CN107991532B - Harmonic threshold value merging method based on multiple operation modes - Google Patents
Harmonic threshold value merging method based on multiple operation modes Download PDFInfo
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- CN107991532B CN107991532B CN201711163179.2A CN201711163179A CN107991532B CN 107991532 B CN107991532 B CN 107991532B CN 201711163179 A CN201711163179 A CN 201711163179A CN 107991532 B CN107991532 B CN 107991532B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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- Y02E40/40—Arrangements for reducing harmonics
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Abstract
The invention relates to the technical field of harmonic processing, in particular to a harmonic threshold value merging method based on multiple operation modes. The invention discloses a harmonic threshold merging method based on multiple operation modes, which comprises the following steps: a, processing harmonic threshold values of all operation modes to obtain a one-dimensional harmonic threshold value matrix; b, calculating the gradient of each adjacent harmonic threshold in the one-dimensional harmonic threshold matrix, and sorting the calculated gradients in size; c, judging whether the adjacent harmonic threshold with the minimum gradient can be merged or not by taking the difference degree of the mean value and the variance of the active power of the corresponding operation mode as a criterion result; d, when the judgment result is smaller than the given difference value, combining adjacent harmonic threshold values, and returning to the step A; when the criterion result is larger than the given difference value, the combination is terminated. The invention can reduce the number of threshold values through reasonable harmonic threshold value combination, thereby achieving the purpose of reducing the calculation workload and having high feasibility.
Description
Technical Field
The invention belongs to the technical field of harmonic processing, and particularly relates to a harmonic threshold merging method based on multiple operation modes.
Background
Harmonics are sub-components obtained by fourier series decomposition of a periodic non-sinusoidal alternating current, which are greater than an integral multiple of the frequency of a fundamental wave, and are generally called higher harmonics, while fundamental waves are components having the same frequency as the power frequency (50 Hz). The interference of higher harmonics is a big 'public nuisance' affecting the quality of electric energy in the current power system, and countermeasures are needed to be taken urgently.
The reasons for the generation of harmonics are mainly: as the sinusoidal voltage is applied to the nonlinear load, the fundamental current is distorted to generate harmonics. The main nonlinear load is provided with a UPS, a switching power supply, a rectifier, a frequency converter, an inverter and the like.
The nonlinear load equipment equipped by the existing power customer has a plurality of corresponding operation modes, the harmonic threshold of each operation mode is not necessarily the same, so that the calculation workload of the harmonic threshold is increased, and the number of the thresholds needs to be reduced during engineering application so as to achieve the purpose of reducing the calculation workload. However, there is no good method for reducing the harmonic threshold in the prior art.
Disclosure of Invention
The invention aims to provide a harmonic threshold merging method based on multiple operation modes to solve the problems.
In order to achieve the purpose, the invention adopts the technical scheme that: a harmonic threshold value merging method based on multiple operation modes comprises the following steps:
a, processing harmonic threshold values of all operation modes to obtain a one-dimensional harmonic threshold value matrix;
b, calculating the gradient of each adjacent harmonic threshold in the one-dimensional harmonic threshold matrix, and sorting the calculated gradients in size;
c, judging whether the adjacent harmonic threshold with the minimum gradient can be merged or not by taking the difference degree of the mean value and the variance of the active power of the corresponding operation mode as a criterion result;
d, when the judgment result is smaller than the given difference value, combining adjacent harmonic threshold values, and returning to the step A; when the criterion result is larger than the given difference value, the combination is terminated.
Further, in the step a, the one-dimensional harmonic threshold matrix is an i × 1 matrix, where i is the number of operation modes.
Further, in the step B, the sorting of the magnitudes of the calculated gradients specifically includes: and sorting the calculated gradients in ascending order of magnitude.
Further, the step C specifically includes:
c1, respectively carrying out variance S calculation and mean value normalization processing on the active power of each operation mode;
c2, weighting the variance S and the normalized mean value P to obtain a weighted value W
W＝w1·S+w2·P
Wherein, w1And w2Are weight coefficients respectively; the result of the criterion is:
|W(i)-W(j)|
wherein, w (i) and w (j) are weighted values corresponding to adjacent harmonic threshold values with minimum gradient, respectively.
Further, in the step C2, w1＝0.7，w2＝0.3。
The invention has the beneficial technical effects that:
the invention provides a reasonable harmonic threshold merging method, which can reduce the number of thresholds, thereby achieving the purpose of reducing the calculation workload and having high feasibility.
Drawings
FIG. 1 is a flow chart of a method of an embodiment of the present invention.
Detailed Description
The invention will now be further described with reference to the accompanying drawings and detailed description.
As shown in fig. 1, a harmonic threshold merging method based on multiple operation modes includes the following steps:
and A, processing the harmonic threshold of each operation mode to obtain a one-dimensional harmonic threshold matrix.
In this embodiment, the harmonic threshold values of the respective operation modes are processed to obtain a one-dimensional harmonic threshold value matrix of i × 1, as follows:
of course, in other embodiments, the harmonic threshold values of the respective operation modes may be processed into a one-dimensional harmonic threshold matrix of 1 × i, which can be easily implemented by those skilled in the art and will not be described in detail.
And B, calculating the gradient of each adjacent harmonic threshold in the one-dimensional harmonic threshold matrix, and sorting the calculated gradient in size.
In this embodiment, the calculation of the gradient of the adjacent harmonic threshold refers to the following formula:
this formula represents the function F (x, y) at point (x)0,y0) The specific calculation process of the gradient is easily realized by those skilled in the art, and is not described in detail. And then sorting the calculated gradients in ascending order of magnitude. Of course, in other embodiments, the sorting may be performed in descending order, which can be easily implemented by those skilled in the art and will not be described in detail.
And C, judging whether the adjacent harmonic threshold with the minimum gradient can be combined or not by taking the difference degree of the mean value and the variance of the active power of the corresponding operation mode as a criterion result.
Specifically, the method comprises the following steps:
and C1, respectively carrying out the calculation of the variance S and the normalization of the mean value on the active power of each operation mode. The variance is calculated using the following formula:
wherein x isiIn order to collect the ith active power data in the operating mode,
the average value of the active power data in the operation mode is acquired.
And (3) normalization processing of the mean value:
wherein x isminFor the minimum value, x, of the active power obtained for this mode of operationmaxThe maximum value of the active power in the operation mode is acquired.
C2, weighting the variance S and the normalized mean value P to obtain a weighted value W
W＝w1·S+w2·P
Wherein, w1And w2Are weight coefficients, respectively, in this embodiment, w1＝0.7，w20.3, of course, in other embodiments, w1And w2Can be selected according to actual needs.
And comparing the weighted values of the two operation modes with the minimum gradient as a criterion result, wherein the weighted values are as follows:
|W(i)-W(j)|
d, when the result of the criterion is less than a given difference value, namely | W (i) -W (j) | <, combining the adjacent harmonic threshold values, taking the combined threshold value as a new threshold value, and then returning to the step A for circulation; when the criterion result is larger than the given difference value, the combination is terminated.
In order to verify the correctness of the method, the following test platform is built by using the existing laboratory equipment: the system comprises 2 frequency converters with different models and 4 motors, wherein each frequency converter respectively controls two motors. Take the 95% probability value of the harmonic current distortion rate as an example.
The test platform has three operation modes, which can generate harmonic current, and is specifically shown in table 1:
TABLE 1 three modes of operation of the test system
Table 2 shows characteristic values of the cloud model of the test data in the three operation modes, and table 3 shows a merging result obtained when values are different.
TABLE 2 eigenvalues of harmonic currents of cloud models under three different operating modes
| Mode of operation | expectation/TDH | Entropy of the entropy | Super entropy | Anomaly threshold |
| Mode 1 | 183.7182 | 2.3278 | 0.1343 | 191.9101 |
| Mode 2 | 181.5384 | 1.3335 | 0.3431 | 188.6265 |
| Mode 3 | 186.1952 | 2.7490 | 1.1113 | 204.4444 |
TABLE 3 harmonic current threshold merging results when taking different values
| ε is selected from the group consisting of | Number of mergers | Merged mode of operation | Non-consolidated mode of operation |
| 0.01 | 0 | Is free of | Mode 1, mode 2, and mode 3 |
| 0.1 | 1 | Modes 1 and 2 | Mode 3 |
| 10 | 2 | Mode 1, mode 2, and mode 3 | Is free of |
Analysis of tables 2 and 3 may yield a threshold after a combination of operating mode 1 and operating mode 2 with a confidence of 99.42% for operating mode 1 and 98.85% for operating mode 2. The feasibility of the merging method is proved by the fact that although the confidence of the merging threshold value is reduced, the reduction amplitude is less than 5%.
While the invention has been particularly shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (5)
1. A harmonic threshold value merging method based on multiple operation modes is characterized by comprising the following steps:
a, processing harmonic threshold values of all operation modes to obtain a one-dimensional harmonic threshold value matrix;
b, calculating the gradient of each adjacent harmonic threshold in the one-dimensional harmonic threshold matrix, and sorting the calculated gradients in size;
c, judging whether the adjacent harmonic threshold with the minimum gradient can be merged or not by taking the difference degree of the mean value and the variance of the active power of the corresponding operation mode as a criterion result;
d, when the judgment result is smaller than the given difference value, combining adjacent harmonic threshold values, and returning to the step A; when the criterion result is larger than the given difference value, the combination is terminated.
2. The harmonic threshold merging method based on multiple operation modes according to claim 1, wherein in the step a, the one-dimensional harmonic threshold matrix is an i × 1 matrix, where i is the number of operation modes.
3. The harmonic threshold merging method based on multiple operation modes according to claim 1, wherein in the step B, the magnitude sorting of the calculated gradients is specifically: and sorting the calculated gradients in ascending order of magnitude.
4. The harmonic threshold merging method based on multiple operation modes according to claim 1, wherein the step C specifically includes:
c1, respectively carrying out variance S calculation and mean value normalization processing on the active power of each operation mode;
c2, weighting the variance S and the normalized mean value P to obtain a weighted value W
W＝w1·S+w2·P
Wherein, w1And w2Are weight coefficients respectively; the result of the criterion is:
|W(i)-W(j)|
wherein, w (i) and w (j) are weighted values corresponding to adjacent harmonic threshold values with minimum gradient, respectively.
5. The harmonic threshold combination method based on multiple operation modes according to claim 4, wherein in the step C2, w1＝0.7，w2＝0.3。
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| US5298888A (en) * | 1992-08-21 | 1994-03-29 | Basic Measuring Instruments | Harmonic measuring instrument for AC power systems with latched indicator means |
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| JPH10243558A (en) * | 1997-02-25 | 1998-09-11 | Shin Kobe Electric Mach Co Ltd | Uninterruptive power unit |
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