A Fractional-Order Wireless Power Transfer System Insensitive to Resonant Frequency

Since electric power was first transferred wirelessly by Tesla over a hundred years ago, wireless power transfer (WPT) systems have always been composed of integer-order components, such as inductors and capacitors. Recent studies have shown that efficient WPT can be achieved in the range of tens of centimeters or even meters by using magnetic-coupling of two or more integer-order resonant circuits. However, their transfer efficiency and output power are highly sensitive to the resonant frequency. Unfortunately, the resonant frequency is easily disturbed by metal or nonresistive load and so on in real-world application, which will unavoidably lead to transfer efficiency reduction and unstable output power in these integer-order circuits. Therefore, this article proposes and experimentally demonstrates a fractional-order WPT system containing a fractional-order capacitor, in which the transfer efficiency and output power are inherently stable and insensitive to the resonant frequency. The results show that the efficiency and output power only change within 1% when the receiver resonant frequency is detuned by ±5%. In contrast, the WPT systems that are sensitive to the resonant frequency suffer from fall in the efficiency of around 30%, and a largely unstable output power. The available experiments verify the effectiveness of the proposed system.