| Wireless power transfer has always been a dream of mainkind and attached much attention in the domestic and overseas.The existing wireless power transfer technologies mainly include electromagnetic radiation,electric-field coupling and magnetic-field coupling.Among them,magnetic-field coupling is the most studied technology,since its long transfer distance,small dependence on transfer media,high transfer efficiency and high security.Currently,the existing magnetic-field coupled wireless power transfer system is based on integer-order circuits.In fact,besides integer-order circuits,there are fractional-order circuits composed of fractional-order components,which are characterized by fractional-order calculus and have different characteristics from traditional integer-order inductor and capacitor.The theory of fractional-order circuit has shown great advantages in modeling and signal processing,but it has not been deeply studied in the field of wireless power transfer.In this paper,fractional-order circuit is applied to wireless power transfer system,hoping to obtain better performance than integer-order wireless power transfer technology.The following research work has been carried out in this paper:(1)Based on the principle of fracional-order calculus,the impedance and energy characteristics of fractional-order capacitor are analyzed;the properties of non-autonomous circuits with fractional-order capacitor are researched,and the influence of the order on circuit is explored;a fractional-order autonomous circuit with fractional-order capacitor is proposed and its steady-state operating properties are studied,providing the basis for the application of fractional-order circuit in wireless power transfer system.(2)Based on fractional order non-autonomous circuit,a fractional order non-autonomous series resonant wireless power transfer sytem is proposed.Its mathematical model is established.The influence of the order on transfer characteristics is studied.It is found that the energy of the secondary resonant circuit can be stable by controling the order,so that the fractional-order series resonant wireless power transfer system has the characteristics of natural constant current output.(3)The existing fractional-order capacitor construction methods have some disadvantages,such as low power,difficult order regulation and so on.Therefore,they can not be applied to wireless power transfer system.For this reason,based on power electronic converter,a method of constructing high-power fractional capacitor with order greater than 1 is proposed.The fractional-order capacitor with controllable power and orders are realized for the first time,which provides hardware basis for the design of fractional order non-autonomous series resonant wireless power transfer system.(4)Based on fractional-order autonomous circuit,a fractional-order autonomous wireless power transfer system is proposed.Its mathematical model is established by using coupled-mode theory,and its steady-state operating point is solved.The influence of fractional-order capacitor on the transfer characteristics of the system is studied.It is found that only fractional order capacitor with constant order is needed,the transfer efficiency and output power of the system can be insensitive to the change of distance and resonant frequency.Therefore,fractional-order wireless power transfer system has a stability that integer-order wireless power transfer system is difficult to achieve.(5)Based on the construction method of high-power fractional-order capacitor in non-autonomous circuit,a circuit and control technology of high-power fractional-order capacitor suitable for fractional-order autonomous circuit is proposed.It can realize the characteristics of negative resistance and fractional-order capacitance at the same time.It provides hardware basis for the design of fractional-order autonomous wireless power transfer system.(6)On the basis of the above research,the fractional-order non-autonomous series resonant circuit and fractional-order autonomous circuit wireless power transfer system are constructed,and the corresponding experimental prototypes are built.The constant-current output characteristic of fractional-order non-autonomous series resonant circuit is systematically verified.The insensitive characteristic of transfer efficiency and output power in fractional-order autonomous circuit system are also verified.From the viewpoint of non-autonomous circuit and autonomous circuit,this paper discusses the principle of fractional-order wireless power transfer system.Its different transfer characteristics from that of integer-order system are proved.This paper lays a foundation for further research on the fractional-order wireless power transfer system. |
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