Design And Research Of Magnetic Coupling Resonant Wireless Power Transmission System Based On PT Symmetry

In recent years,with the increasing demand for wireless power transmission,the technology of wireless power transmission has developed rapidly,and more and more enterprises and research institutes have paid attention to it.Magnetic resonance wireless power transmission technology is a high-tech technology for medium-distance power transmission that has the advantages of low electromagnetic interference caused by non-resonant frequency,no radiation,and high efficiency.It is,however,extremely sensitive to changes in the coupling coefficient and resonant frequency.When the system detuning or coupling coefficient changes,the power transmission performance will be greatly affected.Therefore,this thesis proposes an efficient anti-offset wireless power transmission system based on parity time symmetry.The main contents are as follows:Firstly,the physical meaning of parity time symmetry and its application in wireless power transmission systems are expounded.Based on the theory of circuit and coupled modes,the wireless power transmission system with parity time symmetry is modeled,analyzed,and simulated,and the relationship between resonance frequency,transmission efficiency,and transmission power is determined.Secondly,aiming at the problem that the transmission distance of the existing parity-time symmetric wireless power transmission system is limited,the coupling mechanism is analyzed and optimized,and the coupling coil is modeled and simulated by Ansys finite element analysis software.The influences of the structure,number of turns,turn spacing,size,wire diameter,skin effect,and proximity effect of the coupling coil on the transmission performance of the system are analyzed.At the same time,in order to ensure the electromagnetic shielding function and reduce the magnetic leakage of the system,a magnetic core structure is put forward in the coupling coil,which reduces the coil size and increases the transmission distance of the system.Maxwell and Simplorer are used to jointly simulate the coils before and after optimization under the same conditions,so that the optimized system can keep high efficiency over a longer distance.Then,on the basis of theoretical analysis and simulation models,the design method of a magnetic coupling resonant wireless power transmission system based on parity time symmetry is proposed,and the hardware circuit design of each module is introduced in detail.At the same time,a control method based on phase-locked loop（PLL）is proposed to solve the distortion problem of a zero-crossing comparator when the input voltage frequency rises above kHz.Phase-locked loop technology can realize zero phase difference tracking,which can effectively realize the control of power switches and ensure control accuracy.In addition,the inductance value and resistance value of the designed coil are obtained through experiments,and the coupling coefficients of the two coils before and after optimization at different distances are measured.Finally,the system is modeled and simulated by the Simulink modeling tool of Matlab software,and the control method and transmission characteristics of the system are analyzed.According to the design scheme,an experimental platform is set up,and the phase-locked range of the phase-locked loop and the dead-time of the dead-time circuit are determined.At the same time,the output voltage and current of the inverter are measured at different distances in the strong coupling region,and it is verified that the output voltage and current of the inverter can always ensure that the system works in parity time symmetry.The experimental results prove that the designed system can maintain constant high efficiency and power transmission in the strong coupling region,and the correctness of the theoretical and simulation results in this paper is verified.