| Magnetically coupled resonant energy transfer(MCR)transmits power from the transmitting coil to the receiving coil through a spatial magnetic field through wireless mode.It is inevitably to encounter coil offset problems when using the MCR transfer method.In the case of an electric vehicle,firstly,the heights of the base of different electric vehicles(EV)to the ground are different.Then the driver can't put the car with a receiving coil parked to the desired location.The former will cause axial offset between the transmitting and receiving coils,the latter will result in a radial offset between the two coils.The MCR system includes non-linear elements such as high-frequency inverters and rectifier circuits,which make it complicated to obtain the system parameters when the coil is in the offset state.Random position changing of the receiving coil will easily result in decreasing the performance and stability of the system.This thesis analyzes the variation of the system transmission parameters when position of the receiving coil changes,which is of great engineering significance to improve the system transmission characteristics and the transmission efficiency on the offset condition.In the thesis,the energy transfer between the coils is divided into three categories according to the size of the receiving coil:TL-RS,T=R and TS-RL.The system transmission characteristics of these three transmission modes in the offset state are studied in the thesis.First of all,the MCR system with the primary side and the secondary side both in series structure is chosen for the comparatively analysis.The relation between primary current,secondary current,output power and mutual inductance parameter is deduced by circuit equations.The impact of mutual inductance on system transmission parameters is analyzed by Matlab software.Then,the impact of coil shape and tilt angle on mutual inductance is analyzed.The axial offset and radial offset of the circle-circle coils are determined as the main research contents of this thesis.The variation regularity of the mutual inductance when the receiving coil is in the axial offset and the radial offset is analyzed in three transmission modes,and then the impact of the variation of mutual inductance on the transmission characteristic parameters of the system is analyzed.Then,the change regulation of the mutual inductance and the system power-efficiency parameters under axial offset and radial offset is verified in the two transmission modes of TS-RL and T=R.A offset skeleton structure is designed and coils of different sizes are manually wound to test the mutual inductance of the two transmission modes in the offset state.The hardware circuit is established,and the voltage and current data are obtained in the two transmission modes when position of the receiving coil changes.The parameters of power and efficiency of system transmission in offset state are analyzed and verified.Aiming at the problem of reducing the system transmission efficiency under the offset condition,a method to improve the transmission efficiency of the MCR system under the condition of the coil offset is proposed.Finally,the thesis study the electromagnetic radiation in the offset state in T=R and TS-RL transmission modes. |
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