Method for measuring and calculating shafting parameters of synchronous generator set

Abstract

The invention relates to the technical field of steam turbine generator set parameter measurement and calculation, in particular to a synchronous generator set shafting parameter measurement and calculation method, which comprises the following steps: acquiring a voltage signal through an acquisition instrument; performing FFT processing on the voltage signal to obtain a frequency spectrum sequence; and determining the natural vibration frequency and the torsional vibration inherent frequency of the shaft system through the frequency spectrum sequence. The method has the advantages that the natural vibration frequency and the inherent torsional vibration frequency of the shaft system can be effectively recognized and calculated through accurate measurement and analysis, additional sensors do not need to be additionally arranged on the shaft system, the equipment cost is remarkably reduced, and the installation process is simplified. Besides, the method ingeniously utilizes the existing voltage transformer and data acquisition equipment of the power plant to realize real-time and continuous monitoring of the voltage signal, so that the measurement precision and the data reliability are greatly improved.

Description

Technical Field

[0001] The invention relates to the technical field of compressed air energy storage units, and in particular to a method for measuring and calculating shaft system parameters of a synchronous generator set. Background Art

[0002] Synchronous generator sets are important equipment in thermal power plants, compressed air energy storage and other power plants. The current power system composed of large power grids and large units will produce shaft torsional vibration problems under subsynchronous oscillation of the power system under certain working conditions. The biggest hazard is that it will cause the rotor of the synchronous generator set to become unstable and damaged, causing major production accidents and threatening the safe operation of the power system. Summary of the invention

[0003] In view of the above problems or problems existing in the prior art, the present invention is proposed.

[0004] In order to solve the above technical problems, the present invention provides the following technical solutions: a method for measuring parameters of a shaft system of a synchronous generator set, comprising obtaining a voltage signal through a collector;

[0005] Perform FFT processing on the voltage signal to obtain a spectrum sequence;

[0006] The natural frequency and torsional vibration natural frequency of the shaft system are determined through the spectrum sequence.

[0007] As a preferred solution of the method for calculating the shaft system parameters of a synchronous generator set of the present invention, the voltage signal includes:

[0008] The voltage signal is obtained through the generator stator voltage transformer.

[0009] As a preferred solution of the method for calculating the shaft system parameters of a synchronous generator set of the present invention, the voltage signal obtained by the generator stator voltage transformer includes:

[0010] Control the output power of the generator set to above 15%;

[0011] Disconnect the generator set from the grid, and the voltage transformer obtains the stator voltage signal at the moment of disconnection.

[0012] As a preferred solution of the method for calculating the shaft system parameters of a synchronous generator set of the present invention, the voltage signal is subjected to FFT processing to obtain a spectrum sequence, including:

[0013] X(f)=FFT(E(t)).

[0014] As a preferred solution of the method for calculating the shaft system parameters of a synchronous generator set of the present invention, wherein: the natural frequency of the shaft system is determined by a spectrum sequence, including:

[0015] x max=max(X(f))

[0016] And determine X max The corresponding frequency value is the shaft system natural frequency f e .

[0017] As a preferred solution of the method for calculating the shaft system parameters of a synchronous generator set of the present invention, wherein: determining the natural frequency of the shaft system torsional vibration through the spectrum sequence includes:

[0018] Determine the frequency f from the spectrum sequence t ;

[0019] Through the frequency f t and the shaft system natural frequency f e Calculate the shaft system torsional vibration natural frequency f.

[0020] As a preferred solution of the method for calculating the shaft system parameters of a synchronous generator set of the present invention, the frequency f is determined by the spectrum sequence. t ,include,

[0021] The shaft system natural frequency f e In the surrounding area, determine the closest to f e Another crest of X t The corresponding frequency f t .

[0022] As a preferred solution of the method for calculating the shaft parameters of a synchronous generator set of the present invention, wherein: t and the shaft system natural frequency f e Calculate the shafting torsional vibration natural frequency f, including,

[0023] f=f t -f e .

[0024] As a preferred solution of the method for calculating the shaft parameters of a synchronous generator set of the present invention, the method of determining the closest f e Another crest of X t The corresponding frequency f t ,include,

[0025] Crest X t , calculated by the following formula:

[0026] x t -x t+1 >=e

[0027] x t -x t-1 >=e

[0028] Wherein, t is the serial number of the spectrum sequence X(f), and e is the anti-interference coefficient.

[0029] As a preferred solution of the method for calculating the shaft system parameters of a synchronous generator set of the present invention, the value of e is:

[0030] e=0.0.1x max .

[0031] The beneficial effects of the present invention are as follows: the natural frequency and natural torsional frequency of the shaft system can be effectively identified and calculated through precise measurement and analysis, and no additional sensors need to be installed on the shaft system, which significantly reduces the equipment cost and simplifies the installation process. In addition, the present method cleverly utilizes the existing voltage transformers and data acquisition equipment of the power plant to achieve real-time and continuous monitoring of the voltage signal, thereby greatly improving the measurement accuracy and data reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0033] Figure 1 The figure is an overall flow chart of the method for calculating the shaft system parameters of a synchronous generator set.

[0034] Figure 2 Schematic diagram of the rotor rotation of a steam turbine generator set.

[0035] Figure 3 This is the stator voltage waveform when the unit has torsional vibration (unit operating frequency 51Hz).

[0036] Figure 4 This is the stator voltage waveform when the unit undergoes torsional vibration (the waveform is magnified on a time scale).

[0037] Figure 5 This is the frequency spectrum diagram obtained by performing FFT on the stator voltage changes when the unit undergoes torsional vibration.

[0038] Figure 6 This is a schematic diagram of enlarging the spectrum in the amplitude direction. DETAILED DESCRIPTION

[0039] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings.

[0040] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0041] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0042] Example 1

[0043] Reference Figure 1 , which is a first embodiment of the present invention, provides a method for calculating shaft system parameters of a synchronous generator set, comprising:

[0044] S1. Obtain voltage signal through a data acquisition instrument.

[0045] It should be noted that the sampling rate of the data collector is greater than 20k and the resolution is greater than 16bit.

[0046] Furthermore, the voltage signal includes,

[0047] The voltage signal is obtained through the generator stator voltage transformer.

[0048] Furthermore, the voltage signal obtained by the generator stator voltage transformer includes:

[0049] Control the output power of the generator set to be above 15%, wherein the output power is controlled above 15% which means the generator set is in a stable operating state;

[0050] Disconnect the generator set from the grid, and the voltage transformer obtains the stator voltage signal at the moment of disconnection.

[0051] It should be noted that the generator stator voltage is measured while being disconnected from the grid through a voltage transformer and recorded for 2 seconds.

[0052] S2. Perform FFT processing on the voltage signal to obtain a spectrum sequence.

[0053] Furthermore, the voltage signal is processed by FFT to obtain a spectrum sequence, including:

[0054] X(f)=FFT(E(t)).

[0055] S3. Determine the natural frequency of the shaft system and the torsional vibration natural frequency through the spectrum sequence.

[0056] Furthermore, the natural frequency of the shaft system is determined by the spectrum sequence, including:

[0057] x max =max(X(f))

[0058] And determine X max The corresponding frequency value is the shaft system natural frequency f e .

[0059] It should be noted that f e ∈(0,N / 2), N is the number of samples, X max Indicates the frequency value f corresponding to the frequency component with the largest amplitude in the results of spectrum analysis e , that is, the natural frequency of the shaft system is determined by calculating the maximum value in the spectrum diagram.

[0060] Preferably, the method can perform spectrum analysis on the voltage signal through fast Fourier transform (FFT) and extract the natural vibration frequency of the system (i.e., self-oscillation frequency) therefrom. Furthermore, this frequency is the frequency of natural vibration of the system without external excitation, which can reflect the inherent vibration characteristics of the system.

[0061] Furthermore, the natural frequency of the shaft torsional vibration is determined by the spectrum sequence, including:

[0062] Determine the frequency f from the spectrum sequence t ;

[0063] Through the frequency f t and the shaft system natural frequency f e Calculate the shaft system torsional vibration natural frequency f.

[0064] Furthermore, the frequency f is determined by the spectrum sequence t ,include,

[0065] The shaft system natural frequency f e In the surrounding area, determine the closest to f e Another crest of X t The corresponding frequency f t .

[0066] It should be noted that f t is X(f) in (0, f e ) is closest to f e The peak of the interval X t The corresponding frequency.

[0067] Preferably, in f e Find another peak frequency f in the frequency range nearby t , which is convenient for confirming and calibrating the natural frequency.

[0068] Furthermore, by frequency f t and the shaft system natural frequency f e Calculate the shafting torsional vibration natural frequency f, including,

[0069] f=f t -f e .

[0070] Furthermore, determine the closest e Another crest of X t The corresponding frequency f t ,include,

[0071] Crest X t , calculated by the following formula:

[0072] x t -x t+1 >=e

[0073] x t -x t-1 >=e

[0074] In the formula, t is the serial number of the spectrum sequence X(f), e is the anti-interference coefficient, and t∈(1,n e -1), n e For X max The corresponding serial number in X(f).

[0075] It should be noted that the initial value of t is (n e -1) and gradually decrease by 1 until the above equation is satisfied or t is equal to 1; if the above equation is still not true when t is equal to 1, it means that the process has not found the natural frequency of the shaft system, and the generator output power needs to be kept above 20% and re-measured to increase the clarity of the signal and make the peaks in the spectrum more obvious.

[0076] Furthermore, the value of e is:

[0077] e=0.0.1x max .

[0078] Preferably, by setting e, it can be ensured that the monitored peak is a real frequency peak rather than being caused by noise or other interference, so that the frequency data finally extracted is more reliable and accurate.

[0079] In summary, the beneficial effect of the method for calculating the shaft parameters of a synchronous generator set of the present invention is that it can effectively identify and calculate the natural frequency and natural torsional frequency of the shaft through precise measurement and analysis, and there is no need to install additional sensors on the shaft, which significantly reduces the equipment cost and simplifies the installation process. In addition, the method cleverly utilizes the existing voltage transformers and data acquisition equipment of the power plant to achieve real-time and continuous monitoring of the voltage signal, thereby greatly improving the measurement accuracy and data reliability.

[0080] Example 2

[0081] Reference Figures 2 to 6 , which is the second embodiment of the present invention, is based on the change of the generator voltage amplitude and phase, and by measuring the change of one-phase or three-phase voltage of the generator, the torsional vibration of the generator rotor is calculated.

[0082] The change of electromotive force E of each phase of a generator in the absence of torsional vibration is:

[0083]

[0084] In the formula, C e : motor structural constant, φ: magnetic flux per pole, n: speed, f: rotation frequency.

[0085] Reference Figure 2 , when torsional vibration occurs, the rotor rotation model of the steam turbine generator set is shown as follows:

[0086] Assume that the motor structural constant C e , the magnetic flux φ of each pole is constant. When torsional vibration occurs, the speed n1 changes:

[0087] n1=n+θsin(2πf n t+α)×30 / π

[0088] Further, the derivation process of n1:

[0089] For ease of understanding, the linear speed V1 of the generator rotation is used as an example.

[0090] V=2πnR / 60

[0091] V1=V+θRsin(2πf n t+α)

[0092] n1=60×V1 / 2πR

[0093] n1=n+θRsin(2πf n t+α)×60 / 2πR

[0094] n1=n+θsin(2πf n t+α)×30 / π

[0095] Where, θ: torsional vibration angle (amplitude), R: magnetic flux radius, f n : Torsional vibration frequency, α: Initial phase of torsional vibration, used to distinguish the initial phase of electromotive force.

[0096] Similarly, the rotation angle λ = sin(2πft) will also undergo corresponding transformations:

[0097] λ1=sin(2πft+θsin(2πf n t+α))

[0098] Further, the derivation process of λ1 is:

[0099] λ=sin(2πft)

[0100] Consider the motion of a particle on the generator rotor. The angle of the particle at time t consists of two parts:

[0101] The angle of rotation of the generator rotor: δ = 2πft,

[0102] Angle change caused by the torsional vibration of the generator rotor: δ1=θsin(2πf n t+α).

[0103] Then the generator rotation angle λ1 is the sum of the two angles: λ1=sin(2πft+θsin(2πf n t+α))

[0104] That is, when torsional vibration occurs, the electromotive force of each phase changes:

[0105]

[0106] Further E t can be simplified to:

[0107] E t =k1 sinω1t+k2sin(ω1t)*sin(ω2t+a)

[0108] In the formula, k is a constant (related to the characteristics of the generator).

[0109] Further E t Can be transformed into:

[0110] E t =k1 sinω1t+k3sin((ω1-ω2)t+a1)+k4sin((ω1+ω2)t+a2)

[0111] In the formula, k is a constant (related to the characteristics of the generator).

[0112] It should be noted that the frequency after FFT transformation includes ω1 and ω2 components.

[0113] In this disclosure, a simulation experiment was conducted for the above inference:

[0114] Specifically, within a certain period of time, assuming that the motor structure constant C e , magnetic flux per pole φ, speed n is a constant, initial phase angle of torsional vibration α is a constant, take n = 3000r / min, f n =12Hz, α=0.3, generator frequency 51.1.

[0115] Combination Figures 3 to 6 In the simulation state, the frequency after FFT is completely consistent with the actual frequency. The set torsional vibration frequency is 12Hz, which can also be fully reflected after the FFT change (51-39=12Hz)

[0116] In summary, after FFT transformation, the torsional vibration frequency cannot be obtained directly, but must be obtained through the difference between the operating frequency of the steam turbine generator and the previous and next (any) frequencies.

[0117] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for calculating shaft parameters of a synchronous generator set, characterized in that: include, Acquire voltage signals through a data acquisition instrument; Performing FFT processing on the voltage signal to obtain a frequency spectrum sequence; The natural frequency of the shaft system and the torsional vibration natural frequency are determined by the frequency spectrum sequence.

2. The method for calculating shaft parameters of a synchronous generator set according to claim 1, characterized in that: The voltage signal, include, The voltage signal is obtained through the generator stator voltage transformer.

3. The method for calculating shaft parameters of a synchronous generator set according to claim 2, characterized in that: The voltage signal obtained by the generator stator voltage transformer includes: Control the output power of the generator set to above 15%; The generator set is disconnected from the power grid, and the voltage transformer obtains the stator voltage signal at the moment of disconnection.

4. The method for calculating shaft parameters of a synchronous generator set according to claim 3, characterized in that: The voltage signal is subjected to FFT processing to obtain a spectrum sequence, including: X(f)=FFT(E(t)).

5. The method for calculating shaft parameters of a synchronous generator set according to claim 4, characterized in that: Determining the natural frequency of the shaft system through the spectrum sequence includes: x max =max(X(f)) And determine X max The corresponding frequency value is the shaft system natural frequency f e .

6. The method for calculating shaft parameters of a synchronous generator set according to claim 5, characterized in that: The determining of the shaft system torsional vibration natural frequency by the frequency spectrum sequence includes: The frequency f is determined by the spectrum sequence t ; By the frequency f t and the shafting natural frequency f e Calculate the shaft system torsional vibration natural frequency f.

7. The method for calculating shaft parameters of a synchronous generator set according to claim 6, characterized in that: The frequency f is determined by the spectrum sequence t ,include, At the shaft system natural frequency f e In the surrounding area, determine the closest to f e Another crest of X t The corresponding frequency f t .

8. The method for calculating shaft parameters of a synchronous generator set according to claim 7, characterized in that: The frequency f t and the shafting natural frequency f e Calculate the shaft system torsional vibration natural frequency f, including, f = f t -f e .

9. The method for calculating shaft parameters of a synchronous generator set according to claim 8, characterized in that: The determination of the closest f e Another crest of X t The corresponding frequency f t ,include, Crest X t , calculated by the following formula: x t -x t+1 >=e x t -x t-1 >=e Where t is the serial number of the spectrum sequence X(f), and e is the anti-interference coefficient.

10. The method for calculating shaft parameters of a synchronous generator set according to claim 9, characterized in that: The value of e is: e=0.0.1x max 。

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