CN205210751U - It trails hardware systems to become step -length photovoltaic maximum power - Google Patents

Abstract

The utility model discloses an it trails hardware systems to become step -length photovoltaic maximum power. The utility model discloses a hardware systems comprises photovoltaic array, boost circuit, DSP controller, load, and detection device includes current transformer and voltage transformer, the boost circuit input is connected with photovoltaic array, and the output is connected with the load, and detection device loads the output at photovoltaic array, transmits the controller for DSP with the current -voltage testing result, and photovoltaic system maximum power tracking control is realized according to testing result control boost circuit's work to the DSP controller. The utility model discloses simple structure, when external illumination intensity acutely changed, the system still can be fast, accurately tracker change, reach new stable state operating point fast, with low costs, the good reliability.

Description

A kind of variable step photovoltaic maximal power tracing hardware system

Technical field

The utility model relates to technical field of photovoltaic power generation, particularly relates to variable step photovoltaic maximal power tracing hardware system.

Background technology

Solar energy power generating is a kind of important form of Solar use, is to adopt solar cell luminous energy to be converted to the generation mode of electric energy, and along with technology constantly progress, and photovoltaic cell is one of generation technology most with prospects.The ultimate principle of solar cell is the photovoltaic effect of semiconductor, namely under sunlight, produces photovoltage phenomenon.U.S.'s Bell Laboratory in 1954 first utility model take PN junction as the crystal-silicon solar cell had use value of basic structure, and from then on first solar cell is used widely in space technology, starts now to be progressively widely applied on ground.Solar energy power generating is not due to by the restriction of energy resources, starting material and applied environment, and have most vast potential for future development, being that various countries put forth effort one of renewable energy technologies developed most, is the main source of future world and electric power.

In photovoltaic generating system, the utilization factor of photovoltaic cell except outside the Pass having with the bulk properties of photovoltaic cell, also by environment for use as the impact of the factors such as intensity of illumination, load and temperature.Under different external condition, photovoltaic cell may operate at difference and on unique maximum power point (MaximumPowerPoint, MPP).In order to improve the energy conversion efficiency of photovoltaic generation as much as possible, make photovoltaic cell when applied environment constantly changes, keep maximum power output, photovoltaic generating system MPPT (MaximumPowerPointTracking, maximal power tracing) technology is arisen at the historic moment always.By maximal power tracing, the output power from photovoltaic cells can be realized and maximize, greatly improve the utilization ratio of photovoltaic cell.Therefore, research one of focus becoming field of photovoltaic power generation of photovoltaic maximal power tracing control technology is directed to.

Find a kind of novel maximal power tracing system and method, rapidity when making it simultaneously meet MPPT maximum power point tracking and accuracy requirement, and the tracer request met when illumination or temperature conditions acute variation is that modern photovoltaic demand for development is to the requirement of maximum power tracking and controlling method.Find by prior art documents, (a kind of novel maximal power tracing algorithm and hardware implementing thereof, China Patent No.: CN201410504089.5) propose a kind of maximum power tracking method, it is by the current solar panel open-circuit voltage of sampled measurements and battery tension, export different curve in different situations, by comparing current sampling unit real-time sampling output current, obtain solar panel maximum power point, and do not limit by environmental factors such as illumination, temperature, shade block.But sampling process is complicated, be not easy to be applied in various environment.In order to improve rapidity when maximum power tracking method carries out MPPT maximum power point tracking and accuracy, the utility model proposes variable step maximum power tracking method on the basis of traditional fixed step size maximum power tracking method.Meanwhile, we introduce and guarantee the constringent variable proportion coefficient of maximum power tracking method, can change along with tracing process, and the selection of this scale-up factor ensure that system can obtain good dynamic response and stability.The utility model can tracker change quickly and accurately, arrives new steady operation point fast, has better dynamic response characteristic.In the design of photovoltaic generating system, there is important theory significance and practical value.

Utility model content

The purpose of this utility model is for photovoltaic generating system, proposes a kind of novel variable step maximal power tracing hardware system based on conductance increment method (IncrementalConductance, INC).

Variable step photovoltaic maximal power tracing hardware system of the present utility model is made up of photovoltaic array, pick-up unit, booster circuit, dsp controller, load, and pick-up unit comprises current transformer and voltage transformer (VT).Booster circuit input end is connected with photovoltaic array, output terminal is connected with load, pick-up unit is loaded in the output terminal of photovoltaic array, current/voltage testing result is passed to dsp controller, dsp controller controls the work of booster circuit according to testing result, realizes photovoltaic system maximal power tracing and controls.

Traditional INC method adopts a fixing iteration step length to carry out MPPT maximum power point tracking usually.But the conductance increment method of this fixed step size exists open defect: if step-length is less, the photovoltaic cell long period can be made to be trapped in low-power output area; If step-length is excessive, system concussion can be aggravated again.Traditional INC method can only take into account the two requirement, in dynamic response performance and the concussion of maximal power tracing stable state, obtain a compromise effect.In order to improve rapidity when conductance increment method carries out MPPT maximum power point tracking and accuracy, the basis of INC method proposes the scheme of variable step.

Compared with prior art, the utility model tool has the following advantages and technique effect: the utility model structure is simple, easy realization, by pick-up unit (current transformer and voltage transformer (VT)), booster circuit, away from maximum power point region, the step-length appropriateness utilizing dsp controller to follow the tracks of becomes large, to improve maximal power tracing speed; And at maximum power point near zone, the step-length of system keeps track suitably diminishes, to improve maximal power tracing precision.

Accompanying drawing explanation

Fig. 1 is photovoltaic maximal power tracing hardware system block diagram.

Fig. 2 is photovoltaic system P-V family curve and threshold function table (C) curve map in example.

Fig. 3 is variable step INC method control flow chart in example.

Fig. 4 is the step sizes variation diagram of variable step INC method in example.

Fig. 5 is photovoltaic output voltage variation diagram in example.

Fig. 6 is photovoltaic output power variation diagram in example.

Embodiment

Below in conjunction with embodiment and accompanying drawing, the utility model is described in further detail, if it is noted that have below and relate to software program portion, be all that those skilled in the art can refer to prior art programming realization.

Fig. 1 is Novel photovoltaic maximal power tracing hardware system block diagram, is made up of Photovoltaic array, booster circuit, DSP (digitalsignalprocessing) controller, load.Enter dsp controller by sampling photovoltaic cell output voltage, output current, dsp controller output point is empty than signal, thus realizes the control of photovoltaic system maximal power tracing.

The utility model key is the design of hardware configuration, below as an example, in conjunction with built-in program in dsp, is described detailed process.

Fig. 2 is photovoltaic system P-V family curve and threshold function table (C) curve map, and as shown in the figure, INC algorithm operational mode is according to parting cutpoint (LDP) on the left side and parting cutpoint (RDP) on the right side and change.The dot interlace that parts on the left side of this threshold function table curve corresponds to magnitude of voltage (V on the left of maximum power point ₁), part cutpoint on the right side and correspond to magnitude of voltage (V on the right side of maximum power point ₂).When photovoltaic array is operated between LDP and RDP, INC operates in variable step pattern.Otherwise it is operated in fixed step size pattern.This process can be represented as:

Wherein, Δ N/ Δ V is the increment of threshold function table; P (k) is k moment photovoltaic output power value; N (k) is k moment threshold function table value.

Traditional variable step INC method adopts fixing scale factor, tracer request when easily causing method cannot meet illumination or temperature conditions acute variation.The utility model proposes novel variable step INC method and adopt variable scale factor thus the size determining variable step size.

By average inequality

$\sqrt{\frac{a^2+b^2}{2}}\≥\frac{a+b}{2}\≥\sqrt{ab}\≥\frac{2}{\frac{1}{a}+\frac{1}{b}}$

Can derive:

$0<\frac{{(a+b)}^2}{2(a^2+b^2)}<1$

Order $a=N\left(k\right)=V\left(k\right)*\left|\frac{dP}{dV}\right|,$ B=1, then:

$0<\frac{{(a+b)}^2}{2(a^2+b^2)}=\frac{{\left(N\right(k)+1)}^2}{2(N{\left(k\right)}^2+1)}<1$

As shown in Figure 2, photovoltaic cell P-V family curve is asymmetric about MPP point, therefore can adopt different tracing step in the MPP left and right sides.Adopt d ₁and d ₂as fixing step sizes (d ₁be applicable on the left of maximum power point, d ₂be applicable on the right side of maximum power point), therefore variable step size size can be determined by following equation:

$\mathrm{\&Delta;}D\left(k\right)=\{\begin{array}{c}\frac{{\left(N\right(k)+1)}^2}{2(N{\left(k\right)}^2+1)}*d_1,0\&le;V\&le;V_{mpp}\\ \frac{{\left(N\right(k)+1)}^2}{2(N{\left(k\right)}^2+1)}*d_2,V_{mpp}\&le;V\&le;V_{OC}\end{array},k=1,2,\mathrm{3...}$

Make Δ D _max=min{d ₁, d ₂, can obtain: Δ D (k) < Δ D _max

Variable step rule meets above formula, and therefore this novel variable step INC method can restrain according to update rule, guarantees the convergence of maximum power tracking method.As shown in Figure 3, novel variable step variation diagram as shown in Figure 4 for novel variable step INC method control flow chart.

For correctness and the superiority of the novel variable step INC method that the utility model proposes are described, the utility model sets up photovoltaic maximum power tracking method verification model, and contrasts fixed step size INC method, traditional variable step INC method, novel INC method three tracking effect when tracking effect and external environmental condition acute variation under stable external environment.

According to the one novel variable step INC method that the utility model proposes, based on setting up photovoltaic maximum power tracking method checking realistic model under Simulink simulated environment.This model is made up of photovoltaic array model, booster circuit model, maximal power tracing control module.Enter maximal power tracing control module by sampling photovoltaic cell output voltage, output current, maximal power tracing control module output point is empty than signal, thus realizes the control of photovoltaic system maximal power tracing.Use fixed step size Fix-Step pattern in emulation, discrete method, simulation time is 1s, and minimum interval is 1e-6.

Change by arranging intensity of illumination in realistic model carrys out the acute variation of environmental test condition.When 0.8s, intensity of illumination is from 1000W/m ²bust is to 600W/m ², when 2s again from 600W/m ²rise to 1000W/m ²dynamic response and stable state shock range is followed the tracks of when extraneous ambient stable by comparing three kinds of methods, whether there is erroneous judgement in external environmental condition sudden change moment and whether can come back to steady state (SS) and required time, thus the relative merits of contrast three kinds of methods.One refer to novel variable step INC method in method below, method two refers to traditional variable step size method, and method three refers to fixed step size INC method.

Fig. 5 and Fig. 6 is respectively photovoltaic output voltage, the situation of change of photovoltaic output power under intensity of illumination change.System is 1000W/m in initial time intensity of illumination ², method one is through Δ t ₅time arrives stable state, and its steady state voltage shock range is about 19.1548V, and steady state power shock range is about 117.5W, and exporting average power in 0.8s is 4922.7W; Method two is through Δ t ₄time arrives stable state, and its steady state voltage shock range is about 31.4121V, and steady state power shock range is about 239.6W, and exporting average power in 0.8s is 4833.3W; Method three is through Δ t ₃time arrives stable state, and its steady state voltage shock range is about 24.5481V, and steady state power shock range is about 131.5W, and exporting average power in 0.8s is 4336.8W; Interpretation of result is as shown in table 1.In like manner can analyze intensity of illumination at 600W/m ²time, the tracking effect of three kinds of methods.Integrated comparative can obtain, and under stable external environmental condition, the tracking dynamic response performance of three kinds of methods successively decreases successively, and method one is optimum, and method two takes second place, and method three effect is the poorest.

Table 1 three class maximum power tracking method statistical effect

System when 0.8s intensity of illumination from 1000W/m ²bust is to 600W/m ², method one can enter new stable state immediately, and of short duration erroneous judgement occurs method two, through Δ t ₁time arrives stable state; There is of short duration erroneous judgement equally in method three, through Δ t ₂time arrives stable state.Three kinds of effect stable state concussions after the new stable state of arrival are all very little.In like manner can analytic system intensity of illumination when 2s again from 600W/m ²suddenly 1000W/m is risen to ²the tracking effect of Shi Sanzhe.Integrated comparative can obtain, and when external environment generation acute variation, method one energy challenging changes fast, erroneous judgement did not occur, and comparatively fast entered new stable state; All there is of short duration erroneous judgement in method two and method three, all can through after a while laggard enter new stable state, but the power that method two lose because there is erroneous judgement is 265.5W, and the power that method three is lost because occurring to judge by accident is 605.1W.

Simulation result shows, the novel variable step INC method proposed can take into account photovoltaic system dynamic response performance and steady oscillation requirement simultaneously, has tracking velocity fast, the advantage that precision is high; Simultaneously when extraneous intensity of illumination acute variation, the method can tracker change quickly and accurately, does not judge by accident, arrives new steady operation point fast, have better dynamic response characteristic.

Claims (1)

1. a novel variable step maximal power tracing system, comprise dsp controller, it is characterized in that, also comprise photovoltaic array, pick-up unit, booster circuit and load, pick-up unit comprises current transformer and voltage transformer (VT); Booster circuit input end is connected with photovoltaic array, output terminal is connected with load, pick-up unit is loaded in the output terminal of photovoltaic array, current/voltage testing result is passed to dsp controller, dsp controller controls the work of booster circuit according to testing result, realizes photovoltaic system maximal power tracing and controls.