Comparison of methods for compensation capacitor calculation in a three-phase wireless power transfer system

This paper proposes a new approach to calculate the compensation capacitors values for high power three-phase wireless power transfer systems, suitable for deployment in wireless EV chargers. The proposed approach increases the power factor of transmitter phases, and thus reduces the DC bus voltage requirement significantly for systems with non-decoupled transmitter coils. The proposed approach derives the compensation capacitor values as a function of rated transmitter currents. The paper applies the transmitter currents from perfect alignment and extreme misalignment into the proposed approach to derive two sets of compensation capacitors. One set of capacitors provides unity power factors for each phase at perfect alignment while the other set of capacitors provides unity power factor for the phase delivering highest power for all misalignments. Simulation verification is performed at 3.3 kW output power and 300 V battery voltage showing that the proposed method can reduce the DC bus voltage requirement to below 800 V for all misalignments. Experimental results are obtained at 1000 W output power and 150 V battery voltage verifying the proposed approach.