Method for reducing low-frequency vibration of stator of hydro-generator

Abstract

The invention discloses a method for reducing low-frequency vibration of a stator of a hydro-generator, which comprises the following steps of: A, collecting the vibration waveform of the stator of the hydro-generator, and obtaining the corresponding relationship between the vibration waveform of the stator and the position of each magnetic pole of a rotor; b, decomposing and reconstructing the original vibration waveform of the stator core to obtain each harmonic component; c, performing descending order arrangement on each harmonic component of the vibration of the stator core according to the amplitude, and continuously selecting two harmonic components as analysis objects from the first harmonic component of the sequence; and D, for the magnetic pole corresponding to the wave crest and the wave trough of the harmonic component with the maximum amplitude, observing whether the other harmonic component is superposed in the same direction or in the opposite direction on the magnetic pole, and then adding and subtracting point gaskets to suppress vibration. According to the invention, the defects in the prior art can be improved, the harmonic wave can be effectively suppressed, and the amplitude of other harmonic waves cannot be increased, so that the low-frequency vibration amplitude of the stator is greatly reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of synchronous generator operation, and in particular to a method for reducing the low-frequency vibration of the stator of a hydro-generator. Background Art

[0002] The poles of the rotor of a hydro-generator are independently installed. During the installation and operation processes, due to factors such as installation accuracy and centrifugal force, it is easy to cause radial displacements of various poles to varying degrees, resulting in changes in the air-gap length at each pole, namely the so-called rotor pole non-circularity fault.

[0003] The rotor pole non-circularity fault will lead to different magnetic field strengths of each pole of the rotor. During the rotation of the rotor, in addition to the 100Hz frequency component, the electromagnetic force received by any fixed part of the stator core will also have electromagnetic forces at the rotation frequency and its integer multiples, and cause low-frequency vibration of the stator core. Strong vibration of the stator core is likely to cause insulation wear of the stator winding, loosening of the stator core laminations or inter-laminar short-circuit faults, affecting the service life and operation safety of the generator. Severe pole non-circularity faults may also cause stator-rotor rubbing, resulting in the scrapping of the unit.

[0004] In recent years, the problem of stator core vibration of hydro-generators caused by rotor pole non-circularity has occurred many times in power plants. The harm of the fault is becoming increasingly prominent. Therefore, it is very necessary to propose measures to solve the stator core vibration induced by rotor pole non-circularity.

[0005] Regarding the problem of stator low-frequency vibration induced by rotor pole non-circularity, theoretically, the air-gap length of each pole of the generator can be actually measured according to the air-gap measurement sensors installed on the generator, and then the radial displacement of each pole can be adjusted accordingly to improve the non-circularity state. However, according to the actual measurement data on site, it is found that the stronger the magnetic field of the hydro-generator rotor pole is not necessarily the more prominent (the smaller the air-gap), and there is no good corresponding relationship between the two, which makes it difficult to improve the low-frequency vibration of the stator core by adjusting the rotor pole non-circularity through the observed air-gap value.

[0006] See Figure 1 , currently, for the hidden pole non-circularity problem, the proposed solution is to adjust the radial position of each pole based on the stator core vibration. The specific adjustment method is as follows:

[0007] Pads are added to the poles corresponding to the peak positions of the stator low-frequency vibration waveform, that is, the air-gap is reduced to enhance its magnetic pulling force; pads are removed from the poles corresponding to the trough positions of the stator low-frequency vibration waveform, that is, the air-gap is increased to reduce its magnetic pulling force. In most cases, this can reduce the amplitude of the stator low-frequency vibration. Taking a generator in a hydropower station as an example, its stator vibration waveform is shown in Figure 1, it can be seen that the peaks of the stator vibration are near the 11th and 32nd magnetic poles, and the troughs are near the 1st, 2nd, and 22nd magnetic poles. Pad 0.5 mm to the 1st, 2nd, and 22nd magnetic poles at the trough positions respectively. Finally, the vibration value of the stator core is reduced from 146 μm to 95 μm.

[0008] Although the above adjustment method is simple, it is not clear what the main cause of the induced low-frequency vibration of the stator is, so targeted adjustment measures cannot be taken. Sometimes, the amplitudes of some vibration harmonics are reduced, while the amplitudes of harmonics at other frequencies increase, and the overall vibration does not decrease or even increases, making it difficult to achieve the desired effect. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to provide a method for reducing the low-frequency vibration of the stator of a hydro-generator, which can solve the deficiencies of the prior art, effectively suppress this harmonic, and will not cause an increase in the amplitudes of other harmonics, so that the amplitude of the low-frequency vibration of the stator is greatly reduced.

[0010] To solve the above technical problems, the technical solutions adopted by the present invention are as follows.

[0011] A method for reducing the low-frequency vibration of the stator of a hydro-generator includes the following steps:

[0012] A. Collect the stator vibration waveform of the hydro-generator and obtain the corresponding relationship between the stator vibration waveform and the positions of each magnetic pole of the rotor;

[0013] B. Decompose and reconstruct the original vibration waveform of the stator core to obtain each harmonic component;

[0014] C. Arrange the harmonic components of the stator core vibration in descending order according to the amplitude, and continuously select two harmonic components starting from the first harmonic component in the sequence as the analysis objects;

[0015] D. For the magnetic poles corresponding to the peak and trough positions of the harmonic component with the largest amplitude, observe whether the other harmonic component is superimposed in the same direction or in the opposite direction at this magnetic pole, and then perform the operation of adding or subtracting shims to suppress the vibration.

[0016] Preferably, a vibration sensor is used to collect the stator vibration waveform of the hydro-generator.

[0017] Preferably, the original vibration waveform of the stator core is decomposed and reconstructed to obtain the fundamental wave, second harmonic, third harmonic, fourth harmonic, and fifth harmonic.

[0018] Preferably, for the magnetic pole at the peak position of the harmonic component with the largest amplitude, if the two harmonic components are superimposed in the same direction here, perform the operation of adding shims here.

[0019] Preferably, for the magnetic poles at the peak positions of the harmonic components with the largest amplitude, if the two harmonic components are superposed in the reverse direction here, they are left as they are without any shim addition or subtraction operation.

[0020] Preferably, for the magnetic poles at the trough positions of the harmonic components with the largest amplitude, if the two harmonic components are superposed in the same direction here, a shim subtraction operation is performed here.

[0021] Preferably, for the magnetic poles at the trough positions of the harmonic components with the largest amplitude, if the two harmonic components are superposed in the reverse direction here, they are left as they are without any shim addition or subtraction operation.

[0022] Preferably, the amount of shim addition or subtraction is determined according to the values of the peaks and troughs.

[0023] The beneficial effects brought by adopting the above technical solutions are as follows: Compared with the traditional method of simply adjusting the magnetic poles by referring to the peaks and troughs of the stator vibration waveform, the present invention can effectively avoid significantly increasing the vibration of other harmonics while reducing the vibration of a certain harmonic, thereby achieving the goal of significantly reducing the vibration value of the hydrogenerator. The present invention is simple and easy to implement, has good pertinence and good adjustment effect, and is a strong basis and important reference for reducing the low-frequency vibration of the stator core by adjusting the non-circularity of the rotor magnetic poles of the hydrogenerator. Description of the Drawings

[0024] Figure 1 is a comparison diagram of the stator vibration before and after suppression in the prior art.

[0025] Figure 2 is the low-frequency vibration waveform diagram of the stator before adjustment in the embodiment of the present invention.

[0026] Figure 3 is the low-frequency vibration waveform diagram of the stator after adjustment in the embodiment of the present invention.

[0027] Figure 4 is the low-frequency vibration spectrum diagram of the stator before adjustment in the embodiment of the present invention.

[0028] Figure 5 is the low-frequency vibration spectrum diagram of the stator after adjustment in the embodiment of the present invention. Detailed Embodiments

[0029] Taking a hydrogenerator in a certain hydropower plant as an example, the difference between the peak and trough values of its stator low-frequency vibration has long exceeded 80 μm specified in the national standard, and the vibration waveform is shown in Figure 2 .

[0030] For Figure 2The time-domain vibration waveform of the stator vibration is decomposed to obtain the fundamental wave, second harmonic, third harmonic, and fourth harmonic. It can be seen that the amplitude of the second harmonic in the low-frequency vibration of the stator core is the largest, reaching 20 μm, followed by the fundamental wave. Therefore, suppressing the stator vibration should mainly aim at suppressing the amplitude of the second harmonic.

[0031] From Figure 2 It can also be seen that:

[0032] The peak position of the second harmonic corresponds to the 10th magnetic pole. At this magnetic pole position, the fundamental wave and the second harmonic, which are the main components, are in the same direction. Therefore, weakly cutting the second harmonic will inevitably also weaken the fundamental wave. This is an important adjustment area. Therefore, a gasket should be added to this magnetic pole, which can significantly reduce the vibration peak;

[0033] The peak position of the second harmonic corresponds to the 30th magnetic pole. At this magnetic pole position, the fundamental wave and the second harmonic, which are the main components, are in the opposite direction. Therefore, weakly cutting the second harmonic will inevitably cause an increase in the fundamental wave. Therefore, it is not advisable to add or subtract gaskets to this magnetic pole, and it should be maintained as it is;

[0034] The trough position of the second harmonic corresponds to the 20th magnetic pole. At this magnetic pole position, the second harmonic, which is the main component, is the negative maximum value, and the fundamental wave is close to zero. Therefore, slightly reducing the gasket for this magnetic pole can weakly cut the second harmonic, and the fundamental wave will not change significantly;

[0035] The trough position of the second harmonic corresponds to the 40th magnetic pole. At this magnetic pole position, the fundamental wave and the second harmonic, which are the main components, are in the same direction. Therefore, reducing the gasket for this magnetic pole can weakly cut the second harmonic and also cut the fundamental wave at the same time.

[0036] Due to the particularity of this generator, the method of adding gaskets has not been implemented. Based on the above analysis, the final proposed magnetic pole adjustment plan is as follows:

[0037] Reduce the gasket by 0.5 mm for the 20th and 40th magnetic poles at the trough position of the second harmonic to reduce the second harmonic value and decrease the overall vibration.

[0038] After adjustment, the stator vibration waveform during the no-load operation of the generator is as Figure 3 shown. It can be seen that the amplitude of the second harmonic drops to about 10 μm, significantly reducing the peak value of the stator low-frequency vibration. The difference between the peak and valley values is within 80 μm specified by the national standard, achieving the expected effect. Further, Fourier decomposition is performed on the stator vibration waveforms of the generator before and after adjustment, as shown in Figure 4 and Figure 5 . It can be seen that after adjustment, the amplitude of the fundamental wave of the stator core vibration remains basically unchanged, and the amplitude of the second harmonic decreases significantly, proving the effectiveness of the adjustment method of this method.

[0039] The present invention can specifically weaken the fundamental wave, second harmonic, third harmonic, fourth harmonic, etc. in the low-frequency vibration of the stator of a hydro-generator, and fully consider the superposition effect among various harmonics. It is simple to operate and has good specificity.

[0040] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0041] The foregoing has shown and described the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments, and what is described in the above embodiments and the specification is only to illustrate the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for reducing the low-frequency vibration of the stator of a hydro-generator, characterized in that It includes the following steps: A. Collect the stator vibration waveform of the hydrogenerator and obtain the corresponding relationship between the stator vibration waveform and the positions of each rotor pole; B. Decompose and reconstruct the original vibration waveform of the stator core to obtain each harmonic component; C. Arrange the harmonic components of the stator core vibration in descending order according to the amplitude, and continuously select two harmonic components starting from the first harmonic component in the sequence as the analysis objects; D. For the poles corresponding to the peak and trough positions of the harmonic component with the largest amplitude, observe whether the other harmonic component is superimposed in the same direction or in the opposite direction at this pole, and then perform the operation of adding or subtracting shims to suppress the vibration.

2. The method for reducing the low-frequency vibration of the stator of a hydro-generator according to claim 1, wherein: Use a vibration sensor to collect the stator vibration waveform of the hydrogenerator.

3. The method for reducing the low-frequency vibration of the stator of a hydro-generator according to claim 1, wherein: Decompose and reconstruct the original vibration waveform of the stator core to obtain the fundamental wave, second harmonic, third harmonic, fourth harmonic, and fifth harmonic.

4. The method for reducing the low-frequency vibration of the stator of a hydro-generator according to claim 1, characterized in that: For the pole at the peak position of the harmonic component with the largest amplitude, if the two harmonic components are superimposed in the same direction here, perform the operation of adding shims here.

5. The method for reducing the low-frequency vibration of the stator of a hydro-generator according to claim 1, characterized in that: For the pole at the peak position of the harmonic component with the largest amplitude, if the two harmonic components are superimposed in the opposite direction here, keep it as it is and do not perform the operation of adding or subtracting shims.

6. The method for reducing the low-frequency vibration of the stator of a hydro-generator according to claim 1, wherein: For the pole at the trough position of the harmonic component with the largest amplitude, if the two harmonic components are superimposed in the same direction here, perform the operation of subtracting shims here.

7. The method for reducing the low-frequency vibration of the stator of a hydro-generator according to claim 1, characterized in that: For the pole at the trough position of the harmonic component with the largest amplitude, if the two harmonic components are superimposed in the opposite direction here, keep it as it is and do not perform the operation of adding or subtracting shims.

8. The method for reducing the low-frequency vibration of the stator of a hydro-generator according to any one of claims 4-7, characterized in that: The amount of shims added or subtracted is determined according to the values of the peaks and troughs.

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