CN102611109B - 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 middle-and-high voltage system, particularly a kind of control method that turns the LC formula hybrid active electric filter of two switch arms.

Background technology

In industrial application, press the application scenario in some, reach the alternating-current actuating system of hundreds of kilowatts as capacity such as blower fan, electromagnetic agitation, do not need dynamic response and regenerative braking fast, 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 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 electric power system, has a strong impact on the safe and reliable operation of electric power system.

For the problems such as harmonic wave that above-mentioned AC Drive load produces, method commonly used is installed LC passive filter (passive power filter, PPF) exactly, carries out the compensation of some specific subharmonic, and compensates certain idle.Along with the development of power electronic technology, active filter (active power filter, APF) is used to the load harmonic wave is dynamically administered.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, there is the scholar to propose the concept of hybrid active filter (hybrid active power filter, HAPF), the advantage of comprehensive passive and active filter, the capacity of active filter reduces greatly.Typical structure has passive and the active filter parallel connection, and active filter is incorporated into the power networks by step-down transformer; Then active filter is connected with electric capacity or LC filter and is incorporated into the power networks by in parallel with by-pass inductor after transformer coupled; There is the scholar to propose further to reduce the active filter capacity at coupling transformer one side first-harmonic resonance branch road in parallel.Foregoing hybrid active filter has step-down transformer, and is bulky, and cost advantage is not obvious.For this reason, the red wooden Thai language of Japanese scholars has proposed a kind of LC formula hybrid active filter (LC-HAPF), the three-phase tri-level inverter is by LC passive filter access electrical network, and active part can be to electrical network harmonic electric current in order to the harmonic component in the compensating load electric current.Because the electric capacity of LC filter can be born most electrical network fundamental voltage, in the situation that do not set up step-down transformer, can greatly reduce equally the capacity of active part, installation cost reduces greatly.

Existing list of references demonstration, 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, due to the closed-loop control of not adopting the inverter output current, 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, for 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 solution adopted in the present invention is: a kind of control method of LC formula hybrid active electric filter of two switch arms, comprise the 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, based on the three-level inverter of three-phase two arms by between LC passive filter access in parallel electrical network and load; Comprise the tri-level switch arm of two parallel connections, a capacitive branch that is formed by at least two capacitances in series based on the three-level inverter of three-phase two arms, capacitive branch is in parallel 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 comprised of the switching tube of four series connection and the fly-wheel diode of two series connection, the fly-wheel diode of two series connection and middle two paralleled power switches, and the concrete steps of this control method are as follows:

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) the output current i based on three-phase two arms _Ca, i _Cb, i _Cc, by three or two coordinate transforms of ip-iq algorithm, can obtain representing respectively the idle component i of threephase load electric current _qWith real component i _d, and the idle component i that represents inverter three-phase output current _Cq, then by after the low pass filter filters out alternating component, can obtain the flip-flop I of component separately _q, I _d, I _CqCan obtain like this correcting value I of idle component _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 controls

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 _dSuperpose, can obtain the reference quantity of System Reactive Power and real component

Then two three-dimensional inverse transformations of ip-iq algorithm can obtain the fundamental current component i of three-phase inverter A, B two-phase _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 respectively i _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 and harmonic 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 processed by 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 is controlled

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 output line voltage of three-phase inverter, i _Ca, i _Cb, i _CcBe the AC 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 balance, and there is no the neutral line, and 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, the mean value that three-phase inverter exchanges terminal voltage can be expressed as follows:

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

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 be expressed 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 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 represents, can get the dead beat dominated formulate:

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

In following formula, T _SBe control cycle.

8) according to top duty ratio computing formula, by 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 PI to control the closed-loop adjustment that can carry out voltage and keeps 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 greatly improved the compensation performance of system.

Description of drawings

Fig. 1 is 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 single-phase fundamental territory of LC-HAPF; (a) Fundamental Wave Equivalent Circuit; (b) harmonic wave equivalent electric circuit;

Fig. 4 is 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.In 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 is by LC passive filter access electrical network, active part can be to electrical network harmonic electric current in order to the harmonic component in the compensating load electric current, and provides the meritorious and reactive current of first-harmonic with compensating reactive power and keep the stable of dc voltage.Because the electric capacity of LC filter can be born most electrical network fundamental voltage, can greatly reduce the capacity of active part, and the LC filter presents high impedance at the switching frequency place, system need not to arrange independent switching harmonics filter.This structure can compensate fixing First Harmonic Reactive Power, can be subject to decay in various degree when then the harmonic current of inverter output is through LC.On the whole, this kind structure is utilized the low-cost advantage of passive filter, bears most electrical network fundamental voltage, greatly reduces the voltage withstand class of inverter, and then reduces capacity and the cost of system.This kind hybrid active filter can be applied to the 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 one based on three-level inverter 3 and three output LC filters 1 of three-phase two arms.Output LC passive filter 1 is comprised of three single tuned filters that inductance L and capacitor C consist of.Three-level inverter 3 based on three-phase two arms is comprised of A, B, C parallel three phase, A phase tri-level switch arm by upper to switch transistor T _a1And T _a2, lower to switch transistor T ' _a1And T ' _a2And two sustained diode _a1And D _a2Consist of; The B phase tri-level switch arm of three-phase inverter by upper to switch transistor T _b1And T _b2, lower to switch transistor T ' _b1And T ' _b2And two sustained diode _b1And D _b2Consist of; 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 by three output LC passive filters 1.

In 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 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 as follows to deserved each brachium pontis output state:

If suppose that the capacitance voltage of dc bus equates, exchanges terminal voltage as follows:

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

As seen by adopting suitable control method to control the switching tube of two switch arms, each switch arm can be exported corresponding 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 by the electric capacity of LC filter, the capacity of active part can be greatly reduced.Generally speaking, this structure combines three-level inverter and LC formula hybrid active filter advantage, can realize harmonic wave, the reactive power compensation of middle-and-high voltage system, and can greatly reduce cost and the capacity of system.

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

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, have,

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

Fundamental current i _CfBe all the capacitive reactive power electric current, the size of the reactive current that can produce according to load is carried out suitably design to passive filter parameters and is compensated certain idle.

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

i _C＝-i _Lh (16)

Referring to Fig. 4, Fig. 4 is 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 to regulate, 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 of two capacitances in series together, if unreasonable or do not work good in control, two dc voltages are unequal, can cause like this deviation of output current, even larger Voltage unbalance will affect compensation effect and the safe and reliable operation of device.In order to keep the balance of two capacitance voltages, guarantee the normal 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 specifically controlled step as follows as shown in Figure 4:

A. the detection of current signal

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

B. the PI of dc voltage controls

In order to keep the loss of stablizing and make up power switch pipe of dc voltage, a PI controller is used to realize the closed-loop adjustment of 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 like this correcting value I of real component _outWith I _Cq, I _outRespectively and I _q, I _dStack can obtain the reference quantity of the idle and real component of inverter

Then by two three-dimensional inverse transformations of ip-iq algorithm, can obtain the fundamental current component i of three-phase inverter A, B two-phase _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 respectively i _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 and harmonic 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).Then after difference being processed by 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 is controlled

When supposing stable state, the three-phase voltage of three-level inverter output is balance, and there is no the neutral line, and 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 voltage _acAnd v _bcCan be expressed as follows:

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

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 be expressed 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 that realizes interior circular current is followed the tracks of, adopt dead-beat control method, the further discrete form of duty ratio computing formula shown in 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 represents.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 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, by 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 (4)

1. the control method of the LC formula hybrid active electric filter of a switch arm, comprise the 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, based on the three-level inverter of three-phase two arms by between LC passive filter access in parallel electrical network and load; Comprise the tri-level switch arm of two parallel connections, a capacitive branch that is formed by at least two capacitances in series based on the three-level inverter of three-phase two arms, capacitive branch is in parallel 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 comprised 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 and middle two paralleled power switches is characterized in that, the method is:

1) sensed current signal: detect the threephase load current i _La, i _Lb, i _LcWith the output current i based on the three-level inverter of three-phase two arms _Ca, i _Cb, i _Cc, by three or two coordinate transforms of ip-iq algorithm, obtain the idle component i of threephase load electric current _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, by the low pass filter filters out alternating component, obtain the flip-flop I of component separately _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 controls: 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 idle component I _CqAnd I _qStack is with the correcting value I of real component _outAnd I _dStack obtains idle and reference quantity real component By two three-dimensional inverse transformations of ip-iq algorithm, obtain based on the three-level inverter A of three-phase two arms, the fundamental current component i of B two-phase _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 based on the three-level inverter of three-phase two arms: with A, B two phase load i _La, i _LbDeduct respectively i _af, i _bf, obtain the 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 and harmonic 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) by after the processing of PI controller, obtain all pressures regulating command △ I of three-phase inverter _out, V _C1, V _C2Be respectively DC side two capacitance voltage values;

6) ask for total current reference signal based on the three-level inverter of three-phase two arms: will be based on all pressures regulating command △ I of 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 based on the three-level inverter of three-phase two arms the mean value of terminal voltage, thereby obtain A, B two-phase duty ratio d _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 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 step 7) _aAnd d _bThe further discretization of expression formula, and with total current reference signal in step 6) 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 represents k constantly, T _SBe control cycle;

9) according to 8) in the duty ratio discrete expression, by 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 described 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 described 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: △ 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 described step 3), two three-dimensional inverse transformation formula of ip-iq algorithm are:

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

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