Design And Optimization Of The Spatial Free-Positioning Wireless Power Transfer System

With the development of the portable electronics,it is imperative to optimize the wireless power transfer(WPT)system to improve the convenience.The spatial free-positioning WPT system can charge the electronics with good tolerance of positional and angular misalignments,which will bring a good user experience compared with the traditional conductive and wireless charging.Firstly,we research the modeling of the magnetically coupled resonant WPT(MCR-WPT)system.The basic principles and methods of modeling of the loosely-coupled transformer is analyzed.We research the calculation of the AC resistance of the coils and compare different inverter topologies and compensation circuits.Based on the above analysis,we build the model of MCR-WPT system with the LCC-S compensation circuit.Then,on the basis of the electromagnetic field(EMF)simulation of the planar spiral square coil and the DD coil,the tolerance of the misalignment of the different coils with symmetrical and asymmetrical structures is analyzed.Based on the EMF simulation results and the application environments,the new three-dimensional(3D)transmitting(Tx)coil is proposed for spatial free-positioning wireless charging system in work space.Compared with the traditional orthogonal 3D Tx coil,the proposed 3D Tx coil can strength the magnetic field in the whole charging area and improve the tolerance of misalignments.The proposed 3D coil is optimized to achieve better coupling with the receiving(Rx)coil.For the indoor spatial WPT system,we calculate the magnetic flux density in the Helmholtz coils,and analyze the condition to generate the uniform magnetic field in the space.The analysis is proved by the EMF simulation.Based on the above analysis and the application environments of two systems,two Tx coils and three Rx coils of different sizes are designed and litz wire is selected in consideration of the skin depth.And the compensation inductors and capacitors of LCC-S compensation circuit are designed and manufactured.At last,the experimental platforms are built based on the above analysis.For the spatial free-positioning wireless charging system,we test the transfer power and total efficiency of the system.The highest efficiency of 77.9%and the average efficiency of 26.6%are achieved and a prismatic charging area is created with good tolerance of positional and angular misalignments.For the indoor spatial WPT system,the uniform of the magnetic fiedl and the simultaneous charging for multiple devices are proved by the experimental results,and a 1 m × 1 m ×1m charging area is created by the system with good tolerance of positional misalignment.