CN103995558A - Photovoltaic array maximum power point tracking method based on chaos optimization search - Google Patents

Abstract

The invention discloses a photovoltaic array maximum power point tracking method based on chaos optimization search. By sampling the direct-current voltage Vpv and the current Ipv which are output by a photovoltaic array in real time, the output power p(k) of the photovoltaic array is calculated and compared with the current maximum power value p* prestored by an MPPT controller; if p(k)>p*, the value of p(k) is assigned to p*, and the value of Vpv is assigned to the output voltage x* of the MPPT controller; otherwise, the value of p(k) is abandoned, and the value of p* and the value of x* are kept unchanged. Then, the voltage x* output by the MPPT controller and the voltage Vpv output by the photovoltaic array are added to a summator, and a generated error voltage is added to the in-phase end of the summator after being subjected to the proportion-integration link and then compared with a sawtooth voltage added to the anti-phase end of a comparator, so that the duty ratio of gate drive signals of a switch tube in a DC/DC converter is changed, the parameters of a DC/DC conversion circuit are regulated and controlled, and maximum power tracking control can be achieved. The photovoltaic array maximum power point tracking method based on chaos optimization search is high in tracking speed and control precision.

Description

A kind of photovoltaic array maximum power point tracing method based on chaos optimization search

Technical field

The present invention relates to a kind of photovoltaic generating system, specifically, relate to a kind of photovoltaic array maximum power point tracing method based on chaos optimization search, utilize MPPT method to improve the efficiency of photovoltaic battery array in photovoltaic generation process, make sun power be converted into electric energy output with maximal efficiency, belong to photovoltaic power generation technology field.

Background technology

When photovoltaic generating system work, at certain temperature and intensity of sunshine, photovoltaic battery array has unique maximum power point, but be subject to the impact of the factors such as load condition, intensity of sunshine, environment temperature due to the output characteristics of photovoltaic battery array, the output voltage of photovoltaic battery array and electric current all can produce very large variation thereupon, thereby make output power unstable, if can not real-time follow-up its change, can reduce the output efficiency of photovoltaic system.In addition, because the output characteristics of photovoltaic battery array has complicated nonlinear characteristic, be difficult to accurately determine its mathematical model, cannot ask for peak power by analytical method.In order to make the output power maximum of photovoltaic array, just must utilize the maximum power point of corresponding control method real-time follow-up, control photovoltaic battery array, maximally utilise sun power, the adjustment process that this guarantee photovoltaic array continues Maximum Power Output is called MPPT maximum power point tracking (MPPT).

At present, common maximum power point-tracing control method has constant Control of Voltage method, disturbance observation, increment node-pair method and single Chaos Search etc., but diverse ways all exists different relative merits in actual use.Constant voltage process is a kind of simple maximum power point tracing method, and its advantage is to control simply, easily realize, and still this tracking is in the time of temperature variation, and its tracking efficiency is not high, has comparatively serious power loss.Disturbance observation and increment node-pair method all can be shaken operation near maximum power point, cause Partial Power loss.Although the method for single Chaos Search can be followed the tracks of global maximum accurately, if but have the situation that has thick and fast many local maximums near global maximum time, although there is ergodicity in chaotic motion, but jumping out local maximum often needs for a long time, and the randomness having due to chaotic motion makes likely in the time approaching global maximum, but jump farly, thereby cause Optimizing Search waste of time.

Summary of the invention

The problem to be solved in the present invention is for above deficiency, a kind of photovoltaic array maximum power point tracing method based on chaos optimization search is provided, the method adopts second carrier wave chaos optimization searching algorithm after searching the current optimum solution with certain guarantee, dwindle the search volume of optimized variable, make algorithm to converge to globally optimal solution sooner, more accurately, therefore search efficiency improves a lot.

The present invention solves the technical scheme that above technical matters adopts: a kind of photovoltaic array maximum power point tracing method based on chaos optimization search, is characterized in that: described tracking comprises the following steps:

Step 1: primary carrier is selected Logistic mapping

（1）

Wherein, k is the iterations of Chaos Variable, and μ is one and controls parameter, in the time of μ=4, described Logistic shines upon the Chaos Variable producing in Complete Chaos state, and [0,1] in scope, travel through, set it as the primary carrier of chaos optimization searching method;

Step 2: the Chaos Variable that described primary carrier is produced convert new Chaos Variable to by (2) formula whole traversal interval [0,1] is mapped to the interval [c, d] of optimized variable simultaneously;

（2）

Step 3: utilize described primary carrier, carry out Chaos Search the 1st time;

The arbitrary width producing by chaos generator carries out disturbance in output voltage interval [c, d] the scope interior focusing volt system of photovoltaic array, and output voltage V pv, the electric current I pv of simultaneity factor real-time sampling photovoltaic array current time, calculate photovoltaic output power and and the current maximum power value that prestores of MPPT controller compare, if > , value be assigned to , the value of Vpv is assigned to , otherwise give up some step search all remain unchanged, think that coarse search reaches satisfied;

Step 4: utilize second carrier wave to carry out the 2nd chaos optimization search, the second carrier wave mode of chaos optimization search is as shown in (3) formula, and it can be created near the larger Chaos Variable of Orbit probability density of a certain specified point;

（3）

In formula for the maximum power point in described primary carrier search procedure corresponding output voltage, for the Chaos Variable of (1) formula generation, for another Chaos Variable that (1) formula produces, 0< α <1, β >1; Be less value when getting α, when β gets larger value, can obtain with centered by chaos sequence , and can make Chaos Search near maximum power point, have good ergodicity;

Step 5: adopt the method for dwindling search volume to improve tracking efficiency, with current optimum solution centered by, through type (4) is adjusted c, and the value of d realizes and re-constructs optimized variable interval;

(4)

Wherein r is greater than 1 constant;

Step 6: turn back to step 2, continue cyclic search, when cycle index reaches setting value, search finishes; Now be the peak power of photovoltaic array, for the optimum output voltage of photovoltaic array.

Based on a photovoltaic array maximum power point tracing method for chaos optimization search, it is characterized in that: described tracking comprises the following steps:

Start from step S101;

Then,, at step S102, according to the demand of system, systematic parameter is carried out to initialization: Chaos Variable initial value be 0.126; The up-and-down boundary value c of voltage search, the initial value of d is c=0, d=90; The power α of second carrier wave gets 0.6, β and gets 3; Current peak power =0; Constant r=2.1; Major cycle number of times =0;

At step S103, making primary carrier iterations k initial value is 0, and cycle index i=0, then enters step S104;

At step S104, by the initial value of Chaos Variable substitution carry out interative computation, and above formula is obtained substitution , obtain mppt controller output voltage , order , then enter step S105;

At step S105, calculate photovoltaic array output instantaneous power , then enter step S106;

At step S106, judge photovoltaic array output instantaneous power whether be greater than the current maximum power value that MPPT controller prestores , if so, enter step S108; If not, enter step S107;

At step S107, carry out i=i+1, then enter step S109;

At step S108, photovoltaic array is exported to instantaneous power value be assigned to the current maximum power value that MPPT controller prestores , by instantaneous voltage value compose the output voltage of MPPT controller , then enter step S109;

At step S109, judge cycle index i whether be greater than 10 or the Chaos Variable iterations k of primary carrier whether be greater than 100, if enter step S110, if not, enter step S104;

At step S110, make the Chaos Variable iterations of second carrier wave initial value is 0, and then cycle index i=0 enters step S111;

At step S111, by the initial value of Chaos Variable substitution carry out interative computation, and above formula is obtained substitution

Order , then enter step S112;

At step S112, calculate , then enter step S113;

At step S113, judgement whether be greater than , if so, realtime power is greater than the peak power of current preset, enters step S115; If not, enter step S114;

At step S114, carry out i=i+1, then enter step S116;

At step S115, by realtime power value compose the output voltage of MPPT controller , by voltage value compose the output voltage of MPPT controller , then enter step S116;

At step S116, judge second carrier wave cycle index i whether be greater than 10 or the Chaos Variable iterations k of second carrier wave whether be greater than 100, if enter step S117, if not, enter step S111;

At step S117, carry out

, , adjust c, the value of d realizes and re-constructs optimized variable interval, then major cycle number of times , then enter step S118;

At step S118, judge major cycle number of times whether be greater than 3, if so, enter step S119; If not, enter step S103;

At step S119, Maximum Power Output value optimum output voltage with mppt controller , then enter step S120;

At step S120, search finishes.

The present invention adopts above technical scheme, compared with prior art, has the following advantages:

(1) adopt primary carrier and second carrier wave to combine and carry out iterative search, more traditional Chaos Search method more can improve tracking velocity; (2) owing to having adopted second carrier wave method to search for further accurate tracking control, improved control accuracy, the photovoltaic system MPPT maximum power point tracking that has also solved part shade easily falls into the problem of local maximum; (3) the present invention can meet the needs of photovoltaic generating system maximal power tracing control, the tracking efficiency of the more effective raising system of energy.

Below in conjunction with drawings and Examples, the present invention is further described.

Brief description of the drawings

Fig. 1 is the structural drawing of control system in the embodiment of the present invention;

Fig. 2 is the process flow diagram of tracking in the embodiment of the present invention;

In figure,

1-PV Array is photovoltaic array, 2-MPPT controller, 3-totalizer, 4-proportional integral circuit, 5-comparer, 6-DC/DC transducer output capacitance, 7-fly-wheel diode, 8-switching tube, 9-inductance, 10-filter capacitor.

Embodiment

Embodiment, as shown in Figure 1, a kind of photovoltaic array maximum power point tracing method based on chaos optimization search, the real-time output voltage that Vpv is photovoltaic array, the real-time output current that Ipv is photovoltaic array, for photovoltaic array instantaneous output, the current maximum power value of photovoltaic array prestoring for MPPT controller, for with the optimum output voltage of corresponding MPPT controller, [c, d] is the output voltage interval of the photovoltaic array of the i time iteration in mppt process, and c is lower boundary, and d is coboundary. it is the cycle index of major cycle. for the Chaos Variable of primary carrier, for the photovoltaic array instantaneous output voltage in primary carrier iterative process,

The DC voltage Vpv that MPPT controller 2 is exported by real-time sampling photovoltaic array 1 and electric current I pv, calculate the output power of photovoltaic array , and and the current maximum power value that prestores of MPPT controller compare, if > , value be assigned to , the value of Vpv is assigned to the output voltage of MPPT controller otherwise,, value give up, with value remain unchanged.Then the voltage that, MPPT controller 2 is exported be added in totalizer with the voltage Vpv of photovoltaic array output, the error voltage producing is added to comparer 5 in-phase end through proportional integral link 4 compares with the sawtooth voltage that is added to comparer 5 end of oppisite phase, change the gate drive signal dutycycle of switching tube 8 in DC/DC transducer, thereby regulate the parameter of controlling DC/DC translation circuit, realize maximal power tracing control.

The primary carrier of chaos optimization search is selected Logistic mapping

（1）

Wherein k is the iterations of Chaos Variable, and μ is a control parameter, and in the time of μ=4, described Logistic shines upon the Chaos Variable producing in Complete Chaos state, and travels through in (0,1) scope.

The second carrier wave mode of chaos optimization search is as shown in (3) formula, and it can be created near the larger Chaos Variable of Orbit probability density of a certain specified point.

（3）。

In formula for the maximum power point in described primary carrier search procedure corresponding mppt controller output voltage, for the Chaos Variable of (1) formula generation, for another Chaos Variable that (1) formula produces, 0< α <1, β >1.Be less value when getting α, when β gets larger value, can obtain with centered by second carrier wave chaos sequence , can make Chaos Search near maximum power point, have good ergodicity. for second carrier wave iterations.

As shown in Figure 2, for following the tracks of the basic controlling flow process of maximum power point, this flow process starts from step S101.Then,, at step S102, according to the demand of system, systematic parameter is carried out to initialization: Chaos Variable initial value be 0.126; The up-and-down boundary value c of voltage search, the initial value of d is c=0, d=90; The power α of second carrier wave gets 0.6, β and gets 3; Current peak power =0; Constant r=2.1; Major cycle number of times =0.

At step S103, making primary carrier iterations k initial value is 0, and cycle index i=0, then enters step S104;

At step S104, by the initial value of Chaos Variable substitution carry out interative computation, and above formula is obtained substitution , obtain mppt controller output voltage , order , then enter step S105;

At step S105, calculate photovoltaic array output instantaneous power , then enter step S106;

At step S106, judge photovoltaic array output instantaneous power whether be greater than the current maximum power value that MPPT controller prestores , if so, realtime power is greater than the peak power of current preset, enters step S108; If not, enter step S107;

At step S107, carry out i=i+1, then enter step S109;

At step S108, photovoltaic array is exported to instantaneous power value be assigned to the current maximum power value that MPPT controller prestores , by instantaneous voltage value compose the output voltage of MPPT controller , then enter step S109;

At step S109, judge cycle index i whether be greater than 10 or the Chaos Variable iterations k of primary carrier whether be greater than 100, if enter step S110, if not, enter step S104;

At step S110, make the Chaos Variable iterations of second carrier wave initial value is 0, and then cycle index i=0 enters step S111;

At step S111, by the initial value of Chaos Variable substitution carry out interative computation, and above formula is obtained substitution

When during for odd number

Order , then enter step S112;

At step S112, calculate , then enter step S113;

At step S113, judgement whether be greater than , if so, realtime power is greater than the peak power of current preset, enters step S115; If not, enter step S114;

At step S114, carry out i=i+1, then enter step S116;

At step S115, by realtime power value compose the output voltage of MPPT controller , by voltage value compose the output voltage of MPPT controller , then enter step S116;

At step S116, judge second carrier wave cycle index i whether be greater than 10 or the Chaos Variable iterations k of second carrier wave whether be greater than 100, if enter step S117, if not, enter step S111;

At step S117, carry out ,

, adjust c, the value of d realizes and re-constructs optimized variable interval, then major cycle number of times , then enter step S118;

At step S118, judge major cycle number of times whether be greater than 3, if so, enter step S119; If not, enter step S103;

At step S119, Maximum Power Output value optimum output voltage with mppt controller , then enter step S120;

At step S120, search finishes.

Through test, tracking velocity and control accuracy are high.

Those skilled in the art will recognize that; above-mentioned embodiment is exemplary; in order to make those skilled in the art can better understand content of the present invention; should not be understood as limiting the scope of the invention; as long as the improvement of doing according to technical solution of the present invention, all fall into protection scope of the present invention.

Claims (2)

1. the photovoltaic array maximum power point tracing method based on chaos optimization search, is characterized in that: described tracking comprises the following steps:

Step 1: primary carrier is selected Logistic mapping

（1）

Wherein, k is the iterations of Chaos Variable, and μ is one and controls parameter, in the time of μ=4, described Logistic shines upon the Chaos Variable producing in Complete Chaos state, and [0,1] in scope, travel through, set it as the primary carrier of chaos optimization searching method;

Step 2: the Chaos Variable that described primary carrier is produced convert new Chaos Variable to by (2) formula whole traversal interval [0,1] is mapped to the interval [c, d] of optimized variable simultaneously;

（2）

Step 3: utilize described primary carrier, carry out Chaos Search the 1st time;

The arbitrary width producing by chaos generator carries out disturbance in output voltage interval [c, d] the scope interior focusing volt system of photovoltaic array, and output voltage V pv, the electric current I pv of simultaneity factor real-time sampling photovoltaic array current time, calculate photovoltaic output power and and the current maximum power value that prestores of MPPT controller compare, if > , value be assigned to , the value of Vpv is assigned to , otherwise give up some step search all remain unchanged, think that coarse search reaches satisfied;

Step 4: utilize second carrier wave to carry out the 2nd chaos optimization search, the second carrier wave mode of chaos optimization search is as shown in (3) formula, and it can be created near the larger Chaos Variable of Orbit probability density of a certain specified point;

（3）

In formula for the maximum power point in described primary carrier search procedure corresponding output voltage, for the Chaos Variable of (1) formula generation, for another Chaos Variable that (1) formula produces, 0< α <1, β >1; Be less value when getting α, when β gets larger value, can obtain with centered by chaos sequence , and can make Chaos Search near maximum power point, have good ergodicity;

Step 5: adopt the method for dwindling search volume to improve tracking efficiency, with current optimum solution centered by, through type (4) is adjusted c, and the value of d realizes and re-constructs optimized variable interval;

(4)

Wherein r is greater than 1 constant;

Step 6: turn back to step 2, continue cyclic search, when cycle index reaches setting value, search finishes; Now be the peak power of photovoltaic array, for the optimum output voltage of photovoltaic array.

2. the photovoltaic array maximum power point tracing method based on chaos optimization search, is characterized in that: described tracking comprises the following steps:

Start from step S101;

Then,, at step S102, according to the demand of system, systematic parameter is carried out to initialization: Chaos Variable initial value be 0.126; The up-and-down boundary value c of voltage search, the initial value of d is c=0, d=90; The power α of second carrier wave gets 0.6, β and gets 3; Current peak power =0; Constant r=2.1; Major cycle number of times =0;

At step S103, making primary carrier iterations k initial value is 0, and cycle index i=0, then enters step S104;

At step S104, by the initial value of Chaos Variable substitution carry out interative computation, and above formula is obtained substitution , obtain mppt controller output voltage , order , then enter step S105;

At step S105, calculate photovoltaic array output instantaneous power , then enter step S106;

At step S106, judge photovoltaic array output instantaneous power whether be greater than the current maximum power value that MPPT controller prestores , if so, enter step S108; If not, enter step S107;

At step S107, carry out i=i+1, then enter step S109;

At step S108, photovoltaic array is exported to instantaneous power value be assigned to the current maximum power value that MPPT controller prestores , by instantaneous voltage value compose the output voltage of MPPT controller , then enter step S109;

At step S109, judge cycle index i whether be greater than 10 or the Chaos Variable iterations k of primary carrier whether be greater than 100, if enter step S110, if not, enter step S104;

At step S110, make the Chaos Variable iterations of second carrier wave initial value is 0, and then cycle index i=0 enters step S111;

At step S111, by the initial value of Chaos Variable substitution carry out interative computation, and above formula is obtained substitution

Order , then enter step S112;

At step S112, calculate , then enter step S113;

At step S113, judgement whether be greater than , if so, realtime power is greater than the peak power of current preset, enters step S115; If not, enter step S114;

At step S114, carry out i=i+1, then enter step S116;

At step S115, by realtime power value compose the output voltage of MPPT controller , by voltage value compose the output voltage of MPPT controller , then enter step S116;

At step S116, judge second carrier wave cycle index i whether be greater than 10 or the Chaos Variable iterations k of second carrier wave whether be greater than 100, if enter step S117, if not, enter step S111;

At step S117, carry out

, , adjust c, the value of d realizes and re-constructs optimized variable interval, then major cycle number of times , then enter step S118;

At step S118, judge major cycle number of times whether be greater than 3, if so, enter step S119; If not, enter step S103;

At step S119, Maximum Power Output value optimum output voltage with mppt controller , then enter step S120;

At step S120, search finishes.