International Review on Modelling and Simulations (I.RE.MO.S.), Vol. 3, N. 5
October 2010
A New Approach for Modeling the Photovoltaic Cell
Using Orcad Comparing with the Model Done in Matlab
A. Blorfan, D. Flieller, P. Wira, G. Sturtzer, J. Merckle
Abstract – This paper represents two model of photovoltaic, the first uses the Matlab, it explains
the Photovoltaic Cell I-V Characterization and how we can get the Maximum peak power
tracking(MPPT), the other is done in Orcad(new version of Pspice), in Orcad we propose an
electronic circuit to be realize easily, a newer technique will be discussed in the last one, it is a
new geometric approach, it depends on the characteristic of the photovoltaic diode, this approach
give an approximation reasonable to this model, more than the classical one. Copyright © 2010
Praise Worthy Prize S.r.l. - All rights reserved.
Keywords: Solar Cell, Photovoltaic, MPPT, Simulink, Orcad
I.
Nomenclature
I-V
MPPT
ORCAD
WL,
WV
I
ID
iL
I0
K
I SC
voc
FF
Pmax
Vout
I out
Kec
Pin
I t Ac
iPV
v pv
I0
vT
PPV
Ri
PWM
Introduction
Solar cells are in fact large area semiconductor diodes.
Due to photovoltaic effect energy of light (energy of
photons) converts into electrical current [1]. At p-n
junction, an electric field is built up which leads to the
separation of the charge carriers (electrons and holes). At
incidence of photon stream into semiconductor material
the electrons are released, if the energy of photons is
sufficient [2]. Contact to a solar cell is realized due to
metal contacts. If the circuit is closed, meaning an
electrical load is connected, then direct current flows.
The energy of photons comes in "packages" which are
called quants. The energy of each quantum depends on
the wavelength of the visible light or electromagnetic
waves. The electrons are released, however, the electric
current flows only if the energy of each quantum is
greater than WL - WV (boundaries of valence and
conductive bands). The relation between frequency and
incident photon energy is as follows:
Current-voltage characteristic
Maximum peak power tracking
A proprietary software tool suite used
primarilyfor electronic design automation
Boundaries of valence and conductive bands
Overall current
Diode dark current
Light–induced current
Saturation current
Boltzmann’s constant
Short circuit current
Open circuit voltage
Fill factor
Maximum power
Output voltage of the solar cell
Output current of the solar cell
Solar cell efficiency
Input power
Incident solar radiation
W
h Q
(1)
where there is: h - Planck constant (6.626·10-34 Ws2), v frequency (Hz).
Area of solar cell
Output current(solar cell)
Output voltage(solar cell)
II.
Crystalline Silicon Solar Cells
Among all kinds of solar cells we describe silicon
solar cells only, for they are the most widely used [3].
Their efficiency is limited due to several factors. The
energy of photons decreases at higher wavelengths. The
highest wavelength when the energy of photon is still big
enough to produce free electrons is 1.15 µm (valid for
silicon only). Radiation with higher wavelength causes
only heating up of solar cell and does not produce any
electrical current. Each photon can cause only production
Reverse saturation current
Thermal voltage
Output power
Resistance of diode number i
Pulse width modulation
Manuscript received and revised September 2010, accepted October 2010
948
Copyright © 2010 Praise Worthy Prize S.r.l. - All rights reserved
A. Blorfan, D. Flieller, P. Wira, G. Sturtzer, J. Merckle
connecting the positive and negative terminals by copper
wire.
of one electron-hole pair. So even at lower wavelengths
many photons do not produce any electron-hole pairs, yet
they effect on increasing solar cell temperature. The
highest efficiency of silicon solar cell is around 23 %, by
some other semi-conductor materials up to 30 %, which
is dependent on wavelength and semiconductor material.
Self loses are caused by metal contacts on the upper side
of a solar cell, solar cell resistance and due to solar
radiation reflectance on the upper side (glass) of a solar
cell. Crystalline solar cells are usually wafers, about 0.3
mm thick, sawn from Si ingot with diameter of 10 to 15
cm. They generate approximately 35 mA of current per
cm2 area (together up to 2 A/cell) at voltage of 550 mV
at full illumination. Lab solar cells have the efficiency of
up to 20 %, and classically produced solar cells up to15
%.
III.3. Open Circuit Voltage voc
Open circuit voltage is obtained by setting I 0 in
the expression for overall current i.e. I 0 when
V Voc :
Voc
·
kT § I L
ln ¨ 1¸
e © I0
¹
(3)
The open circuit voltage is the voltage for maximum
load in the circuit.
III.4. Fill Factor (FF)
The fill factor, also known as the curve factor (Fig. 2),
is a measure of sharpness of the knee in an I-V curve. It
indicates how well a junction was made in the cell and
how low the series resistance has been made. It can be
lowered by the presence of series resistance and tends to
be higher whenever the open circuit voltage is high. The
maximum value of the fill factor is one, which is not
possible. Its maximum value in Si is 0.88:
FF
Fig. 1. The structure of a silicon solar cell and working mechanism
Pmax
Voc I SC
Vmax I max
Voc I SC
(4)
III. Basic Parameters of Solar Cells
There are certain parameters to be mentioned in the IV characteristics of a solar cell [4].
III.1. Overall Current I
Overall current is determined by subtracting the lightinduced current from the diode dark current and can be
expressed as:
i I D iL : Overall current
I D : Diode dark current
iL : light–induced current
i
I0
eV
KT
e
1 IL
Fig. 2. Characteristic curve for determining the fill factor
A larger fill factor is desirable, and corresponds to an
I-V sweep that is more square-like.
Typical fill factors range from 0.5 to 0.82. Fill factor
is also often represented as a percentage.
(2)
where I 0 is the saturation current, which is also known
as the leakage or diffusion current; e is the charge on an
electron and hole and K is Boltzmann’s constant. Both
I L and I 0 depend on the structure of solar cells.
III.5. Maximum Power Pmax
No power is generated under short or open circuit.
The power output is defined as:
III.2. Short Circuit Current I SC
Pout
Short circuit current is the light-generated current or
photo current, I L . It is the current in the circuit when the
load is zero in the circuit. It can be achieved by
Vout I out
(5)
The maximum power Pmax provided by the device is
achieved at a point on the characteristics, where the
Copyright © 2010 Praise Worthy Prize S.r.l. - All rights reserved
International Review on Modelling and Simulations, Vol. 3, N. 5
949
A. Blorfan, D. Flieller, P. Wira, G. Sturtzer, J. Merckle
Vmax I max
Idc = 3.1
Rs = 10
R1
(6)
D1
Pmax
PARAMETERS:
PARAMETERS:
product IV is maximum. Thus:
The maximum possible output can also be given as
Pmax
Voc I SC FF
Idc1
{Idc}
(7)
Rs
Rp
Rd
{Rs}
Vd
where FF is the fill factor given by eqn (4).
0
III.6. Solar Cell Efficiency Kec
Fig. 3. Simple PV cell Simulink model
The solar cell power conversion efficiency can be
given as:
Kec
Kec
Vmax I max
Pmax
Pin
IncidentSolarRadiation AreaOfSolarCell
Pmax
Pin
Voc I SC FF
I t Ac
PV power
Ppv
Vpv
Ppv
Ipv
Product
Vpv
PV
To Workspace
(8)
Vpv
Vpv
1e-9*(exp(u/26e-3)-1)
PN-Junction characteristic
Id
I-V characteristic
1
where I max and Vmax are the current and voltage for
maximum power, corresponding to solar intensity I t .
IV.
i
Ipv
Output power PPV (i.e. the product of iPV and vPV )
as a function of vPV is immediately displayed in a X-Y
(Fig. 5).
The simplest solar cell model consists of diode and
current source connected parallel [5]. Current source
current is directly proportional to the solar radiation.
Diode represents PN junction of a solar cell. Equation of
ideal solar cell, which represents the ideal solar cell
model, is:
iPV I SC iD
§ eV
·
I 0 ¨ e KT 1¸ I L
¨
¸
©
¹
V
D
§
·
I 0 ¨ e VT 1¸ I D
¨
¸
©
¹
Isc
Insolation to ISC current gain
Fig. 4. Model of PV using Simulink
Solar Cell Model Using Matlab
i
1
Insolation
(9)
where is:
I SC - photocurrent (A),
I 0 - reverse saturation current (A) (approximately range
10-8/m2),
vD - diode voltage (V),
vT - thermal voltage (see equation below),
vT = 25.7 mV at 25°C,
m - diode ideality factor = 1...5 x vT (-) (m = 1 for ideal
diode).
The simple model of the solar cell is shown in the Fig.
3 [6, 7].
Fig. 5. PPV as a function of the vPV
Output current iPV as a function of vPV is
immediately displayed in another X-Y Plot window.
The Fig. 6 shows this characteristic as a function of
vPV . Output power PPV , current iPV , voltage vPV , and
simulation time are stored in a "structure" variable PV,
which is made available (using the "To Workspace"
block) for further processing in the MATLAB Command
Window [8].
As a result of the last model done using Simulink we
could get the power and the current for the solar cell as a
function of the its voltage.
Copyright © 2010 Praise Worthy Prize S.r.l. - All rights reserved
International Review on Modelling and Simulations, Vol. 3, N. 5
950
A. Blorfan, D. Flieller, P. Wira, G. Sturtzer, J. Merckle
Ri
1
mi mi 1
m0
0
Vi
Ei
(10)
The new approach is modulated using the Orcad 15.7
which is considered as a new version of the Pspice with a
high ability to produce an electronic board from the
circuit simulated.
The Fig. 8 shows this new model with four branches
parallel.
PARAMETERS:
PARAMETERS:
Idc = 3.1
Idc
{Idc}
R1
5.88
V1
9
R2
12.5
V2
13.5
D1N4001
D4
D1N4001
D3
D1N4001
D2
D1
But the question here could we find another model
using another utilities more accurate and elastic to
transfer towards the electronic circuit easily.
This paper uses the Orcad such as a new software to
modulate the photovoltaic and using Orcad we shall
propose a new approach depends on the characteristic of
the photovoltaic diode.
Rs = 10
D1N4001
Fig. 6. iPV =f( v pv )
R5 0.02
R3
0.86
R4
0.38
V3
15
V4
18
Rp
50
Rs
{Rs}
0
V.
Fig. 8. Real Model of the photovoltaic
Solar Cell Model Using Orcad
The characteristic of the photo diode is performance
by the producer of the photovoltaic array.
The Fig. 7 shows the characteristic of the photo diode
given with the array of photovoltaic.
The characteristic of the photovoltaic is represented
by the two graph, first graph is the current( I pv ) as a
function of the voltage of the Photovoltaic( V pv ) and the
second is the power( P ) as a function of the same
variable( V pv ).
m4
by
s
tion
m3
pro
x
ima
Id
eg
m
en
ts
Diode I-V curve
The I-V curve of an illuminated PV cell has the shape
shown in Fig. 9 as the voltage across the measuring load
is swept from zero to V0 , and many performance
parameters for the cell can be determined from this data,
as described in the sections below.
Ap
m2
m1
E1
Vd
E2
E3
E4
Fig. 9. I PV
Fig. 7. I d
f Vd
f VPV
The power produced by the cell in Watts can be easily
calculated along the I-V sweep by the equation P=IV. At
the Io and VO points, the power will be zero and the
maximum value for power will occur between the two.
The voltage and current at this maximum power point are
denoted as Vmp and I mp respectively.
If we stare at the last figure we conclude that an
geometric approximation represented by four segments
will be satisfied to our need, so the new model will be
shown in the Fig. 8.
The values of the resistance are calculated using the
equation (10)[9]:
Copyright © 2010 Praise Worthy Prize S.r.l. - All rights reserved
International Review on Modelling and Simulations, Vol. 3, N. 5
951
A. Blorfan, D. Flieller, P. Wira, G. Sturtzer, J. Merckle
Fig. 10. P
f VPV
However, for most orders MPPT, to achieve
convergence in good conditions, whatever the algorithm,
it is necessary that the power curves issued by the
generator are constant or slowly varying. If this
assumption is not respected (abrupt changes in operating
conditions) the system can diverge.
The principle of MPPT controllers is often based on
the "elbow" of the P-V characteristics. It's more or less a
trial and error, as shown in following figure.
It is located in an area of the curve (X1) and if you
look at the value of the next item is higher or not. If so,
we move to the next point (X2), until the next term (Xn)
will be lower than the previous (Xn-1). At this time, we
take an interval value between every point lower, and
repeat from (Xn-1) to obtain MPP (X).
The Fig. 12 is shown this technique of MPPT.
The above arc shape(Fig. 10) is obtain by making use
of different resistance, starting from lower resistance say
1ȍ and increasing in 5 units up to 5 or 10 K ȍ. The
below figure depict show to take voltage and current
measurement for varying resistance.
VI.
Maximum Power Point Tracking
Power output of a Solar PV module changes with
change in direction of sun, changes in solar insolation
level and with varying temperature [10].
Hence maximization of power improves the utilization
of the solar PV module. A maximum power point tracker
(MPPT) is used for extracting the maximum power from
the solar PV module and transferring that power to the
load. A dc/dc converter(step up/step down) serves the
purpose of transferring maximum power from the solar
PV module to the load.
We choose the Hill Climbing method, which consists
of observing the current and voltage at the output of the
generator(PV). Multiply these data we shall get the
power, then we use two montages integrators to save this
power and to make a delay between two values of the
power the actual value and the new value. Both montage
have different time constants.
By comparing these two signals, we could know the
derivation of the power, and thus if it increases or it
decreases. Then, using a toggle JK, a third integrator and
a triangular signal we will create the PWM control to be
sent to the driver of the transistor(here we used Pchannel
Mosfet).
The Fig. 11 shows the diagram of this technique.
Fig. 12. Principle operation of MPPT
The controller type of MPPT consists of two distinct
parts:
1. Control part whose purpose is to determine the
operating point, where the solar cell can transfer the
power towards the batteries.
2. The power part which transfers energy between the
solar panels and batteries.
These two parts are shown in Fig. 13.
Fig. 11. Proposed MPPT controller block diagram
The control MPPT finally presenting a good
compromise yields
static and dynamic but also
robustness are based on continual assessment power and
a comparison with the state at the previous instant.
Fig. 13. The block diagram of this type of control
Copyright © 2010 Praise Worthy Prize S.r.l. - All rights reserved
International Review on Modelling and Simulations, Vol. 3, N. 5
952
A. Blorfan, D. Flieller, P. Wira, G. Sturtzer, J. Merckle
Now it is easy to get the electronic schematic from the
Orcad's library, it is shown in the Fig. 14.
PARAMETERS:
PARAMETERS:
D17
MUR150
Rs = 50
Idc = 25
V1
9Vdc
D4
D1N4001
D3
D1N4001
D2
R1
5.88
R3
0.86
V2
13.5Vdc
V3
15Vdc
L2
D1N4001
1
2
1mH
D15
Rp
50
R4
0.38
R2
12.5
D13
IRFP9140 M1
20m
V4
18Vdc
12 V11
R27
0
100
C8
4
V
-VCC
+ 8
U18A V+ VCC
R38
0
VCC
0
0
W
3
7
7
22k
220n
0
-VCC
AD633/AD
VCC
C2
6
R11
220k
220n
C3
1k
+
U12A
1
LM139 OUT
1
V-VCC
3
12
6
U15
J
Q
K
Q
JKFF
R12
7
V
C4
1k
5
R22
1k
5
R21
1k
15
OUT
+ 3
U13A V+
[1]
S. D. Gopal Nath Tiwari, Fundamentals of Photovoltaic Modules
and their Applications, (Royal Society of Chemistry p. 326 pages
2010).
[2] S. H. Antonio Luque, Handbook of Photovoltaic Science and
Engineering ( vol. Vol. 7, No. 6, p. 1168 pages, 25 avril 2003).
[3] V. M. ANGAMI, photovoltaic for beginners,( p. 87 2009).
[4] J. V. Roger A. Messenger, Photovoltaic Systems Engineering, ( p.
480 July 28, 2003).
[5] S.S.LuisCastaner, Modelling Photovoltaic Systems Using PSpice
( p. 376 January 7, 2003).
[6] A. Assi, , MATLAB - based modeling tool for designing,
predicting and analyzing grid tied photovoltaic systems, in
Advances in Computational Tools for Engineering Applications,
2009. ACTEA '09. International Conference on, 2009, pp. 508513.
[7] Y. Yusof, et al., Modeling and simulation of maximum power
point tracker for photovoltaic system, in Power and Energy
Conference, 2004. PECon 2004. Proceedings. National, 2004, pp.
88-93.
[8] H. Patel and V. Agarwal, MATLAB-Based Modeling to Study the
Effects of Partial Shading on PV Array Characteristics, Energy
Conversion, IEEE Transactions on, vol. 23, pp. 302-310, 2008.
[9] S. Chowdhury, et al., Mathematical modelling and performance
evaluation of a stand-alone polycrystalline PV plant with MPPT
facility, in Power and Energy Society General Meeting Conversion and Delivery of Electrical Energy in the 21st Century,
2008 IEEE, 2008, pp. 1-7.
[10] M.Stürtzer, Projet Simulation Panneaux Photovoltaïques ( p. 8,
2009).
1
R34
1k
-VCC
0
-
LM324
Jcc
LM239
VCC
3.3u
6
5
15
-
4
CLK
V-
15
V-
-VCC
0
R20
1k
References
0
VCC
2
- 12
7
+ 8
U19B V+VCC
8.2k
R33
V+
R10
11
0
R16
8 5k
+ 4
U6C V+
VCC
VCC
V- U16 V+
LM324 OUT
10
5
10k
X1
X2
Y1
Y2
Z
5
-
V-
11
1k
1
2
3
4
6
OUT
R39
VCC
8
R17
22k
100k
-VCC
-VCC
2.2k
3
9
TL082
6
-
R37
1
OUT
4
6n
V-
TL082
2
-
0
R29
This work was supported by Laboratory of MIPS in
Mulhouse, and grateful for all authors.
R19
0.1
R28
Acknowledgements
Rs
{Rs}
C6
3.5u
MUR150
100
C5
V-
Idc
{Idc}
D1N4001
D1
D1N4001
R5
The efficiency of the photovoltaic is very important
especially nowadays where all the world is seeking for
the renewal energy.
+ 4
U7B
7
OUT
0
V+
VCC
0
0
-VCC
Fig. 14. Proposed controller circuit diagram
VII.
Simulation Results
The simulation of this method using Orcad shows that
the control pulses PWM changes according to the
voltage of the generator, the PWM and the output
voltage are shown in the Fig. 15.
V
V
V
V
V
V
V
280us
V(R27:1)
290us
V(U15:Q)
300us
V(R39:2)
310us
320us
330us
340us
350us
360us
370us
380us
390us
400us
Time
Fig. 15. Control pulses for the DC-DC converter
Authors’ information
Ayman Blorfan was received the B.Sc in 1997
and M.Sc degrees in 2007 from the of
Polytechnic School of Nantes in France, In 2009
He joined to the laboratory of MIPS and ERGE
to work in the research in domain of power
electronics and automatic.
VIII. Conclusion
This paper explained to us the classical module of the
photovoltaic, the first is done in Matlab, and the second
using Orcad, the two modules are shown the same
characteristic of the I-V but the second module is more
nearest to the solar cell itself, because it is depends on
the characteristic of the photo diode, it is shown the real
model of the solar cell, by using it we could determine
the exact value of the Pmax , our objective is to conserve
the power about its maximum values, we estimate the
value of the power by tracking the maximum value of
this power, where the old technique is not accurate so it
could not give us high efficiency such as this new
method.
Then we discussed the flow chart of the maximum
point power tracking (MPPT) technique, The role of the
MPPT is to place the operating point of the assembly at
the top of this bell, and how could be realized the
prototype using an electronic components.
Damien Flieller was born in Epernay, France,
on October 15, 1966. He received the M.Sc.
degree in electrical engineering from the Ecole
Normale Supérieure (Cachan), France, in 1988
and the Ph.D.degree in Electrical Engineering
from the University of Paris, France, in 1995 till
1995. He has been an Associate Professor in
the Department of Electrical Engineering,
(Institut National des Sciences Appliquées INSA), Strasbourg,
France. He is now director of the ERGE laboratory, INSA. His
research interest are in the Þeld of modeling and control of
synchronous motors, power system, active Þlter, and induction heating
DC-AC converters.
Copyright © 2010 Praise Worthy Prize S.r.l. - All rights reserved
International Review on Modelling and Simulations, Vol. 3, N. 5
953
A. Blorfan, D. Flieller, P. Wira, G. Sturtzer, J. Merckle
Patrice Wira has the BS.c in Mathematics in
1996, then the M.Sc in automatic and industrial
informatics in July 1997. In sept.2001 he has
become a Teacher assistant of Higher Education,
then he has getten the PhD from the university of
the High Alsace jan. 2002. In Sept.2002 he
became a lecturer (61 section).
He has the
Habilitation to supervise the research in Nov.
2009 (Habiliation à Diriger des Recherches ). His research concerns
the study of modularity in ANNs And the automatic control using
Artificial Neural Network.
Jean Merckle received the M.Sc. and
Ph.D.degrees in electrical from University
Nancy I, Nancy, France, in 1982 and 1988,
respectively.
In 1988, he joined the MIPS Laboratory,
University of Haute Alsace, Mulhouse, France,
where he participated in several adaptive signal
processing projects. From 1991 to 1993, he was
with the departement of Electrical and Computer Engineering,
University of California and San Diego, contributing to a 3-D
optoelectronic neural architecture with efficient learning. He is
currently a professor of Electrical and Computer Engineering. His
research interests include adaptive neural computation with application
to power electronic systems control and digital hardware
impementation.
Copyright © 2010 Praise Worthy Prize S.r.l. - All rights reserved
International Review on Modelling and Simulations, Vol. 3, N. 5
954
