Study On Wireless Power Transfer Via Coupled Magnetic Resonances And Optimized Design Of The Coil

As a new type of power transmission technology,wireless power transmission has been widely used in industrial production,medical assistance,rail transportation and portable mobile devices in recent years.The wireless power transfer via coupled magnetic resonances is currently the most popular.The research direction is quite rich,and great progress has been made,but there are still some problems to be solved,such as low transmission power and large transmission loss.After research,it is found that the structure of the coupled coil is one of the reasons for this problem.Based on this problems,this paper studied system characteristics and coil optimization.Firstly,establish the equivalent model of the transmission system by using the coupled mode theory.By simulating and solving the coupled mode equation of the oscillating system,the general law of wireless energy transmission and the conditions for improving the transmission efficiency are analyzed.Establish simplified circuit model through mutual inductance theory,and equations for simplified circuit,verify the correctness of the coupled mode theory,solve the equation to obtain the normalized voltage expression on the load side and the frequency response of the The wireless power transfer via coupled magnetic resonances system,that is,the frequency splitting characteristics and laws;research the compensation for capacitance,which based on the mutual inductance theory,then select the best compensation scheme through theoretical derivation and simulation;combine the above theoretical research to simulate the entire system of wireless power transfer via coupled magnetic resonances.Established the electromagnetic field model of the coupled coil by the derivation of Maxwell's equations;using the method of finite element analysis to analyze the high frequency effect of the conductor,Then use the finite element simulation software Ansoft Maxwell to simulate the skin effect and proximity effect of the conductor when high-frequency current is passed,the results show that the traditional single-wound coupling coil is seriously affected by high-frequency effects during the wireless power transmission process,resulting in serious heating of the coil and increased loss.Therefore,this article introduces the multi-strand litz wire structure into the coupling coil and uses Ansoft Maxwell software The simulation of the eddy current field,current density,and resistance loss when using the coil of the litz wire structure and the traditional single-stranded coil,the comparison proves that the Coupling coil wound by the litz wire in the wireless power transfer via coupled magnetic resonances system can reduce the system loss;subsequent experiments found that the high-frequency magnetic field interfered with surrounding electronic components.After analysis,it was caused by high-frequency magnetic field leakage.Therefore,in this paper,magnetic materials distributed according to certain rules were added to the coupling coil.The material not only improves the shielding effect,but also improves the magnetic induction intensity of the transmission area and the coil's own parameters.Finally,according to the results of coil optimization,design and manufacture of litz coil with shield and wireless power transfer via coupled magnetic resonances system,then obtain and compare system data through the built experimental device,it shows that the transmission efficiency of the system with optimized coil structure is increased by 18.3%.