Structural fatigue evaluation method and system for tower drum of wind turbine generator, equipment and storage medium

Abstract

The invention relates to a structural fatigue evaluation method and system for a tower drum of a wind turbine generator, equipment and a storage medium, and the evaluation method comprises the steps: S1, obtaining the shape functions of a plurality of nodes on a target tower drum; the plurality of nodes are uniformly divided along the height direction of the target tower drum; s2, acquiring operation data of a target wind turbine generator; s3, inputting the operation data and the shape function on each node into a preset wind turbine generator model to obtain a bending moment time sequence corresponding to each node on the target tower; s4, according to the bending moment time sequence of each node, the accumulated damage degree of each node is determined; and S5, according to the accumulated damage degree of the at least one node, outputting a structural fatigue evaluation result of the target tower drum. According to the evaluation method, the structural fatigue condition of the tower drum can be accurately estimated without depending on an external sensor.

Description

Technical Field

[0001] The present invention relates to the field of offshore wind turbines, and in particular to a method and system, equipment and storage medium for evaluating the structural fatigue of a tower of a wind turbine. Background Art

[0002] Offshore wind turbines are subject to complex and variable loads during operation, including combined loads from wind, waves, and the movement of the turbine itself. Long-term load accumulation will cause fatigue damage to the tower structure, affecting the operating life and safety of the turbine.

[0003] Traditional tower load monitoring methods rely on the deployment of a large number of sensors, which not only increases the manufacturing and maintenance costs of wind turbines, but also has problems such as short sensor life and complex installation. Since offshore wind turbines are greatly affected by the marine environment, long-term use of sensors in harsh environments will lead to frequent failures. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a structural fatigue assessment method and system, equipment and storage medium related to the tower of a wind turbine generator set.

[0005] The technical solution adopted by the present invention to solve the technical problem is: constructing a structural fatigue assessment method for a tower of a wind turbine generator set, comprising the following steps:

[0006] S1: Obtain shape functions of multiple nodes on the target tower; the multiple nodes are evenly divided along the height direction of the target tower;

[0007] S2: Obtaining the operating data of the target wind turbine;

[0008] S3: inputting the operating data and the shape function at each node into a preset wind turbine model to obtain a bending moment time series corresponding to each node on the target tower;

[0009] S4: determining the cumulative damage degree of each node according to the bending moment time series of each node;

[0010] S5: Outputting a structural fatigue assessment result of a target tower according to the accumulated damage degree of at least one node.

[0011] In some embodiments, in step S1, the shape function at each node is expressed as:

[0012]

[0013] In the formula, For the The nodes correspond to the relative height of the tower; a1-a5 are the associated parameters associated with the shape of the tower, LT The total height of the tower including the rigid foundation, L B is the rigid foundation height.

[0014] In some embodiments, the method for obtaining the associated parameters a1-a5 of each node includes the following steps:

[0015] S11: Obtain reference association parameters used as reference;

[0016] S12: Obtaining estimated correlation parameters of the target tower at the corresponding node according to the reference correlation parameters;

[0017] S13: Obtaining an estimated bending moment at a corresponding node according to the estimated relationship parameter;

[0018] S14: Obtain the actual bending moment at the corresponding node, and compare the actual bending moment with the estimated bending moment; wherein, when the difference between the estimated bending moment and the actual bending moment is within a preset error range, the estimated associated parameters are used as associated parameters for calculating the bending moment at the corresponding node; when the difference between the estimated bending moment and the actual bending moment is not within the preset error range, the estimated associated parameters are adjusted until the difference between the estimated bending moment and the actual bending moment is within the preset error range.

[0019] In some embodiments, the step of obtaining the bending moment time series of any node specifically includes:

[0020] Inputting the operating data and the shape function at each node into a preset wind turbine model to obtain the displacement of the tower at a height z at time t;

[0021] The tower bending moment at the tower at the time t and the height z is calculated according to the following formula:

[0022] M(z, t) = EI(z)κ(z, t) (4)

[0023]

[0024] Wherein, κ(z, t) is the curvature of the tower at the time t and the height z; q(z, t) is the displacement of the tower at the time t and the height z; EI(z) is the stiffness coefficient of the tower at the height z; M(z, t) is the tower bending moment at the time t and the height z;

[0025] By analogy, the tower bending moment at continuous moments is calculated to obtain the bending moment time series at any node.

[0026] In some embodiments, the wind turbine model is a 2-DOF wind turbine model, which is related to the axial displacement of the tower and the rotation of the transmission shaft.

[0027] In some embodiments, the wind turbine model is represented as:

[0028]

[0029] Where, T a is the aerodynamic thrust, Q a is the aerodynamic torque, Q g is the equivalent generator torque, q is the axial displacement of the tower, is the tower axial displacement velocity, is the tower axial displacement acceleration, ψ is the transmission shaft rotation angle, is the angular velocity of the transmission shaft, is the angular acceleration of the transmission shaft, M is the generalized mass of the wind turbine, Jx, R is the moment of inertia of the transmission shaft around the x-axis, D is the generalized damping coefficient of the tower axial bending, and K is the generalized stiffness coefficient of the tower axial bending;

[0030] Alternatively, the wind turbine model is expressed as:

[0031]

[0032] In the formula, F q is the generalized thrust on the tower, Q a is the aerodynamic torque, Q g is the equivalent generator torque, M is the generalized mass of the wind turbine, is the tower axial displacement acceleration, is the angular acceleration of the transmission shaft, JX, R is the moment of inertia of the transmission shaft around the x-axis.

[0033] In some embodiments, the generalized thrust F q It can be obtained by the following formula, specifically:

[0034]

[0035]

[0036] D=2ζM e ω e (14)

[0037]

[0038]

[0039] K=Ke +K g (17)

[0040]

[0041] K g =K gt +K gw (19)

[0042]

[0043]

[0044]

[0045]

[0046] In the formula, f e K is the elastic load generated by external force on the tower, e is the elastic stiffness of the tower, K g is the geometric deformation coefficient of the tower, D is the generalized damping coefficient of the tower axial bending, is the axial displacement speed of the tower, T a is the aerodynamic thrust, M N is the cabin mass, M R is the rotor mass, x NG is the distance between the center of gravity of the cabin and the center point of the cabin on the x-axis projection, x NR Z is the distance between the rotor center of gravity and the center of the nacelle on the x-axis projection, NG Z is the distance between the center of gravity of the nacelle and the center point of the connection between the nacelle and the tower on the z-axis projection, NR is the distance between the center of gravity of the rotor and the center point of the connection between the nacelle and the tower on the z-axis projection, q is the axial displacement of the tower, and v y is the angle coefficient, θ t is the static angle of attack of the nacelle at time t; p(z, t) represents the axial external force on the tower at height z and time t; (is the axial bending damping coefficient of the tower, ω e is the natural frequency of the tower axial bending, M e is the mass of the tower; K is the generalized stiffness coefficient of the tower axial bending, EI(z) is the stiffness coefficient of the tower at the height z position, K gt is the deformation coefficient of the rotor and nacelle, K gw is the deformation coefficient of the tower, g is the acceleration of gravity, m(z) is the mass surface density of the tower at height z; ρ a is the air density, A r is the swept area of ​​the fan blade, V is the inflow velocity, C t(λ, β) is the thrust coefficient, which is a binary mapping of the tip speed ratio λ and the pitch angle β; C dt is the tower damping coefficient, D t (z) is the cross-sectional diameter of the tower at height z.

[0047] In some embodiments, the generalized mass M of the wind turbine generator set can be obtained by the following formula, specifically:

[0048]

[0049]

[0050] In the formula, M e is the tower mass, M N is the cabin mass, M R is the rotor mass of the generator, x NG is the distance between the center of gravity of the cabin and the center point of the cabin on the x-axis projection, x NR Z is the distance between the rotor center of gravity and the center of the nacelle on the x-axis projection, NG Z is the distance between the center of gravity of the nacelle and the center point of the connection between the nacelle and the tower on the z-axis projection, NR J is the distance between the center of gravity of the rotor and the center point of the connection between the nacelle and the tower on the z-axis projection; Y,N is the moment of inertia of the cabin around the y-axis, J Y，R is the moment of inertia of the rotor around the y-axis, v y is the angle coefficient; q is the axial displacement of the tower.

[0051] In some embodiments, the aerodynamic torque Q a It can be obtained by the following formula, specifically:

[0052]

[0053] In the formula, ρ a is the air density, A r is the swept area of ​​the fan blade, V is the inflow wind speed, R is the radius of the wind wheel, C q (λ, β) is the torque coefficient, which is a binary mapping of the tip speed ratio λ and the pitch angle β;

[0054] The equivalent generator torque can be obtained by the following formula, specifically:

[0055]

[0056] In the formula, is the electromagnetic torque of the generator; N g is the gearbox speed ratio.

[0057] In some embodiments, determining the cumulative damage degree of each node according to the bending moment time series of each node includes:

[0058] According to the rain flow counting method, each complete stress cycle is extracted from the bending moment time series at each node to obtain relevant data associated with the stress cycle;

[0059] The accumulated damage degree of each node is obtained according to the relevant data associated with the stress cycle.

[0060] In some embodiments, the cumulative damage degree of any node can be obtained by the following formula, specifically:

[0061]

[0062]

[0063]

[0064] In the formula, represents the cumulative damage degree of a single corresponding node; n represents the total number of stress cycles; i represents the i-th stress cycle; f i represents the probability of occurrence of the i-th stress cycle; T i represents the running time of the i-th stress cycle; N eq，i represents the fatigue life under the i-th stress cycle; N i * Indicates the number of cycles that a single corresponding node can withstand under the i-th stress cycle; K SN Represents the SN curve constant of a single corresponding node; M eq represents the equivalent load of a single corresponding node; m represents the slope of the SN curve of a single corresponding node; M i represents the amplitude of the i-th stress cycle, N i represents the number of the i-th stress cycle; T represents the total load time length.

[0065] In some embodiments, outputting the structural fatigue assessment result of the target tower according to the cumulative damage degree of at least one node comprises the following steps:

[0066] S51: Compare the accumulated damage level in each node with a preset threshold;

[0067] S52: When the comparison result is that the cumulative damage degree of at least one node is greater than the preset threshold, the result that the target tower structure exceeds the fatigue limit is output; when the comparison result is that the cumulative damage degree of each node is less than the preset threshold, the result that the target tower structure is good is output; when the comparison result is that the cumulative damage degree of each node is not greater than the preset threshold, and there is at least one node whose cumulative damage degree is equal to the preset threshold, the result that the target tower structure reaches the fatigue limit is output.

[0068] In some embodiments, in step S5, it further includes:

[0069] When the comparison result is that the cumulative damage degree of each node is less than the preset threshold, the preset interval range of the cumulative damage degree closest to the preset threshold among all nodes is determined, and the fatigue life estimation result corresponding to the preset interval range is output.

[0070] The present invention also constructs a structural fatigue assessment system for a tower of a wind turbine generator set, which comprises:

[0071] The first acquisition module is used to acquire the shape function of each node of the target tower; the multiple nodes are evenly divided along the height direction of the target tower;

[0072] The second acquisition module is used to acquire the operating data of the target wind turbine group;

[0073] A first operation module, used for inputting the operation data and the shape function at each node into a preset wind turbine model to obtain a bending moment time series corresponding to each node on the target tower;

[0074] A second operation module is used to determine the cumulative damage degree of each node according to the bending moment time series of each node;

[0075] The output module is used to output the structural fatigue assessment result of the target tower according to the cumulative damage degree of at least one node.

[0076] The present invention also constructs a structural fatigue assessment device for a tower of a wind turbine generator set, the device comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, the computer program being configured to implement the steps of the above-mentioned structural fatigue assessment method for the tower of a wind turbine generator set.

[0077] The present invention also constructs a computer-readable storage medium storing a computer program, and when the computer program is executed by a processor, the above-mentioned method for evaluating the structural fatigue of the tower of a wind turbine generator set is implemented.

[0078] The implementation of the present invention has the following beneficial effects: the structural fatigue assessment method of the tower of a wind turbine generator set can accurately estimate the structural fatigue of the tower without relying on external sensors. BRIEF DESCRIPTION OF THE DRAWINGS

[0079] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0080] Figure 1 It is a simplified flow chart of a structural fatigue assessment method for a tower of a wind turbine generator set according to an embodiment of the present invention;

[0081] Figure 2 is a specific flow chart of a structural fatigue assessment method for a tower of a wind turbine generator set according to an embodiment of the present invention;

[0082] Figure 3 is a schematic diagram of an offshore wind turbine generator system provided by an embodiment of the present invention in a static state;

[0083] Figure 4 is a schematic diagram of an offshore wind turbine provided by an embodiment of the present invention under tower bending;

[0084] Figure 5 It is a time series diagram of the bending moments of several tower nodes provided by an embodiment of the present invention.

[0085] Reference numerals: tower 1 , rigid foundation 2 , nacelle 3 , transmission shaft 4 , wind wheel 5 . DETAILED DESCRIPTION

[0086] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described in detail with reference to the accompanying drawings.

[0087] It should be noted that the flowcharts shown in the accompanying drawings are only exemplary and do not necessarily include all the contents and operations / steps, nor do they have to be executed in the order described. For example, some operations / steps can be decomposed, while some operations / steps can be combined or partially combined, so the actual execution order may change according to actual conditions.

[0088] The block diagrams shown in the accompanying drawings are merely functional entities and do not necessarily correspond to physically independent entities. That is, these functional entities may be implemented in software form, or in one or more hardware modules or integrated circuits, or in different networks and / or processor devices and / or microcontroller devices.

[0089] The present invention provides a method for evaluating the structural fatigue of a tower of a wind turbine generator set, which can be applied to offshore wind turbine generator sets, such as 5.5MW offshore wind turbine generator sets. Of course, the method can also be applied to onshore wind turbine generator sets.

[0090] Here is a supplementary explanation. The loads borne by offshore wind turbines are characterized by long duration, large fluctuations, and large amplitudes. During operation, they are subjected to complex and variable loads, including composite loads generated by wind, waves, and the movement of the unit itself. Long-term load accumulation will cause fatigue damage to the structure of the tower, affecting the operating life and safety of the unit. Not only that, offshore wind turbines are more susceptible to erosion by seawater or humid water vapor. The fatigue life of key components such as offshore wind turbine towers, gearboxes, and fan blades is greatly shortened, and the failure rate is greatly increased compared to onshore wind turbines. Therefore, unlike onshore wind turbines, offshore wind turbines need to face more harsh environmental factors.

[0091] In some embodiments, reference may be made to Figure 1 The structural fatigue assessment method of the tower of a wind turbine generator system may include the following steps:

[0092] S1: On the target tower, multiple nodes are evenly divided along its height direction, and the shape function of each node is obtained;

[0093] S2: Obtaining the operating data of the target wind turbine;

[0094] S3: inputting the operating data and the shape function at each node into a preset wind turbine model to obtain a bending moment time series corresponding to each node on the target tower;

[0095] S4: Determine the cumulative damage degree of each node based on the bending moment time series of each node;

[0096] S5: Output the structural fatigue assessment result of the target tower according to the cumulative damage degree of at least one node.

[0097] Understandably, reference can be made to Figure 3 The wind turbine generator set may include a rigid foundation 2, a tower 1 connected to the top of the rigid foundation 2, a nacelle 3 connected to the top of the tower 1, and a transmission shaft 4 arranged in the nacelle 3, and a part of the transmission shaft 4 extends out of the nacelle 3. The wind turbine generator set also includes a wind rotor 5, a generator and a gearbox; the wind rotor 5 is installed on the structural part of the transmission shaft 4 extending out of the nacelle 3, and the wind rotor includes a hub and blades arranged on the hub; the generator converts the mechanical energy generated by the rotation of the wind rotor 5 into electrical energy, and the gearbox is responsible for adjusting the speed and torque between the wind rotor 5 and the generator.

[0098] In step S1, the shape function at each node can be expressed as:

[0099]

[0100] In the formula, For the The nodes correspond to the relative height of the tower; a1-a5 are the associated parameters associated with the shape of the tower, L T The total height of the tower including the rigid foundation, L B is the rigid foundation height.

[0101] It can be understood that the tower is divided into c nodes along its height direction, among which Indicates the tower nodes, and z represents the tower The node height of the node. Then, The nodes correspond to the relative height of the tower. It can be obtained by the following formula. Specifically:

[0102]

[0103]

[0104] Furthermore, the tower height and the rigid foundation height can be obtained by measuring means such as a ruler, or can be obtained from the technical manual of the wind turbine.

[0105] The method for obtaining the associated parameters a1-a5 of each node of the tower may include the following steps:

[0106] S11: Obtain reference association parameters used as reference;

[0107] S12: Obtaining estimated correlation parameters of the target tower at the corresponding node according to the reference correlation parameters;

[0108] S13: Obtaining the estimated bending moment at the corresponding node according to the estimated relationship parameters;

[0109] S14: Obtain the actual bending moment at the corresponding node, and compare the actual bending moment with the estimated bending moment; wherein, when the difference between the estimated bending moment and the actual bending moment is within a preset error range, the estimated associated parameters are used as associated parameters for calculating the bending moment at the corresponding node; when the difference between the estimated bending moment and the actual bending moment is not within the preset error range, the estimated associated parameters are adjusted until the difference between the estimated bending moment and the actual bending moment is within the preset error range.

[0110] It can be understood that the reference correlation parameters can adopt the correlation parameters of other towers with the same shape as the target tower, or directly use the historical correlation parameters of the target tower. After obtaining the reference correlation parameters, the estimated correlation parameters can be adjusted based on the reference correlation parameters; the adjustment here can be made by the staff according to their own experience, or it can be increased or decreased regularly.

[0111] Secondly, the method of obtaining the real bending moment at the corresponding node can be obtained by installing a measuring device for measurement. For example, a strain gauge bending moment sensor can be arranged on the corresponding node, and the real bending moment at the corresponding node can be measured by the strain gauge bending moment sensor. It should be noted here that how to measure the bending moment by the strain gauge bending moment sensor can refer to the relevant technology, which will not be explained here.

[0112] One additional point to be noted here is that, due to the difficulty in installing the tower stress and strain measurement and the short effective measurement life, it is necessary to estimate the circumferential bending moment of each node of the tower through this method, rather than using the strain gauge bending moment sensor measurement method. Moreover, since the associated parameters a1-a5 of each node of the tower are associated with the shape of the tower and will not change with the use of the tower, the associated parameters can be pre-calculated before the evaluation method is executed, and it is also possible to directly use the associated parameters when the evaluation method is executed; the specific method of obtaining the associated parameters is explained here only to improve the integrity of the data source, and it is not limited to executing steps S11-S14 in the evaluation method.

[0113] When the difference between the estimated bending moment and the actual bending moment is within the preset error range, that is, the difference between the estimated bending moment and the actual bending moment is zero, or less than or equal to the preset error threshold, the associated parameters a1-a5 of the target tower at the corresponding node can be determined. Subsequently, the associated parameters a1-a5 can be substituted into the above formula to obtain the shape function at the corresponding node. Repeat the above steps to obtain the shape function at each node.

[0114] In step S2, the operation data of the wind turbine may include inflow wind speed, pitch angle and power generation. These data may be obtained from a SCADA system (Supervisory Control and Data Acquisition) connected to the wind turbine. The SCADA system is used to collect and analyze the real-time operation data of the wind turbine. The specific structure can refer to the relevant technology and will not be described here.

[0115] In step S3, the wind turbine model is a relationship model related to the axial displacement of the tower and the rotation of the transmission shaft. Figure 2 The wind turbine model is a 2-DOF wind turbine model. The 2 DOFs are the axial displacement of the tower and the rotation of the transmission shaft. Moreover, the bending moment of the tower is related to the shape function of the tower.

[0116] After inputting the operating data and the shape function at each node into the preset wind turbine model, the displacement of the tower at time t and height z can be obtained. Figure 4 , the displacement refers to the axial displacement of the tower.

[0117] Then, the tower bending moment at the tower at time t and height z is calculated according to the following formula. Specifically:

[0118] M(z, t) = EI(z)κ(z, t) (4)

[0119]

[0120] Wherein, κ(z, t) is the curvature of the tower at the time t and the height z; q(z, t) is the displacement of the tower at the time t and the height z; EI(z) is the stiffness coefficient of the tower at the height z; M(z, t) is the tower bending moment at the time t and the height z.

[0121] It can be explained here that the stiffness coefficient of the tower can be obtained from the product data provided by the manufacturer.

[0122] Then, by analogy, by calculating the tower bending moment at continuous moments, the bending moment time series corresponding to each node on the tower can be obtained. Thus, the bending moment time series of each node in the entire operation and maintenance cycle can be obtained. For example, in this embodiment, the tower is divided into 9 nodes; Figure 5 , Figure 5 The bending moment time series of the nine nodes are shown respectively.

[0123] In some embodiments, the following wind turbine model may be used for calculation, and the wind turbine model may be expressed as:

[0124]

[0125] This formula can be understood as the Lagrangian dynamics equation of the wind turbine model. In this formula, T a is the aerodynamic thrust, Q a is the aerodynamic torque, Q g is the equivalent generator torque, q is the axial displacement of the tower, is the tower axial displacement velocity, is the tower axial displacement acceleration, ψ is the transmission shaft rotation angle, is the angular velocity of the transmission shaft, is the angular acceleration of the transmission shaft, M is the generalized mass of the wind turbine, J X,R is the moment of inertia of the transmission shaft around the x-axis, D is the generalized damping coefficient of the tower axial bending, and K is the generalized stiffness coefficient of the tower axial bending. The specific method of obtaining the above parameters can be found below and will not be repeated here.

[0126] It can be added here that the tower axial displacement speed is related to the tower axial displacement and time, and the tower axial displacement acceleration is related to the tower axial displacement speed and time. Therefore, when calculating the tower axial displacement, the tower axial displacement speed and / or the tower axial displacement acceleration can be directly transformed into an equation containing the tower axial displacement. Similarly, the drive shaft rotational angular acceleration is related to the aerodynamic torque and the moment of inertia of the drive shaft, and the drive shaft rotational angular velocity can be obtained by time-integrating the drive shaft rotational angular acceleration. The method of obtaining other parameters can be found below. Preferably, in order to facilitate load analysis, the following wind turbine model can also be used for calculation. The wind turbine model is specifically expressed as:

[0127]

[0128] The above formula can be understood as the dynamic equation between the acceleration and load of the wind turbine model. Since this formula involves the generalized thrust acting on the tower, load analysis can be performed more conveniently.

[0129] In the formula, F q is the generalized thrust on the tower, Q a is the aerodynamic torque, Q g is the equivalent generator torque, M is the generalized mass of the wind turbine, is the tower axial displacement acceleration, is the angular acceleration of the transmission shaft, J X,R is the moment of inertia of the transmission shaft around the x-axis.

[0130] Here, let me explain that the generalized thrust, aerodynamic torque, equivalent generator torque and generalized mass of the wind turbine unit on the tower can be obtained by referring to the following. The moment of inertia can be obtained from the product data provided by the manufacturer.

[0131] Furthermore, the aerodynamic torque Q a It can be obtained by the following formula. Specifically:

[0132]

[0133] In the formula, ρ a is the air density, A r is the swept area of ​​the fan blade, V is the inflow wind speed, R is the radius of the wind wheel, C q (λ, β) is the torque coefficient, which is a binary mapping of the tip speed ratio λ and the pitch angle β.

[0134] Here, it can be explained that the swept area of ​​the fan blade and the radius of the wind wheel can be obtained by measurement means or from the product data provided by the manufacturer. The tip speed ratio λ can be obtained by the rotation speed of the fan blade × its length / inflow wind speed.

[0135] Secondly, the equivalent generator torque can be obtained by the following formula. Specifically:

[0136]

[0137] In the formula, is the electromagnetic torque of the generator, which can be obtained according to the generated power; N g is the gearbox speed ratio.

[0138] Then, the generalized mass M of the wind turbine can be obtained by the following formula. Specifically:

[0139]

[0140]

[0141] In the formula, M e is the tower mass, M N is the cabin mass, M R is the rotor mass of the generator, x NG is the distance between the center of gravity of the cabin and the center point of the cabin on the x-axis projection, x NR Z is the distance between the rotor center of gravity and the center of the nacelle on the x-axis projection, NG Z is the distance between the center of gravity of the nacelle and the center point of the connection between the nacelle and the tower on the z-axis projection, NR It is the distance between the center of gravity of the rotor and the center point of the connection between the nacelle and the tower on the z-axis projection; the above parameters can be obtained by measurement means or from the product data provided by the manufacturer.

[0142] J Y，N is the moment of inertia of the cabin around the y-axis, J Y，R is the moment of inertia of the rotor around the y-axis, v y is the angle coefficient; the above parameters can be obtained from the product data provided by the manufacturer. Generally, v y Generally it is 0.0185.

[0143] q is the axial displacement of the tower, which is equivalent to the displacement q(z, t) of the tower at the time t and the height z. vyq can represent the bending angle of the tower.

[0144] Also, F. q It includes the elastic load, rigid load, damping load, gravity force of the nacelle-rotor assembly, centrifugal force of the nacelle-rotor assembly and generalized torque generated by aerodynamic thrust caused by external forces acting on the tower.

[0145] The generalized thrust F g It can be obtained by the following formula. Specifically:

[0146]

[0147]

[0148]

[0149] D=2ζM e ω e (14)

[0150]

[0151]

[0152] K=K e +K g (17)

[0153]

[0154] K g =K gt +K gw (19)

[0155]

[0156]

[0157]

[0158]

[0159] In formula 12-13, f e K is the elastic load generated by external force on the tower, e is the elastic stiffness of the tower, K g is the geometric deformation coefficient of the tower, D is the generalized damping coefficient of the tower axial bending, is the axial displacement speed of the tower, T a is the aerodynamic thrust, M N is the cabin mass, M R is the rotor mass, x NG is the distance between the center of gravity of the cabin and the center point of the cabin on the x-axis projection, x NR Z is the distance between the rotor center of gravity and the center of the nacelle on the x-axis projection, NG Z is the distance between the center of gravity of the nacelle and the center point of the connection between the nacelle and the tower on the z-axis projection, NR is the distance between the center of gravity of the rotor and the center point of the connection between the nacelle and the tower on the z-axis projection, q is the axial displacement of the tower, and v y is the angle coefficient, θ tis the static angle of attack of the nacelle at time t; p(z, t) represents the axial external force received by the tower at height Z and time t.

[0160] In equations 14-16, ζ is the tower axial bending damping coefficient, ω e is the natural frequency of the tower axial bending, M e is the mass of the tower, K is the generalized stiffness coefficient of the tower axial bending, and m(z) is the mass surface density of the tower at height z. It can be explained here that the tower axial bending damping coefficient, the tower axial bending natural frequency and the tower mass surface density can be obtained from the product data provided by the manufacturer.

[0161] In formula 17-21, EI(z) is the stiffness coefficient of the tower at height z, K gt is the deformation coefficient of the rotor and nacelle, K gw is the deformation coefficient of the tower, g is the gravitational acceleration,.

[0162] In Equation 22, ρ a is the air density, A r is the swept area of ​​the fan blade, V is the inflow velocity, C t (λ, β) is the thrust coefficient, which is a binary mapping of the tip speed ratio λ and the pitch angle β.

[0163] In formula 23, C dt is the tower damping coefficient, which is related to the tower shape and material and can be obtained from the product data provided by the manufacturer; D t (z) is the cross-sectional diameter of the tower at height z. It can be obtained by measurement or from product data provided by the manufacturer.

[0164] Secondly, in the above formula, there are also the first-order derivative and the second-order derivative of the tower shape function; here is a supplementary explanation, the specific equations of the first-order derivative and the second-order derivative of the tower shape function are expressed as:

[0165]

[0166]

[0167] In summary, after the operating data and the shape function at each node are input into the preset wind turbine model, the displacement of the tower at the time t and the height z can be obtained, and then the bending moment of the tower at the height z at consecutive moments can be calculated, and the bending moment time series corresponding to each node on the tower can be obtained. One point that can be supplemented here is that structural parameters such as mass, distance on the projection, etc. that are only related to the structure of the wind turbine can be input into the wind turbine model in advance, or can be input into the wind turbine model together with the operating data, and there is no specific restriction here. As an optional solution, a database storing the structural parameters of each wind turbine can also be established, and the database can directly import the structural parameters of the target wind turbine into the wind turbine model.

[0168] It can be understood that the curves of the bending moment of each node of the tower changing with time (i.e., the bending moment time series) calculated by the above series of formulas are intended to simplify the irregular load history into a series of equivalent stress cycles, and then analyze the structural fatigue life of the tower.

[0169] Then, in step S4, all local maximum values ​​(peak values) and local minimum values ​​(valley values) are extracted from each bending moment time series using the rain flow counting method, and the peak values ​​and valley values ​​are paired to form a stress amplitude cycle; at the same time, some incomplete stress cycles (such as edge cycles) are removed, and only complete stress cycles are considered, and relevant data associated with the stress cycles are recorded and obtained. Then, based on these relevant data, the cumulative damage degree of each node is obtained.

[0170] In some embodiments, the cumulative damage degree of any node can be obtained by the following formula. Specifically:

[0171]

[0172]

[0173]

[0174] In the formula, Indicates the cumulative damage degree of a single corresponding node; n represents the total number of stress cycles, and the equivalent amplitude of the same stress cycle is the same; i represents the i-th stress cycle; f i represents the probability of occurrence of the i-th stress cycle; T i represents the running time of the i-th stress cycle; N eq,i represents the fatigue life under the i-th stress cycle, and N i * It represents the number of cycles that a single corresponding node can withstand under the i-th stress cycle, where the fatigue life can be equivalent to the number of cycles; K SNRepresents the SN curve constant of a single corresponding node; M eq represents the equivalent load of a single corresponding node; m represents the slope of the SN curve of a single corresponding node; M i represents the amplitude of the i-th stress cycle, N i represents the number of the i-th stress cycle; T represents the total load time length.

[0175] It can be supplemented here that the total number of stress cycles, the number of types, the probability of occurrence of the ith stress cycle, the running time of the ith stress cycle, the number of cycles that a single corresponding node can withstand under the ith stress cycle, the amplitude of the ith stress cycle, the number of the ith stress cycle and the total load time length can all be obtained from the relevant data associated with the stress cycle. Among them, the probability of occurrence of the ith stress cycle can be understood as follows: assuming that the bending moment time series of a node can obtain 10 stress cycles according to the rain flow analysis method, and the amplitudes of 5 stress cycles are the same, then the probability of occurrence of this stress cycle is 1 / 2.

[0176] The SN curve constant and the SN curve slope can be obtained from the product data provided by the manufacturer; of course, the SN curve can also be fitted by experimental data, which is not specifically limited here.

[0177] In step S5, according to the cumulative damage degree of at least one node, the structural fatigue assessment result of the target tower is output, which may be:

[0178] S51: comparing the accumulated damage level in each node with a preset threshold;

[0179] S52: when the comparison result shows that the cumulative damage degree of at least one node is greater than a preset threshold, outputting a result that the tower structure exceeds the fatigue limit;

[0180] When the comparison result shows that the cumulative damage degree of each node is less than the preset threshold, the result that the tower structure is good is output;

[0181] When the comparison result is that the cumulative damage degree of each node is not greater than the preset threshold, and there is at least one node whose cumulative damage degree is equal to the preset threshold, the result that the tower structure reaches the fatigue limit is output.

[0182] For example, when When the tower structure has not yet reached the fatigue limit, no obvious fatigue failure will occur. In this case, the tower structure is still within the safe working range. When the accumulated damage reaches the fatigue limit, the tower structure has reached the upper limit of its design life, which means fatigue failure is likely to occur. This requires attention and necessary repair or replacement. When the accumulated damage exceeds the fatigue limit, it indicates that the tower structure has exceeded the designed fatigue life and significant structural failure may have occurred. At this time, it is recommended to stop using it immediately and take repair or replacement measures.

[0183] In addition, this method can also comprehensively evaluate the equivalent fatigue load and cumulative damage rate under different stress cycles to predict the fatigue life of the tower. It can be understood that the fatigue life of the tower follows the rule that the smaller the cumulative damage degree, the longer the fatigue life. Therefore, when the cumulative damage degree of each node is less than the preset threshold, when the cumulative damage degree of one of the nodes is closer to the preset threshold, it means that the fatigue life of the tower is shorter. Based on this, multiple intervals arranged continuously can be set up, each interval corresponds to a fatigue life estimate; when the cumulative damage degree of each node is less than the preset threshold, it can continue to determine in which preset interval range the cumulative damage degree closest to the preset threshold among all nodes is, and then output the fatigue life estimate result corresponding to the preset interval range.

[0184] For example, when the cumulative damage degree closest to the preset threshold is 0.8, it can be estimated that the fatigue life of the tower is 3-4 years left; when the cumulative damage degree closest to the preset threshold is 0.6, it can be estimated that the fatigue life of the tower is 6-8 years left.

[0185] Alternatively, if Figure 2 As shown, when outputting the structural fatigue assessment results, preventive maintenance guidance opinions can be output simultaneously. Specifically, when the assessment result shows that the tower structure has reached the fatigue limit, the output requires the tower to be repaired or replaced; when the assessment result shows that the tower structure exceeds the fatigue limit, the output requires the tower to be stopped from use immediately and repaired or replaced.

[0186] In summary, the present invention is based on SCADA data and combined with a 2-DOF wind turbine model to estimate the bending moment time series of the tower at different nodes, and then introduces the rain flow counting method to analyze the bending moment time series of the tower at different nodes, extract stress cycles with different amplitudes, and calculate the number of times corresponding to each stress cycle, so as to obtain the cumulative fatigue damage degree of the tower during the entire operation and maintenance cycle, and evaluate whether the structure of the tower has reached or exceeded the fatigue limit according to the cumulative fatigue damage degree.

[0187] In this way, the work unit can reasonably arrange preventive maintenance according to the actual fatigue condition of the unit, avoid unnecessary downtime and high-cost maintenance operations, and further improve the economic benefits and operational reliability of offshore wind turbines. Compared with traditional sensor solutions, the present invention can accurately estimate the load changes at different tower height nodes without relying on external sensors, and realize low-cost and low-maintenance load monitoring. This technology greatly improves the reliability and economy of offshore wind turbine operation, and provides technical guarantee for the long-term stable operation of wind turbines in extreme environments.

[0188] In addition, the present invention also constructs a structural fatigue assessment system for a tower of a wind turbine generator set, which may include:

[0189] The first acquisition module is used to acquire the shape function of each node of the target tower; the node is a plurality of nodes evenly divided along the height direction of the target tower;

[0190] The second acquisition module is used to acquire the operating data of the target wind turbine group;

[0191] The first operation module is used to input the operation data and the shape function at each node into a preset wind turbine model to obtain a bending moment time series corresponding to each node on the target tower;

[0192] The second operation module is used to determine the cumulative damage degree of each node according to the bending moment time series of each node;

[0193] The output module is used to output the structural fatigue assessment result of the target tower according to the cumulative damage degree of at least one node.

[0194] Secondly, the system may also include a storage module, which is used for the wind turbine model. The specific composition of the wind turbine model can be referred to above and will not be repeated here. The first operation module can be connected to the storage module to call the wind turbine model therein.

[0195] Furthermore, the first acquisition module includes a first acquisition unit for acquiring the associated parameters a1-a5 of each node. It may include:

[0196] A reference parameter acquisition unit, used to acquire reference associated parameters used as a reference;

[0197] An estimation unit, used for obtaining an estimated correlation parameter of a target tower at a corresponding node according to a reference correlation parameter;

[0198] A calculation unit, used for obtaining an estimated bending moment at a corresponding node according to the estimated relationship parameter;

[0199] A comparison unit is used to obtain the actual bending moment at the corresponding node and compare the actual bending moment with the estimated bending moment; wherein, when the difference between the estimated bending moment and the actual bending moment is within a preset error range, the estimated associated parameters are used as associated parameters for calculating the bending moment at the corresponding node; when the difference between the estimated bending moment and the actual bending moment is not within the preset error range, the estimated associated parameters are adjusted until the difference between the estimated bending moment and the actual bending moment is within the preset error range.

[0200] Furthermore, the second acquisition module may be connected to the SCADA system to obtain the operation data of the wind turbine generator set from the SCADA system.

[0201] Furthermore, the second operation module is used to extract each complete stress cycle in the bending moment time series of each node according to the rain flow counting method to obtain relevant data associated with the stress cycle; and, based on the relevant data associated with the stress cycle, obtain the cumulative damage degree of each node.

[0202] Furthermore, the output module is used to compare the cumulative damage degree in each node with a preset threshold; wherein, when the comparison result is that the cumulative damage degree of at least one node is greater than the preset threshold, the result that the tower structure exceeds the fatigue limit is output; when the comparison result is that the cumulative damage degree of each node is less than the preset threshold, the result that the tower structure is good is output; when the comparison result is that the cumulative damage degree of each node is not greater than the preset threshold, and there is at least one node whose cumulative damage degree is equal to the preset threshold, the result that the tower structure reaches the fatigue limit is output.

[0203] Optionally, the output module is also used to determine the preset interval range of the cumulative damage degree closest to the preset threshold among all nodes when the comparison result is that the cumulative damage degree of each node is less than the preset threshold, and output the fatigue life prediction result corresponding to the preset interval range.

[0204] Optionally, the output module is also used to output preventive maintenance guidance opinions simultaneously when outputting the structural fatigue assessment results.

[0205] In addition, the present invention also constructs a structural fatigue assessment device for a tower of a wind turbine generator set, the device comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, the computer program being configured to implement the steps of the structural fatigue assessment method for a tower of a wind turbine generator set as described above.

[0206] The present invention also constructs a computer-readable storage medium storing a computer program, and when the computer program is executed by a processor, the structural fatigue assessment method of the tower of the wind turbine generator set is implemented.

[0207] It can be understood that the above embodiments only express the preferred implementation modes of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the patent scope of the present invention. It should be pointed out that, for ordinary technicians in this field, the above technical features can be freely combined without departing from the concept of the present invention, and several deformations and improvements can be made, which all belong to the protection scope of the present invention. Therefore, all equivalent changes and modifications made to the scope of the claims of the present invention should belong to the coverage of the claims of the present invention.

Claims

1. A method for evaluating the structural fatigue of a tower of a wind turbine generator set, characterized in that: The following steps are involved: S1: Obtain shape functions of multiple nodes on a target tower; the multiple nodes are evenly divided along the height direction of the target tower; S2: Obtaining the operating data of the target wind turbine; S3: inputting the operating data and the shape function at each node into a preset wind turbine model to obtain a bending moment time series corresponding to each node on the target tower; S4: determining the cumulative damage degree of each node according to the bending moment time series of each node; S5: Outputting a structural fatigue assessment result of a target tower according to the accumulated damage degree of at least one node.

2. The structural fatigue assessment method of a wind turbine tower according to claim 1, characterized in that: In step S1, the shape function at each node is expressed as: In the formula, For the The nodes correspond to the relative height of the tower; a1-a5 are the associated parameters associated with the shape of the tower, L T The total height of the tower including the rigid foundation, L B is the rigid foundation height.

3. The structural fatigue assessment method of the tower of a wind turbine generator set according to claim 2, characterized in that: The method for obtaining the associated parameters a1-a5 of each node comprises the following steps: S11: Acquire reference association parameters used as reference; S12: Obtaining estimated correlation parameters of the target tower at the corresponding node according to the reference correlation parameters; S13: Obtaining an estimated bending moment at a corresponding node according to the estimated relationship parameter; S14: Obtain the actual bending moment at the corresponding node, and compare the actual bending moment with the estimated bending moment; wherein, when the difference between the estimated bending moment and the actual bending moment is within a preset error range, the estimated associated parameters are used as associated parameters for calculating the bending moment at the corresponding node; when the difference between the estimated bending moment and the actual bending moment is not within the preset error range, the estimated associated parameters are adjusted until the difference between the estimated bending moment and the actual bending moment is within the preset error range.

4. The structural fatigue assessment method of a tower of a wind turbine generator set according to claim 1, characterized in that: The step of obtaining the bending moment time series of any node specifically includes: Inputting the operating data and the shape function at each node into a preset wind turbine model to obtain the displacement of the tower at a height z at time t; The tower bending moment at the tower at the time t and the height z is calculated according to the following formula: M(z,t)=EI(z)κ(z,t) (4) Wherein, κ(z,t) is the curvature of the tower at the time t and the height z; q(z,t) is the displacement of the tower at the time t and the height z; EI(z) is the stiffness coefficient of the tower at the height z; M(z,t) is the tower bending moment at the time t and the height z; By analogy, the tower bending moment at continuous moments is calculated to obtain the bending moment time series at any node.

5. The method for evaluating the structural fatigue of a tower of a wind turbine generator set according to claim 4, characterized in that: The wind turbine model is a 2-DOF wind turbine model, which is related to the axial displacement of the tower and the rotation of the transmission shaft.

6. The method for evaluating the structural fatigue of a tower of a wind turbine generator set according to claim 5, characterized in that: The wind turbine model is expressed as: Where, T a is the aerodynamic thrust, Q a is the aerodynamic torque, Q g is the equivalent generator torque, q is the axial displacement of the tower, is the tower axial displacement velocity, is the tower axial displacement acceleration, ψ is the transmission shaft rotation angle, is the angular velocity of the transmission shaft, is the angular acceleration of the transmission shaft, M is the generalized mass of the wind turbine, J X,R is the moment of inertia of the transmission shaft around the x-axis, D is the generalized damping coefficient of the tower axial bending, and K is the generalized stiffness coefficient of the tower axial bending; Alternatively, the wind turbine model is expressed as: In the formula, F q is the generalized thrust on the tower, Q a is the aerodynamic torque, Q g is the equivalent generator torque, M is the generalized mass of the wind turbine, is the tower axial displacement acceleration, is the angular acceleration of the transmission shaft, J X,R is the moment of inertia of the transmission shaft around the x-axis.

7. The method for evaluating the structural fatigue of a tower of a wind turbine generator set according to claim 6, characterized in that: The generalized thrust F q It can be obtained by the following formula, specifically: D=2ζM e oh e (14) K=K e +K g (17)、 K g =K gt +K gw (19) In the formula, f e K is the elastic load generated by external force on the tower, e is the elastic stiffness of the tower, K g is the geometric deformation coefficient of the tower, D is the generalized damping coefficient of the tower axial bending, is the axial displacement speed of the tower, T a is the aerodynamic thrust, M N is the cabin mass, M R is the rotor mass, x NG is the distance between the center of gravity of the cabin and the center point of the cabin on the x-axis projection, x NR is the distance between the rotor center of gravity and the center point of the nacelle on the x-axis projection, z NG is the distance between the center of gravity of the nacelle and the center point of the connection between the nacelle and the tower on the z-axis projection, NR is the distance between the center of gravity of the rotor and the center point of the connection between the nacelle and the tower on the z-axis projection, q is the axial displacement of the tower, and v y is the angle coefficient, θ t is the static angle of attack of the nacelle at time t; p(z, t) represents the axial external force on the tower at height z and time t; (is the axial bending damping coefficient of the tower, ω e is the natural frequency of the tower axial bending, M e is the mass of the tower; K is the generalized stiffness coefficient of the tower axial bending, EI(z) is the stiffness coefficient of the tower at the height z position, K gt is the deformation coefficient of the rotor and nacelle, K gw is the deformation coefficient of the tower, g is the gravitational acceleration, m(z) is the mass surface density of the tower at height z; ρ a is the air density, A r is the swept area of ​​the fan blade, V is the inflow velocity, C t (λ, β) is the thrust coefficient, which is a binary mapping of the tip speed ratio λ and the pitch angle β; C dt is the tower damping coefficient, D t (z) is the cross-sectional diameter of the tower at height z.

8. The method for structural fatigue assessment of a tower of a wind turbine generator set according to claim 6, characterized in that: The generalized mass M of the wind turbine generator set can be obtained by the following formula, specifically: In the formula, M e is the tower mass, M N is the cabin mass, M R is the rotor mass of the generator, x NG is the distance between the center of gravity of the cabin and the center point of the cabin on the x-axis projection, x NR Z is the distance between the rotor center of gravity and the center of the nacelle on the x-axis projection, NG Z is the distance between the center of gravity of the nacelle and the center point of the connection between the nacelle and the tower on the z-axis projection, NR J is the distance between the center of gravity of the rotor and the center point of the connection between the nacelle and the tower on the z-axis projection; Y，N is the moment of inertia of the cabin around the y-axis, J Y，R is the moment of inertia of the rotor around the y-axis, v y is the angle coefficient; q is the axial displacement of the tower.

9. The method for evaluating the structural fatigue of a tower of a wind turbine generator set according to claim 6, characterized in that: The aerodynamic torque Q a It can be obtained by the following formula, specifically: In the formula, ρ a is the air density, A r is the swept area of ​​the fan blade, V is the inflow wind speed, R is the radius of the wind wheel, C q (λ, β) is the torque coefficient, which is a binary mapping of the tip speed ratio λ and the pitch angle β; The equivalent generator torque can be obtained by the following formula, specifically: In the formula, is the electromagnetic torque of the generator; N g is the gearbox speed ratio.

10. The method for evaluating the structural fatigue of a tower of a wind turbine generator set according to claim 1, characterized in that: Determining the cumulative damage degree of each node according to the bending moment time series of each node includes: According to the rain flow counting method, each complete stress cycle is extracted from the bending moment time series at each node to obtain relevant data associated with the stress cycle; The accumulated damage degree of each node is obtained according to the relevant data associated with the stress cycle.

11. The method for evaluating the structural fatigue of a tower of a wind turbine generator set according to claim 10, characterized in that: The cumulative damage degree of any node can be obtained by the following formula, specifically: In the formula, represents the cumulative damage degree of a single corresponding node; n represents the total number of stress cycles; i represents the i-th stress cycle; f i represents the probability of occurrence of the i-th stress cycle; T i represents the running time of the i-th stress cycle; N eq,i represents the fatigue life under the i-th stress cycle; N i * Indicates the number of cycles that a single corresponding node can withstand under the i-th stress cycle; K SN Represents the SN curve constant of a single corresponding node; M eq represents the equivalent load of a single corresponding node; m represents the slope of the SN curve of a single corresponding node; M i represents the amplitude of the i-th stress cycle, N i represents the number of the i-th stress cycle; T represents the total load time length.

12. The method for evaluating the structural fatigue of a tower of a wind turbine generator set according to claim 1, characterized in that: The step of outputting the structural fatigue assessment result of the target tower according to the cumulative damage degree of at least one node comprises the following steps: S51: Compare the accumulated damage level in each node with a preset threshold; S52: When the comparison result is that the cumulative damage degree of at least one node is greater than the preset threshold, the result that the target tower structure exceeds the fatigue limit is output; when the comparison result is that the cumulative damage degree of each node is less than the preset threshold, the result that the target tower structure is good is output; when the comparison result is that the cumulative damage degree of each node is not greater than the preset threshold, and there is at least one node whose cumulative damage degree is equal to the preset threshold, the result that the target tower structure reaches the fatigue limit is output.

13. The method for evaluating the structural fatigue of a tower of a wind turbine generator set according to claim 12, characterized in that: In step S5, it also includes: When the comparison result is that the cumulative damage degree of each node is less than the preset threshold, the preset interval range of the cumulative damage degree closest to the preset threshold among all nodes is determined, and the fatigue life estimation result corresponding to the preset interval range is output.

14. A structural fatigue assessment system for a tower of a wind turbine generator, characterized in that: It includes: The first acquisition module is used to obtain the shape function of each node of the target tower; The multiple nodes are evenly divided along the height direction of the target tower; The second acquisition module is used to acquire the operating data of the target wind turbine group; A first operation module, used for inputting the operation data and the shape function at each node into a preset wind turbine model to obtain a bending moment time series corresponding to each node on the target tower; A second operation module is used to determine the cumulative damage degree of each node according to the bending moment time series of each node; The output module is used to output the structural fatigue assessment result of the target tower according to the cumulative damage degree of at least one node.

15. A structural fatigue assessment device for a tower of a wind turbine generator set, the device comprising: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the computer program is configured to implement the steps of the method for structural fatigue assessment of a tower of a wind turbine set as described in any one of claims 1 to 13.

16. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the structural fatigue assessment method for the tower of a wind turbine generator set described in any one of claims 1 to 13 is implemented.

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