A Wireless In-Flight Charging Range Extended PT-WPT System Using S/Single-Inductor-Double-Capacitor Compensation Network for Drones

To address the special challenges for drone wireless in-flight charging systems, namely the continuous fluctuation of mutual inductance, large charging distance, and limited payload of the pickup, a novel high-order primary-series (S) and secondary-single-inductor-double-capacitor (SLDC) topology for parity-time (PT) symmetric wireless power transfer (WPT) system is proposed in this article. The reduced-order model of the proposed system is first established and analyzed based on the coupled-mode theory. It shows the critical coupling coefficient can be reduced by two additional degrees of freedom (λ and L_r), thus effectively expanding the constant power (CP) region of PT-WPT system. In addition, the inductor L_r can be placed freely in drones and λ can be flexibly adjusted to meet the demands of various environments, which enhance the system flexibility. Also, the communication link and dc–dc converter are not needed, which improve the real time and reduce the drone payload. Simulated and experimental results prove that the transfer distance can be extended by 102% with λ = 0.6 and L_r = 60.5 μH while keeping the CP of 75 W and efficiency of 87.5% against the misalignment and change of the charging distance. Accordingly, with the proposed S/SLDC topology, drone in-flight charging systems can obtain a larger CP region with high efficiency, thus extending the flight time of drones.