Variable pitch control wind turbine with blade connection members

Abstract

A variable pitch controlled wind turbine (1) is disclosed, comprising a tower (2), a nacelle (3) mounted on the tower (2), a hub (4) rotatably mounted on the nacelle (3), and at least three wind turbine blades (5). Each wind turbine blade (5) extends between a root end (10) connected to the hub (4) via a pitch mechanism and a tip end. The wind turbine (1) further comprises at least three blade connection members (6), each blade connection member (6) extending between a connection point (7) on one wind turbine blade (5) and a connection point (7) on an adjacent wind turbine blade (5), the connection points (7) being arranged at a distance from the root end (10) and at a distance from the tip end of the wind turbine (5). The wind turbine (1) further comprises at least three pretension members (8), each pretension member (8) being connected to one of the blade connection members (6) and to a hub portion (4, 9, 26), the pretension members (8) thereby providing a pretension force in the blade connection members (6).

Description

Technical Field

[0001] The present invention relates to a pitch-controlled wind turbine, which includes a tower, a nacelle mounted on the tower, a hub rotatably mounted on the nacelle, and at least three wind turbine blades connected to the hub via a pitch mechanism. Background Technology

[0002] During wind turbine operation, the components of a wind turbine are subjected to various loads. For example, the wind turbine blades are affected by loads from gravity acting on them, wind pressure, and changes in wind direction or speed, turbulence, etc. Gravity acting on the wind turbine blades primarily results in edgewise loads, while wind primarily results in flapwise loads.

[0003] As the size of wind turbines increases, so does the load on them. To handle this increased load, the amount of material used in manufacturing the wind turbines can be increased. However, this increases the weight of the wind turbines and the manufacturing cost. Summary of the Invention

[0004] The purpose of embodiments of the present invention is to provide a pitch-controlled wind turbine in which the edge and / or flapping loads on the wind turbine blades are reduced compared to prior art wind turbines of the same length.

[0005] The present invention provides a pitch-controlled wind turbine comprising a tower, a nacelle mounted on the tower, a hub rotatably mounted on the nacelle, and at least three wind turbine blades, wherein each wind turbine blade extends between a root end and a tip end connected to the hub via a pitch mechanism. The wind turbine also includes at least three blade connection members, each blade connection member extending between a connection point on one wind turbine blade and a connection point on an adjacent wind turbine blade, wherein the connection point on a given wind turbine blade is arranged at a distance from the root end of the wind turbine blade and at a distance from the tip end of the wind turbine blade.

[0006] The wind turbine also includes at least three pretensioning members, each of which is connected to one of the blade connecting members and to the hub portion, thereby providing pretension force in the blade connecting member to which it is connected.

[0007] Therefore, the present invention provides a pitch-controlled wind turbine, namely a wind turbine comprising wind turbine blades capable of rotating about a pitch axis of substantially longitudinal direction in order to adjust the angle of attack between the wind turbine blades and the incoming wind during wind turbine operation.

[0008] The wind turbine includes a tower and a nacelle mounted on the tower. It also includes a hub rotatably mounted on the nacelle and at least three wind turbine blades. Each wind turbine blade extends between its root and tip, connected to the hub via a pitch mechanism. Therefore, relative to the nacelle, the wind turbine blade rotates with the hub, while the tip of the blade points away from the hub. Because the wind turbine blades are connected to the hub via the pitch mechanism, each blade can rotate relative to the hub, i.e., perform pitch movement. The hub and wind turbine blades form the rotor of the wind turbine. Therefore, this type of wind turbine is a horizontal axis wind turbine (HAWT), whose main axis is typically within 10° of the horizontal direction. The blade root is connected to the hub via the pitch mechanism, meaning the blade root is connected to the hub by the pitch mechanism, thus allowing the blade to pitch along the longitudinal pitch axis.

[0009] The nacelle is typically mounted on the tower via a yaw system, which allows the nacelle to rotate relative to the tower in order to properly position the rotor according to the direction of the wind.

[0010] The wind turbine also includes at least three blade connecting members. Each blade connecting member extends between a connection point on one wind turbine blade and a connection point on an adjacent wind turbine blade. Thus, each connecting member connects two adjacent wind turbine blades to each other. The connection point on a given wind turbine blade is arranged at a distance from the root end of the blade (such as at least 10% of the length of the wind turbine blade from the root to the tip) and at a distance from the tip end of the wind turbine blade (such as at least 10% of the length of the wind turbine blade from the root to the tip). Therefore, the connection point is not located at either the root or the tip, but rather at a position between these two ends, and the distance to each end is not zero, such as at least 10% of the length of the wind turbine blade from the root to the tip.

[0011] The wind turbine also includes at least three pretensioning members. Each pretensioning member is connected to one of the blade connecting members and to the hub. Thus, the pretensioning members pull the blade connecting members toward the hub, thereby providing tension to the blade connecting members, so that the blades connected by the blade connecting members are tensioned toward each other.

[0012] In this document, the term “member” in connecting members and pretensioning members shall be interpreted broadly to encompass any suitable type of tensioning member, such as braided or twisted ropes of metal wire (e.g., steel wire), polymer fibers (e.g., polyethylene, polypropylene, nylon, polyester, aramid, inorganic fibers (e.g., carbon fiber), or mixed ropes of such materials, composite pultrusions, metal rods, etc.

[0013] The stiffness of the blade connecting member can be different from that of the pretensioning member, or the stiffness of the blade connecting member and the pretensioning member can be the same.

[0014] In this document, the term "hub portion" should be interpreted as referring to the hub, or a component or element attached to the hub, meaning that it rotates with the hub relative to the nacelle. Such a component or element may be attached to the outer surface of the hub, protrude from the hub, be positioned inside the hub, or be positioned in any other suitable manner as long as it rotates with the hub.

[0015] The pretensioning member can be connected to the blade connection member at a certain distance from each of the connection points on the wind turbine blade, for example, at a distance substantially equal to the connection points, i.e., along the blade connection member at approximately halfway down the wind turbine blade.

[0016] Pre-tensioned blade connections allow wind turbine blades to support each other, meaning that the loads on the wind turbine blades (especially edge and flapping loads) are "shared" between the blades via these pre-tensioned connections. Therefore, during wind turbine operation, the loads on the wind turbine blades can be handled with reduced material thickness. Furthermore—or alternatively—this can be achieved with the same or reduced weight and / or with the same or reduced manufacturing cost compared to existing blades of the same length.

[0017] Since the pretension in the blade connection is provided by a pretensioning member that interconnects the blade connection and the hub, it is possible to control the pretension force in both the pretensioning member and the blade connection from the hub, thus providing a convenient path for maintaining or adjusting the pretension force. Furthermore, it is possible to adjust how much the average swing load is affected at a given pretension. For example, a shorter pretensioning member will result in a larger change in the average swing bending moment, while a longer pretensioning member will result in a larger reduction in the amplitude of the edge bending moment. Finally, by using a pretensioning member, the risk of slack in the blade connection is reduced, because the pretensioning system can be softer than the blade connection, or the tension and / or length of the pretensioning member can be actively adjusted.

[0018] The pretensioning member can be arranged to provide an adjustable pretension force in the blade connection member. The tension force in the blade connection member can be determined based on the tension force in the pretensioning member and the angle between the pretensioning member and the blade connection member.

[0019] According to this embodiment, the pretension force in the blade connection member can be adjusted by appropriately adjusting the pretensioning member or an adjustable pretensioning mechanism connected to the pretensioning member. For example, the pretension force can be adjusted during installation to accurately obtain the desired pretension force and / or to properly balance the pretension forces relative to each other in the respective blade connection members.

[0020] Alternatively or additionally, the pretension can be adjusted continuously or repeatedly during wind turbine operation. This can be related, for example, to ensuring that the pretension is appropriate under the prevailing operating conditions (e.g., regarding environmental conditions such as wind speed, wind shear, turbulence conditions, temperature, humidity, etc.) and / or wind turbine conditions (e.g., blade azimuth, blade pitch angle, and tip speed / rotational (angular) velocity).

[0021] By designing pretensioning components to provide adjustable pretension to the blade connection components, it is possible to obtain the desired pretension accurately in a simple way, and even adapt the pretension to the operating conditions at the time.

[0022] One way to adjust the pretension force is, for example, to roll up or unroll the pretensioner on a rotatable member, thereby adjusting the length of the pretensioner, extending / retracting to form part of the pretensioner, or using a linear actuator (such as a hydraulic actuator) that acts on the pretensioner.

[0023] Connection points can be located outside the outer surface of the wind turbine blades.

[0024] According to this embodiment, the blade connecting member is attached to the respective wind turbine blade at a location located outside the outer surface of the wind turbine blade (such as outside the outer casing of the wind turbine blade). For example, the blade connecting member may be attached to a structure located outside the wind turbine blade (such as outside the blade casing) but connected to it.

[0025] In one aspect of the invention, the connection points of a wind turbine blade are arranged adjacent to each other, such as structural elements close to each other or even sharing connection points. In certain cases, two blade connection members (connected to different blades at opposite ends) are connected to the same connection point (7) on a single blade. The advantage of this is that when tension is applied to the blade connection member, the blade is subjected to a resultant force, and therefore the blade is not exposed to tension forces from the blade connection member in two different directions. Furthermore, when the connection points are adjacent to each other or two blade connection members use the same connection point, it is possible to arrange the connection points of the two blade connection members closer to or even on the blade pitch axis.

[0026] By arranging the connection points outside the wind turbine blades, the surface of the wind turbine blades can remain largely intact. Furthermore, the wind turbine blades can be pitched without affecting the blade connection members, at least with the pitch axis carefully positioned relative to the connection points. The structure connecting the blade connection members to the wind turbine blades can, for example, be provided with a cover that improves the aerodynamic characteristics of the structure (e.g., in terms of increasing lift and / or reducing drag) to minimize the impact on the aerodynamic characteristics of the wind turbine blades.

[0027] The blade connection member can be connected to the respective wind turbine blade via a bearing structure mounted on or forming part of the wind turbine blade. The bearing structure can be, for example, a roller bearing, a plain bearing, a ball bearing, or any other suitable type of bearing.

[0028] The bearing structure ensures that the wind turbine blades are allowed to rotate relative to the blade connection member via the bearing structure. Therefore, the wind turbine blades can pitch without affecting the blade connection member, thus avoiding the application of undesirable loads, torsional forces, or tension forces to the blade connection member during pitch control. When the blade connection member is connected to the wind turbine blade via the bearing structure, it is preferable that the pitch axis passes through the blade at the spanwise position of the blade connection member. In particular, it is advantageous that the pitch axis passes through the shape formed by the bearing structure at this spanwise position.

[0029] When the bearing structure is, or includes, a ball bearing, the blade connection member can rotate freely about the connection point relative to the wind turbine blade. Therefore, at the connection point, only tension force is transmitted between the blade connection member and the wind turbine blade.

[0030] When the bearing structure protrudes from or is arranged circumferentially relative to the wind turbine blades, the bearing structure may be provided with a fairing or similar aerodynamic structure to improve the aerodynamic characteristics of the wind turbine blades in the bearing structure area.

[0031] The connection point on the wind turbine blade can preferably be arranged at a distance from the root tip, such that the distance is between 10% and 60% of the length of the wind turbine blade from the root tip to the tip, for example, between 20% and 50% of the length of the wind turbine blade, for example, between 25% and 40% of the length of the wind turbine blade, for example, about 30% of the length of the length of the wind turbine blade. In other cases, the connection point on the wind turbine blade is preferably arranged at a distance from the root tip, such that the distance is between 25% and 60% of the length of the wind turbine blade from the root tip to the tip, for example, between 35% and 55% of the length of the wind turbine blade, for example, between 40% and 50% of the length of the length of the wind turbine blade.

[0032] According to this embodiment, the connection points on the wind turbine blades are arranged at positions away from the root and tip of the wind turbine blades.

[0033] The location of the connection point along a wind turbine blade can be chosen in a way that appropriately balances various considerations. For example, positioning the connection point near the tip of the wind turbine blade results in very effective support of the blade via the blade connection member. However, this comes at the cost of significant drag generated by the blade connection member during rotor rotation, reducing energy production. On the other hand, positioning the connection point near the root of the wind turbine blade results in reduced drag from the blade connection member, minimizing the adverse effects on the wind turbine's energy production. However, the support of the wind turbine blade by the blade connection member will not be very effective. By positioning the connection point at a certain distance from the root (between 10% and 60% of the wind turbine blade's length), these considerations are balanced in such a way that effective support is achieved without introducing unacceptable drag. Furthermore, by positioning the connection point within this region, it is ensured that the blade connection member is attached to the wind turbine blade where the structural stiffness of the wind turbine blade is sufficiently high. For example, the structural stiffness of wind turbine blades decreases towards the tip. Therefore, connecting blade connecting components too close to the tip may cause significant pre-deformation of the wind turbine blades, which may hinder the blades' pitch control capability.

[0034] Connection points on wind turbine blades can be positioned where the ratio of the blade's thickness to its chord length is between 20% and 50%, such as between 25% and 35% or 30% and 45%. As mentioned above, this is also the area where the wind turbine blade strikes a balance between effective support and introduced drag, while maintaining sufficient structural rigidity.

[0035] Wind turbine blades can each consist of two independent parts, including an inner blade part at the root end and an outer blade part at the tip end. The inner blade part and the outer blade part are connected to each other at the split position, and the connection point on the wind turbine blade can be arranged at the split position.

[0036] According to this embodiment, each wind turbine blade is formed from two parts, namely an inner blade part and an outer blade part, which can be manufactured separately and then joined together to form a wind turbine blade. This is sometimes referred to as a "split-type wind turbine blade". This also allows the blade parts to be transported separately to the wind turbine site, so that even large wind turbine blades can be transported without introducing excessive transportation costs.

[0037] When using this type of split-type wind turbine blade, it has been found advantageous to position the connection point—the point where the blade connecting member is attached to the wind turbine blade—at the junction of the inner and outer blade sections. This is because suitable attachment structures can be added to the wind turbine blade at this location without significantly reducing its strength or aerodynamic characteristics. For example, when the blade connecting member is attached to the wind turbine blade via a bearing structure, the bearing structure can advantageously form the interface between the inner and outer blade sections.

[0038] The hub may include a hub member extending substantially along a direction defined by the hub's axis of rotation, and a pretensioning member may be attached to the hub member. The hub member may extend, for example, in front of the rotor plane defined by the rotor of the wind turbine, i.e., facing the oncoming wind in the case of a headwind wind turbine.

[0039] According to this embodiment, the pretensioning member is not directly connected to the hub, but rather to a member forming the hub portion, which extends from the hub along a direction defined by the hub's axis of rotation. Furthermore, the connection point between the pretensioning member and the hub member can be positioned at a distance from the point where the wind turbine blade connects to the hub, along the direction defined by the hub's axis of rotation. Therefore, the pretensioning member not only pulls the blade connecting member towards the hub but also along the hub's axis of rotation, thus moving it away from the tower. This also causes the wind turbine blade to be pulled in this direction, having an effect similar to that of introducing a cone angle. This reduces edge loads at the blade root, particularly flapping loads, and ensures tower clearance.

[0040] The hub assembly can be arranged to provide adjustable pretension and / or adjustable stiffness in the pretensioning member and / or blade connection member via the pretensioning member. According to this embodiment, as described above, the adjustable pretension is obtained by means of a mechanism connected to or forming part of the hub assembly. The adjustment mechanism can be, for example, a hydraulic or other type of (linear) actuator, such as an electric, pneumatic, or mechanical (such as a spring-loaded) actuator. In this case, the hub assembly can be provided with a hydraulic piston, for example, movable along a direction defined by the axis of rotation of the hub. Such a mechanism can be used, for example, to adjust the pretension in the blade connection member to handle flapping loads and / or control tower clearance during high-thrust operation of the wind turbine.

[0041] It has been found highly advantageous that the tension of each of the blade pretensioning members can be adjusted individually, as this allows for improved tension balance in the blade connection members. Furthermore, individual adjustment allows for better control and reduction of the risk of slack in the blade connection members. This is preferably achieved by actuating each pretensioning member separately with an independent adjustment mechanism, such as a hydraulic or another type of (linear) actuator, such as an electric actuation, pneumatic actuation, mechanical spring actuation, or a combination thereof. Surprisingly, it has been found that by using individually adjustable pretensioning members, the actuators can also act as vibration dampers for the blade connection members and pretensioning members by adjusting the effective stiffness of the pretensioning members. Moreover, carefully controlled piston movement can reduce vibration in the blade connection members and / or pretensioning members, thereby reducing fatigue wear on wind turbine generator components such as blade connection members, pretensioning members, and wind turbine blades, and / or reducing noise emissions from the wind turbine generator. Therefore, the use of individually adjustable pretensioning members has been found to be highly advantageous.

[0042] The hub assembly may include an adjustment mechanism comprising a linear actuator arranged in the direction between the hub's axis of rotation and the connection point between the blade connecting member and the pretensioning member. This allows for simple and effective individual adjustment of the distance between the connection points of the hub and (multiple) blade connecting members, thereby adjusting the tension in the corresponding pretensioning member. The linear actuator in this aspect of the invention is preferably a hydraulic linear actuator (such as a hydraulic piston) or a pneumatic actuator, as this allows for controlled movement under high tension and has been found to also act as a vibration damper for the blade connecting member and / or the pretensioning member by adjusting the effective stiffness of the pretensioning member and / or by offsetting vibrations through piston movement. Hydraulic and pneumatic actuators have been found particularly advantageous because they can be directly switched from a master mode (where it controls the length of the actuator piston) to a first slave mode (where it maintains the tension of the blade connecting cable or pretensioning cable in response to blade wind load) and / or a second slave mode (where it suppresses vibrations of the blade connecting cable or pretensioning cable) based on sensor input related to tension or vibration. Other types of linear actuators are also useful, such as electric actuators, mechanical (such as spring-type) actuators, or combinations of these (such as combinations of springs and hydraulic actuators).

[0043] Alternatively, pretensioning members can be connected to a common point located within the hub. This common point within the hub can be "floating," meaning it can move slightly to allow for load sharing among the pretensioning members during wind turbine operation. Furthermore, connecting the pretensioning members to the common point allows the pretensioning members to be tensioned from that point. The advantage of this is that only one location needs to be approached to tension all the pretensioning members, for example, by moving the common point forward / backward along the hub's axis of rotation, or by moving the common point in a direction away from the hub's axis of rotation, thus changing the ratio of tension forces among all the pretensioning members. This movement can, for example, be performed using one or more hydraulic actuators.

[0044] The pretension force of the pretensioning members is set and / or adjusted so that the blade connection members can be installed or commissioned at once as part of the wind turbine installation. However, it is preferable to adjust the pretension force multiple times, such as periodically, for example, after measuring the pretension force of at least one of the blade connection members or at least one of the pretensioning members. The measurement may be part of a periodic monitoring procedure via at least one sensor arranged in the blade, blade connection members, pretensioning members, and / or adjustment mechanism. In one case, the pretension force is adjusted as the blades are oriented during rotor rotation. In another case, the pretension force is adjusted as part of the pitch control process, i.e., before, during, and / or after pitch control.

[0045] Wind turbine blades can be defined with a taper angle ranging from 2° to 20°, such as between 5° and 10°. In this document, the term "taper angle" should be interpreted as the angle between a plane substantially perpendicular to the direction defined by the axis of rotation of the hub and a direction along which the wind turbine blade extends. Therefore, increasing the taper angle positions the tip of the wind turbine blade further away from the plane orthogonal to the axis of rotation of the hub and passing through the center of the blade root.

[0046] Introducing a cone angle increases tower clearance and reduces wagging load at the root of wind turbine blades.

[0047] Connection points on wind turbine blades can be located at or near the pitch axis of the wind turbine blade. In this document, the term "pitch axis" should be interpreted as the axis around which the wind turbine blade rotates during pitch movement. In this document, a connection point located "at or near" the pitch axis means that the distance from the connection point to the pitch axis (when the blade is not wind-loaded) is within a) 2% of the rotor diameter, and b) the highest of the two blade chord lengths at the connection point.

[0048] Therefore, according to this embodiment, when the wind turbine blades rotate during pitch control, the connection point does not move, or moves only to a very limited extent. Correspondingly, the blade connection members also do not move, or move only to a very limited extent. This minimizes the variation in tension of the blade connection members and minimizes the force applied at the connection point. Furthermore, this preserves complete freedom of pitch control.

[0049] Alternatively, the connection points on the wind turbine blades can be positioned offset relative to the pitch axis. In this case, the blade connection components will move during pitch control. In this configuration, the wind turbine blades can be interconnected in a manner that allows for collective pitch control of the wind turbine blades, but only allows for individual pitch control to a limited extent.

[0050] The relative position of the pitch axis and the connection point can be advantageously chosen in a way that minimizes the pitch load (i.e., the load required to pitch the wind turbine blades at various wind speeds). In particular, it has been found highly advantageous to arrange the connection point of the blade connection member at or near the pitch axis of the blade as defined above.

[0051] Each wind turbine blade may have at least one groove formed in the outer casing of the wind turbine blade, the groove being arranged to receive a portion of the blade connecting member. The groove may advantageously be formed on the pressure side of the wind turbine blade.

[0052] According to this embodiment, the blade connection member can be received in a corresponding groove at certain pitch angles, while at other pitch angles it is arranged outside the corresponding groove. This allows the connection point to be located at or near the pitch axis, even extending within the wind turbine blade, and the wind turbine blade can still pitch move without colliding with the blade connection member.

[0053] Each of the wind turbine blades can be bent in at least one direction between its root and tip, such that the pitch axis of the wind turbine blade (at least at the junction) is located externally relative to the wind turbine blade. The wind turbine blade can be bent in the flapping direction and / or the edge direction. For example, the bending of the wind turbine blade can be in the form of a sweeping motion. The curve can extend along the entire length of the wind turbine or only along a portion of the length of the wind turbine blade. For example, in the case where the wind turbine blade is divided into inner and outer blade portions, then only one of the blade portions (e.g., the outer blade portion) can be bent. Alternatively or additionally, the bending can be introduced in the form of an angle between the inner and outer blade portions.

[0054] According to this embodiment, the connection point can be located at or near the pitch axis, while still being positioned outside the wind turbine blade. This allows the wind turbine blade to pitch without colliding with the blade connection members.

[0055] Each of the wind turbine blades can extend in a longitudinal direction, which can form a non-zero angle relative to the pitch axis of the wind turbine blade's pitch mechanism. This non-zero angle can be, for example, within the range of 0.1° to 10.0°, such as within the range of 0.5° to 3.0°. Because each wind turbine blade extends in a direction forming a non-zero angle with respect to the pitch axis, the pitch axis and the wind turbine blade's direction do not coincide. Therefore, during pitch movement, the wind turbine blades rotate about an axis that does not coincide with their longitudinal axis.

[0056] According to this embodiment, similar to the above situation, since the axes do not coincide, the pitch axis can also be arranged outside the wind turbine blade at the connection point.

[0057] A non-zero angle between the pitch axis and the longitudinal direction of the wind turbine blade can be achieved, for example, by introducing one or more wedges (e.g., in the form of one or more shims) at the root end of the wind turbine blade. In this case, one or more shims can be connected to the hub and the wind turbine blade via individual bearings, or they can be connected to adjacent shims. Therefore, the shims can rotate independently, thereby changing the angle between the pitch axis and the longitudinal direction of the wind turbine blade. Furthermore, these bearings can operate independently, for example, collective pitch via one bearing and individual pitch via another. This reduces the load on the pitch mechanism, particularly on the bearings.

[0058] The pretensioning member and / or blade connection member may include a vibration damping mechanism.

[0059] According to this embodiment, vibrations of the pre-tensioned members and / or blade connecting members can be suppressed during wind turbine operation, thereby reducing the load on the members and the wind turbine blades. Furthermore, the wire ropes can passively provide additional structural damping for blade movement because the individual fibers in the wire ropes will interact when stretched.

[0060] Vibration suppression mechanisms can be passive, such as oil dampers or flexible components. In this case, vibration suppression is provided automatically during wind turbine operation. Alternatively, vibration suppression mechanisms can be active, such as hydraulic cylinders. In this case, vibration suppression can be actively controlled.

[0061] The pretensioned members and / or blade connecting members may be equipped with aerodynamic devices. According to this embodiment, by providing aerodynamic devices to the members and thereby improving the aerodynamic characteristics of the members, the adverse aerodynamic effects introduced by the mounting members between the wind turbine blades are reduced. Aerodynamic devices can be, for example, of the kind that increase lift and / or reduce drag of the members. For example, the aerodynamic devices can be in the form of airfoils or teardrops.

[0062] Wind turbines can be upwind turbines. In this case, the turbine rotor faces the oncoming wind, so the wagging load originating from the wind on the turbine blades pushes the blades towards the hub. Blade connection components are well-suited for mitigating this wagging load.

[0063] Alternatively, a wind turbine can be a downwind turbine. In this case, the rotor of the wind turbine is in the opposite direction to the wind, so the wagging load on the wind turbine blades originating from the wind pushes the wind turbine blades away from the hub. Attached Figure Description

[0064] The invention will now be described in further detail with reference to the accompanying drawings, in which: Figure 1 and Figure 2 The illustration shows a wind turbine according to a first embodiment of the present invention. Figure 3a and Figure 3b This is a side view of a wind turbine according to a second embodiment of the present invention. Figure 4-6 The illustration shows a wind turbine blade of a wind turbine according to an embodiment of the present invention. Figure 7-10 The illustration shows a wind turbine blade of a wind turbine according to an alternative embodiment of the present invention. Figure 11 and Figure 12 The illustration shows a curved wind turbine blade for a wind turbine according to an embodiment of the present invention. Figure 13 The diagram illustrates the pitch control of a wind turbine blade, with the pitch axis positioned externally relative to the wind turbine blade. Figure 14 and Figure 15 The illustrations depict the attachment of a blade connecting member to a wind turbine blade according to two embodiments of the present invention. Figure 16 and Figure 17 The illustrations depict the attachment of a pre-tensioned member to a wheel hub according to two embodiments of the present invention, and Figure 18 The illustration shows a hub component with a separate tension adjustment mechanism. Detailed Implementation

[0065] Figure 1 and Figure 2 A pitch-controlled wind turbine 1 according to a first embodiment of the present invention is shown. Figure 1 This is a front view of wind turbine 1. Figure 2 This is a side view of wind turbine 1.

[0066] The wind turbine 1 includes a tower 2 and a nacelle 3 mounted on the tower 2. A hub 4, which carries three wind turbine blades 4, is rotatably mounted on the nacelle 3.

[0067] Three blade connecting members 6 connect adjacent wind turbine blades 5 to each other between connection points 7 of the wind turbine blades 5. Furthermore, the wind turbine 1 includes three pretensioning members 8, each extending between one of the blade connecting members 6 and the hub 4. Therefore, the pretensioning members 8 provide pretension force in the blade connecting members 6.

[0068] The pre-tensioned blade connecting member 6 enables the wind turbine blades 5 to support each other, meaning that the loads on the wind turbine blades 5 (especially edge loads and flapping loads) are "shared" among the wind turbine blades 5.

[0069] Figure 3a and Figure 3b This is a side view of a pitch-controlled wind turbine 1 according to a second embodiment of the present invention. Figure 3a and Figure 3b Wind turbine 1 and Figure 1 and Figure 2 The wind turbine 1 is very similar, so it will not be described in detail here.

[0070] exist Figure 3a and Figure 3b In this embodiment, the pretensioning member 8 is not directly connected to the hub 4. Instead, the pretensioning member 8 is connected to a hub portion in the form of a hub member 9, which extends substantially from the hub 4 along a direction defined by the axis of rotation of the hub 4. Therefore, with Figure 1 and Figure 2 Compared to the previous embodiment, the connection point of the pretensioning member 8 is further away from the hub 4, and thus further away from the location where the wind turbine blade 5 is connected to the hub 4. As a result, the pretensioning member 8 also pulls the blade connecting member (not shown) away from the hub 4 and away from the tower 2. This also causes the wind turbine blade 5 to be pulled in this direction, thereby further reducing the edge load and flapping load at the root of the wind turbine blade 5 and ensuring tower clearance, similar to the effects obtained when introducing the cone angle. Due to the use of the connecting member, it has been found that this tends to result in an increase in the stiffness of the internal portion of the blade.

[0071] Figure 4-6 The illustration shows a wind turbine blade 5 for a wind turbine according to an embodiment of the present invention. Figure 4 This is a perspective view of wind turbine blade 5. Figure 5 This is a cross-sectional view of wind turbine blade 5 along the longitudinal direction. Figure 6 This is a cross-sectional view of wind turbine blade 5 along the chord direction.

[0072] The wind turbine blade 5 includes: a root end 10 adapted to be connected to a hub via a pitch mechanism; and a tip end (not shown) positioned opposite to the root end 10. The wind turbine blade 5 is formed by an inner blade portion 5a including the root end 10 and an outer blade portion 5b including the tip end. The inner blade portion 5a and the outer blade portion 5b are interconnected to form the wind turbine blade 5.

[0073] A bearing structure 11 is arranged at the junction of the inner blade portion 5a and the outer blade portion 5b. Two blade connecting members 6 are connected to the wind turbine blade 5 via connection points 7 on the bearing structure 11. Therefore, when the wind turbine blade 5 performs pitch control, the blade connecting members 6 do not rotate with the wind turbine blade 5. This avoids applying undesirable torsional or tensional forces to the blade connecting members 6 during pitch control of the wind turbine blade 5.

[0074] exist Figure 5 As can be seen, the bearing structure 11 includes a portion 11a that is bolted to the blade portions 5a and 5b, and a portion 11b to which the blade connecting member 6 is attached. The two portions 11a and 11b of the bearing structure 11 can rotate relative to each other.

[0075] Figure 6 yes Figure 4 A cross-sectional view of the wind turbine blade 5 along the chord direction at the location of the bearing structure 11. Therefore, Figure 6 It is essentially a side view of the bearing structure 11, and clearly shows the two parts 11a and 11b of the bearing structure 11.

[0076] Figure 7-10 The illustration shows a wind turbine blade 5 of a wind turbine according to an alternative embodiment of the present invention. Figure 7 This is a perspective view of wind turbine blade 5. Figure 8-10 This is a cross-sectional view of wind turbine blade 5 along the chord direction.

[0077] Figure 7-10 Wind turbine blades 5 and Figure 4-6 The wind turbine blades 5 are very similar, so they will not be described in detail here.

[0078] exist Figure 7-10 In the wind turbine blade 5, the bearing structure 11 is arranged inside the outer casing of the wind turbine blade 5. This is in Figure 7 As can be seen, the connection point 7 between the bearing structure 11 and the blade connecting member 6 is also arranged within the outer casing of the wind turbine blade 5, and is more compact than... Figure 4-6 The illustrated embodiment is closer to the pitch axis 12 of the wind turbine blade 5. This minimizes the load on the blade connection member 6 and the force applied at the connection point 7.

[0079] To prevent the wind turbine blade 5 from colliding with the blade connecting member 6 during pitch control, the wind turbine blade 5 is provided with a groove 13, which is formed on the pressure side of the wind turbine blade 5. The groove 13 is arranged to receive a portion of the blade connecting member 6. Figure 7In the middle, one of the blade connecting members 6 is received in the groove 13.

[0080] Figure 8 yes Figure 7 A cross-sectional view of the wind turbine blade 5 along the chord direction. The wind turbine blade 5 is located in the blade connecting member 6 where the pitch angle is received in the groove 13. Pitch movement is indicated by arrow 14.

[0081] exist Figure 9 In the middle, the wind turbine blade 5 has been moved to where the blade connecting member 6 is no longer received in the groove 13 at the pitch angle.

[0082] Figure 10 A similar embodiment, in the form of a cross-sectional view of a wind turbine blade 5 along the chord direction, is illustrated. The wind turbine blade 5 is positioned such that one of the blade connecting members 6 is received in a groove 13 at a pitch angle. Figure 10 In this embodiment, two aerodynamic devices in the blade connecting member 6 are provided in the form of airfoils 15. This improves the aerodynamic characteristics of the blade connecting member 6, thereby minimizing the adverse effects on the efficiency of the wind turbine introduced by providing the blade connecting member 6 for the wind turbine.

[0083] Figure 11 and Figure 12 The illustration shows a curved wind turbine blade 5 for a wind turbine according to an embodiment of the present invention. Figure 11 The wind turbine blade 5 is shown along the chord length direction. Figure 12 The wind turbine blade 5 is shown along its perpendicular direction.

[0084] Figure 11 and Figure 12 The dashed lines represent examples of prior art wind turbine blades, and the solid lines represent wind turbine blade 5 for a wind turbine according to an embodiment of the present invention. Dashed line 16 marks the locations where the wind turbine blade 5 is divided into inner and outer portions.

[0085] Figure 11 The leading edge 17 and trailing edge 18 of each of the represented wind turbine blades 5 are shown. It can be seen that the wind turbine blade 5 according to the invention is bent relative to the prior art wind turbine blade 5 in such a way that, on the leading edge 17 side and at the split position 16, the pitch axis 12 of the wind turbine blade 5 according to the invention is positioned outside the wind turbine blade 5.

[0086] Figure 12The pressure side 19 and suction side 20 of each of the represented wind turbine blades 5 are shown. Also along this direction, the wind turbine blade 5 according to the invention is bent relative to the prior art wind turbine blade 5 in such a way that, on the pressure side 19 and at the split position 16, the pitch axis 12 of the wind turbine blade 5 according to the invention is positioned outside the wind turbine blade 5.

[0087] Therefore, according to one embodiment of the invention, the wind turbine blade 5 for a wind turbine is curved in two directions, having a shape such that the pitch axis 12 of the wind turbine blade 5 is arranged at the split position 16 outside the leading edge 17 and outside the pressure side 19 of the wind turbine blade 5. Thus, if the blade connecting member is connected to the wind turbine blade 5 at the split position 16, the connection point can be located at or near the pitch axis 12, but outside the wind turbine blade 5. Consequently, the blade connecting member can be connected to the wind turbine blade 5 in a simple manner, while reducing the load on the blade connecting member and the connection point during pitch control of the wind turbine blade 5.

[0088] It is important to note that Figure 11 and Figure 12 The wind turbine blade 5 is not drawn to scale in order to emphasize the modified shape of the wind turbine blade 5 according to the invention.

[0089] Figure 13 The illustration shows the pitch of a wind turbine blade 5, with the pitch axis 12 arranged externally relative to the wind turbine blade 5. The dashed lines represent prior art wind turbine blades 5, and the solid lines represent wind turbine blades 5 for a wind turbine according to an embodiment of the present invention, at two extreme pitch angles.

[0090] The blade connecting member is connected to the wind turbine blade 5 according to the invention at connection point 7, which is located outside the wind turbine blade 5 and at or near the pitch axis 12. Figure 13 It can be seen that this allows the wind turbine blade 5 to move in a pitched manner without affecting the blade connection components.

[0091] Figure 14 The illustration shows a wind turbine blade 5 for a wind turbine according to an embodiment of the present invention. The wind turbine blade 5 includes an inner blade portion 5a and an outer blade portion 5b interconnected via a casting structure 21. A blade connecting member 6 is connected to the casting structure 21 via a hinge 22, which forms a connection point 7 between the blade connecting member 6 and the wind turbine blade 5. The wind direction is indicated by arrow 27.

[0092] Because the blade connecting member 6 is connected to the wind turbine blade 5 via hinge 22, the blade connecting member 6 is allowed to move relative to the wind turbine blade 5. This can be relevant, for example, during pitch control of the wind turbine blade 5.

[0093] Figure 15 The illustration shows a wind turbine blade 5 for a wind turbine according to an alternative embodiment of the present invention. Figure 14 Similar to other embodiments, the wind turbine blade 5 includes an inner blade portion 5a and an outer blade portion 5b interconnected via a cast structure 21. Figure 15 In this embodiment, the blade connection member 6 is connected to the cast structure 21 via a ball bearing 23 and a flexible cable 24. The ball bearing 23 allows the blade connection member 6 to move freely relative to the wind turbine blade 5. The flexible cable 24 provides damping for the blade connection member 6. The wind direction is indicated by arrow 27.

[0094] Figure 16 This is a cross-sectional view of the hub 4 of a wind turbine according to an embodiment of the present invention. Three pretensioning members 8 are connected to the hub 4. The pretension force provided by the pretensioning members 8 can be adjusted individually by means of an adjustment mechanism 25 arranged within the hub 4. Therefore, the pretension force of all three pretensioning members 8 can be adjusted from within the hub 4. Thus, the individual adjustment of the pretension force of the pretensioning members 8 can be easily coordinated and performed substantially simultaneously to avoid uneven forces on the wind turbine blades due to large differences in the pretension force of the pretensioning members 8.

[0095] Figure 17 This is a cross-sectional view of a hub 4 for a wind turbine according to an alternative embodiment of the present invention. Figure 17 The hub 4 also has three pretensioning members 8 connected to it, and the pretension force provided by the pretensioning members 8 can be adjusted individually by means of the adjustment mechanism 25. However, in Figure 17 In the hub 4, pretensioning members 8 are connected to a common anchoring portion 26 arranged within the hub 4. The anchoring portion 26 is floating, meaning it is allowed to move within the hub 4 to a certain extent. Therefore, load sharing and balancing are achieved among the pretensioning members 8 during wind turbine operation.

[0096] Figure 18This is a view of the hub assembly 9, in which a separate tension adjustment mechanism 25 actuates each of the pretensioning members 8. The adjustment mechanism 25 forms part of the hub assembly 9 and is arranged in the direction between the axis of rotation of the hub (28) and the connection point between the blade connecting member (6) and the pretensioning member (7). Typically, the adjustment mechanism is arranged on an element (such as a tripod or beam) extending along the axis of rotation of the rotor to provide a stable anchor point for the adjustment mechanism. The adjustment mechanism preferably includes a linear actuator (such as hydraulic, electric, pneumatic, mechanical, or one of these). The hub assembly 9 may extend beyond the nose cone. Preferably, the hub assembly 9 extends far beyond the nose cone such that the direction of the pretensioning member intersects (intercepts) the plane of rotation downwind of the blade connection point 7, as this enhances the stiffness of the rotor.

Claims

1. A pitch-controlled wind turbine (1), comprising: Tower (2); nacelle (3) mounted on the tower (2); A hub (4) rotatably mounted on the nacelle (3); and at least three wind turbine blades (5), wherein each wind turbine blade (5) extends between a root end (10) and a tip end connected to the hub (4) via a pitch mechanism. The wind turbine (1) also includes at least three blade connecting members (6), each blade connecting member (6) extending between a connection point (7) on a wind turbine blade (5) and a connection point (7) on an adjacent wind turbine blade (5), wherein a connection point (7) on a given wind turbine blade (5) is arranged at a distance from the tip end of the wind turbine blade (5) and a distance from the root end (10). The wind turbine (1) further includes at least three pretensioning members (8), each pretensioning member (8) being connected between adjacent wind turbine blades (5) to one of the blade connecting members (6) and to the hub portion (4, 9, 26), each pretensioning member (8) thereby providing pretension force in the blade connecting member (6) to which it is connected.

2. The pitch-controlled wind turbine (1) according to claim 1, wherein, The pretensioning member (8) is arranged to provide an adjustable pretension force in the blade connection member (6).

3. The pitch-controlled wind turbine (1) according to claim 1 or 2, wherein, The connection point (7) is located outside the outer surface of the wind turbine blade (5).

4. The pitch-controlled wind turbine (1) according to claim 1 or 2, wherein, The blade connecting member (6) is connected to the corresponding wind turbine blade (5) via a bearing structure (11) mounted on the wind turbine blade (5) or forming part of the wind turbine blade (5).

5. The pitch-controlled wind turbine (1) according to claim 1 or 2, wherein, The connection point (7) on the wind turbine blade (5) is arranged at a certain distance from the root end (10), the distance being between 10% and 60% of the length of the wind turbine blade (5) from the root end (10) to the tip end.

6. The pitch-controlled wind turbine (1) according to claim 1 or 2, wherein, The connection point (7) on the wind turbine blade (5) is arranged at a position where the ratio of the thickness to the chord length of the wind turbine blade (5) is between 20% and 50%.

7. The pitch-controlled wind turbine (1) according to claim 1 or 2, wherein, Each of the wind turbine blades (5) includes: an inner blade portion (5a) including the root end (10); and an outer blade portion (5b) including the tip end, the inner blade portion (5a) and the outer blade portion (5b) being connected to each other at a split position (16), and wherein the connection point (7) on the wind turbine blade (5) is arranged at the split position (16).

8. The pitch-controlled wind turbine (1) according to claim 1 or 2, wherein, The hub (4) includes a hub member (9) extending substantially along a direction defined by the axis of rotation of the hub (4), and wherein the pretensioning member (8) is connected to the hub member (9).

9. The pitch-controlled wind turbine (1) according to claim 8, wherein, The hub member (9) is arranged to provide adjustable pretension force and / or adjustable stiffness in the pretension member (8) and / or blade connection member (6) via the pretension member (8).

10. The pitch-controlled wind turbine (1) according to claim 1 or 2, wherein, The pretensioning member (8) is connected to a common point (26) arranged in the hub (4).

11. The pitch-controlled wind turbine (1) according to claim 1 or 2, wherein, The wind turbine blades (5) are limited to a cone angle within the range of 2° to 20°.

12. The pitch-controlled wind turbine (1) according to claim 1 or 2, wherein, The connection point (7) on the wind turbine blade (5) is located at or near the pitch axis (12) of the wind turbine blade (5).

13. The pitch-controlled wind turbine (1) according to claim 1 or 2, wherein, Each of the wind turbine blades (5) is provided with at least one groove (13) formed in the outer shell of the wind turbine blade (5), and the at least one groove (13) is arranged to receive part of the blade connecting member (6).

14. The pitch-controlled wind turbine (1) according to claim 1 or 2, wherein, Each of the wind turbine blades (5) is bent in at least one direction between the root end (10) and the tip end, such that the pitch axis (12) of the wind turbine blade (5) is located externally relative to the wind turbine blade (5) at least at the connection point (7).

15. The pitch-controlled wind turbine (1) according to claim 1 or 2, wherein, Each of the wind turbine blades (5) extends along a longitudinal direction, and wherein the longitudinal direction forms a non-zero angle with respect to the pitch axis (12) of the pitch mechanism of the wind turbine blade (5).

16. The pitch-controlled wind turbine (1) according to claim 1 or 2, wherein, The pretensioning member (8) and / or the blade connecting member (6) include a vibration damping mechanism.

17. The pitch-controlled wind turbine (1) according to claim 1 or 2, wherein, The pretensioning member (8) and / or the blade connecting member (6) are provided with an aerodynamic device (15).

18. The pitch-controlled wind turbine (1) according to claim 1 or 2, wherein, The wind turbine (1) is a headwind wind turbine.

19. The pitch-controlled wind turbine (1) according to claim 1 or 2, wherein, The connection point (7) of one wind turbine blade is arranged adjacent to each other and / or two blade connecting members (6) are connected to the same connection point (7).

20. The pitch-controlled wind turbine (1) according to claim 1 or 2, wherein, The tension force in the pre-tensioned member (8) can be adjusted individually.

21. The pitch-controlled wind turbine (1) according to claim 9, wherein, The hub component (9) includes an adjustment mechanism (25) having a linear actuator arranged in the direction between the rotation axis of the hub (4) and the connection point between the blade connecting component (6) and the pretensioning component (8).

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