CN104483542A - Rogowski-coil-based electric energy metering method - Google Patents

Abstract

The invention discloses a Rogowski-coil-based electric energy metering method. The method comprises the following steps: firstly acquiring a voltage sampling value and a current channel induction voltage sampling value by virtue of manner such as the Rogowski coil; then carrying out zero-cross detection on a voltage signal, calculating an actual sampling point number and voltage as well as direct-current components of the current channel when an effective zero-cross point is detected, and correcting the voltage and the direct-current of the current channel at the same time; subsequently carrying out digital integration on current channel signals for correcting the direct current to reduce the detected current signals, and compensating a primary integration value of the current integration by using a dynamic direct current canceling method; finally carrying out dot product accumulation on the former processed voltage and the current values, and calculating effective values of the voltage and the current, power and electric energy. According to the Rogowski-coil-based electric energy metering method, a digital integrator is used for replacing an analog integrator; the integration is not influenced by the environment factors and actual devices; the digital integrator is good in phase property, simple in structure, accurate and stable in integration, and high in metering accuracy; the hardware cost is not increased.

Description

Based on the electric energy gauging method of Rogowski coil

Technical field

The present invention relates to a kind of electric energy gauging method, particularly relate to a kind of electric energy gauging method based on Rogowski coil.

Background technology

The current measurement of current electric energy meter mainly adopts the measuring method of current transformer (CT) or divertor, and what wherein current transformer extensively adopted is electromagnetic current transducer, and what divertor adopted is copper-manganese resistance.Along with the development of electric system, electrical power transmission system capacity constantly increases, and working voltage grade improves gradually, and the inherent shortcoming of conventional current measuring method shows become increasingly conspicuous.As: the dynamic range of CT is not wide, easily saturated under big current, cannot measure direct current, easily by the impact of high-intensity magnetic field interference; Copper-manganese exist self-heating serious, cannot to isolate or isolation scheme is complicated, there is the defects such as certain potential safety hazard.

In order to overcome the defect of conventional current measuring method, a kind of novel current transformer of safe and reliable, superior performance must be found.Rogowski coil is one of representative wherein.Rogowski coil is a kind of Novel electronic current transformer, compares with copper-manganese with traditional electromagnetic current transducer, and Rogowski coil has wide dynamic range, low cost and other advantages little, lightweight, easy for installation without magnetic saturation phenomenon, volume.

It is trend of the times that Rogowski coil is applied to electric energy metrical, in the market the existing Rogowski coil being applicable to electric energy meter metering.But Rogowski coil is applied to the solution that electric energy metrical there is no comparative maturity at present.Although the at present existing the special metering IC supporting Rogowski coil, all there is respective defect in these computation chips, as not high in small area analysis accuracy and less stable etc., and expensive.Therefore, the accuracy and the stability that how to improve Rogowski coil metering are current problem demanding prompt solutions.

Summary of the invention

The object of the present invention is to provide a kind of accuracy and the stability that can improve Rogowski coil metering, and the electric energy gauging method based on Rogowski coil that application cost is low.

This electric energy gauging method based on Rogowski coil provided by the invention, comprises the steps:

Step one, voltage signal u (t) of sampling input and current signal i (t), obtain discrete voltage sample value u (n) and current channel induced voltage sampled value e (n);

Step 2, obtains the DC component of voltage and the DC component of current channel induced voltage, and carries out direct current correction by the DC component obtained to voltage sample value u (n) and current channel induced voltage sampled value e (n);

Step 3, the induced voltage sampled value obtained after correcting direct current in step 2 by following formula carries out digital integration, reduction current signal i (n):

$i\left(n\right)=i\left(0\right)-\frac{1}{M}\·\frac{\mathrm{\ΔT}}{2}[e^{\′}\left(0\right)+2\underset{k=1}{\overset{n-1}{\mathrm{\Σ}}}{e}^{\′}\left(k\right)e^{\′}\left(n\right)]$

In formula, i (n) reduces through digital integration the current signal obtained; The initial value for integral that i (0) is electric current; Δ T is the signal sampling time interval; E ' (0), e ' (k) and e ' (n) are the data of current channel induced voltage sampled value after direct current corrects; M is the coefficient of mutual inductance of Rogowski coil and tested electric current;

Step 4, obtains described integration and reduces the DC component of current signal i (n) obtained, and reduces current signal i (n) obtained carry out initial value for integral compensation by the DC component obtained to described integration;

Step 5, the described integration that the data u ' (n) of voltage sample value u (n) obtained step 2 after direct current corrects and step 4 obtain reduce the data i ' (n) of current signal i (n) after initial value for integral compensates obtained to carry out dot-product operation and accumulates, acquisition voltage effective value, current effective value, power and electric energy.

Described step 2 comprises: a. voltage signal u (t) adopts electric resistance partial pressure to sample and obtains voltage sampling signal u ' (t); Current signal adopts Rogowski coil sampling to obtain induced voltage e (t)=di (t)/dt; B. voltage sampling signal u ' (t) and current sampling signal e (t) are input to the AFE (analog front end) of MCU respectively through signal conditioning circuit, sample and be converted to discrete voltage sample value u (n) and current channel induced voltage sampled value e (n) through the built-in A/D converter of MCU;

The DC component of described voltage obtains according to the following formula, and the DC component of described current channel induced voltage obtains according to the following formula:

$U_{\mathrm{dc}}=\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}u\left(n\right)/N$

$E_{\mathrm{dc}}=\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}e\left(n\right)/N$

In formula, each periodic voltage that u (n) and e (n) collect for described step one and current channel induced voltage n-th sampling point value, N is the sampling number in each cycle.

Described voltage sample value u (n) carries out direct current correction according to the following formula according to its DC component, and described current channel induced voltage sampled value e (n) carries out direct current correction according to the following formula according to its DC component;

u′(n)＝u(n)-U _dc

e′(n)＝e(n)-E _dc

In formula, each periodic voltage that u (n) and e (n) collect for described step one and current channel induced voltage n-th sampling point value; U ' (n) is the data of voltage sample value u (n) after direct current corrects; E ' (n) is the data of current channel induced voltage sampled value e (n) after direct current corrects; U _dcfor DC component and the E of voltage _dcfor the DC component of current channel induced voltage.

The DC component of described integration current signal i (n) is pressed following formula and is obtained:

$I_{\mathrm{dc}}=\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}i\left(n\right)/N$

In formula, i (n) reduces through digital integration the current signal obtained for step 3, and N is the sampling number in each cycle.

Described integration reduces current signal i (n) that obtains and carries out initial value for integral compensation according to the following formula according to the DC component obtained:

i′(n)＝i(n)-I _dc

In formula, i (n) reduces through digital integration the current signal obtained for step 3; I ' (n) carries out the data after initial value compensation for reducing current signal i (n) that obtains through digital integration; I _dcfor reducing the DC component of current signal i (n) obtained through integration.

The sampling number N in described each cycle is the sampling number between adjacent 2 positive going zeror crossing points.

The method of discrimination of described positive going zeror crossing point is: when detect voltage sample value by bear become positive time, namely previous sample amplitude when reproduced value is negative, and a rear sampled point is positive number, then this positive number point is an effective zero crossing; This positive number point is positive going zeror crossing point.

The signal sampling time interval Δ T of described step 3 is 156us.

The present invention effectively can solve some problems often run into when Rogowski coil is applied to electric energy metrical, as small area analysis accuracy problems, integral equalization sex chromosome mosaicism, frequency influence amount problem and harmonic effects amount problem.The present invention adopts digital integrator to substitute analogue integrator, integration is not completely by the impact of environmental factor, practical devices, phase propetry is good, structure is simple, integration is accurate, stable, the accuracy of measuring is high, and does not increase hardware cost, can be widely used in the electric energy metrical field based on Rogowski coil.

Accompanying drawing explanation

Fig. 1 is ultimate principle block diagram of the present invention.

Fig. 2 is process flow diagram of the present invention.

Embodiment

Below in conjunction with accompanying drawing, the present invention is further illustrated.

As shown in Figure 1, the present invention is mainly based on digital integrator.First sample input current signal by Rogowski coil, the induced voltage signal utilizing A/D converter sampled voltage signal and Rogowski coil to export, obtains voltage sample value and current channel induced voltage sampled value; Then zero passage detection is carried out to voltage signal, when effective zero crossing being detected, calculating actual samples and counting and voltage, current channel DC component, carrying out voltage simultaneously, current channel direct current corrects; Then the current channel signal corrected direct current carries out digital integration and reduces tested current signal, carries out initial value for integral compensation by the method for the direct current that dynamically disappears to current integration; Finally dot product accumulation is carried out to the voltage obtained through previous processed, current value, calculating voltage, current effective value, power and electric energy.

As shown in Figure 2, concrete implementation step of the present invention is as follows:

First, the voltage signal of input and the current signal of input are sampled.Specifically comprise:

(1) carry out sampling by voltage signal u (t) of resistance pressure-dividing network to input and obtain voltage sampling signal u ' (t), carry out sampling by current signal i (t) of Rogowski coil to input and obtain induced voltage e (t)=di (t)/dt;

(2) voltage sampling signal u ' (t) and current sampling signal e (t) are input to the AFE (analog front end) of MCU through signal conditioning circuit, then sampled signal is sampled by MCU built-in A/D converter, changes, obtain discrete voltage sample value u (n) and discrete current channel induced voltage sampled value e (n).The signal sampling time interval is 156us, and namely sample frequency is 6.4kHz.

Secondly, discrete voltage sample value, discrete current channel induced voltage sampled value are processed in real time, comprise direct current correction, voltage zero-cross detection, digital integration, initial value for integral compensates and voltage, current point accumulation are amassed.Concrete implementation step is as follows.

A. by judging that the positive and negative of voltage sample value carries out zero-crossing examination, when detect voltage sample value by bear become positive time, namely previous sample amplitude when reproduced value is negative, a rear sampled point is positive number, then positive number point is an effective zero crossing, obtains the actual samples points N in each cycle according to adjacent 2 zero crossing interval calculation.

B. by asking the mean value of one-period to obtain voltage, current channel induced voltage DC component, applicable formula is:

$U_{\mathrm{dc}}=\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}u\left(n\right)/N---\left(1\right)$

$E_{\mathrm{dc}}=\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}e\left(n\right)/N---\left(2\right)$

In formula, u (n) and e (n) are each periodic voltage of collecting and current channel induced voltage n-th sampling point value, and N is the sampling number in each cycle.

C. carry out direct current correction to voltage sample value u (n) and current channel induced voltage sampled value e (n), updating formula is:

u′(n)＝u(n)-U _dc(3)

e′(n)＝e(n)-E _dc(4)

In formula, u (n) and e (n) are each periodic voltage of collecting and current channel induced voltage n-th sampling point value; U ' (n) is the data of voltage sample value u (n) after direct current corrects; E ' (n) is the data of current channel induced voltage sampled value e (n) after direct current corrects; U _dcfor DC component and the E of voltage _dcfor the DC component of current channel induced voltage.

D. carry out digital integration, reduction current signal to correcting after-current signal in step c, integral formula is:

$i\left(n\right)=i\left(0\right)-\frac{1}{M}\·\frac{\mathrm{\ΔT}}{2}[e^{\′}\left(0\right)+2\underset{k=1}{\overset{n-1}{\mathrm{\Σ}}}{e}^{\′}\left(k\right)e^{\′}\left(n\right)]---\left(5\right)$

In formula, i (n) reduces through digital integration the current signal obtained; The initial value for integral that i (0) is electric current; Δ T is the signal sampling time interval; E ' (0), e ' (k) and e ' (n) are the data of current channel induced voltage sampled value after direct current corrects; M is the coefficient of mutual inductance of Rogowski coil and tested electric current.M is a constant, and this M value is found from Rogowski technical manual.

E. carry out initial value for integral compensation to digital integration, compensation formula is:

i′(n)＝i(n)-I _dc(6)

In formula, i (n) reduces through digital integration the current signal obtained; I ' (n) carries out the data after initial value compensation for reducing current signal i (n) that obtains through digital integration; I _dcfor reducing the DC component of current signal i (n) obtained through integration.

Wherein this DC component I _dcformula (7) can be adopted to obtain:

$I_{\mathrm{dc}}=\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}i\left(n\right)/N---\left(7\right)$

In formula, i (n) reduces through digital integration the current signal obtained, and N is the sampling number in each cycle.

F. the described integration that the data u ' (n) of voltage sample value u (n) obtained step c after direct current corrects and step e obtains reduce the data i ' (n) of current signal i (n) after initial value for integral compensates obtained to carry out dot-product operation and accumulates, acquisition voltage effective value, current effective value, power and electric energy.

Voltage effective value is suitable for formula:

Current effective value is suitable for formula:

Active power is suitable for formula:

Active energy is suitable for formula:

Claims (9)

1., based on an electric energy gauging method for Rogowski coil, comprise the steps:

Step one, voltage signal u (t) of sampling input and current signal i (t), obtain discrete voltage sample value u (n) and current channel induced voltage sampled value e (n);

Step 2, obtains the DC component of voltage and the DC component of current channel induced voltage, and carries out direct current correction by the DC component obtained to voltage sample value u (n) and current channel induced voltage sampled value e (n);

Step 3, the induced voltage sampled value obtained after correcting direct current in step 2 by following formula carries out digital integration, reduction current signal i (n):

In formula, i (n) reduces through digital integration the current signal obtained; The initial value for integral that i (0) is electric current; Δ T is the signal sampling time interval; E ' (0), e ' (k) and e ' (n) are the data of current channel induced voltage sampled value after direct current corrects; M is the coefficient of mutual inductance of Rogowski coil and tested electric current;

Step 4, obtains described integration and reduces the DC component of current signal i (n) obtained, and reduces current signal i (n) obtained carry out initial value for integral compensation by the DC component obtained to described integration;

Step 5, the described integration that the data u ' (n) of voltage sample value u (n) obtained step 2 after direct current corrects and step 4 obtain reduce the data i ' (n) of current signal i (n) after initial value for integral compensates obtained to carry out dot-product operation and accumulates, acquisition voltage effective value, current effective value, power and electric energy.

2. the electric energy gauging method based on Rogowski coil according to claim 1, is characterized in that, described step 2 comprises:

A. voltage signal u (t) adopts electric resistance partial pressure to sample and obtains voltage sampling signal u ' (t); Current signal adopts Rogowski coil sampling to obtain induced voltage e (t)=di (t)/dt;

B. voltage sampling signal u ' (t) and current sampling signal e (t) are input to the AFE (analog front end) of MCU respectively through signal conditioning circuit, sample and be converted to discrete voltage sample value u (n) and current channel induced voltage sampled value e (n) through the built-in A/D converter of MCU.

3. the electric energy gauging method based on Rogowski coil according to claim 1, is characterized in that, the DC component of described voltage obtains according to the following formula, and the DC component of described current channel induced voltage obtains according to the following formula:

In formula, each periodic voltage that u (n) and e (n) collect for described step one and current channel induced voltage n-th sampling point value, N is the sampling number in each cycle.

4. the electric energy gauging method based on Rogowski coil according to claim 3, it is characterized in that, described voltage sample value u (n) carries out direct current correction according to the following formula according to its DC component, and described current channel induced voltage sampled value e (n) carries out direct current correction according to the following formula according to its DC component;

u′(n)＝u(n)-U _dc

e′(n)＝e(n)-E _dc

In formula, each periodic voltage that u (n) and e (n) collect for described step one and current channel induced voltage n-th sampling point value; U ' (n) is the data of voltage sample value u (n) after direct current corrects; E ' (n) is the data of current channel induced voltage sampled value e (n) after direct current corrects; U _dcfor DC component and the E of voltage _dcfor the DC component of current channel induced voltage.

5. the electric energy gauging method based on Rogowski coil according to claim 1, is characterized in that, the DC component of described integration current signal i (n) is pressed following formula and obtained:

In formula, i (n) reduces through digital integration the current signal obtained for step 3, and N is the sampling number in each cycle.

6. the electric energy gauging method based on Rogowski coil according to claim 5, is characterized in that, described integration reduces current signal i (n) that obtains and carries out initial value for integral compensation according to the following formula according to the DC component obtained:

i′(n)＝i(n)-I _dc

In formula, i (n) reduces through digital integration the current signal obtained for step 3; I ' (n) carries out the data after initial value compensation for reducing current signal i (n) that obtains through digital integration; I _dcfor reducing the DC component of current signal i (n) obtained through integration.

7. the electric energy gauging method based on Rogowski coil according to claim 3, is characterized in that, the sampling number N in described each cycle is the sampling number between adjacent 2 positive going zeror crossing points.

8. the electric energy gauging method based on Rogowski coil according to claim 7, it is characterized in that, the method of discrimination of described positive going zeror crossing point is: when detect voltage sample value by bear become positive time, namely previous sample amplitude when reproduced value is negative, a rear sampled point is positive number, then this positive number point is an effective zero crossing; This positive number point is positive going zeror crossing point.

9. the electric energy gauging method based on Rogowski coil according to claim 1, is characterized in that, the signal sampling time interval Δ T of described step 3 is 156us.