Multi-frequency Wireless Charging System And Its Foreign Object Detection Technology

Under the "double carbon" strategic goal,electric vehicles are popularized by virtue of their advantages such as low energy consumption and light pollution.Compared with the wired charging mode,wireless charging technology of electric vehicles is more flexible and convenient,which has become a research hotspot at home and abroad.Based on the Magnetic Coupled Resonant Wireless Power Transfer(MCR-WPT)technology,this article conducts indepth research on the multi-load synchronous power supply and foreign object detection requirements of high-power wireless charging systems,including the selection of system compensation structure,the establishment of multi-frequency system circuit models and the design of magnetic coupling structure,as well as the implementation of metal and living foreign object detection functions.The main work is as follows:The compensation structures of LCC-LCC and S-S are compared and analyzed.Firstly,four kinds of basic resonant compensation structures are introduced,and the high applicability of S-S compensation structure is demonstrated by analyzing the influence factors of primary side compensation capacitance in resonant state.Secondly,the equivalent model of LCC-LCC and S-S compensation structure system is established,and the mathematical expressions of power and efficiency are derived.Finally,the output characteristics of the two systems are compared,and the applicable scenarios of the LCC-LCC and S-S compensation structures are determined.The establishment of circuit model of multi-frequency system and the optimization design of magnetic coupling mechanism.Firstly,the circuit model of multi-frequency MCR-WPT system is established.According to the resonant frequency,the whole system is divided into three subsystems:main power system,auxiliary power system,and foreign object detection system.The equivalent decoupling circuit of the system under the independent action of each power supply is analyzed.Secondly,introduce the current interference coefficient W to design the frequency,transmitting and receiving coils,and coupling coefficient of the auxiliary power source system,and optimize the design to ensure that the current interference coefficient is below 3%.Next,establish an integrated simulation model of the magnetic coupling mechanism and analyze the magnetic field distribution of the transmitting and receiving coils in the auxiliary power source system.Finally,to address the cross-coupling problem between subsystems,use Ansys Maxwell finite element simulation software to optimize the dimensions of the magnetic coupling mechanism,and select 60%and 90%of the initial size in the x and y directions as the standard sizes for the transmitting and receiving coils in the auxiliary power source system,effectively improving the multi-frequency system’s anti-offset capability.Research on active Metal foreign object Detection technology based on array detection coil.Firstly,the detection method of metal foreign object based on active coilwas analyzed,the proportional coefficient β was defined to characterize the detection effect of the system,and the appropriate circuit parameters were selected.Secondly,the inner diameter,turns and line spacing of the structure parameters of the detection coil were optimized.The double-layer cowinding mode was used to strengthen the detection ability of the coil.The series coil set was designed to eliminate the coupling effect between the energy transmission coil and the foreign object detection coil under the non-uniform magnetic field,and the capacitor and inductance connection mode was improved to improve the detection ability of small metal foreign objects.Finally,the parallel resonant circuit is analyzed,and on this basis,the anti-parallel strengthening detection coil set is designed.Research on Detection technology of living foreign object based on Comb capacitor.Firstly,the equivalent circuit of the living foreign object detection system was established,and the working principle of the detection system was analyzed by deducing formulas.Secondly,the simulation model of the comb capacitor was constructed,and the electrode spacing,wire thickness and capacitance spacing of the comb capacitor were designed according to the proportional coefficient γ,to explore the influence of the height and bottom area of the living foreign object on the comb capacitor.Finally,the combination mode of array detection coil and comb capacitor is proposed to realize the function of simultaneously detecting metal and living foreign objects.The compensation capacitor is introduced to make the detection system in resonant state.An equivalent circuit containing the compensation capacitor is established and the compensation capacitor interval satisfying the proportional coefficient change is greater than 30%is determined by the equivalent induction of the resonant unit.The multi-frequency system experiment platform was built to verify the feasibility of theoretical derivation and simulation analysis.Firstly,the components of the experimental platform are introduced,and the structural parameters of the integrated magnetic coupling mechanism are listed.Secondly,the experiment of independent power supply and synchronous power supply for the main power supply system and auxiliary power supply system is carried out,and the input and output circuit parameters of the two systems under different power levels and different offset degrees are obtained under the independent power supply.The interference coefficient of the synchronous power supply of each branch of the 20,25,30kHz auxiliary power supply system and the 85kHz main power supply system is compared.The experimental results show that the offset tolerance of the system is strong in a certain range,and the interference between the 20kHz auxiliary power supply system and the 85kHz main power supply system is small,which verifies the feasibility of synchronous operation of the two systems.Finally,the detection experiment of metal and living foreign objects was carried out to test the sensitivity of common metal foreign objects,and the change of detection signals in different regions of single coil was obtained.The experimental results showed that the location of metal foreign objects could be determined by series coil set,and the anti-series and antiparallel strengthening detection coil set could significantly enhance the detection sensitivity.The combination mode of detecting coil and comb capacitor is proved to be effective.