A

Project Report
on

“Maximum Power Point Tracking (MPPT) using Boost converter for

Photovoltaic Array."
BACHELOR OF TECHNOLOGY
Electrical Engineering
Submitted by
Omkar Sanjay Chaudhari (2017BTEEL00019)
Sanket Suresh Bhise (2017BTEEL00076)
Ajay Ishwar Patil (2017BTEEL00010)
Under the guidance of
Mr. R. P. HASABE
Department of Electrical Engineering

WALCHAND COLLEGE OF ENGINEERING, SANGLI

AN AUTONOMOUS INSTITUTE
[2019-2020]

1
List Of Tables

Table 2. 1 Electrical Characteristics Data of Green SolarIndia37W (AT-37) PV Module .................... 16

Table 3. 1 Specification for Boost Converter.............................................................................................. 27

Table 4. 1 Characteristics of Different MPPT Technique.......................................................................... 32

2
 List of Figures

Figure 1. 1 MPPT Technique with Solar Cell ............................................................................................. 11

Figure 1. 2 Global Energy Consumption in the Year 2008 ........................................................................ 12

Figure 2. 1 Different Solar Modules ............................................................................................................. 13

Figure 2. 2 Schematic Cross-Section of a Typical Solar Cell ..................................................................... 14
Figure 2. 3 Equivalent Circuit of PV Cell .................................................................................................... 14
Figure 2. 4 Block For Temperature Conversion ......................................................................................... 17
Figure 2. 5 Block Module Photo Current .................................................................................................... 17
Figure 2. 6 Block For Reverse Saturation Current .................................................................................... 18
Figure 2. 7 Block for Output Current .......................................................................................................... 19
Figure 2. 8 Interconnection of All Blocks .................................................................................................... 20
Figure 2. 9 Complete Block of PV Module .................................................................................................. 20
Figure 2. 10 Detailed circuit model of PV module. ..................................................................................... 21
Figure 2. 11 PV Interfacing to Load............................................................................................................. 21
Figure 2. 12 Output Power of PV Module At Rload > Rmpp ......................................................................... 22
Figure 2. 13Output Power of PV Module at RLOAD < RMPP ........................................................................ 23
Figure 2. 14 Output Power of PV Module at RLOAD = RMPP ....................................................................... 23

Figure 3. 1 Circuit Diagram of a Boost Converter ..................................................................................... 25

Figure 3. 2 Mode 1 Operation of the Boost Converter ............................................................................... 25
Figure 3. 3 Mode 2 Operation of the Boost Converter ............................................................................... 25
Figure 3. 4 Modelling of Boost DC-DC Converter...................................................................................... 26

Figure 4. 1 Graph of Power VS Voltage for IC Algorithm ........................................................................ 33

Figure 4. 2 Flowchart Of Incremental Conductance Algorithm ............................................................... 34
Figure 4. 3 Complete Model of PV Panel With MPPT ............................................................................... 36

Figure 5. 1 P-V Characteristic of Solar Panel ............................................................................................. 37

Figure 5. 2 I-V Characteristic of Solar Cell ................................................................................................. 37
Figure 5. 3 Change in Irradiation ................................................................................................................. 38
Figure 5. 4 Output Power of 213W PV Module With Change In Irradiation ......................................... 39
Figure 5. 5 Efficiency ..................................................................................................................................... 40

3
 INDEX

Sr.No. Content Page

No.
1. CHAPTER 1- Introduction 5
2. CHAPTER 2- Modelling of PV Panel 13
3. CHAPTER 3- Boost Converter 24
4. CHAPTER 4- MPPT Algorithm 29
5. CHAPTER 5- Results 37
6. CHAPTER 6- Conclusion 41

4
 CHAPTER 1
INTRODUCTION
It's certainly clear that fossil fuels are mangling the climate and that the status quo is
unsustainable. There is now a broad scientific consensus that the world needs to reduce
greenhouse gas emissions more than 25 percent by 2020 -- and more than 80 percent by
2050. The idea of harnessing the sun’s power has been around for ages. The basic process
is simple. Solar collectors concentrate the sunlight that falls on them and convert it to
energy. Solar power is a feasible way to supplement power in cities. In rural areas, where
the cost of running power lines increases.
Solar power, a clean renewable resource with zero emission, has got tremendous potential
of energy which can be harnessed using a variety of devices. With recent developments,
solar energy systems are easily available for industrial and domestic use with the added
advantage of minimum maintenance. Solar energy could be made financially viable with
government tax incentives and rebates. An exclusive solar generation system of capacity
250KWh per month would cost around Rs. 20 lakhs, with present pricing and taxes (2013).
Most of the developed countries are switching over to solar energy as one of the prime
renewable energy source.

5
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) 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.

6
1.2 DIFFERENT SOURCES OF RENEWABLE ENERGY

1.2.1 WIND POWER

Wind turbines can be used to harness the energy available in airflows. Current day turbines
range from around 600 kW to 5 MW 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 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.

1.2.3 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.

1.2.4 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.

7
1.2.5 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.
As the Photovoltaic module exhibits non-linear V-I Characteristics, which are dependent
on solar Insolation and environment factors, the development of an accurate power
electronic circuit-oriented model is essential to simulate and design the photovoltaic
integrated system. In this paper, the design of PV system using simple circuit model with
detailed circuit modelling of PV module using MATLAB/Simulink and the physical
equations governing the PV module is presented.

8
1.3 LITERATURE REVIEW
Studies show that a solar panel converts 21-40% 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 trade-off between
complexity and efficiency.
It is seen that to get maximum efficiency we are getting which type of converter. We are
choosing here boost converter because it provide us more voltage at output then

input. We can also choose buck-boost converter but due to our simplification and
requirement we are selecting boost converter. It is very simple to implement and has
high efficiency both under stationary and time varying atmospheric conditions.

N. Pandiarajan and Ranganath Muth, This paper presents a unique step-by-step

procedure for the simulation of photovoltaic modules with Matlab/ Simulink. One- diode
equivalent circuit is employed in order to investigate I-V and P-V characteristics of a
typical 36 W solar module. The proposed model is designed with a user-friendly icons and
a dialog box like Simulink block libraries [1].

Alpesh P. parekh, Bhavarty N. Vaidya and Chirag T. Patel, In this paper, the design of
PV system using simple circuit model with detailed circuit modelling of PV module is
presented. In this paper, Equivalent circuit of the PV module & Simulink model for each
equation has presented and complete circuit oriented9model has also presented [2].
Pandiarajan N, Ramaprabha R and Ranganath Muthu, Circuit model of photovoltaic
(PV) module is presented in this paper that can be used as a common platform for the
material scientists as well as power electronic circuit designers to develop the better PV
power plant. Detailed modeling procedure for the circuit model with numerical dimensions
is presented using power system block set of MATLAB/ Simulink. The developed model
is integrated with DC-DC boost converter with closed loop control of maximum power
point tracking (MPPT) algorithm. The simulation results are validated with the
experimental set up [3].

P.Sathya, Dr.R.Natarajan, this paper presents the design and implementation of high
performance closed loop Boost converter for solar powered HBLED lighting system. The
proposed system consists of solar photovoltaic module, a closed loop boost converter and
LED lighting module. The closed loop boost converter is used to convert a low level dc
input voltage from solar PV module to a high level dc voltage required for the load. To
regulate the output of the converter, closed loop voltage feedback technique is used. The
feedback voltage is compared with a reference voltage and a control signal is generated
and amplified. The amplified signal is fed to 555 Timer which in turn generates a PWM
signal which controls the switching of MOSFET. Thus by switching of MOSFET it would
try to keep output as constant. Initially the boost converter, timer circuit, amplifier circuit
and LED light circuits are designed, simulated and finally implemented in printed circuit
board. The simulation studies are carried out in MULTISIM. The experimental results for
solar PV and boost converter obtained in both software and hardware was presented in this
paper.

G. Venkateswarlu and Dr.P.Sangameswar Raju, The study of photovoltaic systems in

an efficient manner requires a precise knowledge of the IV and PV characteristic curves of
photovoltaic modules. A Simulation model for simulation of a single solar cell and two
solar cells in series has been developed using Sim electronics (Mat lab /Simulink)
environment and is presented here in this paper. A solar cell block is available in
simelectronics, which was used with many other blocks to plot I- V and P-V characteristics
under variations of parameters considering one parameter variation at a time. Effect of two
environmental parameters of temperature and irradiance variations could also be observed
from simulated characteristics [4].

10
1.4 OBJECTIVE

The basic objective would be to study MPPT and successfully implement the MPPT
algorithms either in code form as well as using the Simulink/Simscape model. Modelling
of the solar cell in Simulink/Simscape and interfacing both with the MPPT algorithm to
obtain the maximum power point operation would be of prime importance.

Figure 1. 1 MPPT Technique with Solar Cell

1.5 FUTURE SCOPE OF RENEWABLE ENERGY RESOURCES

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.
Renewables accounted for 60% of the newly installed power capacity in Europe in 2009
and nearly 20% of the annual power production.

11
 Figure 1. 2 Global Energy Consumption in the Year 2008

1.6 THESIS OUTLINE

This thesis has been broadly divided into 7 chapters. The first one being the introduction,
chapter 2 is on photovoltaic effect and modelling of solar cell with Matlab
Simulink/Simscape and effect of load mismatching. In chapter 3 we will study about Boost
Converter. Chapter 4 is on maximum power point tracking and study of the various
algorithms.. Result and conclusion is discussed in chapter 5 & 6.

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 CHAPTER 2
MODELLING OF PV PANEL

2.1 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.
However a photovoltaic cell is different from a photodiode. In a photodiode light falls on
n-channel of the semiconductor junction and gets converted into current or voltage signal
but a photovoltaic cell is always forward biased.

2.2 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.

2.3 PV ARRAY
A PV array consists of several photovoltaic cells in series and parallel connections. Series
connections are responsible for increasing the voltage of the module whereas the parallel
connection is responsible for increasing the current in the array.

Figure 2. 1 Different Solar Modules

13
2.4 PV MODELLING
Typically a solar cell can be modelled by a current source and an inverted diode connected
in parallel to it. It has its own series and parallel resistance. Series resistance is due to
hindrance in the path of flow of electrons from n to p junction and parallel resistance is due
to the leakage current.
When irradiance hits the surface of solar PV cell, an electrical field is generated inside the
cell. As seen in Fig.3 this process separates positive and negative charge carriers in an
absorbing material (joining p-type and n-type). In the presence of an electric field, these
charges can produce a current that can be used in an external circuit. This generated current
depends on the intensity of the incident radiation. The higher the level of light intensity,
the more electrons can be unleashed from the surface, the more current is generated.

Figure 2. 2 Schematic Cross-Section of a Typical Solar Cell

The most important component that affects the accuracy of the simulation is the PV cell
model. Modelling of PV cell involves the estimation of the I-V and P-V characteristics
curves to emulate the real cell under various environmental conditions. An ideal solar cell
is modelled by a current source in parallel with a diode. However no solar cell is ideal and
thereby shunt and series resistances are added to the model as shown in the Fig.4

Figure 2. 3 Equivalent Circuit of PV Cell

14
The current source Ipv represents the cell photo current, Rsh and Rs are used to represent the
intrinsic series and shunt resistance of the cell respectively. Usually the value of Rsh is very
large and that of Rs is very small, hence they may be neglected to simplify the analysis.
The PV mathematical model used to simplify our PV array is represented by the) equations

Module Photo Current

λ
Iph=[Iscr+Ki(T-298)]×
1000

Module Reverse Saturation Current

𝐼𝑠𝑐𝑟
Irs= 𝑞𝑉𝑜𝑐
exp( )−1
𝑁𝑠𝑘𝐴𝑡

The Current Output of PV module is

Where
Vpv is output voltage of a PV module (V) Ipv
is output current of a PV module (A) Tr is
the reference temperature = 298 K
T is the module operating temperature in Kelvin
Iph is the light generated current in a PV module (A) Io
is the PV module saturation current (A)
A = B is an ideality factor = 1.6
k is Boltzmann constant = 1.3805 × 10-23 J/K q
is Electron charge = 1.6 × 10-19 C
Rs is the series resistance of a PV module
ISCr is the PV module short-circuit current at 25 oC and
1000W/m2 = 2.55A
Ki is the short-circuit current temperature co-efficient at
ISCr = 0.0017A / oC
λ is the PV module illumination (W/m2) = 1000W/m2

15
Ego is the band gap for silicon = 1.1 Ev
Ns is the number of cells connected in series Np is
the number of cells connected in parallel

Table 2. 1 Electrical Characteristics Data of Green SolarIndia37W (AT-37) PV Module

Electrical Characteristics
Maximum power - Pmax
36.917 W

Voltage at Pmax - Vmp

17.905 V
Current at Pmax - Imp
2.062 A
Short-circuit current - Isc
2.226 A
Open-circuit voltage - Voc
21.425 V

Total number of cells in series (Ns) 36

Total number of cells in parallel (Np) 1

2.5 MATLAB SIMULINK MODEL OF PHOTOVOLTAIC CELL

(A) Temperature Conversion (°C to °F)
Trk=273+25(ref.temp.)
Tak=273+Top(operating Temp.)

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 Figure 2. 4 Block For Temperature Conversion

(B) Module Photo Current

Figure 2. 5 Block Module Photo Current

17
(C) Module Reverse Saturation Current

𝐼𝑠𝑐𝑟
Irs= 𝑞𝑉𝑜𝑐
exp( )−1
𝑁𝑠𝑘𝐴𝑡

Figure 2. 6 Block For Reverse Saturation Current

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(D) The Output Current of PV module

Figure 2. 7 Block for Output Current

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 Figure 2. 8 Interconnection of All Blocks

Figure 2. 9 Complete Block of PV Module

Now we have to add a current controlled source which is connected with Ipv of panel. The
series and parallel resistances are also connected to make this model practicle.Fig.2.12
show the complete model.

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 Figure 2. 10 Detailed circuit model of PV module.

2.6 EFFECT OF LOAD MISMATCHING

From PV module P-V characteristics we have seen there is only one point where power is
maximum, the corresponding voltage is VMPP and current is IMPP. If load line crosses this
point the maximum power is transferred to load. This value of load resistance is given by:

Figure 2. 11 PV Interfacing to Load

A PV cell behaves differently depending on the size/type of load connected to it. The output
power of PV panel is greatly depended upon the load at output side. The delivered power
cannot be maximum if there is load mismatching. Load mismatching is a difference
between the internal resistance of source and load at output side.
According to maximum power transfer theorem, when the equivalent resistance of source
is equal to the load resistance, the maximum power will delivered. The

21
equivalent resistance is called characteristics impedance which can be easily find out from
the data sheet given by manufacturer. If load is equal to this characteristic impedance, then
we will get maximum power from the solar panel. We can calculate characteristic
impedance from VMPP and IMPP values given in data sheet. For present case RMPP is 7.9Ω.
Here we take three conditions.

Case (1): When Load resistance is more than characteristic impedance in Fig.15. The
output power is 19.83Watt which is less than its rated maximum power 36 Watt (at
1000W/m2).
Case (2): When Load resistance is less than characteristic impedance in Fig.16 The output
power is 32 Watt which is less than its rated maximum power 36 Watt (at 1000W/m2).
Case (3): When Load resistance is equal to characteristics impedance in Fig.17. The output
power is about 36 Watt which is maximum at 1000 W/m2.

Figure 2. 12 Output Power of PV Module At Rload > Rmpp

22
 Figure 2. 13Output Power of PV Module at RLOAD < RMPP

Figure 2. 14 Output Power of PV Module at RLOAD = RMPP

Figure 2.14, 2.15 & 2.16 shows the effect on efficiency of PV module due to different load
applied by user. The PV module power reduces if the load is not properly match with the
characteristics resistance of the PV module. This problem can be solved by applying DC-
DC converter in between PV module & Load.

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 CHAPTER 3
BOOST CONVERTER
A boost converter is designed to step up a fluctuating or variable input voltage to a constant
output voltage of 24 volts with input range of 6-23volts in. To produce a constant output
voltage feedback loop is used. The output voltage is compared with a reference voltage and
a PWM wave is generated, here Spartan 6 FPGA kit is used to generate PWM signal to
control switching action.

A DC to DC converter is used to step up from 12V to 24V. The 12V input voltage is from
the battery storage equipment and the 24V output voltage serves as the input of the inverter
in solar electric system. In designing process, the switching frequency, f is set at 20 kHz
and the duty cycle, D is 50%.

Here we want to introduced an approach to design a boost converter for photovoltaic (PV)
system using microcontroller. The converter is designed to step up solar panel voltage to a
stable 24V output without storage elements such as battery. It is controlled by a FPGA unit
using voltage-feedback technique. The output of the boost converter is tracked, measured
continuously and the values are sent to the microcontroller unit to produce pulse-width-
modulation (PWM) signal. The PWM signal is used to control the duty cycle of the boost
converter. Typical application of this boost converter is to provide DC power supply for
inverter either for grid- connected or standalone system. Simulation and experimental
results describe the performance of the proposed design. Spartan 6 FPGA is used to perform
tasks in the proposed design.

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 Vat the output end, so we use a boost converter.

24
 Figure 3. 1 Circuit Diagram of a Boost Converter

3.1. 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 g of the capacitor.

Figure 3. 2 Mode 1 Operation of the Boost Converter

3.2. 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 waveform for a boost
converter are shown in figure.

Figure 3. 3 Mode 2 Operation of the Boost Converter

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3.3. MODELING OF BOOST CONVERTER USING MATLAB
SIMSACPE

Figure 3. 4 Modelling of Boost DC-DC Converter

3.4. DESIGN APPROACH OF PROPOSED BOOST CONVERTER

Load Requirement: The load is a simple 4 x 4 LED panel and each row containing 4 LED
in a line would require a current of 10- 15 mA and thus total of 60 mA to all four branches
and thus having a resistance of 570Ω. As each LED gives a drop of 2.1 volts to become
forward biased, so a minimum of 8.4 volts is required to glow 4 LED in series, for this a
voltage of 24 V is required to be supplied to LEDs. Thus the load requirement is 570 Ω
with 42 mA of total current thus required voltage was 24 V. Since a potential divider is
used whose total resistance is 1100Ω so total equivalent resistance is Req = (1100) ││
(570) = 375Ω.Based on this load requirement the other parameters would be calculated and
the specifications are tabulated in the following table.

26
 Table 3. 1 Specification for Boost Converter

S.No. Component Value

1 Inductor 290µH
2 MOSFET 1N5408 IRF 840
3 Power Diode IN5408
4 Input Capacitor 470µF
5 Output Capacitor 330 µF
6 Resistive Load 50Ω, 50W

Duty Cycle:
The duty cycle can be found using the following relation-

Inductor value:
The value of inductor is determined using the following relation

Lmin=D (1-D2)*R/2*Fs

An inductor is practically designed using the following parameters and is shown in the
figure 22.
Formula for inductor design, L = (d2n2) / (l + 0.45d)
Required dimensions of inductor
Coil length, l= 8.1 cm
Diameter, d= 6.3 cm
Inductance value required, L= 151 μH
Number of turns, n=64
Where L is inductance in micro Henrys, d
is coil diameter in meters,
l is coil length in meters, and n
is number of turns

Capacitor value:
The value of capacitor is determined from the following equation
C=D/Fs*R*Vr
Where
C is the minimum value of capacitance,

27
D is duty cycle,
R is output resistance,
Fs is switching frequency, and
Vr is output voltage ripple factor.

28
 CHAPTER 4
MAXIMUM POWER POINT TRACKING ALGORITHM

4.1. AN OVERVIEW OF MAXIMUM POWER POINT TRACKING

A typical solar panel converts only 30 to 40 percent of the incident solar irradiation into
electrical energy. Maximum power point tracking technique is used to improve the
efficiency of the solar panel.

According to Maximum Power Transfer theorem, the power output of a circuit is

maximum when the Thevenin impedance of the circuit (source impedance) matches with
the load impedance. Hence our problem of tracking the maximum power point reduces to
an impedance matching problem.

In the source side we are using a boost convertor connected to a solar pan el in order to
enhance the output voltage so that it can be used for different applications like motor
load. By changing the duty cycle of the boost converter appropriately we can match the
source impedance with that of the load impedance.

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

29
4.3 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.

4.4. 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

0=I+VdI/dVMPP

dI/dVMPP = - I/V

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.

30
4.5. 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

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.

4.6. 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

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.

4.7. 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.

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 4.8. 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.

Table 4. 1 Characteristics of Different MPPT Technique

4.9. DETAILS OF INCREMENTAL CONDUCTANCE ALGORITHM

The disadvantage of the perturb and observe method to track the peak power under fast varying atmospheric
condition is overcome by IC method. The IC can determine that the MPPT has reached the MPP and stop
perturbing the operating point. If this condition is not met, the direction in which the MPPT operating point
must be perturbed can be calculated using the relationship between dl/dV and –I/V. This relationship is
derived from the fact that dP/dV is negative when the MPPT is to the right of the MPP and positive when it
is to the left of the MPP. This algorithm has advantages over P&O in that it can determine when the MPPT
has reached the MPP, where P&O oscillates around the MPP. Also, incremental conductance can track
rapidly increasing and decreasing irradiance conditions with higher accuracy than P and O

32
 Figure 4. 1 Graph of Power VS Voltage for IC Algorithm

Fig- shows that the slope of the P-V array power curve is zero at The MPP, increasing on the left of the MPP
and decreasing on the Right hand side of the MPP. The basic equations of this method are as follows:

This method exploits the assumption of the ratio of change in output conductance is equal to the negative
output Conductance Instantaneous conductance.
We have, P = V I
Applying the chain rule for the derivative of products yields to
∂P/∂V = [∂(VI)]/ ∂V At MPP, as ∂P/∂V=0
The above equation could be written in terms of array voltage V and array current I as ∂I/∂V = - I/V The
MPPT regulates the PWM control signal of the dc – to – dc boost converter until the condition: (∂I/∂V) +
(I/V) = 0 is satisfied. In this method the peak power of the module lies at above 98% of its incremental
conductance. The Flow chart of incremental conductance MPPT is shown below.

33
 Figure 4. 2 Flowchart Of Incremental Conductance Algorithm

Program for Incremental Conductance Algorithm:

function duty = MPPT_algorithm(vpv,ipv,delta)

duty_init = 0.1;
% min and max value are used to limit duty between
% 0 and 0.85
duty_min=0;
duty_max=0.85;

persistent Vold Pold duty_old;

% persistent variable type can be store the data
% we need the old data by obtain difference
% between old and new value
if isempty(Vold)
Vold=0;
Pold=0;
duty_old=duty_init;
end
P= vpv*ipv; % power 34
dV= vpv - Vold; % difference between old and new voltage
dP= P - Pold;% difference between old and new power

% the algorithm in below search the dP/dV=0

% if the derivative equal to zero
% duty will not change
% if old and new power not equal
% &
% pv voltage bigger than 30V
% the algorithm will works
if dP ~= 0 && vpv>30
if dP < 0
if dV < 0
duty = duty_old - delta;
else
duty = duty_old + delta;
end
else
if dV < 0
duty = duty_old + delta;
else
duty = duty_old - delta;
end
end
else
duty = duty_old;
end

%the below if limits the duty between min and max

if duty >= duty_max
duty=duty_max;
elseif duty<duty_min
duty=duty_min;
end

% stored data
duty_old=duty;
Vold=vpv;
Pold=P;

35
4.10. COMPLETE MODEL OF PV PANEL WITH MPPT

Figure 4. 3 Complete Model of PV Panel With MPPT

36
 CHAPTER 6

RESULT

SIMULATION RESULT FOR 213 WATT SOLAR PANEL ARRAY

Figure 5. 1 P-V Characteristic of Solar Panel

Figure 5. 2 I-V Characteristic of Solar Cell

37
With Varying Irradiation

Figure 5. 3 Change in Irradiation

38
 Output Power Curve:

Figure 5. 4 Output Power of 213W PV Module With Change In Irradiation

39
Efficiency:

Figure 5. 5 Efficiency of the Energy

extracted from solar PV Array

40
 CHAPTER 6

CONCLUSION

The model shown in above Figure was simulated using SIMULINK and MATLAB. The
plots obtained in the different scopes have been shown in Chapter 5. The simulation was
run with the switch on MPPT mode and the MPPT algorithm block in the circuit.
Therefore, the conversion efficiency came out to be very high. This included the MPPT
block in the circuit and this was calculated by the Incremental Conductance algorithm.. The
loss of power from the available wattage 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 Incremental Conductance MPPT technique increased
the efficiency of the photovoltaic system.

41
 REFERNCES
[1] N. Pandiarajan and Ranganath Muth” Mathematical Modeling of Photovoltaic Module
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[2] Alpesh P. Parekh, Bhavarty N. Vaidya and Chirag T. Patel”Modeling and Simulation
Based Approach of Photovoltaic System” in Global Research Analysis Volume 2 Issue 4
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[3] Pandiarajan N, Ramaprabha R and Ranganath Muthu” Application Of Circuit Model

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[4] G. Venkateswarlu and Dr.P.Sangameswar Raju” Simscape Model Of Photovoltaic

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[5] Vandana Khanna, Bijoy Kishore Das, Dinesh Bisht

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[D]http://en.wikipedia.org/wiki/Copper_indium_selenide

[E]Nielsen, R. 2005, 'Solar Radiation', http://home.iprimus.com.au/nielsens/.

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[E]http://express.howstuffworks.com/gif/solar-power-diagram.jpg

[F]http://science.howstuffworks.com/solar-cell1.htm

[G]http://www.pvresources.com/en/module.php

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[I] http://www.autospectator.com/cars/files/images/Photovoltaic-Cell.jpg

[J] http://en.wikipedia.org/wiki/Photovoltaic_array

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