Wireless Power Transfer by Electric Field Resonance and Its Application in Dynamic Charging

In this paper, the electric field resonance (EFR) method, similar to the four-coil configuration of the magnetic field resonance wireless power transfer, is proposed for the capacitive coupling power transfer. The characteristics of the proposed method are derived and analyzed. With the EFR method, not only unity power factor for the power source is achieved, but also high power factor and low reactive power for the capacitive coupling stage are achieved. Effective power transfer is realized by the EFR method. Based on the proposed method, a dynamic charging concept for railway vehicles is then proposed. A prototype powering system is designed and built to prove the validity of the proposed method. Analytical, simulation, and experimental results are given and compared. A 23-cm model vehicle is put on a 150-cm track. It is shown that about 700-W power is transferred through a 24-pF coupling capacitor. The proposed method reaches 91% dc-dc overall efficiency at switching frequency 2 MHz.