Design and optimization method for single-point mooring system of floating type double-fan foundation structure

Abstract

The invention belongs to the technical field of ocean engineering, and discloses a design and optimization method of a single-point mooring system of a floating type double-fan foundation structure, which comprises the following steps: selecting an initial mooring mode; analyzing and calculating to find out control working conditions of mooring line tension and platform motion response and corresponding wind wave flow directions; the ship-shaped buoy is rotated to the optimal wave facing angle, and frequency domain hydrodynamic analysis is carried out; mooring time domain analysis is carried out, and parameters of a mooring line are modified; judging a mooring mode; carrying out mooring time domain analysis under the working condition corresponding to the maximum platform motion response, and judging the length of a mooring cable; s8, judging whether the motion response of the platform meets the specification or not, and if not, executing S8; redefining a group of mooring systems configured with counterweight chains, and finding out a counterweight chain sensitivity parameter combination meeting the specification requirements; and the counterweight chain with the lowest cost is selected for mooring time domain analysis until the platform motion response meets the standard design requirement, and the final mooring mode is determined. The construction and construction installation cost of the floating foundation mooring system is remarkably reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of ocean engineering, and particularly relates to a design and optimization method of a single-point mooring system of a floating double-wind-turbine foundation structure. BACKGROUND

[0002] As a renewable clean energy, offshore wind power is valued by coastal countries around the world. In recent years, with the progress of offshore wind power technology, offshore wind farm construction and development have entered a fast track. China's offshore wind power has advantages such as abundant resources, high power generation utilization hours, and close proximity to load centers. Although it started late, it has developed rapidly. In 2024, China's offshore wind power added 5.62 million kilowatts of installed capacity, accounting for 6.5% of the total additional installed capacity. It is estimated that the additional installed capacity will reach 7.7 million kilowatts in 2025. Due to the limited space resources in the coastal area, the development of offshore wind power will inevitably move from shallow sea to deep sea like the past offshore oil and gas industry. Therefore, floating wind power technology is becoming a research hotspot and gradually being applied in offshore demonstration.

[0003] There are four main floating wind power foundation technology routes: single-pile type, semi-submersible type, barge type, and tension leg type. At present, the single-pile type and semi-submersible type foundation technology are slightly better in feasibility, and are in the stage of small-batch demonstration wind farms, but the single-pile type has a relatively high overall cost and is suitable for water depths of generally >100m; the semi-submersible floating foundation is mature, has a wide water depth range, and has been applied in multiple projects, with advantages such as a wide applicable water depth range and low installation difficulty. Overall, the semi-submersible type has the most promising prospects for commercialization and large-scale application, but its stability is lower than that of the single-pile type foundation structure, and the movement amplitude is larger; the construction and installation costs of the barge type and tension leg type account for a large proportion of the overall project development cost, and the construction and installation costs of the floating foundation mooring system are high.

[0004] To make greater use of wind resources, reduce steel consumption and costs, match large wind turbines, and adapt to deeper water depths, the double-wind-turbine design can save wind turbine foundations and achieve cost reduction and efficiency improvement. Related reference CN 118907327A discloses a lightweight floating double-wind-turbine foundation device that can face the waves head-on, achieving minimization of the main dimensions of the floating cylinder structure and lightweight structure. However, to achieve its function of facing the waves head-on, the foundation device needs to use single-point mooring. If a conventional catenary mooring is used, a large mooring radius needs to be designed and a sufficient bottom-lying section needs to be reserved. For water depths of about 70-150m, the platform movement cannot be well limited, and the mooring cost is relatively high. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a design and optimization method of a single-point mooring system of a floating double-wind-turbine foundation structure, which can limit platform movement, reduce mooring cost, and significantly reduce the construction and installation costs of the floating foundation mooring system.

[0006] To solve the above technical problems, the application provides a design and optimization method of a single-point mooring system of a floating double-wind-turbine foundation structure, comprising the following steps: S1: according to the environmental condition parameters of the wind turbine operation sea area, fixing the ship-type buoy orientation, and initially designing a 3*3 single-point mooring mode; S2: applying wind wheel aerodynamic load, tower wind pressure, wave load and water flow load, predicting the mooring line tension and platform motion response under power generation and shutdown working conditions through dynamic time domain analysis, and finding out the control working condition of the mooring line tension and platform motion response and the corresponding wind, wave and flow direction; S3: rotating the ship-type buoy to the optimal wave-encountering angle according to the control strategy, updating the center of gravity, moment of inertia and ballast water weight information of the floating double-wind-turbine foundation after rotating the ship-type buoy, and re-performing frequency domain hydrodynamic analysis; S4: performing mooring time domain analysis under the working condition corresponding to the maximum mooring line tension based on the rotated ship-type buoy in S3, and modifying the parameters of the mooring line including the mooring line diameter, weight, stiffness and breaking force according to the maximum mooring line tension; S5: after updating the parameters of the mooring line, judging whether the maximum mooring line tension meets the specification requirements, if yes, performing trial calculation on a 3*2 mooring scheme again, if the 3*2 mooring scheme can meet the specification design requirements, adopting the 3*2 mooring mode, otherwise, adopting the 3*3 mooring mode; S6: performing mooring time domain analysis under the working condition corresponding to the maximum platform motion response by using the mooring mode determined in S5, if the platform offset meets the specification design requirements, extracting the shortest bottom-lying length in the time domain analysis process, if the shortest bottom-lying length is significantly abundant, further shortening the mooring line length to a certain range, otherwise, using the mooring line length in the initial design; S7: judging whether the pitch motion amplitude and balance position of the platform meet the specification design requirements by using the mooring mode determined in S6, if yes, taking the mooring mode as the final mooring mode, otherwise, performing the optimization design step of S8; S8: redefining a set of mooring systems configured with counterweight chains, adding counterweight chains to the mooring line of the mooring system with the maximum tension, taking the unit length weight of the counterweight chain, the counterweight chain length and the distance from the counterweight chain to the hanger as sensitive parameters, performing time domain mooring analysis for a certain time, determining the maximum pitch angle of the platform in the certain time, and finding out the counterweight chain sensitive parameter combination meeting the specification requirements; S9: Calculate the mooring cost of different combinations of weight chain sensitivity parameters, select the weight chain with the lowest cost for mooring time domain analysis, judge whether the maximum pitch angle of the dual wind turbine platform in this time meets the requirements, if not, select the weight chain scheme with one level higher mooring cost in step S8 for analysis, until the motion response of the platform meets the specification design requirements, the mooring scheme is the final mooring mode.

[0007] The method performs time domain analysis on the floating dual wind turbine foundation structure under sea environmental conditions, adjusts the tension distribution of the mooring system, determines the parameters of each mooring line and the parameters of each weight chain, effectively improves the stress of the mooring system, effectively limits the platform motion, reduces the requirements of the dual wind turbine single point mooring system on the size, number and material of the mooring line, and significantly reduces the construction and installation cost of the floating foundation mooring system.

[0008] Preferably, in step S1, the mooring radius is selected as 6-8 times the water depth, and the angle between each mooring line is selected as 3-5°, the anchor point position coordinates are determined by determining the mooring radius and the angle between the mooring lines; the mooring line length is determined by the mooring line pretension, to ensure uniform tension distribution on each mooring line.

[0009] Preferably, in step S5, the 3*3 mode uses three groups of mooring systems, each group of mooring system is provided with three mooring lines; the 3*2 mode uses three groups of mooring systems, each group is provided with two mooring lines.

[0010] The floating dual wind turbine foundation structure mainly comprises two symmetrical ship-shaped pontoons and columns, wind turbines and tower drums, a bow column, a triangular truss, a single point mooring device, and a mooring system; the two ship-shaped pontoons and the bow column are connected through the triangular truss; the two columns are respectively arranged on the respective ship-shaped pontoons through rotating members; the single point mooring device is rigidly connected with the bow, and a lifting lug is arranged outside the single point mooring device; the mooring system is installed on the lifting lug. The ship-shaped pontoons can be rotated to the optimal wave-encountering angle through a control strategy, to reduce the wave load and flow load acting on the foundation structure. The mooring system 400 optimizes the mooring line type by adding weight blocks / floatation blocks, and determines the key design parameters through dynamic optimization design, to effectively limit the platform motion and minimize the maximum mooring line tension, thereby reducing the cost and installation cost of the mooring line.

[0011] Preferably, the ship-shaped pontoon is an ellipsoid. Compared with a cylindrical pontoon, the design effectively reduces the wet surface area of the ship-shaped pontoon under the same displacement.

[0012] Preferably, the top of the ship-shaped pontoon is a plane. The plane-shaped ship-shaped pontoon has a large working space, which is beneficial to arranging deck equipment, facilitates personnel boarding, and facilitates facility maintenance.

[0013] The waterline position is preferably located in the upper part of the ship-shaped buoy, which reduces the requirement for the water depth of the wharf when the fan is installed, and the waterline area of the floating double-fan foundation is greatly increased, and the stability performance is significantly improved compared with the traditional semi-submersible foundation.

[0014] The middle part of the ship-shaped buoy is preferably provided with an empty cabin, and a rotating member is arranged in the empty cabin. The stability during rotation against waves is improved by using symmetrical ballast at the head and tail.

[0015] The head column and the single-point mooring device are preferably rigidly connected through a truss structure.

[0016] The mooring system is preferably composed of an anchor, an anchor chain I and an anchor chain II; wherein the anchor is a suction anchor, a large-grab anchor, a drag anchor or an anchor pile.

[0017] The anchor chain I and the anchor chain II are preferably provided with a counterweight chain.

[0018] Compared with the prior art, the beneficial effects of the present application are as follows: 1. The design and optimization method of the present application performs time-domain analysis on the floating double-fan foundation structure under sea environmental conditions, adjusts the tension distribution of the mooring system, determines the parameters of the mooring lines and the parameters of the counterweight chain, effectively improves the stress of the mooring system, effectively limits the platform movement, reduces the requirements of the double-fan single-point mooring system on the size, number and material of the mooring lines, and significantly reduces the construction and installation cost of the floating foundation mooring system.

[0019] 2. The design and optimization method of the mooring provided by the present application considers the influence of the time-domain dynamic environmental load, ensures that the maximum offset of the double-fan foundation, the pitch angle and the stress of the mooring system meet the specification design requirements.

[0020] 3. The mooring system optimization method provided by the present application can effectively improve the stress of the mooring system, effectively limit the platform movement, reduce the requirements of the double-fan single-point mooring system on the size, number and material of the mooring lines, reduce the mooring cost, and has high economic efficiency for medium and shallow water depth.

[0021] 4. Compared with the tension mooring and the semi-tension mooring, the counterweight chain combination design of the present application effectively reduces the installation and design difficulty of the multi-section mooring system. DETAILED DESCRIPTION

[0022] Figure 1 is a structural diagram of the present application; Figure 2 is a platform structure diagram of the present application; Figure 3 is a flowchart of the present application; Figure 4This is a schematic diagram of the single-point mooring system layout of the present invention; Figure 5 This is a comparison diagram of the mooring system of the present invention after dynamic design optimization; Figure 6 This is a schematic diagram of the initial mooring system in step S1 of the present invention; Figure 7 This is a schematic diagram of the counterweight chain arrangement and its effect in shallow waters during step S8 of the present invention. Table 1 is a table analyzing the mooring sensitivity parameters of the counterweight chain of the present invention.

[0023] Drawing No.: 101, hull-shaped buoy; 102, column; 103, tower; 104, wind turbine; 301, bow column; 302, triangular truss; 303, single-point mooring device; 400, mooring system; 401, anchor; 402, anchor chain I; 403, counterweight chain; 404, anchor chain II; 405, anchor chain III; 5, truss structure; 6, lifting lug. Detailed Implementation

[0024] like Figure 1 , Figure 2 The diagram shows a schematic of the floating dual-wind turbine foundation structure provided by the present invention; it consists of two symmetrically arranged ship-shaped pontoons 101 and two columns 102, two wind turbines 104 and two towers 103, a bow column 301, a triangular truss 302, a single-point mooring device 303, and a mooring system 400. The two ship-shaped pontoons 101, the two columns 102, the bow column 301, and the triangular truss 302 form a platform. The two ship-shaped pontoons 101 and one bow column 301 are connected by the triangular truss 302. Two columns 102 are respectively mounted on their respective hull-shaped buoys 101 via rotating components. The hull-shaped buoys 101 can be rotated to the optimal wave-facing angle through a control strategy. When an angle is formed between the wave direction and the orientation of the hull-shaped buoys 101, the hull-shaped buoys 101 rotate to maintain their side facing the waves, further adjusting the wave-facing area, which can significantly reduce the wave load on the hull-shaped buoys 101 and reduce the wave and current loads on the foundation structure. The bow column 301 and the single-point mooring device 303 are rigidly connected, achieving automatic wind alignment through the wind vane effect, improving the power generation efficiency of the wind turbine 104. The single-point mooring device 303 is equipped with a lifting lug 6 structure. The mooring system 400 is installed through the external lifting lug 6 structure on the single-point mooring device 303. The single-point mooring device 303 can be rotated by internal rotating components (such as bearings) to prevent the anchor chain from getting tangled during wind alignment between the two wind turbines. Because when the wind is not directly overhead, the entire floating twin-fan foundation structure will rotate around the central axis of the single-point mooring device 303 due to the wind vane effect. If the rotation angle is too large, the anchor chain is prone to twisting and entanglement.

[0025] The hull-shaped buoy 101 is a slender elliptical body. Compared with cylindrical buoys, this design effectively reduces the wetted surface area of ​​the buoy for the same displacement. Furthermore, the hull-shaped buoy 101 can be rotated to the optimal wave-facing angle through a control strategy. When there is an angle between the wave direction and the orientation of the hull-shaped buoy 101, the hull-shaped buoy 101 rotates to keep its side facing the wave, further adjusting the wave-facing area, which can significantly reduce the wave load on the hull-shaped buoy 101.

[0026] The top of the hull-shaped buoy 101 is flat. The flat surface of the hull-shaped buoy 101 provides a larger working space, which is conducive to the arrangement of deck equipment, facilitates the boarding of maintenance personnel, and makes facility maintenance easier.

[0027] The floating dual-fan foundation structure is designed with its draft located in the upper part of the ship-shaped pontoon 101. This reduces the water depth restrictions on the wharf during the installation of the fan 104. Furthermore, compared to traditional semi-submersible foundations, the waterline area of ​​the floating dual-fan foundation structure is significantly increased, resulting in a substantial improvement in stability.

[0028] While ensuring stability requirements, the wind turbine foundation structure can still generate a good restoring moment for the wind tilting moment generated by the high-power dual wind turbines 104. Under the premise that the stability meets the standard design requirements, the length and width of the wind turbine foundation structure can be further reduced, and the amount of steel used in the connecting triangular truss 302 can be reduced.

[0029] The hull-shaped buoy 101 has an empty compartment in the middle, and rotating components are installed in the empty compartment. Symmetrical ballast is adopted at the bow and stern to improve stability during rotation and wave action.

[0030] The head column 301 and the single-point mooring device 303 are rigidly connected by the truss structure 5.

[0031] like Figure 7 As shown, the optimized mooring system 400 consists of an anchor 401, anchor chain I 402, anchor chain II 404, and a counterweight chain 403. The anchor 401 can be selected from suction anchors, high-holding-force anchors, towed anchors, or anchor piles depending on the geological conditions. The counterweight chain 403 is installed between anchor chain I 402 and anchor chain II 404. The mooring system 400 optimizes the mooring alignment by adding counterweights / buoyancy blocks, and through dynamic optimization design, determines key design parameters. While effectively limiting platform movement, it minimizes the maximum mooring tension, thereby reducing mooring costs and installation expenses. Compared to tensioned mooring and semi-tensioned mooring, the counterweight chain combination design provided in this application effectively reduces the installation and design difficulty of multi-segment mooring systems.

[0032] Traditional catenary mooring provides mooring restoring force through the weight of anchor chain, generally has a long laying length, and is not economical for medium and shallow water. The wind load on the double wind turbine 104 is more significant than that on the single wind turbine 104. In order to balance the environmental load, if a tension mooring is used, the size, number and material of the mooring line are required to be higher. In order to solve the above problems, the mooring system 400 adopts a catenary mooring with counterweight / float block. The position of the counterweight is determined by optimization design, which effectively limits the platform motion while leaving a reasonable laying length, effectively reducing the cost and installation difficulty of the mooring system 400.

[0033] As shown in Figure 3 The design and optimization method of the single point mooring system of the floating double wind turbine foundation structure includes the following steps: S1: As shown in Figure 6 According to the environmental condition parameters (water depth, wind speed, flow rate, 50-year wave, etc.) of the wind turbine 104 operation sea area, the fixed ship-shaped buoy 101 orientation is determined, and a 3*3 mode single point mooring mode is preliminarily designed. The mooring radius is selected to be 6-8 times the water depth, and the angle between each mooring line is selected to be 3-5°. The anchor point coordinate is determined by determining the mooring radius and the angle between the mooring lines. The mooring line length is determined by the size of the pre-tension of the mooring line, so as to ensure that the tension on each mooring line is evenly distributed. At this time, the mooring line length is the length parameter of the anchor chain I 402, the anchor chain III 405 and the anchor chain II 404 added together. The fixed ship-shaped buoy 101 orientation is as shown in Figure 4 The water depth is set to 80m, the mooring radius R is selected to be 6.8 times the water depth, and the angle Θ between each mooring line is selected to be 3°. The anchor point coordinate is determined, and the most initial mooring system 400 design is completed. After the anchor chain I 402, the anchor chain III 405 and the anchor chain II 404 are connected together to form a mooring line, the horizontal distance between the lifting lug 6 and the anchor 401 is R.

[0034] S2: Apply wind turbine aerodynamic load, tower 103 wind pressure, wave load, and flow load environmental load. Through dynamic time domain analysis, the mooring line tension and platform motion response under certain power generation and shutdown conditions are predicted, and the control condition of the mooring line tension and platform motion response and the corresponding wind wave flow direction are found out. The mooring line tension and platform motion response under different wind wave flow directions (including wind wave flow in the same direction and wind wave flow in different directions) are calculated, and the control condition of the mooring line tension and platform motion response and the corresponding wind wave flow direction are found out. According to the time domain mooring analysis, the maximum mooring line tension is 8500kN and the minimum laying length of the mooring line is 90m under the condition that the wind wave flow is in the same direction, which is the maximum condition of the mooring line tension. The maximum platform motion is 6.99° under the condition that the wind wave flow is in different directions, which is the maximum condition of the platform motion.

[0035] S3: In the numerical analysis software, the hull-shaped buoy 101 is rotated to the optimal wave-facing angle according to the control strategy. After rotating the hull-shaped buoy 101, the information such as the center of gravity, moment of inertia, and ballast water weight of the two wind turbine 104 foundations is updated, and the frequency domain hydrodynamic analysis is performed again. First, based on the working condition of maximum mooring force (the wave is downward and the wave-facing angle of the hull-shaped buoy 101 does not need to be adjusted), the mooring scheme is changed to a 3*2 configuration, and the mooring radius R and mooring length are reduced. The mooring length that meets the specifications is determined based on the maximum mooring force. In this example, after this optimization, the configuration was changed from 3*3 to 3*2, the mooring radius R was reduced from 550m to 480m, and the mooring length was reduced from 610m to 540m.

[0036] S4: Based on the rotating hull-shaped buoy 101 in S3, perform a time-domain analysis of mooring under the condition corresponding to the maximum mooring tension. Based on the maximum mooring tension, modify the mooring parameters in the numerical analysis software, including mooring diameter, weight, stiffness, and breaking force. Using the mooring method defined in step S3, perform a time-domain analysis of mooring under the condition corresponding to the maximum platform motion response. If the platform's pitching amplitude is >5°, continue with the following optimization design steps.

[0037] Based on the maximum operating condition of the platform motion, the two ship-shaped pontoons 101 are rotated by 15°, the center of gravity, moment of inertia, and ballast water weight information of the two wind turbines 104 are updated, and frequency domain hydrodynamic analysis is performed again.

[0038] S5: After updating the mooring parameters, determine whether the maximum mooring tension meets the specifications. If it does, recalculate using the 3*2 mooring scheme. If the 3*2 mooring scheme meets the design specifications, then use the 3*2 method for mooring; otherwise, use the 3*3 method. The 3*3 method uses three sets of mooring systems 400, with three mooring lines in each set. The 3*2 method uses three sets of mooring systems 400, with two mooring lines in each set.

[0039] S6: Using the mooring method determined in step S5, perform a time-domain analysis of the mooring under the working condition corresponding to the maximum platform motion response. If the platform offset meets the design requirements, extract the shortest bottom length during the time-domain analysis. If the shortest bottom length is significantly sufficient, further shorten the mooring length to a certain range; otherwise, use the mooring design length from the initial design.

[0040] S7: Using the mooring method determined in step S6, determine whether the platform's pitch amplitude and equilibrium position meet the relevant design specifications. Extract the platform's motion response and mooring tension in the numerical analysis software, output the platform's pitch response, and determine whether it varies within the range of -5° to 5°. If it meets the requirements, it is adopted as the final mooring method; otherwise, proceed to the optimization design step in S8.

[0041] S8: As Figure 7 As shown, a new set of mooring systems 400 with a counterweight chain 403 is defined, and the mooring line of the mooring system 400 with the greatest tension is ( Figure 5 In the mooring system (corresponding to mooring lines #1 and #2), anchor chain Ⅲ405 is replaced with counterweight chain 403 (generally corresponding to mooring lines facing the wind). The weight per unit length of counterweight chain 403, counterweight chain length L2, and distance L1 from the counterweight chain to lifting lug 6 are used as sensitivity parameters for a time-domain mooring analysis. This implementation uses a 3600-second time-domain mooring analysis to determine the maximum pitch angle of the platform during this period and to find the combination of sensitivity parameters for counterweight chain 403 that meets the specifications. In this implementation, when L1=L2=40m, the platform's pitch angle meets the design requirements.

[0042] S9: Calculate the mooring cost for different combinations of sensitivity parameters for counterweight chain 403. Select the counterweight chain 403 with the lowest cost and perform a 3-hour mooring time-domain analysis. Determine whether the maximum pitch angle of the dual-fan 104 platform meets the requirements during this time. If not, select the counterweight chain 403 scheme with the higher mooring cost from step S8 for analysis. At this point, the mooring length is the combined length of anchor chain I 402, counterweight chain 403, and anchor chain II 404.

[0043] Table 1:

[0044] Refer to Table 1 for the mooring sensitivity parameter analysis of the counterweight chain. In the table, L1 is the distance from the counterweight chain to lug 6, which is the length of anchor chain I 402. L2 is the length of counterweight chain 403. L3 is the length of anchor chain II 404. Step 1 in the table indicates that the value of variable L1 is initially kept constant, and sensitivity analysis is performed using the counterweight chain length L2 as the variable to find the minimum pitch angle corresponding to L2=40m. Step 2, based on step 1, fixes L2=40m, modifies the length L1 of anchor chain I 402, performs sensitivity analysis, finds the set with the smallest difference between the maximum and minimum pitch angles, and determines L1=40m that meets the specification requirements. The length L3 is then obtained based on the total length requirement of the mooring cable corresponding to the mooring radius R. This process continues until the platform's motion response meets the specification design requirements. The mooring scheme was adopted as the final mooring method, and mooring analysis was conducted under both power generation and shutdown conditions for 3 hours. The mooring safety factor was 1.82 under power generation conditions and 1.68 under shutdown conditions, both exceeding the design specification requirement of 1.67. Under the cable breakage condition, the mooring safety factor was 1.21, exceeding the design specification requirement of 1.05. The maximum platform offset in this application is 19m, less than 30% of the design water depth. The maximum pitch angle was 4.8° under power generation conditions and 7.6° under shutdown conditions, effectively reducing the impact of the floating platform's motion response on the power generation efficiency of wind turbine 104. The table above only represents the design optimization approach; for actual engineering projects, the range of sensitivity parameters can be defined, and an appropriate genetic algorithm can be selected for iterative optimization.

[0045] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A design and optimization method for a single-point mooring system on a floating dual-fan foundation structure, characterized in that, Includes the following steps: S1: Based on the environmental conditions of the wind turbine operating area, the orientation of the fixed buoys is determined, and the initial design adopts a 3*3 single-point mooring method. S2: Apply wind turbine aerodynamic load, tower wind pressure, wave load, and water flow load. Through dynamic time domain analysis, predict the mooring tension and platform motion response under power generation and shutdown conditions, and find the control conditions of mooring tension and platform motion response and the corresponding wind, wave and flow directions. S3: Rotate the hull-shaped pontoon to the optimal wave angle according to the control strategy. After rotating the hull-shaped pontoon, update the center of gravity, moment of inertia, and ballast water weight information of the floating twin wind turbine foundation, and re-perform frequency domain hydrodynamic analysis. S4: Based on the rotating hull-shaped buoy in S3, perform a time-domain analysis of mooring under the working condition corresponding to the maximum mooring tension, and modify the parameters of the mooring cable according to the maximum mooring tension, including the mooring cable diameter, weight, stiffness, and breaking force. S5: After updating the mooring parameters, determine whether the maximum mooring tension meets the specification requirements. If it does, recalculate using the 3*2 mooring scheme. If the 3*2 mooring scheme meets the specification design requirements, then use the 3*2 mooring scheme; otherwise, use the 3*3 mooring scheme. S6: Using the mooring method determined in step S5, perform a time-domain analysis of the mooring under the working condition corresponding to the maximum platform motion response. If the platform offset meets the design requirements, extract the shortest bottom length during the time-domain analysis. If the shortest bottom length is significantly sufficient, further shorten the mooring length to a certain range; otherwise, use the mooring length from the initial design. S7: Using the mooring method determined in step S6, determine whether the platform's pitch motion amplitude and equilibrium position meet the standard design requirements. If they do, it is taken as the final mooring method; otherwise, proceed with the optimization design step in S8. S8: Redefine a set of mooring systems with counterweight chains, add counterweight chains to the mooring line of the mooring system with the highest tension, and use the three variables of counterweight chain weight per unit length, counterweight chain length, and distance from counterweight chain to lifting lug as sensitivity parameters to perform time-domain mooring analysis for a certain period of time, determine the maximum pitch angle of the platform during this period, and find the combination of counterweight chain sensitivity parameters that meet the specifications. S9: Calculate the mooring cost for different combinations of counterweight chain sensitivity parameters, select the counterweight chain with the lowest cost for mooring time-domain analysis, and determine whether the maximum pitch angle of the dual-wind turbine platform meets the requirements during this time. If it does not meet the requirements, select the counterweight chain scheme with the higher mooring cost in step S8 for analysis until the motion response of the platform meets the design requirements. This mooring scheme is the final mooring method.

2. The design and optimization method for a single-point mooring system of a floating dual-wind turbine foundation structure according to claim 1, characterized in that: In step S1, the mooring radius is selected as 6-8 times the water depth, and the included angle between each mooring line is selected as 3-5°. The anchoring point coordinates are determined by determining the mooring radius and the angle between the mooring lines. The mooring line length is determined by the magnitude of the mooring line pretension.

3. The design and optimization method for a single-point mooring system of a floating dual-wind turbine foundation structure according to claim 1, characterized in that: In step S5, the 3*3 method uses three sets of mooring systems, with three mooring lines in each set; the 3*2 method uses three sets of mooring systems, with two mooring lines in each set.

4. The design and optimization method for a single-point mooring system of a floating dual-wind turbine foundation structure according to claim 1, characterized in that: The floating twin-wind turbine foundation structure mainly consists of two symmetrical ship-shaped pontoons and columns, wind turbines and towers, a bow column, a triangular truss, a single-point mooring device, and a mooring system. The two ship-shaped pontoons and one bow column are connected by the triangular truss. The two columns are respectively mounted on their respective ship-shaped pontoons by rotating parts. The single-point mooring device is rigidly connected to the bow column, and a lifting lug structure is set on the outside of the single-point mooring device. The mooring system is installed on the lifting lug.

5. The design and optimization method for a single-point mooring system of a floating dual-fan foundation structure according to claim 4, characterized in that: The hull-shaped pontoon is an ellipse.

6. The design and optimization method for a single-point mooring system of a floating dual-wind turbine foundation structure according to claim 5, characterized in that: The top of the ship-shaped pontoon is flat.

7. The design and optimization method for a single-point mooring system of a floating dual-wind turbine foundation structure according to claim 6, characterized in that: The hull-shaped pontoon has an empty compartment in the middle, and a rotating component is installed in the empty compartment.

8. The design and optimization method for a single-point mooring system of a floating dual-wind turbine foundation structure according to claim 4, characterized in that: The head post and the single-point mooring device are rigidly connected by a truss structure.

9. The design and optimization method for a single-point mooring system of a floating dual-wind turbine foundation structure according to claim 4, characterized in that: The mooring system mainly consists of an anchor, anchor chain I, and anchor chain II; the anchor is a suction anchor, a high holding capacity anchor, a towed anchor, or an anchor pile.

10. The design and optimization method for a single-point mooring system of a floating dual-wind turbine foundation structure according to claim 9, characterized in that: A counterweight chain is installed between anchor chain I and anchor chain II.

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