Comparison of Maximum Power Point Technique for Solar Photovoltaic Array

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 04 Issue: 11 | Nov -2017 www.irjet.net p-ISSN: 2395-0072
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Comparison of Maximum power point Technique for solar
Photovoltaic array
P.Parthasaradhi1, S.R.REDDY2, V.C.Shekar3
1GNITC, EEE Department, Professor, Ibrahimpatnam Hyderabad, India.
2 GNITC, EEE Department, Asst Professor, Ibrahimpatnam Hyderabad, India.
3 GNITC, EEE Department Professor, Hyderabad, India.
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Abstract - An In this paper the control mechanism of
Maximum power point tracking using DC-DC converters is
presented. First the photovoltaic module is analyzed using
SIMULINK software. The main aim of this paper is to track the
maximum available power from the solar PV module in
accordance with irradiation conditions using different MPPT
algorithms to utilize the efficiency of the solar panel. The DC-
DC converter is used along with a Maximum Power Point
Tracking control mechanism. The MPPT is responsible for
extracting the maximum possiblepowerfromthephotovoltaic
and feed it to the load via the DC-DC converter which steps
up/down the voltage to the required magnitude. The
algorithms utilized for MPPT are generalized algorithms and
are easy to model or use as a code. The algorithms are written
in m files of MATLAB and utilized in simulation. This project
presents in detail the comparative study between two most
popular algorithm techniques which is incremental
conductance algorithm and perturb and observe algorithm.
The DC-DC converter circuit is driven by the PWM pulses
obtain by comparison of triangular wave and Duty cycle
obtained from the MPPT embedded functionblock. Theoutput
of the DC-DC converter circuit matches the impedance of the
panel and the converter circuit in order to transfer the
maximum power.
Key Words: Solar PV module, DC-DC converter, MPPT
control, incremental conductance algorithm, Perturb
and observe Controller algorithm
1. INTRODUCTION
This As people are much concerned with the fossil fuel
exhaustion and the environmental problems caused by the
conventional power generation, renewable energy sources
and among them photovoltaic panels and wind-generators
are now widely used. So Solar Energy is a good choice for
electric power generation. The solar energy is directly
converted into electrical energy by solar photovoltaic
module. Photovoltaic sources are used today in many
applications such as battery charging, water pumping,home
power supply, swimming-pool heating systems, satellite
power systems etc [1]. They have the advantage of being
maintenance and pollution-free but their installation cost is
high and in most applications; they require a power
conditioner (DC/DC or DC/AC converter) for load interface.
Since PV modules still have relatively low conversion
efficiency, the overall system cost can be reduced using high
efficiency power conditioners which, in addition, are
designed to extract the maximum possible power from the
PV module. We know that the efficiency of the solar PV
module is low about 13%. To increase the efficiency of the
PV module it is desirable to operate the module at the
maximum power point condition. So that the maximum
power can be delivered to the load under varying
temperature and isolation conditions. Hence it improvesthe
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 tothe
load. The maximum power is achieved with the help of a
dc/dc converter by adjusting its duty cycle [2]. The duty
cycle was achieved by the following methods. 1. Perturband
observe. 2. Incremental Conductance3.ParasiticCapacitance
4. Voltage Based Maximum Power Tracking5.CurrentBased
Maximum power Tracking. In which two most popular
algorithm techniques which is incremental conductance
algorithm and perturb and observe algorithmarecompared.
The comparison of two algorithms is observed using hard
ware and software (MATLAB) Simulations. This paper is
organized as follows: Section 2.PresentsSolarCell Modeling,
Section 3. Maximum power point Tracking, Section 4.DC-DC
Converter, Section 5. Presents ResultsandDiscussion,finally
Section 6. Presents Conclusion.
2. SOLAR CELL MODELING
Practical behavior of solar cell is deviated from ideal due
to the optical and electrical losses. Hence to model the
practical solar cellappropriatecomponents should be added
with the ideal current source [3]. Fig-1. Shows the
mathematical model of asolar cell. Fig-2. Shows theSimulink
model of a solar cell
Fig-1.Shows the mathematical model of a solar cell.

Fig-2. Simulink model of a solar cell.
The mathematical model design of a solar cell is given by
using the equations (1) – (4).
The output current of PV module is
(1)
Where Iph is Module photo current
(2)
Modules reverse saturation current (Irs)
(3)
Module saturation current IS varies with the cell
temperature, which is given by
(4)
abbreviations in the title or heads unless they are
unavoidable.
3. MAXIMUM POWER POINT TRACKING
Solar panel converts 30-40% of energy incident on it to
electrical energy. A Maximum Power Point Tracking
algorithm is necessary to increase the efficiency of the solar
panel. Maximum Power Point Tracking is done to extract the
maximum power from solar cell or module by operating it at
maximum power point of its I-V characteristics. MPPT
mechanism makesuseofanalgorithm.Manytechniqueshave
been developed for the maximum power point techniques.
These techniques use the principle of impedance matching
between load and PV-module [4]. 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. A dc/dc converter acts as an interface
between the load & module.
3.1 Methods of Maximum Power Point Tracking
Sample The maximum power is reached with the helpofa
dc/dc converter by adjusting its duty cycle. The duty cycle
was achieved by the following methods.
1. Perturb and observe
2. Incremental Conductance
3. Parasitic Capacitance
4. Voltage Based Maximum Power Tracking
5. Current Based Maximum power Tracking
The algorithms are implemented in a microcontroller to
implement the maximum power point tracking. The
algorithm changes the duty cycle of the DC/DC converter to
maximize the power output of the module and make it
operate at the maximum power point of the module. Among
all the methods Perturb and observe (P&O) andIncremental
conductance are most commonly used because of their
simple implementation, lesser time to track the MPP and
several other economic reasons [5].
Finally, complete content and organizational editing
before formatting. Please take note of the following items
when proofreading spelling and grammar:
3.1.1 Perturb and observe (P&O) method
Sample Hill climbing method is one form of the P&O
method. However, the hill climbing method uses the
condition to judge. It is applied by perturbing the duty cycle
D at regular intervals and by recording the resulting array
current and voltage values, thereby obtaining power. Once
power is known, a check for the slope of the P-V curve or the
operating region (current sourceorvoltagesource region)is
carried out and then the change in D is effected in a direction
so that the operating point approaches MPP on the power-
voltage characteristics. Referring Fig-3.the algorithm can be
explained as follows.The algorithm for this scheme is
described below along with mathematical expressions [6].
In the current source region,
(5)
In the voltage source region,
(6)
At MPPT,
(7)
As per the equations above, if is greater thanzerotheduty
cycle is to decreased. This means the slope is positive and
the module is operating in current source region. In case the
slope is negative, the duty ration is increased, as module is
operating in voltage source region, in this case.

Fig-3. Flow chart for Hill climbing method
3.1.2 Incremental Conductance Method
In the incremental conductance method, the MPP is tracked
by matching the PV array impedance with the effective
impedance of the converter reflected across the array
terminals. The latter is tuned by suitably increasing or
decreasing the value of the duty cycle.ReferringtoFig-4.The
algorithm can be explained as follows [7].
In the voltage source region,
(8)
(Rate of change of current with respect to voltage is high)
In the current source region,
(9)
(Rate of change of current with respect to voltage is low)
(10)
Fig-4. Flow chart for incremental conductance method
3. MAXIMUM DC-DC CONVERTERS
Solar panel A DC-DC converter one it control the output
voltage level, either to a higher or a lower value. This is done
by controlling a switch that will feed a load with a voltage in
pulses with different width this control method is known as
pulse width modulation (PWM). PWM control is the most
comely used control method for all applications and also in
this paper same control method has been used. Generally
three DC-DC converter configurations as Used
 Buck Converter (Step Down)
 Boost Converter (Step Up)
 Buck Boost Converter (Step Down / Step Up)
In this paper buck converter is used for MPPT Tracking
method.
4.1 Methods Buck Converter
The step-down dc-dc converter, commonly known as a buck
converter, is shown in Fig-5. It consists of dc input voltage
source VS, controlled switch S, diode D, filter inductor L,
filter capacitor C, and load resistance R. Typical waveforms
in the converter are shown in Fig-6. Under the assumption
that the inductor current is always positive [8].
Fig-5. Buck converter
The state of the converter in which the inductorcurrentis
never zero for any period of time is called the continuous
conduction mode. It can be seen from the circuit that when
the switch S is commanded to the on state, the diode D is
reverse-biased. When the switch S is off, the diode conducts
to support an uninterrupted current in the inductor. The
relationship among the input voltage,outputvoltage,andthe
switch duty ratio D can be derived, for instance, from the
inductor voltage VL waveform (see Fig-6). According to
Faraday’s law, the inductor volt-second product over a
period of steady-state operation is zero. For the buck
converter [9].
(11)
4.2 Modes of Operation
The DC-DC converters can operate in two distinct mode
switch respect to the inductor current iL. Fig-6. Depicts the
CCM in which the inductor current is always greater than
zero. When the average value of the output current is low
(high R) and/or the switching frequency f is low, the
converter may enter the discontinuous conduction mode
(DCM).

Fig-6. Waveforms of various signal of a Buck converter
In the DCM, the inductor current is zero during a portion of
the switching period. The CCM is preferred for high
efficiency and good utilization of semiconductor switches
and passive components [10]. The DCM may be used in
applications with special control requirements because the
dynamic order of the converter is reduced (the energy
stored in the inductor is zero at the beginning and at the end
of each switching period). It is uncommon to mix these two
operating modes because of different control algorithms.
4.3 Buck Converter Design
The For the buck converter, the value of the filterinductance
that determines the boundary between CCM and DCM is
given by
(12)
(13)
To regulate V0 with variations in Vi, the value of D should be
changed. Thus if Vimax is the maximum input voltage swing,
then Dmin will be the corresponding minimum duty cycle to
obtain a specified V0. If Vimin is the minimum input voltage
swing, then Dmax will be the corresponding maximum duty
cycle to obtain the specified V0. Thus, for a regulated V0,
V0=Vimax*Dmin=Vimin*Dmax (14)
The values Vo, Vimax, Vimin are known from specifications of
the converter. Dmax is a design choice that is dependent on
the specific application [11]. Then
The inductor current should have a currentripplethatis less
than or equal to the specified ΔiL. Therefore the inductor
should at the duty ratio corresponding to Dmin. Thus,
Where is ripple current generally 1to 10%
Vdc is the input DC voltage, D is duty ratio, where fs is
switching frequency
The Value of the capacitor is calculated by applyingtheamp-
second rule. Referring to the capacitor current waveform
given in Fig-6. If there is to be no charge build up or charge
reduction in the capacitor, then the area under the capacitor
current curve in one period should be zero. The area under
the positive portion of the current curve implies charging of
the capacitor and that under the negative portion implies
discharging of the capacitor. For charge balance both these
areas should be equal. The change is the capacitorcharge ΔQ
is given by the area under either positive or the negative
portion of the capacitor current curve [12]. Thus,
Where ΔV0 is voltage ripple generally 1 to 10%. The valueof
C should be greater than the value calculated by Eq-16.
5. RESULTS AND DISCUSSION
The modelling of PV module connected with Buck converter
with MPPT simulation along with the discussion of the
results. When the PV model isconnectedwithoutMPPTthere
is loss of output power. For increasing the out power of PV
model, the PV Model is connected to MPPT through the buck
converter. The Hard ware & Software result with Buck
converter is observed.
5.1 Software Simulations
Fig-7. Shows the simulink model ofthePVmoduleconnected
to the load through MPPT. Where 10W panel is taken as the
reference module for simulation.
Fig-7. Simulink model of PV module with MPPT.
Waaree made 10W panel is taken as the reference module
for simulation and name-plate details are mentioned in
Table-1. The electrical specifications are under test
conditions of irradiance of 1000W/m2, spectrum of 1.5 air
mass and cell temperature of 25oC.
Table-1. Electrical Characteristicsdata ofWaaree10Wpanel

Fig-8(a).Shows the subsystem fortheMPPT block connected
to the Load for operates the PV Model in maximum power
point tracking mode. Fig-8(b).Shows subsystem system
simulink model for Buck converter.
Fig-8(a). Subsystem of the Fig- 8(b). Subsystem for
MPPT Block Buck converter
a. Output Results of MPPT with the Buck converter
Here simulated the Buck converter withthePVmodel shown
in Fig-7.
Voc=21, Vmp=17, Isc=0.62, Imp=0.59, Pin=10W
RL = 10 ; L= 2mH; C= 10μF
Switching Frequency= 20 kHz
Fig-9.shows the increasing irradiation level at every 0.3 sec.
Fig-9. Irradiation Level of Buck Converter
Fig-10.shows variation of the duty ratio to reach MPP at
respective irradiation levels applied by using P&O (Perturb
and Observe) method and Inc(Incremental Conductance)
method.
Fig- 10(a) Fig- 10(b)
Fig-10(a). Duty Ratio of Buck Converter P&O method. Fig-
10(b). Duty Ratio of Buck Converter Inc method.
Fig 11(a) and (b) shows the variation of PV Panel power for
P&O method and Inc method respectively for respective
irradiations levels shown in Fig -9. From the Fig-11. It is
observed P&O method oscillates at MPP and Inc method
reaches MPP efficiently
Fig- 11(a) Fig-11(b)
Fig-11(a). Panel Power P&O method. Fig-11(b). Panel
Power (b) Inc method
Fig-12. (a) And (b) shows the variation of load (output)
power for P&O method and Inc method respectively for
respective irradiations levels shown in fig-9. From Fig-
11.and Fig-12. it is observed the maximumpowertracked by
the P&O and Inc method was transferredfromsourcetoload
by using buck converter
Fig- 12(a) Fig-12(b)
Fig-12(a). Boost Converter Output Power P&O method.
Fig-12(b). Boost Converter Output Power Inc method.
Buck converter transfers the maximum power with 98%
efficiency which can be observed from the Table 1 and 2.
Table -2. Efficiency of Buck Converter (P&O method)
Irra
diati
on
(w/
m2)
Pane
l
pow
er
(w)
Pane
l
volta
ge(v
)
Pane
l
curr
ent(
a)
Lo
ad
(ω
)
Duty
ratio
Outp
ut
pow
er
(w)
Effici
ency
(%)
1000 9.81 17 0.58 20 0.83 9.55 97.4
800 7.7 16.5 0.47 20 0.76 7.5 97.4
700 6.66 16.5 0.4 20 0.71 6.55 98.3
Table -3. Efficiency of Buck Converter (Inc method).
Irra
diati
on
(w/
m2)
Pane
l
pow
er
(w)
Pane
l
volt
age(
v)
Pane
l
curr
ent(
a)
Lo
ad
(ω
)
Duty
ratio
Outp
ut
pow
er
(w)
Effici
ency
(%)
1000 9.81 17 0.58 20 0.84 9.65 98.2
800 7.7 16.5 0.47 20 0.77 7.6 98.7
700 6.66 16.5 0.4 20 0.73 6.55 98

At 1000 W/m2 actual PV panel power mentioned by the
manufacturer shown in the Table -1. Are 10 W. Form the
Table-2 and 3. It is observed both P&O and Inc method
tracks the maximum power with the efficiency of 98%. But
only the difference is oscillation at the MPP was reduced in
Inc method when compared to the P&O method.
By observing the Table 4. Buck converter is more
efficient. Incremental conductance methods track the
maximum power very efficiently but perturb and observe
method oscillates at the maximum power.
Table-4. Comparison of MPPT algorithms
MPPT method Buck converter
P&O 97%
INC 98%
Under the assumption that the inductor current is always
positive [8].
5.2 Hardware Implementation
The development of prototype model in the laboratory, the
necessary interface circuits and software control algorithm.
A 10W solar panel with DC-DC converter was built with
necessary control carried out through STM32F4
microcontroller Kit. The simulated system was downscaled
due to limitations of available devices in laboratory. The
experimental setup and the block diagram of the
implemented hardware are shown in Figure 13.
Fig- 13. Block diagram of complete hardware setup
The complete image setup of the MPPT system as shown in
Fig-14.
Fig- 14. Image of complete hardware set up
Hardware circuit was built and tested in the laboratory the
results obtained by implementing the MPPT methods
through embedded C code written in STM32F4
microcontroller kit. Measurements were carried out using
display given in STM32F4 controller and Tektronix TDS
2014C digital storage oscilloscope.
The duty ratio of the Buck converter was adjusted
automatically by using P&O method. The following data was
taken on 25-6-2014 from 11am to 4pm with an interval of
one hour. Load is kept at 10Ω.
Table -5. P&O data with buck converter
Time Voc Isc Vmp Imp Pm D
11AM 19.36 0.46 14 0.43 6.02 0.54
12PM 19.25 0.56 13.6 0.50 6.93 0.58
1PM 19.35 0.55 14.03 0.49 6.88 0.57
2PM 19.25 0.50 13.9 0.43 5.97 0.54
3PM 19.30 0.37 14.3 0.34 4.86 0.47
4PM 19.18 0.28 14.9 0.24 3.57 0.39
Fig-15. Buck converter with P&O method
Fig-15. Shows the variation of maximum power with
respective irradiation level when panel is connected to load
with buck converter P&O method MPPT system.
The duty ratio of the Buck converter was adjusted
automatically by using Inc method. The following data was
taken on 27-4-2015 from 11am to 4pm with an interval of
one hour. Load is kept at 10Ω.
Table-6. Inc method data with buck converter
Time Voc Isc Vmp Imp Pm D
11AM 19.40 0.49 17.3 0.38 6.64 0.49
12.30 19.25 0.53 16.2 0.42 6.804 0.55
1PM 19.35 0.43 16.3 0.32 5.216 0.47
2PM 19.1 0.54 16.2 0.40 6.48 0.57
2.30PM 18.92 0.46 16.1 0.33 5.313 0.49
3PM 18.98 0.44 15.9 0.31 5.11 0.44
3.30PM 18.91 0.36 17.4 0.24 4.176 0.36

Fig-16. Buck converter with Inc method
Fig-16. Shows the variation of maximum power with
respective irradiation level when panel is connected to load
with buck converter Inc method MPPT system.
3. CONCLUSIONS
In this work was to study the most conventional MPPT’s for
Photovoltaic and to implement the same in
MATLAB/SIMULINK as well as to make a hardware
prototype using STM32F4 micro controller. To achieve this
Goal initially the PV array model was prepared in
MATLAB/SIMULINK. Results of the simulated PV array
model showed satisfactory performance. Then thedesign of
the boost and buck converter was presented. It showed
satisfactory results when simulatedwithMPPTcontrol ofPV
array. The two most usual (perturb & observe and
incremental conductance) methods used for MPPT. It is
interesting to point out that the differences in performances
among the analyzed MPPTs are very slight, and these
algorithms must be evaluated according to each situation.
Overall, the outcome of the P&O algorithm tests were quite
good. It responded faster and performed better than the Inc
algorithm. Boost converter transfer the input power to the
load better than buck converter because in buck converter
switch is connected in series with the switch.
REFERENCES
[1] Chetan Singh Solanki, “Solar Photovoltaic’s
Fundamentals, technologies and Applications”, Second
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[3] Power Electronics, Converters, ApplicationsandDesign,
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[4] Power Electronics Essentials & Applications, L
UMANAND.
[5] Soren Bakhojkjar,”Evaluation of the “Hill Climbing” and
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