Development Of Magnetic Coupling Resonance Wireless Power Transfer System

Wireless power transfer is a technology that can transmit energy by electromagnetic field or electromagnetic wave.At present,microwave radiation,electromagnetic inductive coupling and magnetic coupling resonance are three main ways of wireless power transfer.The magnetic coupling resonance way allowed the research on wireless power transfer technology to achieve a new stage.The technique realizes safe and efficient electric energy transmission by using non-radiated electromagnetic field of resonance coupling.Compared with the first two ways,the magnetic coupling resonance has great prospects of application in the medium power occasion,because of its high transmission efficiency,large transmission power and long transmission distance.However,the transmission distance and efficiency of magnetic coupling resonance wireless power transfer need to be extended to meet the requirement of some application environment.Moreover,this technique not only cannot transfer power at long distance but also at close distance and the transfer efficiencyreduces rapidly.Therefore,this technique suffers dramatically variation of transfer efficiency.In view of the existing drawbacks,this paper developed a magnetic coupling resonance wireless power transfer system with variable coil structure,solved the problem that transmission efficiency is limited by transmission distance,and realized the maximization of transmission efficiency under different transmission distance.First,the basic principle of magnetic coupling resonance is briefly analyzed.According to this principle,the working modes,merits and drawbacks of two-coil structure system and four-coil structure system are determined.The mutual inductance coupling theory is adopting to establish the equivalent circuit of two kinds of coil structure system,and the mathematical expressions of output power and transmission efficiency of two kinds of coil structure system are obtained according to the impedance reduction method.The factors that affect the transmission characteristic of magnetic coupling resonance wireless power transfer are analyzed such as coupling coil,transmission distance,system frequency and load.Then the coupling coil parameters,transmission distance,system frequency and load are controlled as variable in sequence to get the transmission characteristic of system,the value of four factors are determined to get the optimal performance of transmission system,and the performance are verified through simulation.In addition,the variable coil structure is proposed to realize maximization transmission efficiency under different transmission distance.According to the demand of wireless power transfer,this paper analyzed the working principle of each circuit,including class-E inverter,resonance coupling unit and improved non-controlled rectifier circuit,which compose the magnetic coupling resonance wireless power transmission system,determined the design steps of the key parameters of each circuit.Then according to the proposed variable coil structure,a magnetic coupling resonance wireless power transfer system with variable coil structure is designed,and the feasibility of the variable coil structure proved by MATLAB simulation.Finally,according to the actual situation,this paper developed a magnetic coupling resonance wireless power transfer system with variable coil structure,analyzed the practicability of variable coil structure.The experimental results show that the system developed in this paper under the conditions of transmission distance 7cm to achieve the transmission efficiency of 41% and the output power of 15 W,and the realization of maximum transmission efficiency under different transmission distances.In this paper,the device can realize the wireless power supply of ordinary incandescent lamp,which proves the rationality and effectiveness of the system structure and design method.