CN103185837A - Method for measuring frequency of power system - Google Patents
Method for measuring frequency of power system Download PDFInfo
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- CN103185837A CN103185837A CN2013100966991A CN201310096699A CN103185837A CN 103185837 A CN103185837 A CN 103185837A CN 2013100966991 A CN2013100966991 A CN 2013100966991A CN 201310096699 A CN201310096699 A CN 201310096699A CN 103185837 A CN103185837 A CN 103185837A
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Abstract
The invention provides a method for measuring the frequency of a power system, which is mainly applied to a power system. The method comprises the steps of sampling input signals at intervals to obtain discrete equally-spaced sampling points; carrying out direct current filtration on the equally-spaced sampling points; accumulating the discrete points slightly exceeding a fundamental wave period point number by taking a point near a peak value as a starting point for the filtered data, if the accumulated sum is zero, recording the last point, and if the accumulated sum is not zero, sequentially reducing from the last point until the accumulated sum reverses, and recording the point enabling the accumulated sum to reverse; and determining the period of a measured signal through the recorded point, the sampling interval number between the point and the starting point and the reversed accumulated sum to obtain a frequency value. According to the method, the theoretical basis is that an upper integral of a trigonometric function on a fundamental wave period is zero, higher harmonics are not needed to be filtered, the anti-interference is strong, the realization is simple, and the accuracy, the reliability and the rapidness of fundamental wave frequency measurement are improved.
Description
Technical field
The present invention relates to a kind of measuring technique that is applied to electric system, specifically a kind of method of power system frequency measurement.
Background technology
Frequency is the important parameter of reflection operation states of electric power system.
The conventional frequency measuring method mainly contains hardware frequency measurement and two kinds of methods of software frequency measurement.Hardware frequency measurement principle is with after the measured signal process wave filter filtering harmonic component, sinusoidal signal after will nursing one's health again converts the square-wave signal of same frequency to by voltage comparator, catch the rising edge of square wave after the shaping and negative edge constantly by digital processing unit at last, pass through rolling counters forward and simple mathematical computing again, thereby obtain the frequency of measured signal.The hardware frequency measuring method very easily is subjected to the influence of harmonic wave and undesired signal, and the precision of measuring in containing the electric system of enriching harmonic wave is difficult to be guaranteed.The software frequency measuring method is to carry out mathematical analysis and calculating by sampled value to measured signal, adopts certain algorithm to obtain the method for frequency parameter.In traditional software frequency measuring method, the voltage over zero algorithm is easier to realize, but zero crossing will definitely not attract error; Some software frequency measurement algorithm operation quantity is excessive.
Summary of the invention
The objective of the invention is in order to overcome above-mentioned the deficiencies in the prior art part, the method that provides a kind of power system frequency to measure, it can effectively solve problems such as low precision that the common frequencies measuring method occurs, low-response in application process, improved the measurement noise immunity.
The objective of the invention is to realize by following technical measures.
The method that a kind of power system frequency is measured, this method may further comprise the steps:
(1) input signal to measured signal carries out equal interval sampling, obtains the discrete equal interval sampling point of measured signal; Described measured signal is voltage or current signal;
(2) the equal interval sampling point being carried out DC filtering handles;
(3) to filtered sampled point, with the sampled value that slightly surpasses the sampled point that a primitive period counts add up obtain adding up and, if add up and be zero just, the total sampling interval time that then participates in the sampled point that adds up is the measured signal cycle; If add up with non-vanishing, then reject last sampled point that participation adds up successively, until adding up and reversion comprises by negative and just becoming or by just becoming negative or becoming zero by non-zero, this tense marker participates in last sampled point k of adding up, and the sampling interval of noting between the starting point of the sampled point that this point and participation add up is counted N
2And adding up and S after the reversion;
(4) count N according to the sampled point k of mark, the sampling interval of record
2And adding up after the reversion determined cycle and the frequency of measured signal with S.
In technique scheme, the equal interval sampling point carried out the concrete mode that DC filtering handles handle the direct current signal in the filtering input signal for using digital filter that sampled point is carried out DC filtering described in the step (2).
In technique scheme, determine that the concrete mode of measured signal cycle and frequency is:
(A) as if adding up and being zero just, total sampling interval number of all sampled points that the participation of recording this moment adds up is N
1, then use formula
Determine the fundamental frequency value, f is frequency values, t
sBe the sampling interval time between adjacent two sampled points;
(B) if add up with non-vanishing, by rejecting last sampled point that participation adds up successively, until adding up and reversion, the sampled value of last sampled point k that the participation of record at this moment adds up is X
k, the sampled point add up of this point and participate in starting point between the sampling interval number be N
2, adding up and be S after the reversion
(B-1) as if adding up and by rejecting last sampled point that participation adds up successively, until adding up and being zero, then using formula
Determine the fundamental frequency value, f is frequency values, t
sBe the sampling interval time between adjacent two sampled points;
(B-2) if add up and last sampled point by reject participating in successively adding up, until adding up and by just becoming negative or just being become by negative, then using formula
Determine the fundamental frequency value, described
, f is frequency values, t
sBe the sampling interval time between adjacent two sampled points.
In technique scheme, the sampling number that participation adds up, namely the sampling number of slightly counting above a primitive period is defined as
And round t
sBe the sampling interval time between adjacent two sampled points.
In the frequency measurement method provided by the invention, owing to only need the DC component of filtering measured signal, do not need the filtering higher hamonic wave, so strong interference immunity, realize simply effectively eliminating the interference of actual electric network harmonic wave in service, improved accuracy and the rapidity of measuring fundamental frequency.
Description of drawings
Fig. 1 is that the sampled value of all sampled points that participation adds up in the inventive method adds up and the exemplary plot that is 0 just.
Fig. 2 is that the sampled value that participates in all sampled points add up in the inventive method adds up and is not 0, but participates in last sampled point of adding up by rejecting successively, adds up and can become 0 exemplary plot.
Fig. 3 is that the sampled value that participates in all sampled points add up in the inventive method adds up and is not 0, participates in last sampled point of adding up by rejecting successively, adds up and by just becoming negative or becoming positive exemplary plot by negative.
Embodiment
Below in conjunction with accompanying drawing the present invention is described in further detail.
Essence of the present invention is to adopt rectangle method equivalent point, seeks to make and adds up and be zero point and total sampling interval and then the calculated rate of starting point; Under the situation that can realize, sampling interval t
sMore little, calculate more accurate, but calculated amount can increase thereupon, therefore, the user chooses suitable sampling interval according to actual conditions and calculates.
The concrete implementation step of the inventive method is as follows:
(1) input signal to measured signal carries out equal interval sampling, obtains the discrete equal interval sampling point of measured signal;
(2) use digital filter that sampled point is carried out DC filtering and handle the direct current signal in the filtering input signal;
(3) to filtered sampled point, adopt the rectangular integration method, be starting point with near the point the peak value, with the sampled value that slightly surpasses the sampled point that a primitive period counts add up obtain adding up and, determining of the sampling number that participation adds up: because the frequency of normal electrical network can not be lower than 45Hz, so the sampling number that participates in adding up can be defined as
And round; If add up be zero just, the total sampling interval time that then participates in the sampled point that adds up is the measured signal cycle; If add up with non-vanishing, then reject last sampled point that participation adds up successively, until adding up and reversion comprises by negative and just becoming or by just becoming negative or becoming zero by non-zero, this tense marker participates in last sampled point k of adding up, and the sampling interval of noting between the starting point of the sampled point that this point and participation add up is counted N
2And adding up and S after the reversion;
(4) count N according to the sampled point k of mark, the sampling interval of record
2And adding up after the reversion determined cycle and the frequency of measured signal with S.
In technique scheme, determine that the concrete mode of measured signal cycle and frequency is:
(A) as shown in Figure 1, the adding up and be zero just of M sampled point, this moment, total sampling interval number of all sampled points of adding up of participation of record was N
1, then use formula
Determine the fundamental frequency value, f is frequency values, t
sBe the sampling interval time between adjacent two sampled points, N
1=M;
(B) adding up with non-vanishing of M sampled point, by rejecting last sampled point that participation adds up successively, until adding up and reversion, the sampled value of last sampled point k that the participation of recording this moment adds up is X
k, the sampled point add up of this point and participate in starting point between the sampling interval number be N
2, adding up and be S after the reversion
(B-1) M sampled point add up and S non-vanishing, will add up and S cuts the sampled value that participates in last sampled point add up, the sampled value of penult sampled point successively ... when cutting X
kAfter add up and become 0, last sampled point k and add up and starting point between total sampling interval number be N
2, use formula this moment
Determine the fundamental frequency value, f is frequency values, t
sBe the sampling interval time between adjacent two sampled points;
(B-2) M sampled point add up and S also non-vanishing, will add up and S cuts the sampled value that participates in last sampled point of adding up, the sampled value of penult sampled point successively ... when cutting X
kAfter add up and sign modification (among this figure by just becoming negative), by the rectangular equivalent integral method
, use formula
Determine the fundamental frequency value, f is frequency values, t
sBe the sampling interval time between adjacent two sampled points.
In sum, a kind of power system frequency measuring method involved in the present invention, its theoretical foundation is that trigonometric function is zero a primitive period upper integral, do not need the filtering higher hamonic wave, simultaneously do not need to convert measured signal to square wave, strong interference immunity is realized simple, improved accuracy, reliability and rapidity that fundamental frequency is measured, application prospect has comparatively widely been arranged.
Claims (4)
1. the method measured of a power system frequency is characterized in that this method may further comprise the steps:
(1) input signal to measured signal carries out equal interval sampling, obtains the discrete equal interval sampling point of measured signal;
(2) the equal interval sampling point being carried out DC filtering handles;
(3) to filtered sampled point, with the sampled value that slightly surpasses the sampled point that a primitive period counts add up obtain adding up and, if add up and be zero just, the total sampling interval time that then participates in the sampled point that adds up is the measured signal cycle; If add up with non-vanishing, then reject last sampled point that participation adds up successively, until adding up and reversion, comprise by negative and just becoming or by just becoming negative or becoming zero by non-zero, this tense marker participates in last sampled point k of adding up, and the sampling interval of noting between the starting point of the sampled point that this point and participation add up is counted N
2And adding up and S after the reversion;
(4) count N according to the sampled point k of mark, the sampling interval of record
2And adding up after the reversion determined cycle and the frequency of measured signal with S.
2. the method measured of a kind of power system frequency according to claim 1, it is characterized in that: the equal interval sampling point is carried out the concrete mode that DC filtering handles handle the direct current signal in the filtering input signal for using digital filter that sampled point is carried out DC filtering described in the step (2).
3. the method measured of a kind of power system frequency according to claim 1 is characterized in that the concrete mode of determining measured signal cycle and frequency is:
(A) as if adding up and being zero just, total sampling interval number of all sampled points that the participation of recording this moment adds up is N
1, then use formula
Determine the fundamental frequency value, f is frequency values, t
sBe the sampling interval time between adjacent two sampled points;
(B) if add up with non-vanishing, by rejecting last sampled point that participation adds up successively, until adding up and reversion, the sampled value of last sampled point k that the participation of record at this moment adds up is X
k, the sampled point add up of this point and participate in starting point between the sampling interval number be N
2, adding up and be S after the reversion
(B-1) as if adding up and by rejecting last sampled point that participation adds up successively, until adding up and being zero, then using formula
Determine the fundamental frequency value, f is frequency values, t
sBe the sampling interval time between adjacent two sampled points;
(B-2) if add up and last sampled point by reject participating in successively adding up, until adding up and by just becoming negative or just being become by negative, then using formula
Determine the fundamental frequency value, described
, f is frequency values, t
sBe the sampling interval time between adjacent two sampled points.
4. the method measured of a kind of power system frequency according to claim 1 is characterized in that: participate in the sampling number that adds up in the step (3), namely slightly surpass the sampling number that a primitive period counts and be defined as
And round t
sBe the sampling interval time between adjacent two sampled points.
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Cited By (11)
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| CN103913631A (en) * | 2014-04-30 | 2014-07-09 | 乐山一拉得电网自动化有限公司 | Grid frequency measuring method and system for digital display meter |
| CN104459320A (en) * | 2014-12-29 | 2015-03-25 | 广东电网有限责任公司电力科学研究院 | Power signal harmonic wave phase measurement method and system |
| CN104502675A (en) * | 2014-12-29 | 2015-04-08 | 广东电网有限责任公司电力科学研究院 | Fundamental wave amplitude method and system of power signal |
| CN104569569A (en) * | 2015-01-20 | 2015-04-29 | 天津市英贝特航天科技有限公司 | Electrical characteristic determination method for any fixed-frequency AC |
| CN104614586A (en) * | 2015-01-13 | 2015-05-13 | 上海惠安***控制有限公司 | GPS-based self-adaptive sampling method for electric quantity signals |
| CN104808054A (en) * | 2014-01-26 | 2015-07-29 | 南京邮电大学 | Method for measuring the frequency of electrical signals |
| CN104808055A (en) * | 2014-01-26 | 2015-07-29 | 南京邮电大学 | Electrical signal frequency digitized measurement method |
| CN106597092A (en) * | 2016-10-13 | 2017-04-26 | 江苏海事职业技术学院 | High-precision anti-interference fixed-point computer three-phase voltage frequency measurement phase-locking algorithm |
| CN107271770A (en) * | 2017-07-19 | 2017-10-20 | 乐山拉得电网自动化有限公司 | Digital measuring method for measuring frequency in power circuit |
| CN108876088A (en) * | 2018-04-19 | 2018-11-23 | 国电南京自动化股份有限公司 | A kind of effective value calculating method of electrical quantity based on integral algorithm |
| CN109188076A (en) * | 2018-09-28 | 2019-01-11 | 北京金风科创风电设备有限公司 | Frequency measurement device, method, apparatus and storage medium |
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| CN104808054B (en) * | 2014-01-26 | 2017-09-22 | 南京邮电大学 | A kind of measuring method of signal frequency |
| CN104808054A (en) * | 2014-01-26 | 2015-07-29 | 南京邮电大学 | Method for measuring the frequency of electrical signals |
| CN104808055A (en) * | 2014-01-26 | 2015-07-29 | 南京邮电大学 | Electrical signal frequency digitized measurement method |
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| CN104459320A (en) * | 2014-12-29 | 2015-03-25 | 广东电网有限责任公司电力科学研究院 | Power signal harmonic wave phase measurement method and system |
| CN104502675A (en) * | 2014-12-29 | 2015-04-08 | 广东电网有限责任公司电力科学研究院 | Fundamental wave amplitude method and system of power signal |
| CN104502675B (en) * | 2014-12-29 | 2017-05-24 | 广东电网有限责任公司电力科学研究院 | Fundamental wave amplitude method and system of power signal |
| CN104614586A (en) * | 2015-01-13 | 2015-05-13 | 上海惠安***控制有限公司 | GPS-based self-adaptive sampling method for electric quantity signals |
| CN104614586B (en) * | 2015-01-13 | 2019-01-18 | 上海惠安***控制有限公司 | A kind of electrical quantity signal adaptive method of sampling based on GPS |
| CN104569569A (en) * | 2015-01-20 | 2015-04-29 | 天津市英贝特航天科技有限公司 | Electrical characteristic determination method for any fixed-frequency AC |
| CN104569569B (en) * | 2015-01-20 | 2019-03-01 | 天津市英贝特航天科技有限公司 | Arbitrarily determine the electrical characteristic measuring method of frequency alternating current |
| CN106597092A (en) * | 2016-10-13 | 2017-04-26 | 江苏海事职业技术学院 | High-precision anti-interference fixed-point computer three-phase voltage frequency measurement phase-locking algorithm |
| CN107271770A (en) * | 2017-07-19 | 2017-10-20 | 乐山拉得电网自动化有限公司 | Digital measuring method for measuring frequency in power circuit |
| CN108876088A (en) * | 2018-04-19 | 2018-11-23 | 国电南京自动化股份有限公司 | A kind of effective value calculating method of electrical quantity based on integral algorithm |
| CN109188076A (en) * | 2018-09-28 | 2019-01-11 | 北京金风科创风电设备有限公司 | Frequency measurement device, method, apparatus and storage medium |
| CN109188076B (en) * | 2018-09-28 | 2021-01-29 | 北京金风科创风电设备有限公司 | Frequency measurement device, method, apparatus and storage medium |
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