Wind turbine

Abstract

In a first aspect of the invention, a wind turbine is provided that includes a tower, a nacelle mounted on the tower, and a rotor mounted to the nacelle. The rotor includes a hub and at least three wind turbine blades. Each blade extends between a root portion and an end portion. Each blade also includes a connection point between the root portion and the end portion. The wind turbine further includes a plurality of blade connection members, each blade connection member connected between a corresponding connection point of a pair of wind turbine blades. The wind turbine also includes a tensioning system for adjusting the tension in each blade connection member. The tensioning system includes a plurality of linear actuators, each linear actuator coupled between the hub and a respective blade connection member. Each linear actuator is configured to adjust a tension force in the blade connection member.

Description

Technical Field

[0001] The present invention relates generally to wind turbines and, more particularly, to a wind turbine having a rotor including at least three wind turbine blades and a plurality of blade connection members, each blade connection member being connected between a pair of wind turbine blades. Background Art

[0002] There is a continuing desire to generate increased levels of electricity from both onshore and offshore wind farms. One way to achieve this is to provide modern wind turbines with larger wind turbine blades. Providing larger blades increases the swept area of ​​the rotor, allowing the wind turbine to capture more energy from the wind. However, wind turbine blades are subject to a variety of loads and stresses in use, and increasing the length of wind turbine blades increases the magnitude of the loads that the blades, hub, and blade bearings must withstand. For example, flapping loads resulting from wind pressure on the blades and edgewise loads resulting from the weight of the blades are both greater for larger blades.

[0003] A wind turbine blade includes a blade root configured to connect the blade to a hub of the wind turbine. To help withstand the increased loads in use, longer blades typically have a larger blade root diameter. However, this can make the manufacture and transportation of the blades more difficult. In some cases, a support frame or support cables may be included on the rotor to transfer part of the blade load to the hub and / or other blades. As a result, part of the blade load may bypass the blade root, which may reduce the structural requirements on the blade root.

[0004] However, during operation of the wind turbine, the loads to which the wind turbine blades are subjected may vary. For example, the loads may vary due to variable wind conditions and / or due to the varying effects of gravity on the blades as the blades are in different positions around the rotor. Therefore, the wind turbine, and in particular any supporting components on the rotor, must be configured to account for the varying blade loads in order to ensure safe and reliable operation of the wind turbine.

[0005] The present invention just arises at the historic moment under this background.

[0006] 2022P00030WOCN(JPHEN) Summary of the invention

[0007] In a first aspect of the present invention, a wind turbine is provided, comprising a tower, a nacelle mounted on the tower, and a rotor mounted on the nacelle. The rotor comprises a hub and at least three wind turbine blades. Each blade extends between a root and an end (tip). Each blade also comprises a connection point located between the root and the end. The wind turbine also comprises a plurality of blade connection members, each blade connection member being connected between corresponding connection points of a pair of wind turbine blades. The wind turbine also comprises a tensioning system for adjusting the tension in each blade connection member. The tensioning system comprises a plurality of linear actuators, each linear actuator being coupled (coupled) between the hub and a corresponding blade connection member. Each linear actuator is configured to adjust the tension in the blade connection member.

[0008] In a preferred example, the connection point between the root and the end is located away from the root of the blade and away from the end of the blade. For example, in some examples, the connection point can be located at a position at least 20% of the total blade length away from the root of the blade. Similarly, in some examples, the connection point can be located at a position at least 20% of the total blade length away from the end of the blade. In a preferred example, the connection point can be located at a position at least 30% of the total blade length away from both the root of the blade and the end of the blade. Separating the connection point from the root of the blade ensures that most of the blade load can be transferred to the blade connection member through the connection point, bypassing the root of the blade. In addition, separating the connection point from the blade end reduces the drag-increasing effect caused by the connection point, and also reduces the noise generated by the connection point and the blade connection member during use.

[0009] Each linear actuator may be directly connected to the hub and / or directly connected to the blade connection member. Alternatively, each linear actuator may be indirectly connected to the hub via another component, and / or indirectly connected to the blade connection member via another component. Therefore, "coupled between the hub and the corresponding blade connection member" includes both direct connection with the hub and the blade connection member and indirect connection with the hub and the blade connection member. Therefore, it can be understood that in some examples, the linear actuator may be one of a plurality of components coupled together between the hub and the blade connection member.

[0010] In the present context, "blade connection member" should be interpreted broadly, including, for example, flexible connection members and rigid connection members. Therefore, in some examples, the blade connection member may include a cable. Therefore, preferably, the blade connection member may be a blade connection cable, and the rotor may be a cable-stayed rotor. For example, in the present context, a "cable" may be a rope woven or laid by metal wires (such as steel wires, etc.), polymer fibers (such as polyethylene, polypropylene, nylon, polyester, aramid fibers, etc.), inorganic fibers (such as carbon fibers, etc.), or a hybrid rope composed of these materials. In some other examples, the blade connection member may include a composite member such as a pultruded part, or 2022P00030WOCN(JPHEN)

[0011] Alternatively the blade connection member may comprise a metal rod, just to name a few possible examples.

[0012] In some examples, the tensioning system may be referred to as a pre-tensioning system, as the tensioning system is preferably configured to pre-tension the wind turbine blade via the connection member. Thus, the tensioning system may be configured to apply a pre-tensioning force (pre-tensioning force) in a direction that counteracts the gravity and / or wind load forces to which the blade is subjected during use. Applying a pre-tensioning force may help pull the rotor blade further upwind, away from the tower, thereby helping to reduce the risk of the blade striking the tower in high wind conditions.

[0013] Each linear actuator preferably has an adjustable length to facilitate adjustment of the tension in the blade connection member. It will be appreciated that the length of the linear actuator refers to the distance between the points at which other wind turbine components (e.g., the hub and the blade connection member) can be connected to the linear actuator. The stroke length of the linear actuator may be at least 1 meter, preferably at least 2 meters, and more preferably at least 3 meters. The stroke length is the maximum length adjustment that the linear actuator can achieve. The maximum stroke length varies depending on the actual design, for example, the stroke length may be up to 6 meters, preferably up to 5 meters. For example, the stroke length is the difference between the maximum (i.e., extended) length and the minimum (i.e., retracted) length of the linear actuator. Similarly, the maximum length and minimum length of the linear actuator refer to the maximum distance and minimum distance between the connection points at which the linear actuator can be connected to other components of the wind turbine.

[0014] In a preferred example, the stroke length is configured or set based on predicted changes during operation of the wind turbine. For example, factors that affect the stroke length configuration include predicted changes in operating conditions, predicted changes in blade connection member pretensioning (e.g., during maintenance operations), and predicted material creep of coupling components between blades and hub. The stroke length of the linear actuator selected should take these changes into account.

[0015] Additionally, the adjustable length of the linear actuator can help to improve the assembly and maintenance of the wind turbine. For example, the actuator can be fully extended, i.e. extended to a maximum stroke length, in order to loosen the blade connection member when the wind turbine is not in operation. Therefore, in a preferred example, the linear actuator can be configured with a maximum stroke length to facilitate loosening the blade connection member (i.e. unloading it). In examples where the blade connection member is a flexible member (such as a rope or cable), loosening the blade connection member by extending the linear actuator can be particularly helpful in simplifying the assembly and maintenance of the wind turbine. In some examples, the facility to extend the actuator and thereby loosen the blade connection member may mean that maintenance operations can be performed on the blade without disconnecting the blade connection member from the blade.

[0016] In some examples, the linear actuator can be an electric linear actuator. For example, in some examples 2022P00030WOCN (JPHEN)

[0017] In some examples, the linear actuator may include an electric motor. The electric actuator may facilitate the use of standard electrical components, which may reduce the cost of the tensioning system. Additionally, the electric actuator also has a reduced risk of liquid leakage because only a small amount of liquid (e.g., liquid used to lubricate the moving parts) is included. Moreover, in some examples, the wind turbine may include an electric pitch mechanism for adjusting the pitch of the wind turbine blades. In such examples, the use of an electric actuator in the tensioning system may be particularly advantageous because the existing electrical infrastructure in the wind turbine can be reused for the electric linear actuator.

[0018] The wind turbine may further include a plurality of tension force sensors, each tension force sensor being configured to measure tension in a corresponding blade connection member and / or a corresponding linear actuator. Such tension force sensors may be in contact with or coupled to the blade connection member, or in other examples, the tension force sensors may be used to determine / estimate tension in the blade connection member without being located on or in the blade connection member.

[0019] In a preferred example, the linear actuator may be a hydraulic actuator or a pneumatic actuator. Advantageously, a hydraulic or pneumatic linear actuator facilitates measuring the tension in the blade connection member by measuring the fluid pressure in the linear actuator. Therefore, an additional sensor for measuring the tension in the blade connection member may be unnecessary and / or may be included only as a precaution.

[0020] Each linear actuator may include a piston, and the tensioning system may further include a plurality of stiffness response systems, each stiffness response system including a high pressure fluid source and a low pressure fluid source. Each high pressure fluid source is preferably selectively fluidly coupled to a first side of a piston in the linear actuator, and each low pressure fluid source is preferably selectively fluidly coupled to a second side of a piston in the linear actuator to facilitate control of the stiffness response of the linear actuator. Thus, the stiffness response of the linear actuator may be controlled or set by changing the pressure across the piston, for example, by changing the pressure in each of the high pressure fluid source and the low pressure fluid source.

[0021] As previously mentioned, the linear actuator may be a hydraulic linear actuator or a pneumatic linear actuator. Therefore, it is understood that any "fluid" referred to herein includes liquid and / or gas, unless otherwise specified. For example, for a pneumatic linear actuator, the high-pressure fluid source and the low-pressure fluid source may be a high-pressure gas source and a low-pressure gas source. For a hydraulic linear actuator, the high-pressure fluid source and the low-pressure fluid source may be a high-pressure liquid source and a low-pressure liquid source.

[0022] The stiffness response of a linear actuator may also be referred to as the stiffness of the linear actuator. For example, a linear actuator may operate as a hydraulic or pneumatic spring. Thus, the linear actuator may extend or retract in response to the tension of the blade connection member in use. Thus, the stiffness response of the linear actuator may be similar to the spring constant.

[0023] Number synonyms.

[0024] Each linear actuator is preferably fluidly coupled to its respective high pressure fluid source and its respective low pressure fluid source via a respective hydraulic or pneumatic manifold. Such manifolds are preferably constructed of substantially rigid (hard) conduits. In particular, for the high pressure manifolds that fluidly couple the linear actuators to the high pressure fluid sources, the use of substantially rigid conduits helps reduce the risk of fluid leakage when the wind turbine is in operation.

[0025] In some examples, the high-pressure fluid source may be a high-pressure accumulator. In addition, in some examples, the low-pressure fluid source may be a low-pressure accumulator. The pressure in the high-pressure accumulator and the low-pressure accumulator may determine the stiffness response of the linear actuator. In some examples, one or both of the accumulators may be charged by gas pressure. For example, each accumulator may be a piston accumulator, a bladder accumulator, or a film / diaphragm accumulator. Each of these types of accumulators includes a partition element between a gas volume and a high-pressure or low-pressure fluid volume. Changing the gas pressure on one side of the partition element helps control the fluid pressure on the other side of the partition element. In some other examples, one or both of the accumulators may be additionally or alternatively charged by a mechanical spring. For example, a mechanical spring may apply a force to one side of the partition element, and a high-pressure or low-pressure fluid acts on the partition element from the other side. Therefore, the pressure of the high-pressure or low-pressure fluid in the accumulator may be determined by the mechanical spring.

[0026] In some examples, the high pressure fluid sources may be selectively fluidly coupled to each other. Additionally or alternatively, the low pressure fluid sources may be selectively fluidly coupled to each other. The high pressure fluid sources are preferably selectively fluidly coupled to each other through one or more regulating valves. The low pressure fluid sources are preferably selectively fluidly coupled to each other through one or more regulating valves. In the initial stage, the regulating valve may be opened to fluidly couple the high pressure fluid sources, thereby balancing the pressure in each high pressure fluid source. In addition, before the operation of the wind turbine, the regulating valve may be opened to fluidly couple the low pressure fluid sources, thereby balancing the pressure in each low pressure fluid source. After balancing the pressure in each high pressure fluid source and / or balancing the pressure in each low pressure fluid source, the regulating valve may be closed to isolate each high pressure or low pressure fluid source from other high pressure or low pressure fluid sources. During the operation of the wind turbine, each linear actuator and an associated pair of high pressure fluid sources and low pressure fluid sources may serve as an independent stiffness response system for the blade connection member.

[0027] In some examples, each linear actuator may be coupled to a corresponding blade connection member via a separate tension member. It will be appreciated that the term "tension member" should be interpreted broadly to include examples such as flexible tension members and rigid tension members. Thus, in some examples, the tension member may include a composite member such as a pultrusion, or alternatively may include a metal rod (just to name a few possible examples). However, in preferred examples, the tension member may include a cable. For example, in this context, a "cable" may be a rope woven or laid from metal wires (such as steel wire, etc.), polymer fibers (such as polyethylene, polypropylene, nylon, polyester, aramid fibers, etc.), inorganic fibers (such as carbon fibers, etc.), or a hybrid rope composed of these materials. Most preferably, the tension member includes a polymer rope, such as a braided polymer rope. For example, the tension member may include ultra-high molecular weight polyethylene fibers, such as based on Polymer rope of DM20.

[0028] It will be appreciated that an example comprising a tensioning member coupled between the linear actuator and the blade connection member is an example in which the linear actuator is indirectly connected to the blade connection member via another component. Thus, in such an example, the tensioning member is one of a plurality of components (including the linear actuator) coupled between the hub and the blade connection member. In some other examples, the wind turbine may additionally or alternatively comprise a tensioning member coupled between the linear actuator and the hub. Thus, the linear actuator may be indirectly connected to the hub. However, in a preferred example, the linear actuator may be located as close to the hub as possible, i.e. as inwardly as possible, to reduce the moment of inertia of the rotor.

[0029] A separate tension member coupled between the linear actuator and the blade connection member may make assembly of the wind turbine simpler. Particularly in examples where the tension member is a flexible tension member (e.g., comprising a rope or cable), coupling the linear actuator between the hub and the blade connection member via the tension member may be easier. Furthermore, coupling one or more tension members between the linear actuator and the blade connection member and / or between the linear actuator and the hub may facilitate the use of smaller linear actuators and / or shorter blade connection members, thereby saving cost and weight.

[0030] The total distance between the hub and the blade connection member may be referred to as the tensioning system length. The maximum tensioning system length may be defined by the maximum extension length of the actuator and the length of any tensioning force member through which the actuator is coupled between the hub and the blade connection member. The tension in the blade connection member may be adjusted by adjusting the tensioning system length, for example by changing the length of the linear actuator.

[0031] The stroke length of each linear actuator, i.e. the maximum length adjustment amount achieved by adjusting the length of the linear actuator, may be at least 10%, preferably at least 15%, and more preferably at least 20% of the maximum tensioning system length. For example, the maximum tensioning system length may be 15 meters, wherein in certain preferred examples, the stroke length of the linear actuator may be 3 meters.

[0032] In some examples, each linear actuator is preferably rotatably coupled to the hub so that the linear actuator can freely rotate relative to the hub. Therefore, the linear actuator is preferably self-orienting according to the tension in the tension member, so that, for example, the tension member is adjusted due to gusts, pitch changes, maintenance and / 2022P00030WOCN(JPHEN)

[0033] Orientation changes due to, for example, creep or other reasons are taken into account. Therefore, in a preferred example, the extension axis of the linear actuator can be coaxial with the resultant tension in the corresponding tension member. Advantageously, this configuration reduces the risk of moment loads on the linear actuator, which may cause wear, damage or misalignment problems of the linear actuator. In addition, this configuration advantageously reduces fatigue of the tension member.

[0034] In a preferred example, each linear actuator may be rotatably coupled to the hub with three rotational degrees of freedom. This configuration advantageously ensures that tensioning forces do not cause any moment forces or torsional loads on the linear actuators during operation of the wind turbine when blade loads and their magnitudes may vary or move, such as during operation (e.g., due to gusts, pitch changes, and / or creep) or during installation or maintenance.

[0035] In a preferred example, the hub may include an upwind hub extension. That is, the hub may include an extension or device extending in an upwind direction. The linear actuator may be coupled to the upwind extension of the hub. Advantageously, this configuration may cause the tension in the blade connection member to pull the wind turbine blade in the upwind direction, thereby reducing the risk of the blade striking the tower in high wind conditions. Additionally, this configuration may also effectively increase the stiffness of the wind turbine blade in the span direction (spanwise direction). In particular, coupling the linear actuator between the blade connection member and the upwind hub extension increases the stiffness of the inner portion of the blade between the connection point and the root of the blade.

[0036] In a preferred example, the linear actuator (or other components of the tensioning system, such as a tensioning force member, through which the linear actuator is coupled to the hub) is preferably coupled to the hub at coupling points that are evenly distributed around the axis of rotation of the rotor. Thus, the tensioning forces in the respective linear actuators can substantially cancel each other out. The linear actuator can be coupled to the hub via a suspension bracket. For example, the suspension bracket can define the coupling point. The suspension bracket can help ensure that the loads transmitted by the linear actuator are resolved in the same plane, thereby minimizing the loads transmitted to the hub.

[0037] In some examples, the wind turbine may include wind turbine blades with variable pitch. For example, each wind turbine blade may be rotatably connected to the hub via a variable pitch mechanism. Therefore, in some examples, the rotor may be referred to as a "cable-stayed variable pitch rotor".

[0038] The pitch mechanism is preferably a hydraulic pitch mechanism. In some examples, a high-pressure fluid source (e.g., a high-pressure accumulator) in the stiffness response system can be selectively coupled to the hydraulic pitch mechanism fluid. Alternatively or additionally, in some examples, a low-pressure fluid source (e.g., a low-pressure accumulator) in the stiffness response system can be selectively coupled to the hydraulic pitch mechanism fluid. Such a configuration can be convenient when needed, such as during maintenance operations, during initial assembly of the turbine, and / or as a safety backup system.

[0039] For simple and efficient supply and removal of hydraulic fluid from the accumulator.

[0040] In another aspect of the present invention, a method for operating a wind turbine is provided. The wind turbine includes a tower, a nacelle mounted on the tower, and a rotor mounted on the nacelle. The rotor includes a hub and at least three wind turbine blades. Each wind turbine blade extends between a root and an end. Each blade also includes a connection point located between the root and the end. The wind turbine also includes a plurality of blade connection members. Each blade connection member is connected between corresponding connection points of a pair of wind turbine blades. The wind turbine also includes a tensioning system, which includes a plurality of linear actuators. Each linear actuator is coupled between the hub and a corresponding blade connection member. The method includes adjusting each linear actuator according to the tension in the corresponding blade connection member, thereby adjusting the tension in the blade connection member.

[0041] In a preferred example, each linear actuator has an adjustable length. Thus, adjusting each linear actuator preferably comprises adjusting the length of the respective linear actuator, thereby adjusting the tension in the blade connection member. Advantageously, this facilitates a simple operation of adjusting the tension in the blade connection member of the wind turbine.

[0042] In some examples, the method may include setting a target tension of the blade connection member and, depending on the tension of the blade connection member in use, a) extending the linear actuator, or b) retracting the linear actuator to maintain the target tension in the blade connection member. In preferred examples, maintaining the target tension or maintaining a consistent tension may involve maintaining the tension within a predetermined range. For example, in some examples, the tension may be maintained within a range of 3-10% of the target tension.

[0043] If the tensioning system is rigid, high wind loads may cause an increase in the tension in the blade connection member. However, in such high wind conditions, the linear actuator of the tensioning system described above can be extended, i.e., the total length of the tensioning system is extended, thereby maintaining a consistent tension in the blade connection member. In addition, when the rigid tensioning system is set to an appropriate average tension, in low wind conditions, the tension in the blade connection member may drop significantly, causing the blade connection member to relax. However, in such low wind conditions, the linear actuator of the tensioning system described above can be retracted, i.e., the total length of the tensioning system is shortened, thereby maintaining a consistent tension in the blade connection member, which ensures that part of the blade load can still be transferred to the blade connection member. Therefore, the linear actuator can respond to external factors such as wind and / or gravity effects to maintain a consistent tension in the blade connection member. In addition, the tensioning system and the use of the tensioning system described herein can compensate for other factors, such as temperature effects and material creep, which may cause the length of the blade connection member to change during use.

[0044] 2022P00030WOCN(JPHEN)

[0045] Furthermore, adjusting the linear actuator, for example by extending or retracting the linear actuator to adjust the tension in the blade connection member, also adjusts the stiffness of the tensioning system and the associated blade connection member. By facilitating the adjustable stiffness of the blade connection member and the tensioning system, the tensioning system and the use of the tensioning system described herein ensure that variable blade loads experienced during operation of the wind turbine are distributed between the blade and the blade connection member. In a preferred example, due to the adjustable stiffness of the blade connection member and the tensioning system, the variable blade load can be evenly distributed (distributed) between the blade and the blade connection member.

[0046] In some examples, the linear actuator can be a hydraulic actuator or a pneumatic actuator. Thus, in use, the linear actuator can extend and retract with pressure without any active electronic control input. Therefore, the extension and retraction of the linear actuator can be referred to as passive, because the extension and retraction of the actuator may occur without active electronic control input. Therefore, in use, the linear actuator can be a dumb system, such as a spring, which only responds passively to external stimuli (such as pressure changes) that cause the linear actuator to extend and retract. In a preferred example, the tensioning system can be configured to allow the linear actuator to passively extend / retract + / -0.3 meters, preferably + / -0.45 meters, and more preferably + / -0.6 meters in use. In a preferred example, the tensioning force in the blade connection member can be measured or calculated by measuring the pressure in the hydraulic or pneumatic linear actuator.

[0047] For example, when the wind turbine is operating under high wind conditions or other conditions where the blades are subject to high loads, the tensioning system, in particular the linear actuator of the tensioning system, can act as a driven component, following the load in the blade connection member and extending the actuator to reduce the tension in the blade connection member. When the blades are subject to high loads, the linear actuator can be passively extended, i.e. without the need for active electrical control input. In addition, when the wind turbine is operating under low load conditions, the linear actuator can act as an active component and can be retracted to increase the tension in the blade connection member. This ensures that the blade connection member is still loaded and maintained in tension, so that at least some of the blade load can still be transmitted to the blade connection member. Under low load conditions, the linear actuator can be passively retracted, i.e. without the need for active electrical control input.

[0048] In some examples, each linear actuator may include a piston, and the tensioning system may include a plurality of stiffness response systems. Each stiffness response system may include a high pressure fluid source and a low pressure fluid source. Each high pressure fluid source may be selectively fluidly coupled to a first side of a piston in the linear actuator, and each low pressure fluid source may be selectively fluidly coupled to a second side of a piston in the linear actuator. The method may also include controlling the linear actuation by controlling the pressure of the high pressure fluid and the pressure of the low pressure fluid.

[0049] Controlling the stiffness of the linear actuator also results in controlling the combined stiffness of the tensioning system and the blade connection member. Controlling this combined stiffness facilitates controlling the load distribution between the blade and the blade connection cable. For example, if the combined stiffness of the blade connection cable and the tensioning system is increased, it results in a greater proportion of the blade load being transferred to the blade connection cable. This therefore ensures that control is exercised over how much of the load is transferred to the hub through the blade root and the inner part of the blade, and how much of the load bypasses the blade root and the inner part and is transferred to the hub through the blade connection member.

[0050] In some examples, the high pressure fluid source may be a high pressure accumulator and the low pressure fluid source may be a low pressure accumulator. Thus, controlling the stiffness response of the linear actuator may include controlling the pressure in the high pressure accumulator and / or controlling the pressure in the low pressure accumulator.

[0051] In some examples, the high pressure fluid sources may be selectively fluidly coupled to each other. Additionally, the low pressure fluid sources may be selectively fluidly coupled to each other. The method may also include equalizing the pressure in the high pressure fluid sources by fluidly coupling the high pressure fluid sources to each other, rotating the rotor at least one full revolution, and then fluidly decoupling the high pressure fluid sources from each other. The method may also include equalizing the pressure in the low pressure fluid sources by fluidly coupling the low pressure fluid sources to each other, rotating the rotor at least one full revolution, and then fluidly decoupling the low pressure fluid sources from each other. In a preferred example, the pressure equalization of the high pressure fluid sources and the pressure equalization of the low pressure fluid sources may result in the tension in the blade connection member being adjusted to a target tension of the blade connection member. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Examples of the invention will now be described, by way of non-limiting example only, with reference to the accompanying drawings:

[0053] Figure 1 is a schematic perspective view of a wind turbine including a plurality of blades, a plurality of blade connection members connected between pairs of blades, and a tensioning system for adjusting tension in the blade connection members;

[0054] Figure 2 is a schematic perspective view of a tensioning system and a hub of a wind turbine; and

[0055] Figure 3 is a flow diagram describing an example of a tensioning system including a hydraulic or pneumatic actuator. DETAILED DESCRIPTION

[0056] Figure 1 A wind turbine 10 is shown that includes a tower 12 and a nacelle 14 mounted on the tower 12. A rotor 16 is mounted to the nacelle 14, the rotor 16 including a hub 18 and a plurality of wind turbine blades 20. In this example, the wind turbine 10 includes three wind turbine blades 2022P00030WOCN(JPHEN)

[0057] 20. The blades 20 may be adjustable pitch wind turbine blades 20, i.e. the pitch of the blades 20 may be adjustable. Thus, the wind turbine blades 20 may be connected to the hub 18 via corresponding pitch mechanisms (not shown), by means of which the blades 20 may be rotated relative to the hub 18. Thus, in a preferred example, the pitch of the wind turbine blades 20 may be controlled depending on the relative speed of the incident wind to ensure that the blades 20 are oriented at a favorable angle of attack to capture energy from the wind.

[0058] Each wind turbine blade 20 extends in a span direction between a blade root 22 and a blade tip 24. The blade root 22 is preferably configured to be directly (eg, Figure 1The blades 20 are connected to the hub 18 by the blade root 22 and the blade end 24 (not shown) or by another wind turbine component such as a blade root extension (not shown). Each blade 20 includes a connection point 26 located between the root 22 and the end 24. The connection point 26 of each blade 20 is configured to facilitate connecting a blade connection member 28 to the wind turbine blade 20. Figure 1 As shown, the wind turbine 10 includes a plurality of blade connection members 28 , each of which is connected between corresponding connection points 26 of a pair of wind turbine blades 20 .

[0059] The blade connection member 28 may be a flexible connection member, such as a cable, or a substantially rigid connection member, such as a rod or pultrusion. Figure 1 In the example shown, the blade connection members 28 include cables, so that the rotor 16 can be referred to as a "cable-stayed rotor." The blade connection members 28 are configured to transfer a portion of the loads to which the blade 20 is subjected in use to another wind turbine blade 20 and / or the hub 18. In particular, the blade connection members 28 reduce the loads to which the inboard portion 30 of the blade 20 is subjected, thereby also reducing the amount of blade loads that are transferred from the blade 20 to the hub 18 via the blade root 22. This is because a portion of the blade loads are transferred to the blade connection members 28 at the connection point 26, and these loads are then transferred to another blade 20 or the hub 18 via a separate path, bypassing the blade root 22.

[0060] As described as background, increasing the length of a wind turbine blade 20 typically requires increasing the diameter of the blade root 22 in order to provide greater strength to the inboard portion 30 of the blade 20 to accommodate the greater loads to which the longer blade is subjected during use. However, the wind turbine 10 described herein includes a blade connection member 28 that facilitates the use of longer wind turbine blades 20 without necessarily increasing the blade root size for structural purposes. Thus, the use of the blade connection member 28 at least reduces the extent to which the blade root size of longer blades 20 is increased (compared to blades of a wind turbine that does not include a blade connection member), and in preferred examples, the use of the blade connection member 28 can advantageously facilitate an increase in blade length without increasing the blade root size. As described above, this is because a portion of the blade load is unloaded at the connection point 26, i.e., transferred to the blade connection member 28. As a result, the swept area of ​​the rotor 16 can be increased, which means that the rotor 16 can be increased without increasing the blade root size.

[0061] Increasing the diameter of the blade root 22 captures more energy from the wind.

[0062] Still reference Figure 1, wind turbine 10 also includes a tensioning system 32 for adjusting the tension in each blade connection member 28. Tensioning system 32 includes a plurality of linear actuators 34, each linear actuator 34 being coupled between hub 18 and a corresponding blade connection member 28. Linear actuators 34 are configured to adjust the tension in their associated blade connection members 28. For example, linear actuators 34 may be adjusted based on the tension in their associated blade connection members 28, as will be described in more detail below.

[0063] Additional reference Figure 2 , Figure 2 A schematic diagram of the hub 18 and the tensioning system 32 is shown, and in some examples, each linear actuator 34 can be coupled to a corresponding blade connection member 28 via a separate tensioning force member 36. The tensioning force member 36 can be rigid, or alternatively, the tensioning force member 36 can be flexible. Because the tensioning force member 36 can be configured to have a certain length to span the desired distance between the linear actuator 34 and the blade connection member 28, the inclusion of the tensioning force member 36 can facilitate the use of smaller (i.e., shorter) linear actuators 34. Additionally, coupling the linear actuator 34 to the blade connection member 28 via the tensioning force member 36 means that the mass of the linear actuator 34 is substantially maintained on the inside, i.e., close to the rotor axis, thereby reducing the rotational inertia of the rotor 16.

[0064] Each linear actuator 34 preferably has an adjustable length to facilitate adjusting the tension in the blade connection member 28. Therefore, in some examples, adjusting the linear actuator 34 to adjust the tension in the blade connection member 28 may involve adjusting the length of the corresponding linear actuator 34. It is understood that the length of the linear actuator 34 refers to the distance between the point where the actuator 34 is connected to other components of the wind turbine 10. The linear actuator 34 can be retracted, i.e., shortened, to increase the tension in the blade connection member 28 coupled to the actuator 34. Then, the linear actuator 34 can be extended to reduce the tension in the blade connection member 28.

[0065] In some examples, operation of the wind turbine 10 may involve setting a target tension in the blade connection member 28, and varying the length of the linear actuator 34 to achieve or maintain the target tension in the blade connection member 28. For example, depending on the tension in the blade connection member 28 during use, the linear actuator 34 may be extended or retracted to maintain the target tension in the blade connection member 28.

[0066] In effect, adjusting the length of the linear actuator 34 changes the stiffness of the associated blade connection member 28 (and in some examples the stiffness of the associated tensioning force member 36). Controlling the stiffness of the blade connection member 28 relative to the stiffness of the inner portion 30 of the blade 20 determines the load distribution between the inner portion 30 of the blade 202022P00030WOCN(JPHEN) and the blade connection member 28. For example, by increasing the stiffness of the blade connection member 28 relative to the blade 20, a higher proportion of the blade load may be transferred to the blade connection member 28. This ensures that the varying loads to which the blade 20 is subjected during use are safely distributed between the blade root 22 and the blade connection member 28. The stiffness of the blade connection member 28 may be increased by retracting (i.e. shortening) the associated linear actuator 34, wherein the increase in stiffness results in an increase in tension in the blade connection member 28, as more load is transferred from the blade 20 to the blade connection member 28, as described above.

[0067] The linear actuator 34 is preferably rotatably coupled to the hub 18. Thus, in a preferred example, the linear actuator 34 can freely rotate relative to the hub 18. This means that the linear actuator 34 can self-orient according to the tensioning force in the tensioning force member 36, which is particularly advantageous when the direction of the tensioning force changes during use. Therefore, the linear actuator 34 preferably maintains an orientation in which the axis of extension of the actuator 34 is substantially coaxial with the tensioning force to which the linear actuator 34 is subjected during operation of the wind turbine 10. Determining the orientation of the linear actuator 34 and the tensioning force member 36 in this manner effectively reduces fatigue of the tensioning force member 36 because the tensioning force is always oriented along the longitudinal axis of the tensioning force member 36. Such an orientation also reduces the risk of moment loads acting on the linear actuator 34, which moment loads may cause wear, damage or misalignment problems of the actuator 34.

[0068] In some examples, the hub 18 may include an upwind hub extension 38, i.e., a portion of the hub 18 that extends in an upwind direction. The linear actuator 34 may be coupled (e.g., rotatably coupled) to the upwind hub extension 38. This configuration may help pull the wind turbine blade 10 upwind (via the blade connection member 28 and the tension in the tension member 36), thereby reducing the risk of the blade 20 striking the tower 12 in high wind conditions. This may also increase the stiffness of the wind turbine blade 20 in the span direction, and in particular, this configuration may increase the stiffness of the inner portion 30 of the blade 20.

[0069] like Figure 2As shown, in a preferred example, the linear actuator 34 can be a hydraulic actuator or a pneumatic actuator, i.e., an actuator driven by liquid pressure or gas pressure, respectively. Therefore, the linear actuator 34 can extend and retract with the liquid pressure (i.e., liquid pressure or gas pressure). As will be described in detail later, in a preferred example, the linear actuator 34 can extend and retract without any active electronic control input. For example, in use, the linear actuator 34 can extend and retract due to the tension force generated by the fluid pressure in the actuator 34.

[0070] Reference now Figure 3 , which shows a fluid system diagram describing a wind vortex 2022P00030WOCN(JPHEN)

[0071] An example of a tensioning system 32 for a turbine 10 is shown. Figure 3 As shown, the tensioning system 32 may include a plurality of stiffness response systems 40, Figure 3 The dashed boundary lines in schematically represent each system.

[0072] Each stiffness response system 40 is preferably configured to control the stiffness of the blade connection member 28 by controlling the fluid pressure in the associated linear actuator 34. Thus, each stiffness response system 40 preferably includes a high-pressure fluid source 42 and a low-pressure fluid source 44. The high-pressure fluid source 42 in the associated stiffness response system 40 can be selectively fluidly coupled to a first side of a piston 46 in the linear actuator 34. Thus, the low-pressure fluid source 44 in the associated stiffness response system 40 can be selectively fluidly coupled to a second side of the piston 46.

[0073] The position of the piston 46 within the linear actuator 34 may determine the length of the linear actuator 34. For example, moving the piston 46 within the linear actuator 34 may cause the actuator 34 to extend or retract. The movement of the piston 46 within the linear actuator 34 is resisted by the high pressure and low pressure fluids on both sides of the piston 46. Therefore, the stiffness response of the linear actuator 34 may be controlled by controlling the pressure of the high pressure fluid and the pressure of the low pressure fluid.

[0074] like Figure 3 As shown, and again briefly referred to Figure 2In some examples, the high pressure fluid source 42 may be a high pressure accumulator and the low pressure fluid source 44 may be a low pressure accumulator. In some examples, the high and low pressure accumulators 44, 42 of each stiffness response system 40 may be located within the hub 18, or in other examples, the accumulators 44, 42 may be mounted to the hub 18 or the inner portion 30 of the blade 20. The pressure in the accumulators 42, 44 may determine the stiffness response of the associated linear actuator 34. Thus, the stiffness response of the linear actuator 34 may be controlled by controlling the pressure in the high pressure accumulator 42 and / or the pressure in the low pressure accumulator 44. Additionally, the accumulators 42, 44 may provide a damping effect when the linear actuator 34 is extended or retracted in use due to changes in tension in the blade connection member 28.

[0075] In some examples, the high pressure fluid source 42 and / or the low pressure fluid source 44 may be selectively fluidly coupled to a hydraulic pitch mechanism (not shown) configured to adjust the pitch of the wind turbine blades 20. In some examples, such a configuration may facilitate easy addition and removal of fluid from the high pressure fluid source and the low pressure fluid source 42, 44, such as during the initial stages of operating the wind turbine 10, after maintenance work, or to replace fluid lost from leakage, etc.

[0076] Still refer to Figure 3 In some preferred examples, the high pressure fluid sources 42 can be selectively fluidly coupled to each other. When the high pressure fluid sources 42 are fluidly coupled to each other, the pressure in each high pressure fluid source 42 can be equalized, as described in more detail below. In addition, the low pressure fluid source 44 can be selectively 2022P00030WOCN(JPHEN)

[0077] Fluidically coupled to each other, this arrangement means that the pressure in each low pressure fluid source 44 can also be equalized.

[0078] Referring first to the high pressure fluid sources 42, the tensioning system 32 may include a plurality of regulating valves 48 by which the high pressure fluid sources 42 may be selectively fluidly coupled and decoupled from one another. Each stiffness response system 40 may also include one or more one-way valves 50 for controlling the direction of fluid flow between the high pressure fluid sources 42 of each stiffness response system 40. In an initial stage, i.e., before the wind turbine 10 is operated to generate electricity, the regulating valves 48 may be opened to fluidly couple the high pressure fluid sources 42 to one another. Similarly, the regulating valves 52 may also be opened to fluidly couple the low pressure fluid sources 44 to one another. The rotor 16 may then idle or rotate. In an example including adjustable pitch wind turbine blades 20, this may involve rotating the adjustable pitch wind turbine blades 20 to a feathered position so that the wind does not drive the rotor 16. Coupling of the low pressure fluid sources or the high pressure fluid sources may also be performed during operation, if desired.

[0079] By rotating the rotor 16, the loads to which the blades 20 are subjected throughout the cycle may vary, for example, because the weight forces acting on the blades 20 may vary when the blades 20 are in different positions during the rotation of the rotor 16. Therefore, the tension in the blade connection member 28 may also vary during the rotation of the rotor 16. Therefore, the linear actuator 34 and the stiffness response system 40 of each actuator 34 will also be subjected to varying tensions and pressures, respectively. When opened, the regulating valve 48 allows high pressure fluid to flow between each stiffness response system 40. The regulating valve 48 can be configured to open and close to allow and prevent fluid communication between the high pressure fluid sources 42, respectively, until the pressure in each high pressure fluid source 42 is substantially the same, i.e., balanced. It will be appreciated that the balanced pressure in the high pressure fluid source 42 is preferably the average pressure, i.e., the mean pressure, to which the high pressure fluid source 42 is subjected during the rotation of the rotor 16.

[0080] After pressure equalization, the high pressure fluid sources 42 are preferably decoupled, i.e., fluidly isolated from one another, so that during operation of the wind turbine 10, each stiffness response system 40 functions as a separate system with the associated linear actuator 34 and blade connection member 28. The linear actuator 34 is preferably configured with a stroke length, i.e., a maximum variable length, that accommodates changes in tension and pressure changes above and below the equalization pressure during operation of the wind turbine 10.

[0081] It is understood that the above process for equalizing the pressure in the high-pressure fluid source 42 is also applicable to equalizing the pressure in the low-pressure fluid source 44 using the regulating valve 52. Therefore, for the sake of brevity, the pressure equalization process of the low-pressure fluid source 44 will not be repeated here. In a preferred example, the pressure equalization of the low-pressure fluid source 44 is performed simultaneously with the pressure equalization of the high-pressure fluid source 42, that is, when the wind turbine 2022P00030WOCN(JPHEN) is running.

[0082] The initial phase of 10 is carried out simultaneously.

[0083] Fluid can be introduced into each stiffness response system 40 through the fluid inlet. Fluid can be removed from each stiffness response system 40 through the fluid return port. Figure 3As shown, each stiffness response system 40 preferably includes one or more controllable valves 54 between the corresponding linear actuator 34 and the fluid inlet and fluid return ports. The controllable valves 54 help ensure that each stiffness response system 40 has controlled fluid access to an external fluid supply. Therefore, during normal operation of the wind turbine, the stiffness response system 40 can be isolated from the external supply (fluid inlet / return port). This reduces the risk of fluid leakage, saves energy, and ensures that the linear actuator 34 and the associated stiffness response system 40 can act as a damper during operation of the wind turbine 10. This in turn helps to increase the service life of the tensioning system 32, and in particular reduces fatigue of the linear actuator components, the tensioning force member 36, and the blade connection member 28.

[0084] like Figure 3 As shown, in some examples, each stiffness response system 40 can include one or more overpressure relief valves 56. The overpressure relief valves 56 facilitate fluid communication with the fluid return port to reduce the pressure in the high-pressure or low-pressure sources 42, 44 when the pressure in these sources rises above a predetermined level. Therefore, the overpressure relief valves 56 help promote safe and reliable operation of the tensioning system 32.

[0085] The wind turbine 10 and associated method of operating the wind turbine 10 described herein provide a number of advantages over prior art wind turbines. As described above, the blade connection member 28 offloads (i.e., transfers) a portion of the loads to which the blade 20 is subjected in use to a location around the inboard portion 30 and the blade root 22. This enables the use of larger (i.e., longer) wind turbine blades 20 without increasing the size and strength of the root 22 of the blade 20, or with a smaller increase in the size and strength of the root 22 of the blade 20, as compared to a wind turbine without the blade connection member 28. As a result, the diameter of the rotor 16 may be increased without necessarily increasing the size of the rotor hub 18 and the associated interface with the blade 20, or with a smaller increase in the size of the rotor hub 18 and the associated interface with the blade 20.

[0086] Furthermore, as described above, the tensioning system 32 and the method of operating the wind turbine 10 enable control of the blade load distribution between the inboard portion 30 and the root 22 of the blade 20 and the blade connection member 28. In particular, the linear actuator 34 can be configured to adjust the stiffness and tension of its associated blade connection member 28, which means that the tension in the blade connection member 28 can be maintained within a safe range. By facilitating adjustment of the stiffness and tension of the blade connection member 28, the linear actuator 34 of the tensioning system 32 helps to ensure that the varying loads to which the blade 20 is subjected during use are able to be adjusted within the blade 2022P00030WOCN(JPHEN)

[0087] The tensioning system 32 may be configured to evenly distribute the tension in the blade connection member 28 between the inner portion 30 of the blade connection member 20 and the associated blade connection member 28. Furthermore, by facilitating adjustment of the stiffness and tension of the blade connection member 28, the tensioning system 32 advantageously helps maintain a given tension in the blade connection member 28 even under factors that change during operation of the wind turbine 10. For example, the stiffness and tension of the blade connection member 28 may be adjusted using the tensioning system 32 to account for manufacturing tolerances, material creep over time, and changes in material properties due to temperature changes, just to name a few possible examples.

[0088] The description provided herein is intended to show multiple possible examples of the invention. Features described above with respect to any example may be easily combined with any other features described with reference to a different example without departing from the scope of the invention as defined in the appended claims.

Claims

1. A wind turbine (10), comprising: Tower (12); A nacelle (14) mounted on the tower; a rotor (16) mounted to the nacelle, the rotor comprising a hub (18) and at least three wind turbine blades (20), each blade extending between a root (22) and an end (24), each blade further comprising a connection point (26) between the root and the end; a plurality of blade connection members (28), each blade connection member connected between corresponding connection points of a pair of wind turbine blades; as well as A tensioning system (32) for adjusting the tension in each blade connection member, the tensioning system comprising a plurality of linear actuators (34), each linear actuator being coupled between the hub and a corresponding blade connection member and each linear actuator being configured to adjust the tension in the blade connection member.

2. The wind turbine (10) according to claim 1, wherein: Each linear actuator (34) has an adjustable length to facilitate adjustment of tension in the blade connection member (28).

3. The wind turbine (10) according to claim 1 or claim 2, wherein: The linear actuator (34) is an electric linear actuator.

4. The wind turbine (10) according to claim 1 or claim 2, wherein: The linear actuator (34) is a hydraulic actuator or a pneumatic actuator.

5. The wind turbine (10) according to claim 4, wherein: Each linear actuator (34) includes a piston (46), wherein the tensioning system (32) further includes a plurality of stiffness response systems (40), each stiffness response system (40) including a high pressure fluid source (42) and a low pressure fluid source (44), Each high pressure fluid source is selectively fluidly coupled to a first side of a piston in a linear actuator, and each low pressure fluid source is selectively fluidly coupled to a second side of a piston in the linear actuator to facilitate controlling a stiffness response of the linear actuator.

6. The wind turbine (10) according to claim 5, wherein: The high-pressure fluid source (42) is a high-pressure accumulator, the low-pressure fluid source (44) is a low-pressure accumulator, and the pressures in the high-pressure accumulator and the low-pressure accumulator determine the stiffness response of the linear actuator (34).

7. A wind turbine (10) according to claim 5 or claim 6, wherein: The high pressure fluid sources (42) are selectively fluidically coupled to each other, and / or wherein the low pressure fluid sources (44) are selectively fluidically coupled to each other.

8. A wind turbine (10) according to any preceding claim, wherein: Each linear actuator (34) is coupled to a corresponding blade connection member (28) via a separate tensioning force member (36).

9. The wind turbine (10) according to claim 8, wherein: Each linear actuator (34) is rotatably coupled to the hub (18) such that the linear actuator is free to rotate relative to the hub to self-orient according to the tensioning force in the tensioning force member (36).

10. A method of operating a wind turbine (10), the wind turbine comprising: Tower (12); A nacelle (14) mounted on the tower; a rotor (16) mounted to the nacelle, the rotor comprising a hub (18) and at least three wind turbine blades (20), each blade extending between a root (22) and an end (24), each blade further comprising a connection point (26) between the root and the end; a plurality of blade connection members (28), each blade connection member connected between corresponding connection points of a pair of wind turbine blades; and a tensioning system (32) comprising a plurality of linear actuators (34), each linear actuator coupled between the hub and a respective blade connection member; The method comprises: Each linear actuator is adjusted according to the tension in the corresponding blade connection member, thereby adjusting the tension in the blade connection member.

11. The method according to claim 10, wherein: Each linear actuator (34) has an adjustable length, and wherein adjusting each linear actuator includes adjusting the length of the respective linear actuator, thereby adjusting the tension in the blade connection member (28).

12. The method of claim 11, further comprising setting a target tension of the blade connection member and, depending on the tension of the blade connection member (28) in use, a) extending the linear actuator (34) or b) retracting the linear actuator to maintain the target tension in the blade connection member.

13. The method according to claim 11 or claim 12, wherein: The linear actuator (34) is a hydraulic actuator or a pneumatic actuator, and wherein, in use, the linear actuator extends and retracts in response to pressure without any active electronic control input.

14. The method according to claim 13, wherein: Each linear actuator (34) includes a piston (46), wherein the tensioning system (32) includes a plurality of stiffness response systems (40), each stiffness response system including a high pressure fluid source (42) and a low pressure fluid source (44), each high pressure fluid source selectively fluidly coupled to a first side of a piston in the linear actuator, and each low pressure fluid source selectively fluidly coupled to a second side of a piston in the linear actuator, The method also includes controlling a stiffness response of the linear actuator by controlling a pressure of the high pressure fluid and a pressure of the low pressure fluid.

15. The method according to claim 14, wherein: The high pressure fluid source (42) is a high pressure accumulator, the low pressure fluid source (44) is a low pressure accumulator, and wherein controlling the stiffness response of the linear actuator (34) includes controlling the pressure in the high pressure accumulator and / or the pressure in the low pressure accumulator.

16. The method according to claim 14 or claim 15, wherein: The high pressure fluid sources (42) are selectively fluidically coupled to one another, and wherein the low pressure fluid sources (44) are selectively fluidically coupled to one another, the method further comprising: equalizing pressure in the high pressure fluid sources by fluidly coupling the high pressure fluid sources to one another, rotating the rotor (16) at least one full revolution, and then fluidly decoupling the high pressure fluid sources from one another; and Pressures in the low pressure fluid sources are equalized by fluidly coupling the low pressure fluid sources to one another, rotating the rotor at least one full revolution, and then fluidly decoupling the low pressure fluid sources to one another.

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