CONTROLLING FLAP LOADING ON A WIND TURBINE BLADE BASED ON PREDICTED FLAP LOADING

The present invention provides a method of controlling loading on a wind turbine blade in the flap-wise direction. The method includes defining a system model that has a description of flap loading on the blade, and predicting flap loading on the blade over a prediction horizon using the system model. The method includes determining a dynamic flap loading limit based on predicted flap loading and a measured flap loading, and defining a constraint to limit flap loading on the blade based on the dynamic flap loading limit. The method includes using the predicted flap loading in a cost or performance function, and optimising the cost function subject to the constraint to determine pitch for the blade to control flap loading on the blade. Advantageously, the dynamic limit varies based on discrepancies between predicted and measured flap loading to allow for adaptive back-off from extreme loads prior to such loads building up or being exceeded.