Controlled pitch wind turbine

Abstract

A first aspect of the invention provides a controlled pitch 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 tip end and a root end connected to the hub via a pitch mechanism; the wind turbine further comprises at least three blade connection members, each blade connection member extending from a connection point on one wind turbine blade towards a connection point on an adjacent wind turbine blade, a connection point on a given wind turbine blade is arranged at a distance from the root end and from the tip end of the wind turbine blade; wherein each wind turbine blade comprises a leading edge, a leading edge extension and a pitch axis about which the blade is rotated relative to the hub by the pitch mechanism, where the leading edge extension extends in front of the leading edge and a connection point of the respective wind turbine blade is located on the leading edge extension in front of the leading edge, and when the blade is in an unloaded state, the variable pitch axis is positioned behind the front edge.

Description

Technical Field

[0001] The invention relates to a wind turbine with controlled pitch. Background Art

[0002] Wind turbine blades are subject to a variety of loads. The loads typically include aerodynamic forces generated by the wind (including air pressure on the blades, varying wind speed and direction), as well as loads from the blades' own deadweight.

[0003] Due to the increased energy production generated, there is a continuing drive to produce larger wind turbine blades. However, as the size of wind turbine blades continues to increase, the loads on the wind turbine blades also continue to increase. The increased loads generally require further strengthening of the blades, however, such strengthening further increases the weight of the blades, with the result that the loads acting on the blades are further increased. Summary of the invention

[0004] A first aspect of the 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 tip end and a root end connected to the hub via a pitch mechanism;

[0005] The wind turbine further comprises at least three blade connection members, each blade connection member extending from a connection point on one wind turbine blade towards a connection point on an adjacent wind turbine blade, wherein the connection point on a given wind turbine blade is arranged a distance from the root end and a distance from the tip end of the wind turbine blade;

[0006] Each wind turbine blade comprises a leading edge, a leading edge extension and a pitch axis, and the blade is rotated relative to the hub about the pitch axis by a pitch mechanism.

[0007] Therein, the leading edge extension extends in front of the leading edge, and the connection point of the respective wind turbine blade is located on the leading edge extension in front of the leading edge, and the pitch axis is located behind the leading edge when the blade is in an unloaded state.

[0008] The pitch axis may be located outside the surface of the respective blade and downwind of the blade.

[0009] The pitch mechanism connects the root end of the blade to the hub. For example, the pitch mechanism may include an outer bearing ring mounted on the hub and an inner bearing ring connected to the blade, or an inner bearing ring mounted on the hub and an outer bearing ring connected to the blade.

[0010] Each wind turbine blade may be coupled to two of the blade connection members, each of the two blade connection members extending from a respective connection point of one of the blades. The connection points of one of the wind turbine blades may be adjacent to each other on the same leading edge extension.

[0011] The blade connection member may be connected to a respective wind turbine blade via a bearing structure at a respective connection point.

[0012] The respective connection of the blade connection member to one of the wind turbine blades may be independently movable, preferably each connection being movable in two orthogonal directions.

[0013] Each wind turbine blade may include a blade shell defining a suction side and a pressure side around the blade, and the connection point on the leading edge extension is arranged in front of the leading edge and adjacent to the pressure side, preferably, the pitch axis is arranged behind the leading edge and on the suction side. The pitch axis may be located outside the blade and closer to the suction side than to the pressure side.

[0014] The wind turbine blades may each comprise an inner blade part comprising a root end and an outer blade part comprising a tip end, the inner blade part comprising a root end, the outer blade part comprising a tip end, the inner blade part and the outer blade part being connected to each other at a split location, and wherein the connection point on the wind turbine blade is arranged at the split location.

[0015] The inboard blade part may be connected to the outboard blade part by a connection joint comprising a connector, wherein the leading edge extension is integrally formed with the connector.

[0016] The connector may be a metal part, preferably a cast part. The connector may be a machined part. The connector may be a composite part. The connector may be a co-cured or co-bonded part.

[0017] The connector may be coupled to transfer load between the spar cap portion of the inboard blade part and the spar cap portion of the outboard blade part and arranged to transfer load from the blade connection member into the spar cap portion of the inboard blade part.

[0018] The connector may connect the inner blade part and the outer blade part so that they are rigidly connected together. In other words, the inner blade part and the outer blade part do not rotate relative to each other.

[0019] The leading edge extension may have a fairing to smoothly transition the leading edge extension into the leading edge of the wind turbine blade outboard of the leading edge extension.

[0020] The connection point on the wind turbine blade may be arranged at a distance from the root end that is between 10% and 60% of the length of the wind turbine blade from the root end to the tip end.

[0021] The connection point on the wind turbine blade may be arranged at a location where the thickness to chord ratio of the wind turbine blade is between 20% and 50%.

[0022] The wind turbine may further comprise at least three pretensioning members, each pretensioning member being connected between one of the blade connection members and the hub, each pretensioning member being arranged to provide a pretensioning in the blade connection member to which it is connected.

[0023] The pretensioning members may be connected to a common point arranged at or adjacent to the hub.

[0024] The hub may include a hub member extending from the hub substantially in a direction defined by a rotational axis of the hub, and wherein the pretensioning member is connected to the hub member.

[0025] The wind turbine may be an upwind wind turbine.

[0026] A second aspect of 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 tip end and a root end connected to the hub via a pitch mechanism, wherein each wind turbine blade comprises: a first blade portion having a shell defining a suction side, a pressure side, a leading edge, a trailing edge, and a first spar cap portion, the first blade portion further comprising a first blade portion end surface at one end of the first blade portion; a second blade portion having a shell defining a suction side, a pressure side, a leading edge, a trailing edge, and a second spar cap portion, the second blade portion further comprising a second blade portion end surface at one end of the second blade portion, wherein The first blade portion and the second blade portion are configured to be connected together at the first blade portion end surface and the second blade portion end surface; and a connection joint for connecting the first blade portion and the second blade portion together, wherein the connection joint includes a connector for connecting to the first blade portion end surface and to the second blade portion end surface, and wherein the pitch-controlled wind turbine also includes at least three blade connection members, each wind turbine blade including a first connection point and a second connection point, wherein each blade connection member extends from a first connection point on one wind turbine blade toward a second connection point on an adjacent wind turbine blade, wherein each connection point on a given wind turbine blade is located on a connector of the connection joint of that wind turbine blade.

[0027] By this arrangement, the connection joint can be used as a connector for connecting blade sections together while allowing connection of blade connection members extending between adjacent wind turbine blades. This minimizes disruption to the wind turbine blade construction, thereby allowing a simpler construction and reducing discontinuities in the wind turbine blade that would otherwise be required if the location of the blade split and the connection point of the blade connection member were spaced apart from each other.

[0028] The connector may be adapted to transfer loads between a first spar cap portion of a first blade portion and a second spar cap portion of a second blade portion.

[0029] The first blade portion may be an inboard blade part including a root end, and the second blade portion may be an outboard blade part including a tip end, and the connector may be adapted to transfer loads from a blade connection member coupled to the first connection point and the second connection point into the first spar cap portion of the inboard blade part.

[0030] The connector may include a generally U-shaped connector portion having a first side wall adjacent to an end surface of a first blade portion, a second side wall adjacent to an end surface of a second blade portion, and a base extending between the first side wall and the second side wall; wherein the connection joint also includes a first set of fasteners connecting the first side wall to the end surface of the first blade portion, a second set of fasteners connecting the second side wall to the end surface of the second blade portion, and a third set of fasteners extending across the generally U-shaped connector portion and attached to the first side wall and the second side wall.

[0031] The base may be below a mid-plane of the first and second spar cap portions, and the third set of fasteners may be above a mid-plane of the first and second spar cap portions.

[0032] The first set of fasteners and the second set of fasteners may both be located between the base and the third set of fasteners.

[0033] The connector may be a unitary component having a first row of holes for receiving a first set of fasteners, a second row of holes for receiving a second set of fasteners, and one or more third rows of holes for receiving a third set of fasteners.

[0034] A distance from the base to a mid-plane of the first and second spar cap portions may be substantially equal to a distance from each fastener of the third set of fasteners to the mid-plane of the first and second spar cap portions.

[0035] The first blade portion may include a first set of inserts embedded in the first spar cap portion, and the second blade portion may include a second set of inserts embedded in the second spar cap portion; wherein the first set of fasteners connects the first sidewall to the first set of inserts, and the second set of fasteners connects the second sidewall to the second set of inserts.

[0036] The pitch controlled wind turbine may further include a set of bushings extending across the generally U-shaped connector between the first sidewall and the second sidewall, wherein each fastener of the third set of fasteners extends through a respective bushing.

[0037] The connector may include a first branch for connecting the suction side of the first blade portion and the suction side of the second blade portion and a second branch for connecting the pressure side of the first blade portion and the pressure side of the second blade portion, wherein each of the first branch and the second branch has a generally U-shaped connector portion with a first set of fasteners, a second set of fasteners, and a third set of fasteners.

[0038] The connector may be an integral component.

[0039] The first branch and the second branch may be connected towards the leading edge and towards the trailing edge. Thus, the connector may form a ring.

[0040] The connector may further comprise a leading edge extension.The connecting member may be attached to a respective wind turbine blade at the leading edge extension.

[0041] The connector can be a metal part. The connector can be a cast part or a machined part. The connector can be a composite part. The connector can be a co-cured or co-bonded part.

[0042] The wind turbine may comprise at least three fairings, each fairing being arranged to cover the connection joint and / or the first connection point and / or the second connection point.

[0043] The connector may be a first connector, and wherein the connection joint further comprises a second connector separate from the first connector, the second connector being located towards a trailing edge of each of the first blade portion and the second blade portion.

[0044] The wind turbine may further comprise at least three pretensioning members, each pretensioning member being connected between one of the blade connection members and the hub, each pretensioning member being arranged to provide a pretensioning in the blade connection member to which it is connected.

[0045] The pretensioning members may be connected to a common point arranged at or adjacent to the hub.

[0046] The hub may include a hub member extending from the hub substantially in a direction defined by the axis of rotation of the hub.The pretensioning member may be connected to the hub member.

[0047] The wind turbine may be an upwind wind turbine.

[0048] A third aspect of 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 tip end and a root end connected to the hub via a pitch mechanism, the wind turbine further comprising at least three blade connection members, each blade comprising a first connection point and a second connection point, wherein each blade connection member extends from the first connection point on one wind turbine blade toward the second connection point on an adjacent wind turbine blade, wherein each connection point on a given wind turbine blade is arranged at a distance from the root end and at a distance from the tip end of the wind turbine blade and adjacent to a leading edge of the wind turbine blade, and wherein each connection member is independently movable in two orthogonal directions at the respective first connection point and second connection point to which it is attached.

[0049] Each wind turbine blade may comprise a leading edge and a leading edge extension, wherein the leading edge extension extends in front of the leading edge, and the first connection point and / or the second connection point are located on the leading edge extension in front of the leading edge.

[0050] Each wind turbine blade may have a pitch axis about which the blade is rotated relative to the hub by the pitch mechanism and which is located behind the leading edge when the blade is in an unloaded state. The pitch axis may be located outside the surface of the respective blade and downwind of the blade.

[0051] Each wind turbine blade may include a blade shell defining a suction side and a pressure side around the blade, and the first and second connection points are arranged in front of the leading edge and adjacent to the pressure side. The pitch axis may be located outside the blade and closer to the suction side than to the pressure side.

[0052] Each of the first connection point and the second connection point may include a bearing structure.

[0053] Each connection member may be connected via a bearing structure at a first connection point on one wind turbine blade and a bearing structure at a second connection point on an adjacent wind turbine blade.

[0054] Each bearing arrangement may comprise a spherical plain bearing.

[0055] Each bearing arrangement may comprise a pin about which the respective blade connection member is rotatable.

[0056] Each blade connection member may have an eyelet at one end for receiving a pin at a respective connection point.

[0057] The bearing structures of the first connection point and the second connection point of each wind turbine blade may be mounted on an integral connector component of the wind turbine blade.

[0058] The bearing arrangement may allow each blade connection member to rotate about a respective connection point in at least two orthogonal rotational degrees of freedom.

[0059] The wind turbine blades may each comprise an inner blade part comprising a root end and an outer blade part comprising a tip end, the inner blade part and the outer blade part being connected to each other at a split location, and wherein the connection point on the wind turbine blade is arranged at the split location.

[0060] The inboard blade part may be connected to the outboard blade part by a connection joint comprising a connector, wherein the leading edge extension is integrally formed with the connector.

[0061] The connector may be a metal part, preferably a cast part or a machined part. The connector may be a composite part. The connector may be a co-cured or co-bonded part.

[0062] The connector may be coupled to transfer load between the spar cap portion of the inboard blade part and the spar cap portion of the outboard blade part and arranged to transfer load from the blade connection member into the spar cap portion of the inboard blade part.

[0063] The connection point on the wind turbine blade may be arranged at a distance from the root end which is between 10% and 60% of the length of the wind turbine blade from the root end to the tip end, preferably radially inside 50% of the length of the respective wind turbine blade from the root end to the tip end, and more preferably radially inside 45% of the length of the respective wind turbine blade from the root end to the tip end.

[0064] The connection point on the wind turbine blade may be arranged at a location where the thickness to chord ratio of the wind turbine blade is between 20% and 50%.

[0065] The wind turbine may comprise at least three fairings, each fairing being arranged to cover the first connection point and / or the second connection point.

[0066] The wind turbine may further comprise at least three pretensioning members, each pretensioning member being connected between one of the blade connection members and the hub, each pretensioning member being arranged to provide a pretensioning in the blade connection member to which it is connected.

[0067] The pretensioning members may be connected to a common point arranged at or adjacent to the hub.

[0068] The hub may include a hub member extending from the hub substantially in a direction defined by a rotational axis of the hub, and wherein the pretensioning member is connected to the hub member.

[0069] It should be understood that any / all features of the first, second and third aspects of the present invention are compatible and can be combined. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Embodiments of the present invention will now be described with reference to the accompanying drawings, in which:

[0071] Figure 1 shows a front view of a wind turbine according to a first example;

[0072] Figure 2 A side view of a wind turbine is shown;

[0073] Figure 3 A wind turbine according to a second example is shown;

[0074] Figure 4 A wind turbine blade is shown;

[0075] Figure 5 An exploded view of the connection joint is shown;

[0076] Figure 6 shows a detailed view of a connector for connecting blade sections;

[0077] Fig. 7A A leading edge extension of the connector is shown;

[0078] Figure 7B A close-up of the connector is shown;

[0079] Figure 8 A connecting member extending from a connector for interconnecting adjacent wind turbine blades is shown;

[0080] Fig. 9 A cross section of a connection joint is shown;

[0081] Fig. 10A and Fig. 10B An alternative example is shown in which the connection joint includes a plurality of connectors;

[0082] Fig.11A and Fig. 11B A cross section of a blade portion is shown;

[0083] Fig. 12A and Fig. 12B The fairing of the blade is shown. DETAILED DESCRIPTION

[0084] In this specification, the terms leading edge, trailing edge, pressure side, suction side, thickness, chord length, etc. are used. Although these terms are well known and understood by those skilled in the art, for the avoidance of doubt, the following definitions are given.

[0085] The term "leading edge" is used to refer to the edge of a blade which is at the front of the blade when the blade rotates in the normal direction of rotation of the wind turbine rotor.

[0086] The term "trailing edge" is used to refer to the edge of a wind turbine blade which is at the rear of the blade when the blade is rotating in the normal direction of rotation of the wind turbine rotor.

[0087] The chord length of a blade is the straight line distance from the leading edge to the trailing edge in a given cross section perpendicular to the spanwise direction of the blade. The term "chordwise" is used to refer to the direction from the leading edge to the trailing edge, or vice versa.

[0088] The pressure side (or windward side) of a wind turbine blade is the surface between the leading edge and the trailing edge which has a higher pressure than the suction side of the blade when the blade is in use.

[0089] The suction side (or leeward surface) of a wind turbine blade is the surface between the leading edge and the trailing edge which has a lower pressure acting on it than the pressure side when the blade is in use.

[0090] The thickness of a wind turbine blade is measured perpendicular to the chord length of the blade and is the maximum distance between the pressure side and the suction side in a given cross section perpendicular to the spanwise direction of the blade.

[0091] The term "spanwise" is used to refer to the direction from the root end of a wind turbine blade to the tip end of the blade, or vice versa. When the wind turbine blade is mounted on a wind turbine hub, the spanwise direction and the radial direction are substantially the same.

[0092] The term "spar cap" is used to refer to a longitudinal, generally span-wise extending reinforcement member of a blade. The spar cap may be embedded in or attached to a blade shell. The spar cap on the windward side of the blade and the spar cap on the leeward side may be connected by one or more shear webs extending through the internal hollow space of the blade. The blade may have more than one spar cap on each of the windward side and the leeward side of the blade. The spar cap may form part of a longitudinal reinforcement spar or support member of the blade. In particular, the spar cap may form part of a load-bearing structure extending in the longitudinal direction, which carries the flapping direction bending loads of the blade. The spar cap may include spar cap portions on either side of a connection joint between portions of the blade.

[0093] The term "outboard" refers to the radial direction from the hub of the blade towards the tip end of the blade. The term "inboard" refers to the radial direction from the tip end towards the hub.

[0094] Figure 1 and Figure 2 A pitch-controlled wind turbine 1 according to a first example is shown. Figure 1 is a front view of a wind turbine 1, Figure 2 is a side view of a wind turbine 1. The wind turbine 1 comprises a tower 2 and a nacelle 3 mounted on the tower 2. A hub 4 is rotatably mounted on the nacelle 3 and carries three wind turbine blades 5 protruding outward from the nacelle 3. Figure 1 and Figure 2 The example shown has three blades 5 , but it will be appreciated that other numbers of blades 5 are possible.

[0095] When wind blows towards the wind turbine 1 , the wind turbine blades 5 generate lift, which causes a generator (not shown) in the nacelle 3 to generate electrical energy.

[0096] It will be appreciated that the depicted wind turbine 1 may be any suitable type of wind turbine 1. The wind turbine 1 shown is an upwind wind turbine, but it will be appreciated that the wind turbine 1 may be a downwind wind turbine. The wind turbine 1 may be an onshore wind turbine, such that the foundation is embedded in the ground, or the wind turbine 1 may be an offshore facility, in which case the foundation will be provided by a suitable offshore platform.

[0097] The three blade connection members 6 are connected to the wind turbine blade 5 at the connection points 7a, 7b (such as at Figure 6 7 ) interconnects adjacent wind turbine blades 5. The connection members 6 are cables, such as steel cables. The pretensioning member 8 extends between one of each blade connection member 6 and a common point arranged at or adjacent to the hub 4. Figure 1 and Figure 2 In the example shown, the pretensioning member 8 extends to the hub 4. The pretensioning member 8 is configured to provide a pretensioning in the blade connection member 6.

[0098] The pre-tensioned blade connection members 6 enable the wind turbine blades 5 to mutually support loads on the wind turbine blades 5 , in particular edgewise loads and flapping direction loads, in the sense that they are “shared” between the wind turbine blades 5 .

[0099] Figure 3 is a side view of a pitch-controlled wind turbine 1 according to a second example. Figure 3 The wind turbine 1 is similar to Figure 1 and Figure 2 The wind turbine 1 is described above and therefore the same features will not be described in detail here.

[0100] exist Figure 3 In the embodiment of the present invention, the pretensioning member 8 is not directly connected to the hub 4. Instead, the pretensioning member 8 is connected adjacent to the hub 4 to a hub member 9, which extends from the hub 4 substantially in a direction defined by the axis of rotation of the hub 4. As a result, the connection point of the pretensioning member 8 is shorter than that of the hub 4. Figure 1 and Figure 2 The example of the embodiment of FIG. 1 is further away from the hub 4 and thereby further away from where the wind turbine blade 5 is connected to the hub 4. This has the result that the pretensioning member 8 can also pull the blade connection member 6 away from the hub 4 and away from the tower 2. This can also cause the wind turbine blade 5 to be pulled in this direction, thereby further reducing the edgewise and flapping direction loads at the root of the wind turbine blade 5 and ensuring tower clearance, similar to the clearance obtained when the taper angle is introduced.

[0101] The wind turbine blade 5 has a root end 11 close to the hub 4 and a tip end 12 remote from the hub 4, the root end 11 being adapted to be connected to the hub 4 via a pitch mechanism. The blade 5 comprises a leading edge 13 and a trailing edge 14 extending between the respective root end 11 and the tip end 12. The blade 5 comprises a suction side 15 and a pressure side 16. A thickness dimension of the blade 5 extends between the suction side 15 and the pressure side 16.

[0102] Each blade 5 may have a cross-section having a generally circular profile near the root end 11. The blade 5 may transition from a circular profile to an airfoil profile moving outboard from the root end 11 of the blade 5. The blade 5 may include a "shoulder" 28 outboard of the root end 11, the shoulder 28 being the widest part of the blade where the blade 5 has its maximum chord length. The blade 5 may have an airfoil profile with a gradually decreasing thickness in the outboard portion of the blade. The gradually decreasing thickness may extend from the shoulder 28 to the tip end 12.

[0103] Each blade 5 is a split blade formed by a first blade part 22 and a second blade part 24 coupled together, such as Figure 4 Each blade portion 22, 24 has a shell defining a respective leading edge 30a, 30b, a trailing edge 32a, 32b, a suction side 34a, 34b and a pressure side 36a, 36b.

[0104] The first portion 22 and the second portion 24 of each blade 5 may be connected at a connection joint indicated by a connection line 40. The connection line 40 between the first blade portion 22 and the second blade portion 24 may be a spanwise crack, wherein the connection line 40 is chordwise. The first blade portion 22 extends from the blade root 11 to the connection line 40. The second blade portion 24 extends from the blade connection line 40 to the blade tip 12.

[0105] It will be appreciated that the blade 5 may have any number of blade portions 22, 24 with corresponding connecting joints therebetween.

[0106] As described above, the first blade portion 22 and the second blade portion 24 are connected by a connector 41 (such as Figure 5 and Figure 6 In particular, the connector 41 connects the first blade end surface 26 of the first blade portion 22 to the second blade end surface 27 of the second blade portion 24 (as shown in FIG. Fig. 9 As explained in further detail below, the connection points 7a, 7b of the connecting member 6 are located on the connector 41 at the connection joint.

[0107] The connector 41 is adapted to transfer loads between the first blade portion 22 and the second blade portion 24, in particular between the first spar cap portion 23 of the first blade portion 22 and the second spar cap portion 25 of the second blade portion 24. Fig. 9 Further discussion.

[0108] The connector 41 is a cast metal component, but it should be understood that the connector 41 can be formed from any suitable material (e.g., a composite material) and produced by any suitable manufacturing technique (e.g., machining, co-curing, or co-bonding). The connector 41 is a single integral connector component 43, but it should be understood that in some examples, the connector 41 can be formed from two or more components.

[0109] exist Figure 5 In the example shown, the connector 41 includes a first branch 54 for connecting the suction side 15 of the first blade portion 22 and the suction side 15 of the second blade portion 24 and a second branch 55 for connecting the pressure side 16 of the first blade portion 22 and the pressure side 16 of the second blade portion 24. The first branch 54 and the second branch 55 may be connected by a first link 56 positioned toward the leading edge 13 of the blade 5, and connected by a second link 57 positioned toward the trailing edge 14 of the blade 5. In this way, a ring is formed by the first branch 54, the second branch 55, the first link 56 and the second link 57. The first branch 54 and the second branch 55 may be formed integrally with the first link 56 and the second link 57, but it should be understood that the first branch 54 and the second branch 55 may be separate components from each other and / or separate components from the first link 56 and the second link 57. It should be understood that the connector 41 may take other forms, for example, the second link 57 may be positioned away from the trailing edge 14 of the blade 5 so as to form a generally "A"-shaped connector.

[0110] The connector 41 may extend across substantially the entire chord of the wind turbine blade 5, although preferably the connector 41 extends across only a portion of the chord of the wind turbine blade, such as Figure 5 This helps reduce the weight of the connector 41 while allowing the connector 41 to be positioned near the spar cap portions 23, 25 of the blade portions 22, 24, which may carry most of the load. The connector 41 may include a plurality of holes: a first set of holes 71, a second set of holes 72, and a third set of holes 73, Figure 5 Only some of them are labeled in order to improve clarity. In this way, the first blade portion 22 and the second blade portion 24 can be attached together by a plurality of sets of fasteners 61, 62, 63 extending through the holes, as shown in FIG. Fig. 9 Described in more detail.

[0111] The connector 41 may extend through any chord-wise portion of the blade 5 adjacent to the spar cap portions 23, 25, although Figure 5 The example shown in FIG. 5 extends to the leading edge 13 of the blade 5 .

[0112] The blade 5 has a pitch axis 19 about which the blade 5 is rotated relative to the hub 4 by the pitch mechanism. The pitch axis may be located outside the surface of the respective blade and downwind of the blade. The pitch axis may be located outside the blade and closer to the suction side 15 of the blade 5 than to the pressure side 16. The pitch axis 19 may be located behind the leading edge 13 and / or adjacent to the suction side 15 of the blade 5, e.g. Figure 6 In particular, when the blade 5 is in an unloaded state, the pitch axis 19 may be located behind the leading edge 13 and / or adjacent to the suction side 15. The unloaded state is defined as the state of the blade 5 when no wind load or gravity load acts on the blade 5.

[0113] The leading edge extension 42 may extend forwardly of the leading edge 13 of the blade 5. The leading edge extension 42 is integrally formed with the connector 41, but it will be appreciated that the leading edge extension 42 may be a separate component from the connector 41 in alternative examples.

[0114] The leading edge extension 42 includes connection points 7a, 7b attached to the connection member 6. In the present example, the leading edge extension 42 includes a first connection point 7a and a second connection point 7b, but in alternative examples, the leading edge extension 42 may include any suitable number of connection points. The first connection point 7a and the second connection point 7b may be arranged forward of the leading edge 13 and adjacent to the pressure side 16, such as Figure 5 As shown in . This provides additional clearance for the connection member 6 when the wind turbine blade 5 rotates around the nacelle 3 together with the hub 4. In particular, when the blade 5 is pitched between 0 degrees and 90 degrees, sufficient clearance is provided between the connection member 6 and the first blade part 22.

[0115] It will be appreciated that the connection points 7a, 7b may be adjacent to each other on the leading edge extension 42. Alternatively, the connection points 7a, 7b may be spaced apart from each other. For example, the first connection point 7a may be located further towards the pressure side 16 than the second connection point 7b.

[0116] In some examples, connector 41 may include a plurality of leading edge extensions 42 integrally formed with connector 41. The leading edge extensions may be spaced apart from one another, for example, one may be located further toward pressure side 16 than another, wherein each leading edge extension 42 has a respective connection point 7a, 7b.

[0117] The connection points 7a, 7b may allow at least some freedom of movement of the connection member 6 at its respective connection point 7a, 7b. Fig. 7A In the example shown, the connection points 7a, 7b allow each blade connection member 6 to rotate about the respective connection point 7a, 7b with two orthogonal rotational degrees of freedom. This allows each connection member 6 to move independently of each other, thereby reducing constraints on the wind turbine 1.

[0118] Two orthogonal rotational degrees of freedom can be provided by a bearing structure, such as Figure 7B In this example, the first rotational freedom 49a is provided by a pin 46 of the bearing structure, about which the corresponding blade connection member 6 can rotate, and the second rotational freedom 49b is provided by a spherical plain bearing 47 between the pin 46 and the corresponding connection member 6. However, it should be understood that other bearing structures may also be applicable.

[0119] To facilitate attachment of the connection members 6 to the bearing structure, each connection member 6 may include an eyelet 48 at one end for receiving a respective pin 46 .

[0120] The bearing structure of the first connection point 7a and the second connection point 7b of each wind turbine blade may be mounted on a connector 41 of the wind turbine blade 5, such as Fig. 7A as shown in .

[0121] Each connection member 6 is connected to one wind turbine blade 5 at a first connection point 7a and to an adjacent wind turbine blade 5 at a second connection point 7b, such as previously described with respect to Figures 1 to 3 As described.

[0122] like Figure 8 As shown, the connection joint indicated by line 40 can be centrally located so as to be equidistant from the spanwise ends of the connector 41. In particular, the connection joint can be equidistant from the first side wall 51 and the second side wall 52 of the connector 41, which will combine Fig. 9 Further description.

[0123] As previously mentioned, the first blade portion 22 includes the first spar cap portion 23 and the second blade portion 24 includes the second spar cap portion 25 , wherein the connector 41 is adapted to transfer loads between the first spar cap portion 23 of the first blade portion 22 and the second spar cap portion 25 of the second blade portion 24 .

[0124] like Fig. 9 As shown, the connector 41 may include a generally U-shaped connector portion 50 having a first side wall 51 adjacent to the first blade portion end surface 26 , a second side wall 52 adjacent to the second blade portion end surface 27 , and a base 53 extending between the first side wall 51 and the second side wall 52 .

[0125] A first set of fasteners 61 may extend through first row of holes 71 to connect first sidewall 51 to first blade portion end surface 26 , and a second set of fasteners 62 may extend through second row of holes 72 to connect second sidewall 52 to second blade portion end surface 27 .

[0126] The base 53 may be spaced apart from a mid-plane of the first spar cap portion 23 and the second spar cap portion 25. Fig. 9 In the example shown, the base 53 is below the mid-plane of the first and second spar cap portions 23, 25 (i.e., toward the center of the blade 5). Positioning the base 53 below the mid-plane of the first and second spar cap portions 23, 25 provides access to the first and second sets of fasteners 61, 62 from the exterior of the blade 5 as the sidewalls 51, 52 extend outwardly from the base 53. It will be appreciated that access to the fasteners 61, 62 may be provided without providing a generally U-shaped connector portion 50, for example the connector portion 50 may form a closed loop wherein the outer end opposite the base 53 includes one or more apertures through which the fasteners 61, 62 are accessible.

[0127] The third set of fasteners 63 may extend through a third row of holes 73 ( Figure 5 5 (most clearly shown in the third row of holes) to extend across the generally U-shaped connector portion 50 and attached to the first side wall 51 and the second side wall 52. It should be understood that in examples where the connector portion 50 forms a closed loop, etc., the third set of fasteners 63 may not be required.

[0128] The third set of fasteners 63 may be above the mid-plane of the first spar cap portion 23 and the second spar cap portion 25, such as Fig. 9 In particular, each fastener in the third set of fasteners 63 may preferably be located at the same distance from the outer surface of the first blade portion 22 and the second blade portion 24 .

[0129] The first group of fasteners 61 and the second group of fasteners 62 may be positioned between the base 53 and the third group of fasteners 63. Each of the first group of fasteners 61 and the second group of fasteners 62 may be located at the center of the corresponding spar cap portion 23, 25 in the thickness direction of the blade 5. Each of the base 53 and the third group of fasteners 63 may be equally spaced from the mid-plane of the first spar cap portion 23 and the second spar cap portion 25. In other words, the distance from the base 53 to the mid-plane of the first spar cap portion 23 and the second spar cap portion 25 may be substantially equal to the distance from each of the third group of fasteners 63 to the mid-plane of the first spar cap portion 23 and the second spar cap portion 25.

[0130] In some examples, such as Fig. 9 In the example shown, the first set of fasteners 61 and the second set of fasteners 62 can extend into respective inserts 67, 68. Each fastener in the first set of fasteners 61 can extend into an insert 67 having a hole 61A into which the fasteners of the first set of fasteners 61 extend, and each fastener in the second set of fasteners 62 can extend into an insert 68 having a hole 62A into which the fasteners of the second set of fasteners 62 extend.

[0131] The inserts 67, 68 may be embedded in the respective first and second spar cap portions 23, 25. The inserts 67, 68 may each include a threaded bushing, and each of the first and second sets of fasteners 61, 62 may be a threaded fastener for engaging the respective threaded bushing. The threaded fastener may include a threaded rod for engaging the respective threaded bushing and a nut for pre-tensioning the connector against the respective blade portion end surface, or the threaded fastener may include a bolt with a headed end, or any suitable device apparent to those skilled in the art. It should be understood that the inserts 67, 68 may be any suitable device, for example, the inserts 67, 68 may be barrel nuts, the inserts 67, 68 may be T-bolts attached to respective T-sleeves, or may form part of a sleeve nut device, wherein the sleeve nut is attached to the threaded end of the respective inserts 67, 68.

[0132] The fasteners in the third set of fasteners 63 may each extend through a respective bushing 65. The bushing 65 may extend between the first side wall 51 and the second side wall 52 to prevent over-tightening of the third set of fasteners 63, thereby preventing undesirable deformation of the generally U-shaped connector portion 50. The fasteners in the third set of fasteners 63 may be any suitable fastener means, such as a threaded rod having a nut at each end, or a bolt having a headed end adjacent to the first side wall 51 or the second side wall 52 and a nut adjacent to the other of the first side wall 51 and the second side wall 52, or a threaded hole in one of the side walls that receives a bolt extending through a clearance hole in the other side wall.

[0133] In some examples, the connection joint may include a plurality of discrete connectors 41a, 41b separated in a generally chord-wise direction. This may help minimize the weight of the connection joint because the connectors 41a, 41b may serve as discrete portions of the connection joint where needed, without requiring connectors to span between the discrete portions.

[0134] Fig. 10A An example is shown in which a first connector 41a is provided. The first connector 41a is connected to Figures 5 to 9 The connectors 41 of the blade 5 are substantially the same. Thus, the first connector 41a is positioned towards the leading edge 13 of the blade 5 and may be arranged to extend upwardly to the leading edge 13 of the blade 5. Furthermore, the connector 41a may include a leading edge extension 42 including connection points 7a, 7b attached to the connection member 6.

[0135] Fig. 10A and Fig. 10B A second connector 41b is also shown, positioned relative to the first connector 41a toward the trailing edge 14. The second connector 41b may be connected to the third spar cap portion 33 and the fourth spar cap portion 35 (the two spar cap portions 33, 35 are located at the rear edge 14) via fasteners. Fig.11A and Fig. 11B The second connector 41b may include a first set of fasteners 61 ( Fig. 10B only one of which is shown in FIG. 1 ) and a second set of fasteners 62 ( Fig. 10B , wherein the connector 41b includes a plurality of holes 71, 72 through which a plurality of sets of fasteners 61, 62 extend to secure the connector 41b to the third spar cap portion 33 and the fourth spar cap portion 35. Similar to the arrangement of the first connector 41a, the first set of fasteners 61 and the second set of fasteners 62 may extend into corresponding inserts 77, 78, as shown. Fig.11A and Fig. 11B shown.

[0136] The second connector 41b may include a generally U-shaped connector portion, similar to Figures 5 to 9 Alternatively, as described above with respect to the connector portion of connector 41. Fig. 10B As shown in the example of , the second connector 41b may include a plurality of support members 53a extending between the first side wall 51 and the second side wall 52. Therefore, the second connector 41b may not include the third set of fasteners. Since the number of fasteners in the first set of fasteners 61 and the second set of fasteners 62 is small (in Fig. 10A and Fig. 10B In the example of the third spar cap portion 33 and the fourth spar cap portion 35, there are two fasteners in each of the third spar cap portion 33 and the fourth spar cap portion 35), it may be practicable so that each fastener can be accessed and fastened from the direction of the leading edge 13 and the trailing edge 14 of the blade 5, as opposed to the need to access from the suction side 34a, 34b and the pressure side 36a, 36b of the blade 5 when there are a large number of fasteners in each of the first set of fasteners 61 and the second set of fasteners 62. Alternatively, access to the fasteners may be provided through one or more holes in one or more supports 53a.

[0137] As mentioned before, the blade 5 may include a third spar cap portion 33 and a fourth spar cap portion 35. The second connector 41b is adapted to transfer loads between the first blade portion 22 and the second blade portion 24, in particular between the third spar cap portion 33 of the first blade portion 22 and the fourth spar cap portion 35 of the second blade portion 24. An example of such an arrangement of spar caps 23, 25, 33, 35 integrated into the blade portions 22, 24 is shown in FIG. Fig.11A and Fig. 11B As previously mentioned Fig. 9 As described above, the first spar cap portion 23 and the second spar cap portion 24 may have inserts 67, 68 embedded therein. In addition, the third spar cap portion 33 and the fourth spar cap portion 35 may have inserts 77, 78 similar to the inserts 67, 68 of the first spar cap portion 23 and the second spar cap portion 24, into which fasteners of the respective first set of fasteners 61 and the second set of fasteners 62 may be engaged.

[0138] The fasteners connecting the second connector 41b to the blade portion may be of different sizes (e.g., smaller bolt diameter) than the fasteners connecting the first connector 41a to the blade portion. The corresponding inserts 77, 67 may also be of different sizes. The loads near the trailing edge at the second connector 41b will generally be less than the loads across the first connector 41a, so material can be saved by appropriately changing the size of the fasteners. Similarly, the fasteners at the pressure side and suction side may be of different sizes to accommodate different loads.

[0139] It should be appreciated that in alternative examples, the first connector 41 a and the second connector 41 b may be integral so as to extend adjacent the first spar cap portion 23 , the second spar cap portion 25 , the third spar cap portion 33 , and the fourth spar cap portion 35 .

[0140] The connection joint may be covered by a fairing 90, in which case the fairing 90 may provide a surface covering the connection joint that provides minimal deterioration of the aerodynamic profile of the two blade parts 22, 24. The fairing 90 may extend from the leading edge 13 of the blade 5 to the trailing edge 14 of the blade 5 so as to cover substantially the entire connection joint, or may extend over only a portion of the connection joint.

[0141] In those examples that include the leading edge extension 42 , the fairing 90 may extend to cover the leading edge extension 42 , such as Fig. 12A and Fig. 12B As shown. The fairing 90 may be arranged to cover at least one of the first connection point 7a and the second connection point 7b. The fairing 90 may have one or more holes 91, 92. The holes 91, 92 may be dimensioned individually for each connection member 6 and in particular dimensioned to take into account the possible range of movement of the connection member 6 due to the freedom of movement of the connection member 6 at the connection points 7a, 7b.

[0142] exist Fig. 12A and Fig. 12B In the example shown, the apertures 91 , 92 of the fairing 90 are substantially elongated, but it will be appreciated that the apertures 91 , 92 may be any suitable size and shape to account for movement of the connecting members 6 as they extend from the connection points 7a , 7b through the apertures 91 , 92 of the fairing 90 .

[0143] Although the invention has been described above with reference to one or more preferred embodiments, it will be appreciated that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims.

Claims

1. 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 tip end and a root end connected to the hub via a pitch mechanism; The wind turbine further comprises at least three blade connection members, each blade connection member extending from a connection point on one wind turbine blade towards a connection point on an adjacent wind turbine blade, wherein the connection point on a given wind turbine blade is arranged a distance from the root end and a distance from the tip end of the wind turbine blade; wherein each wind turbine blade comprises a leading edge, a leading edge extension and a pitch axis, the blade being rotated relative to the hub about the pitch axis by the pitch mechanism, Therein, the leading edge extension extends in front of the leading edge, and the connection point of the respective wind turbine blade is located on the leading edge extension in front of the leading edge, and the pitch axis is located behind the leading edge when the blade is in an unloaded state.

2. The pitch-controlled wind turbine according to claim 1, wherein: Each wind turbine blade is coupled to two of the blade connection members, each of which extends from a respective connection point of one of the blades, and preferably wherein the connection points of the one of the wind turbine blades are adjacent to each other on a same leading edge extension.

3. A pitch-controlled wind turbine according to claim 1 or 2, wherein: The blade connection members are connected to respective wind turbine blades at respective connection points via bearing structures.

4. A pitch-controlled wind turbine according to any one of the preceding claims, wherein: The respective connection of the blade connection member to one of the wind turbine blades is independently movable, preferably each connection being movable in two orthogonal directions.

5. A pitch-controlled wind turbine according to any one of the preceding claims, wherein: Each wind turbine blade comprises a blade shell defining a suction side and a pressure side around the blade, and the connection point on the leading edge extension is arranged in front of the leading edge and adjacent to the pressure side, preferably the pitch axis is arranged behind the leading edge and on the suction side.

6. A pitch controlled wind turbine according to any one of the preceding claims, wherein: The wind turbine blades each comprise an inner blade part comprising the root end and an outer blade part comprising the tip end, the inner blade part and the outer blade part being connected to each other at a split location, and wherein a connection point on the wind turbine blade is arranged at the split location.

7. The pitch-controlled wind turbine of claim 6, wherein: The inner blade part is connected to the outer blade part via a connection joint, the connection joint comprising a connector, wherein the leading edge extension is integrally formed with the connector.

8. The pitch-controlled wind turbine of claim 7, wherein: The connector is a metal component, preferably a cast component.

9. A pitch-controlled wind turbine according to claim 7 or 8, wherein: The connector is coupled to transfer loads between the spar cap portion of the inboard blade part and the spar cap portion of the outboard blade part and is arranged to transfer loads from the blade connection member into the spar cap portion of the inboard blade part.

10. A pitch controlled wind turbine according to any one of the preceding claims, wherein: The leading edge extension has a fairing to smoothly transition the leading edge extension into the leading edge of the wind turbine blade outboard of the leading edge extension.

11. A pitch controlled wind turbine according to any one of the preceding claims, wherein: The connection point on the wind turbine blade is arranged at a distance from the root end that is between 10% and 60% of the length of the wind turbine blade from the root end to the tip end.

12. A pitch controlled wind turbine according to any one of the preceding claims, wherein: The connection point on the wind turbine blade is arranged at a position where a thickness to chord ratio of the wind turbine blade is between 20% and 50%.

13. A pitch controlled wind turbine according to any one of the preceding claims, wherein: The wind turbine further comprises at least three pre-tensioning members, each pre-tensioning member being connected between one of the blade connection members and the hub, each pre-tensioning member being arranged to provide a pre-tensioning in the blade connection member to which it is connected.

14. A pitch controlled wind turbine according to claim 13, wherein: The pretensioning members are connected to a common point arranged at or adjacent to the hub.

15. A pitch controlled wind turbine according to claim 13 or 14, wherein: The hub includes a hub member extending from the hub substantially along a direction defined by a rotational axis of the hub, and wherein the pretensioning member is connected to the hub member.

16. A pitch controlled wind turbine according to any one of the preceding claims, wherein: The wind turbine is an upwind wind turbine.

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