Dynamic Impedance Matching Technology For Radial Moving Loads In Wireless Power Transmission System

With the application of wireless charging in life,the research on wireless energy transmission has been paid more and more attention in recent years.The principle of wireless energy transmission can be roughly divided into three types: microwave radiation type,electromagnetic induction type and magnetic coupling resonance type.Because the magnetic coupling resonance wireless charging has a long transmission distance,it does not require the absolute directness of the coil during the transmission process,and the radiation is small,and the application scenarios are wide.In actual use,the coils are usually not completely coaxial,and radial misalignment will cause impedance mismatch of the system,resulting in reduced transmission power and efficiency of the system.Therefore,this paper studies the radial misalignment of the coil in the magnetic coupling resonance wireless transmission system.This paper proposes to adopt the method of fixed-point impedance matching to improve the transmission power and efficiency of the system.The main research work is as follows:(1)Using coupled mode theory and mutual inductance theory to theoretically analyze the magnetically coupled resonant wireless charging,establish a self-inductance and mutual inductance model of the dual-coil transmission structure,and derive the mutual inductance calculation when the coil is not coaxial.The transmission efficiency of the system is calculated,and the conditions for maximum power transmission are given.(2)Analyze the impedance matching.After analyzing the commonly used impedance matching network,the L-type matching circuit with a simple structure is selected.The calculation formulas of the parameters of the L-type matching circuit are given.At the same time,the impedance using the Smith original image is proposed.Matching method.After the coil model is established,the joint design of HFSS and ADS is optimized,and the equivalent input impedance,power gain and other information during the coil transmission are obtained.The Smith original diagram is used for impedance matching design for each radial offset distance.The simulation results verify that increasing the impedance matching circuit improves the transmission power and efficiency of the entire system.(3)The equivalent input impedance of the actual test circuit,design and manufacture of the relay capacitor array impedance matching circuit board,design the flow block diagram of dynamic impedance matching and the selection of each module.Build a wireless charging experiment platform,including signal generator,DC power supply,primary and secondary power amplifiers,rectifier voltage regulator circuit and load.(4)Debug and test each module of dynamic impedance matching,perform the experiment of the radial movement of the receiving coil,and compare the experimental results before and after adding the impedance matching network to the system to verify the feasibility of the designed impedance matching scheme.In this paper,the wireless power supply system with dual coil structure under the condition of radial misalignment of the receiving coil is studied,and an impedance matching scheme is proposed to improve the transmission power and efficiency.An impedance matching circuit board is made on the basis of simulation experiments for experimental verification It proves the feasibility of the designed scheme and provides a basis and experimental basis for related research.