Research On Electric Vehicle Battery Charging System Based On Magnetically Coupled Resonance WPT

In order to improve the energy consumption structure,reduce environmental pollution,and realize the leap-forward development of the automobile industry,the state has given a large number of policies and resources to support the development of electric vehicles in recent years,but the charging technology has limited the popularity of electric vehicles to a certain extent,and the development of wireless charging technology offers a new way to solve the problem.Compared with the traditional electric vehicle wired charging method,wireless charging has the advantages of safety,convenience,reliability,and intelligence.In the present study of wireless power transmission,the magnetically coupled resonance wireless power transmission technology(MCR-WPT)has superior performance in terms of transmission power,efficiency and distance.It has become a research hotspot in the field of wireless charging.Based on this technology,this paper designs a set of wireless energy transmission system suitable for constant current and constant voltage charging of electric vehicle batteries.Firstly,the charging method of electric vehicle battery is analyzed,and the current constant current and constant voltage charging method based on MCR-WPT is compared.The relatively optimal topology charging mode is used to realize battery charging as the research object of this paper.The mathematical models of four basic compensation topologies and LCC-S complex compensation topologies of MCR-WPT system are established by using the theory of circuit mutual inductance.The current and voltage output characteristics and input impedance characteristics of each model are analyzed in detail.According to the analysis results,aiming at the disadvantages of other switching methods,a better constant current and constant voltage charging system based on SS and LCC-S topological network switching is designed,and the selection method of each component parameter is given.On this basis,a complete wireless charging system simulation model is built by using Simulink platform.The constant current constant voltage and zero phase angle characteristics are verified,and the changes of system transmission efficiency are analyzed.Secondly,the coupled coil is a key part of the wireless charging system,and its influencing factors of transmission efficiency are analyzed in this paper.At the same time,with the help of JMAG electromagnetic simulation software,the coupling degree between different shapes of coils is analyzed from the perspective of coupling coefficient between coils,and the square-square coupling coil is determined as the optimal coupling mechanism.According to the size of the actual electric vehicle coupling coil,a 2:1 simulation scale model was established,and the selection of wire and core material was introduced.The size of the coupling coil and the configuration of the magnetic core are further optimized,and method for calculating mutual inductance and coupling coefficient of asymmetric coils is presented.Finally,the hardware design of the power circuit,inverter circuit,drive circuit and control circuit in the wireless charging system is introduced.The models of the diodes,MOSFETs,driver chips,controllers,etc.used in the circuit were selected and described.A complete experimental platform for EV battery charging is built.Through this experimental platform,the constant-current and constant-voltage output characteristics and ZPA characteristics of the wireless charging system are verified,which are basically the same with the theoretical analysis and simulation results.