Research On Transmission Characteristics And Control Of Two-phase Multi-Frequency Multi-Load Magnetically Coupled Resonant Wireless Power Transfer System

With the rapid development of economy and technology,the requirements on the convenient,flexible,safe and green charging methods for electrical devices are put forward.Therefore,the researches and development of wireless power transfer(WPT)technology is attracting an increasing attention.Among all kinds of WPT technologies,Magnetically Coupled Resonant(MCR)WPT technology has many advantages,such as long transmission distance,high efficiency and immunity from non-magnetic obstacles,which has broad application prospects in medium transmission distance.In practical applications,MCR WPT system should have the functions of high robustness of transmission characteristics to spatial scale,constant output voltage,load identification and power distribution.In this thesis,a two-phase multi-frequency multi-load system is proposed,which reduces the influence of spatial scale on the transmission characteristics of the system through multi-phase coils,and introduces multiple operating frequencies to realize load identification and power distribution.For simplicity,this thesis mainly studies a two-phase dual-frequency dual-load system and proposes two control strategies based on phase modulation.This thesis establishes the equivalent circuit model of the system and deduces the expression of system output power and transmission efficiency.The model of mutual inductances between coils is analyzed.The change of spatial scales between coils is reflected by the variation of rotation angle.According to the expression of transmission characteristics,the power distribution strategy by adjusting the resonant frequency of the transmitter is proposed,and the open-loop transmission characteristics of the system under two phase modulation schemes is obtained.The phenomenon of cross-interference is analyzed and its influence on targeted power distribution is avoided.Referring to the comparison among common closed-loop control methods of MCR WPT system,the closed-loop control method based on the phase modulation in the transmitter is adopted,and two closed-loop control schemes of MCR WPT system with phase modulation are proposed.Finally,a prototype of two-phase dual-frequency dual-load MCR WPT system is built in the laboratory.The experimental results prove the correctness of the theoretical analysis.The results show that the power distribution can be achieved by adjusting the resonant frequency of the transmitter.Under the proposed phase modulation schemes,the system can overcome the influence of the misalignment of coils on the transmission characteristics and achieve constant output voltage on multiple loads.