Research On Power Factor Correction For Wireless Power Transfer System

Wireless power transfer(WPT) technology is a new technology of safety and convenience with great potential commercial value. High power WPT applications will cause a series of effects on the grid, including the harmonic pollution, which requires the corresponding active power factor correction(APFC) device to improve it. Taking EV wireless charging as the background, requirements for the APFC for WPT system are quite demanding: high power factor to reach more than 0.95, high efficiency to achieve 96%~97%, and power level of 1~10kW or higher.According to EV wireless charging technical requirements, this paper focuses on the inductive WPT system with a full-bridge resonant converter and a series-parallel compensation network, the electrical characteristics of which are analyzed, especially on the power characteristics under the condition of parameter mismatch. Then the necessity and the role of APFC in WPT system are clarified.Based on the requirements of WPT system, a three-stage interleaved APFC is designed with a new current-sensing method for the average current control: inductor current substituted by IGBT current for the voltage and current double closed-loop control. The simulation results show the feasibility of this alternative current-sensing method, which realizes the high power factor of 0.999. This paper also proves that with the three-stage interleaved APFC applying to WPT system, power factor correction results are good under various power levels; the input current ripple suppression effect is obvious; the efficiency is above 97%.Based on the theoretical analysis and the simulation verifications, a 2.5kW three-stage interleaved APFC is designed with the multi-channel analog controller FAN9673, using IGBT current substituting inductor current for the average current control. The prototype is tested under 0.5~2.5k W various power levels. Results are achieved: power factor >0.99 of and efficiency >96%. The following study of this paper will focus on the prototype used in a complete WPT system for further experimental verification.