METHOD FOR OPERATING A WIND TURBINE IN EMERGENCY MODE, AND CONTROLLER AND WIND TURBINE

Abstract

A method for a wind turbine in an emergency mode. In that case a change in the wind direction and/or a force exerted on the wind turbine is detected and at least one of the rotor blades is adjusted in dependence on the change while maintaining the yaw angle of the yaw setting. A control means for a wind turbine and a wind turbine.

Claims

1. A method comprising: operating a wind turbine in an emergency mode, the wind turbine comprising a plurality of rotor blades, the operating comprising: a) detecting at least one of: a change in a wind direction or a change in at least one force exerted on the wind turbine, b) maintaining a yaw angle of a yaw setting, and c) adjusting at least one rotor blade of the plurality of rotor blades in dependence on the detected change.

2. The method according to claim 1 wherein in step c) the at least one rotor blade is adjusted to an angle which differs from an angle for a feathered position of the respective rotor blade with the yaw angle.

3. The method according to claim 1 wherein the at least one rotor blade in step c) is set to an angle at which a force on the wind turbine is minimized in comparison with a plurality of or all other angles.

4. The method according to claim 1 wherein the change in the wind direction is detected when a horizontal differential value between a first wind direction and a second wind direction is above a predefined differential angle threshold value and no change in the wind direction is detected when the differential angle is at or below the differential angle threshold value.

5. The method according to claim 1 further comprising determining a wind speed, and wherein step c) is carried out when the wind speed is above a predefined wind speed threshold value.

6. The method according to claim 1 wherein the detecting is step a) comprises detecting the change in the at least one force when a monitored force exceeds a predefined force threshold value.

7. The method according to claim 1 wherein the adjusting comprises using an emergency power supply for power for adjustment the at least one of the plurality of rotor blades.

8. The method according to claim 7 wherein the emergency power supply in an emergency mode is designed for two or more adjustment operations for all of the plurality of rotor blades.

9. The method according to claim 1 wherein the plurality of rotor blades are rotatable through 360 degrees about the longitudinal axis of the respective rotor blade.

10. The method according to claim 1 wherein each of the plurality of rotor blades are individually adjusted.

11. A control means for a wind turbine wherein the control means is adapted to carry out the method according to claim 1.

12. The control means according to claim 11 wherein the control means includes one or more sensors for detecting at least one of: a change in a wind direction and/or or a change in a force exerted on the wind turbine.

13. A wind turbine comprising the control means according to claim 11.

14. The method according to claim 3 wherein the force includes a plurality of forces exerted on the at least one rotor, the rotor, or the rotor shaft.

15. The method according to claim 3 wherein the force includes bending moments exerted on the at least one rotor blade, the rotor, or the rotor shaft.

16. The method according to claim 1 wherein the change in the at least one force exerted on the wind turbine is detected when a differential force between a first force and a second force is above a first predefined differential force threshold value and no change in the at least one force exerted on the wind turbine is detected when the differential force is at or below the differential force threshold value.

17. The method according to claim 7 wherein the emergency power supply is an accumulator.

18. The method according to claim 8 wherein each adjustment operation includes a rotation of each rotor blade about its longitudinal axis through at least 90 degrees.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0039] Further configurations will be apparent from the embodiments by way of example described in greater detail with reference to the figures.

[0040] FIG. 1 shows a side view of a wind turbine,

[0041] FIG. 2 shows a plan view of a wind turbine with rotor blades in the feathered position,

[0042] FIG. 3 shows the view of FIG. 2 with changed rotor blade position,

[0043] FIG. 4 shows the plan view from FIGS. 2 and 3 with the rotor blade position again changed, and

[0044] FIG. 5 shows the steps of an embodiment of the method.

DETAILED DESCRIPTION

[0045] FIG. 1 shows a wind turbine 10 having a tower 12 and a pod 14. Arranged on the pod 14 is an aerodynamic rotor 16 having three rotor blades 18 and a spinner 20. In operation the rotor 16 is driven in rotation by the wind and thereby drives a generator in the pod 14.

[0046] The pod 14 is adjustable about a perpendicular axis 22 in the direction of the arrow 24. That adjustment is also referred to as the yaw adjustment or wind direction tracking and thus serves for setting the yaw angle of the wind turbine 10. The yaw setting accordingly serves to orient the rotor 16 to the prevailing wind direction 26. The yaw or yaw angle shown here is defined for example as the yaw angle of zero degrees. With the illustrated yaw angle and the prevailing wind direction 26 reference is made to a parallel afflux flow or a symmetrical afflux flow. That is the case when the wind 26 impinges on the rotor 16 substantially parallel to a rotor shaft 28 from the front side 30.

[0047] The rotor blades 18 can also be rotated about their longitudinal axis 32. That is illustrated by the arrow 34. In the present case the rotor blades 18 are oriented in a feathered position. This means that the wind which is incident on the rotor 16 from the wind direction 26 produces no or only a slight torque on the rotor shaft 28. The reason for this is that the position of the rotor blades 18 provides that the forces acting on the respective rotor blade 18 substantially cancel each other out or add up to make zero.

[0048] That feathered position is preferably assumed when the wind turbine 10 is not to feed any energy into the grid or the wind turbine 10 is in an emergency mode of operation in which no power for further controlled adjustment of the wind turbine 10 can be taken from the grid.

[0049] FIG. 2 shows a plan view of the wind turbine 10 of FIG. 1. The identical references denote the same features. In FIG. 2 the wind turbine 10 is also oriented in relation to the wind and this therefore involves a parallel afflux flow. The rotor blades 18 are also set in the feathered position. The loading on the wind turbine 10 is thus minimal.

[0050] FIG. 3 now shows a first example for adjusted rotor blades 18 in accordance with the method. In this case the wind direction 26 has now turned through 90 degrees from the first wind direction 26a as shown in FIG. 2 into a second wind direction 26b in the clockwise direction in relation to the wind direction in FIG. 2. Accordingly this now no longer involves a parallel afflux flow as shown in FIG. 2 but an inclined afflux flow generally or here specifically a transverse afflux flow. Accordingly the wind turbine 10 detects that there has been a change in the wind direction from the first wind direction 26a into the second wind direction 26b. Alternatively or additionally that change in wind direction can also be detected by a change in a force acting on the wind turbine 10. Loads or changes in load are for that purpose monitored for example with strain gauges.

[0051] As shown in FIG. 3 the yaw angle of the yaw setting is maintained in spite of the change in the wind direction and the rotor blades 18 are moved to a different angle which can also be referred to as the second angle. The second angle differs from an angle for a feathered position in relation to a parallel afflux flow with the current yaw orientation. More specifically accordingly the rotor blades 18 are now set in relation to the wind in such a way that as low a force as possible acts on the rotor blade 18 due to the wind. It can be seen from FIG. 3 that the rotor blades 18 are adjusted through 90 degrees in relation to the position in FIG. 2.

[0052] A further example for a detected changed wind direction 26 and/or changed force on the wind turbine 10 is shown in FIG. 4 in which the wind direction 26 is now directed on to the rear side of the wind turbine 10. Here too the rotor blades 18 are adjusted with the yaw angle being maintained as a change in the wind direction or force, namely a wind direction, was detected, which is different from the parallel afflux flow with the current yaw orientation. The rotor blades 18 are here adjusted in such a way that as viewed from the wind direction 26 they are in a feathered position, wherein that feathered position differs from the feathered position with the parallel afflux flow with the current yaw orientation, as in FIG. 2.

[0053] Accordingly the position of the rotor blades 18, namely the pitch angle, is adapted to the changing wind directions 26, in dependence on the wind direction 26.

[0054] FIG. 5 shows an embodiment of the steps in the method according to an embodiment. In step 50 the wind direction 26 or a force on the wind turbine 10 is monitored while step 52 detects that the wind direction 26 or the force has changed. In step 54 therefore the yaw angle of the yaw setting of the wind turbine is maintained and in step 56 the rotor blades 18 are adjusted in dependence on the changed wind direction 26.