CN106200752A - A kind of photovoltaic array under local shadow maximal power tracing System with Sliding Mode Controller - Google Patents

Abstract

The invention discloses a kind of photovoltaic array under local shadow maximal power tracing System with Sliding Mode Controller, first the output power curve of photovoltaic array is scanned, record global maximum power point, introduce sliding formwork control in this process, substantially reduce sweep time；Then use sliding formwork maximum power tracking method by the operating point immediate stability of photovoltaic array in maximum power point, reduce power swing during steady-state operation.Further it is proposed that a kind of new open-circuit voltage detection method, can carry out with power scan simultaneously, be not required to take the extra time.This control system can realize the maximum power tracing of photovoltaic array under the conditions of local shades.Not only there is good dynamic response performance, and reduce the power loss in whole tracing process, improve the efficiency of whole photovoltaic generating system.

Description

A kind of photovoltaic array under local shadow maximal power tracing System with Sliding Mode Controller

Technical field

The present invention relates to photovoltaic control field, specifically a kind of photovoltaic array under local shadow maximal power tracing sliding formwork controls system System.

Background technology

Photovoltaic power generation technology because of its cleaning, the advantage such as easy to use and of great interest.But photovoltaic generation there is also The shortcoming of inefficiency, hinders its development.At present, MPPT controls to be one of basic measures improving photovoltaic efficiency. The disturbance observation method of routine, conductance increment method etc. can track the maximum power point of photovoltaic array when uniform illumination.But, Owing to the change of external environment condition causes photovoltaic array local shades occur so that it is special that the curve of output of photovoltaic array presents multi-peak Property.Now, conventional MPPT controls to be easily trapped into local maximum power point (local maximum power point, LMPP) Rather than global maximum power point (global maximum power point, GMPP), have a strong impact on the effect of photovoltaic generating system Rate.

At present, for the multi-peak maximal power tracing problem of photovoltaic array under the conditions of local shades, Chinese scholars proposes Many methods.Patel, H, Agarwal, V indicate that the power extreme point of photovoltaic array is single in global maximum power point both sides Adjust the feature successively decreased, and propose corresponding MPPT algorithm, but the method is only applicable to the situation of simple optical photograph, in complexity Under illumination, the method is the most inapplicable.Qi Jun points out on the output characteristic curve of photovoltaic array, global maximum power point place Interval usually contain Upv/Ipv=Uoc/Isc this point, wherein Uoc and Isc is respectively the open-circuit voltage of photovoltaic array and short Road electric current, the method needs open-circuit voltage and the short circuit current of precise measuring photovoltaic array.Chen Kai is according to each in photovoltaic array The output voltage of photovoltaic module judges whether shade occurs and the position of global maximum power point, and the method needs to measure each The output voltage of photovoltaic module, adds system cost.B.N.Alajmi,K.H.Ahmed,S.J.Finney,B.W. Williams uses fuzzy control to realize the MPPT maximum power point tracking of photovoltaic array, and also some scholars proposes respectively based on grain Swarm optimization and the overall MPPT control strategy of artificial neural network algorithm.These intelligent algorithms generally have control complexity, The shortcomings such as inefficiency.Scholar is also had to propose the MPPT control strategy controlled under uniform illumination, the method pair based on sliding formwork The change of illumination and load has stronger robustness.But have no that sliding formwork controls the MPPT under the conditions of local shades and controls In application.

Summary of the invention

It is an object of the invention to provide a kind of photovoltaic array under local shadow maximal power tracing System with Sliding Mode Controller, to solve The problem proposed in above-mentioned background technology.

For achieving the above object, the present invention provides following technical scheme:

A kind of photovoltaic array under local shadow maximal power tracing System with Sliding Mode Controller, step is as follows:

(1) initial voltage reference value U is set_refIt is 0；

(2) by the output voltage U of photovoltaic array_pvGradually rise with certain step-length, real-time voltage reference value U_ref(k) =U_ref(k-1)+Δ U, detects the output electric current i of photovoltaic array simultaneously_pvWith photovoltaic array output P_pv；

(3) during step (2), peak power storage program is performed, it is thus achieved that global maximum power point P_maxAnd the overall situation is High-power point voltage U_max；

(4) in the scanning process of step (2), the output electric current i in real time of contrast photovoltaic array_pvWhether less than current threshold i_setIf, the output electric current i in real time of photovoltaic array_pvLess than current threshold i_set, then carry out next step, otherwise proceed step Suddenly (2), current threshold i_setChoosing according to the actual requirements, the value chosen is the least, detected open-circuit voltage U_ocMore Accurately；

(5) open-circuit voltage U_ocValue is output electric current i_pvLess than current threshold i_setTime photovoltaic array output voltage U_pv(k)；

(6) by voltage reference value U_refIt is set as the global maximum power point voltage U tracked_max；

(7) call sliding formwork scanning subprogram, make the actual output voltage U of photovoltaic array_pvMove closer in global maximum power Point voltage U_max；

(8) U is worked as_pvAnd U_maxDifference less than set the first threshold voltage U_set1Time, carry out next step；

(9) call sliding formwork MPPT program, photovoltaic array is stable at global maximum power point；

(10) photovoltaic system realtime power P is calculated_pvWith realtime power variation delta P_pv；

(11) realtime power variation delta P is judged_pvWhether more than changed power threshold values Δ P_set, changed power threshold values Δ P_set Set according to actual light conditions, if realtime power variation delta P_pvMore than changed power threshold values Δ P_set, then carry out next step, Otherwise remain on state；

(12) photovoltaic array current output voltage U is judged_pvPosition, compare (U_pv-0.6U_oc/ N) whether more than (0.85U_oc- U_pv), if being more than, carrying out step (12), otherwise carrying out step (9)；

(13) setting voltage reference value U_refFor 0.85U_oc；

(14) call sliding formwork scanning subprogram, photovoltaic array output voltage will be gradually increasing close to 0.85 from current point of operation U_oc；

(15) photovoltaic array output voltage U is judged_pvWhether close to 0.85U_oc, when both differences are less than the second threshold voltage U_set2Time, carry out next step；

(16) by voltage reference value U_refIt is set as 0.6U_oc/N；

(17) call sliding formwork scanning subprogram, make photovoltaic array output voltage will be gradually reduced close to 0.6 from current point of operation U_oc/ N, performs peak power storage program, it is thus achieved that global maximum power point and global maximum power point voltage U simultaneously_max；

(18) photovoltaic array current output voltage U is judged_pvWhether close to 0.6U_oc/ N, when both differences are less than tertiary voltage Threshold values U_set3Time, carry out step (6), otherwise proceed step (16)；

(19) setting voltage reference value U_refFor 0.6U_oc/N；

(20) call sliding formwork scanning subprogram, photovoltaic array output voltage will be gradually increasing close to 0.6 from current point of operation U_oc/N；

(21) photovoltaic array output voltage U is judged_pvWhether close to 0.6U_oc/ N, when both differences are less than tertiary voltage threshold values U_set3Time, carry out next step；

(22) by voltage reference value U_refIt is set as 0.85U_oc,

(23) call sliding formwork scanning subprogram, make photovoltaic array output voltage will be gradually reduced close to 0.85 from current point of operation U_oc, perform peak power storage program, it is thus achieved that global maximum power point and global maximum power point voltage U simultaneously_max；

(24) photovoltaic array current output voltage U is judged_pvWhether close to 0.85U_oc, when both differences are less than the second voltage valve Value U_set2Time, carry out step (6), otherwise proceed step (22).

As the further scheme of the present invention: the step of described peak power storage program is as follows:

(1) global maximum power point P is set_maxAnd global maximum power point voltage U_maxInitial value is 0；

(2) the real-time output voltage U of photovoltaic array is obtained_pv(k) and in real time output electric current i_pv(k)；

(3) photovoltaic array realtime power P is calculated_pv(k), P_pv(k)=U_pv(k)*i_pv(k)；

(4) photovoltaic array realtime power P is judged_pvK whether () be more than global maximum power point P_maxIf being more than, then carry out Step (5), otherwise carries out step (6)；

(5) global maximum power point P is set_max=P_pv(k), global maximum power point voltage U_max=U_pv(k), weight Multiple step (2)；

(6) global maximum power point P_maxWith global maximum power point voltage U_maxNumerical value is constant, repeats step (2).

Compared with prior art, the invention has the beneficial effects as follows: 1) this control system accurately can follow the trail of under shadow condition Global maximum power point；2) determine optimum scanning direction and optimum scanning scope according to the operation characteristic of photovoltaic array, and carry Go out the power scan system controlled based on sliding formwork, significantly reduce the power swing in sweep time and scanning process；3) should System makes open-circuit voltage detection carry out with power scan simultaneously, is not required to take the extra time, enhances the logical of algorithm The property used；4) this system uses sliding formwork MPPT control method that photovoltaic array is stable at global maximum power point, reduces stable state Power swing.

Accompanying drawing explanation

Fig. 1 is to be respectively adopted optimum scanning direction and the contrast signal scanned from the high border of optimum sweep limits to lower boundary Figure.

Fig. 2 be global maximum power point when being positioned at various diverse location three kinds of scan methods need the voltage range length pair of scanning Ratio.

Fig. 3 is the structural representation of photovoltaic array under local shadow maximal power tracing System with Sliding Mode Controller.

Fig. 4 is that in photovoltaic array under local shadow maximal power tracing System with Sliding Mode Controller, the flow process of peak power storage program is shown It is intended to.

Detailed description of the invention

Below in conjunction with the accompanying drawing in the embodiment of the present invention, the technical scheme in the embodiment of the present invention is carried out clearly and completely Describe, it is clear that described embodiment is only a part of embodiment of the present invention rather than whole embodiments.Based on this Embodiment in invention, the every other reality that those of ordinary skill in the art are obtained under not making creative work premise Execute example, broadly fall into the scope of protection of the invention.

The technical scheme that the present invention provides includes two parts: the maximum power tracing method that (1) controls based on sliding formwork；(2) The power scan method controlled based on sliding formwork.Initially with sliding formwork power scan method, the output of photovoltaic array is swept Retouch, it is thus achieved that global maximum power point, then use sliding formwork maximum power tracking method to be existed by the stable output power of photovoltaic array Global maximum power point.

1. the maximum power tracking method controlled based on sliding formwork

From the output characteristics of photovoltaic cell, meet equation when photovoltaic cell Maximum Power Output:

$\frac{\∂P_{\mathrm{pv}}}{\∂i_{\mathrm{pv}}}=\frac{\∂\left(u_{\mathrm{pv}}{i}_{\mathrm{pv}}\right)}{\∂i_{\mathrm{pv}}}=i_{\mathrm{pv}}\frac{\∂u_{\mathrm{pv}}}{\∂i_{\mathrm{pv}}}+u_{\mathrm{pv}}+0---\left(1\right)$

Therefore choosing sliding-mode surface is:

$s_1=i_{\mathrm{pv}}\frac{\∂u_{\mathrm{pv}}}{\∂i_{\mathrm{pv}}}+u_{\mathrm{pv}}---\left(2\right)$

The control input of sliding mode controller can be made up of on-off control and equivalent control.The effect of on-off control is to make system exist Arbitrary original state arrives sliding-mode surface within the limited time.The effect of equivalent control is to make system variable in the ideal situation Move along sliding-mode surface.Use the super-twisting algorithm design on-off control in Second Order Sliding Mode Control herein, obtain the switch control of system It is made as:

$\mathrm{\Δ}{D}_1=k_1\sqrt{\left|s_1\right|}\mathrm{sgn}\left(s_1\right)+k_2\∫\mathrm{sgn}\left(s_1\right)\mathrm{dt}---\left(2\right)$

K in formula₁, k₂For normal number.Equivalent control is obtained by formula (4):

${\stackrel{\·}{s}}_1={\left[\frac{\∂s_1}{\∂x}\right]}^T\stackrel{\·}{x}={\left[\frac{\∂s_1}{\∂x}\right]}^T(f(t,x)+g(t,x)D_{\mathrm{eq}})=0---\left(4\right)$

Formula (1) and formula (2) substitution formula (4) are obtained equivalent control is:

$D_{\mathrm{eq}1}={-\left[\frac{\∂s_1}{\∂x}\right]}^{T}f(t,x)/{\left[\frac{\∂s_1}{\∂x}\right]}^{T}g(t,x)=1-\frac{u_{\mathrm{pv}}}{u_o}---\left(5\right)$

Therefore, the control input that can obtain sliding formwork MPPT controller is:

D₁=Δ D₁+D_eq1 (6)

Owing to dutycycle D of Boost meets 0≤D≤1, it is therefore desirable to the control input to sliding mode controller limits Width.After obtaining dutycycle, obtain PWM modulation signal through pulse-width modulation circuit, be input in IGBT realize Boost The control of changer.

2. output scanning

(1) scanning imaging system entry condition

When shade generation or intensity of illumination generation large change, the output of photovoltaic array also can occur large change.Cause This, exceed certain threshold value entry condition as scanning imaging system using photovoltaic array output variable quantity:

ΔP_pv=P_pv(k)-P_pv(k-1)>ΔP_set (7)

In formula, P_pv(k),P_pv(k-1) this sampling of photovoltaic array output and sampled value last time, Δ P it are respectively_setFor setting Power variation threshold value.

(2) optimum sweep limits

The output extreme point of photovoltaic array can only be at interval [0.8U_{oc_array}/N,0.8U_{oc_array}Distribution, wherein U in]_{oc_array} For the open-circuit voltage of photovoltaic array, N is the serial number of photovoltaic array.Accordingly, it is considered to certain error, herein by photovoltaic battle array The voltage scan range of row is set to 0.6U_{oc_array}/ N～0.85U_{oc_array}.Own owing to this sweep limits contains photovoltaic array Possible power extreme point, so any one extreme point will not be lost.Additionally, compared with whole scan, this scan method There is a following two advantage:

1) sweep limits is reduced.As a example by N=4, the method by the voltage scan range of photovoltaic array from 0～U_{oc_array} It is reduced to 0.15U_{oc_array}～0.85U_{oc_array}, reduce 30%. thus reduce sweep time.

2) from the output characteristics of photovoltaic array, when the voltage of photovoltaic array is near no-voltage and open-circuit voltage, light The output of photovoltaic array is close to zero.Therefore, this method avoid the output work that photovoltaic array during power scan is relatively low Rate, thus avoid bigger power swing.

(3) optimum scanning direction

Scanning to photovoltaic array output can be from 0.85U_{oc_array}Start, to 0.6U_{oc_array}/ N terminates, it is also possible to anti- Scanning direction.In order to avoid the multiple scanning to photovoltaic array output power curve, to reduce unnecessary power loss, this Literary composition determines scanning direction according to the current point of operation voltage of photovoltaic array.When the current point of operation voltage of photovoltaic array is close 0.85U_{oc_array}Time, power scan is from 0.85U_{oc_array}Start；Otherwise, power scan is from 0.6U_{oc_array}/ N starts.

Peak power process of the present invention comprises two steps: is first scanned the output in the range of most preferably being retouched, obtains Obtain global maximum power point, then the operating point of photovoltaic array is placed in global maximum power point.Optimum scanning scope can be divided Becoming N-1 interval, each length of an interval degree is 0.8V_{oc_module}.In scanning process, inswept interval is the most, during scanning Between the most, simultaneously merit loss the biggest.Use the scanning process in optimum scanning direction as shown in Figure 1.Assume that system is at the moon Run and maximum power point during shadow situation 1, when illumination is become shadow condition 2 from shadow condition 1, used and most preferably sweep Retouch direction and have only to scan 4 voltage ranges, and from the high border of optimum sweep limits to lower boundary scan time, need scanning 8 voltage ranges, it can be seen that when using optimum scanning direction, sweep interval reduces half, sweep time and power Loss is obtained for reduction.

Fig. 2 gives photovoltaic array serial number when being 4, three kinds of scanning sides when global maximum power point is positioned at various diverse location Method needs the voltage range length of scanning.In figure, abscissa represents the position of global maximum power point, Section 1 and in bracket Binomial is respectively the position of global maximum power point before and after illumination variation, wherein numeral " 1 ", " 2 ", " 3 " and " 4 " generation respectively Table 0.2U_{oc_array}、0.4U_{oc_array}、0.6U_{oc_array}And 0.8U_{oc_array}.It can be seen that in 16 kinds of feelings altogether In condition, 16 kinds of situations are wherein had to use the optimum scanning direction proposed to need the voltage range length one direction to be compared of scanning Scanning is short, thus saves sweep time, decreases the power loss in scanning process.

(4) open-circuit voltage detection

The scanning of photovoltaic array output is it is to be appreciated that the open-circuit voltage information of photovoltaic array, but photovoltaic module manufacturer gives Go out is only the parameter of photovoltaic module under nominal environmental.In actual motion, illumination, temperature and photovoltaic module Aging all can impact by open-circuit voltage, thus affect the scanning of output.To this end, set forth herein a kind of new open circuit Voltage detection method, the method is based on the fact that propose, it may be assumed that when the output voltage of photovoltaic array is open-circuit voltage, Its output electric current is zero.

When needing the open-circuit voltage detecting photovoltaic array, the output voltage of photovoltaic array is gradually risen with certain step-length, Detect the output electric current of photovoltaic array simultaneously, when photovoltaic array output electric current is less than certain threshold value, the output of photovoltaic array Voltage is just close to open-circuit voltage, and it is the least that current threshold is chosen, and detected open-circuit voltage is the most accurate.It may be noted that , the detection of open-circuit voltage and the scanning of output can carry out simultaneously, therefore, and the open-circuit voltage scanning side proposed Method is not required to take the extra time.Additionally, i.e. can complete open-circuit voltage detection when system brings into operation, it is possible to With in running at any time open-circuit voltage correct, with the change of response environment.Owing to adding open-circuit voltage detection Program, so this algorithm is not rely on the Given information of photovoltaic array, has stronger versatility.

(5) fast scanning method controlled based on sliding formwork

The scanning speed of photovoltaic array output depends on the voltage adjustment time of Boost.Traditional dutycycle is disturbed Although dynamic method also can realize the regulation of voltage, however it is necessary that the delay of long period, had a strong impact on scanning speed.Therefore, Set forth herein the fast scanning method controlled based on sliding formwork.The control target of sliding formwork scan method is to make the output electricity of photovoltaic array Pressure arrives rapidly reference value, therefore chooses following sliding-mode surface:

$s_2=u_{\mathrm{pv}}^{*}-u_{\mathrm{pv}}---\left(8\right)$

The on-off control of system and equivalent control can be obtained respectively as shown in formula (9) and formula (10) by the method described in Section 1:

$\mathrm{\Δ}{D}_2=-k_3\sqrt{\left|s_2\right|}\mathrm{sgn}\left(s_2\right)-k_4\∫\mathrm{sgn}\left(s_2\right)\mathrm{dt}---\left(9\right)$

$D_{\mathrm{eq}2}=1-\frac{u_{\mathrm{pv}}}{u_o}---\left(10\right)$

Therefore, the control input that can obtain controller is:

D₂=Δ D₂+D_eq2 (11)

Referring to Fig. 3～4, in the embodiment of the present invention, a kind of photovoltaic array under local shadow maximal power tracing sliding formwork controls system System, its step is as follows:

(1) initial voltage reference value U is set_refIt is 0；

(2) by the output voltage U of photovoltaic array_pvGradually rise with certain step-length, real-time voltage reference value U_ref(k) =U_ref(k-1)+Δ U, detects the output electric current i of photovoltaic array simultaneously_pvWith photovoltaic array output P_pv；

(3) during step (2), peak power storage program is performed, it is thus achieved that global maximum power point P_maxAnd the overall situation is High-power point voltage U_max；

(4) in the scanning process of step (2), the output electric current i in real time of contrast photovoltaic array_pvWhether less than current threshold i_setIf, the output electric current i in real time of photovoltaic array_pvLess than current threshold i_set, then carry out next step, otherwise proceed step Suddenly (2), current threshold i_setChoosing according to the actual requirements, the value chosen is the least, detected open-circuit voltage U_ocMore Accurately；

(5) open-circuit voltage U_ocValue is output electric current i_pvLess than current threshold i_setTime photovoltaic array output voltage U_pv(k)；

(6) by voltage reference value U_refIt is set as the global maximum power point voltage U tracked_max；

(7) call sliding formwork scanning subprogram, make the actual output voltage U of photovoltaic array_pvMove closer in global maximum power Point voltage U_max；

(8) U is worked as_pvAnd U_maxDifference less than set the first threshold voltage U_set1Time, carry out next step；

(9) call sliding formwork MPPT program, photovoltaic array is stable at global maximum power point；

(10) photovoltaic system realtime power P is calculated_pvWith realtime power variation delta P_pv；

(11) realtime power variation delta P is judged_pvWhether more than changed power threshold values Δ P_set, changed power threshold values Δ P_set Set according to actual light conditions, if realtime power variation delta P_pvMore than changed power threshold values Δ P_set, then carry out next step, Otherwise remain on state；

(12) photovoltaic array current output voltage U is judged_pvPosition, compare (U_pv-0.6U_oc/ N) whether more than (0.85U_oc- U_pv), if being more than, carrying out step (12), otherwise carrying out step (9)；

(13) setting voltage reference value U_refFor 0.85U_oc；

(14) call sliding formwork scanning subprogram, photovoltaic array output voltage will be gradually increasing close to 0.85 from current point of operation U_oc；

(15) photovoltaic array output voltage U is judged_pvWhether close to 0.85U_oc, when both differences are less than the second threshold voltage U_set2Time, carry out next step；

(16) by voltage reference value U_refIt is set as 0.6U_oc/N；

(17) call sliding formwork scanning subprogram, make photovoltaic array output voltage will be gradually reduced close to 0.6 from current point of operation U_oc/ N, performs peak power storage program, it is thus achieved that global maximum power point and global maximum power point voltage U simultaneously_max；

(18) photovoltaic array current output voltage U is judged_pvWhether close to 0.6U_oc/ N, when both differences are less than tertiary voltage Threshold values U_set3Time, carry out step (6), otherwise proceed step (16)；

(19) setting voltage reference value U_refFor 0.6U_oc/N；

(20) call sliding formwork scanning subprogram, photovoltaic array output voltage will be gradually increasing close to 0.6 from current point of operation U_oc/N；

(21) photovoltaic array output voltage U is judged_pvWhether close to 0.6U_oc/ N, when both differences are less than tertiary voltage threshold values U_set3Time, carry out next step；

(22) by voltage reference value U_refIt is set as 0.85U_oc,

(23) call sliding formwork scanning subprogram, make photovoltaic array output voltage will be gradually reduced close to 0.85 from current point of operation U_oc, perform peak power storage program, it is thus achieved that global maximum power point and global maximum power point voltage U simultaneously_max；

(24) photovoltaic array current output voltage U is judged_pvWhether close to 0.85U_oc, when both differences are less than the second voltage valve Value U_set2Time, carry out step (6), otherwise proceed step (22).

Described peak power storage program step is as follows:

(1) global maximum power point P is set_maxAnd global maximum power point voltage U_maxInitial value is 0；

(2) the real-time output voltage U of photovoltaic array is obtained_pv(k) and in real time output electric current i_pv(k)；

(3) photovoltaic array realtime power P is calculated_pv(k), P_pv(k)=U_pv(k)*i_pv(k)；

(4) photovoltaic array realtime power P is judged_pvK whether () be more than global maximum power point P_maxIf being more than, then carry out Step (5), otherwise carries out step (6)；

(5) global maximum power point P is set_max=P_pv(k), global maximum power point voltage U_max=U_pv(k), weight Multiple step (2)；

(6) global maximum power point P_maxWith global maximum power point voltage U_maxNumerical value is constant, repeats step (2).

The global maximum power that described photovoltaic array under local shadow maximal power tracing System with Sliding Mode Controller controls based on sliding formwork Follow the tracks of new method.First the output power curve of photovoltaic array is scanned, records global maximum power point, in this process In introduce sliding formwork control, substantially reduce sweep time；Then use sliding formwork maximum power tracking method by photovoltaic array Operating point immediate stability, in maximum power point, reduces power swing during steady-state operation.Simulation result shows, the method is not Only there is good dynamic response performance, and reduce the power loss in whole tracing process, improve whole photovoltaic and send out The efficiency of electricity system.

It is obvious to a person skilled in the art that the invention is not restricted to the details of above-mentioned one exemplary embodiment, and do not carrying on the back In the case of the spirit or essential attributes of the present invention, it is possible to realize the present invention in other specific forms.Therefore, no matter from From the point of view of which point, all should regard embodiment as exemplary, and be nonrestrictive, the scope of the present invention is by appended power Profit requires rather than described above limits, it is intended that all by fall in the implication of equivalency and scope of claim Change is included in the present invention.Should not be considered as limiting involved claim by any reference in claim.

Although moreover, it will be appreciated that this specification is been described by according to embodiment, but the most each embodiment only comprises One independent technical scheme, this narrating mode of description is only the most for clarity sake, and those skilled in the art should be by Description is as an entirety, and the technical scheme in each embodiment can also be through appropriately combined, and forming those skilled in the art can With other embodiments understood.

Claims (2)

1. a photovoltaic array under local shadow maximal power tracing System with Sliding Mode Controller, it is characterised in that step is as follows:

(1) initial voltage reference value U is set_refIt is 0；

(2) by the output voltage U of photovoltaic array_pvGradually rise with certain step-length, real-time voltage reference value U_ref(k) =U_ref(k-1)+Δ U, detects the output electric current i of photovoltaic array simultaneously_pvWith photovoltaic array output P_pv；

(3) during step (2), peak power storage program is performed, it is thus achieved that global maximum power point P_maxAnd the overall situation is High-power point voltage U_max；

(4) in the scanning process of step (2), the output electric current i in real time of contrast photovoltaic array_pvWhether less than current threshold i_setIf, the output electric current i in real time of photovoltaic array_pvLess than current threshold i_set, then carry out next step, otherwise proceed step Suddenly (2), current threshold i_setChoosing according to the actual requirements, the value chosen is the least, detected open-circuit voltage U_ocMore Accurately；

(5) open-circuit voltage U_ocValue is output electric current i_pvLess than current threshold i_setTime photovoltaic array output voltage U_pv(k)；

(6) by voltage reference value U_refIt is set as the global maximum power point voltage U tracked_max；

(7) call sliding formwork scanning subprogram, make the actual output voltage U of photovoltaic array_pvMove closer in global maximum power Point voltage U_max；

(8) U is worked as_pvAnd U_maxDifference less than set the first threshold voltage U_set1Time, carry out next step；

(9) call sliding formwork MPPT program, photovoltaic array is stable at global maximum power point；

(10) photovoltaic system realtime power P is calculated_pvWith realtime power variation delta P_pv；

(11) realtime power variation delta P is judged_pvWhether more than changed power threshold values Δ P_set, changed power threshold values Δ P_set Set according to actual light conditions, if realtime power variation delta P_pvMore than changed power threshold values Δ P_set, then carry out next step, Otherwise remain on state；

(12) photovoltaic array current output voltage U is judged_pvPosition, compare (U_pv-0.6U_oc/ N) whether more than (0.85U_oc- U_pv), if being more than, carrying out step (12), otherwise carrying out step (9)；

(13) setting voltage reference value U_refFor 0.85U_oc；

(14) call sliding formwork scanning subprogram, photovoltaic array output voltage will be gradually increasing close to 0.85 from current point of operation U_oc；

(15) photovoltaic array output voltage U is judged_pvWhether close to 0.85U_oc, when both differences are less than the second threshold voltage U_set2Time, carry out next step；

(16) by voltage reference value U_refIt is set as 0.6U_oc/N；

(17) call sliding formwork scanning subprogram, make photovoltaic array output voltage will be gradually reduced close to 0.6 from current point of operation U_oc/ N, performs peak power storage program, it is thus achieved that global maximum power point and global maximum power point voltage U simultaneously_max；

(18) photovoltaic array current output voltage U is judged_pvWhether close to 0.6U_oc/ N, when both differences are less than tertiary voltage Threshold values U_set3Time, carry out step (6), otherwise proceed step (16)；

(19) setting voltage reference value U_refFor 0.6U_oc/N；

(20) call sliding formwork scanning subprogram, photovoltaic array output voltage will be gradually increasing close to 0.6 from current point of operation U_oc/N；

(21) photovoltaic array output voltage U is judged_pvWhether close to 0.6U_oc/ N, when both differences are less than tertiary voltage threshold values U_set3Time, carry out next step；

(22) by voltage reference value U_refIt is set as 0.85U_oc,

(23) call sliding formwork scanning subprogram, make photovoltaic array output voltage will be gradually reduced close to 0.85 from current point of operation U_oc, perform peak power storage program, it is thus achieved that global maximum power point and global maximum power point voltage U simultaneously_max；

(24) photovoltaic array current output voltage U is judged_pvWhether close to 0.85U_oc, when both differences are less than the second voltage valve Value U_set2Time, carry out step (6), otherwise proceed step (22).

Photovoltaic array under local shadow maximal power tracing System with Sliding Mode Controller the most according to claim 1, its feature Being, the step of described peak power storage program is as follows:

(1) global maximum power point P is set_maxAnd global maximum power point voltage U_maxInitial value is 0；

(2) the real-time output voltage U of photovoltaic array is obtained_pv(k) and in real time output electric current i_pv(k)；

(3) photovoltaic array realtime power P is calculated_pv(k), P_pv(k)=U_pv(k)*i_pv(k)；

(4) photovoltaic array realtime power P is judged_pvK whether () be more than global maximum power point P_maxIf being more than, then carry out Step (5), otherwise carries out step (6)；

(5) global maximum power point P is set_max=P_pv(k), global maximum power point voltage U_max=U_pv(k), weight Multiple step (2)；

(6) global maximum power point P_maxWith global maximum power point voltage U_maxNumerical value is constant, repeats step (2).