Steady-state power quality data compression method, decompression method and compression and decompression apparatus

Abstract

The application provides a steady-state power quality data compression method, a decompression method and a compression and decompression device, comprising the following steps: S1, sampling the waveform of an electric energy signal according to a preset sampling point number and a sampling time length to obtain a time-domain waveform data sequence of the electric energy signal to be measured; S2, obtaining the amplitude and phase of different cycles within a preset time length according to the sampling time length, wherein the time-domain waveform data sequence is decomposed into linear superposition of sinusoidal signals according to an analysis formula, and the amplitude and phase of the fundamental wave and the amplitude and phase of each harmonic component in a preset number of times are calculated; S3, calculating the root mean square of the amplitude within the preset time length to obtain an amplitude sequence, and storing the amplitude sequence and the phase of the first cycle. The above method can obtain a higher compression ratio, reduce the storage space, and be decompressed through a decompression method matched with the above method, and during the decompression, a compression and reading device matched with each other is arranged.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power quality monitoring in smart grid, more particularly, to a steady-state power quality data compression method, a decompression method and a compression and decompression device. BACKGROUND

[0002] With the development of social economy, various high-power, nonlinear power equipment are put into operation, which causes serious distortion of voltage and current waveform in the power grid, and the power quality problems such as voltage fluctuation and flicker are becoming more and more serious. At the same time, various complex and precision equipment sensitive to power quality have higher and higher requirements for power quality. In order to ensure the power quality level of power system and avoid problems such as voltage fluctuation and flicker, more and more power quality monitoring points are needed, and more and more power quality data are collected, which causes great pressure on the transmission and storage of power quality data.

[0003] In actual engineering application, the amount of collected power quality data is large, which occupies a lot of storage space, resulting in an increase in data storage cost and additional economic consumption.

[0004] The compression methods in the prior art include a method of compressing power quality monitoring data by using LZ77 algorithm, a method of compressing power quality monitoring recording data by combining wavelet transform and LZ77 algorithm, and a power quality data compression method based on LSA-MP improved atomic decomposition. The above methods do not combine the steady-state power quality index calculation process in the compression process, and the calculation time is long and the hardware resources are large. SUMMARY

[0005] In view of the above problems, the purpose of the present application is to provide a steady-state power quality data compression method, a decompression method and a compression and decompression device, which can reduce the storage amount of power quality data and obtain a higher compression ratio after compressing the collected power quality data and then storing it.

[0006] In one aspect of the present application, a steady-state power quality data compression method is provided, which comprises the following steps:

[0007] S1, sampling the waveform of the power signal according to the preset sampling point number and sampling time length to obtain a time-domain waveform data sequence of the power signal to be measured;

[0008] S2, obtaining the amplitudes and phases of different cycles within the preset time length according to the sampling time length, wherein the time-domain waveform data sequence is decomposed into linear superposition of sinusoidal signals according to an analysis formula, and the fundamental amplitude, the fundamental phase and the amplitudes A n and phases θ n of harmonic components in the preset number of harmonics are calculated. The analysis formula is:

[0009]

[0010]

[0011] In the formula, A0 is a direct current component, A1 is a fundamental wave amplitude, θ1 is a fundamental wave phase, A n is an n-th harmonic component amplitude, θ n is an n-th harmonic component phase, f is a frequency, t is a time, and n is a number of times;

[0012] S3, calculating a root mean square of the amplitudes in a preset time length to obtain an amplitude sequence, storing the amplitude sequence and a phase of the first cycle.

[0013] In addition, a preferred scheme is that the preset sampling time length in S1 is 10 cycles, the number of sampling points per cycle is 256 points, and a time domain waveform data sequence D={d1, d2, … d 2560} is obtained according to the sampling time length and the number of sampling points.

[0014] In addition, a preferred scheme is that the preset number of harmonic component amplitudes in S2 is 2-50.

[0015] In addition, a preferred scheme is that the calculation formula in S3 is

[0016] In the formula, A 3_m is an amplitude sequence, A 1n is an amplitude, θ 1n is a phase, and k is a mark number k=1, 2, … 15.

[0017] In addition, a preferred scheme is that in S4, the waveform is reconstructed according to a restoration formula,

[0018] The restoration formula is

[0019] In the formula, D' is a restored waveform, f is a power grid fundamental wave frequency, θ 3_m = θ 1n .

[0020] Another aspect of the present application provides a steady-state power quality data decompression method for decompressing data obtained by the steady-state power quality data compression method, comprising:

[0021] Reading stored amplitude sequence and phase information to reconstruct a waveform, and combining a steady-state power quality standard to calculate a steady-state power quality index value and output.

[0022] Another aspect of the present application provides a steady-state power quality data compression and decompression device, comprising:

[0023] The acquisition module samples the waveform of the electric energy signal according to a preset sampling point number and a sampling time length, and obtains a time-domain waveform data sequence of the to-be-tested electric energy signal.

[0024] The analysis module obtains the amplitudes and phases of different cycles within the preset time length according to the sampling time length, wherein the time-domain waveform data sequence is decomposed into linear superposition of sinusoidal signals according to an analysis formula, and the fundamental wave amplitude, the fundamental wave phase and the amplitudes A n and the phase θ n of each harmonic component in the preset number of times are calculated. The analysis formula is as follows:

[0025]

[0026]

[0027] In the formula, A0 is a direct current component, A1 is a fundamental wave amplitude, θ1 is a fundamental wave phase, A n is an n-th harmonic component amplitude, θ n is an n-th harmonic component phase, f is a frequency, t is a time, and n is a number of times.

[0028] The storage module calculates a root mean square of the amplitudes within the preset time length to obtain an amplitude sequence, and stores the amplitude sequence and the phase of the first cycle.

[0029] The output module reads the stored amplitude sequence and phase information to reconstruct the waveform, and combines a steady-state electric energy quality standard to calculate a steady-state electric energy quality index value and output.

[0030] By using the steady-state electric energy quality data compression method, the decompression method and the compression and decompression device according to the present application, the to-be-tested electric energy signal is acquired, the data of the fundamental wave amplitude, the fundamental wave phase and the amplitudes and phases of the harmonic components are calculated according to the analysis formula, the specific data is calculated by the root mean square, and the waveform is reconstructed after storage, so that the waveform is output according to the steady-state electric energy quality index value, a higher compression ratio is obtained, and the problem of large storage space occupation is solved.

[0031] To achieve the above and related objects, one or more aspects of the application include features that will be explained in detail below and particularly pointed out in the claims. The following description and the accompanying drawings detail certain illustrative aspects of the application. However, these aspects indicate only some of the ways in which the principles of the application can be employed. In addition, the application is intended to include all such aspects and their equivalents. BRIEF DESCRIPTION OF DRAWINGS

[0032] In the drawings:

[0033] Figure 1 is a flowchart of the steady-state electric energy quality data compression method of the present application; and

[0034] Figure 2 is a flow chart of the steady-state power quality data compression and decompression device of the present application in operation.

[0035] The same reference numbers in all the drawings indicate similar or corresponding features or functions. DETAILED DESCRIPTION

[0036] Example embodiments now will be described more fully hereinafter with reference to the accompanying drawings. Example embodiments, however, can be implemented in many different forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of example embodiments to those skilled in the art. Features, structures or characteristics described in conjunction with the described examples can be combined in any suitable manner in one or more embodiments.

[0037] Figure 1 A flow chart of the steady-state power quality data compression method according to the present application is shown.

[0038] As described above with reference to Figure 1 The steady-state power quality data compression method of the present application is described.

[0039] As shown in Figure 1 The present application provides a steady-state power quality data compression method, which realizes the purpose of reducing the storage amount of power quality data by compressing the collected power quality data before storage. Specifically, the method comprises the following steps:

[0040] S1, sampling the waveform of an electric energy signal (including a voltage signal and a current signal) according to a preset sampling point number and a sampling time length to obtain a time-domain waveform data sequence of the electric energy signal to be measured, so as to convert the continuous electric energy signal into a discrete digital signal. In a specific embodiment, the waveform of the signal to be measured (voltage and current) is sampled according to 256 sampling points per cycle and a sampling time length of 10 cycles to obtain a time-domain waveform data sequence D = {d1, d2, … d 2560 of the signal to be measured, and a high-speed data acquisition card is used to perform 16-bit AD conversion on the sampling signal to obtain a discrete digital signal.

[0041] S2, obtaining the amplitudes and phases of different cycles within a preset time length according to the sampling time length, wherein according to Fourier series theory, any signal satisfying Dirichlet condition can be decomposed into linear superposition of sinusoidal signals, the time-domain waveform data sequence is decomposed into linear superposition of sinusoidal signals according to an analysis formula, and the amplitude A n and the phase θ n of each harmonic component in a preset number of harmonics are calculated.

[0042]

[0043]

[0044] In the formula, A0 is a direct current component, A1 is a fundamental wave amplitude, θ1 is a fundamental wave phase, A n is an n-th harmonic component amplitude, θ n is an n-th harmonic component phase, f is a frequency, t is a time, and n is a number of times;

[0045] Specifically, the time-domain waveform data sequence is subjected to FFT analysis, and the amplitudes A n and the phases θ n of the fundamental wave component and each harmonic component in a preset number of times are calculated.

[0046] In the embodiment, the preset time length is 3s according to the national standard, and therefore, 10 cycles of Fourier analysis in a 3s analysis time are calculated, and the calculation is performed once for each 10 cycles of data collection. The process is a repeated process, and therefore, a flag k is set. According to the formula 3000ms / (20ms / 1 cycle*10 cycles)=15, the value of k is obtained, and the value of k is accumulated from 1 to 15. More specifically, the first 10 cycles of Fourier calculation are performed to obtain the amplitude sequence A 1n , n=1, 2, 3…50, and the phase sequence θ 1n , n=1, 2, 3…50. Then, the second 10 cycles of Fourier calculation are performed to obtain the amplitude sequence A 2n and the phase sequence θ 2n . Until the calculation is completed for 15 times, the amplitude sequence and the phase sequence of the first time of 15 times of 10 cycles in 3s are stored.

[0047] S3, the root mean square of the amplitudes in the preset time length is calculated to obtain the amplitude sequence, and the amplitude sequence and the phase of the first cycle are stored.

[0048] In the embodiment, the amplitude A kn is subjected to 10 cycles of seamless collection, and the fundamental wave amplitude, the fundamental wave phase, and the amplitude sequence A 3_m under the condition of a 3s analysis time interval are calculated.

[0049] The root mean square value of the amplitude sequence is calculated every 10 cycles (15 data) to obtain the fundamental wave n=1 and the harmonic n=2, 3…50 in a 3s analysis time interval, and the calculation formula is as follows:

[0050]

[0051] In the formula, A 3_m is the amplitude sequence, and A1n is the amplitude, θ 1n is the phase, k is the mark number k=1, 2...15, m=1, 2, 3...

[0052] The above amplitude sequence A 3_m (3s analysis time calculated sequence) and the phase θ 3_m Information is stored, and the compression of the steady-state power quality data is completed.

[0053] Another aspect of the present application provides a steady-state power quality data decompression method for decompressing the data in the steady-state power quality data compression method, comprising:

[0054] The stored amplitude sequence and phase information are read to reconstruct the waveform, and the steady-state power quality index value is calculated in combination with the steady-state power quality related standard and output.

[0055] The waveform is reconstructed by the restoration formula, and the restoration formula is

[0056] In the formula, D' is the restored waveform, f is the grid fundamental frequency, f is the frequency, t is the time, and n is the number θ 3_m = θ 1n .

[0057] According to the steady-state power quality data compression method and the decompression method, in the embodiment of the present application, for the 3s long voltage signal and current signal, the data storage space is significantly reduced by the above method, 16-bit AD conversion is performed on the sampled signal, two bytes of data are generated for each sampling point, 256 points are sampled per cycle, the data obtained by sampling is saved in the form of 2-byte integer, and the total storage space occupied by the waveform data is:

[0058]

[0059] The data storage space is 50*2+50*2=100B by processing the data by the steady-state power quality data compression method, the data is compressed by 768 times, the storage space of the steady-state power quality data is greatly reduced, and a higher compression ratio is obtained.

[0060] Another aspect of the present application provides a steady-state power quality data compression and decompression device, comprising:

[0061] The acquisition module samples the waveform of the power signal according to the preset sampling point number and sampling time length to obtain the time-domain waveform data sequence of the to-be-tested power signal;

[0062] The analysis module obtains the amplitudes and phases of different cycles in the preset time length according to the sampling time length, wherein the time domain waveform data sequence is decomposed into linear superposition of sinusoidal signals according to an analysis formula, and the fundamental amplitude, the fundamental phase and the amplitudes A n and the phase θ n of the n-th harmonic component, f is the frequency, t is the time, and n is the order.

[0063]

[0064]

[0065] In the formula, A0 is a direct current component, A1 is the fundamental amplitude, θ1 is the fundamental phase, A n is the n-th harmonic component amplitude, θ n is the n-th harmonic component phase, f is the frequency, t is the time, and n is the order.

[0066] The storage module calculates the root mean square of the amplitudes in the preset time length to obtain an amplitude sequence, and stores the amplitude sequence and the phase of the first cycle.

[0067] The output module reads the stored amplitude sequence and phase information to reconstruct the waveform, and calculates the steady-state power quality index value in combination with the steady-state power quality standard and outputs.

[0068] The steady-state power quality data compression and decompression device designed by the application will be described in detail through specific embodiments.

[0069] Figure 2 is a flow chart for judging the operation of the steady-state power quality data compression and decompression device of the application. The device is implemented according to the steps in the judging block shown in the figure. Figure 2

[0070] Firstly, the acquisition module samples the to-be-tested signal to obtain the time domain waveform of the to-be-tested signal, so as to convert the signal analog quantity of the to-be-tested signal into digital quantity.

[0071] Then, the analysis module obtains the time domain waveform in the acquisition module, and analyzes the data sequence (in this embodiment, the analysis method adopts FFT analysis, and the detailed method is Fourier analysis), calculates the amplitudes A ki and the phases θ ki of the fundamental component and the 2nd to 50th harmonic components (in this embodiment, the amplitudes and phases comply with the above-mentioned differentiations). The amplitude sequence A kn ​The root wave and harmonic amplitude values of the 3s analysis time interval are calculated by calculating the root mean square value every 10 cycles (k=15 data), and the root wave and harmonic amplitude values of the 3s analysis time interval are obtained. At this time, if there are less than 15 data, the k value cannot be output, k=k+1 is returned to the acquisition module, the signal to be measured is acquired, and the k=15 output is output, and the 3s amplitude sequence A is calculated by calculating the root mean square value of the amplitude of the continuous 15 times of FFT analysis 3_m .

[0072] Then, the storage module obtains the root wave, harmonic amplitude and phase of the 3s analysis time obtained by the analysis module, and stores the 3s analysis time interval amplitude and the first phase analysis result of the 10 cycle analysis. The values that do not meet the storage requirements are returned to the first step for recalculation.

[0073] Finally, the output module reads the data in the storage module, and reconstructs the waveform of the data, calculates and outputs the required steady-state power quality index value according to the relevant standards of the steady-state power quality.

[0074] As can be seen from the above specific embodiments, the steady-state power quality data compression method, decompression method and compression and decompression device provided by the present application acquire the power signal to be measured, calculate the root wave amplitude, root wave phase, harmonic component amplitude and phase data according to the analysis formula, and perform root mean square calculation, storage and waveform reconstruction on specific data, so that the waveform is output according to the steady-state power quality index value, a higher compression ratio is obtained, and the problem of large storage space occupation is solved. The problems of voltage deviation, harmonic, flicker and three-phase imbalance can be avoided, and the sampling and collection according to the 3s period can meet the accuracy requirements of power quality analysis. Combined with the accuracy requirements of the steady-state index of power quality, the waveform is reconstructed and output, a higher compression ratio can be obtained, and the storage space is saved.

[0075] As described above by way of example Figure 1 and Figure 2 The steady-state power quality data compression method, decompression method and compression and decompression device according to the present application are described. However, those skilled in the art should understand that various improvements can be made to the steady-state power quality data compression method, decompression method and compression and decompression device according to the present application without departing from the content of the present application. Therefore, the protection scope of the present application should be determined by the content of the appended claims.

Claims

1. A method for compressing steady-state power quality data, characterized in that, Includes the following steps: S1. The waveform of the electrical energy signal is sampled according to the preset number of sampling points and sampling duration to obtain the time-domain waveform data sequence of the electrical energy signal to be measured. S2. Obtain the amplitude and phase of different cycles within a preset time period based on the sampling duration. Specifically, decompose the time-domain waveform data sequence into a linear superposition of sinusoidal signals according to the analysis formula, and calculate the fundamental amplitude, fundamental phase, and the amplitude A of each harmonic component in the preset order. n With phase θ n The analytical formula is as follows: A0=a0、 In the formula, A0 is the DC component, A1 is the fundamental amplitude, θ1 is the fundamental phase, and A n Let θ be the amplitude of the nth harmonic component. n Let f be the phase of the nth harmonic component, f be the frequency, t be the time, and n be the harmonic order. S3. Calculate the root mean square of the amplitude within the preset time period to obtain the amplitude sequence, and store the amplitude sequence and the phase of the first cycle.

2. The steady-state power quality data compression method as described in claim 1, characterized in that, In S1, the preset sampling duration is 10 cycles, and the number of sampling points per cycle is 256. Based on the sampling duration and the number of sampling points, the time-domain waveform data sequence D = {d1, d2, ... d...} is obtained. 2560 } 3. The steady-state power quality data compression method as described in claim 1, characterized in that, In S2, the preset number of harmonic component amplitudes is 2 to 50.

4. The steady-state power quality data compression method as described in claim 2, characterized in that, The calculation formula in S3 is as follows: In the formula, A 3_m For the amplitude sequence, A 1n For amplitude, θ 1n Let k be the phase, and k be the number of markings, k = 1, 2...

15.

5. A method for decompressing steady-state power quality data, used to decompress data obtained by the steady-state power quality data compression method according to any one of claims 1-4, characterized in that, include: The stored amplitude sequence and phase information are read to reconstruct the waveform, and the steady-state power quality index value is calculated and output in combination with the steady-state power quality standard.

6. The steady-state power quality data compression method as described in claim 5, characterized in that, Reconstruct the waveform according to the restoration formula. The reduction formula is In the formula, D' is the restored waveform, f is the fundamental frequency of the power grid, and θ 3_m =θ 1n .

7. A device for compressing and decompressing steady-state power quality data, characterized in that, include: The acquisition module samples the waveform of the electrical energy signal according to the preset number of sampling points and sampling duration to obtain the time-domain waveform data sequence of the electrical energy signal to be measured. The analysis module acquires the amplitude and phase of different cycles within a preset time period based on the sampling duration. Specifically, it decomposes the time-domain waveform data sequence into a linear superposition of sinusoidal signals according to the analysis formula, calculating the fundamental amplitude, fundamental phase, and the amplitude A of each harmonic component in the preset order. n With phase θ n The analytical formula is as follows: A0=a0、 In the formula, A0 is the DC component, A1 is the fundamental amplitude, θ1 is the fundamental phase, and A n Let θ be the amplitude of the nth harmonic component. n Let f be the phase of the nth harmonic component, f be the frequency, t be the time, and n be the harmonic order. The storage module calculates the root mean square of the amplitude within a preset time period to obtain the amplitude sequence, and stores the amplitude sequence and the phase of the first cycle; The output module reads the stored amplitude sequence and phase information to reconstruct the waveform, and calculates and outputs the steady-state power quality index value in conjunction with the steady-state power quality standard.

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