Power distribution network frequency following method and device based on frequency spectrum direct current characteristics and medium

Abstract

The invention relates to the technical field of power control and protection, and discloses a power distribution network frequency following method and device based on frequency spectrum direct current characteristics and a medium, and the method comprises the steps: selecting a plurality of frequency values in a preset frequency band range, determining a corresponding sampling frequency, carrying out the concurrent equal-interval sampling of a band-limited periodic signal through the sampling frequency, and obtaining a plurality of groups of discrete signals; performing differential operation to obtain a plurality of groups of differential signals; executing discrete Fourier transform, and respectively extracting amplitudes of direct current components in transform results to obtain a plurality of direct current component amplitudes; taking a frequency value corresponding to the minimum direct current component amplitude as a measurement result of the band-limited periodic signal fundamental wave frequency; and resetting the sampling interval according to the measurement result of the band-limited periodic signal fundamental wave frequency so as to complete frequency following. According to the method, the fundamental frequency containing the harmonic signal can be accurately identified by analyzing the change characteristics of the direct current component in the discrete Fourier transform, and the problems of inaccurate frequency measurement and following lag under harmonic interference in the traditional method are effectively solved.

Description

Technical Field

[0001] This invention relates to the field of power control and protection technology, and in particular to a distribution network frequency following method, device and medium based on the DC spectrum characteristics. Background Technology

[0002] During the operation of a power distribution network, protection and measurement devices need to sample signals such as voltage and current in real time and perform spectral analysis using Discrete Fourier Transform (DFT) to achieve functions such as fault detection and power quality monitoring. Currently, these devices typically use a fundamental frequency period of 20ms corresponding to a 50Hz power frequency as a reference, performing equally spaced sampling within each period and then performing DFT calculations based on this sampled data. This sampling method, when the fundamental frequency is strictly equal to 50Hz, constitutes equally spaced synchronous sampling, resulting in periodic discrete signals and accurate and reliable DFT calculation results.

[0003] However, the voltage and current signals in actual power distribution networks are not ideal power frequency signals, but rather band-limited periodic signals containing a finite number of harmonics. When the system fundamental frequency deviates from 50Hz, the original fixed-period sampling will become equally spaced asynchronous sampling, leading to spectral leakage and the picket fence effect, which in turn introduces measurement errors in amplitude, phase, etc., seriously affecting the accuracy of protection actions and the reliability of measurement results.

[0004] To eliminate errors caused by asynchronous sampling, frequency following is essential, requiring real-time, accurate measurement of the fundamental frequency and dynamic adjustment of the sampling interval to ensure it remains synchronized with the current fundamental period. Existing frequency measurement methods are mostly designed for pure sinusoidal signals; for band-limited periodic signals with high harmonic content, their frequency measurement accuracy is often insufficient, failing to meet the requirements of high-precision protection and measurement. Therefore, there is an urgent need for a frequency following method applicable to distribution network signals containing harmonics, capable of accurately tracking fundamental frequency changes, providing an accurate synchronous sampling basis for discrete Fourier transform calculations, and improving the measurement and protection performance of the entire system. Summary of the Invention

[0005] In view of the aforementioned existing problems, the present invention is proposed.

[0006] Therefore, this invention provides a distribution network frequency following method, device, and medium based on the DC characteristics of the spectrum. By analyzing the changes in the DC component in the discrete Fourier transform results, the fundamental frequency of the signal can be accurately determined, solving the problem of accurate measurement of the fundamental frequency of band-limited periodic signals, that is, solving the problem of insufficient frequency following accuracy in distribution networks.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0008] In a first aspect, the present invention provides a distribution network frequency following method based on spectral DC characteristics, comprising:

[0009] Multiple frequency values ​​are selected within a preset frequency band range, and corresponding sampling frequencies are determined based on the frequency values. The band-limited periodic signal is sampled concurrently at equal intervals using the sampling frequencies to obtain multiple sets of discrete signals.

[0010] Perform differential operations on the multiple sets of discrete signals to obtain multiple sets of differential signals;

[0011] Perform a discrete Fourier transform on each group of differential signals, and extract the amplitude of the DC component in the transform result to obtain multiple DC component amplitudes.

[0012] The minimum DC component amplitude is determined from the plurality of DC component amplitudes, and the frequency value corresponding to the minimum DC component amplitude is taken as the measurement result of the fundamental frequency of the band-limited periodic signal;

[0013] The sampling interval is reset based on the measurement results of the fundamental frequency of the band-limited periodic signal to complete frequency tracking.

[0014] As a preferred embodiment of the distribution network frequency following method based on spectral DC characteristics described in this invention, the step of selecting multiple frequency values ​​within a preset frequency band includes:

[0015] The frequency offset corresponding to the acceptable sampling error of the setting device is Δf. When the actual fundamental frequency f of the band-limited periodic signal satisfies 50-Δf≤f≤50+Δf, the sampling error is determined to meet the requirements.

[0016] Within the fundamental frequency fluctuation range of the distribution network, a set of frequency values ​​[f1, f2, ..., f] are obtained at intervals of 2·Δf. m ], where m represents the total number of frequency values ​​obtained.

[0017] As a preferred embodiment of the distribution network frequency following method based on spectral DC characteristics described in this invention, wherein determining the corresponding sampling frequency based on the frequency value includes:

[0018] Each frequency value selected within the fundamental frequency fluctuation range of the power distribution network is multiplied by a set fixed integer to calculate the sampling frequency corresponding to the frequency value.

[0019] The corresponding sampling interval, i.e., the time interval between each sampling point, is calculated based on the sampling frequency.

[0020] As a preferred embodiment of the distribution network frequency following method based on spectral DC characteristics described in this invention, the step of concurrently sampling the band-limited periodic signal at equal intervals using the sampling frequency to obtain multiple sets of discrete signals includes:

[0021] Multiple independent sampling channels are set up in parallel according to the corresponding sampling interval;

[0022] Each sampling channel simultaneously samples the same band-limited periodic signal at equal intervals according to its corresponding sampling time interval;

[0023] Each sampling channel continuously samples, collecting and generating a set of discrete signal data points arranged in chronological order, thereby obtaining multiple sets of discrete signals. Each set of discrete signals corresponds to a preset frequency value and its sampling settings.

[0024] As a preferred embodiment of the distribution network frequency following method based on spectral DC characteristics described in this invention, the method for obtaining multiple sets of differential signals includes:

[0025] For each set of discrete signals obtained through concurrent sampling, each sampling point is processed sequentially according to the sampling time order. The value of the next sampling point is subtracted from the value of the previous adjacent sampling point to calculate the difference between adjacent sampling points, thereby obtaining multiple sets of differential signals.

[0026] As a preferred embodiment of the distribution network frequency following method based on spectral DC characteristics described in this invention, the method for obtaining the amplitudes of multiple DC components includes:

[0027] The discrete Fourier transform algorithm is applied to the multiple sets of differential signals to transform the differential signals from the time domain to the frequency domain, and the corresponding frequency domain calculation results are obtained.

[0028] In the frequency domain calculation results obtained after each differential signal transformation, the DC component with a frequency of zero is located and extracted, and the amplitude of each extracted DC component is calculated to obtain multiple DC component amplitudes.

[0029] As a preferred embodiment of the distribution network frequency following method based on spectral DC characteristics described in this invention, the step of determining the minimum DC component amplitude from the plurality of DC component amplitudes includes:

[0030] When the ratio of the actual frequency to the assumed fundamental frequency is equal to 1, the DC component amplitude is zero, and the closer the ratio of the actual frequency to the assumed fundamental frequency is to 1, the closer the DC component amplitude is to zero; the multiple DC component amplitudes obtained are compared to obtain the minimum DC component amplitude.

[0031] Determine the frequency value corresponding to the minimum DC component amplitude and the corresponding sampling and calculation channel;

[0032] The frequency value corresponding to the minimum DC component amplitude is taken as the measurement result of the actual fundamental frequency of the band-limited periodic signal.

[0033] As a preferred embodiment of the distribution network frequency following method based on spectral DC characteristics described in this invention, the step of resetting the sampling interval according to the measurement result of the fundamental frequency of the band-limited periodic signal includes:

[0034] Based on the measurement results of the fundamental frequency of the band-limited periodic signal and the originally set number of sampling points per fundamental period, the sampling frequency is recalculated;

[0035] Based on the recalculated sampling frequency, determine the new sampling time interval;

[0036] The sampling interval of the sampling device is updated to the new sampling time interval, and subsequent input signals are sampled at equal intervals to achieve frequency following.

[0037] In a second aspect, the present invention provides an electronic device, including a memory and a processor; the memory is used to store computer-executable instructions, and the processor, when executing the computer-executable instructions, implements the steps of a distribution network frequency following method based on spectral DC characteristics.

[0038] Thirdly, the present invention provides a computer-readable storage medium storing computer-executable instructions that, when executed by a processor, implement the steps of a distribution network frequency following method based on spectral DC characteristics.

[0039] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention provides a distribution network frequency tracking method, device, and medium based on the DC characteristics of the spectrum. By analyzing the variation characteristics of the DC component in the discrete Fourier transform, it can accurately identify the fundamental frequency of the harmonic signal, effectively solving the problems of inaccurate frequency measurement and tracking lag in traditional methods under harmonic interference. This invention adopts a strategy of concurrent processing of multiple sampling frequencies, which significantly improves computational efficiency and frequency tracking speed. At the same time, by flexibly setting the frequency interval, it achieves high-precision frequency measurement and adaptive adjustment, providing a reliable sampling error correction means for distribution network protection and measurement devices, and greatly improving the measurement accuracy of the signal fundamental and harmonic components and the operational reliability of the equipment. Attached Figure Description

[0040] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. 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.

[0041] Figure 1 This is a schematic diagram of the overall process logic of a distribution network frequency following method based on spectral DC characteristics, provided as an embodiment of the present invention.

[0042] Figure 2 The image shows the DC component result after differential signal discrete Fourier transform operation of a distribution network frequency following method based on spectral DC characteristics provided in an embodiment of the present invention. Detailed Implementation

[0043] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0044] Example 1, referring to Figure 1 As one embodiment of the present invention, a distribution network frequency following method based on spectral DC characteristics is provided, such as... Figure 1 The specific steps shown are as follows:

[0045] S100: Select multiple frequency values ​​within a preset frequency band, determine the corresponding sampling frequency based on the frequency values, and perform concurrent and equally spaced sampling of the band-limited periodic signal using the sampling frequency to obtain multiple sets of discrete signals;

[0046] S200: Perform differential operations on multiple sets of discrete signals to obtain multiple sets of differential signals;

[0047] S300: Perform a discrete Fourier transform on each group of differential signals and extract the amplitude of the DC component in the transform result to obtain multiple DC component amplitudes.

[0048] S400: Determine the minimum DC component amplitude from multiple DC component amplitudes, and use the frequency value corresponding to the minimum DC component amplitude as the measurement result of the fundamental frequency of the band-limited periodic signal;

[0049] S500: The sampling interval is reset based on the measurement results of the fundamental frequency of the band-limited periodic signal to complete frequency tracking;

[0050] It should be noted that this invention aims to solve the technical problem of insufficient frequency tracking accuracy in distribution network protection and measurement devices, and provides a distribution network frequency tracking method based on the DC characteristics of the spectrum. By analyzing the changes in the DC component in the DFT results, the fundamental frequency of the signal can be accurately determined, solving the problem of accurate measurement of the fundamental frequency of band-limited periodic signals, that is, solving the problem of insufficient frequency tracking accuracy in distribution networks. This provides data and technical support for the correction of sampling errors in protection and measurement devices in distribution networks, and improves the measurement accuracy of protection and measurement devices.

[0051] It should be noted that steps S100 to S500 above, by analyzing the variation characteristics of the DC component in the Discrete Fourier Transform, can accurately identify the fundamental frequency of the harmonic signal, effectively solving the problems of inaccurate frequency measurement and tracking lag in traditional methods under harmonic interference. This invention employs a strategy of concurrent processing of multiple sampling frequencies, significantly improving computational efficiency and frequency tracking speed. Simultaneously, by flexibly setting frequency intervals, it achieves high-precision frequency measurement and adaptive adjustment, providing a reliable means of correcting sampling errors for distribution network protection and measurement devices, and greatly improving the measurement accuracy of the signal's fundamental and harmonic components and the operational reliability of the equipment.

[0052] In this embodiment of the invention, step S100 selects multiple frequency values ​​within a preset frequency band, determines the corresponding sampling frequency based on each frequency value, and performs concurrent and equally spaced sampling on the band-limited periodic signal using the sampling frequency to obtain multiple sets of discrete signals, including the following sub-steps A1 to A3:

[0053] In A1: Select multiple frequency values ​​within a preset frequency band;

[0054] Specifically, the frequency offset corresponding to the acceptable sampling error of the setting device is Δf. When the actual fundamental frequency f of the band-limited periodic signal satisfies 50-Δf≤f≤50+Δf, the sampling error is determined to meet the requirements.

[0055] Specifically, the preset frequency band range is the fundamental frequency fluctuation range of the distribution network, i.e., 49.5~50.5Hz; within the fundamental frequency fluctuation range of the distribution network, a set of frequency values ​​[f1,f2,…,f] are obtained at intervals of 2·Δf. m ], where m represents the total number of frequency values ​​acquired; the total number of frequency values ​​acquired, m, and this set of frequency values ​​satisfy the following formula:

[0056]

[0057]

[0058] Among them, f i This represents the i-th frequency value in this set of frequency values.

[0059] In A2: The corresponding sampling frequency is determined based on the selected multiple frequency values;

[0060] Specifically, each frequency value selected within the fundamental frequency fluctuation range of the distribution network is multiplied by a fixed integer to calculate the sampling frequency f corresponding to that frequency value. Si The formula is expressed as:

[0061] f Si =Nf i i = 1, 2, ..., m

[0062] Where N is a fixed integer, representing that the sampling frequency is N times the assumed fundamental frequency.

[0063] Specifically, the corresponding sampling interval is calculated based on the sampling frequency, expressed by the formula:

[0064]

[0065] Among them, T Si This represents the time interval between each sampling point.

[0066] In A3: The band-limited periodic signal is sampled concurrently at equal intervals using a sampling frequency to obtain multiple sets of discrete signals; the specific steps include:

[0067] Multiple independent sampling channels are set up in parallel according to the corresponding sampling interval;

[0068] Each sampling channel simultaneously samples the same band-limited periodic signal at equal intervals according to its corresponding sampling time interval;

[0069] Each sampling channel continuously samples, collecting and generating a set of discrete signal data points arranged in chronological order, thereby obtaining multiple sets of discrete signals. Each set of discrete signals corresponds to a preset frequency value and its sampling settings.

[0070] In this embodiment of the invention, the exponential form expression of the band-limited periodic signal x(t) is defined as follows:

[0071]

[0072] Where h represents the harmonic order of the band-limited periodic signal, H represents the highest harmonic order of the band-limited periodic signal, and A h , Let f represent the amplitude and phase of the h-th harmonic component of the band-limited periodic signal, respectively, where j represents the imaginary unit, t represents time, and f represents the fundamental frequency of the band-limited periodic signal.

[0073] In this embodiment of the invention, each sampling channel simultaneously samples the same band-limited periodic signal at equal intervals according to its corresponding sampling time interval. The sampling process is performed concurrently, resulting in m sets of discrete signals [x1(n), x2(n), ..., x...]. m [(n)], where x is the instantaneous value of the nth sampling point in the i-th discrete signal group. i The expression for (n) is as follows:

[0074]

[0075] It should be noted that step S100 above achieves multi-channel parallel acquisition of band-limited periodic signals by selecting multiple frequency values ​​within a preset frequency band and setting the concurrent sampling frequency accordingly, effectively avoiding synchronization errors caused by frequency offset when a single sampling frequency is used.

[0076] In this embodiment of the invention, step S200 performs differential operations on multiple sets of discrete signals to obtain multiple sets of differential signals, including:

[0077] Specifically, for each set of discrete signals obtained through concurrent sampling, each sampling point is processed sequentially according to the sampling time order. The value of the next sampling point is subtracted from the value of the previous adjacent sampling point to calculate the difference between adjacent sampling points, thereby obtaining multiple sets of differential signals.

[0078] Specifically, by subtracting the previous point from each subsequent point of the obtained discrete signal, m sets of differential signals [x] are obtained. d1 (n),x d2 (n),…,x dm (n)], to achieve the purpose of filtering out the DC component, where the i-th group of differential signals x di The expression for (n) is as follows:

[0079]

[0080] Where, x i (n+1) represents the instantaneous value of the (n+1)th sampling point in the i-th discrete signal group, A dh , These represent the amplitude and phase of the h-th harmonic of the differential signal, respectively.

[0081] It should be noted that step S200 above effectively eliminates the DC component in the signal by performing differential operations on multiple sets of discrete signals, reduces the interference of DC offset on subsequent frequency analysis, and improves the accuracy of frequency measurement in a harmonic environment.

[0082] In this embodiment of the invention, step S300 performs a discrete Fourier transform on each group of differential signals and extracts the amplitude of the DC component in the transform result, obtaining multiple DC component amplitudes including:

[0083] Specifically, a discrete Fourier transform algorithm is applied to multiple sets of differential signals to transform the differential signals from the time domain to the frequency domain, and the corresponding frequency domain calculation results are obtained. In the frequency domain calculation results obtained after the transformation of each set of differential signals, the DC component with a frequency of zero is located and extracted, and the amplitude of each extracted DC component is calculated to obtain the amplitude of multiple DC components.

[0084] In this embodiment of the invention, n∈[0,N-1] is taken in the formula for the i-th group of differential signals, and further simplified, we can obtain:

[0085]

[0086] in, It represents the ratio of the actual frequency to the assumed fundamental frequency;

[0087] Furthermore, the simplified differential signal is processed using the Discrete Fourier Transform algorithm to obtain the frequency domain calculation result, where the h1th harmonic component X... di The expression for (h1) is as follows:

[0088]

[0089] Furthermore, when the harmonic order h1 of the band-limited periodic signal is 0, the expression for the DC component of the discrete Fourier transform can be obtained as follows:

[0090]

[0091] in, ρ h and β h These represent the coefficients of the amplitude and phase results of the discrete Fourier transform, respectively.

[0092] Furthermore, based on the magnitude of each extracted DC component, the DC component amplitude is obtained, expressed by the formula |X di (0)|=A dh ·ρ h .

[0093] It should be noted that in step S300 above, the differential signal is subjected to discrete Fourier transform and the DC component amplitude is extracted. The time-domain signal is converted into frequency-domain features by using spectrum analysis. The change in the amplitude of the DC component reflects the degree of matching between the sampling frequency and the actual frequency, providing a quantitative basis for frequency identification.

[0094] In this embodiment of the invention, step S400, which involves determining the minimum DC component amplitude from multiple DC component amplitudes and using the frequency value corresponding to the minimum DC component amplitude as the measurement result of the fundamental frequency of the band-limited periodic signal, includes:

[0095] The above steps yield m DC component amplitudes: [|X d1 (0)|,|X d2 (0)|,…,|X dm (0)|];And from the formula for calculating the DC component amplitude, we know that when the ratio of the actual frequency to the assumed fundamental frequency is equal to 1, the DC component amplitude is zero; when the ratio of the actual frequency to the assumed fundamental frequency is not equal to 1, the DC component amplitude is not zero; and the closer the ratio of the actual frequency to the assumed fundamental frequency is to 1, the closer the DC component amplitude is to zero.

[0096] The amplitudes of multiple DC components are compared to obtain the amplitude of the smallest DC component.

[0097] Determine the frequency value corresponding to the minimum DC component amplitude and the corresponding sampling and calculation channel;

[0098] The frequency value corresponding to the minimum DC component amplitude is taken as the measurement result of the actual fundamental frequency of the band-limited periodic signal.

[0099] It should be noted that, subsequently, according to the sampling frequency f Sj By performing equally spaced sampling, the signal measurement results will meet the accuracy requirements. Specifically, when the device uses a sampling frequency synchronized with the accurately measured fundamental frequency (i.e., the frequency value corresponding to the minimum DC component amplitude) for equally spaced sampling, synchronous sampling is achieved. This fundamentally eliminates spectral leakage and picket fence effects caused by asynchronous sampling, ensuring that the measurement errors of parameters such as the amplitude and phase of the fundamental and harmonic components of the signal obtained from subsequent DFT calculations are controlled within the range allowed by the device's preset accuracy level.

[0100] It should be noted that step S400 above, by finding the minimum DC component amplitude and determining its corresponding frequency value, can accurately identify the sampling frequency that best matches the actual fundamental frequency, has a strong anti-interference capability against harmonic interference, and realizes high-precision measurement of the fundamental frequency of band-limited periodic signals.

[0101] In this embodiment of the invention, step S500, which resets the sampling interval based on the measurement result of the fundamental frequency of the band-limited periodic signal to complete frequency following, includes:

[0102] Based on the measurement results of the fundamental frequency of the band-limited periodic signal and the originally set number of sampling points per fundamental period, the sampling frequency f is recalculated. Sj ;

[0103] Determine the new sampling time interval T based on the recalculated sampling frequency. S ;

[0104] The sampling interval of the sampling device is updated to a new sampling time interval, and subsequent input signals are sampled at equal intervals to achieve frequency following.

[0105] Specifically, the new sampling time interval T S The calculation method is as follows:

[0106]

[0107] It should be noted that in step S500 above, the sampling interval is reset according to the accurately measured fundamental frequency, so as to realize the real-time synchronization between the sampling frequency and the actual frequency of the signal, effectively correct the measurement error caused by asynchronous sampling, ensure the accuracy of subsequent discrete Fourier transform calculation, and complete the frequency adaptive following function.

[0108] Example 2, refer to Figure 2 Based on the previous embodiment, this embodiment provides an application example of the distribution network frequency following method based on the DC spectral characteristics, to verify and illustrate the technical effects adopted in this method.

[0109] In this embodiment of the invention, a certain band-limited periodic signal in a real power distribution network contains a DC component and 2nd-10th harmonics, and its exponential form expression is as follows:

[0110]

[0111] Where f is the fundamental frequency of the signal, f = 49.784 Hz, and h is the harmonic order of the signal, A h , These represent the amplitude and phase of the h-th harmonic component of the signal, respectively. In this embodiment of the invention, the amplitude and phase of each harmonic are shown in Table 1.

[0112] Table 1: Amplitude and phase of each harmonic.

[0113]

[0114] Furthermore, setting the measurement accuracy requirement for the fundamental amplitude to be 0.2S level, i.e., an error not exceeding 2‰, then when Δf = 0.01Hz, the accuracy requirement is met, and n = 51. Therefore, a set of frequency values ​​[f1, f2, ..., f] is obtained with intervals of 0.02Hz. 51 ], where f i =49.5+0.02(i-1),i=1,2,…,51;

[0115] Furthermore, let the sampling frequency f Si =Nf i The sampling intervals are i = 1, 2, ..., 51. Sampling is performed at equal intervals at these sampling frequencies, with the sampling process occurring concurrently, resulting in 51 sets of discrete signals [x1(n), x2(n), ..., x...]. 51 [n], where the expression for the i-th discrete signal is:

[0116]

[0117] Furthermore, differential operations are performed on the obtained 51 sets of discrete signals, as shown in the following formula:

[0118]

[0119]

[0120] Furthermore, taking n∈[0,63] for the obtained 51 sets of difference signals and simplifying them further, we can obtain:

[0121]

[0122] Furthermore, performing a 64-point DFT on the simplified differential signal and extracting the DC component yields:

[0123]

[0124] Furthermore, based on the magnitude of each extracted DC component, the DC component amplitude |X is obtained. di (0)|=A dh ·ρ h The amplitude obtained therefrom is as follows: Figure 2 As shown.

[0125] Depend on Figure 2 It can be seen that the minimum value of the DC component is |X d15 (0)|=0.0024, correspondingly, f 15 =49.78Hz. Therefore, the accurate measurement result of the fundamental frequency of the band-limited periodic signal is 49.78Hz, and the error meets the accuracy requirements. Based on the accurate measurement result of the fundamental frequency of the band-limited periodic signal, the new sampling interval is calculated to be 20.088ms. The sampling is corrected according to the new sampling interval to complete the frequency tracking.

[0126] The above analysis demonstrates that the theoretical analysis and the frequency measurement results of the embodiments of this invention verify the feasibility and accuracy of the method provided by this invention. By analyzing the variation characteristics of the DC component in the Discrete Fourier Transform, this invention can accurately identify the fundamental frequency of a harmonic signal, effectively solving the problems of inaccurate frequency measurement and lag in traditional methods under harmonic interference. This invention employs a strategy of concurrent processing of multiple sampling frequencies, significantly improving computational efficiency and frequency tracking speed. Simultaneously, by flexibly setting frequency intervals, it achieves high-precision frequency measurement and adaptive adjustment, providing a reliable means of correcting sampling errors for distribution network protection and measurement devices, and greatly improving the measurement accuracy of the signal's fundamental and harmonic components and the operational reliability of the equipment.

[0127] Example 3 provides an electronic device including a processor, memory, communication interface, display screen, and input device connected via a system bus. The processor provides computing and control capabilities. The memory includes a non-volatile storage medium and internal memory. The non-volatile storage medium stores an operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage medium. The communication interface allows for wired or wireless communication with external terminals; wireless communication can be achieved through Wi-Fi, carrier networks, NFC (Near Field Communication), or other technologies. When executed by the processor, the computer program implements a power distribution network frequency following method based on spectral DC characteristics. The display screen can be a liquid crystal display (LCD) or an e-ink display. The input device can be a touch layer covering the display screen, buttons, a trackball, or a touchpad mounted on the device's casing, or an external keyboard, touchpad, or mouse.

[0128] This embodiment also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the method proposed in the above embodiments.

[0129] The storage medium proposed in this embodiment belongs to the same inventive concept as the method proposed in the above embodiments. Technical details not described in detail in this embodiment can be found in the above embodiments, and this embodiment has the same beneficial effects as the above embodiments.

[0130] Based on the above description of the implementation methods, those skilled in the art can clearly understand that the present invention can be implemented using software and necessary general-purpose hardware, and of course, it can also be implemented using hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as a computer floppy disk, read-only memory, random access memory, flash memory, hard disk, or optical disk, and includes several instructions to cause an electronic device (which may be a personal computer, server, or network device, etc.) to execute the method of the embodiments of the present invention.

[0131] It should be noted that the above 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 preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A distribution network frequency following method based on spectral DC characteristics, characterized in that, include: Multiple frequency values ​​are selected within a preset frequency band range, and corresponding sampling frequencies are determined based on the frequency values. The band-limited periodic signal is sampled concurrently at equal intervals using the sampling frequencies to obtain multiple sets of discrete signals. Perform differential operations on the multiple sets of discrete signals to obtain multiple sets of differential signals; Perform a discrete Fourier transform on each group of differential signals, and extract the amplitude of the DC component in the transform result to obtain multiple DC component amplitudes. The minimum DC component amplitude is determined from the plurality of DC component amplitudes, and the frequency value corresponding to the minimum DC component amplitude is taken as the measurement result of the fundamental frequency of the band-limited periodic signal; The sampling interval is reset based on the measurement results of the fundamental frequency of the band-limited periodic signal to complete frequency tracking.

2. The distribution network frequency following method based on spectral DC characteristics as described in claim 1, characterized in that, The step of selecting multiple frequency values ​​within a preset frequency band range includes: The frequency offset corresponding to the acceptable sampling error of the setting device is Δf. When the actual fundamental frequency f of the band-limited periodic signal satisfies 50-Δf≤f≤50+Δf, the sampling error is determined to meet the requirements. Within the fundamental frequency fluctuation range of the distribution network, a set of frequency values ​​[f1, f2, ..., f] are obtained at intervals of 2·Δf. m ], where m represents the total number of frequency values ​​obtained.

3. The distribution network frequency following method based on spectral DC characteristics as described in claim 2, characterized in that, Determining the corresponding sampling frequency based on the frequency value includes: Each frequency value selected within the fundamental frequency fluctuation range of the power distribution network is multiplied by a set fixed integer to calculate the sampling frequency corresponding to the frequency value. The corresponding sampling interval, i.e., the time interval between each sampling point, is calculated based on the sampling frequency.

4. The distribution network frequency following method based on spectral DC characteristics as described in claim 3, characterized in that, The step of concurrently sampling the band-limited periodic signal at the sampling frequency to obtain multiple sets of discrete signals includes: Multiple independent sampling channels are set up in parallel according to the corresponding sampling interval; Each sampling channel simultaneously samples the same band-limited periodic signal at equal intervals according to its corresponding sampling time interval; Each sampling channel continuously samples, collecting and generating a set of discrete signal data points arranged in chronological order, thereby obtaining multiple sets of discrete signals. Each set of discrete signals corresponds to a preset frequency value and its sampling settings.

5. The distribution network frequency following method based on spectral DC characteristics as described in claim 4, characterized in that, The obtained multiple sets of differential signals include: For each set of discrete signals obtained through concurrent sampling, each sampling point is processed sequentially according to the sampling time order. The value of the next sampling point is subtracted from the value of the previous adjacent sampling point to calculate the difference between adjacent sampling points, thereby obtaining multiple sets of differential signals.

6. The distribution network frequency following method based on spectral DC characteristics as described in claim 5, characterized in that, The obtained multiple DC component amplitudes include: The discrete Fourier transform algorithm is applied to the multiple sets of differential signals to transform the differential signals from the time domain to the frequency domain, and the corresponding frequency domain calculation results are obtained. In the frequency domain calculation results obtained after each differential signal transformation, the DC component with a frequency of zero is located and extracted, and the amplitude of each extracted DC component is calculated to obtain multiple DC component amplitudes.

7. The distribution network frequency following method based on spectral DC characteristics as described in claim 6, characterized in that, Determining the minimum DC component amplitude from the plurality of DC component amplitudes includes: When the ratio of the actual frequency to the assumed fundamental frequency is equal to 1, the DC component amplitude is zero, and the closer the ratio of the actual frequency to the assumed fundamental frequency is to 1, the closer the DC component amplitude is to zero; the multiple DC component amplitudes obtained are compared to obtain the minimum DC component amplitude. Determine the frequency value corresponding to the minimum DC component amplitude and the corresponding sampling and calculation channel; The frequency value corresponding to the minimum DC component amplitude is taken as the measurement result of the actual fundamental frequency of the band-limited periodic signal.

8. The distribution network frequency following method based on spectral DC characteristics as described in claim 7, characterized in that, The step of resetting the sampling interval based on the measurement result of the fundamental frequency of the band-limited periodic signal includes: Based on the measurement results of the fundamental frequency of the band-limited periodic signal and the originally set number of sampling points per fundamental period, the sampling frequency is recalculated; Based on the recalculated sampling frequency, determine the new sampling time interval; The sampling interval of the sampling device is updated to the new sampling time interval, and subsequent input signals are sampled at equal intervals to achieve frequency following.

9. An electronic device comprising a memory and a processor, characterized in that: The memory is used to store computer-executable instructions, and when the processor executes the computer-executable instructions, it implements the steps of the distribution network frequency following method based on the spectral DC characteristics as described in any one of claims 1 to 8.

10. A computer-readable storage medium having computer-executable instructions stored thereon, characterized in that: When the computer-executable instructions are executed by the processor, they implement the steps of the distribution network frequency following method based on the spectral DC characteristics as described in any one of claims 1 to 8.

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