CN103887822B - A kind of LCL type single-phase grid-connected inverter power controls and active damping optimization method - Google Patents

Abstract

The invention discloses a kind of LCL type single-phase grid-connected inverter power to control and active damping optimization method, adopt equivalent synchronous coordinate system PI controller, adopt all-pass filter structure two-phase virtual orthographic system, overcome the problem that the data used of building method in the past have asynchronism or introduce noise jamming, realize grid-connected current to regulate at fundamental frequency zero steady state error, improve the stability of a system.Once differentiation and the high fdrequency component of Real-time Feedback grid-connected current of the present invention add system damping, suppress the resonance spikes of LCL filter, and give the parameter selection method of optimization, single current feedback coefficient is reduced to a variable, overcome the shortcoming that in single electric current high fdrequency component feedback, parameter is not easily chosen, improve system reliability and dynamic.

Description

A kind of LCL type single-phase grid-connected inverter power controls and active damping optimization method

Technical field

The present invention relates to PWM inversion control and new energy field thereof, specifically a kind of LCL type single-phase grid-connected inverter power controls and active damping optimization method.

Background technology

The shortage of fossil energy and the environmental pollution caused make photovoltaic generation become one of study hotspot, at the tip of electrical network, a large amount of accesses of non-resistive load can produce reactive current, this requires that distributed photovoltaic grid-connected system can provide the active current of low harmonics distortion, also needs to provide reactive current to load.Corresponding research is carried out to the grid-connected control strategy having no-power compensation function concurrently both at home and abroad, it regulates can the ratio resonance of equivalence grid-connected current in pairs control the meritorious and idle PI that carries out respectively under synchronous rotating frame, realize floating and the power factor of grid-connected electric current, and the detection of load reactive current is the key realizing Active Generation and reactive power compensation, usual employing structure three-phase system or two-phase orthogonal system and the virtual three-phase that obtains under different coordinates or biphase current, but the latency issue all introduced so undoubtedly in various degree, larger impact is had on the stability of system.

The orthogonal system of structure only realizes power adjustments at first-harmonic, and do not consider humorous wave zone, this will with the harm of dealing public electric wire net harmonic.In order to reduce the harm of harmonic wave to public electric wire net, require that it has extremely low total harmonic distortion.In grid-connected system, the suppression to low-order harmonic can be realized by HC (Harmoniccompensator) strategy, adopt LCL filter, better can suppress high order harmonic component, and reduce total inductance amount.But LCL filter is a third-order system has the very low resonance spikes of a damping coefficient, easily occur to vibrate and cause system unstable, therefore the control of system being had higher requirement.The method of usual employing active damping suppresses resonance spikes, capacitance current in sampling LCL filter also carries out FEEDBACK CONTROL or adopts net side inductive drop micro component to replace capacitance current to suppress resonance spikes, but all can introduce extra current sensor, add the hardware cost of system, reduce system reliability.Therefore, reducing the extra transducer of introducing adopts single current feedback to become study hotspot, have at present and adopt grid-connected current twice Derivative Feedback and estimation capacitance present current value and the strategy of feedback, but the coefficient of two subdifferentials is not easily chosen and the evaluation method of capacitance current comparatively complicated and time consumption, and easily introduces error.

Summary of the invention

Technical problem to be solved by this invention is, not enough for prior art, a kind of LCL type single-phase grid-connected inverter power is provided to control and active damping optimization method, solve idle detection of traditional single phase there is larger time delay or introduce the problem of interference signal, solve current single-phase LCL type combining inverter needs additional sensors or introduces the problem that single current feedback parameters not easily chooses simultaneously.

For solving the problems of the technologies described above, the technical solution adopted in the present invention is: a kind of LCL type single-phase grid-connected inverter power controls and active damping optimization method, and the method is:

1) in the starting point in each sampling period, the A/D sample circuit of LCL type single-phase grid-connected inverter is to line voltage u _swith grid-connected current i _gand the inverter circuit DC capacitor voltage U of LCL type single-phase grid-connected inverter _dcsample respectively, and sampled data is given the control module process of LCL type single-phase grid-connected inverter;

2) to grid-connected current i _gβ phase virtual orthographic signal i is obtained by all-pass filter _β, construct two-phase virtual orthographic system, obtain two-phase quadrature current i _α, i _β:

$\left\{\begin{array}{c}{i}_{\mathrm{\α}}=i_g\\ i_{\mathrm{\β}}=\frac{{\mathrm{\ω}}_0-s}{{\mathrm{\ω}}_0+s}{i}_g\end{array}\right.;$

Wherein, ω ₀for power frequency angular frequency; S=j ω, j are imaginary part unit symbols;

3) to i _α, i _βdo α β/dq coordinate transform and obtain single-phase grid-connected active current value i _dwith grid-connected reactive current value i _q;

4) to DC side reference voltage U _dc ^*with inverter circuit DC capacitor voltage U _dcbe PI to regulate, obtain the grid-connected current active current command value i of DC side voltage stabilizing link _d ^*, according to the reactive power Q that need compensate _sdetermine the command value i of reactive current _q ^*:

$I_q^{*}=\sqrt{2}{Q}_s^{*}/U_s;$

Wherein Q _s ^*for compensating reactive power amount, U _sfor the effective value of line voltage;

5) to single-phase grid-connected active current i _d, grid-connected current active current command value i _d ^*and grid-connected reactive current i _q, reactive current command value i _q ^*carry out PI adjustment respectively, and the adjusted value after PI regulates is done to dq/ α β coordinate transform and obtains command signal i _{1 α}, i _{1 β}; It can be equivalent to synchronous coordinate system PI controller to the control effects of grid-connected current, then grid-connected current i _gwith grid-connected current command value i _g ^*equivalent difference E under α phase _αto inverter control signal i _{1 α}transfer function G _c(s) be:

$G_c\left(s\right)==\frac{K_p{s}^3+(K_p{\mathrm{\ω}}_0+K_i)s^2+(K_p{\mathrm{\ω}}_0^2+2{\mathrm{\ω}}_0{K}_i)s+K_p{\mathrm{\ω}}_0^3-K_i{\mathrm{\ω}}_0^2}{s^3+{\mathrm{\ω}}_0{s}^2+{\mathrm{\ω}}_0^{2}s+{\mathrm{\ω}}_0^3}$

G _cs () is infinitely great in the gain of fundamental frequency place, very little in non-fundamental frequency place gain, and the zero steady-state error realizing grid-connected current regulates.Wherein K _p, K _igain merit and PI parameter in reactive current PI controller for grid-connected.

6) to grid-connected current i _gintroduce 3,5,7 subharmonic compensators, obtain offset current i ₃, and by command signal i _{1 α}with offset current i ₃make difference and obtain current signal i ₀;

7) to grid-connected current i _gintroduce feedback and increase system damping, obtain grid-connected current value of feedback; Wherein feedback factor is H ₁(s):

$H_1\left(s\right)=K_{d}s+\frac{K_c}{s+{\mathrm{\ω}}_d}s;$

Wherein K _d, K _cbe respectively grid-connected current differential, high fdrequency component coefficient; ω is electrical network angular frequency;

8) by current signal i ₀poor with grid-connected current value of feedback, obtain SPWM modulation wave signal d;

9) bipolar modulation is carried out to SPWM modulating wave and triangular carrier, obtain the duty cycle signals of inverter circuit switching tube, through the Drive Protecting Circuit of LCL type single-phase grid-connected inverter, control opening and shutoff of inverter circuit switching tube.

Described step 7) in, K _cwith K _dpass be:

K _c＝(1-T _sω _d)K _d/T _s；

ω _dand K _dvalue be:

$\left\{\begin{array}{c}{\mathrm{\ω}}_d=4\sqrt{{\mathrm{\ξ}}^2/(4{\mathrm{\ξ}}^2+1)}{\mathrm{\ω}}_{res}\\ K_d=\frac{2T_s\mathrm{\ξ}}{K_{inv}\sqrt{(4{\mathrm{\ξ}}^2+1)}}{\mathrm{\ω}}_{res}\[2(L+L_g)-\frac{{\mathrm{LL}}_{g}C}{4{\mathrm{\ξ}}^2+1}{\mathrm{\ω}}_{res}^2\]\end{array}\right.;$

Wherein, ω _resfor the resonance frequency of LCL filter, ξ is the target damping coefficient of LCL type inverter in grid-connected current feedback, ω _nfor grid-connected current introduces the resonance frequency after feedback, K _invfor the equivalent gain of LCL type inverter, L, Lg are the inductance inductance value in LCL filter, and C is the capacitor's capacity of LCL filter, T _sfor the sampling period.

Compared with prior art, the beneficial effect that the present invention has is: directly can not realize the problem of grid-connected power control by application of synchronized rotating coordinate system for single phase system, the present invention adopts equivalent synchronous coordinate system PI controller, adopt all-pass filter structure two-phase virtual orthographic system, overcome the problem that the data used of building method in the past have asynchronism or introduce noise jamming, realize grid-connected current to regulate at fundamental frequency zero steady state error, improve the stability of a system.The once differentiation of Real-time Feedback grid-connected current of the present invention and high fdrequency component, add system damping, suppress the resonance spikes of LCL filter, and give the parameter selection method of optimization, single current feedback coefficient is reduced to unitary variant, overcome the shortcoming that in single electric current high fdrequency component feedback, parameter is not easily chosen, improve system reliability and dynamic.

Accompanying drawing explanation

Fig. 1 is that one embodiment of the invention LCL type combining inverter power controls and active damping optimization method structure chart;

Fig. 2 is that one embodiment of the invention LCL type combining inverter power controls and active damping optimization method control block diagram;

Fig. 3 is single current feedback active damping Optimal Control Strategy control block diagram schematic diagram of one embodiment of the invention LCL type combining inverter;

Fig. 4 is one embodiment of the invention K ₁transfer function during ratio different from ζ bode diagram;

Fig. 5 is one embodiment of the invention line voltage u _scurrent i is surveyed with net _gsimulation waveform.

Embodiment

As shown in Figure 1, one embodiment of the invention single-phase photovoltaic grid-connected inverter comprises inverter circuit, LCL filter circuit, A/D sample circuit, phase-locked loop circuit, controller DSP 2812, Drive Protecting Circuit, and described photovoltaic array, boost chopper, inverter circuit, LCL filter circuit, electrical network connect successively; Described A/D sample circuit input is connected with described LCL filter circuit; Described controller DSP 2812 is connected with described Drive Protecting Circuit input, A/D sample circuit output, phase-locked loop circuit output; Described phase-locked loop circuit input is connected with electrical network; Described Drive Protecting Circuit drives described inverter circuit.Inverter circuit is connected with LCL filter circuit, and dsp controller is connected with A/D sample circuit, phase-locked loop pll circuit, Drive Protecting Circuit respectively, and Drive Protecting Circuit is connected with the switching tube of rectification circuit.The output of Drive Protecting Circuit controls the break-make of inverter circuit breaker in middle pipe.Inductance L and inductance L _g,and electric capacity C forms the filter circuit of single-phase photovoltaic grid-connected inverter, be used for the high order harmonic component of filtering grid-connected current, there is significant attenuation.U _dcfor inverter circuit DC capacitor voltage, i _gfor grid-connected current, u _sfor line voltage.

LCL type combining inverter power of the present invention control and active damping optimization method as follows:

1) in the starting point in each sampling period, A/D sample circuit is to line voltage u _swith grid-connected current i _gand inverter circuit DC capacitor voltage U _dcsample respectively, and give control module process by sampled data;

2) to grid-connected current i _gβ phase virtual orthographic signal i is obtained by all-pass filter _β, construct two-phase virtual orthographic system, do α β/dq coordinate transform and obtain single-phase grid-connected active current i _dwith grid-connected reactive current i _q;

3) to grid-connected active current i _dwith grid-connected reactive current i _qvalue and grid-connected current active current command value i _d ^*, reactive current command value i _q ^*carry out PI adjustment, do dq/ α β coordinate transform and obtain command signal i _{1 α}, i _{1 β}, wherein i _{1 α}it is the signal of control inverter;

4) introduce 3,5,7 subharmonic compensators, obtain offset current i ₃, instruction current i _{1 α}with offset current i ₃make difference and obtain current signal i ₀;

5) introduce feedback to grid-connected current and increase system damping, feedback factor is H ₁(s), current signal i ₀poor with value of feedback, obtain SPWM modulation wave signal d;

6) SPWM modulating wave and triangular carrier carry out bipolar modulation, draw the duty cycle signals of inverter circuit switching tube, through Drive Protecting Circuit, control opening and shutoff of inverter circuit switching tube.

Fig. 2 is that the LCL type combining inverter power of invention controls and active damping optimization method control block diagram.

By single order all-pass filter, construct i _β, its time delay sampling period T _s, it is fast that it follows the tracks of load dynamic change response, stability and real-time high, solve the problem that the data used of building method in the past have asynchronism.

$i_{\mathrm{\β}}\left(s\right)=\frac{{\mathrm{\ω}}_0-s}{{\mathrm{\ω}}_0+s}{i}_g\left(s\right)$

Can be obtained, through C by moment reactive power theory _{α β-pq}can obtain grid-connected current active current and reactive current component after coordinate transform under p-q rotating coordinate system, both obtain DC component I by low pass filter filtering of ac _pand I _q, be expressed as:

$\left[\begin{array}{c}{I}_p\\ I_q\end{array}\right]=\left[\begin{array}{c}\sqrt{2}{I}_{g1}cos{\mathrm{\θ}}_1\\ \sqrt{2}{I}_{g1}{\mathrm{sin\θ}}_1\end{array}\right]$

Wherein, I _g1for the effective value of fundamental current, θ ₁for the phase deviation of fundamental current.

Under p-q two-phase rotating coordinate system, grid-connected meritorious and reactive current component subtracts each other to obtain difference E with its command value respectively _p, E _qfor:

$\left\{\begin{array}{c}{E}_p=I_{sp}^{*}-I_p\\ E_q=I_{sq}^{*}-I_q\end{array}\right.$

E _pand E _qbe E at α β two-phase rest frame down conversion _αand E _β, wherein E _αand E _βbe respectively i _αand i _βwith the difference of its set-point, and E _αbe grid-connected current i simultaneously _swith grid-connected current command value i _s ^*difference, thus realize closed-loop control to grid-connected current.It regulates grid-connected PI that is meritorious and reactive current under p-q two-phase rotating coordinate system, converts under α β two-phase static coordinate.This controls can be expressed as under frequency domain:

$\left[\begin{array}{c}{i}_{1\mathrm{\α}}\left(s\right)\\ i_{1\mathrm{\β}}\left(s\right)\end{array}\right]=\frac{1}{2}\left[\begin{array}{c}\left(\begin{array}{c}{G}_{PI}(s+{\mathrm{j\ω}}_0)\\ +G_{PI}(s-{\mathrm{j\ω}}_0)\end{array}\right)\left(\begin{array}{c}-{\mathrm{jG}}_{PI}(s+{\mathrm{j\ω}}_0)\\ +{\mathrm{jG}}_{PI}(s-{\mathrm{j\ω}}_0)\end{array}\right)\\ \left(\begin{array}{c}{\mathrm{jG}}_{PI}(s+{\mathrm{j\ω}}_0)\\ -{\mathrm{jG}}_{PI}(s-{\mathrm{j\ω}}_0)\end{array}\right)\left(\begin{array}{c}{G}_{PI}(s+{\mathrm{j\ω}}_0)\\ +G_{PI}(s-{\mathrm{j\ω}}_0)\end{array}\right)\end{array}\right]\left[\begin{array}{c}{E}_{\mathrm{\α}}\left(s\right)\\ E_{\mathrm{\β}}\left(s\right)\end{array}\right]$

Wherein, i _{1 α}and i _{1 β}for the control signal that this controller exports.

Then have:

$\left[\begin{array}{c}{i}_{1\mathrm{\α}}\left(s\right)\\ i_{1\mathrm{\β}}\left(s\right)\end{array}\right]=\frac{1}{2}\left[\begin{array}{cc}{K}_p+\frac{K_{i}s}{s^2+{\mathrm{\ω}}_0^2}& -\frac{K_i{\mathrm{\ω}}_0}{s^2+{\mathrm{\ω}}_0^2}\\ \frac{K_i{\mathrm{\ω}}_0}{s^2+{\mathrm{\ω}}_0^2}& K_p+\frac{K_{i}s}{s^2+{\mathrm{\ω}}_0^2}\end{array}\right]\left[\begin{array}{c}{E}_{\mathrm{\α}}\left(s\right)\\ E_{\mathrm{\β}}\left(s\right)\end{array}\right]$

Wherein

E _β(s)＝((ω ₀-s)/(ω ₀+s))E _α(s)

Then grid-connected current difference E _αto inverter control command value i ₂transfer function G _c(s) be:

$G_c\left(s\right)==\frac{K_p{s}^3+(K_p{\mathrm{\ω}}_0+K_i)s^2+(K_p{\mathrm{\ω}}_0^2+2{\mathrm{\ω}}_0{K}_i)s+K_p{\mathrm{\ω}}_0^3-K_i{\mathrm{\ω}}_0^2}{s^3+{\mathrm{\ω}}_0{s}^2+{\mathrm{\ω}}_0^{2}s+{\mathrm{\ω}}_0^3}$

From the viewpoint controlled, G _cs () equivalence can become synchronous coordinate system PI wherein K under rest frame _p=0.05, K _i=10, ω ₀=2 π * 50, transfer function G _cs () is infinitely great in the gain of fundamental frequency place, very little in non-fundamental frequency place gain, it is identical that the zero steady-state error realizing grid-connected current controls to control (PR) control effects with ratio resonance, but the ratio of gains PR near fundamental frequency controls to want high, when can reduce mains frequency skew, on the impact of harmonic suppression effect.

Its single current feedback active damping control strategy elaborates in figure 3.

Fig. 3 is single current feedback active damping Optimal Control Strategy control block diagram of LCL type combining inverter.

Introduce this single current feedback, ignore the dead resistance of filter, now inverter output voltage u _invto current on line side i _gclosed loop transfer function, be:

$G_{u_{inv}}^{i_g}\left(s\right)=\frac{s+{\mathrm{\ω}}_d}{s({\mathrm{LL}}_g{\mathrm{Cs}}^3+{\mathrm{LL}}_g{\mathrm{C\ω}}_d{s}^2+(L+L_g)s+(L+L_g){\mathrm{\ω}}_d-K_d{K}_{inv}/T_s)}$

Its characteristic equation can be expressed as:

$D\left(s\right)={\mathrm{LL}}_{g}Cs(s+K_1{\mathrm{\ω}}_n)(s^2+2{\mathrm{\ξ\ω}}_n+{\mathrm{\ω}}_n^2)$

Wherein ξ is the target damping coefficient of system under this strategy, ω _nfor introducing the resonance frequency after feedback, K ₁for the limit introduced is to the distance of the imaginary axis and complex-conjugate poles to the coefficient ratio of imaginary axis distance.

Obtain according to the coefficient of same power is identical:

$\left\{\begin{array}{c}{\mathrm{\ω}}_n=\sqrt{1/(2K_1\mathrm{\ξ}+1)}{\mathrm{\ω}}_{res}\\ {\mathrm{\ω}}_d=(K_1+2\mathrm{\ξ}){\mathrm{\ω}}_n\\ K_d=T_s\[(L+L_g){\mathrm{\ω}}_d-K_1{\mathrm{\ω}}_n^3{\mathrm{LL}}_{g}C\]/K_{inv}\end{array}\right.$

From above formula, ω _ndeviate from the resonance frequency omega of LCL filter _res, and ω _nthan ω _reslittle.As selection ω _nduring for certain value, then K ₁the value of ζ is constant, if K ₁what become is increasing, and so ζ change is more and more less, then die down to the rejection ability of LCL resonance spikes; If it is increasing that ξ becomes, so K ₁what become is more and more less, be then difficult to the higher dynamic responding speed of maintenance one.Therefore K ₁, ζ must ensure that the prerequisite that system has good resonance spikes rejection ability and a very fast response speed gets off to design.

Can be obtained fom the above equation:

${\mathrm{\ω}}_d=(\sqrt{\frac{K_1}{\mathrm{\ξ}}}+2/\sqrt{\frac{K_1}{\mathrm{\ξ}}})\sqrt{K_1\mathrm{\ξ}/(2K_1\mathrm{\ξ}+1)}{\mathrm{\ω}}_{res}$

Work as K ₁=2 ζ, then ω _dthere is minimum to make the suppression of the stability of system and response speed and resonance spikes have optimal value, then have:

$\left\{\begin{array}{c}{\mathrm{\ω}}_d=4\sqrt{{\mathrm{\ξ}}^2/(4{\mathrm{\ξ}}^2+1)}{\mathrm{\ω}}_{res}\\ K_d=\frac{2T_s\mathrm{\ξ}}{K_{inv}\sqrt{(4{\mathrm{\ξ}}^2+1)}}{\mathrm{\ω}}_{res}\[2(L+L_g)-\frac{{\mathrm{LL}}_{g}C}{4{\mathrm{\ξ}}^2+1}{\mathrm{\ω}}_{res}^2\]\end{array}\right.$

ω _d, K _dvalue can be determined by ζ, therefore in single current feedback, two variablees of feedback factor reduce to a variable, and the resonance inhibition of ζ and system is proportionate, and just can change system damping by means of only ζ, simultaneously the stability margin of ζ variable effect system and response speed.As shown in table 1, along with the increase of ζ, the steady state error of system and Phase margin first increase and diminish afterwards; And ω _nsuccessively decrease always.In order to system has good transient process, usually require that Phase margin reaches 45 ° ~ 70 °.System has identical ζ, ω _nlarger, response speed is faster, in order to have good dynamic property, ω _ncan not be too small.

Get ζ=0.5 ~ 0.6, ω _n/ ω _resratio be 0.64 ~ 0.7, now system overshoot appropriateness, regulating time is shorter, has good inhibition to LCL resonance spikes, and system has dynamic property faster.

The present invention gives the method for designing of this single current feedback.When system parameters has certain range of choices, in satisfied increase system damping, under improving the prerequisite of the stability of a system and response speed requirement, its feedback parameter can be optimized further: (1) first according to parameter of inverter, determines K _cand K _drelation, and use K _drepresent K _c; (2) the later resonance frequency of supposition skew is determined, from stability and resonance rejection ability angle analysis, works as K ₁minimum ω can be obtained during=2 ζ _dmake systematic function best; (3) when changing according to ζ, the stability margin of system and response speed, determine the span of ζ; (4) adjust the value of ζ, make system have good stability and response speed faster.

Fig. 4 is K ₁transfer function during ratio different from ζ bode diagram.Work as K ₁>2 ζ, along with K ₁increase with the ratio of ζ, K ₁ω _nvalue become large, real pole departs from the imaginary axis, and dynamic performance strengthens, but it is deteriorated gradually to the inhibition of system damping, works as K ₁<2 ζ, resonance spikes rejection ability and K ₁=2 ζ are suitable, but along with K ₁successively decrease with the ratio of ζ, the bad dynamic performance of system, Phase margin diminishes, and magnitude margin increases, and the stability of system is deteriorated, and works as K ₁during=0.6 ζ, its phase frequency curve passes the frequency of-180 ° lower than the frequency of amplitude frequency curve through 0dB, and system is unstable.Therefore work as K ₁=2 ζ, system has optimum performance.Fig. 5 is line voltage u _scurrent i is surveyed with net _gsimulation waveform.Establish system simulation model with Matlab/Simulink, emulation initial condition is 500W/m ², ambient temperature 25 °.T=0s moment grid-connected inverters, local load does not access, and during 0.085s, illumination Intensity Abrupt is 1000W/m ², during 0.18s, when access load (3+j2) kVA, 0.265s, combining inverter provides reactive power.For the ease of observing, the line voltage u in figure _samplitude is 0.1 times of actual value.The system that can obtain has response speed fast.When accessing local load, inverter can adjust power coefficient, while providing active power to load, the object realizing reactive power compensation can be crossed, thus reach the quality of power supply improving electrical network tip, overall control reduces grid-connected aberration rate, improves the quality of power supply and the antijamming capability of photovoltaic parallel in system.

Claims (2)

1. LCL type single-phase grid-connected inverter power controls and an active damping optimization method, and it is characterized in that, the method is:

1) in the starting point in each sampling period, the A/D sample circuit of LCL type single-phase grid-connected inverter is to line voltage u _swith grid-connected current i _gand the inverter circuit DC capacitor voltage U of LCL type single-phase grid-connected inverter _dcsample respectively, and sampled data is given the control module process of LCL type single-phase grid-connected inverter;

2) to grid-connected current i _gβ phase virtual orthographic signal i is obtained by all-pass filter _β, construct two-phase virtual orthographic system, obtain two-phase quadrature current i _α, i _β:

$\left\{\begin{array}{c}{i}_{\mathrm{\&alpha;}}=i_g\\ i_{\mathrm{\&beta;}}=\frac{{\mathrm{\&omega;}}_0-s}{{\mathrm{\&omega;}}_0+s}{i}_g\end{array}\right.;$

Wherein, ω ₀for power frequency angular frequency; S=j ω, j are imaginary part unit symbols, and ω is electrical network angular frequency;

3) to i _α, i _βdo α β/dq coordinate transform and obtain single-phase grid-connected active current value i _dwith grid-connected reactive current value i _q;

4) to DC side reference voltage U _dc ^*with inverter circuit DC capacitor voltage U _dcbe PI to regulate, obtain the grid-connected current active current command value i of DC side voltage stabilizing link _d ^*, according to the reactive power Q that need compensate _sdetermine the command value i of reactive current _q ^*:

$I_q^{*}=\sqrt{2}{Q}_s^{*}/U_s;$

Wherein Q _s ^*for compensating reactive power amount, U _sfor the effective value of line voltage;

5) to single-phase grid-connected active current i _d, grid-connected current active current command value i _d ^*and grid-connected reactive current i _q, reactive current command value i _q ^*carry out PI adjustment respectively, and the adjusted value after PI regulates is done to dq/ α β coordinate transform and obtains command signal i _{1 α}, i _{1 β};

6) to grid-connected current i _gintroduce 3,5,7 subharmonic compensators, obtain offset current i ₃, and by command signal i _{1 α}with offset current i ₃make difference and obtain current signal i ₀;

7) to grid-connected current i _gintroduce feedback and increase system damping, obtain grid-connected current value of feedback; Wherein feedback factor is H ₁(s):

$H_1\left(s\right)=K_{d}s+\frac{K_c}{s+{\mathrm{\&omega;}}_d}s;$

Wherein K _d, K _cbe respectively grid-connected current differential, high fdrequency component coefficient; wherein, ω _resfor the resonance frequency of LCL filter, ξ is the target damping coefficient of LCL type inverter in grid-connected current feedback;

8) by current signal i ₀poor with grid-connected current value of feedback, obtain SPWM modulation wave signal d;

9) bipolar modulation is carried out to SPWM modulating wave and triangular carrier, obtain the duty cycle signals of inverter circuit switching tube, through the Drive Protecting Circuit of LCL type single-phase grid-connected inverter, control opening and shutoff of inverter circuit switching tube.

2. LCL type single-phase grid-connected inverter power according to claim 1 controls and active damping optimization method, it is characterized in that, described step 7) in, K _cwith K _dpass be:

K _c＝(1-T _sω _d)K _d/T _s；

ω _dand K _dvalue be:

$\left\{\begin{array}{c}{\mathrm{\&omega;}}_d=4\sqrt{{\mathrm{\&xi;}}^2/(4{\mathrm{\&xi;}}^2+1)}{\mathrm{\&omega;}}_{res}\\ K_d=\frac{2T_s\mathrm{\&xi;}}{K_{inv}\sqrt{(4{\mathrm{\&xi;}}^2+1)}}{\mathrm{\&omega;}}_{res}\&lsqb;2(L+L_g)-\frac{{\mathrm{LL}}_{g}C}{4{\mathrm{\&xi;}}^2+1}{\mathrm{\&omega;}}_{res}^2\&rsqb;\end{array}\right.;$

Wherein, ω _resfor the resonance frequency of LCL filter, ξ is the target damping coefficient of LCL type inverter in grid-connected current feedback, ω _nfor grid-connected current introduces the resonance frequency after feedback, K _invfor the equivalent gain of LCL type inverter, L, Lg are the inductance inductance value in LCL filter, and C is the capacitor's capacity of LCL filter, T _sfor the sampling period.