Research On Parameter Optimization Of Dynamic Wireless Charging System For EVs With Parameter Time-varying

Compared with traditional wired charging system,wireless charging system is more safe,convenient and intelligent.However,for the electric vehicle dynamic inductive wireless charging system based on loose coupling,the time-varying self-inductance and mutual inductance lead to time-varying output power and efficiency.The aim of this dissertation is to put forward a kind of parameter optimization method in view of the parameters of coupling coil structure and system circuit,respectively,in order to realize lightweight while ensuring the performance of coupling coil and transfer the most energy at the highest efficiency.Firstly,the topology and basic working principle of the wireless charging system for electric vehicles are analyzed.Aiming at the wireless charging system using seriesseries compensation network,the mutual inductance model and its equivalent circuit model are established so that the system characteristics are analyzed in detail.Secondly,the parameters of coupling coil structure are optimized.By analyzing the influence of the parameters on mutual inductance and total mass,the parameters that need to be optimized are determined.And,a high-precision finite element simulation model for coupling coil is established.Accordingly,a parameter optimization method for coupling coil based on orthogonal experimental design,approximate model and multi-island genetic algorithm is designed.As a result,the optimal parameters such as ferrite diameter,ferrite thickness and coil turns are obtained.Based on the optimization results,the misalignment characteristics of coupling coil are analyzed.Then,the parameters of system circuit are optimized.The parameter time-varying characteristics of dynamic wireless charging system are analyzed by establishing parameter time-varying models for mutual inductance and self-inductance.Accordingly,in order to adapt to different charging scenarios,charging modes are divided into constant power charging and variable power charging.For constant power charging mode,considering the multiple constraints such as parameter range,soft switch,maximum output power,effective coupling zone,the optimization model for maximum average efficiency is established.By introducing the particle swarm optimization algorithm,the maximum average efficiency under different effective coupling zones and the corresponding optimal parameters are obtained.For variable power charging mode,considering the time-varying equivalent load,a multi-objective optimization model for the maximum transfered energy and the maximum efficiency is established.And different combinations of the maximum transfered energy and the maximum efficiency are obtained,as well as the corresponding optimal parameters.Finally,the optimization methods and results are verified by simulation and experiment.Under constant power charging mode,the average efficiency of the system is significantly improved.Under variable power charging mode,by selecting the appropriate combination of optimized parameters,the total transferred energy can be improved while ensuring high efficiency.