Research on Interference Suppression of Injection Stator Grounding Protection

During the gas turbine startup process, the static variable frequency startup device（SFC） drags the unit from the static to the self-sustaining speed and then exits the operation, but the output fundamental wave frequency(f_SFC) will have a dynamic conflict with the injection signal frequency(f_inj) of the stator grounding protection of the injection generator, resulting in misoperation of the protection and interruption of the startup process. To solve this problem, a protection optimization method based on real-time frequency tracking and dynamic collision avoidance is proposed in this paper. Firstly, the mechanism of signal flooding and the characteristics of difference frequency oscillation are revealed by theoretical modeling. Secondly, a phase-locked loop（PLL） is designed to track the dynamic changes in real time and adjust to the frequency band, and an adaptive notch filter is integrated to suppress residual interference. Finally, the seamless switching of protection parameters is triggered by the SFC status signal（run/exit）, ensuring that the device returns to standard detection mode immediately after the SFC exits.