Research On Key Techniques Of Magnetic Coupling Resonant Wireless Power Transmission

Magnetic coupled resonant wireless power transfer(MCRWPT)technology,which is an important direction in the field of wireless power transfer,can realize high power transfer efficiency in a mid-range and has high tolerance to the misalignment between the transmitting and receiving coils.It has become a hotspot in this field.It shows the promising prospect especially when it is applied to wearable devices,implantable medical devices,and consumer electronics.In this dissertation,some key technologies of MCRWPT are studied in theory and experiment.When designing MCRWPT systems for smart wearable devices,the energy transfer efficiency of the system changes with the shapes and sizes of transmitting/receiving coils.Optimizing the geometries of the coils is an effective way to increase the energy transfer efficiency.In this thesis,the single-turn wound coil and the wireless power transmission system are modeled analytically,and the optimal transmission efficiency under any load is obtained with the help of impedance matching network.The analytical solution of the optimal transmitting coil radius corresponding to the optimal transmission efficiency is obtained through the analytical derivation of the coupling coefficient between the coils.For the case that the transmitting and the receiving coils are both single-turn rectangular printed coils,a novel optimization method is proposed by modeling the self-inductance,mutual-inductance,parasitic resistance,parasitic capacitance of the transmitting and receiving coils.Under the application of wireless power supply for implantable devices,when the receiving coil diameter and energy transfer distance are fixed,the transfer efficiency of the system is optimized by optimizing the conductor width of the transmission and receiving coils,the diameter of the transmitting coil,and operating frequency.About 30% efficiency improvement by using this new optimization method,compared to previous results.Inserting metamaterials in the energy transfer path of the system is considered to be an effective way to improve the energy transfer efficiency and extend the transfer distance.The self-resonant frequency is a key parameter of metamaterials that distinguishes the polarity of permeability(i.e.,positive or negative).In this thesis,aneffective method to accurately measure the self-resonant frequency of metamaterials is proposed and verify in theory and simulation.When the operating frequency of the system is lower than the self-resonant frequency of metamaterials,the permeability of the metamaterials is positive which is called as the paramagnetic response.Our experiments show that the case with paramagnetic response improves the energy transfer efficiency,compared to the case without metamaterials.More interesting,we compares different cases when operating frequencies are lower than,equal to,and higher than the self-resonant frequencies of the metamaterials(i.e.,the permeability is larger than,equal to,and smaller than zero)for the capability of improving the energy transfer efficiency.The experiments show that the case when the operating frequency is close to the self-resonant frequency is the best one.