CN103346585B - 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 control method of grid-connected inverter based on state observer

Technical field

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

Background technology

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

For suppressing LCL combining inverter resonance, there is scholar to propose to utilize the method for its networking electric current of inverter leg Current Indirect Control, the method improving the stability of system, but grid current waveform quality can not be ensured.Subsequently, a lot of scholar begins one's study and adopts the double-closed-loop control method of direct networking Current Control, and outer shroud adopts networking current closed-loop, and inner ring adopts the Damping Schemes such as capacitor current feedback, capacitance voltage feedback, bridge arm current closed loop respectively.Above-mentioned double-closed-loop control scheme, suppresses system oscillation by inner ring, improves the stability of a system; But in each scheme there is coupling, influential system control performance in inner and outer ring design; And these schemes need to increase extra transducer, add system hardware cost.

Scholar is had to propose to transform controlled device by state feedback, and then the control program of simplified control system design of Regulator, ensure that the control performance of grid-connected current.But the realization of state feedback, needs the multiple quantity of state of detection system, adds extra transducer.For this reason, scholars begin one's study and carry out observer state feedback variable by design Legacy Status observer, replace the additional sensors that active damping link and state feedback increase, but the method does not consider that state observer eigenmatrix Parameters variation and state observer input deviation are on the impact of observation effect, can not ensure system control performance.

Summary of the invention

The object of the invention is to overcome Legacy Status observer and do not consider that state observer eigenmatrix Parameters variation and state observer input deviation are on the deficiency of the impact of observation effect, a kind of control method of grid-connected inverter based on state observer and state observer thereof are proposed, the 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:

Based on a control method of grid-connected inverter for 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 inverting 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 be connected with two inputs of three-phase full-bridge inverting circuit respectively, the three-phase output end of three-phase full-bridge inverting circuit is connected with the three-phase input end one_to_one corresponding of LCL filter, the three-phase output end of LCL filter respectively with three phase network e _a, e _b, e _cbe connected; Described LCL filter is by inverter side inductance L ₁, net side filter inductance L ₂with filter capacitor C ₁composition; This control method comprises the steps:

Step one, the current sensor of bridge arm current is utilized to detect brachium pontis current i _l1; Utilize grid voltage sensor detection of grid voltage e _ghorizontal 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 observer state amount through the state observer based on internal mold: observation bridge arm current observation capacitance voltage and observation current on line side

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

1. state feedback matrix K is tried to achieve by expected pole assignment method, K=[k ₁, k ₂, k ₃], k ₁, k ₂, k ₃be state feedback coefficient;

2. by the described observer state amount in step 2, namely bridge arm current is observed observation capacitance voltage observation current on line side be multiplied by state feedback coefficient k respectively ₁, k ₂, k ₃, described quantity of state feedback signal can be obtained $X_{\mathrm{fd}}=[k_1\×{\hat{i}}_{L1};k_2\×{\hat{u}}_C;k_3\×{\hat{i}}_{L2}];$

Step 4, current on line side will be observed current on line side real component i is obtained through abc-dq coordinate transform _{d_fdb}with current on line side idle component i _{q_fdb}, the given marker signal i with current on line side respectively _{d_fref}, given without function signal i _{q_ref}differ from, obtain 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 PI controller to the current on line side error signal e obtained in 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, by described wave voltage u _i1with described quantity of state feedback signal X _fdsuperposition can generate the SVPWM control signal u of three-phase full-bridge inverting circuit _i.

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

1. bridge arm current i is selected _l1, capacitance voltage u _c, current on line side i _l2as system state amount, by bridge arm voltage u _iwith line voltage e _gas input variable, obtain grid-connected inverter system separate manufacturing firms 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 formula (1), A _dfor grid-connected inverter system eigenmatrix, B _dfor grid-connected inverter system input matrix, C _d1for grid-connected inverter system output matrix, D _dfor the direct transmission matrix of grid-connected inverter system;

X (k) represents described system state amount: bridge arm current i _l1, capacitance voltage u _cand current on line side i _l2;

X (k+1) is the system state amount of clapping time delay through;

U (k) is grid-connected inverter system input variable;

Y (k) is grid-connected inverter system output variable;

2. according to described grid-connected inverter system separate manufacturing firms equation, state observer eigenmatrix Parameters variation is considered respectively and state observer input deviation Δ u (k), by the principle of duality, utilize the state observer state space equation that following formula obtains based on internal mold:

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

In formula (2), for state observer eigenmatrix, for state observer input matrix, for state observer output matrix, for the direct transmission matrix of state observer;

represent described observer state amount: observation bridge arm current observation capacitance voltage and observation current on line side for clapping the observer state amount of time delay through one;

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

for state observer output variable, y (k) is grid-connected inverter system output variable, for state observer output error;

for internal mold item.

3. described state observer eigenmatrix when parameter changes, the observation error Δ x obtained by described formula (1) and formula (2) ₁be expressed from the next for:

In formula (3), for state observer eigenmatrix variable quantity, for considering state observer eigenmatrix the internal mold item arranged during Parameters variation, according to described state observer output error be set to First-order Integral link or ratio resonance link;

(a) part in formula (3) reaches 0 value by expected pole assignment method, and formula (3) is by (b) part internal mold setting, make (b) part with both (c) parts and reach 0 value, final described observation error Δ x ₁reach 0 value.

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

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

for considering the internal mold item that state observer input u ' (k) is arranged when there is deviation, according to described state observer output error be set to First-order Integral link or ratio resonance link;

(d) part in formula (4) reaches 0 value by expected pole assignment method, and formula (4) is by (e) part internal mold setting, make (e) part with both (f) parts and reach 0 value, final described observation error Δ x ₂reach 0 value.

Contemplated by the invention state observer eigenmatrix Parameters variation and state observer input deviation to the impact of observation effect, by obtaining observer state amount accurately based on the state observer of internal mold, through state feedback transformation controlled device, adopt observation current on line side to carry out combining inverter current loop control, obtain good dynamic and steady-state behaviour.

Accompanying drawing explanation

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

Fig. 2 is Legacy Status Observer Structure figure.

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

Fig. 4 a, 4b are Legacy Status observer respectively and dynamically observe Contrast on effect analogous diagram based on the state observer of internal mold in rest frame bridge arm current.

Fig. 5 a, 5b are Legacy Status observer respectively and dynamically observe Contrast on effect analogous diagram based on the state observer of internal mold in rotating coordinate system bridge arm current.

Fig. 6 a, 6b be respectively Legacy Status observer and based on the state observer of internal mold at rest frame bridge arm current stable state observation effect contrast simulation figure.

Fig. 7 a, 7b be respectively Legacy Status observer and based on the state observer of internal mold at rest frame bridge arm current dynamic contrast experimental waveform.

Fig. 8 a, 8b be respectively Legacy Status observer and based on the state observer of internal mold at rest frame bridge arm current stable state contrast experiment waveform.

Fig. 9 a, 9b be respectively Legacy Status 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 Legacy Status observer and based on the state observer of internal mold at rest frame capacitance voltage dynamic contrast experimental waveform.

The current on line side dynamic experiment waveform that Figure 11 a, 11b are Legacy Status observer respectively and are feeding back based on observer state based on the state observer of internal mold.

Embodiment

In order to more specifically describe the present invention, below in conjunction with the drawings and the specific embodiments, the control method of grid-connected inverter and state observer thereof that the present invention is based on state observer are described in detail.

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

Based on a control method of grid-connected inverter for state observer, comprise the following steps:

1, the current sensor H of bridge arm current is utilized _l1a, H _l1bdetect brachium pontis current i _l1; Utilize grid voltage sensor H _ea, H _ebdetection of grid voltage e _a, e _b, e _chorizontal lock of going forward side by side obtains phase angle theta;

2, according to bridge arm voltage u _iwith line voltage e _gfollowing observer state amount is obtained: observation bridge arm current through the state observer based on internal mold observation capacitance voltage and observation current on line side

The present embodiment is as follows:

Choose state variable: bridge arm current i _l1, capacitance voltage u _c, current on line side i _l2, be designated as x=[i _l1, u _c, i _l2] ^t; Choose input variable: inverter leg output voltage u _iwith electrical network electromotive force e _g, be designated as u=[u _i, e _g] ^t,

Set up LCL grid-connected inverter system state-space model:

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

In above formula, A is grid-connected inverter system eigenmatrix, $A=\left[\begin{array}{ccc}-\frac{r_1+R_p}{L_1}& -\frac{1}{L_1}& \frac{R_p}{L_1}\\ \frac{1}{C}& 0& -\frac{1}{C}\\ \frac{R_p}{L_2^{\′}}& \frac{1}{L_2^{\′}}& -\frac{r_2+R_P}{L_2^{\′}}\end{array}\right];$

Wherein, R _pfor filter capacitor C ₁the damping resistance of upper series connection;

L ₂' be net side filter inductance L ₂with electric network impedance equivalent inductance L _gsum;

B is grid-connected inverter system input matrix, $B=\left[\begin{array}{ccc}& .& \\ B_1& .& B_2\\ & .& \end{array}\right]=\left[\begin{array}{cc}1/L_1& 0\\ 0& 0\\ 0& -1/{L_2}^{\′}\end{array}\right];$

C is grid-connected inverter system output matrix, as selection bridge arm current i _l1during as output, C ₁=[1,0,0]; As selection current on line side i _l2during as output, C ₂=[0,0,1];

D is the direct transmission matrix of grid-connected inverter system, D=[0,0].

For the ease of digital control, select sample frequency f _s=10kHz, utilizes the discretization method of zero-order holder: c _d1=C ₁, D _d=D, by continuous state equation discretization, obtains LCL combining inverter separate manufacturing firms 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 above formula, C _d1=[1,0,0], namely selects bridge arm current as output;

X (k) is discretization quantity of state x (k)=[i _l1(k), u _c(k), i _l2(k)] ^t, wherein: i _l1k () is discrete domain bridge arm current, u _ck () is discrete domain capacitance voltage, i _l2k () is discrete domain current on line side;

U (k) is discrete domain input variable, u (k)=[u _i(k), e _g(k)] ^t, wherein: u _ik () is discrete domain inverter leg output voltage, e _gk () is discrete domain electrical network electromotive force.

According to LCL combining inverter separate manufacturing firms model, on the basis of Legacy Status observer (as shown in Figure 2), consider the change of state observer eigenmatrix Parameters variation and observer input, obtain the state observer based on internal mold, its state space is expressed as:

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

Wherein, for state observer eigenmatrix, for state observer input matrix, for state observer output matrix, for the direct transmission matrix of state observer, for state observer eigenmatrix variable quantity;

represent described observer state amount: observation bridge arm current observation capacitance voltage and observation current on line side

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

G is the feedback matrix of state observer;

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

represent internal mold item.

With reference to the accompanying drawings 3, the described state observer based on internal mold, on the basis of LCL separate manufacturing firms equation, by combining inverter output variable y (k), i.e. combining inverter brachium pontis side filter inductance current i _l1with state observer output variable namely bridge arm current is observed differ from, obtain output error e (k); Due in different coordinate systems, the expression-form of output error is different, for ease of analyzing, considering the general type of output error, being designated as E;

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

φ _e(z)＝det(zI-E)

In formula, φ _ez () represents output error E proper polynomial, z is discrete transform operator;

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

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

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

Internal mold φ ^-1z () is realized 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 formula, G _cfor internal mold realizes 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 realizes input matrix, b _c=[0,0 ... 0,1] ^t;

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

In three-phase rotating coordinate system, error and the quantity of state of output variable are constant, internal mold usually First-order Integral adjuster can be set to; In rest frame, error and the quantity of state of output variable are sinusoidal quantity, and internal mold can be set to resonant regulator.

As Fig. 3, by output error e (k) and the output item x through internal mold _ck () is added, can obtain observer state amount accurately through state observation matrix G: observation bridge arm current observation capacitance voltage observation current on line side

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

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

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

Separate manufacturing firms expression formula based on state feedback is

x(k+1)＝(A _d-B _dK)x(k)+B _du(k)

Damping resistance R is comprised according to capacitive branch _psystem features matrix A _d, A _din get filter capacitor series resistance R _p=0.5 Ω, obtains the system features multinomial comprising passive damping; According to the system features matrix A through state feedback _d-B _dk, utilizes respective items coefficient equal, tries to achieve state feedback matrix K, namely

det(zI-A _d)＝det(zI-(A _d-B _dK))

Wherein, z is 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 state feedback coefficient;

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

k ₂=-0.42233855315199843186755694448278，

k ₃=-2.8075596495029625451005704996724；

By observer state amount described in step 2: observation bridge arm current observation capacitance voltage observation current on line side be multiplied by state feedback coefficient k respectively ₁, k ₂, k ₃, obtain quantity of state feedback signal $X_{\mathrm{fd}}=[k_1\×{\hat{i}}_{L1};k_2\×{\hat{u}}_C;k_3\×{\hat{i}}_{L2}].$

4, current on line side will be observed current on line side real component i is obtained through coordinate transform _{d_fdb}with current on line side idle component i _{q_fdb}, the given marker signal i with current on line side respectively _{d_fref}, given without function signal i _{q_ref}differ from, obtain current on line side error signal e _d, e _q;

5, by PI controller to current on line side error signal e _d, e _qcarry out closed-loop process, wherein, k got by PI controller _p=15, k _i=1800, through coordinate inverse transformation, obtain sending out wave voltage u _i1.

6, by u _i1with status feedback signal X _fdsuperposition generates the SVPWM control signal u of converter bridge switching parts pipe and three-phase full-bridge inverting circuit _i, and then control combining inverter networking electric current.

Fig. 4 a ~ Fig. 6 b be Legacy Status observer and based on the state observer of internal mold when netting side impedance variation, observation effect dynamically, stable state contrast simulation waveform.Fig. 4 a, 4b rest frame bridge arm current dynamically observes Contrast on effect analogous diagram, and number in the figure ' 1 ' represents bridge arm current actual measurement waveform, and label ' 2 ' represents bridge arm current observation waveform; Fig. 5 a, 5b rotating coordinate system bridge arm current dynamically observes Contrast on effect analogous diagram, 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 Legacy Status observer and based on internal mold state observer when netting side impedance variation, observation effect dynamically, stable state contrast experiment waveform.As can be seen from analogous diagram and lab diagram, based on the state observer of internal mold, no matter be all better than Legacy Status observer from dynamic effect or steady state effect, and observer state amount is used for state feedback, and then control for grid-connected current, current on line side dynamic waveform is good.

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

Claims (6)

1., based on a control method of grid-connected inverter for 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 inverting 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 be connected with two inputs of three-phase full-bridge inverting circuit respectively, the three-phase output end of three-phase full-bridge inverting circuit is connected with the three-phase input end one_to_one corresponding of LCL filter, the three-phase output end of LCL filter respectively with three phase network e _a, e _b, e _cbe connected; Described LCL filter is by inverter side inductance L ₁, net side filter inductance L ₂with filter capacitor C ₁composition; It is characterized in that comprising the steps:

Step one, the current sensor of bridge arm current is utilized to detect brachium pontis current i _l1; Utilize grid voltage sensor detection of grid voltage e _ghorizontal 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 observer state amount through the state observer based on internal mold: observation bridge arm current observation capacitance voltage and observation current on line side

Step 3, by observer state amount described in step 2, obtain quantity of state feedback signal X through state feedback matrix K _fd;

Step 4, current on line side will be observed current on line side real component i is obtained through abc-dq coordinate transform _{d_fdb}with current on line side idle component i _{q_fdb}, the given marker signal i with current on line side respectively _{d_fref}, given without function signal i _{q_ref}differ from, obtain 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 PI controller to the current on line side error signal e obtained in step 4 _d, e _qcarry out closed-loop process, then abc-dq coordinate inverse transformation, obtain sending out wave voltage u _i1;

Step 6, by described wave voltage u _i1with described quantity of state feedback signal X _fdsuperposition can generate the SVPWM control signal u of three-phase full-bridge inverting circuit _i;

The state observer based on internal mold described in step 2 is realized by following steps:

1. bridge arm current i is selected _l1, capacitance voltage u _c, current on line side i _l2as system state amount, by bridge arm voltage u _iwith line voltage e _gas input variable, obtain grid-connected inverter system separate manufacturing firms equation by following formula:

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

In formula (1), A _dfor grid-connected inverter system eigenmatrix, B _dfor grid-connected inverter system input matrix, C _d1for grid-connected inverter system output matrix, D _dfor the direct transmission matrix of grid-connected inverter system;

X (k) represents described system state amount: bridge arm current i _l1, capacitance voltage u _cand current on line side i _l2;

X (k+1) is the system state amount of clapping time delay through;

U (k) is grid-connected inverter system input variable;

Y (k) is grid-connected inverter system output variable;

2. according to described grid-connected inverter system separate manufacturing firms equation, state observer eigenmatrix Parameters variation is considered respectively and state observer input deviation Δ u (k), by the principle of duality, utilize the state observer state space equation that following formula obtains based on internal mold:

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

In formula (2), for state observer eigenmatrix, for state observer input matrix, for state observer output matrix, for the direct transmission matrix of state observer;

represent described observer state amount: observation bridge arm current observation capacitance voltage and observational network side current i _l2; for clapping the observer state amount of time delay through one;

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

for state observer output variable, y (k) is grid-connected inverter system output variable, for state observer output error;

for internal mold item.

2. a kind of control method of grid-connected inverter 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 step 3 _fdstep as follows:

1. state feedback matrix K is tried to achieve by expected pole assignment method, K=[k ₁, k ₂, k ₃], k ₁, k ₂, k ₃be state feedback coefficient;

2. by the observer state amount described in step 2, namely bridge arm current is observed observation capacitance voltage observation current on line side be multiplied by state feedback coefficient k respectively ₁, k ₂, k ₃, quantity of state feedback signal can be obtained $X_{\mathrm{fd}}=[k_1\×{\hat{i}}_{L1};k_2\×{\hat{u}}_C;k_3\×{\hat{i}}_{L2}].$

3. a kind of control method of grid-connected inverter based on state observer according to claim 1, is characterized in that: described state observer eigenmatrix when parameter changes, the observation error Δ x obtained by described formula (1) and formula (2) ₁be expressed from the next for:

In formula (3), for state observer eigenmatrix variable quantity, for considering state observer eigenmatrix the internal mold item arranged during Parameters variation,

(a) part in formula (3) reaches 0 value by expected pole assignment method, and formula (3) is by (b) part internal mold setting, make (b) part with both (c) parts and reach 0 value, final described observation error Δ x ₁reach 0 value.

4. a kind of control method of grid-connected inverter based on state observer according to claim 1, it is characterized in that: when described state observer input variable u ' (k) exists deviation, the observation error Δ x that through type (1) and formula (2) obtain ₂be expressed from the next for:

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

for considering the internal mold item that state observer input u ' (k) is arranged when there is deviation,

(d) part in formula (4) reaches 0 value by expected pole assignment method, and formula (4) is by (e) part internal mold setting, make (e) part with both (f) parts and reach 0 value, final described observation error Δ x ₂reach 0 value.

5. a kind of control method of grid-connected inverter based on state observer according to claim 3, is characterized in that: the internal mold item in described formula (3) according to described state observer output error be set to First-order Integral link or ratio resonance link.

6. a kind of control method of grid-connected inverter based on state observer according to claim 4, is characterized in that: the internal mold item in described formula (4) according to described state observer output error be set to First-order Integral link or ratio resonance link.