Research On Realization Of Maximum Transfer Efficiency Of Dual-load Wireless Power Transfer Systems Considering Cross-coupling Between Receiving Coils

The magnetic resonant coupling wireless power transfer(WPT)system features long transfer distance,high transfer efficiency and safety,which has received more and more attention.In recent years,many researchers from home and abroad have conducted a lot of research on a single-load WPT system,and thus,a strong theoretical foundation has been laid for its commercial application.However,a single-load system cannot meet the requirements for simultaneous WPT of multiple devices,so the multi-load system is becoming one of the current research hotspots in WPT technology.Generally,there are multiple receiving coils in the multiload WPT system.Cross-coupling between the receiving coils is likely to occur in practical applications,which affects the efficiency of the multi-load WPT system.As a result,there are critical issues to be urgently solved for a multi-load WPT system that the impact of crosscoupling between the receiving coils needs to be eliminated and then maximum system efficiency is achieved.Taking a dual-load WPT system as the research objective,this thesis analyzes the effects of cross-coupling and equivalent loads on the characteristic of system efficiency,and proposes a method to eliminate cross-coupling and achieve maximum transfer efficiency of the system.The main research contents of this thesis are as follows:(1)The mathematical model of the dual-load WPT system is established,and its efficiency expression is derived.On this basis,the effect of the cross-coupling between the receiving coils and the equivalent loads on the efficiency characteristic of the dual-load WPT system is analyzed in detail.The analytical result shows that the cross-coupling will reduce the efficiency of the dual-load WPT system.Meanwhile,it is found that when the cross-coupling is eliminated in a dual-load system,there exists optimal loads to enable the system to achieve maximum efficiency.(2)In order to address the issue of cross-coupling in the dual-load WPT system,a method of eliminating cross-coupling using capacitance compensation is proposed,and the principle of decoupling is analyzed in detail.On this basis,the load condition of the dual-load WPT system to achieve maximum transfer efficiency is further analyzed.(3)A method to achieve capacitance compensation and optimal equivalent load matching is proposed by adjusting the amplitude and phase of the input voltage and current of the PWM rectifier on the receiving side.Compared to the existing methods that use fixed compensation,impedance matching network,or multi-frequency power transfer,this method does not need to change the hardware parameters.By adjusting the control parameters of the PWM rectifier on the receiver side,the system can be decoupled and operated at the maximum efficiency point,which has the advantages of simplicity and high flexibility.(4)Finally,the design method of the dual-load WPT system is analyzed in detail.The design parameters of the system are given,and the experimental prototype is built.The experimental results show that the proposed method can effectively eliminate the crosscoupling between the coils on the receiving side,and make the system work at the point of maximum efficiency.Compared to the dual-load system using uncontrolled rectification,the transfer efficiency has been significantly improved.The correctness and effectiveness of the proposed method are verified.