Research On Principle And Method For Improving Distance Of PT-symmetric Wireless Power Transfer Based On Receiver Circuit And Coupler

The output power and efficiency of PT-symmetric wireless power transfer technology in the strong coupling region are independent of the coupling coefficient,and it can achieve constant output power and transfer efficiency.However,when the transfer distance is greater than the critical transfer distance or exceeds the strong coupling region,the transfer efficiency reduces rapidly with the decrease of the coupling coefficient,which restricts the further improvement of the transfer distance.Therefore,to improve the transfer distance and broaden its application,based on the in-depth analysis of the factors affecting the PT-symmetric wireless power transfer distance,the principle of improving the PT-symmetric wireless power transfer distance is systematically discussed,and the method to improve the transfer distance by the structure of receiver circuit and coupler is proposed,which improves the PT-symmetric wireless power transfer technology and promotes its application.The main research work of this thesis is as follows:(1)Based on the coupled mode theory,the transfer characteristics of four basic types of PT-symmetric wireless power transfer systems are analyzed,and the main factors affecting the PT-symmetric wireless power transfer distance are studied.The study indicates that the critical coupling coefficient of the PT-symmetric wireless power transfer system is only related to the type and parameters of the receiver circuit,and the transfer distance can be effectively improved by changing the receiver circuit and coupler.(2)The PT-symmetric wireless power transfer system with additional inductive elements on the receiver is proposed,and its system model is established.The relationship between the additional inductive elements and the transfer distance is studied,and the optimal parameters of the additional inductive elements on the receiver are obtained.The theoretical and experimental results demonstrate that the additional inductive elements on the receiver can increase the PT-symmetric wireless power maximum transfer distance by 29.1%.(3)To improve the transfer efficiency and reduce the size of the additional inductive elements on the receiver,the PS type of PT-symmetric wireless power transfer system with additional capacitive elements on the receiver is proposed.The transfer characteristics of the system are studied and analyzed,and it is found that the transfer efficiency of the PS type is higher than that of the PT-symmetric wireless power transfer system with additional inductive elements on the receiver when the transfer distance is the same.The theoretical and experimental results indicate that the additional capacitive elements on the receiver can increase the PT-symmetric wireless power maximum transfer distance by 29.4%.(4)In order to further improve the transfer distance,the LCC type of PT-symmetric wireless power transfer system with additional inductive and capacitive elements on the receiver is proposed.The mathematical model of the system is established by the circuit theory,and the effect of inductive and capacitive elements on the transfer performance is studied.It is found that the additional inductive and capacitive elements on the receiver can increase the PT-symmetric wireless power maximum transfer distance by 61.8%.(5)Based on the above researches,the effect of different couplers on the transfer distance is analyzed,the coupling performance of different coil structures is studied,and the effect of coil parameters such as turn pitch and wire diameter on the coupling performance is discussed.Four kinds of shielding layer structures are designed,and the effect of shielding layer thickness and aluminum plate on the coupling coefficient is analyzed.The results demonstrate that increasing the diameter or side length of the coil can enhance the transfer distance,and raising the thickness of the shielding layer can also improve the transfer distance.Therefore,it can be comprehensively applied to the research of improving the PT-symmetric wireless power transfer distance.(6)Aiming at the need to change the charging position of the intelligent lawn mower in a wide range,by the technology of additional inductive elements on the receiver,the wireless charging device of constant current and constant voltage lawn mower with wide distance variation is developed.The technical index requirements are output power of 40 W,transfer distance of 6～7.5cm and overall efficiency of 82%.The test results of the prototype indicate that the device can move within the transfer distance of 6～9.2cm,the moving range is increases by 22.67%,and the overall efficiency is greater than 85.8%,which exceeds the required index.The correctness of theoretical research and the feasibility of practical application are verified.