Floating type wind power anchoring system considering seabed terrain influence and optimization method thereof

Abstract

The invention discloses an optimization method of a floating type wind power anchoring system considering seabed terrain influence, and relates to a floating type wind power generation technology. Seabed data is acquired, and matrix mapping about point coordinates is generated according to the seabed data so as to acquire coordinate values of each point in the seabed terrain; according to a segmented extrapolation method, the length of a suspension section of the anchor chain is iteratively solved with the water depth as a constraint condition, and the reference length of a lying section and the coordinates of a grounding point of the lying section are obtained according to the difference value between the total length of the anchor chain and the length of the suspension section; and taking the reference length of the lying section as a constraint condition, and obtaining the form of the anchor chain after the terrain is considered according to the length of the suspension section, the coordinates of the ground contact point and the coordinate values. The invention further discloses a floating type wind power anchoring system considering the seabed terrain influence. According to the method, the problem that the terrain influence is not considered in the existing intelligent optimization technology of the mooring system is solved, the reliability and the accuracy of an optimization design result are improved, and the method better serves actual engineering.

Description

Technical Field

[0001] The present invention relates to floating wind power generation technology, and more specifically, to a floating wind power mooring system considering the influence of seabed topography and its optimization method. Background Art

[0002] In recent years, the proportion of renewable energy power generation has been increasing globally, and the development cost has been continuously decreasing. In 2021, 38% of the global electricity came from clean energy, exceeding the proportion of coal power generation (36%). Wind energy and solar energy provided more than 10% of the global electricity for the first time, with wind energy accounting for 6.59%. For most countries, developing clean energy, reducing dependence on fossil fuels, and restructuring the energy supply system are not only to address the increasingly severe environmental and climate problems but also to prevent restrictive unilateral policies that may be promulgated by energy-exporting countries.

[0003] Offshore wind power is basically not affected by topography and does not occupy land resources, having less impact on human production and life. Moreover, the wind speed is higher offshore, and the annual utilization hours are higher. However, as the water depth in the development and utilization area of offshore wind energy resources gradually increases, the total length of traditional offshore fixed wind turbines increases sharply, highlighting the advantages of floating wind turbines. Floating wind turbines can not only develop wind resources in farther and deeper areas, expand the utilization range of offshore wind resources, and break through the limitations of water depth on the construction and installation of wind power systems but also effectively reduce the impact on nearshore fishing areas and tourist areas. Therefore, the development of floating wind turbines is an inevitable trend in the development of offshore wind energy resources.

[0004] Different from other offshore floating structures such as deep-sea oil platforms, there is a strong coupling relationship between the aerodynamic characteristics of the rotor and the hydrodynamic characteristics of the floating platform in a floating wind power system. Therefore, there are also significant differences in the analysis and design requirements of floating wind power system equipment. The mooring system has an important impact on the operation safety, economic cost, and power generation efficiency of floating wind turbines. In recent years, in order to improve power generation efficiency and economic performance, the development of offshore floating wind turbines has shown a trend of larger rotor diameters and higher towers. The upper rotor diameter of the wind turbine is up to the hundred-meter level, and the whole machine system is subjected to great environmental loads, which leads to greater difficulties in the optimal design of the floating wind turbine mooring system. In addition, some sea areas are affected by typhoons all year round, and the marine environment is harsh, posing higher requirements for the design of the floating wind turbine mooring system serving this area.

[0005] The mooring system has an important impact on the operation safety, power generation efficiency and economic cost of floating wind turbines. Scholars at home and abroad have carried out a series of in-depth studies on the optimal design and performance analysis of mooring systems. The factors affecting the design of mooring systems usually include environmental conditions, economic cost, fatigue life and operation requirements. Xu Kun et al. [1] studied the influence of different environmental loads on semi-submersible wind turbines and their mooring systems in the water depth range of 50 - 200m. The results show that the contribution of the second-order difference frequency force increases significantly with the decrease of water depth, and using the Newman approximation method will lead to a smaller result of the second-order motion response. Therefore, the full QTF method, which can calculate the second-order force more accurately, is recommended in shallow water. In addition, the economic cost of the catenary mooring line system also has a great relationship with water depth. The research by Huang et al. [2] shows that the chain weight increases exponentially with the decrease of water depth. When the water depth is 50m, the mooring line composed of anchor chains is the heaviest. Generally, the cost of shallow water mooring systems mainly comes from the heavier anchor chains, while the cost of deep water mooring systems comes from the length of the mooring line. In addition, the type and bearing capacity of the anchoring foundation have a great impact on the cost and performance of the mooring system.

[0006] In addition to environmental conditions, the mooring performance depends to a large extent on some key mooring line parameters. The pre-tension has a great influence on the dynamic tension response of the mooring line. Generally speaking, a smaller pre-tension will result in a smaller mooring restoring force stiffness and mooring tension, as well as a larger offset of the floating platform; at the same time, it will also increase the amplitude and standard deviation of the mooring tension, which has an adverse effect on fatigue damage. Ali et al. [3] studied the influence of the mooring line diameter on the operation response of a deep-water FPSO. The results showed that with the increase of the mooring line diameter, the surge response in the low-frequency range decreased significantly, which was due to the larger the mooring line diameter, the greater the mooring damping. Zhang et al. [4] proposed an explicit expression for mooring stiffness and studied the influence of mooring materials, pre-tension and different water depths in the range of 300m - 1200m on the nonlinear mooring stiffness. Montasir et al. [5][6] found that under a smaller wave frequency excitation, the influence of different mooring line angle arrangements on the platform motion response in the mooring system was obvious; when the mooring line broke, the mooring system with a symmetric mooring line angle arrangement had better restoring performance. Campanile et al. [7] studied the number of mooring lines, and the results showed that for a floating platform operating in the water depth range of 50 - 350m, it was more appropriate to arrange 6 mooring lines in the mooring system. Amaechi et al. [8] conducted a comparative analysis of multi-component mooring systems, and the results showed that the mooring line composed of chain - composite fiber cable - chain was beneficial to the wave frequency motion response of the floating platform. Wang [9] and Bach-Gansmo

[10] et al. compared and analyzed the advantages and disadvantages of the catenary mooring system and the taut mooring system from aspects such as mooring static and dynamic characteristics and mooring loads. The results showed that compared with the catenary mooring system, the taut mooring system had better hydrodynamic performance and a smaller mooring tension amplitude, but it was not conducive to the pitch motion response of the floating platform. In addition, the taut mooring system required more complex technologies and higher economic costs for the design, installation and maintenance of the anchoring foundation. Therefore, the catenary mooring system is still the main choice for the mooring system of floating wind turbines.

[0007] To sum up, the optimal design of the catenary mooring system involves multiple key design parameters, such as pre-tension, mooring line length, diameter, stiffness, number and arrangement method, etc. The existing design of the mooring system for floating wind power equipment mainly relies on experience, and usually optimizes the mooring system design in a Trial-and-Error manner, which requires a large amount of computing resources and time costs in the design stage.

[0008] To improve the design and optimization efficiency of the mooring system, some researchers have used intelligent optimization algorithms to study the design and optimization methods of the mooring system. Shafieefar and Rezvani

[11] proposed a design method for the mooring system based on the genetic algorithm. This method normalizes the objective function based on the weighted sum method and establishes a single-objective optimization problem for the mooring system with the minimization of surge and sway responses as the objective.

[0009] Felix-Gonzalez and Mercier

[12] proposed a mooring design method based on static equivalence and the genetic algorithm, and took the minimization of the six-degree-of-freedom motion influence as the optimization objective. The research shows that the selection of the weight coefficient has an important influence on the design results of the mooring system. Brommundt et al.

[13] established a mooring optimization problem based on 4 design variables and 3 constraint conditions and solved it using the Nelder–Mead simplex algorithm. However, the minimum value of the mooring line length is the only objective of this optimal design.

[0010] At present, there is little research on the intelligent optimal design of the mooring system, and most of them take reducing the motion amplitude or improving the economic performance as a single objective. In addition, under transitional water depth conditions, the difference in the height of the mooring point is not a small quantity compared with the overall water depth, and at this time, the catenary mooring line has the characteristics of a small catenary section and a large dragged section, and the mooring damping caused by seabed friction accounts for a relatively large proportion. The research shows that the asymmetric mooring stiffness caused by the seabed inclination has a very obvious influence on the response of the floating structure, and as the stiffness difference between the two sides of the mooring system gradually increases, the surge and sway motions of the platform become more intense. However, there is no optimization method for the mooring system considering the influence of the seabed topography.

[0011] References:

[0012] [1]Xu, K., Gao, Z., & Moan, T. (2018). Effect of hydrodynamic load modelling on the response of floating wind turbines and its mooring system in small water depths. In Journal of Physics: Conference Series (Vol. 1104, No. 1, p. 012006). IOP Publishing.

[0013] [2] Huang, W. H., & Yang, R. Y. (2021). Water depth variation influence on the mooring line design for FOWT within shallow water region. Journal of Marine Science and Engineering, 9(4), 409.

[0014] [3] Ali, M. O. A., Ja'e, I. A., & Hwa, M. G. Z. (2020). Effects of water depth, mooring line diameter and hydrodynamic coefficients on the behaviour of deepwater FPSOs. Ain Shams Engineering Journal, 11(3), 727 - 739.

[0015] [4] Zhang, J., Ren, H., & Zhang, L. (2012). A nonlinear restoring effect study of mooring system and its application. Journal of Marine Science and Application, 11(1), 74 - 82.

[0016] [5] Montasir, O. A., Yenduri, A., & Kurian, V. J. (2015). Effect of mooring line configurations on the dynamic responses of truss spar platforms. Ocean Engineering, 96, 161 - 172.

[0017] [6] Montasir, O. A., Yenduri, A., & Kurian, V. J. (2016). Evaluation of the dynamic responses of truss spar platforms for various mooring configurations with damaged lines. Ocean Engineering, 123, 411 - 421.

[0018] [7]Campanile,A.,Piscopo,V.,&Scamardella,A.(2018).Mooringdesign andselection for floating offshore wind turbines on intermediateand deep waterdepths.Ocean Engineering,148,349-360.

[0019] [8]Amaechi,C.V.,Odij ie,A.C.,Wang,F.,&Ye,J.(2022).Numericalinvestigation on mooring line configurations of a Paired ColumnSemisubmersible for its global performance in deep water condition.OceanEngineering,250,110572.

[0020] [9]Wang,T.Y.,Yang,L.J.,Xu,Z.G.,&Liu,J.K.(2013).Design and comparisonof catenary and taut mooring systems for new concept FPSO IQFP in shallowwaters.In Applied Mechanics and Materials(Vol.353,pp.2670-2675).Trans TechPublications Ltd.

[0021]

[10] Bach-Gansmo,M.T.,Garvik,S.K.,Thomsen,J.B.,&Andersen,M.T.(2020).Parametric study of a taut compliant mooring system for a FOWT compared to acatenary mooring.Journal of Marine Science and Engineering,8(6),431.

[0022]

[11] Shafieefar M, Rezvani A. Mooring optimization of floating platforms using a genetic algorithm[J]. Ocean Engineering, 2007, 34(10): 1413-1421.

[0023]

[12] Felix-Gonzalez I, Mercier R S. Optimized design of statically equivalent mooring systems[J]. Ocean Engineering, 2016, 111: 384-397.

[0024]

[13] Brommundt M, Krause L, Merz K, et al. Mooring system optimization for floating wind turbines using frequency domain analysis[J]. Energy Procedia, 2012, 24: 289-296. Summary of the Invention

[0025] The technical problem to be solved by the present invention is to provide a floating wind power mooring system and its optimization method considering the influence of seabed topography in view of the deficiencies of the prior art, solve the problem that the influence of topography is not considered in the existing intelligent optimization technology of mooring systems, and improve the reliability and accuracy of the optimization design results.

[0026] The optimization method of the floating wind power mooring system considering the influence of seabed topography according to the present invention obtains seabed data, generates a matrix mapping about point coordinates according to the seabed data to obtain the coordinate values of each point in the seabed topography; according to the piecewise extrapolation method, using the water depth as a constraint condition, iteratively solve the suspended section length of the anchor chain, and obtain the reference length of the lying section and its touchdown point coordinates according to the difference between the total length of the anchor chain and the suspended section length; using the reference length of the lying section as a constraint condition, obtain the anchor chain shape considering the topography according to the suspended section length, touchdown point coordinates and coordinate values.

[0027] Preferably, the iterative solution method for the suspended section length is as follows:

[0028] First step, set N nodes on the anchor chain, and the N nodes divide the anchor chain into N-1 units; let the angle between the first unit of the mooring line of the anchor chain and the horizontal direction be the top tension angle θ extracted from historical data;

[0029] Step 2: Simplify the gravity, buoyancy, and drag force on each unit to the center position of each unit;

[0030] Step 3: Take the end node of the (n - 1)-th unit as the starting point of the n-th mooring cable unit; where N is from 1 to n;

[0031] Step 4: Solve the force condition of each unit according to static equilibrium to obtain the node tension and its node coordinates of the unit, and sequentially judge the magnitude relationship between the node tension and the horizontal tension of each unit; if the node tension of the unit is equal to the horizontal tension, then take the current unit as the touchdown point, and then take the node coordinates corresponding to the touchdown point as the reference origin, and calculate the suspended section length according to the node coordinates of other units;

[0032] Step 5: Extract the vertical coordinate from the node coordinates corresponding to the touchdown point as the depth calculated under the top tension angle θ, compare and verify the depth with the set water depth. If the depth is equal to the water depth, the water depth boundary condition is satisfied, and take the top tension angle θ as the top tension angle of the anchor chain; otherwise, iteratively change the top tension angle θ in the historical parameters by the golden section method, and then return to Step 1.

[0033] Preferably, when solving the suspended section length of the anchor chain, the influence of the seabed topography is not considered.

[0034] Preferably, the specific method for obtaining the anchor chain shape considering the topography is as follows:

[0035] Step 1: Divide the lying section of the anchor chain into M micro-sections, where M is any natural number from 1 to m;

[0036] Step 2: Take a coordinate value (x0, y0, h(x0, y0)), assume the touchdown point coordinates of the lying section are (x0, y0, z(x0, y0)), and the angle between the arrangement direction of the anchor chain and the horizontal direction is α. Then the end coordinates of each micro-section are (x(m - 1) + cosα, y(m - 1) + sinα, z(x(m - 1) + cosα, y(m - 1) + sinα) - z(x(m - 1), y(m - 1))); calculate the length of each micro-section according to the coordinates at both ends of each micro-section, and sum up the lengths of all the micro-sections to obtain the actual length of the lying section;

[0037] Step 3. Determine whether the actual length of the lying section meets the constraint requirements of the reference length of the lying section. If the actual length of the lying section is equal to the reference length of the lying section, it meets the constraint requirements, and the catenary shape after considering the terrain is that the touch point coordinates are (x0, y0, z(x0, y0)), the length of the lying section of the catenary is the actual length of the lying section, and the length of the suspended section of the catenary is the suspended section length; otherwise, reselect the coordinates of the touch point in Step 2 and perform calculations until the constraint conditions are met.

[0038] Preferably, the projection length of each micro-segment on the coordinate plane xOy is 1.

[0039] Preferably, the seabed terrain is scanned by technologies such as sonar or remote sensing to obtain the seabed data.

[0040] Preferably, the specific method for generating the matrix mapping of point coordinates is as follows:

[0041] Organize the seabed data into discrete scattered points and write them into a txt file in a set format;

[0042] Read in the txt file, and use the griddata function in matlab to generate the matrix mapping of point coordinates. In the matrix mapping of point coordinates, the x and y in the coordinate values of each point correspond to the depth z of this point.

[0043] A floating wind power mooring system considering the influence of seabed terrain includes a catenary arranged under a floating wind power platform, and the catenary is connected to a heavy block located on the seabed; the catenary is optimized and designed by using the optimization method of the floating wind power mooring system considering the influence of seabed terrain described above.

[0044] Beneficial effects

[0045] The advantages of the present invention are as follows:

[0046] 1. Based on the analysis of seabed data and combined with the constraints of water depth and lying section, the present invention solves the problem that the existing intelligent optimization technology of mooring systems does not consider the influence of terrain, and the above method can input actual terrain data in the optimization design analysis process, improving the reliability and accuracy of the optimization design results and better serving the actual project.

[0047] 2. The corresponding mooring system optimization method developed based on the static equilibrium and iterative solution of the mooring system avoids the traditional Trial-and-Error method for mooring system design, improves the optimization design efficiency of the mooring system and saves computing resources. Brief description of the drawings

[0048] Figure 1 It is a schematic diagram of the seabed terrain distribution of the present invention;

[0049] Figure 2 Schematic diagram of the flat file of the present invention;

[0050] Figure 3 Schematic diagram of the scatter arrangement of the present invention;

[0051] Figure 4 Schematic diagram of the division of the mooring line unit of the anchor chain of the present invention;

[0052] Figure 5 Schematic diagram of the shape of the lying section of the anchor chain considering the terrain of the present invention. Detailed implementation manners

[0053] The following combines examples to further describe the present invention, but does not constitute any limitation to the present invention. Any person's limited modifications within the scope of the claims of the present invention are still within the scope of the claims of the present invention.

[0054] Example 1

[0055] An optimization method for a floating wind power mooring system considering the influence of seabed terrain according to the present invention. The method mainly includes: obtaining seabed data, generating a matrix mapping about point coordinates according to the seabed data to obtain the coordinate values of each point in the seabed terrain; according to the piecewise extrapolation method, using the water depth as a constraint condition, iteratively solving the length of the suspended section of the anchor chain, and obtaining the reference length of the lying section and its touchdown point coordinates according to the difference between the total length of the anchor chain and the length of the suspended section; using the reference length of the lying section as a constraint condition, obtaining the shape of the anchor chain considering the terrain according to the length of the suspended section, the touchdown point coordinates and the coordinate values. The above method is mainly based on the analysis of seabed data and combines the constraints of water depth and lying section, solves the problem that the influence of terrain is not considered in the existing intelligent optimization technology of mooring systems, and the above method can input actual terrain data in the optimization design analysis process, improves the reliability and accuracy of the optimization design results, and better serves the actual project.

[0056] Specifically, when optimizing the mooring system considering the seabed terrain, if the terrain distribution is known, the terrain must be converted into a mathematical model and the terrain parameters must be introduced into the mooring optimization program. This operation requires importing the global coordinate system into the calculation program and modifying the corresponding calculation logic. The following gives the optimization calculation principle when the terrain distribution is known.

[0057] It is known that the seabed terrain distribution in a certain place is as Figure 1 shown. In order to be able to import the terrain into the calculation program, the terrain must be simplified into a mathematical model of a continuous function. According to the results of on-site surveys, the terrain is converted into scatter points and recorded in a matrix according to the accuracy requirements. The specific method is as follows:

[0058] Step 1: Use technologies such as sonar or remote sensing to scan the seabed topography and obtain seabed data;

[0059] Step 2: Organize the seabed data into discrete scatter points and write them into a txt file in a certain format. As Figure 2 shown is a schematic diagram of a simple plane file.

[0060] In the figure, the first three lines are definition content: the first line is the seabed name; the data in the second line respectively represent the number of scatter points in each row, the number of scatter points in each column, the lower bound of the x-axis coordinate, the upper bound of the x-axis coordinate, the lower bound of the y-axis coordinate, the lower bound of the y-axis coordinate, the length of the terrain boundary along the x-axis, and the length of the terrain boundary along the y-axis. The unit of the upper and lower bounds and the length is meter; the third line is the origin coordinate. Starting from the fourth line, it represents the z-axis coordinate of each scatter point, and the unit is meter. The scatter points are arranged row by row, as Figure 3 shown. Among them, if there is an "&" symbol after a number, it means no line break. If there is no "&" symbol, it will line break to the next line. For example, based on Figure 1 the seabed map of Figure 3 the coordinates of the first two points are (-1000m, 1000m, -100m) and (1000m, 1000m, -100m) respectively; the coordinates of the last two points are (-1000m, -1000m, -100m) and (1000m, -1000m, -100m) respectively. These points are equally spaced in each row and each column, and parameters such as the number of scatter points and the seabed size can be set according to the accuracy requirements.

[0061] Step 3: Read the txt file and use the griddata function in matlab to generate a matrix mapping of the point coordinates. And in the matrix mapping of the point coordinates, the x and y in the coordinate value of each point correspond to the depth z of this point.

[0062] In the optimization design considering the seabed topography, the catenary span of the mooring chain should be determined first under the condition of no topographic influence (flat seabed). When there is no topographic influence, based on the top tension angle θ, according to the piecewise extrapolation method, with the water depth as the constraint condition, the catenary span of the mooring chain is iteratively solved. The specific implementation method is as follows.

[0063] As Figure 4 shown, discretize the mooring line of the mooring chain. Divide the top AB, middle BC, and bottom OC of the mooring line into n1, n2, and n3 units respectively, where AB, BC, and OC can use mooring cables with the same or different materials.

[0064] Step 1: Assume that the angle between the top unit of a mooring line and the horizontal direction (i.e., the top tension angle) is the top tension angle θ. Among them, the top tension angle θ is extracted from the historical data of the mooring system. Specifically, the optimal solution can be obtained through the genetic iteration algorithm.

[0065] Step 2: Simplify the gravity, buoyancy, and drag force on each unit to the center position of each unit.

[0066] Step 3: Take the end point of the previous mooring line unit as the starting point of the next mooring line unit.

[0067] Step 4: Solve the force condition of each unit according to static equilibrium to obtain the node tension and its node coordinates of the unit, and judge the magnitude relationship between the node tension and the horizontal tension of each unit in turn; if the node tension of the unit is equal to the horizontal tension, then take the current unit as the touchdown point, and then use the node coordinates corresponding to the touchdown point as the reference origin, and calculate the suspension section length according to the node coordinates of other units. Among them, the above static equilibrium solution uses the existing technology in the mooring system, and the present invention does not improve it.

[0068] Step 5: Extract the vertical coordinate from the node coordinates corresponding to the touchdown point as the depth calculated under the top tension angle θ, compare and verify the depth with the set water depth. If the depth is equal to the water depth, the water depth boundary condition is satisfied, and the top tension angle θ is used as the top tension angle of the anchor chain; otherwise, the top tension angle θ in the historical parameters is iteratively changed by the golden section method, and then return to Step 1.

[0069] The part of the anchor chain after the touchdown point is a straight line segment lying flat on the seabed, that is, the lying section, and the rest is the suspension section. When considering the terrain, the constraint condition of the water depth changes from a constant to a spatial function, that is, h = z(x, y). Therefore, in the iteration, this part of the logic must be replaced, and h is replaced by z(x, y), where z(x, y) is the function of the seabed.

[0070] When considering the terrain, in addition to considering the change of the water depth constraint condition, the shape of the lying section must also be considered. Due to the uneven seabed, the shape of the lying section is no longer a horizontal straight line segment. Figure 5 Shows the shape of the lying section on the seabed. To emphasize the research focus, only the shape of the lying section is drawn in this figure, and the suspension section is not shown.

[0071] In the suspension section length obtained in the previous calculation, subtract the suspension section length from the total length of the anchor chain to obtain the reference length of the lying section. Take this length as the constraint condition, and analyze the shape of the anchor chain considering the terrain according to the layout direction of the anchor chain and the horizontal direction. The specific numerical integration process is as follows:

[0072] Divide the lying section into n micro-segments, and the projected length of each micro-segment on the xOy plane is 1;

[0073] Take a coordinate value (x0, y0, h(x0, y0)). Assume that the coordinates of the touchdown point are (x0, y0, h(x0, y0)), and the angle between the layout direction of the anchor chain and the horizontal direction is α. Then the coordinates of the end of the first micro-segment are (x0 + cosα, y0 + sinα, h(x0 + cosα, y0 + sinα) - h(x0, y0)). And so on, the coordinates of the end of the lying section can be obtained. After each calculation, sum the lengths of all micro-segments to obtain the actual length of the lying section. Take the length of the lying section as a constraint condition. If the actual length of the lying section is equal to the reference length of the lying section, it meets the constraint requirements. The shape of the anchor chain considering the terrain is that with (x0, y0, z(x0, y0)) as the coordinates of the touchdown point, the length of the lying section of the anchor chain is the actual length of the lying section, and the length of the suspended section of the anchor chain is the length of the suspended section; otherwise, reselect the coordinates of the touchdown point in step two and perform the calculation until the constraint conditions are met.

[0074] The shape of the anchor chain finally obtained considering the terrain has a good consistency with the shape of the anchor chain obtained in practical applications, and the average error is within 2.5%, indicating that the influence of the terrain on the anchor chain can be well simulated.

[0075] Embodiment 2

[0076] A floating wind power mooring system considering the influence of seabed terrain in this embodiment includes an anchor chain arranged under the floating wind power platform, and the anchor chain is connected to a heavy block located on the seabed; the anchor chain is optimized and designed by applying the above-mentioned optimization method of the floating wind power mooring system considering the influence of seabed terrain, so as to obtain the shape of the anchor chain considering the terrain with (x0, y0, z(x0, y0)) as the coordinates of the touchdown point, the length of the lying section of the anchor chain being the actual length of the lying section, and the length of the suspended section of the anchor chain being the length of the suspended section, improving the reliability and accuracy of the optimization design results and better serving the actual project.

[0077] The above are only the preferred embodiments of the present invention. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several deformations and improvements can be made, which will not affect the implementation effect of the present invention and the practicality of the patent.

Claims

1. Optimization method for a floating wind power mooring system considering the influence of seabed topography, characterized in that, Obtain seabed data, generate a matrix mapping of point coordinates based on the seabed data to obtain the coordinate values of each point in the seabed topography; According to the piecewise extrapolation method, using water depth as a constraint condition, iteratively solve the length of the suspended section of the anchor chain, and obtain the reference length of the lying section and its touchdown point coordinates based on the difference between the total length of the anchor chain and the length of the suspended section; using the reference length of the lying section as a constraint condition, obtain the anchor chain shape considering the topography based on the length of the suspended section, touchdown point coordinates, and coordinate values.

2. The optimization method of the floating wind power mooring system considering the influence of seabed topography according to claim 1, characterized in that The iterative solution method for the length of the suspended section is as follows: First step, set N nodes on the anchor chain, and the N nodes divide the anchor chain into N - 1 units; let the angle between the first unit of the mooring line of the anchor chain and the horizontal direction be the top tension angle θ extracted from historical data; Second step, simplify the gravity, buoyancy, and drag force on each unit to the center position of each unit; Third step, take the end node of the (n - 1)-th unit as the starting point of the n-th mooring cable unit; where N is from 1 to n; Fourth step, solve the force condition of each unit according to static equilibrium to obtain the node tension and its node coordinates of the unit, and sequentially judge the magnitude relationship between the node tension and the horizontal tension of each unit; if the node tension of the unit is equal to the horizontal tension, then take the current unit as the touchdown point, and then use the node coordinates corresponding to the touchdown point as the reference origin, and calculate the length of the suspended section according to the node coordinates of other units; Fifth step, extract the vertical coordinate from the node coordinates corresponding to the touchdown point as the depth calculated under the top tension angle θ, compare and verify the depth with the set water depth. If the depth is equal to the water depth, the water depth boundary condition is satisfied, and use the top tension angle θ as the top tension angle of the anchor chain; otherwise, iteratively change the top tension angle θ in the historical parameters by the golden section method, and then return to the first step.

3. The optimization method of the floating wind power mooring system considering the influence of seabed topography according to claim 2, characterized in that When solving the length of the suspended section of the anchor chain, the influence of the seabed topography is not considered.

4. The optimization method of the floating wind power mooring system considering the influence of seabed topography according to claim 2, characterized in that The specific method for obtaining the anchor chain shape considering the topography is as follows: Step one, divide the lying section of the anchor chain into M micro-sections, where M is any natural number from 1 to m; Step two, take a coordinate value (x0, y0, h(x0, y0)), let the touchdown point coordinates of the lying section be (x0, y0, z(x0, y0)), and the angle between the layout direction of the anchor chain and the horizontal direction be α, then the end coordinates of each micro-section are (x(m - 1)+cosα, y(m - 1)+sinα, z(x(m - 1)+cosα, y(m - 1)+sinα)-z(x(m - 1), y(m - 1))); calculate the length of the micro-section according to the coordinates at both ends of each micro-section, and sum the lengths of all the micro-sections to obtain the actual length of the lying section; Step 3: Determine whether the actual length of the lying section meets the constraint requirements of the reference length of the lying section. If the actual length of the lying section is equal to the reference length of the lying section, the constraint requirements are met, and the catenary shape considering the terrain is such that the touchdown point coordinates are (x0, y0, z(x0, y0)), the length of the lying section of the catenary is the actual length of the lying section, and the length of the suspended section of the catenary is the suspended section length; otherwise, reselect the coordinates of the touchdown point in Step 2 and perform calculations until the constraint conditions are met.

5. The optimization method of the floating wind power mooring system considering the influence of seabed topography according to claim 4, characterized in that The projection length of each of the micro-sections on the coordinate plane xOy is 1.

6. The optimization method of the floating wind power mooring system considering the influence of seabed topography according to claim 1, characterized in that Scan the seabed terrain through technologies such as sonar or remote sensing to obtain the seabed data.

7. The optimization method of the floating wind power mooring system considering the influence of seabed topography according to claim 1, characterized in that, The specific way to generate the matrix mapping of point coordinates is as follows: Organize the seabed data into discrete scatter points and write them into a txt file in a set format; Read in the txt file and use the griddata function in matlab to generate the matrix mapping of point coordinates. In the matrix mapping of point coordinates, the x and y in the coordinate values of each point correspond to the depth z of that point.

8. A floating wind power mooring system considering the influence of seabed topography, characterized in that, It includes a catenary provided below the floating wind power platform, and the catenary is connected to a heavy block located on the seabed; the catenary is optimized and designed by applying the optimization method of the floating wind power mooring system considering the influence of seabed terrain as described in any one of claims 1-7.

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