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Matlab/Simulink Model of Solar PV Array with Perturb and Observe MPPT for
Maximising PV Array Efficiency

Conference Paper · October 2015

DOI: 10.1109/CENCON.2015.7409549

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 Matlab/Simulink Model of Solar PV Array with Perturb
and Observe MPPT for Maximising PV Array
Efficiency
Oladimeji Ibrahim, Member IEEE Nor Zaihar Yahaya, Member IEEE,
Department of Electrical and Electronics Engineering Nordin Saad, Member IEEE
Universiti Teknologi PETRONAS, Muhammad Wasif Umar
Bander Seri Iskander, Perak 32610, Malaysia Universiti Teknologi PETRONAS
reacholaibrahim@gmail.com Bandar Seri Iskandar, Perak 32610, Malaysia
norzaihar_yahaya@petronas.com.my
nordiss@petronas.com.my
cmwasif@yahoo.com

Abstract—The efficiency of commercially available solar PV module The performance of a PV cell largely depends on quality of
is very low in the range of 10-25%. In order to maximise their cell material such as absorption capacity and reflectance of the
operating efficiency and to reduce installation cost, maximum power surface. The operating condition like solar irradiance level,
point trackers (MPPT) are coupled with the system. The output incident angle, temperature and load current plays a big role in
power of solar PV depends on solar irradiance level, incident angle,
dictating the performance of PV array output voltage, current and
temperature and load current which all contribute to non-linear
varying I-V characteristic during operation. MPPT ensures that a power delivery [2, 3]. The available commercial solar PV cells
PV cell, module or panel is operated and maintained at the reference have low efficiency in the range of 10-25% necessitating the need
voltage that correspond to maximum power point for particular to ensure that maximum available power is extracted for better
operating solar irradiance and cell temperature. A 220W solar PV utilization efficiency and cost reduction. Research effort in solar
panel is modelled in Matlab-Simulink to study solar PV energy studies are directed towards increasing cell efficiency via
characteristics under different solar irradiance and working cell manufacturing technologies, improving power quality of PV
temperature. A Perturb & Observation MPPT technique power generation for grid connection and extracting maximum
incorporated for maximising the output power of the PV panel shows output power termed maximum power point tracking (MPPT).
that the percentage deviation from the ideal PV power is about 10%
for different operating solar irradiance and cell temperature. MPPT are used for operating PV array at the point of
maximum power irrespective of irradiance, temperature and load
Keywords: Solar PV; Perturb and Observe; Solar Irradiance; DC-DC
boost converter; PV cell temperature
current variation. In literature, different MPPT techniques have
been proposed but their suitability largely depends on factors like
I. INTRODUCTION the end application, dynamic of irradiance, design simplicity,
convergence speed, hardware implementation and the cost [4].
Solar energy is a readily available, clean, and inexhaustible The available MPPT methods ranges from simple voltage
energy source considered as a sustainable alternative energy relationships to complex multiple sample based analysis which
source for electricity generation. The contribution of solar energy includes but not limited to constant voltage method, short current
to the world total electricity generation has been on increase in pulse method, open voltage method, perturb and observe method,
the past decades, the global installed capacity of solar incremental conductance method, and temperature method [5].
photovoltaic (PV) system increased from below 10 GW in 2007 The design and implementation simplicity coupled with good
to over 100 GW capacity in year 2012 [1]. Solar energy system performance has make perturb and observe (P&O) MPPT to be
generates electricity by direct conversion of solar photon (light) one of the most widely used MPPT techniques for solar PV
energy to electricity using solar cells and indirectly using solar applications [4, 6].
thermal to produce superheated steam for driving electrical
turbines. Solar photovoltaic cells used in solar PV system are This paper presents studies on solar PV model module, the
made of a light absorber materials of p-n junction semiconductor energy pattern was investigated under different operating weather
that absorbs solar photons above certain minimum threshold conditions and MPPT was incorporated to maximize energy
energy called “energy gap” or “band gap” (Eg) to free electrons harvesting. A model a 220W solar PV panel intended to be fed to
generate electricity. an inverter for stand-alone AC network system is modelled in
Matlab-Simulink environment. The characteristic behaviour of

This work was supported by Universiti Teknologi PETRONAS and Malaysian

Research Assessment Instrument ( MyRA) Grant No: 0153AB-J17

978-1-4799-4848-2/14/$31.00 ©2015 IEEE

the PV panel is analysed considering different operating To show the non-linear characteristic of PV array under
conditions of irradiance and temperature level and P&O MPPT different irradiance and temperature, a 220W solar panel
algorithm was used for maximum power tracking. The simulation comprises of 3 modules with each module having 36 cells
results shows that system performed satisfactorily as the connected in series. The electrical specifications of the solar panel
maximum output power from solar PV panel with MPPT show a based on standard test conditions (STC) at 1000W/m2 irradiance,
close relationship with the maximum power available from the AM of 1.5 and, 25°C is presented in Table I.
PV under test at different irradiance levels.

II. MODELING OF SOLAR PV CELL

Solar PV cell is the basic unit of solar PV array/panel, they are TABLE I: ELECTRICAL CHARACTERISTICS OF PV PANEL
combined in series and parallel to achieve require voltage and Parameters Symbol Value
current level. A PV cell is a p–n junction semiconductor that Rated power P MP 220W
Open circuit voltage V OC 54V
generate current when exposed to light. The mathematical model
Short circuit current I SC 5.52A
of PV cell is useful for simulation purpose to reveal the voltage, Voltage at maximum power V MP 44.63V
current and power behaviour under different operating conditions. Current at maximum power I MP 4.94A
A simplified equivalent circuit of PV cell with 5 parameter is Total number of cells in series NS 108
presented in Fig.1. A cell series resistance (𝑅𝑠 ) is connected in Total number of cells in parallel NP 1
series with a parallel combination of cell photocurrent (𝐼𝑝ℎ ),
Matlab-Simulink tools was used to simulate the solar panel I-
exponential diode (𝐷), and shunt resistance(𝑅𝑠ℎ ) . 𝐼𝑃𝑣 , and 𝑉𝑃𝑣 V and P-V curve under variable irradiance and temperature as
are the PV cell’s current and voltage respectively. presented in Fig.2. The simulation result of I-V and P-V
characteristic at 1000W/m2, 800W/m2, and 600W/m2 irradiance at
constant temperature of 25°C is presented in Fig.3 and Fig.4
respectively. The result shows that the PV output current and
power increases as solar irradiance increase.

Fig.1. Equivalent circuit of PV cell

The PV cell output current 𝐼𝑃𝑣 is expressed as:

 q VPV  I PV Rs nKT 

I PV  I ph  I s  e  1  v PV  I PV  Rs  / Rsh (1)
 
Where:
I ph = Solar-induced current
I s = Diode saturation current Fig.2. Simulink model of solar panel
19
q = Electron charge (1.6e C )
K = Boltzmann constant (1.38e 23 J / K )
n = Ideality factor (1 ~ 2)
0
T =Temperature K
The solar induced current of the solar PV cell depends on the solar
irradiation level and the working temperature expressed as eq. (2):
Ir
I ph  I sc  K (T  T )  (2)
i c r 1000
I sc = short-circuit current of cell at STC
K = cell short-circuit current/temperature coefficient ( A / K )
i
I r = irradiance in W/m2 covering cell surface Fig.3. I-V curve for different solar irradiance
T , T = cell working and reference temperature at STC
c r
 MPPT automatically finds the voltage (reference voltage (𝑉𝑟𝑒𝑓 )
at which the PV array outputs maximum power and ensure that it
maintains the system operation at the point under different
irradiance, temperature and load current. The basic unit of
maximum power point tracker is shown in Fig.7 with MPPT
power stage and the MPPT control algorithm [7].
VPV,IPV Vo,Io
MPPT
power Load
circuit

D
Fig.4. P-V curve for different solar irradiance PV Array MPPT
control
The simulation result of I-V and P-V characteristic of the PV algorithm
panel for different working temperature 25°C, 50°C and 75° Fig 7. Block diagram of MPPT control
with constant irradiance are shown in Fig.5 and Fig.6. The PV
output voltage and power decreases with increasing solar cell In this work, a DC-DC boost converter is used at power stage
operating temperature. to achieve the source to load impedance matching controlled by
variable switching duty cycle. The Perturb and Observation
(P&O) MPPT algorithm is used for the duty cycle (𝐷) control to
obtain reference voltage for maximum power point. The flow
chart of P&O algorithm is shown in Fig.8, where the PV voltage
and current are sensed to obtain the output power. The power is
checked by varying the voltage, with increase voltage the power
also increased, then the duty cycle (𝐷)is increased in the same
direction otherwise duty cycle decreases with a step(𝛥𝐷). The
iteration continues until maximum power point is reached and the
converter output voltage is maintained at the point [8-11].
The output voltage (𝑉𝑜𝑢𝑡 ) of the converter is maintained
constant by varying the duty cycle which determines the output
Fig.5. I-V curve for different cell temperature voltage value from the solar PV at every switching cycle. The
solar PV array output voltage which is input to the converter is
defined by (3) [12]:
VPV  (1  D)Vout (3)
The solar irradiation or temperature changes will results in PV
array output voltage variation expressed as:
/ V PV /  / D / Vout (4)
Where V PV and D are the PV output voltage and converter
duty cycle variations. The MPPT P&O coding was done in Matlab
m file and embedded in the Simulink using Matlab-function
block. In order to ensure that the possible voltage oscillation
around the maximum power point is minimised and at the same
Fig.6. P-V curve for different cell temperature time achieving fast tracking, the duty cycle step change was D
chosen as 0.0005.
III. MPPT CONTROL TECHNIQUE
PV arrays exhibits non-linear varying I-V characteristic during
operation based on solar irradiance and temperature at particular
time. In order to ensure that PV arrays operates at maximum
power point under different operating conditions, maximum
power point tracker (MPPT) are incorporated. This will improve
the PV panel efficiency and reduce the system installation cost.
 TABLE II: BOOST CONVERTER PARAMETERS
Start
Parameters Symbol Value
Sample V(k), I(k) Input voltage Vin 45 [V]
Output voltage Vout 90 [V] at D=0.5
Load resistance RL 36.8 [Ω]
P(k) = V(k)*I(k)
Inductor L 500 [µH]
Output capacitor C 100 [µF]
N Y fs
Switching frequency 5 [kHz]
P(k)>P(k-1)

Y N
Y N IV. RESULTS AND DISCUSSIONS
V(k)>V(k-1) V(k)>V(k-1)
The Matlab_Simulink model of PV panel developed with the
MPPT controller is presented in Fig. 10 for studying the
D=D1-ΔD D=D1+ΔD D=D1+ΔD D=D1-ΔD
performance of the MPPT at different irradiances and cell
temperatures is presented in Fig.10. The results of output power
k = k+1 from the PV at different solar irradiance of 1000 W/m2, 800
W/m2, 600 W/m2 and cell temperature of 25°C, 50°C, 75°C are
Return presented in Fig. 11 and Fig.12 respectively. The results show
decrease in MPPT duty cycle and PV output power as solar
Fig.8. Flow chart of P&O MPPT method
irradiance decreases and with cell temperature increases. The PV
A DC-DC boost converter is used to achieve the MPPT power output power from application of MPPT power is closed to
stage owing to the advantage of high reliability, less component maximum available power from the PV panel test parameters.
parts to reduce implementation cost. The boost converter
configuration comprises of power MOSFET as the switching
transistor with input inductor (𝐿) placed in series with the PV
voltage (𝑉𝑖𝑛 ) as shown in Fig. 9.
L
D
iin(t) iL(t) +
ic(t)
Vin Q1 RL Vout(t)
Vc(t) C
PWM
-
Fig.10. Simulink model of PV array with P&O MPPT
Fig.9. Equivalent circuit of DC-DC boost converter
The steady state conversion ratio (input-output voltage) of the
converter is given by:
Vin
Vout  (5)
1 D
The magnitude of peak-to-peak inductor current ripple I L is
given by:
Vin D (6)
I L 
fs L

And, also the output capacitor voltage ripple Vc is:

IoD
Vc  Vout  (7)
f sC

Fig.11. Duty cycle and PV output power at 25°C cell temperature

 ACKNOWLEDGMENT
The authors would like to thank Universiti Teknologi PETRONAS and
Malaysian Research Assessment Instrument (MyRA) Grant No:
0153AB-J17 for presentation and publication of this work.

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