| The MHz level magnetic resonant coupling wireless power transfer(MRC-WPT)system with a relay coil can effectively improve the energy transmission distance.It has a promising future in the field of mid-range transfer and multi loads charging.Because class E power amplifier(PA)is used as the power source,the coupling between adjacent loads will aggravate the influence of load resistance on the soft switching state of class E PA,so that the output power and efficiency will sharply reducing.Therefore,in order to ensure the output power stability of the WPT system,it is necessary to ensure the soft switching state of class E PA is not affected by loads couplings.Based on the fully study of the WPT system with relay coil and the optimal parameter configuration method of class E PA,the thesis designs a MHz level three-coil WPT system.An impedance matching circuit is also designed to ensure the stable operation of class E PA is not affected by the load coupling.The research result of this thesis combines the characteristics of the MHz WPT system and the WPT system with relay coil,which improves the transmission efficiency and effectively increases the energy transmission distance.It has a wide application prospect in the field of medium and long distance wireless power transmission.The main research results are as follows:1)Research on the relationship between system frequency and energy transmission distance.The principle of resonance compensation of WPT system is studied,and it is demonstrated that: the transmitting and receiving coils should be compensated by resonant capacitance respectively,and the transmission efficiency can be maximized when the system operates at resonance frequency.Based on that,the calculation formula of mutual inductance and the output characteristics of series resonance compensation topology are studied.According to the above research,the influence of system frequency on the energy transmission distance is explored.Simulation results show that: when the coil size is fixed,improving the system frequency can effectively improve the transmission efficiency and energy transmission distance.2)The method of parameter configuration for MHz WPT system is studied.The soft switch mechanism of class E PA is studied,and the optimal parameter configuration method of class E PA is obtained.Based on the optimal parameter configuration method of class E PA and the output characteristic expression of series resonant compensation topology,the parameter configuration method of two-coil WPT system at MHz level is studied.According to the two-coil WPT system,the output characteristics of the three-coil WPT system are studied by the method of digital configuration.The parameter configuration method of the three-coil WPT system at MHz level is obtained.And the simulation results show that the three-coil WPT system has a longer energy transmission distance than the two-coil WPT system when the coils are the same size.3)The impedance matching circuit is designed for the load coupling problem of three-coil WPT system.The relationship between load coupling strength and load spacing is studied according to the calculation formula of mutual inductance.Based on the equivalent circuit of the three-coil radio energy WPT system when the load is coupled,the expression of the input impedance of the wireless power transfer part is studied,and the change of the input impedance is obtained when the load resistance change.In the other hand,the output characteristics of class E power amplifier are studied when the equivalent load changes,and the range of equivalent load which can stabilize the output power and energy conversion efficiency of class E PA is obtained.Based on the above research,the parameter configuration method of impedance matching circuit is studied.And the ? type impedance matching circuit is obtained,which can effectively reduce the influence of load coupling on the soft switching state of class E power amplifier,so that the system will be stable. |
PDF Full Text Request