Optimization Research On Dynamic Wireless Charging Coils Of Electric Vehicle

In recent years,the problems of energy shortage and carbon emissions have attracted the attention of various countries."Low carbon,environmental protection" has become a global consensus.However,there is no obvious improvement in the current growth rate of carbon emissions,and human society is facing severe challenges during the process of transition to a low carbon economy.The oil consumption of traditional vehicles occupies a large proportion of the total oil consumption.Therefore,with the advantages of low carbon and pollution-free,electric vehicle(EV)are highly valued and actively promoted by various countries.At present,the development of EV is mainly limited by the unsatisfactory charging mode.The traditional wired charging mode has some disadvantages such as inconvenience and insecurity.The application of wireless power transfer(WPT)technology in EV brings the EV wireless charging mode,which provides a promising direction for solving the EV charging problem.EV wireless charging mode includes static wireless charging mode and dynamic wireless charging mode.Compared with static wireless charging mode,dynamic wireless charging mode can greatly increase the endurance of EV,but it is more difficult to achieve.There are still many problems such as lateral movement tolerance and charging standard to be solved.Therefore,in order to improve the lateral movement tolerance of EV dynamic wireless charging system,the coils optimization is studied in this paper for the receiving coil lateral offset problem.Firstly,EV dynamic wireless charging system is analyzed.The power supply schemes of segmented EV dynamic wireless charging system are compared.Starting from the two coils series-series(S-S)mutual inductance circuit model of static wireless charging system,the multi transmitting coils S-S mutual inductance circuit model of segmented dynamic wireless charging system is analyzed.And the expression of transfer efficiency is obtained.After analyzing the transfer efficiency expression,it is found that the receiving coil lateral offset problem comes from the change of mutual inductance.And it is determined to optimize mutual inductance through coil design.In order to facilitate the optimization design of coil,the four optimization factors and horizontal offset characteristics of coil are analyzed and simulated.Then,on the basis of the above research works,the coils optimization of segmented EV dynamic wireless charging system is studied.In order to further understand the influence of coil size parameters on coil mutual inductance,the mutual inductance expression of rectangular coils is derived.According to the research results of the coil horizontal offset characteristics,the power on mode of transmitting coils in segmented dynamic wireless charging system is analyzed.And the power on mode of two transmitting coils connected in series is determined.The equivalent circuit of WPT system with two transmitting coils in series is analyzed,and its charging process is simulated.In the simulation,the complementary effect of two transmitting coils is found,and the effectiveness of the power on mode of two transmitting coils connected in series is verified.For the problem of receiving coil lateral offset,transmitting coil is optimized by mutual inductance analysis,so that the mutual inductance and transfer efficiency can remain stable in the case of lateral offset.And the secondary-only resonant S-S topology is adopted to reduce the system output power fluctuation caused by receiving coil lateral offset.In the simulations,the optimization of mutual inductance,transfer efficiency and output power are verified.Finally,in order to further verify the correctness of the theoretical analysis and simulation results,an 85 kHz WPT experimental platform is built.And by using the experimental platform,five experiments are carried out,where the electric energy transmission implementation experiment and the transfer distance experiment verify the effectiveness of the WPT experimental platform;the coil horizontal offset characteristic experiment verifies the correctness of the analysis results on coil horizontal offset characteristics;the experiment of WPT system with two transmitting coils in series verifies the effectiveness of the power on mode with two transmitting coils connected in series;the optimization experiment of receiving coil lateral offset verifies the effectiveness of transmitting coil optimization design.