Method for controlling a wind turbine during safety operation

A control unit for controlling pitch angles of a wind turbine, the wind turbine comprising a rotor carrying at least two wind turbine blades adapted to be pitched individually, the control unit being adapted to providing a safety pitch control system adapted to pitch the blades individually at a number of pre-set approximately constant pitch rates including a first pitch rate and a second pitch rate lower than the first pitch rate, and further adapted to perform an operation, comprising:

• receiving a command for initiating the safety operation of the wind turbine whereupon the blades are pitched towards a feathering position by the safety pitch control system;
• and
• pitching the blades according to a safety pitch strategy wherein for all the blades, the pitch rate is changed between the first pitch rate and the second pitch rate according to a function of each blade azimuthal position, such that each blade in turn is closer to the feathering position than the others;
• wherein the safety pitch strategy is performed while pitching the blades towards a feathering position.

A wind turbine, comprising:

• a rotor carrying at least two wind turbine blades adapted to be pitched individually;
• and
• a control unit adapted to providing a safety pitch control system adapted to pitch the blades individually at a number of pre-set approximately constant pitch rates including a first pitch rate and a second pitch rate lower than the first pitch rate, and further adapted to perform an operation, comprising:
• receiving a command for initiating the safety operation of the wind turbine whereupon the blades are pitched towards a feathering position by the safety pitch control system;
• and
• pitching the blades according to a safety pitch strategy wherein for all the blades, the pitch rate is changed between the first pitch rate and the second pitch rate according to a function of each blade azimuthal position, such that each blade in turn is closer to the feathering position than the others;
• wherein the safety pitch strategy being performed while pitching the blades towards a feathering position.