09 chapter 1

1
CHAPTER 1
INTRODUCTION
1.1 PREAMBLE
Energy is an essential component for all social activities, which is
required for the manufacture of every goods and provision of all services. The
cost of energy is increasing now-a-days due to the fast depleting of fossil
fuels. Hence, a demand for low cost energy becomes an increasingly
important concern. Due to the demand for low cost energy and the growing
concern about the global warming and the harmful environmental eơects due
to the fossil fuels, such as greenhouse effect, air pollution etc., focus has been
turned towards the alternative energy sources that are cleaner, renewable, and
produce little environmental impact. Among the energy sources coming under
the purview of the alternative energy sources, the direct conversion of
photonic energy into electrical energy through photovoltaic cells shall be
regarded as a natural source of energy that is more vital, due to its abundance,
cleanliness, freely and distributed everywhere over the earth’s surface.
One of the important advantages of the photovoltaic cells is its lack
of carbon-di-oxide emission. It has been reported by de Brito et al (2013) that
by the end of 2030, the annual reduction rate of CO2 emission due to the use
of the photovoltaic cells may be around 2GTons/year, which is equivalent to
India’s total emissions in the year 2004 or the emissions of 300 coal plants.
Moreover it is reported by Tey & Mekhilef (2014), that the electricity
generated by the photovoltaic modules is an unstable energy source because

2
of its strong dependence on factors such as the solar irradiation level and the
atmospheric temperature. The currently accepted limiting conversion
efficiency as reported by Goetzberger et al (2003) for single junction solar
cells is about 31%. But the highest confirmed efficiencies of a Photovoltaic
(PV) cell and a module are reported as approximately 25% and 23%
respectively by Green et al (2012) for the crystalline silicon type. Petreus et al
(2011) have confirmed that the efficiency is also further influenced by the
load connected to the PV system. Hence in order to effectively utilize the
photovoltaic cells, techniques should be used to extract maximum possible
energy from them, at any atmospheric conditions. Therefore, invariably a
Maximum Power Point Tracking (MPPT) controller is needed in order to
ensure that the PV system is working at a higher efficiency.
1.2 THE GENESIS OF THE THESIS
Extraction of power from the PV modules becomes popular and
vital in the recent days as it provides a cheaper source of energy in the
situations wherein the energy from the other conventional sources becomes
costlier. At the same time the energy from the PV sources is environment
friendly too. However, harnessing the power from the PV modules is an
arduous task as the characteristics exhibited by the PV modules are non-linear
in nature. Also the solar irradiation and the atmospheric parameters such as
temperature, wind velocity etc. alter the PV modules characteristics, creating
a situation such that the extraction of the optimal energy from them turn to be
a gruelling task.
As a consequence, extensive researches have been undergoing since
long back to find methods and means to extract maximum possible energy
from the PV modules. Some of the methods, meant for optimal power
extraction, are simple, but inaccurate and less efficient, whereas some other
techniques though having better efficiency and accuracy are complex in

3
nature and may not be cost effective. Hence an intensive exploration and
research have been done with the consideration of developing methods which
should be cost effective, high efficient, accurate and simple in form.
1.3 HARNESSING THE PV ENERGY
The Electrical Energy coming from the PV modules called as PV
energy should be appropriately harnessed in order to improve the efficiency
of extraction. Because when the PV modules are connected directly to the
loads, the efficiency of power extraction from them is poor. Hence in order to
improve the efficiency of extraction, the power output from the PV modules
should be harnessed properly and hence the PV modules which are connected
to the loads are controlled either through a DC-DC converter or through an
inverter depends upon the nature of the load. When the PV modules are
connected through the DC-DC converter or standalone inverter, a single task
is imposed on the converter or the inverter, which is to optimize the power
output from the PV modules, whereas when the PV modules are connected
through the grid connected inverter, then the inverter has two tasks such as to
inject sinusoidal current into the grid and to optimize the power output from
the PV modules (Tsang et al 2013).
The main intension of interposing a power electronic circuit,
between the PV source and the load is to harness them in a well-coordinated
manner at all atmospheric conditions such that maximum possible power can
be extracted from the PV source. Such power electronic circuits, called as the
maximum power point trackers (Eltawil & Zhao 2013), when used to harness
the PV energy, in a properly sized PV system, increases the power output
from the PV sources by a margin of 15% to 30%. The aim of this thesis work
is to develop new methods to harness the PV energy efficiently from the PV
modules.

4
1.4 LITERATURE SURVEY
The technique of Maximum Power Point Tracking (MPPT) for
photovoltaic modules is one among the techniques which was researched in a
greater extent with different heuristic approaches. Ishaque & Salam (2013a)
and Lorente et al (2014) have reported that the MPPT methods vary in
complexity, types of sensors required, convergence speed, cost, range of
eơectiveness, implementation hardware, popularity, and in other respects.
Hence the MPPT techniques for PV modules proposed so far shall be
categorized in different ways according to the perception of the researchers.
Salas et al (2006) have categorized the different techniques of
MPPT in many ways. Of them the most appealing way of categorizing the
MPPT techniques is by two different methods as “indirect or quasi seeking”
and “direct or true seeking”. Also Ishaque & Salam (2013a) have categorized
nicely all the MPPT techniques in a broad way as conventional techniques
and soft computing techniques. In addition Ishaque & Salam (2013a) have
clearly stressed the importance of another category called the hybrid MPPT
due to the availability of the tremendous computing powers in the modern
microprocessors. Further Salam et al (2013) have even provided in a heuristic
way, the various categories of the soft computing methods used in the MPPT
techniques for the PV modules.
Whereas Masoum et al (2007) have categorized the MPPT
techniques proposed so far into four main branches as Load matching,
Computational, Perturb and Observation (P&O) and Intelligent techniques. It
is also reported by Weddell et al (2012) that the most of the methods proposed
to track the MPP are suitable for outdoor applications because those methods
consume large quiescent current and hence consumes more quiescent power
inherently. Hence Weddell et al (2012) have proposed a new method enabling

5
successful maximum power point tracking at indoors. This has further leads to
another kind of classification as indoor and outdoor MPPT techniques.
Recently de Brito et al (2013) have given a picture about the
evaluation study of the various existing MPPT techniques. It is true as stated
by Salam et al (2013) that providing a fair benchmark is very difficult because
different researchers have used dissimilar PV systems having diverse rating,
technology, size etc and even at different atmospheric conditions. In this
scenario the research made by de Brito et al (2013) provides a reasonable
standard to various researchers for comparing the efficiency of the MPPT
technique devised by them with the popular MPPT techniques. Hence the
literature survey pertaining to this research work is classified in terms of
different MPPT techniques which are very popular and presented in the
following sub-headings:
1.4.1 Fractional Open Circuit Voltage (Vfrac) Technique
Castaner & Silvestre (2002), delineates that the I-V behaviour of a
PV module can be appropriately modelled analytically and can be represented
by a characteristic equation as given in Equation (1.1)
exp 1
sse sse
ph OS
sT s sh
V INR V INR
II I nNV N R
½
§·§·
°°
®¾
¨¸¨¸
°°
©¹©¹
¯¿
(1.1)
where ‘I’ is the PV module’s terminal current, ‘Iph’ is the photo-generated
current, ‘Ios’ is the reverse saturation current, ‘V’ is the PV module’s terminal
voltage, ‘VT’ is the volt equivalent to temperature, ‘Ns’ is the number of PV
cells connected in series, ‘Rse’ is the series resistance of the PV cell, ‘Rsh’ is
the shunt resistance of the PV cell and ‘n’ is the diode ideality factor.