Optimization Of Electromagnetic Coupler In Wireless Power Transfer System Of Electric Vehicle

Compared with the traditional wired charging method,wireless power transfer(WPT)technology has the advantages of environmental adaptability,flexibility and convenience,safety and reliability,and is widely used in transportation and other fields.In the WPT system,the electromagnetic coupling mechanism is the main component to realize the transmission of electrical energy,which largely determines the efficiency,power and other output characteristics of the system.In this paper,the coupling mechanism is optimized for the stationary wireless power transfer of electric vehicles,and the proposed reverse series integrated coil structure and raised core structure can further improve the parking flexibility,safety and economy of the system,thereby promoting the integration and lightweight development of the coupling mechanism.Firstly,the WPT system under the LCC/S compensation topology is analyzed,the relationship between the performance parameters of the coupling mechanism including self-inductance,mutual inductance and resistance and the energy efficiency parameters including efficiency,output power,capacitance voltage are analyzed based on theoretical formula derivation.The power,efficiency,short circuit and open circuit protection characteristics of the integrated LCC/S topology are analyzed by further considering the mutual inductance between the compensating inductor and the secondary coil.Therefore,the mechanism of using this topology to improve the anti-offset ability of the coupling mechanism is proposed,and the electromagnetic simulation platform and coil modeling method used in the research process are briefly introduced.Secondly,based on the calculation formula and finite element electromagnetic simulation,the relationship between the structural parameters such as the number of turns and size of the coil and the performance parameters of the coupling mechanism is analyzed,which provides a theoretical basis for the design of coil parameters;By laying the compensation inductance above the primary coil in the form of plane coil,an integrated coupling coil structure and its design method are proposed.The "reverse series" structure of the compensation coil can realize its decoupling from the primary coil,so as to meet the design requirements;The circuit simulation model is built and compared with the traditional coil structure to verify that the proposed new coil structure has the ability to improve the anti-offset of the coupling mechanism.Then,the relationship between the core material,size,thickness and the performance parameters of the coupling mechanism is analyzed,which provides a reference for the selection of core material and structural parameters in this paper;Based on the spatial magnetic field distribution,the principle of temperature rise caused by coil lead passing through the core is analyzed,and the solution is put forward to ensure the safety of the system in the process of operation;Based on the distribution law of magnetic lines of force and the structural characteristics of double-layer coil of integrated coil,a new convex core structure is proposed.The convex part in the middle of the core can guide more magnetic lines of force to produce hinges with the secondary coil,so as to further reduce the volume of the core and improve the mutual inductance of the coupling mechanism while making rational use of space.Finally,the completed coupling mechanism is connected to the high-power WPT experimental platform,the anti-offset characteristics of the coupling mechanism are tested,and the mutual inductance of the coupling mechanism under different core laying modes is measured and compared.The above experimental results can verify the correctness of theoretical analysis and simulation.