CN105471313A - Load current state observer-based three-phase inverter double-loop optimization control method - Google Patents

Abstract

The invention discloses a load current state observer-based three-phase inverter double-loop optimization control method, which can be applied to a microgrid for stabilizing load fluctuation and removing higher harmonic pollution, so that stable operation of the microgrid is strengthened; and the electric energy quality of a distributed photovoltaic grid-connected current is improved. Observation on a load current of an inverter is achieved by a state observer on the basis of a static alpha-beta coordinate system; the load current is loaded to a double-loop control circuit as a feedforward; and the dynamic response performance of the system on the load fluctuation is improved. A multi-PR controller is adopted by the control circuit, so that tracking of a sine signal and compensation on a higher harmonic wave are achieved; and the total harmonic distortion rate of an output signal is restrained. Compared with a traditional double-loop control on the basis of a dq0 coordinate system, the control strategy disclosed by the invention is faster in dynamic response rate on the load fluctuation; the stability margin of a system is higher; and the total harmonic distortion rate in a plurality of load conditions (a balanced load, an unbalanced load and a nonlinear load) is lower.

Description

Based on the three-phase inverter dicyclo optimal control method of load current state observer

Technical field

The present invention relates to a kind of network optimization method, relate to a kind of three-phase inverter dicyclo optimal control method based on load current state observer in particular.

Background technology

Along with highlighting of global energy crisis and environmental problem, the micro-grid system that to impel with new and renewable sources of energy be main forms of electricity generation gets the attention.The electric energy quality optimizing control technology of research micro-capacitance sensor, contributes to the economy and the reliability that improve micro-grid system operation, contributes to the operational efficiency of raising system, be conducive to the discharge capacity reducing carbon dioxide, be also conducive to provide high-quality electric energy service.

In micro-grid connection inverter electric energy quality optimizing controls, be target mainly with the dynamic response of the grid-connected output signal of raising to load end, also need the optimization by control strategy in addition, the interference of effective harmonic inhabitation.Can be applied to micro-capacitance sensor stabilizing load fluctuation, Eliminate highter harmonic pollutes, thus strengthens the stable operation of micro-capacitance sensor, improves the quality of power supply of distributed photovoltaic grid-connected current.

In existing optimal control method, the main transducer that adopts realizes observation, and transducer needs under the environment of accurate no signal, noise jamming, and cannot ensure in Practical Project, and thus the existing control method scope of application is little, cost is high.

Summary of the invention

For the deficiency that prior art exists, the object of the present invention is to provide a kind of scope of application wide, with low cost, effectively can stabilize load fluctuation, Eliminate highter harmonic pollutes, thus strengthen the stable operation of micro-capacitance sensor, improve the microgrid inverter dicyclo optimal control method based on state observer of the quality of power supply of distributed photovoltaic grid-connected current.

For achieving the above object, the invention provides following technical scheme: a kind of three-phase inverter dicyclo optimal control method based on load current state observer, comprises the steps:

Step one, first given three-phase inverter parameter, build the Mathematical Modeling of three-phase inverter, and judge the reasonability of given three-phase inverter parameter according to this Mathematical Modeling;

Step 2, sampled feedback signal and carry out coordinate transform, wherein sampled feedback signal adopts state observer real-time monitored to go out load current and sampling system runs feedback signal, and coordinate transform is static α β coordinate system by the static abc coordinate system transformation of Mathematical Modeling in step one;

Step 3, the load current sampled by state observer and system cloud gray model feedback signal are input in electric current and voltage Double Loop Control System, generate the work of inverter control instruction control inverter, output load current and system cloud gray model feedback signal after inverter work, and return step 2.

As a further improvement on the present invention, the control loop in the electric current and voltage Double Loop Control System in described step 3, to stabilize high order harmonic component for target, adopts multiple PR controller in it, in order to regulation output signal higher harmonic content.

As a further improvement on the present invention, the Mathematical Modeling of the three-phase inverter built in described step one is as follows:

$v_{abc}-u_{abc}=L\frac{{\mathrm{di}}_{abc}}{dt}+{\mathrm{Ri}}_{abc};$

$C\frac{{\mathrm{du}}_{abc}}{dt}=i_{abc}-i_{labc};$

In formula, i _abcfor filter inductance electric current, u _abcfor electric capacity both end voltage, i _labcfor load current, V _abcfor the output voltage of inverter, L is inductance, and C is electric capacity, and t is the moment, and d is small line element.

As a further improvement on the present invention, under the coordinate system transformation in described step 2 transforms to α β coordinate system by Clark transformation for mula, the model after conversion is as follows:

$v_{\mathrm{\α}\mathrm{\β}}-u_{\mathrm{\α}\mathrm{\β}}=L\frac{{\mathrm{di}}_{\mathrm{\α}\mathrm{\β}}}{dt}+{\mathrm{Ri}}_{\mathrm{\α}\mathrm{\β}};$

$C\frac{{\mathrm{du}}_{\mathrm{\α}\mathrm{\β}}}{dt}=i_{\mathrm{\α}\mathrm{\β}}-i_{l\mathrm{\α}\mathrm{\β}};$

In formula: i _{α β}=[i _αi _β] ^t; u _{α β}=[u _αu _β] ^t; i _{l α β}=[i _{l α}i _{l β}]; v _{α β}=[v _αv _β] ^t; i _αand i _βfor the filter inductance electric current after coordinate transform, u _αand u _βfor the shunt capacitance terminal voltage after coordinate transform, v _αand v _βfor the inverter outlet voltage after coordinate transform, T is transposed matrix, and L is inductance, and C is electric capacity, and t is the moment, and d is small line element.

As a further improvement on the present invention, the employing state observer in described step 2 observes that the observational equation of load current is as follows:

$\left\{\begin{array}{c}\stackrel{.}{Uc}=\frac{1}{C}\[I_0-\widehat{I_{ld}}\]-h_1\[\widehat{Uc}-Uc\]\\ \stackrel{.}{\widehat{I_{ld}}}=-h_2\[\widehat{Uc}-Uc\]\end{array}\right.$

In formula: Uc is shunt capacitance both end voltage; I ₀and I _ldinductive current and load current respectively; C is electric capacity; h ₁, h ₂for state gain vector.

As a further improvement on the present invention, the transfer function that the PR in described step 3 controls is as follows:

$G_{PR}\left(s\right)=K_P+\frac{2K_{r}s}{s^2+{\mathrm{\ω}}^2};$

In formula: K _pwith the parameter that Kr is PR controller, K _pfor proportionality constant, K _rfor integral constant, ω is first-harmonic angular frequency, and s is differential, G _pRs () is transfer function.

As a further improvement on the present invention, the Optimal Control System of application this method comprises inverter, PWM device, current inner loop, outer voltage, the inductance being coupled to the mutual series connection of inverter output end, electric capacity and load current observer, described current inner loop and outer voltage are all coupled between inverter output end and PWM device, control the output of PWM device, after described load current observer observes load current, load current is input in current inner loop and outer voltage as feedforward.

Beneficial effect of the present invention, by the setting of step one, just effectively can construct the Mathematical Modeling of three-phase inverter, and by the setting of step 2, just can effectively collect corresponding feedback signal and load current, and effective is static α β coordinate system by static abc coordinate system transformation, so compared in prior art by static abc coordinate system transformation being the dq0 coordinate system rotated, do not need to carry out decoupling computation, reduce and assess the cost, and by the setting of step 3, the load current that just can effectively realize using state observer to observe is carried in electric current and voltage Double Loop Control System as feedforward, raising system is to the dynamic response performance of the fluctuation of load, the stable operation of effective enhancing micro-capacitance sensor, improve the quality of power supply of distributed photovoltaic grid-connected current.

Accompanying drawing explanation

Fig. 1 is the flow chart of the three-phase inverter dicyclo optimal control method based on load current state observer of the present invention;

Fig. 2 is the control schematic diagram of the three-phase inverter dicyclo optimal control method based on load current state observer of the present invention;

Fig. 3 is the schematic flow sheet of the load current observer of the three-phase inverter dicyclo optimal control method based on load current state observer of the present invention;

Fig. 4 is the observation effect figure of state observer;

Fig. 5 is the simulation result comparison diagram before and after offered load current feed-forward;

Fig. 6 is the illustraton of model of observational equation at continuous domain.

Embodiment

Below in conjunction with the embodiment given by accompanying drawing, the present invention is described in further detail.

Shown in 6, a kind of three-phase inverter dicyclo optimal control method based on load current state observer of the present embodiment, comprises the steps:

Step one, first given three-phase inverter parameter, build the Mathematical Modeling of three-phase inverter, and judge the reasonability of given three-phase inverter parameter according to this Mathematical Modeling;

Step 2, sampled feedback signal and carry out coordinate transform, wherein sampled feedback signal adopts state observer real-time monitored to go out load current and sampling system runs feedback signal, and coordinate transform is static α β coordinate system by the static abc coordinate system transformation of Mathematical Modeling in step one;

Step 3, the load current sampled by state observer and system cloud gray model feedback signal are input in electric current and voltage Double Loop Control System, generate the work of inverter control instruction control inverter, output load current and system cloud gray model feedback signal after inverter work, and return step 2, in the process that control method is run, first carry out step one, three-phase inverter structure is determined in conjunction with actual, construct the Mathematical Modeling of three-phase inverter, then this Mathematical Modeling is analyzed, and then enter into step 2, just effectively can be sampled by step 2 and control feedback signal and utilization state observer and observe load current, and be static α β coordinate system by static abc coordinate system transformation, so just can effectively realize without the need to decoupling computation, reduce the effect assessed the cost, and pass through step 3, the load current that just can effectively realize using state observer to observe is carried in electric current and voltage Double Loop Control System as feedforward, raising system is to the dynamic response performance of the fluctuation of load, the stable operation of effective enhancing micro-capacitance sensor, improve the quality of power supply of distributed photovoltaic grid-connected current, this method is made to can be good at realizing the scope of application wide, with low cost, effectively can stabilize load fluctuation, Eliminate highter harmonic pollutes, thus strengthen the stable operation of micro-capacitance sensor, improve the effect of the quality of power supply of distributed photovoltaic grid-connected current, given wherein for three-phase inverter parameter in step one, it is the parameter according to photovoltaic DC-to-AC converter in electrical network, and the parameter of miscellaneous part realizes given, and judge that whether given three-phase inverter parameter is reasonable, it is then the Bode diagram by analyzing Mathematical Modeling, and mains-power circuit structural principle realizes judging that whether the parameter of given three-phase inverter is rational.

As a kind of embodiment improved, control loop in electric current and voltage Double Loop Control System in described step 3, to stabilize high order harmonic component for target, multiple PR controller is adopted, in order to regulation output signal higher harmonic content, by adopting multiple PR controller in it, PR controller is ratio resonant controller, effectively can regulate harmonic wave, with just effectively total harmonic distortion factor can be reduced here, effectively improve the also network electric energy quality of distributed photovoltaic inverter.

As a kind of embodiment improved, the Mathematical Modeling of the three-phase inverter built in described step one is as follows:

$v_{abc}-u_{abc}=L\frac{{\mathrm{di}}_{abc}}{dt}+{\mathrm{Ri}}_{abc};$

$C\frac{{\mathrm{du}}_{abc}}{dt}=i_{abc}-i_{labc};$

In formula, i _abcfor filter inductance electric current, u _abcfor electric capacity both end voltage, i _labcfor load current, V _abcfor the output voltage of inverter, L is inductance, and C is electric capacity, and t is the moment, and d is small line element, by the Mathematical Modeling of above-mentioned three-phase inverter, just can effectively analyze it.

As a kind of embodiment improved, under the coordinate system transformation in described step 2 transforms to α β coordinate system by Clark transformation for mula, the model after conversion is as follows:

$v_{\mathrm{\α}\mathrm{\β}}-u_{\mathrm{\α}\mathrm{\β}}=L\frac{{\mathrm{di}}_{\mathrm{\α}\mathrm{\β}}}{dt}+{\mathrm{Ri}}_{\mathrm{\α}\mathrm{\β}};$

$C\frac{{\mathrm{du}}_{\mathrm{\α}\mathrm{\β}}}{dt}=i_{\mathrm{\α}\mathrm{\β}}-i_{l\mathrm{\α}\mathrm{\β}};$

In formula: i _{α β}=[i _αi _β] ^t; u _{α β}=[u _αu _β] ^t; i _{l α β}=[i _{l α}i _{l β}] ^t; v _{α β}=[v _αv _β] ^t; i _αand i _βfor the filter inductance electric current after coordinate transform, u _αand u _βfor the shunt capacitance terminal voltage after coordinate transform, v _αand v _βfor the inverter outlet voltage after coordinate transform, T is transposed matrix, and L is inductance, C is electric capacity, and t is the moment, and d is small line element, in the process of conversion, the inverter Mathematical Modeling under static abc coordinate system is transformed into the equivalent model under α β coordinate system by Clark transformation for mula:

$T_{3s\→2s}=\frac{2}{3}\left[\begin{array}{ccc}1& -\frac{1}{2}& -\frac{1}{2}\\ 0& \frac{\sqrt{3}}{2}& -\frac{\sqrt{3}}{2}\end{array}\right]$

Electric current and voltage Mathematical Modeling after conversion is as follows:

$v_{\mathrm{\α}\mathrm{\β}}-u_{\mathrm{\α}\mathrm{\β}}=L\frac{{\mathrm{di}}_{\mathrm{\α}\mathrm{\β}}}{dt}+{\mathrm{Ri}}_{\mathrm{\α}\mathrm{\β}}$

in formula: i _{α β}=[i _αi _β] ^t; u _{α β}=[u _αu _β] ^t; i _{l α β}=[i _{l α}i _{l β}] ^t; v _{α β}=[v _αv _β] ^t; i _αand i _βfor the filter inductance electric current after coordinate transform, u _αand u _βfor the shunt capacitance terminal voltage after coordinate transform, v _αand v _βfor the inverter outlet voltage after coordinate transform, T is transposed matrix, and L is inductance, and C is electric capacity, t is the moment, d is small line element, so just effectively obtains the Mathematical Modeling after conversion, and considers that α β coordinate is separate, independently can process at α axle when analysis and design controls, therefore from above equation, the Mathematical Modeling of three-phase voltage source inverter can be transformed to state-space model, as follows:

$\left[\begin{array}{c}{\stackrel{\·}{U}}_{\mathrm{\α}}\\ {\stackrel{\·}{U}}_{\mathrm{\β}}\\ {\stackrel{\·}{i}}_{\mathrm{\α}}\\ {\stackrel{\·}{i}}_{\mathrm{\β}}\end{array}\right]=\left[\begin{array}{cccc}0& 0& \frac{1}{C}& 0\\ 0& 0& 0& \frac{1}{C}\\ -\frac{1}{L}& 0& -\frac{R}{L}& 0\\ 0& -\frac{1}{L}& 0& -\frac{R}{L}\end{array}\right]\left[\begin{array}{c}{U}_{\mathrm{\α}}\\ U_{\mathrm{\β}}\\ i_{\mathrm{\α}}\\ i_{\mathrm{\β}}\end{array}\right]+\left[\begin{array}{cccc}0& 0& -\frac{1}{C}& 0\\ 0& 0& 0& -\frac{1}{C}\\ \frac{1}{L}& 0& 0& 0\\ 0& \frac{1}{L}& 0& 0\end{array}\right]\left[\begin{array}{c}{V}_{\mathrm{\α}}\\ V_{\mathrm{\β}}\\ i_{l\mathrm{\α}}\\ i_{l\mathrm{\β}}\end{array}\right]$

Corresponding Controlling model is expressed as follows:

From above Mathematical Modeling, without coupled relation between the state variable of α axle and β axle.Therefore, the Mathematical Modeling of three-phase equilibrium PWM inverter can be equivalent to two Single-phase PWM Inverters after the conversion that abc coordinate is tied to α β coordinate system.This also shows, in the control that the control strategy of single-phase inverter can be applied to based on the three-phase inverter of α β coordinate system, to simplify the design of controller.

As a kind of embodiment improved, the employing state observer in described step 2 observes that the observational equation of load current is as follows:

$\left\{\begin{array}{c}\stackrel{.}{Uc}=\frac{1}{C}\[I_0-\widehat{I_{ld}}\]-h_1\[\widehat{Uc}-Uc\]\\ \stackrel{.}{\widehat{I_{ld}}}=-h_2\[\widehat{Uc}-Uc\]\end{array}\right.$

In formula: Uc is shunt capacitance both end voltage; I ₀and I _ldinductive current and load current respectively; C is electric capacity; h ₁, h ₂for state gain vector, observe load current at introducing state observer, and be loaded in control loop using this observed quantity as feedforward, when drawing observational equation, first known inverter ac side is as follows:

$C\frac{dUc}{dt}=I_0-I_{ld}$

In formula: Uc is shunt capacitance both end voltage; I0 and Ild is inductive current and load current respectively.

Discretization is carried out to above formula:

$\left\{\begin{array}{c}\stackrel{\·}{X}=AX+Bu\\ y=CX\end{array}\right.$

In formula: $A=\left[\begin{array}{cc}0& -\frac{1}{C}\\ 0& 0\end{array}\right],B=\left[\begin{array}{c}\frac{1}{C}\\ 0\end{array}\right],C=\[\begin{array}{cc}1& 0\end{array}\],X=\left[\begin{array}{c}Uc\\ I_{ld}\end{array}\right],\stackrel{\·}{X}=\left[\begin{array}{c}\stackrel{.}{Uc}\\ \stackrel{.}{I_{ld}}\end{array}\right],$ y＝Uc，u＝I ₀

State observer dynamic model then based on Luenberger theory is:

$\left\{\begin{array}{c}\stackrel{\·}{\hat{X}}=A\hat{X}+Bu-H(\hat{y}-y)\\ \stackrel{\·}{\hat{y}}=C\hat{X}\end{array}\right.$

In formula with be respectively observed quantity and output valve.H=[h1h2] ^tfor state gain vector.

Based on above-mentioned discrete state equations, the structure of state observer of the present invention is as follows:

Error state vector is:

$\stackrel{\·}{\hat{X}}-\stackrel{\·}{X}=(A-HC)(\hat{X}-X)$

Its solution is:

$\hat{X}-X=e^{(A-HC)(t-t_0)}\[\hat{X}\left(t_0\right)-X\left(t_0\right)\]$

As long as at this moment ensure that the characteristic value of A-HC has negative real part, initial state vector error always exponentially decays, and its rate of decay depends on the POLE PLACEMENT USING of A-HC, thus ensures that observed quantity converges on actual value.Expand state equation above and by its discretization, the observational equation of load current can be obtained:

$\left\{\begin{array}{c}\stackrel{.}{Uc}=\frac{1}{C}\[I_0-\widehat{I_{ld}}\]-h_1\[\widehat{Uc}-Uc\]\\ \stackrel{.}{\widehat{I_{ld}}}=-h_2\[\widehat{Uc}-Uc\]\end{array}\right.$

So just effectively can obtain the observational equation of load current, determine that feedback oscillator puts to the proof H below.Because observer is second-order system, its characteristic equation is:

det[λI-(A-HC)]＝0；

$\left|\begin{array}{cc}\mathrm{\λ}+h_1& 1/C\\ h_2& \mathrm{\λ}\end{array}\right|={\mathrm{\λ}}^2+{\mathrm{\λh}}_1-\frac{h_2}{C}=0;$

Because λ 1 and λ 2 must have negative real part, it can be made all to equal real number k (k < 0), and equation becomes:

${\mathrm{\&lambda;}}^2+h_1\mathrm{\&lambda;}-\frac{h_2}{C}={\mathrm{\&lambda;}}^2-2k\mathrm{\&lambda;}+k^2;$

Then: H=[2k-Ck ²], so just effectively can put to the proof H.

As a kind of embodiment improved, the transfer function that the PR in described step 3 controls is as follows:

$G_{PR}\left(s\right)=K_P+\frac{2K_{r}s}{s^2+{\mathrm{\&omega;}}^2};$

In formula: K _pwith the parameter that Kr is PR controller, K _pfor proportionality constant, K _rfor integral constant, ω is first-harmonic angular frequency, and s is differential, G _pRs () is transfer function, according to internal model principle, the best solution of following the tracks of sinusoidal reference signal and harmonics restraint adopts PR to regulate exactly.PR controls to be one proportional component (P) control mode in parallel with improper integral link (R), the effect of proportional component is the same with the P link in PI control, systematic function can be improved on the whole comprehensively, comprise its response speed, the stability of direct decision systems, the cross-over frequency of system, dynamic response and system bandwidth, directly can carry out filtering and suppression to the harmonic frequency outside broadband.Improper integral link is then form resonance at setpoint frequency, this resonance point is made to have close to infinitely-great gain, realize following the tracks of the zero error of given sinusoidal signal, as long as make the resonance frequency of resonant controller equal line voltage fundamental frequency, just can realize without following difference first-harmonic.PR controller does not exist coupling terms does not need feedforward compensation item yet, and easily can realize the compensation to low-order harmonic, and elevator system exports the precision of target.So utilize PR to control to realize good control, thus transfer function is conventional transmission function, so just effectively can realize the control of PR controller

As a kind of embodiment improved, the Optimal Control System of application this method comprises inverter, PWM device, current inner loop 1, outer voltage 2, be coupled to the inductance of the mutual series connection of inverter output end, electric capacity and load current observer, described current inner loop 1 and outer voltage 2 are all coupled between inverter output end and PWM device, control the output of PWM device, after described load current observer observes load current, load current is input in current inner loop 1 and outer voltage 2 as feedforward, by the setting of current inner loop 1 and outer voltage 2, just effectively can realize double-loop control, and pass through the setting of PWM device, just effectively can match with current inner loop 1 and outer voltage 2 and realize double-loop control, and pass through the setting of load current observer, just effectively can observe load current.

In sum, three-phase inverter dicyclo optimal control method based on load current state observer of the present invention, by step, the setting of step 2 and step 3, just effectively can construct the Mathematical Modeling of three-phase inverter, can also sampled feedback signal and the Mathematical Modeling of three-phase inverter is carried out coordinate transform, make it based on static α β coordinate system, so just do not need decoupling computation, reduce and assess the cost, and observe load current by state observer, then load current is loaded in double-loop control loop as feedforward, raising system is to the dynamic response performance of the fluctuation of load.

The above is only the preferred embodiment of the present invention, protection scope of the present invention be not only confined to above-described embodiment, and all technical schemes belonged under thinking of the present invention all belong to protection scope of the present invention.It should be pointed out that for those skilled in the art, some improvements and modifications without departing from the principles of the present invention, these improvements and modifications also should be considered as protection scope of the present invention.

Claims (10)

1., based on a three-phase inverter dicyclo optimal control method for load current state observer, it is characterized in that: comprise the steps:

Step one, first given three-phase inverter parameter, build the Mathematical Modeling of three-phase inverter, and judge the reasonability of given three-phase inverter parameter according to this Mathematical Modeling;

Step 2, sampled feedback signal and carry out coordinate transform, wherein sampled feedback signal adopts state observer real-time monitored to go out load current and sampling system runs feedback signal, and coordinate transform is static α β coordinate system by the static abc coordinate system transformation of Mathematical Modeling in step one;

Step 3, the load current sampled by state observer and system cloud gray model feedback signal are input in electric current and voltage Double Loop Control System, generate the work of inverter control instruction control inverter, output load current and system cloud gray model feedback signal after inverter work, and return step 2.

2. the three-phase inverter dicyclo optimal control method based on load current state observer according to claim 1, it is characterized in that: the control loop in the electric current and voltage Double Loop Control System in described step 3, to stabilize high order harmonic component for target, multiple PR controller is adopted, in order to regulation output signal higher harmonic content in it.

3. the three-phase inverter dicyclo optimal control method based on load current state observer according to claim 1 and 2, is characterized in that: the Mathematical Modeling of the three-phase inverter built in described step one is as follows:

$v_{abc}-u_{abc}=L\frac{{\mathrm{di}}_{abc}}{dt}+{\mathrm{Ri}}_{abc};$

$C\frac{{\mathrm{du}}_{abc}}{dt}=i_{abc}-i_{labc};$

In formula, i _abcfor filter inductance electric current, u _abcfor electric capacity both end voltage, i _labcfor load current, V _abcfor the output voltage of inverter, L is inductance, and C is electric capacity, and t is the moment, and d is small line element.

4. the three-phase inverter dicyclo optimal control method based on load current state observer according to claim 3, it is characterized in that: under the coordinate system transformation in described step 2 transforms to α β coordinate system by Clark transformation for mula, the model after conversion is as follows:

$v_{\mathrm{\&alpha;}\mathrm{\&beta;}}-u_{\mathrm{\&alpha;}\mathrm{\&beta;}}=L\frac{{\mathrm{di}}_{\mathrm{\&alpha;}\mathrm{\&beta;}}}{dt}+{\mathrm{Ri}}_{\mathrm{\&alpha;}\mathrm{\&beta;}};$

$C\frac{{\mathrm{du}}_{\mathrm{\&alpha;}\mathrm{\&beta;}}}{dt}=i_{\mathrm{\&alpha;}\mathrm{\&beta;}}-i_{l\mathrm{\&alpha;}\mathrm{\&beta;}};$

In formula: i _{α β}=[i _αi _β] ^t; u _{α β}=[u _αu _β] ^t; i _{1 α β}=[i _{1 α}i _{1 β}] ^t; v _{α β}=[v _αv _β] ^t; i _αand i _βfor the filter inductance electric current after coordinate transform, u _αand u _βfor the shunt capacitance terminal voltage after coordinate transform, v _αand v _βfor the inverter outlet voltage after coordinate transform, T is transposed matrix, and L is inductance, and C is electric capacity, and t is the moment, and d is small line element.

5. the three-phase inverter dicyclo optimal control method based on load current state observer according to claim 1 and 2, is characterized in that: the employing state observer in described step 2 observes that the observational equation of load current is as follows:

$\left\{\begin{array}{c}\stackrel{.}{Uc}=\frac{1}{C}\&lsqb;I_0-\widehat{I_{ld}}\&rsqb;-h_1\&lsqb;\widehat{Uc}-Uc\&rsqb;\\ \stackrel{.}{\widehat{I_{ld}}}=-h_2\&lsqb;\widehat{Uc}-Uc\&rsqb;\end{array}\right.$

In formula: Uc is shunt capacitance both end voltage; I ₀and I _ldinductive current and load current respectively; C is electric capacity; h ₁, h ₂for state gain vector.

6. the three-phase inverter dicyclo optimal control method based on load current state observer according to claim 3, is characterized in that: the employing state observer in described step 2 observes that the observational equation of load current is as follows:

$\left\{\begin{array}{c}\stackrel{.}{Uc}=\frac{1}{C}\&lsqb;I_0-\widehat{I_{ld}}\&rsqb;-h_1\&lsqb;\widehat{Uc}-Uc\&rsqb;\\ \stackrel{.}{\widehat{I_{ld}}}=-h_2\&lsqb;\widehat{Uc}-Uc\&rsqb;\end{array}\right.$

In formula: Uc is shunt capacitance both end voltage; I ₀and I _ldinductive current and load current respectively; C is electric capacity; h ₁, h ₂for state gain vector.

7. the three-phase inverter dicyclo optimal control method based on load current state observer according to claim 4, is characterized in that: the employing state observer in described step 2 observes that the observational equation of load current is as follows:

$\left\{\begin{array}{c}\stackrel{.}{Uc}=\frac{1}{C}\&lsqb;I_0-\widehat{I_{ld}}\&rsqb;-h_1\&lsqb;\widehat{Uc}-Uc\&rsqb;\\ \stackrel{.}{\widehat{I_{ld}}}=-h_2\&lsqb;\widehat{Uc}-Uc\&rsqb;\end{array}\right.$

In formula: Uc is shunt capacitance both end voltage; I ₀and I _ldinductive current and load current respectively; C is electric capacity; h ₁, h ₂for state gain vector.

8. the three-phase inverter dicyclo optimal control method based on load current state observer according to claim 2, is characterized in that: the transfer function that the PR in described step 3 controls is as follows:

$G_{PR}\left(s\right)=K_P+\frac{2K_{r}s}{s^2+{\mathrm{\&omega;}}^2};$

In formula: Kp and Kr is the parameter of PR controller, Kp is proportionality constant, and Kr is integral constant, and ω is first-harmonic angular frequency, and s is differential, G _pRs () is transfer function.

9. the three-phase inverter dicyclo optimal control method based on load current state observer according to claim 1 and 2, it is characterized in that: the Optimal Control System of application this method comprises inverter, PWM device, current inner loop (1), outer voltage (2), be coupled to the inductance of the mutual series connection of inverter output end, electric capacity and load current observer, described current inner loop (1) and outer voltage (2) are all coupled between inverter output end and PWM device, control the output of PWM device, after described load current observer observes load current, load current is input in current inner loop (1) and outer voltage (2) as feedforward.

10. the three-phase inverter dicyclo optimal control method based on load current state observer according to claim 3, it is characterized in that: the Optimal Control System of application this method comprises inverter, PWM device, current inner loop (1), outer voltage (2), be coupled to the inductance of the mutual series connection of inverter output end, electric capacity and load current observer, described current inner loop (1) and outer voltage (2) are all coupled between inverter output end and PWM device, control the output of PWM device, after described load current observer observes load current, load current is input in current inner loop (1) and outer voltage (2) as feedforward.