| Wireless power transmission technology is a kind of energy transmission mode,in which power is transmitted from power source to load without wire connection.Compared with traditional power transmission technology,it has been widely recognized by the society because of its security,convenience and reliability.Among many wireless energy transmission technologies,magnetic coupling resonance wireless power transmission(MCRWPT)technology has been widely concerned because of its advantages of long transmission distance and large output power.With the help of the weak coupling of magnetic field and the principle of electrical resonance,the technology realizes the wireless transmission of electric energy.Aiming at the problem that the output power of traditional two-coil ICPT(Inductance Contactless Power Transfer)system is too small because the position of transmitting coil and receiving coil is fixed and the distance between the two coils is too large,a scheme of adding a relay coil between the transmitting coil and receiving coil is proposed to improve the output power of the system,thereby establishing the relay coil ICPT system.Considering that the introduction of relay coil may cause the mutual inductance between adjacent two coils to be too large,which will lead into the charging state of the system changing directly from under-coupled state to over-coupled state,which leads to the frequency splitting phenomenon.In order to solve this problem,this paper proposes some measures to restrain frequency splitting by adjusting the position of relay coil,rotating the relay coil and changing the resistance of the load.Study and analyze the mathematical model of relay coil ICPT system,the relationship between the mutual inductance of coils and the position of coils can be obtained according to the theory of spatial mutual inductance;the relationship between the mutual inductance of coils and the rotation angle of relay coils can be obtained according to the theory of space geometry.According to the circuit principle,the relationship between the mutual inductance of coils and the output power of the system and the relationship between the load and the output power of the system can be obtained respectively.On the premise that the mechanical parameters of the system are determined,the relay coil ICPT system in critical coupling state and over coupling state is established respectively,and the parameters such as the distance between the coils,the rotation angle of the relay coil,the load and the output power of the system are analyzed,and also the corresponding relationship between each two is obtained.In the model of relay coil ICPT system,the output power of the system is taken as the objective function.According to the constraints,the distance between coils,the rotation angle of relay coil and the load are considered comprehensively,and an optimal scheme for the optimal objective function is obtained.In this paper,genetic algorithm is used to optimize the output power of the system,and the optimal parameters of relay coil position,rotation angle and load resistance are obtained.The simulation results show that the transmission efficiency and output power of the system can be significantly improved by adding a relay coil between the transmitting coil and the receiving coil and taking measures to suppress the frequency splitting phenomenon.The optimal parameter scheme proposed in this paper can effectively suppress the frequency splitting phenomenon and increase the output power by about 15.68%. |
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