CN103995558B - A kind of maximum power point of photovoltaic array tracking based on chaos optimization search - Google Patents

Abstract

The invention discloses a kind of maximum power point of photovoltaic array tracking based on chaos optimization search, the DC voltage Vpv exported by real-time sampling photovoltaic array and electric current I pv, calculates the output power of photovoltaic array , and and the current maximum power value that prestores of MPPT controller compare, if > , then value be assigned to , the value of Vpv is assigned to the output voltage of MPPT controller otherwise, then value give up, with value remain unchanged.Then, the voltage of MPPT controller output the voltage Vpv exported with photovoltaic array is added in totalizer, the error voltage produced is added to comparer in-phase end through proportional integral link compares with the sawtooth voltage being added to comparer end of oppisite phase, change the dutycycle of DC/DC transducer breaker in middle tube grid drive singal, thus the parameter of regulable control DC/DC translation circuit, realize maximal power tracing to control, tracking velocity is fast, control accuracy is high.

Description

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

Technical field

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

Background technology

During photovoltaic generating system work, at certain temperature and intensity of sunshine, photovoltaic battery array has unique maximum power point, but the output characteristics due to photovoltaic battery array is subject to the impact of the factors such as load condition, intensity of sunshine, environment temperature, the output voltage of photovoltaic battery array and electric current all can produce very large change thereupon, thus make output power unstable, if can not its change of real-time follow-up, then can reduce the output efficiency of photovoltaic system.In addition, the output characteristics due to photovoltaic battery array has complicated nonlinear characteristic, is difficult to accurately determine its mathematical model, cannot asks for peak power by analytical method.In order to make the output power of photovoltaic array maximum, just must utilize corresponding control method real-time follow-up, control the maximum power point of 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 voltage control 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 controls simply, easily to realize, but this tracking is when temperature variation, and its tracking efficiency is not high, has comparatively serious power loss.Disturbance observation and increment node-pair method all can shake operation near maximum power point, cause Partial Power to lose.Although the method for single Chaos Search can follow the tracks of global maximum accurately, if but when having the situation that there is many local maximums thick and fast near global maximum, although there is ergodicity in chaotic motion, but jump out local maximum often to need for a long time, and the randomness had due to chaotic motion makes likely when close to global maximum, but jump far, thus 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 maximum power point of photovoltaic array tracking 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, reduce the search volume of optimized variable, make algorithm can 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 maximum power point of photovoltaic array tracking based on chaos optimization search, is characterized in that: described tracking comprises the following steps:

Step 1: primary carrier selects Logistic to map

（1）

Wherein, k is the iterations of Chaos Variable, and μ is a controling parameters, when μ=4, then the Chaos Variable that described Logistic mapping produces is in Complete Chaos state, and [0,1] be traversal in scope, it can be used as the primary carrier of chaos optimization searching method;

Step 2: the Chaos Variable that described primary carrier is produced new Chaos Variable is converted 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, carries out the 1st Chaos Search;

The arbitrary width produced by chaos generator is at the output voltage interval [c of photovoltaic array, d] scope interior focusing volt system carry out disturbance, output voltage Vpv, 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 > , then value be assigned to , the value of Vpv is assigned to , otherwise give up, some step search all remain unchanged, then 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 produce the Chaos Variable that Orbit probability density is larger near 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 that (1) formula produces, 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 reducing search volume to improve and follow the tracks of efficiency, namely with current optimum solution centered by, the value of through type (4) adjustment c, d realizes re-constructing optimized variable interval;

(4)

Wherein r be greater than 1 constant;

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

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

Start from step S101;

Then, in step S102, according to the demand of system, initialization is carried out to systematic parameter: 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;

In step S103, make primary carrier iterations k initial value be 0, cycle index i=0, then enter step S104;

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

In step S105, calculate photovoltaic array and export instantaneous power , then enter step S106;

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

In step S107, perform i=i+1, then enter step S109;

In step S108, photovoltaic array is exported 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;

In 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;

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

In step S111, by the initial value of Chaos Variable substitute into carry out interative computation, and above formula is obtained substitute into

Order , then enter step S112;

In step S112, calculate , then enter step S113;

In step S113, judge whether be greater than , if so, namely realtime power is greater than the peak power of current preset, then enter step S115; If not, then step S114 is entered;

In step S114, perform i=i+1, then enter step S116;

In 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;

In 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;

In step S117, perform

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

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

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

In step S120, search terminates.

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) carry out searching for further accurate tracking control owing to have employed second carrier wave method, improve control accuracy, the photovoltaic system MPPT maximum power point tracking also solving partial phantom easily falls into the problem of local maximum; (3) the present invention can meet the needs that photovoltaic generating system maximal power tracing controls, the tracking efficiency of the more effective raising system of energy.

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

Accompanying drawing explanation

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 maximum power point of photovoltaic array tracking based on chaos optimization search, Vpv is the real-time output voltage of photovoltaic array, and Ipv is the real-time output current of photovoltaic array, for photovoltaic array instantaneous output, for the current maximum power value of photovoltaic array that MPPT controller prestores, for with the optimum output voltage of corresponding MPPT controller, [c, d] for the output voltage interval of the photovoltaic array of i-th iteration in mppt process, c be lower boundary, 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,

MPPT controller 2 passes through DC voltage Vpv and the electric current I pv of real-time sampling photovoltaic array 1 output, calculates the output power of photovoltaic array , and and the current maximum power value that prestores of MPPT controller compare, if > , then value be assigned to , the value of Vpv is assigned to the output voltage of MPPT controller otherwise, then value give up, with value remain unchanged.Then, the voltage of MPPT controller 2 output the voltage Vpv exported with photovoltaic array is added in totalizer, the error voltage produced is added to comparer 5 in-phase end through proportional integral link 4 compares with the sawtooth voltage being added to comparer 5 end of oppisite phase, change the gate drive signal dutycycle of DC/DC transducer breaker in middle pipe 8, thus the parameter of regulable control DC/DC translation circuit, realize maximal power tracing and control.

The primary carrier of chaos optimization search selects Logistic to map

（1）

Wherein k is the iterations of Chaos Variable, and μ is a controling parameters, and when μ=4, then the Chaos Variable that described Logistic mapping produces is in Complete Chaos state, and is traversal in (0,1) scope.

The second carrier wave mode of chaos optimization search is as shown in (3) formula, and it can produce the Chaos Variable that Orbit probability density is larger near 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 that (1) formula produces, 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, in step S102, according to the demand of system, initialization is carried out to systematic parameter: 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.

In step S103, make primary carrier iterations k initial value be 0, cycle index i=0, then enter step S104;

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

In step S105, calculate photovoltaic array and export instantaneous power , then enter step S106;

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

In step S107, perform i=i+1, then enter step S109;

In step S108, photovoltaic array is exported 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;

In 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;

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

In step S111, by the initial value of Chaos Variable substitute into carry out interative computation, and above formula is obtained substitute into

When during for odd number

Order , then enter step S112;

In step S112, calculate , then enter step S113;

In step S113, judge whether be greater than , if so, namely realtime power is greater than the peak power of current preset, then enter step S115; If not, then step S114 is entered;

In step S114, perform i=i+1, then enter step S116;

In 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;

In 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;

In step S117, perform ,

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

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

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

In step S120, search terminates.

Through test, tracking velocity and control accuracy high.

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

Claims (1)

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

Step 1: primary carrier selects Logistic to map

（1）

Wherein, k is the iterations of Chaos Variable, and μ is a controling parameters, when μ=4, then the Chaos Variable that described Logistic mapping produces is in Complete Chaos state, and [0,1] be traversal in scope, it can be used as the primary carrier of chaos optimization searching method;

Step 2: the Chaos Variable that described primary carrier is produced new Chaos Variable is converted 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, carries out the 1st Chaos Search;

The arbitrary width produced by chaos generator is at the output voltage interval [c of photovoltaic array, d] scope interior focusing volt system carry out disturbance, output voltage Vpv, 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 > , then value be assigned to , the value of Vpv is assigned to , otherwise give up, some step search all remain unchanged, then 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 produce the Chaos Variable that Orbit probability density is larger near a certain specified point;

In formula for the maximum power point in described primary carrier search procedure corresponding output voltage, for the Chaos Variable that (1) formula produces, 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 reducing search volume to improve and follow the tracks of efficiency, namely with current optimum solution centered by, the value of through type (4) adjustment c, d realizes re-constructing optimized variable interval;

(4)

Wherein r be greater than 1 constant;

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