CN101969204A - Vector control-based static volt-ampere reactive compensation (SVC) method and device - Google Patents

Abstract

The invention provides a vector control-based static volt-ampere reactive compensation (SVC) method and a vector control-based SVC device. A thyristor valve bank phase-controlled reactor unit and an FC filter unit are in parallel connection with high voltage buses respectively; the thyristor valve bank phase-controlled reactor unit comprises a thyristor valve bank and a phase-controlled reactor; the thyristor valve bank consists of a pair of antiparallel thyristors; and a digital signal processing (DSP) full-digital control system is connected with the thyristor bank. In the method, the system parameters of an access point are detected in real time; the detected system parameters are transformed into the parameters in an alpha/beta coordinate system through alpha/beta transformation; the parameters in the alpha/beta coordinate system are transformed into the parameters in a rotating coordinate system through d/q transformation; and according to an instantaneous reactive power theory, an instantaneous admittance value of each phase is calculated and the inductive reactive power of each phase is adjusted respectively. The method and the device meet the requirements on the adaptability and accuracy of the conventional electric power system harmonic detection and reactive compensation, improve SVC electrical susceptance calculation accuracy, and have high dynamic performance, robustness and response speed.

Description

A kind of static var compensation compensation method and device thereof based on vector control

(1) technical field

The present invention relates to the power transmission and transformation technology, is exactly a kind of static var compensation compensation method and device thereof based on vector control specifically.

(2) background technology

In recent years, because the continuous development of science and technology, various power electronic equipments are widely applied, and along with the continuous increase of various non-linear, impact loads, the reactive power impact of electrical network, fluctuation, loss also are the trend of continuous rising, particularly not enough and be equipped with irrational phenomenon in the construction of China's electrical network and the reactive compensation capacity that exists in service always, and this situation easier useful life of causing the system voltage fluctuation, reducing electric equipment also will absorb a large amount of reactive powers simultaneously.The appearance of reactive power not only causes generator output to descend, and reduces equipment for power transmission and distribution efficient, and has increased network loss, has a strong impact on power supply quality and economy.Therefore, need compensating power in the power system operation process, high order harmonic component is eliminated in the control asymmetric operation.

Adopt Static Type Dynamic Reactive Compensation Device (SVC) can play improvement system imbalance, improve load power factor, the filtering harmonic current, therefore to power system voltage stabilization with improve the quality of power supply and played tangible effect, also obtained application more and more widely simultaneously.Yet for the certain user, what be concerned about most is the flickering problem of being brought by voltage flicker, if this problem solves and badly will directly have influence on safety and production.The inhibiting rate of flickering and the compensation capacity of SVC and the response speed of controller have direct relation as can be seen from the past SVC operating experience, under same compensation capacity, the fast controller of response speed is being better than the slow controller of response speed aspect the flickering inhibition.The principal element that influences the controller response speed is the detection and the computational methods of signal, traditional algorithm mostly is based upon on the basis of asking power, when the SVC that adopts power algorithm towards the fast industrial load of some pace of change, during as arc furnace etc., because of containing more harmonic components in the detection signal, can cause before and after the filtering has bigger time-delay, also can introduce the detection error simultaneously, cause the controller computational accuracy to descend, the compensation arrangement response speed is slow, can not satisfy the requirement of industry spot.

(3) summary of the invention

The object of the present invention is to provide a kind of real-time detection access point system parameters, according to system voltage, load current sampled signal, calculate compensation susceptance value in real time, control thyristor trigger angle realizes static var compensation compensation method and device thereof based on vector control to the Controlled Reactor quick control.

The object of the present invention is achieved like this: described a kind of static passive compensation device based on vector control, it is by thyristor valve group Controlled Reactor unit, FC filter cell and DSP full-digital control system form, thyristor valve group Controlled Reactor unit, the FC filter cell is parallel on the high voltage bus respectively, thyristor valve group Controlled Reactor unit comprises thyristor valve group and Controlled Reactor, the thyristor valve group is made up of a pair of antiparallel thyristor, the thyristor valve group is connected between the Controlled Reactor, the FC filter cell is made up of filter reactor and power capacitor, filter reactor connects power capacitor, and the DSP full-digital control system connects the thyristor valve group.Described as follows: as to be parallel to and to detect the system parameters of access point in real time based on the static passive compensation device of vector control on the high voltage bus by the method that realizes based on the static passive compensation device of vector control, acquisition system voltage, the load current signal, become parameter under α/β coordinate system through α/β conversion, become the rotating coordinate system parameter through the d/q conversion again, calculate the instantaneous admittance value of every phase respectively according to the instantaneous reactive theory, send the trigger angle of corresponding phase again according to result of calculation, regulate the perceptual idle of every phase, thereby satisfy the reactive requirement of every phase, realize continuously, the reactive power of phase-splitting and approximately linear is regulated;

The three-phase imbalance electric current of load is:

In the following formula, electric current is represented with positive sequence component instantaneous value and negative sequence component instantaneous value form, after the conversion of two-phase quadrature α β coordinate system, obtains current phasor at process abc three-phase rotating coordinate system, according to the instantaneous reactive theory, obtain active power and reactive power again:

Become the rotating coordinate system parameter through the d/q conversion then, this moment, fundametal compoment was converted into DC component, and harmonic component is a rotational component, and through low-pass filtering, remaining DC component promptly obtains the fundamental positive sequence active power and the reactive power of loading:

After this moment a, b, c middle mutually b, c being changed mutually, voltage will become negative phase-sequence, and selecting the negative phase-sequence synchronous rotating frame is reference frame, simultaneously, it is synchronous that two phase coordinate systems that needs are converted to also make negative phase-sequence into, can obtain first-harmonic negative phase-sequence active power and reactive power:

With fundamental positive sequence, negative phase-sequence active power and reactive power substitution matrix determinant, can obtain the compensation susceptance of three-phase load:

$\left\{\begin{array}{c}{B}_{\mathrm{ab}}^{\left(c\right)}=B_{\mathrm{pab}}^{\left(c\right)}+B_{\mathrm{nab}}^{\left(c\right)}=\frac{1}{3U^2}(\frac{1}{3}\stackrel{\‾}{q}+\frac{1}{\sqrt{3}}\stackrel{\‾}{p^{\′}}+\frac{1}{3}\stackrel{\‾}{q^{\′}})\\ B_{\mathrm{bc}}^{\left(c\right)}=B_{\mathrm{pbc}}^{\left(c\right)}+B_{\mathrm{nbc}}^{\left(c\right)}=\frac{1}{3U^2}(\frac{1}{3}\stackrel{\‾}{q}-\frac{2}{3}\stackrel{\‾}{q^{\′}})\\ B_{\mathrm{ca}}^{\left(c\right)}=B_{\mathrm{pca}}^{\left(c\right)}+B_{\mathrm{nca}}^{\left(c\right)}=\frac{1}{3U^2}(\frac{1}{3}\stackrel{\‾}{q}-\frac{1}{\sqrt{3}}\stackrel{\‾}{p^{\′}}+\frac{1}{3}\stackrel{\‾}{q^{\′}})\end{array}\right.$

Thereby realize the reactive power compensation of three-phase imbalance load.

The present invention a kind of static var compensation compensation method and device thereof based on vector control, use instantaneous reactive power theory and replace traditional in the past control theory, promptly utilize instantaneous value to replace traditional effective value to analyze three-phase electrical power system, being fit to very much the detection of current power system harmonics and the adaptability of reactive power compensation, the requirement of accuracy, is a kind of very promising theory and control method.The real-time system parameters that detects access point, and according to system voltage, load current sampled signal, calculate compensation susceptance value in real time, and control the thyristor trigger angle, thereby realize quick control to Controlled Reactor (TCR).Control strategy can carry out the equilibrating compensation of uncompensated load, can stablize control again, has improved SVC susceptance computational accuracy, has good dynamic characteristics, higher robustness and very fast response speed.Real-time of the present invention is good, response speed is fast, control precision is high, good stability, antijamming capability are strong.

(4) description of drawings

Fig. 1 is a structural representation of the present invention;

Fig. 2 is a DSP algorithm flow block diagram of the present invention.

(5) embodiment

The invention will be further described for example below in conjunction with accompanying drawing.

Embodiment 1: in conjunction with Fig. 1, Fig. 2, a kind of static passive compensation device of the present invention based on vector control, it is by thyristor valve group Controlled Reactor unit, FC filter cell and DSP full-digital control system form, thyristor valve group Controlled Reactor unit, the FC filter cell is parallel on the high voltage bus respectively, thyristor valve group Controlled Reactor unit comprises thyristor valve group and Controlled Reactor, the thyristor valve group is made up of a pair of antiparallel thyristor, the thyristor valve group is connected between the Controlled Reactor, the FC filter cell is made up of filter reactor and power capacitor, filter reactor connects power capacitor, and the DSP full-digital control system connects the thyristor valve group.

Described static var compensation compensation method: be parallel to and detect the system parameters of access point in real time based on the static passive compensation device of vector control on the high voltage bus based on vector control, acquisition system voltage, the load current signal, become parameter under α/β coordinate system through α/β conversion, become the rotating coordinate system parameter through the d/q conversion again, calculate the instantaneous admittance value of every phase respectively according to the instantaneous reactive theory, send the trigger angle of corresponding phase again according to result of calculation, regulate the perceptual idle of every phase, thereby satisfy the reactive requirement of every phase, realize continuously, the reactive power of phase-splitting and approximately linear is regulated;

The three-phase imbalance electric current of load is:

In the following formula, electric current is represented with positive sequence component instantaneous value and negative sequence component instantaneous value form, after the conversion of two-phase quadrature α β coordinate system, obtains current phasor at process abc three-phase rotating coordinate system, according to the instantaneous reactive theory, obtain active power and reactive power again:

Become the rotating coordinate system parameter through the d/q conversion then, this moment, fundametal compoment was converted into DC component, and harmonic component is a rotational component, and through low-pass filtering, remaining DC component promptly obtains the fundamental positive sequence active power and the reactive power of loading:

After this moment a, b, c middle mutually b, c being changed mutually, voltage will become negative phase-sequence, and selecting the negative phase-sequence synchronous rotating frame is reference frame, simultaneously, it is synchronous that two phase coordinate systems that needs are converted to also make negative phase-sequence into, can obtain first-harmonic negative phase-sequence active power and reactive power:

With fundamental positive sequence, negative phase-sequence active power and reactive power substitution matrix determinant, can obtain the compensation susceptance of three-phase load:

$\left\{\begin{array}{c}{B}_{\mathrm{ab}}^{\left(c\right)}=B_{\mathrm{pab}}^{\left(c\right)}+B_{\mathrm{nab}}^{\left(c\right)}=\frac{1}{3U^2}(\frac{1}{3}\stackrel{\‾}{q}+\frac{1}{\sqrt{3}}\stackrel{\‾}{p^{\′}}+\frac{1}{3}\stackrel{\‾}{q^{\′}})\\ B_{\mathrm{bc}}^{\left(c\right)}=B_{\mathrm{pbc}}^{\left(c\right)}+B_{\mathrm{nbc}}^{\left(c\right)}=\frac{1}{3U^2}(\frac{1}{3}\stackrel{\‾}{q}-\frac{2}{3}\stackrel{\‾}{q^{\′}})\\ B_{\mathrm{ca}}^{\left(c\right)}=B_{\mathrm{pca}}^{\left(c\right)}+B_{\mathrm{nca}}^{\left(c\right)}=\frac{1}{3U^2}(\frac{1}{3}\stackrel{\‾}{q}-\frac{1}{\sqrt{3}}\stackrel{\‾}{p^{\′}}+\frac{1}{3}\stackrel{\‾}{q^{\′}})\end{array}\right.$

Thereby realize the reactive power compensation of three-phase imbalance load.

Embodiment 2: in conjunction with Fig. 1, Fig. 2, Fig. 1 has provided the static passive compensation device structural representation, static passive compensation device is parallel on the high voltage bus, detect the system parameters of access point in real time, and according to system voltage, load current sampled signal, in dsp controller, calculate the admittance value of required compensation, thereby draw the size of trigger angle, and send by controller, change the trigger angle of thyristor, adjust the perceptual reactive current that flows through in the Controlled Reactor, realized power supply grid because the dynamic tracking of the reactive power fluctuation that the variation of load causes is regulated.The static passive compensation device main circuit is made up of thyristor valve group, Controlled Reactor (TCR), fixed capacitor group (FC) and controller four parts: the thyristor valve group is made up of a pair of antiparallel thyristor, is connected between the Controlled Reactor (TCR); The Controlled Reactor of thyristor control is used for balance sysmte because the lagging reactive power that fluctuation produced of load; The FC filter is made up of filter reactor and capacitor, is used to provide capacitive reactive power and harmonic.

After system voltage and load current were handled through PT, CT, the A/D sample circuit of sending into controller carried out conversion process, and the access point of establishing compensator and load is the PCC point, its three-phase voltage be symmetry with distortionless, be expressed as with the form of instantaneous value

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

In the formula: U is a bus phase voltage effective value, V; ω is the voltage angle frequency, rad/s.

The three-phase imbalance electric current of load is represented with positive sequence component instantaneous value and negative sequence component instantaneous value form:

In the formula: I _1kPositive sequence component effective value for the k subharmonic;

Initial phase angle for the positive sequence component of k subharmonic; I _2kNegative sequence component effective value for the k subharmonic;

Initial phase angle for the negative sequence component of k subharmonic.

Detect fundamental positive sequence power then, according to the electrical engineering theory, three-phase voltage, electric current are from abc three-phase rotating coordinate system being transformed to two-phase quadrature α β coordinate system:

$\left[\begin{array}{c}{u}_{\mathrm{\α}}\\ u_{\mathrm{\β}}\end{array}\right]=C_{32}\left[\begin{array}{c}{u}_a\\ u_b\\ u_c\end{array}\right]=\left[\begin{array}{c}\sqrt{3}U\cos \mathrm{\ωt}\\ \sqrt{3}U\sin \mathrm{\ωt}\end{array}\right]---\left(3\right)$

According to the instantaneous reactive theory, have

Through low-pass filtering, remaining DC component

Promptly obtain the fundamental positive sequence active power and the reactive power of loading.

After supposing here that with a, b, c b, c change mutually in mutually, voltage will become negative phase-sequence, be reference frame if select the negative phase-sequence synchronous rotating frame, and simultaneously, it is synchronous that two phase coordinate systems that needs are converted to also make negative phase-sequence into.Can copy said method to try to achieve the first-harmonic negative sequence power.

The u of switch type (1) _b, u _cOrder, clear in order to represent, establish u ' _a=u _a, u ' _b=u _c, u ' _c=u _bHave

$\left\{\begin{array}{c}{u}_a^{\′}=\sqrt{2}U\cos \mathrm{\ωt}\\ u_b^{\′}=\sqrt{2}U\cos (\mathrm{\ωt}+2\mathrm{\π}/3)\\ u_c^{\′}=\sqrt{2}U\cos (\mathrm{\ωt}-2\mathrm{\π}/3)\end{array}\right.---\left(7\right)$

Current expression is constant.Then, voltage and load current that PCC is ordered transform in the synchronous two-phase α ' β ' coordinate system of negative phase-sequence, and transformation matrix changes into

$C_{32}^{\′}=\sqrt{\frac{2}{3}}\left[\begin{array}{ccc}1& -\frac{1}{2}& -\frac{1}{2}\\ 0& -\frac{\sqrt{3}}{2}& \frac{\sqrt{3}}{2}\end{array}\right]---\left(8\right)$

At this moment have,

$\left[\begin{array}{c}{u}_{{\mathrm{\α}}^{\′}}\\ u_{{\mathrm{\β}}^{\′}}\end{array}\right]=C_{32}^{\′}\left[\begin{array}{c}{u}_a^{\′}\\ u_b^{\′}\\ u_c^{\′}\end{array}\right]=\left[\begin{array}{c}\sqrt{3}U\cos \mathrm{\ωt}\\ \sqrt{3}U\sin \mathrm{\ωt}\end{array}\right]---\left(9\right)$

Through low-pass filtering, remaining DC component

Promptly obtain first-harmonic negative phase-sequence active power and reactive power.

In formula (6), formula (12) relative section substitution formula (5), have

$\left\{\begin{array}{c}{B}_{\mathrm{ab}}^{\left(c\right)}=B_{\mathrm{pab}}^{\left(c\right)}+B_{\mathrm{nab}}^{\left(c\right)}=\frac{1}{3U^2}(\frac{1}{3}\stackrel{\‾}{q}+\frac{1}{\sqrt{3}}\stackrel{\‾}{p^{\′}}+\frac{1}{3}\stackrel{\‾}{q^{\′}})\\ B_{\mathrm{bc}}^{\left(c\right)}=B_{\mathrm{pbc}}^{\left(c\right)}+B_{\mathrm{nbc}}^{\left(c\right)}=\frac{1}{3U^2}(\frac{1}{3}\stackrel{\‾}{q}-\frac{2}{3}\stackrel{\‾}{q^{\′}})\\ B_{\mathrm{ca}}^{\left(c\right)}=B_{\mathrm{pca}}^{\left(c\right)}+B_{\mathrm{nca}}^{\left(c\right)}=\frac{1}{3U^2}(\frac{1}{3}\stackrel{\‾}{q}-\frac{1}{\sqrt{3}}\stackrel{\‾}{p^{\′}}+\frac{1}{3}\stackrel{\‾}{q^{\′}})\end{array}\right.---\left(13\right)$

Can realize the reactive power compensation of three-phase imbalance load by formula (13).

When PCC point voltage three-phase imbalance or distortion, above-mentioned algorithm will have error, considers that the degree of unbalance of PCC point voltage is very little generally speaking, and SVC can filtering the most harmonic current that produces of load, the influence of voltage distortion is also very little, and therefore above-mentioned algorithm is suitable for.

In addition, when the load three-phase equilibrium or when in a basic balance, negative sequence component does not have or is very little, and the amount relevant with negative sequence component is zero or approaches zero in this up-to-date style (13), can adopt the following formula supplement to repay susceptance

$\left\{\begin{array}{c}{B}_{\mathrm{ab}}^{\left(c\right)}=B_{\mathrm{pab}}^{\left(c\right)}=\frac{1}{9U^2}\stackrel{\‾}{q}\\ B_{\mathrm{bc}}^{\left(c\right)}=B_{\mathrm{pbc}}^{\left(c\right)}=\frac{1}{9U^2}\stackrel{\‾}{q}\\ B_{\mathrm{ca}}^{\left(c\right)}=B_{\mathrm{pca}}^{\left(c\right)}=\frac{1}{9U^2}\stackrel{\‾}{q}\end{array}\right.---\left(14\right)$

As seen, balance is the special case of uneven situation, and the compensation susceptance calculates simple relatively.

Figure 2 shows that DSP algorithm flow block diagram, adopt the DSP arithmetic element of TMS320F2812 type, with the C language is programming language, at first the three-phase voltage, the three-phase current signal that collect are analyzed to the coordinate system of alpha-beta two-phase quadrature by a, b, c three-phase coordinate axis transform, and then through the d-q coordinate axis transform, become the rotating coordinate system parameter, harmonic component is filtered out, and obtain real-time reactive power by the algorithm of computing module.

Suppose that electrical network three-phase voltage, three-phase current instantaneous value are respectively u _a, u _b, u _cAnd i _a, i _b, i _cTo its conversion of carrying out being tied to α β two-phase orthogonal coordinate system, have from the abc coordinate

$\left[\begin{array}{c}{u}_{\mathrm{\α}}\\ u_{\mathrm{\β}}\end{array}\right]=C_{32}\left[\begin{array}{c}{u}_a\\ u_b\\ u_c\end{array}\right]---\left(15\right)$

$\left[\begin{array}{c}{i}_{\mathrm{\α}}\\ i_{\mathrm{\β}}\end{array}\right]=C_{32}\left[\begin{array}{c}{i}_a\\ i_b\\ i_c\end{array}\right]---\left(16\right)$

Wherein,

$C_{32}=\sqrt{\frac{2}{3}}\left[\begin{array}{ccc}1& -\frac{1}{2}& -\frac{1}{2}\\ 0& \frac{\sqrt{3}}{2}& -\frac{\sqrt{3}}{2}\end{array}\right]$

The three-phase instantaneous active power is then arranged

p＝u _αi _α+u _βi _β (17)

The three-phase instantaneous reactive power

q＝u _βi _α-u _αi _β (18)

Write as the form of matrix

$\left[\begin{array}{c}p\\ q\end{array}\right]=\left[\begin{array}{cc}{u}_{\mathrm{\α}}& u_{\mathrm{\β}}\\ u_{\mathrm{\β}}& -u_{\mathrm{\α}}\end{array}\right]\·\left[\begin{array}{c}{i}_{\mathrm{\α}}\\ i_{\mathrm{\β}}\end{array}\right]---\left(19\right)$

According to idle size, calculate the pilot angle of thyristor, at last so that Controlled Reactor is controlled in real time.For fear of some interference at scene, can in a cycle, gather the multiple spot data and calculate meritorious and reactive power simultaneously, again result of calculation be averaged, to improve computational accuracy.

Claims (2)

1. static passive compensation device based on vector control, it is by thyristor valve group Controlled Reactor unit, FC filter cell and DSP full-digital control system form, it is characterized in that: thyristor valve group Controlled Reactor unit and FC filter cell are parallel on the high voltage bus respectively, thyristor valve group Controlled Reactor unit comprises thyristor valve group and Controlled Reactor, the thyristor valve group is made up of a pair of antiparallel thyristor, the thyristor valve group is connected between the Controlled Reactor, the FC filter cell is made up of filter reactor and power capacitor, filter reactor connects power capacitor, and the DSP full-digital control system connects the thyristor valve group.

2. method that realizes by the described static passive compensation device based on vector control of claim 1, it is characterized in that: be parallel to and detect the system parameters of access point in real time based on the static passive compensation device of vector control on the high voltage bus, acquisition system voltage, the load current signal, become parameter under α/β coordinate system through α/β conversion, become the rotating coordinate system parameter through the d/q conversion again, calculate the instantaneous admittance value of every phase respectively according to the instantaneous reactive theory, send the trigger angle of corresponding phase again according to result of calculation, regulate the perceptual idle of every phase, thereby satisfy the reactive requirement of every phase, realize continuously, the reactive power of phase-splitting and approximately linear is regulated;

The three-phase imbalance electric current of load is:

In the following formula, electric current is represented with positive sequence component instantaneous value and negative sequence component instantaneous value form, after the conversion of two-phase quadrature α β coordinate system, obtains current phasor at process abc three-phase rotating coordinate system, according to the instantaneous reactive theory, obtain active power and reactive power again:

Become the rotating coordinate system parameter through the d/q conversion then, this moment, fundametal compoment was converted into DC component, and harmonic component is a rotational component, and through low-pass filtering, remaining DC component promptly obtains the fundamental positive sequence active power and the reactive power of loading:

After this moment a, b, c middle mutually b, c being changed mutually, voltage will become negative phase-sequence, and selecting the negative phase-sequence synchronous rotating frame is reference frame, simultaneously, it is synchronous that two phase coordinate systems that needs are converted to also make negative phase-sequence into, can obtain first-harmonic negative phase-sequence active power and reactive power:

With fundamental positive sequence, negative phase-sequence active power and reactive power substitution matrix determinant, can obtain the compensation susceptance of three-phase load:

$\left\{\begin{array}{c}{B}_{\mathrm{ab}}^{\left(c\right)}=B_{\mathrm{pab}}^{\left(c\right)}+B_{\mathrm{nab}}^{\left(c\right)}=\frac{1}{3U^2}(\frac{1}{3}\stackrel{\‾}{q}+\frac{1}{\sqrt{3}}\stackrel{\‾}{p^{\′}}+\frac{1}{3}\stackrel{\‾}{q^{\′}})\\ B_{\mathrm{bc}}^{\left(c\right)}=B_{\mathrm{pbc}}^{\left(c\right)}+B_{\mathrm{nbc}}^{\left(c\right)}=\frac{1}{3U^2}(\frac{1}{3}\stackrel{\‾}{q}-\frac{2}{3}\stackrel{\‾}{q^{\′}})\\ B_{\mathrm{ca}}^{\left(c\right)}=B_{\mathrm{pca}}^{\left(c\right)}+B_{\mathrm{nca}}^{\left(c\right)}=\frac{1}{3U^2}(\frac{1}{3}\stackrel{\‾}{q}-\frac{1}{\sqrt{3}}\stackrel{\‾}{p^{\′}}+\frac{1}{3}\stackrel{\‾}{q^{\′}})\end{array}\right.$

Thereby realize the reactive power compensation of three-phase imbalance load.

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