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

Abstract

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, 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 700W power is transferred through a 24 pF coupling capacitor. The proposed method reaches 91% DC-DC overall efficiency at switching frequency 2 MHz.Index Terms-Capacitive power transfer (CPT), electric fielding resonance, dynamic charging. interests include simulation of wireless power transfer and electric-field coupled power transfer.Chunyan Shuai received the B.S. and M.S. degrees in control science engineering and computer application science from Kunming

A Review on the Recent Development of Capacitive Wireless Power Transfer Technology

“…It needs to be emphasized that the derivation of the equivalent inductances is a simplification of the inductive networks. Regardless of the complexity of the inductive networks, they can be simplified as equivalent inductances with their losses, which mean this analysis is independent of the circuit topology [33][34][35].…”

“…For example, a good compensation circuit should be able to increase the voltages on metal plates for high power transfer [34]. In addition, it needs to achieve a high coupling coefficient kC and an optimum load ratio α to maximize the system efficiency [35].…”

“…For example, one receiver terminal can be directly grounded. In the application of the propulsion of a high-speed train, the metal wheels can be used as the returning path, which can replace the conventional pantograph and improve the system reliability [34]. In addition, since it is easy to get access to the earth ground in most applications and there are usually parasitic capacitances between the plates to the earth ground, the earth ground is therefore used as the conductive returning path.…”

Optimum Receiver-Side Tuning Capacitance for Capacitive Wireless Power Transfer

“…The large resistive impedance of the receiver 2 of 9 increased the power factor here because the CP impedances were highly imaginary. A matching network design [10] also aimed toward power-factor maximization. Unfortunately, as will be discussed later in this paper, power-factor maximization does not necessarily maximize efficiency.…”

“…Unfortunately, as will be discussed later in this paper, power-factor maximization does not necessarily maximize efficiency. Hence, any design method that focused on achieving maximum efficiency would be different from the methods in [8,10]. Figure 1 shows the equivalent circuit of capacitive power transfer.…”