A terminal waveform alignment method based on zero-voltage abrupt change point

Abstract

This invention proposes a terminal waveform alignment method based on zero-voltage abrupt change points, comprising the following steps: Step S1, waveform denoising, removing high-frequency noise from the zero-sequence voltage waveform; Step S2, calculation window calculation, calculating the effective values ​​of the zero-sequence voltage waveforms within one cycle of two adjacent groups, and calculating the absolute value of the difference between them; if the absolute value is lower than a set threshold, the calculation window is shifted back one cycle, and step S2 is re-entered; if the absolute value is higher than the set threshold, step S3 is entered; Step S3, zero-voltage abrupt change point selection, i.e., finding the extreme point in the waveform range with a large effective value; Step S4, terminal waveform alignment, aligning the abrupt change points by waveform translation to achieve terminal waveform alignment; This invention can be deployed on the main station side or substation side aggregation unit without modifying the distribution terminal, to achieve synchronous alignment of electrical quantity waveforms collected by all in-station and out-of-station distribution terminals under the same substation and the same busbar, indirectly achieving synchronous acquisition.

Description

Technical Field

[0001] This invention relates to the field of power distribution automation technology, and in particular to a terminal waveform alignment method based on zero-voltage abrupt change points. Background Technology

[0002] Single-phase grounding faults are one of the most common fault types in distribution networks, and also one of the most difficult to diagnose. Currently, distribution terminals collect electrical quantity information such as zero-sequence voltage and zero-sequence current on-site, and comprehensively use algorithms such as the first half-wave method, the group amplitude and phase comparison method, or the phase current mutation method to diagnose single-phase grounding faults. However, due to limitations such as insufficient information collected by a single terminal and weak characteristics of high-resistance grounding faults, the accuracy of the diagnosis is low, and false alarms and missed faults frequently occur.

[0003] To improve the accuracy of single-phase grounding fault detection, some existing methods utilize a data collection unit on the main station side or substation side to gather electrical quantity information from all in-station and out-of-station distribution terminals under the same busbar and substation. A centralized detection algorithm is then used to detect single-phase grounding faults, replacing the previous method of on-site detection at the distribution terminals. This has yielded initial success. However, the alignment accuracy of the waveforms collected by each distribution terminal significantly affects the accuracy of the centralized detection algorithm. Existing algorithms require high alignment accuracy for the waveforms from each terminal; poor alignment can negatively impact the algorithm's effectiveness. This results in distribution terminals with insufficient synchronous acquisition accuracy being unable to participate in centralized detection, especially the large number of existing distribution terminals in the field. If existing distribution terminals are to participate in centralized detection, additional hardware modules and software algorithm updates are required, incurring extremely high costs. This limits the centralized detection technology for single-phase grounding faults to pilot applications and prevents large-scale deployment. Summary of the Invention

[0004] This invention proposes a terminal waveform alignment method based on zero-voltage abrupt change points. Addressing the shortcomings and deficiencies of existing technologies, this method can be developed into a corresponding software algorithm module and deployed on the main station side or the substation side aggregation unit without modifying the distribution terminal. This enables synchronous alignment of electrical quantity waveforms collected by all in-station and out-of-station distribution terminals under the same substation and the same busbar, thereby indirectly achieving synchronous acquisition.

[0005] In the scenario addressed by the method described in this invention, after a single-phase ground fault occurs on the line, the collection unit on the main station side or the substation side begins to collect electrical quantity waveforms collected by the power distribution terminals inside and outside the substation. At this time, the waveforms are easily affected by the internal clock error of the terminals, and the sampling time of each terminal may deviate from the actual time. It is impossible to synchronously collect the waveforms of each terminal based on a unified sampling time, which affects the accuracy of the centralized judgment algorithm for single-phase ground faults. Therefore, it is necessary to align the electrical quantity waveforms collected by each terminal to indirectly achieve synchronous collection.

[0006] The present invention adopts the following technical solution.

[0007] A terminal waveform alignment method based on zero-voltage abrupt change points includes the following steps:

[0008] Step S1: Waveform denoising, removing high-frequency noise from the zero-sequence voltage waveform;

[0009] Step S2: Calculate the effective value of the zero-sequence voltage waveform within one cycle for two adjacent groups, and calculate the absolute value of the difference between them. If the absolute value is lower than the set threshold, the calculation window moves forward by one cycle and re-enters step S2. If the absolute value is higher than the set threshold, proceed to step S3.

[0010] Step S3: Selection of zero-voltage abrupt change point. Find the extreme point in the waveform range with large effective value. This point is the zero-voltage abrupt change point.

[0011] Step S4: Terminal waveform alignment. The waveforms collected by each terminal are aligned by waveform translation to make the abrupt change points of their respective zero-sequence voltage waveforms aligned, thereby achieving terminal waveform alignment.

[0012] In step S1, noise in the zero-sequence voltage waveform signal is filtered out using Fourier transform or wavelet transform methods to obtain the noise-removed signal, thus avoiding the noise signal from affecting subsequent processing.

[0013] When the wavelet transform method is used in step S1, the specific steps include:

[0014] Step S1-1: Parameter selection; Select an appropriate wavelet basis and number of decomposition layers.

[0015] Step S1-2: Waveform decomposition; Wavelet transform is used to process the original waveform and decompose it into multiple frequency band signals.

[0016] Step S1-3: Denoising; Denoising is performed on the wavelet coefficients of each frequency band signal to reduce the impact of noise on the signal.

[0017] Step S1-4: Waveform reconstruction; The waveform is reconstructed using a waveform reconstruction algorithm to obtain the waveform after noise removal.

[0018] In step S2, the effective value of the waveform for an adjacent cycle is calculated using the waveform effective value calculation formula, and the absolute value of the difference between the two is obtained.

[0019] In step S2, if the terminal waveform is affected by the operating conditions of the equipment, the on-site environment, and the aging of the equipment, making it a non-sinusoidal voltage waveform, then the effective value of the terminal waveform is set to the square root of the sum of the squares of its DC component, fundamental wave, and each higher harmonic.

[0020] In step S2, the formula for calculating the effective value of the sinusoidal voltage waveform is as follows:

[0021] Then we have:

[0022]

[0023] In the formula, T is the waveform period, u n u nm and U n These represent the instantaneous, peak, and effective values ​​of the voltage waveform, respectively; R is the resistance value; and w is the angular velocity.

[0024] In step S2, the formula for calculating the effective value of the non-sinusoidal voltage waveform is as follows:

[0025]

[0026] In the formula, U is the effective value of the non-sinusoidal voltage waveform, and U0, U1 and U2 are the values ​​of the voltage waveform. k These represent the effective values ​​of the DC component, the fundamental frequency, and each higher harmonic, respectively.

[0027] In step S3, the extreme point is found in the waveform range with a large effective value by using mathematical induction or search algorithm. The extreme point found is the zero-voltage change point.

[0028] When it is not permissible to modify the distribution terminal, the terminal waveform alignment method based on the zero-voltage abrupt change point is deployed as a software algorithm module on the main station side or the substation side aggregation unit. It is used to synchronously align the electrical quantity waveforms collected by all in-station and out-of-station distribution terminals under the same substation and the same busbar, so as to indirectly achieve synchronous acquisition.

[0029] When the terminal waveform alignment method based on zero-voltage mutation point verifies the waveform alignment accuracy of the electrical quantity waveform used for centralized judgment algorithm, a judgment warning is issued when the waveform alignment accuracy is poor.

[0030] When verifying the waveform alignment accuracy of electrical quantity waveforms used in centralized judgment algorithm using the terminal waveform alignment method based on zero-voltage abrupt change point, waveform alignment is performed when the waveform alignment accuracy is poor. The aligned terminal waveform data continues to participate in the centralized judgment of single-phase grounding faults to improve the reliability of the centralized judgment algorithm.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] (1) Terminal waveform alignment. The terminal waveform alignment method based on zero-voltage change point proposed in this invention can be programmed into a corresponding software algorithm module and deployed on the main station side or the substation side aggregation unit without modifying the distribution terminal. This enables synchronous alignment of electrical quantity waveforms collected by all in-station and out-of-station distribution terminals under the same substation and the same bus, thereby indirectly achieving synchronous acquisition. The modification cost is small and the method is highly scalable.

[0033] (2) Waveform alignment verification. For each distribution terminal device participating in centralized analysis, the terminal waveform alignment method based on zero-voltage sudden change point proposed in this invention can verify the waveform alignment accuracy of electrical quantity waveforms used in centralized analysis algorithm. When the waveform alignment accuracy is poor, an analysis warning is issued and waveform alignment is performed at the same time. The aligned terminal waveform data can still participate in the centralized analysis of single-phase grounding faults, thereby improving the reliability of centralized analysis algorithm. Attached Figure Description

[0034] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0035] Appendix Figure 1 This is a schematic diagram of the method flow of the present invention;

[0036] Appendix Figure 2 This is a schematic diagram of the terminal waveform alignment method of the present invention;

[0037] Appendix Figure 3 This is a schematic diagram illustrating the specific process of the waveform denoising algorithm of the present invention. Detailed Implementation

[0038] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0039] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0040] To make the features and advantages of this patent application more apparent and understandable, specific embodiments are provided below, along with accompanying drawings, for detailed explanation:

[0041] like Figure 1 As shown, this implementation proposes a terminal waveform alignment method based on zero-voltage abrupt change points. Without modifying the distribution terminals, this method is developed into a corresponding software algorithm module and deployed on the main station side or the substation side aggregation unit. This achieves synchronous alignment of electrical quantity waveforms collected by all in-station and out-of-station distribution terminals under the same substation and busbar, indirectly realizing synchronous acquisition. The specific technical solution is as follows:

[0042] After a single-phase ground fault occurs on the line, the collection unit on the main station side or the substation side begins to collect electrical quantity waveforms collected by the distribution terminals inside and outside the substation. At this time, the waveforms are easily affected by the internal clock error of the terminal, and the sampling time of each terminal may deviate from the actual time. It is impossible to use a unified sampling time as a reference to synchronously collect the waveforms of each terminal, which affects the accuracy of the centralized judgment algorithm for single-phase ground faults. Therefore, it is necessary to align the electrical quantity waveforms collected by each terminal to indirectly achieve synchronous collection.

[0043] Furthermore, a schematic diagram of the terminal waveform alignment method is shown below. Figure 2 As shown, the specific steps include:

[0044] A terminal waveform alignment method based on zero-voltage abrupt change points includes the following steps:

[0045] Step S1: Waveform denoising, removing high-frequency noise from the zero-sequence voltage waveform;

[0046] Step S2: Calculate the effective value of the zero-sequence voltage waveform within one cycle for two adjacent groups, and calculate the absolute value of the difference between them. If the absolute value is lower than the set threshold, the calculation window moves forward by one cycle and re-enters step S2. If the absolute value is higher than the set threshold, proceed to step S3.

[0047] Step S3: Selection of zero-voltage abrupt change point. Find the extreme point in the waveform range with large effective value. This point is the zero-voltage abrupt change point.

[0048] Step S4: Terminal waveform alignment. The waveforms collected by each terminal are aligned by waveform translation to make the abrupt change points of their respective zero-sequence voltage waveforms aligned, thereby achieving terminal waveform alignment.

[0049] In step S1, noise in the zero-sequence voltage waveform signal is filtered out using Fourier transform or wavelet transform methods to obtain the noise-removed signal, thus avoiding the noise signal from affecting subsequent processing.

[0050] When the wavelet transform method is used in step S1, the specific steps include:

[0051] Step S1-1: Parameter selection; Select an appropriate wavelet basis and number of decomposition layers.

[0052] Step S1-2: Waveform decomposition; Wavelet transform is used to process the original waveform and decompose it into multiple frequency band signals.

[0053] Step S1-3: Denoising; Denoising is performed on the wavelet coefficients of each frequency band signal to reduce the impact of noise on the signal.

[0054] Step S1-4: Waveform reconstruction; The waveform is reconstructed using a waveform reconstruction algorithm to obtain the waveform after noise removal.

[0055] In step S2, the effective value of the waveform for an adjacent cycle is calculated using the waveform effective value calculation formula, and the absolute value of the difference between the two is obtained.

[0056] In step S2, if the terminal waveform is affected by the operating conditions of the equipment, the on-site environment, and the aging of the equipment, making it a non-sinusoidal voltage waveform, then the effective value of the terminal waveform is set to the square root of the sum of the squares of its DC component, fundamental wave, and each higher harmonic.

[0057] In step S2, the formula for calculating the effective value of the sinusoidal voltage waveform is as follows:

[0058] Then we have:

[0059]

[0060] In the formula, T is the waveform period, u n u nm and U n These represent the instantaneous, peak, and effective values ​​of the voltage waveform, respectively; R is the resistance value; and w is the angular velocity.

[0061] In step S2, the formula for calculating the effective value of the non-sinusoidal voltage waveform is as follows:

[0062]

[0063] In the formula, U is the effective value of the non-sinusoidal voltage waveform, and U0, U1 and U2 are the values ​​of the voltage waveform. k These represent the effective values ​​of the DC component, the fundamental frequency, and each higher harmonic, respectively.

[0064] In step S3, the extreme point is found in the waveform range with a large effective value by using mathematical induction or search algorithm. The extreme point found is the zero-voltage change point.

[0065] When it is not permissible to modify the distribution terminal, the terminal waveform alignment method based on the zero-voltage abrupt change point is deployed as a software algorithm module on the main station side or the substation side aggregation unit. It is used to synchronously align the electrical quantity waveforms collected by all in-station and out-of-station distribution terminals under the same substation and the same busbar, so as to indirectly achieve synchronous acquisition.

[0066] When the terminal waveform alignment method based on zero-voltage mutation point verifies the waveform alignment accuracy of the electrical quantity waveform used for centralized judgment algorithm, a judgment warning is issued when the waveform alignment accuracy is poor.

[0067] When verifying the waveform alignment accuracy of electrical quantity waveforms used in centralized judgment algorithm using the terminal waveform alignment method based on zero-voltage abrupt change point, waveform alignment is performed when the waveform alignment accuracy is poor. The aligned terminal waveform data continues to participate in the centralized judgment of single-phase grounding faults to improve the reliability of the centralized judgment algorithm.

[0068] The above description is a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

[0069] This patent is not limited to the above-described preferred embodiments. Anyone can derive other forms of terminal waveform alignment methods based on zero-voltage mutation points under the guidance of this patent. All equivalent changes and modifications made within the scope of this patent application shall fall within the scope of this patent.

Claims

1. A terminal waveform alignment method based on zero-voltage abrupt change point, characterized in that: Includes the following steps: Step S1: Waveform denoising, removing high-frequency noise from the zero-sequence voltage waveform; Step S2: Calculate the effective value of the zero-sequence voltage waveform within one cycle for two adjacent groups, and calculate the absolute value of the difference between them. If the absolute value is lower than the set threshold, the calculation window moves forward by one cycle and re-enters step S2. If the absolute value is higher than the set threshold, proceed to step S3. Step S3: Selecting the zero-voltage abrupt change point: Find the extreme point in the waveform range with a large effective value. This point is the zero-voltage abrupt change point. Step S4: Terminal waveform alignment. The waveforms collected by each terminal are aligned by waveform translation to make the abrupt change points of their respective zero-sequence voltage waveforms aligned, thereby achieving terminal waveform alignment. In step S2, the formula for calculating the effective value of the sinusoidal voltage waveform is as follows: Then we have: In the formula, T is the waveform period, u n u nm and U n These represent the instantaneous, peak, and effective values ​​of the voltage waveform, respectively; R is the resistance value; and w is the angular velocity. In step S2, the formula for calculating the effective value of the non-sinusoidal voltage waveform is as follows: In the formula, U is the effective value of the non-sinusoidal voltage waveform, and U0, U1 and U2 are the values ​​of the voltage waveform. k These represent the effective values ​​of the DC component, the fundamental frequency, and each higher harmonic, respectively.

2. The terminal waveform alignment method based on zero-voltage abrupt change point according to claim 1, characterized in that: In step S1, noise in the zero-sequence voltage waveform signal is filtered out using Fourier transform or wavelet transform methods to obtain the noise-removed signal, thus avoiding the noise signal from affecting subsequent processing. When the wavelet transform method is used in step S1, the specific steps include: Step S1-1: Parameter selection; Select appropriate wavelet basis and number of decomposition layers; Step S1-2: Waveform decomposition; Wavelet transform is used to process the original waveform, decomposing it into multiple frequency band signals; Step S1-3: Denoising; Denoising is performed on the wavelet coefficients of each frequency band signal to reduce the impact of noise on the signal. Step S1-4: Waveform reconstruction; The waveform is reconstructed using a waveform reconstruction algorithm to obtain the waveform after noise removal.

3. The terminal waveform alignment method based on zero-voltage abrupt change point according to claim 1, characterized in that: In step S2, the effective value of the waveform for an adjacent cycle is calculated using the waveform effective value calculation formula, and the absolute value of the difference between the two is obtained.

4. The terminal waveform alignment method based on zero-voltage abrupt change point according to claim 3, characterized in that: In step S2, if the terminal waveform is affected by the operating conditions of the equipment, the on-site environment, and the aging of the equipment, making it a non-sinusoidal voltage waveform, then the effective value of the terminal waveform is set to the square root of the sum of the squares of its DC component, fundamental wave, and each higher harmonic.

5. The terminal waveform alignment method based on zero-voltage abrupt change point according to claim 1, characterized in that: In step S3, the extreme point is found in the waveform range with a large effective value by using mathematical induction or search algorithm. The extreme point found is the zero-voltage change point.

6. The terminal waveform alignment method based on zero-voltage abrupt change point according to claim 1, characterized in that: When it is not permissible to modify the distribution terminal, the terminal waveform alignment method based on the zero-voltage abrupt change point is deployed as a software algorithm module on the main station side or the substation side aggregation unit. It is used to synchronously align the electrical quantity waveforms collected by all in-station and out-of-station distribution terminals under the same substation and the same busbar, so as to indirectly achieve synchronous acquisition.

7. The terminal waveform alignment method based on zero-voltage abrupt change point according to claim 1, characterized in that: When the terminal waveform alignment method based on zero-voltage mutation point verifies the waveform alignment accuracy of electrical quantity waveforms used in the centralized judgment algorithm, a judgment warning is issued when the waveform alignment accuracy is poor.

8. The terminal waveform alignment method based on zero-voltage abrupt change point according to claim 7, characterized in that: When verifying the waveform alignment accuracy of electrical quantity waveforms used in centralized judgment algorithm using the terminal waveform alignment method based on zero-voltage abrupt change point, waveform alignment is performed when the waveform alignment accuracy is poor. The aligned terminal waveform data continues to participate in the centralized judgment of single-phase grounding faults to improve the reliability of the centralized judgment algorithm.

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