A Segmented Floating Frequency Tracking Control Strategy for Wireless Power Transfer Systems

Wireless power transfer (WPT) systems often face frequency detuning issues when the transmission distance changes. To address this problem, traditional Phase-Locked Loop (PLL) frequency tracking control is commonly used. However, during the transition from open-loop to steady-state operation, the PLL suffers from startup impact issues. To reduce the adjustment time and optimize frequency control, a segmented floating frequency tracking control strategy (SFFTCS) is proposed. Specifically, the control process under detuned conditions is divided into three stages: initial open-loop, table lookup to determine the target frequency, and PLL control. A smooth transition control based on the weighted averaging method is designed between the initial open-loop phase and the target frequency. In the transition region, weight coefficients are used to gradually reduce the frequency deviation between the switching frequency and the adjacent frequencies. Through theoretical analysis, this paper designs a phase detector, switching algorithm, and pulse modulation method. Experimental results show that this method can simultaneously reduce startup impact and adjustment time. The system has been successfully applied to a space wireless power transfer device, significantly improving the rapid tracking capability during distance changes.