Enhancing Simplified Control and Misalignment Tolerance in Autonomous Fractional-Order Wireless Power Transfer System With an Improved Primary-Side Control Strategy

Abstract

In wireless charging applications for drones and automatic guided vehicles (AGVs), the wireless power transfer (WPT) system is required to achieve stable power output under primary- and secondary-side offset. Previous research has shown that an autonomous fractional-order WPT (FOWPT) system can address this issue. However, the autonomous FOWPT system faces certain challenges, such as limitations in critical coupling strength during frequency control, the need to sample large and distorted coil voltage signals, and the fact that output power is not entirely independent of the coupling strength under specific parameters. This article aims to analyze the existing issues in autonomous FOWPT and establish the specific relationship between output power and original system parameters through derivation. By shifting the sampling points and control variables from the equivalent fractional-order capacitor (FOC) to the inverter, an enhanced primary-side control strategy is proposed to ensure stable output power under coil misalignment by controlling the constant active power of the inverter output. This new strategy can achieve the same control effect as autonomous FOWPT without requiring FOC conversion, simplifying the control logic, reducing sampling difficulty, improving control accuracy, and expanding the system’s adjustment range. Simulations confirm the effectiveness of the proposed control strategy and compare the differences and connections between the two control methods. A prototype test generating 106 W shows that based on the improved control strategy, the system can maintain stable output within a dynamic coupling range of 0.14–0.6, with a power fluctuation range of only 4.5%.