Fatigue damage analysis method and system for floating body structure of floating fan

Abstract

The invention relates to the technical field of floating body structure fatigue analysis, and particularly discloses a floating type fan floating body structure fatigue damage analysis method and system, and the method comprises the steps: constructing a floating type fan model; only the wind action is considered, and wind load action responses at the structural section of the floating body structure under different wind conditions are obtained; in the fan shutdown state, only the wave action is considered, and wave load action responses at the structural section under different wave actions are obtained; obtaining the total load response at the structure section under the corresponding marine environment working condition; the total load response is converted into local nominal stress; calculating short-term fatigue damage corresponding to the marine environment working condition; and calculating the long-term fatigue damage. According to the method, the problems of large calculation amount and long calculation time caused by existing full-coupling time domain analysis are solved, the calculation precision is ensured while the fatigue analysis efficiency is improved, and long-term fatigue evaluation can be quickly and accurately carried out in engineering application.

Description

Technical Field

[0001] The present invention relates to the technical field of fatigue damage analysis, and in particular to a method and system for fatigue damage analysis of a floating structure of a floating wind turbine based on wind-wave decoupling. Background Art

[0002] Offshore floating wind turbines are subjected to complex environmental loads such as wind, waves, and currents for a long time, which causes their floating structures to face the risk of fatigue damage.

[0003] Existing fatigue analysis methods mainly use the fully coupled time domain analysis method. This analysis method has high calculation accuracy, but the calculation process is complex and the amount of calculation is large, which limits its application in large-scale engineering projects. It usually includes the following parts: (1) wind-wave coupling calculation, considering the combined effect of wind and wave loads on the floating structure; (2) using full time domain coupling simulation to calculate the dynamic response under all short-term environmental conditions, and combining the rain flow counting method and SN curve to calculate fatigue damage; (3) statistically analyzing the combined probability distribution of wind and waves to estimate long-term fatigue damage.

[0004] Due to the significant wind-wave coupling effect, fully coupled analysis requires a large amount of time-domain calculations, which usually takes weeks or even months to calculate, seriously affecting the efficiency of engineering design and optimization; and traditional fully coupled analysis methods are difficult to apply to different floating structures. Summary of the invention

[0005] In order to solve the above technical problems, one of the objectives of the present invention is to provide a method for fatigue damage analysis of the floating structure of a floating wind turbine. By decoupling wind and waves and calculating the wind load response and the wave load response respectively, the wind and wave stresses are obtained to estimate the short-term fatigue damage, thereby solving the problems of large amount of calculation and long calculation time brought about by the existing fully coupled time domain analysis, improving the efficiency of fatigue analysis while ensuring the calculation accuracy, and being able to quickly and accurately perform long-term fatigue assessment in engineering applications.

[0006] In order to achieve the above-mentioned purpose, the present invention adopts the following technical solutions: The present application relates to a method for analyzing fatigue damage of a floating wind turbine buoy structure, comprising: Constructing a model of a floating wind turbine, wherein a floating structure in the floating wind turbine is modeled as a plurality of rigid body structure segments, and a structure section is formed between adjacent structure segments; Considering only the wind force, the wind load response at the structural section of the floating structure under different wind conditions is obtained; When the wind turbine is in a shutdown state, only the wave action is considered to obtain the wave load action response at the cross section of the structure under different wave actions; Linearly superimpose the wind load response and the wave load response corresponding to a single marine environment condition to obtain a total load response at the structural cross section under the corresponding marine environment condition; converting the total load response into a local nominal stress; Performing rain flow counting on the local nominal stress and combining it with the SN curve, calculating the short-term fatigue damage corresponding to the marine environment condition; The short-term fatigue damage under all marine environmental conditions is integrated, and the long-term fatigue damage is estimated by combining the joint distribution probability of wind and wave parameters under the corresponding marine environmental conditions.

[0007] In some embodiments of the present application, the initial value of the linearly superimposed total load response is corrected, specifically, corrected to the initial value of the total load response obtained by using a traditional fully coupled time domain analysis method.

[0008] In some embodiments of the present application, the wind load response at the structural cross section of the floating structure under different wind conditions is obtained, specifically: Calculating the blade aerodynamic load based on blade element momentum theory, wherein the blade aerodynamic load includes wind excitation load, impeller additional mass load and aerodynamic damping load; Time domain simulation is performed for different wind conditions to obtain the wind load response at the structural section of the floating structure under different wind conditions.

[0009] In some embodiments of the present application, the wave load response at the cross section of the structure under different wave actions is obtained, specifically: The potential flow theory is used to calculate the wave forces on floating bodies; Calculate the viscous damping force of the floating body based on the Morison equation; Time domain simulation is carried out for wave actions with different significant wave heights, spectral peak periods and directions to obtain the wave load response at the structural section.

[0010] In some embodiments of the present application, the total load response is converted into a local nominal stress σ i , specifically: Based on the Euler-Bernoulli beam theory, the following formula is used for conversion: ; in, F x represents the axial force of the structural section, M y and M z Respectively represent the structural cross section around y Axis and z Bending moment of the shaft, Arepresents the cross-sectional area of ​​the structural cross section, W y and W z Respectively represent the structural cross section around y Axis and z Section modulus of the shaft.

[0011] In some embodiments of the present application, the following formula is used to calculate the short-term fatigue damage corresponding to the marine environment conditions: D : ; in, n Indicates the number of load cycles corresponding to the stress range △s, i Indicates i stress range, N is the number of fatigue damage cycles given by the SN curve.

[0012] In some embodiments of the present application, the following formula is used to calculate the long-term fatigue damage: D tot : ; in, p is the joint distribution probability of wind and wave parameters, θ i Indicates i wind and wave direction, j Representative j Marine environment conditions, U w , H s and T p represent the average wind speed, significant wave height and spectral peak period respectively.

[0013] The fatigue damage analysis method of the floating wind turbine buoy structure provided in some embodiments of the present application has the following advantages and beneficial effects: (1) Decoupling wind and waves, respectively calculating the wind load response at the structural section of the floating structure under different wind conditions and the wave load response at the structural section of the floating structure under different wave conditions, and then performing stress superposition in the post-processing stage. Compared with full wind and wave coupling, this greatly reduces the amount of calculation and significantly reduces the demand for high-performance computing resources; (2) The decoupled calculation method can effectively reduce the number of working conditions, so that the complete fatigue damage analysis of the floating structure can be completed within a few days. Compared with the traditional fully coupled analysis that takes several weeks or even longer, the decoupled calculation method greatly shortens the calculation time and greatly improves the efficiency of engineering design and optimization; (3) The present application performs fatigue damage analysis based on the structural cross-section of the floating structure, which is applicable to different floating structures (e.g., semi-submersible, tension leg, Spar) and different floating structure types (e.g., three-column semi-submersible, four-column semi-submersible), and can also be applied to a variety of marine environment conditions, making the fatigue damage analysis method based on wind-wave decoupling more widely used in engineering; (4) A fatigue damage analysis method for floating structures based on wind-wave decoupling is developed. The contribution of fatigue damage under different wind and wave conditions is estimated through the statistical integration method of marine environmental conditions, thereby improving the accuracy of long-term fatigue life assessment.

[0014] Some embodiments of the present application also relate to a floating wind turbine floating structure fatigue damage analysis system, including: A unit model building module, which is used to build a model of a floating wind turbine, wherein the floating structure of the floating wind turbine is modeled as a plurality of rigid body structure segments, and a structure section is formed between adjacent structure segments; A wind load acquisition module, which is used to obtain the wind load response at the structural cross section of the floating structure under different wind conditions; A wave load acquisition module, which is used to obtain the wave load response at the structural cross section under different wave actions when the wind turbine is in a shutdown state; A total load response acquisition module, which is used to linearly superimpose the wind load response and the wave load response corresponding to a single marine environment condition to obtain the total load response at the structural section under the corresponding marine environment condition; a response-to-stress conversion module, which is used to convert the total load response into a local nominal stress; A short-term fatigue damage calculation module, which is used to perform rain flow counting on the local nominal stress and calculate the short-term fatigue damage corresponding to the marine environment working condition in combination with the SN curve; The long-term fatigue damage calculation module is used to integrate the short-term fatigue damage under all marine environmental conditions and estimate the long-term fatigue damage by combining the joint distribution probability of wind and wave parameters under the corresponding marine environmental conditions.

[0015] After reading the specific embodiments of the present invention in conjunction with the accompanying drawings, other features and advantages of the present invention will become more clear. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0017] Figure 1It is a flow chart of an embodiment of a method for analyzing fatigue damage of a floating structure of a floating wind turbine proposed in the present application; Figure 2 The model simulation of the floating wind turbine involved in the embodiment of the floating wind turbine floating structure fatigue damage analysis method proposed in this application; Figure 3 The embodiment of the fatigue damage analysis method for the floating structure of a floating wind turbine proposed in this application shows the bending moment of the third structural section of the floating structure of the wind turbine under the rated wind speed condition. M y The time domain response of the wind turbine and the bending moment of the third structural section of the floating structure under rated wind speed conditions using the traditional fully coupled time domain analysis method M y Comparison of the time domain responses of Figure 4 The embodiment of the fatigue damage analysis method for the floating structure of a floating wind turbine proposed in this application shows the bending moment of the third structural section of the floating structure of the wind turbine under the cut-out wind speed condition. M y The time domain response of the wind turbine and the bending moment of the third structural section of the floating structure under the cut-out wind speed condition are analyzed by the traditional fully coupled time domain analysis method. M y Comparison of the time domain responses of Figure 5 A comparison diagram of short-term fatigue damage under different average wind speed conditions obtained at the third structural section of the floating structure using the fatigue damage analysis method for the floating wind turbine buoy structure proposed in the present application and the traditional fully coupled time domain analysis method is shown; Figure 6 A comparison diagram showing long-term fatigue damage at a first structural section evaluated at six different offshore locations using the fatigue damage analysis method of the present application and the traditional fully coupled time domain analysis method; Figure 7 A comparison diagram showing long-term fatigue damage at a second structural section evaluated at six different offshore locations using the fatigue damage analysis method of the present application and the traditional fully coupled time domain analysis method; Figure 8 A comparison diagram showing the long-term fatigue damage at the third structure section evaluated at six different offshore locations using the fatigue damage analysis method of the present application and the traditional fully coupled time domain analysis method. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0019] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. In the description of the present invention, it should be understood that the orientation or position relationship indicated by the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. is based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0020] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. In the description of the above embodiments, specific features, structures, materials or characteristics can be combined in any one or more embodiments or examples in a suitable manner.

[0021] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0022] In order to solve the problems of long calculation cycle, large amount of calculation and inapplicability to different floating structures caused by the traditional fully coupled time domain analysis method in evaluating the fatigue damage of floating structures, see Figure 1 , the present application relates to a method for analyzing fatigue damage of a floating wind turbine buoy structure.

[0023] Figure 1 A flow chart of a floating wind turbine floating structure fatigue damage analysis method is shown. The floating wind turbine floating structure fatigue damage analysis method is implemented based on a floating wind turbine floating structure fatigue damage analysis system. As follows, the floating wind turbine floating structure fatigue damage analysis method will be described in combination with the floating wind turbine floating structure fatigue damage analysis system.

[0024] refer to Figure 1 , the fatigue damage analysis method of floating wind turbine buoy structure is described in detail as follows.

[0025] S1: Build a model of a floating wind turbine.

[0026] Floating wind turbines mainly include wind rotors (including impellers and hubs), rotating shafts, nacelles, towers, floating structures and mooring chains.

[0027] This model construction can be implemented by using the unit model construction module (not shown) in the floating wind turbine floating structure fatigue damage analysis system.

[0028] In some embodiments of the present application, SIMA software is used to establish a model of, for example, a 10MW floating wind turbine, wherein the floating body modeling adopts a multi-segment floating body modeling method to decompose it into multiple rigid body structure segments, and adjacent structure segments are connected by high-rigidity beam units for calculating the load response of the internal structural section of the floating body structure.

[0029] The modeling process of the wind turbine also provides models of other parts of the floating wind turbine except the floating structure (including the upper unit part and the mooring system of the floating wind turbine). There is a coupling effect between the floating structure and the upper unit part and the mooring system. Taking the floating structure as the research object, the upper unit part and the mooring system will bring external loads to the floating structure, and the loads will be transferred through the contact position. Therefore, when focusing on the floating structure, the upper unit part and the mooring system provide complete boundary conditions to the floating structure to ensure the calculation accuracy of the structural section response under the marine environment (that is, the wind and wave environment).

[0030] The above-mentioned modeling process of the fan is prior art and will not be described in detail here.

[0031] The schematic diagram of the fan modeling is shown in Figure 2 As shown, three structural sections in the floating structure are exemplarily shown (the yellow part on the left shows the floating structure, and section 1 marked with data 1 thereon is recorded as the first structural section, section 2 marked with data 2 is recorded as the second structural section, and section 3 marked with data 3 is recorded as the third structural section). The structural sections are located between adjacent structural segments, and the internal load response of the floating structure is the stress acting on the structural sections.

[0032] S2: Obtain the wind load response at the structural section of the floating structure under different wind conditions.

[0033] The wind load can be acquired by using a wind load acquisition module (not shown) in the floating structure fatigue damage analysis system of a floating wind turbine.

[0034] In some embodiments of the present application, a wind-wave decoupling analysis method is used to obtain the internal load response of the floating structure, that is, the wind load response and the wave load response are calculated separately.

[0035] In some embodiments of the present application, see Figure 2In the middle left part, the wind turbine is set to normal operation, the wind turbine control effect is considered, and then the aerodynamic-structure-control system coupling effect is considered, and the wave effect is not considered.

[0036] The blade aerodynamic loads, including wind excitation loads, impeller additional mass loads and aerodynamic damping loads, are calculated based on the blade element momentum (BEM) theory.

[0037] Specifically, the aerodynamic load of the blade is calculated based on the load coefficient description in the airfoil library file and the blade element momentum theory method, and this part of the technology is the existing technology.

[0038] Furthermore, time domain simulations are performed for different wind conditions to obtain the wind load responses at the structural cross-sections of the floating structure under different wind conditions. That is, using dynamic inflow, the BEM method will give the correct time series of rotor and blade loads (that is, the time series of the response of the internal structural cross-section of the floating structure) under the conditions of changing blade pitch angles, wind speed and direction, and tower movement.

[0039] The different wind conditions mentioned above include rated wind speed conditions, cut-in wind speed conditions, cut-out wind speed conditions and shutdown wind speed conditions.

[0040] As described above, for a given structural cross section, when only the wind action is considered, the wind load action response under different wind conditions can be obtained.

[0041] S3: Obtaining the wave load response at the structural cross section under different wave actions.

[0042] The acquisition of the wave load may be achieved by using a wave load acquisition module (not shown) in the floating wind turbine buoy structure fatigue damage analysis system.

[0043] In some embodiments of the present application, see Figure 2 In the middle right part, when calculating the response to wave load, the wind turbine is set to the shutdown state, and the aerodynamic load of the wind turbine and the control system effect are not considered, only the wave effect is considered.

[0044] The potential flow theory is used to calculate the hydrodynamic coefficients of each structural section, including the added mass, potential flow damping and wave excitation force transfer function, and then the floating wave force of the floating structure is calculated.

[0045] The viscous damping force of each structural segment is calculated based on the viscous damping force term in the Morison equation.

[0046] Furthermore, time domain simulation is performed for wave actions with different significant wave heights, spectral peak periods and directions (i.e. different wave actions) to obtain the wave load response at the structural section.

[0047] The process of obtaining the response under wave loads as described above is also prior art and will not be elaborated here.

[0048] As described above, for a given structural section, in the wind turbine shutdown state, only considering the wave action, the responses under wave loads under different wave actions can be obtained.

[0049] S4: Obtain the total load response at the structural section under the corresponding marine environmental conditions.

[0050] The process of obtaining this total load response can be implemented by using the total load response acquisition module (not shown) in the fatigue damage analysis system of the floating wind turbine floating body structure.

[0051] The marine environmental conditions as described above are the wind-wave environmental conditions. For example, a single marine environmental condition is waves with a significant wave height of 5 m, a spectral peak period of 9 s, and a wind speed of 11 m / s.

[0052] For a given structural section, linearly superimpose the wind load action response and the wave load action response corresponding to a single marine environmental condition to obtain the total load response.

[0053] As described above, through the wind-wave decoupling analysis method, the wind load action responses under different wind conditions of a given structural section have been obtained in S2, and the wave load action responses under different wave actions of a given structural section have been obtained in S3. Therefore, when the given structural section is under an actual single marine environmental condition, linearly superimpose the corresponding wind load action response and wave load action response.

[0054] For example, for the third structural section, the calculation of the total load response under the actual single marine environmental condition of waves with a significant wave height of 5 m, a spectral peak period of 9 s, and a wind speed of 11 m / s is the sum of the linear superposition of the wind load action response corresponding to a wind speed of 11 m / s in S2 and the wave load action response corresponding to waves with a significant wave height of 5 m and a spectral peak period of 9 s in S3.

[0055] Therefore, the total load response of any structural section under the actual marine environmental conditions can be calculated according to the requirements, and then the fatigue damage of any structural section can be calculated, improving the universality of this analysis method in engineering applications. Therefore, it is applicable to different floating body structures (such as semi-submersible, tension leg type, Spar type) and different floating body structure types (such as three-column semi-submersible type, four-column semi-submersible type), and can also be applicable to a variety of marine environmental conditions.

[0056] In some embodiments of the present application, in order to avoid duplication of the initial static response of the structural section under the action of wind load and wave load, the initial value of the total load response after linear superposition is corrected to eliminate the repeated calculation effect, thereby accurately reflecting the dynamic response under the combined action of wind and waves.

[0057] In some embodiments of the present application, the initial value of the total load response after the modified linear superposition (for example, denoted as C) is equal to the initial value after the linear superposition (for example, denoted as A) minus the difference between the initial value and the initial value of the total load response obtained by using the traditional fully coupled time domain analysis method (for example, denoted as B), that is, C=A-(AB), that is, the initial value C of the total load response after the modified linear superposition is the initial value B of the total load response obtained by using the traditional fully coupled time domain analysis method.

[0058] S5: Convert the total load response to local nominal stress.

[0059] The process of obtaining the local nominal stress can be implemented by using a response-stress conversion module (not shown) in the floating wind turbine floating structure fatigue damage analysis system.

[0060] In some embodiments of the present application, in order to perform fatigue damage assessment on the internal load of the floating structure, based on the Euler-Bernoulli beam theory, the following formula (1) is used to convert the total load response into the local nominal stress.

[0061] (1) in, σ i represents the local nominal stress, F x represents the axial force in a structural section (e.g. the third structural section), M y and M z Respectively represent the structural section (such as the third structural section) around y Axis and z Bending moment of the shaft, A represents the cross-sectional area of ​​a structural section (e.g., the third structural section), W y and W z Respectively represent the structural section (such as the third structural section) around y Axis and z Section modulus of the shaft.

[0062] in, W y = I y / R, W z =I z / R, I y and I z Respectively represent the structural section (such as the third structural section) around y Axis and z The area moment of inertia is about the axis, and R is about the radius.

[0063] in, xyz The coordinate system is based on x The direction is axial force, y and z The directions conform to the coordinate system established by the right-hand rule.

[0064] S6: Calculate short-term fatigue damage corresponding to marine environmental conditions.

[0065] The process of obtaining the short-term fatigue damage may be implemented by using a short-term fatigue damage calculation module (not shown) in a floating wind turbine floating structure fatigue damage analysis system.

[0066] Obtain local nominal stress in S5 σ i , for local nominal stress σ i The rain flow meter is used to extract the load cycle, and combined with the SN curve, the following formula (2) is used to calculate the short-term fatigue damage corresponding to the marine environment condition: D .

[0067] The SN curve is a curve with the fatigue strength of the standard specimen of the material as the vertical coordinate and the logarithm of the fatigue life lgN as the horizontal coordinate. It represents the relationship between the fatigue strength and fatigue life of the standard specimen under certain cycle characteristics, also known as the stress-life curve.

[0068] (2) in, n Indicates the number of load cycles corresponding to the stress range △s, i Indicates i stress range, N is the number of fatigue damage cycles given by the SN curve, which can be given by the SN curve.

[0069] S7: Calculation of long-term fatigue damage.

[0070] The process of obtaining the long-term fatigue damage may be implemented by using a long-term fatigue damage calculation module (not shown) in a floating wind turbine floating structure fatigue damage analysis system.

[0071] In some embodiments of the present application, the fatigue damage contribution under different wind and wave environment conditions is estimated through the statistical integration method of marine environment conditions combined with the joint distribution probability of wind and wave parameters to estimate long-term fatigue damage and achieve the accuracy of long-term fatigue life assessment.

[0072] In some embodiments of the present application, the following formula (3) is used to calculate the long-term fatigue damage D tot .

[0073] (3) in, p is the joint distribution probability of wind and wave parameters, θ i Indicates i wind and wave direction, j Representative j Marine environment conditions, U w , H s and T p represent the average wind speed, significant wave height and spectral peak period respectively.

[0074] It should be noted that the joint distribution probability of wind and wave parameters p Generally, there is an existing probability distribution for each sea area.

[0075] See also Figures 3 to 8 , which gives comparative analysis results of the calculation results obtained using the traditional fully coupled time domain analysis method and the calculation results obtained using the fatigue damage analysis method involved in this application.

[0076] See also Figure 3 , which shows that the fatigue damage analysis method of the present application (i.e. Figure 3 The decoupling method marked in () is the bending moment of the third structural section of the floating structure under the rated wind speed condition of the wind turbine. M y The time domain response curve (see the red curve), and the bending moment of the third structural section of the floating structure under rated wind speed conditions using the traditional fully coupled time domain analysis method M y A plot of the time domain response of (see the blue curve).

[0077] See also Figure 4 , which shows that the fatigue damage analysis method of the present application (i.e. Figure 4 The decoupling method marked in () is used to calculate the bending moment of the third structural section of the floating structure under the wind turbine cut-out wind speed condition. M yThe time domain response curve (see the red curve), and the bending moment of the third structural section of the floating structure under the wind turbine cut-out wind speed condition using the traditional fully coupled time domain analysis method M y A plot of the time domain response of (see the blue curve).

[0078] pass Figure 3 and Figure 4 It can be seen that the bending moment of the third structural section obtained by the fatigue analysis method involved in this application is M y The time domain response results and the bending moment of the third structural section obtained by the traditional fully coupled time domain analysis method M y The time domain response results show a high degree of consistency. Therefore, it also indirectly reflects that the fatigue damage loss method based on wind-wave decoupling in the present application still maintains the same accuracy in time domain response calculation as the traditional fully coupled time domain analysis method.

[0079] Figure 5 A comparison diagram of short-term fatigue damage under different average wind speed conditions obtained at the third structural section of the floating structure using the fatigue damage analysis method proposed in this application and the traditional fully coupled time domain analysis method is shown, where LC1-LC15 corresponds to conditions with average wind speeds ranging from 1m / s to 29m / s, with a wind speed interval of 2m / s, covering the complete operating range of the wind turbine from cut-in to shutdown.

[0080] based on Figure 5 The results shown calculate the short-term fatigue damage involved in this application and the short-term fatigue damage involved in the traditional fully coupled time domain analysis method. It can be seen that the maximum relative difference under different average wind speed conditions is about 15%, which retains the high accuracy of the traditional fully coupled time domain analysis method for calculating short-term fatigue damage, ensuring the accuracy of estimating short-term fatigue damage using the method of this application.

[0081] Figure 6 A comparison diagram of long-term fatigue damage at a first structural section evaluated at six different offshore locations using the fatigue damage analysis method of the present application and a traditional fully coupled time domain analysis method is shown.

[0082] Figure 7 A comparison diagram of long-term fatigue damage at a second structure section evaluated at six different offshore locations using the fatigue damage analysis method of the present application and the traditional fully coupled time domain analysis method is shown.

[0083] Figure 8 A comparison diagram showing the long-term fatigue damage at the third structure section evaluated at six different offshore locations using the fatigue damage analysis method of the present application and the traditional fully coupled time domain analysis method.

[0084] Among them, the six different offshore locations were selected as Norwegian North Sea 1, Norwegian North Sea 2, Norwegian North Sea 3, Norwegian North Sea 4, Norwegian North Sea 5 and the South China Sea.

[0085] See also Figures 6 to 8 For these six different offshore locations, the traditional fully coupled time domain analysis method and the method of this application performed 10182 and 1590 one-hour simulation analyses respectively. The calculation cost of the method of this application was reduced by about 84% (i.e., 1-1590 / 10182=84%), which significantly reduced the calculation cost, significantly reduced the demand for high-performance computing resources, shortened the fatigue damage analysis cycle, and improved the efficiency of engineering design iteration.

[0086] based on Figures 6 to 8 The results shown in the figure show that at the first structural section, the second structural section and the third structural section, the maximum percentage difference between the long-term fatigue damage estimated by the method of the present application and the traditional full-coupling method is about 15%, which retains the high accuracy of the traditional full-coupling time-domain analysis method for calculating long-term fatigue damage and ensures the accuracy of estimating long-term fatigue damage using the method of the present application.

[0087] The method provided in this application is based on wind-wave decoupling, which greatly improves the efficiency of fatigue damage assessment while ensuring calculation accuracy, and provides an efficient and feasible solution for the structural optimization and engineering application of floating wind turbines.

[0088] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for a person skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to replace some of the technical features therein by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions claimed to be protected by the present invention.

Claims

1. A method for analyzing fatigue damage of a floating wind turbine buoy structure, characterized in that: include: Constructing a model of a floating wind turbine, wherein a floating structure in the floating wind turbine is modeled as a plurality of rigid body structure segments, and a structure section is formed between adjacent structure segments; Considering only the wind force, the wind load response at the structural section of the floating structure under different wind conditions is obtained; When the wind turbine is in a shutdown state, only the wave action is considered to obtain the wave load action response at the cross section of the structure under different wave actions; Linearly superimpose the wind load response and the wave load response corresponding to a single marine environment condition to obtain a total load response at the structural cross section under the corresponding marine environment condition; converting the total load response into a local nominal stress; Performing rain flow counting on the local nominal stress and combining it with the SN curve, calculating the short-term fatigue damage corresponding to the marine environment condition; The short-term fatigue damage under all marine environmental conditions is integrated, and the long-term fatigue damage is calculated by combining the joint distribution probability of wind and wave parameters under the corresponding marine environmental conditions.

2. The method for analyzing fatigue damage of a floating wind turbine buoy structure according to claim 1, characterized in that: The initial value of the linearly superimposed total load response is corrected, specifically, corrected to the initial value of the total load response obtained by using a traditional fully coupled time domain analysis method.

3. The method for analyzing fatigue damage of a floating wind turbine buoy structure according to claim 1, characterized in that: Obtain the wind load response at the structural section of the floating structure under different wind conditions, specifically: Calculating the blade aerodynamic load based on blade element momentum theory, wherein the blade aerodynamic load includes wind excitation load, impeller additional mass load and aerodynamic damping load; Time domain simulation is performed for different wind conditions to obtain the wind load response at the structural section of the floating structure under different wind conditions.

4. The method for analyzing fatigue damage of a floating wind turbine buoy structure according to claim 1, characterized in that: The wave load response at the structural section under different wave actions is obtained, specifically: The potential flow theory is used to calculate the wave forces on floating bodies; Calculate the viscous damping force of the floating body based on the Morison equation; Time domain simulation is carried out for wave actions with different significant wave heights, spectral peak periods and directions to obtain the wave load response at the structural section.

5. The method for analyzing fatigue damage of a floating wind turbine buoy structure according to claim 1, characterized in that: Convert the total load response to local nominal stress σ i , specifically: Based on the Euler-Bernoulli beam theory, the following formula is used for conversion: ； in, F x represents the axial force of the structural section, M y and M z Respectively represent the structural cross section around y Axis and z Bending moment of the shaft, A represents the cross-sectional area of ​​the structural cross section, W y and W z Respectively represent the structural cross section around y Axis and z Section modulus of the shaft.

6. The method for analyzing fatigue damage of a floating wind turbine buoy structure according to claim 1, characterized in that: The following formula is used to calculate the short-term fatigue damage corresponding to the marine environment conditions: D : ； in, n Indicates the number of load cycles corresponding to the stress range △s, i Indicates i stress range, N is the number of fatigue damage cycles given by the SN curve.

7. The method for analyzing fatigue damage of a floating wind turbine buoy structure according to claim 6, characterized in that: The long-term fatigue damage is calculated using the following formula: D tot : ; in, p is the joint distribution probability of wind and wave parameters, θ i Indicates i wind and wave direction, j Representative j Marine environment conditions, U w , H s and T p represent the average wind speed, significant wave height and spectral peak period respectively.

8. A floating wind turbine floating structure fatigue damage analysis system, characterized in that: include: A unit model building module, which is used to build a model of a floating wind turbine, wherein the floating structure of the floating wind turbine is modeled as a plurality of rigid body structure segments, and a structure section is formed between adjacent structure segments; A wind load acquisition module, which is used to consider only the wind force and obtain the wind load response at the structural cross section of the floating structure under different wind conditions; A wave load acquisition module, which is used to obtain the wave load response at the structural cross section under different wave actions by only considering the wave action when the wind turbine is stopped; A total load response acquisition module, which is used to linearly superimpose the wind load action response and the wave load action response corresponding to a single marine environment condition to obtain the total load response at the structural cross section under the corresponding marine environment condition; a response-to-stress conversion module, which is used to convert the total load response into a local nominal stress; A short-term fatigue damage calculation module, which is used to perform rain flow counting on the local nominal stress and calculate the short-term fatigue damage corresponding to the marine environment working condition in combination with the SN curve; The long-term fatigue damage calculation module is used to integrate the short-term fatigue damage under all marine environmental conditions and estimate the long-term fatigue damage by combining the joint distribution probability of wind and wave parameters under the corresponding marine environmental conditions.

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