Droop Control of Wind Turbines to Provide Upward Support in Frequency Regulation

An advanced control strategy is adopted to implement an upward frequency regulation contribution from wind farms in case of grid under-frequency. The power variation carried out takes into account both the deviation of grid frequency from its nominal value and the one of rotor speed from its minimum value. This strategy allows to avoid the occurrence of a further frequency perturbation due to the restoration of the pre-fault operating conditions of wind turbines after they are slowed down by rotor speed control to supply the additional power contribution. Control parameter optimisation, based on compliance with constraints on the frequency time behaviour, is presented. The control strategy and tuning process are tested on a future scenario of the Sardinian power system.