CN102928666A - Digital measurement method for phase difference of alternating current - Google Patents

Abstract

The invention discloses a digital measurement method for phase difference of alternating current, which comprises the following steps of: sequentially selecting sampling points P1, P2 and P3 after a signal passes through a negative peak in allusion to continuous digital sampling signals; leading a negative value of a P1 sampling value to be between a P2 sampling value and a P3 sampling value; solving a point P4 on a line segment comprising the P2 and the P3 by an interpolation method; leading a numerical value of the P4 to be equal to the negative value of the P1 sampling value; and acquiring virtual generation time of the P4; calculating a zero point of an electric signal according to sampling generation time of the P1 and the virtual generation time of the P4; calculating a period of the electric signal according to a series of zero crossing points of the electric signal; and calculating the phase difference between signal acquisition according to time difference of different signals passing through the zero points and a signal period. By the digital measurement method, the defect of poor anti-jamming capability of the traditional zero crossing point detection is overcome, the digital measurement method is particularly suitable for measurement on the phase difference of a low-frequency signal, data is accurate and reliable when the method is implemented, and the digital measurement method has wide application prospect.

Description

A kind of digital measuring method of phase differential of alternating current

Technical field

The present invention relates to a kind of Digital Measuring Technique of phase differential of alternating current, also can be used for the phase difference measurement of other low-frequency signals.

Background technology

Usually need to measure the phase differential of ac signal in daily life, production run, the phase differential of measurement is more accurate, and the effect of application is often better.In existing method for measuring phase difference, great majority adopt signal are transformed into square wave, then measure the mistiming of rising edge between two square waves, thereby draw the phase differential of two signals,, this algorithm needs extra hardware and the impact that easily is interfered but being easy to realize.

Summary of the invention

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

The present invention is for solving the problems of the technologies described above by the following technical solutions:

A kind of digital measuring method of phase differential of alternating current may further comprise the steps:

Step 1) is sampled to tested electric signals, obtains the sampled value of tested electric signals, then generates sampled signal;

Step 2), in the sampled signal of tested electric signals, select a sampled point as the first sampled point P1 when after the cycle of tested electric signals is crossed negative peak, not arriving zero point _i, establish this first sampled point P1 _iSampling time be T1 _i, sampled value is S1 _i

Step 3) when not arriving positive peak after the cycle of tested electric signals is crossed zero point, is chosen two continuous sampled points, i.e. the second sampled point P2 in this section sampled signal _iWith the 3rd sampled point P3 _i, the sampling time of establishing these two points is respectively T2 _iAnd T3 _i, sampled value is respectively S2 _iAnd S3 _i, sampled value S2 wherein _iAnd S3 _iNeed to satisfy | S2 _i|≤| S1 _i|≤| S3 _i| and | S2 _i|＜| S3 _i|;

Step 4) is with the first sampled point P1 _iThe inverse value of sampled value is corresponding as virtual sampled point P4 _i, calculate virtual sampled point P4 _iVirtual time of origin ${T4}_i={T2}_i+\frac{({T3}_i-{T2}_i)\×({S1}_i+{S2}_i)}{{S2}_i-{S3}_i};$

Step 5), calculate the zero crossing time: $T_{\mathrm{zi}}=\frac{{T1}_i+{T4}_i}{2};$

Step 6), repeating step 2) obtains several zero crossings time: T to step 5) _Z1, T _Z2, T _Z3... T _Zi, T _Zi+1, T _Zi+2... T _Zn, wherein, i=1,2 ... n, n are positive integer; The cycle of tested electric signals: T then _Pi=T _Zi+1-T _Zi, the cycle of the signal that therefore obtains is followed successively by T _P1, T _P2, T _P3... T _Pn-1

Step 7) for two tested electric signals that frequency is identical, obtains respectively the zero crossing time of two tested electric signals according to step 1) to step 6); Again according to the difference of zero crossing time of two tested electric signals, and the cycle of two tested electric signals, calculate two phase differential between the tested electric signals.

Further, the digital measuring method of the phase differential of a kind of alternating current of the present invention, the described sampling of step 1) is constant duration sampling or not constant duration sampling.

Further, the digital measuring method of the phase differential of a kind of alternating current of the present invention, described being sampled as of step 1) sampled to the complete cycle ripple.

Further, the digital measuring method of the phase differential of a kind of alternating current of the present invention, the concrete steps of described step 7) are as follows:

If the zero crossing time of the first via tested electric signals that is calculated by step 1) to step 6) is T1 _Zi, the second tunnel tested electric signals the zero crossing time be T2 _Zi, then the value of the phase differential of two-way tested electric signals is expressed as with the number of degrees:

Perhaps be expressed as with radian: $P_r=\frac{{T2}_{\mathrm{zi}}-{T1}_{\mathrm{zi}}}{T_p}\×2\×\mathrm{\π},$ Wherein, T _pThe instantaneous value in tested electric signals cycle of calculating according to step 6), or the mean value of front several periodic quantities of the tested electric signals that calculates according to step 6).

Further, the digital measuring method of the phase differential of a kind of alternating current of the present invention, in described step 3), when the sampled value of the first to the 3rd sampled point of choosing meets | S2 _i|=| S1 _i|=| S3 _i| during condition, take in following two kinds of processing schemes any one:

A), again choose the second sampled point P2 _iWith the 3rd sampled point P3 _i, so that the sampled value S2 of the second sampled point _iSampled value S3 with the 3rd sampled point _iMust satisfy | S2 _i|＜| S3 _i|, then continue step 4) to step 7);

B), at the second sampled point P2 _iWith the 3rd sampled point P3 _iInterval [T2 of sampling time _i, T3 _i] take up an official post and get a bit as virtual sampled point P4 _iCorresponding virtual sampling time T4 _i, then continue step 5) to step 7).

Further, the digital measuring method of the phase differential of a kind of alternating current of the present invention is in described scheme b) in, the second sampled point P2 got _iWith the 3rd sampled point P3 _iInterval [T2 of sampling time _i, T3 _i] on mid point, calculate virtual sampled point P4 _iVirtual time of origin ${T4}_i=\frac{{T3}_i+{T2}_i}{2}.$

The present invention adopts above technical scheme compared with prior art, has following technique effect:

1) traditional two opposite continuity points of zero friendship method symbolization are determined zero point, although the algorithm clear physics conception easily is subjected to the interference of harmonic wave, measuring error etc., measuring accuracy is low.Only have accurate location zero point, just can calculate accurate phase differential.The present invention can be through calculating zero crossing by 3 sampled points choosing.Determined after the zero crossing of signal, can calculate frequency and the cycle of AC signal.At last according to difference and the signal period of zero crossing time of unlike signal, calculate the phase differential that obtains between the signal.Traditional zero friendship method of comparing, operand increases to some extent, but precision, the anti-interference measured are greatly improved.

2) sampling involved in the present invention can be the constant duration sampling, also can be not constant duration sampling.

Description of drawings

Fig. 1 is that Fig. 1 is by P1 _i, P2 _i, P3 _iMode by interpolation is obtained P4 _i, more further by T1 _iAnd T4 _iCalculate the schematic diagram of zero crossing;

Fig. 2 is the schematic diagram that calculates the signal period;

Fig. 3 is the schematic diagram that calculates the two paths of signals phase differential.

Embodiment

Below in conjunction with accompanying drawing technical scheme of the present invention is described in further detail:

Essence of the present invention is to choose a sampled point P1 after signal is crossed negative peak, then selects continuous two some P2 and P3 behind signal zero crossing, and the condition of choosing of P2 and P3 is that the negative value of P1 sampled value is in interval [P2 sampled value, P3 sampled value].Method that then can be by interpolation is asked for 1 P4 at the line segment that P2 and P3 form, so that the numerical value of P4 equals the negative value of P1 sampled value, can obtain the virtual time of origin that P4 is ordered simultaneously.Calculated the zero point of electric signal by the virtual time of origin of the sampling time of origin of P1 and P4, calculated the cycle of electric signal by the zero crossing of series of electrical signals.At last according to difference and the signal period of zero crossing time of unlike signal, calculate the phase differential that obtains between the signal.The P1 that chooses should not be too near zero point, if cause measurement result not accurate enough near the interference that easily is subject to noise zero point.

For obtaining comparatively accurate measurement result, the Choice of the sampled point P1 of suggestion is: should not be too near zero point.

The features and advantages of the invention will be elaborated by reference to the accompanying drawings by example.Principle of the present invention describes by the phase differential of measuring low frequency signal, and along with the raising of sample rate, the sampling number of the generation in a cycle is also more and more.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. after crossing negative peak, the survey electric signal selects a sampled point P1 _i, the sampling time of establishing this sampled point is T1 _i, sampled value is S1 _iAfter sampled signal is crossed zero point, in follow-up sampled value, choose two continuous some P2 _iAnd P3 _i, the sampling time of establishing these two points is respectively T2 _iAnd T3 _i, the sampled value of two points is respectively S2 _iAnd S3 _i, these two points have following characteristics: S1 _iBe negative, S2 _iAnd S3 _iBe all positive number, and satisfy | S2 _i|≤| S1 _i|≤| S3 _i, | S2 _i|＜| S3 _i|.

3. the process that obtains zero crossing is as follows, at first need calculate P4 _iThe virtual time of origin T4 of point _i, because P4 _iNumerical value equal P1 _iThe negative value of sampled value, then: T4 _iCan be expressed as ${T4}_i={T2}_i+\frac{({T3}_i-{T2}_i)\×({S1}_i+{S2}_i)}{{S2}_i-{S3}_i};$ When the sampled value of the sampled point of choosing meets | S2 _i|=| S1 _i|=| S3 _i| during condition, can take two kinds of disposal routes: a kind of method is again to choose P2 _iAnd P3 _iAnd recomputate; Another kind method is T4 _iAt interval [T2 _i, T3 _i] take up an official post and get a bit, calculate for convenient, get this interval mid point, then

According to calculating the T4 that obtains _i, being calculated as follows of zero crossing time:

$T_{\mathrm{zi}}=\frac{{T1}_i+{T4}_i}{2};$

4. concrete operations can be referring to Fig. 1.Hollow round spot P1 on Fig. 1 _i, P2 _i, P3 _iThree points selecting as requested, hollow triangle point P4 _iThe virtual point through obtaining after the interpolation, some P4 _iNumerical value for the some P1 _iThe negative value of sampled value.T1 _iP1 _iSampling time, T4 _iP4 _iVirtual time of origin, the hollow round spot T on the transverse axis _ZiIt is the zero crossing that obtains after calculating.

5. obtain several zero crossings and can carry out the calculating of signal period after the time, the low frequency signal one among Fig. 2 co-exists in 3 negative peaks, has therefore carried out altogether 3 interpolation and also calculate after negative peak occurs, and the time is respectively T on the transverse axis _Z1, T _Z2, T _Z3Hollow round spot be 3 zero crossings that calculate because cycle of measured signal can be expressed as: T _Pi=T _Zi+1-T _Zi, so among Fig. 2 the signal period can be expressed as: T _P2=T _Z3-T _Z2, T _P1=T _Z2-T _Z1

6. the calculating of phase differential can be referring to Fig. 3, and sinusoidal wave I has two zero crossings among the figure after negative peak occurs, and the time of these two zero crossings is respectively T1 _ZiAnd T1 _Zi+1, sinusoidal wave II also has two zero crossings after negative peak occurs, and the time of these two zero crossings is respectively T2 _ZiAnd T2 _Zi+1, then the phase differential of sinusoidal wave I and sinusoidal wave II can be expressed as:

Perhaps

T in the formula _pThe cycle of signal, T _pCan be the instantaneous value of signal period of calculating, or the mean value of the front several periodic quantities that calculate.Formula also can be write as the form that radian is expressed.

Preferred version is the described constant duration sampling that is sampled as.

In sum, the digital measuring method of the phase differential of a kind of alternating current involved in the present invention, do not need to convert low frequency signal to square wave, overcome the shortcoming that traditional zero crossing detects poor anti jamming capability, be particularly suitable for the phase difference measurement of low frequency signal, system is easy to detect, and hardware spending is little; The method has certain antijamming capability; Implement advantages of simple, data accurately, reliably; More widely application prospect is arranged.Certainly, the present invention also can be applied to phase difference measurement, measuring power angle of civilian three-phase alternating current etc.

Claims (6)

1. the digital measuring method of the phase differential of an alternating current 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, then generates sampled signal;

Step 2), in the sampled signal of tested electric signals, select a sampled point as the first sampled point P1 when after the cycle of tested electric signals is crossed negative peak, not arriving zero point _i, establish this first sampled point P1 _iSampling time be T1 _i, sampled value is S1 _i

Step 3) when not arriving positive peak after the cycle of tested electric signals is crossed zero point, is chosen two continuous sampled points, i.e. the second sampled point P2 in this section sampled signal _iWith the 3rd sampled point P3 _i, the sampling time of establishing these two points is respectively T2 _iAnd T3 _i, sampled value is respectively S2 _iAnd S3 _i, sampled value S2 wherein _iAnd S3 _iNeed to satisfy | S2 _i|≤| S1 _i|≤| S3 _i|;

Step 4) is with the first sampled point P1 _iThe inverse value of sampled value is corresponding as virtual sampled point P4 _i, calculate virtual sampled point P4 _iVirtual time of origin ${T4}_i={T2}_i+\frac{({T3}_i-T{2}_i)\×({S1}_i+{S2}_i)}{{S2}_i-S{3}_i};$

Step 5), calculate the zero crossing time:

Step 6), repeating step 2) obtains several zero crossings time: T to step 5) _Z1, T _Z2, T _Z3... T _Zi, T _Zi+1, T _Zi+2... T _Zn, wherein, i=1,2 ... n, n are positive integer; The cycle of tested electric signals: T then _Pi=T _Zi+1-T _Zi, the cycle of the signal that therefore obtains is followed successively by T _P1, T _P2, T _P3... T _Pn-1

Step 7) for two tested electric signals that frequency is identical, obtains respectively the zero crossing time of two tested electric signals according to step 1) to step 6); Again according to the difference of zero crossing time of two tested electric signals, and the cycle of two tested electric signals, calculate two phase differential between the tested electric signals.

2. the digital measuring method of the phase differential of a kind of alternating current according to claim 1 is characterized in that: the described sampling of step 1) is constant duration sampling or not constant duration sampling.

3. the digital measuring method of the phase differential of a kind of alternating current according to claim 1, it is characterized in that: described being sampled as of step 1) sampled to the complete cycle ripple.

4. the digital measuring method of the phase differential of a kind of alternating current according to claim 1, it is characterized in that: the concrete steps of described step 7) are as follows:

If the zero crossing time of the first via tested electric signals that is calculated by step 1) to step 6) is T1 _Zi, the second tunnel tested electric signals the zero crossing time be T2 _Zi, then the value of the phase differential of two-way tested electric signals is expressed as with the number of degrees:

Perhaps be expressed as with radian: $P_r=\frac{T{2}_{\mathrm{zi}}-{T1}_{\mathrm{zi}}}{T_p}\×2\×\mathrm{\π},$ Wherein, T _pThe instantaneous value in tested electric signals cycle of calculating according to step 6), or the mean value of front several periodic quantities of the tested electric signals that calculates according to step 6).

5. the digital measuring method of the phase differential of a kind of alternating current according to claim 1 is characterized in that: in described step 3), when the sampled value of the first to the 3rd sampled point of choosing meets | S2 _i|=| S1 _i|=| S3 _i| during condition, take in following two kinds of processing schemes any one:

A), again choose the second sampled point P2 _iWith the 3rd sampled point P3 _i, so that the sampled value S2 of the second sampled point _iSampled value S3 with the 3rd sampled point _iMust satisfy | S2 _i|＜| S3 _i|, then continue step 4) to step 7);

B), at the second sampled point P2 _iWith the 3rd sampled point P3 _iInterval [T2 of sampling time _i, T3 _i] take up an official post and get a bit as virtual sampled point P4 _iCorresponding virtual sampling time T4 _i, then continue step 5) to step 7).

6. the digital measuring method of the phase differential of a kind of alternating current according to claim 5 is characterized in that: in described scheme b) in, the second sampled point P2 got _iWith the 3rd sampled point P3 _iInterval [T2 of sampling time _i, T3 _i] on mid point, calculate virtual sampled point P4 _iVirtual time of origin

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