CN106094972A - A kind of maximum power point of photovoltaic power generation system tracking based on function model - Google Patents

Abstract

The present invention discloses a kind of maximum power point of photovoltaic power generation system tracking based on function model, and the method mainly solves the MPPT maximum power point tracking problem in photovoltaic generating system.The present invention is with Boost circuit for photovoltaic generating system main circuit, first output voltage and the electric current of photovoltaic generating system are detected, then dutycycle disturbance step function is determined according to error and error rate, and then determining the disturbance step value of subsequent time, disturbance step function is made up of two-dimensional Gaussian function and arctan function.Algorithm often runs time delay after onceT Ms, until determining the dutyfactor value at maximum power point.The method introduces two-dimensional Gaussian function and arctan function, determine the most general a kind of dutycycle perturbation motion method, MPPT maximum power point tracking can be more precisely carried out, also provide a kind of calculating reference method for other maximum power point tracing methods based on Disturbance Model.

Description

A kind of maximum power point of photovoltaic power generation system tracking based on function model

Technical field

The present invention is that arctan function common in art of mathematics and two-dimensional Gaussian function are applied to photovoltaic generating system In MPPT maximum power point tracking technology, solve the problem that maximum power point of photovoltaic power generation system is followed the tracks of, belong to photovoltaic power generation technology neck Territory.

Background technology

Along with developing rapidly of countries in the world economy, energy problem become restriction sustainable economic development principal element it One.Solar energy is paid close attention to widely as a kind of new green energy resource, in order to utilize solar energy, solar energy to greatest extent Volt generation technology arises at the historic moment, and most important of which one technology is exactly MPPT maximum power point tracking technology.According to algorithm types Difference, the technology of main flow is divided into traditional algorithm and biological intelligence algorithm.

Wherein, traditional algorithm mainly thankss for your hospitality dynamic observational method and climbing method etc., and its essence is to utilize disturbance constantly to search for currently Moment maximum power point, but there is perturbation direction erroneous judgement thus cause following the tracks of inefficient problem in traditional algorithm.Biological intelligence Algorithm includes particle cluster algorithm, wolf pack algorithm etc., and the life habit of such algorithm simulation nature biotechnology carries out photovoltaic generation system System maximum power point global optimizing, finds the peak power of current time.Biological intelligence algorithm often amount of calculation is complicated, needs ratio Algorithm is processed by processor faster, is unfavorable for that commercial Application is promoted.Although intelligent algorithm is the most emerging Algorithm, but in commercial Application or mainly apply traditional algorithm to carry out MPPT maximum power point tracking.

Therefore, prior art is needed badly a kind of the most effective, and other traditional algorithms are had the peak power of reference significance Point-tracking method.

Summary of the invention

It is an object of the invention to: in order to solve that tradition MPPT maximum power point tracking algorithm causes by mistake when extraneous environmental change The problem sentenced, and a kind of maximum power point of photovoltaic power generation system tracking based on function model is proposed, and determine one The most general perturbation motion method.

The technical solution adopted in the present invention is: a kind of maximum power point of photovoltaic power generation system based on function model is followed the tracks of Method, it is characterised in that: photovoltaic generating system with Boost circuit as main circuit, according to photovoltaic generation power and dutycycle and Power and the relation of voltage, i.e. P-D, P-U relation curve, is 0 in the slope of curve, i.e. when dP/dD=0, dP/dU=0, now reaches At maximum power point；First described tracking detects output voltage and the electric current of photovoltaic array, then according to error and mistake Difference rate of change determines dutycycle disturbance step function, and then determines the dutycycle disturbance step value of subsequent time, and dutycycle is disturbed Dynamic step function is made up of two-dimensional Gaussian function and arctan function；Method often runs time delay Tms after once, until determining maximum Dutyfactor value at power points；Described maximum power point of photovoltaic power generation system tracking based on function model comprises as follows Step:

Step 1: the voltage U in detection k moment_(k), electric current I_(k), according to P_(k)=U_(k)I_(k)Calculate current time performance number；

Step 2: definition dutycycle disturbance step function is about error E_(k)With error rate Δ E_(k)Function, it may be assumed that

$\begin{array}{c}\mathrm{\Δ}D=f(E_{\left(k\right)},{\mathrm{\ΔE}}_{\left(k\right)})=1.4312\×{\mathrm{\ΔD}}_{\max }\×{\tan }^{-1}\left(\frac{E_{\left(k\right)}-{\mathrm{\ΔE}}_{\left(k\right)})}{\mathrm{\γ}}\right)\\ \×e^{(-(a{(E-\mathrm{\α})}^2+2b(\mathrm{\Δ}E-\mathrm{\β})(E-\mathrm{\α})+c{(\mathrm{\Δ}E-\mathrm{\β})}^2\left)\right)}\end{array}---\left(1\right)$

Wherein k moment errorP_(k-1)、U_(k-1)It is power and the magnitude of voltage in k-1 moment respectively, error Rate of change Δ E (k)=E (k)-E (k-1), E_(k-1)For the error in k-1 moment, Δ D_maxLargest duty cycle disturbance step-length, α, β, γ is constant, and a, b, c can be determined by following formula:

$a=\frac{{\cos }^2\mathrm{\θ}}{2{\mathrm{\σ}}_E^2}+\frac{{\sin }^2\mathrm{\θ}}{2{({\mathrm{\σ}}_{{\mathrm{\ΔE}}_0}+k|E-\mathrm{\Δ}E\left|\right)}^2}$

$b=\frac{sin2\mathrm{\θ}}{4{\mathrm{\σ}}_E^2}+\frac{sin2\mathrm{\θ}}{4{({\mathrm{\σ}}_{{\mathrm{\ΔE}}_0}+k|E-\mathrm{\Δ}E\left|\right)}^2}$

$c=\frac{{\sin }^2\mathrm{\θ}}{2{\mathrm{\σ}}_E^2}+\frac{{\cos }^2\mathrm{\θ}}{2{({\mathrm{\σ}}_{{\mathrm{\ΔE}}_0}+k|E-\mathrm{\Δ}E\left|\right)}^2}$

σ in formula_E、K, θ are constant, determine occurrence according to trial-and-error method；

Voltage and current value according to the k moment and the performance number calculated can draw error now and error rate；

Step 3: after being determined k moment dutycycle disturbance step delta D by formula (1), dutycycle D in k+1 moment can be drawn_(k+1), That is:

D_(k+1)=D_(k)±ΔD (2)

Wherein D_(k)It it is the dutyfactor value in kth moment；

Step 4: the dutycycle disturbance step-length determined according to formula (1), calculation perturbation cycle T, setting disturbance cycle T is about accounting for The empty linear function than disturbance step-length absolute value | Δ D |, T=f (| Δ D |)=m × | Δ D |+n, wherein m and n is constant, by The method of linear fit determines occurrence；

Step 5: determine the dutycycle at maximum power point according to the relation of power and dutycycle and power and voltage, thus with Track is to peak power.

The invention has the beneficial effects as follows: the maximum power point of photovoltaic power generation system track side based on function model of the present invention Method, introduces common two-dimensional Gaussian function and arctan function to determine dutycycle disturbance step-length, with a kind of relatively simple ginseng The adjustable univeral mathematics formula of number solves the traditional algorithm problem that tracking velocity is slow when disturbance step-length is fixed, and through too much The availability of the secondary simulation results show present invention and effectiveness, it is possible to more fast and effeciently carry out MPPT maximum power point tracking.

Accompanying drawing explanation

Fig. 1 is dutycycle disturbance step function image.

Fig. 2 is the maximum power point of photovoltaic power generation system tracking block flow diagram based on function model of the present invention.

Detailed description of the invention

In order to be more fully understood that the present invention, it is further elucidated with present disclosure below in conjunction with embodiment, but the present invention Content is not limited solely to the following examples.The present invention can be made various changes or modifications by those skilled in the art, these The equivalent form of value is equally within the scope of claims listed by the application limit.

The present invention proposes a kind of maximum power point of photovoltaic power generation system tracking based on function model, and method is main Introduce two-dimensional Gaussian function common in mathematics and arctan function to determine dutycycle disturbance step function.Disturbance step-length letter Count figure as it is shown in figure 1, in this function, selecting Gaussian function to be because Gaussian function can affect the amplitude of disturbance step-length, When external environment generation acute variation, the value of E and Δ E all becomes big, and now Gaussian function can be used to avoid the mistake of dutycycle Degree change；Select arctan function to be because arctan function and can increase or reduce the change of disturbance step-length, the most permissible Improve the dynamic responding speed of MPPT, also additionally be able to be limited in the vibration near MPP thus improve the steady-state behaviour of system. Maximum power point of photovoltaic power generation system tracking framework based on function model is as shown in Figure 2.

The present invention determines dutycycle disturbance step function mainly by two-dimensional Gaussian function and arctan function, profit By the character of two functions to improve speed and the precision of MPPT maximum power point tracking, implement step refinement as follows:

Step 1: detection photovoltaic array output

Photovoltaic generating system uses Boost circuit as system main circuit, the voltage U in detection photovoltaic array k moment_(k), electric current I_(k), according to P_(k)=U_(k)I_(k)Calculate k moment performance number.

Step 2: determine perturbation direction

Relatively k moment performance number P_(k)With k-1 moment performance number P_(k-1)And k moment magnitude of voltage U_(k)With k-1 moment magnitude of voltage U_(k-1), in actual applications, due toValue the least, availableApproximate EquivalentTherefore according to merit Rate and the relation of voltage, whenTime now error E_(k)=0 reaches maximum power point, and concrete judgment mode is as follows:

(1)E_(k)=0, reach maximum power point；

(2)E_(k)> 0, D_(k+1)=D_(k)-ΔD；

(3)E_(k)< 0, D_(k+1)=D_(k)+ΔD。

Step 3: determine dutycycle disturbance step function

Dutycycle disturbance step function is mainly made up of two common mathematical functions, and one is two-dimensional Gaussian function, and other one Individual is arctan function, and dutycycle disturbance step function sets as follows:

Dutycycle disturbance step function is about error E_(k)With error rate Δ E_(k)Function, wherein: errorP_(k)And U_(k)It is power and the magnitude of voltage in k moment, error rate Δ E (k)=E (k)-E (k- 1), E_(k-1)Being the error in k-1 moment, therefore dutycycle disturbance step function is defined as:

$\begin{array}{c}\mathrm{\&Delta;}D=f(E_{\left(k\right)},{\mathrm{\&Delta;E}}_{\left(k\right)})=1.4312\&times;{\mathrm{\&Delta;D}}_{\max }\&times;{\tan }^{-1}\left(\frac{E_{\left(k\right)}-{\mathrm{\&Delta;E}}_{\left(k\right)}}{\mathrm{\&gamma;}}\right)\\ \&times;e^{(-(a{(E-\mathrm{\&alpha;})}^2+2b(\mathrm{\&Delta;}E-\mathrm{\&beta;})(E-\mathrm{\&alpha;})+c{(\mathrm{\&Delta;}E-\mathrm{\&beta;})}^2\left)\right)}\end{array}---\left(1\right)$

Δ D in formula_maxIt is largest duty cycle disturbance step-length, takes Δ D_max=0.05, α, β, γ are constants, respectively 0,0 and 5, a, B, c can be determined by following formula:

$a=\frac{{\cos }^2\mathrm{\&theta;}}{2{\mathrm{\&sigma;}}_E^2}+\frac{{\sin }^2\mathrm{\&theta;}}{2{({\mathrm{\&sigma;}}_{{\mathrm{\&Delta;E}}_0}+k|E-\mathrm{\&Delta;}E\left|\right)}^2}$

$b=\frac{sin2\mathrm{\&theta;}}{4{\mathrm{\&sigma;}}_E^2}+\frac{sin2\mathrm{\&theta;}}{4{({\mathrm{\&sigma;}}_{{\mathrm{\&Delta;E}}_0}+k|E-\mathrm{\&Delta;}E\left|\right)}^2}$

$c=\frac{{\sin }^2\mathrm{\&theta;}}{2{\mathrm{\&sigma;}}_E^2}+\frac{{\cos }^2\mathrm{\&theta;}}{2{({\mathrm{\&sigma;}}_{{\mathrm{\&Delta;E}}_0}+k|E-\mathrm{\&Delta;}E\left|\right)}^2}$

σ in formula_E、K, θ determine occurrence according to trial-and-error method, wherein σ_E=40,K=0.25,

Step 4: determine delay time T (disturbance cycle)

After photovoltaic generating system obtains a disturbance, the regular hour is needed to can be only achieved next running status, therefore Needing to arrange a time delay, setting delay function is about the linear function about dutycycle disturbance step-length absolute value | Δ D |, That is:

T=f (| Δ D |)=m × | Δ D |+n

Wherein m and n is constant, the method for linear fit determine m=1.364, n=4.975.

Step 5: the dutycycle at Maximum Power Output point

When meetingTime, the most now error E_(k)When=0, the most i.e. reach maximum power point.

Last it should be noted that, above content is only in order to illustrate technical scheme, rather than the present invention is protected The restriction of scope, simple modification that technical scheme is carried out by those of ordinary skill in the art or equivalent, Spirit and scope all without departing from technical solution of the present invention.

Claims (1)

1. a maximum power point of photovoltaic power generation system tracking based on function model, it is characterised in that: photovoltaic generation system System is with Boost circuit as main circuit, according to photovoltaic generation power and dutycycle and power and the relation of voltage, i.e. P-D, P-U Relation curve, is 0 in the slope of curve, i.e. when dP/dD=0, dP/dU=0, now reaches at maximum power point；Described track side First method detects output voltage and the electric current of photovoltaic array, then determines that dutycycle disturbance walks according to error and error rate Long function, and then determine the dutycycle disturbance step value of subsequent time, dutycycle disturbance step function by two-dimensional Gaussian function and Arctan function is constituted；Method often runs time delay Tms after once, until determining the dutyfactor value at maximum power point；Described Maximum power point of photovoltaic power generation system tracking based on function model comprises the steps of:

Step 1: the voltage U in detection k moment_(k), electric current I_(k), according to P_(k)=U_(k)I_(k)Calculate current time performance number；

Step 2: definition dutycycle disturbance step function is about error E_(k)With error rate △ E_(k)Function, it may be assumed that

$\begin{array}{c}\mathrm{\&Delta;}D=f(E_{\left(k\right)},{\mathrm{\&Delta;E}}_{\left(k\right)})=1.4312\&times;{\mathrm{\&Delta;D}}_{\max }\&times;{\tan }^{-1}\left(\frac{E_{\left(k\right)}-{\mathrm{\&Delta;E}}_{\left(k\right)})}{\mathrm{\&gamma;}}\right)\\ \&times;e^{(-(a{(E-\mathrm{\&alpha;})}^2+2B(\mathrm{\&Delta;}E-\mathrm{\&beta;})(E-\mathrm{\&alpha;})+c{(\mathrm{\&Delta;}E-\mathrm{\&beta;})}^2\left)\right)}\end{array}---\left(1\right)$

Wherein k moment errorP_(k-1)、U_(k-1)It is power and the magnitude of voltage in k-1 moment respectively, error Rate of change Δ E (k)=E (k)-E (k-1), E_(k-1)For the error in k-1 moment, △ D_maxLargest duty cycle disturbance step-length, α, β, γ is constant, and a, b, c can be determined by following formula:

$a=\frac{{\cos }^2\mathrm{\&theta;}}{2{\mathrm{\&sigma;}}_E^2}+\frac{{\sin }^2\mathrm{\&theta;}}{2{({\mathrm{\&sigma;}}_{{\mathrm{\&Delta;E}}_0}+k|E-\mathrm{\&Delta;}E\left|\right)}^2}$

$b=\frac{sin2\mathrm{\&theta;}}{4{\mathrm{\&sigma;}}_E^2}+\frac{sin2\mathrm{\&theta;}}{4{({\mathrm{\&sigma;}}_{{\mathrm{\&Delta;E}}_0}+k|E-\mathrm{\&Delta;}E\left|\right)}^2}$

$c=\frac{{\sin }^2\mathrm{\&theta;}}{2{\mathrm{\&sigma;}}_E^2}+\frac{{\cos }^2\mathrm{\&theta;}}{2{({\mathrm{\&sigma;}}_{{\mathrm{\&Delta;E}}_0}+k|E-\mathrm{\&Delta;}E\left|\right)}^2}$

σ in formula_E、K, θ are constant, determine occurrence according to trial-and-error method；

Voltage and current value according to the k moment and the performance number calculated can draw error now and error rate；

Step 3: after being determined k moment dutycycle disturbance step-length △ D by formula (1), dutycycle D in k+1 moment can be drawn_(k+1), That is:

D_(k+1)=D_(k)±△D (2)

Wherein D_(k)It it is the dutyfactor value in kth moment；

Step 4: the dutycycle disturbance step-length determined according to formula (1), calculation perturbation cycle T, setting disturbance cycle T is about accounting for The empty linear function than disturbance step-length absolute value | △ D |, T=f (| △ D |)=m × | △ D |+n, wherein m and n is constant, by The method of linear fit determines occurrence；

Step 5: determine the dutycycle at maximum power point according to the relation of power and dutycycle and power and voltage, thus with Track is to peak power.