CN103455081A - Maximum power point tracking method based on disturbance observation - Google Patents

Abstract

The invention discloses a maximum power point tracking method based on disturbance observation. The method comprises the steps of firstly, sampling a photovoltaic array voltage, a grid voltage and a grid-connected current signal; then, establishing a dynamic model of a single-stage photovoltaic grid-connected generation system; finally, carrying out maximum power point tracking on the single-stage photovoltaic grid-connected generation system. According to the method, only the photovoltaic array voltage is detected, and a grid-connected reference current amplitude signal Iref is taken as an equivalent signal of output power of a grid-connected inverter, so that the influence on a maximum power point tracking algorithm caused by sampling quantization errors is lowered effectively, and the problems of the traditional disturbance observation methods that in the single-stage photovoltaic grid-connected generation system, the stability of the control strategy is poor and the bus voltage collapses or the output power oscillates are solved.

Description

The maximum power point tracing method of observing based on disturbance

Technical field

The invention belongs to the renewable generation of electricity by new energy technical field of distributed solar, relate to a kind of MPPT maximum power point tracking control strategy of applicable Single-Stage Grid Connected Solar Inverter System, be specifically related to a kind of maximum power point tracing method of observing based on disturbance.

Background technology

The characteristics of output power of photovoltaic cell has very strong non-linear, and its peak power output and peak power output point voltage and electric current are along with the factors vary such as unbalanced degree of temperature, intensity of illumination, illumination.Only have the effective MPPT maximum power point tracking algorithm of employing, could improve the utilization factor of photovoltaic generating system to the photovoltaic cell component electric energy.

At present, photovoltaic generating system realizes that the method for MPPT maximum power point tracking has a lot: determine voltage method, disturbance observation, increment conductance method, short-circuit current method etc., but these methods respectively have its relative merits and the scope of application.The control strategy that common disturbance observation fado is single order, by changing relevant controlled quentity controlled variable, make output power or some correlated variabless of photovoltaic array change, next step control mode of the location positioning of these variablees on curve before and after changing by judgement, thus make system works point progressively close to maximum power point.This control mode is feasible in the photovoltaic DC-to-AC converter of twin-stage or off-line type, and still its control strategy poor stability in the photovoltaic parallel in system of single stage type, will cause busbar voltage collapse or output power vibration, and system can't work.

Summary of the invention

The purpose of this invention is to provide a kind of maximum power point tracing method of observing based on disturbance; solved the problem of the traditional disturbance observation collapse of control strategy poor stability and busbar voltage or output power vibration in the photovoltaic parallel in system of single stage type, and be not subject to that algorithm is digitized to be affected.

The technical solution adopted in the present invention is: the maximum power point tracing method of observing based on disturbance, specifically according to following steps, implement:

Step 1: photovoltaic array voltage, line voltage and grid-connected current signal are sampled;

Step 2: the dynamic model of setting up Single-Stage Grid Connected Solar Inverter System;

Step 3: Single-Stage Grid Connected Solar Inverter System is carried out to MPPT maximum power point tracking.

Characteristics of the present invention also are,

Step 2 is wherein set up the dynamic model of Single-Stage Grid Connected Solar Inverter System, specifically according to following steps, implements:

With i _pV, i _c, i _outthe momentary current that means respectively photovoltaic array output momentary current, the instantaneous charging current of DC filter capacitor and filter capacitor aft section circuit, v _pVmean photovoltaic array output instantaneous voltage, p _outfor the photovoltaic array instantaneous output:

$i_{\mathrm{pv}}=i_c+i_{\mathrm{out}}=C\frac{{\mathrm{dv}}_{\mathrm{pv}}}{\mathrm{dt}}+\frac{p_{\mathrm{out}}}{v_{\mathrm{pv}}},$

In conjunction with photovoltaic cell component mathematical model I _z=f (I _ph, V)=I _ph-ε [exp (ξ V _z)-1] with above formula, obtain as shown in the formula the photovoltaic generating system dynamic model meaned, in formula,

$\left\{\begin{array}{c}{\stackrel{\·}{v}}_{\mathrm{pv}}=\frac{I_{\mathrm{ph}}}{C}-\frac{\mathrm{\ϵ}}{C}[\exp \left({\mathrm{\ξv}}_{\mathrm{pv}}\right)-1]-\frac{p_{\mathrm{out}}}{{\mathrm{Cv}}_{\mathrm{pv}}},\\ v_{\mathrm{pv}}=v_{\mathrm{pv}}\left(0\right)+{\stackrel{\·}{v}}_{\mathrm{pv}}\end{array}\right.$

Wherein, I _zfor photovoltaic module output current, I _phfor the equivalent photogenerated current of battery component, V _zfor photovoltaic module output voltage, ε=n _pi ₀, n _pfor batteries in parallel connection number of unit, I ₀for the P-N knot reverse saturation current of photovoltaic cell inside equivalent diode, ξ=q/n _ck _ctn _s, q is electronic charge, n _cfor the diode characteristic factor, k _cfor Boltzmann constant, T is photovoltaic cell absolute temperature, n _sfor the series-connected cell number of unit.

Step 3 wherein pair Single-Stage Grid Connected Solar Inverter System carries out MPPT maximum power point tracking, specifically according to following steps, implements:

(1) obtaining of photovoltaic array output power information:

Can make combining inverter output current real-time follow-up reference current signal owing to controlling by current controller, and line voltage is generally stable, so reference current amplitude I _refto the combining inverter output power, be directly proportional; Also have proportional relationship due to combining inverter output power and photovoltaic array output power again, thus under stable situation with reference current amplitude signal I _refreplace the equivalent signal of photovoltaic array output power, this stable situation refers to the situation after the array actual output voltage traces into reference voltage;

(2) photovoltaic array output voltage control:

Given magnitude of voltage V _refwith sample voltage value V _pVerror regulated through pi regulator, the output of pi regulator is given as the grid-connected current amplitude, by controlling grid-connected power, busbar voltage is controlled; Pi regulator passing ratio link k _upwith integral element k _uirealize; G _{inv (s)}the combining inverter link that comprises the Current Control link, I _refit is the amplitude of the given current signal of this link; I _invgrid-connected output current, it and line voltage v _gridproduct be grid-connected output power P _out; P _outwith V _pVrelation be reduced to: V _pV=f _pVC(V _pV(0), P _out);

(3) adopt disturbance to observe and carry out MPPT maximum power point tracking:

Take the photovoltaic array output voltage as regulating benchmark, according to different output power grades, adopt different disturbance bandwidth to carry out disturbance to the photovoltaic array reference voltage signal, and the reference current in observation contrast disturbance bandwidth changes to determine the direction of voltage disturbance: V _reffor photovoltaic array reference voltage, V _pVfor photovoltaic array output voltage sampled signal, e _vv _refwith V _pVerror signal, V _refsbe the central point voltage in the voltage disturbance scope, dV is the voltage disturbance amount, J _mxbe forward disturbance bandwidth, LOR represents perturbation direction, I _mfor the maximum I obtained in the disturbance cycle _refvalue, I _refamplitude given as the amplitude of grid-connected reference current signal or the active current signal is given; Control and make e by increment type PI _vbe tending towards 0, work as V _pVtenacious tracking V _refafter, with I _refinstead of optical photovoltaic array output power is as observed quantity; If this I _refvalue is greater than I _mvalue, incite somebody to action I now _refvalue is assigned to I _m, simultaneously voltage V now _refbe assigned to V _refs, as the central value of voltage disturbance, then with V _refsfor basis, continue V _refcarry out the voltage disturbance of dV size, when disturbance quantity dV reaches disturbance upper limit J _mxor disturbance lower limit-J _mxthe time in order to prevent from can't continuing to realize disturbance, must to the conversion perturbation direction; If this I _refvalue is less than or equal to I _mvalue, continue V _refcarry out disturbance; J _mxsize by I _refsize determine, due to the decline along with power, the I of unit _refvariation can cause the variation of larger array voltage, along with the decline of power, disturbance bandwidth J _mxalso increase, to cause I thereupon _refvariation, carry out observation and comparison, be equivalent to variable step and control.

The invention has the beneficial effects as follows:

(1) reduced to a great extent the impact of A/D sampling on the MPPT maximum power point tracking algorithm;

(2) guarantee in the situation that illumination variation is quite violent, system also can be stably to the electrical network feedback electric energy, not the collapse of reason busbar voltage and system is stopped power supply;

(3) the steady track error is little.

The accompanying drawing explanation

Fig. 1 is the impact that quantization error gathers the photovoltaic array output power, wherein (a) is the power collecting waveform under specified illumination condition, (b) be the power collecting waveform under 60% specified illumination condition, (c) be under 40% specified illumination condition the power collecting waveform, (d) be under 20% specified illumination condition the power collecting waveform;

Fig. 2 is photovoltaic array band power source realistic model;

Fig. 3 is the DC bus-bar voltage control block diagram;

Fig. 4 is two kinds of P-V, I-V family curves under different modes, and wherein (a) is array voltage and electric current phase multiplication, is (b) with I _refpower information method of equal value;

Fig. 5 is process flow diagram of the present invention;

Fig. 6 is two class Single-Stage Grid Connected Solar Inverter Systems, and wherein (a) is single-phase single-grade formula grid-connected photovoltaic system, is (b) three-phase single-level formula grid-connected photovoltaic system.

Embodiment

Below in conjunction with the drawings and specific embodiments, the present invention is described in detail.

When the MPPT maximum power point tracking algorithm adopts digitized form to realize, the digitizing meeting of some algorithm causes some impacts to the MPPT maximum power point tracking performance, even can make in some cases MPPT maximum power point tracking lose efficacy, in the situation that do not consider noise, quantization error is one of reason that causes digitizing MPPT maximum power point tracking algorithm to lose efficacy.

The digital sample resolution of voltage and electric current can be expressed as:

$r_v=\frac{V_{\mathrm{ms}}}{2^{N_c}}$ With $r_i=\frac{I_{\mathrm{ms}}}{2^{N_c}}$ （1）

Wherein, V _mswith I _msbe respectively the sampling range of A/D passage to voltage and electric current, N _cfor A/D Channel-shifted figure place.Quantization error refers to the difference of sampling numerical value and actual numerical value.Because common A/D passage all adopts house tail error, so quantization error is along with the continuous variation indentation variation of sample objects in the sampling range ability, this zig-zag peak value equates with corresponding sampling resolution, note e _qvwith e _qibe respectively the sample quantization error of voltage and electric current, have:

V _pv=V _pvc+ e _qvwith I _pv=I _pvc+ e _qi(2)

Wherein, V _pVwith I _pVbe respectively photovoltaic array actual output voltage and electric current, V _pVCwith I _pVCbe respectively the sampled value of photovoltaic array output voltage and output current, so exist:

P _pvc=P _pv-(V _pv·e _qi+I _pv·e _qv-e _qv·e _qi)=P _pv-e _qp （3）

Wherein, P _pVwith P _pVCbe respectively as photovoltaic array real output and sampled power, e _qpfor the power samples error.Due to V _pVin operating voltage range, all change continuously, and e _qvwith operating voltage V _pVlinear change be periodically zigzag and change, e _qiwith working current I _pVlinear change be periodically zigzag and change.

To current sample resolution, be 0.2A, voltage sample resolution is in the 1V situation, for different illumination intensity, the output electric weight of 50kW photovoltaic array is sampled, and obtains its P-V family curve and e _qpchange curve, as shown in Fig. 1 (a)～(d).Fig. 1 (a) exports for array the P-V curve obtained under specified power situation, although the sampled power value has discontinuous characteristics, but itself and real power value are substantially identical in operating voltage range, yet along with reducing of intensity of illumination, this coincideing is broken gradually, and the multi-peak characteristic even appears in the P-V family curve, and illumination is more weak, this multimodal characteristic is more serious, and Fig. 1 (d) has shown at the P-V family curve that approximately 20% specified illumination condition down-sampling obtains.The P-V family curve obtained due to the weak situation down-sampling of illumination has the characteristics of multi-peak, and traditional MPPT maximum power point tracking algorithm all be take, photovoltaic module is exported smooth P-V or the I-V family curve is the tracking foundation, so the discontinuous variation that the photovoltaic property curve after digital sample presents can affect the efficiency of traditional MPPT maximum power point tracking algorithm, even make the MPPT maximum power point tracking algorithm lose efficacy.

The present invention is based on the maximum power point tracing method that disturbance is observed, Fig. 6 is hardware circuit of the present invention basis, and wherein C is the DC side filter capacitor, and L is the AC filter inductance, specifically according to following steps, implements:

Step 1: photovoltaic array voltage, line voltage and grid-connected current signal are sampled;

Step 2: the dynamic model of setting up Single-Stage Grid Connected Solar Inverter System;

Because line voltage is normally stable, and the variation with grid-connected current does not change, so the amplitude of grid-connected current size is directly proportional to the output power of combining inverter, the grid-connected current of take be take output power as controlled quentity controlled variable as controlled quentity controlled variable can be equivalent to, so can set up the realistic model of photovoltaic array band power source load as shown in Figure 2, ignore the pressure drop of anti-reverse charging diode, the voltage at capacitor C two ends equates with photovoltaic array voltage, with i _pV, i _c, i _outthe momentary current that means respectively photovoltaic array output momentary current, the instantaneous charging current of DC filter capacitor and filter capacitor aft section circuit, v _pVmean photovoltaic array output instantaneous voltage, p _outfor the photovoltaic array instantaneous output, exist:

$i_{\mathrm{pv}}=i_c+i_{\mathrm{out}}=C\frac{{\mathrm{dv}}_{\mathrm{pv}}}{\mathrm{dt}}+\frac{p_{\mathrm{out}}}{v_{\mathrm{pv}}}---\left(4\right)$

In conjunction with photovoltaic cell component mathematical model (I _z=f (I _ph, V)=I _ph-ε [exp (ξ V _z)-1]) can obtain with formula (4) the photovoltaic generating system dynamic model meaned suc as formula (5).In formula,

$\left\{\begin{array}{c}{\stackrel{\·}{v}}_{\mathrm{pv}}=\frac{I_{\mathrm{ph}}}{C}-\frac{\mathrm{\ϵ}}{C}[\exp \left({\mathrm{\ξv}}_{\mathrm{pv}}\right)-1]-\frac{p_{\mathrm{out}}}{{\mathrm{Cv}}_{\mathrm{pv}}},\\ v_{\mathrm{pv}}=v_{\mathrm{pv}}\left(0\right)+{\stackrel{\·}{v}}_{\mathrm{pv}}\end{array}\right.---\left(5\right)$

Wherein, I _zfor photovoltaic module output current, I _phfor the equivalent photogenerated current of battery component, V _zfor photovoltaic module output voltage, ε=n _pi ₀(n _pfor batteries in parallel connection number of unit, I ₀p-N knot reverse saturation current for photovoltaic cell inside equivalent diode), ξ=q/n _ck _ctn _s(q is electronic charge, n _cfor the diode characteristic factor, k _cfor Boltzmann constant, T is photovoltaic cell absolute temperature, n _sfor the series-connected cell number of unit).

Step 3: Single-Stage Grid Connected Solar Inverter System is carried out to MPPT maximum power point tracking.

This novel disturbance observation is being stablized on the basis of busbar voltage, change reference voltage level, when feedback voltage and observation output power value after given voltage equates, and take this point voltage value and this point output power value as according to changing given voltage to realize the peak power output tracking of pair array.At first to guarantee the stable of busbar voltage in the system course of normal operation, in busbar voltage, under stable prerequisite, go again the regulation output electric current to feed back to the power of electrical network with control.So just, can guarantee in the situation that illumination variation is quite violent, system also can be stably to the electrical network feedback electric energy, not the collapse of reason busbar voltage and system is stopped power supply.Specifically be divided into again following step:

(1) the photovoltaic array output power information obtains

Can make combining inverter output current real-time follow-up reference current signal owing to controlling by current controller, and line voltage is generally stable, so reference current amplitude I _refto the combining inverter output power, be directly proportional.Also there is proportional relationship due to combining inverter output power and photovoltaic array output power again, so can use reference current amplitude signal I fully under stable situation _refreplace the equivalent signal of photovoltaic array output power, this stable situation refers to the situation after the array actual output voltage traces into reference voltage.

Fig. 4 is two kinds of resulting P-V of different modes and I-V family curve.Wherein, Fig. 4 (a) is sampled light photovoltaic array output voltage and output current, by the P-V family curve drawn after multiplying; Fig. 4 (b) is with grid-connected reference current amplitude signal I _refthe I-V family curve that replaces the photovoltaic array output power.Visible by contrasting, when illumination variation, the curvilinear characteristic of two kinds of waveforms is basically identical, thereby has proved and use variable I _refthe feasibility that replaces the photovoltaic array output power.Obviously see that from Fig. 4 (a) there are a plurality of sawtooth like shape peak values in the P-V family curve, be unfavorable for that the tracking of maximum power point is controlled; From Fig. 4 (b), the I-V family curve has relatively level and smooth unimodal value characteristics, be applicable to very much being used as tracking target, so the present invention is with I _refreplace the photovoltaic array output power to realize MPPT maximum power point tracking.

(2) photovoltaic array output voltage control strategy

In order to make photovoltaic array output voltage tracing preset voltage, can adopt control block diagram as shown in Figure 3 to be controlled it.In Fig. 3, given magnitude of voltage V _refwith sample voltage value V _pVerror regulated through pi regulator, the output of pi regulator is given as the grid-connected current amplitude, so the method is controlled busbar voltage by controlling grid-connected power; Pi regulator is passing ratio link k _upwith integral element k _uirealize; G _{inv (s)}the combining inverter link that comprises the Current Control link, I _refit is the amplitude of the given current signal of this link; I _invgrid-connected output current, it and line voltage v _gridproduct be grid-connected output power P _out; P _outwith V _pVrelation can describe by formula (5), be reduced to: V _pV=f _pVC(V _pV(0), P _out).The method realizes in the mode of outer voltage current inner loop, and interior ring controlled frequency is fast, to realize the quick tracking to set-point, the outer shroud control cycle mutually internally ring slowly to realize and the decoupling zero of interior ring, due to P _outrate of change and V _pVrate of change oppositely relevant, so can realize respectively that by the method the Linear Control of grid-connected current and the local linear of busbar voltage control.

(3) realization of modified disturbance observation method

Novel disturbance observation: take the photovoltaic array output voltage as regulating benchmark, according to different output power grades, adopt different disturbance bandwidth to carry out disturbance to the photovoltaic array reference voltage signal, and observe the interior reference current of contrast disturbance bandwidth change to determine the direction of voltage disturbance, the specific implementation flow process is as shown in Figure 5.In figure, V _reffor photovoltaic array reference voltage, V _pVfor photovoltaic array output voltage sampled signal, e _vv _refwith V _pVerror signal, V _refsbe the central point voltage in the voltage disturbance scope, dV is the voltage disturbance amount, J _mxbe forward disturbance bandwidth, LOR represents perturbation direction, I _mfor the maximum I obtained in the disturbance cycle _refvalue, and I _refamplitude given as the amplitude of grid-connected reference current signal or the active current signal is given.Control and make e by increment type PI _vbe tending towards 0, work as V _pVtenacious tracking V _ref(for example time delay count value j1>=10) afterwards, with I _refinstead of optical photovoltaic array output power is as observed quantity.If this I _refvalue is greater than I _mvalue, incite somebody to action I now _refvalue is assigned to I _m, simultaneously voltage V now _refbe assigned to V _refs, as the central value of voltage disturbance, then with V _refsfor basis, continue V _refcarry out the voltage disturbance of dV size, when disturbance quantity dV reaches disturbance upper limit J _mxor disturbance lower limit-J _mxthe time in order to prevent from can't continuing to realize disturbance, must to the conversion perturbation direction; If this I _refvalue is less than or equal to I _mvalue, continue V _refcarry out disturbance.J _mxsize by I _refsize determine, due to the decline along with power, the I of unit _refvariation can cause the variation of larger array voltage, so along with the decline of power, disturbance bandwidth J _mxalso should increase, to cause I thereupon _refvariation, thereby can carry out observation and comparison, this is equivalent to variable step and controls.

Its steady track error of disturbance observation of the present invention is little, particularly in the miniwatt situation, its quiescent potential approaches maximum power point voltage very much, increase along with output power, the voltage disturbance scope reduces gradually, and under steady state conditions, its operating voltage approaches the maximum power point voltage of photovoltaic array more.Although the sampling of power still is subject to the impact of quantization error, but it does not have the multi-peak characteristic, do not depart from its maximum power point tracking error phenomenon far away so this algorithm can not produce because of the power of illumination, solved tracking error phenomenon under the steady state conditions caused due to quantization error.

Claims (3)

1. the maximum power point tracing method of observing based on disturbance, is characterized in that, specifically according to following steps, implements:

Step 1: photovoltaic array voltage, line voltage and grid-connected current signal are sampled;

Step 2: the dynamic model of setting up Single-Stage Grid Connected Solar Inverter System;

Step 3: Single-Stage Grid Connected Solar Inverter System is carried out to MPPT maximum power point tracking.

2. the maximum power point tracing method of observing based on disturbance according to claim 1, is characterized in that, described step 2 is set up the dynamic model of Single-Stage Grid Connected Solar Inverter System, specifically according to following steps, implements:

With i _pV, i _c, i _outthe momentary current that means respectively photovoltaic array output momentary current, the instantaneous charging current of DC filter capacitor and filter capacitor aft section circuit, v _pVmean photovoltaic array output instantaneous voltage, p _outfor the photovoltaic array instantaneous output:

$i_{\mathrm{pv}}=i_c+i_{\mathrm{out}}=C\frac{{\mathrm{dv}}_{\mathrm{pv}}}{\mathrm{dt}}+\frac{p_{\mathrm{out}}}{v_{\mathrm{pv}}},$

In conjunction with photovoltaic cell component mathematical model I _z=f (I _ph, V)=I _ph-ε [exp (ξ V _z)-1] with above formula, obtain as shown in the formula the photovoltaic generating system dynamic model meaned, in formula,

$\left\{\begin{array}{c}{\stackrel{\·}{v}}_{\mathrm{pv}}=\frac{I_{\mathrm{ph}}}{C}-\frac{\mathrm{\ϵ}}{C}[\exp \left({\mathrm{\ξv}}_{\mathrm{pv}}\right)-1]-\frac{p_{\mathrm{out}}}{{\mathrm{Cv}}_{\mathrm{pv}}},\\ v_{\mathrm{pv}}=v_{\mathrm{pv}}\left(0\right)+{\stackrel{\·}{v}}_{\mathrm{pv}}\end{array}\right.$

Wherein, I _zfor photovoltaic module output current, I _phfor the equivalent photogenerated current of battery component, V _zfor photovoltaic module output voltage, ε=n _pi ₀, n _pfor batteries in parallel connection number of unit, I ₀for the P-N knot reverse saturation current of photovoltaic cell inside equivalent diode, ξ=q/n _ck _ctn _s, q is electronic charge, n _cfor the diode characteristic factor, k _cfor Boltzmann constant, T is photovoltaic cell absolute temperature, n _sfor the series-connected cell number of unit.

3. the maximum power point tracing method of observing based on disturbance according to claim 1, is characterized in that, described step 3 pair Single-Stage Grid Connected Solar Inverter System carries out MPPT maximum power point tracking, specifically according to following steps, implements:

(1) obtaining of photovoltaic array output power information:

Can make combining inverter output current real-time follow-up reference current signal owing to controlling by current controller, and line voltage is generally stable, so reference current amplitude I _refto the combining inverter output power, be directly proportional; Also have proportional relationship due to combining inverter output power and photovoltaic array output power again, thus under stable situation with reference current amplitude signal I _refreplace the equivalent signal of photovoltaic array output power, this stable situation refers to the situation after the array actual output voltage traces into reference voltage;

(2) photovoltaic array output voltage control:

Given magnitude of voltage V _refwith sample voltage value V _pVerror regulated through pi regulator, the output of pi regulator is given as the grid-connected current amplitude, by controlling grid-connected power, busbar voltage is controlled; Pi regulator passing ratio link k _upwith integral element k _uirealize; G _{inv (s)}the combining inverter link that comprises the Current Control link, I _refit is the amplitude of the given current signal of this link; I _invgrid-connected output current, it and line voltage v _gridproduct be grid-connected output power P _out; P _outwith V _pVrelation be reduced to: V _pV=f _pVC(V _pV(0), P _out);

(3) adopt disturbance to observe and carry out MPPT maximum power point tracking:

Take the photovoltaic array output voltage as regulating benchmark, according to different output power grades, adopt different disturbance bandwidth to carry out disturbance to the photovoltaic array reference voltage signal, and the reference current in observation contrast disturbance bandwidth changes to determine the direction of voltage disturbance: V _reffor photovoltaic array reference voltage, V _pVfor photovoltaic array output voltage sampled signal, e _vv _refwith V _pVerror signal, V _refsbe the central point voltage in the voltage disturbance scope, dV is the voltage disturbance amount, J _mxbe forward disturbance bandwidth, LOR represents perturbation direction, I _mfor the maximum I obtained in the disturbance cycle _refvalue, I _refamplitude given as the amplitude of grid-connected reference current signal or the active current signal is given; Control and make e by increment type PI _vbe tending towards 0, work as V _pVtenacious tracking V _refafter, with I _refinstead of optical photovoltaic array output power is as observed quantity; If this I _refvalue is greater than I _mvalue, incite somebody to action I now _refvalue is assigned to I _m, simultaneously voltage V now _refbe assigned to V _refs, as the central value of voltage disturbance, then with V _refsfor basis, continue V _refcarry out the voltage disturbance of dV size, when disturbance quantity dV reaches disturbance upper limit J _mxor disturbance lower limit-J _mxthe time in order to prevent from can't continuing to realize disturbance, must to the conversion perturbation direction; If this I _refvalue is less than or equal to I _mvalue, continue V _refcarry out disturbance; J _mxsize by I _refsize determine, due to the decline along with power, the I of unit _refvariation can cause the variation of larger array voltage, along with the decline of power, disturbance bandwidth J _mxalso increase, to cause I thereupon _refvariation, carry out observation and comparison, be equivalent to variable step and control.

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