CN113433408A - Method for evaluating steady-state power quality - Google Patents
Method for evaluating steady-state power quality Download PDFInfo
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- CN113433408A CN113433408A CN202110707557.9A CN202110707557A CN113433408A CN 113433408 A CN113433408 A CN 113433408A CN 202110707557 A CN202110707557 A CN 202110707557A CN 113433408 A CN113433408 A CN 113433408A
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Abstract
The invention discloses a steady-state power quality evaluation method, which comprises the following steps: A. the current sensor and the voltage sensor respectively collect electric signals of a power grid; B. the acquired analog electric signal is converted into a digital signal through a signal conversion module, and the digital electric signal is preprocessed; C. the processed electric energy signals are output to an electric energy quality evaluation model for evaluation, and the evaluation method adopted by the invention can determine whether the electric energy quality indexes of each calculation time period are qualified or not, and can help the power users to intuitively and specifically master the electric energy quality condition of self power utilization; the adopted denoising processing method adopts a multi-scale and multi-resolution wavelet transform decomposition technology to accurately distinguish the wavelet coefficients of the electric energy signal and the noise, and the wavelet coefficient threshold is self-adaptive to the change of the noise.
Description
Technical Field
The invention relates to the technical field of power quality evaluation, in particular to a steady-state power quality evaluation method.
Background
In recent years, with the wide application and development of power electronic technology, a large number of nonlinear loads are added in a power supply system, which can cause distortion of current and voltage waveforms of a power grid and cause harmonic wave pollution of the power grid. Such as large-scale rolling mills, electric locomotives and the like, not only can a large amount of higher harmonics be generated in the operation process, but also the voltage fluctuation, the flicker and the three-phase imbalance become serious day by day. These adverse effects on the grid not only result in reduced safety of the electricity supply and utilization equipment itself, but also severely interfere with the economic operation of the grid, causing a "nuisance" to the grid. On the other hand, the requirements of new processes and new technical equipment on the quality of power supply are more and more demanding, such as various equipment in places such as a lot of industrial pipelines, precision manufacturing industry, computer networks, service monitoring centers and the like. The improvement of the requirement of users on the power supply quality leads the problem of the power quality to be increasingly outstanding, and a power quality monitoring system is necessary to be established, so that the power quality data of the whole power distribution network are monitored and analyzed, and measures are taken to improve the power quality of the power distribution network. The existing power quality evaluation system is complex and has low evaluation accuracy, so that improvement is needed.
Disclosure of Invention
The present invention is directed to a method for evaluating steady-state power quality, so as to solve the problems in the background art.
In order to achieve the purpose, the invention provides the following technical scheme: a steady-state power quality assessment method comprises the following steps:
A. the current sensor and the voltage sensor respectively collect electric signals of a power grid;
B. the acquired analog electric signal is converted into a digital signal through a signal conversion module, and the digital electric signal is preprocessed;
C. and outputting the processed electric energy signal to an electric energy quality evaluation model for evaluation.
Preferably, the pretreatment method in step B is as follows:
a. performing wavelet decomposition on the collected electric energy data to obtain high-frequency and low-frequency wavelet coefficients after decomposing to the finest scale;
b. reordering the high-frequency wavelet coefficients and the low-frequency wavelet coefficients of each scale from big to small;
c. in different scales, estimating the noise variance of the high-frequency wavelet coefficient and the low-frequency wavelet coefficient, and calculating the median of a new sequence and the minimum value of an estimator;
d. calculating a high-frequency wavelet coefficient threshold value and a low-frequency wavelet coefficient value of each scale according to the constraint factors;
e. d, reserving the coefficients larger than the absolute value of the threshold in each scale, and calculating a new threshold by the coefficients smaller than the absolute value of the threshold according to the step d;
f. repeating the steps b to e, and storing the new high-frequency wavelet coefficient and the new low-frequency wavelet coefficient after the processing of each scale;
g. and obtaining the denoised electric energy data by adopting wavelet inverse transformation.
Preferably, the method for creating the power quality assessment model in step C is as follows:
a. determining all sub-evaluation tasks for realizing the power quality evaluation algorithm and logic relations among the sub-evaluation tasks through a power quality evaluation algorithm;
b. selecting plug-ins for realizing the sub-evaluation tasks from the pre-created evaluation model plug-ins, and establishing a connection relation between the selected plug-ins according to a logic relation between the sub-evaluation tasks so as to establish the power quality evaluation model.
Preferably, the power quality evaluation algorithm comprises the following methods:
1) firstly, receiving electric energy quality indexes of power grid users in each time period;
2) calculating corresponding electric energy parameters in each time interval according to each electric energy quality index;
3) and dividing each electric energy parameter by a preset limiting value and then evaluating whether the electric energy quality is qualified or not.
Preferably, if the electric energy parameter is greater than 1 after being divided by the preset limit value, the electric energy quality is unqualified; if the electric energy parameter is divided by the preset limit value and then is equal to 1, the electric energy quality is in the best state; and if the electric energy parameter is greater than 1 after being divided by the preset limit value, the electric energy quality is qualified.
Compared with the prior art, the invention has the beneficial effects that: the evaluation method adopted by the invention can determine whether the power quality index of each calculation time interval is qualified or not, and can help the power consumer to intuitively and specifically grasp the power quality condition of own power consumption; the adopted denoising processing method adopts a multi-scale and multi-resolution wavelet transform decomposition technology to accurately distinguish the wavelet coefficients of the electric energy signal and the noise, and the wavelet coefficient threshold is self-adaptive to the change of the noise.
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FIG. 1 is a flow chart of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the description of the present invention, it should be noted that the terms "upper", "lower", "inner", "outer", "front", "rear", "both ends", "one end", "the other end", and the like indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the description of the present invention, it is to be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "disposed," "connected," and the like are to be construed broadly, such as "connected," which may be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
Referring to fig. 1, the present invention provides the following technical solutions: a steady-state power quality assessment method comprises the following steps:
A. the current sensor and the voltage sensor respectively collect electric signals of a power grid;
B. the acquired analog electric signal is converted into a digital signal through a signal conversion module, and the digital electric signal is preprocessed;
C. and outputting the processed electric energy signal to an electric energy quality evaluation model for evaluation.
In the invention, the pretreatment method in the step B is as follows:
a. performing wavelet decomposition on the collected electric energy data to obtain high-frequency and low-frequency wavelet coefficients after decomposing to the finest scale;
b. reordering the high-frequency wavelet coefficients and the low-frequency wavelet coefficients of each scale from big to small;
c. in different scales, estimating the noise variance of the high-frequency wavelet coefficient and the low-frequency wavelet coefficient, and calculating the median of a new sequence and the minimum value of an estimator;
d. calculating a high-frequency wavelet coefficient threshold value and a low-frequency wavelet coefficient value of each scale according to the constraint factors;
e. d, reserving the coefficients larger than the absolute value of the threshold in each scale, and calculating a new threshold by the coefficients smaller than the absolute value of the threshold according to the step d;
f. repeating the steps b to e, and storing the new high-frequency wavelet coefficient and the new low-frequency wavelet coefficient after the processing of each scale;
g. and obtaining the denoised electric energy data by adopting wavelet inverse transformation.
In the invention, the method for creating the power quality evaluation model in the step C is as follows:
a. determining all sub-evaluation tasks for realizing the power quality evaluation algorithm and logic relations among the sub-evaluation tasks through a power quality evaluation algorithm;
b. selecting plug-ins for realizing the sub-evaluation tasks from the pre-created evaluation model plug-ins, and establishing a connection relation between the selected plug-ins according to a logic relation between the sub-evaluation tasks so as to establish the power quality evaluation model.
The power quality evaluation method has the advantages that multiple or one plug-in can be selected from the pre-created evaluation model plug-ins directly according to different power quality evaluation algorithms to complete the power quality evaluation task together, the whole system does not need to be replaced comprehensively, the plug-ins can be combined freely to adapt to the latest environmental requirements, and the updating cost of the system is reduced.
In the invention, the power quality evaluation algorithm comprises the following steps:
1) firstly, receiving electric energy quality indexes of power grid users in each time period;
2) calculating corresponding electric energy parameters in each time interval according to each electric energy quality index;
3) and dividing each electric energy parameter by a preset limiting value and then evaluating whether the electric energy quality is qualified or not.
In the invention, if the electric energy parameter is greater than 1 after being divided by the preset limit value, the electric energy quality is unqualified; if the electric energy parameter is divided by the preset limit value and then is equal to 1, the electric energy quality is in the best state; and if the electric energy parameter is greater than 1 after being divided by the preset limit value, the electric energy quality is qualified.
In conclusion, the evaluation method adopted by the invention can determine whether the power quality index of each calculation time interval is qualified or not, and can help the power consumer to intuitively and specifically grasp the power quality condition of own power consumption; the adopted denoising processing method adopts a multi-scale and multi-resolution wavelet transform decomposition technology to accurately distinguish the wavelet coefficients of the electric energy signal and the noise, and the wavelet coefficient threshold is self-adaptive to the change of the noise.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.
Claims (5)
1. A steady state power quality assessment method is characterized in that: the method comprises the following steps:
A. the current sensor and the voltage sensor respectively collect electric signals of a power grid;
B. the acquired analog electric signal is converted into a digital signal through a signal conversion module, and the digital electric signal is preprocessed;
C. and outputting the processed electric energy signal to an electric energy quality evaluation model for evaluation.
2. The method of claim 1, wherein the method comprises: the pretreatment method in the step B is as follows:
a. performing wavelet decomposition on the collected electric energy data to obtain high-frequency and low-frequency wavelet coefficients after decomposing to the finest scale;
b. reordering the high-frequency wavelet coefficients and the low-frequency wavelet coefficients of each scale from big to small;
c. in different scales, estimating the noise variance of the high-frequency wavelet coefficient and the low-frequency wavelet coefficient, and calculating the median of a new sequence and the minimum value of an estimator;
d. calculating a high-frequency wavelet coefficient threshold value and a low-frequency wavelet coefficient value of each scale according to the constraint factors;
e. d, reserving the coefficients larger than the absolute value of the threshold in each scale, and calculating a new threshold by the coefficients smaller than the absolute value of the threshold according to the step d;
f. repeating the steps b to e, and storing the new high-frequency wavelet coefficient and the new low-frequency wavelet coefficient after the processing of each scale;
g. and obtaining the denoised electric energy data by adopting wavelet inverse transformation.
3. The method of claim 1, wherein the method comprises: the method for creating the power quality evaluation model in the step C comprises the following steps:
a. determining all sub-evaluation tasks for realizing the power quality evaluation algorithm and logic relations among the sub-evaluation tasks through a power quality evaluation algorithm;
b. selecting plug-ins for realizing the sub-evaluation tasks from the pre-created evaluation model plug-ins, and establishing a connection relation between the selected plug-ins according to a logic relation between the sub-evaluation tasks so as to establish the power quality evaluation model.
4. The method of claim 3, wherein the method comprises: the power quality evaluation algorithm comprises the following steps:
1) firstly, receiving electric energy quality indexes of power grid users in each time period;
2) calculating corresponding electric energy parameters in each time interval according to each electric energy quality index;
3) and dividing each electric energy parameter by a preset limiting value and then evaluating whether the electric energy quality is qualified or not.
5. The method of claim 4, wherein the method comprises: if the electric energy parameter is greater than 1 after being divided by the preset limit value, the electric energy quality is unqualified; if the electric energy parameter is divided by the preset limit value and then is equal to 1, the electric energy quality is in the best state; and if the electric energy parameter is greater than 1 after being divided by the preset limit value, the electric energy quality is qualified.
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| CN104408555A (en) * | 2014-11-12 | 2015-03-11 | 国家电网公司 | Building method of power quality assessment model and power quality assessment method |
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| CN110276558A (en) * | 2019-06-27 | 2019-09-24 | 广东电网有限责任公司 | A kind of maintaining method of power grid, system and computer readable storage medium |
| CN110824282A (en) * | 2019-11-20 | 2020-02-21 | 湖南铁路科技职业技术学院 | High-voltage charging pile electric energy quality monitoring system |
| CN110907885A (en) * | 2019-12-06 | 2020-03-24 | 国网湖北省电力有限公司计量中心 | Method and system for evaluating field operation state of digital electric energy metering system |
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2021
- 2021-06-24 CN CN202110707557.9A patent/CN113433408A/en active Pending
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103837777A (en) * | 2014-03-18 | 2014-06-04 | 深圳市康必达中创科技有限公司 | Method and system for power quality assessment of power supply system |
| CN104408555A (en) * | 2014-11-12 | 2015-03-11 | 国家电网公司 | Building method of power quality assessment model and power quality assessment method |
| CN107565551A (en) * | 2017-09-13 | 2018-01-09 | 国网上海市电力公司 | Electricity quality evaluation method |
| CN108020736A (en) * | 2017-11-15 | 2018-05-11 | 哈尔滨理工大学 | A kind of power quality detection method |
| CN110276558A (en) * | 2019-06-27 | 2019-09-24 | 广东电网有限责任公司 | A kind of maintaining method of power grid, system and computer readable storage medium |
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Application publication date: 20210924 |