Research On Key Technical Index And Optimization Method Of Resonant Coil For Wireless Charging Of Electric Vehicle

Electric vehicle wireless power transfer(EV-WPT)technology has become a key position in the development of a low-carbon economy.This technology can achieve safe and stable energy transmission and can meet the requirements of multiple transmission distances and transmission powers.The EV-WPT has been an important means to reduce coal emissions and improve comprehensive energy utilization.The core of EV-WPT is a pair of coils with the same resonance frequency,and the design and optimization of the coils are directly related to the EV-WPT system.Therefore,promoting the industrialization of wireless charging electric vehicles is inseparable from the design and optimization of resonant coils.Promoting the industrialization of wireless charging electric vehicles requires the guidance of national standards.However,the establishment of wireless charging standards in China begun slowly and there is still a lack of unified coil design and optimization methods as a support.At present,the current domestic coil design and optimization methods are diverse,and the regulation of key technical indicators of coil is not uniform.So there is still a lack of a unified reasonable coil design and optimization method to guide the formulation of national standards.Aiming at the above problems,this dissertation conducts the following researches on the design and optimization of resonant coil for EV-WPT system and draws relevant conclusions:(1)Determination of key technical indicators of wireless charging resonance coils for electric vehicles and analysis of related characteristics.Firstly,the power and load parts except the resonant coil part are analyzed and simplified.The topological characteristics and applicability of the eight EV-WPT system topologies are compared,and the most suitable topology for the coil design and optimization scenario of this article is chosed.The charging system circuit model is established.Subsequently,the main components and design parameters of the resonant coil system are introduced,and the resonant coil winding type and ferrite structure type are optimized.The key technical indicators and peripheral technical indicators of wireless charging resonant coil are researched and pointed out,and the evaluation parameters of the key technical indicators of resonant coil are analyzed.The electromagnetic model of the resonant coil was established.Through the finite element analysis method,the correlation characteristics between the critical technical indicators and the design parameters of the resonant coil are solved.The correlations between various design parameter and the key technical indicators are compared,which provides theoretical basis for subsequent analysis.(2)Based on the loss analysis method and the correlation characteristics of key technical indicators and design parameters,starting from efficiency,a set of general coil design methods is proposed.In view of the efficiency and the external electromagnetic environment of the coil,a set of dimensionality reduction optimization strategies based on sensitivity analysis is proposed.By performing sensitivity analysis on multiple coil design parameters,high sensitivity variables are extracted and low sensitivity variables are fixed to achieve dimensionality reduction of coil design parameters,and then use a mature multi-objective optimization algorithm to optimize the coil system.The optimization results demonstrate that the proposed optimization strategy has rapidity advantage and good optimization effect.Aiming at the key technical indicator of the internal electromagnetic environment of the coil,the impact of the complex metal environment on the WPT system is analyzed.Based on the magnetic field aggregation technology,an additional ferrite optimization method is proposed.The ferrite distribution parameters are designed according to the specific situation.The optimization results demonstrate that the ferrite optimization method can eliminate the influence of the large metal plate outside the coil on the electromagnetic environment inside the coil,and can improve the influence of the large metal plate on the electromagnetic parameters of the coil.(3)The wireless charging resonant coil experiment platform is built,and the coil physical design and auxiliary equipment are introduced.The corresponding experimental resonant coil is established according to the multi-objective dimensionality reduction optimization strategy and the additional ferrite optimization method.The experimental results verify the correctness of the optimization method in this dissertation.