Wind turbine control system and method

A wind turbine control system for wind turbines comprising a rotor, an asynchronous generator driven by the rotor and configured for providing an active power to a power grid, and a power converter connected to the generator and configured to interact with the generator for generating active power for the power grid, the control system comprising

• a converter control unit configured for controlling the power converter and
• a wind turbine controller for the wind turbine, the wind turbine controller having a rotor speed controller configured for calculating an active power reference to be provided by the wind turbine and the rotor speed controller including an inertia emulation block configured for calculating a synthetic inertia to be provided to the power grid, in the form of active power, to counteract a frequency disturbance in the power grid, the synthetic inertia being negatively proportional to the frequency change rate or frequency derivative of the frequency of the power grid, wherein the converter control unit comprises
• an estimator block configured for receiving the frequency of the power grid and for estimating the grid voltage phase angle or frequency, for synchronizing the actuation of the power converter with the frequency of the power grid, and
• a frequency derivative estimator configured for receiving the frequency of the power grid and for estimating the frequency derivative of the frequency, and wherein the wind turbine controller and the converter control unit are communicated such that the wind turbine controller can receive the frequency derivative estimated by the frequency derivative estimator of the converter control unit, the rotor speed controller of the wind turbine controller being configured for considering the received frequency derivative for determining the synthetic inertia.