CN102095936A - Method for measuring phase difference of alternating-current electric signals quickly - Google Patents

Abstract

The invention provides a method for measuring the phase difference of alternating-current electric signals quickly, which comprises the following steps of: firstly, pretreating a sampling value; secondly, calculating the zero crossing point time of two or multiple paths of alternating-current electric signals during change from low to high directly; thirdly, calculating the period of the signals by using zero crossing points; and finally, calculating the phase difference among the signals by using the difference of the zero crossing point time of different signals and the signal period. In the method, the alternating-current electric signals are not needed to be converted into a square wave, and the defect of poor anti-interference capacity in the conventional zero crossing point detection is overcome. The method is also suitable for measuring the phase difference of low-frequency signals, a system is convenient to detect, and low hardware expenditures are realized; the anti-interference capacity of the system is high; and the method is realized simply and reasonably, has accurate and reliable data, and has a wide application prospect.

Description

A kind of method of quick measurement ac signal phase differential

Technical field

The present invention relates to the method for measuring phase difference of ac signal, the present invention also can be used for the phase difference measurement of low-frequency signals.

Background technology

Usually need to measure the phase differential between the ac signal in daily life, production run, the phase differential of measurement is accurate more, and the effect of application 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 extra hardware, and the influence that is interfered easily.What industry needed is the software method for measuring phase difference that a kind of operand is little and have certain measuring accuracy.

Summary of the invention

Technical matters to be solved by this invention is not accurate enough at the Phase Difference Measuring Precision of ac signal in the prior art, has proposed a kind of method of quick measurement ac signal phase differential.

The present invention provides a kind of method for measuring phase difference of quick ac signal for solving the problems of the technologies described above, and 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 zero point when tested electric signals some changes from low to high;

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:

$M_j=\frac{\underset{1}{\overset{n}{\mathrm{\Σ}}}{y}_i}{n},$ $T_j=\frac{\underset{1}{\overset{n}{\mathrm{\Σ}}}{t}_i}{n};$

In the following formula, n 〉=1, n, i, j are natural number, then (M _j, T _j) virtual point of expression;

Step 3), the process, electric signal effective value or the peak value that change from low to high at the ac signal of near zero-crossing point according to tested electric signals, and step 2) the mean value M of sampled value of a described n sampled point _j, obtain a mistiming T ' by calculation mode _j, described 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; Then Dui Ying zero crossing time representation is: T _Zj=T _j+ T ' _j

Near approximate straight line, then the zero crossing time T regarded as of sinusoidal signal that will be zero point _ZjComputing method as follows:

F wherein _cBe the ac voltage standard frequency, T _cBe the ac voltage standard cycle, U _MAXBe the ac signal maximal value, U _EMSBe the ac signal effective value, the condition that following formula is set up is

Perhaps

Value approach 0;

Step 4), near other zero point that changes from low to high of the sampled value of electric signal, select n sampled point of combination in any successively, 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 aforesaid quick measurement ac signal phase differential, described electric signal is sampled of step 1) is constant duration sampling or not constant duration sampling.

Further, in the method for aforesaid quick measurement ac signal phase differential, 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 aforesaid quick measurement ac signal phase differential, the concrete steps in the calculating tested electric signals cycle described in the step 4) are as follows: _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, therefore the cycle of the signal that 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 aforesaid quick measurement ac signal phase differential, the described concrete steps of step 5) are as follows: 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 aforesaid quick measurement ac signal phase differential, during the cycle, adopt predetermined period T ' of current cycle in the step 3) at tested alternating current actual cycle skew ac voltage standard _cReplace the ac voltage standard period T _cCalculate, obtain T ' _cMethod as follows:

A) 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, 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 Yu Ce current cycle is shown:

T ' _c=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.

The present invention adopts technique scheme to have following beneficial effect:

1) traditional two opposite continuity points of zero friendship method symbolization are determined zero crossing, though the algorithm clear physics conception is subjected to 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 the particular location that obtains zero crossing after the direct calculating of choosing of several sampled points processes.Determined 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 further reduce through optimizing.

3) this method can be chosen several sampled points and participate in calculating when calculating, and this can reduce the stochastic error of system to a certain extent; The another one advantage of this method is that the calculated amount of algorithm and the number of the sampled point of choosing only present linear dependence, and when the sampling number of choosing increased, the precision of computing can improve greatly but operand can not present exponential increase.

4) the present invention fits to straight line with sinusoidal curve near sinusoidal zero point, has certain error of calculation, but at the M of the virtual point of choosing _jVery near zero the time, error almost can be ignored.

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 directly calculate 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 determined according to concrete actual conditions.

Characteristics of the present invention and advantage will be elaborated in conjunction with the accompanying drawings by example.Principle of the present invention describes by the phase differential of measuring ac signal, raising along with sample rate, the sampling number that takes place in a cycle is also more and more, when sampling number is abundant, can select several sampled points near the zero point when ac signal changes from low to high, calculate the mean value M and the average sample time of origin T of several sampled points, obtain T ' according to the characteristics and the mean value M calculating of current demand signal then, come the approximate representation cycle signal zero-cross point 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.Specific implementation process of the present invention is as follows:

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 the zero point of ac signal when changing from low to high said zero point.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.S0 on Fig. 1, 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 to obtain 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 negative sampled point equates or about equally.

3. the step of calculating the mean value M of several sampled points and average sample time of origin T is as follows:

1) selects several sampled points of combination in any near the zero point when the changing from low to high of ac signal;

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:

$M_j=\frac{\underset{1}{\overset{n}{\mathrm{\Σ}}}{y}_i}{n},$ $T_j=\frac{\underset{1}{\overset{n}{\mathrm{\Σ}}}{t}_i}{n};$

In the following formula, n 〉=1, i, j are natural number, then (M _j, T _j) can regard a virtual point as;

The process that obtains zero crossing is as follows: obtain (M _j, T _j) after, by the characteristics of current demand signal, the effective value of signal (perhaps peak value) and M _jObtain T ' by direct calculating _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 in step 2) in the sampled point chosen choose T ' then near the zero point when the changing from low to high of ac signal _jCan be expressed as:

${T_j}^{\′}=-1\×\frac{\arcsin \frac{M_j}{U_{\mathrm{EMS}}\×\sqrt{2}}}{2\×\mathrm{\π}\×f}=-1\×\frac{\arcsin \frac{M_j}{U_{\mathrm{MAX}}}}{2\×\mathrm{\π}\×f}$

When

Hour, T ' _jBut approximate representation is:

${T_j}^{\′}=-1\×\frac{\arcsin \frac{M_j}{U_{\mathrm{EMS}}\×\sqrt{2}}}{2\×\mathrm{\π}\×f}\≈-1\×\frac{M_j}{U_{\mathrm{EMS}}\×\sqrt{2}\×2\×\mathrm{\π}\×f_c}=-1\×\frac{M_j\×T_c}{U_{\mathrm{EMS}}\×\sqrt{2}\×2\×\mathrm{\π}}$

${T_j}^{\′}=-1\×\frac{\arcsin \frac{M_j}{U_{\mathrm{MAX}}}}{2\×\mathrm{\π}\×f}\≈-1\×\frac{M_j}{U_{\mathrm{MAX}}\×2\×\mathrm{\π}\×f_c}=-1\×\frac{M_j\×T_c}{U_{\mathrm{MAX}}\×2\×\mathrm{\π}};$

In above-mentioned several formula, f _cBe the ac voltage standard frequency, T _cBe the ac voltage standard cycle, U _MAXBe the ac signal maximal value, U _EMSIt is the ac signal effective value.The establishment condition of above-mentioned several formula is

Perhaps

As far as possible little.Under normal conditions,

More little, then the effect of Ying Yonging is good more, requirement in the follow-up application

Scope just carry out the calculating of zero crossing in [0.1,0.1].

After the calculating, then the Dui Ying zero crossing time can be expressed as: T _Zj=T _j+ T ' _j

4. point (the M at the hollow triangle place among Fig. 2 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 obtains after as calculated; 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 obtains after as calculated; 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 obtains after as calculated; Sampling in the example of Fig. 2, Fig. 3, Fig. 4 is the constant duration sampling.Fig. 5 is the result schematic diagram 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 obtains after as calculated.

5. obtain several zero crossings and can carry out the calculating of signal period after the time, ac signal among Fig. 6 has carried out calculating for four times (near 2 positive levels and 2 the negative level sampled points zero point are adopted in each calculating) near zero point (zero crossing when signal changes from low to high), obtain the virtual point at four hollow triangle places, obtained four zero crossing: T at open circles place after calculating by four virtual point 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

6. 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 has two zero crossing T1 as calculated among Fig. 7 when changing from low to high _iAnd T1 _I+1, AC signal II has two zero crossing T2 as calculated when changing from low to high _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 with the form that becomes radian to express.

7. the present invention adopts the ac voltage standard period T _cCalculate zero crossing T _Zj, when little, can obtain measurement result comparatively accurately in the tested alternating current actual cycle skew ac voltage standard cycle.When the tested alternating current actual cycle skew ac voltage standard cycle has to a certain degree, if still adopt the ac voltage standard period T _cCalculate zero crossing T _Zj, then may produce the bigger error of calculation, can adopt predetermined period T ' of current cycle this moment _cReplace the ac voltage standard period T _cCalculate.Obtain T ' _cMethod as follows: 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 Yu Ce current cycle can be expressed as: T ' _c=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.As adopt predetermined period T ' of current cycle _cCalculate zero crossing T _Zj, can obtain result more accurately.In above-mentioned experiment, make K ₁=1, K ₂=K ₃=K ₄=0, T ' then _c=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 of a kind of quick measurement ac signal phase differential involved in the present invention, do not need to 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. method of measuring fast the ac signal phase differential 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 zero point when tested electric signals some changes from low to high;

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:

$M_j=\frac{\underset{1}{\overset{n}{\mathrm{\Σ}}}{y}_i}{n},$ $T_j=\frac{\underset{1}{\overset{n}{\mathrm{\Σ}}}{t}_i}{n};$

In the following formula, n 〉=1, n, i, j are natural number, then (M _j, T _j) virtual point of expression;

Step 3), the process, electric signal effective value or the peak value that change from low to high at the ac signal of near zero-crossing point according to tested electric signals, and step 2) the mean value M of sampled value of a described n sampled point _j, obtain a mistiming T ' by calculation mode _j, described 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; Then Dui Ying zero crossing time representation is: T _Zj=T _j+ T ' _j

Near approximate straight line, then the zero crossing time T regarded as of sinusoidal signal that will be zero point _ZjComputing method as follows:

F wherein _cBe the ac voltage standard frequency, T _cBe the ac voltage standard cycle, U _MAXBe the ac signal maximal value, U _EMSBe the ac signal effective value, the condition that following formula is set up is

Perhaps

Value approach 0;

Step 4), near other zero point that changes from low to high of the sampled value of electric signal, select n sampled point of combination in any successively, 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 quick measurement ac signal phase differential according to claim 1 is characterized in that: described electric signal is sampled of step 1) is constant duration sampling or not constant duration sampling.

3. the method for quick measurement ac signal phase differential according to claim 1 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 quick measurement ac signal phase differential according to claim 1 is characterized in that: the concrete steps in the calculating tested electric signals cycle described in the step 4) are as follows: _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, therefore the cycle of the signal that 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 quick measurement ac signal phase differential according to claim 1 is characterized in that: the described concrete steps of step 5) are as follows: 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.

6. according to the method for each described quick measurement ac signal phase differential in the claim 1 to 5, it is characterized in that: during the cycle, adopt predetermined period T ' of current cycle in the step 3) at tested alternating current actual cycle skew ac voltage standard _cReplace the ac voltage standard period T _cCalculate, obtain T ' _cMethod as follows:

A) 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, 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 Yu Ce current cycle is shown:

T ' _c=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.

Images