All-coupling numerical simulation method and system for offshore wind turbine

Abstract

The invention discloses an offshore wind turbine full-coupling numerical simulation method and system. The method comprises the steps that wind turbine system parameters are initialized, and external environment parameters are input; calculating external exciting force of the wind turbine system at the current moment, wherein the external exciting force comprises aerodynamic force, hydrodynamic force and earthquake force; establishing a kinetic equation of the wind turbine system based on the multi-body kinetic model; solving the kinetic equation by adopting a generalized-alpha direct integration method to obtain motion displacement, speed and load information of each component; and outputting and analyzing a numerical calculation result. According to the method, the dynamic response of the wind turbine under various environmental conditions is comprehensively analyzed, so that the reliability and efficiency of the wind turbine can be remarkably improved, and the failure rate caused by improper design is reduced; in addition, the method can also be used for maintenance and improvement work of the wind turbine, maintenance personnel are guided to check and maintain key components of the wind turbine by analyzing simulation results, the service life of the wind turbine is prolonged, and the maintenance cost is reduced.

Description

Technical Field

[0001] The present invention relates to a numerical simulation method and system, and in particular to a fully coupled numerical simulation method and system for offshore wind turbines. Background Art

[0002] Offshore wind turbines are complex new energy equipment that integrates multidisciplinary technologies such as aerodynamics, hydrodynamics, structural dynamics, and servo control systems. Since these devices are usually installed in sea areas with complex external environments, they are often affected by changing marine environmental loads such as wind, waves, and currents. Inside the wind turbine system, there are complex interactions and couplings between the components and between the components and the external environmental loads. The characteristics of these coupled dynamic responses are difficult to evaluate using traditional analysis methods.

[0003] In order to analyze these complex dynamic responses more efficiently and accurately, researchers and engineers have developed a series of time-domain numerical simulation software that can simulate the dynamic response of offshore wind turbines under various environmental conditions, including the interaction of aerodynamics, hydrodynamics, structural forces, and servo control.

[0004] Although existing simulation tools such as OpenFAST, Bladed, and HAWC2 provide extensive numerical analysis capabilities, they still have some limitations. These software mostly focus on specific types of foundation design, such as fixed or floating foundations, and are generally only applicable to the calculation of large-scale structures. In addition, these programs usually do not consider seismic loads, which is a significant omission for wind turbine design in some areas. Especially for wind turbines with new foundation forms, existing simulation tools may not be able to fully meet the needs of research and design.

[0005] Therefore, developing a more comprehensive and widely applicable offshore wind turbine simulation program has become an urgent need in this field. Summary of the invention

[0006] Purpose of the invention: The purpose of the present invention is to propose a fully coupled numerical simulation method and system for offshore wind turbines, which integrates the solution of aerodynamic loads, hydrodynamic loads, seismic loads and structural responses, and is suitable for the calculation of single rigid body models and multi-body rigid-flexible coupling dynamic models of offshore wind turbines.

[0007] Technical solution: The present invention includes: initializing wind turbine system parameters and inputting external environment parameters; calculating the external excitation forces of the wind turbine system at the current moment, including: aerodynamic force, hydrodynamic force and seismic force; establishing the dynamic equation of the wind turbine system based on the multi-body dynamic model; solving the dynamic equation using the generalized-α direct integration method to obtain the motion displacement, velocity and load information of each component; outputting and analyzing the numerical calculation results.

[0008] The steps of solving the kinetic equation using the generalized-α direct integration method include:

[0009] Determine the integration parameters of the generalized-α direct integration method and set the initial conditions;

[0010] Perform time stepping on the dynamic equations and calculate the system state at each time step based on the previous solution and the current external excitation;

[0011] The motion displacement, velocity and corresponding dynamic load of each component of the system are updated after each time step.

[0012] The calculation of the seismic force includes:

[0013] Determine the characteristics and seismic fortification intensity of the seismic zone where the wind farm is located, and based on this data determine the target seismic response spectrum suitable for the geological conditions of the operation site;

[0014] generating seismic wave data according to a target earthquake response spectrum;

[0015] The generated seismic wave data is loaded into the seismic dynamics model of the wind turbine in the form of seismic acceleration time history;

[0016] Define and apply the damping and stiffness parameters of the spring oscillator to calculate and obtain the seismic loads on the wind turbine system under earthquake action.

[0017] The aerodynamic force calculation comprises the following steps:

[0018] Determine the relative inflow wind speed at each blade element position;

[0019] Calculate the aerodynamic force at each blade element position, and calculate the aerodynamic load of the entire wind rotor system according to the following formula:

[0020]

[0021] Among them, F thrust is the thrust of the wind wheel, P is the power of the wind wheel, ρ is the air density, U inflow is the inflow wind speed, Ω is the wind wheel rotation speed, a is the axial induction factor, a′ is the tangential induction factor, r is the distance from the hub center to the blade tip, and dr is the differential length of the blade element.

[0022] The calculation of the hydrodynamic force includes the following steps:

[0023] Frequency domain calculation to generate the hydrodynamic parameters of the wind turbine;

[0024] Initialize the input wave environment parameters and establish the time domain wave field model of wind turbine operation;

[0025] Calculate the first-order and second-order wave forces:

[0026] First-order wave force:

[0027]

[0028] Second order wave force:

[0029]

[0030] Among them, η i is the wave amplitude, H1(ω i ) is the first-order wave force transfer function, H 2s (ω i ,ω j ) is the sum frequency wave force transfer function, H 2d (ω i ,ω j ) is the difference frequency wave force transfer function, ω i ,ω j is the wave frequency, φ i ,φ j is the phase angle;

[0031] Calculate wave radiation force and hydrostatic restoring force, as well as damping force:

[0032] Wave Radiation Force:

[0033]

[0034] Still Water Recovery:

[0035]

[0036] Damping force:

[0037]

[0038] Among them, A jj (∞) is the additional mass coefficient at infinite frequency, h jj (t-τ) is the damping coefficient function, is the hydrostatic restoring moment coefficient, C D is the damping coefficient, is the velocity vector of the component;

[0039] The total hydrodynamic load of the wind turbine system is obtained by comprehensive calculation:

[0040]

[0041] Among them, F H is the total hydrodynamic load of the wind turbine system.

[0042] The dynamic equation of the wind turbine system is established based on the multi-body dynamics model, which is specifically:

[0043] Dynamics model selection and initialization, where the dynamics model includes a single rigid body or a multi-body dynamics model;

[0044] Single rigid body model processing: Apply the linear single-step method to solve and obtain the time history information of the wind turbine foundation motion;

[0045] Multibody model processing:

[0046] If the component is a flexible body, finite element discretization is performed to establish the dynamic equation of the flexible body, and the influence of the intrinsic elastic characteristics and deformation of the structure on the dynamic response of the system is considered;

[0047] If the component is a rigid body, the motion and dynamic equations of each rigid body component are established; and the coupling relationship between adjacent components is considered;

[0048] Equation assembly and solution: Assemble the dynamic equations of all components to form a group of dynamic equations of the multi-body system.

[0049] The output and analysis of numerical calculation results include motion response, load response and spectrum analysis.

[0050] A fully coupled numerical simulation system for offshore wind turbines, comprising:

[0051] Pre-processing module: used to initialize wind turbine system parameters and input external environment parameters;

[0052] Solver module: used to receive the data provided by the pre-processing module and calculate the external excitation force of the wind turbine system at the current moment;

[0053] Post-processing module: used to receive the output results of the solver module and perform data analysis, including motion response, load response and spectrum analysis.

[0054] The pre-processing module comprises:

[0055] A structural parameter definition unit, used for defining and storing structural parameters of the wind turbine;

[0056] An environmental parameter input unit for receiving and processing external environmental information, including wind speed, wave and earthquake data;

[0057] The data preprocessing unit is used to preprocess the input data.

[0058] The solver module includes:

[0059] An aerodynamic force calculation unit, used for calculating aerodynamic force according to input wind field parameters;

[0060] A hydrodynamic calculation unit, used for performing frequency domain and time domain calculation of hydrodynamics based on input wave environment parameters;

[0061] A seismic force calculation unit, used for generating seismic waves and calculating seismic forces according to input seismic data;

[0062] Dynamics modeling unit, used to establish dynamic equations based on multi-body dynamics model;

[0063] Numerical solution unit, used to implement the generalized-alpha direct integration method to solve the dynamic equations.

[0064] Beneficial effects: The present invention has the following advantages:

[0065] (1) The simulation method of the present invention can provide scientific data support for the design of wind turbines, making the design more reasonable and the operation safer; by comprehensively analyzing the dynamic response of wind turbines under various environmental conditions, the reliability and efficiency of wind turbines can be significantly improved, and the failure rate caused by improper design can be reduced; in addition, the present invention can also be used for the maintenance and improvement of wind turbines. By analyzing the simulation results, maintenance personnel can be guided to inspect and maintain the key components of wind turbines, thereby extending the service life of wind turbines and reducing maintenance costs;

[0066] (2) The present invention has reliable calculation accuracy in offshore wind turbine model establishment, load simulation and response analysis. Compared with traditional wind turbine numerical tools, it has greater openness and can be used for wind-

[0067] The numerical simulation research of offshore wind turbines under complex marine environmental loads such as waves and earthquakes is particularly suitable for scientific research work on new and more innovative and diverse basic platforms. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Figure 1 is a flow chart of the present invention;

[0069] Figure 2 It is a schematic diagram of the aerodynamic force calculation process of the present invention;

[0070] Figure 3 It is a schematic diagram of the hydrodynamic calculation process of the present invention;

[0071] Figure 4 It is a schematic diagram of the seismic force calculation process of the present invention;

[0072] Figure 5 A schematic diagram of a flow chart for establishing the dynamic equations of the wind turbine system of the present invention;

[0073] Figure 6 It is a schematic diagram of the system structure of the present invention;

[0074] Figure 7 Schematic diagram of aerodynamic response time history comparison under LC5.1 working condition in an embodiment of the present invention; wherein (a) is the impeller thrust; (b) is the power generation;

[0075] Figure 8 Schematic diagram of aerodynamic response time history comparison under LC5.3 working condition in an embodiment of the present invention; wherein (a) is the impeller thrust; (b) is the power generation;

[0076] Fig. 9 It is a schematic diagram of the time history of the seismic acceleration of the EI Centro seismic wave in an embodiment of the present invention;

[0077] Fig.10 Schematic diagram of the wind dynamic response time history under shutdown conditions in an embodiment of the present invention; wherein (a) is the displacement of the tower top in the front-to-back direction; (b) is the displacement of the tower top in the lateral direction; (c) is the acceleration of the nacelle in the front-to-back direction; (d) is the acceleration of the nacelle in the lateral direction;

[0078] Fig.11 Schematic diagram of the dynamic response of a wind turbine under power generation conditions in an embodiment of the present invention; wherein (a) is the displacement of the tower top in the front-to-back direction; (b) is the displacement of the tower top in the lateral direction; (c) is the acceleration of the nacelle in the front-to-back direction; (d) is the acceleration of the nacelle in the lateral direction;

[0079] Fig.12 It is a schematic diagram of verifying the convergence of the tower column discrete unit in an embodiment of the present invention;

[0080] Fig.13 Schematic diagram of the free vibration displacement curve of the tower top in the front-to-back direction in the embodiment of the present invention; wherein (a) is the free vibration time history curve of the tower top; (b) is the response spectrum;

[0081] Fig.14 It is a schematic diagram of verifying the convergence of the blade discrete unit in an embodiment of the present invention;

[0082] Fig.15 Schematic diagram of the change of natural frequency of blade tip in different deformation directions at different rotation speeds in an embodiment of the present invention;

[0083] Fig.16 Schematic diagram of basic pitch response in an embodiment of the present invention; wherein (a) is a basic pitch time history curve; (b) is a basic response spectrum curve;

[0084] Fig.17 Schematic diagram of the displacement response of the tower top in the embodiment of the present invention; wherein (a) is the displacement time history curve of the tower top in the front-to-back direction; (b) is the displacement response spectrum curve of the tower top in the front-to-back direction;

[0085] Fig.18Schematic diagram of blade tip flapping deformation response in an embodiment of the present invention; wherein (a) is a deformation history curve in the flapping direction; (b) is a deformation response spectrum curve in the flapping direction;

[0086] Fig.19 Schematic diagram of the deformation response of the blade tip in the embodiment of the present invention; wherein (a) is the deformation time history curve in the swing direction; and (b) is the deformation response spectrum curve in the swing direction. DETAILED DESCRIPTION

[0087] The present invention will be further described below in conjunction with the accompanying drawings.

[0088] like Figure 1 As shown, the fully coupled numerical simulation method for offshore wind turbines of the present invention comprises the following steps:

[0089] S1. Initialize wind turbine system parameters

[0090] Initialize the parameters of the main structural components of the wind turbine, including the structural parameters of the blades, towers, nacelles and foundations, including the length, twist angle, chord length distribution of the blades, the height and diameter of the towers, the mass of the nacelles and the size of the foundations. The detailed parameter settings in this step provide the necessary basic data for the dynamic modeling of the wind turbine to ensure the accuracy and reliability of the simulation.

[0091] S2. Input external environment parameters

[0092] Input external environmental parameters that affect the operation of wind turbines, including wind field, wave field and earthquake field parameters, including wind speed, wind direction, wave height, period, direction and characteristics of earthquake waves, etc. The above parameters are set according to the meteorological and geological data of the location of the wind farm to ensure that the simulation conditions are as consistent as possible with the actual operating environment.

[0093] S3. Calculate the external excitation force of the wind turbine system at the current moment: Use the input environmental parameters to calculate the aerodynamic force, hydrodynamic force and seismic force on the wind turbine at a specific moment. The aerodynamic force is calculated by considering the interaction between the blades and the wind flow; the hydrodynamic force considers the impact of waves on the wind turbine foundation and substructure; the seismic force analyzes the seismic response of the wind turbine foundation based on seismic wave data.

[0094] like Figure 2 As shown in the figure, aerodynamic calculation optimizes the performance and safety of wind turbines by accurately simulating the impact of aerodynamic forces on wind turbines. It specifically includes the following steps:

[0095] S311. Load the structural parameters of the wind turbine, including blades, towers, and nacelles, etc. In this embodiment, the parameters of the blades, such as airfoil, length, and twist angle, etc., adopt the standard parameters of the NREL 5MW wind turbine, which provides the necessary physical and geometric basis for aerodynamic calculation.

[0096] S312. The program defines the wind field environmental conditions, including wind speed, wind direction, etc., so as to determine the relative inflow wind speed for each blade element (blade element). This is achieved by calculating the local wind speed at different positions of the blade, and taking into account the change of wind speed along the blade height.

[0097] S313. The aerodynamic force of each blade element is calculated by blade element momentum theory. The key is to solve the axial and tangential induction factors a and a'. These induction factors describe the changes in air flow caused by blade movement, and their calculation is completed through a continuous iterative process to ensure the accuracy of the calculation.

[0098] S314. Calculate the aerodynamic load of the entire impeller according to the following formula:

[0099]

[0100] Among them, F thrust is the thrust of the wind wheel, P is the power of the wind wheel, ρ is the air density, U inflow is the inflow wind speed, Ω is the wind wheel rotation speed, a is the axial induction factor, a′ is the tangential induction factor, r is the distance from the hub center to the blade tip, and dr is the differential length of the blade element.

[0101] The implementation of this aerodynamic calculation can more accurately simulate the aerodynamic performance of wind turbines in actual operation, providing a scientific basis for wind turbine design and performance optimization. The calculation results can be used to optimize blade design, reduce energy losses, and improve the energy efficiency of wind turbines. In addition, more accurate aerodynamic calculations can also help predict the behavior of wind turbines under extreme wind speed conditions, thereby enhancing the safety and reliability of their operation.

[0102] like Figure 3 As shown in the figure, hydrodynamic calculation can accurately predict and analyze the hydrodynamic effects on wind turbines in complex marine environments to improve the design efficiency and operational stability of wind turbines. Specifically, it includes the following steps:

[0103] S321. Frequency domain calculation

[0104] The SESAM software developed by DNVGL, especially the Wadam module, is used for frequency domain calculations. The software can generate the hydrodynamic parameters of wind turbines, including the first-order wave force transfer function, the second-order difference frequency and sum frequency wave force transfer functions, as well as the added mass and potential flow damping. These parameters provide the basis for time domain calculations and ensure the accuracy of hydrodynamic analysis.

[0105] S322. Time domain wave field model establishment

[0106] Based on the wave environment parameters input by the program initialization, the time domain wave field model of wind turbine operation is established, including determining the wave height, period and direction, etc., to ensure the consistency between the simulated environment and the actual marine environment.

[0107] S323. Calculation of wave forces

[0108] First-order wave force:

[0109]

[0110] Second order wave force:

[0111]

[0112] Among them, η i is the wave amplitude, H1(ω i ) is the first-order wave force transfer function, H 2s (ω i ,ω j ) is the sum frequency wave force transfer function, H 2d (ω i ,ω j ) is the difference frequency wave force transfer function, ω i ,ω j is the wave frequency, φ i ,φ j is the phase angle;

[0113] S324. Calculation of wave radiation force and hydrostatic restoring force and damping force:

[0114] Wave Radiation Force:

[0115]

[0116] Still Water Recovery:

[0117]

[0118] Damping force:

[0119]

[0120] Among them, A jj (∞) is the additional mass coefficient at infinite frequency, h jj (t-τ) is the damping coefficient function, is the hydrostatic restoring moment coefficient, C D is the damping coefficient, is the velocity vector of the component;

[0121] S325. The total hydrodynamic load of the wind turbine system is obtained by comprehensive calculation, and all the calculated wave load components are superimposed to obtain the final hydrodynamic load F of the wind turbine system.H :

[0122]

[0123] Among them, F H is the total hydrodynamic load of the wind turbine system.

[0124] The calculation of hydrodynamic forces can provide wind turbine designers with detailed dynamic response data under various marine environmental conditions, supporting structural strength and stability analysis. By accurately simulating the hydrodynamic effects, designers can optimize the foundation design of wind turbines, reduce the risk of structural failure caused by hydrodynamic forces, and improve the reliability and life cycle of wind turbines. In addition, the implementation of this calculation step also helps reduce the need for field testing, thereby reducing R&D costs and time.

[0125] like Figure 4 As shown in the figure, the calculation of seismic force can ensure the structural safety and operational reliability of wind turbines in extreme events such as earthquakes. Specifically, it includes:

[0126] S331. Determine the characteristics of earthquake zones and seismic fortification intensity

[0127] Assess the characteristics of the seismic zone where the wind farm is located, including the frequency of seismic activity, historical earthquake data, etc., and determine the seismic fortification intensity to ensure that the wind turbine design can meet the seismic requirements of the specific area.

[0128] S332. Generate seismic wave data

[0129] Based on the determined target earthquake response spectrum, seismic wave data are generated by matching the measured earthquake database or artificial synthesis. These data will be used to simulate the response of wind turbines in earthquake events to evaluate the seismic performance of their structures.

[0130] S333. Loading seismic data into the dynamic model

[0131] The generated seismic wave data are loaded into the seismic dynamics model of the articulated foundation wind turbine in the form of seismic acceleration time history. This model can simulate the dynamic response of the wind turbine foundation and structure under the action of seismic force in detail.

[0132] S334. Calculation of seismic loads on wind turbine systems

[0133] Define the damping and stiffness parameters of the spring oscillator, which are crucial for simulating the seismic response of the structure. With these parameters, the program can calculate the seismic loads on the wind turbine system under earthquake action.

[0134] By calculating seismic forces, structural behavior in earthquake situations can be more accurately predicted and evaluated, allowing safer wind turbines to be designed. This not only improves the reliability of wind turbines, but also reduces potential repair costs. In addition, accurate seismic dynamics analysis can also optimize the foundation and structural design of wind turbines to adapt to the most extreme earthquake situations that may be encountered, ensuring stability and safety during operation.

[0135] S4. Based on the multi-body dynamics model, the dynamic equations of the wind turbine system are established to ensure accurate simulation of the structural stability and response effects of the wind turbine under various dynamic environments. The model distinguishes the various components of the wind turbine as rigid bodies or flexible bodies, and applies corresponding dynamic processing methods to different types of components. For example, the rigid body directly applies the Newton-Euler equation, and the flexible body uses the finite element method to describe its deformation behavior. Figure 5 As shown, specifically:

[0136] S41. Kinetic model selection and initialization

[0137] First, according to the actual structure and functional requirements of the wind turbine, select a suitable dynamic calculation model, including a single rigid body or multi-body dynamic model. The program needs to load the structural parameters of each component of the wind turbine system, such as the specific data of the blades, tower, nacelle and foundation, in order to establish the initial dynamic model of each component.

[0138] S42. Single rigid body model processing

[0139] For the single rigid body model, the fourth-order-Runge-Kutta numerical method of the linear single-step method is used to solve it. This method is suitable for calculating the dynamic response of relatively simple structures to obtain the time history information of the wind turbine foundation motion.

[0140] S43. Multi-body model processing

[0141] For multi-body models, first determine whether each component is a flexible body or a rigid body based on its physical properties:

[0142] If the part is a flexible body, do the following:

[0143] Perform finite element discretization and select a zero-order approximate model suitable for dynamic modeling or a high-order deformation model that considers coupled deformation terms; establish the dynamic equation of the flexible body, considering the intrinsic elastic properties of its structure and the influence of deformation on the dynamic response of the system.

[0144] If the part is a rigid body, do the following:

[0145] According to the theory of multi-body dynamics and kinetics, the motion and dynamic equations of each rigid body component are established based on the absolute coordinate system; the coupling relationship between adjacent components is considered to ensure that the model can accurately reflect the actual motion state.

[0146] S44. Equation assembly and solution

[0147] The dynamic equations of all components are assembled based on the Lagrange multiplier method to form a complete set of multi-body system dynamic equations to describe the dynamic behavior of the entire wind turbine system.

[0148] S5. The generalized-α direct integration method is used to solve the dynamic equations to obtain the motion displacement, velocity and load information of each component, which can more accurately predict and evaluate the performance of wind turbines under actual operating conditions, especially the stability and responsiveness in complex dynamic environments. This not only improves the design quality and safety of wind turbines, but also helps to reduce maintenance costs and potential operational risks caused by improper design. In addition, it can also accelerate the design process of wind turbines and improve the flexibility and iteration speed of the design. The solution steps include:

[0149] S51. Determine the integration parameters and initial conditions

[0150] Before solving the dynamic equations, we first need to determine the integral parameters of the generalized-α method, including the integral time step, numerical damping parameters, etc. These parameters directly affect the stability and accuracy of the solution. Set the initial conditions, including the initial displacement, velocity, and acceleration of the system; correct initial conditions are the key to ensuring the accuracy of the solution.

[0151] S52, time stepping processing

[0152] The time-stepping method is used to process the dynamic equations. At each time step, the program first calculates the next state of the system based on the solution of the previous time step and the external excitation at the current moment (such as wind, waves, and earthquakes). The generalized-alpha method is particularly suitable for processing nonlinear responses of dynamic systems because it can effectively balance numerical dissipation and frequency response, thereby improving the physical fidelity of the solution.

[0153] S53. Update system status

[0154] After each time step, the motion displacement, velocity and corresponding dynamic load of each component of the system are updated. These data are essential for monitoring the dynamic behavior of the system and evaluating the structural safety. The updating process includes recalculating the state of each component to ensure that all physical and engineering constraints are met.

[0155] The use of this method not only enhances the scientific nature and technological advancement of wind turbine design, but also provides strong technical support for the long-term stable operation of wind turbines. It has important practical application value and broad market prospects.

[0156] S6. Output and analyze numerical calculation results, including motion response, load response and spectrum analysis

[0157] The motion displacement, velocity and load information of each wind turbine component during the entire simulation time are output and detailed data analysis is performed. The analysis includes but is not limited to the time history analysis of motion response, peak value and spectrum analysis of load response, etc., which helps to evaluate the risks that may be encountered during the design and operation of the wind turbine.

[0158] The simulation method of the present invention can provide scientific data support for the design of wind turbines, making the design more reasonable and the operation safer. By comprehensively analyzing the dynamic response of wind turbines under various environmental conditions, the reliability and efficiency of wind turbines can be significantly improved, and the failure rate caused by improper design can be reduced. In addition, the present invention can also be used for the maintenance and improvement of wind turbines. By analyzing the simulation results, maintenance personnel can be guided to inspect and maintain the key components of wind turbines, thereby extending the service life of wind turbines and reducing maintenance costs.

[0159] The fully coupled numerical simulation system for offshore wind turbines of the present invention is as follows: Figure 6 As shown, including:

[0160] Pre-processing module: used to initialize wind turbine system parameters and input external environment parameters; including:

[0161] A structural parameter definition unit, used for defining and storing structural parameters of the wind turbine;

[0162] An environmental parameter input unit for receiving and processing external environmental information, including wind speed, wave and earthquake data;

[0163] The data preprocessing unit is used to perform necessary preprocessing on the input data to meet the requirements of the solver module.

[0164] Solver module: used to receive the data provided by the pre-processing module and calculate the external excitation force of the wind turbine system at the current moment; based on the multi-body dynamics model, the dynamic equation of the wind turbine system is established, and the generalized-α direct integration method is used to solve the dynamic equation to obtain the motion displacement, velocity and load information of each component; including:

[0165] An aerodynamic force calculation unit, used for calculating aerodynamic force according to input wind field parameters;

[0166] A hydrodynamic calculation unit, used for performing frequency domain and time domain calculation of hydrodynamics based on input wave environment parameters;

[0167] A seismic force calculation unit, used for generating seismic waves and calculating seismic forces according to input seismic data;

[0168] Dynamics modeling unit, used to establish dynamic equations based on multi-body dynamics model;

[0169] Numerical solution unit, used to implement the generalized-alpha direct integration method to solve the dynamic equations.

[0170] Post-processing module: used to receive the output results of the solver module and perform data analysis, including motion response, load response and spectrum analysis, including:

[0171] Result output unit, used to output the motion displacement, velocity and load information of the calculation results;

[0172] The data analysis unit is used to perform statistical calculations and spectrum analysis on the output results to evaluate the dynamic performance of the wind turbine.

[0173] Example:

[0174] This embodiment describes the calibration process of the fully coupled time-domain numerical simulation program ADRT for offshore wind turbines. The effectiveness of the ADRT program is verified by comparing it with standard model test data and other numerical simulation results. This calibration process includes the calibration of aerodynamic response, seismic response and structural dynamic response.

[0175] Research objects and test conditions

[0176] The research object is the designed articulated foundation wind turbine. In order to comprehensively evaluate the dynamic response of the wind turbine, a variety of working conditions were selected for analysis:

[0177] 1. Regular wave sea conditions: Analyze the dynamic response of wind turbines under the action of regular waves.

[0178] 2. Uniform steady wind conditions in time and space: Evaluate the performance of wind turbines under continuous uniform wind speed.

[0179] 3. Typical seismic wave conditions: examine the structural safety and response of wind turbines under the influence of earthquakes.

[0180] These numerical results will be compared with the NREL 5MW single-column floating wind turbine model test data. The test data serves as a calibration benchmark to ensure the consistency of the test condition parameters.

[0181] Test condition parameter setting

[0182] The specific parameters of the calibration test are shown in Table 1:

[0183] Table 1 Program verification test conditions

[0184]

[0185]

[0186] In all test conditions, the direction of wind, wave and seismic wave is set to 0°. In order to maintain the consistency and comparability of the results, the numerical simulation wind speed is set to take into account that the impeller thrust measured at the theoretical wind speed in the model test is generally smaller than the target thrust value. Therefore, the results of the actual test wind speeds of 12.8m / s and 11.1m / s are compared with the numerical simulation wind speeds of 11.4m / s and 18m / s.

[0187] 1. Aerodynamic response verification

[0188] The test conditions LC5.1 and LC5.3 with only wind action were selected to calculate the impeller thrust and power generation response of the articulated foundation wind turbine system, and the numerical results were compared with the results of the SJTU test and the FAST / AeroDyn aerodynamic program. In order to eliminate the influence of the initial value and the unstable stage data of the initial operation of the program, the data before 200s of calculation were omitted, and the numerical calculation results under the stable state were statistically analyzed. The statistical results are shown in Table 2. At the same time, the 100s data of the stable stage of system operation were selected for plotting, and the time history curves of the impeller thrust and power generation under the two test conditions were obtained, as shown in Table 2. Figure 7 and 8 As shown, (a) is the impeller thrust; (b) is the generated power.

[0189] Table 2 Comparison of impeller thrust and power generation under wind conditions only

[0190]

[0191] From the statistical results, it can be seen that under the LC5.1 rated wind speed condition, the impeller thrust value calculated by the ADRT program is 788kN, and the power generation is around 5MW. Under the LC5.3 condition, the impeller thrust value calculated by the ADRT program is reduced to 448kN, and the power generation is still maintained at around 5MW, indicating that when the wind speed exceeds the rated wind speed, the servo control system begins to work, and the blade angle of attack is changed by adjusting the pitch angle, thereby affecting the lift coefficient and drag coefficient of the airfoil, so that the tangential torque of the impeller aerodynamic load remains constant and the axial thrust component is reduced. Compared with the calculation results of FAST program, the mean values ​​of impeller thrust and power generation calculated by ADRT program are not much different from those of FAST results, but the standard deviation is relatively large, especially in power generation response, the response fluctuation of ADRT program results is relatively large compared with FAST results. This is because FAST adopts a more accurate PID servo control strategy, while ADRT adopts a quasi-static pitch angle control method, which is a simplified control strategy. At the same time, FAST also considers other correction factors such as dynamic stall and tower shadow effect, which leads to a large fluctuation of aerodynamic response calculated by ADRT program. However, considering that the impeller aerodynamic load mainly acts on the wind turbine system in the form of aerodynamic thrust, ADRT aerodynamic module program can simulate the impeller aerodynamic thrust response relatively well. In general, the calculation accuracy meets the error allowance.

[0192] 2. Earthquake Response Verification

[0193] The seismic response of the ADRT program was checked by selecting the seismic action test condition LC5.4, and the calculation results were compared with those of the FAST / Seismic seismic program. The articulated foundation wind turbine was used as the research object, and the seismic dynamic model was constructed in the ADRT and FAST / Seismic programs respectively. The 1969 EI Centro earthquake was selected as the input seismic excitation. The peak acceleration PGA of the earthquake was 0.37g. The acceleration time history curve of the EI Centro earthquake wave is shown in the figure below. Fig. 9 shown.

[0194] The total calculation time is set to 600s, the time step is 0.01s, and the seismic wave is added at the 300th second to calculate the tower top displacement and cabin acceleration response of the articulated foundation wind turbine when it is in the shutdown state and subjected to seismic excitation. The calculation results are as follows: Fig.10 As shown, (a) is the displacement of the tower top in the fore-and-aft direction; (b) is the displacement of the tower top in the lateral direction; (c) is the acceleration of the cabin in the fore-and-aft direction; (d) is the acceleration of the cabin in the lateral direction.

[0195] As can be seen from the figure, the calculation results of ADRT and FAST programs are generally consistent, among which the tower top displacement response is highly consistent throughout the entire earthquake stage. For the cabin acceleration response, the two results deviate within 10 seconds after the earthquake wave occurs, and then the response results tend to be consistent. Quantitatively, under the shutdown condition, the maximum displacement of the tower top calculated by the ADRT program is 0.509m in the lateral direction of the tower column, while the maximum displacement of the tower top calculated by the FAST / Seismic program is also in the lateral direction of the tower column, which is 0.516m, with a relative error of 1.31%; for the cabin acceleration response, the maximum acceleration of the cabin calculated by the ADRT program occurs in the front and rear direction of the tower column, which is 2.620m / s2, while the maximum acceleration of the cabin calculated by the FAST / Seismic program is also in the front and rear direction of the tower column, which is 2.557m / s2, with a relative error of 2.48%.

[0196] In order to further verify the reliability of the ADRT program, the test condition LC5.5 under the combined action of wind and earthquake is selected to study the tower top displacement and cabin acceleration response of the articulated foundation wind turbine under seismic excitation in the power generation operation state. In order to ensure that the overall dynamic response of the wind turbine system is in a dynamic equilibrium state before the seismic excitation is added, the seismic wave effect is added when the articulated foundation wind turbine system is running for 300s, and the seismic action time is 50s. The calculation results are as follows: Fig.11 As shown, (a) is the displacement of the tower top in the front-to-back direction; (b) is the displacement of the tower top in the lateral direction; (c) is the acceleration of the cabin in the front-to-back direction; and (d) is the acceleration of the cabin in the lateral direction.

[0197] As can be seen from the figure, the calculation results of the ADRT program are well matched with the results of the FAST / Seismic program. In the strong earthquake stage (300s-320s), the tower top displacement and cabin acceleration respond violently under the combined action of wind and earthquake. However, after the seismic wave passes, unlike the case of a single earthquake, the response of the tower column in the front and rear directions decays rapidly, indicating that when the wind turbine is affected by aerodynamic damping under the action of aerodynamic load, the seismic energy decays more rapidly, indicating that the ADRT program can well simulate the coupling effect under the combined action of wind and earthquake. At the same time, in the lateral direction of the tower column, due to the additional aerodynamic load in the front and rear directions, the tower top displacement and cabin acceleration response calculated by the two programs have a slight deviation. Quantitatively, the maximum displacement of the tower top calculated by the ADRT program in the front and rear directions is 0.897m, and the maximum displacement of the tower top calculated by the FAST / Seismic program is 0.915m, with a relative error of 1.96%; the maximum acceleration of the cabin in the front and rear directions calculated by the ADRT program is 1.464m / s2, and the maximum acceleration of the cabin in the front and rear directions calculated by the FAST / Seismic program is 1.543m / s2, with a relative error of 5.11%. In general, the seismic response results of the ADRT program and the FAST / Seismic program match well, and have high reliability and accuracy in studying the structural response of wind turbines under earthquake action.

[0198] 3. Structural dynamic response verification

[0199] The offshore articulated foundation wind turbine system is a multi-body system composed of different components such as the foundation platform, tower, nacelle, transmission chain, hub and blades. The articulated foundation swings in the wind and wave environment, and the flexible structures such as tower and blades are prone to flexible deformation under the action of environmental loads. Based on the theory of spatial flexible beams, the previous article established a blade structure dynamics model considering high-order deformation and a tower dynamics model with terminal concentrated mass. This embodiment will combine the model test and numerical program verification. First, the inherent characteristics analysis of the tower and blade structure established in this embodiment is carried out to verify the rationality of the structural model, and then the test condition LC5.2 under the combined action of wind and waves is selected to check the structural dynamic response of the wind turbine blades, towers and articulated foundation structures.

[0200] Intrinsic characteristics analysis

[0201] (1) Tower column

[0202] Since the finite element method is used in this embodiment to discretize the wind turbine tower structure, the convergence of the tower unit needs to be verified first. By inputting the tower structure parameters, a tower dynamic model with terminal concentrated mass is established in the ADRT program. At the same time, it is assumed that the bottom of the tower is a rigid fixed constraint, and an impulse load is applied to the top of the tower. The first-order natural frequency of the tower in the front and rear directions with different numbers of divided units is analyzed. The calculation results are as follows: Fig.12 shown.

[0203] It can be seen from the figure that when the number of tower column division units is 7, the calculation results tend to be stable and convergent. Considering the program calculation efficiency and accuracy requirements, the number of tower column finite element discrete units is set to 7 in the subsequent numerical calculation. This section conducts inherent characteristic analysis on the tower column structure model with terminal mass, ignoring the influence of structural damping. By applying pulse loads at the top of the tower to make the tower column vibrate freely, the displacement of the tower column in the front and rear directions is analyzed, such as Fig.13 As shown, (a) is the tower top displacement and (b) is the amplitude.

[0204] It can be seen from the figure that the vibration of the tower top of the tower column model with terminal mass almost only shows the first-order vibration mode, and its first-order natural frequency in the front-to-back direction is 0.336 Hz, and the natural period is 2.976 s. The ADRT program is used to perform free decay motion analysis on the front-to-back and lateral directions of the tower column structure designed in this embodiment, and the tower column natural frequency results are compared with the results of the NREL 5MW tower column model in the SJTU test and the FAST program, as shown in Table 3.

[0205] Table 3 Comparison of tower column natural frequencies

[0206]

[0207] In the table, 1st FA represents the first-order tower column vibration in the front-to-back direction, and 1st SS represents the first-order tower column lateral vibration. It can be seen from the data in the table that the calculation results of the ADRT program are relatively close to the test and FAST program results, which verifies the reliability of the tower column dynamic model established in this embodiment. Taking into account factors such as the selection of tower column model materials and measurement errors in the test, the natural frequency of the tower column calculated by ADRT is slightly different from the test value, but is relatively close to the calculation of the FAST program, with a relative error of about 5%. At the same time, the natural frequency of the first-order vibration of the tower column is also not within the range of the impeller rotation frequency, which avoids resonance with the impeller, and further verifies the rationality of the tower column structure designed in this embodiment.

[0208] (2) Blades

[0209] Similar to the tower structure, the convergence of the blade unit needs to be verified first. By inputting the blade structural parameters, the blade structural dynamic model is established in the ADRT program, the wind turbine rotor is controlled to be in a stopped state, and a pulse load is applied to the blade tip. The first-order natural frequency of the blade flapping direction with different numbers of divided units is analyzed. The calculation results are as follows: Fig.14 shown.

[0210] It can be seen from the figure that when the number of blade division units is 12, the calculation results tend to be stable and convergent. Considering the calculation efficiency and accuracy requirements of the program, the number of blade finite element discrete units is set to 12 in the subsequent numerical calculation. At the same time, the ADRT program is used to calculate the vibration frequencies of the blade tip flapping and swing directions at zero rotor speed, and compared with the calculation results of the FAST program, as shown in Table 4.

[0211] Table 4 Comparison of blade natural frequencies

[0212]

[0213]

[0214] It can be seen from the data in the table that the calculation results of the ADRT program are in good agreement with the FAST results, which verifies the reliability of the blade dynamics model established in this embodiment. However, for the blade structure, when the wind turbine is operating normally, the blade is always in a high-speed rotation state. The high-speed rotating blade structure may cause an increase in the blade stiffness term, that is, the "dynamic stiffening" phenomenon. For different speed conditions, this embodiment uses the ADRT program and the finite element preprocessing program Bmode to analyze the inherent characteristics of the blade tip in different deformation directions, and obtains the changes in the natural frequency of the blade tip flapping and swing directions at different speeds, such as Fig.15 shown.

[0215] The solid line in the figure is the calculation result of the ADRT program, and the dotted line is the calculation result of the Bmode program, and the two are basically consistent. From the results in the figure, it can be seen that with the increase of the impeller speed, the natural frequencies of the blades in the flapping and swing directions both increase, and the faster the speed, the higher the rate of increase of the natural frequency. This reflects that the difficulty of flexible deformation of the blades is increasing, that is, "gradual rigidification", in which the increase in stiffness in the flapping direction is more obvious than that in the swing direction. The above calculation results also further verify the reliability of the blade dynamics model.

[0216] Structural dynamic performance verification

[0217] The tower, blades and hinged foundation are important structural components of the articulated foundation wind turbine system. Their deformation and motion response under environmental loads have an important impact on the safe operation of the wind turbine system. The above introduces the derivation of the dynamic equations of the tower, blades and hinged foundation and the development of the structural dynamic module program. In order to verify the reliability of the ADRT structural dynamic module program, this embodiment selects the test condition LC5.2 under the combined action of wind and waves, and constructs an articulated foundation wind turbine model in the ADRT and FAST programs respectively. The response results such as the foundation pitch motion and the deformation of the tower and blades when the wind turbine system is subjected to aerodynamic loads and wave loads are calculated, as shown in FIG. Figures 16 to 19 As shown, Fig.16(a) Basic pitch time history curve; Fig.16 (b) is the basic response spectrum curve; Fig.17 (a) is the displacement history curve of the tower top in the front and rear directions; Fig.17 (b) is the displacement response spectrum curve of the tower top in the front and rear directions; Fig.18 (a) is the deformation history curve in the swinging direction; Fig.18 (b) is the deformation response spectrum curve in the flapping direction; Fig.19 (a) is the deformation history curve in the swing direction; Fig.19 (b) is the deformation response spectrum curve in the swing direction. The statistical results are shown in Table 5.

[0218] Table 5 Comparison of response results between ADRT and FAST programs

[0219]

[0220]

[0221] The solid line in the figure represents the calculation results of the ADRT program, and the dotted line represents the calculation results of the FAST program. It can be seen from the results in the figure that the two are highly consistent. The articulated foundation wind turbine undergoes pitch motion under the combined action of aerodynamic loads and wave loads, and the response peak is mainly concentrated at the wave frequency, indicating that the wind turbine foundation motion is mainly affected by wave loads; the tower top displacement has a large offset in the front and rear directions, mainly affected by the wave frequency and the impeller 3P frequency; while the blades are mainly affected by aerodynamic loads, and their swinging direction undergoes a large position deflection under the action of the impeller thrust. It can be seen from the response spectrum that the response peak is mainly concentrated at the impeller 1P, 2P, 3P and wave frequency, among which the coupling frequency of aerodynamic loads and wave loads is also generated between the 1P and 2P impeller frequencies; the swing direction is mainly affected by the gravity load that rotates with the blades, and the response peak corresponds to the 1P frequency of the impeller rotation.

[0222] From the statistical results in the table, "Pitch" represents the basic pitch angle, "TTipDx" represents the offset at the top of the tower in the front-rear direction of the tower column, "BTipDx" represents the deformation in the flapping direction of the blade tip, and "BTipDy" represents the deformation in the swing direction of the blade tip. In general, the calculation results of the ADRT program are relatively close to those of the FAST program, which verifies the rationality of the ADRT calculation program to a certain extent.

Claims

1. A fully coupled numerical simulation method for offshore wind turbines, characterized in that: include: Initialize wind turbine system parameters and input external environment parameters; Calculate the external excitation forces of the wind turbine system at the current moment, including aerodynamic force, hydrodynamic force and seismic force; establish the dynamic equation of the wind turbine system based on the multi-body dynamics model; use the generalized-α direct integration method to solve the dynamic equation to obtain the motion displacement, velocity and load information of each component; output and analyze the numerical calculation results.

2. A fully coupled numerical simulation method for offshore wind turbines according to claim 1, characterized in that: The calculation of the seismic force includes: Determine the characteristics and seismic fortification intensity of the seismic zone where the wind farm is located, and based on this data determine the target seismic response spectrum suitable for the geological conditions of the operation site; generating seismic wave data according to a target earthquake response spectrum; The generated seismic wave data is loaded into the seismic dynamics model of the wind turbine in the form of seismic acceleration time history; Define and apply the damping and stiffness parameters of the spring oscillator to calculate and obtain the seismic loads on the wind turbine system under earthquake action.

3. A fully coupled numerical simulation method for offshore wind turbines according to claim 1 or 2, characterized in that: The dynamic equation of the wind turbine system is established based on the multi-body dynamics model, which is specifically: Dynamics model selection and initialization, where the dynamics model includes a single rigid body or a multi-body dynamics model; Single rigid body model processing: Apply the linear single-step method to solve and obtain the time history information of the wind turbine foundation motion; Multibody model processing: If the component is a flexible body, finite element discretization is performed to establish the dynamic equation of the flexible body, and the influence of the intrinsic elastic characteristics and deformation of the structure on the dynamic response of the system is considered; If the component is a rigid body, the motion and dynamic equations of each rigid body component are established; and the coupling relationship between adjacent components is considered; Equation assembly and solution: Assemble the dynamic equations of all components to form a group of dynamic equations of the multi-body system.

4. A fully coupled numerical simulation method for offshore wind turbines according to claim 3, characterized in that: The steps of solving the kinetic equation using the generalized-α direct integration method include: Determine the integration parameters of the generalized-α direct integration method and set the initial conditions; Perform time stepping on the dynamic equations and calculate the system state at each time step based on the previous solution and the current external excitation; The motion displacement, velocity and corresponding dynamic load of each component of the system are updated after each time step.

5. A fully coupled numerical simulation method for offshore wind turbines according to claim 1, characterized in that: The aerodynamic force calculation comprises the following steps: Determine the relative inflow wind speed at each blade element position; Calculate the aerodynamic force at each blade element position, and calculate the aerodynamic load of the entire wind rotor system according to the following formula: Among them, F thrust is the thrust of the wind wheel, P is the power of the wind wheel, ρ is the air density, U inflow is the inflow wind speed, Ω is the wind wheel rotation speed, a is the axial induction factor, a′ is the tangential induction factor, r is the distance from the hub center to the blade tip, and dr is the differential length of the blade element.

6. A fully coupled numerical simulation method for offshore wind turbines according to claim 1, characterized in that: The calculation of the hydrodynamic force includes the following steps: Frequency domain calculation to generate the hydrodynamic parameters of the wind turbine; Initialize the input wave environment parameters and establish the time domain wave field model of wind turbine operation; Calculate the first-order and second-order wave forces: First-order wave force: Second order wave force: Among them, η i is the wave amplitude, H1(ω i ) is the first-order wave force transfer function, H 2s (ω i ,ω j ) is the sum frequency wave force transfer function, H 2d (ω i ,ω j ) is the difference frequency wave force transfer function, ω i ,ω j is the wave frequency, φ i ,φ j is the phase angle; Calculate wave radiation force and hydrostatic restoring force, as well as damping force: Wave Radiation Force: Still Water Recovery: Damping force: Among them, A jj (∞) is the additional mass coefficient at infinite frequency, h jj (t-τ) is the damping coefficient function, is the hydrostatic restoring moment coefficient, C D is the damping coefficient, is the velocity vector of the component; The total hydrodynamic load of the wind turbine system is obtained by comprehensive calculation: Among them, F H is the total hydrodynamic load of the wind turbine system.

7. A fully coupled numerical simulation method for offshore wind turbines according to claim 1, characterized in that: The output and analysis of numerical calculation results include motion response, load response and spectrum analysis.

8. A fully coupled numerical simulation system for offshore wind turbines, characterized in that: include: Pre-processing module: used to initialize wind turbine system parameters and input external environment parameters; Solver module: used to receive the data provided by the pre-processing module and calculate the external excitation force of the wind turbine system at the current moment; Post-processing module: used to receive the output results of the solver module and perform data analysis, including motion response, load response and spectrum analysis.

9. A fully coupled numerical simulation system for offshore wind turbines according to claim 8, characterized in that: The pre-processing module comprises: A structural parameter definition unit, used for defining and storing structural parameters of the wind turbine; An environmental parameter input unit for receiving and processing external environmental information, including wind speed, wave and earthquake data; The data preprocessing unit is used to preprocess the input data.

10. The fully coupled numerical simulation system for offshore wind turbines according to claim 8, characterized in that: The solver module includes: An aerodynamic force calculation unit, used for calculating aerodynamic force according to input wind field parameters; A hydrodynamic calculation unit, used for performing frequency domain and time domain calculation of hydrodynamics based on input wave environment parameters; A seismic force calculation unit, used for generating seismic waves and calculating seismic forces according to input seismic data; Dynamics modeling unit, used to establish dynamic equations based on multi-body dynamics model; Numerical solution unit, used to implement the generalized-alpha direct integration method to solve the dynamic equations.

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