CN111766471A

CN111766471A - Power waveform compression algorithm

Info

Publication number: CN111766471A
Application number: CN202010594835.XA
Authority: CN
Inventors: 董锁英; 吴洪伟; 高志辉; 张菡洁
Original assignee: HEBEI XUHUI ELECTRIC CO Ltd
Current assignee: HEBEI XUHUI ELECTRIC CO Ltd
Priority date: 2020-06-28
Filing date: 2020-06-28
Publication date: 2020-10-13

Abstract

The invention discloses a power waveform compression algorithm, which specifically comprises the following steps: carrying out noise reduction processing on the acquired analog quantity data according to a set period, and carrying out filtering pretreatment on the analog quantity subjected to noise reduction processing to form a new sampling value; performing incremental calculation on the new sampling value and the old sampling value obtained in the previous sampling period until a minimum digit data sequence is obtained and storing the minimum digit data sequence; and performing later compression by adopting a conventional compression algorithm. The invention achieves higher compression ratio by organically combining the compression algorithm of incremental calculation with the traditional compression algorithm, the compression ratio can reach below 25% under the condition of steady-state power waveform, and the power waveform data of not less than one month can be continuously recorded and stored by combining the size of the storage module, thereby providing data support for the research and analysis of a power system.

Description

Power waveform compression algorithm

Technical Field

The invention relates to the technical field of data processing of power system operation equipment, in particular to a method for processing power waveform data.

Background

The fault diagnosis, the electric energy quality analysis and the research of the power grid operation state in the operation process of the power system all depend on power waveform recording data, and the collection of the power waveform is usually completed by wave recording equipment. However, because the operating frequency of the power system is relatively fixed, the sampling rate of a common wave recording device is far higher than the operating frequency of the system, the sampling resolution is generally 12 to 24 bits, and the increment of adjacent sampling points is small, the existing wave recording device can only record short-term data at the fault moment or store waveform data in a short time, and cannot provide support for research and analysis of the power system.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a power waveform compression algorithm with a high compression ratio to realize the storage of a large amount of power waveform data and provide data support for the research and analysis of a power system.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows.

A power waveform compression algorithm specifically comprises the following steps:

A. the acquired analog data is subjected to noise reduction processing according to a set period,

B. carrying out filtering pretreatment on the analog quantity subjected to noise reduction treatment to form a new sampling value;

C. performing incremental calculation on the new sampling value and the old sampling value obtained in the previous sampling period until a minimum digit data sequence is obtained and storing the minimum digit data sequence;

D. and performing later compression by adopting a conventional compression algorithm.

In the above power waveform compression algorithm, the incremental calculation method in step C includes: subtracting the data of the previous sampling point from the original data of the current sampling point to obtain a first difference value; and subtracting the previous difference value from the current difference value to obtain data of a second difference value, wherein the second difference value sequence of the group of data is the finally obtained minimum digit data sequence.

In the above power waveform compression algorithm, in the step C, the minimum number of bits is represented by 4 bits, the highest bit in the 4-bit byte is a deviation out-of-range bit, the deviation out-of-range bit is an extended data byte followed by the extended data byte, the highest bit of the extended data byte is 1, which indicates that the next byte is still an extended byte, and the highest bit is 0, which indicates that the next byte is no longer an extended byte.

The power waveform compression algorithm is characterized in that the conventional compression algorithm in the step D adopts an LZ77 compression algorithm.

Due to the adoption of the technical scheme, the technical progress of the invention is as follows.

The invention is suitable for the optimized compression of power waveforms, achieves higher compression ratio by organically combining the compression algorithm of incremental calculation with the traditional compression algorithm, can achieve the compression ratio of below 25% under the condition of steady-state power waveforms, can continuously record and store power waveform data for not less than one month by combining the size of the storage module, is convenient for fault integrity analysis, daily information rule summary analysis, pre-judgment on impending faults and the like, and has great significance for the safe and stable operation of a power system.

Drawings

FIG. 1 is a flow chart of the compression algorithm of the present invention.

Detailed Description

In order to make the technical solution of the present invention better understood, the technical solution of the present invention will be clearly and completely described below with reference to the specific embodiments and the accompanying drawings.

The power waveform compression algorithm is suitable for data processing of power waveforms, and a flow diagram of the compression algorithm is shown in fig. 1 and specifically comprises the following steps.

A. And carrying out noise reduction processing on the acquired analog quantity data according to a set period. The invention adopts a mode of adding an active low-pass filter on an analog quantity acquisition hardware circuit to carry out noise reduction processing on the acquired analog quantity data.

B. And carrying out amplitude limiting average filtering pretreatment on the analog quantity subjected to the noise reduction treatment to form a new sampling value. And the new data sampled every time is firstly subjected to amplitude limiting processing and then is sent to a queue for recursive average filtering processing, so that the accidental impulsive interference is eliminated.

C. And performing incremental calculation on the new sampling value and the old sampling value obtained in the previous sampling period until a minimum digit data sequence is obtained and storing.

Subtracting the data of the previous sampling point from the current sampling point of the original data to obtain a first difference value; and subtracting the previous difference value from the current difference value to obtain data of a second difference value, wherein the second difference value sequence of the group of data is the finally obtained expected minimum digit data sequence, and the group of minimum digit data sequence is compressed to obtain the ideal compression ratio.

The first data of each channel keeps original data; the input sequence is set as: a1, a2, A3, … … An;

the first step output sequence of the encoding calculation is as follows: b1, B2, B3, … … Bn.

Wherein, B1 is A1; b2 ═ a2-a 1; b3 ═ A3-a 2; b4 ═ a 4-A3; … … Bn is An-A (n-1).

The second step of coding calculation output sequence is as follows: c1, C2, C3, … … Cn.

Wherein, C1 ═ B1; c2 ═ B2-B1; c3 ═ B3-B2; c4 ═ B4-B3; … … Cn ═ Bn-B (n-1).

In the embodiment, 13-bit fundamental wave data of 1024 sampling points are used for simulation, and 0.3 time of 3-order harmonic, 0.2 time of 5-order harmonic and 0.1 time of 7-order harmonic are added to obtain original data; specific coded data is shown in table 1.

TABLE 1

In this embodiment, the minimum-bit data sequence is represented by 4 bits from-7 to + 7; 1000 indicates that the deviation is out of range followed by an extended data byte, with the most significant bit of the extended data byte being 1 indicating that the next byte is still an extended byte and 0 indicating that the next byte is no longer an extended byte. As shown in table 2.

TABLE 2

Serial number	Data of	Binary system
			1	-7	1001
2	-6	1010
			3	-5	1011
4	-4	1100
			5	-3	1101
6	-2	1110
			7	-1	1111
8	0	0000
			9	1	0001
10	2	0010
			11	3	0011
12	4	0100
			13	5	0101
14	6	0110
			15	7	0111

The original data sequence is shown in table 3.

TABLE 3

Serial number	Data of	Binary system
			1	-8191	1000 1100 0000 0000 0001
2	-64	1000 1111 1111 0100 0000
			3	64	1000 1000 0000 0100 0000
4	8191	1000 1011 1111 0111 1111

It can be seen that after two times of early compression, the data sequence with the minimum number of bits can be obtained; compared with the original data sequence, the compression rate is greatly improved.

D. And finally, performing later compression by adopting a conventional compression algorithm to obtain a better compression effect.

The algorithm of the invention has simple operation and low requirement on the processor, and is efficient and feasible from the aspects of CPU and hardware realization.

After the electric power waveform data stored by the invention is transmitted, the first decoding and the second decoding can be obtained according to the inverse operation, and the original data is finally obtained.

The decoding calculates the first step output sequence as: d1, D2, D3, … … Dn;

wherein, D1 ═ C1; d2 ═ D1+ C2; d3 ═ D2+ C3; d4 ═ D3+ C4; … … Dn is D (n-1) + Cn.

The second step of decoding calculation output sequence is: e1, E2, E3, … … En;

wherein, E1 ═ D1; e2 ═ E1+ D2; e3 ═ E2+ D3; e4 ═ E3+ D4; … … En ═ E (n-1) + Dn.

In this embodiment, data of the decoding process is shown in table 4.

TABLE 4

It can be seen from table 4 that the data after the second decoding is the same as the original data, which shows that the compression method of the present invention can improve the compression ratio on the basis of ensuring the integrity of the data, thereby providing more information amount for the storage space with fixed capacity.

The above detailed description of embodiments of the invention presented in the drawings is not intended to limit the scope of the invention as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.

Claims

1. The power waveform compression algorithm is characterized by comprising the following steps:

2. The power waveform compression algorithm of claim 1 wherein the incremental calculation method in step C is: subtracting the data of the previous sampling point from the original data of the current sampling point to obtain a first difference value; and subtracting the previous difference value from the current difference value to obtain data of a second difference value, wherein the second difference value sequence of the group of data is the finally obtained minimum digit data sequence.

3. The power waveform compression algorithm of claim 1 wherein the minimum number of bits in step C is represented by 4 bits, the highest bit in the 4-bit byte is the offset out-of-range bit followed by the extended data byte, the highest bit in the extended data byte being 1 indicating that the next byte is still an extended byte, the highest bit being 0 indicating that the next byte is no longer an extended byte.

4. The power waveform compression algorithm of claim 1, wherein the conventional compression algorithm of step D employs an LZ77 compression algorithm.