Coupling Mechanism And Parameter Optimization Of Combined Series-wound Hexagonal Coils In WPT System

As a contemporary emerging energy transmission method,the Wireless Power Transmission has the characteristics of convenience,safety and reliability,and has received wide attention in recent years.As an important part of the WPT system,the coupling coefficient of the coil directly affects the transmission efficiency of the wireless energy transmission system.The coil structure and its physical parameters are closely related to the coupling coefficient.Therefore,it is important to carry out the research on the optimization of coil structure and its parameters to improve the transmission efficiency of WPT system.The problem of improving the coupling coefficient between coils has been solved by traditional methods mainly by optimizing the structure and parameters of coils such as circular and square,but there are still problems such as uneven magnetic field distribution and poor offset tolerance.To this end,taking into account that hexagonal coils have features such as seamless splicing and high cost effectiveness,we first analyze the characteristics of the boundary and central magnetic fields in tightly wound and loosely wound hexagonal coils,and propose a combined series-wound hexagonal coil structure for wireless power transmission.Parameter optimization for this structure to make the magnetic induction intensity distribution more uniform,so as to improve the transmission efficiency of the WPT system under offset conditions.In this paper,the following work is carried out for the structural design,mutual inductance modeling and parameter optimization of the combined series-wound hexagonal coil of WPT system:(1)Based on electromagnetic theory,mutual inductance and self-inductance were modeled for conventional hexagonal coils,the model is verified by simulation,and the constructed mechanism model was used to analyze the coupling characteristics of tightly and loosely wound hexagonal coils.(2)Combining the advantages of compact and loose winding coil structures,a combined series-wound hexagonal coil structure is proposed.The mutual inductance model of the proposed coil structure is established,and the correctness of the model is confirmed by Maxwell software simulation.On this basis,the coupling characteristics of the combined series-wound hexagonal coil structure are analyzed using the control variable method.(3)The objective function and the constraints for the optimization of the coupling coefficient of the combined series-wound hexagonal coil are established,and the automatic optimization of the coil parameters is realized by combining the genetic algorithm.Meanwhile,the effect of the core layout on the coupling coefficient is comparatively analyzed with the help of Maxwell software.Finally,the experimental platform of WPT system is built to verify the effectiveness of the proposed coil structure and parameter optimization method,and the coupling coefficient is improved after the coil optimization,which enhances the transmission efficiency of WPT system.