Wind turbine control methods and systems

A method of controlling the operation of a variable speed wind turbine (11), tracking a power curve (25, 27) which includes a nominal operational region (3) and sub-nominal operational regions (2, 1, 0), wherein the method comprises an adaptive predictive algorithm that allows the operation of the wind turbine (11) in the nominal operation region (3) or in the sub-nominal operation regions of the power curve (25, 27) depending on the wind situations and comprises the steps of:

• a) implementing a control strategy to follow said power curve (25, 27) in said nominal operational region (3) based on the use of demanded torque Td for controlling power P and on the use of demanded pitch θd for controlling demanded torque Td;
• b) implementing a control strategy to follow said power curve (25, 27) in sub-nominal operational regions (2, 1, 0) based on the use of demanded torque Td for controlling power P and on the setting of a constant optimum value for demanded pitch θd in each sub-nominal operational region (2, 1, 0).