A method of controlling the operation of a variable speed wind turbine (11), tracking a power curve (25, 27) including a nominal operational region (3 ) and sub-nominal operational regions (2, 1, 0), comprising steps of: a) implementing a control strategy to follow said power curve 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 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). The invention also refers to a control system comprising one or more Adaptive Predictive Controllers (51, 53, 55, 59).