CN105549676A - Photovoltaic maximum power tracking method based on back-testing and curve-fitting - Google Patents

Photovoltaic maximum power tracking method based on back-testing and curve-fitting Download PDF

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CN105549676A
CN105549676A CN201610087886.7A CN201610087886A CN105549676A CN 105549676 A CN105549676 A CN 105549676A CN 201610087886 A CN201610087886 A CN 201610087886A CN 105549676 A CN105549676 A CN 105549676A
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photovoltaic
maximum power
curve
point
voltage
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潘三博
林成栋
房亚军
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Shanghai Dianji University
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Shanghai Dianji University
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    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
    • G05F1/00—Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
    • G05F1/66—Regulating electric power
    • G05F1/67—Regulating electric power to the maximum power available from a generator, e.g. from solar cell
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/56—Power conversion systems, e.g. maximum power point trackers

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Abstract

The invention discloses a photovoltaic maximum power tracking method based on back-testing and curve-fitting. The photovoltaic maximum power tracking method comprises: in a back-testing manner, ensuring that working points of three photovoltaic modules are obtained by an MPPT (maximum power point tracking) controller at the same time; utilizing the three working points obtained in the back-testing manner, judging the positional relation between a current photovoltaic module working point and a maximum power point based on a preset MPPT tracking direction judgment basis, and judging whether illumination abrupt variation appears; in case of illumination abrupt variation, searching for the maximum power point with the least disturbance again based on newest measured data; when the measured working points of the photovoltaic modules approaches to the maximum power point, fitting an approximate P-U curve of the photovoltaic modules in a Lagrange's interpolation manner through the three data points on a photovoltaic cell P-U curve obtained by back-test. The method adopts back-testing combined with Lagrange's interpolation to fit the photovoltaic cell P-U curve, reduces the back-and-forth disturbance near an MPP, and lowers efficiency loss brought by the disturbance.

Description

Based on the photovoltaic maximum power tracing method returning survey and curve
Technical field
The present invention relates to a kind of photovoltaic maximum power tracing method, particularly relating to a kind of photovoltaic maximum power tracing method based on returning survey and curve.
Background technology
Along with photovoltaic generating system deployment worldwide, photovoltaic generating system also exposes many problems gradually.Photovoltaic battery panel price is still higher, and this makes the cost of investment of photovoltaic generating system higher; Photovoltaic cell work efficiency is on the low side, and photovoltaic cell can not play its usefulness completely.
Under existence conditions, the price of photovoltaic cell cannot significantly decline, and can only improve the work efficiency of photovoltaic cell as much as possible to make full use of sun power, this needs good control algolithm, particularly photovoltaic maximal power tracing control algolithm.Photovoltaic cell can be made to be operated in maximum power point by photovoltaic maximal power tracing control algolithm always, realize the maximum output of power, promote the efficiency of whole system.
Should be used for doing by people the algorithm that photovoltaic maximal power tracing controls at first is fixed voltage method (CVT), and namely the output voltage of fixed light photovoltaic array is constant, and this voltage determines according to the output P-U curve of photovoltaic cell.Fixed voltage method controls the simplest, and easily realize, run also reliable and stable, current some systems that still have adopt this algorithm.But fixed voltage method dynamic perfromance is bad, can not tackle the change of external environment, as the change etc. of environment temperature, intensity of illumination, this can make photovoltaic array lose certain energy.
In order to tackle the continuous change of external environment, accomplish real tracing control, people investigated again disturbance observation (P & O), are commonly called as climbing method.This algorithm is based on the output P-V curve of photovoltaic cell, timing increase disturbance to photovoltaic array, increase or reduce output voltage, and observing the change of output power before and after disturbance, determine the direction of disturbance next time according to comparative result, thus search out peak power working point.This algorithm really achieves the dynamic tracking of photovoltaic array peak power, simultaneously lower to the requirement of testing circuit, is one of maximal power tracing control algolithm be most widely used now.But disturbance observation also has the deficiency of self, after tracing into maximum power point, understand oscillate in its vicinity, lose portion of energy.
While disturbance observation is constantly applied, in order to adapt to environmental change more fast, realizing the quick tracking of photovoltaic system to maximum power point, having scholar to propose conductance increment method (INC).Conductance increment method exports P-V curve by analyzing photovoltaic cell, and the method proposed by calculating output conductance increment decides tracking direction.This algorithm realizes maximal power tracing by the method calculated, its reaction velocity is fast, easily realize rapid track and control, relatively be suitable for external environment and change region use faster, but conductance increment method also has its shortcoming simultaneously, testing circuit precision as required is high, and controller arithmetic speed will be sought quickness.
Summary of the invention
For overcoming the deficiency that above-mentioned prior art exists, one of the present invention object is to provide a kind of photovoltaic maximum power tracing method based on returning survey and curve, it adopts back surveys and in conjunction with the P-U curve of method of interpolation matching photovoltaic cell, MPP (maximum power point) is determined by the mode calculated, reduce the disturbance back and forth near MPP, significantly reduce the efficiency losses brought thus.
Another object of the present invention is to provide a kind of photovoltaic maximum power tracing method based on returning survey and curve, and its occasion for illuminance abrupt variation can identify response fast, and disturbance is less near MPP, is applicable to the MPPT occasion of high-power photovoltaic assembly.
For reaching above-mentioned and other object, the present invention proposes a kind of photovoltaic maximum power tracing method based on returning survey and curve, comprises the steps:
Step one, by returning the mode surveyed, ensures that synchronization MPPT controller at least obtains the working point of 3 photovoltaic modulies;
Step 2, utilizes three working points to return the photovoltaic module that survey mode obtains, follows the trail of walking direction foundation, judge the position relationship between current photovoltaic module working point and maximum power point, and judge whether to occur illuminance abrupt variation according to the MPPT preset;
Step 3, in time there is illuminance abrupt variation situation, according to the up-to-date data recorded, finds maximum power point with minimal disturbances again;
Step 4, when the working point of the photovoltaic module recorded is close to maximum power point, by returning three data points on the photovoltaic cell P-U curve that records, uses Lagrange's interpolation mode to carry out the approximate P-U curve of matching photovoltaic module.
Further, step one comprises:
Step 1.1, control system detects photovoltaic cell component open-circuit voltage when start, and setting photovoltaic cell output voltage initial reference value is measure battery component output voltage now and output power, be recorded as (U b, P b);
Step 1.2, to MPP circuit disturbance voltage Δ U ref, by two other working point of output voltage record of disturbance light photovoltaic cell components, the battery component output voltage U that these two working points are corresponding a=U b-Δ U ref, U c=U b+ Δ U ref, the working point (U that record is corresponding a, P a), (U c, P c), according to P a, P b, P crelation determines that next step follows the trail of direction, and determines next step disturbance voltage amplitude Δ U ref;
Step 1.3, in step 1.2 closest to the voltage of the working point of maximum power point as new voltage starting point, to obtain new disturbance voltage Δ U through PI link reffor disturbance step-length, continue back the method surveyed, then survey two points, and the power that record is corresponding, then next step perturbation direction and step sizes is judged by the mode of step 1.2.
Further, in step 1.1, control system detects photovoltaic cell component open-circuit voltage U when start oc, setting photovoltaic cell output voltage initial reference value is 0.8U oc.
Further, in step 1.2, Δ U ref=0.01U oc.
Further, before step 4, also comprise:
Increase and follow the trail of stopping criterion, to stop the tracking to photovoltaic module peak power according to this tracking stopping criterion.
Further, this tracking stopping criterion is max{|P b-P a|, | P b-P c| < ε, when meeting this criterion, judging that output power of photovoltaic module reaches maximum power point, stopping the tracking to photovoltaic module peak power.
Further, in step 1.2, determine after following the trail of direction, according to the rate of change e of current power relative voltage 1, next step disturbance voltage amplitude Δ U is determined by a PI controller ref.
Further, approaching with larger step-length away from during maximum power point, carry out with comparatively microvariations close to during maximum power point.
Further, in step 1.3, take the up-to-date photovoltaic cell output services point recorded as up-to-date benchmark job point, then according to the minimal disturbances step delta U that the present invention proposes ref=0.01U ocnext step tracking direction is decided with time survey mode.
Further, after step 4, also comprise:
After the approximate P-U curve of this photovoltaic module is by matching out, obtain photovoltaic module voltage corresponding to the maximum power point of curve by the mode of mathematical computations, then by magnitude of voltage that the reference work voltage of controller setting battery component calculates for this reason.
Compared with prior art, the present invention is a kind of based on returning the photovoltaic maximum power tracing method of survey and curve based on returning the mode surveyed, ensure that MPPT controller can judge position relationship between current photovoltaic module working point and maximum power point by a working point, 3 of photovoltaic module, and algorithm lost efficacy when can avoid illuminance abrupt variation, when close to maximum power point, return the P-U curve that 3 working points recorded can be used to matching photovoltaic module, the method of mathematical computations is adopted to find optimum solution, the loss in efficiency on hardware can be reduced, at utmost can improve the efficiency of photovoltaic module.
Accompanying drawing explanation
To be that the present invention is a kind of survey and the flow chart of steps of photovoltaic maximum power tracing method of curve based on returning Fig. 1;
Fig. 2 is the output power from photovoltaic cells of the present invention and voltage curve schematic diagram;
Fig. 3 is surveying and the photovoltaic maximum power tracing method process flow diagram of curve based on returning of the specific embodiment of the invention.
Embodiment
Below by way of specific instantiation and accompanying drawings embodiments of the present invention, those skilled in the art can understand other advantage of the present invention and effect easily by content disclosed in the present specification.The present invention is also implemented by other different instantiation or is applied, and the every details in this instructions also can based on different viewpoints and application, carries out various modification and change not deviating under spirit of the present invention.
To be that the present invention is a kind of survey and the flow chart of steps of photovoltaic maximum power tracing method of curve based on returning Fig. 1.As shown in Figure 1, a kind of photovoltaic maximum power tracing method based on returning survey and curve of the present invention, comprises the steps:
Step 101, by returning the mode surveyed, ensures that synchronization MPPT (MaximumPowerPointTracking, maximum power tracing) controller at least obtains the working point of 3 photovoltaic modulies.
The tracking anisotropy that this step avoids illuminance abrupt variation to cause by the mode of returning survey, specifically comprises as follows:
1, control system detects photovoltaic cell component open-circuit voltage U when start oc, setting photovoltaic cell output voltage initial reference value is 0.8U oc, according to pertinent literature, photovoltaic cell component when this output voltage very close to MPP (maximum power point).Measure battery component output voltage now and output power, be recorded as (U b, P b).
2, to MPP circuit disturbance voltage Δ U ref=0.01U oc, by two other working point of output voltage record of disturbance light photovoltaic cell components, the battery component output voltage U that these two working points are corresponding a=U b-Δ U ref, U c=U b+ Δ U ref.Working point (the U that record is corresponding a, P a), (U c, P c).According to P a, P b, P crelation judges that next step follows the trail of direction, and determines next step disturbance voltage amplitude Δ U ref.As shown in Figure 2, if P a< P b< P c, then U cmore close to MPP (maximum power point).Determine after following the trail of direction, the rate of change e of current power relative voltage here 1, namely next step disturbance voltage amplitude Δ U is determined by a PI controller ref.Thus ensure that the step-length of tracking is adaptive, approaching with larger step-length away from during MPP, carry out again close to during MPP with comparatively microvariations, guarantee can not disturbance back and forth near MPP, reduces loss.
3, after determining perturbation direction and step-length, with the voltage (U closest to the working point of maximum power point in step 2 c) as new voltage starting point, to obtain new disturbance voltage Δ U through PI link reffor disturbance step-length, continue back the method surveyed, then survey two some U c-Δ U refand U c+ Δ U ref, and the power that record is corresponding, then (judgment mode of step 2) judges next step perturbation direction and step sizes by the way.Here U c-Δ U refbe go back to the photovoltaic cell working point surveyed, the present invention compares traditional algorithm, adds this step, and the criterion that the present invention is directed to illuminance abrupt variation situation needs this working point data.
Step 102, utilizes three working points to return the photovoltaic module that survey mode obtains, follows the trail of walking direction foundation, judge the position relationship between current photovoltaic module working point and maximum power point, and judge whether to occur illuminance abrupt variation according to the MPPT preset.Specifically describe as follows:
As shown in Figure 2, controller passes through the basic working point U of setting one b, to photovoltaic cell component disturbance operating voltage Δ U ref, controller can record photovoltaic cell at U btwo the some U in left and right aand U cperformance number, if at U atime, life approved for distribution enhanced suddenly, and the power detected will be P a', can P be seen from Fig. 2 curve a' > P b.If adopt traditional disturbance observation, U a< U band P a' > P b, then according to the P-U curve of photovoltaic cell, current U is drawn aon the right side of MPP, therefore next step tracking direction is the output voltage reducing photovoltaic cell.Composition graphs 2, now continue the output voltage reducing photovoltaic module, the output power of photovoltaic module will reduce further, and this tracking direction is wrong.
And three working points adopting of the present invention time survey method to record, U a< U b< U c, and there is P a' > P band P c> P b, follow the trail of walking direction foundation by MPPT, illuminance abrupt variation situation can be determined to be.
Step 103, in time there is illuminance abrupt variation situation, according to the up-to-date data recorded, finds maximum power point with minimal disturbances again.
When judging to have occurred illuminance abrupt variation situation, the present invention will take the up-to-date photovoltaic cell output services point (U recorded a, P a') as up-to-date benchmark job point, then according to the minimal disturbances step delta U that the present invention proposes ref=0.01U ocnext step tracking direction is decided with time survey mode.
Step 104, when the working point of the photovoltaic module recorded is close to maximum power point, by returning three data points on the photovoltaic cell P-U curve that records, uses Lagrange's interpolation mode to carry out the approximate P-U curve of matching photovoltaic module.The approximate P-U curve of photovoltaic module, by after matching out, obtains photovoltaic module voltage corresponding to the maximum power point of curve by the mode of mathematical computations, then by magnitude of voltage that the reference work voltage of controller setting battery component calculates for this reason.
Preferably, before step 104, also comprise the steps:
Increase and follow the trail of stopping criterion, to stop the tracking to photovoltaic module peak power according to this tracking stopping criterion.
By above-mentioned steps, the present invention can well avoid the problem of the erroneous judgement produced when the left side of MPP (maximum power point) or right side illuminance abrupt variation.Meanwhile, the present invention is by increase criterion max{|P b-P a|, | P b-P c| < ε, when meeting this criterion, thinking that output power of photovoltaic module has reached MPP (maximum power point), stopping the tracking to photovoltaic module peak power.
To coordinate Fig. 3 and Fig. 2, by a specific embodiment, surveying and the photovoltaic power method for tracing of curve based on returning of the present invention is described below:
Control system detects photovoltaic cell component open-circuit voltage U when start oc, setting photovoltaic cell output voltage initial reference value is 0.8U oc, measure battery component output voltage now and output power, be recorded as (U b, P b).To MPP circuit disturbance voltage Δ U ref=0.01U oc, by two other working point of output voltage record of disturbance light photovoltaic cell components, the battery component output voltage U that these two working points are corresponding a=U b-Δ U re, U c=U b+ Δ U ref, the working point (U that record is corresponding a, P a), (U c, P c).According to P a, P b, P crelation judges that next step follows the trail of direction.As shown in Figure 2, if P a< P b< P c, then U cmore close to MPP.Determine after following the trail of direction, the rate of change e of current power relative voltage here 1, namely next step disturbance voltage amplitude Δ U is determined by a PI controller ref.Thus ensure that the step-length of tracking is adaptive, approaching with larger step-length away from during MPP, carry out again close to during MPP with comparatively microvariations, guarantee can not disturbance back and forth near MPP, reduces loss.After determining perturbation direction and step-length, with U cas new voltage starting point, to obtain new disturbance voltage Δ U through PI link reffor disturbance step-length, continue back the method surveyed, then survey two some U c-Δ U refand U c+ Δ U ref, and the power that record is corresponding, then judge next step perturbation direction and step sizes by the way, U here c-Δ U refbe go back to the photovoltaic cell working point surveyed.
As mentioned above, controller passes through the basic working point U of setting one b, to photovoltaic cell component disturbance operating voltage Δ U ref, controller can record photovoltaic cell at U btwo the some U in left and right aand U cperformance number, if at U atime, life approved for distribution enhanced suddenly, and the power detected will be P a', can P be seen from Fig. 2 curve a' > P b.If adopt traditional disturbance observation, U a< U band P a' > P b, then according to the P-U curve of photovoltaic cell, current U is drawn aon the right side of MPP, therefore next step tracking direction is the output voltage reducing photovoltaic cell.Now continue the output voltage reducing photovoltaic module, the output power of photovoltaic module will reduce further, but this tracking direction is wrong.
Adopt three working points that of the present invention go back to survey method records, U a< U b< U c, and there is P a' > P band P c> P b, therefore increase default MPPT and follow the trail of walking direction foundation, can be determined to be illuminance abrupt variation, the present invention will take the up-to-date photovoltaic cell output services point (U recorded a, P a') as up-to-date benchmark job point, then according to the minimal disturbances step delta U that the present invention proposes ref=0.01U ocnext step tracking direction is decided with time survey mode.
Visible, present invention, avoiding the problem judged by accident when the left side of MPP or right side illuminance abrupt variation.Meanwhile, can increase by a tracking stopping criterion max{|P b-P a|, | P b-P c| < ε, when meeting this criterion, thinking that output power of photovoltaic module reaches MPP, stopping the tracking to photovoltaic module peak power.Following table 1 is that in the specific embodiment of the invention, MPPT follows the trail of walking direction foundation:
Table 1MPPT follows the trail of direction criterion
As in table 1, when occurring P b> P a> P cor P b> P c> P atime, illustrate that the MPP of photovoltaic cell is at (U a, U c) this voltage range, when three working points returning the photovoltaic cell surveyed meet this condition, no longer return survey, use the method for interpolation fitting, the output power from photovoltaic cells can be drawn by formula (1):
P = U ( I L G - I O S { exp &lsqb; q &alpha; K T ( U + IR S ) &rsqb; - 1 } - U + IR S R s h ) - - - ( 1 )
This expression formula is comparatively loaded down with trivial details, can not solve this equation to find the MPP of photovoltaic cell in actual engineer applied.The MPP method that the present invention proposes, 3 photovoltaic cell working points are had owing to returning survey method, therefore method of interpolation is adopted to carry out the P-U curve of matching photovoltaic cell, find elementary function expression formula approximate near a P-U curve maximum power point, such general reduced data disposal route greatly, obtain the maximum power point of photovoltaic cell, and another benefit of process like this is, near MPP, adopt the mode of mathematical computations to carry out the mode of alternative disturbance observation, reduce efficiency losses greatly, this has application value very much in the MPPT occasion of high-power photovoltaic assembly.As follows to the principles illustrated of interpolation fitting:
Suppose three interpolation knot (U a, P a), (U b, P b), (U c, P c), then interpolation polynomial is such as formula (2)
L 2(U)＝P a·l a(U)+P b·l b(U)+P c·l c(U)(2)
Wherein:
l a ( U ) = ( U - U b ) &CenterDot; ( U - U c ) ( U a - U b ) &CenterDot; ( U a - U c ) - - - ( 3 )
l b ( U ) = ( U - U a ) &CenterDot; ( U - U c ) ( U b - U a ) &CenterDot; ( U b - U c ) - - - ( 4 )
l c ( U ) = ( U - U a ) &CenterDot; ( U - U b ) ( U c - U a ) &CenterDot; ( U c - U b ) - - - ( 5 )
The general expression that can obtain quadratic function is as follows:
L 2(U)＝x 1U 2+x 2U+x 3(6)
x 1 = P a ( U a - U b ) &CenterDot; ( U a - U c ) + P b ( U b - U a ) &CenterDot; ( U b - U c ) + P c ( U c - U a ) &CenterDot; ( U c - U b ) - - - ( 7 )
x 2 = P a &CenterDot; ( U b + U c ) ( U a - U b ) &CenterDot; ( U a - U c ) + P b &CenterDot; ( U a + U c ) ( U b - U a ) &CenterDot; ( U b - U c ) + P c &CenterDot; ( U a + U b ) ( U c - U a ) &CenterDot; ( U c - U b ) - - - ( 8 )
x 3 = P a &CenterDot; U b &CenterDot; U c ( U a - U b ) &CenterDot; ( U a - U c ) + P b &CenterDot; U a &CenterDot; U c ( U b - U a ) &CenterDot; ( U b - U c ) + P c &CenterDot; U a &CenterDot; U b ( U c - U a ) &CenterDot; ( U c - U b ) - - - ( 9 )
The maximum of points of matched curve is when carrying out approximate fits to photovoltaic cell P-U curve, only need three the point (U that will select a, P a), (U b, P b), (U c, P c) bring formula (7) into, (8), (9), obtain coefficient x 1, x 2, x 3, corresponding according to the approximate P-U parabolic curve peak power output P that matching obtains adopt the method for interpolation fitting just can obtain the voltage at photovoltaic module maximum power point place with less calculating, control photovoltaic cell output reference voltage U according to calculated value by controller ref=U m, and photovoltaic cell component output power P under recording this voltage m.
Again from (U a, P a), (U b, P b), (U c, P c), (U m, P m) three point (U selecting output power maximum in these 4 1, P 1), (U 2, P 2), (U 3, P 3), attentional selection power points out must meet P 1< P 2< P 3and U 1< U 2< U 3condition the method for interpolation fitting just can be used to solve new maximum power point.Carry out interpolation curve matching further according to three working points elected and try to achieve reference voltage corresponding to maximum power point, method step repeats no more.
The photovoltaic cell peak power output P that present sample arrives by the present invention nowwith the peak power P of last circulation beforecompare.When | P now-P before| during < ε, stop curve, namely think and found maximum power point.
In sum, the present invention is a kind of based on returning the photovoltaic maximum power tracing method of survey and curve based on returning the mode surveyed, ensure that MPPT controller can judge position relationship between current photovoltaic module working point and maximum power point by a working point, 3 of photovoltaic module, and algorithm lost efficacy when can avoid illuminance abrupt variation, when close to maximum power point, return the P-U curve that 3 working points recorded can be used to matching photovoltaic module, the method of mathematical computations is adopted to find optimum solution, the loss in efficiency on hardware can be reduced, at utmost can improve the efficiency of photovoltaic module.
Above-described embodiment is illustrative principle of the present invention and effect thereof only, but not for limiting the present invention.Any those skilled in the art all without prejudice under spirit of the present invention and category, can carry out modifying to above-described embodiment and change.Therefore, the scope of the present invention, should listed by claims.

Claims (10)

1., based on the photovoltaic maximum power tracing method returning survey and curve, comprise the steps:
Step one, by returning the mode surveyed, ensures that synchronization MPPT controller at least obtains the working point of 3 photovoltaic modulies;
Step 2, utilizes three working points to return the photovoltaic module that survey mode obtains, follows the trail of walking direction foundation, judge the position relationship between current photovoltaic module working point and maximum power point, and judge whether to occur illuminance abrupt variation according to the MPPT preset;
Step 3, in time there is illuminance abrupt variation situation, according to the up-to-date data recorded, finds maximum power point with minimal disturbances again;
Step 4, when the working point of the photovoltaic module recorded is close to maximum power point, by returning three data points on the photovoltaic cell P-U curve that records, uses Lagrange's interpolation mode to carry out the approximate P-U curve of matching photovoltaic module.
2. a kind ofly as claimed in claim 1 survey and the photovoltaic maximum power tracing method of curve based on returning, it is characterized in that, step one comprises:
Step 1.1, control system detects photovoltaic cell component open-circuit voltage when start, and setting photovoltaic cell output voltage initial reference value is measure battery component output voltage now and output power, be recorded as (U b, P b);
Step 1.2, to MPP circuit disturbance voltage Δ U ref, by two other working point of output voltage record of disturbance light photovoltaic cell components, the battery component output voltage U that these two working points are corresponding a=U b-Δ U ref, U c=U b+ Δ U ref, the working point (U that record is corresponding a, P a), (U c, P c), according to P a, P b, P crelation determines that next step follows the trail of direction, and determines next step disturbance voltage amplitude Δ U ref;
Step 1.3, in step 1.2 closest to the voltage of the working point of maximum power point as new voltage starting point, to obtain new disturbance voltage Δ U through PI link reffor disturbance step-length, continue back the method surveyed, then survey two points, and the power that record is corresponding, then next step perturbation direction and step sizes is judged by the mode of step 1.2.
3. a kind ofly as claimed in claim 2 survey and the photovoltaic maximum power tracing method of curve based on returning, it is characterized in that: in step 1.1, control system is detection photovoltaic cell component open-circuit voltage U when start oc, setting photovoltaic cell output voltage initial reference value is 0.8U oc.
4. a kind ofly as claimed in claim 3 to survey and the photovoltaic maximum power tracing method of curve based on returning, it is characterized in that: in step 1.2, Δ U ref=0.01U oc.
5. a kind ofly as claimed in claim 2 to survey and the photovoltaic maximum power tracing method of curve based on returning, it is characterized in that, before step 4, also comprise:
Increase and follow the trail of stopping criterion, to stop the tracking to photovoltaic module peak power according to this tracking stopping criterion.
6. a kind ofly as claimed in claim 5 to survey and the photovoltaic maximum power tracing method of curve based on returning, it is characterized in that: this tracking stopping criterion is max{|P b-P a|, | P b-P c| < ε, when meeting this criterion, judging that output power of photovoltaic module reaches maximum power point, stopping the tracking to photovoltaic module peak power.
7. a kind ofly as claimed in claim 4 to survey and the photovoltaic maximum power tracing method of curve based on returning, it is characterized in that: in step 1.2, after determining tracking direction, according to the rate of change e of current power relative voltage 1, next step disturbance voltage amplitude Δ U is determined by a PI controller ref.
8. a kind ofly as claimed in claim 7 to survey and the photovoltaic maximum power tracing method of curve based on returning, it is characterized in that: approaching with larger step-length away from during maximum power point, carry out with comparatively microvariations close to during maximum power point.
9. a kind ofly as claimed in claim 8 to survey and the photovoltaic maximum power tracing method of curve based on returning, it is characterized in that: in step 1.3, take the up-to-date photovoltaic cell output services point recorded as up-to-date benchmark job point, then according to the minimal disturbances step delta U that the present invention proposes ref=0.01U ocnext step tracking direction is decided with time survey mode.
10. a kind ofly as claimed in claim 9 to survey and the photovoltaic maximum power tracing method of curve based on returning, it is characterized in that, after step 4, also comprise:
After the approximate P-U curve of this photovoltaic module is by matching out, obtain photovoltaic module voltage corresponding to the maximum power point of curve by the mode of mathematical computations, then by magnitude of voltage that the reference work voltage of controller setting battery component calculates for this reason.
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