Method and controller for operating a wind turbine

Abstract

The method according to the invention for operating a wind turbine, comprising a tower and a rotor arranged at the top of the tower and having at least one rotor blade, which can be adjusted about a blade setting axis, has a first operating mode in which the at least one rotor blade has an operating angular position about the blade setting axis and a wind-force-dependent rotation of the rotor is converted into electrical power using a generator unit, which power is delivered from the wind turbine into an electrical network and/or stored, and a second operating mode in which the at least one rotor blade is adjusted by at least 60° and/or max. 110° about the blade setting axis relative to the operating angular position into a damping angular position, and a counter torque braking the rotor is controlled based on a vibration of the tower.

Claims

1. A method for operating a wind turbine comprising a tower and a rotor arranged at the top of the tower which has at least one rotor blade adjustable about a blade setting axis, wherein in a first operating mode, the at least one rotor blade has an operating angular position about the blade setting axis and a wind force-dependent rotation of the rotor is converted with the aid of a generator unit into electrical power which is transferred from the wind turbine to an electrical network or stored; and wherein in a second operating mode, the at least one rotor blade is adjusted by at least 60° about the blade setting axis relative to the operating angular position into a damping angular position and a counter torque which is braking the rotor and which is imparted by or induced by the generator unit is controlled on the basis of a lateral vibration of the tower.

2. The method according to claim 1, wherein a switch is made from the first operating mode into the second operating mode should a wind speed exceed a cut-out speed or should a malfunction be detected.

3. The method according to claim 1, wherein a wind force-dependent rotation of the rotor is converted with the aid of the generator unit into electrical power in the second operating mode, wherein the electrical power is used to adjust the at least one rotor blade about the blade setting axis or to supply loads of the wind turbine, or is output from the wind turbine into the electrical network, or is stored, wherein said output or respectively stored power amounts to at most 2% of the wind turbine's rated output, or wherein a rotational speed of the rotor in the second operating mode amounts to a maximum of 20% of the wind turbine's rated rotational speed.

4. The method according to claim 1, wherein the tower is arranged in a body of water, or wherein the generator unit comprises a gearbox, or wherein the rotor comprises at least two rotor blades, each of the at least two rotor blades being adjustable about a respective blade setting axis, and having an operating angular position about their blade setting axis in the first operating mode, and each of the at least two rotor blades being adjusted by at least 60° about the blade setting axis relative to the operating angular position into a damping angular position in the second operating mode.

5. The method according to claim 1, wherein the at least one rotor blade is adjustable by at least 80° or by a maximum of 100° about the blade setting axis from the operating angular position into a feathering position in which the rotor converts an inflow of wind parallel to its rotational axis into a minimum rotational speed.

6. The method according to claim 1, wherein, in the first operating mode or the second operating mode, the rotor is adjusted about a tracking axis transverse to its rotational axis as a function of a wind direction.

7. A computer program product comprising a program code which is stored on a non-transitory computer-readable medium, for carrying out the method according to claim 1.

8. The method according to claim 1, wherein the counter torque which is braking the rotor is controlled on the basis of at least one vibration sensor.

9. The method according to claim 8, wherein the at least one vibration sensor is arranged at between 25% and 70% of the tower height.

10. The method according to claim 8, wherein the at least one vibration sensor is arranged at between 70% and 100% of the tower height.

11. The method according to claim 8, wherein the at least one vibration sensor is arranged in or below a nacelle of the tower supporting the rotor.

12. The method according to claim 1, wherein the lateral vibration of the tower is a first natural mode of the tower or a second natural mode of the tower.

13. The method according to claim 1, wherein the lateral vibration of the tower is transverse to a rotational axis of the rotor.

14. The method according to claim 1, wherein the counter torque which is braking the rotor is controlled for maintaining a direction of a torque driving the rotor.

15. The method according to claim 1, wherein the counter torque which is braking the rotor is controlled on the basis of a tower vibration in the first operating mode.

16. A controller for a wind turbine, wherein the wind turbine comprises a tower and a rotor arranged at the top of the tower which has at least one rotor blade adjustable about a blade setting axis, wherein the controller has: a first operating mode in which the at least one rotor blade has an operating angular position about the blade setting axis and a wind force-dependent rotation of the rotor is converted into electrical power with the aid of a generator unit, which electrical power is transferred from the wind turbine into an electrical network or is stored; and a second operating mode in which the at least one rotor blade is adjusted by at least 60° about the blade setting axis relative to the operating angular position into a damping angular position, and a counter torque which is braking the rotor and which is imparted by or induced by the generator unit is controlled on the basis of a lateral vibration of the tower.

17. A wind turbine comprising the controller of claim 16.

Description

(1) Further advantages and features will become apparent from the dependent claims and example embodiments. In the figures:

(2) FIG. 1 shows, partially schematically, a wind turbine having a controller for operating the wind turbine according to an embodiment of the present invention; and

(3) FIG. 2 shows, partially schematically, a method for operating the wind turbine according to an embodiment of the present invention.

(4) FIG. 1 shows a wind turbine with a controller 10 for operating the wind turbine according to an embodiment of the present invention which comprises a tower having a tower top in the form of a nacelle 20 and a tower body 21 on which the nacelle 20 is rotatable about a vertical tracking axis N by a drive 22 and can thus track a direction of wind as indicated in FIG. 1 by an arrow indicating adjustment. The controller 10 controls the drive 22 to that end, as indicated in FIG. 1 by a control arrow.

(5) The tower (body 21) in the example embodiment is at sea, as indicated by a water surface W.

(6) A rotor with rotor blades 30 is rotatably mounted in the nacelle 20 about a rotational axis R, as indicated in FIG. 1 by a rotation arrow.

(7) The rotor blades 30 can each be rotated about their blade setting axis B, as indicated in FIG. 1 by arrows indicating adjustment. The controller 10 controls a blade adjustment drive to that end, as indicated in FIG. 1 by a control arrow.

(8) The rotor is coupled to a generator 41 of a generator unit via a gearbox 40.

(9) The controller 10 controls a counter torque braking the rotor which the generator 41 imparts when or respectively by converting a rotation of the rotor into electrical energy which is output to a load 50 and/or storage 51 and/or electrical network 52.

(10) In a method for operating the wind turbine according to an embodiment of the present invention as illustrated in FIG. 2, the rotor blades are or respectively will be set to a pitch angle of approximately 0° in a step S10, or first operating mode in the form of partial load operation respectively, and a wind force-dependent rotation of the rotor is converted into electrical power with the aid of the generator unit 40, 41, which electrical power is then output from the wind turbine to the electrical network 52. In full-load operation, the rotor blades are operated with a variable blade pitch angle of between 0° and 45°.

(11) Should a malfunction of the wind turbine or of the electrical network 52 or a wind speed above a preset cut-out (wind) speed be detected (S20: “Y”), the controller 10 switches into a second operating mode. The rotor blades are to that end rotated by approximately 84° to 94° about their blade setting axes toward the feathering position, i.e. their leading edges (left in FIG. 1) are rotated (in)to the oncoming (wind) flow (FIG. 2: S30). Otherwise (S20: “N”), the first operating mode is maintained, or a switch is made to a further operating mode (not illustrated).

(12) In a step S40, or the second operating mode respectively, the counter torque imparted by the generator unit during or respectively through the generation of electrical energy is controlled or modulated such that a lateral vibration of the tower transverse to the rotational axis R and to the tracking axis N (perpendicular to the paper plane of FIG. 1) is reduced.

(13) To that end, an acceleration sensor 11 detects a lateral acceleration of the top of the tower 20 and transmits a corresponding signal to the controller 10, as indicated in FIG. 1 by a signal arrow.

(14) Based on this, the controller 10 determines an output variable which can for example be proportional to the lateral acceleration, in one embodiment a band-limited lateral acceleration, whereby the proportionality factor can for its part be dependent upon the amount of lateral acceleration, in one embodiment an asymmetrically ramp-limited and/or smoothed amount of lateral acceleration, in one embodiment in a linear or non-linear manner, and/or in a manner which is limited by an upper and/or lower limit. The 90° phase-shifted and potentially harmonized output variable forms a control variable which is used to control the counter torque imparted by the generator unit during or respectively through the generation of electrical energy, and which for example forms a target generator torque or which is superimposed to a desired target generator torque mean value.

(15) In this context, the counter torque is controlled such that a torsional moment in the drive train comprising the rotor and the generator unit 40, 41 does not change its sign, in order to prevent rattle in the gearbox 40.

(16) As long as the malfunction of the wind turbine or respectively the electrical network 52 or respectively a wind speed above a preset cut-out (wind) speed is detected (S50: “Y”), step S40, or respectively the second operating mode, continues to be carried out; otherwise (S50: “N”), the method or respectively the controller 10 or respectively the wind turbine reverts to step S10 or the first operating mode respectively.

(17) Although example embodiments have been outlined in the preceding description, it is to be pointed out that a plurality of modifications are possible. It is also to be noted that the example embodiments are only examples that are not in any way intended to limit the scope of protection, the applications and the configuration. Rather, the preceding description provides a person skilled in the art with a guideline for the implementation of at least one example embodiment, whereby various modifications can be made, in particular as regards the function and arrangement of the described components, without departing from the scope of protection as provided by the claims and feature combinations equivalent thereto.