| The wireless power transfer(WPT)via magnetic resonance coupling has many advantages,such as long transfer distance,highly efficiency.It is widely used in the fields of electric vehicles,sensors,medical instrument and household appliances.Focusing on the performance enhance of the WPT system,this thesis analyzes the structure design of the negative and near-zero permeability metamaterials,and the application.The performance of the metamaterial is studied by theoretical analysis,numerical simulation and experiment.The metamaterial can achieve a double effects on improving the transfer efficiency and reducing the leakage magnetic field of the WPT system.The main works of this thesis are organized as follows:(1)The metamaterial of the square spiral resonant ring with negative permeability and near-zero permeability are designed by electromagnetic simulation at 13.56 MHz.The equivalent electromagnetic parameters of the metamaterials are extracted by S-method.The technical support for design of negative and near-zero permeability metamaterial with excellent performance is provided.(2)An experiment equipment of WPT system with frequency of 13.56 MHz is constructed.The relationship of variation rule between the loading position,misalignment of the negative metamaterial and the efficiency are discussed.It can achieve high efficiency when the metamaterial placed in the middle of the system and without misalignment.Meanwhile,the efficiency as a function of transfer distance is explored.The transfer efficiency of the WPT system is increased by 16.79% at the transfer distance of 40 cm.(3)A model and experiment setup is built when the near-zero permeability metamaterials are placed on both sides of the WPT system.The influence on the transfer efficiency and shielding performance are analyzed.The result shows that the average attenuation of the magnetic field strength is 58.24% at the distance of 25cm(from the receiving coil),which the near-zero permeability metamaterial can effectively reduce the magnetic field leakage.When the distance between the near-zero permeability metamaterial and receiving coil is changed,it is found that the near-zero permeability metamaterial close to the receiving coil has the better shielding performance,but it has little influence on the efficiency of the system.Also,the influence on the efficiency is not obvious when the distance is great than 20 cm.(4)The effect of WPT system with negative and near-zero permeability metamaterials are studied.The results show that the combination of the two kind of metamaterial can improve the transfer efficiency and reduce the magnetic field leakage.It is shown that the efficiency is improved by 12.06% when the negative permeability is placed in the middle of the system.And,the magnetic field strength are reduced by 62.09% and 25.73% when the distance between the near-zero permeability metamaterial and transmitting coil,receiving coil is 25 cm,respectively.This work expands the electromagnetic characteristics of the metamaterial in MHz and solve the magnetic shielding of the wireless power technology,which effectively enhance the overall performance of the system.Meanwhile,the results have provided a feasible technical approach for promoting the practical application of the WPT system. |
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