Patent Application
20230323860
The present disclosure relates to wind turbines comprising a flexible coupling. More specifically, the present disclosure relates to wind turbines comprising flexible couplings between a primary frame and a secondary structure. The present disclosure also relates to secondary structures and methods for refurbishing a secondary structure of a wind turbine.
Modern wind turbines are commonly used to supply electricity into the electrical grid. Wind turbines of this kind generally comprise a tower, a nacelle and a rotor. The rotor, which typically comprises a hub and a plurality of blades, is set into rotation under the influence of the wind on the blades. This rotation is normally transmitted to a generator, either directly (“directly driven”) or through the use of a gearbox. This way, the generator produces electricity which can be supplied to the electrical grid.
In order to extract more energy from the wind, the size of the rotor diameter has increased significantly over the last years by increasing the dimensions of the wind turbine blades. The larger size of the blades implies higher aerodynamic loads that are transferred through the blades into the rotor, nacelle and tower. For example, larger rotor blades may experience increased stresses, deformations and vibrations due to higher aerodynamical moments and others, and these are transmitted to the rotor hub and to the nacelle. The transmitted stresses, deformations and vibrations may lead to challenging design constraints, both in terms of extreme events and fatigue life requirements.
The likelihood of structural failure in wind turbine components, such as a frames of the wind turbine nacelle, is generally compensated by the manufacture of bigger, heavier and more resistant components. In the case of the nacelle frames, this approach leads to an increase in material costs, and a considerable increase in the overall weight of the nacelle. Further, the installation of bigger frames may require providing more robust tower structures so that the tower can safely withstand the nacelle and the loads acting on it. Even if bigger and heavier frames are used, they can still suffer and ultimately fail due to dynamic loads.
The present disclosure provides examples of systems and methods that avoid or reduce premature failure of frames of the wind turbine nacelle and that overcome some of the drawbacks of existing approaches.
In a first aspect, a wind turbine is provided. The wind turbine comprises a wind turbine tower, and a nacelle including a primary frame, wherein the primary frame is connected to the tower. The wind turbine further comprises a secondary structure that is connected to the primary frame and one or more flexible couplings between the primary frame and the secondary structure configured to reduce transmission of deformations from the primary frame to the secondary structure.
According to this first aspect, the one or more flexible couplings installed between the primary frame and the secondary structure of the wind turbine reduce the magnitude of the deformations transferred from the primary frame to the secondary structure, thus reducing the level of stress induced into the secondary structure. The primary frame may suffer asymmetric deformations due to asymmetric loads on the wind turbine rotor. These asymmetric deformations of the primary frame, if transferred to the secondary structure, could lead to significant stresses and strains in the secondary structure. The flexible couplings can avoid or significantly reduce those stresses. Thus, the secondary structure may be manufactured taking into account a narrower load envelope compared with a scenario where the flexible coupling is not provided. As a result, the secondary structure may be manufactured as a lighter frame and may have a simpler structure.
In another aspect, a method of refurbishing a secondary structure of a wind turbine, that is connected to a primary frame is provided. The method comprises cutting a piece of a structural element of the secondary structure that is connected to the primary frame and providing a flexible coupling in a portion of the structural element in replacement of the cut piece. The method then further comprises coupling the secondary structure to the primary frame through the flexible coupling, wherein the flexible coupling is configured to reduce transmission of deformations of the primary frame to the secondary structure.
The method according to this aspect allows refurbishing a secondary structure of a wind turbine in wind turbines that are already in operation. Particularly, the method allows considerably increasing the service life of nacelle frame assemblies.
In yet a further aspect, a secondary structure of a wind turbine is provided. The secondary structure comprises a plurality of structural elements configured to be connected to a primary frame of the wind turbine. At least one of the structural elements comprises a flexible coupling configured to reduce the transmission of horizontal deformations of the primary frame to the secondary frame. And at least another one of the structural elements comprises a flexible coupling configured to reduce the transmission of both horizontal and vertical deformations of the primary frame to the secondary structure.
And in yet a further aspect, a method for reducing oscillations in a secondary structure is provided. The secondary structure is connected to a primary frame of a wind turbine. The method comprises providing one or more flexible couplings between the primary frame and the secondary structure, such that deformations of the primary frame are partially absorbed by the flexible couplings, and at least some of the oscillations of the primary frame are not transmitted to the secondary structure.
Throughout the present disclosure, a primary frame is to be regarded as a load carrying structure arranged in the main load path between the wind turbine rotor and wind turbine tower. I.e. the primary frame is the load carrying structure that transmits the loads to the tower, generally through a yaw bearing. A primary frame may also be called a central frame or a main frame.
A secondary structure as used throughout the present disclosure may be regarded as a (load-carrying) structure that is not arranged in the main load path. The secondary structure may be used for accommodating or housing auxiliary systems such as auxiliary mechanical or electrical systems, and in particular the power conversion assembly or components thereof.
Throughout the present disclosure, a vertical direction should be understood as a direction substantially parallel to the direction of gravity, and a horizontal direction should be understood as a direction substantially parallel to ground and perpendicular to the vertical direction.
Non-limiting examples of the present disclosure will be described in the following, with reference to the appended drawings, in which:
Reference now will be made in detail to embodiments of the present disclosure, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation only, not as a limitation. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present disclosure covers such modifications and variations as come within the scope of the appended claims and their equivalents.
The rotor blades 22 are spaced about the hub 20 to facilitate rotating the rotor 18 to enable kinetic energy to be transferred from the wind into usable mechanical energy, and subsequently, electrical energy. The rotor blades 22 are mated to the hub 20 by coupling a blade root portion 24 to the hub 20 at a plurality of load transfer regions 26. The load transfer regions 26 may have a hub load transfer region and a blade load transfer region (both not shown in
As wind strikes the rotor blades 22 from a wind direction 28, the rotor 18 is rotated about a rotor axis 30. As the rotor blades 22 are rotated and subjected to centrifugal forces, the rotor blades 22 are also subjected to various forces and moments. As such, the rotor blades 22 may deflect and/or rotate from a neutral, or non-deflected, position to a deflected position.
Moreover, a pitch angle of the rotor blades 22, i.e., an angle that determines an orientation of the rotor blades 22 with respect to the wind direction, may be changed by a pitch system 32 to control the load and power generated by the wind turbine 10 by adjusting an angular position of at least one rotor blade 22 relative to wind vectors. Pitch axes 34 of rotor blades 22 are shown. During operation of the wind turbine 10, the pitch system 32 may particularly change a pitch angle of the rotor blades 22 such that the angle of attack of (portions of) the rotor blades are reduced, which facilitates reducing a rotational speed and/or facilitates a stall of the rotor 18.
In the example, a blade pitch of each rotor blade 22 is controlled individually by a wind turbine controller 36 or by a pitch control system 80. Alternatively, the blade pitch for all rotor blades 22 may be controlled simultaneously by said control systems.
Further, in the example, as the wind direction 28 changes, a yaw direction of the nacelle 16 may be rotated about a yaw axis 38 to position the rotor blades 22 with respect to wind direction 28.
In the example, the wind turbine controller 36 is shown as being centralized within the nacelle 16, however, the wind turbine controller 36 may be a distributed system throughout the wind turbine 10, on the support system 14, within a wind farm, and/or at a remote-control center. The wind turbine controller 36 includes a processor 40 configured to perform the methods and/or steps described herein. Further, many of the other components described herein include a processor.
The gearbox 46, generator 42 and transformer 90 may be supported by a main support structure frame of the nacelle 16, optionally embodied as a main frame 52. The gearbox 46 may include a gearbox housing that is connected to the main frame 52 by one or more torque arms 103. In the example, the nacelle 16 also includes a main forward support bearing 60 and a main aft support bearing 62. Furthermore, the generator 42 can be mounted to the main frame 52 by decoupling support means 54, in particular in order to prevent vibrations of the generator 42 to be introduced into the main frame 52 and thereby causing a noise emission source.
Optionally, the main frame 52 is configured to carry the entire load caused by the weight of the rotor 18 and components of the nacelle 16 and by the wind and rotational loads, and furthermore, to introduce these loads into the tower 15 of the wind turbine 10. The rotor shaft 44, generator 42, gearbox 46, high speed shaft 48, coupling 50, and any associated fastening, support, and/or securing device including, but not limited to, support 52, and forward support bearing 60 and aft support bearing 62, are sometimes referred to as a drive train 64.
In some examples, the wind turbine may be a direct drive wind turbine without gearbox 46. Generator 42 operate at the same rotational speed as the rotor 18 in direct drive wind turbines. They therefore generally have a much larger diameter than generators used in wind turbines having a gearbox 46 for providing a similar amount of power than a wind turbine with a gearbox.
The nacelle 16 also may include a yaw drive mechanism 56 that may be used to rotate the nacelle 16 and thereby also the rotor 18 about the yaw axis 38 to control the perspective of the rotor blades 22 with respect to the wind direction 28.
For positioning the nacelle 16 appropriately with respect to the wind direction 28, the nacelle 16 may also include at least one meteorological measurement system 58 which may include a wind vane and anemometer. The meteorological measurement system 58 can provide information to the wind turbine controller 36 that may include wind direction 28 and/or wind speed. In the example, the pitch system 32 is at least partially arranged as a pitch assembly 66 in the hub 20. The pitch assembly 66 includes one or more pitch drive systems 68 and at least one sensor 70. Each pitch drive system 68 is coupled to a respective rotor blade 22 (shown in
In the example, the pitch assembly 66 includes at least one pitch bearing 72 coupled to hub 20 and to a respective rotor blade 22 (shown in
Pitch drive system 68 is coupled to the wind turbine controller 36 for adjusting the pitch angle of a rotor blade 22 upon receipt of one or more signals from the wind turbine controller 36. The pitch assembly 66 may also include one or more pitch control systems 80 for controlling the pitch drive system 68 according to control signals from the wind turbine controller 36, in case of specific prioritized situations and/or during rotor 18 overspeed.
The wind turbine comprises a rotor including a plurality of blades (not shown). In this example, the rotor is located at a first side of the primary frame 110. The secondary structure 120 is connected to the primary frame 110 at a second side of the primary frame 110. The first side is opposite to the second side.
The first side of the primary frame 110 at which the rotor is arranged may typically be an upwind side of the primary frame 110. The second side of the primary frame 110 may thus be the downwind side. In other examples, the first side of the primary frame 110 may be the downwind side, and the second side of the primary frame 110 may be the upwind side.
The wind turbine comprises one or more flexible couplings 130 between the primary frame 110 and the secondary structure 120. The flexible couplings 130 are configured to reduce transmission of deformations from the primary frame 110 to the secondary structure 120. Note that the flexible couplings 130 in
The flexible couplings 130 may be or comprise any element that reduces the level of loads and stresses induced from the primary frame 110 to the secondary structure 120 while it withstands the loads acting on the secondary structure 120. Thus, the flexible couplings may provide a secure connection between secondary structure 120 and primary frame 110.
In examples, the flexible couplings 130 may comprise an elastomeric material or a material substantially more flexible than the material from which the secondary structure 120 is manufactured. Additionally, the flexible couplings 130 may comprise a metal spring or a grower washer to allow certain degree of motion between the secondary structure 120 and the central frame 110. In some examples, the flexible couplings 130 may also comprise a sliding mechanism that allows relative displacement between the central frame 110 and the secondary structure 120.
In some examples, such as in
In further examples, the rotor support structure connected to the vertical plane of the primary frame may be a front frame or an intermediate frame. Depending on the arrangement of the wind turbine components, the rotor support structure may also be a stator structure of a generator stator.
In some examples, the wind turbine may be a direct drive wind turbine. In other examples, the wind turbine according to this example may be a wind turbine with a gearbox.
As can be seen in
At least one of the structural elements 122, e.g. substantially horizontal beams comprises a flexible coupling 130 specifically configured to reduce the transmission of horizontal deformations induced on the primary frame. The flexible coupling 130 may have specific flexibility in the horizontal direction to achieve such an effect, i.e. the flexible coupling between primary frame 110 and horizontal beams 122 may have more flexibility in the horizontal direction than in the vertical direction.
Further, at least another one of the structural elements 123, e.g. vertical struts comprises a flexible coupling 130 specifically configured to reduce the transmission of both horizontal and vertical deformations of the central frame 110 to the secondary structure 120.
Also illustrated in
In the example illustrated in
In some examples, at least one of the flexible couplings 130 is configured to reduce the transmission of deformations and vibrations specifically in a single direction. In some further examples, at least one of the flexible couplings 130 is configured to reduce the transmission of deformations and vibrations in at least two directions.
Additionally, the flexible couplings 130 substantially reduce the vibrations transmitted from the central frame 110 to the secondary structure 120 in a frequency range that has a significant influence in the level of stress/damage induced into the secondary frame. Specifically, the frequency range may be between 1 Hz and 50 Hz.
Silentblocks may be formed by an annular cylinder of flexible material inside a considerably rigid casing, i.e. a metallic casing. The flexible material may be connected between two ends of the casing, providing a flexible coupling between the respective ends. In some examples, the silentblocks may comprise an internal crush tube configured to protect the silentblocks from being crushed by the fastener connections that hold it in place. In further examples, the silentblocks may allow sliding at the interface between one fastener connection and the flexible material.
The flexible coupling 130 illustrated in
In further examples, two or more of such damping devices may be arranged in series, i.e. a load path inevitable passes through both of the damping devices. In a parallel arrangement, parallel load paths between the primary frame and secondary structure may be provided.
In some additional examples, the secondary structure 120 may comprise flexible couplings 130 in all structural elements that are coupled to the central frame 110. Alternatively, the secondary structure 120 may comprise flexible couplings 130 in some of the structural elements that are coupled to the central frame 110. In this case, other types of connections between the central frame 110 and the secondary structure 120 may be employed, i.e. partially rotatable connections.
The method 700 may further comprise coupling the secondary structure 120 to the primary frame 110 through the flexible coupling 130. The flexible coupling, as in other examples of the present disclosure is specifically configured to limit the transmission of deformations from the primary frame 110 to the secondary structure.
Further, the method 700 may also comprise supporting the structural element 123, 122 since before the cutting 701 until the moment of coupling to the primary frame, or even until after.
In some examples, supporting the structural element 123, 122 may be performed using one or more jacks, e.g. hydraulic jacks or any other suitable system. Additionally, the steps of cutting 701 a piece of a structural element 123, 122 and providing 702 a flexible coupling 130 may be performed in all structural elements configured to be connected to the central frame 110. In such a case, a flexible coupling is provided at each of connection of the primary frame to the secondary structure.
Note that some of the technical features described in relation with the wind turbine, the secondary structure and the flexible couplings of the examples of
With the method of refurbishing, at the same time, a method for reducing oscillations in the secondary structure is provided. The secondary structure is connected to a primary frame of a wind turbine. By providing one or more flexible couplings between the primary frame and the secondary structure, deformations of the primary frame are partially absorbed by the flexible couplings, and at least some of the oscillations of the primary frame are not transmitted to the secondary structure.
Examples of such a method for reducing oscillations in the secondary structure may use any of the features of the various examples of
This written description uses examples to disclose the present teaching, including the preferred embodiments, and also to enable any person skilled in the art to practice it, including making and using any devices or systems and performing any incorporated methods. The patentable scope is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. Aspects from the various embodiments described, as well as other known equivalents for each such aspects, can be mixed and matched by one of ordinary skill in the art to construct additional embodiments and techniques in accordance with principles of this application. If reference signs related to drawings are placed in parentheses in a claim, they are solely for attempting to increase the intelligibility of the claim, and shall not be construed as limiting the scope of the claim.
| Number | Date | Country | Kind |
|---|---|---|---|
| 22382350.1 | Apr 2022 | EP | regional |
