OVERLOAD PROTECTION ON WIND POWER PLANTS USING STRAIN SENSORS

1 . A method for controlling a wind turbine with a rotor having at least one rotor blade, the method comprising:

measuring, with a sensor, a strain of the at least one rotor blade;

changing a pitch angle of the at least one rotor blade based at least partially on the measured strain of the at least one rotor blade;

whereby the measuring of the strain of the at least one rotor blade measures at least one strain in an area of a blade root of the at least one rotor blade.

2 . A method according to claim 1 , whereby measuring the strain of the at least one rotor blade detects a bending of the at least one rotor blade, which indicates imminent acceleration of the rotor.

3 . A method according to claim 2 , whereby the pitch angle of the at least one rotor blade is changed as soon as the bending is detected in order to prevent the imminent acceleration of the rotor.

4 . A method according to claim 1 , whereby changing the pitch angle is configured to prevent overload of a generator and/or a converter of the wind turbine by limiting power that is transmitted from the at least one rotor blade to the generator and/or the converter.

5 . A method according to claim 1 , whereby the measurement of the strain is performed with a fiber-optic strain sensor,

which is arranged in the blade root of the at least one rotor blade, and

which includes a Fiber Bragg Grating.

6 . A method according to claim 1 , whereby a strain is measured with a sensor for all rotor blades of the rotor, and whereby the changing of the pitch angle is based on the measured strain of all rotor blades.

7 . A method according to claim 1 , whereby changing the pitch angle is additionally based on a power and/or a rotational speed of the rotor.

8 . A method according to claim 1 , whereby the changing of the pitch angle is additionally based on a measured wind speed.

9 . A method according to claim 1 , whereby the step of measuring the strain includes measuring a strain between a first point on the at least one rotor blade and a distant second point on the at least one rotor blade, where an optical fiber is clamped between the first point and the distant second point.

10 . A wind turbine configured to operate according to the method of claim 1 , the wind turbine comprising:

the sensor configured for measuring a strain of the at least one rotor blade of the wind turbine;

a control unit configured to change a pitch angle of the at least one rotor blade, based at least partially on a strain of the at least one rotor blade as measured by the sensor; and

wherein the control unit is configured to control at least the pitch angle of the at least one rotor blade.

11 . A wind farm with at least one wind turbine according to claim 10 .

12 . A method according to claim 8 , where the measured wind speed is measured by one or more of a wind gauge, an anemometer, and LIDAR.

13 . A wind turbine configured to operate according to the method of claim 1 , the wind turbine comprising:

the sensor for measuring a strain of the at least one rotor blade of the wind turbine being configured as a fiber-optic strain sensor arranged in the blade root of the at least one rotor blade;

a control unit configured to change a pitch angle of the at least one rotor blade, based at least partially on a strain of the at least one rotor blade as measured by the sensor; and

wherein the control unit is configured to control at least the pitch angle of the at least one rotor blade.

14 . A wind turbine according to claim 13 , where the fiber-optic strain sensor includes a Fiber Bragg Grating.

15 . A wind turbine according to claim 13 , comprising an optical fiber clamped between a first point of the at least one rotor blade and a second point of the at least one rotor blade.

16 . A wind turbine according to claim 15 , where the optical fiber includes a Fiber Bragg Grating.

17 . A wind farm with at least one wind turbine according to claim 16 .

18 . A wind turbine according to claim 13 , where the control unit is further configured to change the pitch angle based additionally on a power of the rotor and/or a rotational speed of the rotor.

19 . A wind turbine comprising:

a rotor including at least one rotor blade;

a fiber-optic strain sensor configured for measuring a strain between a first point and a second point, remote from the first point, of the at least one rotor blade of the wind turbine; and

a control unit configured to change a pitch angle of the at least one rotor blade, based at least partially on a strain of the at least one rotor blade as measured by the sensor;

wherein the sensor configured as a fiber-optic strain sensor arranged in a blade root of the at least one rotor blade.

20 . A wind turbine according to claim 19 , where the optical fiber includes a Fiber Bragg Grating, and where the control unit is configured to change the pitch angle based additionally on a power of the rotor and/or a rotational speed of the rotor.