TW202242251A - Tower vibration damper - Google Patents

Abstract

A tower vibration damper for mounting in a tower of a wind turbine is provided. The damper comprises: a pendulum structure configured to be suspended in the tower, said pendulum structure comprising a pendulum body; a suspension arrangement for suspending the pendulum structure in the tower such that the pendulum body is allowed to displace from a neutral position for the pendulum body; a chamber holding a damping liquid into which the pendulum body is at least partly immersed such that movement of the pendulum body within the chamber is inhibited due to a drag force asserted by the damping liquid on the pendulum body; and means for changing the drag force asserted on the pendulum body by the damping liquid held in the chamber, so as to adjust a damping characteristic of the damper.

Description

Tower Vibration Damper

field of invention

This invention relates to a tower vibration damper for a wind turbine, and more particularly to a pendulum damper for installation in a tower forming part of an offshore or onshore wind turbine.

Background of the invention

A typical wind turbine consists of a tower on which is mounted a nacelle housing a generator shaft-connected to a drive hub, and a number of rotor blades attached to the drive hub. For installation of an onshore wind turbine, the base of the tower is fixed to the ground providing the foundation. For offshore wind turbine installations, the foundation is usually provided by the seabed or a floating foundation moored to the seafloor. Once the tower is assembled, the nacelle is hoisted with a crane for installation on top of the tower. Once the nacelle is secured to the tower, the rotor blades are craned into position for attachment to the drive hub and thus the nacelle. Alternatively, the nacelle and blades may be assembled before installing the nacelle.

The resulting wind turbine is a tall and heavy structure that requires dynamic stability in strong winds. In the case of offshore wind turbines, the wind turbine is also subjected to forces from water waves in addition to wind forces which are generally stronger than onshore. These external forces may cause the tower to oscillate (eg, low frequency vibrations), such as causing the wind turbine to generate considerable lateral motion (or sway) that increases towards the upper half of the tower. For example, it may be possible to cause the tower to bend under the force so that the nacelle is displaced laterally by as much as one meter from its rest position above the base of the tower.

Wind turbines often minimize these low frequency vibrations by employing "tuned" mass dampers, where a mass is attached to the structure that is free to oscillate relative to the structure of the wind turbine (ie, tower and/or nacelle) rather than using traditional mechanical dampers. structure. The properties (or characteristics) of this mass damper are typically tuned to cause the mass to oscillate out of phase with the motion of the structure, which has the effect of damping vibrations in the wind turbine. One form of tuned mass damper considered particularly suitable for controlling the natural low frequency vibrations of wind turbine towers is the pendulum damper.

For example, the general construction and operation of exemplary pendulum dampers for wind turbines can be found in World Patent Nos. WO2018/059638 and WO2018/153416. It will thus be appreciated that a pendulum damper of a wind turbine tower may be considered to comprise a pendulum structure having a pendulum body immersed (or submerged) in a chamber (eg, an oil sump) containing a damping fluid. A plurality of damping elements, such as springs, may be configured to help dampen motion of the suspended pendulum body. The motion of the wind turbine tower is transferred to the pendulum structure as kinetic energy which can be dissipated via damping elements.

However, this kinetic energy is usually dissipated in the form of heat via the movement of the pendulum body within a damping fluid held in a chamber (eg this may be referred to as internal damping). By sinking the "free" pendulum body into the damping fluid chamber, the motion of the pendulum is damped as it moves due to the resistance acting on the pendulum body within the chamber.

Pendulum dampers generally have damping and tuning characteristics, which are assembled according to the ratio between the mass of the pendulum body, the mass of the completed wind turbine, and the operating characteristics of the wind turbine. However, during the installation/construction of a wind turbine, the mass of the wind turbine changes as it is assembled, in particular when the nacelle is fitted and the blades are attached. Therefore, since the mass of the pendulum body is selected based on the mass of the finished wind turbine, it does not provide optimal damping during the assembly of the wind turbine. This may cause the wind turbine to experience excessive movements during assembly, for example caused by wind or waves, which can inhibit assembly of the wind turbine, thereby delaying its installation. The present invention aims to solve this problem.

Summary of the invention

A tower vibration damper for installation in a tower of a wind turbine is described herein, the damper comprising: a pendulum structure assembled to be suspended in the tower, the pendulum structure including a pendulum body; a suspension arrangement for suspending the pendulum structure in the tower so as to allow displacement of the pendulum body away from a neutral position of the pendulum body; a chamber holding a damping fluid, the pendulum The body is at least partially immersed in the damping fluid such that movement of the pendulum body within the chamber is inhibited due to a resistance exerted by the damping fluid on the pendulum body; and means for varying the resistance, for varying The resistance to the pendulum body is acted on by the damping fluid retained in the chamber to adjust a damping characteristic of the damper.

The present invention recognizes that since the movement of the pendulum body through the damping fluid held in the chamber is inhibited by the resistance exerted on it by the damping fluid held in the chamber, by changing the resistance Adjusts the damping characteristics of this damper.

在此： F _D 為阻力，ρ為流體的密度， A為物件在移動方向面向流體的(橫截面)面積， C _D 為物件在流體中的阻力係數、且 v為物件相對於流體的速度。 The term "resistance" as used herein preferably means the force acting on an object to resist its movement through a fluid. Thus, it is the force that opposes the relative motion of any object with respect to the fluid surrounding it (eg, in the present invention a specific type of "damping" fluid). When drag occurs in water, it is called hydrodynamic drag. In fluid dynamics, the following equation is conveniently used to calculate the resistance experienced by an object as it moves through a completely enclosed fluid:

Here: F _{D is} the resistance, ρ is the density of the fluid, A is the (cross-sectional) area of the object facing the fluid in the moving direction, CD is the drag coefficient of the object in the fluid, and v is the velocity of the object relative to the fluid.

Although other factors may affect the drag acting on the object, the general principles of the above equation still apply. Therefore, with respect to the body of the pendulum, the magnitude of the resistance F _D will be proportional to the square of the speed of the moving object and the area A of the object facing the fluid in the direction of movement. In addition, it is well known that the viscosity η of a fluid, which is proportional to the resistance, decreases as its temperature increases, and vice versa.

The means for varying the resistance is preferably operable to vary, eg increase and/or decrease, the resistance to the pendulum body by the damping fluid retained in the chamber when the pendulum structure is suspended in the tower. In this way, the effectiveness of the dampers may be optimized during installation of the wind turbine as the overall mass of the wind turbine structure changes.

In fact, with the present invention, it is possible to adjust the amount of damping of the pendulum in situ so that the wind turbine can optimize the damping at any time. In addition to protecting the wind turbine from damage during adverse conditions during use, maintaining optimal damping of the wind turbine until completion will make the final stages of the installation process easier and safer. This also increases the window of conditions such as weather where tower, nacelle and blade installation can be done due to better tower vibration damping.

It will be apparent that there is more than one means for varying the resistance to the pendulum body by the damping fluid retained in the chamber.

In one aspect, the means for changing the resistance can be configured to change a immersion distance of the pendulum body immersed in the damping fluid. Optionally, the means for varying the resistance may comprise means for raising or lowering the pendulum body relative to the chamber. The means for varying the resistance may comprise one or more capstans housed in the tower. Each winch is operatively coupled to one or more wires attached to the pendulum body. If multiple wires are attached, they are preferably evenly distributed around the pendulum body so that the suspended pendulum body is evenly balanced.

Alternatively, or in addition, a fluid reservoir holding damping fluid may be provided, fluidly coupled to the chamber, and configured such that damping fluid may flow from the fluid reservoir to the chamber under the force of gravity. The liquid sump may be located at a higher position than the chamber, and may further comprise: a valve to control the flow of damping fluid from the liquid sump to the chamber. A second fluid reservoir holding damping fluid and a second valve may be configured, wherein the fluid reservoir is fluidly coupled to the chamber via the second valve and configured to be lower than the chamber such that, at the second When the valve is open, damping fluid can flow by gravity from the chamber to the second fluid sump.

Alternatively, or in addition, a pump operable to pump damping fluid between the liquid sump and the chamber may be provided.

In another aspect, the means for varying the resistance on the pendulum body may comprise means for varying the temperature of the damping fluid in order to vary its viscosity. Preferably, a pump is provided operable to pump damping fluid from the chamber to the temperature changing member and back to the chamber, wherein the temperature changing member is outside the chamber, optionally wherein it is outside the column .

The temperature changing means may comprise a heating arrangement and/or a cooling arrangement.

The heating arrangement may include an immersion heater disposed within the chamber. The immersion heater may be configured such that, in use, the heating element is submerged in the damping fluid. Alternatively, or in addition, the temperature change member may comprise a heat exchanger.

As used herein, the term "means for changing the temperature [of the damping fluid]" (equivalently referred to as "temperature changing means" or "temperature changing arrangement") preferably refers to devices, equipment or systems. Thus, preferably means an arrangement for heating and/or cooling the damping fluid, each of which may be described herein as a "heater" and/or a "cooler" for convenience, without limiting the arrangement form, structure or operation. Such arrangements for heating and cooling liquids are well known and need not be described in detail. The temperature changing member may comprise a liquid "heater", a liquid "cooler", or a combination of both, either independently or as part of a single device, apparatus or system. Providing both a heater and a cooler advantageously increases the reachable temperature range of the damping fluid and allows for faster temperature adjustments. Furthermore, it allows the temperature variable member to compensate for changes in the ambient temperature of the tower.

The pendulum body is preferably ring-shaped, but other shapes such as blocks or rods may be used.

According to a further aspect, there is provided a wind turbine comprising a tower vibration damper as described above and herein.

According to yet another aspect, there is provided a method for adjusting the damping characteristics of the tower vibration damper of a wind turbine as described above and herein during its installation, comprising the steps of: during a (eg, first) installation stage, varying The resistance to the pendulum body by the damping fluid retained in the chamber causes the damper to be configured to damp the movement of the wind turbine during the installation phase; and in a subsequent (e.g., second ) during an installation stage, changing the resistance exerted by the damping fluid stored in the chamber on the pendulum body, so that the damper is configured to damp the movement of the wind turbine during the subsequent installation stage.

According to yet another aspect, there is provided a method for adjusting the damping characteristics of the tower vibration damper of a wind turbine as described above and herein during its decommissioning, comprising the steps of: , changing the resistance to the pendulum body by the damping fluid stored in the chamber, so that the damper is configured to damp the movement of the wind turbine during the decommissioning phase; and in a subsequent (for example , second) decommissioning stage, changing the resistance to the pendulum body by the damping fluid stored in the chamber, so that the damper is configured to be used to damp the wind turbine in the subsequent decommissioning stage move.

The pendulum structure can be made of iron and, depending on specific requirements, its mass can be between 3-30 tons. The chamber may include an outer wall, an inner wall, and a bottom extending between the outer wall and the inner wall. The chamber can thus form a container structure suitable for holding the damping fluid in which the body of the pendulum is at least partially immersed. The chamber can be a separate element, or it can be integrated in some way into the wind turbine tower structure. For example, the outer wall of the chamber may form part of a wind turbine tower wall.

The suspension arrangement may comprise a plurality of wires suspending the pendulum structure. Tuning members configured to adjust the natural frequency of the tower damper may also be provided. The natural frequency can be adjusted by adjusting the lengths of the plurality of steel wires. For each of the plurality of wires, the tuning member may comprise a clamp fastened at one end to the tower and at the other end to the wire. In order to adjust the length of the steel wires and thus the natural frequency of the tower damper, the fastening of the clamp to the tower is configured such that the clamp can move longitudinally along the steel wire. In the present context, the term "the length of the wires" is to be understood as the length over which the wires are free to swing, i.e. the distance between the tuning member and the pendulum structure where the wires are attached to the tower structure. distance. The wires are angularly movable beneath the tuning member, allowing the pendulum structure to oscillate.

The damping fluid may comprise a suitable damping oil including products such as Texaco Way Lubricant x320, Exxon Mobilgear 600 XP 320 or Uno Vibration Absorber 320. Other damping fluids such as glycols and silicone oils may also be suitable.

While the invention is susceptible to various modifications and alternative forms, several specific embodiments have been shown by way of illustration in the drawings and will be described herein in detail. It should be understood that the invention is not intended to be limited to the particular forms disclosed. On the contrary, the invention is to cover all modifications, equivalents and alternatives falling within the scope of the invention as defined by the appended patent claims.

In the following description and drawings, corresponding reference numerals are used to preferably identify corresponding features so as not to require detailed description of such common features for each and every embodiment. Furthermore, it should be understood that the drawings are in the form of simplified schematic diagrams, and their purpose is to illustrate the general relationship between the components and features of the disclosed vibration damper so that readers can understand the content disclosed herein. Accordingly, no limitation as to the form or construction of any particular embodiment of the disclosed vibration damper should be inferred from the drawings; rather, any such limitation with respect to the vibration damper is defined by the following description.

FIG. 1 illustrates a typical wind turbine 100 . It comprises a tower 120 , a nacelle 140 , a rotor hub 160 , and a plurality of rotor blades 180 . Tower 120 comprises a tubular structure 122 having a longitudinal or vertical axis Z. The lower end 124 of the tower 120 is fixed to the ground 125 or, in the case of the offshore wind turbine 100 , to the seafloor or to a floating foundation moored to the seafloor. Nacelle 140 is mounted to upper end 126 of tower 120 . Nacelle 140 contains a generator (not shown). A rotor hub 160 protrudes from the nacelle 140 and is connected (directly or indirectly) to the generator with a shaft (not shown) having an axis X. Rotor blades 180 are attached to rotor hub 160 . In use, wind force acting on the rotor blades 180 causes the rotor blades 180 to rotate about the axis X, thereby driving a generator via the shaft to generate electrical energy.

2A is a schematic cutaway plan view illustrating a conventional tower vibration damper 200 for a wind turbine 100 in the form of a pendulum damper. The pendulum body 210 is immersed in the liquid chamber 220 .

The illustrated pendulum body 210 is annular, and therefore the vibration damper 200 will be described accordingly by way of example herein. However, it should be understood that other shapes, such as blocks or sticks, are also useful and could be used. For example, an annular pendulum is advantageous because it allows maintenance personnel to safely pass through the damper. The mass of the pendulum body 210 can be between 3 and 10 tons, depending on the necessary damping efficiency and the size of the tower 120 of the wind turbine 100 . Usually, the mass of the pendulum body 210 is about 3 to 20 tons.

To accommodate the annular pendulum body 210, the chamber 220 has a base 222, an inner wall (or boundary) 224 having a diameter d _i , and an outer wall (or boundary) 226 having a diameter d _o . The annular pendulum body 210 has a diameter _dp . The outer wall 226 of the chamber 220 may share the tubular structure 122 of the tower 120 of the wind turbine 100 . The inner wall 224 of the chamber 220 may provide an opening 228 for maintenance personnel to safely pass through the damper 200 if necessary, such as in the event that the upper half of the wind turbine 100 requires maintenance or repair. In use, the chamber 220 is at least partially filled with a suitable damping fluid 240 in which the pendulum body 210 is immersed.

A pendulum structure comprising a pendulum body 210 is secured to the tower 120 and is suspended therein. The suspension arrangement for suspending the pendulum structure comprises a plurality of wires (not shown) secured to the pendulum body 210 via attachment points 214 , 215 , 216 which may be evenly distributed around the pendulum body 210 . The suspension arrangement is configured to suspend the pendulum structure within the tower 120 so as to allow horizontal displacement of the pendulum body 210 away from the neutral position of the pendulum structure.

Reference is now made to FIG. 2B which depicts a cross-sectional side view of damper 200 . As mentioned above, the annular pendulum body 210 is suspended from the chamber 220, thus forming part of the suspension arrangement. It is shown that the length of the steel wires 211 , 212 , 213 determines the natural frequency of the pendulum damper 200 . Therefore, by changing the length of the steel wires 211, 212, 213, the natural frequency of the damper 200 can be adjusted to be "tuned" to specific needs.

As mentioned earlier, the term "length of the wire" means the length of the wire that can swing freely. This may be from the attachment points of the steel wires 211 , 212 , 213 to the tower 120 . Alternatively, or in addition, the length of the wires can be set with clamps (or "wheels") 217, 218, (219 not shown) that move vertically along the wires 211, 212, 213 to control the individual wires 211, 212. , 213 the freely swingable length (for example, "effective length").

In use, the chamber 220 holds damping fluid 240 filling the chamber 220 to a height (h) measured from the base 222 of the chamber 220 . Then, the pendulum body 210 is sunk into the damping fluid 240 . Then, as it moves within the chamber 220, the movement of the pendulum body 210 is damped due to the resistance applied to the pendulum body 210 by the damping fluid. To allow it to move within the damping fluid 440, the pendulum body 210 is sunk into the damping fluid such that the bottom 221 of the pendulum body 210 is sunk a distance (s) below the surface of the damping fluid 440 such that the base 222 of the chamber 220 is in contact with the pendulum A gap ( g ) is left between the hammer bodies 210 . The sinking distance (s) is also referred to as the distance by which the pendulum body 210 sinks into the damping fluid 240 .

When there is an undesired motion (eg, sway) in the wind turbine 100 induced by factors such as wind or waves, the pendulum body 210 also moves relative to the tower 120 through the damping fluid 240 held in the chamber 220 . The viscosity of the damping fluid 240 is selected to cause the motion of the pendulum body 210 to be damped due to the effect of viscous drag through the damping fluid 240, which dissipates the unwanted kinetic energy, typically in the form of heat, that causes the undesired motion. The effectiveness of the overall damping of wind turbine 100 ("turbine damping") depends on the degree to which pendulum body 210 is damped by damping fluid 240 ("pendulum damping").

Ideally, pendulum damper 200 is configured to fit as high as possible within tower 120 . Generally, it is considered preferable to install the pendulum damper 200 in the upper half of the tower 120 and in the upper third to provide the most effective vibration damping in the tower 120 .

As wind turbine 100 is installed and its mass increases, the damper characteristics are preferably changed to optimize for the increased wind turbine 100 mass. The easiest way to change the characteristics of the damper is to change (ie increase) the mass of the pendulum body. However, due to the heavy weight of the pendulum body (usually between 3 and 20 tons), it cannot be easily replaced or significantly changed in mass, so this is simply not feasible.

As will be described here, maintaining optimal damping of the wind turbine 100 during all installation phases can be achieved by varying the resistance experienced by the pendulum body 210 as it moves through the damping fluid 240 held in the chamber 220, i.e., The resistance of the pendulum body 210 is exerted by the damping fluid 240 stored in the chamber 220 to adjust the damping characteristic of the damper 200 , thereby providing an adjustable damper 200 .

As mentioned above in explaining the resistance equation, the amount of resistance F _D experienced by the pendulum body 210 when it moves through the damping fluid 240 depends on a number of factors, one of which is the degree of resistance of the pendulum body 210 facing the damping fluid 240 in the moving direction. Area A (ie, causing the damping fluid 240 to flash away). Another parameter is the density of the damping fluid 240 . In addition, the resistance exerted on the pendulum body 210 by the damping fluid 240 stored in the chamber 220 is related to the viscosity of the damping fluid 240 .

3 is a schematic cut-away illustration of a specific embodiment of a tower vibration damper 300 (ie, in the form of a pendulum damper) in which the resistance can be varied to adjust the degree of damping of the damper 300 in accordance with the present invention. The viewing angle of the cross-sectional view in FIG. 3A is the same as that in FIG. 2B . The construction of the damper 300 is similar to that of the damper 200 mentioned in the description of FIG. 353 other than.

By increasing the length of the wires 311 , 312 , 313 with winches 351 , 352 , 353 , the pendulum body 310 can be lowered into the damping fluid 340 held in the chamber 320 . As the sinking distance ( s ) increases, the size of the gap ( g ) decreases. Furthermore, the area A of the sunken pendulum body 310 facing the damping fluid 340 in the direction of movement thus increases. Consequently, the resistance experienced by the pendulum body 310 as it moves through the damping fluid 340 increases, which in turn increases the degree of pendulum damping. Conversely, by retracting the wires 311 , 312 , 313 with the winches 351 , 352 , 353 , the pendulum body 310 can be raised so that it sinks less into the damping fluid 340 held in the chamber 320 . As the sinking distance ( s ) of the pendulum body 310 into the damping fluid 340 decreases, the size of the gap ( g ) increases. Furthermore, the sunken pendulum body 310 thus reduces the area A facing the damping fluid 340 in the direction of movement. The reduced area A sunken into the pendulum body 310 thus results in less resistance to the pendulum body 310 as it moves in the damping fluid 340, which in turn reduces the degree of pendulum damping. Thus, a means for varying the resistance to the pendulum body 310 by the damping fluid 340 held in the chamber 320 is thereby provided.

In this way, during installation of the wind turbine 100, the winches 351, 352, 353 can initially raise the pendulum body 310 slightly off the damping fluid 340 to account for the mass of the partially completed wind turbine 100 and thus the pendulum required for it. Damping to match the appropriate resistance. Then, as the wind turbine 100 is further installed and its mass increases, the winches 351 , 352 , 353 can further lower the pendulum body 310 into the damping fluid 340 to correspondingly increase the resistance acting on the pendulum body 310 . The reverse process may occur if wind turbine 100 subsequently requires repair or decommissioning.

When raising or lowering the pendulum body 310, it is possible for the capstans 351, 352, 353 to slightly change the effective length of the wires 311, 312, 313, which independently affect the frequency tuning or damping characteristics of the damper. Even though the change in length of the wires 311, 312, 313 is generally small compared to their original length, the clamps 317, 318, 319 can still be adjusted to compensate for the change in length.

There may be less than or more than one winch 351 , 352 , 353 per wire 311 , 312 , 313 , eg a winch 351 may be configured to retract or unwind more than one wire 311 , 312 , 313 .

The exemplary indications in Table 1 below provide the weight change of the wind turbine (WTG) 100 during installation, and the entry of the pendulum body 310 into the damping fluid 340 (with constant viscosity) held in the chamber 320 to optimize damping Corresponding variation of the optimal immersion depth, which is represented by the gap (g) between the pendulum body 310 and the base of the chamber 320: Table 1: tower tower + nacelle Tower + nacelle + rotor blades WTG weight 300-600 tons 500-1200 tons 550-1300 tons Clearance (g) 100 mm 60 mm 35 mm

4A is a schematic cut-away diagram illustrating a second embodiment of a tower vibration damper 400 (in the form of a pendulum damper) in which the resistance _FD can be varied to adjust the degree of damping in the damper 400 according to the present invention. The perspective of the sectional view of FIG. 4A is again the same as that of FIG. 2B , and the construction of the damper 400 is identical to that of FIG. The tower damper 200 referred to in describing FIG. 2A is similar. Reservoir 460 may be cylindrical, or any other suitable shape. Storage tank 460 preferably adjoins tubular structure 122 of column 120 within column 120 . Pump 470 is configured to pump liquid 440 of reservoir 460 into and out of chamber 420 .

By pumping the damping fluid 440 from the sump 460 into the chamber 420 , the height ( h ) of the damping fluid 440 in the chamber 420 can be increased, and the pendulum body 410 thereby becomes more submerged in the damping fluid 440 . 3, as it sinks into the pendulum body 410 and thus increases the area A facing the damping fluid 440 in the moving direction, the resistance of the pendulum body 410 also increases when it moves in the damping fluid 440, This in turn increases the degree of pendulum damping. Conversely, by pumping the damping fluid 440 from the chamber 420 to the sump 460, the height ( h ) of the damping fluid 440 held in the chamber 420 can be reduced, and the pendulum body 410 thus becomes less sinking into the damping Liquid 440. Again, as mentioned above, as the area A sinks into the pendulum body 410 and thus faces the damping fluid 440 in the direction of movement decreases, as it moves in the damping fluid 440, the pendulum body 410 experiences less resistance, which in turn reduces the pendulum degree of damping. Therefore, another means for changing the resistance to the pendulum body 410 by the damping fluid 440 stored in the chamber 420 is provided.

In this way, during the installation of the wind turbine 100 , the chamber 420 can initially be filled with a quantity of damping fluid 440 suitable to assemble the resistance, thus suitable for pendulum damping which partially completes the mass of the wind turbine 100 . The sump 460 contains the remainder of the necessary damping fluid 440 . Then, as the wind turbine 100 is further installed and its mass increases, the pump 470 can deliver the damping fluid 440 from the storage tank 460 into the chamber 420 so that the height ( h ) of the damping fluid 440 in the chamber can increase and cause the pendulum body to 410 becomes more submerged in damping fluid 460 . The reverse process may occur if wind turbine 100 subsequently requires repair or decommissioning.

A variant of the second embodiment of the damper 400 is shown in a schematic cross-sectional view of FIG. 4B from the same perspective as that of FIG. 4A . Here, a sump 460 is shown mounted above the chamber 420 in the column 120 , the sump 460 being connected to the chamber 420 via an adjustable valve 461 . There is also a second sump 465 for holding damping fluid 440 which is housed in column 120 below chamber 420 and is fluidly coupled to chamber 420 via a second adjustable valve 466 . In this configuration, as the column 120 is further installed, the valve 461 can be opened to control the flow of the damping fluid 440 from the first sump 460 to the chamber 420 in order to increase resistance and increase pendulum damping. Then, if wind turbine 100 is decommissioned, valve 466 may be opened to control the flow of damping fluid 440 from chamber 420 to second sump 465 in order to reduce drag and reduce pendulum damping. Advantageously with this variant, the damping fluid 440 can be delivered via gravity, which eliminates the need for a pump. Therefore, another means for changing the resistance to the pendulum body 410 by the damping fluid 440 stored in the chamber 420 is provided.

The exemplary indications in Table 2 below provide the weight change of the wind turbine (WTG) 100 during installation, and the corresponding change in the height (h) of the damping fluid 440 (with constant viscosity) held in the chamber 420 . Table 2: tower tower + nacelle Tower + Nacelle + Blades WTG weight 300-600 tons 500-1200 tons 550-1300 tons Height of damping fluid (h) 200 mm 350 mm 450 mm

In each of the configurations depicted in Figures 4A and 4B, the degree of damping is substantially changed by changing the amount of damping fluid in the chamber, rather than raising or lowering the pendulum structure in the tower, as in illustrating Figure 3 mentioned. However, the common feature of each of these embodiments is that the resistance of the pendulum body is changed by changing the area A of the pendulum body sinking into the damping fluid kept in the chamber.

The schematic diagram of FIG. 5 illustrates a third specific embodiment of a tower vibration damper 500 (in the form of a pendulum damper) in which the resistance F _D can be varied to adjust the degree of damping of the damper 500 according to the invention. The perspective of the cross-sectional view of FIG. 5 is again the same as that of FIG. 2B , and the damper 500 is aligned with The tower damper 200 referred to in describing FIG. 2A is similar. The change in viscosity of the damping fluid 540 changes the resistance exerted on (and experienced by) the pendulum body 510 as it moves through the damping fluid 540 .

To change the temperature of damping fluid 540 to achieve this change in resistance, pump 580 may receive damping fluid 540 via outlet 582 of chamber 520 , send it through heater 590 and back into chamber 520 via inlet 584 . By activating the pump 580 and increasing the power supplied to the heater 590, the damping fluid 540 in the chamber 520 can be heated and substantially maintained at a specific (ie, higher) temperature. Also, to lower the temperature of the damping fluid 540, the power to the heater 590 may be reduced or completely turned off so that the damping fluid 540 may cool to the temperature of the ambient environment, or ambient temperature. The chamber 520 may be equipped with a temperature sensor (not shown) to assist in monitoring the temperature of the damping fluid 540 .

Alternatively, or in addition, a liquid cooler (not shown) may be installed. In fact, the variable temperature configuration 590 may include both heaters and coolers. Utilizing both a heater and a cooler allows for faster changes in the temperature of the damping fluid 540, eg, the cooler can operate while the heater 590 is off, and vice versa. Furthermore, the use of heaters and/or coolers allows adjustment of the damping fluid 540 to a temperature higher or lower than the ambient temperature of the wind turbine 100 (eg, its surrounding environment), and further maintains the damping fluid 540 at the temperature.

As previously mentioned, there are many suitable damping fluids with suitable properties for use here, eg, oils. When the damping fluid 540 is maintained at a lower temperature, the fluid will be more viscous than when the damping fluid 540 is maintained at a higher temperature. The increased viscosity of the damping fluid 540 at lower temperatures increases the resistance experienced by the pendulum body 510 as it moves through the damping fluid 540, increasing the degree of pendulum damping. Conversely, if the damping fluid 540 is maintained at a higher temperature, it will be less viscous. The lower viscosity reduces the resistance experienced by the pendulum body 510 as it moves through the damping fluid 540, resulting in less damping of the pendulum.

Therefore, another means for changing the resistance to the pendulum body 510 by the damping fluid 540 stored in the chamber 520 is provided. In this way, during installation of wind turbine 100 , pump 580 and variable temperature arrangement 590 may be activated to control the viscosity of damping fluid 540 such that it is suitable for partially accomplishing the mass and thus necessary damping of wind turbine 100 . Then, as the wind turbine 100 is further installed and its mass increases, the temperature can be adjusted so that the liquid 540 becomes cooler and thus more viscous. This causes the pendulum damping to increase as the mass of the wind turbine 100 increases, which allows the wind turbine 100 to remain optimally damped during overall installation. The reverse process may occur if wind turbine 100 subsequently requires repair or decommissioning. The damping fluid may of course be heated in other ways, including by means of immersion heaters (not shown) provided in the chamber.

The exemplary indications in Table 3 below provide the weight change of the wind turbine (WTG) 100 during installation, and the optimum viscosity and corresponding temperature (and thus the required temperature change of the ambient temperature) of the damping fluid 540: Table 3: tower tower + nacelle Tower + nacelle + rotor blades Weight (WTG) 300-600 tons 500-1200 tons 550-1300 tons Viscosity of damping fluid 5000 cSt 3000 cSt 2000 cSt damping fluid temperature 10°C 20°C 30°C

It should be appreciated that the variable temperature arrangement 590 may be assembled into one device capable of heating and cooling, or may have several independent heaters and coolers at different locations within the damper 500 . The variable temperature arrangement 590 may have heating and cooling elements in direct thermal contact with the damping fluid 540 in use. Alternatively, the variable temperature arrangement 590 can be assembled as a heat exchanger, where the heating and cooling elements change the temperature of the damping fluid 540 via an intermediate liquid that communicates with both the damping fluid 540 and the heating and cooling elements of the variable temperature arrangement 590 thermal contact.

Damping fluid 540 is preferably selected such that it provides the desired damping for a fully installed wind turbine 100 at a temperature approximately equal to the average ambient temperature of wind turbine 100 . As such, the damping fluid 540 does not need to be heated or cooled during normal operation of the fully installed wind turbine 100 .

The damper described herein can be used throughout the life of the wind turbine, not just during its installation and decommissioning. For example, during inclement weather such as a storm, the temperature of the damping fluid may increase due to friction generated by increased motion of the pendulum body, which may result in a decrease in viscosity and damping. According to the present invention, such adverse effects may be temporarily counteracted by increasing pendulum damping, for example by one or more of the embodiments described herein.

Indeed, it should be appreciated that any of the specific embodiments described herein may be implemented alone or together in any combination, for example to increase the maximum achievable pendulum damping range. Furthermore, any features described herein of a particular embodiment can be applied to another embodiment, in any suitable combination. It will also be appreciated that particular combinations of the various features described and defined in any aspect herein may be implemented and/or supplied and/or used independently. Any apparatus feature described herein may also be incorporated as a method feature, and vice versa.

While the foregoing description has been directed to several exemplary specific embodiments of the present invention, it should be understood that the invention has been described herein by way of illustration only and that modifications of detail may be made within the scope of the invention. Indeed, other and further embodiments of the invention will be apparent to those skilled in the art from this patent specification and can be devised without departing from the basic scope of the invention as defined by the following patent claims.

100: wind turbine/WTG 120: tower 122: tubular structure 124: lower end 125: ground 126: upper end 140: nacelle 160: rotor hub 180: rotor blade 200: damper 210: pendulum body 211, 212, 213: steel wire 214, 214, 215: attachment point 217, 218, 219: clamp/runner 220: liquid chamber 221: bottom 222: base 224: inner wall 226: outer wall 228: opening 240: damping fluid 300: damper 310: pendulum body 311, 312, 313: steel wire 317, 318, 319: clamp 320: Chamber 340: Damping Fluid 351, 352, 353: Winch 400: Damper 410: Pendulum Body 420: Chamber 440: Damping Fluid 460: Tank/Liquid 461: Adjustable Valve 465: Tank 466: Valve 470: Pump 500: Damper 510 : pendulum body 520 : chamber 540 : damping fluid 580 : pump 582 : outlet 584 : inlet 590 : heating configuration/heater A: area d _i : diameter of inner wall of chamber 220 d _o : outer wall of chamber 220 Diameter _dp : diameter F _D of the ring-shaped pendulum main body 210: resistance g: gap h: height ρ: density C _D of the fluid: drag coefficient of the object in the fluid v : velocity η of the object relative to the fluid: fluid viscosity s: the sinking distance X: the axis of the shaft Z: the longitudinal or vertical axis of the tubular structure 122

Embodiments of the invention are now described with reference to the accompanying drawings, in which: Fig. 1 is a schematic side view of the structure of a typical wind turbine; Figure 2A is a schematic plan view illustrating a portion of a pendulum structure immersed in a chamber inside a wind turbine to provide a tower vibration damper; Fig. 2B is a schematic cross-sectional side view of the pendulum structure of Fig. 2A; Fig. 3 is a schematic sectional side view of the pendulum structure according to the first embodiment; Fig. 4A is a schematic cross-sectional side view of a pendulum structure according to a second embodiment; Figure 4B is a schematic cross-sectional side view of a pendulum structure illustrating a variation of the second embodiment of Figure 4A; and Fig. 5 is a schematic sectional side view of a pendulum structure according to a third embodiment.

300: damper

310: pendulum body

311, 312, 313: steel wire

317, 318, 319: clamps

320: chamber

340: damping fluid

351, 352, 353: Winch

g: gap

h: height

s: sinking distance

Claims (15)

A tower vibration damper for installation in a wind turbine tower, the damper comprising: assembled as a pendulum structure suspendable in the tower, the pendulum structure comprising a pendulum body; a suspension arrangement for suspending the pendulum structure in the tower so as to allow displacement of the pendulum body away from a neutral position of the pendulum body; a chamber retaining a damping fluid into which the pendulum body is at least partially immersed such that movement of the pendulum body within the chamber is inhibited due to a resistance exerted by the damping fluid on the pendulum body; and The member for changing the resistance is used for changing the resistance acting on the pendulum body by the damping fluid stored in the chamber, so as to adjust a damping characteristic of the damper. The damper of claim 1, wherein the means for varying the resistance is operable to increase and/or decrease action by the damping fluid retained in the chamber when the pendulum structure is suspended in the tower The resistance to the body of the pendulum. The damper according to claim 1 or 2, wherein the member for changing the resistance is configured to change a sinking distance of the pendulum body immersed in the damping fluid. The damper of claim 3, wherein the means for varying the resistance comprises means for raising or lowering the pendulum body relative to the chamber. The damper of claim 3, further comprising a fluid reservoir configured to hold damping fluid, the fluid reservoir fluidly coupled to the chamber, and configured such that the damping fluid can flow from the fluid reservoir under the force of gravity flow into the chamber. The damper of claim 5, wherein the liquid storage tank is located at a higher position than the chamber, and the damper further comprises a valve to control the flow of damping fluid from the liquid storage tank to the chamber. The damper according to claim 5 or 6, further comprising: a second liquid storage tank configured to retain damping fluid and a second valve, wherein the liquid storage tank is fluidly coupled to the chamber through the second valve and configured to be lower than the chamber such that, when the second valve is open, damping fluid can flow by gravity from the chamber to the second liquid sump. The damper according to claim 5, further comprising: a pump operable to pump damping fluid between the fluid storage tank and the chamber. The damper according to claim 1 or 2, wherein the member for changing the resistance includes a temperature changing member for changing the temperature of the damping fluid so as to change its viscosity. The damper of claim 9, further comprising: a pump operable to pump damping fluid from the chamber to the temperature changing member and back to the chamber, wherein the temperature changing member is outside the chamber. The damper according to claim 9 or 10, wherein the temperature changing component includes a heating arrangement and/or a cooling arrangement. The damper of claim 11, wherein the heating arrangement comprises an immersion heater disposed within the chamber. A wind turbine comprising the tower vibration damper according to any one of claims 1 to 12. A method for adjusting the damping characteristics of a tower vibration damper during the installation of a wind turbine according to claim 13, the method comprising the following steps: During an installation stage, varying the resistance to the pendulum body by the damping fluid retained in the chamber, such that the damper is configured to damp movement of the wind turbine during the installation stage; and In a subsequent installation stage, changing the resistance to the pendulum body by the damping fluid stored in the chamber causes the damper to be configured to damp the movement of the wind turbine in the subsequent installation stage. A method for adjusting the damping characteristics of a tower vibration damper during decommissioning of a wind turbine according to claim 13, comprising the steps of: During a decommissioning phase, varying the resistance to the pendulum body by the damping fluid retained in the chamber such that the damper is configured to damp movement of the wind turbine during the decommissioning phase; and In a subsequent decommissioning stage, changing the resistance to the pendulum body by the damping fluid stored in the chamber, so that the damper is configured to damp the wind turbine during the subsequent decommissioning stage move.

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