Method for controlling position of blade lift yoke and blade lift yoke of rotor blade of wind turbine

Abstract

A method for controlling the position of a blade lift yoke (1) of a rotor blade (2) of a wind turbine is disclosed. The blade lift yoke used comprises a yoke unit (6) and a suspension unit (7) connected to a crane (41) at a crane attachment point (P). The yoke unit comprises a base section (61) and a holding device (61) comprising a lower clamping member (64) and an upper clamping member (65). The suspension unit comprises a plurality of actuators (71, 72, 73, 74) each attached to the yoke unit at a yoke attachment point (70) and extending from said yoke attachment point towards the crane attachment point such that these actuators are angled relative to each other. The first actuator (71), the second actuator (72), and the third actuator (73) are individually controlled by a control unit, thereby changing the length of at least one of the first actuator, the second actuator, and the third actuator, and moving the position of the lower clamping member relative to the crane attachment point.

Description

Technical Field

[0001] The present invention relates to a method for controlling the position of a blade lifting yoke of a rotor blade of a wind turbine, the blade lifting yoke comprising a yoke unit and a suspension unit, the yoke unit comprising a base section and a holding device, and the suspension unit being connected to a crane at a crane attachment point, wherein the holding device comprises a lower clamping member and an upper clamping member, the lower clamping member being configured to support the rotor blade, the upper clamping member being configured to press the rotor blade against the lower clamping member and being spaced apart from the lower clamping member in a height direction perpendicular to a longitudinal direction, and wherein the suspension unit comprises a plurality of actuators, each actuator being attached to the yoke unit at a yoke attachment point and extending from the yoke attachment point towards the crane attachment point, the yoke attachment points being spaced apart from one another such that the actuators are angled relative to one another. The present invention further relates to a blade lifting yoke of a rotor blade of a wind turbine. Background Art

[0002] The blade lifting yoke is used to hold a rotor blade to be installed on a wind turbine while it is being lifted using a crane from a location on the ground or on a vessel to the nacelle of the wind turbine. The rotor blade is held by the blade lifting yoke in such a way that the longitudinal axis of the rotor blade extends parallel to the longitudinal direction of the blade lifting yoke.

[0003] When attaching rotor blades to a wind turbine's hub, the bolts at the rotor blade's root need to be precisely aligned with openings in the hub. This can be accomplished by using a crane to move the entire blade lift yoke holding the rotor blade, by rotating the hub, and / or by changing the hub's pitch. However, a wind turbine's hydraulically driven blade pitch system cannot move freely due to limitations imposed by the stroke length of the hydraulic cylinder, and electrically operated blade pitch systems can only move when the wind turbine is powered. This is not the case, particularly at sea.

[0004] Some prior art blade lift yokes can tilt and pitch rotor blades by extending or shortening actuators (typically hydraulic cylinders). However, as rotor blades get larger, a small change in position at the blade lift yoke can result in a larger movement at the root. This makes it difficult to maneuver large rotor blades with sufficient precision, especially during high winds.

[0005] Another problem that has become increasingly problematic as rotor blades have grown in size is that the blade lift yokes also need to become larger and stronger, making them more difficult to control when latching onto and releasing the rotor blades. Releasing the rotor blade can result in the blade lift yoke sliding off the rotor blade prematurely, with the risk of swinging back and hitting the rotor blade, or the load of the blade lift yoke being carried by the rotor blade, potentially overloading the rotor blade. When viewed in the longitudinal direction, the blade lift yoke typically has the overall shape of the letter C, spanning either the leading or trailing edge of the rotor blade, with the opposite edge of the rotor blade protruding away from the body of the C. This results in an imbalance in the blade lift yoke when it is not carrying a rotor blade, which is usually compensated for by providing counterweights at the free ends of the legs of the C, thereby reducing the risk of a swinging motion when the rotor blade is released. However, the counterweights make the blade lift yoke heavier and more difficult to control. The precise weight balance also means that it is typically necessary to have several different blade lift yokes for different sizes and types of rotor blades. Summary of the Invention

[0006] Against this background, it is an object of the present invention to provide a method which allows for a more precise control of the blade lifting yoke during operation.

[0007] This and further objects are achieved by the method mentioned in the introduction, which is further characterized in that the first actuator, the second actuator and the third actuator are individually controlled by a control unit, thereby changing the length of at least one of the first actuator, the second actuator and the third actuator and moving the position of the lower clamping member relative to the crane attachment point, wherein the yoke attachment points to which the first actuator and the second actuator are attached are arranged spaced apart from each other in the longitudinal direction, and wherein the yoke attachment point to which the third actuator is attached is arranged spaced apart from at least one of the yoke attachment points to which the first actuator and the second actuator are attached in a width direction, the width direction being perpendicular to the longitudinal direction and the height direction.

[0008] This allows the overall center of gravity of the blade lifting yoke, when viewed in the longitudinal direction, to remain in the same vertical plane as the crane attachment point, even when the load changes, such as when latching onto or releasing the rotor blade. With the center of gravity located directly below the crane attachment point, the blade lifting yoke holding the rotor blade can be pitched about the center of gravity, which is not possible with prior art blade lifting yokes. This makes it easier to control the pitch of the blade lifting yoke, making the rotor blade less sensitive to external factors, such as wind. Precise control of pitch can be particularly advantageous when attaching the rotor blade to the hub of a wind turbine, where the geometric center of the blade root needs to be aligned with the geometric center of the hub. Controlling the pitch in this way also allows the rotor blade to be intentionally pitched with high precision to align the bolts at the blade root with the openings in the hub, because when the geometric center of the rotor blade is close to the center of gravity, undesirable translation of the geometric center of the rotor blade due to pitching is limited.

[0009] The center of gravity can also be maintained in the same vertical plane as the crane attachment point when viewed in the width direction, thereby providing pitch stability and / or control in addition to or instead of pitch stability and / or control. This can, for example, allow the root of the rotor blade to remain substantially stationary while the rest of the rotor blade is tilted, thereby allowing the root to be aligned with the hub of the wind turbine, for example, if the bolts at the root are angled relative to the opening in the hub into which they are to be inserted.

[0010] Another advantage of keeping the center of gravity aligned with the crane attachment point is that the same blade lifting yoke can be used for many different rotor blade designs, where the center of gravity, and therefore the overall center of gravity, of the rotor blade will be located at many different positions relative to the lower clamping member. This could be due to, for example, different positions of the center of gravity within the blade profile, or due to rotor blades of varying sizes or weights. This shift in the center of gravity position can then be compensated for by changing the length of one or more actuators before starting the lift.

[0011] In addition to being more stable when carrying the rotor blade, the ability to shift the position of the lower clamping member relative to the position of the crane attachment point also allows the blade lifting yoke itself to have better stability by, for example, compensating for one side being heavier than the other. Thus, the need for counterweights is reduced or potentially even eliminated.

[0012] When viewed in the vertical direction, counterweights are typically positioned higher on the blade lift yoke. Removing or reducing the counterweight will therefore lower the blade lift yoke's center of gravity when viewed in the longitudinal direction. This, in turn, means that the blade lift yoke's center of gravity, and therefore the combined center of gravity of the blade lift yoke and rotor blade, is closer to the geometric center of the rotor blade root, which is carried by the blade lift yoke. As also mentioned above, this facilitates precise pitching of the rotor blade, thereby facilitating connection to the wind turbine hub.

[0013] The actuator may, for example, be selected from the group consisting of: a hydraulic linear cylinder, an electric linear cylinder, a cable system including one or more electrically or hydraulically driven winches, a rack and pinion mechanism, a threaded rod, and combinations thereof.

[0014] The yoke attachment points can be located on the retaining device or on the base section, depending on, for example, the load-bearing capacity of the different parts of the yoke unit. To optimize the ability to adjust the position of the rotor blade (e.g., pitch), the yoke attachment points are advantageously located far apart from one another. The yoke attachment points can be implemented, for example, as brackets, supports, hooks, bolts, threaded openings, etc. The actuator can be provided with a hook, shackle, bolt, etc. for interconnecting with the yoke attachment points.

[0015] The holding device or base section may comprise a frame having the shape of the letter C and spanning an edge of the rotor blade, preferably a leading edge of the rotor blade, during operation.

[0016] In one embodiment, the method further comprises varying the length of a fourth actuator, the yoke attachment point to which the fourth actuator is attached being spaced longitudinally from the yoke attachment point to which the first actuator is attached and being in the same plane extending widthwise as the yoke attachment point to which the second actuator is attached, the fourth actuator being individually controlled by a control unit. In this embodiment, it may be advantageous that the yoke attachment points to which the first and third actuators are attached are also arranged in the same plane extending widthwise, said plane being spaced longitudinally from the plane to which the yoke attachment points of the second and fourth actuators are attached. This allows for even better control of the blade lift yokes when stabilisation or variation of pitch and / or tilt is required. The use of two sets of actuators may also reduce torsional loads on the rotor blades.

[0017] In one embodiment, the root of the rotor blade is aligned with the hub of the wind turbine by varying the length of actuators attached to widthwise spaced yoke attachment points, thereby varying the pitch of the rotor blade.

[0018] In one embodiment, all actuators are shortened to raise the blade lifting yoke, or extended to lower it. While this only applies to minor movements of the blade lifting yoke, it can be advantageous during the final stages of installing the rotor blades, as this height adjustment can be performed by the yoke operator, eliminating the need for a crane operator.

[0019] If the blade lift yoke holding the rotor blade is simply lifted and unaffected by external factors such as wind, the position of the center of gravity will be essentially constant, but this is rarely the case. Therefore, continuous adjustment of the actuator length can be advantageous. For example, when a rotor blade is released, the blade lift yoke is typically released gradually, causing the center of gravity to gradually shift from the position of the overall center of gravity to the position of the blade lift yoke's center of gravity. By gradually adjusting the actuator length, good control of the blade lift yoke is maintained at all times, thereby reducing the risk of sudden movement of the blade lift mechanism at the end of the release process, for example.

[0020] The length of the actuator can be varied according to a predetermined pattern that can be programmed into the control unit, but it is currently considered advantageous to vary the length in response to changes in the loads acting on the blade lift yoke. It is also possible to initiate a combination of several predetermined patterns after operator input has been reached or a certain process step has been completed, such that some portions of the rotor blade lift can follow a predetermined pattern while other portions are controlled solely based on real-time data and / or user input.

[0021] The control unit may be in data communication with a control system, such as an external control system, which may perform real-time calculations of the necessary changes in length of the actuators. These calculations may be based on data obtained from sensors provided on or at the blade lift yoke, based on weather data, and / or based on user input (such as an indication from an operator that the rotor blades need to be lowered, raised, tilted or pitched). Sensors provided on or at one or more actuators, such as pressure sensors or force sensors, may provide data about the loads affecting each actuator. Other examples of sensors are stroke length sensors and angle sensors. Vision-based sensor systems may also be used to provide data about the status and / or position of the actuators, yoke units or other relevant parts.

[0022] In a second aspect of the invention, the above-mentioned and further objects are achieved by a blade lifting yoke of the type mentioned in the introduction, which is further characterized in that the first actuator, the second actuator and the third actuator can be individually controlled by a control unit, each of these actuators has an adjustable length and is at least controllable so that one actuator can be extended and the other actuator can be shortened, and the yoke attachment points to which the first actuator and the second actuator are attached are arranged at intervals from each other in the longitudinal direction, and the yoke attachment point to which the third actuator is attached is arranged at intervals from at least one of the yoke attachment points to which the first actuator and the second actuator are attached in a width direction, and the width direction is perpendicular to the longitudinal direction and the height direction.

[0023] The above description of the method includes several examples of embodiments of the blade lift yoke, and it should be understood that these examples and the advantages provided by these examples also apply to the second aspect of the present invention. Similarly, it should be understood that the embodiments and advantages described below with reference to one aspect of the present invention also apply to the other aspect, unless otherwise stated. In general, embodiments and advantages will be described with reference to only one embodiment to avoid excessive repetition. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In the following description, embodiments of the present invention will be described with reference to the accompanying schematic drawings, in which:

[0025] Figure 1 Schematic diagram of a wind turbine and a crane lifting the blade lifting yoke holding the rotor blades.

[0026] Figure 2 is a perspective view of a section of a rotor blade carried by a blade lifting yoke suspended from a crane,

[0027] Figure 3 is a cross-sectional view of a rotor blade carried by a blade lift yoke,

[0028] Figure 4 is a cross-sectional view of the blade lifting yoke and rotor blades suspended from a crane.

[0029] Figure 5 Corresponding to Figure 4 , but the rotor blades are carried by the blade lift yoke,

[0030] Figure 6 Corresponding to Figure 5 , but showing three different positions of the blade lift yoke, and

[0031] Figure 7 It is a perspective view of another blade lift yoke holding the rotor blade. DETAILED DESCRIPTION

[0032] First reference Figure 1 , a blade lifting yoke 1 holds a rotor blade 2 while being lifted by a crane 4 to a nacelle 31 of a wind turbine 3. Here, an offshore installation is shown, wherein both the crane and the wind turbine are supported on a seabed 51 below sea level 52, but it will be appreciated that the present invention is not limited to offshore use and may be used for any operation involving the lifting of rotor blades.

[0033] Hereinafter, the same reference numerals will be used for elements having substantially the same function even though the elements are not necessarily identical.

[0034] Blade lifting yoke 1 Figure 2 and Figure 3 , the blade lifting yoke holds a segment of the rotor blade 2. The blade lifting yoke comprises a yoke unit 6 and a suspension unit 7, and the yoke unit further comprises a base segment 61 and two holding devices 62, which are arranged at opposite ends of the base segment at a distance from each other in the longitudinal direction L.

[0035] As in Figure 2 As best seen in FIG, the suspension unit 7 is connected at a crane attachment point P to the hook 41 of the crane.

[0036] Each retaining device 62 comprises a frame 63 in the shape of the letter C, wherein a lower clamping member 64 on a lower leg 631 of the C supports the rotor blade 2, and an upper clamping member 65 on an upper leg 632 presses the rotor blade against the lower clamping member. Here, the C-shape spans the leading edge 21 of the rotor blade, while the trailing edge 22 extends beyond the C-shape. This is considered advantageous because the portion of the rotor blade closer to the leading edge is heavier than the portion closer to the trailing edge, but this does not exclude the possibility of the C-shape spanning the trailing edge.

[0037] The lower clamping member 64 and the upper clamping member 65 are spaced apart from each other in a height direction H perpendicular to the longitudinal direction L. The width direction D is perpendicular to both the longitudinal direction and the height direction. Here, the holding device further includes a support member 66 spaced apart from the lower clamping member 64 in the width direction.

[0038] As viewed in the longitudinal direction L Figure 3 As shown, the reinforcing web 23 extends vertically inside the rotor blade 2, and the lower clamping members 64 and the upper clamping members 65 engage the rotor blade where the web joins the rotor blade shell 24. The blade lifting yoke and the overall center of gravity 8 of the rotor blade are close to the web, slightly towards the trailing edge of the rotor blade.

[0039] exist Figure 2In the embodiment of the invention, the suspension unit 7 comprises four yoke attachment points 70, two yoke attachment points at each holding device 62, which are spaced apart from each other in the width direction W. An actuator 71, 72, 73, 74 is connected to each yoke attachment point at one end and to a cable 75 extending to the crane attachment point P at the other end. Since the yoke attachment points 70 are spaced apart from each other in the width direction W and the longitudinal direction L, the actuators extend at angles to each other in the longitudinal direction and the width direction. Figure 2 and Figure 3 The distances between the yoke attachment points in the width direction vary slightly.

[0040] Figure 2 All of the actuators 71 , 72 , 73 , 74 shown are hydraulic cylinders, but it will be appreciated that other types of actuators may be employed.

[0041] Figure 4 and Figure 5 The process of arranging a rotor blade 2 in / on the blade lifting yoke 1 is shown.

[0042] Figure 4 Only the center of gravity 81 of the blade lifting yoke 1 is shown to the left of the clamping members 64, 65, and only the center of gravity 82 of the rotor blade 2 is shown to the right of the web 23. As indicated by the dot-dash line, the crane attachment point P is located directly above the center of gravity 81 of the blade lifting yoke 1. Figure 2 This is achieved by shortening the left actuator 71 and extending the right actuator 73 compared to that shown.

[0043] When Figure 4 When the rotor blade 2 is inserted into the holding device 62 (or the blade lifting yoke 1 is displaced in the opposite direction) as indicated by the arrow in FIG. 1 , the rotor blade rests on the lower clamping member 64 and the support member 66, and then Figure 5 The overall center of gravity 8 is shown positioned. To compensate for this shift in the center of gravity of the load carried by the crane, the left actuator 71 is extended and the right actuator 73 is shortened, so that the crane attachment point P is shifted to the right as indicated by the arrow until it is directly above the center of gravity 8.

[0044] Figure 6 Three positions of the same blade lifting yoke 1 holding a rotor blade 2 are shown, the left position corresponding to Figure 5 In the diagram. Figure 6In the position shown in the center of the figure, the blade lifting yoke 1 is pitched forward by shortening the left actuator 71 and extending the right actuator 73, while in the position shown on the right, the blade lifting yoke is pitched leftward by extending the left actuator 71 and shortening the right actuator 73. As indicated by lines A and B, the vertical distance between the crane attachment point P and the center of gravity 8 remains the same regardless of the pitch change, which helps to stabilize and control the blade lifting yoke 1 when in use.

[0045] like Figure 6 The pitch control shown can be used for several different purposes, including facilitating latching or releasing of the rotor blades and compensating for wind loads. However, it is particularly advantageous to allow the root of the rotor blade (not shown) to be aligned with the hub of the wind turbine.

[0046] like Figure 6 As shown, the height direction H (which is defined as extending between the lower clamping member 64 and the upper clamping member 65) therefore rotates together with the blade lifting yoke during pitch change. The same applies to the W direction which is perpendicular to the height direction.

[0047] exist Figure 2 、 Figure 4 、 Figure 5 and Figure 6 In the embodiment of the present invention, the actuators 71, 72, 73, 74 can be shortened and extended independently, but it is also possible to interconnect two actuators so that shortening of one actuator causes extension of the other actuator, and vice versa.

[0048] Figure 7 Another embodiment of a blade lift yoke 1 holding a segment of a rotor blade 2 is seen in FIG. In this embodiment, the base segment 61 has the shape of the letter C, and the holding device comprises a lower portion (not visible) on the lower leg of the C and an upper portion 621 on the upper leg 611 of the C. The C-shape spans the leading edge 21 of the rotor blade, while the trailing edge 22 extends out of the C-shape. An upper clamping member 65 is arranged on the upper portion 621 of the holding device, it being understood that the lower clamping member (not visible) is located on the lower portion of the holding device, so that the rotor blade is held in a manner similar to that of the blade lift yoke 1 . Figure 3 is held in the same manner as shown, except that this embodiment does not include a support member.

[0049] exist Figure 7 In the embodiment, the first actuator 71 is an electrically operated cable winch, while the second actuator 72 and the third actuator 73 are Figure 2 This combination is intended to illustrate different embodiments of the actuators, but it is generally advantageous for all actuators to be of the same type.

[0050] The yoke attachment point, to which the first actuator 71 and the second actuator 72 are connected, is located here on the upper part 621 of the holding device, while the yoke attachment point, to which the third actuator 73 is connected, is located on the base section 61 .

[0051] The embodiments of the different parts of the blade lifting yoke 1 described herein can be combined in different ways, which can result in blade lifting yokes different from the one shown. The embodiments shown in the drawings are intended only as examples and numerous variations are possible within the scope of the claims.

Claims

1. A method for controlling the position of a blade lifting yoke of a rotor blade of a wind turbine, the blade lifting yoke comprising a yoke unit and a suspension unit, the yoke unit comprising a base section and a holding device, and the suspension unit being connected to a crane at a crane attachment point, in, The holding device comprises a lower clamping member and an upper clamping member, the lower clamping member being configured to support the rotor blade, the upper clamping member being configured to press the rotor blade against the lower clamping member and being spaced apart from the lower clamping member in a height direction, the height direction being perpendicular to the longitudinal direction, and wherein the suspension unit comprises a plurality of actuators, each actuator being attached to the yoke unit at a yoke attachment point and extending from said yoke attachment point towards the crane attachment point, and said yoke attachment points being spaced from one another such that the actuators are angled relative to one another, Characterized in that the first actuator, the second actuator and the third actuator are individually controlled by a control unit, thereby changing the length of at least one of the first actuator, the second actuator and the third actuator and moving the position of the lower clamping member relative to the crane attachment point, wherein the yoke attachment points to which the first actuator and the second actuator are attached are arranged spaced apart from each other in the longitudinal direction, and wherein the yoke attachment point to which the third actuator is attached is arranged spaced apart from at least one of the yoke attachment points to which the first actuator and the second actuator are attached in a width direction, the width direction being perpendicular to the longitudinal direction and the height direction.

2. The method according to claim 1 further includes changing the length of a fourth actuator, which is attached to a yoke attachment point, the yoke attachment point to which the fourth actuator is attached is spaced apart from the yoke attachment point to which the first actuator is attached in the longitudinal direction, and is in the same plane extending along the width direction as the yoke attachment point to which the second actuator is attached, and the fourth actuator is individually controlled by the control unit.

3. The method according to one or more of the preceding claims, wherein: The root of the rotor blade is aligned with the hub of the wind turbine by varying the length of actuators attached to yoke attachment points spaced apart from one another in the width direction, thereby varying the pitch of the rotor blade.

4. The method according to one or more of the preceding claims, wherein: Shorten all actuators to raise the blade lift yoke, or extend all actuators to lower the blade lift yoke.

5. The method according to one or more of the preceding claims, wherein: The lengths of the actuators vary in response to changes in loads affecting the blade lift yoke.

6. The method according to one or more of the preceding claims, wherein: One or more control units are in data communication with an external control system.

7. The method according to one or more of the preceding claims, wherein: The necessary change in length of the one or more actuators is calculated based on data obtained from sensors provided on or at the blade lifting yoke, based on weather data and / or based on user input.

8. A blade lifting yoke for a rotor blade of a wind turbine, the blade lifting yoke comprising a yoke unit and a suspension unit, the yoke unit comprising a base section and a holding device, and the suspension unit comprising a crane attachment point, in, The holding device includes a lower clamping member and an upper clamping member, the lower clamping member being configured to support the rotor blade, the upper clamping member being configured to press the rotor blade against the lower clamping member and being spaced apart from the lower clamping member in a height direction, the height direction being perpendicular to the longitudinal direction, wherein the suspension unit comprises a plurality of actuators, each actuator being attached to the yoke unit at a yoke attachment point and extending from said yoke attachment point towards the crane attachment point, and said yoke attachment points being spaced from one another such that the actuators are angled relative to one another, It is characterized in that the first actuator, the second actuator and the third actuator can be individually controlled by a control unit, each of these actuators has an adjustable length and is at least controllable so that one actuator can be extended and the other actuator can be shortened, and the yoke attachment points to which the first actuator and the second actuator are attached are arranged at intervals from each other in the longitudinal direction, and the yoke attachment point to which the third actuator is attached is arranged at intervals from at least one of the yoke attachment points to which the first actuator and the second actuator are attached in the width direction, and the width direction is perpendicular to the longitudinal direction and the height direction.

9. The blade lifting yoke according to claim 8 further includes a fourth actuator, which is an actuator arranged at intervals from the first actuator in the longitudinal direction and is in the same plane extending along the width direction as the second actuator, and the fourth actuator is independently controlled by the control unit.

10. The blade lifting yoke according to claim 8 or 9, wherein: The blade lifting yoke includes two holding devices, which are arranged at opposite ends of the base section at a distance from each other in the longitudinal direction, and the first actuator and the third actuator are located at one holding device, and the second actuator and the fourth actuator, if present, are located at the other holding device.

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