alignment. The three-coil decoupled transmitter is compatible with a typical three-phase inverter for industrial practical application, which halves the power electronic switches used with previous topologies. The simulation verification is performed at 3.3 kW, achieving 93.76% efficiency at perfect alignment and 92.54% efficiency at 20 cm misalignment. The experimental verification is implemented at 3.3 kW with 200 mm ground clearance, realizing a 92.97% efficiency at perfect alignment and 90.57% efficiency at 20 cm misalignment.