Research And Application Of Transmission Characteristics Of Wireless Power Transfer System With Asymmetric Coil Structure And Parameters

In recent years wireless power transfer(WPT)technology has been studied widely in home and abroad.In some fields,WPT has replaced the traditional wire power transfer,making our lives more convenient.It is a trend nowadays to update electronic products by replacing the traditional wire charging with emerging wireless charging.However,in order to cultivate the users’ habit,other features of the products must generally be left unchanged when being wireless,limiting the options in receiver design.As a result,asymmetric coil designs should be considered in wireless charging systems.Studying the asymmetric coil structure and parameters further in WPT system helps guide the design in various practical applications.In this thesis,the transfer characteristics of WPT system with asymmetric coil structure and parameters are further studied to acquire better transfer performance in real implementations.The major contents of this thesis are as follows:Firstly,the forms of asymmetric structure in WPT system are studied,as well as the factors that lead to asymmetry in WPT system.Meanwhile,the variations of internal resistance,inductance and mutual inductance of transmission coils are discussed for asymmetric system.Then,WPT system with series compensation is modeled with circuit theory.Considering asymmetric coil structure and parameters,power transfer characteristics are discussed.The frequency splitting phenomenon and influences of coupling coefficient,load and resonant frequencies are analyzed in detailed.Subsequently,the design of wireless charging prototype with asymmetric coil structure is considered according to the preceding analysis.The lithium-ion battery pack of cordless power tools are taken as the load.All submodules are described in detail,and simulations are carried out to verify the design primarily.Finally,the prototype is implemented,and experiments are conducted to test the output characteristics of WPT system with asymmetric coil structure.The output power for 18 V lithium-ion battery pack reaches approximately 56 W,which is consistent with the analytical result.