Coupled-mode Model And Mechanism Study Of Wireless Power Transfer System Considering Variations Of Direction And Distance

Electric-coupled power transfer and magnetic-coupled power transfer have gradually become the research hot spots and obtained the widespread application because of their high efficiency and appropriate transfer distance.However,the change of the relative position of transmitting device and receiving device and the change of transfer distance influence the system characteristics a lot,which limits the practical application of wireless power transfer.In order to solve these problems and realize effiective and stable power transfer,this paper takes direction and distance variations into consideration,builds the system model and proposes some improvement schemes.The main works of this paper are listed as follows.Firstly,based on perturbation method,the corresponding relationship between the coupled-mode equation and the circuit model of wireless power transfer is deduced.Besides,the effects of load parameters,transfer distance,direction and sourse parameters on the coupled mode equation are analyzed,and a modeling method of system considering parameter variations is obtained.Secondly,the coupled-mode model of the wireless power transfer system considering the direction change is established,and the influence of the direction change on transfer characteristics is analyzed based on the model.A kind of dynamic wireless power transfer using rotary transmitting coils is proposed,which reduces the requirement of the relative positions of the coils;coupled-mode models containing time-vary items of single load,multiple load and dual source systems are built,and the expressions of average transfer efficiency and ouput power are deduced.Thirdly,the coupled-mode model of the wireless power transfer system considering the distance change is established,and the influence of the distance change on transfer characteristics is analyzed based on the model.According to the theory of parity time symmetry and combining magnetic coupling mechanism and electric coupling mechanism,two dual-coupled systems which can eliminate the sensitivity to distance are proposed.The coupled-mode models of two systems are obtained,and the working mechanism and transfer characteristics of system in parity time broken and unbroken states are analyzed respectively.Lastly,simulation and experiment of the system using rotary transmitting coils are carried out,the results show that the rotation of the transmitting coil enables the system to evenly supply power to multiple loads around the transmitting coil at the same time.Besides,increasing the number of rotating coils can eliminate the dead zone of power supply.Furthermore,circuit simulation models are built for the dual-coupled wireless power transfer systems based on parity time symmetry.The results show that when the system is working in the unbroken state,the transfer efficiency and output power remain constant,which has eliminated the sensitivity to the transfer distance.In addition,the introduction of dual-coupled mechanism makes the system transfer efficiency higher than that of the traditional single-coupled systems,so that the transfer distance is extended.The proposed systems can realize stable and high power transfer within a distance of few meters.