CN103560527A - Dynamic voltage reactive compensation method - Google Patents

Abstract

The invention discloses a dynamic voltage reactive compensation method of the field of power grids. According to the dynamic voltage reactive compensation method, sinusoidal signals sinOmegat and cosine signals cosOmegat which have the same phase position as the voltage usa of a power grid A phase power source line are extracted in the step of sine and cosine signal extraction, the currents iLa, the currents iLb and the currents iLc on the three-phase power source lines of the power grid are extracted, C32 conversion and C conversion are conducted on the iLa, the iLb and the iLc in sequence, the components ip and iq of the currents iLa, the currents iLb and the currents iLc in the three-phase power source lines of the power grid in the p-q coordinate system are obtained, then the ip and iq direct-current components are obtained through a third-order Chebyshev filter in the filtering step, C inverse transformation and C23 conversion are conducted on the ip and iq direct-current components, and finally the compensated currents on the three-phase power source lines of the power grid are obtained. The dynamic voltage reactive compensation method has the technical advantages that the response speed of a dynamic voltage reactive compensation device can be improved, the harmonic wave on the three-phase power source lines is effectively constrained, and the THD value of the three-phase power source lines is controlled within 4%.

Description

A kind of dynamic electric voltage reactive-load compensation method

Technical field

The present invention relates to a kind of dynamic electric voltage reactive-load compensation method in electrical network field.

Background technology

Detect accurately and fast harmonic current in electrical network, and to produce the required reactive power compensation electric current of load be the major function of dynamic electric voltage reactive power compensator.Current dynamic electric voltage reactive power compensator, what it mainly adopted is to adopt to obtain load instantaneous current i according to the dynamic electric voltage reactive-load compensation method of instantaneous reactive power _la, i _lb, i _lcfirst-harmonic i _laf, i _lbf, i _lcf.The method is corresponding slow, and the harmonic wave of electrical network is suppressed to poor.

Summary of the invention

The object of the invention is, in order to overcome the deficiencies in the prior art, provides a kind of dynamic electric voltage reactive-load compensation method, and it can improve the response speed of dynamic electric voltage reactive power compensator, and effectively suppresses the harmonic wave on three-phase power line.

A kind of technical scheme that realizes above-mentioned purpose is: a kind of dynamic electric voltage reactive-load compensation method, comprises the following steps:

Cosine and sine signal extraction step: generate one with electrical network A phase power line voltage u _sasynchronous sinusoidal signal sin ω t and one and A phase line voltage u _sasynchronous cosine signal cos ω t, this step is undertaken by a phase-locked loop circuit and a cosine and sine signal circuit for generating;

The first coordinate transform step: extract electric current, i.e. current i on A phase power line on electrical network three-phase power line _la, current i on B phase power line _lbwith current i on C phase power line _lc, to current i on electrical network three-phase power line _la, i _lband i _lccarry out C32 conversion, obtain current i on electrical network three-phase power line _la, i _lband i _lccomponent i under alpha-beta coordinate system _αand i _β, the formula of this step is:

$\left[\begin{array}{c}{i}_{\mathrm{\α}}\\ i_{\mathrm{\β}}\end{array}\right]=C_{32}\left[\begin{array}{c}{i}_a\\ i_b\\ i_c\end{array}\right]=\sqrt{\frac{2}{3}}\left[\begin{array}{ccc}1& -\frac{1}{2}& -\frac{1}{2}\\ 0& \frac{\sqrt{3}}{2}& -\frac{\sqrt{3}}{2}\end{array}\right]\left[\begin{array}{c}{i}_{\mathrm{La}}\\ i_{\mathrm{Lb}}\\ i_{\mathrm{Lc}}\end{array}\right];$

The second coordinate transform step: current i on electrical network three-phase power line _la, i _lband i _lccomponent i under alpha-beta coordinate system _αand i _βcarry out C conversion, obtain current i on electrical network three-phase power line _la, i _lband i _lccomponent i under p-q coordinate system _pand i _q, the computing formula of this step is:

$\left[\begin{array}{c}{i}_p\\ i_q\end{array}\right]=C\left[\begin{array}{c}{i}_{\mathrm{\α}}\\ i_{\mathrm{\β}}\end{array}\right]=\left[\begin{array}{cc}\sin \mathrm{\ωt}& -\cos \mathrm{\ωt}\\ -\cos \mathrm{\ωt}& -\sin \mathrm{\ωt}\end{array}\right]\left[\begin{array}{c}{i}_{\mathrm{\α}}\\ i_{\mathrm{\β}}\end{array}\right];$

Low-pass filtering step: by three rank Chebyshev filters, elimination i _pand i _qhigh order harmonic component, obtain i _pand i _qdC component

with

The first coordinate inversion step: to i _pand i _qdC component

with

carry out C inverse transformation, obtain the component i of current first harmonics under alpha-beta coordinate system on three-phase power line _{α f}and i _{β f}, this step computing formula is:

$\left[\begin{array}{c}{i}_{\mathrm{\αf}}\\ i_{\mathrm{\βf}}\end{array}\right]=C\left[\begin{array}{c}{\stackrel{\‾}{i}}_p\\ {\stackrel{\‾}{i}}_q\end{array}\right]=\left[\begin{array}{cc}\sin \mathrm{\ωt}& -\cos \mathrm{\ωt}\\ -\cos \mathrm{\ωt}& -\sin \mathrm{\ωt}\end{array}\right]\left[\begin{array}{c}{\stackrel{\‾}{i}}_p\\ {\stackrel{\‾}{i}}_q\end{array}\right];$

The second coordinate inversion step, the component i of current first harmonics under alpha-beta coordinate system on three-phase power line _{α f}and i _{β f}carry out C23 conversion, obtain current first harmonics i on three-phase power line _af, i _bf, i _cf;

Offset current calculation procedure: by current first harmonics i on three-phase power line _af, i _bf, i _cfcalculate the offset current on electrical network three-phase power line

Further, between low-pass filtering step and the first coordinate inversion step, add PI regulating step, by described i _qdC component

be adjusted to 0.

Adopt the technical scheme of a kind of dynamic electric voltage reactive-load compensation method of the present invention, by cosine and sine signal extraction step, extracted electrical network A phase power line voltage u _saafter synchronous sinusoidal signal sin ω t and cosine signal cos ω t, extract current i on electrical network three-phase power line _la, i _lband i _lc, carry out successively C32 conversion and C conversion, obtain current i on electrical network three-phase power line _la, i _lband i _lccomponent i under p-q coordinate system _pand i _q, then by three rank Chebyshev filters, carry out filter step and obtain i _pand i _qdC component

with

then right

with

carry out C inverse transformation and C23 conversion, finally obtain calculating the offset current on electrical network three-phase power line

technical scheme.Its technique effect is: can improve the response speed of dynamic electric voltage reactive power compensator, and effectively suppress the harmonic wave on three-phase power line, the THD(total harmonic distortion on three-phase power line) value is controlled in 4%.

Accompanying drawing explanation

Fig. 1 is the topological schematic diagram of a kind of dynamic electric voltage reactive-load compensation method of the present invention.

Embodiment

Refer to Fig. 1, the present inventor is in order to understand technical scheme of the present invention better, below by embodiment particularly, and is described in detail by reference to the accompanying drawings:

The first embodiment:

A reactive-load compensation method, comprises the following steps:

Cosine and sine signal extraction step: generate one with electrical network A phase power line voltage u _sasynchronous sinusoidal signal sin ω t and one and A phase line voltage u _sasynchronous cosine signal cos ω t, this step is undertaken by a phase-locked loop circuit and a cosine and sine signal circuit for generating.

The first coordinate transform step: extract electric current, i.e. current i on A phase power line on electrical network three-phase power line _la, current i on B phase power line _lbwith current i on C phase power line _lc, to current i on electrical network three-phase power line _la, i _lband i _lccarry out C32 conversion, obtain current i on electrical network three-phase power line _la, i _lband i _lccomponent i under alpha-beta coordinate system _αand i _β.The formula of this step is:

$\left[\begin{array}{c}{i}_{\mathrm{\α}}\\ i_{\mathrm{\β}}\end{array}\right]=C_{32}\left[\begin{array}{c}{i}_a\\ i_b\\ i_c\end{array}\right]=\sqrt{\frac{2}{3}}\left[\begin{array}{ccc}1& -\frac{1}{2}& -\frac{1}{2}\\ 0& \frac{\sqrt{3}}{2}& -\frac{\sqrt{3}}{2}\end{array}\right]\left[\begin{array}{c}{i}_{\mathrm{La}}\\ i_{\mathrm{Lb}}\\ i_{\mathrm{Lc}}\end{array}\right].$

The second coordinate transform step: current i on electrical network three-phase power line _la, i _lband i _lccomponent i under alpha-beta coordinate system _αand i _βcarry out C conversion, obtain current i on electrical network three-phase power line _la, i _lband i _lccomponent i under p-q coordinate system _pand i _q.The computing formula of this step is:

$\left[\begin{array}{c}{i}_p\\ i_q\end{array}\right]=C\left[\begin{array}{c}{i}_{\mathrm{\α}}\\ i_{\mathrm{\β}}\end{array}\right]=\left[\begin{array}{cc}\sin \mathrm{\ωt}& -\cos \mathrm{\ωt}\\ -\cos \mathrm{\ωt}& -\sin \mathrm{\ωt}\end{array}\right]\left[\begin{array}{c}{i}_{\mathrm{\α}}\\ i_{\mathrm{\β}}\end{array}\right].$

Low-pass filtering step: by three rank Chebyshev filters, filtering i _pand i _qhigh order harmonic component, obtain i _pand i _qdC component

with

the cut-off frequency of three rank Chebyshev filters is 50Hz, the decay≤1dB in passband, resistance band attenuation≤-35dB.

The first coordinate inversion step: i _pand i _qdC component with

carry out C inverse transformation, obtain the component i of current first harmonics under alpha-beta coordinate system on three-phase power line _{α f}and i _{β f}.This step computing formula is:

$\left[\begin{array}{c}{i}_{\mathrm{\αf}}\\ i_{\mathrm{\βf}}\end{array}\right]=C\left[\begin{array}{c}{\stackrel{\‾}{i}}_p\\ {\stackrel{\‾}{i}}_q\end{array}\right]=\left[\begin{array}{cc}\sin \mathrm{\ωt}& -\cos \mathrm{\ωt}\\ -\cos \mathrm{\ωt}& -\sin \mathrm{\ωt}\end{array}\right]\left[\begin{array}{c}{\stackrel{\‾}{i}}_p\\ {\stackrel{\‾}{i}}_q\end{array}\right];$

The second coordinate inversion step, the component i of current first harmonics under alpha-beta coordinate system on three-phase power line _{α f}and i _{β f}carry out C23 conversion, obtain current first harmonics i on three-phase power line _af, i _bf, i _cf.

Offset current calculation procedure: by current first harmonics i on three-phase power line _af, i _bf, i _cfcalculate the offset current on electrical network three-phase power line

The first embodiment computing is simple, postpones less, and real-time is good, but the sin ω t and the cos ω t that require phase-locked loop circuit to produce are accurate.

The second embodiment:

The second embodiment is with respect to the improvement of the first embodiment: between low-pass filtering step and the first coordinate inversion step, add PI regulating step, by pi regulator by i _qdC component be adjusted to 0, add PI regulating step can reduce sin ω t and the cos ω t requirement accurately producing for phase-locked loop circuit, but the parametric sensitivity of system can reduce.

Adopt said method to carry out after dynamic electric voltage reactive power compensation, realize the inhibition to harmonic current in system.As under drag, that is: nonlinear load adopts three phase rectifier module bridge joint 30 Ω resistance; Compensator transformer no-load voltage ratio is set as 1:1; Side compensation reactor in parallel is made as 3mH, and filter capacitor is 10uF; Series side filter inductance 3mH, filter capacitor 5uF; Line voltage 220V, frequency is 50Hz, and when 0.04s, supply voltage occurs to fall with the voltage of phase hit, and saltus step angle is 30 °, and amplitude drops into 140V.THD(total harmonic distortion) value has dropped to 3.19% by 28.58%.

Those of ordinary skill in the art will be appreciated that, above embodiment is only for the present invention is described, and be not used as limitation of the invention, as long as within the scope of connotation of the present invention, to the variation of the above embodiment, modification, all will drop within the scope of claims of the present invention.

Claims (2)

1. a dynamic electric voltage reactive-load compensation method, comprises the following steps:

Cosine and sine signal extraction step: generate one with electrical network A phase power line voltage u _sasynchronous sinusoidal signal sin ω t and one and A phase line voltage u _sasynchronous cosine signal cos ω t, this step is undertaken by a phase-locked loop circuit and a cosine and sine signal circuit for generating;

The first coordinate transform step: extract electric current, i.e. current i on A phase power line on electrical network three-phase power line _la, current i on B phase power line _lbwith current i on C phase power line _lc, to current i on electrical network three-phase power line _la, i _lband i _lccarry out C32 conversion, obtain current i on electrical network three-phase power line _la, i _lband i _lccomponent i under alpha-beta coordinate system _αand i _β, the formula of this step is:

$\left[\begin{array}{c}{i}_{\mathrm{\α}}\\ i_{\mathrm{\β}}\end{array}\right]=C_{32}\left[\begin{array}{c}{i}_a\\ i_b\\ i_c\end{array}\right]=\sqrt{\frac{2}{3}}\left[\begin{array}{ccc}1& -\frac{1}{2}& -\frac{1}{2}\\ 0& \frac{\sqrt{3}}{2}& -\frac{\sqrt{3}}{2}\end{array}\right]\left[\begin{array}{c}{i}_{\mathrm{La}}\\ i_{\mathrm{Lb}}\\ i_{\mathrm{Lc}}\end{array}\right];$

The second coordinate transform step: current i on electrical network three-phase power line _la, i _lband i _lccomponent i under alpha-beta coordinate system _αand i _βcarry out C conversion, obtain current i on electrical network three-phase power line _la, i _lband i _lccomponent i under p-q coordinate system _pand i _q, the computing formula of this step is:

$\left[\begin{array}{c}{i}_p\\ i_q\end{array}\right]=C\left[\begin{array}{c}{i}_{\mathrm{\α}}\\ i_{\mathrm{\β}}\end{array}\right]=\left[\begin{array}{cc}\sin \mathrm{\ωt}& -\cos \mathrm{\ωt}\\ -\cos \mathrm{\ωt}& -\sin \mathrm{\ωt}\end{array}\right]\left[\begin{array}{c}{i}_{\mathrm{\α}}\\ i_{\mathrm{\β}}\end{array}\right];$

Low-pass filtering step: by three rank Chebyshev filters, elimination i _pand i _qhigh order harmonic component, obtain i _pand i _qdC component

with

The first coordinate inversion step: to i _pand i _qdC component

with

carry out C inverse transformation, obtain the component i of current first harmonics under alpha-beta coordinate system on three-phase power line _{α f}and i _{β f}, this step computing formula is:

$\left[\begin{array}{c}{i}_{\mathrm{\αf}}\\ i_{\mathrm{\βf}}\end{array}\right]=C\left[\begin{array}{c}{\stackrel{\‾}{i}}_p\\ {\stackrel{\‾}{i}}_q\end{array}\right]=\left[\begin{array}{cc}\sin \mathrm{\ωt}& -\cos \mathrm{\ωt}\\ -\cos \mathrm{\ωt}& -\sin \mathrm{\ωt}\end{array}\right]\left[\begin{array}{c}{\stackrel{\‾}{i}}_p\\ {\stackrel{\‾}{i}}_q\end{array}\right];$

The second coordinate inversion step, the component i of current first harmonics under alpha-beta coordinate system on three-phase power line _{α f}and i _{β f}carry out C23 conversion, obtain current first harmonics i on three-phase power line _af, i _bf, i _cf;

Offset current calculation procedure: by current first harmonics i on three-phase power line _af, i _bf, i _cfcalculate the offset current on electrical network three-phase power line

2. according to claim 1. a kind of dynamic electric voltage reactive-load compensation method, is characterized in that: between low-pass filtering step and the first coordinate inversion step, add PI regulating step, by described i _qdC component

be adjusted to 0.

Images