Maximum Power Point Tracking by Incremental Conductance method for PV
Array under Extreme Conditions
R. Jothi Lakshmi1, S. Sivananaithaperumal2,
1PG
student, 2 Professor, Dept of Electrical & Electronics Engineering
Dr. Sivanthi Aditanar College of Engineering, Tiruchendur.
1 rjothilakshmi20@gmail.com, 2s_sivaperumal@yahoo.com
ABSTRACT
The paper deals with the Maximum Power Point
Tracking (MPPT) using Inc conductance algorithm for
PhotoVoltaic (PV) systems. MPPT plays an important role
in PV systems because it maximize the power output from
a PV system for a given set of conditions, and therefore
maximize the array efficiency and minimize the overall
system cost. Since the maximum power point (MPP) varies,
based on the irradiation and cell temperature, appropriate
algorithms must be utilized to track the MPP.
Matlab/Simulink is used to establish a model of PV system
with MPPT function. This system is developed by
combining the models of solar PV module and DC-DC
BOOST Converter. The system is simulated under non
uniform irradiation and temperature conditions. Simulation
results show that the photovoltaic simulation system can
track the maximum power point accurately.
Keywords- PhotoVoltaic(PV), Maximum Power
Point Tracking (MPPT),Increment conductance(Inc cond)
algorithm
1.INTRODUCTION
Among all renewable energy sources, solar
power system provide excellent opportunity to generate
electricity while greenhouse emission are reduced [2].Solar
energy is the most readily available source of energy and it
is free. Moreover, solar energy is the best among all the
renewable energy sources since, it is non-polluting. Energy
supplied by the sun in one hour is equal to the amount of
energy required by the human in one year. PV arrays are
used in many applications such as street lighting in rural
town, water pumping, battery charging, solar water heater
grid connected PV systems, Earth orbiting satellites,
handheld calculators and remote radiotelephones
[6].Another advantage of using solar energy is the portable
operation whenever wherever necessary. But the cost of
extracting the solar energy using the PV cells is high
because of its product cost. Fig.1 gives amount of solar
energy reach the earth. All chemical and radioactive
polluting by products of the thermonuclear reactions
remain behind on the sun, while only pure radiant energy
reaches the Earth.
Due to the high cost of solar cells, it is necessary
that PV module operate at its maximum power point, but
solar cell produces the solar power changes according to
change in solar radiation and temperature. As irradiation
and temperature level changes rapidly, the voltage
produced fluctuates and become inconstant. As known
from a Power-Voltage curve of a solar panel, there is an
optimum operating point such that the PV delivers the
Figure 1.Amount of Solar energy reach the earth
Maximum possible power to the load. There are three ways
to increase the efficiency of a solar photovoltaic system. (1)
By proper selection of material for the solar cell. (2) By
employing a solar panel tracking system. (3) Maximizing
the energy conversion from the solar panel by using MPPT
controller [2]. The tracking system consists of two basic
components Switch mode converter and a control tracking
capability. All MPPT methods follow the same goal which
is maximizing the PV array output power by tracking the
maximum power on every operating condition.
2. PV ARRAY
2.1 PV Cell Operation
Figure 2.Operation of PV cell
Solar cell is a p-n junction fabricated in a thin wafer of
Semiconductor.Fig.2 explain how solar cell works.
Under photovoltaic effect the electromagnetic
radiation of solar energy can be directly converted to
electricity. Being exposed to the sunlight, the bandgap energy of the semiconductor is less than the
photons with energy are absorbed and create electronhole pairs proportional to the incident irradiation.
Under the influence of the internal electric fields of
the p-n junction, these carriers are swept apart and
create a photocurrent. This current is directly
proportional to solar isolation. Naturally PV system
exhibits a nonlinear I-V and P-V characteristics which
vary with solar isolation and temperature [2].
2.2 PV Array Modelling
The solar cells are connected in parallel and series
to form the Photovoltaic array. Consider a single PV
cell; It can be modeled by using a current source, two
resisters and diode. This is a single diode model of
solar cell. Also Two diode models are available but
only single diode model is considered here [1], [3], [5],
[6], [7], [8], [10], [11], [12]. Fig.1 represent PV cell.
Fig .2 represents the single diode model. Fig.3 shows
basic PV system
Irs =
Iscr
qVoc
[exp (
) − 1]
Ns KAT
(2)
Saturation current Io varies with the cell temperature,
which is given by
T
Io = [ ]3 exp [q ∗
Tr
Ego
1
1
)−( )}
Tr
T
BK{(
PV cell output current
Ipv = Np ∗ Iph ∗ Io [
]
(3)
exp{q∗(Vpv +Ipv Rs ))
Ns KAT
} − 1]
(4)
Where Vpv = Voc, Np = 1 and Ns = 36
Vpv : Output Voltage (V)
Ipv : Output Current (A)
Tr : Reference Temperature
T : Operating Temperature
Ns : Number of cells connected in series
Np : Number of cells connected in parallel
3. INCREMENTAL CONDUCTANE
METHOD
The incremental conductance (Inc Cond) method is
comparing the instantaneous panel conductance with the
incremental panel conductance. The input impedance of the
DC-DC converter is matched with optimum impedance of
PV panel. It has a good performance under extreme
conditions. The major advantage of this method is that it
does not oscillate around the MPP. A fast and correct
system response to under extreme conditions. The result
yielding high system efficiency.
The Inc Cond comes from the fact that it uses the
derivative of the PV system conductance, in order to
determine the operating point position in relation to MPP.
The power output from the PV cell is:
P=V*I
Figure 3.PV cell
Maximum Power Point is obtained when
𝜕𝐼pv
=0
∂Vpv
∂Ppv ∂Vpv ∗ 𝐼pv
𝜕𝐼pv
=
= Vpv ∗
+I
∂Vpv
∂Vpv
∂Vpv
∂Ppv
∂Vpv
∂Ppv
Figure 4 Single diode model
∂Vpv
Fig.3 represents single diode model of PV cell Iph
represents the PV cell photocurrent. Rsh and Rs are the
intrinsic shunt and series resistances of the PV cell
respectively. The value of Rsh is very large and that of Rs is
very small, hence they may be neglected to simplify the
analysis.
Mathematical Model for PV array:
Photo Current:
∂Vpv
∂Ppv
Iph = [𝐼scr + 𝐾i (T − Tr )] ∗
Reverse Saturation Current:
λ
1000
(1)
> 0 𝑖𝑓
= 0 if
< 0 𝑖𝑓
𝐼pv
Vpv
𝐼pv
Vpv
>−
=−
𝐼pv
Vpv
<−
𝜕𝐼pv
∂Vpv
𝜕𝐼pv
∂Vpv
𝜕𝐼pv
∂Vpv
On Left of The MPP
At MPP
On Right of the MPP
The values of 𝜕𝐼pv and 𝜕𝑉pv are calculate by using the
present value and the previous value of the PV cell voltage
and current.
If 𝜕𝑉pv = 0 and 𝜕𝐼pv = 0 , then the content
atmospheric conditions and the MPPT is still operating at
the MPP. If 𝜕𝑉pv = 0 and 𝜕𝐼pv > 0, the amount of
irradiation has increased, raising the voltage. Then the
MPPT require increasing the PV cell operating voltage to
track the MPP. Otherwise, if 𝜕𝐼pv < 0 , irradiation has
decreased, decreasing the MPP voltage and then the MPPT
require decrease the PV cell operating voltage. If
𝜕𝐼pv
∂Vpv
then
𝜕𝑃pv
∂Vpv
𝐼pv
Vpv
=-
> 0and the Operating point of the PV cell
is to the left of the MPP on the P-V curve. Thus the PV
Cell voltage must be increased to reach the MPP. Similarly,
if
𝐼pv
Vpv
=-
𝜕𝐼pv
∂Vpv
, then
𝜕𝑃pv
∂Vpv
< 0 and the Operating point of PV
lies to the right of the MPP on the P-V curve, showing that
the voltage must be lowering to reach the MPP. In this
process, a small marginal error could be added to the
maximum power conditions such that the MPP is assumed
to occur if
𝜕𝐼pv
∂Vpv
+
𝜕𝑃pv
∂Vpv
Figure 6. Boost Converter Circuit
< Ɛ,Ɛ value was determined with
consideration of the trade-off between the problem of not
operating exactly at the MPP and the possibility of
oscillating around it..Fig.5 gives Inc cond algorithm.
Figure 7.Charging mode
Figure 8.DisCharging mode
5. SIMULATION RESULTS
Figure 5.Inc Cond method Flow chart
4. BOOST CONVERTER
The boost converter output voltage is greater than
input voltage. The boost converter is also called a step-up
converter because step-up the voltage without transformer.
Due to single transistor, it has high efficiency. Fig.6
represent boost converter circuit. Fig.7 represent charging
mode of the boost converter. Charging mode begins when
SW is switched on at t=0.the input current, which rises,
flow through inductor L and capacitor C [7]. Fig.8
represent Dis charging mode of the boost converter
Discharging mode start when SW is switched off at t=t1.the
current was flowing through the SW, inductor L, capacitor
C. The inductor current falls until transistor is turned on
again in the next cycle. The energy stored in inductor L is
transferred to the load [7].
The Simulink model used for the implementation of the
required PV array with boost converter and is represented
by a block named ‘PVPANEL’. Here the solar cell The
MPPT and gating signal generator are shown in a single
unit called ‘MPPT’.Fig.9 shows PV With MPPT system.
Here the solar cell The MPPT and gating signal generator
are shown in a single unit called ‘MPPT’. The solar cell
was modeled in the Single diode format. This consists of a
10 ohm series resistance and rated output Voltage is 21.6V.
The boost converter consists of a 63 mH inductor and a 5
mF capacitor. This boost converter is used to step up the
voltage to the required value. The gating signal to the boost
converter is generated by comparing the signal generated
by the MPPT algorithm to a square wave. The load of 10
ohm resistance is considered.
The simulations are carried out in Simulink and the
various voltages, currents and power plots were obtained.
The simulation is made for 5sec. Fig.10 to Fig.11
represents the solar cell characteristics under extreme
conditions. The parameters were obtained for a generalized
solar cell. The plot is similar to the theoretically known plot
of the solar cell voltage and current. Since 36 PV cells in
series and single PV cell parallel, a single diode model of
solar cell considered, hence the solar output voltage is less
(21.6V) in this case.
Figure 9.Model of PV ARRAY with boost converter and MPPT system
would increase for the same voltage value. With increase in
the solar irradiation the open circuit voltage increases.
Figure 12.variation of I-V curve with irradiation
Figure 10.I-V curve with variation of temperature
Fig.10 and Fig 11 gives solar output voltage against the
solar output current and output power with variation of
temperature. The temperature increase around the solar cell
has a temperature negative impact on the power generation
Capability Increase in temperature is accompanied by a
decrease in the open circuit voltage value.
Figure 11.P-V curve with variation of temperature
Increase in temperature causes increase in the band gap
of the material and thus more energy is required to cross
this barrier. Thus the efficiency of the solar cell is reduced.
Fig.11 and Fig 12 gives solar output voltage against the
solar output current and output power with variation of
irradiation.
Higher is the solar irradiation, higher would be the
solar input to the solar cell and hence power magnitude
This is due to the fact that, when more sunlight incidents on
to the solar cell, the electrons are supplied with higher
excitation energy, thereby increasing the electron mobility
and thus more power is generated. The initial part of the
plot from 0V to the maximum power point voltage is a
steady slope curve but after the maximum power point
signal is generated by comparing the signal generated.
Figure 13.variation of P-V curve with irradiation
The initial part of the plot from 0V to the maximum
power point voltage is a steady slope curve but after the
maximum power point the curve is a steeply falling curve.
The gating signal is generated by comparing the signal
generated by the MPPT algorithm to a square wave. Gate
signal is given to the boost converter. The incremental
conductance method change in current, change in voltage,
instantaneous voltage and instantaneous current values are
taken into account to do the necessary duty cycle
variations. The on period of the gating signal is (Ton) 0.04.
The off period of the gating signal is (Toff) also 0.04.Duty
cycle value is 0.5. Fig.14 and Fig.15 shows Voltage across
the load, current flow through load, load power.
Figure 14.Load Power, Load Voltage, Load current
with variation of temperature
Figure 15.Load Power, Load Voltage, Load current
with variation of temperature
6. CONCLUSION
A resistive load of 10 ohms was used with the boost
converter thereby making the output current and voltage
similar.
When MPPT is used, there is no need to input the duty
cycle, the algorithm decides the duty cycle by itself. But if
MPPT had not been used, then the user would have had to
input the duty cycle to the system. When there is change in
the solar irradiation the maximum power point changes and
thus the required duty cycle for the operation of the model
also changes. But if constant duty cycle is used then
maximum power point cannot be tracked and thus the
system is less efficient. The various P-V and I-V
Characteristics of PV array, Inductor current Load voltage,
Load current, Load power were obtained by using the plot
mechanism in MATLAB. In the Simulink models the solar
irradiation and the temperature can be given as variable
inputs was done here
7. REFERENCES
[1]
Abdulkadir. M., Samosir. A. S.,Yatim. A. H. M.. and
Yusuf.S.T.2013."A
New
Approach
Of
Moselling,Simulation Of MPPT for Photovoltaic
System in Simulink Model", ARPNJournal of
Engineering and Applied Sciences , Vol.8.
[2] Azadeh safari.2011.,”simulation and Hardware
Implementation of Incremental Conductance MPPt
With
direct
Control Method Using Cuk
converter”,IEEE
Transactions
on
Industrial
Electronics,Vol 58,No 4.
[3] Bhagwan Das.2012." MPPT controller for photo
voltaic systems using cuk dc/dc convertor
",International Journal of Advanced Technology &
Engineering Research (IJATER), Vol 2, Issue 3, MAY
2012.
[4] Ankaiah, and Jalakanuru Nageswararao.2013."MPPT
Algorithm for Solar Photovotaic Cell by Incremental
Conductance Method", International Journal of
Innovations in Engineering and Technology (IJIET),
Vol. 2.
[5] Huan-Liang Tsai, Ci-Siang Tu, and Yi-Jie Su,.2008.
"Development of Generalized Photovoltaic Model
Using MATLAB/SIMULINK", Proceedings of the
World Congress on Engineering and Computer
Science 2008 WCECS October 2008.
[6] Jay pateh,Vishal sheth and Ganurang Sharma.2013.
"Design & Simulation of Photovoltaic System Using
Incremental MPPT Algorithm", International Journal
of Advanced Research in Electrical, Electronics and
Instrumentation Engineering Vol.2,May 2013.
[7] Lokanadham.M and Vijaya Bhaskar. K.2012,
"Incremental Conductance Based Maximum Power
Point Tracking (MPPT) for Photovoltaic System",
International Journal of Engineering Research and
Applications (IJERA), Vol. 2.
[8] Manikanda prabhu.M and Manivannan. A.2013. "
Modelling And Performance Analysis of PV Panel
using Incremental Conductance Maximum Power
Point Tracking", International Journal of Engineering
Research & Technology (IJERT) Vol. 2,March 2013.
[9] Power Electronics circuits devices and applications by
MH.
[10] Saravana Selvans.2013. "Modeling and Simulation of
Incremental Applications", International Journal of
Scientific Engineering and Technology (ISSN : 22771581) Vol.2.
[11] Samer Alsayid and Basims Alsayid.2012."Maximum
Power Point Tracking Simulation for Photovoltaic
Systems Using Perturb and Observe Algorithm",
International Journal of Engineering and Innovative
Technology (IJEIT) Vol.2.
[12] Tarak Salmi, Mounir Bouzguenda, Adel Gastli, and
Ahmed Masmoudi.2012. "MATLAB/Simulink Based
Modelling of Solar Photovoltaic Cell", International
journal of Renewable Energy Research, Vol .2.
[13] Trishan,
L.chapman.2007."Comparison
of
Photovoltaic Array Maximum Power Point Tracking
Techniques", IEEE Transactions on Energy
Conversion, Vol.2.