A tension leg moored offshore floating wind turbine foundation structure

Abstract

The application provides a tension leg mooring offshore floating wind turbine foundation structure, which comprises a floating body, a mooring system and an anchoring system; the floating body comprises a central column and a plurality of groups of pontoons which are connected between the central column and outer side columns and are distributed in a star shape; each group of pontoons comprises two pontoons which are arranged in two layers; the two pontoons are connected to the outer side columns at the ends away from the central column; a gap is formed between the two layers of pontoons at a position close to the central column to allow water flow; and the top of the central column is used for connecting a tower of an offshore floating wind turbine; the floating body is fixed to the seabed through the mooring system and the anchoring system, and the mooring system is always in tension. The floating body has the advantages of less steel consumption, smaller horizontal and vertical wave flow load, uniform platform structure stress, smaller tension tendon stress, increased tension tendon service life, reduced anchoring foundation design load and construction and installation cost.

Description

Technical Field

[0001] This invention relates to offshore floating wind turbine technology, and more particularly to a tension leg mooring offshore floating wind turbine foundation structure. Background Technology

[0002] With the development of offshore wind power engineering technology, offshore wind power generation has gradually demonstrated good economic benefits. Major maritime nations worldwide have increased their investment in the offshore wind power industry and undertaken extensive offshore wind power development. Currently, nearshore wind farms have been largely developed, and the development of deep-sea wind power will become a key focus for various countries in the future. However, due to limitations in engineering technology, the development cost of deep-sea wind power remains high, failing to meet the needs of commercial development. Therefore, finding more cost-optimized floating wind turbine solutions is a current hot research direction in the international offshore wind power industry.

[0003] Currently, numerous demonstration applications of semi-submersible floating wind turbine foundations have been conducted worldwide. These demonstrations indicate that the cost of most semi-submersible platform foundations currently exceeds 30,000 RMB / kW, approximately 2-3 times higher than the cost of commercial development. Therefore, promoting the large-scale application of floating wind power requires a significant reduction in the cost of existing technologies. Summary of the Invention

[0004] To address the problem of excessively high costs associated with existing floating wind turbine foundations, the present invention aims to propose a tension leg mooring offshore floating wind turbine foundation structure. This foundation structure has the advantages of requiring less steel for the floating body, resulting in smaller horizontal and vertical wave and current loads, uniform stress on the platform structure, reduced stress on the tension tendons, extended tension tendon life, and reduced anchorage foundation design load, thereby reducing the structural size and construction and installation costs of the anchorage foundation system.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is: a tension leg mooring offshore floating wind turbine foundation structure, including a float, a mooring system and an anchoring system;

[0006] The floating structure comprises a central column, multiple outer columns, and a series of pontoons symmetrically distributed in a star shape between the central and outer columns. Each group of pontoons consists of two pontoons (an upper pontoon and a lower pontoon), arranged in two layers. The end of each pontoon furthest from the central column is connected to an outer column (which can be circular, square, or polygonal). There is a distance of more than 1 meter between the upper and lower pontoons, and they are arranged non-parallel, with a larger gap near the central column to allow water flow. The top of the central column is used to connect to the offshore floating wind turbine tower. The arrangement of the upper and lower pontoons increases the number of pontoons, providing greater buoyancy, and also reduces the vertical projected area, thus reducing wave loads caused by water particles and structural interactions. Furthermore, the gap between the upper and lower pontoons allows water to flow around them, reducing the horizontal load exerted by the water flow on the pontoons.

[0007] The bottom of the outer support column of the floating body is connected to the mooring system and the anchoring system, meaning the floating body is fixed to the seabed by the mooring and anchoring systems, and the mooring system is always under tension. The tension leg moored offshore floating wind turbine foundation structure can provide greater buoyancy, ensuring that the system maintains positive buoyancy under various marine environmental conditions, that is, the mooring system is always under tension, thus realizing the function of the tension leg floating wind turbine foundation.

[0008] Furthermore, the floating body includes 3-8 sets of buoys, preferably 3-5 sets of buoys. The multiple sets of buoys are arranged symmetrically around the center of the central column.

[0009] Furthermore, the cross-section of the pontoon is circular, square, or polygonal, depending on the specific construction, installation, and operational requirements.

[0010] Furthermore, the pontoon structure is a stiffened plate shell.

[0011] Furthermore, the pontoon cross-section maintains a uniform shape or gradually changes along the axial direction. The pontoon can maintain a uniform cross-section or have a smaller radial cross-section radius on the side away from the central column and a larger radial cross-section radius on the side closer to the central column, so as to withstand a larger bending moment at the center.

[0012] Furthermore, the lower pontoons can be arranged horizontally or tilted downwards (tilt angle of 0-30 degrees), and the upper pontoons can be arranged horizontally or tilted upwards (tilt angle of 0-30 degrees). The tilt angle is determined based on manufacturing, installation, and in-situ operating conditions.

[0013] Furthermore, the pontoon material is steel, concrete, or other composite materials that meet strength and corrosion requirements, including but not limited to glass fiber reinforced materials. This invention reduces steel consumption by optimizing the shape and reducing the volume.

[0014] Furthermore, the mooring system is a tension tendon. Throughout its lifespan, the tension tendon remains taut and maintains a high tension level to prevent overall instability due to movement of the wind turbine and foundation.

[0015] Furthermore, each of the outer columns is connected to 2-3 tension tendons.

[0016] Furthermore, the tension tendon is a steel pipe, anchor chain, steel cable, or composite fiber material.

[0017] Furthermore, the tension tendon can be perpendicular to the seabed or slightly inclined.

[0018] Furthermore, the anchoring system is a suction bucket foundation, a pile foundation, or a gravity foundation.

[0019] Furthermore, a flange is pre-installed at the top of the central column to facilitate connection with the offshore floating wind turbine tower.

[0020] Another objective of this invention discloses an offshore floating wind turbine system, comprising the aforementioned tension leg moored offshore floating wind turbine foundation structure, a tower, and a wind turbine. The wind turbine is mounted on the upper end of the tower, and the lower end of the tower is connected to the top of a central column. The offshore floating wind turbine system employs a double-layer pontoon design, which increases buoyancy without increasing wave load. Simultaneously, the double-layer pontoon design provides greater structural strength, reduces internal stress levels in the joint steel, and improves structural safety.

[0021] The installation of the offshore floating wind turbine system is as follows: 1) The new tension leg type floating wind turbine platform of this invention integrates the foundation structure, tower, turbine unit, and blades of the offshore floating wind turbine at the shore dock. 2) Anchoring and tensioning of the mooring system are pre-installed at the turbine location. The installed tensioning mooring system can be temporarily placed on the seabed or tensioned in the water using temporary buoys. 3) The integrated floating wind turbine system is transported to the turbine location using a transport auxiliary float or barge for installation. 4) After the floating wind turbine arrives at the turbine location, ballast is applied to reduce the draft and connect with the tensioning mooring system. After connection, ballast water is discharged to raise the float, and the tensioning mooring system is tightened, completing the installation of the float.

[0022] The tension leg mooring offshore floating wind turbine foundation structure and offshore floating wind turbine system of this invention have the following advantages compared with the prior art:

[0023] 1) The concept of a tension leg floating wind turbine foundation in this invention considers the stress characteristics of tension leg floating foundations. It employs a two-layer pontoon structure, which increases the overall buoyancy of the structure and reduces the vertical projected area, thereby reducing vertical wave and current loads. This, in turn, reduces the alternating load amplitude of the tension tendons and improves their fatigue life. Furthermore, a horizontal gap is left between the two layers of pontoons, allowing water flow to pass through and reducing horizontal wave and current loads on the platform. This further reduces platform motion and stress on the tension tendons.

[0024] 3) Compared to semi-submersible floating wind turbines, tension leg floating foundations may offer significant cost optimization potential. Tension leg floating wind turbines have several advantages over semi-submersible turbines: First, their dimensions are smaller, requiring approximately 30% less steel than semi-submersible floating wind turbines. Second, their mooring system length is shorter, typically 1 / 5 to 1 / 10 that of a catenary mooring system, resulting in lower costs. Third, their motion performance is superior, with platform sway and roll movements only about 1 / 10 that of semi-submersible foundations. This makes them more compatible with the topside units, significantly increasing turbine reliability and reducing costs. Fourth, tension leg foundations are beneficial for dynamic cable design because the dynamic floating body's movement is smaller, simplifying cable rigging design and significantly reducing fatigue damage.

[0025] 4) This invention is a tension leg type floating wind turbine foundation, which, compared with other floating foundations, can provide more buoyancy with limited steel consumption. It improves steel utilization efficiency and reduces the cost of floating foundations.

[0026] 5) The floating foundation proposed in this invention can provide more buoyancy without increasing the vertical stress on the floating body, reducing the stress on the tension tendons and the anchoring system, thereby reducing the cost of tension mooring and anchoring systems.

[0027] 6) This invention proposes a tension tendon mooring system, which makes full use of the material's own tensile properties to provide mooring stiffness. Compared with the catenary mooring method, its mooring system length is greatly reduced, the number of mooring system components required is less, and the mooring cost is greatly reduced.

[0028] 7) The floating body form proposed in this invention has higher bending stiffness, more reasonable structural stress performance, significantly improved hot spot stress level, and safer structural application. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the offshore floating wind turbine system in Example 1;

[0030] Figure 2This is a schematic diagram of the tension leg mooring offshore floating wind turbine foundation structure in Example 1;

[0031] Figure 3 This is a schematic diagram of the offshore floating wind turbine system in Example 2;

[0032] Figure 4 This is a schematic diagram of the tension leg mooring offshore floating wind turbine foundation structure in Example 2;

[0033] Figure 5 This is a schematic diagram of the offshore floating wind turbine system in Example 3;

[0034] Figure 6 This is a schematic diagram of the tension leg mooring offshore floating wind turbine foundation structure in Example 3;

[0035] Figure 7 This is a schematic diagram of the offshore floating wind turbine system in Example 4;

[0036] Figure 8 This is a schematic diagram of the foundation structure for a tension leg moored offshore floating wind turbine, as shown in Example 4. Detailed Implementation

[0037] The present invention will be further described below with reference to the embodiments:

[0038] Example 1

[0039] This embodiment discloses a tension leg mooring offshore floating wind turbine foundation structure, such as... Figure 1 and Figure 2 As shown, it includes a floating body 3, a mooring system 4, and an anchoring system 5;

[0040] The float 3 comprises a cylindrical central column 6, outer columns, and three sets of pontoons symmetrically distributed in a star shape between the central and outer columns. The three sets of pontoons are arranged symmetrically around the central column 6. Each set consists of two pontoons: an upper pontoon 8 and a lower pontoon 9, arranged in two layers. The lower pontoon 9 is horizontally positioned, while the end of the upper pontoon 8 furthest from the central column 6 is inclined downwards. The distance between the ends of the upper and lower pontoons 8 and 9 closest to the central column 6 exceeds 1 meter, while the distance between the ends furthest from the central column 6 is smaller. The inclination angle of the upper pontoon 8 is determined based on manufacturing, installation, and in-situ operating conditions. A gap is formed between the upper and lower pontoons near the central column to allow water flow, reducing the horizontal load exerted on the pontoons by the water flow.

[0041] The end of the pontoon furthest from the central column is connected to an outer column 7, which is a column with the same outline as the pontoon. The pontoon has a square cross-section, and the outer column 7 has the same square cross-section as the pontoon. The cross-section of the pontoon gradually changes, with a smaller radial radius on the side furthest from the central column and a larger radial radius on the side closer to the central column, in order to withstand the larger bending moment at the center. The pontoon structure is a stiffened plate shell. The pontoon material is glass fiber reinforced material. The arrangement of the upper and lower layers of pontoons increases the number of pontoons, providing more buoyancy, and also reduces the vertical projected area, thereby reducing the wave load caused by the interaction of water particles and the structure.

[0042] The bottom of the outer support column 7 of the float 3 is connected to the anchoring system 5 via a mooring system 4. That is, the float 3 is fixed to the seabed by the mooring system 4 and the anchoring system 5, and the mooring system 4 is always under tension. In this embodiment, the mooring system 4 is a tension tendon, which remains taut throughout its lifespan and maintains a high tension level to prevent overall instability due to wind turbine and foundation movement. In this embodiment, each outer support column 7 is connected to two tension tendons, which are anchor chains, perpendicular to the seabed. The anchoring system is a pile foundation.

[0043] The tension leg moored offshore floating wind turbine foundation structure described in this embodiment can provide greater buoyancy, ensuring that the system maintains positive buoyancy under various marine environmental conditions. The mooring system is always under tension, thus realizing the function of the tension leg floating wind turbine foundation.

[0044] This embodiment also discloses an offshore floating wind turbine system, such as Figure 1 As shown, the structure includes the aforementioned tension leg moored offshore floating wind turbine foundation structure, tower 2, and wind turbine 1. The wind turbine 1 is installed on the upper end of the tower 2, and the lower end of the tower 2 is connected to the top of the central column 6 via a flange. The tension leg type floating wind turbine adopts a double-layer pontoon design, which increases buoyancy without increasing wave load. Simultaneously, the double-layer pontoon provides greater structural strength, reduces the internal stress level of the joint steel, and improves structural safety.

[0045] The installation of the offshore floating wind turbine system of this invention involves the integration of the floating body, tower, wind turbine unit, and blades at a shore dock. Anchoring and tensioning mooring systems are pre-installed at the turbine location. The installed tensioning mooring system can be temporarily placed on the seabed or tensioned in the water using temporary buoys. The integrated floating wind turbine system is transported to the turbine location using a transport auxiliary floating body or barge for installation. After the floating wind turbine arrives at the location, ballast is applied to lower the draft and connect it to the tensioning mooring system. After connection, ballast water is discharged to raise the floating body, and the tensioning mooring system is then tightened. The floating body installation is then complete.

[0046] Example 2

[0047] This embodiment discloses a tension leg mooring offshore floating wind turbine foundation structure, such as... Figure 3 and Figure 4 As shown, it includes a floating body 3, a mooring system 4, and an anchoring system 5;

[0048] The float 3 includes a central column 6 and four sets of pontoons connected to the side wall of the central column and symmetrically distributed in a star shape. The four sets of pontoons are arranged symmetrically around the central column 6. Each set of pontoons consists of two pontoons, namely an upper pontoon 8 and a lower pontoon 9, arranged in two layers. The end of each pontoon away from the central column is connected to an outer column 7, which is a column with the same outline as the pontoon. The pontoon has a square cross-section.

[0049] The pontoon structure is a stiffened plate shell. The radial cross-section of the pontoons remains consistent. The lower pontoon 9 is horizontally arranged, and the upper pontoon 8 is inclined downwards at the end away from the central column 6. The inclination angle is determined according to manufacturing, installation, and in-situ operating conditions. The pontoon material is concrete. A gap is formed between the upper and lower pontoons near the central column to allow water flow and reduce the horizontal load on the pontoons. The top of the central column is used to connect the offshore floating wind turbine tower; the arrangement of the upper and lower pontoons increases the number of pontoons, providing more buoyancy, and also reduces the vertical projected area, reducing wave loads caused by water particles and structural interactions. The bottom of the outer column of the float 3 is connected to the anchoring system 5 through the mooring system 4, meaning the float 3 is fixed to the seabed by the mooring system 4 and the anchoring system 5, and the mooring system is always under tension. The mooring system 4 is a tension tendon. The tension tendon remains taut throughout its lifespan, maintaining a high tension level to prevent overall instability due to wind turbine and foundation movement. Each outer column 7 is connected to two tension tendons. The tension tendons are steel pipes. The angle between the tension tendons and the seabed is slightly less than 90 degrees. The anchoring system is a gravity foundation.

[0050] The tension leg moored offshore floating wind turbine foundation structure described in this embodiment can provide greater buoyancy, ensuring that the system maintains positive buoyancy under various marine environmental conditions. The mooring system is always under tension, thus realizing the function of the tension leg floating wind turbine foundation.

[0051] This embodiment also discloses an offshore floating wind turbine system, such as Figure 4 As shown, the structure includes the aforementioned tension leg moored offshore floating wind turbine foundation structure, tower 2, and wind turbine 1. The wind turbine 1 is installed at the upper end of the tower, and the lower end of the tower is connected to the top of the central column via a flange. The tension leg type floating wind turbine adopts a double-layer pontoon design, which increases buoyancy without increasing wave load. At the same time, the double-layer pontoon provides greater structural strength, reduces the internal stress level of the joint steel, and improves structural safety.

[0052] The installation of the offshore floating wind turbine system of this invention involves the integration of the floating body, tower, wind turbine unit, and blades at a shore dock. Anchoring and tensioning mooring systems are pre-installed at the turbine location. The installed tensioning mooring system can be temporarily placed on the seabed or tensioned in the water using temporary buoys. The integrated floating wind turbine system is transported to the turbine location using a transport auxiliary floating body or barge for installation. After the floating wind turbine arrives at the location, ballast is applied to lower the draft and connect it to the tensioning mooring system. After connection, ballast water is discharged to raise the floating body, and the tensioning mooring system is then tightened. The floating body installation is then complete.

[0053] Example 3

[0054] This embodiment discloses a tension leg mooring offshore floating wind turbine foundation structure, such as... Figure 5 and Figure 6 As shown, it includes a floating body 3, a mooring system 4, and an anchoring system 5;

[0055] The float 3 includes a central column 6 and three sets of pontoons connected to the sidewalls of the central column and symmetrically distributed in a star shape. The three sets of pontoons are arranged symmetrically around the central column 6. Each set consists of two pontoons: an upper pontoon 8 and a lower pontoon 9, arranged in two layers. The end of each pontoon away from the central column is connected to an outer column 7, which is circular. The pontoons have a circular cross-section. The pontoon structure is a stiffened plate shell. The radial cross-section of each pontoon gradually changes, with a smaller radial radius on the side away from the central column and a larger radial radius on the side closer to the central column, to withstand the larger bending moment at the center. The lower pontoon 9 is horizontally arranged, and the end of the upper pontoon 8 away from the central column 6 is inclined downwards. The inclination angle is determined based on manufacturing, installation, and in-situ operating conditions. The pontoons are made of concrete. A gap is formed between the upper and lower pontoons near the central column to allow water flow and reduce the horizontal load on the pontoons. The top of the central column is used to connect the offshore floating wind turbine tower; the upper and lower layers of floating pontoons increase the number of pontoons, which can provide more buoyancy, and reduce the vertical projected area, thereby reducing the wave load caused by the interaction between water particles and the structure.

[0056] The bottom of the outer support column of the float 3 is connected to the anchoring system 5 via the mooring system 4. That is, the float 3 is fixed to the seabed by the mooring system 4 and the anchoring system 5, and the mooring system is always under tension. The mooring system 4 is a tension tendon. Throughout its lifespan, the tension tendon remains taut and at a high tension level to prevent overall instability due to wind turbine and foundation movement. Each outer support column 7 is connected to three tension tendons, which are steel cables. The tension tendons are perpendicular to the seabed. The anchoring system is a suction bucket foundation.

[0057] The tension leg mooring offshore floating wind turbine foundation structure can provide greater buoyancy, ensuring that the system maintains positive buoyancy under various marine environmental conditions, and that the mooring system is always under tension, thus realizing the function of the tension leg floating wind turbine foundation.

[0058] This embodiment also discloses an offshore floating wind turbine system, such as Figure 5 As shown, the structure includes the aforementioned tension leg moored offshore floating wind turbine foundation structure, tower 2, and wind turbine 1. The wind turbine 1 is installed at the upper end of the tower, and the lower end of the tower is connected to the top of the central column via a flange. The tension leg type floating wind turbine adopts a double-layer pontoon design, which increases buoyancy without increasing wave load. At the same time, the double-layer pontoon provides greater structural strength, reduces the internal stress level of the joint steel, and improves structural safety.

[0059] The installation of the offshore floating wind turbine system of this invention involves the integration of the floating body, tower, wind turbine unit, and blades at a shore dock. Anchoring and tensioning mooring systems are pre-installed at the turbine location. The installed tensioning mooring system can be temporarily placed on the seabed or tensioned in the water using temporary buoys. The integrated floating wind turbine system is transported to the turbine location using a transport auxiliary floating body or barge for installation. After the floating wind turbine arrives at the location, ballast is applied to lower the draft and connect it to the tensioning mooring system. After connection, ballast water is discharged to raise the floating body, and the tensioning mooring system is then tightened. The floating body installation is then complete.

[0060] Example 4

[0061] This embodiment discloses a tension leg mooring offshore floating wind turbine foundation structure, such as... Figure 7 and Figure 8 As shown, it includes a floating body 3, a mooring system 4, and an anchoring system 5;

[0062] The float 3 includes a central column 6 and four sets of pontoons connected to the sidewalls of the central column and symmetrically distributed in a star shape. The four sets of pontoons are arranged symmetrically around the central column 6. Each set consists of two pontoons: an upper pontoon 8 and a lower pontoon 9, arranged in two layers. The end of each pontoon furthest from the central column is connected to an outer column 7, which is circular. The pontoons also have circular cross-sections. The pontoon structure is a stiffened plate shell. The radial cross-sections of the pontoons remain consistent. The lower pontoon 9 is horizontally arranged, and the end of the upper pontoon 8 furthest from the central column 6 is inclined downwards. The inclination angle is determined based on manufacturing, installation, and in-situ operating conditions. The pontoons are made of glass fiber reinforced material. A gap is formed between the upper and lower pontoons near the central column to allow water to flow through, reducing the horizontal load on the pontoons. The top of the central column is used to connect the offshore floating wind turbine tower. The arrangement of the upper and lower pontoons increases the number of pontoons, which can provide more buoyancy. On the other hand, it can reduce the vertical projected area and reduce the wave load caused by the interaction between water particles and the structure.

[0063] The bottom of the outer support column of the float 3 is connected to the anchoring system 5 via the mooring system 4. That is, the float 3 is fixed to the seabed by the mooring system 4 and the anchoring system 5, and the mooring system is always under tension. The mooring system 4 is a tension tendon. Throughout its lifespan, the tension tendon remains taut and at a high tension level to prevent overall instability due to wind turbine and foundation movement. Each outer support column 7 is connected to two tension tendons, which are made of composite fiber material and are perpendicular to the seabed. The anchoring system is a suction bucket foundation.

[0064] The tension leg mooring offshore floating wind turbine foundation structure can provide greater buoyancy, ensuring that the system maintains positive buoyancy under various marine environmental conditions, and that the mooring system is always under tension, thus realizing the function of the tension leg floating wind turbine foundation.

[0065] This embodiment also discloses an offshore floating wind turbine system, such as Figure 7 As shown, the structure includes the aforementioned tension leg moored offshore floating wind turbine foundation structure, tower 2, and wind turbine 1. The wind turbine 1 is installed at the upper end of the tower, and the lower end of the tower is connected to the top of the central column via a flange. The tension leg type floating wind turbine adopts a double-layer pontoon design, which increases buoyancy without increasing wave load. At the same time, the double-layer pontoon provides greater structural strength, reduces the internal stress level of the joint steel, and improves structural safety.

[0066] The installation of the offshore floating wind turbine system of this invention involves the integration of the floating body, tower, wind turbine unit, and blades at a shore dock. Anchoring and tensioning mooring systems are pre-installed at the turbine location. The installed tensioning mooring system can be temporarily placed on the seabed or tensioned in the water using temporary buoys. The integrated floating wind turbine system is transported to the turbine location using a transport auxiliary floating body or barge for installation. After the floating wind turbine arrives at the location, ballast is applied to lower the draft and connect it to the tensioning mooring system. After connection, ballast water is discharged to raise the floating body, and the tensioning mooring system is then tightened. The floating body installation is then complete.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A tension leg mooring offshore floating wind turbine foundation structure, characterized in that, It includes a floating body (3), a mooring system (4) and an anchoring system (5); The floating body (3) includes a central column (6), multiple outer columns, and multiple sets of pontoons connected between the central column and the outer columns and distributed in a star-shaped symmetrical pattern. Each set of pontoons consists of two pontoons arranged in two layers, one above the other. The end of the pontoon away from the central column is connected to the outer column (7). A gap is formed between the upper and lower pontoons near the central column. The upper and lower pontoons are spaced more than 1 meter apart at the ends near the central column. The upper and lower pontoons are arranged in a non-parallel manner, with a large gap near the central column to allow water flow and reduce the horizontal load on the pontoons. The top of the central column is used to connect the offshore floating wind turbine tower. The arrangement of the pontoons in two layers increases the number of pontoons, providing more buoyancy, and also reduces the vertical projection area, thus reducing the wave load caused by the interaction between water particles and the structure. The bottom end of the outer column of the float (3) is connected to the anchoring system (5) through the mooring system (4), and the mooring system (4) is always in a tension state; The pontoon cross-section maintains a uniform shape or gradually changes along the axial direction. The pontoon can maintain a uniform cross-section or have a smaller radial cross-section radius on the side away from the central column and a larger radial cross-section radius on the side closer to the central column. The lower pontoons (9) are arranged horizontally or inclined downwards, and the upper pontoons (8) are arranged horizontally or inclined upwards; The pontoon material is steel, concrete, or glass fiber reinforced material; The mooring system (4) is a tension tendon; The tension tendon is made of steel pipe, anchor chain, steel cable or composite fiber material; The tension tendon can be perpendicular to the seabed or slightly inclined.

2. The tension leg mooring offshore floating wind turbine foundation structure according to claim 1, characterized in that, The float (3) includes 3-8 sets of buoys.

3. The tension leg mooring offshore floating wind turbine foundation structure according to claim 1, characterized in that, The radial cross-section of the pontoon is circular, square, or polygonal.

4. A floating offshore wind turbine system, characterized in that, Includes the tension leg moored offshore floating wind turbine foundation structure, tower (2) and wind turbine (1) as described in any one of claims 1-3, wherein the wind turbine (1) is installed at the upper end of the tower (2) and the lower end of the tower (2) is connected to the top of the central column (6).

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