Study On High Efficient Wireless Power Transfer System Integrated With Metamaterials

Metamaterials, also called electromagnetic metamaterials, refer to some artificial medium or structures with some unique characteristics that the conventional materials do not have. Based on the design theory of metamaterials, a highly subwavelength miniaturized magnetic negative(MNG) metamaterial structure is designed for the wireless energy transfer(WPT) system. According to the theoretical analysis and working mechanism of the magnetically coupled resonance wireless energy transmission systems, the effect of different structural parameters on the transmission characteristics of the WPT system is analyzed in the thesis. The integration of the MNG metamaterial with wireless energy transmission system will improve the efficiency and transmission distance of wireless power. Finally, the thesis analyzes the wireless power transmission characteristics of a new WPT system, which is composed of multiple-transmitting resonators and multiple receiving resonators(MTMR). And the designed MNG metamaterial slabs are integrated to explore the effects of electromagnetic metamaterials on the MTMR-WPT system.The main research work of the thesis includes the following aspects:First, design a highly-subwavelength negative permeability metamaterial structure which is composed of a FR4 substrate with metallic spiral rings on both sides. Its cell size is only λ/307, which achieves the miniaturization of subwavelength features. It can be applied to the wireless energy transmission system with different period arrays, such as 4′4 、 6 ′6 、 8 ′8 and 10 ′10 elements. The simulation results show that the magnetic resonance frequency of the designed MNG metamaterial structure is consistent with the required working frequency of WPT system.Second, based on the principle of magnetic coupling resonance, the analysis and design of a wireless power transmission system are taken, and the main structural parameters of the WPT system are analyzed in detail. By varying different parameters coil turns, pitch, coil width, dielectric constant and thickness of the substrate, the reflection coefficient S11, transmission coefficient S21 and transmission efficiencyη characteristics of the WPT systems are observed. And the original WPT system prototype is optimized as a reference. Next, by changing the distance and spatial position of transceivers between the resonators, we analyzed the power transfer efficiency under the conditions of impedance match. By rotating the receiving coil along the axis and transmitting coil in elevation and azimuth planes, we analyzed the wireless power transfer efficiency η of the WPT system. It should be pointed out that the matching circuit in transmitting and receiving ports are considered in different cases to make sure the WPT system is working properly.Third, the designed metamaterial array is integrated into the power transmission system, to explore how it affects the power transportation. By contrast of power transfer efficiency between loading with and without the metamaterial array in match state, the enhancement of metamaterial array on power transportation efficiency can be achieved, which is mainly due to the negative magnetic properties of the material that generates a convergence effect on the magnetic field passing through the metamaterial array. Metamaterial arrays of 4′4 、6 ′6 、 8 ′8 and 10 ′10 are respectively applied to the power transmission system, it can be seen that different array sizes produce different enhancement effects. It is worthwhile to point out that suitable array size is important, since there is dielectric loss in metamaterial array, the enhancement effect would not increase if the array is too large. Two layers of metamaterial arrays can improve much more efficiency and much longer distance on wireless power transmission system than single layer.Fourth, a WPT system consisting of a single transmitter and multiple receivers is designed, by adjusting the system matching, the power from the transmitter can be delivered to all receivers simultaneously. It is clear that the transmission efficiency of the designed electromagnetic wireless power transmission system is improved with the integration of metamaterial array.