CN103269211A - Digital filtering method for three-phase alternating current system measurement data - Google Patents

Abstract

Provided is a digital filtering method for three-phase alternating current system measurement data. The method includes the steps that a three-phase voltage signal VA, a three-phase voltage signal VB and a three-phase voltage signal VC are converted into a voltage signal V alpha and a voltage signal V beta under a two-phase alpha beta coordinate system; lowpass filtering is respectively carried out on the voltage signal V alpha and the voltage signal V beta according to a set transfer function to obtain a voltage signal V' alpha and a voltage signal V' beta; fundamental frequency phases delta of the voltage signal V' alpha and the voltage signal V' beta are calculated; fundamental frequency phase delay angle delta 0 of the lowpass filtering is calcauted according to the transfer function; the voltage signal V' alpha and the voltage signal V' beta are converted into direct current voltage Vd and direct current voltage Vq under a rotating dq two-phase coordinate system according to the fundamental frequency phases delta; the direct current voltage Vd and the direct current voltage Vq are converted into a voltage signal V'A, a voltage signal V'B and a voltage signal V'C under a three-phase coordinate system making delta-delta 0 as a coordinate system angle. The digital filtering method for the three-phase alternating current system measurement data can effectively solve the problem of fundamental frequency phase delay of a traditional filtering mode, and improves phase control precision of an electric system.

Description

The digital filtering method of three-phase alternating current systematic survey data

Technical field

The present invention relates to the digital filtering technique field, particularly relate to a kind of digital filtering method of three-phase alternating current systematic survey data.

Background technology

Along with the application of high-power switch device in fields such as wind power generation, photovoltaic generation, flexible ac transmissions, electric power system presents more and more significant non-linear, especially in voltage source converter (VSC) application scenario based on pulse-width modulation (PWM) technology, high order characteristic harmonics amplitude approaches even may surpass the fundamental frequency amplitude, in order to address the above problem, can take to install additional at system's primary side the scheme of filter, but because popularity, the uncertainty of high order harmonic component frequency spectrum, and the filter apparatus cost is higher, and effect that this technology obtains is extremely undesirable.

Because the wave distortion that high order harmonic component causes can't normally be controlled system and accurately metering, therefore, the existing power system generally can carry out the digital filtering of single order or high-order lowpass to sampled data in the measurement links of secondary system side, and current main research all is the parameter designing that is transfer function H (s).But, all can there be delay in any physically realizable system in the middle of actual, no matter how the coefficient in the transfer function H (s) designs, three-phase alternating current systematic survey data are through after the filtering, all be difficult to the fundamental frequency phase delay situation of avoiding filtering forward and backward, three-phase alternating current systematic survey data percent harmonic distortions (THD) are still higher, make the phase control of electric power system have serious deviation.

Summary of the invention

Based on this, be necessary at the problems referred to above, a kind of digital filtering method of three-phase alternating current systematic survey data is provided.

A kind of digital filtering method of three-phase alternating current systematic survey data comprises the steps:

With three-phase voltage signal V _A, V _B, V _CBe converted to the voltage signal V under the two-phase α β coordinate system _α, V _β

According to the transfer function of setting respectively to described voltage signal V _α, V _βCarry out low-pass filtering and obtain voltage signal V' _α, V' _β

Calculate described voltage signal V' _α, V' _βFundamental frequency phase place δ;

Calculate the fundamental frequency phase delay angle δ of described low-pass filtering according to described transfer function ₀

According to described fundamental frequency phase place δ with described voltage signal V' _α, V' _βBe converted to the direct voltage V under rotation dq two phase coordinate systems _d, V _q

With δ-δ ₀For angle of transformation with described direct voltage V _d, V _qBe converted to the voltage signal V' under three phase coordinates _A, V' _B, V' _C

The digital filtering method of above-mentioned three-phase alternating current systematic survey data, be α β two phase coordinates with three-phase voltage signal from the coordinate transform of ABC three-phase at first, under α β coordinate system, carry out low-pass filtering then, filtered fundamental frequency value is DC quantity under the dq rotating coordinate system by α β coordinate transform, and the fundamental frequency phase delay δ that low-pass filtering produces ₀Compensate returning the ABC coordinate time by the dq coordinate transform, thereby solve the fundamental frequency phase delay problem of traditional filtering mode effectively, improve the phase control precision of electric power system.

Description of drawings

Fig. 1 is the digital filtering method flow chart of the three-phase alternating current systematic survey data of an embodiment;

Fig. 2 is simulation example laboratory model construction schematic diagram;

Fig. 3 is the The simulation experiment result schematic diagram.

Embodiment

Be described in detail below in conjunction with the embodiment of accompanying drawing to the digital filtering method of three-phase alternating current systematic survey data of the present invention.

Fig. 1 shows the digital filtering method flow chart of the three-phase alternating current systematic survey data of an embodiment, comprises the steps:

Step S101: with three-phase voltage signal V _A, V _B, V _CBe converted to the voltage signal V under the two-phase α β coordinate system _α, V _β

In one embodiment, also comprise before step S101: the measurement data of three-phase alternating current system is sampled obtains voltage signal V under three phase coordinates _A, V _B, V _C

Particularly, in step S101, will measure the voltage data V that sampling obtains _A, V _B, V _C, be static α β two phase coordinates from the coordinate transform of static ABC three-phase, the formula of conversion is as follows:

V _α=V _A

；

V _α=V _B-V _C

Wherein, ABC → α β coordinate transform is orthogonal transform, and α and A same axis are set.

Step S102: according to the transfer function of setting respectively to described voltage signal V _α, V _βCarry out low-pass filtering and obtain voltage signal V' _α, V' _β

Particularly, computational process comprises following formula:

V' _α=H(jω)·V _α

；

V' _β=H(jω)·V _β

In the formula, the transfer function of H (s) for setting,

Step S103: calculate described voltage signal V' _α, V' _βFundamental frequency phase place δ.

Particularly, computational process comprises following formula:

δ=arctg(V' _β/V' _α)；

In the formula, δ is the fundamental frequency phase place, V' _α, V' _βBe respectively the voltage signal of α β coordinate after the filtering.

Step S104: the fundamental frequency phase delay angle δ that calculates described low-pass filtering according to described transfer function ₀

Particularly, the angle of transfer function H (j ω) is the phase delay angle δ of low-pass filtering link ₀, namely pass through low-pass filtering after, the fundamental frequency phase place δ of voltage signal is with respect to A, B, C voltage in three phases signal delay δ under three phase coordinates under the two-phase α β coordinate system ₀, δ ₀Computational process comprises following formula:

${\mathrm{\δ}}_0=\mathrm{arctg}\left(\frac{\mathrm{ImH}\left(\mathrm{j\ω}\right)}{\mathrm{ReH}\left(\mathrm{j\ω}\right)}\right);$

The transfer function of described low-pass filtering is H (j ω), and its general formula can be expressed as:

$H\left(\mathrm{j\&omega;}\right)=\frac{a_0+a_1\mathrm{j\&omega;}}{b_0+b_1\mathrm{j\&omega;}-{\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="HDA00003128985800021.png"\; state="\{\{state\}\}">b</figure-callout>}}_2{\mathrm{\&omega;}}^2};$

Wherein, a ₀, a ₁, b ₀, b ₁, b ₂Be default constant, the mould value of H (j ω) | H (j ω) | equaling 1, ω is the fundamental frequency angular frequency.

Step S105: according to described fundamental frequency phase place δ with described voltage signal V' _α, V' _βBe converted to the direct voltage V under rotation dq two phase coordinate systems _d, V _q

Particularly, computational process comprises following formula:

V _d+jV _q=(V _α+jV _β)e ^-jδ；

In the formula, V' _α, V' _βBe respectively the voltage signal of α β coordinate after the filtering, δ is the fundamental frequency phase place, V _d, V _qBe respectively the voltage signal of dq rotating coordinate system.

Step S106: with δ-δ ₀For angle of transformation with described direct voltage V _d, V _qBe converted to the ac voltage signal V' under three phase coordinates _A, V' _B, V' _C

Particularly, variable is returned static ABC three phase coordinates from the coordinate transform of rotation dq two-phase, the leading d axle of q axle is set, angle of transformation is δ-δ ₀, its computational process comprises as follows:

In the formula, θ=δ-δ ₀, by above-mentioned processing procedure, the fundamental frequency phase delay δ that produces in the low-pass filtering process ₀Be compensated in dq → ABC coordinate transform link.

The digital filtering method of three-phase alternating current systematic survey data of the present invention, Measurement and Data Processing at the three-phase alternating current system, at first the three-phase voltage signal (containing high order harmonic component) with sampling is α β two phase coordinates from the coordinate transform of ABC three-phase, under α β coordinate system, carry out low-pass filtering then, filtered fundamental frequency value is DC quantity under the dq rotating coordinate system by α β coordinate transform, and the fundamental frequency phase delay δ that low-pass filtering produces ₀Compensate returning the ABC coordinate time by the dq coordinate transform, thereby effectively solve the fundamental frequency phase delay problem of traditional filtering mode.

For clear more technical scheme of the present invention, set forth a simulation example below in conjunction with accompanying drawing.

Referring to shown in Figure 2, Fig. 2 is simulation example laboratory model construction schematic diagram, and wherein the transfer function of low-pass filtering adopts the simplest first-order filtering H (j ω)=G/ (1+Ts), parameter G=1.606, T=0.004 second.

Then Shu Ru ABC three-phase voltage signal is V _A, V _B, V _C, fundamental frequency (50Hz) phase voltage effective value is that 1.0,7 subharmonic content are that 10%, 19 subharmonic content are 180%, and total percent harmonic distortion (THD) is 180.278%, and the voltage signal of exporting after the filtering is V' _A, V' _B, V' _C

As shown in Figure 3, Fig. 3 is the The simulation experiment result schematic diagram, V among the figure _ABe the A phase voltage signal waveform of input, wherein, V' _ABe the A phase voltage signal waveform that carries out through filtering method of the present invention exporting after the filtering, V' _AThe fundamental frequency effective value be 1.0, and phase place and V _AIdentical, 7 subharmonic content are that 1.812%, 19 subharmonic content are 12.007%, and overall percent harmonic distortion (THD) is 12.143%.

Experimental result by above-mentioned simulation example as can be seen, even transfer function H (s) adopts without optimizing and the simplest single order low-pass filter function, filtering method of the present invention also can make total percent harmonic distortion (THD) reduce more than 90%, and the amplitude of fundamental frequency and phase place remain unchanged.

The above embodiment has only expressed several execution mode of the present invention, and it describes comparatively concrete and detailed, but can not therefore be interpreted as the restriction to claim of the present invention.Should be pointed out that for the person of ordinary skill of the art without departing from the inventive concept of the premise, can also make some distortion and improvement, these all belong to protection scope of the present invention.Therefore, the protection range of patent of the present invention should be as the criterion with claims.

Claims (6)

1. the digital filtering method of three-phase alternating current systematic survey data is characterized in that, comprises the steps:

With three-phase voltage signal V _A, V _B, V _CBe converted to the voltage signal V under the two-phase α β coordinate system _α, V _β

According to the transfer function of setting respectively to described voltage signal V _α, V _βCarry out low-pass filtering and obtain voltage signal V' _α, V' _β

Calculate described voltage signal V' _α, V' _βFundamental frequency phase place δ;

Calculate the fundamental frequency phase delay angle δ of described low-pass filtering according to described transfer function ₀

According to described fundamental frequency phase place δ with described voltage signal V' _α, V' _βBe converted to the direct voltage V under rotation dq two phase coordinate systems _d, V _q

With δ-δ ₀For angle of transformation with described direct voltage V _d, V _qBe converted to the voltage signal V' under three phase coordinates _A, V' _B, V' _C

2. the digital filtering method of three-phase alternating current systematic survey data according to claim 1 is characterized in that, described with three-phase voltage signal V _A, V _B, V _CBe converted to the voltage signal V under the two-phase α β coordinate system _α, V _βStep also comprise:

The measurement data of three-phase alternating current system sampled obtain voltage signal V under three phase coordinates _A, V _B, V _C

3. the digital filtering method of three-phase alternating current systematic survey data according to claim 1 is characterized in that, the described voltage signal V' of described calculating _α, V' _βThe step of fundamental frequency phase place δ comprise:

δ=arctg(V' _β/V' _α)；

In the formula, δ is the fundamental frequency phase place, V' _α, V' _βBe respectively the voltage signal under the α β coordinate after the filtering.

4. the digital filtering method of three-phase alternating current systematic survey data according to claim 1 is characterized in that, calculates the phase delay angle δ of described low-pass filtering according to described transfer function ₀Step comprise:

${\mathrm{\&delta;}}_0=\mathrm{arctg}\left(\frac{\mathrm{ImH}\left(\mathrm{j\&omega;}\right)}{\mathrm{ReH}\left(\mathrm{j\&omega;}\right)}\right);$

Wherein, H (j ω) is transfer function, and its general formula can be expressed as:

$H\left(\mathrm{j\&omega;}\right)=\frac{a_0+a_1\mathrm{j\&omega;}}{b_0+b_1\mathrm{j\&omega;}-b_2{\mathrm{\&omega;}}^2};$

Wherein, a ₀, a ₁, b ₀, b ₁, b ₂Be default constant, the mould value of H (j ω) | H (j ω) | equaling 1, ω is the fundamental frequency angular frequency.

5. the digital filtering method of three-phase alternating current systematic survey data according to claim 1 is characterized in that, described according to described fundamental frequency phase place δ with described voltage signal V' _α, V' _βBe converted to the direct voltage V under rotation dq two phase coordinate systems _d, V _qStep comprise:

V _d+jV _q=(V _α+jV _β)e ^-jδ；

In the formula, V' _α, V' _βBe respectively the voltage signal under the α β coordinate after the filtering, δ is the fundamental frequency phase place, V _d, V _qBe respectively the voltage signal under dq two phase coordinates.

6. the digital filtering method of three-phase alternating current systematic survey data according to claim 1 is characterized in that, with δ-δ ₀For angle of transformation with described direct voltage V _d, V _qBe converted to the voltage signal V' under three phase coordinates _A, V' _B, V' _CStep comprise:

Wherein, θ=δ-δ ₀

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