CN104360153A - Method for detecting and analyzing harmonic waves of power grids in online manner - Google Patents
Method for detecting and analyzing harmonic waves of power grids in online manner Download PDFInfo
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- CN104360153A CN104360153A CN201410564986.5A CN201410564986A CN104360153A CN 104360153 A CN104360153 A CN 104360153A CN 201410564986 A CN201410564986 A CN 201410564986A CN 104360153 A CN104360153 A CN 104360153A
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Abstract
The invention discloses a method for detecting and analyzing harmonic waves of power grids in an online manner. The method includes steps of a, measuring voltage values U of two ends of each parallel capacitor, and defining s(t) as original signals; b, respectively fitting maximum values and minimum values of the original signals to obtain smooth curves and respectively denoting the maximum values and the minimum values as ma(t) and mi(t); c, computing average value curves m(t); d, computing decomposition results of the original signals; d, utilizing the decomposition results as primary decomposition results h<1>(t) of the s(t), utilizing (i-1)<th> decomposition results h<i-1>(t) of the s(t) as original signals and executing steps b, c and d again to obtain i<th> decomposition results h<i>(t) of the s(t); f, setting confidence parameters E, substituting the h<i-1>(t) and the h<i>(t) into a formula as shown in the abstract of the invention, and stopping computation if the formula is tenable; g, denoting the h<i>(t) as primary components s<1>(t) of the s(t), utilizing s(t)-s<1>(t)-...-s<j-2>(t)-s<j-1>(t) as original signals, and executing steps b, c, d, e and f again to obtain j<th> components s<j>(t) of the s(t). The s(t) meets an equation of s(t)=U. The j<th> components s<j>(t) of the s(t) represent components of the harmonic waves of the power grids.
Description
Technical field
The present invention relates to electrical engineering technical field, be specifically related to a kind of mains by harmonics on-line checkingi and analytical approach.
Background technology
Harmonic wave can cause the element in utility network to produce the harmonic loss of annex; reduce generating, transmission of electricity and the efficiency of consumer; the normal work of various electrical equipment can be affected; parallel resonance and the series resonance of local in utility network can be caused; thus make Harmonics amplification cause major accident; relay protection and aut.eq. misoperation can be caused; and it is inaccurate to make electrical measuring instrument measure; also can produce interference to the communication system of closing on; light then produce noise; reduce communication quality, heavy then cause information dropout, communication system cannot normally be worked.Harmonic wave causes various accident and probability of failure to continue to raise, and has become large public hazards of electric system, must carry out suppression and elimination work, but prerequisite carries out accurate determination and analysis to the harmonic wave in electrical network.
The examination and analysb method of current harmonic wave has a variety of, wherein most widely used is frequency domain analysis based on Fourier transform, this method has high requirements to the precision of sampled point each in the sampling period on the one hand, once there be sampled point mistake, final analysis result must be caused to produce deviation, be converted in the process of frequency domain in time domain on the other hand and be easily subject to small-signal interference, precision of analysis is not high.
Summary of the invention
The technical problem to be solved in the present invention is to provide a kind of mains by harmonics on-line checkingi and analytical approach, can solve existing mains by harmonics and mainly adopt frequency domain analysis based on Fourier transform, cause the problem that precision of analysis is not high.
The present invention is achieved through the following technical solutions:
Mains by harmonics on-line checkingi and analytical approach, comprise the following steps:
A. adopt the magnitude of voltage U at shnt capacitor two ends in voltage transformer (VT) and oscilloscope measurement electrical network, definition s (t)=U is as original signal, and wherein t is oscillographic sampling time sequence point, and size is the natural number of 1 to T;
B. all maximum value and the minimal value of original signal is determined, adopt cubic spline interpolation method, all maximum value of original signal are fitted to a smooth curve, be designated as ma (t), all minimal values of original signal are fitted to a smooth curve, is designated as mi (t);
C. the ma (t) obtained according to step b and mi (t), calculating mean value curve m (t), described in
;
D. the decomposition result of original signal is calculated, described decomposition result=original signal-m (t);
E. steps d gained decomposition result is a decomposition result h of s (t)
1(t); By h
1t (), as original signal, re-executes step b to steps d, obtain the twice decomposition result h of s (t)
2(t); Again by h
2t (), as original signal, re-executes step b to steps d, obtain three decomposition result h of s (t)
3(t); By that analogy, by i-1 time of s (t) decomposition result h
i-1t (), as original signal, re-executes step b to steps d, obtain i the decomposition result h of s (t)
i(t), i>=2;
F. confidence parameter E is set, by step e gained h
i-1(t) and h
it () substitutes into formula:
if formula is set up, then stop calculating;
G. by h
it () is designated as the first component s of s (t)
1t (), by s (t)-s
1t (), as original signal, re-executes step b to step f, obtain the second component s of s (t)
2(t); Again by s (t)-s
1(t)-s
2t (), as original signal, re-executes step b to step f, obtain the three-component s of s (t)
3(t); By that analogy, by s (t)-s
1(t)-...-s
j-2(t)-s
j-1t (), as original signal, re-executes step b to step f, obtain the jth component s of s (t)
j(t), j>=2, described s
jt () is the composition of mains by harmonics.
Further improvement of the present invention scheme is, step a first adopts the transport property of vector network analyzer measuring voltage mutual inductor, obtain the voltage compensation factor P of voltage transformer (VT), then measure the voltage measuring value U at shnt capacitor two ends with voltage transformer (VT) and high speed digital oscilloscope
1, calculate the voltage actual value U=U at shnt capacitor two ends
1﹡ P.
Further improvement project of the present invention is, step a also comprises the transport property adopting vector network analyzer measurement current transform er, obtain the current compensation factor Q of current transformer, then Current Transformer and high speed digital oscilloscope measure shnt capacitor loop current measured I
1, calculate shunt capacitance loop current actual value I=I
1* Q, and then the actual capacitance value calculating shunt capacitance
, wherein f is mains frequency.
Further improvement of the present invention scheme is, in step f, the span of confidence parameter E is 0.2 ~ 0.3.
The present invention's advantage is compared with prior art:
One, adopt cubic spline interpolation method process sampled signal, significantly reduce the impact of single sampled point on final analysis result, accuracy is better;
Two, directly carry out time-domain analysis, do not need frequency domain to change, avoid being subject to small-signal interference, improve precision of analysis further;
Three, the transport property of first measuring voltage mutual inductor is measured again, avoids the transport property because of voltage transformer (VT) to affect sampling precision, improves precision of analysis further;
Four, monitor in conjunction with the real-time capacitance of current transformer to shunt capacitance, can the fault of Timeliness coverage grid equipment.
Embodiment
Mains by harmonics on-line checkingi and analytical approach, comprise the following steps:
A. the transport property of vector network analyzer (R & S ZVL3) difference measuring voltage mutual inductor summation current transformer is first adopted, obtain the current compensation factor Q of the voltage compensation factor P summation current transformer of voltage transformer (VT), then use voltage transformer (VT) summation current transformer to measure the voltage measuring value U at shnt capacitor two ends with high speed digital oscilloscope (Tek DPO 5204B) respectively
1, shnt capacitor loop current measured I
1, calculate the voltage actual value U=U at shnt capacitor two ends
1﹡ P, and shunt capacitance loop current actual value I=I
1* Q, and then the actual capacitance value calculating shunt capacitance
, wherein f is mains frequency, and definition s (t)=U is as original signal, and wherein t is oscillographic sampling time sequence point, and size is the natural number of 1 to T;
B. all maximum value and the minimal value of original signal is determined, adopt cubic spline interpolation method, all maximum value of original signal are fitted to a smooth curve, be designated as ma (t), all minimal values of original signal are fitted to a smooth curve, is designated as mi (t);
C. the ma (t) obtained according to step b and mi (t), calculating mean value curve m (t), described in
;
D. the decomposition result of original signal is calculated, described decomposition result=original signal-m (t);
E. steps d gained decomposition result is a decomposition result h of s (t)
1(t); By h
1t (), as original signal, re-executes step b to steps d, obtain the twice decomposition result h of s (t)
2(t); Again by h
2t (), as original signal, re-executes step b to steps d, obtain three decomposition result h of s (t)
3(t); By that analogy, by i-1 time of s (t) decomposition result h
i-1t (), as original signal, re-executes step b to steps d, obtain i the decomposition result h of s (t)
i(t), i>=2;
F. confidence parameter E is set, by step e gained h
i-1(t) and h
it () substitutes into formula:
if formula is set up, then stop calculating, according to different occasion, the span of confidence parameter E is 0.2 ~ 0.3;
G. by h
it () is designated as the first component s of s (t)
1t (), by s (t)-s
1t (), as original signal, re-executes step b to step f, obtain the second component s of s (t)
2(t); Again by s (t)-s
1(t)-s
2t (), as original signal, re-executes step b to step f, obtain the three-component s of s (t)
3(t); By that analogy, by s (t)-s
1(t)-...-s
j-2(t)-s
j-1t (), as original signal, re-executes step b to step f, obtain the jth component s of s (t)
j(t), j>=2, described s
jt () is the composition of mains by harmonics.
Claims (4)
1. mains by harmonics on-line checkingi and analytical approach, is characterized in that comprising the following steps:
A. adopt the magnitude of voltage U at shnt capacitor two ends in voltage transformer (VT) and oscilloscope measurement electrical network, definition s (t)=U is as original signal, and wherein t is oscillographic sampling time sequence point, and size is the natural number of 1 to T;
B. all maximum value and the minimal value of original signal is determined, adopt cubic spline interpolation method, all maximum value of original signal are fitted to a smooth curve, be designated as ma (t), all minimal values of original signal are fitted to a smooth curve, is designated as mi (t);
C. the ma (t) obtained according to step b and mi (t), calculating mean value curve m (t), described in
;
D. the decomposition result of original signal is calculated, described decomposition result=original signal-m (t);
E. steps d gained decomposition result is a decomposition result h of s (t)
1(t); By h
1t (), as original signal, re-executes step b to steps d, obtain the twice decomposition result h of s (t)
2(t); Again by h
2t (), as original signal, re-executes step b to steps d, obtain three decomposition result h of s (t)
3(t); By that analogy, by i-1 time of s (t) decomposition result h
i-1t (), as original signal, re-executes step b to steps d, obtain i the decomposition result h of s (t)
i(t), i>=2;
F. confidence parameter E is set, by step e gained h
i-1(t) and h
it () substitutes into formula:
if formula is set up, then stop calculating;
G. by h
it () is designated as the first component s of s (t)
1t (), by s (t)-s
1t (), as original signal, re-executes step b to step f, obtain the second component s of s (t)
2(t); Again by s (t)-s
1(t)-s
2t (), as original signal, re-executes step b to step f, obtain the three-component s of s (t)
3(t); By that analogy, by s (t)-s
1(t)-...-s
j-2(t)-s
j-1t (), as original signal, re-executes step b to step f, obtain the jth component s of s (t)
j(t), j>=2, described s
jt () is the composition of mains by harmonics.
2. mains by harmonics on-line checkingi as claimed in claim 1 and analytical approach, it is characterized in that: step a first adopts the transport property of vector network analyzer measuring voltage mutual inductor, obtain the voltage compensation factor P of voltage transformer (VT), then measure the voltage measuring value U at shnt capacitor two ends with voltage transformer (VT) and high speed digital oscilloscope
1, calculate the voltage actual value U=U at shnt capacitor two ends
1﹡ P.
3. mains by harmonics on-line checkingi as claimed in claim 2 and analytical approach, it is characterized in that: step a also comprises the transport property adopting vector network analyzer measurement current transform er, obtain the current compensation factor Q of current transformer, then Current Transformer and high speed digital oscilloscope measure shnt capacitor loop current measured I
1, calculate shunt capacitance loop current actual value I=I
1* Q, and then the actual capacitance value calculating shunt capacitance
, wherein f is mains frequency.
4. mains by harmonics on-line checkingi as claimed in claim 1 and analytical approach, is characterized in that: in step f, the span of confidence parameter E is 0.2 ~ 0.3.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107525969A (en) * | 2016-06-21 | 2017-12-29 | 中电普瑞科技有限公司 | A kind of self-adapting type electric harmonic analysis method for merging many algorithms |
| CN108196180A (en) * | 2017-12-14 | 2018-06-22 | 国网江苏省电力有限公司淮安供电分公司 | A kind of shunt capacitor online circuit parameter detection method |
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| CN108196180A (en) * | 2017-12-14 | 2018-06-22 | 国网江苏省电力有限公司淮安供电分公司 | A kind of shunt capacitor online circuit parameter detection method |
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| CN104360153B (en) | 2017-02-08 |
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