CN104849548B - A kind of electric system instantaneous frequency monitoring method and system - Google Patents
A kind of electric system instantaneous frequency monitoring method and system Download PDFInfo
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Abstract
The present invention relates to a kind of electric system instantaneous frequency monitoring method and systems, by obtaining initial samples data set, and the data concentrated to data are iterated processing, so as to accurately estimate the instantaneous frequency of sampled point, the present invention can accurately estimate the instantaneous frequency of sampled point using sampled data, it is fast with arithmetic speed, precision of prediction is high, the advantages that algorithm is relatively easy, possesses wide prospect of the application in electric system instantaneous frequency monitoring field, accurate by instantaneous frequency is estimated, abnormal conditions are run into timely to be alarmed for electric system, the problem of so as to effectively prevent causing due to frequency quality reduces possible electric power system fault and loss.
Description
Technical Field
The invention relates to the field of electric power, in particular to a method and a system for monitoring instantaneous frequency of an electric power system.
Background
The frequency is a crucial parameter for safe and stable operation of the power system, and can reflect the electric energy quality and the safety condition of the whole system. Too high or too low a frequency can be detrimental to the power system.
When the power system has unbalanced and unstable power output, the frequency changes, the load disturbance of the modern power system is larger and larger, the load rate on the power transmission line is also larger and larger, great difficulty is caused to the stability guarantee of the power system frequency, the reduction of the power system frequency quality can cause large-area power failure, and even the whole system is collapsed.
When the system is disturbed, the instantaneous frequency can visually reflect the disturbed degree of the system. The power system generally has various unstable states, for example, the system signal is an off-nominal voltage or current signal, contains harmonics, has a step change, is modulated by other sine or cosine signals, includes an attenuated dc offset current component, and includes additive white gaussian noise interference, which all cause the instability of the power system, thereby affecting the frequency. The accurate estimation of the instantaneous frequency of the power system, particularly the instantaneous frequency estimation and tracking capability during the dynamic change of the system, is a key problem considered by a frequency measurement system of the power system, and is a technical basis for avoiding possible power system faults and losses caused by the reduction of the frequency quality.
The conventional fourier transform method is a common method in frequency monitoring, and is reliable in a stable state, but in an unstable state, the instantaneous frequency change situation is complex, so that the method can not accurately monitor the frequency any more, and therefore, a new method is necessary to monitor the instantaneous frequency, thereby fundamentally solving the problem of possible power system failure and loss caused by reduced frequency quality.
Disclosure of Invention
Therefore, the invention provides a method and a system for monitoring instantaneous frequency of an electric power system, which can accurately estimate the instantaneous frequency of a sampling point by acquiring an initial sampling data set and carrying out iterative processing on data in the data set.
The technical scheme for solving the technical problems is as follows:
a power system instantaneous frequency monitoring method comprises the following steps:
s1, initial frequency f according to power system0Setting a sampling frequency f;
s2, sampling the power system by adopting the sampling frequency f to obtain an initial sampling data set, wherein elements in the initial sampling data set are formed by data pairs, and one data pair comprises a sampling time point and an electrical signal measured at the sampling time point;
s3, obtaining a first time frequency estimated value of a first time point in the initial sampling data set according to the initial sampling data set
S4, first estimating value by using the frequencyIn place of the saidRepeating the steps S2 and S3 to obtain a second time frequency estimation value of the first time point
S5, sequentially acquiring next frequency estimation values according to the method in S4, and stopping acquiring the next frequency estimation values when the frequency of acquiring the frequency estimation values reaches a preset frequency or the difference value between adjacent frequency estimation values is not more than a preset threshold value;
s6, taking the frequency estimation value obtained at the last time as the instantaneous frequency value of the first sampling moment in the initial sampling data set;
and S7, acquiring the instantaneous frequency value of each sampling moment according to the method in S1-S6, and judging whether the instantaneous frequency value falls into the frequency range allowed by the power system, if so, continuing to monitor, and if not, prompting that the frequency is abnormal.
Preferably, S3 includes the following steps:
s11, obtaining a transition parameter X according to the initial sampling data set1And X2Wherein A1Andis an initial amplitude and an initial phase of the electrical signal;
s12, obtaining the first time frequency estimation value according to the transition parameter
Wherein,
if it isOrIs provided withOtherwise
Preferably, the number of elements in the initial sample data set is greater than 2.
Preferably, the sampling frequency in S2 satisfies the formula, f ≧ 2Hhf0，HhIs the highest harmonic order contained in the electrical signal.
Preferably, before sampling in S2, the electrical signal is passed through a low pass filter for frequencies above Hhf0Filtering out the signal.
Preferably, the electrical signal comprises a voltage signal or a current signal.
An instantaneous frequency monitoring system of an electric power system comprises a sampling frequency setting module, a sampling module, a frequency estimation value acquisition module, a frequency estimation value judgment module, an instantaneous value output module and an instantaneous value legality judgment module,
the sampling frequency setting module is used for setting the initial frequency f according to the power system0The sampling frequency f is set to a predetermined value,
the sampling module is used for sampling the power system to obtain an initial sampling data set,
the frequency estimation value acquisition module is used for acquiring a frequency estimation value and transmitting the frequency estimation value to the frequency estimation value judgment module, the frequency estimation value judgment module judges whether the frequency estimation value meets the condition of being an instantaneous frequency value, if not, the frequency estimation value acquisition module is driven to continuously acquire the next frequency estimation value, if so, the last acquired frequency estimation value is transmitted to the instantaneous value output module,
the instantaneous value output module is used for transmitting the frequency estimation value obtained last time as an instantaneous frequency value to the instantaneous value validity judging module,
the instantaneous value validity judging module is used for judging whether the instantaneous frequency value falls into a frequency range allowed by the power system, if so, the monitoring is continued, and if not, the frequency abnormality is prompted.
Preferably, the frequency estimation value obtaining module obtains the frequency estimation value by using the method in S3 in the power system instantaneous frequency monitoring method described herein.
Preferably, the sampling frequency set by the sampling frequency setting module satisfies the formula, and f is more than or equal to 2Hhf0，HhIs the highest harmonic order contained in the electrical signal.
Preferably, a low pass filter is further included for applying a frequency higher than Hhf0Before entering the sampling module.
The invention has the beneficial effects that:
the invention provides a method and a system for monitoring instantaneous frequency of an electric power system, which can accurately estimate the instantaneous frequency of a sampling point by acquiring an initial sampling data set and performing iterative processing on data in the data set.
Drawings
FIG. 1 is a flow chart of a method of obtaining instantaneous frequency of a power system.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings.
In one embodiment, a method for monitoring instantaneous frequency of a power system, wherein an instantaneous frequency acquisition method is shown in fig. 1, the detection method comprises the following steps:
s1, setting the sampling frequency to be 720Hz according to the initial frequency of the power system to be 60 Hz;
s2, sampling the power system by adopting the sampling frequency to obtain an initial sampling data set, wherein elements in the initial sampling data set are formed by data pairs, and one data pair comprises a sampling time point and a voltage signal measured at the sampling time point;
s3, obtaining a first time frequency estimated value of a first time point in the initial sampling data set according to the initial sampling data set
S4, first estimating value by using the frequencyReplacing the initial frequency, repeating the steps S2, S3, and obtaining a second time frequency estimation value of the first time point
S5, sequentially acquiring next frequency estimation values according to the method in S4, and stopping acquiring the next frequency estimation values when the frequency of acquiring the frequency estimation values reaches a preset frequency or the difference value between adjacent frequency estimation values is not more than a preset threshold value;
s6, taking the frequency estimation value obtained at the last time as the instantaneous frequency value of the first sampling moment in the initial sampling data set;
and S7, acquiring the instantaneous frequency value of each sampling moment according to the method in S1-S6, and judging whether the instantaneous frequency value falls into the frequency range allowed by the power system, if so, continuing to monitor, and if not, prompting that the frequency is abnormal.
Wherein S3 includes the following steps:
s31, obtaining a transition parameter X according to the initial sampling data set1And X2Wherein A1Andis an initial amplitude and an initial phase of the electrical signal;
s32, obtaining the first time frequency estimation value according to the transition parameterWherein，
If it isOrIs provided withOtherwise
The number of elements in the initial sampling data set is more than 2, and the purpose is to increase the number of transition parameters, so that an over-determined equation set is established, and the measurement precision is improved.
In order to verify the performance of the instantaneous frequency acquisition method, the input instantaneous frequency of a signal to be detected is known to be 65Hz, the signal to be detected is a sinusoidal signal and does not contain a direct current offset signal and noise, and the instantaneous frequency acquisition result of the instantaneous frequency acquisition method is shown in the table I.
TABLE instantaneous frequency acquisition 1 (f)input＝65Hz)
In another embodiment of the present invention, the sampling frequency and the initial frequency are the same using the method of the first embodiment, the test signal is a sinusoidal signal without dc offset and noise, and the difference from the signal of the first embodiment is that the input instantaneous frequency is 55Hz, and the results of this embodiment are shown in table two.
TABLE II instantaneous frequency acquisition 1 (f)input＝55Hz)
For the method, the initial frequency influences the convergence speed of the iterative process, that is, the reasonable setting of the initial frequency can accelerate the operation speed of the method.
In a third embodiment, a power system instantaneous frequency monitoring system includes a low pass filter, a sampling frequency setting module, a sampling module, a frequency estimation value obtaining module, a frequency estimation value determining module, an instantaneous value output module, and an instantaneous value validity determining module,
the sampling frequency setting module is used for setting the initial frequency f according to the power system0The sampling frequency f is set to a predetermined value,
the sampling module is used for sampling the power system to obtain an initial sampling data set,
the frequency estimation value acquisition module is used for acquiring a frequency estimation value and transmitting the frequency estimation value to the frequency estimation value judgment module, the frequency estimation value judgment module judges whether the frequency estimation value meets the condition of being an instantaneous frequency value, if not, the frequency estimation value acquisition module is driven to continuously acquire the next frequency estimation value, if so, the last acquired frequency estimation value is transmitted to the instantaneous value output module,
the instantaneous value output module is used for transmitting the frequency estimation value obtained last time as an instantaneous frequency value to the instantaneous value validity judging module,
the instantaneous value validity judging module is used for judging whether the instantaneous frequency value falls into a frequency range allowed by the power system, if so, the monitoring is continued, and if not, the frequency abnormality is prompted.
The frequency estimation value obtaining module obtains the frequency estimation value by using the method in S3 in the method for monitoring the instantaneous frequency of the power system in the present embodiment.
The sampling frequency set by the sampling frequency setting module meets the formula, and f is more than or equal to 2Hhf0，HhIs the highest harmonic order contained in the electrical signal. The low pass filter is used for increasing the frequency to be higher than Hhf0Before entering the sampling module.
The above disclosure is only for the purpose of illustrating the preferred embodiments of the present invention, and it is therefore to be understood that the invention is not limited by the scope of the appended claims.
Claims (4)
1. A method for monitoring instantaneous frequency of a power system is characterized by comprising the following steps:
s1, initial frequency f according to power system0Setting a sampling frequency f;
s2, sampling the power system by adopting the sampling frequency f to obtain an initial sampling data set, wherein elements in the initial sampling data set are formed by data pairs, and one data pair comprises a sampling time point and an electrical signal measured at the sampling time point;
s3, according to the initial samplingThe data set obtains a first frequency estimate for a first time point in said initial sample data set
S4, using the first frequency estimation valueReplacing the initial frequency, repeating the steps S2, S3, and obtaining a second time frequency estimation value of the first time point
S5, sequentially acquiring next frequency estimation values according to the method in S4, and stopping acquiring the next frequency estimation values when the frequency of acquiring the frequency estimation values reaches a preset frequency or the difference value between adjacent frequency estimation values is not more than a preset threshold value;
s6, taking the frequency estimation value obtained at the last time as the instantaneous frequency value of the first sampling moment in the initial sampling data set;
s7, acquiring the instantaneous frequency value of each sampling moment according to the method in S1-S6, and judging whether the instantaneous frequency value falls into the frequency range allowed by the power system, if so, continuing to monitor, and if not, prompting that the frequency is abnormal;
wherein the sampling frequency in S2 satisfies the formula, f is not less than 2Hhf0，HhIs the highest harmonic order contained in the electrical signal;
and passing the electrical signal through a low pass filter for passing frequencies above H before sampling in S2hf0Filtering out the signal.
2. The method of claim 1, wherein the number of elements in the initial sample data set is greater than 2.
3. The method of claim 1, wherein the electrical signal comprises a voltage signal or a current signal.
4. An instantaneous frequency monitoring system of an electric power system is characterized by comprising a sampling frequency setting module, a sampling module, a frequency estimation value acquisition module, a frequency estimation value judgment module, an instantaneous value output module and an instantaneous value legality judgment module,
the sampling frequency setting module is used for setting the initial frequency f according to the power system0The sampling frequency f is set to a predetermined value,
the sampling module is used for sampling the power system to obtain an initial sampling data set,
the frequency estimation value acquisition module is used for acquiring a frequency estimation value and transmitting the frequency estimation value to the frequency estimation value judgment module, the frequency estimation value judgment module judges whether the frequency estimation value meets the condition of being an instantaneous frequency value, if not, the frequency estimation value acquisition module is driven to continuously acquire the next frequency estimation value, if so, the last acquired frequency estimation value is transmitted to the instantaneous value output module,
the instantaneous value output module is used for transmitting the frequency estimation value obtained last time as an instantaneous frequency value to the instantaneous value validity judging module,
the instantaneous value validity judging module is used for judging whether the instantaneous frequency value falls into a frequency range allowed by the power system, if so, continuing to monitor, and if not, prompting that the frequency is abnormal;
the sampling frequency set by the sampling frequency setting module meets the formula, and f is more than or equal to 2Hhf0，HhIs the highest harmonic order contained in the electrical signal; further comprising a low pass filter for applying a frequency higher than Hhf0Before entering the sampling module.
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| CN106053936B (en) * | 2016-06-17 | 2019-05-14 | 海南大学 | A kind of method and system obtaining electrical signal instantaneous frequency |
| CN106896338B (en) * | 2017-04-17 | 2019-06-25 | 南京国电南自电网自动化有限公司 | A kind of system based on combining unit identification abnormal data |
| CN110401190B (en) * | 2019-07-25 | 2023-04-07 | 福建睿思特科技股份有限公司 | Real-time frequency detection and identification system for power system |
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| CN103809023A (en) * | 2014-01-26 | 2014-05-21 | 西南交通大学 | Grid synchronization harmonic phasor measurement method based on binary search |
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| JP2622284B2 (en) * | 1989-03-15 | 1997-06-18 | 日本放送協会 | Frequency range detector |
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Patent Citations (8)
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|---|---|---|---|---|
| US4310800A (en) * | 1979-11-07 | 1982-01-12 | General Motors Corporation | Digital frequency measuring circuitry |
| CN1983806A (en) * | 2005-12-13 | 2007-06-20 | 索尼株式会社 | Signal processing apparatus and signal processing method |
| CN101650385A (en) * | 2009-09-11 | 2010-02-17 | 江苏斯菲尔电气有限公司 | Method for modifying sampling frequency with electrical network instrument |
| CN103575980A (en) * | 2012-07-26 | 2014-02-12 | 施耐德电器工业公司 | System frequency measurement method and synchronous phasor measurement method and device |
| CN102982344A (en) * | 2012-11-12 | 2013-03-20 | 浙江大学 | Support vector machine sorting method based on simultaneously blending multi-view features and multi-label information |
| CN103399203A (en) * | 2013-08-09 | 2013-11-20 | 重庆大学 | High-precision harmonic parameter estimation method based on composite iterative algorithm |
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