Recognition and suppression method and device for resonance of direct-cooling generator of wind turbine generator and medium

Abstract

The invention discloses a method and a device for identifying and suppressing resonance of a direct-cooled generator of a wind turbine generator and a medium. The method comprises the following steps: monitoring and collecting vibration signals of the direct-cooled generator in real time; performing spectrum analysis and extracting characteristic frequency, and comparing the characteristic frequency with known electromagnetic excitation frequency to obtain a resonance judgment result; constructing a finite element model of the direct-cooling generator and carrying out modal analysis; a vibration reduction module is arranged between a generator base and a cooler air bellow, and the installation position, rigidity, material, shape and size of the vibration reduction module are obtained according to the modal analysis result; constructing a finite element model of the improved direct-cooled generator and carrying out modal analysis; performing model verification on the improved direct cooling generator; and actual measurement verification is carried out on the improved direct cooling generator. According to the invention, the resonance of the direct-cooling generator can be accurately identified, and the resonance problem is fundamentally solved by changing the connection mode between the direct-cooling generator base and the cooler bellows.

Description

Technical Field

[0001] This invention relates to the field of wind power generation technology, and more specifically to a method, device, and medium for identifying and suppressing resonance in a direct-cooled generator of a wind turbine. Background Technology

[0002] With the increasing size and power density of wind turbine generators, the operational stability of the generator, as a core energy conversion component, is crucial. During operation, the generator is subjected to a strong rotating electromagnetic excitation force. The fundamental frequency of this excitation force is the rotational frequency or a multiple thereof (e.g., 50Hz, 100Hz, 200Hz). Considering the differences in grid frequency at different sites and operating conditions including but not limited to AGC and AVC, electromagnetic resonance occurs when the natural frequencies of certain structural components of the generator (such as the stator core, end windings, and cooling system fan boxes) coincide with or are close to the electromagnetic excitation frequency. The essence of generator resonance is the coupling of the natural frequencies of its structure or rotor system with the external excitation frequency, leading to dynamic instability with a sharp increase in amplitude. This problem not only causes high-frequency vibration and noise in the stator and rotor cores, but also exacerbates bearing wear, winding insulation aging and other faults. In severe cases, it can lead to catastrophic failures such as shaft bending and end cover cracking. According to statistics, generator failures induced by resonance account for more than 25%, and the cost of a single shutdown maintenance can reach millions of dollars. The mean time to recovery (MTTR) is as long as 72 hours or more, which directly affects the economic benefits of wind farms.

[0003] In existing technologies, vibration problems are often addressed through remedial measures or empirical reinforcement, typically by fixing the issue within the generator itself. This requires hoisting the generator below the wind turbine and altering methods such as changing the rotor shaft diameter or thickening the generator casing. These methods have significant drawbacks: Poor targeting: Blindly strengthening may lead to increased weight and cost, and may even push the inherent frequency to another resonance point, resulting in a situation that only treats the symptoms and not the root cause; Lack of foresight: Inability to accurately identify and warn of problems during the design phase or in the early stages of their occurrence; Inefficient: It relies on repeated "trial and error" processes, which take a long time to resolve and affect power generation efficiency.

[0004] Therefore, there is an urgent need for a method that can accurately and efficiently identify and suppress electromagnetic resonance in wind turbine generators. Summary of the Invention

[0005] The purpose of this invention is to solve the problems existing in the prior art by proposing a method, device and medium for identifying and suppressing resonance of direct-cooled generators in wind turbine units.

[0006] To achieve the above objectives, the first aspect of this invention proposes a method for identifying and suppressing resonance in a direct-cooled wind turbine generator, comprising: S1. Vibration signals are monitored and collected in real time by a triaxial vibration accelerometer installed at the drive end and non-drive end of the direct-cooled generator; S2. Perform spectrum analysis on the collected vibration signal, extract the characteristic frequency, and compare it with the known electromagnetic excitation frequency to obtain the resonance judgment result. S3. Construct a finite element model of the direct-cooled generator and perform modal analysis; S4. By installing a vibration damping module between the generator base and the cooler box, the natural frequency of the direct-cooled generator structure is changed, and the installation position, stiffness, material, shape and size of the vibration damping module are determined based on the results of modal analysis. S5. Construct the finite element model of the improved direct-cooled generator and perform modal analysis; S6. Compare the modal analysis results of the improved finite element model of the direct-cooled generator with those of the original finite element model of the direct-cooled generator to obtain the model verification results. S7. Check whether the maximum measured vibration velocity of the improved direct-cooled generator is within the normal range, and determine whether the vibration velocity at frequencies close to the electromagnetic excitation frequency and its harmonics has decreased significantly through spectrum analysis, and obtain the measured verification results.

[0007] Further, step S2 includes: When the deviation between the characteristic frequency and the electromagnetic excitation frequency is within ±3%, and the vibration amplitude exceeds the preset safety threshold, it is determined that the direct-cooled generator has electromagnetic resonance.

[0008] Further, step S3 includes: The cooler air box is simplified to a mass point, and its connection with the generator base is fixed.

[0009] Further, step S5 includes: The connection between the generator base and the cooler box is made into a spring connection.

[0010] Furthermore, the vibration damping module employs four vibration damping components mounted on the upper surface of the generator base. Each vibration damping component includes a metal pad fixedly connected to the upper surface of the generator base and a rubber pad bonded between the lower surface of the cooler air box and the metal pad.

[0011] Further, step S3 includes: The first 10 modal frequencies and mode shapes of the direct-cooled generator were obtained through simulation calculations. The modes coupled with the electromagnetic excitation frequency were determined. The modal data and stress distribution cloud map of each mode were extracted, the specific components that underwent vibration deformation were analyzed, and the results were compared with those obtained in step S2.

[0012] Further, step S3 includes: Calculate the natural frequencies of the linear vibration along the X, Y, and Z axes and the torsional vibration about the X axis of the direct-cooled generator.

[0013] Further, step S5 includes: The stiffness value of the vibration damping module is obtained by calculating the relative amplitude of the mass of the generator winding box and the cooler box.

[0014] A second aspect of the present invention provides a computing device, comprising: Memory, used to store computer programs; A processor is used to implement the above-mentioned method for identifying and suppressing resonance of direct-cooled generators in wind turbine units when executing the computer program.

[0015] A third aspect of the present invention provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the above-described method for identifying and suppressing resonance in a direct-cooled wind turbine generator.

[0016] This invention first accurately identifies resonance through signal acquisition and spectrum analysis. When resonance is detected, it changes the connection between the direct-cooled generator base and the cooler box. The improved generator system is then verified through both modeling and experimental testing, thereby fundamentally solving the resonance problem. Attached Figure Description

[0017] The following figures are included as part of this invention for understanding its principles. The figures illustrate embodiments of the invention and their descriptions, serving to explain the apparatus and principles of the invention. In the figures, Figure 1 This is a flowchart of a method for identifying and suppressing resonance in a direct-cooled wind turbine generator according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of a direct-cooled generator according to an embodiment of the present invention; Figure 3 A perspective view of a direct-cooled generator for modal analysis according to an embodiment of the invention; Figure 4 A front view of a model of a directly cooled generator for modal analysis according to an embodiment of the invention; Figure 5 Stress distribution cloud diagram of the direct-cooled generator before the improvement of the embodiment of the invention; Figure 6 Stress distribution cloud map of the improved direct-cooled generator according to the embodiment of the invention; Figure 7 This is a schematic diagram showing the installation position of the vibration damping module of the improved direct-cooled generator according to an embodiment of the invention. Figure 8 Vibration velocity spectrum analysis diagram of the improved direct-cooled generator according to the embodiment of the invention; Figure 9 The diagram shows the measured vibration data of the improved direct-cooled generator according to the embodiment of the invention. Detailed Implementation

[0018] The present application will now be described in more detail with reference to the accompanying drawings. The following embodiments are only used to illustrate the technical solutions of the present application more clearly and are not intended to limit the scope of protection of the present application.

[0019] This invention provides a method for identifying and suppressing resonance in a direct-cooled generator of a wind turbine. For example... Figure 1 As shown, the method includes: S1. Vibration signals are monitored and collected in real time by a triaxial vibration acceleration transmitter installed at the drive end and non-drive end of the direct-cooled generator.

[0020] The triaxial vibration accelerometer can be installed on the front and rear bearing housings of the direct-cooled generator to monitor and collect vibration signals in the axial direction (X-axis), horizontal direction (Y-axis), and vertical direction (Z-axis) in real time.

[0021] S2. Perform spectral analysis on the collected vibration signal, extract the characteristic frequency, and compare it with the known electromagnetic excitation frequency to obtain the resonance judgment result.

[0022] The main characteristic frequencies extracted by spectrum analysis are automatically compared with the suppressed electromagnetic excitation frequency library (fundamental frequency and harmonics of rotating electromagnetic excitation force, including 50Hz, 100Hz, 200Hz, etc.). When the deviation between the characteristic frequency and the electromagnetic excitation frequency is within ±3%, and the vibration amplitude exceeds the preset safety threshold, it is determined that the direct-cooled generator has electromagnetic resonance.

[0023] S3. Construct a finite element model of the direct-cooled generator and perform modal analysis.

[0024] like Figure 2-4 As shown, the model can be built using ANSYS. The specific steps are as follows: - Establish an accurate model of the generator, including core components such as the rotor system, stator system, bearings, and elastic supports; - Reasonable simplification: The complex windings are simplified to an equivalent average entity, and the cooler air box is simplified as a point mass; the slip rings and encoders are simplified, such as... Figure 3 and Figure 4 As shown; - Material properties and mesh generation: Solid elements are used for the base, end cover and shaft, with a mesh size between 30 and 40, and material properties are assigned according to the actual material parameters; - Set boundary conditions: bearing support, using the bearing stiffness matrix, the driving end adopts end face fixed constraint, and the non-driving end is in a free state; the generator foot elastic support adopts spring constraint, and stiffness values ​​are applied in the X-axis direction, Y-axis direction, and Z-axis direction respectively; the generator base and the cooler air box are treated as a binding process; - Set up the solver: Configure it in the modal analysis system and select Block Lanczos to solve the modes; - Elastic modal order setting: Set at least 10 modes to ensure global and local modes.

[0025] Modal analysis simulation was used to obtain the first 10 modal frequencies and mode shapes of the direct-cooled generator, identify the modes coupled with the electromagnetic excitation frequency, and extract the modal data and contour plots for each mode. The specific components experiencing vibration deformation were analyzed and compared with the results obtained in step S2 by analyzing the measured data. The specific formula for calculating the natural frequency of the generator system during simulation is as follows: via The natural frequency of linear vibration of the shaft Calculation formula: In the formula: Let x be the moment of inertia of the generator about the x-axis; along Shaft translational vibration frequency; ω is the natural angular frequency related to the x-axis; m is the overall mass of the generator; The height of the center of gravity of the entire generator system; Natural frequency of linear vibration along axis Calculation formula: In the formula: Let be the moment of inertia of the generator about the y-axis; The natural angular frequency associated with the y-axis; Natural frequency of linear vibration along the z-axis : In the formula: The vertical stiffness of the engine mounting base; The natural frequency of torsional vibration about the x-axis In the formula: Let x be the moment of inertia of the generator about the x-axis; The frequency of the translational vibration along the y-axis is denoted by m; m is the overall mass of the generator. The natural angular frequency is related to the x-axis.

[0026] S4. By installing a vibration damping module between the generator base and the cooler box, the natural frequency of the direct-cooled generator structure is changed, and the installation position, stiffness, material, shape and size of the vibration damping module are determined based on the results of modal analysis.

[0027] like Figure 7 As shown, the vibration damping module uses four vibration damping components installed on the upper surface of the generator base. Each vibration damping component includes a metal pad fixedly connected to the upper surface of the generator base and a rubber pad bonded between the lower surface of the cooler air box and the metal pad.

[0028] By installing vibration damping components between the generator base and the cooler box, the local stiffness and mass distribution of the directly cooled generator can be altered, thereby specifically changing the natural frequency of the structure to avoid the electromagnetic excitation frequency band. From a dynamic model perspective, this is equivalent to the cooler box and the vibration damping components together forming a dynamic vibration damper for the generator winding housing. That is, a damped dynamic vibration damper is added to the main generator system, turning it into a two-degree-of-freedom system. The relative amplitude of the mass of the generator winding housing and the cooler box can be calculated using the following formula: In the formula: The amplitude of the main mass (generator winding housing), The amplitude of the auxiliary mass (cooler fan box); = —Static displacement of the main system (generator winding housing and cooler wind box) under static force equal to the excitation force amplitude P; = —The ratio of the excitation frequency (electromagnetic resonance frequency and its harmonics) to the natural frequency of the main system; = —The ratio of the natural frequency of the main system to the natural frequency of the vibration damper (vibration damping component); —The inherent frequency of the main system; —The natural frequency of the vibration damper; In the formula: k1 is the stiffness of the ground damper of the generator winding box, and k2 is the stiffness of the damping component (metal pad + rubber pad) installed on the generator base. = —The ratio of auxiliary mass (cooler box) to main mass (generator winding housing); = —damping ratio of the vibration damper In the formula: c is the damping coefficient.

[0029] The stiffness value of the vibration damping component is obtained through calculation, and the material is determined based on the stiffness value.

[0030] For the installation location of vibration damping components, priority should be given to locations with the largest amplitude and feasible installation, or key nodes on the vibration path, and alternative locations with weak structural rigidity. Locations near bearings, sealing surfaces, and electrical connections should be avoided. According to one embodiment of the present invention, vibration damping positions can be set starting 200mm from the drive end cover, with intervals of 200mm. The positions of the four vibration damping points are symmetrical about the center of the upper plane of the base.

[0031] S5. Construct the finite element model of the improved direct-cooled generator and perform modal analysis.

[0032] A spring connection is installed between the generator base and the cooler air box, and the remaining boundary conditions are the same as in step S3. Modal analysis is then performed on the improved generator system. The focus is on analyzing modes whose modal frequencies are close to the electromagnetic excitation frequency and its harmonics, and whose mode shapes are in the same direction as the actual vibration that causes resonance.

[0033] S6. Compare the modal analysis results of the improved finite element model of the direct-cooled generator with those of the original finite element model of the direct-cooled generator to obtain the model verification results.

[0034] like Figure 5 and Figure 6 Previously, the connection between the generator base and the cooler box of the direct-cooled generator was a bolted connection, and the generator base and the cooler box were a whole. Therefore, in step S3, the two were treated as a binding. The analysis results showed that the locations with larger vibration amplitudes were all distributed on the generator base, and the deformation of the drive end was larger. In step S5, when the connection between the generator base and the cooler box was changed to a spring connection, most of the overall deformation of the generator system occurred in the cooler box, and the deformation of the generator base was very small. It can be seen that by setting a vibration damping module between the generator base and the cooler box, the overall vibration deformation of the generator base can be effectively reduced.

[0035] S7. Check whether the maximum measured vibration velocity of the improved direct-cooled generator is within the normal range, and determine whether the vibration velocity at frequencies close to the electromagnetic excitation frequency and its harmonics has decreased significantly through spectrum analysis, and obtain the measured verification results.

[0036] The following is a specific example to illustrate this solution: After a wind farm's high-power units have been in operation for six months, multiple units have experienced generator tail encoder bracket breakage.

[0037] After the unit was connected to the grid, the vibration acceleration sensor collected an effective value of approximately 8.3 mm / s for the horizontal (Y-axis) vibration velocity and approximately 9.7 mm / s for the axial vibration velocity. Spectral analysis of the vibration velocity revealed that the horizontal vibration velocity at 49.6 Hz had an amplitude of approximately 9.63 mm / s, exceeding the preset safety threshold. Furthermore, this frequency was quite close to the grid frequency of 50 Hz. Figure 8 As shown, an electromagnetic resonance phenomenon occurred.

[0038] Based on the structural parameters of this type of direct-cooled generator, modal simulation calculations were performed using ANSYS. A refined finite element model of the generator was established using the simulation modeling and analysis module. The elastic support stiffness of the generator base is 9.5 kN / mm in the Z-axis direction, 10.5 kN / mm in the X-axis direction, and 10.5 kN / mm in the Y-axis direction. The refined finite element model of the generator was established using the simulation modeling and analysis module, and the first 10 modal frequencies and mode shapes were obtained, as shown in Table 1. Table 1 The analysis results show that the first 10 natural modal vibrations of the generator are mainly manifested in the generator base and bearing end cover components. The 7th frequency of the generator is 50.478Hz, with some slight error in the simulation. It is highly consistent with the measured 49.6Hz, and the vibration mode is a horizontal vibration of the entire machine, which is consistent with the measured results mentioned above.

[0039] By selecting shape, position, material, stiffness, and size parameters using finite element analysis and inputting them into the Workbench, the system performs static calculations and frequency domain analysis. Iterates through different parameters to find the optimal solution, and finally selects a combination of a 110mm×110mm×5mm metal pad and rubber. The metal pad is made of Q235B material, and the rubber stiffness is 1Kn / mm. The installation positions are symmetrical about the center point of the upper end face of the base, with four vibration damping positions.

[0040] A finite element model of the improved direct-cooled generator was constructed and modal analysis was performed. The generator base and the cooler box were connected by springs to obtain the corresponding modal frequencies and mode shapes (modes with modal frequencies close to the electromagnetic frequency and mode shapes that are horizontal vibrations were selected), as shown in Table 2. Table 2 Modal analysis of the improved generator system revealed that no electromagnetic resonance frequencies of 50Hz or their harmonics were observed. The frequency around 50Hz was found on the cooler box, which also confirmed that the combination of the cooler box, metal pad, and rubber pad formed a dynamic vibration damper. By optimizing the parameters and tuning the generator system, resonance could be avoided.

[0041] The wind farm units will undergo technical upgrades according to the above plan. Based on the unit operation CMS data, such as... Figure 9 As shown, the maximum horizontal vibration velocity at both the drive and non-drive ends of the direct-cooled generator is 4.61 mm / s, which is within the normal range. Furthermore, the vibration velocity spectrum shows a significant decrease in frequencies around 50 Hz and their harmonics. Therefore, after implementing the above technical modification scheme, the unit's vibration value has significantly decreased, effectively solving the electromagnetic resonance problem of the direct-cooled generator.

[0042] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software may depend on the specific application and design constraints of the technical solution. Those skilled in the art may use different methods for each specific application to implement the described functions, but such implementation should not be considered beyond the scope of the embodiments of this disclosure.

[0043] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein can be implemented directly by hardware, a software module executed by a processor, or a combination of both. The software module can be located in random access memory (RAM), main memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art.

[0044] The methods and products (including but not limited to devices and equipment) disclosed in the embodiments herein can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For instance, the division of units may only be a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. In addition, the mutual coupling or direct coupling or communication connection shown or discussed may be through some interfaces, and the indirect coupling or communication connection of devices or units may be electrical, mechanical, or other forms.

[0045] Unless otherwise defined, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for descriptive purposes only and is not intended to limit the invention. Terms such as “part” or “component” appearing herein can refer to a single part or a combination of multiple parts. Terms such as “installation” or “installation” appearing herein can refer to one component being directly attached to another component or one component being attached to another component via an intermediary. A feature described in one embodiment herein may be applied, alone or in combination with other features, to another embodiment, unless that feature is not applicable in that other embodiment or is otherwise stated.

[0046] The present invention has been described through the above embodiments. However, it should be understood that the above embodiments are for illustrative purposes only and are not intended to limit the present invention to the described embodiments. Furthermore, those skilled in the art will understand that the present invention is not limited to the above embodiments, and many variations and modifications can be made based on the teachings of the present invention, all of which fall within the scope of protection claimed by the present invention. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for identifying and suppressing resonance in a direct-cooled generator of a wind turbine, characterized in that, include: S1. Vibration signals are monitored and collected in real time by a triaxial vibration accelerometer installed at the drive end and non-drive end of the direct-cooled generator; S2. Perform spectrum analysis on the collected vibration signal, extract the characteristic frequency, and compare it with the known electromagnetic excitation frequency to obtain the resonance judgment result. S3. Construct a finite element model of the direct-cooled generator and perform modal analysis; S4. By installing a vibration damping module between the generator base and the cooler box, the natural frequency of the direct-cooled generator structure is changed, and the installation position, stiffness, material, shape and size of the vibration damping module are determined based on the results of modal analysis. S5. Construct the finite element model of the improved direct-cooled generator and perform modal analysis; S6. Compare the modal analysis results of the improved finite element model of the direct-cooled generator with those of the original finite element model of the direct-cooled generator to obtain the model verification results. S7. Check whether the maximum measured vibration velocity of the improved direct-cooled generator is within the normal range, and determine whether the vibration velocity at frequencies close to the electromagnetic excitation frequency and its harmonics has decreased significantly through spectrum analysis, and obtain the measured verification results.

2. The method for identifying and suppressing resonance in a direct-cooled wind turbine generator according to claim 1, characterized in that, Step S2 includes: When the deviation between the characteristic frequency and the electromagnetic excitation frequency is within ±3%, and the vibration amplitude exceeds the preset safety threshold, it is determined that the direct-cooled generator has electromagnetic resonance.

3. The method for identifying and suppressing resonance in a direct-cooled wind turbine generator according to claim 1, characterized in that, Step S3 includes: The cooler air box is simplified to a mass point, and its connection with the generator base is fixed.

4. The method for identifying and suppressing resonance in a direct-cooled wind turbine generator according to claim 3, characterized in that, Step S5 includes: The connection between the generator base and the cooler box is made into a spring connection.

5. The method for identifying and suppressing resonance in a direct-cooled wind turbine generator according to claim 1, characterized in that, The vibration damping module uses four vibration damping components installed on the upper surface of the generator base. Each vibration damping component includes a metal pad fixedly connected to the upper surface of the generator base and a rubber pad bonded between the lower surface of the cooler air box and the metal pad.

6. The method for identifying and suppressing resonance in a direct-cooled wind turbine generator according to claim 1, characterized in that, Step S3 includes: The first 10 modal frequencies and mode shapes of the direct-cooled generator were obtained through simulation calculations. The modes coupled with the electromagnetic excitation frequency were determined. The modal data and stress distribution cloud map of each mode were extracted, the specific components that underwent vibration deformation were analyzed, and the results were compared with those obtained in step S2.

7. The method for identifying and suppressing resonance in a direct-cooled wind turbine generator according to claim 1, characterized in that, Step S3 includes: Calculate the natural frequencies of the linear vibration along the X, Y, and Z axes and the torsional vibration about the X axis of the direct-cooled generator.

8. The method for identifying and suppressing resonance in a direct-cooled wind turbine generator according to claim 1, characterized in that, Step S5 includes: The stiffness value of the vibration damping module is obtained by calculating the relative amplitude of the mass of the generator winding box and the cooler box.

9. A computing device, characterized in that, include: Memory, used to store computer programs; A processor, configured to implement the method for identifying and suppressing resonance of a direct-cooled generator in a wind turbine as described in any one of claims 1-8 when executing the computer program.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program, which, when executed by a processor, implements the method for identifying and suppressing resonance of a direct-cooled generator in a wind turbine as described in any one of claims 1 to 8.

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