CN101950972B - SVC composite control method based on rapid equivalent susceptance calculation - Google Patents

Abstract

The invention discloses an SVC composite control method based on rapid equivalent susceptance calculation, wherein, an SVC comprises a thyristor controlled reactor (TCR) and a passive filter bank. The SVC composite control method comprises the following steps: firstly, calculating the corresponding equivalent susceptance by using an equivalent susceptance computing method after detecting a voltage signal and a current signal; adding up an open-loop equivalent susceptance output value BLabc and a closed-loop PI regulator output value to obtain a total equivalent susceptance compensation value BTabc; calculating the actual input group number n of PPFs and the actual equivalent susceptance value of the TCR by a power divider according to the compensation value; and searching an Hash table by the TCR according to the actual equivalent susceptance value to obtain a corresponding triggering angle and then triggering opening of a corresponding thyristor to send out corresponding inductive reactive current for compensating capacitive reactive power and negative-sequence current, and finally realizing complete compensation of the reactive power and the negative-sequence current of a system. The SVC composite control method effectively reduces the calculated quantity of the system and improves the response time of the system.

Description

A kind of SVC composite control method that calculates based on quick equivalent susceptance

Technical field

The invention belongs to negative phase-sequence and reactive power compensation control technology field, particularly a kind of SVC composite control method that calculates based on quick equivalent susceptance.

Background technology

Along with The development in society and economy, the power consumption of industrial circles such as metallurgy, mine and traffic is increasing.A large amount of utilizations like high-power perception such as gold metallurgy rectifying installation, arc furnace and electric locomotive and non-linear equipment; The negative phase-sequence of bringing thus; Power quality problems such as idle harmonic are also more and more serious; A large amount of negative phase-sequence and idle has not only caused a large amount of electric energy losses, has also reduced the safety and stability performance of system simultaneously.

At present, characteristics such as SVC is high with its cost performance, response is fast and be acknowledged as the best equipment of reactive power compensation carried out the equilibrating compensation to eliminate negative sequence component but also can regulate through phase-splitting to the three-phase asymmetric load.Most SVC is used for realizing that reactive power compensation improves the power factor of system or stablizes line voltage, and mostly it is the PI control method, and its control performance and precision also are difficult to reach requirement, and can not take into account imbalance compensation.Existing domestic and international list of references utilizes the phase splitting compensation principle of Steinmetz, and the method for regulating through phase-splitting is used for compensating negative-sequence current and reactive current with SVC, realizes the balance of system's three phase power.The voltage and current signal positive sequence component that the scholar generally adopts synchronous coordinate conversion or instantaneous reactive power theory to obtain; Phase splitting compensation principle through Steinmetz can calculate three-phase compensation susceptance value then; Because this control method is open loop control; Compensation precision is not high, receives the influence of the system's detection and the error of calculation easily, can not compensate by the real-time tracking power network current.

For compensation precision and the performance of dynamic tracking that improves SVC; Taiwan's scholars S.-Y.Lee professor proposes a kind of SVC Mathematical Modeling based on the negative-sequence current compensation, realizes the dynamic compensation to unbalanced load through dynamic iteration and the The optimal compensation amount that search calculates SVC.But this control method needs complicated iteration and searching and computing.

At present, the detection algorithm of using always is based on the p-q algorithm and the ip-iq algorithm of instantaneous reactive power theory.Wherein, the accuracy in detection of p-q method is influenced by grid voltage waveform, and testing result has error when there is certain distortion in line voltage; And ip-iq algorithm detection method has been owing to comprised space coordinate transformation 2 times, and algorithm is complicated, is unfavorable for that software realizes.

The FBD method of the new a kind of time domain detection that proposes of German scholar in recent years.Its explicit physical meaning, real-time be good, be applicable to single-phase or polyphase system.The basic ideas of FBD method are: is the load equivalent in the side circuit desired electrical guiding element, thinks that the power in the circuit all consumes on this equivalent conductance.According to equivalent conductance electric current is decomposed, the character of each current component is discussed.It is compared with the real-time detection method based on the three-phase instantaneous reactive power theory; Improve the rapidity of detection method, saved Park conversion and 3/2 conversion, need not complicated matrixing; Algorithm obtains simplifying; Greatly reduced the expense of microprocessor, time-delay is further shortened, and also lays the first stone for further improving sample frequency and compensation precision.

Summary of the invention

The defective that exists to the open-loop control method of SVC negative phase-sequence and reactive power compensation; The present invention aims to provide a kind of SVC composite control method that calculates based on quick equivalent susceptance; Can calculate the equivalent susceptance of SVC fast through the FBD algorithm; Its explicit physical meaning directly fast, has effectively improved the compensation performance of SVC.Utilize the open loop feedforward action, realize idle and quick compensation negative-sequence current, improve system response time; Utilize the indifference tracking characteristics of close-loop feedback control; Remedy the deficiency of open loop control, realize the stable state indifference, like this open loop control and closed-loop control are effectively combined; Realize negative phase-sequence and idle full remuneration in the centering high-voltage fence electric current, improved the quality of power supply of electric power system.

For reaching the foregoing invention purpose, the technical scheme that the present invention adopted is:

A kind of SVC composite control method that calculates based on quick equivalent susceptance comprises the steps:

A), at first through detecting three phase network voltage (u _a, u _b, u _c), utilize the positive sequence voltage detection method can calculate the three-phase positive sequence voltage (

With );

B), detect the threephase load current i _Labc, utilize based on the quick equivalent susceptance computational methods of FBD algorithm and try to achieve the corresponding equivalent susceptance value B of threephase load electric current _LabcThrough detecting the threephase load current i _Labc, three-phase TCR current i _TCRabcWith passive filter group current i _PPFabc, their additions can be calculated the three phase network current i _Sabc, again by the three phase network current i that obtains _SabcCalculate the corresponding equivalent susceptance value B of three phase network electric current according to quick equivalent susceptance computational methods based on the FBD algorithm _Sabc

C), the corresponding equivalent susceptance value B of the three phase network electric current that obtains of above-mentioned steps _Sabc, after the adjusting of PI controller, can calculate the closed loop output valve

Again with the closed loop output valve that obtains

The corresponding equivalent susceptance value B of threephase load electric current that obtains with above-mentioned steps _LabcAddition, the three-phase that obtains the total output of compound control compensates susceptance B _Tabc(B _Tab, B _Tbc, B _Tca);

D), the three-phase according to the total output of compound control compensates susceptance B _Tabc, the actual needs that draws SVC through power divider drops into the actual equivalent susceptance value that PPF organizes number n and TCR

Controller sends control signal corresponding and cuts n group PPF like this, for system provides corresponding reactive capability; Simultaneously, TCR is according to actual equivalent susceptance value

Show to obtain relative trigger angle α through searching Hash; Pass through the driving and the amplification of drive circuit then; Trigger opening of corresponding thyristor and send corresponding perceptual reactive current and come compensating reactive power and negative-sequence current, the system that finally realizes is idle and the full remuneration of negative-sequence current.

Said quick equivalent susceptance computational methods based on the FBD algorithm may further comprise the steps:

A), establishing three phase network voltage and three-phase current is:

$\left\{\begin{array}{c}{u}_a=U\sin \left(\mathrm{wt}\right)\\ u_b=U\sin (\mathrm{wt}-2\mathrm{\π}/3)\\ u_c=U\sin (\mathrm{wt}+2\mathrm{\π}/3)\end{array}\right.---\left(1\right)$

Wherein, U is the effective value of three-phase voltage;<img file="BDA0000029189870000042.GIF" he="45" img-content="drawing" img-format="GIF" inline="yes" orientation="portrait" wi="37" />With<img file="BDA0000029189870000043.GIF" he="45" img-content="drawing" img-format="GIF" inline="yes" orientation="portrait" wi="41" />Effective value and phase angle for n forward-order current;<img file="BDA0000029189870000044.GIF" he="41" img-content="drawing" img-format="GIF" inline="yes" orientation="portrait" wi="36" />With<img file="BDA0000029189870000045.GIF" he="40" img-content="drawing" img-format="GIF" inline="yes" orientation="portrait" wi="40" />Effective value and phase angle for n negative-sequence current; Make u<sub >1</sub>=(u<sub >a</sub>, u<sub >b</sub>, u<sub >c</sub>), i=(i<sub >a</sub>, i<sub >b</sub>, i<sub >c</sub>), with voltage u<sub >1</sub>Each component obtain new vector behind the phase shift pi/2 forward and be designated as<img file="BDA0000029189870000046.GIF" he="59" img-content="drawing" img-format="GIF" inline="yes" orientation="portrait" wi="388" />According to the power definition of FBD principle, have that fundamental positive sequence equivalence is meritorious to be respectively ∑ p with reactive power<sup >+</sup>=<u<sub >1</sub>, i>,<img file="BDA0000029189870000047.GIF" he="58" img-content="drawing" img-format="GIF" inline="yes" orientation="portrait" wi="286" />So can push away below fundamental positive sequence equivalence meritorious with idle electricity lead into:

$\left\{\begin{array}{c}{G}_p^{+}\left(t\right)=\frac{\mathrm{\&Sigma;}{p}^{+}}{{\left|\right|u_1\left|\right|}^2}=\frac{2[u_a{i}_a+u_b{i}_b+u_c{i}_c]}{3U^2}\\ G_q^{+}\left(t\right)=\frac{\mathrm{\&Sigma;}{q}^{+}}{{\left|\right|{u^i}_1\left|\right|}^2}=\frac{2[{u^i}_a{i}_a+{u^i}_b{i}_b+{u^i}_c{i}_c]}{3U^2}\end{array}\right.---\left(3\right)$

If in like manner with u ₁In u _bAnd u _cExchange one upper/lower positions then can obtain other one group of voltage vector u each other ₂(u ₂=(u _a, u _c, u _b)) and

Then can push away to such an extent that the meritorious electricity of first-harmonic negative phase-sequence equivalence is led the expression formula of leading with idle electricity:

$\left\{\begin{array}{c}{G}_p^{-}\left(t\right)=\frac{\mathrm{\&Sigma;}{p}^{-}}{{\left|\right|u_2\left|\right|}^2}=\frac{2(u_a{i}_a+u_c{i}_b+u_b{i}_c)}{3U^2}\\ G_q^{-}\left(t\right)=\frac{\mathrm{\&Sigma;}{q}^{-}}{{\left|\right|{u^i}_2\left|\right|}^2}=\frac{2({u^i}_a{i}_a+{u^i}_c{i}_b+{u^i}_b{i}_c)}{3U^2}\end{array}\right.---\left(4\right)$

It is the effective value of phase voltage that

U is wherein arranged;

B); With in the formula (3) behind low pass filter LPF filtering Alternating Component; Obtain direct current composition

that direct current composition that the meritorious electricity of fundamental positive sequence equivalence leads and idle electricity lead with

in the formula (4) behind the low pass filter filters out Alternating Component; Obtain direct current composition

that direct current composition

that the meritorious electricity of first-harmonic negative phase-sequence equivalence leads and idle electricity lead then according to the definition of positive sequence and negative-sequence current, promptly can push away following formula:

Wherein, U is the effective value of phase voltage; I ⁺And I ^-Be fundamental positive sequence and negative-sequence current vector; With Be fundamental positive sequence and negative-sequence current effective value; With Power-factor angle for fundamental positive sequence and negative-sequence current;

C), realize that equilibrating compensation and raising power factor of electric network approach 1, just must satisfy following 2 conditions: the negative sequence component of 1) eliminating load current; 2) making the positive sequence component imaginary part of load current is 0; According to above-mentioned condition, can obtain the equivalent susceptance value that TCR need drop into electrical network and be:

$\left\{\begin{array}{c}{B}_{\mathrm{ab}}=-(\stackrel{-}{G_q^{+}}-\sqrt{3}\stackrel{-}{G_p^{-}}+\stackrel{-}{G_q^{-}})/3\\ B_{\mathrm{bc}}=-(\stackrel{-}{G_q^{+}}-2\stackrel{-}{G_q^{-}})/3\\ B_{\mathrm{ca}}=-(\stackrel{-}{G_q^{+}}+\sqrt{3}\stackrel{-}{G_p^{-}}+\stackrel{-}{G_q^{-}})/3\end{array}\right.---\left(6\right)$

In step a) the positive sequence voltage detection method using the calculated positive-phase-sequence voltage (

and

), follow these steps:

Three phase network voltage (u _a, u _b, u _c) through three or two coordinate transforms, be converted into dq reference axis direct current signal u _dAnd u _q, the three phase network voltage transitions is that dq axial coordinate computing formula is following:

$\left[\begin{array}{c}{u}_d\\ u_q\end{array}\right]=\sqrt{\frac{2}{3}}\left[\begin{array}{ccc}\sin \mathrm{wt}& \sin (\mathrm{wt}-2\mathrm{\&pi;}/3)& \sin (\mathrm{wt}+2\mathrm{\&pi;}/3)\\ -\cos \mathrm{wt}& -\cos (\mathrm{wt}-2\mathrm{\&pi;}/3)& -\cos (\mathrm{wt}+2\mathrm{\&pi;}/3)\end{array}\right]\left[\begin{array}{c}{u}_a\\ u_b\\ u_c\end{array}\right]---\left(7\right)$

Wherein w is meant the first-harmonic angular frequency, the direct current signal u under the above-mentioned dq reference axis that obtains _dAnd u _q, behind LPF, inverse transformation transforms, and is reduced to the three-phase positive sequence voltage

With

Computing formula is following:

$\left[\begin{array}{c}{u}_a^{+}\\ u_b^{+}\\ u_c^{+}\end{array}\right]=\sqrt{\frac{2}{3}}\left[\begin{array}{cc}\sin \mathrm{wt}& -\cos \mathrm{wt}\\ \sin (\mathrm{wt}-2\mathrm{\&pi;}/3)& -\cos (\mathrm{wt}-2\mathrm{\&pi;}/3)\\ \sin (\mathrm{wt}+2\mathrm{\&pi;}/3)& -\cos (\mathrm{wt}+2\mathrm{\&pi;}/3)\end{array}\right]\left[\begin{array}{c}{u}_d^{+}\\ u_q^{+}\end{array}\right]---\left(8\right)$

Further, in the step d), by total output B of compound control _AbcThe actual needs that draws SVC drops into the actual equivalent susceptance value that PPF organizes number n and TCR

Power distribution method be:

If compensation capacity of each group passive filter is Q, then the passive filter group of input compensation is counted n and should be satisfied following condition:

<math> <mrow> <mi>max</mi> <mo>{</mo> <msub> <mi>B</mi> <mi>Tab</mi> </msub> <mo>,</mo> <msub> <mi>B</mi> <mi>Tbc</mi> </msub> <mo>,</mo> <msub> <mi>B</mi> <mi>Tca</mi> </msub> <mo>}</mo> <mo>&lt;;</mo> <mi>min</mi> <mo>|</mo> <mi>n</mi> <mfrac> <mi>Q</mi> <mrow> <mn>3</mn> <msup> <mi>U</mi> <mn>2</mn> </msup> </mrow> </mfrac> <mo>|</mo> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>9</mn> <mo>)</mo> </mrow> </mrow></math>

Wherein U is the effective value of phase voltage, B _Tab, B _Tbc, B _TcaThe total three-phase of exporting of compound control that calculates for step c) compensates susceptance.After input n organized passive filter, because three-phase power supply system is in capacitive and crosses the benefit state, corresponding perceptual idle to reach idle and full remuneration negative phase-sequence through the TCR compensation, then the perceptual idle susceptance of TCR actual needs input was:

$\left\{\begin{array}{c}{B}_{\mathrm{ab}}^{*}=B_{\mathrm{Tab}}-\frac{\mathrm{nQ}}{3U^2}\\ B_{\mathrm{bc}}^{*}=B_{\mathrm{Tbc}}-\frac{\mathrm{nQ}}{3U^2}\\ B_{\mathrm{ca}}^{*}=B_{\mathrm{Tca}}-\frac{\mathrm{nQ}}{3U^2}\end{array}\right.---\left(10\right)$

Further; In the step d), TCR according to actual equivalent susceptance value

through the concrete performing step of searching Hash and showing to obtain relative trigger angle α is:

Because between the equivalent susceptance that trigger angle α and TCR need compensate is a kind of non-linear relation, following is not:

$B=\frac{2\mathrm{\&pi;}-2\mathrm{\&alpha;}-\sin (2\mathrm{\&pi;}-2\mathrm{\&alpha;})}{\mathrm{\&pi;X}}---\left(11\right)$

Wherein X is the reactance value of connecting with thyristor, and α is the trigger angle of TCR; Therefore at first the following formula linearity is changed into the Hash question blank, because the excursion of the trigger angle α of TCR is [90 °, 180 °]; Trigger angle α is since 90 °, with 0.5 ° as incremental change, each trigger angle α can calculate an equivalent susceptance value; (α B), can calculate 180 groups of vectors altogether so just to constitute a vector; Deposit in the corresponding Hash question blank, so just accomplished the linearization process of equivalent susceptance B to trigger angle α; And then obtain relative trigger angle α through searching said Hash question blank according to actual equivalent susceptance value

.

Based on above-mentioned steps, technique effect of the present invention is:

1. owing to need not carry out complicated Park conversion, DQ conversion and inverse transformation thereof in the FBD algorithm that the present invention adopts; And end product does not receive the influence of zero-sequence current; Reduced the load of controller; Said TCR equivalent susceptance acquiring method based on the FBD algorithm can directly detect SVC instruction references signal fast, thereby improved the idle quality with negative sequence compensation of system.

2. through combining open loop and closed loop control method, remedy the shortcoming that open loop control compensation precision is not high and examined and error of calculation influence is big, improved the compensation precision of SVC.

In sum, the SVC composite control method that calculates based on quick equivalent susceptance according to the invention can improve the compensation precision and the dynamic property of SVC device.After adopting composite control method proposed by the invention, the negative phase-sequence and the reactive power compensation of electric power system are all improved greatly.

Description of drawings

Fig. 1 is imbalance compensation entire system block diagram among the present invention;

Fig. 2 among the present invention based on the quick equivalent susceptance computing block diagram of FBD algorithm;

Fig. 3 detects block diagram for three-phase positive sequence voltage among the present invention;

Fig. 4 is SVC composite control method block diagram described in the present invention;

In above-mentioned accompanying drawing,

1-is a thyristor-controlled reactor; The 2-passive filter; The 3-upper computer detection system;

The 4-DSP control system; The 5-Fiber Optical Communication System; 6-drives triggering system;

7-static reactive system.

Embodiment

As shown in Figure 1, include the SVC SVC7 that forms by the thyristor-controlled reactor 1 and the passive filter 2 that are connected in the electrical network among the present invention in the imbalance compensation system.Wherein thyristor-controlled reactor 1 is taked delta connection; Each branch road is taked two equal-sized reactor series connection; The antiparallel two-way thyristor mode of connection placed in the middle can make the voltage to earth of thyristor valve when normal operation lower like this, and when a reactor failed because; Another reactor still can play the effect of limiting short-circuit current, has strengthened reliability of system operation.Wherein PPF passive filter 2 not only can provide jumbo capacitive reactive power, but also has certain harmonic filtration function, can reduce the electrical network aberration rate.

The negative phase-sequence that causes to load; The idle power quality problem that waits; Present embodiment takes the imbalance compensation control method to realize the balance of each phase power; The system configuration of concrete this control method of realization is as shown in Figure 1, comprises the upper computer detection system 3, DSP control system 4, Fiber Optical Communication System 5 and the trigger board 6 that connect successively.Wherein upper computer detection system 3 is used to gather voltage and current signal, and accomplishes the calculating of three-phase compensation equivalent susceptance, and the result is passed to DSP control system 4.The DSP control system 4 main ripples of sending out of accomplishing signal, triggering signal is transferred to trigger board 6 through Fiber Optical Communication System 5, and signal triggers thyristor through the driving and the amplification of trigger board 6.This photoelectricity triggering mode has realized that not only the isolation of high electronegative potential also has comparatively ideal anti-electromagnetic interference capability, and response speed is fast, helps system and moves reliably and with long-term.

As shown in Figure 2, among the present invention based on the equivalent susceptance computing block diagram of FBD algorithm.

If three-phase voltage and electric current are:

$\left\{\begin{array}{c}{u}_a=U\sin \left(\mathrm{wt}\right)\\ u_b=U\sin (\mathrm{wt}-2\mathrm{\&pi;}/3)\\ u_c=U\sin (\mathrm{wt}+2\mathrm{\&pi;}/3)\end{array}\right.---\left(12\right)$

Where, U is the rms phase voltage; <img file = "BDA0000029189870000083.GIF" he = "45" img-content = "drawing" img-format = "tif" inline = "yes" orientation = "portrait" wi = "37" /> and <img file = "BDA0000029189870000084.GIF" he = "45" img-content = "drawing" img-format = "tif" inline = "yes" orientation = "portrait" wi = "41" /> is n times the positive sequence current RMS and phase angle; <img file = "BDA0000029189870000085.GIF" he = "41" img-content = "drawing " img-format =" tif " inline =" yes " orientation =" portrait " wi =" 36 " /> and <img file =" BDA0000029189870000086.GIF " he =" 39 " img-content =" drawing " img-format =" tif " inline =" yes " orientation =" portrait " wi =" 40 " /> is n times the negative sequence current RMS and phase angle.Make u<sub >1</sub>=(u<sub >a</sub>, u<sub >b</sub>, u<sub >c</sub>), i=(i<sub >a</sub>, i<sub >b</sub>, i<sub >c</sub>), with voltage u<sub >1</sub>Each component obtain new vector behind the phase shift pi/2 forward and be designated as<img file="BDA0000029189870000087.GIF" he="57" img-content="drawing" img-format="GIF" inline="yes" orientation="portrait" wi="373" />According to the power definition of FBD principle, have that fundamental positive sequence equivalence is meritorious to be respectively ∑ p with reactive power<sup >+</sup>=<u<sub >1</sub>, i>,<img file="BDA0000029189870000088.GIF" he="57" img-content="drawing" img-format="GIF" inline="yes" orientation="portrait" wi="286" />So can push away below fundamental positive sequence equivalence meritorious with idle electricity lead into:

$\left\{\begin{array}{c}{G}_p^{+}\left(t\right)=\frac{\mathrm{\&Sigma;}{p}^{+}}{{\left|\right|u_1\left|\right|}^2}=\frac{2[u_a{i}_a+u_b{i}_b+u_c{i}_c]}{3U^2}\\ G_q^{+}\left(t\right)=\frac{\mathrm{\&Sigma;}{q}^{+}}{{\left|\right|{u^i}_1\left|\right|}^2}=\frac{2[{u^i}_a{i}_a+{u^i}_b{i}_b+{u^i}_c{i}_c]}{3U^2}\end{array}\right.---\left(14\right)$

that will obtain in the following formula obtains the direct current composition

that direct current composition that the meritorious electricity of fundamental positive sequence equivalence leads and idle electricity are led behind low pass filter LPF filtering Alternating Component

If in like manner with u ₁In u _bAnd u _cExchange one upper/lower positions then can obtain other one group of voltage vector u each other ₂(u ₂=(u _a, u _c, u _b)) and

Then can push away to such an extent that the meritorious electricity of first-harmonic negative phase-sequence equivalence is led the expression formula of leading with idle electricity:

$\left\{\begin{array}{c}{G}_p^{-}\left(t\right)=\frac{\mathrm{\&Sigma;}{p}^{-}}{{\left|\right|u_2\left|\right|}^2}=\frac{2(u_a{i}_a+u_c{i}_b+u_b{i}_c)}{3U^2}\\ G_q^{-}\left(t\right)=\frac{\mathrm{\&Sigma;}{q}^{-}}{{\left|\right|{u^i}_2\left|\right|}^2}=\frac{2({u^i}_a{i}_a+{u^i}_c{i}_b+{u^i}_b{i}_c)}{3U^2}\end{array}\right.---\left(15\right)$

It is the effective value of phase voltage that U is wherein arranged.

that will obtain in the following formula is behind the low pass filter filters out Alternating Component; Obtain direct current composition

that direct current composition

that the meritorious electricity of first-harmonic negative phase-sequence equivalence leads and idle electricity lead then according to the definition of positive sequence and negative-sequence current, promptly can push away following formula:

Wherein, U is the effective value of phase voltage; I ⁺And I ^-Be fundamental positive sequence and negative-sequence current vector;

With

Be fundamental positive sequence and negative-sequence current effective value;

With

Power-factor angle for fundamental positive sequence and negative-sequence current.Realize that equilibrating compensation and raising power factor of electric network approach 1, just must satisfy following 2 conditions: the negative sequence component of 1) eliminating load current; 2) making the positive sequence component imaginary part of load current is 0.According to above-mentioned condition, can obtain the equivalent susceptance value that TCR need drop into electrical network and be:

$\left\{\begin{array}{c}{B}_{\mathrm{ab}}=-(\stackrel{-}{G_q^{+}}-\sqrt{3}\stackrel{-}{G_p^{-}}+\stackrel{-}{G_q^{-}})/3\\ B_{\mathrm{bc}}=-(\stackrel{-}{G_q^{+}}-2\stackrel{-}{G_q^{-}})/3\\ B_{\mathrm{ca}}=-(\stackrel{-}{G_q^{+}}+\sqrt{3}\stackrel{-}{G_p^{-}}+\stackrel{-}{G_q^{-}})/3\end{array}\right.---\left(17\right)$

Can know that through above-mentioned analysis zero-sequence current does not influence testing result, so that the FBD algorithm is applicable to is single-phase, the current detecting of three-phase three-wire system and three-phase four-wire system.And the FBD algorithm do not carry out complicated Park conversion, DQ conversion and inverse transformation thereof, reduced the calculated load amount of controller.

Since when equivalent susceptance less than 0 the time, then to drop into the idle susceptance of corresponding perception, otherwise, then need drop into corresponding capacitive reactive power susceptance.According to the size of load reactive power demand, design N group passive filter carries out the compensation of capacitive reactive power, and the compensation capacity of each group passive filter is Q.Then the passive filter group of input compensation is counted n and should be satisfied following condition:

<math> <mrow> <mi>max</mi> <mo>{</mo> <msub> <mi>B</mi> <mi>Tab</mi> </msub> <mo>,</mo> <msub> <mi>B</mi> <mi>Tbc</mi> </msub> <mo>,</mo> <msub> <mi>B</mi> <mi>Tca</mi> </msub> <mo>}</mo> <mo>&lt;;</mo> <mi>min</mi> <mo>|</mo> <mi>n</mi> <mfrac> <mi>Q</mi> <mrow> <mn>3</mn> <msup> <mi>U</mi> <mn>2</mn> </msup> </mrow> </mfrac> <mo>|</mo> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>18</mn> <mo>)</mo> </mrow> </mrow></math>

At first drop into after the n group passive filter, three-phase power supply system is in capacitive and crosses the benefit state, and is idle to reach idle and full remuneration negative phase-sequence through the corresponding perception of TCR compensation then.Then the perceptual idle susceptance of TCR actual needs input is:

$\left\{\begin{array}{c}{B}_{\mathrm{ab}}^{*}=B_{\mathrm{Tab}}-\frac{\mathrm{nQ}}{3U^2}\\ B_{\mathrm{bc}}^{*}=B_{\mathrm{Tbc}}-\frac{\mathrm{nQ}}{3U^2}\\ B_{\mathrm{ca}}^{*}=B_{\mathrm{Tca}}-\frac{\mathrm{nQ}}{3U^2}\end{array}\right.---\left(19\right)$

Wherein U is the effective value of phase voltage, B _Tab, B _Tbc, B _TcaThree-phase compensation susceptance for the total output of compound control.Through electrical network three-phase voltage and current signal are detected, utilize the FBD algorithm computation to obtain accordingly

And, utilize the composite control method of open loop and closed loop can calculate the total equivalent susceptance B of compound control output through corresponding processing and calculating _Tabc, calculate the actual equivalent susceptance value that the actual input group of PPF is counted n and TCR through above-mentioned power division principle

Controller sends control signal corresponding and cuts n group PPF like this, for system provides corresponding reactive capability, obtains the full remuneration that corresponding perceptual reactive current realizes negative-sequence current through triggering TCR again.Because be a kind of non-linear relation between the equivalent susceptance that trigger angle α and TCR need compensate, as follows:

$B=\frac{2\mathrm{\&pi;}-2\mathrm{\&alpha;}-\sin (2\mathrm{\&pi;}-2\mathrm{\&alpha;})}{\mathrm{\&pi;X}}---\left(20\right)$

Wherein X is the reactance value of connecting with thyristor, and α is the trigger angle of TCR.The control of TCR for ease generally changes into the Hash question blank with the following formula linearity, like this can be according to the equivalent susceptance value, and table look-at obtains corresponding TCR trigger angle.Because the excursion of the trigger angle of TCR is [90 °, 180 °], α is since 90 °; With 0.5 ° as incremental change, each α can calculate an equivalent susceptance value, so just constitutes a vector (α; B); Can calculate 180 groups of vectors altogether, deposit in the corresponding Hash question blank, so just accomplish the linearization process of equivalent susceptance B to trigger angle α.

As shown in Figure 3, positive sequence voltage detects block diagram among the present invention.

Because the imbalance and the harmonic current phenomenon of enterprise's electric power system load are serious, make to exist a large amount of negative phase-sequences and harmonic wave composition in the supply power voltage, make result of calculation that very big error will be arranged.Therefore present embodiment adopts instantaneous reactive power theory to extract the positive sequence voltage detection method, shown in figure (3).Three-phase voltage signal (u _a, u _b, u _c) through three or two coordinate transforms, three-phase voltage signal is converted into dq reference axis direct current signal u _dAnd u _q, come filtering to become corresponding AC signal through low pass filter then by other negative phase-sequence harmonic voltage transitions, can obtain the direct current signal that forms by three-phase fundamental positive sequence voltage transitions like this

With

Like this

With

To change through inverse transformation, be reduced to three-phase fundamental positive sequence voltage

With

It is following that three-phase voltage converts dq axial coordinate computing formula into:

$\left[\begin{array}{c}{u}_d\\ u_q\end{array}\right]=T_{\mathrm{abc}/\mathrm{dq}\left(w\right)}\left[\begin{array}{c}{u}_a\\ u_b\\ u_c\end{array}\right]$

$\left[\begin{array}{c}{u}_d\\ u_q\end{array}\right]=\sqrt{\frac{2}{3}}\left[\begin{array}{ccc}\sin \mathrm{wt}& \sin (\mathrm{wt}-2\mathrm{\&pi;}/3)& \sin (\mathrm{wt}+2\mathrm{\&pi;}/3)\\ -\cos \mathrm{wt}& -\cos (\mathrm{wt}-2\mathrm{\&pi;}/3)& -\cos (\mathrm{wt}+2\mathrm{\&pi;}/3)\end{array}\right]\left[\begin{array}{c}{u}_a\\ u_b\\ u_c\end{array}\right]---\left(21\right)$

U under the above-mentioned dq reference axis that obtains _dAnd u _q, behind LPF, inverse transformation is converted into the component of voltage under three phase coordinates, and computing formula is following:

$\left[\begin{array}{c}{u}_a^{+}\\ u_b^{+}\\ u_c^{+}\end{array}\right]=T_{\mathrm{dq}/\mathrm{abc}\left(w\right)}\left[\begin{array}{c}{u}_d^{+}\\ u_q^{+}\end{array}\right]$

$\left[\begin{array}{c}{u}_a^{+}\\ u_b^{+}\\ u_c^{+}\end{array}\right]=\sqrt{\frac{2}{3}}\left[\begin{array}{cc}\sin \mathrm{wt}& -\cos \mathrm{wt}\\ \sin (\mathrm{wt}-2\mathrm{\&pi;}/3)& -\cos (\mathrm{wt}-2\mathrm{\&pi;}/3)\\ \sin (\mathrm{wt}+2\mathrm{\&pi;}/3)& -\cos (\mathrm{wt}+2\mathrm{\&pi;}/3)\end{array}\right]\left[\begin{array}{c}{u}_d^{+}\\ u_q^{+}\end{array}\right]---\left(22\right)$

Like this through above-mentioned positive sequence voltage detection method, the effective negative phase-sequence harmonic component in the filtering three-phase voltage component improves the counting accuracy and the compensation performance of SVC bucking-out system.

As shown in Figure 4, SVC composite control method according to the invention is described below:

Because the nonlinear characteristic of SVC, its control performance will inevitably be affected.In order to improve the dynamic property of SVC, the present invention combines traditional closed-loop and open loop control, utilizes the fast-response ability of feedforward open loop control, utilizes the performance of dynamic tracking of closed-loop control to carry out online self-adjusting again, makes the dynamic property of SVC more superior.After compensation is stable; Power network current three-phase power balance, negative phase-sequence and reactive current are 0, thereby should be 0 according to the equivalent susceptance that power network current calculates; So equivalent susceptance that can power network current is corresponding, is realized the dynamic tracking compensation of negative phase-sequence and reactive current as the closed-loop control target.

The practical implementation step is following:

1), at first through detecting three phase network voltage (u _a, u _b, u _c), utilize the positive sequence voltage detection method can calculate the three-phase positive sequence voltage (

With

);

2), detect the threephase load current i _Labc, utilize based on the quick equivalent susceptance computational methods of FBD algorithm and try to achieve the corresponding equivalent susceptance value B of threephase load electric current _LabcThrough detecting the threephase load current i _Labc, three-phase TCR current i _TCRabcWith passive filter group current i _PPFabc, their additions can be calculated the three phase network current i _Sabc, can calculate the corresponding equivalent susceptance value B of three phase network electric current according to quick equivalent susceptance computational methods thus _Sabc

3), a last step is waited the corresponding equivalent susceptance B of three phase network electric current that obtains _Sabc, after the adjusting of PI controller, can calculate the closed loop output valve

(

k _p, k _iBe expressed as ratio and integral coefficient respectively), the corresponding equivalent susceptance value B of threephase load electric current that calculates with a last step like this _LabcAddition can obtain total output B of compound control _Tabc

Total output B according to compound control _Tabc, the actual needs that calculates SVC through power divider drops into the actual equivalent susceptance value that PPF organizes number n and TCR

Controller sends control signal corresponding and cuts n group PPF like this, for system provides corresponding reactive capability.Yet TCR shows to obtain the relative trigger angle according to actual equivalent susceptance value

through searching Hash; Pass through the driving and the amplification of drive circuit then; Trigger opening of corresponding thyristor and send corresponding perceptual reactive current and come compensating reactive power and negative-sequence current, the system that finally realizes is idle and the full remuneration of negative-sequence current.Utilize the dynamic adjustments ability of closed-loop control to realize steady-state error like this, effectively remedied the shortcoming of open loop control, improve dynamic compensation performance and the compensation precision of SVC, realize negative phase-sequence and idle compensation and the balance of three phase power.

Claims (4)

1. a SVC composite control method that calculates based on quick equivalent susceptance is characterized in that, comprises the steps:

A), at first through detecting three phase network voltage u _a, u _b, u _c, utilize the positive sequence voltage detection method can calculate the three-phase positive sequence voltage

With

B), detect the threephase load current i _Labc, utilize based on the quick equivalent susceptance computational methods of FBD algorithm and try to achieve the corresponding equivalent susceptance value B of threephase load electric current _LabcThrough detecting the threephase load current i _Labc, three-phase TCR current i _TCRabcWith passive filter group current i _PPFabc, their additions can be calculated the three phase network current i _Sabc, can calculate the corresponding equivalent susceptance value B of three phase network electric current according to quick equivalent susceptance computational methods thus based on the FBD algorithm _Sabc

Said quick equivalent susceptance computational methods based on the FBD algorithm may further comprise the steps:

I. establishing three phase network voltage and three-phase current is:

Wherein, U is the effective value of three-phase voltage; With

Effective value and phase angle for n forward-order current;

With

Effective value and phase angle for n negative-sequence current; Make u ₁=(u _a, u _b, u _c), i=(i _a, i _b, i _c), with voltage u ₁Each component obtain new vector behind the phase shift pi/2 forward and be designated as

According to the power definition of FBD principle, have that fundamental positive sequence equivalence is meritorious to be respectively ∑ with reactive power _p ⁺=<u ₁, i>,

So can push away below fundamental positive sequence equivalence meritorious with idle electricity lead into:

If in like manner with u ₁In u _bAnd u _cExchange one upper/lower positions then can obtain other one group of voltage vector u each other ₂, u ₂=(u _a, u _c, u _b) and

Then can push away to such an extent that the meritorious electricity of first-harmonic negative phase-sequence equivalence is led the expression formula of leading with idle electricity:

It is the effective value of three-phase voltage that U is wherein arranged;

Ii with

in the formula (3) behind low pass filter LPF filtering Alternating Component; Obtain direct current composition

that direct current composition

that the meritorious electricity of fundamental positive sequence equivalence leads and idle electricity lead with in the formula (4) behind the low pass filter filters out Alternating Component; Obtain direct current composition

that direct current composition

that the meritorious electricity of first-harmonic negative phase-sequence equivalence leads and idle electricity lead then according to the definition of positive sequence and negative-sequence current, promptly can push away following formula:

Wherein, U is the effective value of three-phase voltage; I ⁺And I ^-Be fundamental positive sequence and negative-sequence current vector;

With Be fundamental positive sequence and negative-sequence current effective value;

With

Power-factor angle for fundamental positive sequence and negative-sequence current;

Iii. to realize that equilibrating compensation and raising power factor of electric network approach 1, just must satisfy following 2 conditions: the negative sequence component of 1) eliminating load current; 2) making the positive sequence component imaginary part of load current is 0; According to above-mentioned condition, can obtain the equivalent susceptance value that TCR need drop into electrical network and be:

C), last one go on foot the corresponding equivalent susceptance B of three phase network electric current that obtains _Sabc, after the adjusting of PI controller, can calculate the closed loop output valve

Again with the closed loop output valve that obtains

The corresponding equivalent susceptance value B of threephase load electric current that obtains with above-mentioned steps _LabcAddition, the three-phase that obtains the total output of compound control compensates susceptance B _Tabc, B _Tabc=(B _Tab, B _Tbc, B _Tca);

D), the three-phase according to the total output of compound control compensates susceptance B _Tabc, the actual needs that calculates SVC through power divider drops into the actual equivalent susceptance value that PPF organizes number n and TCR

Controller sends control signal corresponding and cuts n group PPF like this, for system provides corresponding reactive capability; Simultaneously, TCR is according to actual equivalent susceptance value Show to obtain the relative trigger angle through searching Hash; Pass through the driving and the amplification of drive circuit then; Trigger opening of corresponding thyristor and send corresponding perceptual reactive current and come compensating reactive power and negative-sequence current, the system that finally realizes is idle and the full remuneration of negative-sequence current.

2. according to the said SVC composite control method that calculates based on quick equivalent susceptance of claim 1; It is characterized in that it is following to utilize the positive sequence voltage detection method to calculate the step of three-phase positive sequence voltage and in the step a):

Three phase network voltage u _a, u _b, u _cThrough three or two coordinate transforms, be converted into dq reference axis direct current signal u _dAnd u _q, the three phase network voltage transitions is that dq axial coordinate computing formula is following:

Wherein w is meant the first-harmonic angular frequency, the direct current signal u under the above-mentioned dq reference axis that obtains _dAnd u _q, behind LPF, inverse transformation transforms, and is reduced to the three-phase positive sequence voltage

With

Computing formula is following:

。

3. according to the said SVC composite control method that calculates based on quick equivalent susceptance of claim 1, it is characterized in that, in the step d), by total output B of compound control _AbcThe actual needs that draws SVC drops into the actual equivalent susceptance value that PPF organizes number n and TCR

Power distribution method be:

If compensation capacity of each group passive filter is Q, then the passive filter group of input compensation is counted n and should be satisfied following condition:

Wherein U is the effective value of three-phase voltage, B _Tab, B _Tbc, B _TcaThe total three-phase of exporting of compound control that calculates for step c) in the claim 1 compensates susceptance; After input n organized passive filter, because three-phase power supply system is in capacitive and crosses the benefit state, corresponding perceptual idle to reach idle and full remuneration negative phase-sequence through the TCR compensation, then the perceptual idle susceptance of TCR actual needs input was:

。

4. according to the said SVC composite control method that calculates based on quick equivalent susceptance of claim 1; It is characterized in that; In the step d), TCR according to actual equivalent susceptance value

through the concrete performing step of searching Hash and showing to obtain relative trigger angle α is:

Because be a kind of non-linear relation between the equivalent susceptance that trigger angle α and TCR need compensate, as follows:

Wherein X is the reactance value of connecting with thyristor, and α is the trigger angle of TCR; Therefore at first formula (11) linearity is changed into the Hash question blank, because the excursion of the trigger angle α of TCR is [90 °, 180 °]; Trigger angle α is since 90 °, with 0.5 ° as incremental change, each trigger angle α can calculate an equivalent susceptance value; (α B), can calculate 180 groups of vectors altogether so just to constitute a vector; Deposit in the corresponding Hash question blank, so just accomplished the linearization process of equivalent susceptance B to trigger angle α; And then obtain relative trigger angle α through searching said Hash question blank according to actual equivalent susceptance value

.

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