Optimal Design Of Transmitting Coil For Wireless Power Transfer In Freely Moving Devices

Wireless power transmission(WPT)is used to transmit power in a wireless way,whereas magnetically coupled resonance-based WPT system with transmission distance up to meter level,has broad applications and extremely high research value.With traditional transmitting coils,the non-uniform magnetic field leads to instable transfer efficiency because the receiving device moves freely in a ranges of size.In this thesis,transmitting coils are optimized for magnetically coupled resonance-based wireless power transfer in freely moving targets.Firstly,magnetically coupled resonance-based wireless power transfer system was analyzed based coupled mode theory,circuit theory,and scattering matrix.The optimal load was obtained for the maximum transmission efficiency,whereas the relationship between efficiency,magnetic induction intensity,and scattering parameters was analyzed.Then,for the improvement of classical transmitting coils,the work focused on the transmitting coils to generate the axial components of the magnetic field intensity as uniform as possible.The relationship between the generated magnetic field intensity from the square planar spiral coil and the turn spacing of the coil was determined by superposition principle,whereas the turn spacing of the coil was optimized using the genetic algorithm.After that,based on the interface of the square planar spiral coil,Matlab is used to program the turn spacing and line width of the coil.Furthermore,Hfss is used to model a square planar spiral coil for simulation.In order to improve the uniformity of magnetic field,Matlab and Hfss were used to further optimize the line width for the transmitter coils with the optimized turn spacing,The simulation and experimental results shows a remarkable improvement on the magnetic field uniformity due to the optimization of turn spacing and line width of the transmitting coil.Compared with the classical planar spiral coils with equal line widths and turn spacing,the magnetic field uniformity increases by 170% because of the optimized turn spacing.Further,the magnetic field uniformity increases by 201% due to the optimization of line width.