CN108957133A - The dynamic evaluation of substation capacitors sample frequency and choosing method - Google Patents
The dynamic evaluation of substation capacitors sample frequency and choosing method Download PDFInfo
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- CN108957133A CN108957133A CN201810914463.7A CN201810914463A CN108957133A CN 108957133 A CN108957133 A CN 108957133A CN 201810914463 A CN201810914463 A CN 201810914463A CN 108957133 A CN108957133 A CN 108957133A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R23/00—Arrangements for measuring frequencies; Arrangements for analysing frequency spectra
- G01R23/16—Spectrum analysis; Fourier analysis
- G01R23/165—Spectrum analysis; Fourier analysis using filters
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R23/00—Arrangements for measuring frequencies; Arrangements for analysing frequency spectra
- G01R23/16—Spectrum analysis; Fourier analysis
- G01R23/165—Spectrum analysis; Fourier analysis using filters
- G01R23/167—Spectrum analysis; Fourier analysis using filters with digital filters
Abstract
The invention discloses a kind of substation capacitors sample frequency dynamic evaluation and choosing methods, analogue low pass filtering is carried out to line voltage using hardware frequency measurement circuit, and interference of the harmonic wave to zero crossing is removed in data processing, it realizes that the high-precision of real-time frequency is obtained to sample with frequency-tracking, guarantees the precision of frequency analysis.
Description
Technical field
The present invention relates to intelligent substation fields, especially capacitor harmonic protection technology.
Background technique
With the development of electric system and the extensive application of power electronic technique, network load structure has occurred great
Variation.The non-linear electrical equipments such as variable-frequency motor, high power electronic equipment, size thyristor voltage regulator increase significantly, power grid
Power quality environment is worsening, and bring power grid public hazards-harmonic pollution have seriously affected itself and coupled electricity
The operational safety of net equipment.
Intelligent substation degree is increasingly improved with the development of power grid, to the switching operation demand of capacitor group also day
Benefit improves, but due to the harmonic pollution of power grid, traditional shunt capacitor group running environment is more and more harsher, Frequent Troubles,
Seriously affect the operational safety of capacitor itself and the other equipment of power grid connected to it.
The further insulating medium loss that harmonic current may cause power capacitor increases, and temperature increases, and accelerates capacitor
Insulation ag(e)ing, or even overheat is caused to damage capacitor；Shelf depreciation caused by harmonic voltage can seriously affect making for capacitor
With the service life, it can also make capacitor bulging, breakdown or explosion.
It, will be in inductance (system sense if close or identical with certain subfrequency in higher hamonic wave with intrinsic frequency
It is anti-), cause in capacitor (compensation device) shunt circuit the Current Voltage of the subharmonic to amplify or even resonance, so that the subharmonic is existed
Harm aggravation in electric system.
A large amount of capacitor group operation data shows the access with nonlinear-loads such as a large amount of frequency conversion equipments of power grid, electricity
Net harmonic pollution is got worse, in power grid capacitor group because caused by Harmfulness Caused by Harmonics accident it is more and more, per average annual in power grid
The failure generation for having a lot of capacitor group overloads, burning.
A large amount of presence of harmonic wave and the use of frequency conversion equipment cause voltage waveform phenomena such as voltage interruption occur, influence
The zero crossing of voltage current waveform affects the correctness and precision of harmonic protection movement.
In, transition effect is mistakenly considered harmonic distortion often by harmonic protection implementation.The measured waveform of transient process
Characteristic with obvious high fdrequency component, but transient state and harmonic wave are two entirely different phenomenons.Electric system is by unexpected
The distorted waveform bring high fdrequency component occurred after disturbance is unrelated with system fundamental frequency.
Although the variation and periodicity of the instantaneous values such as trap or commutation notch that current converter occurs in commutation,
But it is not belonging to harmonic wave scope.
Current capacitor protection error is larger, without the faulty action preventing strategy of corresponding transient event, when transient state occurs in system
When disturbance, it is easy to appear the malfunction of protective device.
When frequency persistently changes, due to the intrinsic hysteresis characteristic of frequency-tracking, biggish spectral leakage can be generated.?
When there is more serious distortion in frequency measurement signal circuit, it will zero crossing offset or continuous zero crossing occur, made to the measurement of frequency
At serious interference, real-time frequency can not be obtained by even resulting in.General power quality analysis device is using longer period of time
Mean value overcomes above-mentioned influence to obtain frequency, and the data window of frequency acquisition is longer, there are the hysteresis quality of long period, nothings
Method meets the real-time quick requirement of protective device.If sample frequency and actual frequency are inconsistent will to will lead to frequency analysis
Error increases, and deviation will will lead to false protection afterwards to a certain extent.
Summary of the invention
The technical problem to be solved by the invention is to provide a kind of substation capacitors sample frequency dynamic evaluation and choosings
Method is taken, guarantees the consistency of sample frequency and actual frequency, solving electric system, there are the protection of transient event time-harmonic wave is possible
The problem of malfunction.
In order to solve the above technical problems, the present invention adopts the following technical scheme: substation capacitors sample frequency dynamic is commented
Estimate and choosing method, it is characterised in that comprise the steps of:
Step 1), hardware frequency measurement circuit carry out analogue low pass filtering to line voltage, filter out frequent mistake caused by harmonic distortion
Zero point and zero crossing deviate the influence to hardware frequency measurement；
Step 2), hardware frequency measurement circuit trigger protection device external interrupt in zero crossing record zero passage point moment, protect
Protection unit calculates Real-time hardware frequency measurement frequency f by being recorded twice the time difference of equidirectional zero crossingh；
Step 3) utilizes the formula of variance
Calculate nearest 5 fhVariance Sh 2；
Step 4) is sampled to by the voltage of protective condenser, electric current；
Step 5) carries out bad point and low-pass digital filter to sampled data, removes the bad point of AD conversion and filters out
Distortion effects of the higher hamonic wave to waveform；
Step 6) finds the sampled point n for passing through zero crossing in sampled value1> 0, n2>=0, n3< 0, n4< 0 or n1< 0,
n2≤ 0, n3> 0, n4> 0, wherein n1, n2, n3, n4For continuous sampling point, and t at the time of record four sampled points respectively1,
t2, t3, t4；
Step 7) utilizes formula
Calculate zero crossing t0；
Step 8) calculates frequency measurement frequency f using the time difference for the zero crossing twice in succession that last computation goes outsAB,
fsBC, fsCA；
Step 9) utilizes formula of variance again
Calculate nearest 5 SsAB, fsBC, fsCAVariance SsAB 2, SsBC 2, SsCA 2；
Step 10) chooses Sh 2, SsAB 2, SsBC 2, SsCA 2In minimum value
Shmin 2=min { Sh 2, SsAB 2, SsBC 2, SsCA 2Corresponding frequency f；
Step 11) adjusts systematic sampling interval using the f found out.
The present invention carries out analogue low pass filtering to line voltage using hardware frequency measurement circuit, and removes in data processing humorous
Interference of the wave to zero crossing is realized that the high-precision of real-time frequency is obtained and is sampled with frequency-tracking, guarantee the precision of frequency analysis.
Specific embodiment
The method that harmonic protection of the present invention is specifically described below:
A kind of capacitor harmonic protection method, including
Voltage, electric current for protected capacitor group are sampled；
Low-pass digital filter is carried out to the data of sampling；
The virtual value of three-phase voltage or electric current is calculated in real time, and calculates the absolute value of the variation of the virtual value in 5ms and have
The ratio of valid value variation；
The ratio for absolute value and the virtual value variation that the virtual value of three-phase voltage or electric current changes in 5ms, which is greater than, to be set
When definite value, it is latched harmonic protection.
Wherein, collective frequency Sudden Changing Rate and sliding window minimum variation algorithm, from hardware frequency measurement, three-phase voltage software
Final sampling frequency is filtered out in frequency measurement.
When there is more serious distortion in frequency measurement signal circuit, it will zero crossing offset or continuous zero crossing occur, to frequency
The measurement of rate causes serious interference, and real-time frequency can not be obtained by even resulting in.General power quality analysis device use is longer
The mean value of a period of time overcomes above-mentioned influence to obtain frequency, and the data window of frequency acquisition is longer, and there are the long periods
Hysteresis quality is unable to satisfy the real-time quick requirement of protective device.If sample frequency and actual frequency be inconsistent will will lead to it is humorous
The error of wave analysis increases, and deviation will will lead to false protection afterwards to a certain extent.To solve the above-mentioned problems, device is being surveyed
Specialized hardware low-pass filtering is used on frequency circuit, and using high performance digital filter extraction element in data processing
Fundametal compoment removes interference of the harmonic wave to zero crossing, realizes that the high-precision of real-time frequency is obtained and samples with frequency-tracking, guarantees
The precision of frequency analysis.
Dynamic evaluation and selection real-time frequency include following steps:
Hardware frequency measurement circuit to line voltage carry out analogue low pass filtering, filter out frequent zero crossing caused by harmonic distortion with
And zero crossing deviates the influence to hardware frequency measurement.
Hardware frequency measurement circuit trigger protection device external interrupt in zero crossing records zero passage point moment, protective device
Time difference by being recorded twice equidirectional zero crossing calculates Real-time hardware frequency measurement frequency fh。
Utilize the formula of variance
Calculate nearest 5 fhVariance Sh 2；
It is sampled to by the electric current of protective condenser, voltage.
Bad point and FIR low-pass digital filter are carried out to sampled data, removes the bad point of AD conversion and filters out high order
Distortion effects of the harmonic wave to waveform.
The sampled point n for passing through zero crossing is found in sampled value1> 0, n2>=0, n3< 0, n4< 0 or n1< 0, n2≤ 0,
n3> 0, n4> 0, wherein n1, n2, n3, n4For continuous sampling point, and t at the time of record four sampled points respectively1, t2；t3,
t4。
Utilize formula
Calculate zero crossing t0。
Using the time difference of the calculated zero crossing twice in succession of previous step, frequency measurement frequency f is calculatedsAB, fsBC,
fsCA。
Formula of variance is utilized again
Calculate nearest 5 fsAB, fsBC, fsCAVariance SsAB 2, SsBC 2, SsCA 2；
Choose Sh 2, SsAB 2, SsBC 2, SsCA 2In minimum value
Shmin 2=min { Sh 2, SsAB 2, SsBC 2, SsCA 2}
Corresponding frequency f.
Systematic sampling interval is adjusted using the f found out.
Calculating three-phase voltage and current effective value variable quantity and change rate includes following steps:
Acquire three-phase voltage and electric current, FIR low-pass digital filter carried out to collected data, prevent High-frequency Interference or
The aliasing of noise signal.
FormulaAndTo the three-phase electricity after low-pass filtered
Pressure and electric current carry out virtual value calculating and remember.
It uses againAndIt calculates current voltage and electric current is effective
Value.
Calculate current voltage virtual value UrmsWith current effective value IrmsWith voltage effective value U before 5msrmspre5Or electric current has
Valid value Irspre5The absolute value of difference DELTA U and Δ I.
| Δ U |=| Urms-Urmspre5|
| Δ I |=| Irms-Irmspre5|
Calculate current voltage and current effective value and voltage or current effective value changing ratio before 5msWithIt is absolute
Value.
It utilizes discrete fourier algorithm (DFT)
Calculate n times harmonic voltage and current amplitude.
According to formulaWherein U1For voltage fundamental value, voltage is calculated
Total harmonic distortion.
According to formula,Wherein I1For current first harmonics value, calculating current
Total harmonic distortion.
Prevent the method logic of computer-based harmonic false protection as follows:
When | Δ U | 0.01 × N of > × U (n)set, the protection of locking n times voltage harmonic and voltage effective value are protected.
When | Δ I | 0.01 × N of > × I (n)set, the protection of locking n times current harmonics and current effective value are protected.
WhenThe protection of blocking voltage aberration rate.
WhenThe protection of latching current aberration rate.
On this basis, the present invention offer single harmonic component voltage, electric current, voltage effective value, current effective value, voltage are abnormal
Variability, the harmonic protections function such as current distortion rate have very high protection act precision and correctness, while can prevent capacitor
The malfunction of device harmonic protection provides better harmonic protection function for power capacitor device.To sum up the present invention has and has as follows
Beneficial effect:
1, hardware frequency measurement is carried out to the line voltage channel of protected capacitor group, effectively reduces the common mode in phase voltage
The influence of interference and 3N subharmonic to frequency-measurement accuracy.
2, frequency measurement meter is carried out after digital low-pass filtering to the voltage sample data of protected capacitor group
It calculates, prevents hardware frequency-survey loop from being influenced system sampling frequency precision by the interference failure of the transient events such as voltage interruption.
3, according to true frequency, the dynamic debugging system sampling interval prevents the calculating error of non-synchronous sampling from letting out with frequency spectrum
Dew.
4, by the virtual value and each harmonic component of the real-time calculating current voltage channel of sliding window, it ensure that harmonic wave
The quick-action of protection.
5, the selectivity and reliability of harmonic protection be ensure that by means such as Sudden Changing Rate lockings.
Claims (1)
1. the dynamic evaluation of substation capacitors sample frequency and choosing method, it is characterised in that comprise the steps of:
Step 1), hardware frequency measurement circuit carry out analogue low pass filtering to line voltage, filter out frequent zero crossing caused by harmonic distortion
And zero crossing deviates the influence to hardware frequency measurement；
Step 2), hardware frequency measurement circuit trigger protection device external interrupt in zero crossing record zero passage point moment, protection dress
It sets and Real-time hardware frequency measurement frequency f is calculated by the time difference for being recorded twice equidirectional zero crossingh；
Step 3) utilizes the formula of variance
Calculate nearest 5 fhVariance Sh 2；
Step 4) is sampled to by the voltage of protective condenser, electric current；
Step 5) carries out bad point and low-pass digital filter to sampled data, removes the bad point of AD conversion and filters out high order
Distortion effects of the harmonic wave to waveform；
Step 6) finds the sampled point n for passing through zero crossing in sampled value1> 0, n2>=0, n3< 0, n4< 0 or n1< 0, n2≤
0, n3> 0, n4> 0, wherein n1, n2, n3, n4For continuous sampling point, and t at the time of record four sampled points respectively1, t2, t3,
t4；
Step 7) utilizes formula
Calculate zero crossing t0；
Step 8) calculates frequency measurement frequency f using the time difference for the zero crossing twice in succession that last computation goes outsAB, fsBC,
fsCA；
Step 9) utilizes formula of variance again
Calculate nearest 5 fsAB, fsBC, fsCAVariance SsAB 2, SsBC 2, SsCA 2；
Step 10) chooses Sh 2, SsAB 2, SsBC 2, SsCA 2In minimum value
Shmin 2=min { Sh 2, SsAB 2, SsBC 2, SsCA 2Corresponding frequency f；
Step 11) adjusts systematic sampling interval using the f found out.
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Cited By (5)
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| CN109709390A (en) * | 2018-12-19 | 2019-05-03 | 深圳市中电电力技术股份有限公司 | A kind of three-phase high-precision harmonic electric energy meter |
| CN110286268A (en) * | 2019-06-17 | 2019-09-27 | 中国人民解放军陆军工程大学 | Power waveform distortion appraisal procedure based on frequency fluctuation |
| CN113253126A (en) * | 2021-04-29 | 2021-08-13 | 南方电网调峰调频发电有限公司 | Method for selecting voltage and current sampling frequency and filtering time window of battery management system |
| CN114859120A (en) * | 2022-06-17 | 2022-08-05 | 烟台东方威思顿电气有限公司 | Harmonic analysis method |
| CN115575706A (en) * | 2022-11-21 | 2023-01-06 | 保定新云达电力设备有限责任公司 | Frequency continuous tracking measurement system and method suitable for electric energy meter calibrator |
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| CN113253126A (en) * | 2021-04-29 | 2021-08-13 | 南方电网调峰调频发电有限公司 | Method for selecting voltage and current sampling frequency and filtering time window of battery management system |
| CN113253126B (en) * | 2021-04-29 | 2022-04-26 | 南方电网调峰调频发电有限公司 | Method for selecting voltage and current sampling frequency and filtering time window of battery management system |
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| CN114859120B (en) * | 2022-06-17 | 2023-09-15 | 烟台东方威思顿电气有限公司 | Harmonic Analysis Method |
| CN115575706A (en) * | 2022-11-21 | 2023-01-06 | 保定新云达电力设备有限责任公司 | Frequency continuous tracking measurement system and method suitable for electric energy meter calibrator |
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