CN103199543B - Angle form chain-type static VAR generator (SVG) directive current extraction method considering negative sequence compensation - Google Patents

Abstract

The invention discloses an angle form chain-type static var generator (SVG) directive current extraction method considering negative sequence compensation. The angle form chain-type SVG directive current extraction method considering the negative sequence compensation comprises a chain-type SVG. The chain-type SVG comprises a three-phase chain link. Each chain link comprises a plurality of H bridge cells which are connected in series. The three-phase link is respectively connected with an electric reactor in serious to form a chain link subcircuit, and after being connected, three chain link subcircuits are accessed between a three-phase power grid and a three-phase load. The angle form chain-type SVG directive current extraction method considering the negative sequence compensation can be applied to a negative sequence, reactive and harmonic current comprehensive compensation system based on the angle form chain-type SVG, and is clear in physical significance and simple in algorithm.

Description

A kind of dihedral chain type SVG instruction current extracting method considering negative sequence compensation

Technical field

The present invention relates to cascade STATCOM (Static Var Generator, SVG), particularly a kind of dihedral chain type SVG instruction current extracting method considering negative sequence compensation.

Background technology

There are a large amount of uneven industrial loads and some single-phase Large Copacity load, such as industrial ac arc furnace, electric railway etc. in electric power system.Idle and the negative-sequence current that these uncompensated loads produce causes the loss of system power, and is on the rise, and threatens safety and the economical operation of electric power system.The negative sequence compensation scheme being applicable to mesohigh power distribution network is divided into two classes: energy circulation type current transformer scheme, the current transformer with public direct-current side is adopted to carry out idle and comprehensive compensation that is negative phase-sequence, with railway power regulator (Railway Power Conditioner, RPC) and isolated form static reacance generator be representative, all need isolating transformer, have influence on device volume, weight and cost; Dihedral Scheme of Reactive Power Compensation, according to Steinmetz principle, adopt pure idle branch road to carry out idle and comprehensive compensation that is negative phase-sequence, with based on the dihedral Static Var Compensator (Static Var Compensator, SVC) of thyristor and dihedral chain type SVG for representative.In dihedral Scheme of Reactive Power Compensation, SVC adopts Thyristors in series technology, can directly be hung on mesohigh power distribution network, but it is based on phase control techniques, and response speed is slow, can produce a large amount of harmonic current.Chain type SVG adopts cascading multiple electrical level technology, can directly be hung on mesohigh power distribution network, be a kind of desirable compensation scheme, have the following advantages: fast response time; The comprehensive regulation of idle, negative phase-sequence and harmonic wave can be carried out; Adopt cascaded multilevel structure, devices switch frequency is low, and running wastage is little, is easy to modularization, is convenient to expansion.

In dihedral Scheme of Reactive Power Compensation, the normal symmetrical component method extraction negative sequence compensation susceptance adopted based on Steinmetz principle, the phasor that the method relies on based on Periodic Mean is theoretical, and method applicability is poor.In the last few years, occurred that some applied the compensation method of instantaneous negative-sequence current component and transient current sampling method, but simultaneously also brought new problem, as complicated in algorithm, precision is not high.

Summary of the invention

Technical problem to be solved by this invention is, not enough for prior art, provides a kind of dihedral chain type SVG instruction current extracting method considering negative sequence compensation, extracts idle, negative phase-sequence, harmonic current comprehensive compensation system instruction current rapidly and accurately.

For solving the problems of the technologies described above, the technical solution adopted in the present invention is: a kind of dihedral chain type SVG instruction current extracting method considering negative sequence compensation, comprise chain type SVG, described chain type SVG comprises three-phase chain link, each chain link comprises the H-bridge unit of several series connection, described three-phase chain link is each is composed in series chain link branch road with a reactor, and access between three phase network and threephase load after described three chain link branch road Angle connections, the method is:

1) by threephase load current instantaneous value i _la, i _lb, i _lcthrough abc/dq ^-conversion, low-pass filtering, obtain the negative phase-sequence active current under two-phase rotating coordinate system with negative phase-sequence reactive current component again through dq/ △ transformation matrix, obtain the negative phase-sequence instruction current i needed for dihedral chain type SVG negative sequence compensation _ab1, i _bc1, i _ca1;

2) by step 1) the negative phase-sequence active current that obtains with negative phase-sequence reactive current component through dq ^-/ abc converts, and obtains negative-sequence current instantaneous value i _a ^-, i _b ^-, i _c ^-;

3) by threephase load current instantaneous value i _la, i _lb, i _lcthrough abc/dq ⁺conversion, low-pass filtering, dq ⁺/ abc converts, and obtains active current instantaneous value i _ap, i _bp, i _cp;

4) by threephase load current instantaneous value i _la, i _lb, i _lcdeduct step 2) the negative-sequence current instantaneous value i that obtains _a ^-, i _b ^-, i _c ^-with step 3) the active current i that obtains _ap, i _bp, i _cp, obtain idle and instantaneous value i that is harmonic current _af, i _bf, i _cf; By idle and instantaneous value i that is harmonic current _af, i _bf, i _cfconvert through Y/ △, obtain idle and instruction current i needed for harmonic compensation _ab2, i _bc2, i _ca2.

5) by step 1) the negative phase-sequence instruction current i that obtains _ab1, i _bc1, i _ca1with step 4) the idle and harmonic wave compensating instruction current i that obtains _ab2, i _bc2, i _ca2be added, obtain idle, negative phase-sequence, harmonic current comprehensive compensation instruction current i _ab ^*, i _bc ^*, i _ca ^*.

Preferably, described H-bridge unit is single-phase full-bridge inverter.

Preferably, described abc/dq ^-transformation matrix is expressed as follows:

$C_{\mathrm{abc}/d{q}^{-}}=\frac{2}{3}\left[\begin{array}{ccc}\sin \mathrm{\ωt}& \sin (\mathrm{\ωt}+2\mathrm{\π}/3)& \sin (\mathrm{\ωt}-2\mathrm{\π}/3)\\ \cos \mathrm{\ωt}& \cos (\mathrm{\ωt}+2\mathrm{\π}/3)& \cos (\mathrm{\ωt}-2\mathrm{\π}/3)\end{array}\right].$

Preferably, dq/ △ transformation matrix is expressed as follows:

$C_{\mathrm{dq}/\mathrm{\Δ}}=\left[\begin{array}{ccc}-\sin (\mathrm{\ωt}+2\mathrm{\π}/3)& \frac{\sqrt{3}}{3}\sin (\mathrm{\ωt}+2\mathrm{\π}/3)& \\ 0& \frac{2\sqrt{3}}{3}\sin \mathrm{\ωt}& \\ \sin (\mathrm{\ωt}-2\mathrm{\π}/3)& \frac{\sqrt{3}}{3}\sin (\mathrm{\ωt}-2\mathrm{\π}/3)& \end{array}\right]$

Preferably, dq ^-/ abc converts, and matrix notation is as follows:

$C_{d{q}^{-}/\mathrm{abc}}=\left[\begin{array}{cc}\sin \mathrm{\ωt}& \cos \mathrm{\ωt}\\ \sin (\mathrm{\ωt}+2\mathrm{\π}/3)& \cos (\mathrm{\ωt}+2\mathrm{\π}/3)\\ \sin (\mathrm{\ωt}-2\mathrm{\π}/3)& \cos (\mathrm{\ωt}-2\mathrm{\π}/3)\end{array}\right]$

Preferably, described abc/dq ⁺with dq ⁺/ abc transformation matrix represents as follows respectively:

$C_{\mathrm{abc}/d{q}^{+}}=\frac{2}{3}\left[\begin{array}{ccc}\sin \mathrm{\ωt}& \sin (\mathrm{\ωt}-2\mathrm{\π}/3)& \sin (\mathrm{\ωt}+2\mathrm{\π}/3)\\ \cos \mathrm{\ωt}& \cos (\mathrm{\ωt}-2\mathrm{\π}/3)& \cos (\mathrm{\ωt}+2\mathrm{\π}/3)\end{array}\right]$

$C_{d{q}^{+}/\mathrm{abc}}=\left[\begin{array}{cc}\sin \mathrm{\ωt}& \cos \mathrm{\ωt}\\ \sin (\mathrm{\ωt}-2\mathrm{\π}/3)& \cos (\mathrm{\ωt}-2\mathrm{\π}/3)\\ \sin (\mathrm{\ωt}+2\mathrm{\π}/3)& \cos (\mathrm{\ωt}+2\mathrm{\π}/3)\end{array}\right]$

Wherein ω is electrical network angular frequency.

Preferably, described Y/ △ transformation matrix is expressed as follows:

$C_{Y/\mathrm{\Δ}}=\left[\begin{array}{ccc}1/3& -1/3& 0\\ 0& 1/3& -1/3\\ -1/3& 0& 1/3\end{array}\right]$

Compared with prior art, the beneficial effect that the present invention has is: in calculating process of the present invention, data used are instantaneous value, compared with the symmetrical component method based on Steinmetz principle, physical significance is clear, algorithm is simple, can extract idle, negative phase-sequence, harmonic current comprehensive compensation system instruction current rapidly and accurately.

Accompanying drawing explanation

Fig. 1 is one embodiment of the invention dihedral chain type SVG structural representation;

Fig. 2 is the phasor diagram of one embodiment of the invention compensator line voltage and phase current;

Fig. 3 is the phasor diagram of one embodiment of the invention compensator line current and phase current;

Fig. 4 is one embodiment of the invention negative sequence compensation instruction current principle of operation figure;

Fig. 5 is one embodiment of the invention comprehensive compensation instruction current principle of operation figure;

Fig. 6 is one embodiment of the invention comprehensive compensation design sketch;

(a) load current waveform;

B instruction current waveform that () the present invention extracts;

C () compensates rear network side current waveform.

Embodiment

Fig. 1 is the schematic diagram of dihedral chain type SVG, chain type SVG comprises three-phase chain link, each chain link comprises the H-bridge unit of several series connection, described three-phase chain link is connected with reactor, access between three phase network and threephase load after three-phase chain link and reactor series arm Angle connection, described H-bridge unit is single-phase full-bridge inverter.U in figure _a, u _b, u _cfor line voltage, i _sa, i _sb, i _scfor current on line side, i _la, i _lb, i _lcfor load current, i _a, i _b, i _cfor compensator line current, i _ab, i _bc, i _cafor compensator phase current.

Suppose that line voltage is symmetrical and undistorted, u _a, u _b, u _cbe respectively:

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

Wherein, U _mfor line voltage effective value, ω is electrical network angular frequency.

Threephase load is non-linear asymmetric load, load current i _la, i _lb, i _lcfor:

$\begin{array}{c}\left[\begin{array}{c}{i}_{\mathrm{la}}\\ i_{\mathrm{lb}}\\ i_{\mathrm{lc}}\end{array}\right]=\left[\begin{array}{c}\sqrt{2}{I}_p^{+}\sin \mathrm{\ωt}\\ \sqrt{2}{I}_p^{+}\sin (\mathrm{\ωt}-2\mathrm{\π}/3)\\ \sqrt{2}{I}_p^{+}\sin (\mathrm{\ωt}+2\mathrm{\π}/3)\end{array}\right]+\left.,\begin{array}{c}\sqrt{2}{I}_q^{+}\sin (\mathrm{\ωt}+\mathrm{\π}/2)\\ \sqrt{2}{I}_q^{+}\sin (\mathrm{\ωt}-\mathrm{\π}/6)\\ \sqrt{2}{I}_q^{+}\sin (\mathrm{\ωt}+7\mathrm{\π}/6)\end{array}\right]\\ +\left[\begin{array}{c}\sqrt{2}{I}^{-}\sin (\mathrm{\ωt}+{\mathrm{\θ}}^{-})\\ \sqrt{2}{I}^{-}\sin (\mathrm{\ωt}+2\mathrm{\π}/3+{\mathrm{\θ}}^{-})\\ \sqrt{2}{I}^{-}\sin (\mathrm{\ωt}-2\mathrm{\π}/3+{\mathrm{\θ}}^{-})\end{array}\right]+\left[\begin{array}{c}{i}_{\mathrm{lha}}\\ i_{\mathrm{lhb}}\\ i_{\mathrm{lhc}}\end{array}\right]\end{array}---\left(2\right)$

Wherein, I _p ⁺for the effective value of fundamental positive sequence real component, I _q ⁺for the effective value of fundamental positive sequence idle component, I ^-for the effective value of first-harmonic negative sequence component, θ ^-for the initial phase angle of first-harmonic negative sequence component, i _lha, i _lhb, i _lhcfor harmonic component.

Compensator provides contrary with load current idle, negative phase-sequence and harmonic current.After compensation, current on line side i _sa, i _sb, i _sconly containing fundamental positive sequence real component, power factor is 1.When only considering negative sequence compensation, the order line current i of compensator _a ^*, i _b ^*, i _c ^*be respectively:

$\left[\begin{array}{c}{i}_a^{*}\\ i_b^{*}\\ i_c^{*}\end{array}\right]=-\left[\begin{array}{c}\sqrt{2}{I}^{-}\sin (\mathrm{\ωt}+{\mathrm{\θ}}^{-})\\ \sqrt{2}{I}^{-}\sin (\mathrm{\ωt}+2\mathrm{\π}/3+{\mathrm{\θ}}^{-})\\ \sqrt{2}{I}^{-}\sin (\mathrm{\ωt}-2\mathrm{\π}/3+{\mathrm{\θ}}^{-})\end{array}\right]---\left(3\right)$

Dihedral chain type SVG is often with phase current i _ab, i _bc, i _cafor controlled quentity controlled variable carries out current follow-up control, the transformational relation of phase current and line current is as follows:

$\left[\begin{array}{ccc}1& 0& -1\\ -1& 1& 0\\ 0& -1& 1\end{array}\right]\left[\begin{array}{c}{i_{\mathrm{ab}}}^{*}\\ {i_{\mathrm{bc}}}^{*}\\ {i_c}^{*}\end{array}\right]---\left(4\right)$

Obviously, coefficient matrix is not full rank, and known line current solves phase current, exists and organizes solution more, cannot determine phase current.

Fig. 2 is the phasor diagram of compensator line voltage and phase current.Chain type SVG DC side is separate, and adopt the supporting role of electric capacity starting voltage, cannot provide a large amount of active currents, every phase chain link can be equivalent to pure wattless component.By device physical restrain condition, the phase current fundametal compoment that compensator provides must be vertical with system line voltage phasor, respectively with straight line l _ab, l _bc, l _caparallel, can line voltage in advance, also can delayed line voltage, its size and final direction to be determined.

Fig. 3 is the phasor diagram of compensator line current and phase current.Line current phasor form equilateral triangle Δ opq, get o point for the origin of coordinates, phase voltage direction be x-axis, set up plane right-angle coordinate.When the initial phase angle theta of load current first-harmonic negative sequence component ^-during change, p point and q point circumferentially move, and its movement locus is as follows:

(x _p,y _p)＝(I ^-cosθ ^-，I ^-sinθ ^-)

(5)

(x _q,y _q)＝(I ^-cos(θ ^--π/3)，I ^-sin(θ ^--π/3))

(6)

Straight line l is made at o point _abparallel lines, make straight line l at p point _caparallel lines, make straight line l at q point _bcparallel lines.By the slope of parallel lines and the coordinate of o point, p point and q point, the equation that can obtain three straight lines is:

$\left\{\begin{array}{c}y=-\sqrt{3}x\\ y=\sqrt{3}x+I^{-}\sin {\mathrm{\θ}}^{-}-\sqrt{3}{I}^{-}\cos {\mathrm{\θ}}^{-}\\ y=I^{-}\sin ({\mathrm{\θ}}^{-}-\mathrm{\π}/3)\end{array}\right.---\left(7\right)$

Solve, known three straight line intersection are in a bit, and this point coordinates is:

$(x_r,y_r)=(\frac{I^{-}({\mathrm{\θ}}^{-}-\mathrm{\π}/3)}{\sqrt{3}},I^{-}\sin ({\mathrm{\θ}}^{-}-\mathrm{\π}/3))---\left(8\right)$

Phasor can be determined by the coordinate of this point and o point, p point and q point phasor employing polar form is expressed as follows:

$\left\{\begin{array}{c}{\stackrel{.}{I}}_{\mathrm{ab}}=\frac{2\sqrt{3}{I}^{-}\sin ({\mathrm{\θ}}^{-}-\mathrm{\π}/3)}{3}\∠\frac{2\mathrm{\π}}{3}\\ {\stackrel{.}{I}}_{\mathrm{bc}}=\frac{2\sqrt{3}{I}^{-}\sin ({\mathrm{\θ}}^{-}-\mathrm{\π})}{3}\∠0\\ {\stackrel{.}{I}}_{\mathrm{ca}}=\frac{2\sqrt{3}{I}^{-}\sin ({\mathrm{\θ}}^{-}+\mathrm{\π}/3)}{3}\∠\frac{-2\mathrm{\π}}{3}\end{array}\right.---\left(9\right)$

Gained phasor and line voltage vertical, and meet the phasor relation of phase current and line current, be required compensator instruction phase current.

Fig. 4 is negative sequence compensation instruction current principle of operation figure.

According to instantaneous power theory, threephase load current instantaneous value i _la, i _lb, i _lcthrough abc/dq ^-conversion, can obtain

$\left[\begin{array}{c}{i_p}^{\′}\\ {i_q}^{\′}\end{array}\right]=\frac{2}{3}\left[\begin{array}{ccc}\sin \mathrm{\ωt}& \sin (\mathrm{\ωt}-2\mathrm{\π}/3)& \sin (\mathrm{\ωt}+2\mathrm{\π}/3)\\ \cos \mathrm{\ωt}& \cos (\mathrm{\ωt}-2\mathrm{\π}/3)& \cos (\mathrm{\ωt}+2\mathrm{\π}/3)\end{array}\right]\left[\begin{array}{c}{i}_{\mathrm{la}}\\ i_{\mathrm{lb}}\\ i_{\mathrm{lc}}\end{array}\right]---\left(15\right)$

After low-pass filtering, first-harmonic negative phase-sequence real component can be obtained with first-harmonic negative phase-sequence idle component with negative-sequence current effective value I ^-with initial phase angle θ ^-relation as follows:

$\left\{\begin{array}{c}{I}^{-}=\sqrt{{\stackrel{\‾}{i}}_p^{\′p}+{\stackrel{\‾}{i}}_q^2)/2}\\ {\mathrm{\θ}}^{-}=\arctan \frac{{\stackrel{\‾}{i}}_q^{\′}}{{\stackrel{\‾}{i}}_p^{\′}}\end{array}\right.---\left(11\right)$

Formula (11) is substituted into formula (9), compensator instruction phase current i can be obtained _ab ^*, i _bc ^*, i _ca ^*with relation as follows:

$\left[\begin{array}{c}{i_{\mathrm{ab}}}^{*}\\ {i_{\mathrm{bc}}}^{*}\\ {i_{\mathrm{ca}}}^{*}\end{array}\right]=C_{\mathrm{dq}/\mathrm{\Δ}}\left[\begin{array}{c}{\stackrel{\‾}{i}}_p^{\′}\\ {\stackrel{\‾}{i}}_q^{\′}\end{array}\right]---\left(12\right)$

Wherein,

$C_{\mathrm{dq}/\mathrm{\Δ}}=\left[\begin{array}{cc}-\sin (\mathrm{\ωt}+2\mathrm{\π}/3)& \frac{\sqrt{3}}{3}\sin (\mathrm{\ωt}+2\mathrm{\π}/3)\\ 0& \frac{2\sqrt{3}}{3}\sin \mathrm{\ωt}\\ \sin (\mathrm{\ωt}-2\mathrm{\π}/3)& \frac{\sqrt{3}}{3}\sin (\mathrm{\ωt}-2\mathrm{\π}/3)\end{array}\right]---\left(13\right)$

Through type (10), (12), can instruction phase current needed for load current instantaneous value determination negative sequence compensation.Threephase load current instantaneous value i _la, i _lb, i _lcthrough abc/dq ^-conversion, low-pass filtering, obtain the negative phase-sequence active current under two-phase rotating coordinate system with negative phase-sequence reactive current component again through the dq/ △ transformation matrix of above-mentioned derivation, the instruction phase current i needed for dihedral chain type SVG negative sequence compensation can be obtained _ab1, i _bc1, i _ca1.

Fig. 5 is comprehensive compensation instruction current principle of operation figure.

The instruction current i of idle, negative phase-sequence, harmonic current comprehensive compensation system _ab ^*, i _bc ^*, i _ca ^*by negative sequence compensation electric current (i _ab1, i _bc1, i _ca1) and idle, harmonic compensation current (i _ab2, i _bc2, i _ca2) two parts composition, wherein, negative sequence compensation electric current is detected by method described in Fig. 4 and obtains.

By first-harmonic negative phase-sequence real component with first-harmonic negative phase-sequence idle component through dq ^-/ abc converts, and obtains negative-sequence current instantaneous value

$\left[\begin{array}{c}{i_a}^{-}\\ {i_b}^{-}\\ {i_c}^{-}\end{array}\right]=\left[\begin{array}{cc}\sin \mathrm{\ωt}& \cos \mathrm{\ωt}\\ \sin (\mathrm{\ωt}+2\mathrm{\π}/3)& \cos (\mathrm{\ωt}+2\mathrm{\π}/3)\\ \sin (\mathrm{\ωt}-2\mathrm{\π}/3)& \cos (\mathrm{\ωt}-2\mathrm{\π}/3)\end{array}\right]\left[\begin{array}{c}{\stackrel{\‾}{i}}_p^{\′}\\ {\stackrel{\‾}{i}}_q^{\′}\end{array}\right]---\left(14\right)$

According to instantaneous reactive power theory, threephase load current instantaneous value is through abc/dq ⁺conversion, can obtain i _p, i _q:

$\left[\begin{array}{c}{i}_p\\ i_q\end{array}\right]=\frac{2}{3}\left[\begin{array}{ccc}\sin \mathrm{\ωt}& \sin (\mathrm{\ωt}-2\mathrm{\π}/3)& \sin (\mathrm{\ωt}+2\mathrm{\π}/3)\\ \cos \mathrm{\ωt}& \cos (\mathrm{\ωt}-2\mathrm{\π}/3)& \cos (\mathrm{\ωt}+2\mathrm{\π}/3)\end{array}\right]\left[\begin{array}{c}{i}_{\mathrm{la}}\\ i_{\mathrm{lb}}\\ i_{\mathrm{lc}}\end{array}\right]$

Through low-pass filtering, obtain fundamental positive sequence real component again through dq ⁺/ abc converts, and obtains active current instantaneous value i _ap, i _bp, i _cp:

$\left[\begin{array}{c}{i}_{\mathrm{qp}}\\ i_{\mathrm{bp}}\\ i_{\mathrm{cp}}\end{array}\right]=\left[\begin{array}{cc}\sin \mathrm{\ωt}& \cos \mathrm{\ωt}\\ \sin (\mathrm{\ωt}-2\mathrm{\π}/3)& \cos (\mathrm{\ωt}-2\mathrm{\π}/3)\\ \sin (\mathrm{\ωt}+2\mathrm{\π}/3)& \cos (\mathrm{\ωt}+2\mathrm{\π}/3)\end{array}\right]\left[\begin{array}{c}\stackrel{\‾}{i_p}\\ 0\end{array}\right]---\left(16\right)$

Load current i _la, i _lb, i _lcdeduct fundamental active current i _aq, i _bq, i _cqwith negative-sequence current i _a ^-, obtain idle, harmonic current sum i _af, i _bf, i _cf.For idle, harmonic current, carry out line current and phase current when changing, introduce constraints:

i _ab+i _bc+i _ca＝0

(17)

Solve, Y/ △ transformation matrix C can be obtained _{y/ △}:

$C_{Y/\mathrm{\Δ}}=\left[\begin{array}{ccc}1/3& -1/3& 0\\ 0& 1/3& -1/3\\ -1/3& 0& 1/3\end{array}\right]---\left(18\right)$

Idle, harmonic current sum i _af, i _bf, i _cfthrough Matrix C _{y/ △}conversion, can obtain idle, needed for harmonic current compensation phase current i _ab2, i _bc2, i _ca2, with the phase current i needed for negative sequence compensation _ab1, i _bc1, i _ca1superposition, finally obtains the phase current command signal i needed for comprehensive compensation _ab ^*, i _bc ^*, i _ca ^*.

Phase information ω t above required for all transformation matrixs is by electrical network A phase phase voltage u _aobtain through phase-locked loop pll.

Fig. 6 is comprehensive compensation design sketch.From top to bottom, be load current successively, the instruction current that the present invention extracts, current on line side after compensating.As can be seen from the figure, there is phase difference in load current and voltage, asymmetrical three-phase, and containing harmonic components, power quality problem is given prominence to; Current on line side after compensation and line voltage same-phase, three-phase symmetrical, harmonic content reduces, close to unity power factor.Current waveform before and after contrast compensates, demonstrate the present invention put forward the validity of instruction current extracting method.

Claims (6)

1. consider the dihedral chain type SVG instruction current extracting method of negative sequence compensation for one kind, comprise chain type SVG, described chain type SVG comprises three-phase chain link, each chain link comprises the H-bridge unit of several series connection, described three-phase chain link is each is composed in series chain link branch road with a reactor, access between three phase network and threephase load after three chain link branch road Angle connections, it is characterized in that, the method is:

1) by threephase load current instantaneous value i _la, i _lb, i _lcthrough abc/dq ^-conversion, low-pass filtering, obtain the negative phase-sequence active current under two-phase rotating coordinate system with negative phase-sequence reactive current component again through dq/ △ transformation matrix, obtain the negative phase-sequence instruction current i needed for dihedral chain type SVG negative sequence compensation _ab1, i _bc1, i _ca1; Dq/ △ transformation matrix expression formula is:

$C_{\mathrm{dq}/\mathrm{\Δ}=}\left[\begin{array}{cc}-\sin (\mathrm{\ωt}+2\mathrm{\π}/3)& \frac{\sqrt{3}}{3}\sin (\mathrm{\ωt}+2\mathrm{\π}/3)\\ 0& \frac{2\sqrt{3}}{3}\sin \mathrm{\ωt}\\ \sin (\mathrm{\ωt}-2\mathrm{\π}/3)& \frac{\sqrt{3}}{3}\sin (\mathrm{\ωt}-2\mathrm{\π}/3)\end{array}\right];$

Wherein ω is electrical network angular frequency;

2) by step 1) the negative phase-sequence active current that obtains with negative phase-sequence reactive current component through dq ^-/ abc converts, and obtains negative-sequence current instantaneous value i _a ^-, i _b ^-, i _c ^-;

3) by threephase load current instantaneous value i _la, i _lb, i _lcthrough abc/dq ⁺conversion, low-pass filtering, dq ⁺/ abc converts, and obtains active current instantaneous value i _ap, i _bp, i _cp;

4) by threephase load current instantaneous value i _la, i _lb, i _lcdeduct step 2) the negative-sequence current instantaneous value i that obtains _a ^-, i _b ^-, i _c ^-with step 3) the active current i that obtains _ap, i _bp, i _cp, obtain idle and instantaneous value i that is harmonic current _af, i _bf, i _cf; By idle and instantaneous value i that is harmonic current _af, i _bf, i _cfconvert through Y/ △, obtain idle and instruction current i needed for harmonic compensation _ab2, i _bc2, i _ca2; 5) by step 1) the negative phase-sequence instruction current i that obtains _ab1, i _bc1, i _ca1with step 4) the idle and harmonic wave compensating instruction current i that obtains _ab2, i _bc2, i _ca2be added, obtain idle, negative phase-sequence, harmonic current comprehensive compensation instruction current i _ab ^*, i _bc ^*, i _ca ^*.

2. the dihedral chain type SVG instruction current extracting method of consideration negative sequence compensation according to claim 1, is characterized in that, described step 1) in, abc/dq ^-the matrix expression of conversion is as follows:

$C_{{\mathrm{abc}/\mathrm{dq}}^{-}}=\frac{2}{3}\left[\begin{array}{ccc}\sin \mathrm{\ωt}& \sin (\mathrm{\ωt}+2\mathrm{\π}/3)& \sin (\mathrm{\ωt}-2\mathrm{\π}/3)\\ \cos \mathrm{\ωt}& \cos (\mathrm{\ωt}+2\mathrm{\π}/3)& \cos (\mathrm{\ωt}-2\mathrm{\π}/3)\end{array}\right],$

Wherein ω is electrical network angular frequency.

3. the dihedral chain type SVG instruction current extracting method of consideration negative sequence compensation according to claim 1, is characterized in that, described step 2) in, dq ^-the matrix expression of/abc conversion is:

$C_{{\mathrm{dq}}^{-}/\mathrm{dbc}}=\left[\begin{array}{cc}\sin \mathrm{\ωt}& \cos \mathrm{\ωt}\\ \sin (\mathrm{\ωt}+2\mathrm{\π}/3)& \cos (\mathrm{\ωt}+2\mathrm{\π}/3)\\ \sin (\mathrm{\ωt}-2\mathrm{\π}/3)& \cos (\mathrm{\ωt}-2\mathrm{\π}/3)\end{array}\right]$

Wherein ω is electrical network angular frequency.

4. the dihedral chain type SVG instruction current extracting method of consideration negative sequence compensation according to claim 1, is characterized in that, described step 3) in, abc/dq ⁺with dq ⁺the matrix expression of/abc conversion is respectively:

$C_{{\mathrm{abc}/\mathrm{dq}}^{+}}=\frac{2}{3}\left[\begin{array}{ccc}\sin \mathrm{\ωt}& \sin (\mathrm{\ωt}-2\mathrm{\π}/3)& \sin (\mathrm{\ωt}+2\mathrm{\π}/3)\\ \cos \mathrm{\ωt}& \cos (\mathrm{\ωt}-2\mathrm{\π}/3)& \cos (\mathrm{\ωt}+2\mathrm{\π}/3)\end{array}\right],$

$C_{{\mathrm{dq}}^{+}/\mathrm{dbc}}=\left[\begin{array}{cc}\sin \mathrm{\ωt}& \cos \mathrm{\ωt}\\ \sin (\mathrm{\ωt}-2\mathrm{\π}/3)& \cos (\mathrm{\ωt}-2\mathrm{\π}/3)\\ \sin (\mathrm{\ωt}+2\mathrm{\π}/3)& \cos (\mathrm{\ωt}+2\mathrm{\π}/3)\end{array}\right]$

Wherein ω is electrical network angular frequency.

5. the dihedral chain type SVG instruction current extracting method of consideration negative sequence compensation according to claim 1, is characterized in that, described step 4) in, the matrix expression that Y/ △ converts is as follows:

$C_{Y/\mathrm{\Δ}}=\left[\begin{array}{ccc}1/3& -1/3& 0\\ 0& 1/3& -1/3\\ -1/3& 0& 1/3\end{array}\right].$

6. the dihedral chain type SVG instruction current extracting method of consideration negative sequence compensation according to claim 1, it is characterized in that, described H-bridge unit is single-phase full-bridge inverter.