Pitch-controlled wind turbines with blade connection components and split blades

Abstract

A 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 (6) and a tip end (7) connected to the hub (4). The wind turbine (1) further comprises at least three blade connecting members (8), each blade connecting member (8) extending between a connection point (9) on one wind turbine blade (5) and a connection point (9) on an adjacent wind turbine blade (5). Each wind turbine blade (5) includes an inner blade portion (5a) and an outer blade portion (5b), the inner blade portion including a root end (6) and the outer blade portion including a tip end (7), the inner blade portion (5a) and the outer blade portion (5b) being connected to each other at a separated position (10). The separate position (10) is arranged between the root end (6) and the connection point (9).

Description

Technical Field

[0001] The present invention relates to a pitch-controlled wind turbine, the wind turbine including 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, thereby allowing the wind turbine blades to be fully and / or partially pitched. 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 subjected to loads generated by gravity acting on the blades, loads generated by wind pressure on the blades, and loads generated by changes in wind direction or speed, turbulence, etc. Gravity acting on the wind turbine blades mainly results in edge loads, while wind acting on the blades mainly results in wing 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.

[0004] Furthermore, as the size of wind turbine blades increases, transporting them becomes increasingly difficult. One solution is to manufacture wind turbine blades in at least three parts, which are transported separately and joined together at the location where the wind turbine is positioned to form a complete wind turbine blade. This is sometimes referred to as a "split-type wind turbine blade." However, separating wind turbine blades in this way can introduce weaknesses into the blade structure because the strength of the blades can be adversely affected.

[0005] In existing split-type wind turbine blades, the separation point is typically positioned closer to the tip of the blade than to the root end. This is to place the separation point where the expected load is lower and thus minimize the adverse effects on the wind turbine blade's load-handling capacity. For example, the separation point may be positioned at a distance from the root end, between 70% and 75% of the blade's length. However, arranging the separation point further from the root end requires adding extra mass to the inner portion of the wind turbine blade to support the additional mass needed at the separation point, thereby providing the required strength to the wind turbine blade. Furthermore, accessing the separation point, for example, to provide repair or maintenance to the connections between blade components, is challenging and typically requires the use of large cranes. Summary of the Invention

[0006] The purpose of embodiments of the present invention is to provide a pitch-controlled wind turbine that allows the transport of large wind turbine blades without reducing the wind turbine's load-handling capacity and without increasing manufacturing costs.

[0007] Another object of embodiments of the present invention is to provide a wind turbine with pitch control of split-type wind turbine blades, which allows for easy repair and maintenance of the connections between blade components.

[0008] 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. The wind turbine further 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 points on a given wind turbine blade are arranged to be spaced apart from both the root end and the tip end of the wind turbine blade.

[0009] Each wind turbine blade includes an inner blade portion and an outer blade portion, the inner blade portion including the root end and the outer blade portion including the tip end, the inner blade portion and the outer blade portion being connected to each other at a separation position, wherein the separation position is arranged between the root end and the connection point.

[0010] Therefore, the present invention provides a pitch-controlled wind turbine, namely a wind turbine comprising wind turbine blades capable of rotating about a substantially longitudinal pitch axis to adjust the angle of attack between the wind turbine blades and the incoming wind during wind turbine operation. The entire wind turbine blade is rotatable, in which case the wind turbine blade is typically connected to the wind turbine hub via a pitch bearing disposed at the root end of the wind turbine blade. This is sometimes referred to as “full pitch.” For full pitch, it is preferable that the entire blade pitches together, so that pitch does not occur between the blade portion on one side of the separated position and the blade portion on the other side of the separated position. This allows for a relatively simple connection between the blade portions in the separated position. Alternatively, only a portion of the wind turbine blade is rotatable, in which case the pitch bearing is typically disposed between the rotatable portion of the wind turbine blade and the portion of the wind turbine blade fixedly connected to the wind turbine hub. This is sometimes referred to as “partial pitch.” This will be described in further detail below.

[0011] The wind turbine is preferably a horizontal axis wind turbine.

[0012] A wind turbine includes a tower and a nacelle mounted on the tower. The wind turbine also includes a hub rotatably mounted on the nacelle and at least three wind turbine blades. Each wind turbine blade extends between a root end and a tip end connected to the hub. Therefore, the wind turbine blade rotates relative to the nacelle together with the hub, and the tip of the wind turbine blade points away from the hub. As described above, at least a portion of each wind turbine blade is capable of rotating relative to the hub, i.e., performing pitch control. The hub and wind turbine blades form the rotor of the wind turbine.

[0013] The nacelle is typically mounted on the tower via a yaw system that allows the nacelle to rotate relative to the tower in order to orient the rotor appropriately according to the wind direction.

[0014] 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 interconnects two adjacent wind turbine blades. The connection points on a given wind turbine blade are arranged to be spaced apart from both the root end and the tip end of the wind turbine blade. Therefore, the connection points are not located at either the root end or the tip end, but rather at a position between these two extremes, and have a non-zero distance from each end.

[0015] In this document, the term "member" in connecting members and pretensioning members shall be interpreted broadly to encompass any suitable type of tension member, such as braided or twisted ropes or hybrid ropes of polymer fibers (e.g., polyethylene, polypropylene, nylon, polyester, aramid, inorganic fibers (e.g., carbon fiber), composite pultruded parts, metal rods, etc.

[0016] Blade connectors enable wind turbine blades to support each other, as loads on the wind turbine blades, particularly edge and wing loads, are "distributed" among the blades via the blade connectors. Therefore, during wind turbine operation, loads on the wind turbine blades can be handled without requiring greater material thickness and thus avoiding increased weight and manufacturing costs.

[0017] Each wind turbine blade includes an inner blade portion and an outer blade portion, the inner blade portion including the root end and the outer blade portion including the tip end. The inner and outer blade portions are connected to each other in a separated position. Therefore, as described above, the wind turbine blade is a split-type wind turbine blade, and the inner and outer blade portions can be transported separately to the wind turbine location. This allows for the design of wind turbines where the length of the wind turbine blade exceeds the maximum permissible length for transportation purposes.

[0018] The separation position is arranged between the root end and the connection point. Therefore, the blade connecting member is connected to the outer blade portion or to the separation position connecting the outer blade portion, and the separation position is arranged along the wind turbine blade at a position inside or including the connection point relative to the connection point.

[0019] Therefore, the separation is positioned where the load sharing provided by the blade connecting member is significant. Consequently, the load occurring in this section of the wind turbine blade is significantly lower than the load occurring in a similar wind turbine blade without the blade connecting member. Therefore, the reduced strength of the wind turbine blade caused by the separation can be incorporated into this section of the wind turbine blade without impairing the wind turbine blade's ability to handle the intended load. In other words, the blade connecting member compensates for the reduced strength introduced by the blade separation.

[0020] Therefore, due to the relative positions of the blade connecting components and the separation and connection points, it is possible to design wind turbines with blades that are longer than required for normal transport without significantly increasing the manufacturing cost of the wind turbine blades and without compromising the wind turbine blades' ability to handle loads.

[0021] The inner and outer blade sections can be connected to each other by bolts. Alternatively, the inner and outer blade sections can be connected by suitable adhesive techniques, such as gluing the blade sections together. Another alternative is that the inner and outer blade sections can be connected to each other via bearings. This will be described in further detail below.

[0022] The separation position of wind turbine blades can be arranged at a distance from the root end, which is between 15% and 60% of the length of the wind turbine blade from the root end to the tip end, for example, between 20% and 50%, or for example, between 25% and 40%.

[0023] According to this embodiment, the separation position is arranged away from both the root end and the tip end. Furthermore, it ensures that both the inner and outer blade portions have significant lengths, but none of the blade portions exceeds the length specified for transport. Additionally, the separation position is close enough to the root end to allow easy access from the hub for maintenance or repair purposes.

[0024] The separation position of the wind turbine blades can be arranged at a position where the thickness-to-chord ratio of the wind turbine blades is between 24% and 70% (e.g., between 24.5% and 55.0%, or between 26% and 50%).

[0025] According to this embodiment, the separate positions are arranged at a location that is also far from the root end and far from the tip end, so the above description also applies here.

[0026] The separation position of wind turbine blades can be arranged at the position of the maximum chord.

[0027] According to this embodiment, an intermediate blade portion can be inserted between the inner and outer blade portions, wherein the intermediate blade defines a maximum chord along its entire length. Therefore, wind turbine blades of various lengths can be manufactured using the same molds for the inner and outer blade portions, respectively. Various lengths of intermediate blade portions can be applied, thereby allowing the manufacture of a range of modularly designed wind turbines with various rotor diameters at minimal manufacturing cost. This will be described in further detail below. Similarly, by applying different inner blade portions having the same outer blade portion, wind turbine blades with various root diameters can be manufactured.

[0028] The separation position of wind turbine blades can be located at or near the center of gravity of the wind turbine blade. For example, the separation position can be located at a position no more than 5% of the length of the wind turbine blade away from the center of gravity.

[0029] When installing wind turbine blades on a wind turbine, it is advantageous to attach the lifting device to the blade at or near its center of gravity to balance the blade during lifting. By arranging the device separately at or near the blade's center of gravity, reinforcement is already provided at that location, thus eliminating the need for additional stiffeners to connect the lifting device.

[0030] The separation position of wind turbine blades can be arranged at a distance between 50m and 100m from the tip (e.g., between 60m and 80m, or between 65m and 75m). This allows the outer portion of the wind turbine blades to be transported by conventional methods, particularly when the separation position is between 60m and 80m (e.g., between 65m and 75m), the outer portion can be transported by road.

[0031] Transporting goods exceeding 100m in length by land is typically difficult, expensive, or even impossible. Therefore, the length of the outer blade section should preferably not exceed 100m. On the other hand, providing an outer blade section that is as long as possible without exceeding transport limitations may be advantageous, as this would result in the inner blade section being as short as possible, thereby positioning the separation position as close as possible to the root end. This allows for easy access from the hub to the connection between the inner and outer blade sections for repair or maintenance purposes.

[0032] Alternatively or additionally, the separation position of the wind turbine blades can be arranged in a position that ensures the weight of the outer blade section and the weight of the inner blade section are substantially equal to each other. Therefore, it is easier to meet the weight requirements during the transportation, handling, and lifting of the blade sections.

[0033] The connection point of a wind turbine blade can be arranged at a distance from the root section, which is between 20% and 70% (e.g., between 25% and 60%, or 30% and 55%) of the length of the wind turbine blade from the root section to the tip. The connection point can be on the blade portion of the wind turbine blade or at a separate location.

[0034] According to this embodiment, the blade connecting member is connected to the wind turbine blade at a location away from the root end and tip end of the wind turbine blade.

[0035] The location of the connection point along the 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 high drag introduced by the blade connection member during rotor rotation, thereby reducing energy production. On the other hand, positioning the connection point near the root end of the wind turbine blade results in low drag introduced by the blade connection member, thereby minimizing the adverse effects on the energy production of the wind turbine. However, support of the wind turbine blade via the blade connection member will not be very effective. By positioning the connection point at a distance between 20% and 70% of the length of the wind turbine blade from the root end, these considerations are balanced in such a way that effective support is achieved without introducing unacceptable drag. Furthermore, by positioning the connection member in this area, 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, and connecting blade members too close to the tip can cause significant pre-deformation of the wind turbine blade, which may hinder the ability to pitch the blade. Connection points within a blade section also include the separation points where that blade section connects to another blade section.

[0036] Each wind turbine blade may further include at least one intermediate blade portion, wherein the inner blade portion and the intermediate blade portion are connected to each other at a first separation position, and the intermediate blade portion and the outer blade portion are connected to each other at a second separation position, and at least the first separation position may be arranged between the root end and the connection point.

[0037] According to this embodiment, the wind turbine blade is made of at least three parts: an inner blade part, an outer blade part, and a middle blade part. The middle blade part is arranged between the inner blade part and the outer blade part. It is not excluded that two or more middle blade parts are connected end-to-end between the inner blade part and the outer blade part, but for clarity, only one middle blade is described below.

[0038] According to this embodiment, since the wind turbine blade comprises three blade sections, it also defines two separate locations where adjacent blade sections connect to each other. More specifically, the inner blade section and the middle blade section connect to each other at a first separate location, and the middle blade section and the outer blade section connect to each other at a second separate location. Therefore, the first separate location is closer to the root end than the second separate location, and the second separate location is closer to the tip end than the first separate location.

[0039] At least the first separation position is arranged between the root end and the connection point, i.e., arranged in the manner described above.

[0040] The second separation position can be arranged between the connection point and the tip. According to this embodiment, the connection point is formed on the middle blade portion.

[0041] Even though the support provided by the blade connecting member is more significant in the portion of the wind turbine blade between the root end and the connecting point than in the portion between the connecting point and the tip end, the load on the wind turbine blade in the latter part is still reduced due to the blade connecting member. Therefore, as long as the first separation position is located between the root end and the connecting point, the second separation position can still be positioned in that portion of the wind turbine blade.

[0042] As an alternative, the first and second separation positions can be located between the root end of the wind turbine blade and the connection point, i.e., in the part of the wind turbine blade where the support provided by the blade connection member has the greatest influence.

[0043] Modular blade designs can be provided by allowing the insertion of at least one intermediate blade section between the inner and outer blade sections. This allows wind turbine blades of various lengths to be manufactured using the same inner and outer blade sections, and with intermediate blade sections of varying lengths and / or a variety of numbers of intermediate blade sections arranged between the inner and outer blade sections. Therefore, only one mold design is needed to manufacture the inner blade section for many different blade sizes, and only one mold design is needed for the outer blade section. This significantly reduces manufacturing costs while allowing for the production of wind turbines with multiple rotor diameters in the same production line.

[0044] As described above, the middle leaf section can have a constant chord along its entire length, and the separation position can be arranged at the position that defines the maximum chord.

[0045] Each wind turbine blade may have at least two connection points, and the two connection points may be located separately between the root end and the first connection point, and the second connection point may be located between the first connection point and the tip end.

[0046] According to this embodiment, the wind turbine blades are supported by at least two sets of blade connecting members, which are connected to the wind turbine blades at two different locations along the length of the blade, i.e., at two different rotor radius locations. Thus, compared to an embodiment where two adjacent wind turbine blades are connected via only one blade connecting member, the support provided to the wind turbine blades by the blade connecting members is increased. Furthermore, the separation position is arranged inside the two connection points. Therefore, the separation position is located in a portion of the wind turbine blade that fully benefits from the support provided by these two sets of blade connecting members.

[0047] The pitch-controlled wind turbine may further include at least three pretensioning members, each pretensioning member being connected to one of the blade connection members and to the hub portion, each pretensioning member thereby providing pretension in the blade connection member to which it is connected, preferably by biasing a portion of the blade connection member toward the hub (e.g., the midway point of the blade connection member between the blade connection points).

[0048] According to this embodiment, the pretensioning member pulls the blade connecting member toward the hub, thereby providing pretension to the blade connecting member.

[0049] The blade connecting member can have a different stiffness than the pretensioning member, or the blade connecting member and the pretensioning member can have the same stiffness.

[0050] In this context, the term "hub portion" should be interpreted as meaning the hub or a part or element attached to the hub, since that part or element rotates with the hub relative to the nacelle. Such a part or element may be attached to the outer surface of the hub, protrude from the hub, be positioned within the hub, or be positioned in any other suitable manner, as long as it rotates with the hub.

[0051] The pretensioning member can be connected to the blade connection member at a location, for example, away from each connection point on the wind turbine blade, at a distance, for example, substantially equal to the connection point, i.e., about halfway between the wind turbine blades along the blade connection member.

[0052] According to this embodiment, since the pretension in the blade connecting member is provided through a pretensioning member that interconnects the blade connecting member and the hub portion, the pretension in both the pretensioning member and the blade connecting member can be controlled from the hub, thus providing an easy path for maintaining or adjusting the pretension. Furthermore, for a given pretension, the degree to which the average spanwise load is affected can be adjusted. For example, a shorter pretensioning member has a smaller effect on the average spanwise bending moment compared to a longer pretensioning member. Finally, since the pretensioning system can be softer than the blade connecting member, the risk of member slack is reduced.

[0053] The pretensioning member can be arranged to provide adjustable pretension in the blade connection member, or the provided pretension can be constant.

[0054] Pitch-controlled wind turbines can further include hub extenders that interconnect the wind turbine blades and hub.

[0055] In this document, the term "hub extender" should be interpreted as a component that connects to the hub at one end and to the root end of a wind turbine blade at the opposite end. This introduces a distance between the hub and the wind turbine blade. The wind turbine blade can be connected to the hub extender, for example, via a pitch bearing, thereby allowing the wind turbine blade to perform pitch motion relative to the hub extender and thus relative to the hub. The hub extender can have an aerodynamic shape or be equipped with aerodynamic enhancement elements such as airfoils, vortex generators, Gurney flaps, stall barriers, etc. Alternatively, the hub extender can have any other suitable shape, such as a cylinder.

[0056] Hub extenders allow for an increase in rotor diameter without altering the design of the wind turbine blades. Since the increased rotor diameter results in increased power production, it is possible to increase the nominal power of a given wind turbine model without replacing the molds used to manufacture the wind turbine blades.

[0057] 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 spherical bearing, or any other suitable type of bearing.

[0058] The bearing structure ensures that the wind turbine blades can rotate relative to the blade connection members via the bearing structure. As a result, the wind turbine blades can perform pitch control without affecting the blade connection members, thereby avoiding the application of undesirable loads, torsion, or tension to the blade connection members during pitch control.

[0059] When the bearing structure is, or includes, a spherical 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 is transmitted between the blade connection member and the wind turbine blade.

[0060] In cases where 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 area of ​​the bearing structure.

[0061] The root end of each wind turbine blade can be connected to the hub via a pitch bearing.

[0062] According to this embodiment, when pitch control is performed, the entire wind turbine blade rotates. This is sometimes referred to as "full pitch control".

[0063] Alternatively or additionally, each wind turbine blade may include a pitch bearing arranged in a separate position, thereby allowing the outer blade portion to perform pitch motion relative to the inner blade portion. This is sometimes referred to as "partial pitch".

[0064] Wind turbine blades capable of partial pitch control need to be divided into inner and outer blade sections to allow one part of the wind turbine blade to perform pitch motion relative to another part of the wind turbine blade. Therefore, it is advantageous that the separation positions for this purpose are arranged along the wind turbine blade according to the invention.

[0065] As an alternative, each wind turbine blade may include a pitch bearing disposed at the connection point, thereby allowing the portion of the wind turbine blade extending from the connection point to the tip to perform pitch motion relative to the portion of the wind turbine blade extending from the root to the connection point.

[0066] According to this embodiment, the wind turbine blade is separated at at least two locations, namely, as described above, between the root end of the wind turbine blade and the location where the blade connecting member is connected to the wind turbine blade.

[0067] Each wind turbine blade may include a first inner blade portion and a second inner blade portion, wherein the first inner blade portion includes a leading edge of the inner blade portion and the second inner blade portion includes a trailing edge of the inner blade portion, and the first inner blade portion and the second inner blade portion may be connected to each other along a separation interface that extends along a direction defined by the length of the wind turbine blade.

[0068] According to this embodiment, in addition to being separated transversely to the longitudinal direction of the wind turbine blade, the wind turbine blade is also separated along this longitudinal direction. However, this additional separation exists only in the inner blade portion. It is anticipated that the chord of the wind turbine blade is larger near the root end than near the tip end. For large wind turbine blades, the maximum chord may exceed the maximum transport size. Therefore, separating the wind turbine blade transversely to the chord direction is necessary to allow for transport of the wind turbine blade. This separation is sometimes referred to as "chord extension."

[0069] A pitch-controlled wind turbine can be a headwind turbine, meaning the rotor is pointed towards the oncoming wind. Alternatively, a wind turbine can be a tailwind turbine, meaning the rotor is away from the direction of the oncoming wind. Attached Figure Description

[0070] The invention will now be described in more detail with reference to the accompanying drawings, in which:

[0071] Figures 1 to 3 A pitch-controlled wind turbine according to a first embodiment of the present invention is shown;

[0072] Figure 4 and Figure 5 A pitch-controlled wind turbine according to a second embodiment of the present invention is shown;

[0073] Figure 6 and Figure 7 A pitch-controlled wind turbine according to a third embodiment of the present invention is shown;

[0074] Figure 8 This is a perspective view of a wind turbine blade for a wind turbine according to an embodiment of the present invention;

[0075] Figure 9 This is a side view of a wind turbine blade for a wind turbine according to an alternative embodiment of the present invention;

[0076] Figure 10 The diagram illustrates the connection between a blade connecting member for a wind turbine and a wind turbine blade according to an embodiment of the present invention; and

[0077] Figure 11 and Figure 12 A bearing structure for connecting a blade connecting member to a wind turbine blade according to an embodiment of the present invention is shown. Detailed Implementation

[0078] Figures 1 to 3 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, and Figure 3 Details of the wind turbine 1 are shown.

[0079] The wind turbine 1 includes a tower 2, a nacelle 3 mounted on the tower 2, and a hub 4 mounted on the nacelle 2. Three wind turbine blades 5 are connected to the hub 4. Each wind turbine blade 5 extends between a root end 6 connected to the hub 4 and an oppositely arranged tip end 7.

[0080] The wind turbine 1 also includes three blade connecting members 8. Each blade connecting member 8 interconnects two adjacent wind turbine blades 5 by connecting to a connection point 9 at the corresponding wind turbine blade 5. The wind turbine blades 5 can support each other via the blade connecting members 8 because the loads on the wind turbine blades 5, particularly the edge loads and wing loads, are distributed among the wind turbine blades 5 via the blade connecting members 8. In particular, due to the presence of the blade connecting members 8, the load on the portion of the wind turbine blade 5 arranged between the root end 6 and the connection point 9 is reduced.

[0081] Each wind turbine blade 5 includes an inner blade portion 5a with a root end 6 and an outer blade portion 5b with a tip end 7. The inner blade portion 5a and the outer blade portion 5b are connected to each other at a separation position 10, i.e., the wind turbine blade 5 is a so-called "split blade". Therefore, the inner blade portion 5a and the outer blade portion 5b can be manufactured separately and transported separately to the location of the wind turbine 1, and the inner blade portion 5a and the outer blade portion 5b can be assembled at the location of the wind turbine 1 to form the wind turbine blade 5. Therefore, the length of the wind turbine blade 5 is allowed to exceed the maximum length specified by transportation requirements.

[0082] The separation point 10 is located between the root end 6 and the connection point 9, which is the point where the blade connecting member 8 connects to the wind turbine blade 5. Therefore, the separation point 10 is positioned in the portion of the wind turbine blade 5 where the load is expected to be significantly reduced due to the blade connecting member 8. Thus, it can be anticipated that the wind turbine blade 5 will be able to handle the loads that occur during the operation of the wind turbine 1, regardless of any weaknesses introduced into the wind turbine blade 5 due to the separation of the wind turbine blade 5.

[0083] Furthermore, arranging the separation position 10 in this part of the wind turbine blade 5 allows easy access to the separation position 10 from the hub 4.

[0084] Figure 4 and Figure 5 A pitch-controlled wind turbine 1 according to a second embodiment of the present invention is shown. Figure 4 This is a front view of wind turbine 1. Figure 5Details of the wind turbine 1 are shown.

[0085] Figure 4 and Figure 5 Wind turbine 1 and Figures 1 to 3 The wind turbine 1 is very similar, so it will not be described in detail here.

[0086] Figure 4 and Figure 5 The wind turbine 1 also includes three pretensioning members 11. Each pretensioning member 11 is connected to one of the blade connection members 8 at approximately halfway between the connection points 9 at the wind turbine blades 5, and is connected to the hub 4. Thus, the pretensioning members 11 pull the blade connection members 8 toward the hub 4, thereby providing pretension in the blade connection members 8.

[0087] The pretension in the blade connecting member 8 can be adjusted by the pretension member 11, thereby controlling the degree to which the wind turbine blades 5 support each other via the blade connecting member 8.

[0088] The blade connection member 8 may include one or more sub-components, such as two sub-components or segments. This is particularly advantageous when the wind turbine includes a pretensioning member. Here, the connection member 8 may, for example and preferably includes two sub-segments, wherein each segment connects the blade connection point to a connector element (not shown), to which the pretensioning member is also connected. This allows for a secure and centered connection between the connection member and the pretensioning member.

[0089] Figure 6 and Figure 7 A pitch-controlled wind turbine 1 according to a third embodiment of the present invention is shown. Figure 6 This is a front view of wind turbine 1. Figure 7 Details of the wind turbine 1 are shown.

[0090] Figure 6 and Figure 7 Wind turbine 1 and Figures 1 to 3 The wind turbine 1 is very similar, so it will not be described in detail here.

[0091] exist Figure 6 and Figure 7In the wind turbine 1, each wind turbine blade 5 also includes an intermediate blade portion 5c arranged between an inner blade portion 5a and an outer blade portion 5b. The inner blade portion 5a and the intermediate blade portion 5c are connected to each other at a first separation position 10a, and the intermediate blade portion 5c and the outer blade portion 5b are connected to each other at a second separation position 10b. Thus, each wind turbine blade 5 is divided into three blade portions 5a, 5b, and 5c, defining two separation positions 10a and 10b. Both separation positions 10a and 10b are arranged between the root end 6 and the connection point 9, i.e., in the portion where the load reduction expected to be caused by the support provided by the blade connection member 8 is most significant. In another example (not shown), the blade connection point is on the intermediate blade portion 5c. The blade connection point could be on the inner blade portion 5a, but this is not preferred because the load borne by the connection member would be relatively low.

[0092] Dividing the wind turbine blade 5 into three parts allows for longer wind turbine blades 5 without conflicting with transportation restrictions. Furthermore, this allows for a modular design of the wind turbine 1, as the rotor diameter of the wind turbine 1 can be varied by appropriately selecting the length of the middle blade section 5c without altering the design of the inner blade section 5a and the outer blade section 5b.

[0093] Figure 8 This is a perspective view of 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 connected to each other at a separated position 10, as shown above. Figures 1 to 3 As mentioned above.

[0094] The inner blade portion 5a and the outer blade portion 5b are connected to each other via a pitch bearing 12. Thus, the outer blade portion 5b can perform pitch movement relative to the inner blade portion 5a, that is, perform partial pitch.

[0095] Figure 9 This is a side view of a wind turbine blade 5 for a wind turbine according to an alternative embodiment of the present invention. The wind turbine blade 5 includes an inner blade portion 5a and an outer blade portion 5b connected to each other at a separated position 10.

[0096] The inner blade portion 5a includes a first inner blade portion 5a' and a second inner blade portion 5a". The first inner blade portion 5a' includes the leading edge 13 of the inner blade portion 5a, and the second inner blade portion 5a" includes the trailing edge 14 of the inner blade portion 5a.

[0097] The first inner blade portion 5a' and the second inner blade portion 5a" are connected to each other along a separation interface 15, which extends substantially along the direction defined by the length of the wind turbine blade 5 and substantially perpendicular to the lateral separation interface between the inner blade portion 5a and the outer blade portion 5b at the separation position 10. Therefore, Figure 9 The wind turbine blade 5 shown is divided into three parts: a first inner blade part 5a', a second inner blade part 5a'", and an outer blade part 5b. Here, the blade connection point is preferably on the first inner blade part 5a' or the outer blade part 5b, including in the separated position.

[0098] The chord of the wind turbine blade 5 is larger in the inner blade portion 5a than in the outer blade portion 5b. By dividing the inner blade portion 5a into a first inner blade portion 5a' and a second inner blade portion 5a" it is possible to ensure that the widths of blade portions 5a', 5a" and 5b do not exceed the maximum transport constraint.

[0099] Figure 10 This is a perspective view of a portion of a wind turbine blade 5 for a wind turbine according to an embodiment of the present invention. More specifically, Figure 10 A portion of a wind turbine blade 5 is shown, including a connection point 9, which is the location where the blade connecting member 8 is connected to the wind turbine blade 5.

[0100] The blade connection member 8 is connected to the wind turbine blade 5 via the bearing structure 16. This allows the wind turbine blade 5 to perform pitch control without affecting the blade connection member 8. This avoids applying undesirable loads, torsion, or tension to the blade connection member 8 during pitch control of the wind turbine blade 5.

[0101] Figure 11 and 12 Two different bearing structures 16 according to embodiments of the present invention are shown for connecting a blade connecting member to a wind turbine blade. For example, Figure 11 and Figure 12 The bearing structure 16 can be applied in Figure 10 The wind turbine blade shown.

[0102] The plate-shaped structure 17 is connected to the wind turbine blade. Figure 11 and Figure 12 Two different structures are shown for providing this connection.

[0103] The blade connecting member is attached to the eyelet 18, which is rotatably mounted on the plate structure 17, thereby allowing the wind turbine blade (attached to the plate structure 17) to pitch relative to the eyelet 18 and thus relative to the blade connecting member connected to the wind turbine blade.

Claims

1. A pitch-controlled wind turbine (1), the wind turbine 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), wherein, Each wind turbine blade (5) extends between a root end (6) and a tip end (7) connected to the hub (4), and the wind turbine (1) further includes at least three blade connecting members (8), each blade connecting member (8) extending between a connection point (9) on a wind turbine blade (5) and a connection point (9) on an adjacent wind turbine blade (5), wherein the connection point (9) on a given wind turbine blade (5) is arranged to be spaced apart from the root end (6) and from the tip end (7) of the wind turbine blade (5). Each wind turbine blade (5) includes an inner blade portion (5a) and an outer blade portion (5b), the inner blade portion including the root end (6) and the outer blade portion including the tip end (7), the inner blade portion (5a) and the outer blade portion (5b) being connected to each other at a separation position (10), wherein the separation position (10) is arranged between the root end (6) and the connection point (9), and wherein the connection point (9) of the wind turbine blade (5) is arranged at a distance from the root end (6) between 20% and 70% of the length of the wind turbine blade (5) from the root end (6) to the tip end (7). The wind turbine further includes at least three pretensioning members (11), each pretensioning member (11) being connected to one of the blade connecting members (8) and to the hub portion (4), each pretensioning member (11) thereby providing pretension in the blade connecting member (8) to which it is connected.

2. The pitch-controlled wind turbine (1) according to claim 1, wherein, The separation position (10) of the wind turbine blade (5) is arranged at a distance from the root end (6) by a distance between 15% and 60% of the length of the wind turbine blade (5) from the root end (6) to the tip end (7).

3. The pitch-controlled wind turbine (1) according to claim 1 or 2, wherein, The separation position (10) of the wind turbine blade (5) is located at a position where the thickness-to-chord ratio of the wind turbine blade (5) is between 24% and 70%.

4. The pitch-controlled wind turbine (1) according to claim 1 or 2, wherein, The separation position (10) of the wind turbine blade (5) is arranged at the position of the maximum chord.

5. The pitch-controlled wind turbine (1) according to claim 1 or 2, wherein, The separation position (10) of the wind turbine blade (5) is arranged at or near the center of gravity of the wind turbine blade (5).

6. The pitch-controlled wind turbine (1) according to claim 1 or 2, wherein, The separation position (10) of the wind turbine blade (5) is arranged at a distance between 50m and 100m from the tip end (7).

7. The pitch-controlled wind turbine (1) according to claim 1 or 2, wherein, The connection point (9) of the wind turbine blade (5) is arranged at a distance from the root end (6) at a distance between 25% and 60% of the length of the wind turbine blade (5) from the root end (6) to the tip end (7).

8. The pitch-controlled wind turbine (1) according to claim 1 or 2, wherein, Each wind turbine blade (5) further includes at least one intermediate blade portion (5c), wherein the inner blade portion (5a) and the intermediate blade portion (5c) are connected to each other at a first separation position (10a), and the intermediate blade portion (5c) and the outer blade portion (5b) are connected to each other at a second separation position (10b), wherein at least the first separation position (10a) is arranged between the root end (6) and the connection point (9).

9. The pitch-controlled wind turbine (1) according to claim 8, wherein, The second separation position (10b) is arranged between the connection point (9) and the tip end (7).

10. The pitch-controlled wind turbine (1) according to claim 1 or 2, wherein, Each wind turbine blade (5) is provided with at least two connection points (9), wherein the separation position (10) is arranged between the root end (6) and the first connection point (9), and the second connection point (9) is arranged between the first connection point (9) and the tip end (7).

11. The pitch-controlled wind turbine (1) according to claim 1 or 2, the wind turbine further comprising a hub extender interconnecting the wind turbine blades (5) and the hub (4).

12. The pitch-controlled wind turbine (1) according to claim 1 or 2, wherein, The blade connecting member (8) is connected to the corresponding wind turbine blade (5) via a bearing structure (16) mounted on the wind turbine blade (5) or forming part of the wind turbine blade (5).

13. The pitch-controlled wind turbine (1) according to claim 1 or 2, wherein, The root end (6) of each wind turbine blade (5) is connected to the hub (4) via a pitch bearing.

14. The pitch-controlled wind turbine (1) according to claim 1 or 2, wherein, Each wind turbine blade (5) includes a pitch bearing (12) arranged at the separated position (10), thereby allowing the outer blade portion (5b) to pitch relative to the inner blade portion (5a).

15. The pitch-controlled wind turbine (1) according to claim 1 or 2, wherein, Each wind turbine blade (5) has an inner blade portion (5a) comprising a first inner blade portion (5a') and a second inner blade portion (5a"), wherein the first inner blade portion (5a') comprises the leading edge (13) of the inner blade portion (5a), and the second inner blade portion (5a") comprises the trailing edge (14) of the inner blade portion (5a), and wherein the first inner blade portion (5a') and the second inner blade portion (5a") are connected to each other along a separation interface (15) extending in a direction defined by the length of the wind turbine blade (5).

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

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