A method and system for calculating equivalent fatigue strain of floating wind turbine blades

Abstract

This invention discloses a method and system for calculating the equivalent fatigue strain of floating wind turbine blades. The method includes: constructing a finite element model of the blade; simulating the strain values ​​of the floating blade under the coupled loads of wind, waves, and current; determining the strain control quantities for each part of the blade based on full-scale type testing and engineering experience; and evaluating and calculating the safety margin of the equivalent fatigue strain for each part of the blade. The system includes: a blade modeling module, a finite element simulation module, a data processing module, an evaluation module, and a judgment module. This invention can easily and efficiently evaluate the strain safety factor of floating blades under equivalent fatigue loads during their service life, enabling safety verification of the structure in the early design stage and avoiding blade failure due to fatigue during operation.

Description

Technical Field

[0001] This invention belongs to the field of wind power generation technology, specifically relating to a method and system for calculating the equivalent fatigue strain of floating wind turbine blades. Background Technology

[0002] Technological advancements in floating wind turbines are key to the future development of wind power in deep-sea areas. As a crucial component of the entire unit, the blades require extremely careful structural design, considering factors such as cost, operation and maintenance, and safety risks. Given the unit's design life of 25 years and the fact that floating blades are constantly subjected to alternating loads from wind, waves, and current coupling, it is necessary to assess blade fatigue strain to ensure that the blades do not experience fatigue failure during their operational lifespan.

[0003] Currently, there are many methods for assessing fatigue strain in wind turbine blades within the industry. However, different turbine manufacturers have varying internal strain control values ​​for different blade components, lacking a unified standard and hindering the industry's development and progress. Therefore, combining type testing of blades, engineering practice experience, and the high safety requirements of floating turbine units, this paper proposes to develop a simple, efficient, and conservative method and system for calculating the equivalent fatigue strain of floating wind turbine blades. Summary of the Invention

[0004] This invention provides a method and system for calculating the equivalent fatigue strain of floating wind turbine blades, with the aim of improving the fatigue safety of floating wind turbine blades during their service life and effectively reducing blade damage and failure accidents caused by fatigue.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for calculating the equivalent fatigue strain of a floating wind turbine blade includes:

[0007] Based on the design data of floating wind turbine blades, a finite element model of the blades was constructed.

[0008] Based on the constructed blade finite element model, input the equivalent fatigue load data considering the coupled effects of wind load, wave load and ice load, and obtain the blade shell strain value under the corresponding boundary conditions.

[0009] Based on the obtained blade shell strain values, the maximum strain of the leading edge, trailing edge and main beam structure of the blade is extracted;

[0010] Based on the maximum strain of the blade leading edge, trailing edge and main beam structure obtained, and combined with blade type testing and engineering practice experience, the safety margin of blade fatigue strain is evaluated.

[0011] The fatigue safety of the blade is determined based on the assessed safety margin of the blade fatigue strain.

[0012] A further improvement of this invention lies in constructing a finite element model of the blade based on the design data of the floating wind turbine blade, including:

[0013] Based on the design geometry information of the floating wind turbine blade, including blade length, blade section airfoil type, airfoil geometry data, airfoil chord length, twist angle and pre-bending information, the three-dimensional geometric shape of the blade is constructed.

[0014] Based on the three-dimensional geometric shape of the blade and the blade structure layup design drawings, input the blade layup information, including the material design at the corresponding position, and give the corresponding material thickness to obtain the three-dimensional structural model of the blade.

[0015] Based on the three-dimensional structural model of the blade and the material test report, reasonable mechanical property parameters of the material are input, including transverse tensile modulus, longitudinal tensile modulus, Poisson's ratio, in-plane shear modulus and out-of-plane shear modulus, to construct the finite element model of the blade; it is required that the parameters used in the model cannot be higher than the results in the test report.

[0016] A further improvement of this invention lies in obtaining the blade shell strain values ​​under corresponding boundary conditions by inputting equivalent fatigue load data considering the coupled effects of wind, wave, and ice loads based on the constructed blade finite element model, including:

[0017] Based on the design load data of the blade, the Markov fatigue load matrix at each section of the floating wind turbine blade is obtained.

[0018] Referring to formula (1), the Markov load matrix is ​​transformed into an equivalent fatigue load with a slope of m=10 on the SN curve, where the load in the oscillation direction is reduced to 2 million cycles and the load in the flailing direction is reduced to 1 million cycles.

[0019]

[0020] in Indicates the blade element design load. Indicates the number of designed blade operations. This represents the equivalent load. Indicates the equivalent number of times. Indicates the slope of the stress-strain curve;

[0021] By utilizing the conversion relationship between torque and concentrated force, the equivalent fatigue torque load of each section is transformed into the form of concentrated force of the section;

[0022] Based on the finite element model of the blade, the processed equivalent fatigue load is applied at the main beam location, in the form of concentrated force data at the cross-section along the blade length.

[0023] Finite element simulation software was used to simulate the stress characteristics of the blade under equivalent fatigue load conditions and obtain the strain value of the blade shell.

[0024] A further improvement of this invention lies in assessing the safety margin of blade fatigue strain based on the obtained maximum strain of the blade's leading edge, trailing edge, and main sparsity, combined with blade type testing and engineering practice experience. This includes:

[0025] Based on the fatigue test results in the flapping and oscillation directions of the blades, and combined with engineering practice experience, the maximum safe strain values ​​for each part of the blades were determined. Among them, under the equivalent fatigue load of 2 million cycles in the oscillation direction, the strain value at the leading edge position should not exceed 2800, and the strain value at the trailing edge position should not exceed 2500. Under the equivalent fatigue load of 1 million cycles in the flapping direction, the strain value for the glass plate main beam should not exceed 2000, and the strain value for the carbon fiber main beam should not exceed 1800.

[0026] Based on the maximum strain of the blade leading edge, trailing edge, and main beam structure obtained from simulation, and combined with the maximum strain control value of each part, the safety margin of blade fatigue strain is evaluated, as shown in formula (2):

[0027] .

[0028] A further improvement of the present invention is that, based on the assessed safety margin of the blade fatigue strain, the fatigue safety of the blade is determined, including:

[0029] When the calculated fatigue strain safety margin is greater than or equal to 1, the blade fatigue safety meets the requirements; when the fatigue strain safety margin is less than 1, the blade fatigue safety does not meet the requirements.

[0030] A system for calculating the equivalent fatigue strain of a floating wind turbine blade includes:

[0031] The blade modeling module constructs a finite element model of the blade based on the design data of the floating wind turbine blade;

[0032] The finite element simulation module, based on the constructed blade finite element model, inputs equivalent fatigue load data considering the coupled effects of wind load, wave load, and ice load, and obtains the blade shell strain value under the corresponding boundary conditions.

[0033] The data processing module extracts the maximum strain of the leading edge, trailing edge, and main beam structure of the blade based on the obtained blade shell strain values.

[0034] The evaluation module assesses the safety margin of blade fatigue strain based on the maximum strain of the blade's leading edge, trailing edge, and main beam structure, combined with blade type testing and engineering practice experience.

[0035] The judgment module determines the fatigue safety of the blade based on the safety margin of the assessed blade fatigue strain.

[0036] A further improvement of this invention lies in that, in the blade modeling module, a finite element model of the blade is constructed based on the design data of the floating wind turbine blade, including:

[0037] Based on the design geometry information of the floating wind turbine blade, including blade length, blade section airfoil type, airfoil geometry data, airfoil chord length, twist angle and pre-bending information, the three-dimensional geometric shape of the blade is constructed.

[0038] Based on the three-dimensional geometric shape of the blade and the blade structure layup design drawings, input the blade layup information, including the material design at the corresponding position, and give the corresponding material thickness to obtain the three-dimensional structural model of the blade.

[0039] Based on the three-dimensional structural model of the blade and the material test report, reasonable mechanical property parameters of the material are input, including transverse tensile modulus, longitudinal tensile modulus, Poisson's ratio, in-plane shear modulus and out-of-plane shear modulus, to construct the finite element model of the blade; it is required that the parameters used in the model cannot be higher than the results in the test report.

[0040] A further improvement of this invention lies in that, in the finite element simulation module, based on the constructed blade finite element model, equivalent fatigue load data considering the coupled effects of wind load, wave load, and ice load are input to obtain the blade shell strain values ​​under the corresponding boundary conditions, including:

[0041] Based on the design load data of the blade, the Markov fatigue load matrix at each section of the floating wind turbine blade is obtained.

[0042] Referring to formula (1), the Markov load matrix is ​​transformed into an equivalent fatigue load with a slope of m=10 on the SN curve, where the load in the oscillation direction is reduced to 2 million cycles and the load in the flailing direction is reduced to 1 million cycles.

[0043]

[0044] in Indicates the blade element design load. Indicates the number of designed blade operations. This represents the equivalent load. Indicates the equivalent number of times. Indicates the slope of the stress-strain curve;

[0045] By utilizing the conversion relationship between torque and concentrated force, the equivalent fatigue torque load of each section is transformed into the form of concentrated force of the section;

[0046] Based on the finite element model of the blade, the processed equivalent fatigue load is applied at the main beam location, in the form of concentrated force data at the cross-section along the blade length.

[0047] Finite element simulation software was used to simulate the stress characteristics of the blade under equivalent fatigue load conditions and obtain the strain value of the blade shell.

[0048] A further improvement of this invention lies in that, in the evaluation module, based on the obtained maximum strain of the blade's leading edge, trailing edge, and main sparsity, combined with blade type testing and engineering practice experience, the safety margin of the blade's fatigue strain is evaluated, including:

[0049] Based on the fatigue test results in the flapping and oscillation directions of the blades, and combined with engineering practice experience, the maximum safe strain values ​​for each part of the blades were determined. Among them, under the equivalent fatigue load of 2 million cycles in the oscillation direction, the strain value at the leading edge position should not exceed 2800, and the strain value at the trailing edge position should not exceed 2500. Under the equivalent fatigue load of 1 million cycles in the flapping direction, the strain value for the glass plate main beam should not exceed 2000, and the strain value for the carbon fiber main beam should not exceed 1800.

[0050] Based on the maximum strain of the blade leading edge, trailing edge, and main beam structure obtained from simulation, and combined with the maximum strain control value of each part, the safety margin of blade fatigue strain is evaluated, as shown in formula (2):

[0051] .

[0052] A computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of a method for calculating the equivalent fatigue strain of a floating wind turbine blade.

[0053] Compared with the prior art, the present invention has at least the following beneficial technical effects:

[0054] This invention provides a method and system for calculating the equivalent fatigue strain of floating wind turbine blades. Addressing the alternating loads borne by floating wind turbine blades under wind, wave, and current coupling, and combining full-scale type testing of the blades with engineering experience, a method and system for calculating the equivalent fatigue strain of floating wind turbine blades has been developed. It has advantages such as simple calculation method, efficient evaluation, and relatively conservative results. Furthermore, it provides strain control values ​​for various parts of the blade at corresponding equivalent fatigue cycles, providing guidance for subsequent fatigue strain value control of the blades and effectively ensuring the fatigue structural safety of floating wind turbine blades. Attached Figure Description

[0055] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0056] Figure 1 A schematic diagram of the Markov matrix for the load component of a floating wind turbine blade design;

[0057] Figure 2 This is a schematic diagram of the concentrated force load data for each section of a floating wind turbine blade.

[0058] Figure 3 This is a schematic diagram of an evaluation system for the equivalent fatigue strain of a floating wind turbine blade. Detailed Implementation

[0059] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0060] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0061] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0062] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0063] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0064] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0065] Example 1

[0066] This invention provides a method for calculating the equivalent fatigue strain of a floating wind turbine blade, comprising:

[0067] Based on the design data of floating wind turbine blades, a finite element model of the blades was constructed.

[0068] Based on the constructed blade finite element model, input the equivalent fatigue load data considering the coupled effects of wind load, wave load and ice load, and obtain the blade shell strain value under the corresponding boundary conditions.

[0069] Based on the obtained blade shell strain values, the maximum strain of the leading edge, trailing edge and main beam structure of the blade is extracted;

[0070] Based on the maximum strain of the blade leading edge, trailing edge and main beam structure obtained, and combined with blade type testing and engineering practice experience, the safety margin of blade fatigue strain is evaluated.

[0071] The fatigue safety of the blade is determined based on the assessed safety margin of the blade fatigue strain.

[0072] In this embodiment, a finite element model of the blade is constructed based on the design data of the floating wind turbine blade, including:

[0073] Based on the design geometry information of the floating wind turbine blade, including blade length, blade section airfoil type, airfoil geometry data, airfoil chord length, twist angle and pre-bending information, the three-dimensional geometric shape of the blade is constructed.

[0074] Based on the three-dimensional geometric shape of the blade and the blade structure layup design drawings, input the blade layup information, including the material design of the corresponding position, such as fiber cloth, core material, pultruded plate and structural adhesive, and give the corresponding material thickness to obtain the three-dimensional structural model of the blade.

[0075] Based on the three-dimensional structural model of the blade and the material test report, reasonable mechanical property parameters of the material are input, including transverse tensile modulus, longitudinal tensile modulus, Poisson's ratio, in-plane shear modulus and out-of-plane shear modulus, to construct the finite element model of the blade; it is required that the parameters used in the model cannot be higher than the results in the test report.

[0076] In this embodiment, based on the constructed blade finite element model, equivalent fatigue load data considering the coupled effects of wind load, wave load, and ice load are input to obtain the blade shell strain values ​​under the corresponding boundary conditions, including:

[0077] Based on the design load data of the blade, the Markov fatigue load matrix at each section of the floating wind turbine blade is obtained.

[0078] Referring to formula (1), the Markov load matrix is ​​transformed into an equivalent fatigue load with a slope of m=10 on the SN curve, where the load in the oscillation direction is reduced to 2 million cycles and the load in the flailing direction is reduced to 1 million cycles.

[0079]

[0080] in Indicates the blade element design load. Indicates the number of designed blade operations. This represents the equivalent load. Indicates the equivalent number of times. Indicates the slope of the stress-strain curve;

[0081] By utilizing the conversion relationship between torque and concentrated force, the equivalent fatigue torque load of each section is transformed into the form of concentrated force of the section;

[0082] Based on the finite element model of the blade, the processed equivalent fatigue load is applied at the main beam location, in the form of concentrated force data at the cross-section along the blade length.

[0083] Finite element simulation software was used to simulate the stress characteristics of the blade under equivalent fatigue load conditions and obtain the strain value of the blade shell.

[0084] In this embodiment, based on the obtained maximum strain of the blade's leading edge, trailing edge, and main sparsity, and combined with blade type testing and engineering practice experience, the safety margin of blade fatigue strain is evaluated, including:

[0085] Based on the fatigue test results in the flapping and oscillation directions of the blades, and combined with engineering practice experience, the maximum safe strain values ​​for each part of the blades were determined. Among them, under the equivalent fatigue load of 2 million cycles in the oscillation direction, the strain value at the leading edge position should not exceed 2800, and the strain value at the trailing edge position should not exceed 2500. Under the equivalent fatigue load of 1 million cycles in the flapping direction, the strain value for the glass plate main beam should not exceed 2000, and the strain value for the carbon fiber main beam should not exceed 1800.

[0086] Based on the maximum strain of the blade leading edge, trailing edge, and main beam structure obtained from simulation, and combined with the maximum strain control value of each part, the safety margin of blade fatigue strain is evaluated, as shown in formula (2):

[0087] .

[0088] In this embodiment, the fatigue safety of the blade is determined based on the assessed safety margin of the blade fatigue strain, including:

[0089] When the calculated fatigue strain safety margin is greater than or equal to 1, the blade fatigue safety meets the requirements; when the fatigue strain safety margin is less than 1, the blade fatigue safety does not meet the requirements.

[0090] Example 2

[0091] This invention provides a method for calculating the equivalent fatigue strain of a floating wind turbine blade, comprising:

[0092] Step 1: Input the geometric information of the floating wind turbine blade, including blade length, airfoil type of each blade section, airfoil geometric data, airfoil chord length, twist angle and pre-bending, etc., and use 3D modeling software to construct the geometric shape of the blade.

[0093] Step 2: Based on the structural layup design drawings of the floating wind turbine blade, perform structural layup on the geometric shape obtained in Step 1, including fiberglass cloth (monoaxial, biaxial, and triaxial), fiberglass pultruded board, core material (Balsa, PVC), and structural adhesive. Layup must be performed at the corresponding positions on the blade according to the design information in the drawings, ensuring the accuracy of the start and end positions, tangential positioning, spanwise positioning, quantity, and material thickness data of each material, striving for consistency with the manufactured blade.

[0094] Step 3: Based on the material parameters of the floating wind turbine blades and the test reports of the mechanical properties of each material, determine reasonable performance parameters and input them into the model obtained in Step 2, including the transverse tensile modulus. Longitudinal tensile modulus In-plane shear modulus out-of-plane shear modulus and and Poisson coupling coefficient A finite element model of the blade was constructed, and Table 1 shows the names of the materials used in the blade and their corresponding mechanical property parameters.

[0095] Table 1 Mechanical property parameters of materials used in the blades

[0096]

[0097] Step 4: Based on the design load data of the floating wind turbine blade, extract the Markov load matrix at the first section in the oscillation direction, i.e., the 0m position of the blade. Some data are shown below. Figure 1 As shown, the first row represents the load amplitude, the first column represents the load mean, and the data in the table represents the number of times the load occurred.

[0098] Step 5: Convert the Markov load matrix data at the first section into the equivalent fatigue load value when the slope of the SN curve (stress-life) is 10 and the number of cycles is 2 million using formula (1);

[0099]

[0100] in Indicates the first row, number The magnitude of the column, This indicates the total number of amplitude values. This represents the slope of the stress-life curve. This indicates the lifespan of a floating wind turbine blade, taken as 100 million cycles. Indicates the equivalent load value. This represents the equivalent number of iterations, taken as 2 million.

[0101] Step 6: Repeat steps 4 and 5 to obtain the equivalent fatigue load data at each section of the floating wind turbine blade. Convert the bending moment load into a concentrated force load. Considering the impact of the real environment on the experiment, multiply the concentrated force load data at each section by the experimental reduction factor of 1.3285. The final concentrated force data for each section is as follows: Figure 2 As shown;

[0102] Step 7: Input the concentrated force load data of the blade section obtained in Step 6 into the main beam position of the blade finite element model in Step 3, and use finite element simulation software to simulate the stress characteristics of the blade under the equivalent fatigue load condition in the oscillation direction.

[0103] Step 8: Based on the stress characteristics of the simulated blade under the equivalent fatigue load in the oscillation direction as described in Step 7, obtain the strain values ​​at all positions of the blade shell.

[0104] Step 9: Extract the maximum absolute values ​​of strain at the leading and trailing edges of the floating wind turbine blade, which are 2388 and 2148 respectively;

[0105] Step 10: Based on blade type testing and engineering practice experience, the maximum strain control values ​​for each part of the blade are determined, with 2500 for the leading edge and 2200 for the trailing edge. Using the above formula (2), the safety margin of blade fatigue strain is evaluated, and the results are as follows:

[0106]

[0107]

[0108] Step 11: Based on the fatigue strain safety margin values ​​of the leading and trailing edges of the blade obtained in Step 10, since they are all greater than 1, it indicates that the fatigue strain design of the blade meets the requirements.

[0109] Example 3

[0110] like Figure 2 As shown, the present invention provides a calculation system for the equivalent fatigue strain of a floating wind turbine blade, comprising:

[0111] The blade modeling module constructs a finite element model of the blade based on the design data of the floating wind turbine blade;

[0112] The finite element simulation module, based on the constructed blade finite element model, inputs equivalent fatigue load data considering the coupled effects of wind load, wave load, and ice load, and obtains the blade shell strain value under the corresponding boundary conditions.

[0113] The data processing module extracts the maximum strain of the leading edge, trailing edge, and main beam structure of the blade based on the obtained blade shell strain values.

[0114] The evaluation module assesses the safety margin of blade fatigue strain based on the maximum strain of the blade's leading edge, trailing edge, and main beam structure, combined with blade type testing and engineering practice experience.

[0115] The judgment module determines the fatigue safety of the blade based on the safety margin of the assessed blade fatigue strain.

[0116] Example 4

[0117] The present invention provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps of a method for calculating the equivalent fatigue strain of a floating wind turbine blade.

[0118] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0119] This application is described with reference to flowchart illustrations and / or block diagrams of methods, systems, and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A system that specifies functions in one or more boxes.

[0120] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0121] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0122] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the scope of the invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0123] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that can be understood by those skilled in the art. The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for calculating the equivalent fatigue strain of a floating wind turbine blade, characterized in that, include: Based on the design data of floating wind turbine blades, a finite element model of the blades was constructed. Based on the constructed blade finite element model, the equivalent fatigue load data considering the coupled effects of wind, wave, and ice loads are input to obtain the blade shell strain values ​​under the corresponding boundary conditions, including: Based on the design load data of the blade, the Markov fatigue load matrix at each section of the floating wind turbine blade is obtained. Referring to formula (1), the Markov load matrix is ​​transformed into an equivalent fatigue load with a slope of m = 10 on the SN curve, where the load in the oscillation direction is reduced to 2 million cycles and the load in the flailing direction is reduced to 1 million cycles. F1 m N1=F2 m N2 (1) Where F1 represents the blade element design load, N1 represents the blade design operation number, F2 represents the equivalent load, N2 represents the equivalent number, and m represents the slope of the stress-strain curve; By utilizing the conversion relationship between torque and concentrated force, the equivalent fatigue torque load of each section is transformed into the form of concentrated force of the section; Based on the finite element model of the blade, the processed equivalent fatigue load is applied at the main beam location, in the form of concentrated force data at the cross-section along the blade length. Using finite element simulation software, the stress characteristics of the blade under equivalent fatigue load conditions are simulated to obtain the strain value of the blade shell. Based on the obtained blade shell strain values, the maximum strain of the leading edge, trailing edge and main beam structure of the blade is extracted; Based on the maximum strain of the blade leading edge, trailing edge and main beam structure obtained, and combined with blade type testing and engineering practice experience, the safety margin of blade fatigue strain is evaluated. The fatigue safety of the blade is determined based on the assessed safety margin of the blade fatigue strain.

2. The method for calculating the equivalent fatigue strain of a floating wind turbine blade according to claim 1, characterized in that, Based on the design data of floating wind turbine blades, a finite element model of the blades was constructed, including: Based on the design geometry information of the floating wind turbine blade, including blade length, blade section airfoil type, airfoil geometry data, airfoil chord length, twist angle and pre-bending information, the three-dimensional geometric shape of the blade is constructed. Based on the three-dimensional geometric shape of the blade and the blade structure layup design drawings, input the blade layup information, including the material design at the corresponding position, and give the corresponding material thickness to obtain the three-dimensional structural model of the blade. Based on the three-dimensional structural model of the blade and the material test report, reasonable mechanical property parameters of the material are input, including transverse tensile modulus, longitudinal tensile modulus, Poisson's ratio, in-plane shear modulus and out-of-plane shear modulus, to construct the finite element model of the blade; it is required that the parameters used in the model cannot be higher than the results in the test report.

3. The method for calculating the equivalent fatigue strain of a floating wind turbine blade according to claim 1, characterized in that, Based on the obtained maximum strain of the blade's leading edge, trailing edge, and main sparsity, and combined with blade type testing and engineering practice experience, the safety margin for blade fatigue strain is assessed, including: Based on the fatigue test results in the flapping and oscillation directions of the blades, and combined with engineering practice experience, the maximum safe strain values ​​for each part of the blades were determined. Among them, under the equivalent fatigue load of 2 million cycles in the oscillation direction, the strain value at the leading edge position should not exceed 2800, and the strain value at the trailing edge position should not exceed 2500. Under the equivalent fatigue load of 1 million cycles in the flapping direction, the strain value for the glass plate main beam should not exceed 2000, and the strain value for the carbon fiber main beam should not exceed 1800. Based on the maximum strain of the blade leading edge, trailing edge, and main beam structure obtained from simulation, and combined with the maximum strain control values ​​of each part, the safety margin of blade fatigue strain is evaluated, as shown in formula (2):

4. The method for calculating the equivalent fatigue strain of a floating wind turbine blade according to claim 1, characterized in that, Based on the assessed safety margin of blade fatigue strain, the fatigue safety of the blade is determined, including: When the calculated fatigue strain safety margin is greater than or equal to 1, the blade fatigue safety meets the requirements; when the fatigue strain safety margin is less than 1, the blade fatigue safety does not meet the requirements.

5. A calculation system for equivalent fatigue strain of a floating wind turbine blade, characterized in that, include: The blade modeling module constructs a finite element model of the blade based on the design data of the floating wind turbine blade; The finite element simulation module, based on the constructed blade finite element model, takes into account the equivalent fatigue load data considering the coupled effects of wind, wave, and ice loads, and obtains the blade shell strain values ​​under the corresponding boundary conditions, including: Based on the design load data of the blade, the Markov fatigue load matrix at each section of the floating wind turbine blade is obtained. Referring to formula (1), the Markov load matrix is ​​transformed into an equivalent fatigue load with a slope of m = 10 on the SN curve, where the load in the oscillation direction is reduced to 2 million cycles and the load in the flailing direction is reduced to 1 million cycles. F1 m N1=F2 m N2 (1) Where F1 represents the blade element design load, N1 represents the blade design operation number, F2 represents the equivalent load, N2 represents the equivalent number, and m represents the slope of the stress-strain curve; By utilizing the conversion relationship between torque and concentrated force, the equivalent fatigue torque load of each section is transformed into the form of concentrated force of the section; Based on the finite element model of the blade, the processed equivalent fatigue load is applied at the main beam location, in the form of concentrated force data at the cross-section along the blade length. Using finite element simulation software, the stress characteristics of the blade under equivalent fatigue load conditions are simulated to obtain the strain value of the blade shell. The data processing module extracts the maximum strain of the leading edge, trailing edge, and main beam structure of the blade based on the obtained blade shell strain values. The evaluation module assesses the safety margin of blade fatigue strain based on the maximum strain of the blade's leading edge, trailing edge, and main beam structure, combined with blade type testing and engineering practice experience. The judgment module determines the fatigue safety of the blade based on the safety margin of the assessed blade fatigue strain.

6. The calculation system for equivalent fatigue strain of a floating wind turbine blade according to claim 5, characterized in that, In the blade modeling module, a finite element model of the blade is constructed based on the design data of the floating wind turbine blade, including: Based on the design geometry information of the floating wind turbine blade, including blade length, blade section airfoil type, airfoil geometry data, airfoil chord length, twist angle and pre-bending information, the three-dimensional geometric shape of the blade is constructed. Based on the three-dimensional geometric shape of the blade and the blade structure layup design drawings, input the blade layup information, including the material design at the corresponding position, and give the corresponding material thickness to obtain the three-dimensional structural model of the blade. Based on the three-dimensional structural model of the blade and the material test report, reasonable mechanical property parameters of the material are input, including transverse tensile modulus, longitudinal tensile modulus, Poisson's ratio, in-plane shear modulus and out-of-plane shear modulus, to construct the finite element model of the blade; it is required that the parameters used in the model cannot be higher than the results in the test report.

7. The calculation system for equivalent fatigue strain of a floating wind turbine blade according to claim 5, characterized in that, In the evaluation module, based on the obtained maximum strain of the blade's leading edge, trailing edge, and main sparsity, and combined with blade type testing and engineering practice experience, the safety margin of blade fatigue strain is evaluated, including: Based on the fatigue test results in the flapping and oscillation directions of the blades, and combined with engineering practice experience, the maximum safe strain values ​​for each part of the blades were determined. Among them, under the equivalent fatigue load of 2 million cycles in the oscillation direction, the strain value at the leading edge position should not exceed 2800, and the strain value at the trailing edge position should not exceed 2500. Under the equivalent fatigue load of 1 million cycles in the flapping direction, the strain value for the glass plate main beam should not exceed 2000, and the strain value for the carbon fiber main beam should not exceed 1800. Based on the maximum strain of the blade leading edge, trailing edge, and main beam structure obtained from simulation, and combined with the maximum strain control values ​​of each part, the safety margin of blade fatigue strain is evaluated, as shown in formula (2):

8. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the steps of a method for calculating the equivalent fatigue strain of a floating wind turbine blade according to any one of claims 1-4.

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