Wind turbine generator blade root bolt fatigue strength analysis method and system

Abstract

The invention discloses a wind turbine generator blade root bolt fatigue strength analysis method and system. The method comprises the following steps that a three-dimensional model for blade root bolt fatigue strength analysis is established and simplified; the model is converted into a finite element model, and contact setting, boundary condition setting and loading setting of all the components are carried out; carrying out finite element calculation to obtain corresponding stresses of key nodes under different load conditions, and drawing a load-stress curve; adopting a rain flow counting method to obtain an amplitude value, a mean value and a cycle index required by fatigue calculation; interpolation is carried out in the load-stress curve, and the amplitude, the mean value and the cycle index of stress are obtained; accumulating the damage quantity values obtained in each stress cycle to obtain the total fatigue damage of the blade root bolt; generating a wind turbine generator blade root bolt fatigue strength checking report; according to the method, the initial gap and the gap judgment radius between the components are adjusted through contact setting, so that the penetration influence caused by large deformation of the model is reduced, and the problem that convergence is not easy due to improvement of the model precision is solved.

Description

Technical Field

[0001] The invention relates to the technical field of fatigue strength analysis of blade root bolts of wind turbines, and in particular to a method and system for fatigue strength analysis of blade root bolts of wind turbines. Background Art

[0002] As an important part of the renewable energy field, wind turbines have developed rapidly in recent years. Among them, wind turbine blades are the core components of wind turbines, and their structural design directly affects the overall performance and reliability of the unit. In wind turbines, the blade root bolts are subjected to complex variable loads and are the key parts connecting the blades and the hub. Therefore, their fatigue strength issues have become an important research topic in blade structural design.

[0003] As the capacity of wind turbines increases, the size of blades continues to increase, which brings higher loads and more severe working environments to the blade root bolts. Bolt fatigue failure may cause the blades to fall off, which not only causes significant economic losses, but may also cause safety accidents. Therefore, the study of the fatigue strength of blade root bolts has important theoretical and practical significance.

[0004] Traditional blade root bolt design methods usually rely on empirical formulas and limited experimental data, which makes it difficult to accurately describe the actual working conditions under complex loads. This method not only leads to conservative design, increases material usage and costs, but also fails to fully utilize the performance of the bolts. In addition, with the advancement of fatigue testing technology and numerical simulation technology, it is necessary to develop a more scientific and reasonable fatigue strength calculation model to achieve accurate prediction and optimization design of the fatigue life of blade root bolts.

[0005] Currently, methods based on numerical simulation are gradually gaining popularity in engineering applications. As an effective tool, finite element analysis can simulate the stress distribution of blade root bolts under various working conditions, and its fatigue life can be predicted through the fatigue analysis module. However, the establishment and solution process of the finite element model is complicated and requires high computing resources. Therefore, how to combine fatigue strength prediction with engineering applications and develop a computational model that is both efficient and accurate is an important direction of current research.

[0006] The existing blade root bolt strength calculation model oversimplifies the nonlinear pitch bearing ball, which is quite different from the actual stress condition, thus affecting the stress state of the bolt.

[0007] For example, in the Chinese invention patent application CN118862346A, a method for calculating the fatigue strength of the blade root bolts of a wind turbine is disclosed. The disadvantage is that the contact relationship between the variable pitch bearing and the bearing ball is oversimplified, and the bearing ball is simply simplified into a spring unit that is only compressed, which is inconsistent with the actual force conditions and has limited simulation accuracy.

[0008] Or in the Chinese invention patent application CN114722683A, a parametric modeling and calculation analysis method for pre-embedded blade roots of wind turbine blades is disclosed, which is convenient for batch processing. The disadvantage is that the model is suitable for double-row ball bearings, not for three-row column bearings, and the bolts are simplified to half, and the simulation accuracy is limited. Summary of the invention

[0009] The purpose of the present invention is to overcome the shortcomings of the prior art and propose a method and system for analyzing the fatigue strength of blade root bolts of wind turbines to help researchers better calculate the fatigue life of blade root bolts, so as to improve the design accuracy and service life of the bolts, thereby enhancing the overall reliability and safety of wind turbines.

[0010] The purpose of the present invention is achieved through the following technical solution: A method for analyzing the fatigue strength of a wind turbine blade root bolt comprises the following steps:

[0011] S1. Perform stress analysis on the blade root bolts of wind turbines, and establish and simplify a three-dimensional model for fatigue strength analysis of blade root bolts;

[0012] S2. Meshing the three-dimensional model to convert it into a finite element model, defining the material properties of the blade root bolts and their connecting parts, and performing contact settings, boundary condition settings, and loading settings between the various parts of the finite element model;

[0013] S3. On the basis of the setting in step S2, loads are set by batch processing, corresponding stresses of key nodes under different load conditions are obtained by finite element calculation, load-stress curves are drawn, and stress responses of blade root bolts under different working conditions and loads are obtained;

[0014] S4. The actual time series fatigue load is extracted into a Markov load spectrum using the rain flow counting method to obtain the amplitude, mean value and number of cycles required for fatigue calculation;

[0015] S5, interpolating the load-stress curve drawn previously according to the amplitude, mean value and number of cycles in the Markov load spectrum to obtain the amplitude, mean value and number of cycles of the stress;

[0016] S6. Each stress cycle causes damage to the material. The damage value is the inverse of the fatigue life under the stress. According to the damage accumulation theory, the damage values ​​obtained from each stress cycle are accumulated to finally obtain the total fatigue damage of the blade root bolt.

[0017] S7. Generate a wind turbine blade root bolt fatigue strength verification report based on the total fatigue damage of the blade root bolts obtained in step S6.

[0018] Further, the step S1 comprises the following steps:

[0019] The force analysis of the blade root bolts of the wind turbine is carried out, and a three-dimensional model for calculating the fatigue strength of the blade root bolts is established. The three-dimensional model used for calculating the fatigue strength of the blade root bolts is simplified, the fillets and chamfers of each component that has little effect on the force of the blade root bolts are removed, the hub structure is removed, and two blade root bolt force models are divided according to the geometric structure. The geometric structure of the blade root bolt inside the blade is retained, the thread features of the blade root bolt and the threaded sleeve are removed, and the rollers in the pitch bearing are retained.

[0020] Further, the step S2 comprises the following steps:

[0021] After the three-dimensional model is established, it is converted into a finite element six-sided solid unit. The entire blade root bolt connection structure is meshed using hexahedral units. The dangerous parts and transition points are locally refined, and the mesh quality is checked and the mesh independence is verified. The anisotropic linear elastic material constitutive model is used for the blades, and metal materials are used for the other materials.

[0022] Further, the step S2 comprises the following steps:

[0023] The contact setting is to set the connection relationship between the various components of the finite element model. The connection relationship between the blade and the connecting flange, the connection relationship between the connecting flange and the pitch bearing, the connection relationship between the pitch bearing and the bearing roller, and the connection relationship between the pitch bearing and the nut are all set to friction contact. The thread engagement relationship of the blade root bolt is set to binding contact. The connection relationship between the various components inside the blade is set to common node connection.

[0024] The boundary conditions are set to divide the load calculation into multiple load steps, apply frictionless contact conditions to the cutting boundaries on both sides of the two blade root bolt models, and apply full constraints to the bottom of the outer ring of the pitch bearing;

[0025] The loading is set to make the limit load equivalent to the axial force on the blade end, and the equivalent load is gradually applied to the blade end in multiple load steps. The finite element model is solved and calculated nonlinearly using finite element software.

[0026] Further, the loading setting includes:

[0027] To perform loading calculation, first apply the bolt preload, then equate the limit load to the axial force on the blade end, and gradually apply the equivalent load to the blade end through multiple load steps, as shown in the following formula:

[0028]

[0029] Among them, F is the axial force on the blade end, M is the blade root bending moment, N is the number of bolts, and D is the blade root pitch diameter.

[0030] Further, the step S5 comprises the following steps:

[0031] According to the amplitude, mean and number of cycles in the Markov load spectrum, interpolate the previously drawn load-stress curve to obtain the amplitude, mean and number of cycles of stress;

[0032] The double slope SN curve of the blade root bolt is calculated according to the GL specification. The slope-related parameter m is 3 and 5 respectively. For the case where the nominal diameter of the bolt is greater than 30, it is multiplied by the reduction factor k. s :

[0033]

[0034] Among them, k s is the reduction factor, D is the nominal diameter of the bolt;

[0035]

[0036] Among them, Δσ A is the stress amplitude when the number of cycles is 2*106, γ m is the material safety factor;

[0037]

[0038] Among them, Δσ D The number of cycles is 5*10 6 The stress amplitude at A is 2*10 6 , N D 5*10 6 .

[0039] Further, the step S6 comprises the following steps:

[0040] According to the Palmgren-Miner law, each stress cycle will cause damage to the material. The damage value is the inverse of the fatigue life under the stress. According to the damage accumulation theory, the damage value obtained from each stress cycle is accumulated to obtain the total fatigue damage of the blade root bolt, as shown in the following formula:

[0041]

[0042] Among them, N i is the allowable number of stress cycles within the i-th stress range, Δσ i is the stress amplitude in the i-th stress range;

[0043]

[0044] Where D' is the fatigue damage value of the bolt, n i is the actual number of stress cycles in the ith stress range.

[0045] A wind turbine blade root bolt fatigue strength analysis system, used to implement the above-mentioned wind turbine blade root bolt fatigue strength analysis method, comprising:

[0046] The blade root bolt three-dimensional modeling module is used to perform stress analysis on the blade root bolts of wind turbines and to establish and simplify the three-dimensional model for blade root bolt fatigue strength calculation;

[0047] The setting module is used to convert the three-dimensional model into a finite element model by meshing, define the material properties of the blade root bolts and their connecting parts, and perform contact settings, boundary condition settings, and loading settings between the various parts of the finite element model;

[0048] The load-stress processing module is used to batch process and set loads, and obtain the corresponding stresses of key nodes under different load conditions through finite element calculations, and draw load-stress curves;

[0049] Markov load extraction module, which uses rain flow counting method to extract time series fatigue load into Markov load spectrum, and obtains the amplitude, mean value and number of cycles required for fatigue calculation;

[0050] The interpolation module interpolates the previously drawn load-stress curve according to the amplitude, mean and number of cycles in the Markov load spectrum to obtain the amplitude, mean and number of cycles of stress;

[0051] The damage superposition module adds up the damage values ​​obtained from each stress cycle according to the damage accumulation theory to obtain the total fatigue damage of the blade root bolt;

[0052] The verification report generation module generates a wind turbine blade root bolt fatigue strength verification report based on the obtained blade root bolt total fatigue damage.

[0053] A non-transitory computer-readable medium storing instructions, when the instructions are executed by a processor, executes the steps according to the above-mentioned method for analyzing fatigue strength of blade root bolts of a wind turbine.

[0054] A computing device comprises a processor and a memory for storing a program executable by the processor. When the processor executes the program stored in the memory, the above-mentioned method for analyzing fatigue strength of blade root bolts of a wind turbine is implemented.

[0055] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0056] 1. The finite element models of the present invention are all three-dimensional solid models, which have improved simulation accuracy and are more realistic than simplified models commonly used.

[0057] 2. The present invention reduces the penetration effect caused by large deformation of the model by adjusting the initial gap and gap determination radius between the various components through contact setting, and solves the problem of difficult convergence caused by improving model accuracy.

[0058] 3. The present invention can automatically generate a fatigue strength verification report for the blade root bolts of a wind turbine generator set, thereby improving the efficiency of data analysis by researchers. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 This is the logic diagram of the fatigue strength analysis method for wind turbine blade root bolts.

[0060] Figure 2 Geometric model diagram of the 3D model for blade root bolt fatigue strength analysis.

[0061] Figure 3 This is a diagram of the ball bearing model in a three-dimensional model.

[0062] Figure 4 Finite element model diagram for blade root bolt fatigue strength calculation.

[0063] Figure 5 Schematic diagram of model loading and boundary conditions for fatigue strength analysis of wind turbine blade root bolts.

[0064] Figure 6 This is the model stress result diagram of the fatigue strength analysis method of the wind turbine blade root bolts.

[0065] Figure 7 The load-stress curve diagram of the fatigue strength analysis method of the wind turbine blade root bolts.

[0066] Figure 8 The model SN curve diagram of the fatigue strength analysis method of the blade root bolts of wind turbines. DETAILED DESCRIPTION

[0067] The present invention will be further described below in conjunction with specific embodiments.

[0068] Example 1

[0069] See also Figure 1 As shown, the fatigue strength analysis method of the wind turbine blade root bolt provided in this embodiment includes the following steps:

[0070] S1. Perform stress analysis on the blade root bolts of the wind turbine, establish and simplify a three-dimensional model for fatigue strength analysis of the blade root bolts, including the following steps:

[0071] Perform stress analysis on the blade root bolts of wind turbines and establish a three-dimensional model for fatigue strength analysis of blade root bolts. Figures 2 to 3As shown, the three-dimensional model components include: blade root bolt 1, pitch bearing inner ring 2, pitch bearing outer ring 3, two side ball bearings 4, middle ball bearing 5, connecting flange 6 and blade 7;

[0072] The three-dimensional model used for fatigue strength analysis of blade root bolts is simplified by removing the fillets and chamfers of components that have little influence on the force of blade root bolts, removing the hub structure, and dividing two blade root bolt force models according to the geometric structure. The geometric structure of the blade root bolts inside the blade is retained, the thread features of the blade root bolts and threaded sleeves are removed, and the rollers in the pitch bearing are retained.

[0073] S2, see Figure 4 As shown, the three-dimensional model is meshed and converted into a finite element model, the material properties of the blade root bolts and their connecting parts are defined, and the contact settings, boundary condition settings and loading settings between the various parts of the finite element model are performed, including the following steps:

[0074] After the three-dimensional model is established, it is converted into a finite element six-sided solid unit. The entire blade root bolt connection structure is meshed using hexahedral units. The dangerous parts and transition points are locally refined, and the mesh quality is checked and the mesh independence is verified. The anisotropic linear elastic material constitutive model is used for the blades, and metal materials are used for the other materials.

[0075] The contact setting is to set the connection relationship between the various components of the finite element model. The connection relationship between the blade and the connecting flange, the connection relationship between the connecting flange and the pitch bearing, the connection relationship between the pitch bearing and the bearing roller, and the connection relationship between the pitch bearing and the nut are all set to friction contact. The thread engagement relationship of the blade root bolt is set to binding contact. The connection relationship between the various components inside the blade is set to common node connection.

[0076] See also Figure 5 As shown, the boundary conditions are set to divide the loading calculation into multiple load steps, and frictionless contact conditions are applied to the cutting boundaries on both sides of the two blade root bolt models, and full constraints are applied to the bottom of the outer ring of the pitch bearing;

[0077] The loading is set to make the limit load equivalent to the axial force on the blade end, and the equivalent load is gradually applied to the blade end in multiple load steps. The finite element model is nonlinearly solved and calculated using finite element software, including:

[0078] To perform loading calculation, first apply the bolt preload, then equate the limit load to the axial force on the blade end, and gradually apply the equivalent load to the blade end through multiple load steps, as shown in the following formula:

[0079]

[0080] Among them, F is the axial force on the blade end, M is the blade root bending moment, N is the number of bolts, and D is the blade root pitch circle diameter.

[0081] S3. Based on the settings in step S2, loads are set by batch processing, and corresponding stresses of key nodes under different load conditions are obtained by finite element calculation. Load-stress curves are drawn to obtain stress responses of blade root bolts under different working conditions and loads. Figure 6 to Figure 7 As shown;

[0082] S4. The actual time series fatigue load is extracted into a Markov load spectrum using the rain flow counting method to obtain the amplitude, mean value and number of cycles required for fatigue calculation;

[0083] S5. According to the amplitude, mean value and number of cycles in the Markov load spectrum, interpolation is performed in the previously drawn load-stress curve to obtain the amplitude, mean value and number of cycles of the stress, including the following steps:

[0084] According to the amplitude, mean and number of cycles in the Markov load spectrum, interpolate the previously drawn load-stress curve to obtain the amplitude, mean and number of cycles of stress;

[0085] See also Figure 8 As shown in the figure, the double slope SN curve of the blade root bolt is calculated according to the GL specification. The slope related parameter m is 3 and 5 respectively. For the case where the nominal diameter of the bolt is greater than 30, it is multiplied by the reduction factor k. s :

[0086]

[0087] Among them, k s is the reduction factor, D is the nominal diameter of the bolt;

[0088]

[0089] Among them, Δσ A The number of cycles is 2*10 6 The stress amplitude at m is the material safety factor;

[0090]

[0091] Among them, Δσ D The number of cycles is 5*10 6 The stress amplitude at A is 2*10 6 , N D 5*10 6 .

[0092] S6. Each stress cycle causes damage to the material. The damage value is the inverse of the fatigue life under the stress. According to the damage accumulation theory, the damage values ​​obtained from each stress cycle are accumulated to finally obtain the total fatigue damage of the blade root bolt, which includes the following steps:

[0093] According to the Palmgren-Miner law, each stress cycle will cause damage to the material. The damage value is the inverse of the fatigue life under the stress. According to the damage accumulation theory, the damage value obtained from each stress cycle is accumulated to obtain the total fatigue damage of the blade root bolt, as shown in the following formula:

[0094]

[0095] Among them, N i is the allowable number of stress cycles within the i-th stress range, Δσ i is the stress amplitude in the i-th stress range;

[0096]

[0097] Where D' is the fatigue damage value of the bolt, n i is the actual number of stress cycles in the ith stress range.

[0098] S7. Generate a wind turbine blade root bolt fatigue strength verification report based on the total fatigue damage of the blade root bolts obtained in step S6.

[0099] Example 2

[0100] The wind turbine blade root bolt fatigue strength analysis system disclosed in this embodiment is used to implement the wind turbine blade root bolt fatigue strength analysis method described in Example 1, including:

[0101] The blade root bolt 3D modeling module is used to perform stress analysis on the blade root bolts of wind turbines and to establish and simplify the 3D model for fatigue strength analysis of blade root bolts.

[0102] The setting module is used to convert the three-dimensional model into a finite element model by meshing, define the material properties of the blade root bolts and their connecting parts, and perform contact settings, boundary condition settings, and loading settings between the various parts of the finite element model;

[0103] The load-stress processing module is used to batch process and set loads, and obtain the corresponding stresses of key nodes under different load conditions through finite element calculations, and draw load-stress curves;

[0104] Markov load extraction module, which uses rain flow counting method to extract time series fatigue load into Markov load spectrum, and obtains the amplitude, mean value and number of cycles required for fatigue calculation;

[0105] The interpolation module interpolates the previously drawn load-stress curve according to the amplitude, mean and number of cycles in the Markov load spectrum to obtain the amplitude, mean and number of cycles of stress;

[0106] The damage superposition module adds up the damage values ​​obtained from each stress cycle according to the damage accumulation theory to obtain the total fatigue damage of the blade root bolt;

[0107] The verification report generation module generates a wind turbine blade root bolt fatigue strength verification report based on the obtained blade root bolt total fatigue damage.

[0108] Example 3

[0109] This embodiment discloses a non-transitory computer-readable medium storing instructions. When the instructions are executed by a processor, the steps of the method for analyzing fatigue strength of blade root bolts of a wind turbine set according to Embodiment 1 are executed.

[0110] The non-temporary computer-readable medium in this embodiment may be a disk, an optical disk, a computer memory, a read-only memory (ROM), a random access memory (RAM), a USB flash drive, a mobile hard disk, or other media.

[0111] Example 4

[0112] This embodiment discloses a computing device, including a processor and a memory for storing a program executable by the processor. When the processor executes the program stored in the memory, the method for analyzing fatigue strength of blade root bolts of a wind turbine set described in Embodiment 1 is implemented.

[0113] The computing device described in this embodiment may be a desktop computer, a laptop computer, a smart phone, a PDA handheld terminal, a tablet computer, a programmable logic controller (PLC), or other terminal devices with a processor function.

[0114] The embodiments described above are only preferred embodiments of the present invention and are not intended to limit the scope of implementation of the present invention. Therefore, all changes made according to the shape and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for analyzing fatigue strength of blade root bolts of wind turbine generator set, characterized in that: The following steps are involved: S1. Perform stress analysis on the blade root bolts of wind turbines, and establish and simplify a three-dimensional model for fatigue strength analysis of blade root bolts; S2. Meshing the three-dimensional model to convert it into a finite element model, defining the material properties of the blade root bolts and their connecting parts, and performing contact settings, boundary condition settings, and loading settings between the various parts of the finite element model; S3. On the basis of the settings in step S2, loads are set by batch processing, corresponding stresses of key nodes under different load conditions are obtained by finite element calculation, load-stress curves are drawn, and stress responses of blade root bolts under different working conditions and loads are obtained; S4. The actual time series fatigue load is extracted into a Markov load spectrum using the rain flow counting method to obtain the amplitude, mean value and number of cycles required for fatigue calculation; S5, interpolating the load-stress curve drawn previously according to the amplitude, mean value and number of cycles in the Markov load spectrum to obtain the amplitude, mean value and number of cycles of the stress; S6. Each stress cycle causes damage to the material. The damage value is the inverse of the fatigue life under the stress. According to the damage accumulation theory, the damage values ​​obtained from each stress cycle are accumulated to finally obtain the total fatigue damage of the blade root bolt. S7. Generate a wind turbine blade root bolt fatigue strength verification report based on the total fatigue damage of the blade root bolts obtained in step S6.

2. A method for analyzing fatigue strength of blade root bolts of a wind turbine according to claim 1, characterized in that: The step S1 comprises the following steps: The force analysis of the blade root bolts of the wind turbine is carried out, and a three-dimensional model for fatigue strength analysis of the blade root bolts is established. The three-dimensional model used for fatigue strength analysis of the blade root bolts is simplified, the fillets and chamfers of each component that has little effect on the force of the blade root bolts are removed, the hub structure is removed, and two blade root bolt force models are divided according to the geometric structure. The geometric structure of the blade root bolt inside the blade is retained, the thread features of the blade root bolt and the threaded sleeve are removed, and the rollers in the variable pitch bearing are retained.

3. A method for analyzing fatigue strength of blade root bolts of a wind turbine according to claim 1, characterized in that: The step S2 comprises the following steps: After the three-dimensional model is established, it is converted into a finite element six-sided solid unit. The entire blade root bolt connection structure is meshed using hexahedral units. The dangerous parts and transition points are locally refined, and the mesh quality is checked and the mesh independence is verified. The anisotropic linear elastic material constitutive model is used for the blades, and metal materials are used for the other materials.

4. A wind turbine blade root bolt fatigue strength analysis method according to claim 1, characterized in that: The step S2 comprises the following steps: The contact setting is to set the connection relationship between the various components of the finite element model. The connection relationship between the blade and the connecting flange, the connection relationship between the connecting flange and the pitch bearing, the connection relationship between the pitch bearing and the bearing roller, and the connection relationship between the pitch bearing and the nut are all set to friction contact. The thread engagement relationship of the blade root bolt is set to binding contact. The connection relationship between the various components inside the blade is set to common node connection. The boundary conditions are set to divide the load calculation into multiple load steps, apply frictionless contact conditions to the cutting boundaries on both sides of the two blade root bolt models, and apply full constraints to the bottom of the outer ring of the pitch bearing; The loading is set to make the limit load equivalent to the axial force on the blade end, and the equivalent load is gradually applied to the blade end in multiple load steps. The finite element model is solved and calculated nonlinearly using finite element software.

5. A method for analyzing fatigue strength of blade root bolts of a wind turbine according to claim 4, characterized in that: The loading settings include: To perform loading calculation, first apply the bolt preload, then equate the limit load to the axial force on the blade end, and gradually apply the equivalent load to the blade end through multiple load steps, as shown in the following formula: Among them, F is the axial force on the blade end, M is the blade root bending moment, N is the number of bolts, and D is the blade root pitch circle diameter.

6. A wind turbine blade root bolt fatigue strength analysis method according to claim 1, characterized in that: The step S5 comprises the following steps: According to the amplitude, mean and number of cycles in the Markov load spectrum, interpolate the previously drawn load-stress curve to obtain the amplitude, mean and number of cycles of stress; The double slope SN curve of the blade root bolt is calculated according to the GL specification. The slope-related parameter m is 3 and 5 respectively. For the case where the nominal diameter of the bolt is greater than 30, it is multiplied by the reduction factor k. s : Among them, k s is the reduction factor, D is the nominal diameter of the bolt; Among them, Δσ A The number of cycles is 2*10 6 The stress amplitude at m is the material safety factor; Among them, Δσ D The number of cycles is 5*10 6 The stress amplitude at A is 2*10 6 , N D 5*10 6 .

7. A method for analyzing fatigue strength of blade root bolts of a wind turbine according to claim 6, characterized in that: The step S6 comprises the following steps: According to the Palmgren-Miner law, each stress cycle will cause damage to the material. The damage value is the inverse of the fatigue life under the stress. According to the damage accumulation theory, the damage value obtained from each stress cycle is accumulated to obtain the total fatigue damage of the blade root bolt, as shown in the following formula: Among them, N i is the allowable number of stress cycles within the i-th stress range, Δσ i is the stress amplitude in the i-th stress range; Where D' is the fatigue damage value of the bolt, n i is the actual number of stress cycles in the ith stress range.

8. A wind turbine blade root bolt fatigue strength analysis system, characterized in that: A method for analyzing fatigue strength of blade root bolts of a wind turbine generator set according to any one of claims 1 to 7, comprising: The blade root bolt 3D modeling module is used to perform stress analysis on the blade root bolts of wind turbines and to establish and simplify the 3D model for fatigue strength analysis of blade root bolts. The setting module is used to convert the three-dimensional model into a finite element model by meshing, define the material properties of the blade root bolts and their connecting parts, and perform contact settings, boundary condition settings, and loading settings between the various parts of the finite element model; The load-stress processing module is used to batch process and set loads, and obtain the corresponding stresses of key nodes under different load conditions through finite element calculation, and draw load-stress curves; Markov load extraction module, which uses rain flow counting method to extract time series fatigue load into Markov load spectrum, and obtains the amplitude, mean value and number of cycles required for fatigue calculation; The interpolation module interpolates the previously drawn load-stress curve according to the amplitude, mean and number of cycles in the Markov load spectrum to obtain the amplitude, mean and number of cycles of stress; The damage superposition module adds up the damage values ​​obtained from each stress cycle according to the damage accumulation theory to obtain the total fatigue damage of the blade root bolt; The verification report generation module generates a wind turbine blade root bolt fatigue strength verification report based on the obtained blade root bolt total fatigue damage.

9. A non-transitory computer-readable medium storing instructions, characterized in that: When the instruction is executed by the processor, the steps of the method for analyzing fatigue strength of blade root bolts of a wind turbine set according to any one of claims 1 to 7 are performed.

10. A computing device comprising a processor and a memory for storing a program executable by the processor, characterized in that: When the processor executes the program stored in the memory, the method for analyzing fatigue strength of blade root bolts of a wind turbine set as described in any one of claims 1 to 7 is implemented.

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