| In recent years,charging equipment is more and more widely used in human life.Wireless power Transfer(WPT)has made rapid progress and development with the advantages of strong reliability,convenient,good performance and high security.However,in the practical WPT system,the relative position between the transmission coils is prone to shift,which leads to the change of the coupling coefficient k,resulting in the sharp fluctuation of the output power and reducing the transmission efficiency of the system.Therefore,in the process of battery charging,when the transmission coil of WPT system deviates,it still needs to meet the constant current,constant voltage and trickle charging performance in order to increase the battery life and charging efficiency.So the misalignment tolerance performance and charging performance of WPT system have become the focus of the research.The main research work and innovations of this thesis are as follows:(1)A new parameter design method of double-sided LCC topology is proposed.According to the design idea of new topology parameters and the output characteristics of S-LCC topology and P-LCC topology,a new parameter design method of double-sided LCC topology is proposed.When the coil of WPT system is offset,the current of transmitting coil can be adjusted adaptively to ensure the relative stability of output power.(2)The selection method of rated coupling coefficient.Aiming at the new parameter design method of double-sided LCC topology,the coupling coefficient interval of the coil is divided.Based on the output power fluctuation range ±10%,the coupling coefficient interval of different partition methods is compared,and the larger effective coupling interval is selected to improve the misalignment tolerance of WPT system.(3)Based on PSO algorithm,the topology parameters optimization method of double-sided LCC is proposed.In order to improve the anti offset ability of WPT system,the original side resonant capacitor parameters of double-sided LCC topology are selected as optimization variables,and the objective function is established.Combined with the constraints,the parameters are optimized by PSO algorithm,and the optimal effective coupling interval,double-sided LCC topology parameters and the corresponding output power curve are obtained.(4)Charging mode switching method based on SOC online estimation.Aiming at the problems of battery charging efficiency and service life,the output of WPT system can meet the three-stage characteristics of battery charging through Buck-boost DC converter.In the charging process,when the transmission coil is offset,it can ensure the constant output of each charging stage.In addition,this paper proposes a method to estimate the switching battery charging mode based on EKF online SOC.Taking the size of SOC as the switching benchmark of each charging mode,it can reflect the battery charge state in real time,which is conducive to increase the service life of the battery.(5)The simulation model and experimental prototype of double-sided LCC topology of WPT system with rated power of 100 W are built.The proposed misalignment tolerance performance optimization and charging performance methods are simulated and verified by experiments.When the transmission coil is offset,the simulated lateral offset percentage λ=46%,the experimental lateral offset percentage λ=40%,the simulated vertical offset percentage θ=50%,and the experimental vertical offset percentage θ=46.7%are obtained.In addition,in the charging performance,the constant current constant voltage trickle three-stage charging mode is realized under the condition of coil offset.Based on the above experimental results,the correctness of the research method proposed in this paper is verified. |
