Method for operating a wind turbine at improved power output

A method for operating a wind turbine, the wind turbine comprising a rotor having a set of wind turbine blades, the rotor being mounted on a tower, the method comprising:

• (a) providing a curve defining optimal pitch angle as a function of tip speed ratio for the wind turbine blades or as a function of wind speed,
• (b) selecting a first safety margin such that there is little to no risk that the blades stall or that components of the wind turbine experience excessive loads in expected worst case wind conditions, wherein the expected worst case wind conditions are historical worst case wind conditions in terms of wind speed, wind direction, wind turbulence, wind ousts, and/or wind shear, as measured, estimated, and/or calculated from estimated values,
• (c) modifying at least a part of the optimal pitch angle curve by applying the first safety margin, thereby obtaining a first safety margin modified pitch angle curve,
• (d) operating the wind turbine in accordance with the first safety margin modified pitch angle curve,
• (e) measuring one or more parameters providing information regarding wind conditions and/or loads on one or more components of the wind turbine, during operation of the wind turbine,
• (f) selecting a second safety margin based on the measurements,
• (g) modifying at least a part of the optimal pitch angle curve by applying the second safety margin, thereby obtaining a second safety margin modified pitch angle curve, and
• (h) operating the wind turbine in accordance with the second safety margin modified pitch angle curve,
• (i) wherein the step of selecting the second safety margin comprises decreasing the second safety margin below the first safety margin in the event that the measurements indicate wind conditions less severe than the expected worst case wind conditions, or increasing the second safety margin above the first safety margin in the event that the measurements indicate wind conditions more severe than the expected worst case wind conditions, and
• repeating steps (e) through (i) to select and implement third and subsequent safety margins during operation of the wind turbine to produce a continuously variable safety margin based on the difference between measured parameters and expected worst case wind conditions based on a historical frame of reference.