Study On Magnetic Coupling Mid-range Wireless Power Transfer Technology

The appearance and development of wireless power transfer technology has greatly changed the way of people's production and life.More and more electronic equipments,electrical appliances,industrial equipments are getting rid of the traditional wired way of charging,making a further expand of the usage scenario of all kinds of electrical equipments.So it can solve the charging problems when equipments are physically contactless.Therefore,wireless power transfer technology has a great developing prospect.In this thesis,we mainly study the power transfer problem of mid-range cases,in which the transmission distance is several times larger than the size of the transmitting and receiving coils.The main research work and innovations are as follows:Firstly,the research background and research status of wireless power transfer are introduced.,and the key technologies and future trends of wireless energy transfer technology are summarized.Secondly,three theories used in the research of wireless power transfer,circuit theory,coupledmode theory and two-port network theory respectively are studied and compared.The simplicity and intuition of the two-port network theory are analyzed by using the formula to deduce the inherent consistency of circuit theory and the coupled-mode theory.The expression of the transmission performance parameters of the two-port theory mode is deduced.Additionally,this thesis studies the magnetic field distribution of spiral resonant coil.In the thesis,the formula of the near-field magnetic field distribution of the coil is deduced.Then,the magnetic field strength,the concavity and convexity of the coil are compared with the change of the radius,the position of the coil and the variation of the coil radius.The influence of the change of size and position on the magnetic field is analyzed.Then,the two-coil network energy system is analyzed by two-port network theory.The scattering matrix of the system is obtained by simulation.The transmission performance of the system is analyzed by S-parameter,and then a method to add a flexible impedance matching network on a two-coil transmission system is proposed.Finally,this thesis presents a design method for introducing a reverse loop in the transceiver coil.By changing the port position in the coil,we can introduce the opposite direction current.Due to the mutual cancellation of the magnetic field,the introduction of reverse current will change the overall magnetic field of the coil convexity,making the coil magnetic field distribution more gentle,the system transmission efficiency changes smaller,and the stability of the system transmission increasing.Theoretical analysis and simulation results show that,compared with the ordinary transmission coil,the design method proposed in this thesis can improve the magnetic field distribution and provide more stable transmission efficiency in a certain transmission range.