VIBRATION DAMPING OF A WIND TURBINE TOWER

Abstract

A coupling element prepared for fastening between a oscillatory body and a tower wall of a tower of a wind turbine in order to influence relative motion between the oscillatory body and the tower wall in order to thereby influence vibration behavior of the tower, comprising a first fastening section for fastening to the oscillatory body and a second fastening section for fastening to the tower wall in order to establish mechanical coupling between the oscillatory body and the tower wall via the coupling element, the coupling permitting relative motion between the oscillatory body and the tower wall, and the relative motion having a first motion direction, in the case of which the first and second fastening sections move toward each other, and a second motion direction, in the case of which the first and second fastening sections move away from each other, and the coupling element having a spring element for spring-elastic coupling between the first and second fastening sections, the spring-elastic coupling being described by a spring function and the spring element being designed in such a way that the spring function is substantially the same for the first and second motion directions and additionally or alternatively the spring element being designed in such a way that motion in the first motion direction leads to compression of a first spring section and to extension of a second spring section in the spring element and motion in the second motion direction leads to extension of the first spring section and to compression of the second spring section in the spring element in order to thereby match the respective spring functions for the first and second motion directions to each other.

Claims

1. A coupling element designed for fastening between a vibratory body and a tower wall of a tower of a wind turbine in order to influence a relative movement between the vibratory body and the tower wall to thereby influence a vibration characteristic of the tower, the coupling element comprising: a first fastening portion for fastening to the vibratory body; and a second fastening portion for fastening to the tower wall and producing a mechanical coupling between the vibratory body and the tower wall via the coupling element, wherein: the coupling permits a relative movement between vibratory body and tower wall, the relative movement has a first movement direction in which the first and the second fastening portion move toward one another, and the relative movement has a second movement direction in which the first and the second fastening portion move away from one another, a spring means for resiliently elastic coupling between the first and second fastening portions, wherein the resiliently elastic coupling is described by a spring function, and wherein the spring means has at least one characteristic of the following characteristics: the spring function is substantially identical for the first and second movement directions, a movement in the first movement direction in the spring means leads to a compression of a first spring portion and to an extension of a second spring portion, and a movement in the second movement direction in the spring means leads to an extension of the first spring portion and to a compression of the second spring portion to thereby equalize the spring function for the first and second movement directions with one another.

2. The coupling element as claimed in claim 1, wherein the coupling element is formed as a spring-damper element and has a damping portion for coupling with damping action between the first and second fastening portions, wherein the coupling with damping action is described by a damping function, and wherein the damping function is substantially equal for the first and second movement directions.

3. The coupling element as claimed in claim 2, wherein at least one of: the spring function is linear or the damping function is linear.

4. The coupling element as claimed in claim 1 further comprising: a first anchor portion and a second anchor portion that are connected to one another, and a central portion arranged between the first and second anchor portions and is movable relative to the first and second anchor portions, wherein: the first or second anchor portions are connected to the second fastening portion, and the central portion is connected to the first fastening portion, such that the relative movement corresponds to a movement of the central portion between the first and second anchor portions.

5. The coupling element as claimed in claim 4, wherein the spring means comprises: a first spring arranged between the central portion and the first anchor portion, and a second spring arranged between the central portion and the second anchor portion, wherein the first spring forms the first spring portion and the second spring forms the second spring portion.

6. The coupling element as claimed in claim 5, wherein the first and second springs are prestressed such that neither of the first or the second springs reaches or overshoots a relaxed state during the movement in the first or second movement directions.

7. The coupling element as claimed in claim 6, wherein a spacing between the first and second anchor portions is adjustable in order to adjust the prestress.

8. A tower of a wind turbine comprising: a tower central axis, a tower wall, and a vibratory apparatus for influencing a vibration of the tower, wherein the vibratory apparatus comprises: has a vibratory body suspended in the tower so as to be spaced apart from the tower wall, and at least one coupling element fastened between the vibratory body and the tower wall, wherein the at least one coupling element is configured to influence a relative movement between the vibratory body and the tower wall, wherein the vibratory body is hollow along a vertical body central axis.

9. The tower as claimed in claim 8, wherein the vibratory body has a substantially hollow truncated cone shape or substantially hollow cylinder shape with a vertical aperture, wherein a tower ladder is arranged on the tower wall at the vertical aperture and configured to provide access for service personnel to climb up and down in the tower along the tower ladder and, in so doing, allowed to pass through the vibratory body in a region of the vertical aperture.

10. The tower as claimed in claim or 8, wherein the vibratory body has a vibratory body wall that encircles the vertical body central axis, the vibratory body wall having a wall thickness, wherein the wall thickness varies in a circumferential direction such that the vibratory body has a center of gravity in the vertical body central axis, wherein the vertical body central axis corresponds to a geometrical center of the vibratory body or coincides, in the rest state of the vibratory body, with the tower central axis.

11. The tower as claimed in claim 8, wherein the vibratory body is suspended so as to be spaced apart from the tower wall centrally with a mean wall spacing, and wherein the mean wall spacing is less than one quarter of a tower inner diameter.

12. The tower as claimed in claim 8, wherein the vibratory body is suspended by a plurality of pendulum rods on a fastening portion on a tower top flange, wherein three or more pendulum rods of the plurality of pendulum rods are provided such that the vibratory body is restricted to translational or tilt-free movements, wherein the plurality of pendulum rods are equipped at both sides with spherical joint heads or a cardanic suspension, such that a movement in horizontal directions is possible.

13. The tower as claimed in claim 8, wherein the vibratory body is produced from a material with a density that is higher than or equal to a density of water wherein the vibratory body includes concrete.

14. The tower as claimed in claim 8, wherein the at least one coupling element is a plurality of coupling elements arranged between the vibratory body and the tower wall and distributed in a circumferential direction around the vibratory body, and wherein each of the plurality of coupling elements are fastened to the vibratory body and to the tower wall to produce a mechanical coupling between the vibratory body and the tower wall, wherein the coupling permits a horizontal relative movement between vibratory body and tower wall.

15. The tower as claimed in claim 8, wherein the plurality of coupling elements are an even number of coupling elements.

16. The tower as claimed in claim 8, wherein the plurality of coupling elements are arranged above or below the vibratory body.

17. The tower as claimed in claim 8, wherein the vibratory body has a center of mass, and wherein the vibratory body is suspended at such a height in the tower that the center of mass is situated in an upper half of the tower.

18. A vibratory apparatus designed for use in a tower of a wind turbine for the purposes of influencing a vibration of the tower, wherein the vibratory apparatus comprises: a vibratory body configured to be suspended in the tower so as to be spaced apart from the tower wall, and at least one coupling element for fastening the vibratory body to the tower wall, the at least one coupling element being configured to influence a relative movement between the vibratory body and the tower wall, wherein: the vibratory body is formed so as to be hollow along a vertical central axis, and each coupling element has a spring function, and the spring function is substantially identical for a first movement direction and a second movement direction which is opposite to the first movement direction.

19. The vibratory apparatus as claimed in claim 18, wherein the vibratory apparatus is fastened to a tower wall of a tower of a wind turbine, wherein the vibratory apparatus includes a plurality of coupling elements that fasten the vibratory body to the tower wall.

20. A method comprising: influencing a tower vibration or a natural frequency of a tower of a wind turbine, wherein the tower has a vibratory apparatus with a plurality of coupling elements, wherein the influencing comprises: detecting a tower natural frequency or a tower vibration amplitude, pre-defining a desired absorber natural frequency or a desired maximum tower vibration amplitude, and setting the plurality of coupling elements to the absorber natural frequency or such that the tower vibration amplitude remains below the desired maximum tower vibration amplitude.

21. (canceled)

22. A wind turbine comprising: a nacelle; an aerodynamic rotor; and a tower have a tower central axis, a tower wall and the vibratory apparatus as claimed in claim 18 coupled to the tower wall.

23. A vibratory body of the vibratory apparatus as claimed in claim 18.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0067] The invention will now be discussed in more detail below by way of example on the basis of exemplary embodiments and with reference to the appended figures.

[0068] FIG. 1 shows a wind turbine in a perspective illustration.

[0069] FIG. 2 shows a detail of a wind turbine tower in a sectional view.

[0070] FIG. 3 shows a detail of FIG. 2 with further details.

[0071] FIG. 4 shows a further detail of FIG. 2 with further details.

[0072] FIG. 5 shows a horizontal section through the tower detail as per FIG. 2.

[0073] FIG. 6 shows a coupling element in a lateral sectional view.

DETAILED DESCRIPTION

[0074] FIG. 1 shows a wind turbine 100 having a tower 102 and a nacelle 104. On the nacelle 104, there is arranged a rotor 106 with three rotor blades 108 and a spinner 110, which is part of a hub. The rotor 106 is, during operation, set in rotational motion by the wind, and thus drives a generator in the nacelle 104.

[0075] FIG. 2 shows a tower portion 2 with a tower wall 4, which may also vary in nature and thickness over the height. The tower portion 2 is closed off by means of a tower top flange 6. The tower top flange 6 is formed as an encircling flange and is provided in particular for holding an azimuth bearing for the rotatable mounting of a nacelle.

[0076] Attached to the tower top flange 6 are suspension fasteners 8, which each pivotably bear a pendulum rod 10, and wherein a vibratory body 12 is suspended on the pendulum rods 10. For this purpose, the pendulum rods 10 are likewise pivotably fastened, by means of vibratory body fasteners 14, to the vibratory body 12.

[0077] The pendulum rods 10 thus function as a suspension for the vibratory body 12. The suspension fasteners 8 may in this case also be referred to as tower top flange fasteners.

[0078] The vibratory body 12 can thus, owing to the relatively long pendulum rods 10, vibrate substantially in a horizontal plane in all directions. Aside from longitudinal vibrations in various directions, consideration is also given to circulating movements, that is to say a superposition of multiple longitudinal vibrations.

[0079] The vibratory body 12 is formed substantially by a vibratory body shell 16, which surrounds a vibratory body cavity 18. The vibratory body shell 16 may, as shown in FIG. 2 and some of the other figures, be formed as a vibratory body container 20 with container filling 22.

[0080] In FIG. 2, there is also shown a tower central axis 24, which thus forms a central axis for the tower and thus the tower portion 2. Here, said tower central axis coincides with a body central axis 26, which forms a vertical central axis for the vibratory body 12.

[0081] The vibratory body 12 may be coupled, at a lower edge 28 and an upper edge 30, by means of coupling elements 32 to the tower wall 4. Details of the coupling in the region of the upper edge 30 are shown in FIG. 3, and details of the coupling in the region of the lower edge 28 are shown in FIG. 4.

[0082] The fastening of each coupling element 32 to the tower wall 4 is realized, in the case of the coupling elements 32 fastened at the upper edge 30, by means of a fastener to a tower bulkhead 34. A tower bulkhead 34 of said type is basically used for creating, in the wind turbine tower, a platform on which work can be performed, or on which breaks can be taken. Such a tower bulkhead 34 also prevents anything from being able to fall down from the nacelle 104 into the tower. The tower bulkhead is fastened uniformly in a circumferential direction to the tower wall 4 and may in this case also form a stiffening ring or a stiffening surface for the tower. By means of the fastening of the coupling elements 32 to the tower bulkhead 34, a punctiform introduction of force into the tower wall can be avoided. Instead, an introduction of force takes place into the tower bulkhead 34, which can in turn transmit said force, uniformly in the circumferential direction, to the tower wall 4 of the tower portion 2.

[0083] In the region of the lower edge 28, the coupling elements 32 are fastened by means of a stiffening ring 36 to the tower wall 4. Said connection by means of the stiffening ring 36 to the tower wall 4 also prevents a punctiform introduction of forces via the respective coupling element 32 into the tower wall 4. If the vibratory body 12 vibrates relative to the tower portion 2, it therefore also vibrates relative to the tower bulkhead 34 and the stiffening ring 36. Since the vibratory body 12 is situated below the tower bulkhead 34, the pendulum rods 10 are led through corresponding openings through the tower bulkhead 34.

[0084] FIG. 3 shows, in an enlarged detail, the coupling of the vibratory body 12 by means of coupling elements 32, of which only one is illustrated in FIG. 3, to the tower wall 4. The coupling element 32, which is shown in a more detailed illustration in FIG. 6, is fastened by means of a central portion 38 to the upper edge 30 of the vibratory body 12 or of the vibratory body casing 16 thereof.

[0085] The central portion 38 is arranged in resiliently elastic fashion between a first armature portion 41 and a second anchor portion 42. The first and the second anchor portion 41, 42 are rigidly connected to one another. The first anchor portion 41 is fastened by means of a fastening angle bracket 44 to the tower bulkhead 34.

[0086] In the event of a vibratory movement of the vibratory body 12 relative to the tower wall 4, an introduction of force thus takes place from the vibratory body 12 via the central portion 38 into the coupling element 32, which transmits this resiliently elastically to the first anchor portion 41, and via this and via the fastening angle bracket 44 to the tower bulkhead 34 and thus the tower wall 4. The vibratory body 12 is thus coupled resiliently elastically to the tower wall 4.

[0087] Furthermore, there is also indicated in FIG. 3 a cable harness 46 which can be led through the tower bulkhead 34 and in particular also through the interior cavity, specifically the vibratory body cavity 18 of the vibratory body 12. For this purpose, in the tower bulkhead 34, there may be provided an opening in which the cable harness 46 is led through a cable guide 48.

[0088] The construction in the region of the lower edge 28 is shown in FIG. 4 and is very similar to the construction in the region of the upper edge 30. In the region of the lower edge 28, too, the vibratory body 12 is coupled to the central portion 38 of the coupling element 32. The coupling element 32 is in turn coupled via the first anchor portion 41 and via a fastening angle bracket 44 to the stiffening ring 36. The stiffening ring 36 may also be referred to as a buckling resistor.

[0089] The vibratory body 12 may also have a cable guide 49 at its bottom side.

[0090] The plan view in FIG. 5 shows in particular the shape of the vibratory body 12. It has substantially a circular cylindrical shape which is equipped with a vertical aperture 50. Said vertical aperture 50 serves for creating space in the region of a tower ladder 52. The vibratory body 12 can thus, owing to its relatively large outer diameter, have a large volume and thus a high mass. The interior space of the tower thus nevertheless remains usable, and in particular, an ascent via the tower ladder 52 is thereby not impeded.

[0091] In order, despite the aperture 50, to realize a central center of mass of the vibratory body 12, the wall thickness of the vibratory body 12 may be formed so as to be slightly greater in the region of the tower ladder 52 than at a region averted from the tower ladder 52. For explanatory purposes, a region 54 close to the tower ladder 52 and a region 56 remote from the tower ladder 52 are indicated. Mass compensation can thus be realized by virtue of a particularly great wall thickness being provided in the region 54 close to the tower ladder, whereas as small a wall thickness as possible is provided in the region 56 remote from the tower ladder.

[0092] FIG. 6 shows, in a lateral sectional view, the coupling element 32 with further details. The first and second anchor portions 41, 42 are fixedly connected to one another by means of tension rods 58. The central portion 38 can be moved relative to the two anchor portions 41 and 42. For this purpose, the tension rods 58 may also form a guide for the central portion 38 for such a movement. Furthermore, each anchor portion may also be referred to as end plate, and the central portion 38 may be referred to as central plate.

[0093] Between the central portion 38 and the first anchor portion 41, there is arranged a first spring 61, which forms a first spring portion. Between the central portion 38 and the second anchor portion 42, there is arranged a second spring 62, which forms a second spring portion.

[0094] Said two springs 61 and 62 together form a common spring means of the coupling element 32. The two springs 61 and 62 are substantially identical, and the two springs 61 and 62 are prestressed. FIG. 6 thus shows a rest position of the coupling element 32. The two springs 61 and 62 are formed as helical springs and are received in each case in a receiving portion on the first or second anchor portion 41, 42 and the central portion 38.

[0095] The statement that the two springs 61 and 62 are prestressed means that they are already compressed in the position shown in FIG. 6. Both springs 61 and 62 therefore already exert a force in each case from the first and second anchor portion 41 and 42 respectively on the central portion 38, or vice versa, wherein said two forces however cancel one another out in the rest position shown. Owing to this prestress, a movement of the central portion 38 along the tension rods 58 experiences substantially a linear relationship between deflection and spring force. As a result of movement in one direction, for example toward the first anchor portion 41, the spring force of the first spring 61 increases, whereas the spring force of the second spring 62 decreases. If the central portion 38 moves from the rest position shown in the opposite direction, the same effect arises, wherein the force imparted by the second spring 62 increases, and that imparted by the first spring 61 decreases. The resultant force on the central portion 38 and thus also on the vibratory body 12 arises from the difference between the spring forces of the two springs 61 and 62. The force relationships are thus equal in both deflection directions.

[0096] Furthermore, a damping portion 64 is provided, which substantially has a damping cylinder 66 in which a damping piston 68 moves. The damping piston 68 has a resistance plunger 70, the movement of which in the damping cylinder 66 is braked by virtue of the fact that a fluid in the damping cylinder 66 must pass said resistance plunger 70. The damping action, that is to say the movement-speed-dependent resistance, is in this case substantially independent of the movement direction of the damping piston 68 and thus of the movement direction of the resistance plunger 70.

[0097] The coupling of the damping piston 68 and thus of the resistance plunger 70 is realized via a cladding tube 72, which is fastened to the central portion 38 and which thus, during a movement of the central portion 38, moves together with the latter and in the process also concomitantly drives the damping piston 68. For the guidance of the central portion 38, guide cylinders 74 are furthermore provided, which guide the central portion 38 on the tension rods 58.

[0098] It can also be seen that the coupling element is designed such that the movement amplitude between the vibratory body 12 and the tower wall 4 and thus between the central portion 38 and the first anchor portion 41 is at most half as great as the spacing between the first anchor portion 41 and the central portion 38 in the rest position thereof. It is thus also achieved that the two springs 61 and 62 are not moved as far as their maximum deflection limit, whereby, for the provided movement range, it is substantially possible to achieve linearity in the operating range.

[0099] Furthermore, FIG. 6 illustrates the attachment of the coupling element 32, and accordingly, the coupling element 32 is fastened by way of its central portion 38 to a top side of a vibratory body 12. By means of its anchor portion 41, said coupling element is fastened via a joint head 43 to the tower wall 4 of the tower whose vibration is to be dampened. A vibratory movement of the tower leads in this case to a relative movement between the tower wall 4 and the vibratory body 12 and thus to a relative movement between the anchor portion 41 and the central portion 38. A small vertical movement of the vibratory body 12 may also arise, which can be allowed for by means of the joint head 43.

[0100] It is pointed out that, for the sake of clarity, the same reference designations have been used for similar but possibly non-identical elements. This applies to the description of all of the figures. A solution has thus been created and proposed which can influence or at least dampen the natural frequencies of the tower and which thus creates greater freedom in designing a new tower. Insofar as vibration dampers have been dispensed with, it is specifically necessary in designing new towers to ensure that the natural frequencies of the bending vibration of the tower do not coincide with or lie close to the excitation frequencies from the operation of the installation, in order to avoid damaging resonance.

[0101] In designing a tower with vibration dampers, there is no need to take into consideration the position of the natural frequency to which the absorber is tuned, whereby greater freedom in the design process can be achieved.

[0102] The vibratory body, which is designed as a hollow cylinder and which can also be referred to as absorber mass, allows cables to be led through centrally in the tower. Through the use of the greatest possible absorber mass radius, the structural space is utilized optimally, or at least highly effectively, in terms of volume, and it is thus possible for a large mass to be accommodated in the vibratory body. A star-shaped arrangement of the spring-damper elements, that is to say a star-shaped arrangement of the coupling elements, permits an omnidirectional, that is to say virtually direction-independent, action of the vibration damper, that is to say of the coupling element.

[0103] The suspension of the vibratory body on the discussed pendulum rods likewise permits a virtually omnidirectional action and forces a tilt-free movement of the vibratory body, that is to say of the absorber mass. The directional independence of the action increases with the number of vibration dampers, that is to say of coupling elements.