Reliability calculation method and system for corrosion fatigue life of offshore wind power structures considering wind turbine operation and its application

Abstract

The application discloses a kind of offshore wind power structure corrosion fatigue life reliability calculation method and system considering fan operation effect, comprising: external load determination, structure corresponding calculation, stress time history calculation, statistical parameter calculation, and reliability calculation.The method can consider the operation of offshore wind turbine in service state, reflect the influence of load randomness, material performance randomness, corrosion degree randomness, and then realize the corrosion fatigue reliability analysis of offshore wind power structure considering fan operation effect.The method and system of the application can be used for the remaining life reliability evaluation of existing offshore wind power structure after corrosion fatigue, and can also provide effective reference for the reliability design process of offshore wind power structure with corrosion fatigue problem.

Description

Technical Field

[0001] The present invention relates to a method for calculating the corrosion fatigue reliability of an offshore wind power structure, and in particular to a method and system for calculating the corrosion fatigue life reliability of an offshore wind power structure taking into account the operation of a wind turbine, and applications thereof. Background Art

[0002] Against the backdrop of global carbon neutrality, offshore wind power has experienced significant development. During their service life, offshore wind turbine structures are subjected to long-term alternating loads such as wind loads, wave loads, and turbine vibrations, leading to cumulative fatigue damage. Furthermore, due to the harsh corrosive nature of their service environment, offshore wind turbines also face the challenge of corrosion. The significant coupling between corrosion and fatigue further degrades their service life. Therefore, research on the corrosion fatigue of offshore wind turbine structures is warranted. Current simulation methods for the corrosion fatigue life of offshore wind turbines often fail to consider the effects of turbine operation and the deteriorating effects of corrosion on fatigue life. This leads to unsafe estimates of the corrosion fatigue life of offshore wind turbine structures under environmental corrosion. Furthermore, existing calculation methods fail to account for the randomness of loads, material properties, and corrosion severity, resulting in a lack of reliable calculation methods for the corrosion fatigue reliability of offshore wind turbine structures. Therefore, to investigate the corrosion fatigue performance of offshore wind turbine structures under service conditions and to study their corrosion fatigue reliability over different service years, a calculation method for the corrosion fatigue reliability of offshore wind turbine structures that considers the effects of turbine operation is needed. Summary of the Invention

[0003] To overcome the shortcomings of the existing technology, the present invention provides a method for calculating the corrosion fatigue life reliability of offshore wind turbine structures, taking into account the effects of wind turbine operation, and its application. The method can take into account the operational effects of offshore wind turbines in service, reflecting the influence of load randomness, material property randomness, and corrosion degree randomness, thereby enabling corrosion fatigue reliability analysis of offshore wind turbine structures taking into account wind turbine operation. The present invention can be used to assess the remaining life reliability of existing offshore wind turbine structures subjected to corrosion fatigue after service, and can also provide an effective reference for the reliability design process of offshore wind turbine structures with corrosion fatigue issues.

[0004] The present invention provides a method and system for calculating the corrosion fatigue life reliability of offshore wind power structures taking into account the effects of wind turbine operation, including:

[0005] (a) Determine environmental load parameters based on the offshore wind power station service location and generate a wind farm with a duration of dT;

[0006] (b) Calculate the structural response of offshore wind turbines within dT time under the wind-wave-structure-wind turbine coupling based on OpenFAST, and extract the displacement and force boundary conditions of the tower top;

[0007] (c) Establish a refined finite element model of the structure in ABAQUS. Input the boundary conditions extracted in step (b) at the top of the tower. Calculate the stress response of the structure within time dT. Identify fatigue risk locations based on stress distribution characteristics. Extract the stress time history S(t) at these locations. Calculate the equivalent stress amplitude S and the number of actions N within time dT using the rain flow counting method.

[0008] (d) Repeat steps (a) to (c) n times to obtain n sets of stress time histories S(t)1 to S(t) n And the corresponding equivalent stress amplitude and number of actions (S, N) 1～n ;

[0009] (e) According to (S,N) 1～n Calculate and determine the statistical parameters of fatigue load;

[0010] (f) Determine the parameters and statistical characteristics of the material corrosion fatigue damage evolution model based on fatigue life data of steel in corrosive environments or corrosion fatigue test results that consider the corrosion fatigue coupling effect and the unified development in the time dimension;

[0011] (g) Carry out corrosion fatigue damage calculation in MATLAB, and conduct corrosion fatigue reliability analysis by combining the Monte Carlo method and the load and material statistical characteristics determined in steps (e) and (f).

[0012] According to a specific embodiment, in step (a), determining environmental load information based on the offshore wind power service location includes:

[0013] (1) Wave and current characteristics, i.e., average seawater velocity and wave height;

[0014] (2) Wind field information, i.e., average wind speed, fluctuating wind speed, turbulence density, etc.;

[0015] According to a specific embodiment, in step (a), the wind field can be artificially generated based on an empirical spectrum or obtained through measured data;

[0016] According to a specific embodiment, in the step (b), a rod system model is established in OpenFAST according to the geometry and material of the analyzed structure;

[0017] According to a specific embodiment, in step (b), the wave current and wind field determined in (a) are introduced;

[0018] According to a specific embodiment, in step (b), the wind turbine mass, power and control are set according to the parameters of the wind turbine unit of the analyzed structure;

[0019] According to a specific embodiment, in step (b), the OpenFAST software is used to calculate the structural response of the offshore wind power structure under the wind-wave-current-turbine operating state within the dT time, and the time history curve of the boundary conditions at the top of the tower within the dT time is extracted, including all the displacement boundary and force boundary of the tower top;

[0020] According to a specific embodiment, in step (c), a refined finite element model of the structure is established in ABAQUS, considering the corrosion development and distribution characteristics of the structure;

[0021] According to a specific embodiment, in step (c), in the ABAQUS model, the boundary condition time history within the dT time extracted from the OpenFAST calculation results is applied at the top of the tower, realizing the simplified consideration of the load condition and the refined consideration of the stress distribution;

[0022] According to a specific embodiment, in step (c), according to the ABAQUS calculation results, the stress distribution of the structure is analyzed, the corrosion fatigue dangerous position is identified in combination with the structure category, and the stress time history S(t) within the dT time is extracted;

[0023] According to a specific embodiment, in step (c), the stress time history S(t) is counted based on the rainflow counting method, and the equivalent stress amplitude S and the action frequency N at the fatigue vulnerable position within the dT time are determined;

[0024] According to a specific embodiment, in step (d), steps (a)-(c) are repeated n times to obtain n groups of stress time histories S(t)1-S(t) n and the corresponding equivalent stress amplitude and action frequency (S, N) 1～n ;

[0025] According to a specific embodiment, in step (e), according to n groups of equivalent stress amplitude and action frequency (S, N) 1～n , the load characteristic statistical parameters are determined, including the standard deviation and the average value of the equivalent stress amplitude S and the action frequency N;

[0026] According to a specific embodiment, in step (f), the material damage evolution model P under each corrosion degree is determined through the corrosion fatigue test data, and the statistical characteristics of each parameter are determined, including the standard deviation and the average value. When there is no corrosion fatigue test data, the data values can be referred to the specifications and existing literature;

[0027] According to a specific embodiment, in step (f), the material damage evolution model P under each corrosion degree can be established based on the linear damage accumulation criterion or based on the continuum mechanics. When there is no corrosion fatigue test data, the corrosion fatigue test data under the same corrosion environment can be fitted and determined according to the existing literature.

[0028] According to a specific embodiment, in step (g), based on MATLAB software, the equivalent stress amplitude S and the standard deviation and mean value of the number of actions N determined in step (e) are randomly generated, the material damage evolution model parameters are randomly generated and the damage dD generated under the action of (S, N) in dT time is calculated through the damage evolution model and the parameter statistical characteristics determined in step (f), and the calculation of dD is repeated until the total damage D＝ ∑ dD＝1 At this time, the service life of the fan is T＝ ∑ dT ;

[0029] According to a specific embodiment, in step (g), based on the Monte Carlo method, the reliability analysis is carried out, the steps described in the preceding are repeated m times, m service lives T of the fan are obtained, and statistical analysis is performed on T to obtain the distribution characteristics and reliability indicators thereof.

[0030] The technical scheme of the present application has the following advantages: the method can consider the coupling of wind-wave flow-structure-fan operation, and the corrosion fatigue damage position identification and stress time history calculation are realized through ABAQUS refined finite element analysis. The method realizes the joint consideration of load randomness, material randomness and corrosion randomness in the reliability analysis process, and can realize the corrosion fatigue reliability calculation of offshore wind power structure considering the operation of the fan; the method can be used for residual corrosion fatigue life reliability evaluation of existing offshore wind power structure, and can also be used for corrosion fatigue life reliability design of newly built offshore wind power structure. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 A flow chart of a method and system for calculating the corrosion fatigue life reliability of offshore wind power structure considering the operation of the fan;

[0032] Figure 2 A schematic diagram of a wind farm;

[0033] Figure 3 A schematic diagram of an offshore wind power model established in OpenFAST;

[0034] Figure 4 A schematic diagram of wave flow time history;

[0035] Figure 5 A schematic diagram of fan operation power;

[0036] Figure 6 A schematic diagram of tower top displacement time history;

[0037] Figure 7 This is a schematic diagram of the time history of the force boundary at the top of the tower;

[0038] Figure 8 Establish a detailed finite element diagram for offshore wind power in ABAQUS;

[0039] Figure 9 Schematic diagram of stress distribution and fatigue-vulnerable location identification of offshore wind power structures;

[0040] Figure 10 This is a schematic diagram of stress history at the fatigue vulnerable position;

[0041] Figure 11 This is a statistical diagram of stress amplitude using the rainflow counting method;

[0042] Figure 12 This is a schematic diagram of the corrosion fatigue life distribution of offshore wind power structures;

[0043] Figure 13 Schematic diagram of reliability analysis of corrosion fatigue life of offshore wind power structures. DETAILED DESCRIPTION

[0044] The present invention will be further described below with reference to the accompanying drawings.

[0045] The present invention discloses a method and system for calculating the reliability of corrosion fatigue life of offshore wind power structures taking into account the operation of wind turbines. The specific process is as follows: Figure 1 As shown. The first step is to determine the environmental load parameters according to the service location of the offshore wind power plant and generate a wind field with a duration of dT; the second step is to calculate the structural response of the offshore wind power plant within dT time under the coupling of wind-wave-structure-wind turbine based on OpenFAST, and extract the displacement and force boundary conditions of the tower top; the third step is to establish a structural refined finite element model in ABAQUS, input the boundary conditions extracted in step (b) at the top of the tower, calculate the stress response of the structure within dT time, identify the fatigue risk position according to the stress distribution characteristics, extract the stress time history S(t) here, and calculate the equivalent stress amplitude S and the number of actions N within dT time by combining the rain flow counting method; the fourth step is to repeat steps (a) to (c) n times to obtain n groups of stress time histories S(t)1 to S(t) n And the corresponding equivalent stress amplitude and number of actions (S, N) 1～n ; Step 5, according to (S, N) 1～n Calculate and determine the statistical parameters of fatigue loads; Step 6: Determine the parameters of the material corrosion fatigue damage evolution model and its statistical characteristics based on the fatigue life data of steel in a corrosive environment or the corrosion fatigue test results that consider the corrosion fatigue coupling effect and the unified development in the time dimension; Step 7: Carry out corrosion fatigue damage calculation in MATLAB, and conduct corrosion fatigue reliability analysis in combination with the Monte Carlo method and the load and material statistical characteristics determined in steps (e) and (f).

[0046] The wind field can be generated by Turbsim software according to Kaimal spectrum, such as Figure 2 shown.

[0047] According to the structural design dimensions, a bar model is established in OpenFAST, such as Figure 3 shown.

[0048] Wave flow and wind field are introduced into the OpenFAST model. Wave flow is as follows: Figure 4 shown.

[0049] According to the structural wind turbine parameters, the wind turbine quality, power and control are set, and the power generation is as follows: Figure 5 shown.

[0050] Use OpenFAST software to calculate the structural response of offshore wind turbine structures under the wind-wave-wind turbine operation state within dT time, and extract the time history curve of the tower top boundary condition within dT time, including the displacement boundary time history of all degrees of freedom of the tower top, such as Figure 6 As shown, and the force boundary time history, as Figure 7 shown.

[0051] A refined finite element model of offshore wind power structure excluding wind turbines is established in ABAQUS, such as Figure 8 As shown in the figure, the boundary condition time history within the dT time extracted from the OpenFAST calculation results is applied to the tower top to simplify the load conditions and refine the stress distribution.

[0052] According to the calculation results of ABAQUS, the structural stress distribution is analyzed, such as Figure 9 As shown in the figure, combined with the structural category, the corrosion fatigue dangerous position is identified and the stress history S(t) within the dT time is extracted, as shown in the figure. Figure 10 shown.

[0053] According to a specific embodiment, in step (c), the stress time history S(t) is statistically analyzed based on the rain flow counting method, such as Figure 11 As shown, determine the equivalent stress amplitude S and the number of actions N at the fatigue vulnerable position within the time dT.

[0054] According to a specific embodiment, in step (d), steps (a) to (c) are repeated n times to obtain n groups of dT time-length internal stress time histories S(t)1 to S(t) n And the corresponding equivalent stress amplitude and number of actions (S, N) 1～n .

[0055] According to a specific embodiment, in step (e), according to n groups of equivalent stress amplitudes and action times (S, N) 1～n, determine the load characteristic statistical parameters, including the standard deviation and average value of the equivalent stress amplitude S and the number of actions N.

[0056] According to a specific embodiment, in the step (f), the material damage evolution model P under each corrosion degree is determined based on the fatigue life data of steel in a corrosive environment or the corrosion fatigue test results that consider the corrosion fatigue coupling effect and develop a unified time dimension, and the statistical characteristics of each parameter are determined, including the standard deviation and the mean. When the corrosion fatigue test data is not available, the fatigue test data after corrosion in the same corrosive environment in the existing literature can be used for fitting and determination.

[0057] According to a specific embodiment, in step (f), the material damage evolution model P at each corrosion degree can be established based on a linear damage accumulation criterion or based on continuum mechanics.

[0058] According to a specific implementation method, in step (g), based on MATLAB software, the equivalent stress amplitude and the number of actions (S, N) within the time dT are randomly generated through the standard deviation and the average value of the equivalent stress amplitude S and the number of actions N determined in step (e). The damage evolution model and parameter statistical characteristics under each corrosion degree determined in step (f) are used to randomly generate material damage evolution model parameters and calculate the damage dD generated under the action of (S, N) within the time dT. The calculation of dD is repeated until the total damage D = ΣdD = 1, at which point the service life of the wind turbine is T = ΣdT.

[0059] According to a specific embodiment, in step (g), reliability analysis is performed based on the Monte Carlo method, and the steps described in the previous paragraph are repeated m times to obtain the service life T of m wind turbines, and statistical analysis is performed on T to obtain its distribution characteristics, such as Figure 12 As shown in Figure 13 shown.

[0060] The method takes into account the coupled effects of wind, wave flow, structure, and wind turbine operation, and enables corrosion fatigue damage location identification and stress history calculation through refined finite element analysis in ABAQUS. During the reliability analysis, the method considers load randomness, material randomness, and corrosion randomness, enabling corrosion fatigue reliability calculation of offshore wind turbine structures that considers wind turbine operation. The method can be used for both residual corrosion fatigue life reliability assessment of existing offshore wind turbine structures and for corrosion fatigue life reliability design of new offshore wind turbine structures.

Claims

1. A reliability calculation method for corrosion fatigue life of offshore wind power structures considering wind turbine operation is characterized by: The method takes into account the load history of offshore wind turbine jackets under the effects of wind, wave, structure, and wind turbine operation, and combines refined finite element model analysis to achieve corrosion fatigue damage location identification and corrosion fatigue reliability calculation; the method includes: (a) Determine environmental load parameters based on the offshore wind power station service location and generate a wind farm with a duration of dT; (b) Calculate the structural response of offshore wind turbines within dT time under the wind-wave-structure-wind turbine coupling based on OpenFAST, and extract the displacement and force boundary conditions of the tower top; (c) Establish a refined finite element model of the structure in ABAQUS. Input the boundary conditions extracted in step (b) at the top of the tower. Calculate the stress response of the structure within time dT. Identify fatigue risk locations based on stress distribution characteristics. Extract the stress time history S(t) at these locations. Calculate the equivalent stress amplitude S and the number of actions N within time dT using the rain flow counting method. (d) Repeat steps (a) to (c) n times to obtain n sets of stress time histories S(t)1 to S(t) n And the corresponding equivalent stress amplitude and number of actions (S, N) 1～n ; (e) According to (S,N) 1～n Calculate and determine the statistical parameters of fatigue load; (f) Determine the parameters and statistical characteristics of the material corrosion fatigue damage evolution model based on fatigue life data of steel in corrosive environments or corrosion fatigue test results that consider the corrosion fatigue coupling effect and the unified development in the time dimension; (g) Corrosion fatigue damage calculations were performed in MATLAB. Combining the Monte Carlo method with the load and material statistical characteristics determined in steps (e) and (f), corrosion fatigue reliability analysis was performed.

2. The method according to claim 1, wherein The environmental load parameters in step (a) include: (1) Wave and current characteristics, including average seawater velocity and wave height; (2) Wind field information, including average wind speed, fluctuating wind speed, and turbulence density; or Wherein, in step (a), the wind field can be artificially generated according to the empirical spectrum or obtained through measured data.

3. The method according to claim 1, wherein In step (b), a bar model is created in OpenFAST based on the geometry and materials of the structure being analyzed; or wherein, in step (b), the wave current and wind field determined in (a) are introduced; or Wherein, in step (b), the wind turbine quality, power and control are set according to the parameters of the wind turbine unit of the analyzed structure; or Among them, in step (b), OpenFAST is used to calculate the structural response of the offshore wind power structure within dT time under the wind-wave flow-wind turbine operation state, and the time history curve of the tower top boundary condition within dT time is extracted, including the displacement boundary and force boundary of all degrees of freedom of the tower top.

4. The method according to claim 1, wherein In step (c), a refined finite element model of the structure is established in ABAQUS, taking into account the development and distribution characteristics of structural corrosion; or wherein, in step (c), in ABAQUS, the boundary condition time history within the time dT extracted from the OpenFAST calculation results in (b) is applied at the top of the tower to simplify the load conditions and refine the stress distribution; or Wherein, in step (c), according to the calculation results of ABAQUS, the structural stress distribution is analyzed, and the corrosion fatigue hazardous position is identified in combination with the structural type, and the stress history S(t) within the time dT is extracted; or In step (c), the stress history S(t) is statistically analyzed based on the rain flow counting method to determine the equivalent stress amplitude S and the number of actions N at the fatigue vulnerable position within the time dT.

5. The method according to claim 1, wherein In step (d), repeat steps (a) to (c) n times to obtain n groups of dT duration internal stress time histories S(t)1 to S(t) n And the corresponding equivalent stress amplitude and number of actions (S, N) 1～n .

6. The method according to claim 1, characterized in that In step (e), according to n groups of equivalent stress amplitudes and action times (S, N) 1～n , determine the load characteristic statistical parameters, including the standard deviation and average value of the equivalent stress amplitude S and the number of actions N.

7. The method according to claim 1, characterized in that In step (f), the material damage evolution model P under each corrosion degree is determined based on the corrosion fatigue test data and continuum mechanics, and the statistical characteristics of each parameter are determined, including the standard deviation and mean. When the corrosion fatigue test data is not available, the fatigue test data after corrosion under the same corrosion environment in the existing literature can be used for fitting and determination.

8. The method according to claim 1, wherein In step (g), based on MATLAB software, the equivalent stress amplitude and the number of actions (S, N) within the time dT are randomly generated by the standard deviation and the average value of the equivalent stress amplitude S and the number of actions N determined in step (e), and the damage evolution model and parameter statistical characteristics under each corrosion degree determined in step (f) are randomly generated. The damage dD generated under the action of (S, N) within the time dT is calculated, and the calculation of dD is repeated until the total damage D = ∑dD = 1, at which point the service life of the wind turbine is T = ∑dT; or In step (g), a reliability analysis is performed based on the Monte Carlo method, and the above steps are repeated m times to obtain the service life T of m wind turbines, and a statistical analysis is performed on T to obtain its distribution characteristics and reliability index.

9. The method according to any one of claims 1 to 8, wherein: The method can take into account the coupling effect of wind-wave flow-structure-wind turbine operation, and realize the identification of corrosion fatigue damage location and stress time history calculation through ABAQUS refined finite element analysis; or in, The method achieves a joint consideration of load randomness, material randomness and corrosion randomness during the reliability analysis process, and can realize the corrosion fatigue reliability calculation of offshore wind power structures considering the operation of wind turbines.

10. An application of the method for calculating the corrosion fatigue life reliability of an offshore wind power structure taking into account the operation of a wind turbine as described in any one of claims 1 to 9, wherein the method can be used for both the residual corrosion fatigue life reliability assessment of an existing offshore wind power structure and the corrosion fatigue life reliability design of a newly built offshore wind power structure.

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