“STUDY OF MAXIMUM POWER POINT TRACKING (MPPT)

TECHNIQUES IN A SOLAR PHOTOVOLTAIC ARRAY”

A Major Project Report
Submitted in partial fulfillment of the requirement for the award of the degree of

BACHELOR OF TECHNOLOGY

(ELECTRICAL & ELECTRONICS ENGINEERING)

To

ARYABHATTA KNOWLEDGE UNIVERSITY

Submitted by

NAME ROLL No. REGISTRATION No.

CHANDRAKANTA 164044 16110103077
AJANAS KUMARI 164045 16110103077
KAMRAN WALID KHAN 1640 16110103077
HEMANT KUMAR 1640 16110103077
DIGVIJAY KUMAR 1640 16110103077

Under the supervision of

Mr. Deepak Kumar

Assistant Professor

NSIT Bihta Patna

Department of Electrical & Electronics Engineering

NETAJI SUBHAS INSTITUTE OF TECHNOLOGY,

BIHTA, PATNA-801118

May 2019
 CANDIDATE’S DECLARATION

We Chandrakanta (164044), Ajanas Kumari (164045), Kamran Walid Khan (16404),

Hemant Kumar (16404), Digvijay Kumar (16404), students of Bachelor of Technology
(Electrical & Electronics Engineering) at Netaji Subhas Institute ofTechnology, Bihta,
Patna,declare that the work presented in this major project titled “Study Of Maximum Power
Point Tracking (MPPT) Techniques in a Solar Photovoltaic Array”, submitted to
Aryabhatta Knowledge University, Patna during academic year (2016-2020)for the award of
Bachelor of Technology degree in Electrical & Electronics Engineering, is our original work. All
work done in this minor project is entirely our own except for the reference quoted. To the best
of our knowledge this work has not been submitted to any other university or institution for
award of any degree.

Date:NAME ROLL No.Sign.

Place: NSIT, Bihta 1. CHANDRAKANTA 164044

2. AJANAS KUMARI 164045
3. KAMRAN WALID KHAN 16404
4. KUMAR HEMANT
KKHAN 16404
5. DIGVIJAY KUMAR 16404
 CERTIFICATE

It is to certify that work embodies in this report entitled “Study Of Maximum Power Point
Tracking (MPPT) Techniques in a Solar Photovoltaic Array”, submitted by Chandrakanta
(164044), Ajanas Kumari (164045), Kamran Walid Khan (16404), Hemant Kumar (16404),
Digvijay Kumar (16404), in partial fulfillment of the requirement for the award of the degree of
“Bachelor of Technology in Electrical & Electronics Engineering” to Aryabhatta Knowledge
University, Bihta,Patnaduring the academic year 2016-2020.According to best of our
knowledge is a record of bonafide piece of work, carried out by then under my guidance in
Department of Electrical & Electronics Engineering, Netaji Subhas Institute of
Technology,Bihta,Patna. To the best of my knowledge this work has not been submitted to any
other university or institution for award of any degree.

Supervisor HOD
Mr. Deepak Kumar Dr. Jyotirmayee Dalei
Assistant Professor Associate Professor & Head
Dept. of EEE Dept. of EEE
N.S.I.T, Bihta N.S.I.T, Bihta
 APPROVAL

This project entitled “Study Of Maximum Power Point Tracking (MPPT) Techniques in a
Solar Photovoltaic Array”, submitted by

SL.No. NAME ROLL No.

1. CHANDRAKANTA 164044
2. AJANAS KUMARI 164045
3. KAMRAN WALID KHAN 16404
4. HEMANT KUMAR 16404
5. DIGVIJAY KUMAR 16404

is approved for the award of degree of Bachelor of Technology in Electrical & Electronics
Engineering.

INTERNAL EXAMINER EXTERNAL EXAMINER

 ACKNOWLEDGEMENT

It is with a feeling of immense gratitude and regard that we thank our guide, Mr. Deepak
Kumar(AssistantProfessor), Dept. of Electrical & Electronics Engineering, for his valuable
and expert guidance which he has provided us within the course of this project. We are indebted
to her valuable suggestions and highly productive discussions from time to time that have been
instrumental in giving direction to this project and without which this project could never have
been completed.

We specially thank our Head of Department, Dr. JyotirmayeeDalei, without whose

permission, this project could not have materialized. We are sincerely thankful to her for
providing us with such sophisticated laboratories and equipment’s wherein we could carry out
the experiments related to the project.

We wish to express our heartfelt thanks to the faculty and staff members of the Department of
Electrical & Electronics Engineering, N.S.I.T, who despite being busy with their own
assignments, gave us time and provided us with all the help we needed. We would also like to
express gratitude to the lab in-charge and technicians who helped us throughout the duration in
carrying out experiments related to the project.

We are highly indebted to the Library Department of our institute which provided us with an
excellent collection of reference books, research journals and articles that helped us in
completing this project. Along with this we would like to thank the IT Department of our
institute for the internet facility that they provided.

We hope this project work will serve as a reference for further research work that may be carried
out in this project.

Student Name Roll No.

1. CHANDRAKANTA 164044
2. AJANAS KUMARI 164045
3. KAMRAN WALID KHAN 16404
4. HEMANT KUMAR 16404
5. DIGVIJAY KUMAR 16404
 ABSTRACT

The need for renewable energy sources is on the rise because of the acute energy crisis in the
world today. India plans to produce 20 Gigawatts Solar power by the Year 2020, whereas we
have only realized less than half a Gigawatts of our potential as of March 2010. Solar energy is a
vital untapped resource in a tropical country like ours. The main hindrance for the penetration
and reach of solar PV systems is their low efficiency and high capital cost. In this thesis, we
examine a schematic to extract maximum obtainable solar power from a PV module and use the
energy for a DC application. This project investigates in detail the concept of Maximum Power
Point Tracking (MPPT) which significantly increases the efficiency of the solar photovoltaic
system. The goal of this project was to design a Maximum Power Point Tracking system for solar
panels that utilized a DC/DC converter and a microcontroller. The Perturb and Observe method
was used to calculate and maintain the maximum voltage for a PV source with various voltage
inputs ranging from 5V to 25V DC. The system was both simulated using Matlab Simulink and
built using a converter.
 CONTENTS

1 Introduction 11
1.1 The need for Renewable Energy 11
1.2 Different sources of Renewable Energy 11
1.2.1 Wind power 11
1.2.2 Solar power 12
1.2.3 Small hydropower 12
1.2.4 Biomass 12
1.2.5 Geothermal 12
1.3 Renewable Energy trends across the globe 13
2 Literature Review 15
3 Standalone Photovoltaic System Components 17
3.1 Photovoltaic cell 17
3.2 PV module 17
3.3 PV modeling 17
3.4 Boost Converter 21
3.4.1 Mode 1 operation of the Boost Converter 22
3.4.2 Mode 2 operation of the Boost Converter 23
4 Maximum Power Point Tracking Algorithms 25
4.1 An overview of Maximum Power Point Tracking 25
4.2 Different MPPT techniques 25
4.2.1 Perturb & Observe 26
4.2.2 Incremental Conductance 26
4.2.3 Fractional open circuit voltage 27
4.2.4 Fractional short circuit current 28
4.2.5 Fuzzy Logic Control 28
4.2.6 Neural Network 28
4.3 Perturb & Observe Algorithm 30
4.4 Limitations of Perturb & Observe algorithm 32
 4.5 Implementation of MPPT using a boost converter 33
5 Modeling of standalone PV system 34
5.1 Solar panel 34
5.2 MPPT Interfacing 36
5.3 Boost Converter 38
5.4 PI Controller 38
6 Results 40
6.1 Case 1: Running the system without MPPT 40
6.2 Case 2: Running the system with MPPT 43
7 Conclusion 47
8 References 48
 Chapter-1

1.1 INTRODUCTION
This chapter gives a introduction on Photovoltaic cell. It gives idea on the parameters used
in the project. It is mainly deals with literature survey. It gives a synopsis on literature
survey, main objective, system under consideration.
1.2 Literature Survey
India has become the top country in the world to make a law of minister called Minister of New and
Renewable energy for non-conventional energy resources. Being the tropical country India has high
solar isolation so the best renewable green energy is solar energy. Our country is the 5th largest
producer. From research it is noted that, by March 2017, the demand of electricity will be increased
from 900 billion kilowatt-hours to 1400 billion kilowatt-hours. Consequently it is in verge of energy
lack with a huge gap of demand and supply. To fulfill the required demand, solar energy is needed. It
is the only entirely available renewable alternative energy source with the fundamental capability to
satisfy the energy needs of our country. Based on PV installed capacity, India has become fourth
After Japan, Germany and U.S. A major drive has also been initiated by the government to trade
Indian PV products, systems, technologies and services. From [1], it is clear that, the performance of
the photovoltaic panel is affected by the environmental condition like Temperature and Solar
Irradiation. In addition to these factors it also shows how he shadow affects it. Under shaded
condition, PV characteristics get more complicated and difficult to analyze. Hence to make it easily
understandable, difficult methods are adopted so far by the researchers. By those techniques I-V and
P-V curves are recovered from partial shading condition. In [2], importance of solar energy, PV
module and its uses in different field are illustrated. Its working procedure, equivalent model with all
sets of equations are also discussed. Different factors affecting the characteristics of PV module are
manifested. In [5] and [3], PV module simulated considering the variation in Temperature and Solar
irradiation. Behavior of the characteristics is all together listed. In [4], need of MPPT controller
circuit is power, so that further operation can be easily carried out without any interruption, as
initially the curve of PV module is non-linear. Different methods of MPPT also described in this
paper. In [6], approach for battery charge controller for stand-alone PV system is manifested. Various
charge performance characteristics are all considered. The studies in [3] and [8] shows that when PV
array is under practically shaded conditions, the array characteristics become more complex with
multiple MPPs. Partial shaded condition is defined as the circumstance where one or more of the PV
modules in the array received less amount of solar irradiance. In [9], [11], [14], it has been clear that
the battery provides dc link constant voltage to the load and also it prevents high voltage stress
problem. From PV panel current and voltage are extracted through current and voltage sensor
respectively and given to battery for maintaining constant dc link voltage.
can be easily carried out without any interruption, as initially the curve of PV module is non-linear.
Different methods of MPPT also described in this paper. In [6], approach for battery charge controller
for stand-alone PV system is manifested. Various charge performance characteristics are all
considered. The studies in [3] and [8] shows that when PV array is under practically shaded
conditions, the array characteristics become more complex with multiple MPPs. Partial shaded
condition is defined as the circumstance where one or more of the PV modules in the array received
less amount of solar irradiance. In [9], [11], [14], it has been clear that the battery provides dc link
constant voltage to the load and also it prevents high voltage stress problem. From PV panel current
and voltage are extracted through current and voltage sensor respectively and given to battery for
maintaining constant dc link voltage.
1.3 MOTIVATION
The key motivation is fascinating the scientists more to research in this field of power
generation. A key point for encouraging to the use of solar power generation system is,
many governments giving centre of attention to their investments in renewable and clean
energy sources. Because every country has limited sources of conventional energy. Even in
India, govt. also aims to achieve generating capability of 20 GW from solar energy by year
2020 and the most bulk part i.e. 40% of it will generate by PV power generation system
according to JNNSM (Jawaharlal Nehru National Solar Mission) India. In this method solar
panel directly convert the sunlight irradiation into electricity by the photovoltaic effect. It
has many advantages like clean and no pollution due to solar power generation as it won't
release any greenhouse gases. The reason behind using the specified model is to minimize
the reverse effect of temperature and irradiation changes in the PV array. The challenge of
the project and the new area of study were the motivations behind the project.
1.4 The System under Consideration
PV system under constant temperature and irradiation
As shown in Fig. 1.1 system consist of a PV module, DC-DC boost converter, MPPT with
constant resistive load. Boost converter consist of two switches S1 and S2, an inductor L,
two 3 capacitor C1 and C2 load resistance R. Switches are operate by control logic, develop
by MPPT. MATLAB coding is use to make MPPT, its purpose is to track maximum power
so that PV module utilizes maximum.
1.1 The need for Renewable Energy
Renewable energy is the energy which comes from natural resources such as sunlight, wind,
rain, tides and geothermal heat. These resources are renewable and can be naturally replenished.
Therefore, for all practical purposes, these resources can be considered to be inexhaustible,
unlike dwindling conventional fossil fuels . The global energy crunch has provided a renewed
impetus to the growth and development of Clean and Renewable Energy sources. Clean
Development Mechanisms (CDMs) [2] are being adopted by organizations all across the globe.
Apart from the rapidly decreasing reserves of fossil fuels in the world, another major factor
working against fossil fuels is the pollution associated with their combustion. Contrastingly,
renewable energy sources are known to be much cleaner and produce energy without the
harmful effects of pollution unlike their conventional counterparts.

1.2 Different sources of Renewable Energy

1.2.1 Wind power
Wind turbines can be used to harness the energy [3] available in airflows. Current day turbines
range from around 600 kW to 5 MW [4] of rated power. Since the power output is a function of
the cube of the wind speed, it increases rapidly with an increase in available wind velocity.
Recent advancements have led to aerofoil wind turbines, which are more efficient due to a better
aerodynamic structure.
1.2.2 Solar power
The tapping of solar energy owes its origins to the British astronomer John Herschel who
famously used a solar thermal collector box to cook food during an expedition to Africa. Solar
energy can be utilized in two major ways. Firstly, the captured heat can be used as solar thermal
energy, with applications in space heating. Another alternative is the conversion of incident solar
radiation to electrical energy, which is the most usable form of energy. This can be achieved with
the help of solar photovoltaic cells or with concentrating solar power plants.
1.2.3 Small hydropower
Hydropower installations up to 10MW are considered as small hydropower and counted as
renewable energy sources. These involve converting the potential energy of water stored in dams
into usable electrical energy through the use of water turbines. Run-of-the-river hydroelectricity
aims to utilize the kinetic energy of water without the need of building reservoirs or dams.
1.2.4 Biomass
Plants capture the energy of the sun through the process of photosynthesis. On combustion, these
plants release the trapped energy. This way, biomass works as a natural battery to store the sun’s
energy and yield it on requirement.
1.2.5 Geothermal
Geothermal energy is the thermal energy which is generated and stored within the layers of the
Earth. The gradient thus developed gives rise to a continuous conduction of heat from the core to
the surface of the earth. This gradient can be utilized to heat water to produce superheated steam
and use it to run steam turbines to generate electricity. The main disadvantage of geothermal
energy is that it is usually limited to regions near tectonic plate boundaries, though recent
advancements have led to the propagation of this technology.

1.3 Renewable Energy trends across the globe

The current trend across developed economies tips the scale in favour of Renewable Energy. For
the last three years, the continents of North America and Europe have embraced more renewable
power capacity as compared to conventional power capacity. Renewable accounted for 60% of
the newly installed power capacity in Europe in 2009 and nearly 20% of the annual power
production.

As can be seen from the figure 1.1, wind and biomass occupy a major share of the current
renewable energy consumption. Recent advancements in solar photovoltaic technology and
constant incubation of projects in countries like Germany and Spain have brought around
tremendous growth in the solar PV market as well, which is projected to surpass other renewable
energy sources in the coming years. By 2009, more than 85 countries had some policy target to
achieve a predetermined share of their power capacity through renewable. This was an increase
from around 45 countries in 2005. Most of the targets are also very ambitious, landing in the
range of 30-90% share of national production through renewable. Noteworthy policies are the
European Union’s target of achieving 20% of total energy through renewable by 2020 and
India’s Jawaharlal Nehru Solar Mission, through which India plans to produce 20GW solar
energy by the year 2022.

Chapter-2
Literature Review
Studies show that a 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.

There are different techniques for MPPT such as Perturb and Observe (hill climbing method),
Incremental conductance, Fractional Short Circuit Current, Fractional Open Circuit Voltage,
Fuzzy Control, Neural Network Control etc. Among all the methods Perturb and observe (P&O)
and Incremental conductance are most commonly used because of their simple implementation,
lesser time to track the MPP and several other economic reasons.

Under abruptly changing weather conditions (irradiance level) as MPP changes continuously,
P&O takes it as a change in MPP due to perturbation rather than that of irradiance and sometimes
ends up in calculating wrong MPP. However this problem gets avoided in Incremental
Conductance method as the algorithm takes two samples of voltage and current to calculate MPP.
However, instead of higher efficiency the complexity of the algorithm is very high compared to
the previous one and hence the cost of implementation increases. So we have to mitigate with a
tradeoff between complexity and efficiency.
It is seen that the efficiency of the system also depends upon the converter.Typically it is
maximum for a buck topology, then for buck-boost topology and minimum for a boost topology.

When multiple solar modules are connected in parallel, another analog technique TEODI is also
very effective which operates on the principle of equalization of output operating points in
correspondence to force displacement of input operating points of the identical operating system.
It is very simple to implement and has high efficiency both under stationary and time varying
atmospheric conditions.

Chapter-3
Standalone Photovoltaic System Components
3.1 Photovoltaic cell
A photovoltaic cell or photoelectric cell is a semiconductor device that converts light to electrical energy
by photovoltaic effect. If the energy of photon of light is greater than the band gap then the electron is
emitted and the flow of electrons creates current. The whole process by which a photovoltaic cell works is
fairly complex. To put it quite simply the mechanism is as such; the light excites electrons to move from
one layer to another through semi-conductive silicon materials. This ultimately produces an electric
current. This whole process is called the photo electric effect. Solar cells called photovoltaic which are
made from thin slices of crystalline silicon, gallium arsenide, or other semiconductor materials which are
capable of converting solar radiation directly into electricity.

Fig: 3.1 Mechanism of a PV Panel

The generation of electric current happens inside the depletion zone of the p-n junction. The area around
the p-n junction is called the depletion zone where the electrons from the “n-type” silicon, have diffused
into the holes of the “p-type” material. Whenever a photon of light hits the surface and is absorbed by one
of these atoms in the “n-type” silicon it will dislodge an electron, thus creating a free electron and a hole.
The free electron and hole produced have sufficient energy to jump out of the depletion zone. If a wire is
connected from the cathode (n-type silicon) to the anode (p-type silicon) electrons will flow (current)
through the wire. The electron is attracted to the positive charge of the “p-type” material and travels
through the external load creating a flow of electric current. The hole which is created by the freed
electron is attracted to the negative charge of “n-type” material and drifts to the back electrical contact. As
the electron enters the “p-type” silicon from the back electrical contact it combines with the hole
reestablishing the electrical neutrality. By connecting large numbers of these cells into modules, the cost
of photovoltaic electricity gets reduced to certain amount per kilowatt-hour. The simplest solar cells
provide small amounts of power for watches and calculators. There are more complex systems which can
provide electricity to houses and electric grids.

3.2 PV module
Usually a number of PV modules are arranged in series and parallel to meet the energy requirements. PV
modules of different sizes are commercially available (generally sized from 60W to 170W). For example,
a typical small scale desalination plant requires a few thousand watts of power. The basic building blocks
of solar or PV system are the solar or PV cells.

Fig: 3.2Equivalent circuit of Single diode model of a solar cell

These individual cells are quite small producing about 1 or 2 KW of power. In order to boost this power
output of the PV cells they have to be connected together forming larger units called modules. These
modules however can be connected to form arrays which are interconnected to produce more power. By
connecting these cells or modules in series the voltage can be increased. On the other hand by connecting
the cells or modules in parallel the output current can reach higher values.

3.3 PV modeling
The characteristics of a PV cell can be further explained using an equivalent circuit shown in the Fig: 2.3.
The PV model consists of a current source, a diode and a series resistance. The effect of parallel resistance
represents the leakage resistance of the cell which is very small in a single module. The current source
represents the current which is generated by the photons, and its output is constant under constant
temperature and constant incident radiation of light.
 Fig: 3.3 Equivalent circuit of PV cell

Current-voltage (I-V) curves are obtained by exposing the cell to a constant level of light, while
maintaining a constant cell temperature, varying the resistance of the load, and measuring the
produced current. When an I-V curve is drawn it normally passes through two points:
 Short-circuit current (𝑰𝒔𝒄 ): This is the current produced when the positive and negative
terminals of the cell are short-circuited (i.e., when the solar cell is short circuited), and the
voltage between the terminals is zero, which corresponds to zero load resistance.
 Open-circuit voltage (𝑽𝒐𝒄 ): This is the voltage across the positive and negative terminals
under open-circuit conditions, when the current is zero, which corresponds to infinite load
resistance.

Where,
I = the output current (A)
Isc= short circuit current (A)
Is = reverse saturation current (A)
VD= voltage (V) across the diode
q= electron charge (1.6x C)
K= Boltzmann’s constant (1.381x J/K)
T= junction temperature (K)
n = diode ideality factor (1~2)
In order to model the solar panel accurately we can use two diode model but in our project our scope of
study is limited to the single diode model. Also, the shunt resistance is very high and can be neglected
during the course of our study.
The I-V characteristics of a typical solar cell are as shown in the Figure 3.2.
When the voltage and the current characteristics are multiplied we get the P-V characteristics as shown
in Figure 3.3. The point indicated as MPP is the point at which the panel power output is maximum.
3.4 Boost Converter
As stated in the introduction, the maximum power point tracking is basically a load matching
problem. In order to change the input resistance of the panel to match the load resistance (by
varying the duty cycle), a DC to DC converter is required. It has been studied that the efficiency
of the DC to DC converter is maximum for a buck converter, then for a buck-boost converter and
minimum for a boost converter but as we intend to use our system either for tying to a grid or for
a water pumping system which requires 230 V at the output end, so we use a boost converter.

3.4.1 Mode 1 operation of the Boost Converter

When the switch is closed the inductor gets charged through the battery and stores the energy. In
this mode inductor current rises (exponentially) but for simplicity we assume that the charging
and the discharging of the inductor are linear. The diode blocks the current flowing and so the
load current remains constant which is being supplied due to the discharging of the capacitor.

3.4.2 Mode 2 operation of the Boost Converter

 In mode 2 the switch is open and so the diode becomes short circuited. The energy stored in the
inductor gets discharged through opposite polarities which charge the capacitor. The load current
remains constant throughout the operation. The waveforms for a boost converter are shown in
Figure 3.7.
 Chapter-4
Maximum Power Point Tracking Algorithms
4.1 An overview of Maximum Power Point Tracking
As previously stated, other methods need to be employed to monitor and improve efficiency of
solar panels. The most popular method is Maximum Power Point Tracking, or MPPT. MPPT is
measuring the power of the solar panel at given intervals and making sure it is always at its
maximum power. A measurement is taken from the solar panel and the power is calculated.
After a specified interval, another measurement is taken. These two measurements are
compared, and adjustments are made to the solar panel to ensure that the most recent
measurement will lead to the maximum power.
MPPT is not a new technology. Some companies have been designing solar trackers for years.
Most solar trackers move with regard to the angle of the sun, and do not constantly calculate
power. Linak, for example, has two different types of solar tracking systems that both use
integrated control actuators. The solar panels can either move 180 degrees (single axis) or can
tilt in all different angles using dual access. First Solar and Solar Flexrack have similar trackers
that follow the movement of the sun throughout the day . These trackers are controlled by
MPPT controllers. Controllers such as the MPPT Tracer Solar Charge Controller are installed
and read a solar panel. Based on the information read, all solar panels are adjusted to follow the
sun’s path.

Though there are some MPPT already on the market, our team has decided to
make our own MPPT using a converter and microcontroller. The following paper illustrates our
thought process during the design of our MPPT, along with results of our working product.
4.2 Different MPPT techniques
There are different techniques used to track the maximum power point. Few of the most popular
techniques are:
1) Perturb and Observe (hill climbing method)
2) Incremental Conductance method
3) Fractional short circuit current
4) Fractional open circuit voltage
5) Neural networks
6) Fuzzy logic

The choice of the algorithm depends on the time complexity the algorithm takes to track the
MPP, implementation cost and the ease of implementation.
4.2.1 Perturb & Observe
Perturb & Observe (P&O) is the simplest method. In this we use only one sensor, that is the
voltage sensor, to sense the PV array voltage and so the cost of implementation is less and hence
easy to implement. The time complexity of this algorithm is very less but on reaching very close
to the MPP it doesn’t stop at the MPP and keeps on perturbing on both the directions. When this
happens the algorithm has reached very close to the MPP and we can set an appropriate error
limit or can use a wait function which ends up increasing the time complexity of the algorithm.

However the method does not take account of the rapid change of irradiation level (due to which
MPPT changes) and considers it as a change in MPP due to perturbation and ends up calculating
the wrong MPP. To avoid this problem we can use incremental conductance method.
4.2.2 Incremental Conductance
Incremental conductance method uses two voltage and current sensors to sense the output voltage
and current of the PV array.
At MPP the slope of the PV curve is 0.
(dP/dV)MPP=d(VI)/dV (4.1)
 0=I+VdI/dVMPP (4.2)
dI/dVMPP = - I/V (4.3)
The left hand side is the instantaneous conductance of the solar panel. When this instantaneous
conductance equals the conductance of the solar then MPP is reached.
Here we are sensing both the voltage and current simultaneously. Hence the error due to change
in irradiance is eliminated. However the complexity and the cost of implementation increases.
As we go down the list of algorithms the complexity and the cost of implementation goes on
increasing which may be suitable for a highly complicated system. This is the reason that Perturb
and Observe and Incremental Conductance method are the most widely used algorithms.
Owing to its simplicity of implementation we have chosen the Perturb & Observe algorithm for
our study among the two.
Benefits:
 It is able to successfully detect any changes in the irradiation and shift its MPP value by
adjusting the duty cycle.
 It has a good tracking efficiency
 This method reduces oscillation around the MPP point
 It is able to reduce power loss and system cost as well
Drawbacks:
 The computational time is increased due to slowing down of the sampling frequency
resulting from the higher complexity of the algorithm compared to the P&O method.

4.2.3 Fractional open circuit voltage

 The near linear relationship between VMPP and VOC of the PV array, under varying irradiance
and temperature levels, has given rise to the fractional VOC method.
VMPP = k1 Voc (4.4)
where k1 is a constant of proportionality.Since k1 is dependent on the characteristics of the PV
array being used, it usually has to be computed beforehand by empirically determining VMPP
and VOC for the specific PV array at different irradiance and temperature levels. The factor k1
has been reported to be between 0.71 and 0.78. Once k1 is known, VMPP can be computed with
VOC measured periodically by momentarily shutting down the power converter. However, this
incurs some disadvantages, including temporary loss of power.

Benefits of using this method:

 The cost is relatively low.
 It is a much simpler method and easy to implement.
Drawbacks of this method:
 It is not a very accurate method and may not operate exactly at the Maximum Power
Point.
 The open circuit of the solar PV module varies with temperature so the open circuit
voltage needs to be measured continuously for temperature variations.
4.2.4 Fractional short circuit current
Fractional ISC results from the fact that, under varying atmospheric conditions, IMPP is
approximately linearly related to the ISC of the PV array.
IMPP =k2 Isc (4.5)
where k2 is a proportionality constant. Just like in the fractional VOC technique, k2 has to be
determined according to the PV array in use. The constant k2 is generally found to be between
0.78 and 0.92. Measuring ISC during operation is problematic. An additional switch usually has
to be added to the power converter to periodically short the PV array so that ISC can be measured
using a current sensor.
Benefits of using this method:
 It is simple and implementation cost is low.
 No input is required for this method.
Drawbacks of this method:
 In most cases the irradiation is never exactly at the MPP due to variations on the array
that are not considered (it is not always accurate). Data varies under different weather
conditions and locations.
 It has low efficiency. In these two methods we have to choose the right constant k value
carefully, to accurately calibrate the solar panel.
4.2.5 Fuzzy Logic Control
Microcontrollers have made using fuzzy logic control popular for MPPT over last decade. Fuzzy
logic controllers have the advantages of working with imprecise inputs, not needing an accurate
mathematical model, and handling nonlinearity .
4.2.6 Neural Network
Another technique of implementing MPPT which are also well adapted for microcontrollers is
neural networks. Neural networks commonly have three layers: input, hidden, and output layers.
The number nodes in each layer vary and are user-dependent. The input variables can be PV
array parameters like VOC and ISC, atmospheric data like irradiance and temperature, or any
combination of these. The output is usually one or several reference signals like a duty cycle
signal used to drive the power converter to operate at or close to the MPP.
4.3 Perturb & Observe Algorithm
The Perturb & Observe algorithm states that when the operating voltage of the PV panel is
perturbed by a small increment, if the resulting change in power ∆P is positive, then we are going
in the direction of MPP and we keep on perturbing in the same direction. If ∆P is negative, we
are going away from the direction of MPP and the sign of perturbation supplied has to be
changed.
Figure 4.1 shows the plot of module output power versus module voltage for a solar panel at a
given irradiation. The point marked as MPP is the Maximum Power Point, the theoretical
maximum output obtainable from the PV panel. Consider A and B as two operating points. As
shown in the figure above, the point A is on the left hand side of the MPP. Therefore, we can
move towards the MPP by providing a positive perturbation to the voltage. On the other hand,
point B is on the right hand side of the MPP. When we give a positive perturbation, the value of
∆P becomes negative, thus it is imperative to change the direction of perturbation to achieve
MPP. The flowchart for the P&O algorithm is shown in Figure 4.2.
Benefits of using the P&O method:
 The simplicity of its algorithm.
 Ease of implementation.
 It has comparatively less implementation cost.
 It is comparatively a more accurate method.
Limitations to using this method:
 It cannot determine when it has actually reached the MPP. Under steady state operation
the output power oscillates around the MPP.
 This method is quite slow to find the MPP if the voltage is far away from MPP.
 In any case if there is any shadow on any of the panels (as they are in series of parallel)
then the power-voltage curve of the PV will have several peaks and the P&O will not be
able to distinguish them and find the genuine peak.
4.4 Limitations of Perturb & Observe algorithm
In a situation where the irradiance changes rapidly, the MPP also moves on the right hand side of
the curve. The algorithm takes it as a change due to perturbation and in the next iteration it
changes the direction of perturbation and hence goes away from the MPP as shown in the figure.
However, in this algorithm we use only one sensor, that is the voltage sensor, to sense the PV
array voltage and so the cost of implementation is less and hence easy to implement. The time
complexity of this algorithm is very less but on reaching very close to the MPP it doesn’t stop at
the MPP and keeps on perturbing in both the directions. When this happens the algorithm has
reached very close to the MPP and we can set an appropriate error limit or can use a wait
function which ends up increasing the time complexity of the algorithm.
4.5 Implementation of MPPT using a boost converter
The system uses a boost converter to obtain more practical uses out of the solar panel. The
initially low voltage output is stepped up to a higher level using the boost converter, though the
use of the converter does tend to introduce switching losses. The block diagram shown in Figure
4.4 gives an overview of the required implementation.
 7. Conclusion
The model shown in Figure 5.4 was simulated using SIMULINK and MATLAB. The plots
obtained in the different scopes have been shown in Chapter 6.
The simulation was first run with the switch on no MPPT mode, bypassing the MPPT algorithm
block in the circuit. It was seen that when we do not use an MPPT algorithm, the power obtained
at the load side was around 95Watts (Figure 6.5) for a solar irradiation value of 85 Watts per sq.
cm. It must be noted that the PV panel generated around 250 Watts power (Figure 6.2) for this
level of solar irradiation. Therefore, the conversion efficiency came out to be very low.

The simulation was then run with the switch on MPPT mode. This included the MPPT block in
the circuit and the PI controller was fed the Vref as calculated by the P&O algorithm. Under the
same irradiation conditions, the PV panel continued to generate around 250 Watts power (Figure
6.8). In this case, however, the power obtained at the load side was found to be around 215 Watts
(Figure 6.12), thus increasing the conversion efficiency of the photovoltaic system as a whole.

The loss of power from the available 250 Watts generated by the PV panel can be explained by
switching losses in the high frequency PWM switching circuit and the inductive and capacitive
losses in the Boost Converter circuit.

Therefore, it was seen that using the Perturb & Observe MPPT technique increased the
efficiency of the photovoltaic system by approximately 126% from an earlier output power of
around 95 Watts to an obtained output power of around 215 Watts.

APPENDIX A

Acronyms

PV- Photo Voltaic

MPPT- Maximum Power Point Tracking
AC- Alternating Current
DC- Direct Current
P&O method- Perturb and Observe Method
I & C method – Incremental and Conductance Method
LED- Light Emitting Diode
SCR- Silicon Controlled Rectifier
MOSFET- Metal Oxide Field Effect Transistor