具有恒压输出特性的电场耦合式动态无线电能传输技术

Electric-field coupled wireless power transfer (EC-WPT) system uses a high-frequency electric field among metal plates to realize power transmission, which has the advantages of light coupling interface, low eddy current, and better anti-misalignment. Dynamic wireless power transfer (DWPT) technology can realize continuous power supply during the moving process of electrical equipment. The advantages of EC-WPT technology are highly consistent with the special requirements of DWPT because the moving equipment has restricted requirements on the volume and weight of the power receiving unit of the DWPT system. DWPT system usually adopts segmented transmitting coils or plates. However, the segmented transmitting structure introduces two new problems for DWPT systems: (1) when the distance between the adjacent transmitting plates is small, the mutual coupling between the transmitting ports will affect the system resonance; on the contrary, when the adjacent plates are far apart, the output voltage will drop when the receiver moves over the segments. (2) How to keep the system voltage gain consistent when the receiver position and load resistance change. In the existing research on the EC-WPT system, a decoupled electric-field coupler suitable for the DWPT system is yet to be proposed, so the same-sided coupling between adjacent transmitters of the EC-WPT system is unavoidable. Moreover, the influence principle of same-sided coupling on the resonance of dynamic EC-WPT system must be better studied. Because the EC-WPT system uses the electric field as the power transfer medium, its intensity around transmitting plates should be evenly distributed to ensure a constant induced voltage on the receiver under different operating conditions. Then the output voltage of the dynamic EC-WPT system can be kept constant under varying receiver positions and load resistance using an LCLC-S compensation network. The main contents of this paper are as follows: An inverse hybrid G-parameter model of a multi-port electric field coupler is proposed based on the existing multi-port Z-parameter model for the segmented coupler of the dynamic EC-WPT system. In the proposed model, the self-capacitance on the primary side is connected with the reflected impedance (or controlled source) in parallel. Then the constant voltage of the transmitting plates is achieved by using a high-order compensation network of LCLC-S topology. Finally, the influence of the same-side coupling between the transmitters on the zero-voltage switching (ZVS) condition of the inverter is also analyzed in detail. Theoretical analysis shows that the proposed system has the properties of constant output voltage against the variable load and different receiver positions. The influence of the same-sided coupling makes the input impedance slightly inductive, which benefits the ZVS condition of inverters. In the experiment, a prototype of a dynamic EC-WPT system is constructed. The experimental results show that when the load varies from 100 Ω to 30 Ω, the maximum change rate of the system output voltage is 11.58%. When the power pickup moves over two adjacent transmitters, the change rate of the system output voltage is no more than 2.33% when the load is 30 Ω, and no more than 2.06% when the load is 100 Ω. Overall, the output voltage of the proposed system is approximately constant in both cases above.