Constant Power Control Against M/R With Expanded PT-Symmetric Range for Wireless in-Flight Charging of Drones

For the drone wireless in-flight charging system, the challenge is to keep a constant charging power under the large range of continuous fluctuation of mutual inductance (
$M$
), the variation of battery load (
$R$
), and the limited payload of drones, which has been rarely studied in the previous research. To address the issue, this article presents a primary-series and secondary-series-inductor-series–parallel-capacitor (SLSPC) high-order topology for the parity-time (PT) symmetric wireless power transfer (WPT) system, which can greatly expand the exact PT-symmetric region (constant power range) by the reduction of critical coupling coefficient in comparison with the traditional series–series topology. In addition, the constant power control scheme is proposed based on the series-SLSPC high-order topology to overcome the change of
$M$
and
$R$
. With the proposed control method, only the primary current needs to be detected, which enhances the real-time performance of the WPT system and reduces the payload of drones. Simulated and experimental results validate the expansion capability of the PT-symmetric range with the proposed series-SLSPC PT-WPT system and the feasibility of the proposed control scheme.