International Journal of Advanced Engineering Science and Technological Research (IJAESTR) ISSN: 2321-1202, www.aestjournal.org @2014 All rights reserved.
SIMULATION OF STANDALONE PV SYSTEM BY VARIOUS APPROACHES
1
MD RIZWAN SAIFEE ,
2ER DURGESH KUMAR
1M.Tech Scholar(Power Electronics & Drives), SWAMI VIVEKANAND SUBHARTI UNIVERSITY
2Asst.Prof. & Head ,Department Of Electrical And Electronics Engineering, SWAMI VIVEKANAND SUBHARTI UNIVERSITY Email: 1[email protected], 2[email protected]
Abstract: This paper presents the simulation of standalone PV system which includes PV module shunt resistance , series resistance since PV cell is a better option to reduce the dependency on conventional sources of energy since today’s world is facing serious problem of electricity after study this paper we will be able to solve the questions like how to design a photovoltaic panel how to study the behavior of PV cell i.e for different different radiations. Nature of PV cell like VI characterstics, PV characterstics PI characterstics.
Index terms: Solar Cell, solar radiation, PV System, MATLAB,
I. INTRODUCTION:
Global warming and energy policies have become a hot topic on the international agenda in the last years. Developed countries are trying to reduce their greenhouse gas emissions.
In this context, photovoltaic (PV) power generation has an important role to play due to the fact that it is a green source.
The only emissions associated with PV power generation are those from the production of its components. After their installation they generate electricity from the solar irradiation without emitting greenhouse gases. In their lifetime, which is around 25 years, PV panels produce more energy than that for their manufacturing [2]. Also they can be installed in places with no other use, such as roofs and deserts, or they can produce electricity for remote locations, where there is no electricity network. The latter .type of installations is known as off-grid facilities and sometimes they are the most economical alternative to provide electricity in isolated areas.
However, most of the PV power generation comes from grid- connected installations, where the power is fed in the electricity network. In fact, it is a growing business in developed countries such as Germany which in 2010 is by far
the world leader in PV power generation followed by Spain, Japan, USA and Italy [3]. On the other hand, due to the equipment required, PV power generation is more expensive than other resources. Governments are promoting it with subsidies or feed-in tariffs, expecting the development of the technology so that in the near future it will become competitive [3]-[4].
II.SOLAR ENERGY
Energy has been harnessed by humans since ancient times using a variety of technologies. Solar radiation, along with secondary solar-powered resources such as wave and wind power, hydroelectricity and biomass, account for most of the available non-conventional type of energy on earth. Only a small fraction of the available solar energy is used [5]. Solar powered electrical generation relies on photovoltaic system and heat engines. Solar energy's uses are limited only by human creativity. To harvest the solar energy, the most common way is to use photo voltaic panels which will receive photon energy from sun and convert to electrical energy. Solar technologies are broadly classified as either passive solar or active solar depending on the way they detain, convert and distribute solar energy. Active solar techniques include the use of PV panels and solar thermal collectors to strap up the energy. Passive solar techniques include orienting a building to the Sun, selecting materials with favorable thermal mass or light dispersing properties and design spaces that naturally circulate air [5].Solar energy has a vast area of application such as electricity generation for distribution, heating water, lightening building, crop drying etc.
International Journal of Advanced Engineering Science and Technological Research (IJAESTR) ISSN: 2321-1202, www.aestjournal.org @2014 All rights reserved.
A. DISTRIBUTION OF SOLAR RADIATION
Figure 1.Solar radiation distribution [11,12].
B. SOLAR RADIATION REACHING EARTH SURFACE
The intensity of solar radiation reaching earth surface which is 1369 watts per square meter is known as Solar Constant. It is important to realize that it is not the intensity per square meter of the Earth’s surface but per square meter on a sphere with the radius of 149,596,000 km and with the Sun at its centre.
The total amount solar radiation intercepted by the Earth is the Solar Constant multiplied by the cross section area of the Earth. If we now divide the calculated number by the surface area of the Earth, we shall find how much solar radiation is received in an average per square meter of the Earth's surface [13]. Hence the average solar radiation R per square meter of the Earth surface is,
approx
...(1)
where S is the solar constant, r is the earth radius[13].
The Handy formula which is used to calculate solar energy received by earth
...(2) where
E is the solar energy in EJ (Exa joule, 1 Exa= 1018) .
S is the Solar Constant in W/m2.
n is the number of hours.
r is the Earth's radius in km[8].
C. SPECTRUM OF SUN
The performance of Photovoltaic device is reliant on the spectral distribution of solar radiation. The standard spectral distribution is mainly used as reference for evaluation of PV devices.
figure 2: standard spectrum for solar cells
DEFINING STANDARD SPECTRA FOR SOLAR PANELS :
the atmosphere does not change the overall intensity , but the whole spectral distribution .for instance ,most of high energy wavelengths that are present in the sunlight are filtered out by the ozone layer .generally, with longer paths through the atmosphere (at higher latitudes or around sunset).The larger the path of infrared light, the low energy spectrum. This filter effect can be expressed by a turbidity factor .
In order to be able to compare solar modules ,standard test conditions have been designed which will be described later .the standard spectra refer to generic locations .they are prefixed ‘’AM’’,which stands for “air mass “ and followed by a number, which refers to the length of the path through the atmosphere in relation to the shortest length if the sun was in the apex. It is roughly
International Journal of Advanced Engineering Science and Technological Research (IJAESTR) ISSN: 2321-1202, www.aestjournal.org @2014 All rights reserved.
with the zenith angle
The committee international d’Eclaraige(CIE) and the American society for testing and materials (ASTM) publish a no of spectra. Their origins are from actual measurements ,which are subsequently declared standard .they are also designed such that the spectrum can be reproduced artificially.
D. STANDARD TEST CONDITIONS (STC) The comparison between different photovoltaic cells can be done on the basis of their performance and characteristic curve. The parameters are always given in datasheet. The datasheet make available the notable parameter regarding the characteristics and performance of PV cells with respect to standard test condition.
Standard test conditions are as follows:
Temperature = 250c Irradiance = 1000W/m2 Spectrum = 1.5 i.e. AM.
III.EQUIVALENT CKT OF PV CELL
The building block of PV array is the solar cell which is basically a p-n junction semiconductor junction that directly converts light energy into electricity. The physical structure and equivalent circuit are shown below.
Figure.4 Structure of a PV cell
Figure.5 equivalent circuit of the PV cell
The simplest equivalent circuit of a solar cell is a current source in anti-parallel with a diode. The output of the current source is directly proportional to the light falling on the cell (photocurrent Iph). During darkness, the solar cell is not an active device; it works as a diode, i.e. a p-n junction. It produces neither a current nor a voltage. However, if it is connected to an external supply (large voltage) it generates a current Id, called diode (D) current or dark current. The diode determines the I-V characteristics of the cell.International Journal of Advanced Engineering Science and Technological Research (IJAESTR) ISSN: 2321-1202, www.aestjournal.org @2014 All rights reserved.
…(3)
Figure.6 relation between voltage and current In an ideal cell Rs = Rsh = 0, which is a relatively common assumption. For this paper, a model of moderate complexity was used. The net current of the cell is the difference of the photocurrent, I and the normal diode current Id:
To simulate PV array, a PV mathematical model is used following set of equations.
...(4)
The model includes the temperature dependence of photocurrent I and saturation current of the diode Io.
…(5)
…(6)
…(7)
…(8)
(9)
TABLE 1 : ABBREVIATIONS USED IN EQUATIONS
SYMBOL EXPANSION
I Photo current from solar cell
G Insolation in w/m2
T Temperature for which characterstics have to be found
T1 Temperature for which characterstics is known
ISC Short circuit current
K-o Increase in amps/degree increase in temperature
q Charge of an electron VOC Open circuit voltage
IV. SIMULINK MODEL OF PV CELL :
Figure.7 The Complete Simulink Circuit Model Of PV Cell V. MATLAB CODING FOR PV CELL :
Matlab Coding is done for followings mathematical equations of PV cell:
…(10)
…(11)
…(12)
...(13)
International Journal of Advanced Engineering Science and Technological Research (IJAESTR) ISSN: 2321-1202, www.aestjournal.org @2014 All rights reserved.
Abbreviations used in coding S.No Abbreviations Expansion
1. Cell photo current
2. Cell short circuit current at refrence temperature and radiation
3. Cell reverse saturation current (varies with temperature)
4. Cell reverse saturation current at Tr 5. Short circuit current temperature
coefficient
6. Ambient temperature (330 for this paper)
7. Cell Refrence temperature
8. Solar constant in W/m2
9. Charge of an electron (1.6022*10-19)
10. Band gap energy of semiconductor used
11. k Boltzman constant (1.38065*10-23) 12. A PN junction ideality factor value
ranges from 1-5 for this paper 2.15
13. No of cells in parallel
14. No of cells in series
15. P0 Output power
16. V0 Output voltage 17. I0 Output current
VI. SIMULATION RESULTS :
0 2 4 6 8 10 12 14 16 18 20
0 50 100 150 200 250 300 350 400
Current(amp) of pv cell
Power (watt) of pv cell
90 mW/sqcm 70 mW/sq cm 50 mW/sq cm 30 mW/sq cm 10 mW/sq cm
POWER V/S CURRENT OF PV CELL
FIGURE .8 POWER V/S CURRENT CHARACTERSTICS (14)
This figure shows relationship between current(in amperes) and power (in watts) as the radiation is keeps on increasing then current is also increasing and as a result of that power is also increasing here current is increasing in large amount but power is increasing in small amount .
International Journal of Advanced Engineering Science and Technological Research (IJAESTR) ISSN: 2321-1202, www.aestjournal.org @2014 All rights reserved.
0 5 10 15 20 25 30 35 40 45 50
0 5 10 15 20
Voltage (volt)of pv cell
Current (amp)of pv cell
90 mW/sq cm 70 mW/sq cm 50 mW/sq cm 30 mW/sq cm 10 mW/sq cm VI CHARACTERSTICS OF PV CELL
FIGURE 9: VI CHARACTERSTICS OF PV CELL (14)
This figure shows the relationship between voltage (in volts) and current (in amperes) when varying solar radiation is incident to it.
0 5 10 15 20 25 30 35 40 45 50
0 50 100 150 200 250 300 350 400
Voltage (volt)of pv cell
Power (watt)of pv cell
90 mW/sq cm 70 mW/sq cm 50 mW/sq cm 30 mW/sq cm 10 mW/sq cm
POWER V/S VOLTAGE OF PV CELL
FIGURE 10 POWER V/S VOLTAGE CHARACTERSTICS (14)
This figure shows the relationship between voltage (in volts) and power (in watts) given by the PV cell when varying solar radiation is incident to it.
VII.CONCLUSIONS:
The P-V, P-I, I-V curves we obtained from the simulation of the PV array designed in MATLAB environment explains in detail its dependence on the irradiation levels . The entire
energy conversion system has been designed in MATLB- SIMULINK environment. The various values of the voltage and current obtained have been plotted in the open circuit I-V curves of the PV array at different irradiations levels.
International Journal of Advanced Engineering Science and Technological Research (IJAESTR) ISSN: 2321-1202, www.aestjournal.org @2014 All rights reserved.
However the performance of the photovoltaic device depends on the spectral distribution of the solar radiation.
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