CN102508193A - Electric energy meter phase calibration method based on FIR (Finite Impulse Response) digital filtering - Google Patents

Abstract

The invention relates to an electric energy meter phase calibration method based on FIR (Finite Impulse Response) digital filtering. The electric energy meter phase calibration method based on the FIR digital filtering is characterized by comprising the steps of: connecting a first-order FIR filter at an output end of a voltage sampling loop, wherein the first-order FIR filter is y[n]=x[n]+beta*x[n-1], where the x is an input voltage, the y is an output voltage after passing through the first-order FIR filter, the n is a sampling sequence, and the beta is a delay gain; and obtaining the delay gain beta by calculating a formula (101) shown as D=beta(beta+cosw)/1+beta<2>+2betacosw, a formula (102) shown as D=phi/w and a formula (103) shown as w=2pifm/fs, wherein the D is a group delay of the first-order FIR filter, the w is an angular frequency after sampling, the phi is a phase difference generated by the current and the current voltage after passing through a current sampling loop and a voltage sampling loop, the fm is a frequency of a power grid system, and the fs is a sampling frequency of the voltage sampling loop. The electric energy meter phase calibration method based on the FIR digital filtering, disclosed by the invention, can save hardware cost, improve the calibration frequency of the meter and calibration precision of the meter and further guarantee stability and reliability of long-term operation of the electric energy meter.

Description

Electric energy meter phase alignment based on the FIR digital filtering

[technical field]

The present invention relates to the electric-power metering field, be specifically related to a kind of electric energy meter phase alignment based on the FIR digital filtering.

[background technology]

As shown in Figure 1, we know that all can there be phase differential θ (being that θ is power network current, voltage self angle) in electric current, voltage in the input electric energy meter, get power P according to electric current, voltage, rating formula (1) ₀:

P ₀=K _V* V _In* K _I* I*COS (θ)---formula (1), K _I, K _VQuantization parameter for electric current, voltage.

In order to gather exact current, voltage signal; Electric energy meter can be provided with a pair of electric current before electric current, voltage signal are gathered, voltage carries out pretreated anti-aliasing filter circuit; But in the anti-aliasing filter circuit; Because the existence of inductance, electric capacity on current transformer CT and the circuit causes producing a variable quantity φ (as shown in Figure 1) again through the phase differential θ of anti-aliasing filter circuit, pass through promptly that the formula (2) of rated output is behind the anti-aliasing filter circuit:

P ₁=K _V* V _Out* K _I* I*COS (θ+φ)---formula (2), K _I, K _VQuantization parameter for electric current, voltage.

Therefore, can get measuring error computing formula (3):

$E_{\left(M\right)}=\frac{P_0-P_1}{P_0}=\frac{\mathrm{COS}\left(\mathrm{\&theta;}\right)-\mathrm{COS}(\mathrm{\&theta;}+\mathrm{\&phi;})}{\mathrm{COS}\left(\mathrm{\&theta;}\right)}$ ---formula (3).

For the precision that guarantees that ammeter measures in LC property system, ammeter manufacturer must calibrate it before ammeter dispatches from the factory accordingly.

Traditional method for correcting phase adopts resistance, capacitance simulation mode to calibrate more; But since the discreteness of resistance capacitance, thermal instability, long-time running reliability and to the phase correction precision and produce in enormous quantities efficient requirement improve constantly, the method for conventional analogue phase calibration can not satisfy present demand.

[summary of the invention]

The technical matters that the present invention will solve provides a kind of electric energy meter phase alignment based on the FIR digital filtering, can the economize on hardware cost, improve calibration efficient, and the calibration precision be can improve again, further long playing stability of ammeter and reliability guaranteed.

Above-mentioned technical problem realizes by the following technical programs:

A kind of electric energy meter phase alignment based on the FIR digital filtering is characterized in that, the output terminal in the voltage sample loop connects a single order FIR wave filter, and this single order FIR wave filter is:

Y [n]=x [n]+β * x [n-1], wherein, x is an input voltage, and y is that n is a sample sequence through the output voltage behind the single order FIR wave filter, and β postpones gain;

Postpone gain beta and calculate gained by formula (101), formula (102) and formula (103):

$D=\frac{\mathrm{\&beta;}(\mathrm{\&beta;}+\mathrm{Cos}w)}{1+{\mathrm{\&beta;}}^2+2\mathrm{\&beta;}\mathrm{Cos}w}$ ---formula (101),

D=φ/w---formula (102),

$w=\frac{2\mathrm{\&pi;}{f}_m}{f_s}$ ---formula (103),

Wherein, D is the group delay of single order FIR wave filter, and w is the angular frequency after sampling, and φ is the phase differential that electric current, voltage are produced through excess current, voltage sample loop, f _mBe network system frequency, f _SSF for the voltage sample loop.

Further scheme is, multiply by the contrary A of single order FIR filter gain through the magnitude of voltage of single order FIR wave filter output ^-1, A ^-1Be specially: A ^-1=[(cos w+ β) ²+ sin ²W] ^-1/2

Principle of the present invention is specially:

1, voltage is relatively stable in electrical network, and the fluctuation of voltage can not surpass 5 percent under the normal condition, so the signal in the voltage sample loop of input electric energy meter is also very stable; But electric current changes with the variation of power load in the electrical network; So non-constant width of dynamic range of change in current; Particularly wide-range, the high-precision technical requirement of electric energy meter proposition now; Cause the dynamic range of electric energy meter metering to require to surpass 1000: 1, very faint, only a little several in the simulating signal of the current sampling circuit of little current point input;

2, in the anti-aliasing filter circuit; The hardware circuit model is in case confirm; Phase difference between current/voltage is just confirmed thereupon; And the phase difference between the current/voltage can not change with the variation of self loading yet, so in the whole measures range of electric energy meter (1000: 1), the phase difference of current/voltage is almost constant;

3, since analyze in the background technology can know the factor that produces power error be electric current, voltage relatively but not the absolute phase variable quantity; But because the electric current variation range is very wide; The input current sampling circuit is very faint when small-signal; If the digital signal to after this moment sampling is carried out processing such as correlated digital filtering, just can produce very large distortion, so for the guaranteed output error in the precision of little current point and the linearity in the gamut; We suppose that electric current does not have phase change; With the current point is reference, and the phase changing capacity of electric current, voltage in the anti-aliasing filter circuit all is superimposed upon on the voltage circuit, utilize single order FIR wave filter to variable quantity compare less, that signal amplitude is bigger, carry out a series of digital filterings through the voltage signal after the analog to digital conversion and handle; Reach adjustment current/voltage phase differential purpose, guarantee the overall precision of electric energy meter;

4, because phase difference confirms and can survey that the present invention applies to this phase difference that can survey in the single order FIR wave filter voltage sample value is handled, so that voltage-phase moves the φ phase place, promptly to move be the group delay of actual average angle to voltage-phase.

The present invention utilizes single order FIR wave filter that the voltage sample value is handled with adjustment current/voltage phase differential, can the economize on hardware cost, improve calibration efficient, and the calibration precision be can improve again, further long playing stability of electric energy meter and reliability guaranteed.

[description of drawings]

Fig. 1 is the input voltage V of anti-aliasing filter circuit _In, output voltage V _OutWith the electric current I is the phase place synoptic diagram of benchmark;

Fig. 2 is that single order FIR wave filter is realized schematic diagram.

[embodiment]

As shown in Figure 2, a kind of electric energy meter phase alignment based on the FIR digital filtering, its output terminal in the voltage sample loop connects a single order FIR wave filter, and this single order FIR wave filter is:

Y [n]=x [n]+β * x [n-1], wherein, x is an input voltage, and y is that n is a sample sequence through the output voltage behind the single order FIR wave filter, and β postpones gain;

Postpone gain beta and calculate gained by formula (101), formula (102) and formula (103):

$D=\frac{\mathrm{\&beta;}(\mathrm{\&beta;}+\mathrm{Cos}w)}{1+{\mathrm{\&beta;}}^2+2\mathrm{\&beta;}\mathrm{Cos}w}$ ---formula (101),

D=φ/w---formula (102),

$w=\frac{2\mathrm{\&pi;}{f}_m}{f_s}$ ---formula (103),

Wherein, D is the group delay of single order FIR wave filter, and w is the angular frequency after sampling, and φ is the phase differential that electric current, voltage are produced through excess current, voltage sample loop, f _mBe network system frequency, f _SSF for the voltage sample loop.

In order to compensate the non-normalized gain of single order FIR wave filter, multiply by the contrary A of single order FIR filter gain through the magnitude of voltage of single order FIR wave filter output ^-1, A ^-1Be specially:

A ^-1＝[(cos?w+β) ²+sin ²?w] ^-1/2。

The present invention is not limited to the foregoing description, based on simple replacement the foregoing description, that do not make creative work, should belong to the scope that the present invention discloses.

Claims (2)

1. the electric energy meter phase alignment based on the FIR digital filtering is characterized in that, the output terminal in the voltage sample loop connects a single order FIR wave filter, and this single order FIR wave filter is:

y[n]＝x[n]+β*x[n-1]

Wherein, x is an input voltage, and y is that n is a sample sequence through the output voltage behind the single order FIR wave filter, and β postpones gain;

Postpone gain beta and calculate gained by formula (101), formula (102) and formula (103):

$D=\frac{\mathrm{\&beta;}(\mathrm{\&beta;}+\mathrm{Cos}w)}{1+{\mathrm{\&beta;}}^2+2\mathrm{\&beta;}\mathrm{Cos}w}$ ---formula (101),

D=φ/w---formula (102),

$w=\frac{2\mathrm{\&pi;}{f}_m}{f_s}$ ---formula (103),

Wherein, D is the group delay of single order FIR wave filter, and w is the angular frequency after sampling, and φ is the phase differential that electric current, voltage are produced through excess current, voltage sample loop, f _mBe network system frequency, f _SSF for the voltage sample loop.

2. the electric energy meter phase alignment based on the FIR digital filtering according to claim 1 is characterized in that, multiply by the contrary A of single order FIR filter gain through the magnitude of voltage of single order FIR wave filter output ^-1, A ^-1Be specially: A ^-1=[(cos w+ β) ²+ sin ²W] ^-1/2

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