Method, system and electronic device for evaluating mechanical state of on-load tap changer

Abstract

This invention provides a method, system, and electronic device for assessing the mechanical state of an on-load tap changer. The method includes: acquiring vibration signal samples of the on-load tap changer at a preset frequency; performing time-frequency analysis on the vibration signal samples using a Short-Time Fourier Transform (STFT) to obtain the STFT signal; identifying the peak value of the STFT signal and using the peak value as the pseudo-excitation force corresponding to the vibration signal sample; constructing a state-space model based on the vibration signal samples and their corresponding pseudo-excitation forces; acquiring the current vibration signal and the previous vibration signal of the on-load tap changer under test; determining the current pseudo-excitation force corresponding to the current vibration signal and the previous pseudo-excitation force corresponding to the previous vibration signal based on the state-space model; and determining the mechanical state of the on-load tap changer under test based on the current and previous pseudo-excitation forces. This invention can simulate various operating conditions while ensuring high accuracy of the physical model.

Description

Technical Field

[0001] This invention relates to the field of condition assessment technology for power equipment, and in particular to a method, system, and electronic equipment for assessing the mechanical condition of on-load tap changers. Background Technology

[0002] On-load tap changers (OLTCs) are the only components in power transformers that operate frequently. Because they bear the burden of breaking and closing large currents repeatedly over long periods, OLTCs are prone to mechanical fatigue, leading to issues such as loose contacts, spring failure, and motor jamming. This makes OLTCs susceptible to mechanical failures, which can then cause overheating faults in other electrical components. To prevent major accidents caused by OLTC failures, regular maintenance is generally required after 6-7 years of transformer operation or after the OLTC has operated 20,000-100,000 times. However, this maintenance strategy incurs unnecessary operating costs and may result in accidents due to human error, such as assembly errors or visual inspection mistakes.

[0003] To address this issue, current state-based maintenance is gradually replacing periodic maintenance. By monitoring the state variables during OLTC operation, it is possible to analyze whether there are mechanical defects / faults, thereby formulating reasonable maintenance strategies.

[0004] Currently, the maintenance strategies based on state variables are mainly divided into two types: data-driven state assessment methods and physical model-based state assessment methods. However, the vibration signals used in data-driven state assessment methods are mostly artificially simulated faults under experimental conditions. This may require significant experimental costs and human resources, and the results under experimental conditions differ from actual operating conditions, with limited applicability. Furthermore, accuracy and efficiency are difficult to guarantee when fault signals are insufficient. Physical model-based state assessment methods rely on the accuracy of the physical model; however, it is currently difficult to ensure simulation of various operating conditions while maintaining high physical model accuracy. Summary of the Invention

[0005] This invention provides a method, system, and electronic device for assessing the mechanical condition of on-load tap changers, in order to address the current problems of poor versatility in maintenance strategies for on-load tap changers and the difficulty in simulating multiple operating conditions while maintaining high accuracy in the physical model.

[0006] In a first aspect, embodiments of the present invention provide a method for evaluating the mechanical condition of an on-load tap changer, comprising:

[0007] Vibration signal samples of on-load tap changers at a preset frequency are collected, and time-frequency analysis of the vibration signal samples is performed through short-time Fourier transform (STFT) to obtain the STFT signal. The peak value of the STFT signal is found and used as the pseudo-excitation force corresponding to the vibration signal sample.

[0008] A state-space model is constructed based on the vibration signal samples and their corresponding pseudo-excitation forces.

[0009] Acquire the current vibration signal and the previous vibration signal of the on-load tap changer under test;

[0010] Based on the state-space model, determine the current pseudo-excitation force corresponding to the current vibration signal of the on-load tap changer under test and the previous pseudo-excitation force corresponding to the previous vibration signal.

[0011] Based on the current pseudo-excitation force and the previous pseudo-excitation force, determine the mechanical state of the on-load tap changer under test.

[0012] Secondly, embodiments of the present invention provide a mechanical condition assessment system for on-load tap changers, comprising:

[0013] The acquisition module is used to collect vibration signal samples of the on-load tap changer at a preset frequency, and to perform time-frequency analysis on the vibration signal samples through short-time Fourier transform (STFT) to obtain the STFT signal. The peak value of the STFT signal is then found and used as the pseudo-excitation force corresponding to the vibration signal sample.

[0014] The construction module is used to build a state-space model based on vibration signal samples and their corresponding pseudo-excitation forces;

[0015] The acquisition module is also used to acquire the current vibration signal and the previous vibration signal of the on-load tap changer under test;

[0016] The determination module is used to determine the current pseudo-excitation force corresponding to the current vibration signal of the on-load tap changer under test and the previous pseudo-excitation force corresponding to the previous vibration signal, based on the state space model.

[0017] The determination module is also used to determine the mechanical state of the on-load tap changer under test based on the current pseudo-excitation force and the previous pseudo-excitation force.

[0018] Thirdly, embodiments of the present invention provide an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the method as described in the first aspect or any possible implementation of the first aspect.

[0019] Fourthly, embodiments of the present invention provide a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the method as described in the first aspect or any possible implementation thereof.

[0020] This invention provides a method, system, and electronic device for assessing the mechanical state of an on-load tap changer. By collecting vibration signal samples of the on-load tap changer at a preset frequency and obtaining the corresponding pseudo-excitation force from these samples, the accuracy of the constructed state-space model can be improved. Based on the pseudo-excitation force corresponding to the vibration signal sample and the vibration signal sample itself, a state-space model is constructed. This requires only a small number of samples and does not require extensive prior knowledge to obtain the correspondence between the vibration signal and the pseudo-excitation force. According to the state-space model, the current pseudo-excitation force corresponding to the current vibration signal of the on-load tap changer under test and the previous pseudo-excitation force corresponding to the previous vibration signal are determined. Based on the current pseudo-excitation force and the previous pseudo-excitation force, the mechanical state of the on-load tap changer under test is determined. This invention does not rely on prior knowledge when training the state-space model, and the obtained state-space model is applicable to all states of the on-load tap changer. Finally, by comparing the pseudo-excitation forces corresponding to two adjacent vibration signals, the mechanical state assessment result of the on-load tap changer under test can be obtained. This ensures high accuracy of the physical model while simulating various operating conditions. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a flowchart illustrating the implementation of the on-load tap changer mechanical condition assessment method provided in this embodiment of the invention.

[0023] Figure 2 This is the MED algorithm iteration flow of the on-load tap changer mechanical condition assessment method provided in this embodiment of the invention;

[0024] Figure 3 This is a comparison diagram of filtered vibration signals from the on-load tap changer mechanical condition assessment method provided in this embodiment of the invention.

[0025] Figure 4 This is a comparison chart of the simulated and actual values ​​of the vibration signal in the on-load tap changer mechanical condition assessment method provided in this embodiment of the invention.

[0026] Figure 5 This is a diagram illustrating the vibration signal generation mechanism of the on-load tap changer mechanical condition assessment method provided in this embodiment of the invention.

[0027] Figure 6 This is a comparison diagram of vibration signal and pseudo-excitation force in the on-load tap changer mechanical condition assessment method provided in this embodiment of the invention;

[0028] Figures 7-8 This is a comparison diagram of normal vibration signals and fault vibration signals of the on-load tap changer mechanical condition assessment method provided in this embodiment of the invention;

[0029] Figure 9 This is a system architecture diagram of the on-load tap changer mechanical condition assessment method provided in this embodiment of the invention;

[0030] Figure 10 This is a schematic diagram of the structure of the on-load tap changer mechanical condition assessment system provided in an embodiment of the present invention;

[0031] Figure 11 This is a schematic diagram of an electronic device provided in an embodiment of the present invention. Detailed Implementation

[0032] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of the invention. However, those skilled in the art will understand that the invention can be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of the invention with unnecessary detail.

[0033] To make the objectives, technical solutions, and advantages of the present invention clearer, specific embodiments will be described below in conjunction with the accompanying drawings.

[0034] Figure 1 This is a flowchart illustrating the implementation of the on-load tap changer mechanical condition assessment method provided in this embodiment of the invention. Figure 1 As shown:

[0035] Step 110: Collect vibration signal samples of the on-load tap changer at a preset frequency, and perform time-frequency analysis on the vibration signal samples through short-time Fourier transform (STFT) to obtain the STFT signal. Find the peak value of the STFT signal and use the peak value as the pseudo-excitation force corresponding to the vibration signal sample.

[0036] In this embodiment, traditional on-load tap changer mechanical state analysis methods rely on prior knowledge, and vibration signals from on-load tap changer faults in actual operating conditions are difficult to obtain. Therefore, the required vibration signals are mostly obtained under experimental conditions with artificially created faults. This method consumes a lot of experimental costs and human resources, differs from actual operating conditions, and the results have limited applicability (possibly only applicable to the OLTC model used in the experiment). To solve this problem, this embodiment collects vibration signal samples of the on-load tap changer at a preset frequency, performs time-frequency analysis on the vibration signal samples using STFT, and extracts time-domain and frequency-domain features that reflect the characteristics of the vibration signal samples to obtain the STFT signal. Since the STFT signal has peak transformation, the peak value of the STFT signal can be found and used as the pseudo-excitation force corresponding to the vibration signal sample. Among them, since a vibration signal of 10.24kHz can reflect the state of the on-load tap changer to the greatest extent, the preset frequency can be 10.24kHz.

[0037] In this embodiment, a certain excitation force needs to be applied to the on-load tap changer before it generates a vibration signal; that is, each vibration signal has a corresponding excitation force. Unlike traditional methods that determine the mechanical state of the on-load tap changer by analyzing the characteristic quantities of the vibration signal, this embodiment determines the mechanical state of the on-load tap changer by analyzing the excitation force corresponding to the generation of the vibration signal. When building the model, a large amount of data is not required; only a set of vibration signals from any type of on-load tap changer under normal operating conditions is needed, making it more applicable. Furthermore, since the excitation force corresponding to the generation of the on-load tap changer vibration signal cannot be collected, this embodiment preprocesses the vibration signal samples to obtain a simulated excitation force, hence it is called a pseudo-excitation force.

[0038] Step 120: Construct a state-space model based on the vibration signal samples and their corresponding pseudo-excitation forces.

[0039] In this embodiment, there is a certain correspondence between the vibration signal sample and its corresponding pseudo-excitation force. In order to obtain this correspondence, a state-space model can be constructed based on the vibration signal sample and its corresponding pseudo-excitation force.

[0040] Step 130: Obtain the current vibration signal and the previous vibration signal of the on-load tap changer under test.

[0041] In this embodiment, the previous vibration signal of the on-load tap changer under test can be a vibration signal sample of the on-load tap changer sample, that is, the Tth vibration signal of the on-load tap changer under test. The corresponding current vibration signal can be the T+1th vibration signal of the on-load tap changer under test. The previous vibration signal can also be the vibration signal previously detected by the on-load tap changer under test, or it can be the vibration signal detected last week. That is, the previous vibration signal precedes the current vibration signal. The specific previous vibration signal selected can be chosen according to actual needs.

[0042] Step 140: Based on the state-space model, determine the current pseudo-excitation force corresponding to the current vibration signal of the on-load tap changer under test and the previous pseudo-excitation force corresponding to the previous vibration signal.

[0043] In this embodiment, after obtaining the state space model, the current pseudo-excitation force corresponding to the current vibration signal of the on-load tap changer under test and the previous vibration signal can be determined based on the current vibration signal and the previous pseudo-excitation force corresponding to the previous vibration signal.

[0044] Step 150: Determine the mechanical state of the on-load tap changer under test based on the current pseudo-excitation force and the previous pseudo-excitation force.

[0045] In this embodiment, the pseudo-excitation force can reflect the excitation force generated by the on-load tap changer when switching. The excitation force can reflect the state of the on-load tap changer when switching. By comparing the two pseudo-excitation forces, it can be determined whether the on-load tap changer under test has malfunctioned.

[0046] In summary, this embodiment of the invention improves the accuracy of constructing the state-space model by collecting vibration signal samples of on-load tap changers at a preset frequency and obtaining the corresponding pseudo-excitation forces from these samples. Based on the pseudo-excitation forces and the vibration signal samples themselves, a state-space model is constructed, requiring only a small number of samples to obtain the correspondence between vibration signals and pseudo-excitation forces without the need for extensive prior knowledge. According to the state-space model, the current pseudo-excitation force corresponding to the current vibration signal of the on-load tap changer under test and the previous pseudo-excitation force corresponding to the previous vibration signal are determined. Based on these two pseudo-excitation forces, the mechanical state of the on-load tap changer under test is determined. This embodiment of the invention does not rely on prior knowledge when training the state-space model, and the resulting state-space model is applicable to all states of the on-load tap changer. Finally, by comparing the pseudo-excitation forces corresponding to two adjacent vibration signals, the mechanical state evaluation result of the on-load tap changer under test can be obtained, ensuring high accuracy of the physical model while simulating various operating conditions.

[0047] In some embodiments, step 110, which involves performing time-frequency analysis on the vibration signal sample using a short-time Fourier transform (STFT) to obtain the STFT signal, finding the peak value of the STFT signal, and using the peak value as the pseudo-excitation force corresponding to the vibration signal sample, may include:

[0048] The vibration signal sample is filtered and denoised using the minimum entropy deconvolution method to obtain the denoised vibration signal.

[0049] The STFT signal is obtained by performing time-frequency analysis on the denoised vibration signal using the Short Time Fourier Transform (STFT) method.

[0050] The STFT signal is edge-processed to obtain the edge-processed STFT signal;

[0051] Based on the peak-finding algorithm, the peak value of the marginalized STFT signal is found, and the peak value is used as the pseudo-excitation force corresponding to the vibration signal sample.

[0052] Figure 2 This is the MED algorithm iteration flow of the on-load tap changer mechanical condition assessment method provided in this embodiment of the invention. The following is in conjunction with... Figure 2 This embodiment will be described as follows:

[0053] In this embodiment, due to external noise interference in the acquired vibration signal, and because the on-load tap changer is located in the transformer and is surrounded by other coils, which interfere with the acquired vibration signal, it is necessary to filter and reduce the noise of the acquired vibration signal. This embodiment uses the Minimum Entropy Deconvolution (MED) algorithm to find an optimal inverse filter to highlight the signal pulse during the deconvolution process, and uses the maximum kurtosis value as the stopping condition for iteration, so as to minimize the disorder of the original vibration signal and achieve the purpose of eliminating external background noise and other environmental interference, including the vibration signal of the transformer winding and iron core under the action of electromagnetic force.

[0054] w(n) represents the inverse transfer function, which needs to be initialized during MED calculation. i represents the number of iterations, with an initial value of 1; y(n) represents the vibration signal of the on-load tap changer; f(n) represents the vibration signal obtained after filtering and denoising.

[0055] The vibration signal collected during the OLTC switching process can be represented as:

[0056] y(n) = h(n) * x(n) n = 1, 2, ..., N

[0057] Where x(n) is the impact signal generated by the OLTC action, and h(n) is the transfer function.

[0058] The convolution of the impact signal with the transfer function becomes complex. The MED algorithm is equivalent to the deconvolution process, finding an optimal inverse transfer function w(n) to restore the impact signal x(n), i.e., the input signal, from the output signal y(n): x(n) = w(n). (i-1) *y(n)

[0059] Using whether w(n) reaches its optimum to measure the entropy of x(n), the expression for the new input signal obtained by deconvolving the above equation is:

[0060]

[0061] Where L is the filter length, l∈L.

[0062] After obtaining x(n), calculate b sequentially. i (l), w i , d.

[0063]

[0064]

[0065] w i =A -1 b i (l)

[0066]

[0067] Where A is the Toeplitz autocorrelation matrix of y(n). The iteration stops when d is greater than a preset threshold.

[0068] Figure 3 This is a comparison diagram of filtered vibration signals from the on-load tap changer mechanical condition assessment method provided in this embodiment of the invention.

[0069] The figures show the original vibration signal extracted from the on-load tap changer and the vibration signal after filtering and noise reduction using the MED algorithm. It can be seen that the filtered and noise-reduced vibration signal reflects the vibration state of the on-load tap changer while minimizing the disorder of the original vibration signal.

[0070] After obtaining the filtered and denoised vibration signal, this embodiment of the invention utilizes the Short Time Fourier Transform (STFT) method to perform time-frequency analysis on the denoised vibration signal, that is, to extract the vibration characteristics in the time and frequency domains of the filtered and denoised vibration signal, thus obtaining the STFT signal. The STFT signal can be represented as...

[0071]

[0072] Where t and f are the time step and frequency, respectively, w(τ) is the window function, y(τ) represents the vibration signal at time step τ, and Y(t,f) is the amplitude of the signal at time step t and frequency f.

[0073] Since the vibration signal during the OLTC switching process is a transient pulse signal, a uniform window function can be used after obtaining the STFT signal. The length of the window function can be adjusted according to the sampling rate to control the STFT signal.

[0074] To establish a state-space model of the simulated vibration signal, the input signal of the OLTC system needs to be obtained. To extract the pseudo-OLTC input signal, the STFT signal needs to be edge-trimmed to obtain the edge STFT signal.

[0075]

[0076] Among them, f min and f max These are the minimum and maximum frequency values ​​of the STFT signal, respectively.

[0077] To extract features from edge STFT signal sequences, a peak-finding algorithm is used to find edged STFT signals. The peak value.

[0078] After obtaining the peak value, the input signal can be defined as:

[0079]

[0080] in, and t j The peak amplitude and peak time of the edge STFT signal are given, respectively, and the amplitude of the normalized initial input signal ranges from 0 to 1. The resulting input signal is the pseudo-excitation force u(t).

[0081] In some embodiments, the step 120 of constructing a state-space model based on the vibration signal samples and their corresponding pseudo-excitation forces may include:

[0082] Step 121: Construct the Hankle matrix by taking the pseudo-excitation force corresponding to the vibration signal sample as input and the vibration signal sample as output.

[0083] Step 122: Perform singular value decomposition on the Hankle matrix to obtain the eigenvectors and singular values ​​of the Hankle matrix.

[0084] Step 123: Based on the subspace system identification algorithm, the eigenvectors and singular values ​​of the Hankle matrix, determine the pseudo-excitation force corresponding to the vibration signal sample and the functional relationship between the vibration signal sample and the vibration signal sample.

[0085] Step 124: Obtain the model parameters based on the functional relationship and the pseudo-excitation force corresponding to the vibration signal sample.

[0086] Step 125: Construct a state-space model based on the model parameters.

[0087] In this embodiment, in order to obtain the functional relationship between the pseudo-excitation force and the vibration signal, the pseudo-excitation force corresponding to the obtained vibration signal sample can be used as the current input and the vibration signal sample as the current output to construct the current Hankle matrix.

[0088] Among them, the past input Hankle matrix U p It can be represented as:

[0089]

[0090] Past output Hankle matrix Y p It can be represented as:

[0091]

[0092] Therefore, the past Toeplitz data matrix can be represented as:

[0093]

[0094] Similarly, the current input Hankle matrix U f It can be represented as:

[0095]

[0096] The current output Hankle matrix Y f It can be represented as:

[0097]

[0098] Accordingly, the current Toeplitz data matrix can be represented as:

[0099]

[0100] Where A, B, C, and D represent the system matrix, input matrix, output matrix, and feedthrough matrix, respectively.

[0101] The extended observability matrix is:

[0102] Based on the above formula, the relationship between the pseudo-excitation force corresponding to the current vibration signal sample and the vibration signal sample is obtained: Y f =O k X f +Ψ k Uf

[0103] The merged data matrix can be decomposed into a lower triangular matrix L and an orthogonal matrix Q.

[0104]

[0105] Where L ij (i,j=1,2,3) is a lower triangular matrix block; L 33 =0, because all inputs in the past and present times are zero, and the outputs in the past times are also zero. Q1 and Q2 are orthogonal.

[0106] From the above formula, we can obtain:

[0107]

[0108]

[0109]

[0110] The output matrix can then be derived as:

[0111] Y f =L 31 L 11 -1 U f +L 32 L 22 -1 (W p -L 21 L 11 -1 U f )=(L 31 -L 32 L 22 -1 L 21 )L 11 -1 U f +L 32 L 22 -1 W p

[0112] Based on the relationship between the pseudo-excitation force corresponding to the current vibration signal sample and the vibration signal sample, and the derived output matrix, it can be seen that: O k X f =L 32 L 22 -1 W p

[0113] Performing Singular Value Decomposition (SVD) yields:

[0114]

[0115]

[0116]

[0117] Based on the state sequence X f and input / output data (U f Y f The system matrix parameters, i.e., the model parameters, can be estimated using the least squares method:

[0118]

[0119] Among them, X k Y k U k Let X be the state sequence, output sequence, and input sequence from time k to k+N-2. k+1 It is the state sequence from time k+1 to k+N-1.

[0120] Finally, the state space model is determined based on the Numerical Subspace State Space System Identification (N4SID) algorithm and model parameters.

[0121] The state-space model can be expressed as: Among them, X and Y pre U and U represent the state vector, output vector, and input vector, respectively. The state-space model can also be derived using the finite element method and lumped dynamics model, but these require prior knowledge of the system. The method provided in this embodiment does not require prior knowledge.

[0122] The state-space model constructed in this embodiment can be viewed as a digital twin model. Its construction does not rely on prior knowledge of the OLTC, making it applicable to all mechanical OLTCs. Furthermore, it eliminates the need to build a dataset of vibration signals under fault conditions and train the model. This embodiment uses vibration signal samples from OLTC operation to construct a digital twin model (using N4SID to build the state-space model of the OLTC system), connecting the real-world physical problem with the virtual digital twin using the OLTC system's vibration signals. Moreover, this embodiment can dynamically update the model using real-time monitored vibration signals, enabling monitoring of the OLTC's mechanical state and early fault warning.

[0123] Furthermore, the state-space model provided in this embodiment can also be applied to power equipment such as vacuum circuit breakers that generate vibration signals due to contact collisions after improvement.

[0124] In some embodiments, obtaining the model parameters in step 124 based on the functional relationship and the pseudo-excitation force corresponding to the vibration signal sample may include:

[0125] The simulated values ​​of the vibration signal samples are obtained based on the functional relationship and the pseudo-excitation force corresponding to the vibration signal samples.

[0126] Extract the simulated values ​​of the vibration signal samples and the discrete Fourier transform amplitudes of the vibration signal samples;

[0127] Based on the L2 norm formula, the discrete Fourier transform amplitude of the simulated vibration signal sample, and the discrete Fourier transform amplitude of the vibration signal sample, calculate the simulated vibration signal sample and the norm error value of the vibration signal sample.

[0128] If the norm error value meets the preset condition, then the parameters in the current functional relationship will be used as model parameters;

[0129] If the norm error value does not meet the preset conditions, the pseudo-excitation force corresponding to the vibration signal sample is adjusted, and the process of constructing the Hankle matrix is ​​returned, with the pseudo-excitation force corresponding to the vibration signal sample as the input and the vibration signal sample as the output.

[0130] In this embodiment, although the pseudo-excitation force corresponding to the vibration signal sample is obtained by preprocessing the vibration signal sample, since the pseudo-excitation force is obtained by calculation and simulation, it will inevitably have a certain deviation. Therefore, the state space model constructed based on the pseudo-excitation force will also have a deviation, resulting in inaccurate prediction results in actual use. Therefore, in the process of constructing the state space model, it is necessary to continuously adjust the model parameters so that the constructed model can accurately derive the pseudo-excitation force corresponding to the vibration signal.

[0131] Specifically, after deriving the functional relationship between the vibration signal sample and its corresponding pseudo-excitation force, the simulated value of the vibration signal sample can be obtained based on the pseudo-excitation force corresponding to the vibration signal sample. Since the error of the vibration signal cannot be directly compared numerically, it is necessary to extract the simulated value of the vibration signal sample and the discrete-time Fourier transform amplitude of the vibration signal sample. By comparing the amplitudes, the error between the simulated value and the actual vibration signal sample is determined. The L2 norm formula is as follows:

[0132]

[0133] Where Y(t,f) and Let θ represent the discrete-time STFT amplitude of the vibration signal sample and the simulated value of the vibration signal sample, respectively, and θ be the optimization parameter.

[0134] A genetic algorithm can be used to select the optimal simulated vibration signal sample value, that is, to select the simulated vibration signal sample value with the smallest norm error. Figure 4 This is a comparison chart of the simulated and actual values ​​of the vibration signal in the on-load tap changer mechanical condition assessment method provided in this embodiment of the invention. The simulated values ​​of the selected vibration signal samples are shown below. Figure 4 As shown.

[0135] If the norm error value meets the preset condition, it means that the pseudo-excitation force corresponding to the vibration signal sample meets the requirements. Correspondingly, the functional relationship obtained from it also meets the requirements, so the parameters in the current functional relationship are used as model parameters. That is, the parameters in the functional relationship are actually the same as the model parameters, but not the parameters in the functional relationship at any time can be used as model parameters. Only when the norm error value meets the preset condition can the parameters in the previous functional relationship be used as model parameters.

[0136] If the norm error value does not meet the preset conditions, then it is necessary to adjust the pseudo-excitation force corresponding to the vibration signal sample and reconstruct the functional relationship between the vibration signal sample and its corresponding pseudo-excitation force. That is, it is necessary to adjust the pseudo-excitation force corresponding to the vibration signal sample and return to the step of constructing the Hankle matrix with the pseudo-excitation force corresponding to the vibration signal sample as input and the vibration signal sample as output.

[0137] This embodiment determines the pseudo-excitation force corresponding to the vibration signal sample by calculating the norm error between the simulated value of the vibration signal sample and the vibration signal sample, and determines the functional relationship between the vibration signal sample and its corresponding pseudo-excitation force, thereby determining the model parameters. This makes the constructed state-space model more accurate. Furthermore, the modeling process does not require a large amount of experimental data or rely on a physical model, and can ensure simulation for various working conditions to obtain the mechanical state of the on-load tap changer under various working conditions.

[0138] In some embodiments, determining the current pseudo-excitation force corresponding to the current vibration signal of the on-load tap changer under test according to the state-space model in step 140 may include:

[0139] The current vibration signal of the on-load tap changer under test is analyzed in time and frequency by using short-time Fourier transform (STFT) to obtain the current STFT signal. The peak value of the current STFT signal is then found and taken as the pseudo-excitation force corresponding to the current vibration signal.

[0140] The pseudo-excitation force corresponding to the current vibration signal is input into the state space model to obtain the simulated value of the current vibration signal.

[0141] Extract the simulated value of the current vibration signal and the discrete Fourier transform amplitude of the current vibration signal.

[0142] Calculate the simulated value of the current vibration signal and the norm error value of the current vibration signal based on the L2 norm formula, the discrete Fourier transform amplitude of the current vibration signal simulation value, and the discrete Fourier transform amplitude of the current vibration signal.

[0143] If the norm error value meets the preset conditions, then the pseudo-excitation force corresponding to the current vibration signal will be taken as the current pseudo-excitation force.

[0144] If the norm error value does not meet the preset conditions, the pseudo-excitation force corresponding to the current vibration signal is adjusted, and the process of inputting the pseudo-excitation force corresponding to the current vibration signal into the state space model to obtain the simulated value of the current vibration signal is repeated until the norm error value meets the preset conditions.

[0145] This embodiment describes the process of using the state-space model. First, the pseudo-excitation force corresponding to the current vibration signal needs to be extracted (the specific extraction method is the same as the method for extracting the pseudo-excitation force corresponding to the vibration signal samples before model construction, and will not be repeated here). Then, the pseudo-excitation force corresponding to the current vibration signal is input into the pre-trained state-space model to obtain the simulated value of the current vibration signal. The norm error value of the simulated value and the current vibration signal is then calculated. Based on the norm error value, it is determined whether the pseudo-excitation force corresponding to the current vibration signal meets the requirements (the step of calculating the norm error value is the same as the step of obtaining the model parameters, and will not be repeated here).

[0146] In this embodiment, during the use of the state-space model, the parameters in the model can be adjusted according to the input pseudo-excitation force, and by adjusting the pseudo-excitation force, the optimal pseudo-excitation force corresponding to the current vibration signal can be obtained.

[0147] In some embodiments, the L2-norm formula includes optimization parameters, which include phase modulation parameters and amplitude modulation parameters; the pseudo-excitation force is adjusted according to the phase modulation parameters and amplitude modulation parameters.

[0148] In this embodiment, θ is the optimization parameter in the L2-norm formula, also known as the update parameter vector, which includes a set of parameters, such as the phase modulation parameter (S) of the nth (n=1-9) pulse input. n ) and amplitude modulation parameters (P n ).

[0149] When updating the pseudo-excitation force, the phase and amplitude of the pseudo-excitation force can be updated according to the parameter tuning formula.

[0150] The parameter tuning formula is as follows:

[0151] In addition, in this embodiment, after determining the pseudo-excitation force corresponding to the vibration signal, the delay and amplitude of the pseudo-excitation force corresponding to the vibration signal can be derived through the state-space model.

[0152] In some embodiments, the pseudo-excitation force includes three different sub-pseudo-excitation forces, each sub-pseudo-excitation force including three different amplitudes; step 150, determining the mechanical state of the on-load tap changer under test based on the current pseudo-excitation force and the previous pseudo-excitation force, may include:

[0153] Based on the state-space model, the delay and amplitude corresponding to the current pseudo-excitation force and the previous pseudo-excitation force are obtained respectively.

[0154] Compare the current delay and amplitude of the pseudo-incentive with the delay and amplitude of the previous pseudo-incentive.

[0155] If the delay between the three amplitudes in each group of sub-pseudo-excitation forces of the current pseudo-excitation force increases, then the on-load tap changer under test will exhibit circulating current.

[0156] If the delay between the three sets of sub-pseudo-excitation forces of the current pseudo-excitation force increases, the on-load tap changer under test will experience spring breakage or mechanism jamming.

[0157] If the amplitudes of three sub-pseudo-excitation forces in each group of the current pseudo-excitation force decrease, the on-load tap changer under test will show insufficient spring energy storage or spring fatigue.

[0158] Figure 5 This is a diagram illustrating the vibration signal generation mechanism of the on-load tap changer mechanical condition assessment method provided in this embodiment of the invention. Figure 5 As shown:

[0159] During the switching process of an on-load tap changer, the two transition contacts and one main contact of each phase will collide with the stationary contact in sequence and generate vibration signals. If each collision is regarded as an instantaneous impact, then the vibration signals generated by the on-load tap changer during the switching process include three sets of sub-vibration signals, and the corresponding pseudo-excitation forces of the vibration signals include three sets of pseudo-excitation forces.

[0160] Figure 6 This is a comparison diagram of vibration signals and pseudo-excitation forces in the on-load tap changer mechanical condition assessment method provided in this embodiment of the invention, as shown in the figure. Figure 6 As shown:

[0161] For a three-phase tap changer, three sets of impacts will occur sequentially during a single switching process. The vibration signals generated by these three sets of impacts affect... Figure 6 The first, second, and third sub-vibration signals; each group of impacts contains three impacts, corresponding to... Figure 6The three peak values ​​of each group of sub-vibration signals are obtained. Based on the vibration signals, three groups of pseudo-excitation forces (1, 2, and 3) are obtained. Each group of pseudo-excitation forces is represented by three phases A, B, and C, which correspond to the three peak values ​​of each group of sub-vibration signals. Among them, phases A, B, and C represent the three different amplitudes of each group of pseudo-excitation forces.

[0162] For example, the time interval between the three sub-pseudo-excitation forces in the previous pseudo-excitation force set 1, 2, and 3 is T1; the time interval between the three phases A, B, and C of each sub-pseudo-excitation force set is t. AB1 t BC1 Taking a group of pseudo-excitation forces as an example, the amplitudes of the three phases A, B, and C of the group of pseudo-excitation forces are A1, B1, and C1, respectively.

[0163] The time interval between the three sub-pseudo-excitation forces in the current pseudo-excitation force group 1, group 2, and group 3 is T2; the time interval between the three phases A, B, and C of each sub-pseudo-excitation force group is t. AB2 t BC2 Taking a group of pseudo-excitation forces as an example, the amplitudes of the three phases A, B, and C of the group of pseudo-excitation forces are A2, B2, and C2, respectively.

[0164] If t AB2 With t BC2 The time interval between them increases, that is, the asynchronous time is greater than 3ms. This indicates that the three phases are out of sync, which may be due to a fault in the on-load tap changer under test, which may be causing a circulating current phenomenon.

[0165] Figures 7-8 This is a comparison diagram of normal vibration signals and fault vibration signals of the on-load tap changer mechanical condition assessment method provided in this embodiment of the invention.

[0166] Figure 7 The diagram shows a comparison of vibration signals when an on-load tap changer experiences a mechanical jamming fault (including spring breakage) with vibration signals during normal operation. The diagram shows that when a mechanical jamming fault occurs, the delay between groups 2 and 3 of the on-load tap changer increases significantly, and correspondingly, the delay between their respective pseudo-excitation forces also increases.

[0167] For example, if T2 increases by 10% compared to T1, this indicates that the switching time is longer, and the on-load tap changer under test may have experienced spring breakage or mechanism jamming.

[0168] Figure 8The image shows a comparison of the vibration signals of an on-load tap changer when the spring energy storage is insufficient (including spring fatigue) with those during normal operation. As can be seen from the image, when the spring energy storage is insufficient, the amplitude of the three sets of vibration signals from the on-load tap changer is significantly reduced compared to the amplitude under normal conditions, and correspondingly, the amplitude of the corresponding pseudo-excitation force also decreases.

[0169] For example, if when A2, B2, C2 are compared with A1, B1, C1 respectively, the corresponding amplitude decreases by more than 20%, it indicates that the on-load tap changer under test may have insufficient spring energy storage or spring fatigue.

[0170] This embodiment can determine the mechanical state of the on-load tap changer under test in actual operation by comparing the delay and amplitude of two pseudo-excitation forces, without requiring a large amount of prior knowledge or training datasets.

[0171] Figure 9 This is a system architecture diagram of the on-load tap changer mechanical condition assessment method provided in this embodiment of the invention, as shown below. Figure 9 As shown:

[0172] In this embodiment, the reference signal at time T used to construct the model is used as the previous vibration signal of the on-load tap changer under test, and the target signal at time T+1 is used as the current vibration signal of the on-load tap changer under test.

[0173] This embodiment is divided into three parts: data acquisition and preprocessing, model construction and updating, and operational status evaluation. The data acquisition and preprocessing part obtains vibration signal samples from the on-load tap changer, i.e., the reference signal at time T. The reference signal at time T is then sequentially processed through MED filtering, STFT time-frequency domain feature analysis, and a peak-finding algorithm to obtain the pseudo-excitation force corresponding to the reference signal at time T.

[0174] The model construction and update process uses the reference signal at time T as the output and the pseudo-excitation force corresponding to the reference signal at time T as the input, obtaining model parameters through the N4SID algorithm. The norm error value is then calculated according to the L2-norm formula, and the pseudo-excitation force corresponding to the reference signal at time T is adjusted based on the norm error value until the norm error value meets the condition. Based on the current model parameters, a state-space model is constructed. In the above embodiment, the parameters in the functional relationship are A, B, C, and D. To distinguish them, the model parameters for constructing the state-space model are denoted as A. ref B ref C ref D ref .

[0175] The operational status assessment section first processes the target signal at time T+1 through MED filtering, STFT time-frequency domain feature analysis, and a peak-finding algorithm to obtain the pseudo-excitation force corresponding to the target signal at time T+1. This pseudo-excitation force is then input into the state-space model to obtain the corresponding simulated value of the target signal at time T+1. The norm error value is calculated using the L2-norm formula. The pseudo-excitation force corresponding to the target signal at time T+1 is adjusted based on the norm error value until the norm error value meets the required condition. The delay and amplitude of the two pseudo-excitation forces are then derived. By comparing the delay and amplitude of the two pseudo-excitation forces, the operational status assessment result of the on-load tap changer under test is output.

[0176] For parts not described in detail in this embodiment, please refer to the other specific embodiments described above, which will not be repeated here.

[0177] In summary, this embodiment of the invention improves the accuracy of constructing the state-space model by collecting vibration signal samples of on-load tap changers at a preset frequency and obtaining the corresponding pseudo-excitation forces from these samples. Based on the pseudo-excitation forces and the vibration signal samples themselves, a state-space model is constructed, requiring only a small number of samples to obtain the correspondence between vibration signals and pseudo-excitation forces without the need for extensive prior knowledge. According to the state-space model, the current pseudo-excitation force corresponding to the current vibration signal of the on-load tap changer under test and the previous pseudo-excitation force corresponding to the previous vibration signal are determined. Based on these two pseudo-excitation forces, the mechanical state of the on-load tap changer under test is determined. This embodiment of the invention does not rely on prior knowledge when training the state-space model, and the resulting state-space model is applicable to all states of the on-load tap changer. Finally, by comparing the pseudo-excitation forces corresponding to two adjacent vibration signals, the mechanical state evaluation result of the on-load tap changer under test can be obtained, ensuring high accuracy of the physical model while simulating various operating conditions.

[0178] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0179] The following are device embodiments of the present invention. For details not described in detail, please refer to the corresponding method embodiments described above.

[0180] Figure 10 The diagram shows a structural schematic of an on-load tap changer mechanical condition assessment system according to an embodiment of the present invention. For ease of explanation, only the parts relevant to the embodiment of the present invention are shown, and are described in detail below:

[0181] like Figure 10As shown, an on-load tap changer mechanical condition assessment system 10 includes:

[0182] The acquisition module 101 is used to acquire vibration signal samples of the on-load tap changer sample at a preset frequency, and to perform time-frequency analysis on the vibration signal samples through short-time Fourier transform (STFT) to obtain the STFT signal, find the peak value of the STFT signal, and use the peak value as the pseudo excitation force corresponding to the vibration signal sample.

[0183] Module 102 is used to construct a state-space model based on vibration signal samples and their corresponding pseudo-excitation forces.

[0184] The acquisition module 101 is also used to acquire the current vibration signal and the previous vibration signal of the on-load tap changer under test;

[0185] The determination module 103 is used to determine the current pseudo-excitation force corresponding to the current vibration signal of the on-load tap changer under test and the previous pseudo-excitation force corresponding to the previous vibration signal, based on the state space model.

[0186] The determination module 103 is also used to determine the mechanical state of the on-load tap changer under test based on the current pseudo-excitation force and the previous pseudo-excitation force.

[0187] In some embodiments, the construction module 102 is specifically used for:

[0188] Using the pseudo-excitation force corresponding to the vibration signal sample as input and the vibration signal sample as output, construct the Hankle matrix;

[0189] Singular value decomposition is performed on the Hankle matrix to obtain the eigenvectors and singular values ​​of the Hankle matrix;

[0190] Based on the subspace system identification algorithm, the eigenvectors and singular values ​​of the Hankle matrix, the pseudo-excitation force corresponding to the vibration signal sample and the functional relationship between the vibration signal samples are determined.

[0191] The model parameters are obtained based on the functional relationship and the pseudo-excitation force corresponding to the vibration signal samples.

[0192] Construct a state-space model based on the model parameters.

[0193] In some embodiments, the construction module 102 is specifically used for:

[0194] The simulated values ​​of the vibration signal samples are obtained based on the functional relationship and the pseudo-excitation force corresponding to the vibration signal samples.

[0195] Extract the simulated values ​​of the vibration signal samples and the discrete Fourier transform amplitudes of the vibration signal samples;

[0196] Based on the L2 norm formula, the discrete Fourier transform amplitude of the simulated vibration signal sample, and the discrete Fourier transform amplitude of the vibration signal sample, calculate the simulated vibration signal sample and the norm error value of the vibration signal sample.

[0197] If the norm error value meets the preset condition, then the parameters in the current functional relationship will be used as model parameters;

[0198] If the norm error value does not meet the preset conditions, the pseudo-excitation force corresponding to the vibration signal sample is adjusted, and the process of constructing the Hankle matrix is ​​returned, with the pseudo-excitation force corresponding to the vibration signal sample as the input and the vibration signal sample as the output.

[0199] In some embodiments, the determining module 103 is specifically used for:

[0200] The current vibration signal of the on-load tap changer under test is analyzed in time and frequency by short-time Fourier transform (STFT) to obtain the current STFT signal. The peak value of the current STFT signal is found and the peak value of the current STFT signal is taken as the pseudo excitation force corresponding to the current vibration signal.

[0201] The pseudo-excitation force corresponding to the current vibration signal is input into the state space model to obtain the simulated value of the current vibration signal;

[0202] Extract the simulated value of the current vibration signal and the discrete Fourier transform amplitude of the current vibration signal;

[0203] Based on the L2-norm formula, the discrete Fourier transform amplitude of the current vibration signal simulation value, and the discrete Fourier transform amplitude of the current vibration signal, calculate the current vibration signal simulation value and the norm error value of the current vibration signal.

[0204] If the norm error value meets the preset condition, then the pseudo excitation force corresponding to the current vibration signal is taken as the current pseudo excitation force.

[0205] If the norm error value does not meet the preset conditions, the pseudo-excitation force corresponding to the current vibration signal is adjusted, and the process of inputting the pseudo-excitation force corresponding to the current vibration signal into the state space model to obtain the simulated value of the current vibration signal is repeated until the norm error value meets the preset conditions.

[0206] In some embodiments, the L2-norm formula includes optimization parameters, which include phase modulation parameters and amplitude modulation parameters; the pseudo-excitation force is adjusted according to the phase modulation parameters and amplitude modulation parameters.

[0207] In some embodiments, the acquisition module 101 is specifically used for:

[0208] The vibration signal samples are filtered and denoised using the minimum entropy deconvolution method to obtain the denoised vibration signal. The short-time Fourier transform (STFT) method is then used to perform time-frequency analysis on the denoised vibration signal to obtain the STFT signal.

[0209] The STFT signal is edge-processed to obtain the edge-processed STFT signal.

[0210] Based on the peak-finding algorithm, the peak value of the marginalized STFT signal is found, and the peak value is used as the pseudo-excitation force corresponding to the vibration signal sample.

[0211] In some embodiments, the pseudo-excitation force includes three different sets of sub-pseudo-excitation forces, each set of sub-pseudo-excitation forces including three different amplitudes; the determining module 103 is specifically used for:

[0212] Based on the state-space model, the delay and amplitude corresponding to the current pseudo-excitation force and the previous pseudo-excitation force are obtained respectively;

[0213] Compare the current delay and amplitude of the pseudo-incentive with the delay and amplitude of the previous pseudo-incentive;

[0214] If the delay between the three amplitudes in each group of sub-pseudo-excitation forces of the current pseudo-excitation force increases, then the on-load tap changer under test will exhibit circulating current.

[0215] If the delay between the three sets of sub-pseudo-excitation forces of the current pseudo-excitation force increases, the on-load tap changer under test will experience spring breakage or mechanism jamming.

[0216] If the amplitudes of three sub-pseudo-excitation forces in each group of the current pseudo-excitation force decrease, the on-load tap changer under test will show insufficient spring energy storage or spring fatigue.

[0217] Figure 11 This is a schematic diagram of an electronic device provided in an embodiment of the present invention. Figure 11 As shown, the electronic device 11 of this embodiment includes: a processor 110, a memory 111, and a computer program 112 stored in the memory 111 and executable on the processor 110. When the processor 110 executes the computer program 112, it implements the steps in the various embodiments of the on-load tap changer mechanical condition assessment method described above, for example... Figure 1 Steps 110 to 150 are shown. Alternatively, when the processor 110 executes the computer program 112, it implements the functions of each module / unit in the above-described device embodiments, for example... Figure 10 The functions of each module are shown.

[0218] For example, the computer program 112 can be divided into one or more modules / units, which are stored in the memory 111 and executed by the processor 110 to complete the present invention. The one or more modules / units can be a series of computer program instruction segments capable of performing a specific function, which describe the execution process of the computer program 112 in the electronic device 11. For example, the computer program 112 can be divided into... Figure 10 The modules shown.

[0219] The electronic device 11 can be a desktop computer, laptop, handheld computer, cloud server, or other computing device. The electronic device 11 may include, but is not limited to, a processor 110 and a memory 111. Those skilled in the art will understand that... Figure 11 This is merely an example of electronic device 11 and does not constitute a limitation on electronic device 11. It may include more or fewer components than shown, or combine certain components, or different components. For example, the electronic device may also include input / output devices, network access devices, buses, etc.

[0220] The processor 110 may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor.

[0221] The memory 111 can be an internal storage unit of the electronic device 11, such as a hard disk or RAM of the electronic device 11. The memory 111 can also be an external storage device of the electronic device 11, such as a plug-in hard disk, Smart Media Card (SMC), Secure Digital (SD) card, or Flash Card equipped on the electronic device 11. Furthermore, the memory 111 can include both internal and external storage units of the electronic device 11. The memory 111 is used to store the computer program and other programs and data required by the electronic device. The memory 111 can also be used to temporarily store data that has been output or will be output.

[0222] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units and modules are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the units and modules in the above system can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0223] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0224] 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 depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0225] In the embodiments provided by this invention, it should be understood that the disclosed devices / electronic devices and methods can be implemented in other ways. For example, the device / electronic device embodiments described above are merely illustrative. For instance, the division of modules or units is only 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. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0226] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0227] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0228] If the integrated module / unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the above embodiments of the present invention can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the above embodiments of the on-load tap changer mechanical condition assessment method. The computer program includes computer program code, which can be in the form of source code, object code, executable file, or some intermediate form. The computer-readable medium can include: any entity or device capable of carrying the computer program code, a recording medium, a USB flash drive, a portable hard drive, a magnetic disk, an optical disk, a computer memory, a read-only memory (ROM), a random access memory (RAM), an electrical carrier signal, a telecommunication signal, and a software distribution medium, etc.

[0229] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A method of evaluating a mechanical state of an on-load tap changer, characterized by, include: Vibration signal samples of on-load tap changers at a preset frequency are collected, and time-frequency analysis of the vibration signal samples is performed through short-time Fourier transform (STFT) to obtain the STFT signal. The peak value of the STFT signal is found, and the peak value is used as the pseudo-excitation force corresponding to the vibration signal sample. Based on the vibration signal samples and their corresponding pseudo-excitation forces, a state-space model is constructed. Acquire the current vibration signal and the previous vibration signal of the on-load tap changer under test; Based on the state space model, determine the current pseudo-excitation force corresponding to the current vibration signal of the on-load tap changer under test and the previous pseudo-excitation force corresponding to the previous vibration signal. The mechanical state of the on-load tap changer under test is determined based on the current pseudo-excitation force and the previous pseudo-excitation force. The pseudo-excitation force includes three different sub-pseudo-excitation forces, each sub-pseudo-excitation force including three different amplitudes; determining the mechanical state of the on-load tap changer under test based on the current pseudo-excitation force and the previous pseudo-excitation force includes: Based on the state-space model, the delay and amplitude corresponding to the current pseudo-excitation force and the previous pseudo-excitation force are obtained respectively; Compare the delay and amplitude of the current pseudo-excitation force with the delay and amplitude of the previous pseudo-excitation force; If the delay between the three amplitudes in each group of sub-pseudo-excitation forces of the current pseudo-excitation force increases, then the on-load tap changer under test will exhibit a circulating current phenomenon. If the delay between the three sets of sub-pseudo-excitation forces of the current pseudo-excitation force increases, the on-load tap changer under test will experience spring breakage or mechanism jamming. If the amplitudes of three sub-pseudo-excitation forces in each group of the current pseudo-excitation force decrease, then the on-load tap changer under test will experience insufficient spring energy storage or spring fatigue.

2. The method for assessing the mechanical condition of an on-load tap changer according to claim 1, characterized in that, The step of constructing a state-space model based on the vibration signal samples and their corresponding pseudo-excitation forces includes: Using the pseudo-excitation force corresponding to the vibration signal sample as input and the vibration signal sample as output, construct the Hankle matrix; The Hankle matrix is ​​subjected to singular value decomposition to obtain the eigenvectors and singular values ​​of the Hankle matrix; Based on the subspace system identification algorithm, the eigenvectors and singular values ​​of the Hankle matrix, the pseudo-excitation force corresponding to the vibration signal sample and the functional relationship between the vibration signal sample are determined. The model parameters are obtained based on the functional relationship and the pseudo-excitation force corresponding to the vibration signal sample. Construct a state-space model based on the model parameters.

3. The method for assessing the mechanical condition of an on-load tap changer according to claim 2, characterized in that, The process of obtaining model parameters based on the functional relationship and the pseudo-excitation force corresponding to the vibration signal sample includes: The simulated value of the vibration signal sample is obtained based on the functional relationship and the pseudo-excitation force corresponding to the vibration signal sample; Extract the simulated values ​​of the vibration signal samples and the discrete Fourier transform amplitudes of the vibration signal samples; Based on the L2-norm formula, the discrete Fourier transform amplitude of the simulated vibration signal sample, and the discrete Fourier transform amplitude of the vibration signal sample, calculate the simulated vibration signal sample and the norm error value of the vibration signal sample. If the norm error value meets the preset condition, then the parameters in the current functional relationship are used as model parameters; If the norm error value does not meet the preset condition, the pseudo-excitation force corresponding to the vibration signal sample is adjusted, and the process of constructing the Hankle matrix is ​​returned, with the pseudo-excitation force corresponding to the vibration signal sample as the input and the vibration signal sample as the output.

4. The method for assessing the mechanical condition of an on-load tap changer according to claim 1, characterized in that, The step of determining the current pseudo-excitation force corresponding to the current vibration signal of the on-load tap changer under test based on the state space model includes: The current vibration signal of the on-load tap changer under test is analyzed by time-frequency analysis through short-time Fourier transform (STFT) to obtain the current STFT signal. The peak value of the current STFT signal is found and the peak value of the current STFT signal is taken as the pseudo excitation force corresponding to the current vibration signal. The pseudo-excitation force corresponding to the current vibration signal is input into the state space model to obtain the simulated value of the current vibration signal; Extract the simulated value of the current vibration signal and the discrete Fourier transform amplitude of the current vibration signal; Based on the L2-norm formula, the discrete Fourier transform amplitude of the current vibration signal simulation value, and the discrete Fourier transform amplitude of the current vibration signal, calculate the current vibration signal simulation value and the norm error value of the current vibration signal. If the norm error value meets the preset condition, then the pseudo excitation force corresponding to the current vibration signal is taken as the current pseudo excitation force. If the norm error value does not meet the preset condition, the pseudo-excitation force corresponding to the current vibration signal is adjusted, and the process returns to the step of inputting the pseudo-excitation force corresponding to the current vibration signal into the state space model to obtain the simulated value of the current vibration signal, until the norm error value meets the preset condition.

5. The method for assessing the mechanical condition of an on-load tap changer according to claim 3 or 4, characterized in that, The L2-norm formula includes optimization parameters, including phase modulation parameters and amplitude modulation parameters; the pseudo-excitation force is adjusted according to the phase modulation parameters and amplitude modulation parameters.

6. The method for assessing the mechanical condition of an on-load tap changer according to claim 1, characterized in that, The step of performing time-frequency analysis on the vibration signal sample using Short-Time Fourier Transform (STFT) to obtain the STFT signal, finding the peak value of the STFT signal, and using the peak value as the pseudo-excitation force corresponding to the vibration signal sample includes: The vibration signal sample is filtered and denoised using the minimum entropy deconvolution method to obtain the denoised vibration signal. The STFT signal is obtained by performing time-frequency analysis on the noise-reduced vibration signal using the Short Time Fourier Transform (STFT) method. The STFT signal is edge-processed to obtain an edge-processed STFT signal; According to the peak-finding algorithm, the peak value of the marginalized STFT signal is found, and the peak value is used as the pseudo-excitation force corresponding to the vibration signal sample.

7. A mechanical condition assessment system for on-load tap changers, characterized in that, include: The acquisition module is used to collect vibration signal samples of a preset frequency of an on-load tap changer sample, and perform time-frequency analysis on the vibration signal sample through short-time Fourier transform (STFT) to obtain the STFT signal, find the peak value of the STFT signal, and use the peak value as the pseudo-excitation force corresponding to the vibration signal sample. The construction module is used to construct a state-space model based on the vibration signal samples and their corresponding pseudo-excitation forces; The acquisition module is also used to acquire the current vibration signal and the previous vibration signal of the on-load tap changer under test; The determination module is used to determine, based on the state space model, the current pseudo-excitation force corresponding to the current vibration signal of the on-load tap changer under test and the previous pseudo-excitation force corresponding to the previous vibration signal; The determining module is further configured to determine the mechanical state of the on-load tap changer under test based on the current pseudo-excitation force and the previous pseudo-excitation force. The pseudo-excitation force includes three different sub-pseudo-excitation forces, each sub-pseudo-excitation force including three different amplitudes; the determining module is specifically used for: Based on the state-space model, the delay and amplitude corresponding to the current pseudo-excitation force and the previous pseudo-excitation force are obtained respectively; Compare the delay and amplitude of the current pseudo-excitation force with the delay and amplitude of the previous pseudo-excitation force; If the delay between the three amplitudes in each group of sub-pseudo-excitation forces of the current pseudo-excitation force increases, then the on-load tap changer under test will exhibit a circulating current phenomenon. If the delay between the three sets of sub-pseudo-excitation forces of the current pseudo-excitation force increases, the on-load tap changer under test will experience spring breakage or mechanism jamming. If the amplitudes of three sub-pseudo-excitation forces in each group of the current pseudo-excitation force decrease, then the on-load tap changer under test will experience insufficient spring energy storage or spring fatigue.

8. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the on-load tap changer mechanical condition assessment method as described in any one of claims 1 to 6.

9. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the on-load tap changer mechanical condition assessment method as described in any one of claims 1 to 6.

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