Design and simulation of MATLAB / Simulink. Influence of external and internal parameters of photovoltaic cells

Received date: December 14, 2014; revised date: February 04, 2015; accepted date: June 27, 2015 Abstract This article is devoted to the simulation of a model of a single photovoltaic cell described by mathematical equations comprises a photoelectric generator, a diode, a series resistance and shunt resistance. The goal is to draw IV and PV characteristics under Changes five parameter, external (temperature settings, illumination) and internal (series resistance, shunt resistance, factor ideality and the saturation current) and the influence of each parameter on the model.


Introduction
The principle of the photoelectric effect (Direct transformation energy from light into electricity) was applied in 1839 by Antoine Becquerel and his son Edmond Becquerel who noted that a chain of elements conduct electricity gave to a current spontaneous electric when she was enlightened. [1]. Later, selenium and silicon (which finally for reasons of cost supplanted cadmium-tellurium or cadmiumindium-selenium also tested) were shown capable of producing the first cells photovoltaic (exposure meters for photography soon 1914, and 40 years later (in 1954) for an electricity production). Research also carries today on organic polymers and materials (possibly flexible) which could replace silicon. [1] 2. Photovoltaic module Msx60 The photovoltaic cell is made of a material semiconductor that absorbs light energy and transformed directly into electric current [2] [3] [4] [5].

polycrystalline Cell
Cells in polycrystalline silicon are formed of several silicon crystals.

Amorphous Cell
The amorphous silicon cells made with amorphous silicon, not crystallized, spread on a plate of glass.

Tandem cell
There are also other types of cells, such as tandems, consisting of several cells and cells in plastiques.
For irradiation and temperature data, equation (1) has different combinations of a, Rs and Rsh allowing passage near the same points ISC, IM, VM and VOC curve I-V. Taken separately, these values of a, Rs and Rsh only are not appropriate. What really makes the significant is the ratio consisting of three parameters.
The relationship of power for a module PV is given by: Thermal voltage is expressed by: Where: q: elementary charge 1,607 10 -19 C A: coefficient of ideality of the cell; it depends on the material. K: Boltzmann's constant = 1.380 10 -23 J / K T: temperature in degreesKel Rs: series resistance of the cell (Ω).
NS :the number of series connected cells.
Applying the short-circuit conditions in equation (1), Iph is obtainable by: Equations (3) and (4) ISC and Voc represent respectively the current short circuit and open circuit voltage..

Photovoltaic module Msx60
We chose a mono-crystalline silicon cells module composed of 36 Msx60 with a maximum power of 60connected in series .W is considered in standard conditions G = 1000W / m2, T = 25 ° C. To realize the modelling of this module, we used MATLAB as a tool for testing and simulation.  The shape of the current-voltage characteristics I(V) and frequency power P (V) obtained using the electric model equations presented in Figure (5) and figure (6). The increase of the illumination with a temperature fixed causes an increase or generator operates as a current generator, but it is one of the increase in the voltage to égerment open circuit, the current is directly proportional to sunlight where the shortcircuit current (Isc) is clearly sensitive to sunlight, For against the voltage is relatively un degraded. We deduce so that the cell can provide a voltage near that correct, even in low lighting. Finally, when the sun raises, the intensity of short circuit increases, the curves characteristics shift to values growing, allowing the module to produce an largest electric power.

Influence of temperature
Temperature is an important parameter in the cell behavior. Increasing temperature with a fixed illumination causes net reduction of the open circuit voltage (Voc) and an increase in the short-circuit current (Isc), and a reduction of the maximum power (Pmax). The influence of temperature is reduced compared to the sun, but it is not negligible on the current / voltage characteristic of a generator. To a temperature which changes from 0 to 100 ° C, it can be seen that the variation of the voltage changes much more than the current. It varies very slightly. Unlike voltage, short-circuit current, meanwhile, increases with an increase in temperature. This is due to better absorption of light, the optical gap with lowering the increase. However, this increase in intensity is very low; it can be neglected to the point of maximum power.

Internal parameters 5.2.1. Influence of series resistance
The series resistance is the slope of the characteristic in the area where the photodiode acts as a voltage generator, and when it is high, it decreases the short circuit current value (Icc).

Conclusion
In this article, we presented the various simulations of the electrical characteristics of the model electrical equivalent of the photovoltaic cell, we can note that the power output of a solar panel does not depend only on the radiation and temperature of the exposure, but also parameters internal (series resistance, shunt resistance, idealityfactor, and the saturation current). [3]