Two-stage adaptive frequency control method for wind power considering second frequency events in rotor speed recovery

The increasing penetration of wind power poses a significant challenge to power system frequency stability, making it vital to enable wind turbine generators (WTGs) to participate in the frequency response of power grids. Considering the frequency response ability of WTGs is closely related to their operation status, how to fully utilize the frequency response ability of WTGs and select appropriate time to exit frequency support according to system frequency characteristics is a key point in designing an effective frequency response method for wind turbines. This paper proposes a two-stage adaptive frequency control method for wind power, through which, the frequency support power of WTGs can be adaptively adjusted according to frequency variation and the operation status of WTGs in frequency support stage, and WTGs can provide maximum frequency support power when the frequency reaches its security constraint. In the rotor speed recovery stage, the proposed method allows the WTG to adaptively exit from the frequency support according to the rate of change of frequency (RoCoF), thus avoiding large power dips and improving the secondary frequency dip (SFD). Meanwhile, through the proposed method, WTGs can provide sufficient frequency support power to respond to subsequent disturbances during rotor speed recovery. The modified IEEE 39-bus system is used to verify the effectiveness of the proposed method.