CN102611109A - Method for controlling LC (inductance and capacitance) hybrid active power filter with two switch arms - Google Patents

Abstract

The invention discloses a method for controlling an LC (inductance and capacitance) hybrid active power filter with two switch arms. By the aid of the method, voltage of a direct-current side is stabilized by means of PI (proportion integration), a deadbeat control method based on an inverter mathematical switch module is adopted for an inner current loop control, quick deadbeat tracking of harmonic current can be carried out, and dynamic balance of capacitance voltage is maintained by a voltage-sharing control method in order to keep the balance of the balance of the capacitance voltage on the direct-current side. Compared with a common indirect control method, the method for controlling the LC hybrid active power filter with the two switch arms has the advantages of high control precision and fine dynamic performance, and a compensation performance of a system is greatly improved.

Description

A kind of control method of LC formula hybrid active electric filter of two switch arms

Technical field

The present invention relates to be applicable to the hybrid active electric filter of mesohigh system, particularly a kind of control method of LC formula hybrid active electric filter of commentaries on classics two switch arms.

Background technology

In industrial application; In some, press the application scenario; Reach hundreds of kilowatts alternating-current actuating system like capacity such as blower fan, electromagnetic agitation; Do not need Fast Dynamic response and regenerative braking, general direct use three-phase is not controlled rectification and is done front stage circuits, and it is having more advantage than PWM rectifier on efficient He on the practicality.Yet three-phase not control rectifier can inject a large amount of harmonic waves to electrical network, brings serious harm for the operation of generating, transmission of electricity and converting equipment in the electric power system, has a strong impact on the safe and reliable operation of electric power system.

To the problems such as harmonic wave that above-mentioned interchange transmission load produces, method commonly used is installed the LC passive filter exactly, and (passive power filter PPF), carries out the compensation of some specific subharmonic, and compensates certain idle.Along with the development of power electronic technology, (active power filter APF) is used to the load harmonic wave is dynamically administered active filter.But in the mesohigh occasion, APF adopts multiple technology, current transformer multilevel converter, and device is complicated, and cost is high, and reliability is not high.For this reason, have the scholar propose hybrid active filter (hybrid active power filter, notion HAPF), the advantage of comprehensive passive and active filter, the capacity of active filter reduces greatly.Typical structure has passive parallelly connected with active filter, and active filter is incorporated into the power networks through step-down transformer; Active filter is connected with electric capacity or LC filter then and is incorporated into the power networks through parallelly connected with by-pass inductor after transformer coupled; There is the scholar to propose parallelly connected first-harmonic resonance branch road, further reduces the active filter capacity on coupling transformer one side.Foregoing hybrid active filter all has step-down transformer, and is bulky, and cost advantage is not obvious.For this reason; The safe literary composition of Japan's red wood of scholar has proposed a kind of LC formula hybrid active filter (LC-HAPF); The three-phase tri-level inverter inserts electrical network through the LC passive filter, and active part can inject the harmonic component of harmonic current in order to the compensating load electric current to electrical network.Because the electric capacity of LC filter can be born most electrical network fundamental voltage, under the situation of not setting up step-down transformer, can reduce the capacity of active part equally greatly, installation cost reduces greatly.

Existing list of references shows that LC-HAPF generally adopts a kind of method for indirectly controlling, is about to inverter output voltage and is controlled to u _c=K*i _ShPerhaps u _c=K*i _Lh, owing to do not adopt the closed-loop control of inverter output current, and its harmonic current compensation ability, performance of dynamic tracking is not good.

Summary of the invention

Technical problem to be solved by this invention is; To the prior art deficiency, a kind of control method of LC formula hybrid active electric filter of two switch arms is provided, strengthen the harmonic current compensation ability; Improve performance of dynamic tracking, improve the compensation performance of control precision and system.

For solving the problems of the technologies described above; The technical scheme that the present invention adopted is: a kind of control method of LC formula hybrid active electric filter of two switch arms; Comprise LC formula mixed active electric power filter based on three-phase two arm inverters; Based on the LC formula mixed active electric power filter of three-phase two arm inverters comprise the LC passive filter, based on the three-level inverter of three-phase two arms, insert between electrical network and the load through the parallel connection of LC passive filter based on the three-level inverter of three-phase two arms; Comprise the tri-level switch arm of two parallel connections, a capacitive branch of forming by at least two capacitances in series based on the three-level inverter of three-phase two arms; Capacitive branch is parallelly connected with the tri-level switch arm; Capacitive branch is the DC side based on the LC formula mixed active electric power filter of three-phase two arm inverters; Two tri-level switch arms are respectively A, B phase, and capacitive branch is the C phase; The tri-level switch arm is made up of the switching tube of four series connection and the fly-wheel diode of two series connection, and the fly-wheel diode of two series connection is parallelly connected with middle two switching tubes, and the concrete steps of this control method are following:

1) detection of current signal

The threephase load current i of detection system _La, i _Lb, i _LcWith three-level inverter (hereinafter to be referred as three-phase inverter) output current i based on three-phase two arms _Ca, i _Cb, i _Cc,, can be represented the idle component i of threephase load electric current respectively through three or two coordinate transforms of ip-iq algorithm _qWith real component i _d, and the idle component i that represents inverter three-phase output current _Cq, through after the low pass filter filters out alternating component, can obtain the flip-flop I of component separately then _q, I _d, I _CqCan obtain the correcting value I of idle component like this _Cq, be the idle component that the LC passive filter produces.Wherein three or two coordinate transform formula of ip-iq algorithm are:

$T_{\mathrm{abc}/\mathrm{dq}}=\sqrt{\frac{2}{3}}\left[\begin{array}{ccc}\sin \mathrm{wt}& \sin (\mathrm{wt}-2\mathrm{\π}/3)& \sin (\mathrm{wt}+2\mathrm{\π}/3)\\ -\cos \mathrm{wt}& -\cos (\mathrm{wt}-2\mathrm{\π}/3)& -\cos (\mathrm{wt}+2\mathrm{\π}/3)\end{array}\right]---\left(1\right)$

2) PI of dc voltage control

The dc voltage outer shroud adopts a PI controller, is used to realize the closed loop accent of dc voltage outer shroud.Wherein the formula of PI controller is:

$I_{\mathrm{out}}=K_P{\mathrm{\Δu}}_{\mathrm{dc}}+\frac{K_P}{T_i}\∫{\mathrm{\Δu}}_{\mathrm{dc}}\mathrm{dt}---\left(2\right)$

Δ u wherein _Dc=U _Ref-u _Dc, U _RefThe dc voltage reference value, u _DcBe dc voltage, u _Dc=V _C1+ V _C2, V _C1, V _C2Be DC side two capacitance voltage values, K _PBe proportionality coefficient, T _iBe integral coefficient, I _OutFor regulating the meritorious correcting value of dc voltage

3) correcting value stack and inverse transformation thereof

With idle and meritorious correcting value I _Cq, I _OutRespectively and I _q, I _dStack, the system that can obtain is idle and the reference quantity of real component

Two three-dimensional inverse transformations of ip-iq algorithm then can obtain the fundamental current component i of three-phase inverter A, B two phases _Af, i _Bf, wherein comprised the meritorious amount of adjusting dc voltage and the idle amount that passive filter produces.Wherein two three-dimensional inverse transformation formula of ip-iq algorithm are:

$T_{\mathrm{dq}/\mathrm{abc}}=\sqrt{\frac{2}{3}}\left[\begin{array}{cc}\sin \mathrm{wt}& -\cos \mathrm{wt}\\ \sin (\mathrm{wt}-2\mathrm{\π}/3)& -\cos (\mathrm{wt}-2\mathrm{\π}/3)\\ \sin (\mathrm{wt}+2\mathrm{\π}/3)& -\cos (\mathrm{wt}+2\mathrm{\π}/3)\end{array}\right]---\left(3\right)$

4) ask for the current reference signal of inverter

With A, B two phase load i _La, i _LbDeduct i respectively _Af, i _Bf, just can obtain the current reference signal i of three-phase inverter two tri-level switch arms _Ar, i _Br, comprised first-harmonic harmonic electric current composition.

5) Pressure and Control of dc voltage

In order to guarantee the stable and balance of DC side two capacitance voltages, adopt a kind of pressure equalizing control method: detect the voltage of DC side two electric capacity, and make difference and can get (V _C1-V _C2), after then difference being handled through the PI controller, can obtain all pressures regulating command Δ I of three-phase inverter _Out

6) ask for the total current reference signal of inverter

All pressures regulating command Δ I with three-phase inverter _OutRespectively with i _Ar, i _BrAddition just can obtain the total current reference signal of two tri-level switch arms of three-phase inverter

$\left\{\begin{array}{c}{i}_a^{*}=i_{\mathrm{ar}}+{\mathrm{\ΔI}}_{\mathrm{out}}\\ i_b^{*}=i_{\mathrm{br}}+{\mathrm{\ΔI}}_{\mathrm{out}}\end{array}\right.---\left(4\right)$

7) dead beat of current inner loop control

Main circuit structure figure according to shown in Figure 2 has following voltage-current relationship:

$\left\{\begin{array}{c}{v}_{\mathrm{Sa}}-v_{\mathrm{Sc}}=L\frac{{\mathrm{di}}_{\mathrm{Ca}}}{\mathrm{dt}}+u_{\mathrm{Ca}}+v_{\mathrm{ac}}-L\frac{{\mathrm{di}}_{\mathrm{Cc}}}{\mathrm{dt}}-u_{\mathrm{Cc}}\\ v_{\mathrm{Sb}}-v_{\mathrm{Sc}}=L\frac{{\mathrm{di}}_{\mathrm{Cb}}}{\mathrm{dt}}+u_{\mathrm{Cb}}+v_{\mathrm{bc}}-L\frac{{\mathrm{di}}_{\mathrm{Cc}}}{\mathrm{dt}}-u_{\mathrm{Cc}}\end{array}\right.---\left(5\right)$

V wherein _Sa, v _Sb, v _ScBe respectively alternating voltage, C is the capacitance of LC passive filter, v _Ac, v _BcBe the AC side output line voltage of three-phase inverter, i _Ca, i _Cb, i _CcBe the AC side output current of three-phase inverter, u _Ca, u _Cb, u _CcBe three phase capacitance magnitude of voltage in the LC passive filter.When supposing stable state, the three-phase voltage of three-level inverter output is a balance, and does not have the neutral line, and then instantaneous three-phase voltage and line current sum are zero, can obtain:

$\left\{\begin{array}{c}{i}_{\mathrm{Cc}}=-(i_{\mathrm{Ca}}+i_{\mathrm{Cb}})\\ u_{\mathrm{Cc}}=-(u_{\mathrm{Ca}}+u_{\mathrm{Cb}})\end{array}\right.---\left(6\right)$

Associating (5) formula and (6) formula, under stable state, according to average on-off principle, three-phase inverter exchanges the mean value of terminal voltage and can express as follows:

$\left[\begin{array}{c}{v}_{\mathrm{ac}}\\ v_{\mathrm{bc}}\end{array}\right]=\left[\begin{array}{c}{d}_a\frac{u_{\mathrm{dc}}}{2}\\ d_b\frac{u_{\mathrm{<figure-callout\; id="2"\; label="dc"\; filenames="HDA0000143349450000011.png,HDA0000143349450000012.png"\; state="\{\{state\}\}">dc</figure-callout>}}}{2}\end{array}\right]=\left[\begin{array}{c}{v}_{\mathrm{Sac}}-L\frac{d}{\mathrm{dt}}({2i}_{\mathrm{Ca}}+i_{\mathrm{Cb}})-({2u}_{\mathrm{Ca}}+u_{\mathrm{Cb}})\\ V_{\mathrm{Sbc}}-L\frac{d}{\mathrm{dt}}(i_{\mathrm{Ca}}+{2i}_{\mathrm{Cb}})-(u_{\mathrm{Ca}}+{2u}_{\mathrm{Cb}})\end{array}\right]---\left(7\right)$

Wherein, d _aAnd d _bBe duty ratio, and d _aAnd d _b∈ [1,1]; v _SacAnd v _SbcExpress for electrical network side line voltage and below satisfying:

$\left\{\begin{array}{c}{v}_{\mathrm{Sac}}=v_{\mathrm{Sa}}-v_{\mathrm{Sc}}=\sqrt{3}U\sin (\mathrm{wt}-\frac{\mathrm{\&pi;}}{6})\\ v_{\mathrm{Sbc}}=v_{\mathrm{Sb}}-v_{\mathrm{Sc}}=\sqrt{3}U\sin (\mathrm{wt}-\frac{\mathrm{\&pi;}}{2})\end{array}\right.---\left(8\right)$

According to formula (7) and formula (8), duty ratio d _aAnd d _bCan express as follows:

$\left\{\begin{array}{c}{d}_a=\frac{2}{u_{\mathrm{dc}}}{v}_{\mathrm{Sac}}-\frac{4L}{u_{\mathrm{dc}}}\frac{{\mathrm{di}}_{\mathrm{Ca}}}{\mathrm{dt}}-\frac{2L}{u_{\mathrm{dc}}}\frac{{\mathrm{di}}_{\mathrm{Cb}}}{\mathrm{dt}}-\frac{2}{u_{\mathrm{dc}}}({2u}_{\mathrm{Ca}}+u_{\mathrm{Cb}})\\ d_b=\frac{2}{u_{\mathrm{dc}}}{v}_{\mathrm{Sbc}}-\frac{2L}{u_{\mathrm{dc}}}\frac{{\mathrm{di}}_{\mathrm{Ca}}}{\mathrm{dt}}-\frac{4L}{u_{\mathrm{dc}}}\frac{{\mathrm{di}}_{\mathrm{Cb}}}{\mathrm{dt}}-\frac{2}{u_{\mathrm{dc}}}(u_{\mathrm{Ca}}+2u_{\mathrm{Cb}})\end{array}\right.---\left(9\right)$

The further discrete form of duty ratio computing formula shown in the formula (9) is represented, and next current value substitution formula constantly of inductance is flow through in the k total current reference signal conduct constantly that (4) formula is represented, can get dead beat control formula:

$\left\{\begin{array}{c}{d}_a\left(k\right)=\frac{2}{u_{\mathrm{dc}}}{v}_{\mathrm{Sac}}\left(k\right)-\frac{4L}{u_{\mathrm{dc}}}\frac{[i_a^{*}\left(k\right)-i_{\mathrm{Ca}}\left(k\right)]}{T_S}-\frac{2L}{u_{\mathrm{dc}}}\frac{[i_b^{*}\left(k\right)-i_{\mathrm{Cb}}\left(k\right)]}{T_S}-\frac{4}{u_{\mathrm{dc}}}{u}_{\mathrm{Ca}}\left(k\right)-\frac{2}{u_{\mathrm{dc}}}{u}_{\mathrm{Cb}}\left(k\right)\\ d_b\left(k\right)=\frac{2}{u_{\mathrm{dc}}}{v}_{\mathrm{Sbc}}\left(k\right)-\frac{2L}{u_{\mathrm{dc}}}\frac{[i_a^{*}\left(k\right)-i_{\mathrm{Ca}}\left(k\right)]}{T_S}-\frac{4L}{u_{\mathrm{dc}}}\frac{[i_b^{*}\left(k\right)-i_{\mathrm{Cb}}\left(k\right)]}{T_S}-\frac{2}{u_{\mathrm{dc}}}{u}_{\mathrm{Ca}}\left(k\right)-\frac{4}{u_{\mathrm{dc}}}{u}_{\mathrm{Cb}}\left(k\right)\end{array}\right.---\left(10\right)$

In the following formula, T _SBe control cycle.

8) according to top duty ratio computing formula, through adopting suitable PWM modulator approach, the electric current and voltage amount that two tri-level switch pipes of driving three-phase inverter can obtain to expect.

Technique effect of the present invention is: the present invention adopts a kind of double loop control of electric current and voltage; Dc voltage adopts the closed-loop adjustment of PI control can carrying out voltage to keep the stable of dc voltage; Current inner loop adopts the dead-beat control method based on the inverter switching device Mathematical Modeling, can realize the closed-loop control to the inverter output current; With respect to general method for indirectly controlling, control method control precision of the present invention is high, and dynamic property is good, has improved the compensation performance of system greatly.

Description of drawings

Fig. 1 is a LC formula mixed active electric power filter structure chart;

Fig. 2 is the LC formula mixed active electric power filter structure chart based on three-phase two arm inverters;

Fig. 3 is the harmonious wave zone equivalent circuit diagram in the single-phase fundamental territory of LC-HAPF; (a) first-harmonic equivalent electric circuit; (b) harmonic wave equivalent electric circuit;

Fig. 4 is a control block diagram of the present invention;

Wherein:

The 1:LC passive filter; 2: the three-phase tri-level inverter; 3: based on the three-level inverter of three-phase two arms.

Embodiment

Referring to Fig. 1, Fig. 1 is general LC formula mixed active electric power filter structure chart.Among the figure, output filter adopts single tuning LC passive filter 1, and general resonance frequency is five times or seven times, with this subharmonic current of filtering.In this structure; Three-phase tri-level inverter 2 inserts electrical network through the LC passive filter; Active part can inject the harmonic component of harmonic current in order to the compensating load electric current to electrical network, and provides first-harmonic meritorious and reactive current stablizing with compensating reactive power and maintenance dc voltage.Because the electric capacity of LC filter can be born most electrical network fundamental voltage, can reduce the capacity of active part greatly, and the LC filter presents high impedance at the switching frequency place, and system need not to be provided with independent switch ripple filter.This structure can compensate fixing fundamental wave reactive power power, can receive decay in various degree when the harmonic current of inverter output is through LC then.On the whole, this kind structure is utilized the low-cost advantage of passive filter, bears most electrical network fundamental voltage, reduces the voltage withstand class of inverter greatly, and then reduces the capacity and the cost of system.This kind hybrid active filter can be applied to mesohigh occasions such as 2kV, 3kV and 6kV.

Referring to Fig. 2, Fig. 2 is the LC formula mixed active electric power filter structure chart based on three-phase two arm inverters.

The structure that the present invention adopts is the collocation structure based on the three-level inverter of three-phase two arms, comprises three-level inverter 3 and three the output LC filters 1 based on three-phase two arms.Output LC passive filter 1 is made up of three single tuned filters that inductance L and capacitor C constitute.Three-level inverter 3 based on three-phase two arms is made up of A, B, C parallel three phase, A phase tri-level switch arm by last to switch transistor T _A1And T _A2, down to switch transistor T ' _A1And T ' _A2And two sustained diode _A1And D _A2Constitute; The B phase tri-level switch arm of three-phase inverter by last to switch transistor T _B1And T _B2, down to switch transistor T ' _B1And T ' _B2And two sustained diode _B1And D _B2Constitute; The C phase arm of three-phase inverter is by capacitor C ₁And C ₂Form.Three-level inverter 3 based on three-phase two arms is connected to the mesohigh electrical network through three output LC passive filters 1.

Among the figure, v _Sa, v _Sb, v _ScBe respectively AC supply voltage, the interchange end output current of inverter is i _Ca, i _Cb, i _Cc, C is a capacitance in the LC passive filter, u _Ca, u _Cb, u _CcBe three phase capacitance magnitude of voltage in the LC passive filter.The c of three-phase alternating current system is directly connected to the mid point of two dc capacitors mutually.In each brachium pontis, three effective on off states can produce three kinds of voltages in the alternating voltage side.Three kinds of switching functions are following to deserved each brachium pontis output state:

Equate that it is following then to exchange terminal voltage if suppose the capacitance voltage of dc bus:

$\left\{\begin{array}{c}{v}_{\mathrm{ac}}=v_{\mathrm{ao}}-v_{\mathrm{co}}=g_a*\frac{u_{\mathrm{dc}}}{2}\\ v_{\mathrm{bc}}=v_{\mathrm{bo}}-v_{\mathrm{co}}=g_b*\frac{u_{\mathrm{dc}}}{2}\\ v_{\mathrm{ab}}=v_{\mathrm{ao}}-v_{\mathrm{bo}}=(g_a-g_b)*\frac{u_{\mathrm{dc}}}{2}\end{array}\right.---\left(12\right)$

It is thus clear that through adopting the appropriate control method to control the switching tube of two switch arms, each switch arm can be exported correspondent voltage.According to main circuit shown in Figure 2, following voltage-current relationship is arranged:

$\left\{\begin{array}{c}{v}_{\mathrm{Sa}}-v_{\mathrm{Sc}}=L\frac{{\mathrm{di}}_{\mathrm{Ca}}}{\mathrm{dt}}+u_{\mathrm{Ca}}+v_{\mathrm{ac}}-L\frac{{\mathrm{di}}_{\mathrm{Cc}}}{\mathrm{dt}}-u_{\mathrm{Cc}}\\ v_{\mathrm{Sb}}-v_{\mathrm{Sc}}=L\frac{{\mathrm{di}}_{\mathrm{Cb}}}{\mathrm{dt}}+u_{\mathrm{Cb}}+v_{\mathrm{bc}}-L\frac{{\mathrm{di}}_{\mathrm{Cc}}}{\mathrm{dt}}-u_{\mathrm{Cc}}\end{array}\right.---\left(13\right)$

The structure that the present invention adopts only needs the electric capacity of two tri-level switch arms and one group of series connection to form an inverter; Compare with common three-level inverter, saved an arm device for power switching, but had identical compensation ability; Can reduce number of devices, reduce switching loss.Most electrical network fundamental voltage can be born through the electric capacity of LC filter, the capacity of active part can be reduced greatly.Generally speaking, this structure has combined three-level inverter and LC formula hybrid active filter advantage, can realize harmonic wave, the reactive power compensation of mesohigh system, and can significantly reduce the cost and the capacity of system.

Referring to Fig. 3, shown in Figure 3 is the single-phase fundamental harmonic equivalent electric circuit of LC-HAPF.The nonlinear load equivalence is become a linear impedance Z _LHarmonic current source i _Lh, an and active inverter compensation harmonic can equivalence become a controlled harmonic current source through closed loop control method, the impedance at the first-harmonic place is zero.At first consider first-harmonic equivalent electric circuit such as Fig. 3 (a), line voltage directly is added in electric network impedance Z _Sf, the passive filter impedance Z _FfIn load,, can get the electrical network fundamental current and be then by Kirchhoff's law:

i _Sf＝U _Sf/[Z _Sf+Z _Ff*Z _L/(Z _Ff+Z _L)] (14)

Wherein, Z is arranged _Ff=jwL+1/jwC, U _SfBe the electrical network fundamental voltage.Because electric network impedance is generally very little, when ignoring, then have,

i _Cf＝U _Sf/Z _Ff＝U _Sf/(jwL+1/jwC) (15)

Fundamental current i _CfAll be the capacitive reactive power electric current, can be according to the size of the reactive current of load generating, to passive filter parameters suitably design compensate certain idle.

To the single-phase harmonic wave equivalent electric circuit of system, can know that from Fig. 3 (b) as long as through adopting the suitable current closed loop control method to come control inverter, make it output current full remuneration load harmonic current, just can make the mains by harmonics current value is 0.Then have:

i _C＝-i _Lh (16)

Referring to Fig. 4, Fig. 4 is a control block diagram of the present invention.

In order to realize the compensation of system load harmonic current, and keep system safety and move reliably, the present invention proposes a kind of double loop control of electric current and voltage.At first outer voltage adopts PI to control to carry out voltage stabilizing and regulates, and current inner loop adopts the quick adjustment that realizes two tri-level switch arms based on the dead-beat control method of inverter switching device model, and the indifference of interior circular current, follows the tracks of fast.Because DC side is to be made up of two capacitances in series together; If unreasonable or do not work good in the control, then two dc voltages are unequal, can cause variation in output current like this; Even bigger Voltage unbalance, will influence the compensation effect and the safe and reliable operation of device.In order to keep the balance of two capacitance voltages, guarantee the normal and stable operation of bucking-out system, adopted a kind of pressure equalizing control method of dc voltage, realize the dynamic equilibrium of dc capacitor voltage.The control block diagram of system is as shown in Figure 4, and concrete controlled step is following:

A. the detection of current signal

The detection algorithm of The whole control system adopts general ip-iq algorithm.At first the threephase load electric current of detection system and three-phase inverter output current through three or two coordinate transforms of ip-iq algorithm, can be represented the idle component i of threephase load electric current respectively _qWith real component i _d, and the idle component i that represents three-phase inverter three-phase output current _Cq, (lower pass filter after LPF) the filtering alternating component, can obtain the flip-flop I of component separately through low pass filter then _q, I _d, I _CqCan obtain the correcting value I of idle component like this _Cq, be the idle component that the LC passive filter produces.

B. the PI of dc voltage control

In order to keep the loss of stablizing and remedy power switch pipe of dc voltage, a PI controller is used the closed-loop adjustment that realizes the dc voltage outer shroud:

$I_{\mathrm{out}}=K_P{\mathrm{\&Delta;u}}_{\mathrm{dc}}+\frac{K_P}{T_i}\&Integral;{\mathrm{\&Delta;u}}_{\mathrm{dc}}\mathrm{dt}---\left(2\right)$

Δ u wherein _Dc=U _Ref-u _Dc, U _RefThe dc voltage reference value, K _PBe proportionality coefficient, T _iBe integral coefficient.Can obtain the correcting value I of real component like this _OutWith I _Cq, I _OutRespectively and I _q, I _dStack can obtain the idle reference quantity with real component of inverter

Through two three-dimensional inverse transformations of ip-iq algorithm, can obtain the fundamental current component i of three-phase inverter A, B two phases then _Af, i _Bf, wherein comprised the meritorious amount of adjusting dc voltage and the idle amount that passive filter produces.

With A, B two phase load i _La, i _LbDeduct i respectively _Af, i _Bf, just can obtain the current reference signal i of three-phase inverter two tri-level switch arms _Ar, i _Br, comprised first-harmonic harmonic electric current composition.

C. the Pressure and Control of dc voltage

In order to guarantee the stable and balance of DC side two capacitance voltages, adopt a kind of pressure equalizing control method.At first detect the voltage of DC side two electric capacity, and make difference and can get difference (V _C1-V _C2).After then difference being handled through pi regulator, can obtain all pressures regulating command Δ I of three-phase inverter _Out, afterwards respectively with i _Ar, i _BrAddition just can obtain the total current reference signal of two tri-level switch arms of three-phase inverter

$\left\{\begin{array}{c}{i}_a^{*}=i_{\mathrm{ar}}+{\mathrm{\&Delta;I}}_{\mathrm{out}}\\ i_b^{*}=i_{\mathrm{br}}+{\mathrm{\&Delta;I}}_{\mathrm{out}}\end{array}\right.---\left(4\right)$

D. the dead beat of current inner loop control

When supposing stable state, the three-phase voltage of three-level inverter output is a balance, and does not have the neutral line, and then instantaneous three-phase voltage and line current sum are zero, can obtain:

$\left\{\begin{array}{c}{i}_{\mathrm{Cc}}=-(i_{\mathrm{Ca}}+i_{\mathrm{Cb}})\\ u_{\mathrm{Cc}}=-(u_{\mathrm{Ca}}+u_{\mathrm{Cb}})\end{array}\right.---\left(6\right)$

Associating (3) formula and (9) formula, under stable state, according to average on-off principle, the mean value v of AC side voltage _AcAnd v _BcCan express as follows:

$\left[\begin{array}{c}{v}_{\mathrm{ac}}\\ v_{\mathrm{bc}}\end{array}\right]=\left[\begin{array}{c}{d}_a\frac{u_{\mathrm{dc}}}{2}\\ d_{\mathrm{<figure-callout\; id="2"\; label="b\; u\; dc"\; filenames="HDA0000143349450000011.png,HDA0000143349450000012.png"\; state="\{\{state\}\}">b</figure-callout>}}\frac{u_{\mathrm{dc}}}{}\frac{{}_{}}{2}\end{array}\right]=\left[\begin{array}{c}{v}_{\mathrm{Sac}}-L\frac{d}{\mathrm{dt}}({2i}_{\mathrm{Ca}}+i_{\mathrm{Cb}})-({2u}_{\mathrm{Ca}}+u_{\mathrm{Cb}})\\ V_{\mathrm{Sbc}}-L\frac{d}{\mathrm{dt}}(i_{\mathrm{Ca}}+{2i}_{\mathrm{Cb}})-(u_{\mathrm{Ca}}+{2u}_{\mathrm{Cb}})\end{array}\right]---\left(7\right)$

Wherein, d _aAnd d _bBe duty ratio, and d _aAnd d _b∈ [1,1]; v _SacAnd v _SbcExpress for electrical network side line voltage and below satisfying:

$\left\{\begin{array}{c}{v}_{\mathrm{Sac}}=v_{\mathrm{Sa}}-v_{\mathrm{Sc}}=\sqrt{3}U\sin (\mathrm{wt}-\frac{\mathrm{\&pi;}}{6})\\ v_{\mathrm{Sbc}}=v_{\mathrm{Sb}}-v_{\mathrm{Sc}}=\sqrt{3}U\sin (\mathrm{wt}-\frac{\mathrm{\&pi;}}{2})\end{array}\right.---\left(8\right)$

According to formula (10) and formula (11), duty ratio d _aAnd d _bCan express as follows:

$\left\{\begin{array}{c}{d}_a=\frac{2}{u_{\mathrm{dc}}}{v}_{\mathrm{Sac}}-\frac{4L}{u_{\mathrm{dc}}}\frac{{\mathrm{di}}_{\mathrm{Ca}}}{\mathrm{dt}}-\frac{2L}{u_{\mathrm{dc}}}\frac{{\mathrm{di}}_{\mathrm{Cb}}}{\mathrm{dt}}-\frac{2}{u_{\mathrm{dc}}}({2u}_{\mathrm{Ca}}+u_{\mathrm{Cb}})\\ d_b=\frac{2}{u_{\mathrm{dc}}}{v}_{\mathrm{Sbc}}-\frac{2L}{u_{\mathrm{dc}}}\frac{{\mathrm{di}}_{\mathrm{Ca}}}{\mathrm{dt}}-\frac{4L}{u_{\mathrm{dc}}}\frac{{\mathrm{di}}_{\mathrm{Cb}}}{\mathrm{dt}}-\frac{2}{u_{\mathrm{dc}}}(u_{\mathrm{Ca}}+2u_{\mathrm{Cb}})\end{array}\right.---\left(9\right)$

For the quick indifference of circular current in realizing is followed the tracks of; Adopt dead-beat control method; The further discrete form of duty ratio computing formula shown in the formula (12) is represented, and next current value substitution formula constantly of inductance is flow through in the k total current reference signal conduct constantly that (8) formula is represented.Can get:

$\left\{\begin{array}{c}{d}_a\left(k\right)=\frac{2}{u_{\mathrm{dc}}}{v}_{\mathrm{Sac}}\left(k\right)-\frac{4L}{u_{\mathrm{dc}}}\frac{[i_a^{*}\left(k\right)-i_{\mathrm{Ca}}\left(k\right)]}{T_S}-\frac{2L}{u_{\mathrm{dc}}}\frac{[i_b^{*}\left(k\right)-i_{\mathrm{Cb}}\left(k\right)]}{T_S}-\frac{4}{u_{\mathrm{dc}}}{u}_{\mathrm{Ca}}\left(k\right)-\frac{2}{u_{\mathrm{dc}}}{u}_{\mathrm{Cb}}\left(k\right)\\ d_b\left(k\right)=\frac{2}{u_{\mathrm{dc}}}{v}_{\mathrm{Sbc}}\left(k\right)-\frac{2L}{u_{\mathrm{dc}}}\frac{[i_a^{*}\left(k\right)-i_{\mathrm{Ca}}\left(k\right)]}{T_S}-\frac{4L}{u_{\mathrm{dc}}}\frac{[i_b^{*}\left(k\right)-i_{\mathrm{Cb}}\left(k\right)]}{T_S}-\frac{2}{u_{\mathrm{dc}}}{u}_{\mathrm{Ca}}\left(k\right)-\frac{4}{u_{\mathrm{dc}}}{u}_{\mathrm{Cb}}\left(k\right)\end{array}\right.---\left(10\right)$

In the following formula, T _SBe control cycle.The situation that on-Line Voltage is fixed, the capacitance voltage of detection inverter output current and passive filter can obtain duty ratio d by formula (13) _aAnd d _bAccording to top duty ratio computing formula, through adopting suitable PWM modulator approach, the electric current and voltage amount that two tri-level switch pipes of driving three-phase inverter can obtain to expect.

Claims (5)

1. the control method of the LC formula hybrid active electric filter of a switch arm; Comprise LC formula mixed active electric power filter based on three-phase two arm inverters; Based on the LC formula mixed active electric power filter of three-phase two arm inverters comprise the LC passive filter, based on the three-level inverter of three-phase two arms, insert between electrical network and the load through the parallel connection of LC passive filter based on the three-level inverter of three-phase two arms; Comprise the tri-level switch arm of two parallel connections, a capacitive branch of forming by at least two capacitances in series based on the three-level inverter of three-phase two arms; Capacitive branch is parallelly connected with the tri-level switch arm; Capacitive branch is the DC side based on the LC formula mixed active electric power filter of three-phase two arm inverters; Two tri-level switch arms are respectively A, B phase, and capacitive branch is the C phase; The tri-level switch arm is made up of the switching tube of four series connection and the fly-wheel diode of two series connection, and the fly-wheel diode of two series connection is parallelly connected with middle two switching tubes, it is characterized in that this method is:

1) sensed current signal: detect the threephase load current i _La, i _Lb, i _LcWith output current i based on the three-level inverter of three-phase two arms _Ca, i _Cb, i _Cc,, obtain the idle component i of threephase load electric current through three or two coordinate transforms of ip-iq algorithm _qWith real component i _d, and based on the idle component i of the three-phase output current of the three-level inverter of three-phase two arms _Cq,, obtain the flip-flop I of component separately through the low pass filter filters out alternating component _q, I _d, I _CqThereby, obtain the correcting value I of idle component _Cq, be the idle component that the LC passive filter produces;

2) PI of dc voltage control: adopt the PI controller, realize the closed-loop adjustment of dc voltage outer shroud, obtain the meritorious correcting value I of dc voltage _Out

3) correcting value stack and inverse transformation thereof: with the correcting value I of idle component and real component _Cq, I _OutRespectively and I _q, I _dStack obtains idle and reference quantity real component

Through two three-dimensional inverse transformations of ip-iq algorithm, obtain the three-level inverter A based on three-phase two arms, the fundamental current component i of B two phases _Af, i _Bf, wherein comprised the meritorious amount of adjusting dc voltage and the idle amount that the LC passive filter produces;

4) ask for current reference signal: with A, B two phase load i based on the three-level inverter of three-phase two arms _La, i _LbDeduct i respectively _Af, i _Bf, obtain current reference signal i based on the three-level inverter two tri-level switch arms of three-phase two arms _Ar, i _Br, comprised first-harmonic harmonic electric current composition;

5) Pressure and Control of dc voltage: adopt and all press the PI controller, with the voltage difference (V of DC side two electric capacity _C1-V _C2) through after the processing of PI controller, obtain all pressures regulating command Δ I of three-phase inverter _Out, V _C1, V _C2Be respectively DC side two capacitance voltage values;

6) ask for total current reference signal: will be based on all pressures regulating command Δ I of the three-level inverter of three-phase two arms based on the three-level inverter of three-phase two arms _OutRespectively with i _Ar, i _BrAddition obtains the total current reference signal based on the three-level inverter two tri-level switch arms of three-phase two arms

7) according to average on-off principle, obtain exchanging the mean value of terminal voltage, thereby obtain A, B two phase duty ratio d based on the three-level inverter of three-phase two arms _aAnd d _bExpression formula:

$\left\{\begin{array}{c}{d}_a=\frac{2}{u_{\mathrm{dc}}}{v}_{\mathrm{Sac}}-\frac{4L}{u_{\mathrm{dc}}}\frac{{\mathrm{di}}_{\mathrm{Ca}}}{\mathrm{dt}}-\frac{2L}{u_{\mathrm{dc}}}\frac{{\mathrm{di}}_{\mathrm{Cb}}}{\mathrm{dt}}-\frac{2}{u_{\mathrm{dc}}}({2u}_{\mathrm{Ca}}+u_{\mathrm{Cb}})\\ d_b=\frac{2}{u_{\mathrm{dc}}}{v}_{\mathrm{Sbc}}-\frac{2L}{u_{\mathrm{dc}}}\frac{{\mathrm{di}}_{\mathrm{Ca}}}{\mathrm{dt}}-\frac{4L}{u_{\mathrm{dc}}}\frac{{\mathrm{di}}_{\mathrm{Cb}}}{\mathrm{dt}}-\frac{2}{u_{\mathrm{dc}}}(u_{\mathrm{Ca}}+2u_{\mathrm{Cb}})\end{array}\right.$

Wherein: v _SacAnd v _SbcBe electrical network side line voltage, d _a, d _b∈ [1,1], i _Ca, i _CbBe the three-level inverter AC side output current based on three-phase two arms, u _Ca, u _CbBe three phase capacitance magnitude of voltage in the LC passive filter, L is the inductance value of LC passive filter, u _DcBe dc voltage, u _Dc=V _C1+ V _C2

8) with duty ratio d in the step 7) _aAnd d _bThe further discretization of expression formula, and with total current reference signal in the step 6)

With

As flowing through next current value substitution formula constantly of inductance, obtain duty ratio d _aAnd d _bDiscrete expression:

$\left\{\begin{array}{c}{d}_a\left(k\right)=\frac{2}{u_{\mathrm{dc}}}{v}_{\mathrm{Sac}}\left(k\right)-\frac{4L}{u_{\mathrm{dc}}}\frac{[i_a^{*}\left(k\right)-i_{\mathrm{Ca}}\left(k\right)]}{T_S}-\frac{2L}{u_{\mathrm{dc}}}\frac{[i_b^{*}\left(k\right)-i_{\mathrm{Cb}}\left(k\right)]}{T_S}-\frac{4}{u_{\mathrm{dc}}}{u}_{\mathrm{Ca}}\left(k\right)-\frac{2}{u_{\mathrm{dc}}}{u}_{\mathrm{Cb}}\left(k\right)\\ d_b\left(k\right)=\frac{2}{u_{\mathrm{dc}}}{v}_{\mathrm{Sbc}}\left(k\right)-\frac{2L}{u_{\mathrm{dc}}}\frac{[i_a^{*}\left(k\right)-i_{\mathrm{Ca}}\left(k\right)]}{T_S}-\frac{4L}{u_{\mathrm{dc}}}\frac{[i_b^{*}\left(k\right)-i_{\mathrm{Cb}}\left(k\right)]}{T_S}-\frac{2}{u_{\mathrm{dc}}}{u}_{\mathrm{Ca}}\left(k\right)-\frac{4}{u_{\mathrm{dc}}}{u}_{\mathrm{Cb}}\left(k\right)\end{array}\right.,$

Wherein: k representes k constantly, T _SBe control cycle;

9) according to 8) in the duty ratio discrete expression, through adopting the PWM modulator approach, drive the electric current and voltage amounts that obtain expectation based on two tri-level switch pipes of the three-level inverter of three-phase two arms.

2. the control method of the LC formula hybrid active electric filter of two switch arms according to claim 1 is characterized in that, in the said step 1), wherein three or two coordinate transform formula of ip-iq algorithm are:

$T_{\mathrm{abc}/\mathrm{dq}}=\sqrt{\frac{2}{3}}\left[\begin{array}{ccc}\sin \mathrm{wt}& \sin (\mathrm{wt}-2\mathrm{\&pi;}/3)& \sin (\mathrm{wt}+2\mathrm{\&pi;}/3)\\ -\cos \mathrm{wt}& -\cos (\mathrm{wt}-2\mathrm{\&pi;}/3)& -\cos (\mathrm{wt}+2\mathrm{\&pi;}/3)\end{array}\right].$

3. the control method of the LC formula hybrid active electric filter of two switch arms according to claim 1 is characterized in that said step 2) in, the formula of PI controller is:

$I_{\mathrm{out}}=K_P{\mathrm{\&Delta;u}}_{\mathrm{dc}}+\frac{K_P}{T_i}\&Integral;{\mathrm{\&Delta;u}}_{\mathrm{dc}}\mathrm{dt},$

Wherein: Δ u _Dc=U _Ref-u _Dc, U _RefThe dc voltage reference value, K _PBe proportionality coefficient, T _iBe integral coefficient, I _OutFor regulating the meritorious correcting value of dc voltage.

4. the control method of the LC formula hybrid active electric filter of two switch arms according to claim 1 is characterized in that, in the said step 3), two three-dimensional inverse transformation formula of ip-iq algorithm are:

$T_{\mathrm{dq}/\mathrm{abc}}=\sqrt{\frac{2}{3}}\left[\begin{array}{cc}\sin \mathrm{wt}& -\cos \mathrm{wt}\\ \sin (\mathrm{wt}-2\mathrm{\&pi;}/3)& -\cos (\mathrm{wt}-2\mathrm{\&pi;}/3)\\ \sin (\mathrm{wt}+2\mathrm{\&pi;}/3)& -\cos (\mathrm{wt}+2\mathrm{\&pi;}/3)\end{array}\right].$

5. the control method of the LC formula hybrid active electric filter of two switch arms according to claim 1; It is characterized in that; In the said step 6), be based on the computing formula of the total current reference signal of the three-level inverter two tri-level switch arms of three-phase two arms:

$\left\{\begin{array}{c}{i}_a^{*}=i_{\mathrm{ar}}+{\mathrm{\&Delta;I}}_{\mathrm{out}}\\ i_b^{*}=i_{\mathrm{br}}+{\mathrm{\&Delta;I}}_{\mathrm{out}}\end{array}\right..$

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