EP4782384A1 - Load stabilization assembly and load stabilization method - Google Patents

Abstract

Stabilization assembly (1) for stabilizing a load (L) suspended from a crane hook (32) of a service crane (3) during vertical displacement of the load (L) between an upper position (P1) and a lower position (P0), comprising a tagline arrangement comprising a tagline (11, 11A, 11B) adapted for connection to the crane hook (32) and a tagline winch (10, 10A, 10B) arranged at a lateral offset from the lower position (P0); and a control arrangement (12) configured to determine a lateral force (F_w) acting on the load (L) during vertical displacement of the load (L), to compute a tagline tension (F₁₁, F_11A, F_11B) on the basis of the determined lateral force (F_w), and to control a tagline winch (10, 10A, 10B) accordingly.

Description

Background
• At various times during the service life of a wind turbine, it can be necessary to raise a load from the base of the tower to the level of the nacelle, or to lower a load from the nacelle to the base of the tower. The load can be a new component, a damaged component, maintenance and repair equipment, etc.
• Instead of transporting a large crane to the wind turbine site, it is usual to install a smaller service crane at nacelle level, for example a service crane can be permanently mounted inside the nacelle or on the roof of the nacelle. Such a service crane or "nacelle crane" can have a cable that extends to the tower base, a motor-driven winch, and a crane hook which can be attached to a load deposited near the tower base.
• In the case of an offshore wind turbine, the task of transferring a load between the nacelle and the tower base can be problematic for various reasons. Wind gusts may push the load sideways when being lifted, and the load may shift so that its centre of mass is no longer underneath the crane hook, resulting in an unstable load transfer manoeuvre. Furthermore, even moderate winds can cause the load to oscillate ("pendulate") while being transferred between the service platform and the nacelle. An unfavourable combination of oscillation direction and amplitude can be hazardous to personnel, and can also result in a collision between load and tower, with possibly costly damage to the load and/or the tower.
• Such unfavourable load oscillation is particularly problematic in the case of wind turbines with very tall towers, since the oscillation amplitude of the load increases with cable (pendulum) length.
• It is known to deploy a rider-block tagline system in order to suppress pendulation of a load being lifted by a crane with a long boom, for example a truck crane, a deck crane of an offshore installation vessel, etc. In such an approach, the load is suspended from a rider-block attached to a hoist line of the crane, and a tagline extends from the rider block to another winch. A hoist line winch controls the vertical displacement of rider block and load, and the tagline winch controls the horizontal displacement of rider block and load. However, such a system is of no use when lifting or lowering a load only in the vertical direction, i.e. between a first position and a second position, one of which is directly above the other.
• It is therefore an object of the invention to overcome the problems outlined above. This object is achieved by the claimed stabilization assembly and by the claimed method of stabilizing a load.
Description
• In the context of the invention, it shall be understood that the load to be stabilized is suspended from a crane hook and that the load is to be vertically displaced between an upper position and a lower position. "Vertical displacement" shall be understood to mean lifting the load from the lower level to the upper level, or lowering the load from the upper level to the lower level. Essentially no horizontal displacement of the load shall be assumed between the upper position and the lower position, so that displacement of the load is along a virtual plumb line extending between the upper position and the lower position.
• According to the invention, the stabilization assembly comprises a tagline arrangement comprising a tagline adapted for connection to the crane hook and a tagline winch arranged at a lateral offset from the lower position; a means of determining a lateral force acting on the load during vertical displacement of the load; and a control arrangement configured to compute a tagline tension on the basis of the determined lateral force, and to control the tagline winch accordingly to prevent or minimize a lateral displacement of the load.
• According to the invention, the method of stabilizing a load comprises steps of providing a tagline arrangement and arranging the winch of the tagline arrangement at a lateral offset from the lower position; connecting the tagline of the tagline arrangement to the crane hook; determining a lateral force acting on the load and, on the basis of the determined lateral force, computing a tagline tension required to prevent lateral displacement of the load; and actuating the tagline winch accordingly.
• The inventive stabilization assembly can be deployed in any situation requiring a load to be raised or lowered vertically. The invention is particularly advantageous in situations that require a load to be transferred over a large vertical distance and in unfavourable weather conditions. For example, a load may need to be raised from a service platform at the base of a wind turbine to an upper position at the level of the wind turbine nacelle; similarly a load may need to be lowered from the nacelle to the service platform. The load may be suspended from the crane hook of a crane mounted on the roof of the nacelle. Using the inventive stabilisation assembly, the load can be safely raised or lowered without risk of oscillations developing, even in the case of strong winds. The invention can therefore save costs, since a load transfer manoeuvre may be carried out in weather conditions that would otherwise require the procedure to be deferred.
• Unfavourable weather conditions are particularly relevant during lifting manoeuvres at offshore wind turbine installations that rely on prior art techniques. This is because high winds can mean that a lifting manoeuvre may need to be deferred until wind speed reduces to an acceptable level, and costs may accrue in the meantime. In the following, without restricting the invention in any way, it may be assumed that the wind turbine is an offshore wind turbine, and the lower position of the load is on a structure such as a service platform of the offshore wind turbine. The winch of a tagline arrangement can be securely anchored-temporarily or permanently - to a structure such as a service platform.
• Particularly advantageous embodiments and features of the invention are given by the dependent claims, as revealed in the following description. Features of different claim categories may be combined as appropriate to give further embodiments not described herein.
• In the following, it may be assumed that the load is to be raised from a lower position at the base of a wind turbine to an upper position at the level of the wind turbine nacelle; or lowered from the upper position to the lower position. Furthermore, without restricting the invention in any way, it may be assumed that the crane hook is suspended from the lifting line of a service crane (also referred to as "nacelle crane" or simply "crane" in the following), which can be a temporary or permanent fixture of the nacelle. In the following, without restricting the invention in any way, it may be assumed that the control arrangement of the stabilization assembly is realised in a portable or handheld remote control device which can be used by an operator during a lifting procedure to monitor the progress of the lifting procedure. For example, the control device may also be configured to control the nacelle crane winch in order to lower or raise the crane hook, and to slew the nacelle crane jib as required.
• The lower position of the load shall be understood as the position at which the load is deposited in preparation for being lifted up to the nacelle, or after being lowered from the nacelle. This lower position is essentially directly underneath the crane hook when the crane has been prepared for the lifting procedure. The terms "lower position" and "lower load position" may be used interchangeably. The upper position of the load can be understood to be at nacelle height. A load can be transferred into or out of the nacelle through a hatch, for example. The terms "upper position" and "upper load position" may be used interchangeably.
• As explained above, the force of the wind acting on a load freely suspended from a nacelle crane will cause that load to oscillate, and the amplitude of oscillation will depend on various parameters. For example, the wind force F_w acting on a suspended load can be expressed as $$F_w=\frac{1}{2}\cdot \rho \cdot A_{\mathit{load}}\cdot C_d\cdot {\upsilon }^2$$ where ρ (kg/m³) is air density, A_load (m²) is the load area seen by the wind, Cd is the drag coefficient of the load, and u (m/s) is the wind speed.
• In a preferred embodiment of the invention, the stabilization assembly comprises a means of obtaining wind speed and wind direction measurements during vertical displacement of the load. The lateral force acting on the load can then be determined at any stage during the lifting manoeuvre on the basis of the wind information. Average wind speed, wind gust and wind direction data can be obtained by suitable sensors, for example dedicated sensors that provide the measurements to the control arrangement of the stabilization assembly. In a particularly preferred embodiment of the invention, these measurements are obtained from sensors already deployed by the wind turbine. For example, the operational wind turbine can transmit the information to the control arrangement of the stabilization assembly over a suitable communications interface. Alternatively, one or more suitable sensors (preferably for measuring one or more of wind speed, wind gust, and wind direction) can be placed at a suitable position, for example a sensor arrangement can be temporarily attached to the wind turbine tower for use during a lifting manoeuvre. Equally, the control arrangement of the inventive stabilization assembly may be configured to obtain relevant wind data from a meteorological service.
• The tagline tension F_t, i.e. the pulling force (N) in the tagline, can be expressed as $$F_t=\frac{W\cdot d}{L_t\cdot \mathit{sin}\left(\mathrm{\theta }\right)}$$ where W (N) is the weight of the load, d (m) is the lateral displacement of the load relative to the vertical, L_t (m) is the length of the tagline, and θ is the angle of the tagline relative to the horizontal.
• As the load is raised or lowered, the length of the lifting line changes accordingly. The total load tension at any one time will therefore depend also on the length of the lifting line, and also on the material of the lifting line. A steel wire rope may have a weight in the order of 2 kg per metre, while a polymer rope may have a weight in the order of 1 kg per metre.
• Since the magnitude of a wind-induced load deflection depends on the lateral wind force F_w and also on the lifting line length, it is possible to express the tagline tension F_t, i.e. the pulling force required to counteract the wind-induced load deflection, as $$F_t=\frac{F_w\cdot L}{L_t\cdot \mathit{sin}\left(\mathrm{\theta }\right)}$$ where L (in metres) is the lifting line length.
• To compute the required tagline tension at any stage during a lifting procedure, the control arrangement is given the relevant information. Some parameters may be entered manually, for example fixed parameters such as the weight W of the load, the area A_load of a side face of the load, tower height, etc. Other parameters are variable and are obtained or determined during the lifting procedure, for example the changing tagline length Lt, the changing lifting line length L, the wind speed u, the tagline angle θ etc.
• As the height of a load increases during a lifting procedure or decreases during a lowering procedure, the tagline angle changes. Similarly, wind shear can mean that wind speeds are higher at nacelle level and lower at the platform level. The invention allows the tagline tension to be adjusted or updated throughout a lifting procedure to allow for the effect of a change in any such variable. The control arrangement can be configured to compute or update the tagline tension at suitable intervals during a lifting manoeuvre, for example at one-second intervals, so that the tagline winch can keep the load steady at all times.
• The tagline tension computed by the control arrangement will act to suppress any lateral displacement of the load, so that oscillations of the load are prevented or at least greatly reduced. A crane is generally constructed to be able to carry loads up to a certain weight, i.e. the capacity of the crane is limited and care must be taken not to exceed this limit. In a preferred embodiment of the invention, therefore, the control arrangement is configured to ensure that the tagline tension will not result in exceeding the capacity of the nacelle crane. To this end, the control arrangement must know the weight of the load. For example, the weight of the load can be made known to an operator of the inventive stabilization assembly, and the operator can input this information to the control arrangement in a preparatory step. During the lifting procedure, the control arrangement uses this information to ensure that a tagline tension value does not result in the crane capacity being exceeded.
• Additionally, the algorithm used to compute the tagline tension can be configured to apply a higher tagline tension when the load is near the platform, since it is important to ensure that worker safety is not compromised by load oscillations.
• However, in a particularly preferred embodiment of the invention, the tension in the lifting line can be determined using a suitable sensor, for example a load cell arranged between the crane hook and the lifting line. The tension in the lifting line is a direct indication of the load weight, and the sensed lifting line tension can be transmitted wirelessly to the control arrangement of the stabilization assembly, or via any other means of transferring data to the control arrangement.
• In an exemplary scenario, the service crane capacity is 1000 N. If the mass of the load results in a pulling force of 600 N on the crane hook (ignoring the weight of the lifting line), the control arrangement will ensure that the vertical component of the tagline tension does not exceed 400 N in order to avoid exceeding the crane capacity.
• When a lighter load (e.g. resulting in a pulling force of 300 N on the crane hook) is being lifted by that crane, high winds would more readily cause the lighter load to oscillate, and the inventive stabilization system can suppress such oscillations by a higher tagline tension (up to 700 N). Such oscillation damping is particularly relevant for a load suspended near the platform, since a person may be present on the platform. A relatively light load may also be deflected sideways by the wind essentially constantly (i.e. without oscillation), and to such an extent as to collide with the tower. The inventive stabilization arrangement can be used to ensure that the load remains essentially underneath the crane hook at all time during the lifting procedure.
• Similarly, when a heavier load (e.g. resulting in a pulling force of 850 N on the crane hook) is being lifted by that crane, it is less prone to oscillation caused by the wind, and the inventive stabilization system can suppress such oscillations by a relative low tagline tension (up to 150 N).
• A tagline winch is preferably arranged at some distance from the lower load position, for example a few metres laterally offset from the lower load position. Placement of the tagline winch may depend on the platform design, which may have regions with significantly different load-bearing capacities. The tension between the tagline winch and the crane hook should not exceed the load-bearing capacity of that part of the platform to which the tagline is mounted. To allow for such considerations, various possible tagline arrangements are possible. In one possible embodiment, the platform design may allow the tagline winch to be arranged at a suitable distance from the lower load position. In this embodiment, the tagline extends directly from the crane hook to the tagline winch.
• In an alternative embodiment, if the platform design requires that the tagline winch must be placed further away from the lower load position, a fixation point such as a deadeye or sheave can be secured to the platform between the tagline winch and the lower load position, so that the tagline passes through the fixation point. This arrangement ensures that a first section of the tagline is close to ground level, passing horizontally between winch and deadeye. Beyond the deadeye, the tagline extends at an angle towards the crane hook. Since the tagline can be placed at a greater distance from the lower load position, this embodiment can be more favourable from the viewpoint of worker safety.
• In a further alternative embodiment, two tagline arrangements are used, i.e. the lower load position is between two tagline winches. In this double tagline configuration, both taglines are connected to the crane hook. The control arrangement is configured to compute a tagline tension for each tagline arrangement, for example the tagline tension of each arrangement can be half as large as the tagline tension in either of the preceding embodiments (all other things being equal). Since a tagline tension is a vector having a vertical component and a horizontal component, this configuration can be more effective at suppressing oscillations since the horizontal components of the tagline tensions have different directions. Furthermore, two smaller (and lighter) winches can be deployed for the tagline arrangements instead of one large (and heavy) winch of a single tagline configuration, and suitable mounting positions on the platform can be identified more easily.
• In an exemplary lifting manoeuvre to raise a load from the service platform to the nacelle, the invention method can be carried out by depositing the load at the lower position; actuating the crane winch to lower the empty crane hook to the lower position on the service platform; attaching the load to the crane hook and then attaching the tagline to the crane hook; actuating the crane winch to raise the load to the height of the nacelle while actuating the tagline winch to stabilize the load; detaching the load from the crane hook; actuating the crane winch to lower the crane hook towards the service platform; detaching the tagline from the crane hook; and actuating the crane winch to raise the crane hook back up to the crane.
• In an exemplary lifting manoeuvre to lower a load from the nacelle down to the service platform, the invention method can be carried out by actuating the crane winch to lower the empty crane hook to the service platform and then attaching the tagline to the crane hook; actuating the crane winch to raise the crane hook back up to the nacelle; attaching the load to the crane hook; actuating the crane winch to lower the load towards the service platform while actuating the tagline winch to stabilize the load; detaching the load from the crane hook; detaching the tagline from the crane hook; and actuating the crane winch to raise the crane hook back up to the crane.
• The inventive stabilization assembly can be provided in the form of a toolkit comprising one or more tagline winches, means of securing a tagline winch to a surface such as the platform of an offshore wind turbine, a handheld control unit for controlling one or more taglines winches, etc. To allow for a situation in which the hook of the service crane is not equipped with a load cell, such a toolkit may also include a load cell which can be arranged to measure and report the weight of the load to the control unit. The toolkit may also include a sensor arrangement configured to measure wind speed and wind direction and to transmit measurements to the control unit. The sensors of the sensor arrangement can be designed for temporary fixation at a suitable position, for example a sensor can be attached by magnet to a steel wind turbine tower.
• Other objects and features of the present invention will become apparent from the following detailed descriptions considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for the purposes of illustration and not as a definition of the limits of the invention.
• Figure 1 shows a prior art arrangement for transferring a load between the service platform and nacelle of a wind turbine;
• Figures 2 - 4 show exemplary embodiments of the inventive stabilization assembly;
• Figure 5 shows a block diagram of the inventive stabilization assembly.
• In the diagrams, like numbers refer to like objects throughout. Objects in the diagrams are not necessarily drawn to scale.
• Figure 1 illustrates a problem that may arise when a load L is lifted using a prior art arrangement for transferring a load between the nacelle 20 of a wind turbine 2 and the base of the tower 21. Here, the wind turbine 2 is an offshore installation, and a load L can be deposited on a service platform 22 so that it is underneath the crane hook. This position is referred to as the lower position P0, and the load L would ideally remain directly above this point P0 at all stages during the lifting procedure.
• Here, the load L is simply suspended from the crane hook of a service crane 3, which can be installed inside the nacelle 20 or on the roof of the nacelle 20 as shown here. In unfavourable wind conditions, the load L may oscillate, and the amplitude of oscillation may be such that the load L can collide with the tower 21. In a procedure in which the load L is lowered from the nacelle 20 to a level 22 at the base of the tower 21, the oscillation amplitude of the load L can present a serious hazard to personnel.
• Figure 2 shows an embodiment of the inventive load stabilizer 1 to illustrate its deployment during a lifting manoeuvre (indicated by stages I - IV) in which the load L is to be raised from the service platform 22 to the nacelle 20. Here, only the lower level of the wind turbine tower 21 is shown, and a similar crane 3 may be assumed to be installed in or on the nacelle 3.
• In a first stage I, the load L is deposited at the lower position P0 on the service platform 22. The crane winch is actuated to lower the crane hook 32 so that is can be attached to the load L. The service crane may already include a load cell 31S or similar, arranged between the lifting line 31 and the crane hook 32 to measure the lifting line tension F₃₁, i.e. the pulling force on the crane hook 32, during a lifting manoeuvre. If the service crane 3 is not equipped with such a load cell, a load cell 19 provided with the stabilization arrangement toolkit can be arranged between the crane hook 32 and the load L.
• A tagline winch 10 is provided on the service platform 22 of the wind turbine 2. Here, the tagline winch 10 is positioned to one side of the lower position P0. The tagline 11 is connected to the load L.
• The crane winch 30 is then actuated to raise the load L. As the load L moves upward as shown in stages II - IV, its weight exerts an essentially vertical pulling force F₃₁ in the lifting line 31. Any lateral force F_w caused by unfavourably high wind speeds is counteracted by controlling the tagline winch 10 to exert a suitably strong pulling force F₁₁ in the tagline 11. The size of the tagline tension F₁₁ as computed using equation (3) is such that the combined vertical force as seen by the crane hook 32 never exceeds the crane's rated capacity.
• In the following, the tagline tension F₁₁ for various different load weights and wind speeds is computed using the exemplary equations (1) and (3). When computing the wind force Fw using equation (1), a linear relationship is assumed between the mass of the load and the area A_load of the load that is "seen" by the wind. To simplify the calculations, a special case is assumed in which the lifting line lengths and tagline length are equal, and the tagline angle is 95°, so that equation (3) reduces to $$F_t=\frac{F_w}{\mathit{sin}\left(\mathrm{\theta }\right)}$$
• For a 500 kg load, the term A_load in equation (1) is assumed to be 2.25 m², so that the required tagline tension F_t (indicated as F₁₁ in the drawings) is about 11 N at a wind speed of 3 m/s, about 122 N at a wind speed of 10 m/s, and about 395 N at a wind speed of 18 m/s. For a 900 kg load, the term A_load in equation (1) is assumed to be 4 m², so that the required tagline tension F₁₁ is about 20 N at a wind speed of 3 m/s, about 217 N at a wind speed of 10 m/s, and about 700 N at a wind speed of 18 m/s. In each case, as explained above, the load can only be lifted if the total pulling force on the crane hook (due to the load and the tagline tension) does not exceed the crane's lifting capacity. In the above examples, it may be possible to lift the heavier load safely even at high wind speeds in the order of 15 m/s, which may not be possible using conventional lifting apparatus.
• Figure 3 shows an alternative embodiment of the inventive load stabilizer 1, as a further development of the embodiment shown in Figure 2. Here, the tagline 11 passes from the tagline winch 10 through a ground-level fixation 11P (for example a deadeye or sheave installed at a suitable position on the service platform 22) and then to the load L. This configuration allows the winch 10 to be placed further away from the lower position P0, making the system even safer for any personnel present on the platform 22. The crane winch 30 and tagline winch 10 are controlled in the same manner as explained in Figure 2 above.
• Figure 4 shows a further alternative embodiment of the inventive load stabilizer 1, similar in principle to the embodiment shown in Figure 2, but with two tagline winches 10A, 10B, one on either side of the lower position P0. Each tagline 11A, 11B is connected to the load L. The crane winch 30 and tagline winches 10A, 10B are controlled in the same manner as in the single tagline configuration of Figure 2. During a lifting procedure, any lateral force F_w caused by unfavourably high wind speeds is counteracted by controlling each tagline winch 10A, 10B to exert a suitably strong pulling force F_11A, F_11B in its tagline 11A, 11B. Here, the size of the total tagline pulling force is such that the combined vertical force (the lifting line tension F₃₁ plus the vertical components of the tagline tensions F_11A, F_11B) as seen by the crane hook 32 never exceeds the crane's rated capacity.
• Figure 5 is a block diagram to illustrate control aspects of the inventive load stabilizer 1. A controller 12 receives various inputs during a lifting manoeuvre and generates various outputs. Here, the controller 12 receives load measurements 130 from a load cell 31S (or equivalent) arranged to measure tension in the lifting cable 31, and also receives wind data 140 (e.g. average wind speed, wind gust, wind direction) from a sensor arrangement 14. The wind sensor 14 can be regarded as part of the load stabilizer 1, but may be realised as a component of the wind turbine itself, and the wind data 140 can be obtained over a suitable interface.
• On the basis of the load measurements 130 and the wind speed measurements 140, the controller 12 generates control commands 100 for the tagline winch 10 to ensure that the pulling force or tension F₁₁ in the tagline 11 is enough to suppress oscillation of the load L, and that the combined magnitude of the tagline force F₁₁ and the lifting line force F₃₁ does not exceed the capacity of the crane 3.
• A user interface 15 can show relevant information to a user, for example the momentary wind speed, the load cell measurements, etc. The user interface 15 can display a progress indicator such as the vertical height of the load L at any stage of the lifting procedure, the speed of travel of the crane hook, etc.
• The controller can also report a potentially hazardous situation, for example if the wind speed is such that the tagline force F₁₁ required to stabilize the load L would result in a total force that would exceed the crane capacity.
• Although the present invention has been disclosed in the form of preferred embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the invention. For example, a handheld controller of the stabilization arrangement may also be configured to control the service crane.
• For the sake of clarity, it is to be understood that the use of "a" or "an" throughout this application does not exclude a plurality, and "comprising" does not exclude other steps or elements. Any pronoun denoting a specific gender shall be understood to apply equally to any gender identity.

Claims (15)

1. A stabilization assembly (1) for stabilizing a load (L) suspended from a crane hook (32) of a service crane (3) during vertical displacement of the load (L) between an upper position (P1) and a lower position (P0), comprising

   - a tagline arrangement comprising a tagline (11, 11A, 11B) adapted for connection to the crane hook (32) and a tagline winch (10, 10A, 10B) arranged at a lateral offset from the lower position (P0);

   - a control arrangement (12) configured to determine a lateral force (F_w) acting on the load (L) during vertical displacement of the load (L), to compute a tagline tension (F₁₁, F_11A, F_11B) on the basis of the determined lateral force (F_w), and to control a tagline winch (10, 10A, 10B) accordingly.
2. A stabilization assembly according to the preceding claim, comprising a means of determining a lifting line tension (F₃₁) during vertical displacement of the load (L), and wherein the required tagline tension (F₁₁, F_11A, F_11B) is determined on the basis of the lifting line tension (F₃₁).
3. A stabilization assembly according to the preceding claim, comprising a means of obtaining data from a load cell (19, 31S) provided between the crane hook (32) and the lifting line (31).
4. A stabilization assembly according to the preceding claim, comprising a load cell arrangement (19) configured for mounting between the crane hook (32) and the load (L).
5. A stabilization assembly according to any of the preceding claims, comprising a means (14) of obtaining wind measurements (140) during vertical displacement of the load (L), and wherein the lateral force (F_w) is determined on the basis of the wind measurements (140).
6. A stabilization assembly according to any of the preceding claims, wherein the control arrangement (12) is configured to compute a tagline tension (F₁₁, F_11A, F_11B) that will not exceed a maximum load capacity of the service crane (3).
7. A stabilization assembly according to any of the preceding claims, wherein the lower position (P0) of the load (L) is on the service platform (22) of an offshore wind turbine (2), and wherein the tagline winch (10, 10A, 10B) is anchored to the service platform (22).
8. A stabilization assembly according to the preceding claim, comprising a tagline guide (11P) for placement between the lower position (P0) and a tagline winch (10, 10A, 10B)
9. A stabilization assembly according to any of the preceding claims, comprising

   - a first tagline arrangement arranged at a first lateral offset from the lower position (P0);

   - a second tagline arrangement arranged at a second lateral offset from the lower position (P0); and wherein

   the control arrangement (12) is configured to compute a tagline tension (F_11A) for the tagline (11A) of the first tagline arrangement, and to compute a tagline tension (F_11B) for the tagline (11B) of the second tagline arrangement.
10. A stabilization assembly according to any of the preceding claims, wherein the control arrangement (12) is configured to receive wind measurements (140) originating from one or more sensors of a wind turbine (2).
11. A method of stabilizing a load (L) suspended from a crane hook (32) during vertical displacement of the load (L) between an upper position (P1) and a lower position (P0), which method comprises

    - arranging the winch (10, 10A, 10B) of a tagline arrangement at a lateral offset from the lower position (P0);

    - connecting the tagline (11, 11A, 11B) of a tagline arrangement to the crane hook (32);

    - determining a lateral force (F_w) acting on the load (L);

    - computing a tagline tension (F₁₁, F_11A, F_11B) required to prevent lateral displacement of the load (L); and

    - actuating a tagline winch (10, 10A, 10B) accordingly.
12. A method according to the preceding claim, wherein a tagline tension (F₁₁, F_11A, F_11B) is computed at intervals during vertical displacement of the load (L).
13. A method according to any of the preceding method claims, wherein, in order to raise the load (L) from the lower position (P0) to the upper position (P1), the method comprises

    - depositing the load (L) at the lower position (P0);

    - actuating the crane winch (10, 10A, 10B) to lower the crane hook (32) to the lower position (P0);

    - attaching the load (L) to the crane hook (32) and then attaching the tagline (11, 11A, 11B) to the crane hook (32);

    - actuating the crane winch (10, 10A, 10B) to raise the load (L) to the upper position (P1) while actuating the tagline winch (10, 10A, 10B) to stabilize the load (L);

    - detaching the load (L) from the crane hook (32);

    - actuating the crane winch (10, 10A, 10B) to lower the crane hook (32) towards the lower position (P0);

    - detaching the tagline (11, 11A, 11B) from the crane hook (32);

    - actuating the crane winch (10, 10A, 10B) to raise the crane hook (32) towards the upper position (P1).
14. A method according to claim 11 or claim 12, wherein, in order to lower the load (L) from the upper position (P1) to the lower position (P0), the method comprises

    - actuating the crane winch (10, 10A, 10B) to lower the crane hook (32) to the lower position (P0) and then attaching the tagline (11, 11A, 11B) to the crane hook (32);

    - actuating the crane winch (10, 10A, 10B) to raise the crane hook (32) to the upper position (P1);

    - attaching the load to the crane hook (32);

    - actuating the crane winch (10, 10A, 10B) to lower the load (L) towards the lower position (P0) while actuating the tagline winch (10, 10A, 10B) to stabilize the load (L);

    - detaching the load (L) from the crane hook (32);

    - detaching the tagline (11, 11A, 11B) from the crane hook (32);

    - actuating the crane winch (10, 10A, 10B) to raise the crane hook (32) towards the upper position (P1).
15. A computer program product comprising a computer program that is directly loadable into a memory of a control arrangement (12) of a stabilization assembly (1) according to any of claims 1 to 10, and which comprises program elements for performing steps of the method according to any of claims 11 to 14.