| Magnetic coupling wireless power transfer technology is the most concerned research direction at home and abroad,existing research mainly focuses on impedance matching,magnetic coupling coils,high-efficiency power converters,foreign object detection,and electromagnetic environment.However,in practical applications,it is still unable to effectively solve the problems of product cost-effectiveness,stability,anti-interference performance,and so on.Based on the theory of fractional-order electrical circuits,and aiming at the frequency characteristics of LC circuits constructed by fractional-order inductors and capacitors that are different from those of integer-order inductors and capacitors,this thesis attempts to systematically and deeply study the fractional-order magnetic coupling wireless power transfer system from several aspects,including the influence of the fractional orders of inductors and capacitors on frequency characteristics,the relationship between frequency and transfer characteristics,frequency control,etc.It is expected to make full use of the frequency characteristics of the fractional-order inductor and capacitor and explore the working characteristics different from the integer-order magnetic coupling wireless power transfer system,so as to promote the practicability of magnetic coupling wireless power transfer technology.The following work has been carried out in the thesis:(1)The frequency characteristics of the fractional-order inductor and capacitor,and the relationship between frequency as well as power and energy are analyzed.Based on the different structural forms of the fractional-order transmitting and receiving circuits,nonautonomous and autonomous fractional-order transmitting and receiving circuits are proposed,and their frequency and power output characteristics are studied.The results show that,the resonant frequency and impedance characteristics of non-autonomous fractional-order transmitting and receiving circuits have a nonlinear relationship with the fractional order.The autonomous fractional-order transmitting and receiving circuits automatically work in resonance.(2)The fundamental fractional-order magnetic coupling wireless power transfer systems based on the non-autonomous and autonomous fractional-order transmitting and receiving circuits are constructed.The circuit model and coupled-mode model of the fractional-order magnetic coupling wireless power transfer system are established respectively,and a novel energy modeling method is proposed.The energy model is more general,covers the coupledmode model,and has the features of the circuit model,which overcomes the problem that the coupled-mode model cannot be directly used for circuit parameter design,and thus providing an analyzing tool for the study of the frequency characteristics of the fractional-order magnetic coupling wireless power transfer system.(3)The resonant frequency characteristics of the fractional-order magnetic coupling wireless power transfer system are analyzed.Based on the nonlinear relationship between the resonant frequency and the fractional order,a method for controlling the resonant frequency of wireless power transfer system by adjusting the fractional order of the inductor and capacitor is proposed.As a result,when the values of inductance and capacitance are small and the resonant frequency is high,the resonant frequency can be reduced by adjusting the fractional order,thereby reducing the frequency of the inverter power supply.When the values of inductance and capacitance are large and the resonant frequency is low,the resonant frequency can be improved by regulating the fractional order to increase the power transfer distance.Therefore,fractional-order magnetic coupling wireless power transfer system has more freedom to adjust the resonant frequency than the integer-order magnetic coupling wireless power transfer system.(4)The effect of frequency on the output power and transfer efficiency of the nonautonomous fractional-order magnetic coupling wireless power transfer system is analyzed.Aiming at the phenomenon that frequency bifurcation and splitting cause the output power and transfer efficiency of the system to drop rapidly,a fractional-order method that effectively suppresses frequency bifurcation and splitting is proposed.The results show that,it is not necessary to change the hardware circuit structure,such as coil structure and impedance matching network,like the integer-order magnetic coupling wireless power transfer system,the frequency bifurcation and splitting can be effectively suppressed or even eliminated by controlling the fractional order of the fractional-order capacitor.(5)The eigenfrequency,output power,and transfer efficiency characteristics of the autonomous fractional-order magnetic coupling wireless power transfer system under both frequency matching and detuning are analyzed.For the problem that the power transfer performance of the wireless power transfer system become worse due to the variations of transfer distance and frequency shifting,the control methods of fractional-order capacitor suitable for frequency matching and detuning are proposed.The study shows that,the system maintains constant output power and transfer efficiency within a certain range of transfer distance,regardless of whether the natural resonant frequencies of the transmitting and receiving circuits are matched or detuned.Moreover,when the frequency is detuned,increasing the fractional order of the fractional-order capacitor can improve the output power and transfer efficiency.(6)A high-order autonomous fractional-order magnetic coupling wireless power transfer system with relay coils is proposed,and the characteristics of eigenfrequency,output power,and transfer efficiency of fractional-order magnetic coupling wireless power transfer systems with single and double relay coils under both frequency matching and detuning are analyzed.It is found that the high-order autonomous fractional-order magnetic coupling wireless power transfer system can significantly improve the transfer distance,and maintain high-efficiency and stable power transfer within a certain range of transfer distance,which solves the problem that the output power and transfer efficiency of the existing integer-order magnetic coupling wireless power transfer system with relay coils are sensitive to the variations of the transfer distance and resonant frequency.This thesis systematically analyzes the frequency and control characteristics of the fractional-order magnetic coupling wireless power transfer system,which lays a theoretical foundation for the further development of fractional-order magnetic coupling wireless power transfer. |
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