CN103580026A - Triangular H-bridge cascading STATCOM with harmonic optimization adjustor - Google Patents

Abstract

The invention provides a triangular H-bridge cascading STATCOM with a harmonic optimization adjustor. The triangular H-bridge cascading STATCOM with the harmonic optimization adjustor comprises a main circuit and a control circuit, wherein the main circuit is of a triangular structure formed by cascading of H-bridge units. The three peaks of the triangular structure are connected to a three-phase power grid in parallel. The control circuit comprises the harmonic optimization adjustor and an STATCOM controller. According to the triangular H-bridge cascading STATCOM with the harmonic optimization adjustor, reactive power compensation, current unbalanced compensation and harmonic compensation can be carried out on the power grid. When the three-phase (a, b and c) harmonic contents of loads are not equal, the harmonic effective values of the phase ab, the phase bc and the phase ca of the triangular STATCOM are approximate as far as possible, and the maximum harmonic effective values of the phase ab, the phase bc and the phase ca of the triangular STATCOM are the minimum, so that the installed capacity of the STATCOM is saved to the greatest extent.

Description

A kind of triangle H bridge cascade STATCOM with resonant wave optimalize adjuster

Technical field

The present invention relates to power system reactive power compensation and harmonic wave control field, relate in particular to a kind of triangle H bridge cascade STATCOM(STATCOM with resonant wave optimalize adjuster).

Background technology

Nonlinear load in electric power system mainly comprises frequency converter, intermediate frequency furnace and electroslag furnace etc.Along with the extensive use of this quasi-nonlinear load, the quality of power supply of electric power system goes from bad to worse, and is mainly reflected in electric power system three-phase current unbalance and contains idle and harmonic current.In high pressure occasion, the star STATCOM with the cascade of H bridge compensates with harmonic wave load is idle conventionally, but the STATCOM of Star topology is limited in one's ability to imbalance compensation, conventionally also wants other equipment (SVC) compensate three-phase current unbalance.In recent years, the triangle STATCOM of H bridge cascade becomes study hotspot, its not only can compensating load idle and harmonic wave, three-phase imbalance that can also compensating load electric current, makes function more integrated.

While utilizing triangle STATCOM to compensate, there is the problem that line current instruction is converted into phase current instruction, i.e. the calculating of phase current instruction.Idle and uneven in load, can adopt that this smooth maze is theoretical calculates phase current instruction.For the harmonic wave in load,, there is the solution of countless versions phase current instruction in the line current instruction under same operating mode.Therefore, be necessary to study the method that the instruction of a kind of harmonic wave line current is converted into the instruction of harmonic wave phase current, and the method should meet and farthest reduces place capacity, makes each close as far as possible requirement of harmonic current effective value of flowing through mutually of triangle STATCOM simultaneously.

Summary of the invention

In order to try to achieve under same operating, the instruction of harmonic wave line current is converted into the optimal solution of harmonic wave phase current instruction, the invention provides a kind of triangle H bridge cascade STATCOM with resonant wave optimalize adjuster, this resonant wave optimalize adjuster is by sampling to load current, and utilize DSP to complete optimized algorithm, required solution can meet and farthest reduces place capacity, makes each close as far as possible requirement of harmonic current effective value of flowing through mutually of triangle STATCOM simultaneously.

The invention provides a kind of triangle H bridge cascade STATCOM with resonant wave optimalize adjuster, its resonant wave optimalize adjuster carries out Fourier decomposition by load current, obtains amplitude and the phase place of each harmonic line current; The algorithm of the real-time computing module of DSP of its resonant wave optimalize adjuster is: in plane right-angle coordinate, make respectively the line current vector of each harmonic, make three phase vectors end to end, shape after end to end according to harmonic wave line current three phase vectors, obtains the harmonic wave phase current instruction that meets triangle STATCOM installed capacity minimum and the close as far as possible requirement of its each phase harmonic current effective value; Finally the instruction of each harmonic phase current is added, obtains optimum triangle STATCOM harmonic wave phase current instruction.

In some embodiments, after harmonic wave line current three phase vectors are end to end be shaped as acute triangle time, take this leg-of-mutton circumscribed circle center of circle is starting point, take this Atria summit is terminal, and three vectors that obtain are respectively three the harmonic wave phase currents instruction that meets the optimum triangle STATCOM requiring.

In some embodiments, after harmonic wave line current three phase vectors are end to end be shaped as right-angled triangle or obtuse triangle time, the mid point of three vectorial mould value the maximum of harmonic wave line current of take is starting point, take this Atria summit is terminal, and three vectors that obtain are respectively three the harmonic wave phase currents instruction that meets the optimum triangle STATCOM requiring.

The invention has the advantages that, when certain subharmonic line current vector is end to end while being acute angle or right-angled triangle, although triple line size of current may be different, but three phase current equal and opposite in directions of the triangle STATCOM trying to achieve, and also at this moment, the maximum of three of triangle STATCOM phase currents obtains minimum; When certain subharmonic line current vector is end to end while be obtuse triangle, although three phase currents of the triangle STATCOM trying to achieve are big or small unequal, the maximum of three phase currents of triangle STATCOM obtains minimum; To sum up, the invention provides a kind of instruction algorithm of realizing triangle STATCOM compensating load harmonic wave, and this algorithm can farthest be saved the installed capacity of equipment.

Accompanying drawing explanation

Fig. 1 is the structure chart of triangle cascade STATCOM compensating load;

Fig. 2 H bridge cellular construction figure;

Fig. 3 is the vectogram that harmonic wave line current is converted into harmonic wave phase current.

Embodiment

Below in conjunction with Figure of description, the specific embodiment of the present invention is described further.

The triangle H bridge cascade STATCOM with resonant wave optimalize adjuster of the present invention, the DSP of its resonant wave optimalize adjuster carries out Fourier decomposition to the load current sampling, obtain amplitude and the phase place of the required each harmonic line current instruction of triangle STATCOM compensating load harmonic wave,

the triple line current-order of nth harmonic is showed in plane coordinate system so that vector form is end to end, according to the feature of three end to end formed figures of vector, obtain max (I _habn, I _hbcn, I _hcan) obtain the solution of minimum value by the solution of each harmonic phase current

with the summation of instantaneous value form, obtain the harmonic wave phase current instruction i of triangle STATCOM _ab, i _bc, i _ca, by the data transmission module of resonant wave optimalize adjuster, send the controller of STATCOM to, control STATCOM load harmonic wave is compensated.First, load current is carried out to Fourier decomposition, solve amplitude and the phase place of each harmonic, as shown in Figure 3, in plane right-angle coordinate, according to the amplitude of three-phase current and phase angle, make outgoing vector

and make it end to end, and the regulation origin of coordinates is

starting point.Then, according to the topological relation of triangle STATCOM,

${\stackrel{\→}{I}}_{\mathrm{hcan}}-{\stackrel{\→}{I}}_{\mathrm{hbcn}}={\stackrel{\→}{I}}_{\mathrm{hcn}},$ Vector relations in respective figure 3, can obtain $\stackrel{\→}{\mathrm{PA}}={\stackrel{\→}{I}}_{\mathrm{habn}},\stackrel{\→}{\mathrm{PB}}={\stackrel{\→}{I}}_{\mathrm{hbcn}},\stackrel{\→}{\mathrm{PO}}={\stackrel{\→}{I}}_{\mathrm{hcan}},$ Therefore three the harmonic wave phase currents instruction that solves triangle STATCOM is the P point coordinates solving in plane right-angle coordinate, can demonstrate,prove: when Δ OAB is acute triangle, P point is the center of circle of Δ OAB circumscribed circle, when Δ OAB is right angle or obtuse triangle, P point is the mid point of Δ OAB longest edge, now can meet max (I _habn, I _hbcn, I _hcan) obtain minimum value.

Δ OAB take below as acute triangle is example, introduce the specific algorithm that solves the instruction of nth harmonic phase current, tried to achieve each harmonic phase current instruction stack is to the harmonic wave phase current instruction i of triangle STATCOM _ab, i _bc, i _ca.

Known

with reference to the accompanying drawings 3, the coordinate of trying to achieve A, B is:

Because P is the Δ OAB circumscribed circle center of circle, so: PA=PB, PA=PO, establishing P point coordinates is P (x ₀, y ₀), therefore can obtain following formula:

(x ₁-x ₀) ²+(y ₁-y ₀) ²＝(x ₂-x ₀) ²+(y ₂-y ₀) ²

(x ₁-x ₀) ²+(y ₁-y ₀) ²＝(0-x ₀) ²+(0-y ₀) ²

Solve above-mentioned equation group and can obtain P point coordinates:

$y_0=\frac{x_1*[{(x_1-x_2)}^2+{(y_1-y_2)}^2]-(x_1-x_2)*({x_1}^2+{y_1}^2)}{2*x_1*(y_1-y_2)-2*(x_1-x_2)*y_1}$

$x_0=\frac{{(x_1-x_2)}^2+{(y_1-y_2)}^2-2*y*(y_1-y_2)}{2*(x_1-x_2)}$

Utilize P point coordinates, can solve vector amplitude and phase place:

The amplitude of harmonic wave phase current instruction is respectively:

$M_{\mathrm{abn}}=\sqrt{{(x_1-x_0)}^2+{(y_1-y_0)}^2}$

$M_{\mathrm{bcn}}=\sqrt{{(x_2-x_0)}^2+{(y_2-y_0)}^2}$

$M_{\mathrm{can}}=\sqrt{{x_0}^2+{y_0}^2}$

The phase place of harmonic wave phase current instruction is respectively:

If (x ₁-x ₀) >0:

If (x ₂-x ₀) >0:

If-x ₀>0:

If (x ₁-x ₀) <0:

If (x ₂-x ₀) <0:

If-x ₀<0:

So far, the optimal solution of the nth harmonic phase current instruction of triangle cascade STATCOM has been tried to achieve, and its instantaneous value expression formula is:

By the instantaneous value stack of tried to achieve each harmonic phase current instruction, try to achieve the instantaneous value of triangle STATCOM harmonic wave phase current instruction.

Concrete sample calculation analysis:

In certain operating mode situation, quintuple harmonics line current is negative-sequence current, and the amplitude of three line currents is unequal, has imbalance to a certain degree.Fft analysis obtains its quintuple harmonics line current:

i _ha5＝19cos(100*π*n*t+0.195*π)；

i _hb5＝17cos(100*π*n*t+0.817*π)；

i _hc5＝20cos(100*π*n*t-0.522*π)；

Through the above-mentioned algorithm of asking optimum phase current instruction, the phase current solving is:

i _hab5＝11cos(100*π*n*t+0.033*π)；

i _hbc5＝11cos(100*π*n*t+0.6*π)；

i _hca5＝11cos(100*π*n*t-0.644*π)；

Visible, the quintuple harmonics phase current instruction amplitude under this operating mode that optimum solution is tried to achieve equates.

The above is only the preferred embodiment of the present invention; be noted that for those skilled in the art; under the premise without departing from the principles of the invention, can also make the some improvements and modifications that can expect, these improvements and modifications also should be considered as protection scope of the present invention.

Claims (4)

1. a triangle H bridge cascade STATCOM with resonant wave optimalize adjuster, is characterized in that: main circuit is that H bridge connects as triangular structure after unit cascaded, and control circuit comprises resonant wave optimalize adjuster and STATCOM controller.

2. the triangle H bridge cascade STATCOM with resonant wave optimalize adjuster according to claim 1, wherein said resonant wave optimalize adjuster comprises signal conditioning circuit, high-speed AD sampling module, the real-time computing module of DSP and data transmission module, and described resonant wave optimalize adjuster is connected with the controller of STATCOM by data transmission module.

3. the triangle H bridge cascade STATCOM according to claim 2 with resonant wave optimalize adjuster, by described high-speed AD sampling module, load current is carried out to high-speed AD sampling, and the load current sampling is carried out to Fourier decomposition, obtain amplitude and the phase place of the required each harmonic line current instruction of triangle STATCOM compensating load harmonic wave,

the real-time computing module of described DSP, according to amplitude and the phase place of the instruction of each harmonic line current, adopts optimized algorithm to calculate amplitude and the phase place of the instruction of each harmonic phase current, and sends the instruction of harmonic wave phase current to data transmission module.

4. the triangle H bridge cascade STATCOM according to claim 3 with resonant wave optimalize adjuster, the real-time computing module of DSP of wherein said resonant wave optimalize adjuster carries out Fourier decomposition to the load current sampling, obtain amplitude and the phase place of the required each harmonic line current instruction of triangle STATCOM compensating load harmonic wave,

the triple line current-order of nth harmonic is end to end with vector form, in plane coordinate system, show, obtain max (I _habn, I _hbcn, I _hcan) obtain the solution of minimum value

by the solution of each harmonic phase current

with the summation of instantaneous value form, obtain the harmonic wave phase current instruction i of triangle STATCOM _ab, i _bc, i _ca, send the instruction of calculating gained harmonic wave phase current to data transmission module.

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