CN103346585A - Grid-connected inverter control method based on state observer - Google Patents

Abstract

The invention discloses a grid-connected inverter control method based on a state observer. The grid-connected inverter control method comprises the steps that (1) a bridge arm current iL1 and network voltage eg are detected, and a phase angle theta is obtained through phase locking of a phase-locked loop; (2) an observation state quantity is obtained through the state observer based on an internal model; (3) a state quantity feedback signal Xfd is obtained through a state feedback matrix K; (4) grid currents of an observational network are processed, and then grid current error signals ed and eq are obtained; (5) closed-loop processing is carried out on the grid current error signals ed and eq through a PI controller, and then through coordinate inverse transformation, wave generation voltage ui1 is obtained; (6) the wave generation voltage ui1 and the state quantity feedback signal Xfd are subtracted from each other to generate a SVPWM control signal ui of an inverter bridge switching tube, output of a three-phase full bridge inverter is controlled, and therefore a distributed power generation system is controlled to be combined to the grid. Practices show that the control method obtains good dynamic and steady-state performance for a grid-connected current.

Description

A kind of combining inverter control method based on state observer

Technical field

The invention belongs to grid converter control technology field, be specifically related to a kind of combining inverter control method based on state observer.

Background technology

Along with the continuous application of renewable resources such as photovoltaic generation, wind power generation, fuel cell, distributed generation system becomes the emphasis of Recent study, is subjected to extensive concern.Combining inverter is as the core of distributed generation system, and the LCL filter construction is often adopted in its filter design.With respect to the L filter, the LCL filter can more effectively suppress the electric current high order harmonic component, and reduces the total inductance amount.Yet the LCL filter has low resistance high-order characteristic, easily causes system resonance.

For suppressing LCL combining inverter resonance, there is the scholar to propose to utilize inverter brachium pontis electric current to control the method for its networking electric current indirectly, this method has been improved the stability of system, but can not guarantee the current waveform quality that networks.Subsequently, a lot of scholars begin one's study and adopt two closed loop control methods of direct networking Current Control, and outer shroud adopts the networking current closed-loop, and interior ring adopts damping schemes such as capacitor current feedback, capacitance voltage feedback, brachium pontis current closed-loop respectively.Above-mentioned pair of close-loop control scheme suppresses system oscillation by interior ring, improves the stability of a system; Yet there is coupling in the inner and outer ring design in each scheme, influences system control performance; And these schemes need increase extra transducer, have increased the system hardware cost.

There is the scholar to propose to transform controlled device by state feedback, and then the control scheme of simplified control system design of Regulator, guaranteed the control performance of grid-connected current.Yet the realization of state feedback needs a plurality of quantity of states of detection system, has increased extra transducer.For this reason, scholars begin one's study and come the observer state feedback variable by designing traditional state observer, the additional sensors that replaces active damping link and state feedback to increase, but the method does not consider that the variation of state observer eigenmatrix parameter and state observer input deviation to the influence of observation effect, can not guarantee system control performance.

Summary of the invention

The objective of the invention is to overcome traditional state observer does not consider that state observer eigenmatrix parameter changes and the state observer input deviation to the deficiency of the influence of observation effect, a kind of combining inverter control method and state observer thereof based on state observer proposed, this method adopts a kind of state observer based on internal mold to obtain observer state amount accurately, transform controlled device by state feedback, and then carry out combining inverter networking Current Control.

To achieve these goals, the present invention is by the following technical solutions:

A kind of combining inverter control method based on state observer, the topological structure of the combining inverter that this control method relates to comprises DC source U _Dc, DC side filter capacitor C _Dc, three phase full bridge inverter circuit, LCL filter, DC side filter capacitor C _DcBe connected in parallel on DC source U _DcTwo ends, DC source U _DcTwo power output ends link to each other with two inputs of three phase full bridge inverter circuit respectively, the three-phase input end of the three-phase output end of three phase full bridge inverter circuit and LCL filter is corresponding linking to each other one by one, the three-phase output end of LCL filter respectively with three phase network e _a, e _b, e _cLink to each other; Described LCL filter is by the inverter side inductance L ₁, net side filter inductance L ₂With filter capacitor C ₁Form; This control method comprises the steps:

Step 1, utilize the current sensor of brachium pontis electric current to detect the brachium pontis current i _L1Utilize line voltage transducer detection of grid voltage e _gThe horizontal lock of going forward side by side obtains phase angle theta;

Step 2, according to bridge arm voltage u _iWith line voltage e _g, obtain the observer state amount through the state observer based on internal mold: observation brachium pontis electric current

The observation capacitance voltage

And observation current on line side

Step 3, with the described observer state amount in the step 2, obtain quantity of state feedback signal X through state feedback matrix K _Fd, specific as follows:

1. try to achieve state feedback matrix K, K=[k by expectation POLE PLACEMENT USING method ₁, k ₂, k ₃], k ₁, k ₂, k ₃Be the state feedback coefficient;

2. with the described observer state amount in the step 2, namely observe the brachium pontis electric current

The observation capacitance voltage

The observation current on line side Multiply by the state feedback coefficient k respectively ₁, k ₂, k ₃, can obtain described quantity of state feedback signal $X_{\mathrm{fd}}=[{\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="HDA00003478918900012.png,HDA00003478918900013.png"\; state="\{\{state\}\}">k</figure-callout>}}_1\&times;{\hat{i}}_{\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="HDA00003478918900012.png,HDA00003478918900013.png"\; state="\{\{state\}\}">L</figure-callout>}1};{\mathrm{<figure-callout\; id="2"\; label="k"\; filenames="HDA00003478918900021.png,HDA00003478918900022.png"\; state="\{\{state\}\}">k</figure-callout>}}_2\&times;{\hat{u}}_C;{\mathrm{<figure-callout\; id="3"\; label="k"\; filenames="HDA00003478918900024.png"\; state="\{\{state\}\}">k</figure-callout>}}_3\&times;{\hat{i}}_{L2}];$

Step 4, will observe current on line side Obtain current on line side real component i through the abc-dq coordinate transform _{D_fdb}With current on line side idle component i _{Q_fdb}, with current on line side is given function signal i arranged respectively _{D_fref}, given no function signal i _{Q_ref}Differ from, obtain the current on line side error signal e _d, e _q, that is:

e _d＝i _{d_fref}－i _{d_fdb}，

e _q＝i _{q_ref}－i _{q_fdb}；

Step 5, by the current on line side error signal e of PI controller to obtaining in the step 4 _d, e _qCarry out closed-loop process, then through dq-abc coordinate inverse transformation, obtain sending out wave voltage u _I1

Step 6, with described wave voltage u _I1With described quantity of state feedback signal X _FdStack can generate the SVPWM control signal u of three phase full bridge inverter circuit _i

Further, the state observer based on internal mold in the described step 2, realize by following steps:

1. select the brachium pontis current i _L1, capacitance voltage u _C, current on line side i _L2As system state amount, with bridge arm voltage u _iWith line voltage e _gAs input variable, obtain combining inverter system discrete state space equation by following formula:

$\left\{\begin{array}{c}x(k+1)=A_{d}x\left(k\right)+B_{d}u\left(k\right)\\ y\left(k\right)=C_{d1}x\left(k\right)+D_{d}u\left(k\right)\end{array}---\left(1\right)\right.$

In the formula (1), A _dBe combining inverter system features matrix, B _dBe combining inverter system input matrix, C _D1Be combining inverter system output matrix, D _dBe the direct transmission matrix of combining inverter system;

X (k) represents described system state amount: the brachium pontis current i _L1, capacitance voltage u _CAnd current on line side i _L2

X (k+1) claps the system state amount of delaying time through one;

U (k) is combining inverter system input variable;

Y (k) is combining inverter system output variable;

2. according to described combining inverter system discrete state space equation, consider that respectively state observer eigenmatrix parameter changes

And state observer input deviation Δ u (k), by the principle of duality, utilize following formula to obtain state observer state space equation based on internal mold:

$\left\{\begin{array}{c}\hat{x}(k+1)={\hat{A}}_d\hat{x}\left(k\right)+{\hat{B}}_d{u}^{\&prime;}\left(k\right)+G(1+{\mathrm{\&phi;}}_e^{-1}\left(z\right))[y\left(k\right)-\hat{y}\left(k\right)]\\ \hat{y}\left(k\right)={\hat{C}}_{d1}\hat{x}\left(k\right)+{\hat{D}}_{d}u\left(k\right)\end{array}\right.---\left(2\right)$

In the formula (2),

Be the state observer eigenmatrix,

Be the state observer input matrix,

Be the state observer output matrix,

Be the direct transmission matrix of state observer;

Represent described observer state amount: observation brachium pontis electric current The observation capacitance voltage

And observation current on line side

For clapping the observer state amount of delaying time through one;

U ' is the state observer input variable (k), and G is the feedback matrix of state observer;

Be the state observer output variable, y (k) is combining inverter system output variable,

Be the state observer output error;

Be the internal mold item.

3. described state observer eigenmatrix When parameter changes, the observation error Δ x that obtains by described formula (1) and formula (2) ₁Be expressed from the next for:

In the formula (3),

Be state observer eigenmatrix variable quantity,

For considering the state observer eigenmatrix

The internal mold item that arranges when parameter changes is according to described state observer output error

Be set to single order integral element or ratio resonance link;

(a) part in the formula (3) reaches 0 value by expectation POLE PLACEMENT USING method, and formula (3) is by (b) part internal mold

Setting, make (b) part and (c) part the two and reach 0 value, final described observation error Δ x ₁ Reach 0 value.

4. described state observer input variable u ' is (k) when existing deviation, the observation error Δ x that through type (1) and formula (2) obtain ₂Be expressed from the next for:

In the formula (4), Δ u (k) is the variable quantity of state observer input variable u (k),

For the internal mold item of considering that state observer input u ' (k) arranges when having deviation, according to described state observer output error

Be set to single order integral element or ratio resonance link;

(d) part in the formula (4) reaches 0 value by expectation POLE PLACEMENT USING method, and formula (4) is by (e) part internal mold

Setting, make (e) part and (f) part the two and reach 0 value, final described observation error Δ x ₂ Reach 0 value.

The present invention considered that state observer eigenmatrix parameter changes and the state observer input deviation to the influence of observation effect, obtain observer state amount accurately by the state observer based on internal mold, transform controlled device through state feedback, adopt the observation current on line side to carry out the combining inverter current loop control, obtained good dynamic and steady-state behaviour.

Description of drawings

Fig. 1 is the combining inverter control structure figure that the present invention is based on state observer.

Fig. 2 is traditional state observer structure chart.

Fig. 3 is based on the state observer structure chart of internal mold.

Fig. 4 a, 4b are respectively traditional state observers and dynamic observe effect contrast simulation figure based on the state observer of internal mold at rest frame brachium pontis electric current.

Fig. 5 a, 5b are respectively traditional state observers and dynamic observe effect contrast simulation figure based on the state observer of internal mold at rotating coordinate system brachium pontis electric current.

Fig. 6 a, 6b be respectively traditional state observer and based on the state observer of internal mold at rest frame brachium pontis electric current stable state observation effect contrast simulation figure.

Fig. 7 a, 7b be respectively traditional state observer and based on the state observer of internal mold at rest frame brachium pontis electric current dynamic contrast experimental waveform.

Fig. 8 a, 8b be respectively traditional state observer and based on the state observer of internal mold at rest frame brachium pontis electric current stable state contrast experiment waveform.

Fig. 9 a, 9b be respectively traditional state observer and based on the state observer of internal mold at rotating coordinate system brachium pontis active current contrast experiment waveform.

Figure 10 a, 10b be respectively traditional state observer and based on the state observer of internal mold at rest frame capacitance voltage dynamic contrast experimental waveform.

Figure 11 a, 11b be respectively traditional state observer and based on the state observer of internal mold at the current on line side dynamic experiment waveform based on the observer state feedback.

Embodiment

In order more specifically to describe the present invention, below in conjunction with the drawings and the specific embodiments combining inverter control method and the state observer thereof that the present invention is based on state observer is elaborated.

In the present embodiment, as shown in Figure 1, three-phase LCL combining inverter converts the 260V direct current to the 220V alternating current, and through importing electrical network behind the LCL filter filtering.

Described LCL filter parameter: brachium pontis filter inductance L ₁=1mH, brachium pontis filter inductance dead resistance r ₁=0.001 Ω, filter capacitor C ₁=20 μ F, net side filter inductance L ₂=0.5mH, net side filter inductance dead resistance r ₂=0.001 Ω, electric network impedance L _gExcursion 0～1.5mH.

A kind of combining inverter control method based on state observer may further comprise the steps:

1, utilizes the current sensor H of brachium pontis electric current _L1a, H _L1bDetect the brachium pontis current i _L1Utilize line voltage transducer H _Ea, H _EbDetection of grid voltage e _a, e _b, e _cThe horizontal lock of going forward side by side obtains phase angle theta;

2, according to bridge arm voltage u _iWith line voltage e _gObtain following observer state amount through the state observer based on internal mold: observation brachium pontis electric current

The observation capacitance voltage

And observation current on line side

Present embodiment is as follows:

Choose state variable: the brachium pontis current i _L1, capacitance voltage u _C, current on line side i _L2, be designated as x=[i _L1, u _C, i _L2] ^TChoose input variable: inverter brachium pontis output voltage u _iWith electrical network electromotive force e _g, be designated as u=[u _i, e _g] ^T,

Set up LCL combining inverter system state space model:

$\left\{\begin{array}{c}\stackrel{\&CenterDot;}{x}=\mathrm{Ax}+\mathrm{Bu}\\ y=\mathrm{Cx}+\mathrm{Du}\end{array}\right.$

In the following formula, A is combining inverter system features matrix, $A=\left[\begin{array}{ccc}-\frac{{\mathrm{<figure-callout\; id="1"\; label="r"\; filenames="HDA00003478918900012.png,HDA00003478918900013.png"\; state="\{\{state\}\}">r</figure-callout>}}_1+R_p}{L_1}& -\frac{1}{L_1}& \frac{{\mathrm{<figure-callout\; id="1"\; label="R\; p\; L"\; filenames="HDA00003478918900012.png,HDA00003478918900013.png"\; state="\{\{state\}\}">R</figure-callout>}}_p}{L_{}}\\ \frac{1}{C}& 0& -\frac{1}{C}\\ \frac{{\mathrm{<figure-callout\; id="2"\; label="R\; p\; L"\; filenames="HDA00003478918900021.png,HDA00003478918900022.png"\; state="\{\{state\}\}">R</figure-callout>}}_p}{L_{}^{}}& \frac{1}{{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="HDA00003478918900021.png,HDA00003478918900022.png"\; state="\{\{state\}\}">L</figure-callout>}}_2^{\&prime;}}& -\frac{{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="HDA00003478918900021.png,HDA00003478918900022.png"\; state="\{\{state\}\}">r</figure-callout>}}_2+{\mathrm{<figure-callout\; id="2"\; label="R\; P\; L"\; filenames="HDA00003478918900021.png,HDA00003478918900022.png"\; state="\{\{state\}\}">R</figure-callout>}}_P}{L_{}^{}}\end{array}\right];$

Wherein, R _pBe filter capacitor C ₁The damping resistance of last series connection;

L ₂' be net side filter inductance L ₂With electric network impedance equivalent inductance L _gSum;

B is combining inverter system input matrix, $B=\left[\begin{array}{ccc}& .& \\ {\mathrm{<figure-callout\; id="1"\; label="B"\; filenames="HDA00003478918900012.png,HDA00003478918900013.png"\; state="\{\{state\}\}">B</figure-callout>}}_1& .& {\mathrm{<figure-callout\; id="2"\; label="B"\; filenames="HDA00003478918900021.png,HDA00003478918900022.png"\; state="\{\{state\}\}">B</figure-callout>}}_2\\ & .& \end{array}\right]=\left[\begin{array}{cc}1/{\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="HDA00003478918900012.png,HDA00003478918900013.png"\; state="\{\{state\}\}">L</figure-callout>}}_1& 0\\ 0& 0\\ 0& -1/{{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="HDA00003478918900021.png,HDA00003478918900022.png"\; state="\{\{state\}\}">L</figure-callout>}}_2}^{\&prime;}\end{array}\right];$

C is combining inverter system output matrix, when selecting the brachium pontis current i _L1During as output, C ₁=[1,0,0]; When selecting current on line side i _L2During as output, C ₂=[0,0,1];

D is the direct transmission matrix of combining inverter system, D=[0,0].

For the ease of digital control, select sample frequency f _s=10kHz, utilize the discretization method of zero-order holder: C _D1=C ₁, D _d=D with continuous state equation discretization, obtains LCL combining inverter discrete state space equation:

$\left\{\begin{array}{c}x(k+1)=A_{d}x\left(k\right)+B_{d}u\left(k\right)\\ y\left(k\right)=C_{d1}x\left(k\right)+D_{d}u\left(k\right)\end{array}\right.$

In the following formula, C _D1=[1,0,0] namely selects the brachium pontis electric current as output;

X (k) is discretization quantity of state x (k)=[i _L1(k), u _C(k), i _L2(k)] ^T, wherein: i _L1(k) be discrete domain brachium pontis electric current, u _C(k) be the discrete domain capacitance voltage, i _L2(k) be the discrete domain current on line side;

U (k) is the discrete domain input variable, u (k)=[u _i(k), e _g(k)] ^T, wherein: u _i(k) be discrete domain inverter brachium pontis output voltage, e _g(k) be discrete domain electrical network electromotive force.

According to LCL combining inverter discrete state spatial model, on traditional state observer basis of (as shown in Figure 2), consider that state observer eigenmatrix parameter changes and the variation of observer input, obtain the state observer based on internal mold, its state space is expressed as:

$\left\{\begin{array}{c}\hat{x}(k+1)={\hat{A}}_d\hat{x}\left(k\right)+{\hat{B}}_d{u}^{\&prime;}\left(k\right)+G(1+{\mathrm{\&phi;}}_e^{-1}\left(z\right))[y\left(k\right)-\hat{y}\left(k\right)]\\ \hat{y}\left(k\right)={\hat{C}}_{d1}\hat{x}\left(k\right)+{\hat{D}}_{d}u\left(k\right)\end{array}\right.$

Wherein,

Be the state observer eigenmatrix,

Be the state observer input matrix,

Be the state observer output matrix, Be the direct transmission matrix of state observer,

Be state observer eigenmatrix variable quantity;

Represent described observer state amount: observation brachium pontis electric current

The observation capacitance voltage And observation current on line side

U (k) is the state observer input variable, and Δ u (k) is the variable quantity of state observer input variable u (k);

G is the feedback matrix of state observer;

Be the state observer output variable, y (k) is the combining inverter output variable;

Expression internal mold item.

With reference to the accompanying drawings 3, described state observer based on internal mold, on the basis of LCL discrete state space equation, with combining inverter output variable y (k), i.e. combining inverter brachium pontis side filter inductance current i _L1With the state observer output variable

Namely observe the brachium pontis electric current Differ from, obtain output error e (k); Because in different coordinate systems, the expression-form difference of output error for ease of analyzing, is considered the general type of output error, is designated as E;

According to described output error E, obtain its proper polynomial:

φ _e(z)＝det(zI-E)

In the formula, φ _e(z) expression output error E proper polynomial, z is the discrete transform operator;

Described output error E is thought of as the input of internal mold, represents φ by following formula _e(z) unstable limit multinomial:

φ(z)＝z ^m+a _m-1z ^m-1+a _m-2z ^m-2+…+a ₁z+a ₀

In the formula, in the formula, φ (z) is the monic polynomial of z, a _iThe expression multinomial coefficient, described a _i∈ [0, m-1], m are discrete transform factor order;

Internal mold φ ^-1(z) realize by following state equation:

$\left\{\begin{array}{c}{x}_c(k+1)=G_c{x}_c\left(k\right)+b_{c}e\left(k\right)\\ y_c\left(k\right)=x_c\left(k\right)\end{array}\right.$

In the formula, G _cFor internal mold is realized the formulation character matrix, $G_c=\left[\begin{array}{cccccc}0& 1& 0& 0& ...& 0\\ 0& 0& 1& 0& ...& 0\\ .& & & & & .\\ .& & & & & .\\ .& & & & & .\\ 0& ...& & & 0& 1\\ -a_0& -a_1& ...& & & -a_{m-1}\\ & & & & & \end{array}\right],$

b _cFor internal mold is realized input matrix, b _c=[0,0 ... 0,1] ^T

x _c(k) be the internal mold quantity of state, x _c(k+1) be that e (k) is actual output error, is expressed as through the internal mold state of a bat time-delay $e\left(k\right)=y\left(k\right)-\hat{y}\left(k\right);$

In the three-phase rotating coordinate system, error and the quantity of state of output variable are constant, internal mold Usually can be set to the single order integral controller; In rest frame, error and the quantity of state of output variable are sinusoidal quantity, and internal mold can be set to the resonance adjuster.

As Fig. 3, with the output item x of output error e (k) with the process internal mold _c(k) addition, G can obtain observer state amount accurately through the state observation matrix: observation brachium pontis electric current The observation capacitance voltage

The observation current on line side

Among Fig. 3, I _gBe net side active current, Zoh is zero-order holder, 1/ (sL ₁+ r ₁) be brachium pontis inductance transfer function, 1/ (sC ₁) be the filter capacitor transfer function, 1/ (sL ₂'+r ₂) be net side filter inductance transfer function.

3, according to the described observer state amount of step 2, obtain quantity of state feedback signal X through state feedback matrix K _FdIntroduce described state feedback, the limit of system is reconfigured, make the pole distribution of system in the unit circle of z territory, thereby increase the damping of control system.

In the present embodiment, separate to obtain according to the described state observer based on internal mold of separation principle state feedback and step 2.

Discrete state space expression formula based on state feedback is

x(k+1)＝(A _d-B _dK)x(k)+B _du(k)

Comprise damping resistance R according to capacitive branch _pThe system features matrix A _d, A _dIn get filter capacitor series resistance R _p=0.5 Ω obtains the system features multinomial that comprises passive damping; According to the system features matrix A through state feedback _d-B _dK utilizes the respective items coefficient to equate, tries to achieve state feedback matrix K, namely

det(zI-A _d)＝det(zI-(A _d-B _dK))

Wherein, z is the discrete transform operator, and I is 3 * 3 unit matrixs, det () representation feature multinomial, and K is state feedback matrix, is designated as K=[k ₁, k ₂, k ₃], k ₁, k ₂, k ₃Be called the state feedback coefficient;

The state feedback coefficient of trying to achieve: k ₁=2.8108609696657359180517147320431,

k ₂=-0.42233855315199843186755694448278，

k ₃=-2.8075596495029625451005704996724；

With the described observer state amount of step 2: observation brachium pontis electric current

The observation capacitance voltage

The observation current on line side

Multiply by the state feedback coefficient k respectively ₁, k ₂, k ₃, obtain the quantity of state feedback signal $X_{\mathrm{fd}}=[{\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="HDA00003478918900012.png,HDA00003478918900013.png"\; state="\{\{state\}\}">k</figure-callout>}}_1\&times;{\hat{i}}_{\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="HDA00003478918900012.png,HDA00003478918900013.png"\; state="\{\{state\}\}">L</figure-callout>}1};{\mathrm{<figure-callout\; id="2"\; label="k"\; filenames="HDA00003478918900021.png,HDA00003478918900022.png"\; state="\{\{state\}\}">k</figure-callout>}}_2\&times;{\hat{u}}_C;{\mathrm{<figure-callout\; id="3"\; label="k"\; filenames="HDA00003478918900024.png"\; state="\{\{state\}\}">k</figure-callout>}}_3\&times;{\hat{i}}_{L2}].$

4, will observe current on line side

Obtain current on line side real component i through coordinate transform _{D_fdb}With current on line side idle component i _{Q_fdb}, with current on line side is given function signal i arranged respectively _{D_fref}, given no function signal i _{Q_ref}Differ from, obtain the current on line side error signal e _d, e _q

5, pass through the PI controller to the current on line side error signal e _d, e _qCarry out closed-loop process, wherein, the PI controller is got k _p=15, k _i=1800, through the coordinate inverse transformation, obtain sending out wave voltage u _I1

6, with u _I1With state feedback signal X _FdIt is the SVPWM control signal u of three phase full bridge inverter circuit that stack generates the converter bridge switching parts pipe _i, and then control combining inverter networking electric current.

Fig. 4 a～Fig. 6 b be traditional state observer and based on the state observer of internal mold when the net side impedance variation, observation effect dynamically, stable state contrast simulation waveform.Fig. 4 a, 4b rest frame brachium pontis electric current dynamic observe effect contrast simulation figure, and number in the figure ' 1 ' represents brachium pontis electric current actual measurement waveform, and label ' 2 ' represents brachium pontis electric current observation waveform; Fig. 5 a, 5b rotating coordinate system brachium pontis electric current dynamic observe effect contrast simulation figure, and number in the figure ' 1 ' represents brachium pontis active current actual measurement waveform, and label ' 2 ' represents brachium pontis active current observation waveform; Label ' 3 ' represents brachium pontis reactive current actual measurement waveform, and label ' 4 ' represents brachium pontis reactive current observation waveform.

Fig. 7 a～Figure 10 b be traditional state observer and based on the internal mold state observer when the net side impedance variation, observation effect dynamically, stable state contrast experiment's waveform.From analogous diagram and lab diagram as can be seen, based on the state observer of internal mold, still be that steady state effect all is better than traditional state observer from dynamic effect no matter, and the observer state amount is used for state feedback, and then being used for grid-connected current control, the current on line side dynamic waveform is good.

The present invention can apply in the multiple combining inverter control structure, reduces the control system cost, improves the control system reliability simultaneously.This method has versatility, is not limited to hardware configuration and control structure.

Claims (7)

1. combining inverter control method based on state observer, the topological structure of the combining inverter that this control method relates to comprises DC source U _Dc, DC side filter capacitor C _Dc, three phase full bridge inverter circuit, LCL filter, described DC side filter capacitor C _DcBe connected in parallel on DC source U _DcTwo ends, DC source U _DcTwo power output ends link to each other with two inputs of three phase full bridge inverter circuit respectively, the three-phase input end of the three-phase output end of three phase full bridge inverter circuit and LCL filter is corresponding linking to each other one by one, the three-phase output end of LCL filter respectively with three phase network e _a, e _b, e _cLink to each other; Described LCL filter is by the inverter side inductance L ₁, net side filter inductance L ₂With filter capacitor C ₁Form; It is characterized in that comprising the steps:

Step 1, utilize the current sensor of brachium pontis electric current to detect the brachium pontis current i _L1Utilize line voltage transducer detection of grid voltage e _gThe horizontal lock of going forward side by side obtains phase angle theta;

Step 2, according to bridge arm voltage u _iWith line voltage e _g, obtain the observer state amount through the state observer based on internal mold: observation brachium pontis electric current

The observation capacitance voltage

And observation current on line side

Step 3, with the described observer state amount of step 2, obtain quantity of state feedback signal X through state feedback matrix K _Fd

Step 4, will observe current on line side

Obtain current on line side real component i through the abc-dq coordinate transform _{D_fdb}With current on line side idle component i _{Q_fdb}, with current on line side is given function signal i arranged respectively _{D_fref}, given no function signal i _{Q_ref}Differ from, obtain the current on line side error signal e _d, e _q, that is:

e _d＝i _{d_fref}－i _{d_fdb}，

e _q＝i _{q_ref}－i _{q_fdb}；

Step 5, by the current on line side error signal e of PI controller to obtaining in the step 4 _d, e _qCarry out closed-loop process, abc-dq coordinate inverse transformation obtains sending out wave voltage u then _I1

Step 6, with described wave voltage u _I1With described quantity of state feedback signal X _FdStack can generate the SVPWM control signal u of three phase full bridge inverter circuit _i

2. a kind of combining inverter control method based on state observer according to claim 1 is characterized in that obtaining quantity of state feedback signal X through state feedback matrix K described in the step 3 _FdStep as follows:

1. try to achieve state feedback matrix K, K=[k by expectation POLE PLACEMENT USING method ₁, k ₂, k ₃], k ₁, k ₂, k ₃Be the state feedback coefficient;

2. with the observer state amount described in the step 2, namely observe the brachium pontis electric current

The observation capacitance voltage The observation current on line side

Multiply by the state feedback coefficient k respectively ₁, k ₂, k ₃, can obtain the quantity of state feedback signal

3. a kind of combining inverter control method based on state observer according to claim 1 is characterized in that the described state observer based on internal mold of step 2 realizes by following steps:

1. select the brachium pontis current i _L1, capacitance voltage u _C, current on line side i _L2As system state amount, with bridge arm voltage u _iWith line voltage e _gAs input variable, obtain combining inverter system discrete state space equation by following formula:

In the formula (1), A _dBe combining inverter system features matrix, B _dBe combining inverter system input matrix, C _D1Be combining inverter system output matrix, D _dBe the direct transmission matrix of combining inverter system;

X (k) represents described system state amount: the brachium pontis current i _L1, capacitance voltage u _CAnd current on line side i _L2

X (k+1) claps the system state amount of delaying time through one;

U (k) is combining inverter system input variable;

Y (k) is combining inverter system output variable;

2. according to described combining inverter system discrete state space equation, consider that respectively state observer eigenmatrix parameter changes

And state observer input deviation Δ u (k), by the principle of duality, utilize following formula to obtain state observer state space equation based on internal mold:

In the formula (2),

Be the state observer eigenmatrix,

Be the state observer input matrix,

Be the state observer output matrix,

Be the direct transmission matrix of state observer;

Represent described observer state amount: observation brachium pontis electric current

The observation capacitance voltage

And observation current on line side

For clapping the observer state amount of delaying time through one;

U ' is the state observer input variable (k), and G is the feedback matrix of state observer;

Be the state observer output variable, y (k) is combining inverter system output variable,

Be the state observer output error;

Be the internal mold item.

4. a kind of combining inverter control method based on state observer according to claim 3 is characterized in that: described state observer eigenmatrix

When parameter changes, the observation error Δ x that obtains by described formula (1) and formula (2) ₁Be expressed from the next for:

In the formula (3),

Be state observer eigenmatrix variable quantity, For considering the state observer eigenmatrix

The internal mold item that arranges when parameter changes,

(a) part in the formula (3) reaches 0 value by expectation POLE PLACEMENT USING method, and formula (3) is by (b) part internal mold

Setting, make (b) part and (c) part the two and reach 0 value, final described observation error Δ x ₁Reach 0 value.

5. a kind of combining inverter control method and state observer thereof based on state observer according to claim 3, it is characterized in that: described state observer input variable u ' is (k) when existing deviation, the observation error Δ x that through type (1) and formula (2) obtain ₂Be expressed from the next for:

In the formula (4), Δ u (k) is the variable quantity of state observer input variable u (k),

Be the internal mold item of considering that state observer input u ' (k) arranges when having deviation,

(d) part in the formula (4) reaches 0 value by expectation POLE PLACEMENT USING method, and formula (4) is by (e) part internal mold Setting, make (e) part and (f) part the two and reach 0 value, final described observation error Δ x ₂Reach 0 value.

6. a kind of combining inverter control method based on state observer according to claim 4 is characterized in that: the internal mold item in the described formula (3)

According to described state observer output error

Be set to single order integral element or ratio resonance link.

7. a kind of combining inverter control method based on state observer according to claim 5 is characterized in that: the internal mold item in the described formula (4)

According to described state observer output error

Be set to single order integral element or ratio resonance link.

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