Design Of Wireless Charging System Based On Double-sided LCC Topology

With the rapid development of electric vehicle industry,wireless charging technology has become a research hotspot in the field of electric vehicle charging technology.Compared with the traditional wired charging method,the wireless charging method greatly improves the convenience and safety of electric vehicle charging.The purpose of this paper is to design a wireless charging system for electric vehicles,which adopts the common charging method of constant current before constant voltage which is commonly used in lithium battery charging.For this purpose,this paper mainly does the following work:First,the basic principle of wireless charging system is analyzed.The leakage inductance model and mutual inductance model of loose-coupled transformer are established by means of circuit theory modeling to compare the output characteristics of different compensation structures.The double-sided LCC topology is selected as the resonant circuit in this design,and the constant current output and constant voltage output characteristics and their conditions are derived.Secondly,MAXWELL software is used to simulate the loose coupling transformer.In the design of the coil structure,considering the height and space of the actual vehicle floor,the plane coil is selected as the loosely coupled transformer structure.Considering the high working frequency of the system,the litz wire was selected to reduce the influence of skin effect.For the design of magnetic core,after the comprehensive comparison of the magnetic permeability,resistivity and other performance and cost of the four main magnetic core materials,ferrite was selected as the magnetic core material,and three different magnetic core structures were designed for the magnetic induction strength and coupling coefficient comparison.Finally,the c-type structure mentioned in the paper was selected.A shielding plate was designed by analyzing the influence of the material and thickness of the shielding plate on the magnetic induction intensity of the area above the automobile chassis.The influence of the relative positions of the two coils on the mutual inductance of the loosecoupled transformer is analyzed for the c-type structure mentioned in the paper.Thirdly,the characteristics of electric vehicle lithium battery are analyzed,and the parameters of compensation circuit are designed based on the previous work results.The parameter design flow of double-sided LCC topology structure is presented,and the accuracy of parameters is verified by PSPICE.Then,the transmission characteristics of the double-sided LCC compensation structure were analyzed,and with the help of MATLAB,the system impedance,system transmission efficiency,system output power and the influence factors of the three-dimensional surface graph were drawn for intuitive observation.Then,the transmission characteristics of the system were analyzed,and with the help of MATLAB,the 3d curve diagram of system impedance,system transmission efficiency and system output power were drawn under the influence of parameters such as input voltage and load resistance.Finally,the overall structure of the wireless charging system based on bilateral LCC compensation structure is presented,and the circuit design of the high-frequency inverter module,the high-frequency rectifier module,the isolated driver module and the signal acquisition and conditioning module is carried out.The switching control strategy of operating frequency of the system is also given,and the simulation verification is carried out with the help of SIMULINK software,which proves that the design can realize the wireless charging of the lithium battery of electric vehicles in the way of constant current first and then constant pressure,and the overall efficiency of the system is not less than 80% when the lowest.