A method for handling rotor unbalance of a wind turbine with hinged wind turbine blades

A method for operating a wind turbine, the wind turbine comprising a tower, a nacelle mounted on the tower via a yaw system, a hub mounted rotatably on the nacelle, the hub comprising a blade carrying structure, and one or more wind turbine blades connected to the blade carrying structure via a hinge, each wind turbine blade thereby being arranged to perform pivot movements relative to the blade carrying structure between a minimum pivot angle and a maximum pivot angle, wherein the pivot angle determines a diameter of a rotor of the wind turbine, the wind turbine further comprising an adjustable biasing mechanism arranged to apply an adjustable biasing force to each wind turbine blade which biases the wind turbine blade towards a position defining minimum pivot angle or towards a position defining maximum pivot angle, the method comprising:

• selecting a biasing force for each wind turbine blade and applying the selected biasing force to the respective wind turbine blades;
• operating the wind turbine while monitoring rotor unbalance of the wind turbine;
• and
• in the case that the rotor unbalance exceeds a first threshold value:
• selecting at least one of the wind turbine blades;
• and
• adjusting the biasing force applied to the selected wind turbine blade(s).