The Frequency Research Of Wireless Power Transfer Via Magnetic Resonance Coupling

With the development of various kinds of portable instruments around the world, such as mobile phone, tablet computer, laptop computer, electric vehicle, and various implantable devices, they are widely applied. The most common characteristic of these devices is that they are not connected with power grid for convenience, so the battery life is the biggest problem. Fortunately, the appearance of magnetic resonance coupling wireless power transfer technology can properly deal with this. Until now, many problems, such as, the efficiency, power, resonance frequency, optimum design of system parameters and impedance matching, efficacy of synchronization, are the essential problems obstructing its wide use. So solving these problems are of great significance. In order to solve the above problems, this paper takes the resonant frequency as the main research object. By selecting the optimum resonance frequency, improving transferring efficiency, enlarging power, realizing efficacy of synchronization, and impedance matching, this provides MCR-WPT system with theory foundation.This thesis respectively applies lumped parameter circuit theory, coupled-model theory, scattering parameter theory based on micro-wave to model the system of WPT, and deduces the expression between efficiency and power of every model. Furthermore, It also analyses the system loss and parameter calculation method of different kinds of coil.On the basis of mathmatical model, this text separetely uses circuit theory and coupled-model theory to prove the existance of the optimum frequency of transferring power,and analyses the influencing factors of the optimum frequency of transferring power and the efficiency.In addition,the application of Math CAD emulates this model and makes an assay of it,and validates the theory by experimental platform.The result proves the existance of the the optimum frequency of transferring power.This text deduces the optimum frequency of transferring power and the optimum frequency of system on the foundation of the optimum frequency of transferring efficiency, and analyses the offset degree of optimum frequency and the influences of optimum transferring power,,and obtains the conditions of efficacy synchronization; it proves the nonexistence of efficacy synchronization about power and efficiency by comparing the optimum frequency of efficiency and the optimum frequency of load power; after analyzing the transferring system, it gets the condition of impedance matching when working on the condition of the optimum frequency, that is to say, automatically realizing impedance matching. The simulation analyses of Math CAD is reasonable, its experimental result proves the existence of the optimum frequency and validates the relationship between the optimum frequency of transferring efficiency and system parameter,and between the optimum transferring efficiency and system parameter,and the realization of efficacy synchronization.