A method for dynamic optimization of offshore wind turbine jacket structure driven by virtual work principle

Abstract

The application provides a kind of offshore wind turbine jacket structure dynamic optimization method driven by virtual work principle, comprising the following steps: parameterization establishes offshore wind turbine jacket structure dynamic analysis model;Design constraint analysis is carried out, and the relationship of design constraint to design variable is deduced based on virtual work principle;With the minimum structure quality as optimization goal, optimization objective function is established;Virtual work principle dynamic optimization framework is established, and optimization algorithm is used to optimize design of offshore wind turbine jacket;The optimal structure is checked for dynamic constraint, and whether it meets the constraint condition is judged, if it meets, optimization is ended, otherwise, the size of structure unit that does not meet the constraint is manually adjusted until the structure unit meets the constraint requirement.The application does not need a large number of samples, reduces the number of time-domain dynamic analysis required for optimization, significantly improves the optimization efficiency, reduces the material consumption and construction cost under the premise of ensuring the safety and dynamic performance of the structure.

Description

Technical Field

[0001] This invention relates to the field of marine structure design technology, and more specifically, to a method for dynamic optimization of offshore wind turbine jacket structures driven by the principle of virtual work. Background Technology

[0002] As offshore wind power development moves into deeper waters, jacket structures and other supporting structures have become crucial foundations for offshore wind turbines due to their superior stability and load-bearing capacity. These structures withstand complex cyclic loads from wind, waves, and currents over extended periods, placing stringent demands on their ultimate strength, fatigue life, and dynamic performance. To ensure structural safety, traditional designs often increase the size of structural units, but this significantly increases material usage and construction costs. In offshore wind power projects, the cost of the supporting structure accounts for approximately 20% of the total cost; therefore, optimized design is essential for cost reduction.

[0003] Currently, structural optimization research on offshore wind turbine jacket structures has received widespread attention, with the core objective being to achieve economical structural design while meeting all regulatory requirements. However, this optimization is an iterative process, heavily reliant on extensive time-consuming time-domain dynamic analysis to evaluate the performance of design schemes, resulting in extremely high computational costs and significantly hindering its application in practical engineering. To improve optimization efficiency, existing methods mainly develop in two directions: one is to simplify using equivalent static loads, and the other is to use surrogate models to replace simulations. These methods alleviate the computational burden to some extent, but still have limitations in balancing accuracy and efficiency. Therefore, developing a dynamic optimization method that can guarantee both accuracy and high computational efficiency is of significant engineering importance for promoting low-cost, high-performance design of jacket structures. Summary of the Invention

[0004] Based on the problems existing in the prior art, this invention provides a dynamic optimization method for offshore wind turbine jacket structure driven by the principle of virtual work, which enables the offshore wind turbine jacket structure to reduce material usage and lower costs while meeting the specifications.

[0005] To achieve the above objectives, the technical solution adopted by this invention is as follows:

[0006] A method for dynamic optimization of offshore wind turbine jacket structure driven by the principle of virtual work, comprising the following steps:

[0007] S1. Parametrically establish a dynamic analysis model of the offshore wind turbine jacket structure;

[0008] S2. Based on the analysis model, perform design constraint analysis. Based on the principle of virtual work, derive the relationship between design constraints and design variables under design load conditions and virtual load conditions. The design constraints include the rotation angle of the wind turbine jacket platform, structural unit strength, overall frequency, and nodal fatigue constraints. Construct a diagonal matrix of structural characteristics composed of the cross-sectional area, shear area, moment of inertia of the cross section, Young's modulus, and shear modulus of the material itself, which are determined by the design variables.

[0009] S3. Establish the objective function for optimizing the wind turbine jacket structure with the goal of minimizing structural mass;

[0010] S4. Establish a dynamic optimization framework based on the principle of virtual work, and use optimization algorithms to optimize the design of offshore wind turbine jackets;

[0011] S5. Perform design constraint verification on the optimal structure. For structural units that fail the verification, manually increase the cross-sectional dimensions until the constraint requirements are met, and complete the dynamic optimization of the offshore wind turbine jacket structure.

[0012] Furthermore, the parameterized establishment of the dynamic analysis model of the offshore wind turbine jacket structure described in S1 specifically involves defining the structural dimensions and boundary conditions of the offshore wind turbine jacket.

[0013] Furthermore, in S2, the design variables are the diameter and wall thickness of the wind turbine jacket structure unit.

[0014] Furthermore, in S2, the relationship between the wind turbine jacket platform rotation angle constraint and the design variables is determined by the number of structural units, the virtual couple applied to the platform, the length of the structural units, the internal forces at the end nodes of the structural units under the extreme design loads of wind, waves and currents and the virtual loads at the platform rotation angle, and the diagonal matrix that determines the structural characteristics by the design variables. The wind turbine jacket platform rotation angle constraint is that the wind turbine jacket platform rotation angle does not exceed 0.25°.

[0015] Furthermore, in S2, the strength constraint of the kth structural element is specifically as follows:

[0016] Solve for the ratio of axial load to resistance of the kth structural element; combine the in-plane bending moment load and out-of-plane bending moment load of the kth structural element with their corresponding reduction factors and Euler yield strength, and solve for the ratio of the bending moment resistance value of the kth structural element; the sum of the last two ratios is not greater than 1 as a constraint condition;

[0017] Specifically, based on the principle of virtual work, the relationship between the axial load, in-plane bending moment load, out-of-plane bending moment load of the kth structural unit and the design variables is derived as follows: taking the length of the kth structural unit, the extreme design loads of wind, waves and current, and the internal forces at the end nodes of the unit under the virtual load condition of the kth structural unit as basic parameters, combined with the structural characteristic matrix determined by the design variables, and obtaining the explicit functional relationship between the three loads and the design variables through the unit axial displacement, in-plane rotation angle and out-of-plane rotation angle under the virtual load condition of the kth structural unit's internal forces, respectively.

[0018] Furthermore, in S2, to meet the overall frequency constraint, the relationship between the overall frequency of the wind turbine jacket structure and the design variables is established, specifically as follows:

[0019] Taking all structural units of the wind turbine jacket as the calculation object, the inertial forces of the end nodes of the structural units under the combined structural unit length, the nth-order array design load condition, and the structural characteristic matrix determined by the design variables are used to solve for the overall frequency. The overall frequency constraint requires that the overall frequency is not less than the wind turbine impeller rotation frequency and not greater than the blade passage frequency.

[0020] Furthermore, in S2, the fatigue constraints of the wind turbine jacket nodes need to be evaluated, specifically:

[0021] The cumulative fatigue damage of the wind turbine jacket node is obtained by the ratio of the number of stress cycles in all stress blocks of the wind turbine jacket node to the allowable number of cycles under the stress range. The fatigue constraint requirement of the wind turbine jacket node is that the cumulative fatigue damage of the wind turbine jacket node should not be greater than the service fatigue coefficient.

[0022] The stress range is obtained from the hot spot stress at the hot spot of the wind turbine jacket node, and the hot spot stress is obtained through the stress concentration factor, the first Axial stress of the first structural unit, the first The in-plane bending stress of the structural unit and the first The out-of-plane bending stress of each structural unit is obtained;

[0023] No. Axial stress of the first structural unit, the first The in-plane bending stress of the structural unit and the first The relationship between the out-of-plane bending stress of a structural element and the design variables is determined by the cross-sectional area of ​​the kth structural element, the section modulus of the kth bending element, the length of the kth structural element, the internal forces at the endpoints of the kth structural element under fatigue design load conditions and the internal forces at the endpoints of the kth structural element under virtual load conditions, and the diagonal matrix of structural characteristics determined by the design variables.

[0024] Furthermore, in S3, the objective function for optimizing the wind turbine jacket structure is the total mass of the wind turbine jacket, which is obtained by solving for the material density of all structural elements, the length of the structural elements, and the cross-sectional area of ​​the structural elements obtained from the design variables.

[0025] Furthermore, the virtual work principle dynamic optimization framework in S4 includes dynamic constraint boundaries and design constraint relationship updates. The dynamic constraint boundaries are: after each round of optimization, the upper and lower bounds of the constraints are dynamically adjusted according to the current value of the design variable, so that the new constraint range is within a certain interval near the current design value.

[0026] The design constraint relationship update involves updating the structural characteristic matrix based on design variables after each round of optimization, performing dynamic analysis on the current jacket design, updating the internal forces of structural unit nodes under design load conditions based on the results of the dynamic analysis, and updating the internal forces of structural unit nodes under virtual load conditions.

[0027] The optimization algorithm used is the least squares sequential quadratic programming algorithm.

[0028] A dynamic optimization system for offshore wind turbine jacket structures driven by the principle of virtual work, used to implement any of the dynamic optimization methods for offshore wind turbine jacket structures, the system comprising:

[0029] The modeling module is used to parametrically establish a dynamic analysis model of the offshore wind turbine jacket structure.

[0030] The constraint analysis module is used to perform design constraint analysis based on the analysis model. Based on the principle of virtual work, it derives the relationship between design constraints and design variables under design load conditions and virtual load conditions. The design constraints include the rotation angle of the wind turbine jacket platform, the strength of structural units, the overall frequency, and nodal fatigue constraints. It constructs a diagonal matrix of structural characteristics, which is composed of the cross-sectional area, shear area, moment of inertia of the cross section, Young's modulus, and shear modulus of the material itself, determined by the design variables.

[0031] The objective function construction module is used to establish the objective function for optimizing the wind turbine jacket structure with the goal of minimizing structural mass.

[0032] The optimization calculation module is used to establish a dynamic optimization framework based on the principle of virtual work, and to use optimization algorithms to optimize the design of offshore wind turbine jackets;

[0033] The constraint verification module is used to verify the design constraints of the optimal structure. For structural units that fail the verification, the cross-sectional dimensions need to be manually increased until the constraint requirements are met, thus completing the dynamic optimization of the offshore wind turbine jacket structure.

[0034] In summary, the present invention has the following beneficial effects:

[0035] This invention eliminates the need for a large number of samples and iterative time-domain dynamic analysis. While ensuring structural safety and dynamic performance, it significantly improves optimization efficiency, reduces material usage and construction costs, and is suitable for the efficient and lightweight design of offshore wind turbine jackets in deep-sea areas. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of a fan duct frame according to an embodiment of the present invention;

[0037] Figure 2 This invention illustrates the variation of catheter holder mass and fatigue damage with iteration count in one embodiment.

[0038] Figure 3 This invention illustrates how the mass of the catheter holder and the platform rotation angle change with the number of iterations in one embodiment.

[0039] Figure 4 The variation of the catheter framework mass and structural fundamental frequency with the number of iterations in one embodiment of the present invention;

[0040] Figure 5 The variation of the mass and structural strength of the catheter holder with the number of iterations in one embodiment of the present invention;

[0041] Figure 6 This is a flowchart of an optimization method according to an embodiment of the present invention;

[0042] Figure 7 This is a schematic diagram of extreme design load conditions for wind, wave and current on an offshore wind turbine jacket and virtual load conditions for platform rotation angle, according to an embodiment of the present invention.

[0043] Figure 8 This is a schematic diagram of the virtual load condition of the internal forces of the structural unit of the offshore wind turbine jacket structure according to an embodiment of the present invention;

[0044] Figure 9 This is a partial coordinate system schematic diagram of a offshore wind turbine jacket structure unit according to an embodiment of the present invention. Detailed Implementation

[0045] To make the technical means, creative features, objectives and effects of this invention easier to understand, the technical solutions in the specific embodiments of this invention are described clearly and completely below to further illustrate this invention. Obviously, the specific embodiments described are only a part of the embodiments of this invention, and not all of them.

[0046] Example:

[0047] This embodiment uses the jacket structure of a deep-sea offshore wind turbine in Zhejiang Province as an example to optimize its dimensions and verify the efficiency of the proposed optimization method. The turbine model used in this embodiment is a 16 MW wind turbine. The offshore wind turbine jacket structure of this embodiment is as follows: Figure 1 The diagram shows a four-legged steel pipe pile guide frame. Adjacent chord members are connected by four X-shaped struts. The pile diameter is 5 m, the wall thickness is 50 mm, and the pile length is 80 m. The dimensions of other structural units are shown in Table 2. The material density is 7850 kg / m³. 3 The Young's modulus is 206 GPa, and the Euler yield strength is 355 MPa. The extreme design load conditions for the wind turbine jacket under wind, wave, and flow conditions are: maximum wave height 25.16 m, significant wave height 13.86 m, and peak period 17.95 s. The 10-minute average wind speed at the hub height under standard air density is 60 m / s. The surface design velocity is 2.17 m / s, and the bottom design velocity is 0.30 m / s. Figure 9 As shown, the local coordinate system xyz of the structural unit in this embodiment is set as follows: the x-axis is along the length of the structural unit, and the y-axis and z-axis are perpendicular to the x-axis and mutually perpendicular, forming a local plane of the unit section; the fatigue load conditions are shown in Table 1:

[0048] Table 1:

[0049]

[0050] The implementation process of the case is as follows:

[0051] A method for dynamic optimization of offshore wind turbine jacket structures driven by the principle of virtual work is provided, the steps of which include:

[0052] S1. Parametrically establish a dynamic analysis model of the offshore wind turbine jacket structure;

[0053] S2. Based on the analysis model, perform design constraint analysis. Based on the principle of virtual work, derive the relationship between design constraints and design variables under design load conditions and virtual load conditions. The design constraints include the rotation angle of the wind turbine jacket platform, structural unit strength, overall frequency, and nodal fatigue constraints. Construct a diagonal matrix of structural characteristics composed of the cross-sectional area, shear area, moment of inertia of the cross section, Young's modulus, and shear modulus of the material itself, which are determined by the design variables.

[0054] S3. Establish the objective function for optimizing the wind turbine jacket structure with the goal of minimizing structural mass;

[0055] S4. Establish a dynamic optimization framework based on the principle of virtual work, and use optimization algorithms to optimize the design of offshore wind turbine jackets;

[0056] S5. Perform design constraint verification on the optimal structure. For structural units that fail the verification, manually increase the cross-sectional dimensions until the constraint requirements are met, and complete the dynamic optimization of the offshore wind turbine jacket structure.

[0057] The parameterized establishment of the dynamic analysis model of the offshore wind turbine jacket structure described in S1 specifically involves defining the structural dimensions, structural unit connection methods, and boundary conditions of the offshore wind turbine jacket.

[0058] The design variables are the diameter and wall thickness of the wind turbine jacket structure unit.

[0059] In S2, the wind turbine jacket platform corner The relationship between the rotation angle constraint of the wind turbine jacket platform and the design variables, not exceeding 0.25°, is as follows:

[0060] ;

[0061] In the formula, N represents the number of structural units of the offshore wind turbine jacket. For the corner of the wind turbine jacket platform, This represents the virtual couple applied to the wind turbine jacket platform, such as Figure 7 As shown, This represents the length of the k-th structural unit. and Let i and j represent the internal forces at nodes i and j of the k-th structural element under extreme design load conditions of wind, waves, and current, where nodes i and j are the endpoints of the k-th structural element. and This represents the internal forces at nodes i and j of the k-th structural element under the virtual load condition of platform corner rotation. Represents the structural characteristic matrix;

[0062] The structural characteristic matrix is ​​shown in the following formula:

[0063] ;

[0064] In the formula, diag represents a diagonal matrix, and E and G represent the first and second diagonal matrices, respectively. Young's modulus and shear modulus of the material of each structural unit , , They represent the first The cross-sectional area of ​​each structural unit section, and the shear area along the local y-axis and z-axis; , , They represent the circumference of the first... The local moments of inertia of the cross sections along the x, y, and z axes of each structural unit. , , , , , All were determined through design variables.

[0065] In S2, the strength constraint of the kth structural element is specifically as follows:

[0066] ;

[0067] In the formula, Let be the strength utilization coefficient of the k-th structural unit. and They represent the first Axial load and resistance of each structural unit and They represent the first The reduction factor of each structural unit along the local y-axis and z-axis; and They represent the first Euler yield strength of each structural element along the local y-axis and z-axis; and They represent the first In-plane bending moment load and out-of-plane bending moment load of each structural unit; Indicates the first Bending moment resistance value of each structural unit;

[0068] To satisfy the first Strength constraints for the first structural unit are established. The relationship between the axial load, in-plane bending moment load and out-of-plane bending moment load of each structural unit and the design variables;

[0069] ;

[0070] In the formula, and Let i be the internal forces at nodes i and j of the k-th structural element under the virtual load case of the structural element internal forces, such as Figure 8 As shown, , and These represent the first and second virtual load cases of internal forces in the structural unit, respectively. The unit axial displacement, in-plane rotation angle, and out-of-plane rotation angle of each structural unit.

[0071] To meet the overall frequency constraints, the relationship between the overall frequency of the wind turbine jacket structure and design variables is established:

[0072] ;

[0073] In the formula, and These represent the inertial forces at nodes i and j of the k-th structural unit under the n-th order array design load condition, respectively.

[0074] The fatigue constraints of the wind turbine jacket nodes need to be evaluated, specifically:

[0075]

[0076] In the formula, D represents the cumulative fatigue damage of the wind turbine jacket joint. and m represent the intercept and slope of the SN stress-life curve of the wind turbine jacket, respectively. Indicates the number of stress blocks. and They represent the first The number and range of stress cycles in each stress block The allowed number of loops; and These represent the fatigue coefficient used and the design fatigue coefficient, respectively.

[0077] For the SN stress-life curve, when N 1.8×10 6 During cycles, =12.18, m=3; when N>1.8×10 6 During cycles, =16.13, m=5;

[0078] Stress range The stress was obtained by calculating the hot spot stress at eight hot spots in the wind turbine jacket support node;

[0079] ;

[0080] In the formula, This represents the stress concentration factor at the crown point. This represents the stress concentration factor at the saddle point. and These represent the stress concentration factors for in-plane and out-of-plane bending loads, respectively. Indicates the first Axial stress of each structural unit and They represent the first In-plane and out-of-plane bending stress of each structural unit; - Indicates the first Hot spot stress at 8 hot spots in each structural unit.

[0081] Establish the first The relationship between the stress at the nodes of each structural unit and the design variables;

[0082] ;

[0083] In the formula, and They represent the first The section modulus of bending of each structural element along the local y and z axes; and The internal forces at nodes i and j of the k-th structural element under fatigue design load conditions.

[0084] Establish the objective function for optimizing the wind turbine jacket structure:

[0085] ;

[0086] In the formula, This represents the objective function to be optimized. Indicates the first Material density of each structural unit; Indicates design variables;

[0087] Establish constraint functions for optimizing the wind turbine jacket structure;

[0088] ;

[0089] In the formula, and These represent the impeller rotation frequency and the blade passage frequency, respectively. and These represent the lower and upper limits of the design variable's value, respectively.

[0090] The virtual work principle dynamic optimization framework in step 4 includes dynamic constraint boundaries and design constraint relationship updates. The dynamic constraint boundaries are: after each round of optimization, the upper and lower bounds of the constraints are dynamically adjusted according to the current value of the design variable, so that the new constraint range is within a certain range near the current design value.

[0091] The design constraint relationship update involves updating the structural characteristic matrix based on design variables after each round of optimization, performing dynamic analysis on the current jacket design, updating the internal forces of structural unit nodes under design load conditions based on the results of the dynamic analysis, and updating the internal forces of structural unit nodes under virtual load conditions.

[0092] The optimization algorithm used is the least squares sequential quadratic programming algorithm.

[0093] The optimal structure needs to be checked for design constraints. For structural elements that do not meet the constraints, the cross-sectional dimensions should be increased until the structural element meets the constraints.

[0094] Depend on Figures 2-5It can be seen that after 10 rounds of optimization, the jacket mass reached 2673 tons, at which point the nodal fatigue coefficient was 0.88, close to the fatigue constraint boundary. The optimally designed jacket platform had a maximum rotation angle of 0.216°, a UC value of 0.49, and a natural frequency of 0.2145, all meeting the specification requirements. Table 2 shows the jacket optimization results: the initial mass of the jacket was 2956 tons, which was reduced to 2673 tons after optimization, a reduction of 283 tons, or approximately 9.6%. This demonstrates that the present invention effectively reduced the mass of the wind turbine jacket.

[0095] Table 2:

[0096]

[0097] Compared to data-driven alternative model-assisted structural optimization methods, the proposed method eliminates the need for sample preparation. Instead, it relies on an explicit constraint model driven by the virtual work principle for rapid constraint evaluation during optimization, thereby reducing the number of required ensemble dynamic analyses and improving computational efficiency. Data-driven alternative models, such as Gaussian process regression models, can be optimized using 200 pipe rack samples. In contrast, the proposed method requires only 10 such samples, reducing computational costs by 95% and demonstrating a significant efficiency improvement. Therefore, the proposed optimization framework effectively improves computational efficiency, providing a sample-free, analytical alternative to traditional data-driven alternative model methods.

[0098] This invention designs a dynamic optimization system for offshore wind turbine jacket structures driven by the principle of virtual work, the system comprising:

[0099] The modeling module is used to parametrically establish a dynamic analysis model of the offshore wind turbine jacket structure.

[0100] The constraint analysis module is used to perform design constraint analysis based on the analysis model. Based on the principle of virtual work, it derives the relationship between design constraints and design variables under design load conditions and virtual load conditions. The design constraints include the rotation angle of the wind turbine jacket platform, the strength of structural units, the overall frequency, and nodal fatigue constraints. It constructs a diagonal matrix of structural characteristics, which is composed of the cross-sectional area, shear area, moment of inertia of the cross section, Young's modulus, and shear modulus of the material itself, determined by the design variables.

[0101] The objective function construction module is used to establish the objective function for optimizing the wind turbine jacket structure with the goal of minimizing structural mass.

[0102] The optimization calculation module is used to establish a dynamic optimization framework based on the principle of virtual work, and to use optimization algorithms to optimize the design of offshore wind turbine jackets;

[0103] The constraint verification module is used to verify the design constraints of the optimal structure. For structural units that fail the verification, the cross-sectional dimensions need to be manually increased until the constraint requirements are met, thus completing the dynamic optimization of the offshore wind turbine jacket structure.

Claims

1. A method for dynamic optimization of offshore wind turbine jacket structure driven by the principle of virtual work, characterized by the following steps: include: S1. Parametrically establish a dynamic analysis model of the offshore wind turbine jacket structure; S2. Based on the analysis model, perform design constraint analysis. Based on the principle of virtual work, derive the relationship between design constraints and design variables under design load conditions and virtual load conditions. The design constraints include the rotation angle of the wind turbine jacket platform, structural unit strength, overall frequency, and nodal fatigue constraints. Construct a diagonal matrix of structural characteristics composed of the cross-sectional area, shear area, moment of inertia of the cross section, Young's modulus, and shear modulus of the material itself, which are determined by the design variables. S3. Establish the objective function for optimizing the wind turbine jacket structure with the goal of minimizing structural mass; S4. Establish a dynamic optimization framework based on the principle of virtual work, and use optimization algorithms to optimize the design of offshore wind turbine jackets; S5. Perform design constraint verification on the optimal structure. For structural units that fail the verification, manually increase the cross-sectional dimensions until the constraint requirements are met, and complete the dynamic optimization of the offshore wind turbine jacket structure. In S2, the strength constraint of the kth structural element is specifically as follows: Solve for the ratio of axial load to resistance of the kth structural element; combine the in-plane bending moment load and out-of-plane bending moment load of the kth structural element with their corresponding reduction factors and Euler yield strength, and solve for the ratio of the bending moment resistance value of the kth structural element; the sum of the last two ratios is not greater than 1 as a constraint condition; Specifically, the relationship between the axial load, in-plane bending moment load, and out-of-plane bending moment load of the kth structural unit and the design variables is derived based on the principle of virtual work. Specifically, the length of the kth structural unit, the extreme design loads of wind, waves and current, and the internal forces at the end nodes of the unit under the virtual load condition of the kth structural unit are used as basic parameters. Combined with the diagonal matrix of structural characteristics determined by the design variables, and through the unit axial displacement, in-plane rotation angle and out-of-plane rotation angle under the virtual load condition of the kth structural unit, the explicit functional relationship between the three loads and the design variables is obtained.

2. The method according to claim 1, characterized in that, The parameterized establishment of the dynamic analysis model of the offshore wind turbine jacket structure described in S1 specifically involves defining the structural dimensions and boundary conditions of the offshore wind turbine jacket.

3. The method according to claim 1, characterized in that, In S2, the design variables are the diameter and wall thickness of the wind turbine jacket structure unit.

4. The method according to claim 1, characterized in that, In S2, the relationship between the wind turbine jacket platform rotation angle constraint and the design variables is determined by the number of structural units, the virtual couple applied to the platform, the length of the structural units, the internal forces at the end nodes of the structural units under the extreme design loads of wind, waves and current and the virtual loads at the platform rotation angle, and the diagonal matrix that determines the structural characteristics by the design variables. The wind turbine jacket platform rotation angle constraint is that the wind turbine jacket platform rotation angle does not exceed 0.25°.

5. The method according to claim 1, characterized in that, In S2, to meet the overall frequency constraint, the relationship between the overall frequency of the wind turbine jacket structure and the design variables is established, specifically as follows: Taking all structural units of the wind turbine jacket as the calculation object, the inertial forces of the end nodes of the structural units under the nth-order array design load condition are combined with the structural characteristic diagonal matrix determined by the design variables to obtain the overall frequency. The overall frequency constraint requires that the overall frequency is not less than the wind turbine impeller rotation frequency and not greater than the blade passage frequency.

6. The method according to claim 1, characterized in that, In S2, the fatigue constraints of the wind turbine jacket nodes need to be evaluated, specifically: The cumulative fatigue damage of the wind turbine jacket node is obtained by the ratio of the number of stress cycles in all stress blocks of the wind turbine jacket node to the allowable number of cycles under the stress range. The fatigue constraint requirement of the wind turbine jacket node is that the cumulative fatigue damage of the wind turbine jacket node should not be greater than the service fatigue coefficient. The stress range is obtained from the hot spot stress at the hot spot of the wind turbine jacket node, and the hot spot stress is obtained through the stress concentration factor, the first Axial stress of the first structural unit, the first The in-plane bending stress of the structural unit and the first The out-of-plane bending stress of each structural unit is obtained; No. Axial stress of the first structural unit, the first The in-plane bending stress of the structural unit and the first The relationship between the out-of-plane bending stress of a structural element and the design variables is determined by the cross-sectional area of ​​the kth structural element, the section modulus of the kth bending element, the length of the kth structural element, the internal forces at the endpoints of the kth structural element under fatigue design load conditions and the internal forces at the endpoints of the kth structural element under virtual load conditions, and the diagonal matrix of structural characteristics determined by the design variables.

7. The method according to claim 1, characterized in that, In S3, the objective function for optimizing the wind turbine jacket structure is the total mass of the wind turbine jacket, which is obtained by solving for the material density, length, and cross-sectional area of ​​all structural elements obtained from the design variables.

8. The method according to claim 1, characterized in that, The virtual work principle dynamic optimization framework in S4 includes dynamic constraint boundaries and design constraint relationship updates. The dynamic constraint boundaries are: after each round of optimization, the upper and lower bounds of the constraints are dynamically adjusted according to the current value of the design variable, so that the new constraint range is within a certain interval near the current design value. The design constraint relationship update involves updating the diagonal matrix of structural characteristics based on design variables after each round of optimization, performing dynamic analysis on the current jacket design, updating the internal forces of structural unit nodes under design load conditions based on the results of the dynamic analysis, and updating the internal forces of structural unit nodes under virtual load conditions. The optimization algorithm used is the least squares sequential quadratic programming algorithm.

9. A dynamic optimization system for offshore wind turbine jacket structure driven by the principle of virtual work, characterized in that, The system for implementing the dynamic optimization method for offshore wind turbine jacket structure according to any one of claims 1-8 comprises: The modeling module is used to parametrically establish a dynamic analysis model of the offshore wind turbine jacket structure. The constraint analysis module is used to perform design constraint analysis based on the analysis model. Based on the principle of virtual work, it derives the relationship between design constraints and design variables under design load conditions and virtual load conditions. The design constraints include the rotation angle of the wind turbine jacket platform, the strength of structural units, the overall frequency, and nodal fatigue constraints. It constructs a diagonal matrix of structural characteristics, which is composed of the cross-sectional area, shear area, moment of inertia of the cross section, and Young's modulus and shear modulus of the material itself, determined by the design variables. The objective function construction module is used to establish the objective function for optimizing the wind turbine jacket structure with the goal of minimizing structural mass. The optimization calculation module is used to establish a dynamic optimization framework based on the principle of virtual work, and to use optimization algorithms to optimize the design of offshore wind turbine jackets; The constraint verification module is used to verify the design constraints of the optimal structure. For structural units that fail the verification, the cross-sectional dimensions need to be manually increased until the constraint requirements are met, thus completing the dynamic optimization of the offshore wind turbine jacket structure.

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