| With the advent of the era of electrification,various types of electrical equipment have become commonplace.Magnetically coupled resonant wireless power transfer(MCR-WPT)has been widely used in many fields due to its advantages of moderate transmission distance and high transmission efficiency.However,MCR-WPT systems also have the problem of transmission efficiency decreasing with the rise of transmission distance.Based on the unique magnetic field regulation ability of metamaterials,this paper introduces them into MCR-WPT systems to comprehensively study the improvement of transmission performance of the system.Firstly,this paper introduces the development of wireless power transfer and the research status of metamaterials in the field of MCR-WPT technology,expounds the working principle of MCR-WPT system and analyzes its transmission characteristics.The mechanism of metamaterials improving the transmission performance of the system is analyzed based on the negative refractive index effect,equivalent circuit model,and magnetic dipole coupling theory,respectively.The S-parameter retrieval and the equivalent circuit method for analyzing and designing metamaterials are introduced in detail and compared.Aiming at the problem of a large amount of repetitive work in the simulation design process of metamaterials,combining two design methods,using HFSS and MATLAB software,an interactive simulation design method for electromagnetic metamaterials is proposed,which effectively improves the design efficiency.The influence of structural parameters of metamaterials on their electromagnetic parameters is explored,and the design rules of metamaterials are summarized.Based on the practical application scenario of MCR-WPT technology,a dual coil MCR-WPT system with a resonant frequency of 6.78 MHz is designed.According to the needs of the system,metamaterial units with square spiral and Koch fractal are designed,respectively.Through simulation analysis and comparison,it is found that compared to the system without metamaterials,the magnetic field distribution of the system with metamaterials has been significantly improved.In order to verify the simulation results,a experimental setup is built based on the simulation model.The experimental results show that metamaterials can effectively improve the transmission efficiency of the system.When the transmission distance is 30 cm,placing a metamaterial slab in the middle of the system can achieve a maximum improvement of 28.4%.The change of transmission efficiency is investigated when the transmission distance changes.The influence of metamaterials with different structures on transmission performance is also studied.In order to further study the influence of metamaterial on the transmission efficiency,the transmission efficiency of metamaterial in different periods at different positions of the system is measured.The experimental results show that when the metamaterial slab is placed in the middle of the system or near the receiving coil,the maximum efficiency improvement of 20.5% and 9.2% is achieved by insertting a metamaterial slab with 6 × 6arrays.When close to the transmitting coil,only a slab with a 1 × 1 array can achieve a maximum efficiency improvement of 12.7%.In addition,this paper further improves the transmission efficiency by using multi-layer metamaterial slabs.The experimental results show that the transmission efficiency increases by 29.3%,13.1%,and 15.7% when two metamaterial slabs are placed in the middle position,near the transmitting coil,and near the receiving coil,respectively.While three metamaterial slabs will reduce transmission efficiency in short distances,they can only improve transmission efficiency over medium to long distances,achieving maximum efficiency improvements of 22.6%,7.1%,and10.9% at three different positions,respectively.Therefore,two metamaterial slabs have the best performance improvement,followed by one metamaterial slab and three metamaterial slab. |
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