Abstract: Charging power based on HF AC-Link technology can be used as a primary power source for high-power microwave systems. In order to improve the adaptability of the power supply in the power grid with non-ideal input, this paper adopts the three-phase phase-locked loop in the decoupled double synchronous coordinate system to obtain the phase and frequency information of the positive sequence voltage. To extract the input line voltage amplitude of the fundamental wave, this paper uses the FIR filter to provide timely and accurate control parameters for the power supply. The model was established by Matlab/Simulink software, and the simulation was carried out under the condition of three-phase input imbalance, frequency change and voltage distortion. Lastly, a control program was written and tested based on DSP2812. The simulation and experimental results show that the method can accurately extract the amplitude, phase and frequency information of the input line voltage in all kinds of grid input, and provide a guarantee for good operation of the power supply.