CN102095934B - Measuring method for phase difference of alternating current signals - Google Patents
Measuring method for phase difference of alternating current signals Download PDFInfo
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Abstract
The invention provides a measuring method for the phase difference of alternating current signals. The method comprises the following steps: firstly, pre-treating a sampling value; then, looking up a table, calculating zero crossing point time for two paths or multiple paths of alternating current signals to increase; calculating the period of the signal according to the zero crossing point; and finally, calculating the phase difference between the signals by utilizing the difference of the zero crossing point time of different signals and the periods of the signals. In the measuring method, the alternating current signal does not need to be converted into square waves, and the defect of poor antijamming capability of the traditional zero crossing point detection can be overcome. The method is also suitable for measuring the phase difference of low-frequency signals, the system is convenient to detect, the hardware cost is small, and the antijamming capability of the system is strong. The measuring method is simple and reasonable to realize, and the data is accurate and reliable, thus the measuring method has a wide application prospect.
Description
Technical field
The present invention relates to the method for measuring phase difference of ac signal, the present invention can be widely used in the power system automatic field such as measuring power angle of generator.
Background technology
In daily life, production run, usually need measure the phase differential between the ac signal, the phase differential of measurement is accurate more, and application results is often better.In existing method for measuring phase difference; Great majority adopt signal transition are become square wave, measure the mistiming of rising edge between two square waves then, thereby draw the phase differential of two signals; This method is easy to realize but needs additional hardware, and the influence that is interfered easily.
Summary of the invention
Technical matters to be solved by this invention is not accurate enough to the Phase Difference Measuring Precision of ac signal in the prior art, has proposed a kind of method for measuring phase difference of ac signal.
The present invention adopts following technical scheme for solving the problems of the technologies described above:
A kind of method for measuring phase difference of ac signal may further comprise the steps:
Step 1) is sampled to tested electric signals, obtains the sampled value of tested electric signals; Select n sampled point of combination in any near by low zero point during to High variation at the sampled value of electric signal some;
Step 2), the sampling time of supposing each sampled point is t
i, sampled value is y
i, then the mean value M of the sampled value of n sampled point and average sample time of origin T are expressed as:
In the following formula, n>=1, n, i, j are natural number, then (M
j, T
j) virtual point of expression;
Step 3), according to tested electric signals near zero-crossing point by low to high change procedure, electric signal effective value or peak value, and step 2) the mean value M of sampled value of a said n sampled point
j, obtain a mistiming T ' through the mode of tabling look-up
j, said mistiming T '
jRepresent under the pure sinusoid signal, from virtual point (M
j, T
j) nearest zero crossing and the mistiming between this virtual point; The corresponding zero crossing time is: T
Zj=T
j+ T '
j
The wherein above-mentioned related form of tabling look-up has two row, and wherein first row are
Perhaps
The secondary series of form is
Time corresponding difference T '
j
Step 4); Successively at other of the sampled value of electric signal by near low n sampled point the zero point of High variation, selecting combination in any; Repeating step 2) and step 3) obtain several zero crossings time, according to these several zero crossing times, calculate the cycle of tested electric signals;
Step 5) in the cycle of the signal that obtains according to the zero crossing temporal differences and the step 4) of unlike signal, calculates phase difference between signals.
Further, in the method for measuring phase difference of aforementioned ac signal, said electric signal is sampled of step 1) is constant duration sampling or not constant duration sampling.
Further, in the method for measuring phase difference of aforementioned ac signal, described being sampled as of step 1) sampled to the complete cycle ripple of electric signal.
Repeating step 2), step 3) obtains several zero crossing time T further, in the method for measuring phase difference of aforementioned ac signal, the concrete steps in the calculating tested electric signals cycle described in the step 4) are following:
Z1, T
Z2, T
Z3... T
Zj, T
Zj+1, T
Zj+2... T
Zn..., the cycle of tested ac signal: T then
Pj=T
Zj+1-T
Zj, the cycle of the signal that therefore obtains is followed successively by T
P1, T
P2, T
P3, T
P4... T
Pk-1, T
Pk..., k is a natural number.
Further, in the method for measuring phase difference of aforementioned ac signal, the said concrete steps of step 5) are following: establishing a certain road cycle signal zero-cross point that is calculated by step 3) is T1
i, other one tunnel cycle signal zero-cross point time is T2
i, the cycle of the ac signal that is calculated by step 4) is T
Pi, then the phase meter of two paths of signals is shown:
Or be expressed as:
The result who calculates is respectively the phase difference value of representing with the number of degrees and radian.
Further, in the method for measuring phase difference of aforementioned ac signal, in step 2) in also comprise the step that the mean value M to sampled point revises, the step of said correction is following:
The cycle of a) establishing by several cycles before the ac signal that calculates is followed successively by T
Pk-3, T
Pk-2, T
Pk-1, T
Pk, the cycle of current several cycles does not exist or when can not get, makes it equal the ac voltage standard cycle;
B) periodic table of the current cycle of prediction is shown:
T
p=K
1* T
Pk+ K
2* T
Pk-1+ K
3* T
Pk-2+ K
4* T
Pk-3K wherein
1, K
2, K
3, K
4Be arbitrary constant, but the K that must satisfy condition
1+ K
2+ K
3+ K
4=1;
C) M
Modified value=M * T
pThe ÷ ac voltage standard cycle.
The present invention adopts above technical scheme to have following beneficial effect:
1) traditional two opposite continuity points of zero friendship method symbolization are confirmed zero crossing, though the algorithm clear physics conception receives the interference of harmonic wave, measuring error etc. easily, measuring accuracy is low.Have only accurate location zero crossing, just can calculate accurate phase differential, for the signal of low frequency (particularly civilian alternating current), the waveform of near zero-crossing point is approximately straight line.Along with the raising of acquisition speed, can near zero point, select several sampled points arbitrarily.By several sampled points of choosing through obtaining the particular location of zero crossing after calculating, tabling look-up.Confirmed after the cycle signal zero-cross point, can accurately calculate the phase differential between the ac signal.Traditional zero friendship method of comparing, operand significantly reduces, and the precision of measurement, anti-interference do not reduce yet.
2) sampling involved in the present invention can be the constant duration sampling, also can be not constant duration sampling, if the constant duration sampling, then operand can pass through and optimize and further the minimizing.
Description of drawings:
Fig. 1 carries out constant duration sampling and the synoptic diagram of 8 sampled points obtaining near zero point.
Fig. 2 is the synoptic diagram that is calculated the signal zero crossing that is obtained by 4 negative level sampled points.
Fig. 3 is the synoptic diagram that is calculated the signal zero crossing that is obtained by 3 negative levels and 1 positive level sampled point.
Fig. 4 is the synoptic diagram that is calculated the signal zero crossing that is obtained by 2 positive levels and 2 negative level sampled points.
Fig. 5 is under the sampling of constant duration not situation, is calculated the synoptic diagram of the signal zero crossing that is obtained by 1 negative level and 3 positive level sampled points.
Fig. 6 is the synoptic diagram in signal calculated cycle.
Fig. 7 is the synoptic diagram that calculates the two paths of signals phase differential.
Embodiment:
Below in conjunction with accompanying drawing technical scheme of the present invention is elaborated:
Essence of the present invention is that several sampled points are carried out pre-service after table look-up, and calculates cycle signal zero-cross point; The cycle of signal calculated and the phase differential between the unlike signal are come by a series of zero crossings in the back.The sampled point of choosing is too much unsuitable, if the sampled point of choosing is more, calculating will be complicated; Choose to such an extent that sampled point is also unsuitable very few, if the sampled point of choosing is less, the influence that is interfered easily.So the user can choose rational sampled point combination as required and number is calculated.
For obtaining comparatively accurate measurement result, the scheme of choosing of the sampled point of suggestion is: the quantity of the quantity of positive sampled point and the sampled point of bearing equates or about equally, the number of sampled point then can be confirmed according to concrete actual conditions.
Characteristics of the present invention and advantage will combine accompanying drawing to be elaborated through instance.Principle of the present invention describes through the phase differential of measuring ac signal; Raising along with sample rate; The sampling number that in a cycle, takes place is also more and more, when sampling number is abundant, can select several sampled points near by low zero point during to High variation at ac signal; Calculate the mean value M and the average sample time of origin T of several sampled points; Table look-up according to the characteristics of current demand signal and mean value M then and obtain T ', come the zero crossing of expression signal by T+T ', thereby calculate the cycle of signal; Further can calculate the phase differential between the unlike signal.All adopt four sampled points to calculate zero crossing in the follow-up embodiment, can suitably increase or reduce the number of sampled point in the practical application as required.Practical implementation process of the present invention is following:
1. measured signal is sampled, described here be sampled as the sampling that the complete cycle ripple is carried out.Can be the constant duration sampling, also can be not constant duration sampling.
2. near each zero point of signal, select several sampled points of combination in any.Here refer to ac signal said zero point by low zero point when the High variation.The sampled value of the sampled point of selecting can just all be; Also can be all to be negative; Also can select as required several sampled values for just, several sampled values are negative sampled point.The S0 that Fig. 1 is last, S1, S2, S3, S4, S5, S6, S7 carry out constant duration sampling and 8 sampled points obtaining near zero point.Can in above-mentioned 8 points (but being not limited only to this 8 points), select several sampled points.Be the comparatively accurate measurement result of acquisition, the scheme of choosing of the sampled point of suggestion is: the quantity of the quantity of positive sampled point and the sampled point of bearing equates perhaps about equally.
3. the step of mean value M and average sample time of origin T of calculating several sampled points is following:
1) ac signal by low zero point during to High variation near select several sampled points of combination in any;
2) suppose that the sampling number of choosing is n, the sampling time of each sampled point is t
i, sampled value is y
i, then the mean value M of n sampled point and average sample time of origin T can be expressed as:
In the following formula, n>=1, i, j are natural number, then (M
j, T
j) can regard a virtual point as;
4. the process that obtains zero crossing is following: obtain (M
j, T
j) after, can be by the characteristics of current demand signal, the effective value of signal (or peak value) and M
jObtain T ' through tabling look-up
j, T '
jPhysical significance be under the pure sinusoid signal, from virtual point (M
j, T
j) nearest zero crossing and the mistiming between this virtual point.Because virtual point is to confirm that near the sampled point that ac signal (frequency is 50Hz) is selected by low zero point during to High variation according to form of this characteristics design, first of form is listed as and is through calculating after
The secondary series of form is
Corresponding T '
jThrough this form, can basis
Numerical value obtain corresponding T '
j, (first row of form also can be designed to concrete form as follows
):
It is thinner that the granularity of above table can also design, and can improve T ' like this
jAccuracy.It should be noted that; The scope of
of above table is [0.5; 0.5], this scope can be done suitable increase or minimizing according to the needs of using.When the signal frequency of measuring if desired is not equal to 50Hz, need design above table again.
After tabling look-up, the then corresponding zero crossing time can be expressed as: T
Zj=T
j+ T '
j
5. point (the M at the hollow triangle among Fig. 2 place
0, T
0) be by the sampled point S0 among Fig. 1, S1, S2, S3 calculate the virtual point that the back obtains, and the point at open circles place is the zero crossing that after computation of table lookup, obtains; Point (the M at the hollow triangle place among Fig. 3
1, T
1) be by the sampled point S1 among Fig. 1, S2, S3, S4 calculate the virtual point that the back obtains, and the point at open circles place is the zero crossing that after computation of table lookup, obtains; Point (the M at the hollow triangle place among Fig. 3
2, T
2) be by the sampled point S2 among Fig. 1, S3, S4, S5 calculate the virtual point that the back obtains, and the point at open circles place is the zero crossing that after computation of table lookup, obtains; Sampling in the example of Fig. 2, Fig. 3, Fig. 4 is the constant duration sampling.Fig. 5 is the synoptic diagram as a result that does not obtain under the constant duration sampling situation, the point (M at hollow triangle place
3, T
3) be by the sampled point S0 among the figure, S1, S2, S3 calculate the virtual point that the back obtains, and the point at open circles place is the zero crossing that after computation of table lookup, obtains.
6. obtain several zero crossings and can carry out the calculating of signal period after the time; Ac signal among Fig. 6 is carrying out calculating for four times (near each 2 positive levels and 2 negative level sampled points that adopt zero point that calculate) near zero point (signal is by low zero crossing during to High variation); Obtained the virtual point at four hollow triangle places, by four zero crossing: T that obtained the open circles place after four virtual point computation of table lookup
1, T
2, T
3, T
4Because the cycle of tested ac signal can be expressed as: T
Pj=T
J+1-T
j, so among Fig. 6 the signal period can be expressed as: T
P3=T
4-T
3, T
P2=T
3-T
2, T
P1=T
2-T
1
7. the calculating of phase differential can be referring to Fig. 7, and the point at figure hollow core triangle place is the virtual point that calculates.AC signal I is having two zero crossing T1s through computation of table lookup by low during to High variation among Fig. 7
iAnd T1
I+1, AC signal II is having two zero crossing T2s through computation of table lookup by low during to High variation
iAnd T2
I+1, then the phase differential of AC signal I and AC signal II can be expressed as:
Perhaps
T in the formula
PiAnd T
Pi+1It is the cycle of the signal that calculates.Formula also can be write as the form that radian is expressed.
8. the present invention can revise the mean value M of sampled point and improve the accuracy of calculating zero crossing, improves the accuracy of period measurement, and then can improve the accuracy of phase difference measurement.The method of revising is following: the cycle of establishing by several cycles before the ac signal that calculates is followed successively by T
Pk-3, T
Pk-2, T
Pk-1, T
Pk(when the cycle of cycle does not calculate in front, can make T partly or completely
Pk-3, T
Pk-2, T
Pk-1, T
PkEqual the ac voltage standard cycle); Then the cycle of the current cycle of prediction can be expressed as: T
p=K
1* T
Pk+ K
2* T
Pk-1+ K
3* T
Pk-2+ K
4* T
Pk-3K in the formula
1, K
2, K
3, K
4Can be arbitrary constant, but the K that must satisfy condition
1+ K
2+ K
3+ K
4=1.Then make M
Modified value=M * T
pThe ÷ ac voltage standard cycle.When measured signal frequency shift (FS) ac voltage standard frequency, adopt M
Modified valueTable look-up and to obtain measurement result more accurately.In above-mentioned experiment, make K
1=1, K
2=K
3=K
4=0, T then
p=T
Pk, think that promptly the cycle of current cycle is identical with the cycle of a last cycle.
Preferred version is the described constant duration sampling that is sampled as.
In sum, the method for measuring phase difference of a kind of ac signal involved in the present invention need not convert ac signal to square wave; Overcome the shortcoming that traditional zero crossing detects poor anti jamming capability; Also be suitable for the phase difference measurement of low frequency signal, system is easy to detect, and hardware spending is little; The antijamming capability of system is stronger; Implement advantages of simple, data accurately, reliably; Have than application prospects.Certainly, the present invention can be applicable to phase difference measurement, measuring power angle of civilian three-phase alternating current or the like usually.
Claims (6)
1. the method for measuring phase difference of an ac signal is characterized in that: may further comprise the steps:
Step 1) is sampled to tested electric signals, obtains the sampled value of tested electric signals; Select n sampled point of combination in any near by low zero point during to High variation at the sampled value of electric signal some;
Step 2), the sampling time of supposing each sampled point is t
i, sampled value is y
i, the mean value M of the sampled value of n sampled point then
jWith average sample time of origin T
jBe expressed as:
In the following formula, n>=1, n, i, j are natural number, then (M
j, T
j) virtual point of expression;
Step 3), according to tested electric signals near zero-crossing point by low to high change procedure, electric signal effective value or peak value, and step 2) the mean value M of sampled value of a said n sampled point
j, obtain a mistiming through the mode of tabling look-up
The said mistiming
Represent under the pure sinusoid signal, from virtual point (M
j, T
j) nearest zero crossing and the mistiming between this virtual point; The corresponding zero crossing time is:
The wherein above-mentioned related form of tabling look-up has two row, wherein first row be
perhaps the secondary series of
form be
time corresponding poor
Step 4); Successively at other of the sampled value of electric signal by near low n sampled point the zero point of High variation, selecting combination in any; Repeating step 2) and step 3) obtain several zero crossings time, according to these several zero crossing times, calculate the cycle of tested electric signals;
Step 5) in the cycle of the signal that obtains according to the zero crossing temporal differences and the step 4) of unlike signal, calculates phase difference between signals.
2. the method for measuring phase difference of ac signal according to claim 1 is characterized in that: said electric signal is sampled of step 1) is constant duration sampling or not constant duration sampling.
3. the method for measuring phase difference of ac signal according to claim 1, it is characterized in that: described being sampled as of step 1) sampled to the complete cycle ripple of electric signal.
Repeating step 2), step 3) obtains several zero crossing time T 4. the method for measuring phase difference of ac signal according to claim 1, it is characterized in that: the concrete steps in the calculating tested electric signals cycle described in the step 4) are following:
Z1, T
Z2, T
Z3... T
Zj, T
Zj+1, T
Zj+2... T
Zn..., the cycle of tested ac signal: T then
Pj=T
Zj+1-T
Zj, the cycle of the signal that therefore obtains is followed successively by T
P1, T
P2, T
P3, T
P4... T
Pk-1, T
Pk..., k is a natural number.
5. the method for measuring phase difference of ac signal according to claim 1, it is characterized in that: the said concrete steps of step 5) are following: establishing a certain road cycle signal zero-cross point time that is calculated by step 3) is T1
i, other one tunnel cycle signal zero-cross point time is T2
i, the cycle of the ac signal that is calculated by step 4) is T
Pi, then the phase meter of two paths of signals is shown:
Or be expressed as:
The result who calculates is respectively the phase difference value of representing with the number of degrees and radian.
6. according to the method for measuring phase difference of each described ac signal in the claim 1 to 5, it is characterized in that: in step 2) in also comprise mean value M to sampled point
jThe step of revising, the step of said correction is following:
The cycle of a) establishing by several cycles before the ac signal that calculates is followed successively by T
Pk-3, T
Pk-2, T
Pk-1, T
Pk, the cycle of current several cycles does not exist or when can not get, makes it equal the ac voltage standard cycle;
B) periodic table of the current cycle of prediction is shown:
T
p=K
1* T
Pk+ K
2* T
Pk-1+ K
3* T
Pk-2+ K
4* T
Pk-3K wherein
1, K
2, K
3, K
4Be arbitrary constant, but the K that must satisfy condition
1+ K
2+ K
3+ K
4=1;
C) M
Modified value=M
j* T
pThe ÷ ac voltage standard cycle.
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| CN103575989A (en) * | 2012-07-26 | 2014-02-12 | 南京邮电大学 | Method for accurately measuring phase differences of alternating current |
| CN103575988A (en) * | 2012-07-26 | 2014-02-12 | 南京邮电大学 | Method for measuring phase difference of alternating current in digital mode |
| CN102928666B (en) * | 2012-07-26 | 2014-08-13 | 南京邮电大学 | Digital measurement method for phase difference of alternating current |
| CN104808059B (en) * | 2014-01-26 | 2017-12-08 | 南京邮电大学 | A kind of digital measuring method of electric signal instantaneous phase |
| CN104808060B (en) * | 2014-01-26 | 2017-12-15 | 南京邮电大学 | A kind of digital measuring method of electrical signal phase difference |
| CN104808061B (en) * | 2014-01-26 | 2017-12-12 | 南京邮电大学 | A kind of measuring method of electrical signal phase difference |
| CN104808058B (en) * | 2014-01-26 | 2017-12-12 | 南京邮电大学 | A kind of measuring method of electric signal instantaneous phase |
| CN104142424B (en) * | 2014-08-15 | 2016-09-14 | 中国计量科学研究院 | A kind of method of accurate measurement non-sinusoidal voltage signal and system thereof |
| CN105954589B (en) * | 2016-04-19 | 2019-03-22 | 杭州万高科技股份有限公司 | A kind of Method for Phase Difference Measurement and device of multichip system |
| CN106645952B (en) * | 2016-10-18 | 2019-06-25 | 上海华虹计通智能***股份有限公司 | A kind of detection method and system of signal phase difference |
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| CN101726664A (en) * | 2008-10-27 | 2010-06-09 | 华为技术有限公司 | Method, device and system for measuring signal phase difference |
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| JPH02272365A (en) * | 1989-04-14 | 1990-11-07 | Omron Corp | Phase detecting circuit for switching device control apparatus |
| JP5214163B2 (en) * | 2007-03-30 | 2013-06-19 | 北海道旅客鉄道株式会社 | Phase difference measurement system and phase difference measurement method |
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