CN104360153B - 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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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 is and in particular to a kind of mains by harmonics on-line checking and analysis method.
Background technology
Harmonic wave can lead to the element in utility network to produce the harmonic loss of adnexa, reduce and generate electricity, transmit electricity and electrical equipment
Efficiency, the normal work of various electrical equipments can be affected, the parallel resonance of local and series resonance in utility network can be caused,
So that Harmonics amplification causes major accident, relay protection and automaton misoperation can be led to, and make electrical measuring instrument meter
Amount is inaccurate, also can produce interference to the communication system closed on, gently then produce noise, reduces communication quality, heavy then lead to information
Lose, make the communication system cannot normal work.Harmonic wave leads to various accident and probability of failure persistently to raise, it has also become electric power
One big public hazards of system are it is necessary to carrying out suppression and eliminating work, but premise is that the harmonic wave in electrical network is accurately detected
And analysis.
At present the detection of harmonic wave and analysis method have many kinds, and wherein most widely used is frequency domain based on Fourier transform
Analytic process, this method one side has high requirements to the precision of each sampled point in the sampling period, once there being sampled point wrong
By mistake, necessarily lead to final analysis result to produce deviation, be on the other hand easily subject to little during time domain is converted to frequency domain
Signal disturbs, and precision of analysis is not high.
Content of the invention
The technical problem to be solved in the present invention is to provide a kind of mains by harmonics on-line checking and analysis method, can solve existing
There is mains by harmonics mainly using the frequency domain analysises based on Fourier transform, lead to the not high problem of precision of analysis.
The present invention is achieved through the following technical solutions：
Mains by harmonics on-line checking and analysis method, comprise the following steps：
A. adopt the magnitude of voltage U at shnt capacitor two ends in voltage transformer and oscilloscope measurement electrical network, define s (t)=U
As primary signal, wherein t is oscillographic sampling time sequence point, and size is 1 natural number arriving T；
B. all maximum and the minimum of primary signal are determined, using cubic spline interpolation method, by original letter
Number all maximum fit to a smooth curve, be designated as ma (t), all minimums of primary signal fitted to one
Smooth curve, is designated as mi (t)；
C. ma (t) and the mi (t) being obtained according to step b, calculates meansigma methodss curve m (t), described；
D. the decomposition result of primary signal, described decomposition result=primary signal-m (t) are calculated；
E. step d gained decomposition result is decomposition result h of s (t)1(t)；By h1(t) as primary signal,
Re-execute step b to step d, obtain twice decomposition result h of s (t)2(t)；Again by h2(t) as primary signal, again
Execution step b, to step d, obtains three decomposition result h of s (t)3(t)；By that analogy, by the i-1 decomposition result of s (t)
hi-1T (), as primary signal, re-executes step b to step d, obtains i decomposition result h of s (t)i(t), i >=2；
F. set confidence parameter E, by step e gained hi-1(t) and hiT () substitutes into formula：If,
Formula is set up, then terminate calculating；
G. by hiT () is designated as the first component s of s (t)1T (), by s (t)-s1T (), as primary signal, re-executes step
Rapid b, to step f, obtains the second component s of s (t)2(t)；Again by s (t)-s1(t)- s2T (), as primary signal, re-executes
Step b, to step f, obtains the three-component s of s (t)3(t)；By that analogy, by s (t)-s1(t)-……-sj-2(t)- sj-1(t)
As primary signal, re-execute step b to step f, obtain the jth component s of s (t)j(t), j >=2, described sjT () is electricity
The composition of net harmonic wave.
Further improvement of the present invention scheme is that step a first adopts vector network analyzer to measure the biography of voltage transformer
Defeated characteristic, obtains voltage compensation factor P of voltage transformer, more in parallel electric with voltage transformer and high speed digital oscilloscope measurement
The voltage measuring value U at container two ends1, it is calculated the voltage actual value U=U at shnt capacitor two ends1P.
The further improvement project of the present invention is that step a also includes measuring Current Mutual Inductance using vector network analyzer
The transmission characteristic of device, obtains the current compensation factor Q of current transformer, then Current Transformer and high speed digital oscilloscope measurement
Shnt capacitor loop current measured I1, it is calculated shunt capacitance loop current actual value I=I1* Q, and then be calculated
The actual capacitance value of shunt capacitance, wherein f is mains frequency.
Further improvement of the present invention scheme is that in step f, the span of confidence parameter E is 0.2 ~ 0.3.
Present invention advantage compared with prior art is：
First, adopt cubic spline interpolation method to process sampled signal, single sampled point is greatly reduced and analyzes to final
The impact of result, accuracy is more preferable；
2nd, directly carry out time-domain analyses it is not necessary to frequency domain is changed, it is to avoid disturbed by small-signal, improve analysis further
The accuracy of result；
3rd, first the transmission characteristic of measurement voltage transformer measures again, it is to avoid because of the transmission characteristic shadow of voltage transformer
Ring sampling precision, improve precision of analysis further；
4th, with reference to current transformer, the real-time capacitance of shunt capacitance is monitored, grid equipment can be found in time
Fault.
Specific embodiment
Mains by harmonics on-line checking and analysis method, comprise the following steps：
A. first adopt vector network analyzer（R&S ZVL3）Measure the transmission of voltage transformer summation current transformer respectively
Characteristic, obtains the current compensation factor Q of the voltage compensation factor P summation current transformer of voltage transformer, then uses voltage transformer
Summation current transformer respectively with high speed digital oscilloscope（Tek DPO 5204B）The voltage measuring value at measurement shnt capacitor two ends
U1, shnt capacitor loop current measured I1, it is calculated the voltage actual value U=U at shnt capacitor two ends1P, and simultaneously
Connection capacitor loop current actual value I=I1* Q, and then it is calculated the actual capacitance value of shunt capacitance, wherein f
For mains frequency, define s (t)=U as primary signal, wherein t is oscillographic sampling time sequence point, size is 1 nature arriving T
Number；
B. all maximum and the minimum of primary signal are determined, using cubic spline interpolation method, by original letter
Number all maximum fit to a smooth curve, be designated as ma (t), all minimums of primary signal fitted to one
Smooth curve, is designated as mi (t)；
C. ma (t) and the mi (t) being obtained according to step b, calculates meansigma methodss curve m (t), described；
D. the decomposition result of primary signal, described decomposition result=primary signal-m (t) are calculated；
E. step d gained decomposition result is decomposition result h of s (t)1(t)；By h1(t) as primary signal,
Re-execute step b to step d, obtain twice decomposition result h of s (t)2(t)；Again by h2(t) as primary signal, again
Execution step b, to step d, obtains three decomposition result h of s (t)3(t)；By that analogy, by the i-1 decomposition result of s (t)
hi-1T (), as primary signal, re-executes step b to step d, obtains i decomposition result h of s (t)i(t), i >=2；
F. set confidence parameter E, by step e gained hi-1(t) and hiT () substitutes into formula：If formula is set up, terminate calculating, according to different occasions, the span of confidence parameter E
For 0.2 ~ 0.3；
G. by hiT () is designated as the first component s of s (t)1T (), by s (t)-s1T (), as primary signal, re-executes step
Rapid b, to step f, obtains the second component s of s (t)2(t)；Again by s (t)-s1(t)- s2T (), as primary signal, re-executes
Step b, to step f, obtains the three-component s of s (t)3(t)；By that analogy, by s (t)-s1(t)-……-sj-2(t)- sj-1(t)
As primary signal, re-execute step b to step f, obtain the jth component s of s (t)j(t), j >=2, described sjT () is electricity
The composition of net harmonic wave.
Claims (4)
1. mains by harmonics on-line checking with analysis method it is characterised in that comprising the following steps：
A. adopt the magnitude of voltage U at shnt capacitor two ends in voltage transformer and oscilloscope measurement electrical network, define s (t)=U conduct
Primary signal, wherein t are oscillographic sampling time sequence point, are 1 natural number arriving T；
B. all maximum and the minimum of primary signal are determined, using cubic spline interpolation method, by primary signal
All maximum fit to a smooth curve, are designated as ma (t), and all minimums of primary signal are fitted to a smooth song
Line, is designated as mi (t)；
C. ma (t) and the mi (t) being obtained according to step b, calculates meansigma methodss curve m (t), described
D. the decomposition result of primary signal, described decomposition result=primary signal-m (t) are calculated；
E. step d gained decomposition result is decomposition result h of s (t)1(t)；By h1T (), as primary signal, holds again
Row step b, to step d, obtains twice decomposition result h of s (t)2(t)；Again by h2T (), as primary signal, re-executes step b
To step d, obtain three decomposition result h of s (t)3(t)；By that analogy, by i-1 decomposition result h of s (t)i-1(t) conduct
Primary signal, re-executes step b to step d, obtains i decomposition result h of s (t)i(t), i >=2；
F. set confidence parameter E, by step e gained hi-1(t) and hiT () substitutes into formula：If
Formula is set up, then terminate calculating；
G. by hiT () is designated as the first component s of s (t)1T (), by s (t)-s1T (), as primary signal, re-executes step b extremely
Step f, obtains the second component s of s (t)2(t)；Again by s (t)-s1(t)-s2T (), as primary signal, re-executes step b extremely
Step f, obtains the three-component s of s (t)3(t)；By that analogy, by s (t)-s1(t)-……-sj-2(t)-sj-1T () is as original
Signal, re-executes step b to step f, obtains the jth component s of s (t)j(t), j >=2, described sjT () is mains by harmonics
Composition.
2. mains by harmonics on-line checking as claimed in claim 1 and analysis method it is characterised in that：Step a first adopts vector
Network Analyzer measures the transmission characteristic of voltage transformer, obtains voltage compensation factor P of voltage transformer, then uses mutual induction of voltage
Device and the voltage measuring value U at high speed digital oscilloscope measurement shnt capacitor two ends1, it is calculated the electricity at shnt capacitor two ends
Compacting actual value U=U1P.
3. mains by harmonics on-line checking as claimed in claim 2 and analysis method it is characterised in that：Step a also includes adopting
The transmission characteristic of vector network analyzer measurement current transform er, obtains the current compensation factor Q of current transformer, then uses electric current
Transformer and high speed digital oscilloscope measurement shnt capacitor loop current measured I1, it is calculated shunt capacitance loop current
Actual value I=I1* Q, and then it is calculated the actual capacitance value of shunt capacitanceWherein f is mains frequency.
4. mains by harmonics on-line checking as claimed in claim 1 and analysis method it is characterised in that：Confidence parameter E in step f
Span be 0.2～0.3.
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| 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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| US4964055A (en) * | 1987-11-25 | 1990-10-16 | Cooper Industries, Inc. | Hand-held power system harmonic distortion meter with selective activation of display |
| US5298888A (en) * | 1992-08-21 | 1994-03-29 | Basic Measuring Instruments | Harmonic measuring instrument for AC power systems with latched indicator means |
| CN101615807B (en) * | 2009-07-29 | 2011-08-31 | 广西诺斯贝电气有限公司 | Stepless rapid phase-control reactive power dynamic compensation device and compensation method thereof |
| CN102116816B (en) * | 2009-12-31 | 2015-06-03 | 深圳先进技术研究院 | Device and method for monitoring grid-connected running of distributed power supply |
| CN201974477U (en) * | 2010-11-24 | 2011-09-14 | 上海仪器仪表研究所 | Detecting and analyzing device for harmonic waves of power system |
| CN103575984A (en) * | 2012-08-02 | 2014-02-12 | 西安元朔科技有限公司 | Harmonic analysis method based on Kaiser window double-spectral-line interpolation FFT |
| CN102841251B (en) * | 2012-08-14 | 2015-01-07 | 华北电力大学 | Electric car charging station harmonic wave detection method in microgrid |
| CN103901273B (en) * | 2012-12-28 | 2017-12-22 | 白晓民 | Power grid harmonic wave detection method and Harmonic Measuring Equipment |
| CN103091554B (en) * | 2013-03-01 | 2015-04-22 | 山东电力集团公司电力科学研究院 | Steady-state harmonic wave analyzing method for line terminal synchronous measurement signal multi-bus micro-grid |
| CN203133169U (en) * | 2013-03-30 | 2013-08-14 | 国家电网公司 | Device employing novel wiring method for detecting current harmonic quality |
| CN103353558B (en) * | 2013-05-31 | 2016-12-28 | 深圳市康必达控制技术有限公司 | A kind of electric energy quality monitoring method |
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