Research On Bowl-shaped Spatial Magnetic-coupled Resonant Wireless Power Transfer

As a new power supply technology,Wireless Power Transfer(WPT)has the characteristics of reliable security and flexible layout.At present,the common couplers in wireless power transfer are composed of circular,rectangular and other planar coils.However,planar couplers cannot be attached to the installation surface completely with inclined angles or grooves,such as hanging rails,resulting in low space utilization of the entire installation environment,which will cause the limitation of transmission power and efficiency.Therefore,a bowl-shaped spatial magnetic coupler for magneticcoupled resonant wireless power transfer system was proposed in this paper.Compared with planar magnetic couplers,bowl-shaped spatial magnetic coupler can be flexibly attached to the groove surface by adjusting the bending angle and bending distance,which is conducive to improving space utilization rate,and can generate a wider range,stronger strength and better uniformity of spatial magnetic field to improve transmission power and efficiency.At the same time,the strong anti-offset performance ensures the stable output of the system.The main research work and achievements of this paper are as follows:Firstly,aiming at the limitation of planar wireless power transfer system,bowlshaped spatial Magnetic-Coupled Resonant Wireless Power Transfer system has been proposed;The coupling mode theory and circuit theory were compared and analyzed.A model of Magnetic-Coupled Resonant Wireless Power Transfer system based on SS topological compensation was established by using circuit theory,and the output power and transmission efficiency of the system were deduced.The influence of mutual inductance and load on output power and transmission efficiency as well as the cause and solutions of frequency splitting are studied.Secondly,the spatial magnetic field distribution models of planar coil and BS coil were deduced by Biot-Savart law,and the relationship between the axial transmission distance and the spatial magnetic field distribution of planar coil and BS coil was compared with the numerical simulation results.The influence of the number of turns and the distance between turns on the coupling degree of transmitting and receiving coils was studied by parametric modeling.The mutual inductance calculation model was established and the relation between the coupling coefficient of the coil in bowl space and the coil in plane and the transmission distance was compared and analyzed,as well as the influence of bending angle and bending distance on the coupling coefficient.The influence of operating frequency on the current density distribution and resistance of the wire section was analyzed by finite element method and the number and diameter of Litz wire are determined.Thirdly,aiming at the magnetic flux leakage problem of bowl-shaped spatial MCR-WPT system,the shielding principle of non-ferromagnetic materials and ferromagnetic materials was analyzed based on electromagnetic field theory,and the eddy current loss model and magnetic circuit reluctance model were established.Aiming at the magnetic flux leakage problem of wireless power transfer system,the shielding principle of non-ferromagnetic materials and ferromagnetic materials was studied,and the eddy current loss model and magnetic circuit reluctance model were established based on electromagnetic field theory.The shielding effect of aluminum plate and ferrite and its influence on the coupling degree of transmitting and receiving coil were compared and analyzed by finite element method.The anti-offset performance of planar magnetic coupler and bowl-shaped spatial magnetic coupler was compared and analyzed by finite element simulation.Besides,a strip ferrite shield structure suitable for bowl-shaped spatial MCR-WPT system was proposed and optimized,which can reduce magnetic flux leakage and improve the anti-migration performance of the system.Finally,the experimental platform of the bowl-shaped spatial MCR-WPT system was fabricated and verified experimentally.When the deviation step is 2 cm,the mutual inductance,transmission power and efficiency of the bowl-shaped spatial magnetic coupler were measured respectively.The experimental results show that when the transmission distance is 10 cm,the transmission power of the system is 60 W and the transmission efficiency can reach 84.17%.When the angle deviation of the receiver coil occurs at 30°,the transmission power and efficiency of the system can remain stable.