Mooring system for floating wind turbines

Abstract

The wind power generation system includes a rotationally asymmetric floating wind power installation and a rotationally asymmetric mooring system connected to the floating wind power installation. The mooring system includes a plurality of mooring lines directly or indirectly connected to the floating wind power installation such that when the wind acting on the wind power installation is blowing from 0 degrees, the mooring system has a lower yaw stiffness than when the wind acting on the wind power installation is blowing from ±90 degrees. The wind blowing from 0 degrees is defined as the wind direction when the horizontal component of the aerodynamic rotor thrust resulting from the wind is directed toward the center of gravity of the floating wind power installation.

Description

[Technical Field]

[0001] The present invention relates to the field of floating wind turbines, and in particular to a mooring system for floating wind turbines. [Background technology]

[0002] Figure 1 is a schematic plan view of a rotationally asymmetric semi-submersible floating wind power plant 1 with a conventional mooring system. The wind power plant 1 comprises a float with three columns: two empty columns 2 and a third column 3 that supports the wind turbines themselves. The three columns 2, 3 are connected in a triangular shape by three connecting members 4 to form the float. The wind power plant 1 is moored by a mooring system comprising three mooring lines 5. As can be seen in Figure 1, one mooring line 5 is directly connected to each column 2, 3 in a rotationally symmetric arrangement around the center of the wind power plant 1.

[0003] The mooring system of Figure 1 is typically dynamically stable in roll-yaw. However, the maneuvering characteristics are considered unfavorable due to the relatively large roll and yaw motions. This is especially true when the wind is directed along the positive or negative y-axis shown in Figure 1. This causes significant dynamic roll and dynamic yaw motions in addition to a large static offset.

[0004] Figure 2 is a schematic plan view of a rotationally asymmetric semi-submersible floating wind power plant 1 with another conventional mooring system. Similar to the mooring system of Figure 1, the mooring system of Figure 2 also includes three mooring lines 5'. However, the mooring lines 5' are not directly connected to the columns 2, 3 of the wind power plant. Instead, each mooring line 5' is It is a bridleThe mooring system of FIG. 2 (i.e., the mooring lines 5' and bridles 6) is arranged rotationally symmetrically around the center of the wind power plant 1, as can be seen in FIG. 2.

[0005] Compared to the mooring system of Figure 1, the yaw stiffness of the mooring system of Figure 2 is significantly increased due to the presence of the attachment 6. This is because the resistance from the mooring system of Figure 2 is taken at the horizontal radius of the attachment point of the attachment 6 to the mooring line 5', rather than at the radius of the wind power installation 1. Summary of the Invention [Problem to be solved by the invention]

[0006] The rotationally symmetric mooring system of Figure 2 has improved motion characteristics for most wind directions compared to the single-line mooring system of Figure 1. However, when the wind is flowing in the negative x-axis direction as shown in Figure 2, the floating wind farm may become dynamically unstable. [Means for solving the problem]

[0007] According to a first aspect of the present invention, there is provided a wind power generation system comprising a rotationally asymmetric floating wind power generation facility and a rotationally asymmetric mooring system connected to the floating wind power generation facility, wherein the mooring system comprises a plurality of mooring lines directly or indirectly connected to the floating wind power generation facility such that when a wind acting on the wind power generation facility is blowing from 0 degrees, the mooring system has a lower yaw stiffness than when the wind acting on the wind power generation facility is blowing from ±90 degrees (i.e., 90 degrees or 270 degrees), and the wind blowing from 0 degrees is defined as the wind direction when the horizontal component of the aerodynamic rotor thrust resulting from the wind is directed towards the center of gravity of the floating wind power generation facility.

[0008] When we say that each of the floating wind power installation and the mooring system is rotationally asymmetric, we mean that it is rotationally asymmetric about a vertical axis (e.g., a vertical axis passing through the center point of the floating wind power installation or the mooring system, respectively).

[0009] A rotationally asymmetric floating wind power installation may comprise a floating support structure (or float) having a rotor supported at the top end of a column or tower extending upward from (the remainder of) the floating support structure. The column or tower supporting the rotor may be positioned off-centre of the floating wind power installation (e.g. when viewed from above / in a horizontal plane) so that the wind power installation is rotationally asymmetric about a vertical axis. The floating support structure may comprise multiple (e.g. three) columns connected (e.g. in a triangle) by connecting members. The connecting members may all be of the same length.

[0010] The mooring system comprises a plurality of mooring lines connected directly or indirectly to the floating wind power installation. The mooring system is preferably arranged to moor the floating wind power installation in a substantially stable position. For example, the end of each mooring line furthest from the floating wind power installation can be connected to or moored to the seabed (or the bottom of another body of water in which the floating wind power installation is located). The mooring system can allow for some small movements of the floating wind power installation due to, for example, wind, currents or waves.

[0011] Because the mooring system is rotationally asymmetric, the mooring system can be (and preferably is) arranged so that when the wind acting on the wind power generation facility is blowing from 0 degrees, the mooring system has a lower yaw stiffness than when the wind acting on the wind power generation facility is blowing from ±90 degrees (i.e., 90 degrees and 270 degrees).

[0012] The wind blowing from 0 degrees is defined as the wind direction when the horizontal component of the aerodynamic rotor thrust caused by the wind is directed toward the center of gravity of the floating wind turbine.

[0013] Since the mooring system has a lower yaw stiffness when the wind acting on the wind power installation is blowing from 0 degrees (as defined above) than when the wind is blowing from ±90 degrees (i.e., 90 degrees and 270 degrees), this means that the mooring system will have a lower yaw stiffness when roll-yaw instability may be a risk, and a higher yaw stiffness when roll-yaw instability is not a risk, thereby resulting in a more stable system, the reasons for which will be explained in more detail below.

[0014] The actual yaw stiffness of a mooring system may depend on various parameters that may vary depending on the particular embodiment, such as the type of float used with the wind power facility, the water depth, the type of mooring lines, the pretensioning of the mooring lines, and the aerodynamic thrust. However, in some embodiments, the yaw stiffness of the mooring system may be about 40% to about 60% greater when the wind acting on the wind power facility is blowing from a 90-degree or 270-degree angle than when the wind acting on the wind power facility is blowing from a 0-degree angle. For example, the mooring system may have a yaw stiffness of about 4000 kNm / degree to about 5000 kNm / degree when the wind acting on the wind power facility is blowing from a 0-degree angle, and about 6000 kNm / degree to about 7000 kNm / degree when the wind acting on the wind power facility is blowing from a 90-degree or 270-degree angle.

[0015] The mooring system may include at least one first mooring line and at least one second mooring line, each of which has a wind farm connection end that directly or indirectly connects (or is connected to) the floating wind farm. In other words, the wind farm connection end of the mooring line is the end of the mooring line that is closest to the wind farm. However, this end is not necessarily directly connected to the wind farm (this end may be indirectly connected to the wind farm).

[0016] The wind power plant connection end of the at least one first mooring line may be located closer to the rotor than the wind power plant connection end of the at least one second mooring line. In some cases, two such first mooring lines are provided. In some cases, one such second mooring line is provided.

[0017] Preferably, the wind power plant connection end of the at least one second mooring line is located farther from the floating wind power installation, i.e., at a location with a greater distance than the wind power installation connection end of the at least one first mooring line. In other words, the distance between the wind power installation connection end of the at least one second mooring line and the floating wind power installation is preferably greater than the distance between the wind power installation connection end of the at least one first mooring line and the floating wind power installation.

[0018] The distance between the wind power plant connection end of the mooring line and the floating wind power plant is understood to be the distance between the wind power generator connection end of the mooring line and the direct or indirect connection point of the mooring line to the floating wind power plant. For example, if the wind power generator connection end of the mooring line is directly connected to the floating wind power plant (e.g., via a connector or a fixing means), there may be no distance or it may be negligible between the wind power plant connection end of the mooring line and the floating wind power plant. On the other hand, if the wind power generator connection end of the mooring line is indirectly connected to the floating wind power plant, for example, via an attachment, there may be a distance greater than zero between the wind power plant connection end of the mooring line and the connection point to the floating wind power plant.

[0019] By positioning the wind power plant connection end of at least one second mooring line farther from the floating wind power plant than the wind power plant connection end of at least one first mooring line (for example, when the wind power plant connection end of at least one first mooring line is positioned closer to the rotor than the wind power plant connection end of at least one second mooring line), it is possible to provide a mooring line that has lower yaw stiffness when the wind acting on the wind power plant is blowing from 0 degrees than when the wind is blowing from ±90 degrees.

[0020] For example, the wind power plant connection end of the at least one second mooring line can be located two to six times, or about four times, farther from the floating wind power plant than the wind power plant connection end of the at least one first mooring line. In one embodiment, the wind power plant connection end of the at least one second mooring line is located about 150 m to about 250 m (e.g., about 200 m) from the floating wind power plant, and the wind power plant connection end of the at least one first mooring line is located about 40 m to about 60 m (e.g., about 50 m) from the floating wind power plant.

[0021] In some embodiments, the wind power plant connection end of the at least one second mooring line is located at a distance from the wind power plant, for example, about 150 m to about 250 m (e.g., about 200 m) from the wind power plant. Meanwhile, the wind power plant connection end of the at least one first mooring line can be directly connected to the wind power plant (e.g., via a connector) so that there is no or negligible distance between the wind power plant connection end of the at least one first mooring line and the wind power plant. Therefore, the wind power plant connection end of the at least one first mooring line can be located 0 m to 100 m from the floating wind power plant.

[0022] The wind power plant connection end of the at least one second mooring line can be positioned farther from the floating wind power plant than the wind power plant connection end of the at least one first mooring line, for example by connecting the at least one second mooring line to the floating wind power plant using or via an attachment.

[0023] The attachment is a means for separating the wind turbine-generator connection end of the mooring line from the wind power installation. Preferably, the attachment connects to the mooring line at the wind turbine-generator connection end of the mooring line (e.g., at a single point) and connects to the wind power installation at two or more different (spaced) points or connection ranges.

[0024] The splice may comprise two or more splice lines, each of which is connected at its first end to one end of the mooring line (the wind power plant connection end), and which are connected (or connectable) at their second ends to the wind power plant at two or more different (spaced) connection points.

[0025] An attachment can be said to have an attachment radius that corresponds to the distance, in the plane of the attachment or mooring line, between the point where the attachment (e.g., its attachment line) is connected to the mooring line (e.g., at the wind turbine connection end of the mooring line) and the center point (e.g., center of gravity) of the floating wind power installation.

[0026] In some cases, the at least one first mooring line may be connected to the floating wind power installation using or via an attachment. In such cases, the attachment connected to the at least one second mooring line may be longer than the attachment connected to the at least one first mooring line (or may have an attachment radius longer than the attachment radius of the attachment connected to the at least one first mooring line). For example, the attachment connected to the at least one second mooring line may be about two to about four times longer than the attachment connected to the at least one first mooring line.

[0027] In preferred embodiments, the splice connected to the at least one second mooring line has a splice radius that is about three times longer than the splice connected to the at least one first mooring line. For example, the (longer) splice connected to the at least one second mooring line can have a splice radius of about 100 m to about 500 m (e.g., about 237 m in some embodiments), while the (shorter) splice connected to the at least one first mooring line can have a splice radius of about 50 m to about 250 m (e.g., about 79 m in some embodiments).

[0028] The attachment can be any connection means that connects the mooring line to the wind power installation, and the attachment is arranged to connect to the end of the mooring line at a single point and to connect to the wind power installation at two or more different points.

[0029] A sling can comprise two or more slings connecting the ends of the mooring lines to the floating wind power installation. In a preferred embodiment, each sling comprises two slings. Each sling of a particular sling is preferably connected to the floating wind power installation at a different location. Two (or more) slings from two (or more) different slings may be connected to the floating wind power installation at the same or a common connection point.

[0030] In one example, a pair of splices from a single splice are connected to the floating wind power installation at locations spaced about 60 m apart, although this distance may depend on the particular wind power installation and, more particularly, its float design.

[0031] The two or more splices of the splice connected to the at least one first mooring line may have a length of about 50 m to about 80 m, for example, 64 m.

[0032] The two or more splices of the splice connected to the at least one second mooring line may have a length of about 200 m to about 230 m, for example, 213 m.

[0033] Preferably, at least one mooring line (eg at least one second mooring line as defined above) is connected to the floating wind power installation by means of a splice.

[0034] Attaching one or more of the mooring lines to the floating wind turbine using one or more attachments (e.g., different lengths when two or more attachments are used) can provide different yaw stiffness to the system when loads (e.g., wind) act on the system from different directions, which can help stabilize the asymmetric floating wind turbine.

[0035] In some embodiments, at least two, and possibly all, of the mooring lines are connected to the floating wind power installation using splices, which can provide a wind power system with a more stable roll-yaw behavior.

[0036] In systems where two or more mooring lines are connected to the floating wind power installation using attachments, the attachments may be, and in some cases preferably are, of at least two different lengths to provide different yaw stiffness when loads (e.g., wind) act on the system from different directions, thereby stabilizing the system. In such cases, preferably, the shorter attachment(s) of the mooring system are connected to the wind power installation at one or more locations closer to the rotor than the longer attachment(s).

[0037] In some embodiments, the wind power installation may include multiple columns, and at least one attachment may be positioned to connect at least one mooring line to one or more of the multiple columns. In some cases, the attachment may connect the mooring line to two (or possibly more than two) columns.

[0038] In some embodiments, at least one (e.g., one or two) mooring lines can be directly connected (e.g., without splices) to a support structure or column of the floating wind power plant. The column to which the at least one mooring line can be directly connected is preferably a column supporting the rotor of the wind power plant. For example, one or two mooring lines can be directly connected (e.g., without splices) to a column supporting the rotor of the wind power plant.

[0039] The mooring system may comprise three mooring lines, at least one of which may be attached to the wind power installation using an attachment. In some cases, just one (and only one) mooring line may be attached to the wind power installation using an attachment (e.g., one or more further mooring lines may be attached directly to the wind power installation, e.g., without an attachment).

[0040] When the mooring system includes three mooring lines, the first and second of the three mooring lines can be positioned closer to the rotor than the third of the three mooring lines. The first and second mooring lines positioned closer to the rotor can be connected directly (e.g., without a splice) or indirectly (e.g., with a splice) to the column of the wind power installation supporting the rotor. However, the first and second mooring lines positioned closer to the rotor do not necessarily have to be connected to the column of the wind power installation supporting the rotor. For example, such first and / or second mooring lines can be connected to another part of the support structure of the wind power installation. In either case, the third mooring line (e.g., the mooring line further from the rotor) can be (and preferably is) attached to the wind power installation using a splice. The wind power plant connection ends of the first and second mooring lines are preferably positioned closer to the wind power plant than the wind power plant connection end of the third mooring line (e.g. by using an attachment that connects the wind turbine connection end of the third mooring line to the wind power plant, or a longer attachment).

[0041] The splices and mooring lines can be made from a variety of materials including mooring chain, wire rope, polyester rope, etc. The splices and mooring lines can be made from the same material or different materials.

[0042] The mooring line may, for example, be formed from multiple segments comprising different materials.

[0043] The splice and mooring line may have the same gauge or may have different gauges.

[0044] The splices may be connected to the mooring lines using vacuum explosion welded dissimilar joints, such as Triplate® joints.

[0045] The splices and / or mooring lines may be connected to the floating wind farm using connectors such as fairleads.

[0046] According to a further aspect, there is provided a method for mooring a rotationally asymmetric wind power installation, the method comprising: providing a rotationally asymmetric mooring system comprising a plurality of mooring lines; and connecting the plurality of mooring lines directly or indirectly to the floating wind power installation such that the mooring system has a lower yaw stiffness when wind acting on the wind power installation is blowing from 0 degrees relative to a rotor of the floating wind power installation than when the wind is blowing from ±90 degrees.

[0047] In such a method, the wind power installation and / or the mooring system may be as described herein with any of their optional or preferred features. Thus, the wind power installation and the mooring system may form a wind power system as described herein with any of their optional or preferred features.

[0048] According to a further aspect, there is provided a wind power generation system comprising a rotationally asymmetric floating wind power installation and a rotationally asymmetric mooring system connected to the floating wind power installation, the mooring system comprises at least one first mooring line and at least one second mooring line, each of the at least one first mooring line and the at least one second mooring line having a wind power installation connection end that directly or indirectly connects to (or is connected to) the floating wind power installation; a wind power plant connection end of at least one first mooring line is arranged closer to the rotor than a wind power plant connection end of at least one second mooring line; The wind power plant connection end of the at least one second mooring line is located farther from the floating wind power plant than the wind power plant connection end of the at least one first mooring line.

[0049] The at least one second mooring line is preferably connected to the wind power installation by means of a splice.

[0050] Embodiments of the present invention (e.g., as described herein) include F thrust A mooring system with lower yaw stiffness can be provided when the aerodynamic rotor thrust is positive (relative to the orientation of the wind power plant 1 in Figures 3 to 5) and roll-yaw instability may be a risk. On the other hand, the yaw stiffness is significantly increased when the wind is blowing from ±90 degrees (relative to the orientation of the wind power plant 1 in Figure 3) and roll-yaw instability is not a risk. Therefore, a more stable wind power system can be provided.

[0051] In particular, embodiments of the present invention include a rotationally asymmetric (about a vertical axis) mooring system having one or more attachments to achieve high overall yaw stiffness without problems with roll-yaw instability. The longest attachment or attachments should be used for the most stable environmental load direction with respect to roll-yaw instability, while one or more shorter attachments (or no attachments) can be used for the most unstable environmental load direction with respect to roll-yaw instability.

[0052] The following mathematical treatment demonstrates the roll-yaw instability problem of floating wind turbines and demonstrates why embodiments of the present invention as described herein can provide high yaw stiffness without encountering the roll-yaw instability problem.

[0053] In the following equations, a spar-type floating wind power plant 20 is considered, but the derivations also apply to different types of floaters, such as semi-submersibles.

[0054] As shown schematically in FIGS. 6 and 7, the spar-type floating wind power generation facility 20 includes a tower 21, a nacelle 22, and a rotor 23.

[0055] The net aerodynamic energy inside and outside the system perpendicular to the wind direction is a harmonic roll motion θ oscillating at the roll natural frequency ω roll By taking this into consideration, it can be calculated as follows:

number

[0056] Amplitude A yaw and phase angle φ yaw Harmonic yaw motion θ oscillating at the same vibration frequency ω with yaw Further consideration leads to the following equation:

number

[0057] FIG. 6 is a schematic plan view of a floating wind power installation 20 illustrating how yaw motion of the floating wind power installation 20 can cause the excitation of a roll moment.

[0058] Referring to Figure 6, the net aerodynamic energy perpendicular to the wind direction over one oscillation cycle (E aero,y ) can be calculated as follows:

number

[0059] Substituting equations (1) and (2) into equation (3), the following equation is obtained:

number

[0060] According to equation (4), the aerodynamic energy perpendicular to the wind direction is φ yaw =0 or φ yaw It increases unless =π.

[0061] Referring again to Figure 6, it can be seen that yaw motion can cause the excitation of a roll moment, which can be expressed as:

number

[0062] FIG. 7 is a schematic plan view illustrating how inertial and gravitational forces resulting from the roll motion of the floating wind power installation 20 can result in the excitation of a yaw moment.

[0063] 7, it can be seen that the inertial force and gravity resulting from the roll motion of the floating wind power plant 20 excite a yaw moment due to the center of gravity of the nacelle 22 being shifted from the center position of the tower. In addition, in combination with the roll motion, an aerodynamic thrust F thrust There are contributions from: Inertial forces act in the opposite direction to the roll acceleration as shown, while gravity and aerodynamic thrust contribute components in the direction of the roll motion.

[0064] The yaw excitation moment from the roll motion is given by:

number

number

[0065] Furthermore, a harmonic roll motion with a natural frequency ω can be assumed, since the roll motion is hardly damped and there are excitation mechanisms with energy in this frequency range, especially near the rated wind speed of the wind power plant 20.

[0066] In the case of harmonic motion, the following equation

number

number

[0067] This means that the phase angle between the roll and yaw motions is the yaw motion phase angle φ yaw This means that φ=φ yaw , ω = natural frequency of the roll, and ω n = yaw natural frequency of a single degree of freedom system is shown in Figure 8. Figure 8 is a phase diagram of a single degree of freedom dynamic system, showing the phase angle between the dynamic response and the forced vibration of the dynamic system as a function of the ratio between the excitation frequency and the natural frequency of the dynamic system for different relative damping ratios ζ.

[0068] Combining the above implications with equation (4) shows that the roll-yaw dynamics of a floating wind turbine are unstable when the roll and yaw natural frequencies are too close to each other, depending on the level of yaw damping present in the system. In other words, the yaw dynamics must be either completely stiffness dominated or completely mass dominated to achieve a roll-yaw stable floating wind turbine.

[0069] As mentioned above, equation (8) applies to rotationally symmetric spar-type floating wind turbines. To apply it to rotationally asymmetric floating bodies, the following factors must be considered: 1. Distance d COG is the horizontal distance from the center of gravity of the floating body to the center of gravity of the tower rotor nacelle assembly. 2.Mass m N is the mass of the tower rotor nacelle assembly. 3.z c1 The variable is the effective moment arm relative to the vertical position of the center of mass of the tower rotor nacelle assembly (z in the case of a rotationally asymmetric floating wind turbine). c1 ≠z c2 (It is). 4. Aerodynamic thrust F thrust can come from various directions. For example, positive or negative F thrust can be considered. aF thrust When d is positive, the gravity and inertia terms in equation (8) contribute more to destabilizing the system than a rotationally symmetric floating wind turbine. COG and m N This is due to the fact that is larger. bF thrust When is negative, the gravity and inertia terms in equation (8) contribute to stabilizing the system, which is not the case for rotationally symmetric floating wind turbines.

[0070] The mooring system of the present invention is designed to meet factor 4b, i.e., F thrust When is negative, the gravity term and the inertia term in equation (8) contribute to stabilizing the system.

[0071] The yaw dynamics of a rotationally asymmetric floating body is usually dominated by mass, so the present invention thrust Compared to when is negative, F thrust is positive. This allows for a significantly greater overall or average yaw stiffness than would be possible with a rotationally symmetric layout, without causing instability.

[0072] As mentioned above, embodiments of the present invention can provide different yaw stiffnesses by adjusting the points where the mooring lines connect to the floating wind power installation, for example by using splices on one mooring line or by using splices of different lengths on all mooring lines. Alternatively, different desired yaw stiffnesses can be provided by using mooring lines of different (intrinsic) stiffness. However, fatigue damage of mooring lines is highly dependent on their pretension, so it is preferable to provide different desired stiffnesses by adjusting the points where at least some of the mooring lines connect to the wind power installation, for example by using splices.

[0073] Preferred embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0074] [Figure 1] 1 is a schematic plan view of a floating wind turbine with a conventional mooring system. FIG. [Figure 2] FIG. 1 is a schematic plan view of a floating wind turbine generator having another conventional mooring system. [Figure 3] 1 is a schematic plan view of a floating wind turbine with a mooring system according to one embodiment. FIG. [Figure 4] 1 is a schematic plan view of a floating wind turbine with a mooring system according to another embodiment. FIG. [Figure 5] 10 is a schematic plan view of a floating wind turbine with a mooring system according to yet another embodiment. FIG. [Figure 6] FIG. 1 is a schematic plan view showing how yaw motion of a floating wind power installation can cause the excitation of a roll moment. [Figure 7] FIG. 1 is a schematic plan view showing how roll motion of a floating wind power installation can cause the excitation of a yaw moment. [Figure 8] FIG. 1 is a topological diagram of a single degree of freedom dynamic system. [Figure 9] 1 is a graph showing the roll motion response of wind power installations with various mooring systems when the environmental load is coming from 0 degrees. [Figure 10] 1 is a graph showing the yaw response of wind power installations with different mooring systems when the environmental load is coming from 0 degrees. [Figure 11] 1 is a graph showing the roll motion response of wind power installations with various mooring systems when the environmental load is coming from 90 degrees. [Figure 12] 1 is a graph showing the yaw response of wind power installations with different mooring systems when the environmental load is coming from 90 degrees. [Figure 13] 1 is a plot of yaw stiffness as a function of polar angle for two different mooring systems. DETAILED DESCRIPTION OF THE INVENTION

[0075] FIG. 3 is a schematic plan view of a rotationally asymmetric semi-submersible floating wind power plant 1 having a mooring system according to the first embodiment.

[0076] As described above with reference to Figures 1 and 2, the rotationally asymmetric floating wind power plant 1 comprises a float formed from three columns 2, 3 joined in a triangle by three connecting members 4. Two columns 2 are empty, while the third column 3 supports the wind turbine itself.

[0077] In the embodiment of FIG. 3, the wind power installation 1 is held in position by means of a mooring system comprising three mooring lines 15 a , 15 b and three splices 16 , 17 .

[0078] The two mooring lines 15a are each connected to the wind power generation facility 1 (specifically, the floating body of the wind power generation facility 1) via a splice 16. Therefore, the mooring system has two splices 16 connected to the mooring lines 15a. Each splice 16 has two splices 16a. In each splice 16, as shown in FIG. 3, one splice 16a is connected to the column 3 supporting the wind turbine generator, and one splice 16a is connected to a (different) empty column 2. Therefore, there are two splices 16a connected to the column 3 supporting the wind turbine generator, and one splice 16a connected to each of the two empty columns 2.

[0079] The third mooring line 15b is connected to the wind power installation 1 via a further splice 17. The splice 17 has two splices 17a. Each of the splices 17a is connected to one of the two empty columns 2, with one splice 17a connected to each empty column 2.

[0080] As can be seen from Figure 3, the splice rope 17a connected to the empty column 2 is longer than the splice ropes 16a, two of which are connected to the columns 3 supporting the wind turbines. Therefore, the mooring system of Figure 3 is rotationally asymmetric about the center of the wind turbine 1.

[0081] The splice radius of the long splice 17 is three times the splice radius of the short splice 16. More specifically, the splice radius of the long splice 17 is approximately 237 m, and the splice radius of the short splice 16 is approximately 79 m. The splice rope 16a of the short splice 16 is approximately 64 m, and the splice rope 17a of the long splice 17 is approximately 213 m.

[0082] In other embodiments, the attachment radius of the short attachments may be in the range of 50 m to 250 m, and the attachment radius of the long attachments may be in the range of 100 m to 500 m, provided that the ends of any attachments (especially the longest attachments) to which the mooring lines are connected should not contact the seabed under all environmental conditions.

[0083] This arrangement of the mooring lines 15a, 15b and splices 16, 17 in the mooring system of FIG. thrust This means that when the horizontal component of is directed toward the center of gravity of the floater (i.e., the negative x-axis direction in Figure 3), the mooring system has lower yaw stiffness, and roll-yaw instability may be a risk. On the other hand, when the wind is blowing from ±90 degrees (with respect to the orientation of the wind power generation facility 1 in Figure 3) (i.e., the positive y-axis direction or the negative y-axis direction), and roll-yaw instability is not a risk, the yaw stiffness increases significantly.

[0084] FIG. 4 is a schematic plan view of a rotationally asymmetric semi-submersible floating wind power plant 1 having a mooring system according to the second embodiment.

[0085] In the embodiment of Figure 4, the wind power installation is held in place using a mooring system comprising three mooring lines 15b, 25 and one splice 17 connected to the mooring line 15b.

[0086] As in the embodiment of FIG. 3, the mooring line 15b is connected to the wind turbine power generation facility 1 via a splice 17. The splice 17 includes two splices 17a. Each of the splices 17a is connected to one of the two empty columns 2, with one splice 17a connected to each empty column 2.

[0087] On the other hand, the two further mooring lines 25 are not connected to the splices. Instead, the two further mooring lines 25 are connected directly to the midpoints of the two connecting members 4 extending from the columns 3 supporting the wind turbines. One mooring line 25 is connected to each connecting member 4 extending from the columns 3.

[0088] As can be seen from Figure 4, the mooring system of Figure 4 is rotationally asymmetric about the centre of the wind power installation 1, as only one attachment 17 is used.

[0089] This arrangement of the mooring lines 15b, 25 and splices 17 in the mooring system of FIG.thrust This means that when the horizontal component of is directed toward the center of gravity of the floater (i.e., the negative x-axis direction in Figure 4), the mooring system has lower yaw stiffness, and roll-yaw instability may be a risk. On the other hand, when the wind is blowing from ±90 degrees (with respect to the orientation of the wind power generation facility 1 in Figure 4) (i.e., the positive y-axis direction or the negative y-axis direction), and roll-yaw instability is not a risk, the yaw stiffness increases significantly.

[0090] FIG. 5 is a schematic plan view of a rotationally asymmetric semi-submersible floating wind power plant 1 having a mooring system according to the third embodiment.

[0091] In the embodiment of Figure 5, the wind power installation is held in place using a mooring system comprising three mooring lines 15b, 35 and one splice 17 connected to the mooring line 15b.

[0092] 3 and 4, the mooring line 15b is connected to the wind turbine power generation facility 1 via a splice 17. The splice 17 includes two splice lines 17a. Each of the splice lines 17a is connected to one of the two empty columns 2, with one splice line 17a connected to each empty column 2.

[0093] On the other hand, the two further mooring lines 35 are not connected to any splices, but instead are connected directly to the columns 3 supporting the wind turbines.

[0094] As can be seen from Figure 5, the mooring system of Figure 5 is rotationally asymmetric about the centre of the wind power installation 1, as only one attachment 17 is used.

[0095] This arrangement of the mooring lines 15b, 35 and splices 17 in the mooring system of FIG. thrustThis means that when the horizontal component of is directed toward the center of gravity of the floater (i.e., the negative x-axis direction in Figure 5), the mooring system has lower yaw stiffness, and roll-yaw instability may be a risk. On the other hand, when the wind is blowing from ±90 degrees (with respect to the orientation of the wind power generation facility 1 in Figure 5) (i.e., the positive y-axis direction or the negative y-axis direction), and roll-yaw instability is not a risk, the yaw stiffness increases significantly.

[0096] The splices 16a, 17a and mooring lines 15a, 15b, 25, 35 described above can be made of a variety of materials including mooring chain, wire rope, polyester rope, etc. The splices 16a, 17a and mooring lines 15a, 15b, 25, 35 can be made of the same material or different materials.

[0097] In some embodiments, the mooring lines 15a, 15b, 25, 35 are formed from multiple segments comprising different materials.

[0098] The splices 16a, 17a and mooring lines 15a, 15b, 25, 35 may have the same thickness or different thicknesses.

[0099] The splices 16a, 17a may be connected to the mooring lines 15a, 15b using vacuum explosion welded dissimilar joints, such as Triplate® joints.

[0100] The splice lines 16a, 17a and / or mooring lines 15a, 15b, 25, 35 can be connected to the floating wind power plant 1 using connectors such as fairleads.

[0101] The dynamic responses of roll, pitch and yaw motions were compared from simulations of the following mooring systems: A. A mooring system with a single mooring line as shown in Figure 1; B. A mooring system using a rotationally symmetric mooring system with a splice as shown in Figure 2; and C. Mooring system using a rotationally asymmetric mooring system with splices as shown in Figure 3.

[0102] System C was simulated to obtain approximately the same average yaw stiffness at no load as System B. Furthermore, the lengths of the splices in System C were chosen such that the length of the long splice 17 was three times the length of the short splice 16.

[0103] The wave height was 2.0 m, the characteristic peak period was 7.5 seconds, and the wave period was 11.5 ms. -1 In the case of a load with a turbulent wind speed of 0° (turbulence class C), we will consider the environmental load occurring from 0° (from above in Figures 1 to 5, i.e., in the negative direction of the x-axis) and the environmental load occurring from 90° (from the right in Figures 1 to 5, i.e., in the positive direction of the y-axis).

[0104] The roll motion response and yaw motion response of the wind power generation facility having the above-described mooring systems A to C when the environmental load is applied from 0 degrees (i.e., in the negative x-axis direction as shown in Figures 1 to 5) are shown in Figures 9 and 10. The following can be seen from these graphs. - Rotationally symmetric configuration B is unstable in roll-yaw dynamics. - the roll and yaw motion characteristics are stable for both the single-line mooring system A and the rotationally asymmetric splint mooring system C; and - The smallest roll and yaw movements are observed for the asymmetrical saddle mooring system C.

[0105] The roll and yaw motion responses of the wind power generation facilities having the above-described mooring systems A to C when the environmental load is applied from 90 degrees (i.e., in the negative y-axis direction as shown in Figures 1 to 5) are shown in Figures 11 and 12. The following can be seen from these graphs. - the largest yaw offset angle (yaw movement) and the largest roll and yaw movements are both observed for the single-line mooring system A; and - The yaw offset angle (yaw movement) of mooring system C with rotationally asymmetric attachments is approximately the same as that of mooring system B with rotationally symmetric attachments.

[0106] Figure 13 is a polar plot of the yaw stiffness (in kNm / degree) in the radial direction when a constant force of 1700 kN is applied to the source of the float from various wind directions, with the wind blowing from 0 to 360 degrees.

[0107] Line 30 shows the yaw stiffness as a function of angle for the rotationally symmetric mooring system of Figure 2. As can be seen from Figure 13, the rotationally symmetric mooring system of Figure 2 has a nearly constant yaw stiffness regardless of wind direction.

[0108] Line 31 shows the yaw stiffness as a function of angle for the rotationally asymmetric mooring system of Figure 3. As can be seen from Figure 13, the rotationally asymmetric mooring system of Figure 3 has a greater yaw stiffness when the wind is blowing from about 90 degrees or about 270 degrees compared to when the wind is blowing from 0 degrees.

Claims

1. A wind power generation system comprising a rotationally asymmetric floating wind power generation facility and a rotationally asymmetric mooring system connected to the wind power generation facility, the mooring system includes a plurality of mooring lines directly or indirectly connected to the wind power generation facility so that the mooring system has a yaw rigidity that is lower when the wind acting on the wind power generation facility is blowing from 0 degrees than when the wind acting on the wind power generation facility is blowing from ±90 degrees; The wind blowing from 0 degrees is defined as a wind direction when the horizontal component of the aerodynamic rotor thrust caused by the wind is directed toward the center of gravity of the wind power generation facility, the mooring system includes at least one first mooring line and at least one second mooring line among the plurality of mooring lines, each of the at least one first mooring line and the at least one second mooring line having a wind power facility connection end for connection to the wind power facility; the wind power plant connection end of the at least one first mooring rope is located closer to the rotor of the wind power plant than the wind power plant connection end of the at least one second mooring rope; A wind power generation system, wherein the wind power generation facility connection end of the at least one second mooring rope is located farther from the wind power generation facility than the wind power generation facility connection end of the at least one first mooring rope.

2. The wind power generation system according to claim 1 , wherein at least one of the plurality of mooring lines is connected to the wind power generation facility using a bridle.

3. The wind power generation system according to claim 1 or 2, wherein at least two or all of the plurality of mooring lines are connected to the wind power generation facility using a bridle.

4. The wind power generation system of claim 3 , wherein the two or more bridles are of at least two different lengths.

5. 5. The wind power system according to claim 4, wherein the shorter bridle or bridles of the mooring system are connected to the wind power installation at one or more positions closer to a rotor of the wind power installation than the longer bridle or bridles of the mooring system.

6. The wind power generation system according to any one of claims 1 to 5, wherein the wind power generation facility includes a plurality of columns, and at least one bridle is arranged to connect at least one mooring line to one or more of the plurality of columns.

7. The wind power system according to any one of claims 1 to 6, wherein at least one mooring line is directly connected to a support structure or column of the wind power installation.

8. The wind power generation system according to claim 7 , wherein the column to which at least one mooring rope is directly connected is a column that supports a rotor of the wind power generation facility.

9. 9. The wind power generation system according to claim 7 or 8, wherein two mooring lines are directly connected to a column or a support structure of the wind power generation installation.

10. The wind power generation system according to any one of claims 1 to 9, wherein the mooring system comprises three mooring lines, and at least one of the mooring lines is attached to the wind power generation facility using a bridle.

11. The wind power generation system according to claim 10 , wherein two of the three mooring lines are arranged closer to a rotor of the wind power generation facility than the remaining of the three mooring lines.

12. The wind power generation system according to claim 11, wherein the two mooring lines arranged closer to the rotor are directly or indirectly connected to a column of the wind power generation installation that supports the rotor.

13. The wind power generation system according to claim 11 or 12, wherein the remaining mooring ropes are attached to the wind power generation installation using a bridle.

14. The wind power generation system according to any one of claims 11 to 13, wherein wind power generation facility connection ends of the two mooring ropes are arranged closer to the wind power generation facility than wind power generation facility connection ends of the remaining mooring ropes.

15. 1. A method for mooring a rotationally asymmetric wind power installation, comprising: providing a rotationally asymmetric mooring system comprising a plurality of mooring lines; connecting the mooring lines directly or indirectly to the wind power generation facility so that the mooring system has a lower yaw stiffness when the wind acting on the wind power generation facility is blowing from 0 degrees than when the wind acting on the wind power generation facility is blowing from ±90 degrees; Including, The wind blowing from 0 degrees is defined as a wind direction when the horizontal component of the aerodynamic rotor thrust caused by the wind is directed toward the center of gravity of the wind power generation facility, the mooring system includes at least one first mooring line and at least one second mooring line among the plurality of mooring lines, each of the at least one first mooring line and the at least one second mooring line having a wind power facility connection end for connection to the wind power facility; the wind power plant connection end of the at least one first mooring rope is located closer to the rotor of the wind power plant than the wind power plant connection end of the at least one second mooring rope; The method, wherein the wind power plant connection end of the at least one second mooring line is located farther from the wind power plant than the wind power plant connection end of the at least one first mooring line.

16. The method according to claim 15, wherein the wind power installation and the mooring system form a wind power system according to any one of claims 1 to 14.

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