| With the rapid development of science and technology,wireless power transfer(WPT)technology has been highly concerned by experts and scholars at home and abroad.The research and rapid popularization of this technology will make the production,transmission,distribution and use of electric energy more diversified ways.Due to its advantages of flexibility,reliability and convenience,WPT technology has been applied in many fields,such as electric vehicles,smart home,portable electronic devices,implanted medical devices and intelligent sensors.However,with the gradual deepening of research on WPT technology,increasing problems have been exposed,such as poor misalignment tolerance,low spatial freedom,weak carrying capacity,short transmission distance and electromagnetic safety problems,which greatly limit the development of practical application of this technology.Therefore,this article focuses on two perspectives: magnetic coupling mechanism optimization design and electromagnetic metamaterials of equivalent circuit analysis,concentrating on four aspects: the resonance coil resistance offset optimization design,design of multiple-load multiple-degrees of freedom coupling mechanism,the problem of mesh aluminum electromagnetic shielding and theoretical research of electromagnetic metamaterials in wireless charging system.The scientific problems,such as respective intrinsic characteristics and transmission performance,are analyzed in detail,to promote the development of magnetic coupling WPT technology and provide some feasible solutions.This paper mainly focuses on the following aspects:(1)Aiming at the wireless charging system of unmanned aerial vehicle,a planar square transmitting coil with unequal spacing was proposed,and a non-equal large circular helical receiving coil was designed based on the spatial magnetic field distribution of the transmitting coil,which effectively improved the anti-offset property of the coupling mechanism and ensured the stability of the transmission performance of the system.The compensation topology of the two-coil wireless charging system is compared and analyzed.Based on the electromagnetic field theory,the magnetic field distribution of the typical structure coil on the charging plane was analyzed.The transmission coil was optimized by 3D simulation software and genetic algorithm,and the iterative analysis of the side length of each turn of the transmitting coil is emphatically carried out.Experimental results show that the new coupling mechanism has good anti-migration performance and stable transmission performance.(2)A multi-load and multi-degree of freedom coupling mechanism based on dipole coils was designed for wireless charging system to meet the requirements of load diversity and multidirectional transmission.In order to demonstrate the advantages of dipole coil theoretically,the equivalent circuit model of air core coil and dipole coil is compared and analyzed.The efficiency analysis of multi-load wireless charging system is carried out,and the electromagnetic theory analysis method of multi-Do F wireless charging system is expounded.Furthermore,the spatial electromagnetic distribution characteristics of the coupling mechanism were simulated and analyzed,and the winding mode and current direction of the cubic transmitting coil were studied,and the receiving coil was optimized.Finally,experiments are designed and verified,the results show that the designed transmitting coil can generate uniform three-dimensional magnetic field and power eight loads at the same time.When the transmission distance is 30 cm,the transmission efficiency can reach 60 %.(3)Aiming at the electromagnetic safety problem of electric vehicle static WPT system,the electromagnetic shielding method of metal mesh aluminum plate was proposed,which can achieve good shielding effect while minimizing the influence on the transmission performance of the system.Based on electromagnetic field theory and equivalent circuit model,the electromagnetic shielding principle of metal aluminum plate is described.The design method of mesh shielding aluminum plate is analyzed in detail.By changing the shape,size,thickness and loading position of mesh shielding aluminum plate,the difference of transmission performance and shielding effect of the system is compared and studied.According to the magnetic field distribution of mesh aluminum plate,a design scheme of non-uniform mesh aluminum plate is proposed.Finally,the experimental platform is set up and a series of comparative experiments are carried out,the experimental results show that compared with the solid aluminum plate,transmission efficiency of electric vehicle charging system with mesh aluminum plate always stay in more than 90 %,compared with no shielding aluminum plate,the magnetic field realize largest-26 d B attenuation in the center,to verify the rationality and practicability of the analysis and design of the mesh shielding aluminum plate.(4)Equivalence circuit analysis is carried out for the mid-range WPT systems with electromagnetic metamaterials,which perfectly explains the working mechanism of negative magnetic metamaterials used to improve the transmission efficiency of the system and the shielding effect of near-zero metamaterials.The impedance variation and transmission characteristics of negative and near-zero metamaterials in wireless charging system were studied,respectively.The optimal loading position of negative metamaterials was analyzed.A three-dimensional simulation model was established to simulate human brain,and the excellent electromagnetic shielding performance of near-zero metamaterials was verified.The variation of electromagnetic field intensity of different shielding materials was compared and studied.The WPT system with two kinds of electromagnetic metamaterials is analyzed deeply for the first time.The experimental results show that the negative magnetic metamaterials can improve the system efficiency up to 15.7%,and the near-zero metamaterials can reduce the electromagnetic field leakage by 15.17%.From three aspects of enhancing anti-offset ability,improving load capacity and Do F,and improving electromagnetic environment,this paper explores the conception method of coupling mechanism of WPT systems,which provides important reference for optimization schemes in other fields.At the same time,the equivalent circuit method is used to explain the working mechanism of the WPT systems with electromagnetic metamaterials,and the WPT systems with negative magnetic metamaterials or near-zero metamaterials is analyzed and studied by theory,simulation and experiment.This paper has a great guiding significance for the future development of WPT technology. |
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