Offshore wind power structure corrosion fatigue life reliability calculation method and system considering fan operation effect and application of offshore wind power structure corrosion fatigue life reliability calculation method and system

Abstract

The invention discloses an offshore wind power structure corrosion fatigue life reliability calculation method and system considering a fan operation effect. The method comprises the steps of external load determination, structure corresponding calculation, stress time history calculation, statistical parameter calculation and reliability calculation. According to the method, the operation effect of the offshore wind power fan in the service state can be considered, the influence of load randomness, material performance randomness and corrosion degree randomness is reflected, and then the corrosion fatigue reliability analysis of the offshore wind power structure considering the operation effect of the fan is achieved. The method and the system can be used for evaluating the reliability of the residual life of the corrosion fatigue of the existing offshore wind power structure after service, and can also provide effective reference for the reliability design process of the offshore wind power structure with the 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] Under the background of global carbon neutrality, offshore wind power has achieved far-reaching development. During the service period, offshore wind power structures will be subjected to long-term alternating loads such as wind loads, wave loads, and wind turbine vibrations, resulting in the accumulation of fatigue damage; at the same time, due to the severe corrosiveness of the service environment, offshore wind power will also face the challenge of corrosion, and the significant coupling between corrosion and fatigue will lead to further degradation of its life. Therefore, it is necessary to carry out research on the corrosion fatigue problem of offshore wind power structures. At present, most simulation methods for the corrosion fatigue life of offshore wind power do not consider the operation of wind turbines and the degradation of fatigue life by corrosion, which will produce an unsafe assessment of the corrosion fatigue life of offshore wind power structures under environmental corrosion. At the same time, the existing calculation methods do not consider the randomness of loads, randomness of material properties, and randomness of corrosion degree, and lack calculation methods for the corrosion fatigue reliability of offshore wind power structures. Therefore, in order to explore the corrosion fatigue performance of offshore wind power structures under service conditions and study their corrosion fatigue reliability under different service years, it is necessary to establish a calculation method for the corrosion fatigue reliability of offshore wind power structures that considers the operation of wind turbines. Summary of the invention

[0003] In order to overcome the shortcomings of the prior art, the present invention provides a method for calculating the reliability of the corrosion fatigue life of an offshore wind power structure taking into account the operation of the wind turbine and its application. The method can take into account the operation of the offshore wind turbine in service, reflect the randomness of loads, randomness of material properties, and randomness of corrosion degree, and thus realize the corrosion fatigue reliability analysis of the offshore wind power structure taking into account the operation of the wind turbine. The present invention can be used to evaluate the remaining life reliability of corrosion fatigue of existing offshore wind power structures after service, and can also provide an effective reference for the reliability design process of offshore wind power structures with corrosion fatigue problems.

[0004] The present invention provides 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, including:

[0005] (a) Determine the environmental load parameters according to the offshore wind power service location and generate a wind field with a duration of dT;

[0006] (b) Based on OpenFAST, the structural response of offshore wind power within dT time under the coupling of wind-wave-structure-wind turbine is calculated, and the displacement and force boundary conditions of the tower top are extracted;

[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 dT time, identify the fatigue danger 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;

[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 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;

[0011] (g) Carry out corrosion fatigue damage calculation in MATLAB, and carry out 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 implementation, in step (a), determining environmental load information according to 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 implementation, 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 implementation, in the step (b), a bar 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 implementation, in step (b), the wind turbine mass, power and control are set according to the parameters of the analyzed structural wind turbine set;

[0019] According to a specific implementation, in step (b), the OpenFAST software 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;

[0020] According to a specific implementation, in the step (c), a structural refined finite element model is established in ABAQUS, taking into account the development and distribution characteristics of structural corrosion;

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

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

[0023] According to a specific implementation, in step (c), the stress time 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;

[0024] According to a specific implementation, in step (d), steps (a) to (c) are repeated 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 ;

[0025] According to a specific implementation, 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;

[0026] According to a specific implementation, in step (f), the material damage evolution model P at each corrosion degree is determined through corrosion fatigue test data, and the statistical characteristics of each parameter are determined, including the standard deviation and the mean. When corrosion fatigue test data is not available, the data in the specification and existing literature can be used for reference;

[0027] According to a specific implementation, in step (f), the material damage evolution model P at each corrosion degree can be established based on the linear damage accumulation criterion or based on the mechanics of continuous media. When there is no corrosion fatigue test data, it can be determined by fitting the fatigue test data after corrosion under the same corrosion environment in the existing literature;

[0028] According to a specific implementation method, in step (g), based on MATLAB software, the equivalent stress amplitude S and the number of actions N determined in step (e) are used to randomly generate the equivalent stress amplitude and the number of actions (S, N) within the dT time. 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 dT time. The calculation of dD is repeated until the total damage is D＝ ∑ dD＝1 , at this time the fan service life is T＝ ∑ dT ;

[0029] According to a specific implementation, in step (g), reliability analysis is performed based on the Monte Carlo method, the steps described in the previous paragraph are repeated m times to obtain m wind turbine service lives T, and statistical analysis is performed on T to obtain its distribution characteristics and reliability index;

[0030] The technical solution of the present invention has the following beneficial effects: the method can take into account the coupling effect of wind-wave flow-structure-wind turbine operation, and realizes the identification of corrosion fatigue damage position and stress time history calculation 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 effect of wind turbine operation; the method can be used for the residual corrosion fatigue life reliability assessment of existing offshore wind power structures, and can also be used for the corrosion fatigue life reliability design of new offshore wind power structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A method and system flow chart for calculating the reliability of corrosion fatigue life of offshore wind power structures taking into account the operation of wind turbines according to the present invention;

[0032] Figure 2 The wind farm diagram.

[0033] Figure 3 Schematic diagram of establishing offshore wind power model in OpenFAST;

[0034] Figure 4 It is a schematic diagram of wave and current time history;

[0035] Figure 5 This is a schematic diagram of the fan operating power;

[0036] Figure 6 It is a schematic diagram of the displacement time history of the tower top;

[0037] Figure 7 It 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] Fig. 9 Schematic diagram of stress distribution and fatigue vulnerable position identification of offshore wind power structures;

[0040] Fig.10 This is a schematic diagram of stress time history at fatigue vulnerable position;

[0041] Fig.11 This is a schematic diagram of stress amplitude statistics using the rainflow counting method;

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

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

[0044] The present invention will be further described below in conjunction with 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 at the top of the tower; 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 danger 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 six: 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 seven: perform 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 the Kaimal spectrum, such as Figure 2 shown.

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

[0048] Wave flow and wind field are introduced into the OpenFAST model. 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] OpenFAST software is used to calculate the structural response of offshore wind power structures under the wind-wave flow-wind turbine operation state within dT time, and the time history curve of the tower top boundary condition within dT time is extracted, including the displacement boundary time history of all degrees of freedom at the tower top, such as Figure 6 As shown, and the force boundary time history, such as Figure 7 shown.

[0051] A refined finite element model of offshore wind power structures 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 Fig. 9 As shown in Figure 2, combined with the structural category, the corrosion fatigue dangerous position is identified and the stress time history S(t) within the dT time is extracted, as shown in Figure 2 Fig.10 shown.

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

[0054] According to a specific implementation, in step (d), steps (a) to (c) are repeated 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 .

[0055] According to a specific implementation, 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 implementation manner, in the step (f), the material damage evolution model P at 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 development in a unified time dimension, and the statistical characteristics of each parameter are determined, including the standard deviation and the mean. When there is no corrosion fatigue test data, 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 implementation, 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 manner, in the 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 the step (e), and the damage evolution model and parameter statistical characteristics under each corrosion degree determined in the step (f) are randomly generated. The material damage evolution model parameters are calculated and the damage dD generated under the action of (S, N) within the time dT is calculated, and dD is repeatedly calculated until the total damage D = ΣdD = 1, at which time the service life of the fan is T = ΣdT.

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

[0060] 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. 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 effect of wind turbine operation; the method can be used for the residual corrosion fatigue life reliability assessment of existing offshore wind power structures, and can also be used for the corrosion fatigue life reliability design of new offshore wind power structures.

Claims

1. A reliability calculation method for corrosion fatigue life of offshore wind power structures considering the operation of wind turbines, characterized in that: The method takes into account the load history of offshore wind power pipe frames under the action 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 the environmental load parameters according to the offshore wind power service location and generate a wind field with a duration of dT; (b) Based on OpenFAST, the structural response of offshore wind power within dT time under the coupling of wind-wave-structure-wind turbine is calculated, and the displacement and force boundary conditions of the tower top are extracted; (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 dT time, identify the fatigue danger 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; (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 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; (g) Corrosion fatigue damage calculations are performed in MATLAB, and corrosion fatigue reliability analysis is performed by combining the Monte Carlo method and the load and material statistical characteristics determined in steps (e) and (f).

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 established in OpenFAST according to 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 mass, 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 at 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 time history of the boundary conditions 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 dangerous position is identified in combination with the structural type, and the stress time history S(t) within the time dT is extracted; or Wherein, in step (c), the stress time 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, characterized in that 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 the continuum mechanics, 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 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 through 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 dD is repeatedly calculated until the total damage D = ∑dD = 1, at which time the service life of the fan is T = ∑dT; or Wherein, in step (g), reliability analysis is carried out based on the Monte Carlo method, the above steps 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 and reliability indicators.

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 corrosion fatigue damage location identification and stress time history calculation through ABAQUS refined finite element analysis; or in, The method takes into account the randomness of loads, materials and corrosion during the reliability analysis process, and can realize the corrosion fatigue reliability calculation of offshore wind power structures taking into account 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 effect of wind turbine operation 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 existing offshore wind power structures and the corrosion fatigue life reliability design of newly built offshore wind power structures.

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