  With increased wind power penetration in modern power systems, wind plants
are required to provide frequency support similar to conventional plants.
However, for the existing frequency regulation scheme of wind turbines, the
control gains in the auxiliary frequency controller are difficult to set
because of the compromise of the frequency regulation performance and the
stable operation of wind turbines, especially when the wind speed remains
variable. This paper proposes a novel frequency regulation scheme (FRS) for
de-loaded wind turbines. Instead of an auxiliary frequency controller,
frequency support is provided by modifying the parametrized power versus rotor
speed curve, including the inertia power versus rotor speed curve and the droop
power versus rotor speed curve. The advantage of the proposed scheme is that it
does not contain any control gains and generally adapts to different wind
speeds. Further, the proposed scheme can work for the whole section of wind
speed without wind speed measurement information. The compared simulation
results demonstrate the scheme improves the system frequency response while
ensuring the stable operation of doubly-fed induction generators (DFIGs)-based
variable-speed wind turbines (VSWTs) under various wind conditions.
Furthermore, the scheme prevents rotor speed overdeceleration even when the
wind speed decreases during frequency regulation control.
