Floating type offshore wind turbine aerodynamic load calculation method based on frequency domain method

Abstract

The invention discloses a floating type offshore wind turbine aerodynamic load calculation method based on a frequency domain method. The method comprises the steps that a state derivative is determined based on a blade element momentum theory quasi-steady-state assumption, and a dynamic inflow model is used for correction; establishing a pneumatic-elastic coupling two-degree-of-freedom linear dynamic model; establishing a wind wheel kinetic model; establishing a control model according to a floating type offshore wind turbine pitch angle control strategy, a torque control strategy and a floating body motion feedback control strategy; based on the pneumatic-elastic coupling two-degree-of-freedom linear dynamic model, the wind wheel dynamic model and the control model, pneumatic additional mass and pneumatic additional damping are obtained; pneumatic exciting force acting on the hub when the position of the cabin is fixed is obtained; and based on the pneumatic additional mass, the pneumatic additional damping and the pneumatic exciting force, an overall linear dynamic model of the fan is established and solved, and overall response is obtained. According to the method, the calculation result precision can be improved while the calculation efficiency is ensured, and a technical support is provided for accelerating the simulation efficiency of the offshore wind turbine.

Description

Technical Field

[0001] This invention relates to the field of wind turbine aerodynamics technology, specifically to a method for calculating the aerodynamic loads of floating offshore wind turbines based on the frequency domain method. Background Technology

[0002] Against the backdrop of global efforts to achieve sustainable development goals, wind energy, as a highly promising green and renewable energy source, has been widely developed and utilized. Compared to onshore wind power, offshore wind power is characterized by high wind speeds, low turbulence intensity, and abundant reserves, and is gradually becoming the mainstream trend in future wind power development. According to the International Energy Agency's forecast, the global installed capacity of offshore wind power is expected to reach 560GW in the future, with Europe and China accounting for 70% of the share, demonstrating the enormous development potential of the offshore wind power industry. Furthermore, over 80% of global offshore wind resources are located in deep water areas with depths greater than 60 meters, and the use of floating offshore wind turbines (FOWTs) is the preferred technology for exploiting deep-water wind energy. FOWTs are typical rigid-flexible multibody coupled dynamic systems with strong nonlinear dynamic characteristics. Compared to traditional offshore oil and gas platforms, wind loads, as one of the dominant loads in FOWTs, have a significant impact on the platform's dynamic response, structural safety, and power generation performance; therefore, aerodynamic analysis of FOWTs is particularly important.

[0003] Currently, the mainstream simulation methods for offshore wind turbines can be divided into time-domain methods and frequency-domain methods. Time-domain simulation software includes OpenFAST, HAWC2, and Bladed. The aerodynamic analysis modules in these software programs are primarily based on Blade Momentum Theory (BEM) to iteratively solve for aerodynamic induction factors at each time step, thereby calculating the aerodynamic loads on the rotor. While time-domain methods can capture the nonlinear characteristics of the structure, they are computationally expensive and suitable for later-stage verification of offshore wind turbines, but not for the early design stages requiring extensive simulation optimization.

[0004] Frequency domain simulation software, including RAFT and QuLAF, linearizes nonlinear systems at their equilibrium points, thus constructing a linear system dynamic model in the frequency domain. This allows for the calculation of FORTs (Forward Wind Turbines) aerodynamic effects, namely aerodynamic thrust, aerodynamic added mass, and aerodynamic added damping. Compared to time-domain methods, frequency-domain methods offer significantly improved computational efficiency. Furthermore, because frequency-domain methods can obtain aerodynamic added mass and damping, they can identify negative aerodynamic damping phenomena earlier, enabling timely adjustments to the wind turbine's control strategy to improve platform stability and reduce structural load fluctuations.

[0005] Currently, frequency domain simulation methods are widely used in the optimization research of FORTs (Foreign Wind Turbines), but some challenges and limitations remain for aerodynamic analysis. First, the incoming flow velocity dynamically changes due to factors such as platform motion and blade pitch, and the airflow passing through the rotor needs time to reach equilibrium again, resulting in a delay effect, namely the dynamic inflow effect. Ignoring the dynamic inflow will lead to a significant difference between the simulated load and the actual load. Second, as wind turbines continue to grow in size, the blade dimensions are constantly increasing, and the influence of blade aeroelasticity on aerodynamic loads becomes increasingly significant, especially for fatigue load analysis. Ignoring these effects will lead to significant differences between the simulation results and the time-domain simulation results, particularly for predicting low-frequency response and 3P response. Summary of the Invention

[0006] This invention provides a frequency domain method for calculating aerodynamic loads on floating offshore wind turbines, thereby improving computational efficiency and accuracy, and providing technical support for accelerating offshore wind turbine simulation.

[0007] In a first aspect, the present invention provides a method for calculating the aerodynamic loads of a floating offshore wind turbine based on a frequency domain method, the method comprising:

[0008] The state derivative is determined based on the quasi-steady-state assumption of leaf element momentum theory, and the state derivative is corrected using a dynamic inflow model.

[0009] Based on the corrected state derivative, the first-order flapping mode of the blade was obtained through finite element software simulation, and a linear dynamic model of aero-elastic coupling two degrees of freedom, consisting of the translational motion of the wind turbine perpendicular to the plane of rotation and the first-order flapping mode of the blade, was established.

[0010] Based on the corrected state derivative, a wind turbine dynamics model is established for the translational motion of the wind turbine system perpendicular to the plane of rotation and the rotational motion around the hub axis.

[0011] Based on the corrected state derivative, and according to the floating offshore wind turbine pitch angle control, torque control, and floating body motion feedback control strategies, a control model is established.

[0012] Based on the aero-elastic coupling two-degree-of-freedom linear dynamic model, the wind turbine dynamic model, and the control model, the aerodynamic added mass and aerodynamic added damping are obtained.

[0013] Based on time-domain or frequency-domain algorithms, obtain the aerodynamic excitation force acting on the wheel hub when the nacelle position is fixed;

[0014] Based on the aerodynamic added mass, the aerodynamic added damping, and the aerodynamic excitation force, a global linear dynamic model of the wind turbine is established, and the global linear dynamic model is solved to obtain the overall response.

[0015] In some embodiments of the present invention, obtaining aerodynamic added mass and aerodynamic added damping based on the linear dynamic model with aero-elastic coupling of two degrees of freedom, the wind turbine dynamic model, and the control model includes:

[0016] The rotor dynamics equations of the wind turbine system under steady wind were determined using the aforementioned wind turbine dynamics model.

[0017] The control model is used to close the rotor dynamics equations to obtain the relationship between translational and rotational motions.

[0018] Based on the control model and the relationship between the translational and rotational motions, the initial expression for the change of aerodynamic thrust is transformed to obtain the transformed expression for the change of aerodynamic thrust.

[0019] Based on the transformed expression of the aerodynamic thrust change, the first aerodynamic additional mass and the first additional damping generated by the control model are obtained;

[0020] When the wind turbine is undergoing simple harmonic forced motion, the linear dynamic model with two degrees of freedom of aerodynamic-elastic coupling is transformed to obtain the first transformed model.

[0021] Solve the first transformed model to obtain the second aerodynamic additional mass and the second additional damping caused by the elasticity of the blade.

[0022] The total aerodynamic additional mass is obtained based on the first aerodynamic additional mass and the second aerodynamic additional mass, and the total additional damping is obtained based on the first additional damping and the second additional damping.

[0023] In some embodiments of the present invention, the overall linear dynamic model is as follows:

[0024]

[0025] In the formula, , as well as These represent the mass matrix, damping matrix, and stiffness matrix of the wind turbine, respectively. Including the aforementioned pneumatic added mass, Including the aforementioned additional pneumatic damping; , and These represent acceleration, velocity, and displacement, respectively. It is aerodynamic excitation force; Indicates the aerodynamic load on the tower; This is a first-order hydrodynamic load; It is a second-order hydrodynamic load.

[0026] In some embodiments of the present invention, the linear dynamic model of the aero-elastic coupling two degrees of freedom is as follows:

[0027]

[0028] In the formula, , , These represent mass, damping, and stiffness, respectively. , , These represent the acceleration, velocity, and displacement of the degrees of freedom, respectively. Indicates external force; subscript " "" indicates the translational degree of freedom of the wind turbine perpendicular to the plane of rotation, indicated by the subscript " "" indicates the first-order flapping mode of the blade, subscript " "and" "" indicates a coupling term between two degrees of freedom.

[0029] In some embodiments of the present invention, the wind turbine dynamics model is as follows:

[0030]

[0031] In the formula, This indicates the total mass of the wind turbine system. The translational velocity is perpendicular to the plane of rotation of the wind turbine. It is expressed as the change in translational velocity perpendicular to the plane of rotation of the wind turbine. Indicates the wind turbine speed. This represents the change in the blade pitch angle. This represents the moment of inertia of the wind turbine. , These represent the changes in aerodynamic thrust and aerodynamic torque, respectively, under given conditions. This indicates the torque of the generator. This indicates the change in generator torque. Indicates the gearbox transmission ratio. For aerodynamic thrust, For aerodynamic torque, The blade pitch angle, This represents the change in acceleration perpendicular to the plane of rotation of the wind turbine. This represents the change in wind turbine speed. The change in the angular acceleration of the wind turbine.

[0032] In some embodiments of the present invention, obtaining the aerodynamic excitation force acting on the wheel hub when the nacelle position is fixed based on the frequency domain algorithm includes:

[0033] The change in aerodynamic torque is calculated based on the cross-power spectral density function of wind speed.

[0034] With the one-dimensional rigid body degree of freedom of the wind turbine fixed, the linear dynamic model of the aerodynamic-elastic coupling two degrees of freedom is transformed to obtain the second transformed model;

[0035] Solve the second transformed model to obtain the change in aerodynamic thrust.

[0036] The aerodynamic excitation force is obtained based on the change in aerodynamic torque and the change in aerodynamic thrust.

[0037] In some embodiments of the present invention, the step of correcting the state derivative using a dynamic inflow model includes:

[0038] Obtain the quasi-steady-state induced velocity vector from the dynamic inflow model. With the actual induced velocity vector The conversion relationship between them;

[0039] The state derivative is corrected using the transformation relationship to obtain the corrected state derivative.

[0040] In some embodiments of the present invention, the dynamic inflow model is as follows:

[0041]

[0042] In the formula, The actual induced velocity vector , This represents the quasi-steady-state induced velocity vector. The average axial induction factor. The average wind speed at the wind turbine plane. Indicates the radius of rotation of the wind turbine. Indicates the radial position of the leaf element. It is the coupling constant;

[0043] The transformation relationship is as follows:

[0044]

[0045] In the formula, It is frequency;

[0046] The corrected state derivative for:

[0047]

[0048] In the formula, Indicates leaf element along The change in relative inflow velocity in the direction of flow. Indicates leaf element The change in relative inflow velocity in the direction of flow. Indicates the change in blade pitch angle; subscript " "" indicates the relevant state derivatives calculated based on the quasi-steady-state assumption in the Ye element momentum theory, with the subscript " "This represents the derivative after dynamic inflow correction, For aerodynamic thrust, For aerodynamic torque, The wind turbine rotation speed, , These represent the translational velocity of the wind turbine perpendicular to the plane of rotation and the blade pitch angle, respectively, with F being the aerodynamic excitation force. , It takes into account the external excitation force after dynamic inflow correction; The change in state; It is the change in relative velocity of the incoming flow in the i-direction; This represents the change in wind speed in the direction i; Let i be the quasi-steady-state induced velocity in the i-direction, with the subscript " "Indicates quasi-steady state"

[0049] Secondly, embodiments of the present invention also provide an apparatus for calculating aerodynamic loads of floating offshore wind turbines based on frequency domain methods, the apparatus comprising:

[0050] The derivative acquisition and correction module is used to determine the state derivative based on the quasi-steady-state assumption of leaf element momentum theory, and to correct the state derivative using a dynamic inflow model;

[0051] The first model construction module is used to obtain the first-order flapping mode of the blade through finite element software simulation based on the corrected state derivative, and to establish a linear dynamic model of two degrees of freedom of aero-elastic coupling between the translational motion of the wind turbine perpendicular to the plane of rotation and the first-order flapping mode of the blade.

[0052] The second model building module is used to establish a wind turbine dynamics model of the wind turbine system based on the corrected state derivative, including the translational motion perpendicular to the plane of rotation and the rotational motion around the hub axis.

[0053] The third model building module is used to establish a control model based on the corrected state derivative and according to the floating offshore wind turbine pitch angle control, torque control and floating body motion feedback control strategies.

[0054] The mass and damping acquisition module is used to obtain aerodynamic added mass and aerodynamic added damping based on the aero-elastic coupling two-degree-of-freedom linear dynamic model, the wind turbine dynamic model, and the control model.

[0055] The aerodynamic excitation force acquisition module is used to acquire the aerodynamic excitation force acting on the wheel hub when the nacelle position is fixed, based on time-domain or frequency-domain algorithms.

[0056] The solution module is used to establish a global linear dynamic model of the wind turbine based on the aerodynamic added mass, the aerodynamic added damping, and the aerodynamic excitation force, and to solve the global linear dynamic model to obtain the overall response.

[0057] Thirdly, the present invention also provides an electronic device, including a memory and a processor; the memory stores a computer program, and the processor is used to run the computer program in the memory to perform operations in the frequency domain-based aerodynamic load calculation method for floating offshore wind turbines provided in the first aspect.

[0058] In the frequency domain-based aerodynamic load calculation method for floating offshore wind turbines provided in this invention, a dynamic inflow model is used to dynamically correct the quasi-steady-state assumptions of the blade element momentum theory based on the relevant state derivatives calculated by the blade element momentum theory, resulting in corrected relevant state derivatives. Furthermore, addressing the shortcomings of existing frequency domain methods in considering blade elasticity, this invention considers the order-of-magnitude difference in time scale between the dynamic analysis considering the influence of control strategies and the structural dynamic analysis considering blade flexibility. The aerodynamic-servo-elastic frequency domain analysis model is decoupled into a blade elasticity model and a wind turbine dynamics model, thus considering the first-order flapping mode elasticity of the blade. In addition, addressing the shortcomings of existing frequency domain methods in considering the influence of control strategies on aerodynamic analysis, this invention establishes a control model considering the pitch angle control, torque control, and floating body motion feedback control strategies of the floating offshore wind turbine, incorporating them into the system dynamic equations. Moreover, based on the frequency domain method, this invention can identify negative aerodynamic damping phenomena earlier, allowing for timely adjustment of the wind turbine's control strategy to improve platform stability and reduce structural load fluctuations. Attached Figure Description

[0059] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0060] Figure 1 This is a flowchart illustrating the aerodynamic load calculation method for floating offshore wind turbines based on the frequency domain method provided in this embodiment of the invention.

[0061] Figure 2 This is a schematic diagram of a floating offshore wind turbine provided in an embodiment of the present invention;

[0062] Figure 3 This is a comparison chart of the thrust spectrum obtained by frequency domain calculation and the thrust spectrum obtained by time domain simulation provided in the embodiments of the present invention;

[0063] Figure 4 This is a comparison chart of the overall response results of the wind turbine provided in the embodiments of the present invention. Detailed Implementation

[0064] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0065] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0066] "A and / or B" includes the following three combinations: A only, B only, and a combination of A and B.

[0067] The use of "applies to" or "configured to" in this invention implies an open and inclusive language, which does not exclude the applicability to or configuration to devices performing additional tasks or steps. Additionally, the use of "based on" implies openness and inclusivity, because processes, steps, calculations, or other actions "based on" one or more conditions or values ​​may in practice be based on additional conditions or values ​​beyond those conditions.

[0068] In this invention, the term "exemplary" is used to mean "serving as an example, illustration, or description." Any embodiment described as "exemplary" in this invention is not necessarily to be construed as being more preferred or advantageous than other embodiments. The following description is provided to enable any person skilled in the art to make and use the invention. Details are set forth in the following description for purposes of explanation. It should be understood that those skilled in the art will recognize that the invention can be made without using these specific details. In other instances, well-known structures and processes will not be described in detail to avoid obscuring the description of the invention with unnecessary detail. Therefore, the invention is not intended to be limited to the embodiments shown, but is consistent with the broadest scope of the principles and features disclosed herein.

[0069] The following describes, with reference to the accompanying drawings, the method for calculating aerodynamic loads of floating offshore wind turbines based on the frequency domain method provided by the embodiments of the present invention.

[0070] like Figure 1 As shown in the figure, this invention provides a method for calculating the aerodynamic load of a floating offshore wind turbine based on the frequency domain method. The method includes the following steps:

[0071] S101, the state derivative is determined based on the quasi-steady-state assumption of leaf element momentum theory, and the state derivative is corrected using the dynamic inflow model Øye.

[0072] Here, the state derivatives are the state derivatives of aerodynamic thrust T and aerodynamic torque Q with respect to the rotor speed Ω, the rotor's translational velocity v perpendicular to the plane of rotation, and the blade pitch angle p, etc. In some examples, such as Figure 2 As shown, the floating offshore wind turbine is a 5MW OC4 DeepCWind.

[0073] In some examples, the state derivative is corrected using the dynamic inflow model Øye, including the following steps:

[0074] Obtain the quasi-steady-state induced velocity vector from the dynamic inflow model. With the actual induced velocity vector The conversion relationship between them.

[0075] The dynamic inflow model is as follows:

[0076]

[0077] In the formula, The actual induced velocity vector , This represents the quasi-steady-state induced velocity vector. The average axial induction factor. The average wind speed at the wind turbine plane. Indicates the radius of rotation of the wind turbine. Indicates the radial position of the leaf element. The coupling constant is usually taken as... .

[0078] Transforming formula (1), we obtain the following transformation relationship:

[0079]

[0080] In the formula, This represents the frequency, measured in rad / s.

[0081] The state derivative is corrected using the transformation relationship to obtain the corrected state derivative.

[0082] Wherein, the corrected state derivative for:

[0083]

[0084] In the formula, Indicates leaf element along The change in relative inflow velocity in the direction of flow. Indicates leaf element along The change in relative inflow velocity in the direction of flow. Indicates the change in blade pitch angle; subscript " "" indicates the relevant state derivatives calculated based on the quasi-steady-state assumption in the Ye element momentum theory, with the subscript " "This represents the derivative after dynamic inflow correction, For aerodynamic thrust, For aerodynamic torque, The wind turbine rotation speed, , These represent the translational velocity of the wind turbine perpendicular to the plane of rotation and the blade pitch angle, respectively, with F being the aerodynamic excitation force. , It takes into account the external excitation force after dynamic inflow correction; Status (including wind speed) Rotation speed and pitch angle The change in ) yes( or , The change in relative velocity of the incoming flow in the direction of i; This represents the change in wind speed in the direction i; for( or , The (quasi-steady-state) induced velocity in the i-direction, subscript " "Indicates a quasi-steady state.

[0085] S102, the first-order flapping mode of the blade is obtained through finite element software simulation, and a linear dynamic model of two degrees of freedom of aerodynamic-elastic coupling is established for the translational motion of the wind turbine perpendicular to the plane of rotation and the first-order flapping mode of the blade.

[0086] In some examples, the elastic blade is modeled as an Euler-Bernoulli beam, considering only the first-order flapping bending mode, and the first-order flapping mode shape of the blade is obtained through simulation using the finite element method. .

[0087] The linear dynamic model with aerodynamic-elastic coupling two degrees of freedom is as follows:

[0088]

[0089] In the formula, , , These represent mass, damping, and stiffness, respectively. , , These represent the acceleration, velocity, and displacement of the degrees of freedom, respectively. Indicates external force; subscript " "" indicates the translational degree of freedom of the wind turbine perpendicular to the plane of rotation, indicated by the subscript " "" indicates the first-order flapping mode of the blade, subscript " "and" "" indicates a coupling term between two degrees of freedom.

[0090] First-order flapping mode mass of the blade Calculate using the following formula:

[0091]

[0092] In the formula, Let L be the blade linear density and L be the blade length.

[0093] Two-degree-of-freedom mass coupling term Calculate using the following formula:

[0094]

[0095] First-order flapping mode damping of the blade It consists of two parts, one from structural deformation and the other from the aerodynamic damping effect caused by the additional inflow velocity at the blade element location due to structural deformation, calculated by the following formula:

[0096]

[0097] In the formula, Indicates the modal damping ratio; This represents the derivative of the aerodynamic thrust at the blade element with respect to the blade element velocity.

[0098] Two-degree-of-freedom damped coupling term Calculate using the following formula:

[0099]

[0100] Modal forces acting on the blade Calculate using the following formula:

[0101]

[0102] In the formula, The load on the leaf element.

[0103] S103, Establish a wind turbine dynamics model of the wind turbine system in translational motion perpendicular to the plane of rotation and rotational motion around the hub axis.

[0104] In some examples, the translational motion of the wind turbine system perpendicular to the plane of rotation and its rotational motion about the hub axis are analyzed, and the aerodynamic excitation force is considered. and A Taylor expansion at the equilibrium point yields a two-degree-of-freedom wind turbine dynamics model. The wind turbine system consists of rigid blades, a hub, a gearbox, and a generator.

[0105] The wind turbine dynamics model is as follows:

[0106]

[0107] In the formula, This indicates the total mass of the wind turbine system. The translational velocity is perpendicular to the plane of rotation of the wind turbine. It is expressed as the change in translational velocity perpendicular to the plane of rotation of the wind turbine. Indicates the wind turbine speed. This represents the change in the blade pitch angle. This represents the moment of inertia of the wind turbine. and These represent the changes in aerodynamic thrust and aerodynamic torque, respectively, under a given condition. This indicates the torque of the generator. This indicates the change in generator torque. Indicates the gearbox transmission ratio. For aerodynamic thrust, For aerodynamic torque, The blade pitch angle, This represents the change in acceleration perpendicular to the plane of rotation of the wind turbine. This represents the change in wind turbine speed. This represents the change in the angular acceleration of the wind turbine.

[0108] S104. A control model is established based on the pitch angle control, torque control, and floating body motion feedback control strategies of floating offshore wind turbines.

[0109] In some examples, control models are established based on the floating offshore wind turbine pitch angle control, torque control, and floating body motion feedback control strategies. In this embodiment, a tip speed ratio tracking PI controller, a blade pitch angle controller, and a floating feedback controller are used, and the control equations are as follows:

[0110]

[0111] In the formula, Indicates angular frequency; A filter indicating the rotational speed of the wind turbine; A filter representing cabin acceleration; Indicates proportional gain; Indicates integral gain; superscript " "" indicates the blade pitch angle controller, indicated by the superscript " "Indicates torque controller, The proportional gain is used for feedback control of the floating body motion.

[0112] S105, based on the aero-elastic coupling two-degree-of-freedom linear dynamic model, the wind turbine dynamic model, and the control model, the aerodynamic added mass and aerodynamic added damping are obtained.

[0113] In some examples, S105 includes the following sub-steps:

[0114] S201, using the aforementioned wind turbine dynamics model, determine the rotor dynamics equations of the wind turbine system under steady wind conditions. That is, ignore the aerodynamic torque variation in the wind turbine dynamics model. The rotor dynamics equations of the wind turbine system under steady wind are obtained as follows:

[0115]

[0116] S202, the control model is used to close the rotor dynamics equations to obtain the relationship between translational and rotational motions. That is, by substituting control equation (11) into equation (12) and performing a series of transformations, the relationship between translational and rotational motions is obtained:

[0117]

[0118] In the formula, The expression is as follows:

[0119]

[0120] In the formula, i is the imaginary unit.

[0121] S203, based on the control model and the relationship between the translational and rotational motions, the initial expression for the change of aerodynamic thrust is transformed to obtain the transformed expression for the change of aerodynamic thrust.

[0122] The change in aerodynamic thrust can be expressed as:

[0123]

[0124] Equations (11), (13), and (15) are combined to determine the control equations for the pitch angle, and it is assumed that the wind turbine system undergoes simple harmonic motion in the one-dimensional translational direction. This leads to the transformed expression for the thrust change:

[0125]

[0126] S204, based on the transformed expression of the aerodynamic thrust change, obtain the first aerodynamic added mass generated by the control model. and the first additional damping .

[0127] in,

[0128] S205, under the condition that the wind turbine is undergoing simple harmonic forced motion, the linear dynamic model of the aerodynamic-elastic coupling two degrees of freedom is transformed to obtain the first transformed model. That is, an external force is applied to the wind turbine. This causes the wind turbine to undergo simple harmonic forced motion, that is... The two-degree-of-freedom dynamic model equation (4) of the one-dimensional translation of the wind turbine and the first-order flapping mode of the blades is transformed into:

[0129]

[0130] S206, Solve the first transformed model to obtain the second aerodynamic additional mass caused by the elasticity of the blade. Second additional damping .

[0131] Schematic, since the inertia and damping of the wind turbine's rigid body motion are already included in the global mass matrix and damping matrix considering the controller, therefore, it contains... and The term can be ignored, and the external force is obtained. and blade deformation displacement expression:

[0132]

[0133] Furthermore, the calculation formulas for the aerodynamic additional mass and additional damping caused by the elastic effect of the blades are obtained:

[0134]

[0135] S207, obtain the total aerodynamic added mass based on the first aerodynamic added mass and the second aerodynamic added mass. The total additional damping is obtained based on the first additional damping and the second additional damping. .

[0136] Schematic, the aerodynamic added mass and damping are calculated by considering the effects of the control system and the blade elasticity respectively, and then added together according to the principle of linear superposition to obtain the total aerodynamic added mass and added damping, as shown in the following formula:

[0137]

[0138] S106, based on time-domain or frequency-domain algorithms, obtains the aerodynamic excitation force acting on the wheel hub when the nacelle position is fixed.

[0139] In some examples, S106 includes the following sub-steps:

[0140] S301, fix the translational degree of freedom of the wind turbine to obtain the dynamic model of the wind turbine system, i.e., equation (22).

[0141] S302, calculate the change in aerodynamic torque based on the cross-power spectral density function of wind speed. .

[0142] S303, based on the aforementioned cross-power spectral density function and combined with a linear dynamic model of aerodynamic-elastic coupling two degrees of freedom, the change in aerodynamic thrust is calculated. .

[0143] S304. Based on the dynamic model of the wind turbine system, the change in aerodynamic torque, and the change in aerodynamic thrust, the aerodynamic excitation force is obtained.

[0144] It is understandable that the change in aerodynamic torque in this embodiment is... and aerodynamic thrust change The frequency domain method is used to obtain the aerodynamic thrust. In other embodiments of the present invention, the time domain simulation method can also be used to obtain the aerodynamic thrust spectrum, that is, the aerodynamic thrust is simulated under turbulent wind when the nacelle is fixed, and then the aerodynamic thrust spectrum is obtained by spectral analysis.

[0145] Specifically, when the computer cabin is fixed in position, the aerodynamic thrust acting on the wind turbine hub is, in the frequency domain dynamics model of the wind turbine system, i.e., equation (10), the change in the translational velocity of the wind turbine in the vertical plane. When the expression is 0, we get the following formula:

[0146]

[0147] The above formula can be calculated using either time-domain or frequency-domain methods. If a time-domain simulation method is used, that is, considering the aerodynamic thrust simulated under turbulent wind when the nacelle is fixed, and then using spectral analysis to obtain the aerodynamic thrust spectrum.

[0148] If a frequency domain method is used, then the cross-power spectral density function of wind speed is calculated, and then... First, calculate the cross-power spectral density function of wind speed according to the following formula. :

[0149]

[0150] In the formula, Indicates the number of blades in the wind turbine; Indicates the wind turbine rotation speed; Indicates wind spectrum; Indicates leaf element Radial position calculated from the center of the wheel hub Indicates leaf element Radial position calculated from the center of the wheel hub; It is the average wind speed at the hub of the wind turbine; It is the turbulence length scale. f is the frequency, in Hz; d represents the distance between two leaf elements.

[0151] Furthermore, calculate using the following formula. :

[0152]

[0153] In the formula, This is a vector consisting of the derivatives of the aerodynamic torque with respect to the wind speed on each blade element. is the cross spectrum matrix in equation (23).

[0154] Furthermore, aerodynamic thrust is calculated considering blade flexibility. According to equation (4), it is assumed that the one-dimensional rigid body degree of freedom of the wind turbine is fixed, i.e. , as well as If all equal to 0, then equation (4) becomes:

[0155]

[0156] Furthermore, solving equation (25) yields... The expression:

[0157]

[0158] In the formula, Let be a vector consisting of the derivatives of aerodynamic thrust with respect to the wind speed on each blade element. It is the mode shape vector of the blade.

[0159] Furthermore, substituting equations (26) and (24) into equation (22) yields the aerodynamic thrust at the wind turbine hub. expression:

[0160]

[0161] It should be noted that the aerodynamic excitation force can be obtained using both time-domain and frequency-domain methods. The time-domain method is based on fully coupled time-domain simulation to obtain the aerodynamic excitation force, and then the aerodynamic thrust spectrum is obtained through spectral analysis, i.e., ΔT in equation (27). hub (ω). If the frequency domain method is used, then ΔT is obtained by combining the aero-elastic coupled dynamics model and the wind turbine dynamics model based on the wind speed cross-power spectral density function. hub (ω). In some examples, such as Figure 3 The figure shows a comparison between the thrust spectra calculated using the frequency domain method under conditions of wind speeds below, above, and above the rated wind speed, and the thrust spectra obtained from time-domain simulation after spectral analysis. Figure 3 It is evident that, under rated wind speed, the complex control strategy leads to significant discrepancies between the predicted low-frequency range of the thrust spectrum and the time-domain results. However, the aerodynamic thrust spectrum calculated by the frequency-domain method-based aerodynamic load calculation model for floating offshore wind turbines can effectively capture the 3P load of the structure, verifying the accuracy of the frequency-domain method-based aerodynamic load calculation model for floating offshore wind turbines and laying a solid foundation for subsequent calculations of aerodynamic loads of floating offshore wind turbines based on the frequency-domain method.

[0162] S107. Based on the aerodynamic added mass, the aerodynamic added damping, and the aerodynamic excitation force, establish a global linear dynamic model of the wind turbine, and solve the global linear dynamic model to obtain the overall response.

[0163] The overall linear dynamic model is as follows:

[0164]

[0165] In the formula, , as well as These represent the mass matrix, damping matrix, and stiffness matrix of the wind turbine, respectively. Including the aforementioned pneumatic added mass, Including the aforementioned additional pneumatic damping; , and These represent acceleration, velocity, and displacement, respectively. It is aerodynamic excitation force; Indicates the aerodynamic load on the tower; This is a first-order hydrodynamic load; It is a second-order hydrodynamic load.

[0166] In some examples, such as Figure 4 As shown, the power spectrum of the overall wind turbine response at rated wind speed, obtained using time-domain and frequency-domain methods respectively, is compared with the results obtained from time-domain and frequency-domain simulations (including sway, pitch, heave, nacelle acceleration, tower root moment, and mooring tension), and the overall wind turbine response obtained from time-domain and frequency-domain simulations. Figure 4 In this context, FD Hybrid represents the overall wind turbine response obtained by further calculation of the thrust spectrum using the time-domain method in step S106 based on the calculation model of this invention, and FD Origin represents the overall wind turbine response obtained by further calculation of the thrust spectrum using the frequency-domain method in step S106 based on the calculation model of this invention. Figure 4 As can be seen, the motion and load response spectra calculated based on the computational model of this invention are closer to the time-domain simulation results than those obtained by RAFT, especially for low-frequency and 3P responses. In contrast, RAFT has poor prediction performance for the 3P response, and may even fail to capture it. The statistical characteristics of each response are shown in Table 1.

[0167] Table 1. Statistical characteristics of each response of DeepCWind FOWT at 5MW OC4 under rated wind speed.

[0168]

[0169] As can be seen from Table 1, the statistical characteristics of motion and load response obtained by the floating offshore wind turbine aerodynamic load calculation model based on the frequency domain method of this invention are generally closer to the statistical characteristics of the time domain simulation results than those obtained by RAFT.

[0170] The aerodynamic load calculation method for floating offshore wind turbines based on the frequency domain method provided in this invention uses a dynamic inflow model to dynamically correct the quasi-steady-state assumptions of the blade element momentum theory based on the relevant state derivatives calculated by the blade element momentum theory, thus obtaining the corrected relevant state derivatives. Furthermore, addressing the shortcomings of existing frequency domain methods in considering blade elasticity, this invention considers the order-of-magnitude difference in time scale between the dynamic analysis considering the influence of control strategies and the structural dynamic analysis considering blade flexibility. It decouples the aerodynamic-servo-elastic frequency domain analysis model into a blade elasticity model and a wind turbine dynamics model, thereby considering the first-order flapping mode elasticity of the blade. In addition, addressing the shortcomings of existing frequency domain methods in considering the influence of control strategies on aerodynamic analysis, this invention establishes a control model considering the pitch angle control, torque control, and floating body motion feedback control strategies of the floating offshore wind turbine, incorporating them into the system dynamic equations. Moreover, based on the frequency domain method, this invention can identify negative inflow aerodynamic damping phenomena earlier, thereby allowing for timely adjustment of the wind turbine's control strategy to improve platform stability and reduce structural load fluctuations.

[0171] This invention also provides an apparatus for calculating the aerodynamic loads of a floating offshore wind turbine based on a frequency domain method, the apparatus comprising:

[0172] The derivative acquisition and correction module is used to determine the state derivative based on the quasi-steady-state assumption of leaf element momentum theory, and to correct the state derivative using a dynamic inflow model.

[0173] The first model construction module is used to obtain the first-order flapping mode of the blade through finite element software simulation based on the corrected state derivative, and to establish a linear dynamic model of aero-elastic coupling two degrees of freedom of the wind turbine's translational motion perpendicular to the plane of rotation and the first-order flapping mode of the blade.

[0174] The second model construction module is used to establish a wind turbine dynamics model of the wind turbine system based on the corrected state derivative, including the translational motion perpendicular to the plane of rotation and the rotational motion around the hub axis.

[0175] The third model construction module is used to establish a control model based on the corrected state derivative and according to the floating offshore wind turbine pitch angle control, torque control and floating body motion feedback control strategies.

[0176] The mass and damping acquisition module is used to obtain aerodynamic added mass and aerodynamic added damping based on the aero-elastic coupling two-degree-of-freedom linear dynamic model, the wind turbine dynamic model, and the control model.

[0177] The aerodynamic excitation force acquisition module is used to acquire the aerodynamic excitation force acting on the wheel hub when the nacelle position is fixed, based on time-domain or frequency-domain algorithms.

[0178] The solution module is used to establish a global linear dynamic model of the wind turbine based on the aerodynamic added mass, the aerodynamic added damping, and the aerodynamic excitation force, and to solve the global linear dynamic model to obtain the overall response.

[0179] Based on any of the above embodiments, another embodiment of the present invention provides an electronic device, which may include: a processor, a communications interface, a memory, and a communication bus, wherein the processor, the communications interface, and the memory communicate with each other through the communication bus. The processor can call logical instructions in the memory to execute the above-described frequency domain-based method for calculating the aerodynamic loads of floating offshore wind turbines.

[0180] Furthermore, the logical instructions in the aforementioned memory can be implemented as software functional units and sold or used as independent products, and can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0181] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0182] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., including several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods of various embodiments or some parts of embodiments.

[0183] The above provides a detailed description of the aerodynamic load calculation method for floating offshore wind turbines based on the frequency domain method provided by the embodiments of the present invention. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for calculating the aerodynamic loads of a floating offshore wind turbine based on the frequency domain method, characterized in that, The method includes: The state derivative is determined based on the quasi-steady-state assumption of leaf element momentum theory, and the state derivative is corrected using a dynamic inflow model. Based on the corrected state derivative, the first-order flapping mode of the blade was obtained through finite element software simulation, and a linear dynamic model of aero-elastic coupling two degrees of freedom, consisting of the translational motion of the wind turbine perpendicular to the plane of rotation and the first-order flapping mode of the blade, was established. Based on the corrected state derivative, a wind turbine dynamics model is established for the translational motion of the wind turbine system perpendicular to the plane of rotation and the rotational motion around the hub axis. Based on the corrected state derivative, and according to the floating offshore wind turbine pitch angle control, torque control, and floating body motion feedback control strategies, a control model is established. Based on the aero-elastic coupling two-degree-of-freedom linear dynamic model, the wind turbine dynamic model, and the control model, the aerodynamic added mass and aerodynamic added damping are obtained. Based on time-domain or frequency-domain algorithms, obtain the aerodynamic excitation force acting on the wheel hub when the nacelle position is fixed; Based on the aerodynamic added mass, the aerodynamic added damping, and the aerodynamic excitation force, a global linear dynamic model of the wind turbine is established, and the global linear dynamic model is solved to obtain the overall response.

2. The method for calculating aerodynamic loads of floating offshore wind turbines based on the frequency domain method according to claim 1, characterized in that, The aerodynamic-elastic coupling two-degree-of-freedom linear dynamic model, the wind turbine dynamic model, and the control model are used to obtain aerodynamic added mass and aerodynamic added damping, including: The rotor dynamics equations of the wind turbine system under steady wind were determined using the aforementioned wind turbine dynamics model. The control model is used to close the rotor dynamics equations to obtain the relationship between translational and rotational motions. Based on the control model and the relationship between the translational and rotational motions, the initial expression for the change of aerodynamic thrust is transformed to obtain the transformed expression for the change of aerodynamic thrust. Based on the transformed expression of the aerodynamic thrust change, the first aerodynamic additional mass and the first additional damping generated by the control model are obtained; When the wind turbine is undergoing simple harmonic forced motion, the linear dynamic model with two degrees of freedom of aerodynamic-elastic coupling is transformed to obtain the first transformed model. Solve the first transformed model to obtain the second aerodynamic additional mass and the second additional damping caused by the elasticity of the blade. The total aerodynamic additional mass is obtained based on the first aerodynamic additional mass and the second aerodynamic additional mass, and the total additional damping is obtained based on the first additional damping and the second additional damping.

3. The method for calculating aerodynamic loads of floating offshore wind turbines based on frequency domain methods according to claim 1, characterized in that, The overall linear dynamic model is as follows: ； In the formula, , as well as These represent the mass matrix, damping matrix, and stiffness matrix of the wind turbine, respectively. Including the aforementioned pneumatic added mass, Including the aforementioned additional pneumatic damping; , and These represent acceleration, velocity, and displacement, respectively. It is aerodynamic excitation force; Indicates the aerodynamic load on the tower; This is a first-order hydrodynamic load; It is a second-order hydrodynamic load.

4. The method for calculating aerodynamic loads of floating offshore wind turbines based on the frequency domain method according to claim 1, characterized in that, The linear dynamic model with two degrees of freedom of aero-elastic coupling is as follows: ； In the formula, , , These represent mass, damping, and stiffness, respectively. , , These represent the acceleration, velocity, and displacement of the degrees of freedom, respectively. Indicates external force; subscript " "Indicates the translational degree of freedom of the wind turbine perpendicular to the plane of rotation, subscript " "Indicates the first-order flapping mode of the blade, subscript " "and" "" indicates a coupling term between two degrees of freedom.

5. The method for calculating aerodynamic loads of floating offshore wind turbines based on the frequency domain method according to claim 1, characterized in that, The wind turbine dynamics model is as follows: ； In the formula, This indicates the total mass of the wind turbine system. The translational velocity is perpendicular to the plane of rotation of the wind turbine. It is expressed as the change in translational velocity perpendicular to the plane of rotation of the wind turbine. Indicates the wind turbine speed. This represents the change in the blade pitch angle. This represents the moment of inertia of the wind turbine. , These represent the changes in aerodynamic thrust and aerodynamic torque, respectively, under given conditions. This indicates the torque of the generator. This indicates the change in generator torque. Indicates the gearbox transmission ratio. For aerodynamic thrust, For aerodynamic torque, The blade pitch angle, This represents the change in acceleration perpendicular to the plane of rotation of the wind turbine. This represents the change in wind turbine speed. The change in the angular acceleration of the wind turbine.

6. The method for calculating aerodynamic loads of floating offshore wind turbines based on frequency domain methods according to claim 1, characterized in that, The frequency domain algorithm-based acquisition of the aerodynamic excitation force acting on the wheel hub when the nacelle position is fixed includes: The translational degrees of freedom of the wind turbine are fixed to obtain a dynamic model of the wind turbine system; The change in aerodynamic torque is calculated based on the cross-power spectral density function of wind speed; Based on the aforementioned cross-power spectral density function, and combined with the linear dynamic model of aero-elastic coupling two degrees of freedom, the change in aerodynamic thrust is calculated. The aerodynamic excitation force is obtained based on the dynamic model of the wind turbine system, the change in aerodynamic torque, and the change in aerodynamic thrust.

7. The method for calculating aerodynamic loads of floating offshore wind turbines based on frequency domain methods according to claim 1, characterized in that, The step of correcting the state derivative using a dynamic inflow model includes: Obtain the quasi-steady-state induced velocity vector from the dynamic inflow model. With the actual induced velocity vector The conversion relationship between them; The state derivative is corrected using the transformation relationship to obtain the corrected state derivative.

8. The method for calculating aerodynamic loads of floating offshore wind turbines based on the frequency domain method according to claim 7, characterized in that, The dynamic inflow model is as follows: ； In the formula, The actual induced velocity vector , This represents the quasi-steady-state induced velocity vector. The average axial induction factor. The average wind speed at the wind turbine plane. Indicates the radius of rotation of the wind turbine. Indicates the radial position of the leaf element. It is the coupling constant; The transformation relationship is as follows: ； In the formula, It is frequency; The corrected state derivative for: ； In the formula, Indicates leaf element along The change in relative inflow velocity in the direction of flow. Indicates leaf element along The change in relative inflow velocity in the direction of flow. Indicates the change in blade pitch angle; subscript " "" indicates the relevant state derivatives calculated based on the quasi-steady-state assumption in the Ye element momentum theory, with the subscript " "This represents the derivative after dynamic inflow correction, For aerodynamic thrust, For aerodynamic torque, The wind turbine rotation speed, , These represent the translational velocity of the wind turbine perpendicular to the plane of rotation and the blade pitch angle, respectively, with F being the aerodynamic excitation force. , It takes into account the external excitation force after dynamic inflow correction; The change in state; It is the change in relative velocity of the incoming flow in the i-direction; This represents the change in wind speed in the direction i; Let "i" represent the quasi-steady-state induced velocity in the i-direction, with the subscript "i". "Indicates a quasi-steady state.

9. A method and apparatus for calculating aerodynamic loads of floating offshore wind turbines based on frequency domain methods, characterized in that, The device includes: The derivative acquisition and correction module is used to determine the state derivative based on the quasi-steady-state assumption of leaf element momentum theory, and to correct the state derivative using a dynamic inflow model; The first model construction module is used to obtain the first-order flapping mode of the blade through finite element software simulation based on the corrected state derivative, and to establish a linear dynamic model of two degrees of freedom of aero-elastic coupling between the translational motion of the wind turbine perpendicular to the plane of rotation and the first-order flapping mode of the blade. The second model building module is used to establish a wind turbine dynamics model of the wind turbine system based on the corrected state derivative, including the translational motion perpendicular to the plane of rotation and the rotational motion around the hub axis. The third model building module is used to establish a control model based on the corrected state derivative and according to the floating offshore wind turbine pitch angle control, torque control and floating body motion feedback control strategies. The mass and damping acquisition module is used to obtain aerodynamic added mass and aerodynamic added damping based on the aero-elastic coupling two-degree-of-freedom linear dynamic model, the wind turbine dynamic model, and the control model. The aerodynamic excitation force acquisition module is used to acquire the aerodynamic excitation force acting on the wheel hub when the nacelle position is fixed, based on time-domain or frequency-domain algorithms. The solution module is used to establish a global linear dynamic model of the wind turbine based on the aerodynamic added mass, the aerodynamic added damping, and the aerodynamic excitation force, and to solve the global linear dynamic model to obtain the overall response.

10. An electronic device, characterized in that, It includes a memory and a processor; the memory stores a computer program, and the processor is used to run the computer program in the memory to perform the steps in the frequency domain method for calculating the aerodynamic load of a floating offshore wind turbine as described in any one of claims 1 to 8.

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