Research on four-coil structure of magnetically coupled resonant wireless power transmission system

For the position of four coils of traditional four-coil magnetically coupled resonant wireless power transmission system is relatively fixed and cannot be changed at will, which leads to limitation of its use, a new four-coil structure was proposed: power coil and load coil are connected with the lumped capacitor separately to form power resonant circuit and load resonant circuit, the power coil can produce magnetic resonance with transmitting coil, the load coil can produce magnetic resonance with receiving coil. At the same time, the relative position of the four coils can be changed, the distance between the four coils can be adjusted appropriately, which not only can increase transmission distance of wireless electric energy, but also can improve frequency splitting, so as to maximize output power and transmission efficiency of the system. The effects of different coupling coefficients between the four coils on transmission efficiency and output power of the system were analyzed by simulation and experiment. The results show that the larger the coupling coefficient between the power coil and the transmitting coil is, the higher the transmission efficiency of the system will be, with the increase of the coupling coefficient, the transmission efficiency increases first and then decreases. The output power and transmission efficiency decrease obviously with the increase of the transmission distance between the load coil and the receiving coil. For different transmission distances, adjusting the distance between the load coil and the receiving coil enables the system to obtain the maximum transmission efficiency and output power under the same load.