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DESIGN AND DEVELOPMENT OF HYBRID RENEWABLE ENERGY SYSTEM
GROUP MEMBERS
Umar Ashraf 08-HITEC-EE-179
Saroosh Baig 08-HITEC-EE-155
S.M. Mudassar 08-HITEC-EE-168
PROJECT ADVISOR
(Mr. Masood Arain)
Assistant Professor, Department of Electrical
Engineering, HITEC University Taxila Cantt.
CO-ADVISOR
(Engr. Bilal Assad)
Lecturer, Department of Electrical Engineering,
HITEC University Taxila Cantt.
Department of Electrical Engineering HITEC University Taxila Cantt, Pakistan
September, 2012
Department of Electrical Engineering HITEC University Taxila Cantt, Pakistan
The project “Design and Development of Hybrid Renewable Energy System”
presented by:
1. Umar Ashraf 08-HITEC-EE-179
2. Saroosh Baig 08-HITEC-EE-155
3. S.M. Mudassar 08-HITEC-EE-168
Under the supervision of their project advisor and approved by the project
examination committee, has been accepted by the HITEC University Taxila Cantt,
Pakistan, in partial fulfillment of the requirements for the four year degree of B.S
(Electrical Engineering).
____________________ ____________________ (Mr.Masood Arain) (Engr. Bilal Assad) Asst. Professor Lecturer Advisor Co-Advisor
____________________ (Dr. Jameel Ahmed) Professor Head, Dept. of Electrical Engineering HITEC University
DEDICATION
“We would like to dedicate our work to our parents. Whatever we are and whatever we have achieved is all due to their constant support and affection.
We would also like to dedicate this project to our teachers who have guided us and
helped us in our educational endeavors.”
Acknowledgements
Praise be to Allah Almighty, the creator of the heavens and the earth. We are
thankful for His countless blessings on us, for giving us the strength and courage
to complete our project in time and without His benevolence we would not had
been able to complete this task. All respects for the Prophet Muhammad (PBUH),
whose teachings are the true source of knowledge and guidance for whole of the
humanity.
We express our deep gratitude for our project advisor Mr. Masood Ahmed Arain,
Assistant Professor in the Department of Electrical Engineering, HITEC
University Taxila, for his support, inspiring guidance, worthy discussions and
encouragement that had enable us to complete this project.
We are thankful to the HOD Dr.Jameel Ahmed for taking various steps in order to
facilitate the students with their projects. We are also thankful to our faculty
especially Dr. Fawad Ahmed, Sir Bilal Assad, Sir Kashif Imdad and Sir Adeel
for their technical guidance regarding the fundamental aspects of this project. We
appreciate their valuable help.
We would also like to thank the Lab attendants Mr. Sohail, Mr. Adnan, and Mr.
Alamgir and the others who had cooperated with us in the project lab.
TABLE OF CONTENTS
CONTENTS PAGE
Certificate I
Dedication II
Acknowledgements III
Abstract VI
PART 1: INTRODUCTION
CHAPTER 1: Introduction to hybrid energy 2
1.1 Background 2
1.2 Renewable energy 3
1.3 Hybrid Renewable Energy System (HRES) 3
1.4 International standards for storing energy 7
CHAPTER 2: Theory related to the project 8
2.1 Basic structure of the hybrid systems 8
2.2 Major Modules 9
2.2.1 Sources 9
2.2.2 Switching Mode DC Regulators 9
2.2.3 Voltage controller 12
2.2.4 Rechargeable battery bank 12
2.2.5 Inverters 12
2.2.6 Protection systems 13
2.3 Power Inverters 13
2.3.1 Main types 13
2.3.2 Inverter topologies 14
2.3.3 Major components of an inverter 15
2.3.3.1 Microcontroller 15
2.3.3.2 Bipolar junction transistors (BJTs) 15
2.3.3.3 H-Bridge 17
2.3.3.4 Filters 20
2.3.3.5 Transformer 21
2.4 Pulse Width Modulation (PWM) 22
2.4.1 Advantages 23
2.4.2 Basic Principle 23
2.4.3 Application 24
2.4.4 Problems associated with improper use of PWM 25
2.4.5 Pulse Width Modulation techniques 25
2.5 Protection System 26
PART 2: DESIGN AND IMPLEMENTATION 27
CHAPTER 3: Buck Regulator Module 28
3.1 Overview 28
3.2 Pulse Width Modulation circuit 28
3.2.1 Working 28
3.2.2 Observations 29
3.3 Buck Circuit 30
3.4 Calculations for Buck Converter 31
CHAPTER 4: Charge control Module 34
4.1 Working 34
4.2 Calculations 35
CHAPTER 5: Inverter module 37
5.1 Overview 37
5.2 Design and Development of Pure Sine Wave Inverter 37
5.2.1 Modules of Pure Sine-Wave Inverter 38
5.2.2 AVR Micro-Controller Unit 38
5.2.2.1 Advantages of AVR 38
5.2.2.2 Technical specifications 39
5.2.2.3 Code and Explanation for PWM in AVR 39
5.2.3 H-Bridge Circuit 43
5.2.3.1 Working of H-Bridge 44
5.2.3.2 Results 46
5.3.3.3 Observations 46
5.3.3.4 Problems 46
5.3.4 LC Filter 47
5.3.4.1 Working 47
5.3.4.2 Problems 48
5.3.5 Working of Sine Wave Inverter 48
5.4 Design and Development of Modified Sine Wave Inverter 49
5.4.1 Explanation 50
5.4.2 Working 51
5.4.3 Results 51
5.4.4 Problems 51
5.5 Transformer Design 52
5.6.1 Calculations 52
5.6.3 Problems Faced 53
5.7 Results 54
CHAPTER 6: Automatic Temperature Controller 55
6.1 Main Components Used 55
6.2 Block Diagram 57
6.3 Circuit Diagram 57
6.4 Working 57
6.5 Calculations 58
CHAPTER 7: Conclusion and Scope 62
Future recommendations 63
CHAPTER 8: References 64
CHAPTER 9: Appendix 65
LIST OF FIGURES
CONTENTS PAGE
FIGURE 1.1 Hybrid system topology 4
FIGURE 1.2 A wind solar hybrid 5
FIGURE 1.3 Output comparisons of wind and solar systems 6
FIGURE 2.1 Block diagram of Hybrid Systems 8
FIGURE 2.2 Basic configuration of a Boost converter 10
FIGURE 2.3 Basic configuration of a Buck converter 10
FIGURE 2.4 Basic circuit configuration of a Buck-Boost converter 11
FIGURE 2.5 Basic circuit configuration of a Cuk-converter 11
FIGURE 2.6 BJT symbols 15
FIGURE 2.7 NPN and PNP transistors 16
FIGURE 2.8 H-Bridge working 18
FIGURE 2.9 MOSFET Types and symbols 18
FIGURE 2.10 Ideal Transformer 21
FIGURE 2.11 Varying Duty Cycles 23
FIGURE 2.12 PWM Generation 24
FIGURE 2.13 Sinusoidal PWM 26
FIGURE 3.1 PWM circuit. 29
FIGURE 3.2 PWM output . 30
FIGURE 3.3 Buck circuit 31
FIGURE 3.4 Buck output 31
FIGURE 4.1 Switching Circuit module 35
FIGURE 4.2 Relay switch 35
FIGURE 5.1 Block diagram of pure sine wave inverter 38
FIGURE 5.2 H-Bridge Circuit 44
FIGURE 5.3 H-Bridge Conduction Modes 45
FIGURE 5.4 Wave-forms of H-bridge conduction cycle 46
FIGURE 5.5 LC Filter 47
FIGURE 5.6 Modified Sine wave circuit 49
FIGURE 5.7 Practical delay circuit 49
FIGURE 5.8 Block diagram of modified sine wave inverter 50
FIGURE 5.9 Delayed Inverted output 51
FIGURE 5.10 Proteus Circuit of pure sine wave inverter 54
FIGURE 5.11 Simulated Output of Pure-Sine wave inverter 54
FIGURE 6.1 Block diagram of Fan control circuit 57
FIGURE 6.2 Temperature based fan controller 57
FIGURE 6.3 Complete Circuit Layout of the Project 61
DESIGN AND DEVELOPMENT OF HYBRID
RENEWABLE ENERGY SYSTEM
ABSTRACT: The report describes the theory and the steps for the Design and development of a
“Hybrid Renewable Energy System” (HRES). With depleting oil and gas reserves
globally, Hybrid Energy Systems are the future of green energy. Today in Pakistan,
as we all know the country is facing serious energy crises and the situation is
getting worse day by day. Pakistan is one of the most feasible countries for
renewable energy implementation as its potential for producing energy (solar,
wind) is great thanks to its geographical location. Thus keeping it in view of the
various problems and opportunities, our project demonstrates a practical
implementation of simple home based Hybrid Power generation system which will
give an efficient energy output.
Our Hybrid Energy System comprises of two independent energy producing
sources which charge a battery in a way that when output of one source drops as
compared to the other source, the other source starts charging the battery.
It involves different various modules. To control the output of the solar panel, the
voltage is stepped down by the means of a Buck converter. The converter adjusts
the voltage levels as per requirements automatically to charge the battery.
A Hybrid switching circuit is designed for the comparison of voltage levels of the
sources and switching between them for better charging efficiency.
To convert the DC battery output (12Vdc) into AC output (220Vac). A Sinusoidal
Pulse Width Modulation (SPWM) is generated by means of AVR microcontroller.
The results were verified both on software and hardware. The H-bridge is designed
to operate at high frequency input (i.e. 15 KHz). The output is finally filtered, by
means of a LC filter, before being supplied to the load. The output is finally verified
by using an Oscilloscope.
A temperature control module is designed so that the temperature of the
components is maintained low. Whenever temperature rises above 33 degrees
Celsius, the temperature sensor senses it and turns on the fan automatically.
When the temperature falls from 33 degree Celsius, the fan is turned off likewise.
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PART 1
BASIC INTRODUCTION
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CHAPTER 1:
INTRODUCTION TO HYBRID RENEWABLE
ENERGY
1.1 Background
“Necessity is the mother of inventions”.
Many centuries ago to fulfill his needs, man invented ways to harness energy from
the environment. In doing so he invented fire, then with the passage of time the
human demands kept on increasing, so did the dependency of mankind on energy
producing materials such as wood and other natural fissile material. With the
passage of time, man stumbled upon the wonder of electricity, which opened the
gates of prosperity and advancement to the human race. This also increased the
dependency of the humans on fossil fuels such as coal, gas, diesel, petrol etc.
In nature, two types of energy resources exist, Renewable energy resources and
the non-renewable energy resources. Since the beginning humans had been
dependent on the non-renewable energy resources and with the passage of time,
the consumption of natural fuel resources to produce electric energy has increased
so much that the natural reservoirs have started to deplete and it is estimated that
within a century or so, these resources will run scarce.
We are living in the era of mass industrialization, where every single thing is
energy dependent. Foreseeing the havoc of not shifting the sole dependency of
human race on non-renewable sources at this moment and keeping in view the
ever increasing and the never ending demand of energy, the experts have started
to shift their needs from non-renewable energy resources to the renewable energy
resources. They have innovated new ideas and ways to harness the natural
energy, which is abundantly available, free of cost and eco-friendly.
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Thus the concept of renewable energy is quickly making its place in the market,
and a time will come in the near future that the dependency of humans on the fossil
fuels will become exceptionally low.
1.2 Renewable energy
Renewable energy is the energy which can be used again and again without the
fear of it getting depleted. Renewable energy resources are the free source of
unlimited energy. Sun, wind, water etc. are the main sources of renewable energy
from which energy is harnessed by using conversion systems know as renewable
energy systems.
There are various types of renewable energy conversion systems for example
solar energy system, Wind energy system, tidal energy system geothermal system
and hybrid systems. Some of these are discussed briefly in subsequent topics.
1.3 Hybrid renewable energy systems.
Hybrid energy systems also known as Hybrid renewable energy system (HRES) is
the latest innovation in the field of technology. It consists of at least two or more
renewable energy resources used together to provide increased system efficiency
as well as greater balance in energy supply. This idea is penetrating rapidly not
only at commercial level but also on household level. This innovation is becoming
very popular for fulfilling remote area energy requirements due to the subsequent
rise in petroleum product prices and non-availability of grid energy in some areas.
In Pakistan,about 64%(according to internet resources) of the net power produced
depends on fossil fuels. Energy production by fossil fuels is not a cost efficient
method of energy production, and with the depleting resources, the experts have a
big question in front of them… what then if the resources deplete sooner or later!
Will the sole solar energy systems or wind energy systems be adequate enough or
efficient enough to maintain the uninterrupted supply of energy?
There is a single answer to these questions which is a „no‟, and yes we have a
solution too which is „Hybrid energy‟.
Mechanism of Hybrid Systems.
As pointed out earlier, a HRES consists of at least two or more renewable energy
resources used together to provide increased system efficiency as well as greater
balance in energy supply.This system facilitates when one system fails to work or
fails to give an appropriate output, it is automatically switched to the second
system if it is providing an acceptable output. In this way multiple sources of
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energy can be attached on preference level that which system should start work
after the failure of first system.
FIGURE 1.1 (Hybrid system topology)
Types of Hybrid Systems.
Depending on the potential of renewable energy available in a particular
geographic region, different types of hybrid systems can be used. These can be
Wind-solar hybrids, Solar-fuel hybrids, Wind-fuel hybrids or any of these sources
combined with the grid.
In some areas wind blows at certain level which is suitable for hybrid like
solar+wind. In hot regions hybrid of solar+fuel is quite effective, thus solar energy
can be put in preference. In case of bad weather or during night hours it can be
switched to fuel system/generator. Also if a hybrid of solar+generator is created it
will be a good source of energy in daylight consuming sunlight directly and using
the generator at night with solar conserving power.
Below is a figure of a practical wind solar hybrid system.
Page | 5
FIGURE 1.2 (A wind solar hybrid)
Reservations and backup of a HRES:
Where the hybrid renewable energy is profitable, there are certain issues to put it in
to function. Talking about the wind solar hybrid, obviously, solar panels do not
provide power during the night, but that‟s when the wind usually picks up and
conversely, on the longest, hottest days of summer, the wind often does not blow,
but the sun is at its strongest which is great for solar power. The wind is more likely
to blow at night or during the cold, short days of winter when the sun is at its
weakest. But what to do when neither of them are working? What about the energy
storage? This situation can be avoided by tying the system to the grid, by using a
battery bank or a backup generator.
Adding a second and a third power supply to a system adds both cost and
complexity to a somewhat already complex system, but special electric controllers
are designed to integrate all three (the DC power from the solar array, the AC/DC
or three-phase AC from the wind turbine, and the power from the backup). The
power controller integrates the wind, solar and backup system providing power to
the user, and sends additional power to a battery bank or the grid, giving the user a
reliable, stable source of energy.
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Figure below is an example ofenergy output of solar and wind systems on a
month‟s average.
FIGURE 1.3 (output comparison of wind and solar systems)
Advantages and disadvantages of Hybrid Systems.
Like every system, hybrid energy systems have their pros and cons. With pros
being more than the cons, hybrid systems are very successful. Some of the
advantages and disadvantages are given below.
a) Advantages
Hybrid renewable energy is versatile and has many useful features some of which
are described below.
1. The resources HRES use are renewable thus they are in abundance thus is
long lasting.
2. There is no pollution or waste material from the system.
3. Wind, tidal and solar sources produce energy which is freely available.
4. It requires a very low maintenance and can last 20-30 years depending on the
type of system, as the complex systems with moving parts require more repairs
and maintenance.
5. It is cheap source of energy as hybrid is built among sustainable and renewable
energies.
6. Hybrid Renewable Energy is a clean and safe source of energy.
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b) Disadvantages
Hybrid systems have some drawbacks too for example,
1. The energy sources have their own separate set up so they need proper place
to arrange them without making them an obstacle at home or in the industry.
2. Hybrid renewable technology is dependent on the region, environment and
capacity. It is not possible to utilize same type of renewable technology
everywhere. Some areas are hot some are cold and are only suitable for
specific energy systems. So, it is preferred to attach fossil fuel energy system
with either solar, water or wind renewable energies.
1.4 International standards for the storage of energy.
According to the international standards a battery bank being used with the system
should be designed in such a way that it is able to store 3 days‟ worth of energy
keeping in view the daily energy requirement.
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CHAPTER 2
PROJECT THEORY
2.1 Basic structure and working of the Hybrid Systems
Basic structure of hybrid systems is composed of multiple energy sources which
give their output in the form of DC (as in solar energy systems) or in AC/DC (as in
Wind turbines). The output of both the systems is converted into appropriate DC
level required to charge the battery by the help of converters and regulators. The
output of both sources is then compared by a control circuit, which disconnects the
system with low output and provides charge to the battery or a battery bank. The
output from the battery/ battery bank is fed into the inverter which converts and
steps it up into 220 Volts AC.
Following figure shows the block diagram of a basic hybrid energy system.
FIGURE 2.1 (block diagram of Hybrid Systems)
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2.2 Major Modules
Major modules of a hybrid energy system are the sources, converter module,
voltage control/ charge control module, inverter module, protection systems
module etc. these modules are discussed in the subsequent topics.
2.2.1 Sources
Solar energy
Solar power is the conversion of sunlight into electricity either directly using photo-
voltaic (PV), or indirectly using Concentrated Solar Power (CSP). A photovoltaic
cell is a device that converts light into electric current using the photo-electric
effect.
CSP systems use lenses or mirrors and tracking systems to focus a large area of
sunlight into a small beam.
Wind energy
Wind is a renewable energy source as it can be used again and again without the
fear of it becoming scarce. As the quality of wind to exist in abundance without
depletion along with its usage as a source implies no possible threat to nature,
makes it desirable to use wind as an source of energy.
In wind energy systems, the wind pressure forces the rotor to rotate. The rotor has
magnets attached to it which on rotating induces changing magnetic flux in the
stator,thus becoming an electricity generator.
Bio gas
Bio gas provides a clean and easily controlled source of renewable energy from
Organic waste materials. Small scale Bio gas units are simple to build and operate.
In bio gas systems, the organic waste materials are processed. This processing of
the material produces ethane which then can be used as fuel.
2.2.2 Switching Mode DC Regulators
DC converters can be used as switching mode DC regulators to convert an
unregulated DC voltage (depending upon the output of the source); in to regulated
DC output voltage. This voltage regulation is achieved by PWM at a fixed
frequency and the switching device is normally a BJT, a MOSFET or an IGBT.
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DC regulators are of four types.
Boost Regulator
In boost converter/regulator, the output voltage is greater than the input voltage;
hence the name of “Boost” is given to it. Its operation is divided into two modes;
mode 1 begins when the switching device is turned ON and Mode two begins
when it is turned OFF. The basic configuration of a Boost converter is given
below.
FIGURE 2.2 (Basic configuration of a Boost converter)
Buck Regulator
In buck converter/regulator, the average output voltage is less than the input
voltage hence the name “Buck” is given to it. This is like a step down converter.
Its operation can be divided into two modes. Mode1 begins when the switching
device is switched ON and mode 2 begins when it is switched OFF. The basic
configuration of a Buck converter is given below.
FIGURE 2.3 (Basic configuration of a Buck converter)
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Buck-Boost Regulator
A buck-boost converter/regulator provides an output voltage that may be less
than or greater than the input voltage hence the name “buck-boost” is given to
it. In this the output polarity is opposite to that of the input voltage. This
regulator is also known as an inverting regulator. Basic circuit configuration of a
buck-boost is given below.
FIGURE 2.4 (Basic circuit configuration of a Buck-Boost converter)
CükRegulator
A Cük Regulator is quite similar to the Buck-Boost regulator. The only
difference between the two is that the Cük Regulator has much lower ripple
current in fact, by carefully adjusting the inductor values, the ripple in either
input or output can be nulled completely.
The basic circuit configuration of Cük Regulator is given below.
FIGURE 2.5 (Basic circuit configuration of a Cuk-converter)
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2.2.3 Voltage controller
A voltage/ charge controller acts as a comparator and compares the output voltage
levels of two systems. It switches the higher value output to the battery bank or a
battery for charging. When the output of the initial source drops as compared to the
other source, the charge controller connects the other source with the batteries.
2.2.4 Rechargeable battery bank
Collection of batteries joined in series form a battery bank. A battery bank allows
greater energy storage. The battery plays a very important part in Hybrid
energy.The basic two types of batteries that can be used are as under,
I. Dry batteries
The most common application of this kind of battery is in low power equipment like
computer supplies etc. The most common type of battery is simply Nickel metal
hydride battery. A lot of work is being done on some other kind of batteries like
lithium-polymer, lithium-ion batteries, and nickel-cadmium batteries. Dry batteries
are a bit expensive but are maintenance free.
II. Wet batteries
The most commonly used batteries are the wet batteries also known to us as lead-
acid batteries. These are widely used because of their availability in different
Voltages and Ampere-hours configurations.
2.2.5 Inverters
Inverters convert DC into AC. In an inverter, we can achieve output of desired
magnitude and frequency. A variable output voltage can be obtained by varying the
input DC voltage and maintaining the gain of inverter constant. On the other hand if
the DC input voltage is fixed and it is not controllable, a variable output voltage can
be obtained by varying the gain of the inverter, which is normally accomplished by
PWM or pulse width modulation control within the inverter. The inverter gain may
be defined as ratio of the AC output voltage to DC input voltage.
The details about inverters and inverter topologies are given in the article below
(refer article 2.3).
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2.2.6 Protection systems
Protection systems are systems which ensure the safe, proper and efficient
operation of a system. In hybrid systems, high power electronic components are
being used (like in the inverter); high switching rate and high power of the power
electronic components heat up very much. If this situation is not checked, so much
heat can damage the component or at least make the components inefficient. To
cool things down, temperature controllers are used. These sense the temperature
and automatically turn on the cooling fans.
For over voltage protection we have used a LM 358 comparator which compares
battery voltage with 12V reference voltages from an externally defined source.
Whenever battery voltages exceed 12V, the circuit turns off.
2.3 Power Inverters
An Inverter is an integral part of any renewable system as the DC from the battery
bank is to be converted into AC and then stepped up to 220 volts (mainly) for the
consumers. There are various types of an inverter
2.3.1 Main types
There are many types of inverters e.g. sine-wave inverters, square wave inverters,
Modified sine wave inverters, multi-level inverters, and resonant inverters (etc.).
The main three of which are discussed below,
Modified sine-wave inverters
The output of a modified square wave, quasi square, or modified sine wave
inverter is similar to a square wave output except that the output goes to zero volts
for a time before switching positive or negative. It is simple, low cost and is
compatible with most electronic devices, except for sensitive or specialized
equipment, for example certain laser printers, fluorescent lighting, and audio
equipment.
Most AC motors can run on this power source but with reduction in efficiency of
approximately 20%.
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Sine-wave inverters
A pure sine wave inverter produces a nearly perfect sine wave output, which is
essentially the same as utility-supplied grid power. Thus it is compatible with all AC
electronic devices. This is the type used in grid-tied inverters. Its design is more
complex, and costs more per unit power.
Square wave inverters
The square wave output has a high harmonic content, not suitable for certain AC
loads such as motors or transformers. Square wave units were the pioneers of
inverter development.
2.3.2Inverter topologies.
There are many different power circuit topologies and control strategies used in
inverter designs. Different design topologies address various issues that may be
more or less important depending on the way that the inverter is intended to be
used.
Inverters normally use H-bridge configuration. However, the voltage level at which,
the H-bridge is operated can be varied.
The normal inverters convert the DC into AC at 12 Volts. After this inversion, this
12Volt AC is stepped up into 220 Volts AC by the means of a transformer.
The advantage of such an approach is that the bridge construction is easy, as it is
not exposed to high voltages. The disadvantages accompanying such an approach
are
The transformer steps up the harmonic content.
The size and weight of the transformer increases considerably, as the
capacity of inverter is increased.
To overcome such problems, we can use a topology of converting DC into AC at
the output voltage of the inverter. At firstboosting the battery voltages by the means
of a DC-DC converter and then giving these voltages toa specially designed H-
bridge. This arrangement can overcome the previously mentioned
disadvantages.The main disadvantage of such an approach is that the bridge
circuit becomes too complex.
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That‟s why we have chosen to work with the first topology as filtering the output
greatly reduces the harmonics.
2.3.3 Major components of an inverter
An inverter‟s design and components vary with requirements as discussed earlier.
Our inverter has following major components.
2.3.3.1 Microcontroller
Microcontroller is an integral part of an inverter. It controls the switching of signals
according to set requirements. A single microcontroller can perform multiple
functions (e.g.) generating PWM for switching, controlling the protection systems
etc. there are various types and families of microcontrollers available in the market
(e.g.) PIC family, AVRs (ATMEGA series) etc. Depending on the design
specifications, any microcontroller can be used.
2.3.3.2 Bipolar junction transistors (BJTs)
BJT or a bipolar junction transistor is a three layered device which is capable of
controlling the current flow. In a BJT, a small current at the input of the device can
control larger currents at the output. Thus, BJTs can amplify currents. BJTs have
many applications. They can be used as a relay driver, as a switch, as a constant
current source, as an amplifier (etc.).
Circuit symbol
Circuit symbol of a BJT is given in figure 2.3.1
FIGURE 2.6 (BJT symbols)
Types
There are two types of transistors, NPN and PNP transistors.
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i. NPN transistor
NPN is one of the two types of bipolar transistors, in which the letters "N" and "P"
refer to the majority charge carriers inside the different regions of the transistor.
Most BJTs used today are NPN transistors because electron mobility is higher than
the hole mobility allowing greater currents and faster operation.
NPN transistors consist of a layer of P-doped semiconductor (the "base") between
two N-doped layers. A small current entering the base in common-emitter mode is
amplified in the collector output. In other terms, an NPN transistor is "on" when its
base is pulled high relative to the emitter.
The arrow in the NPN transistor symbol is on the emitter leg and points in the
direction of the conventional current flow when the device is in forward active
mode.
ii. PNP transistor
PNP transistors consist of a layer of N-doped semiconductor between two layers of
P-doped material. A small current leaving the base in common-emitter mode is
amplified in the collector output. In other terms, a PNP transistor is "on" when its
base is pulled low relative to the emitter.
The arrow in the PNP transistor symbol is on the emitter leg and points in the
direction of the conventional current flow when the device is in forward active
mode.
Figure 2.2 shows both NPN and PNP transistors.
FIGURE 2.7(NPN and PNP transistors)
Page | 17
Working
The collector–emitter current can be viewed as being controlled by the base–
emitter current (current control), or by the base–emitter voltage (voltage control).
These views are related by the current–voltage relation of the base–emitter
junction, which is just the usual exponential current–voltage curve of a p-n junction
(diode).
The physical explanation for collector current is the amount of minority-carrier
charge in the base region. The charge-control view easily handles photo-
transistors, where minority carriers in the base region are created by the absorption
of photons, and handles the dynamics of turn-off, or recovery time, which depends
on charge in the base region recombining. However, since base charge is not a
signal that is visible at the terminals, the current- and voltage-control views are
usually used in circuit design and analysis.
2.3.3.3 H-Bridge
H –bridge is a topology in which four switching devices BJTs, MOSFETs or IGBTs
are integrated together in a single circuit. The name H-Bridge is given to it because
of the typical arrangement of this circuit.
Mainly used switching devices in the H-bridge circuits are BJTs, MOSFETs or
IGBTs.
Working
In an H-bridge, corresponding to the figure below when the switches S1 and S4 are
closed, the switches S2 and S3 are open. Thus a positive voltage issupplied
across the motor or any other load attached to it instead of motor (e-g) transformer.
When S1 and S4 switches are opened, and S2 and S3 switches are closed, the
voltage is reversed, supplying negative voltages to the load.
A problem with this is that the switches S1 and S2 should never be closed at the
same time, as this causes a short circuit on the input voltage source. The same
thing applies on the switches S3 and S4. This condition is generally known as the
shoot-through condition.
Following figure describes the above phenomena.
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FIGURE 2.8 (H-Bridge working)
MOSFETs
The Metal-Oxide-Semiconductor-Field-Effect-Transistor (MOSFET) is a voltage
controlled device and requires a very small input current. It is mainly used for
switching of electronic signals as its switching speed is very high. It is the most
commonlyused FET in low-power high-frequency circuits.
The MOSFET is composed of a channel of n-type or p-type semiconductor
material, and is accordingly called an N-MOSFET or a P-MOSFET
Circuit symbol
Circuit symbols of MOSFET are shown in the figure below
FIGURE 2.9(MOSFET Types and symbols)
Page | 19
Types
There are two main types of MOSFETs. The Depletion-type MOSFET (D-
MOSFET) and the Enhancement-type MOSFET (E-MOSFET)
i) Depletion-MOSFET
D- MOSFETs are the devices that are doped in a way that a channel exists even
with zero voltage from gate to source. To control the channel, a negative voltage is
applied to the gate (for n-channel), depleting the channel, which reduces the
current flow through the device. So, the depletion mode device is equivalent to a
normally closed switch (on), while the enhancement mode device is equivalent to a
normally open switch (off).
Due to their low noise figure in the Radio Frequency (RF) region and better gain,
these devices are often preferred to bi-polar devices in RF front-ends such as in
TV sets.
ii) Enhancement-MOSFETs
In these MOSFETs, a voltage drop across the oxide induces a conducting channel
between the source and drain contacts via the field effect. The term "enhancement
mode" refers to the increase of conductivity with increase in oxide field that adds
carriers to the channel, also referred to as the inversion layer. The channel can
contain electrons (N-MOSFET) or holes (P-MOSFET), opposite in type to the
substrate, so N-MOS is made with a p-type substrate and P-MOS with an n-type
substrate. In the less common depletion mode MOSFET, described further later
on, the channel consists of carriers in a surface impurity layer of opposite type to
the substrate, and conductivity is decreased by application of a field that depletes
carriers from this surface layer.
Which is the better option for H-bridge? BJTs, MOSFETs or IGBTs?
A BJT is current control device. It requires continuous base current, which causes
loading on the microcontroller(that is giving gating signals). Therefore, this option is
not feasible.
MOSFETs are suitable switching elements for an inverter. They are much faster
switches than IGBTs and in many low power cases they are less expensive than
the IGBTs.
Page | 20
2.3.3.4 Filters
At times it is desirable to have circuits capable of selectively filtering one frequency
or range of frequencies out of a mix of different frequencies in a circuit. A circuit
designed to perform this frequency selection is called a filter circuit.
A practical application of filter circuits is in the conditioning of non-sinusoidal
voltage waveforms in power circuits. Some electronic devices are sensitive to the
presence of harmonics in the power supply voltage, and so require power
conditioning for proper operation. A distorted sine-wave voltage behaves like a
series of harmonic waveforms added to the fundamental frequency; we can
construct a filter circuit that only allows the fundamental waveform frequency to
pass through, blocking all (higher-frequency) harmonics.
Low-Pass Filters
A low-pass filter is a circuit offering easy passage to low-frequency signals and
difficult passage to high-frequency signals. There are two basic kinds of circuits
capable of accomplishing this objective, and many variations of each one:
Inductive Low-Pass Filters
The inductor‟s impedance increases with the increase in frequency. This high
impedance in series tends to block high-frequency signals from getting to the load.
The inductive low pass filter is very simple, with only one component comprising
the filter. This filter is preferred in AC-DC power supplies to filter out AC ripple
waveform.
Capacitive low pass filter (RC filter)
The capacitor's impedance decreases with increasing frequency. This low
impedance in parallel with the load resistance tends to sort out high-frequency
signals, dropping most of the voltage across series resistor R. One frequent
application of the capacitive low-pass filter principle is in the design of circuits
having components or sections sensitive to electricalnoise.
LC Filter
An LC filter is a low-pass filter which consists of an inductor attached in parallel
with the capacitor and the load.L and C connected together act asan electrical
resonator.
Page | 21
LC Filter over RC Filter
RC filters have R thus they dissipate power. They have attenuation even in the
pass band. To achieve a narrow transition band, RC circuits have to be of higher
orders. Only certain types of filters can be implemented by an RC filter.
Whereas, LC filter does not dissipate power. Better characteristics can be achieved
by the LC filter than RC with a lower order. Thus it is desirable to choose an LC
over an RC in the case of an inverter.
2.3.3.5 Transformer
A transformer is a device that transfers electrical energy from one circuit to another
through inductively coupled electrical conductors.Transformers are some of the
most efficient electrical 'machines', with some large units able to transfer 99.75% of
their input power to their output. Transformers come in a range of sizes from a
thumbnail-sized coupling transformer hidden inside a stage microphone to huge
units weighing hundreds of tons used to interconnect portions of national power
grids. All operate with the same basic principles, although the range of designs is
wide.
FIGURE 2.10(Ideal transformer)
Working
A changing electric flux in the primary of the transformer creates a changing
magnetic field which induces a changing voltage in the secondary. By adding load,
one can transfer energy from one part to another.
Page | 22
The secondary voltage Vs of an ideal transformer is scaled from the primary
voltage Vpby a factor equal to the ratio of the number of turns of wire in their
respective windings.
By appropriate selection of the numbers of turns, a transformer thus allows an
alternating voltage to be stepped up by making Ns more than Np or stepped down,
by making it less.
If the secondary coil is attached to a load that allows current to flow, electrical
power is transmitted from the primary circuit to the secondary circuit.
Ideally,
Pin = Pout
Or
IpVp= IsVs
Where,
Pin = Input Power.
Pout = Output Power.
Ip = Primary Current.
Vp = Primary Voltage.
Is = Primary Current.
Ip = Primary Voltage
2.4 Pulse Width Modulation (PWM)
Pulse-width modulation control works by rapidly switching the power supplied,
between on and off positions. The DC voltage is converted to a square-wave
signal, alternating between fully on and zero, in such a technique. By adjusting the
duty cycle of the signal (modulating the width of the pulse, hence the 'PWM') i.e.
the time fraction it is "on", the average power can be varied. The duty cycle of a
waveform is defined as
Duty Cycle = (time on) / (total time period)
Page | 23
FIGURE2.11(Varying Duty Cycles).
2.4.1 Advantages
There are many advantages of using PWM as
PWM is less exposed to the noise due to its digital nature.
Less power is wasted as heat and smaller heat-sinks can be used.
The power delivered can effectively be controlled by means of controlling
PWM.
The PWM can be used to effectively control the speed of motors.
2.4.2 Basic Principle
The classical technique for producing a PWM is to compare a saw tooth waveform
with a reference waveform (as shown in figure). It should be noted here that higher
the frequency of the saw tooth waveform, higher will be the frequency of generated
PWM.
Normally, an oscillator is used to generate a triangle or saw tooth waveform. As the
frequency of PWM depends upon the frequency of the saw tooth waveform so, the
saw tooth of the required frequency is generated.
A potentiometer is used to set a steady reference voltage. A comparator compares
the saw tooth voltage with the reference voltage. When the saw tooth voltage rises
above the reference voltage, a power transistor is switched on, and when the saw
Page | 24
tooth voltage falls below the reference, it is switched off. This gives a square wave
output, which may have a constant or a variable duty cycle, depending upon the
nature of reference voltage. E.g. If the reference voltage is DC then the square
wave will have a constant duty cycle, whereas in case of sinusoidal reference
voltage, the square wave will have a varied duty cycle.
If the potentiometer is adjusted to give a high reference voltage, and the saw tooth
never reaches it, the output shall be zero. On the other hand, a low reference
voltage implies that the comparator is always on, hence giving full power, all the
time.
FIGURE 2.12(PWM generation)
2.4.3 Application
Voltage regulation
PWM is used in efficient voltage regulators. By switching voltage to the load with
the appropriate duty cycle, the output will approximate a voltage at the desired
level. The switching noise is usually filtered with a filter.
In another method the output voltage is measured, continuously. When it is lower
than the desired voltage, the switch is turned on & when the output voltage is
above the desired voltage, the switch is turned off.
Power delivery
PWM can be used to reduce the total amount of power delivered to a load without
losses normally incurred when a power source is limited by resistive means. This is
because the average power delivered is proportional to the modulation duty cycle.
With a sufficiently high modulation rate, passive electronic filters can be used to
smooth the pulse train and recover an average analog waveform.
Page | 25
High frequency PWM power control systems are easily realizable with
semiconductor switches. The discrete on/off states of the modulation are used to
control the state of the switch which correspondingly controls the voltage across or
current through the load. The major advantage of this system is that the switches
are either off and not conducting any current, or on and have no voltage drop
across them. The product of the current and the voltage at any given time defines
the power dissipated by the switch, thus no power is dissipated by the switch.
Realistically, semiconductor switches such as MOSFETs or BJTs are non-ideal
switches, but high efficiency controllers can still be built.
2.4.4 Problems associated with improper use of PWM
There are many problems that occur when we use PWM improperly, some of
which are
Output has low power.
Output voltage & frequency fluctuates from the required output wave.
The output wave shape varies undesirably, under the load.
The components are heated and power dissipation is large
The Harmonics are added into the output Waveform.
The Spikes and transients may occur.
Time varying characteristics in the output.
Back currents, lags and sags due to inductive load
2.4.5 Pulse Width Modulation techniques
There are many techniques by which Pulse Width Modulation can be made. Some
of the common techniques are mentioned below.
Single Pulse Width Modulation
In such a modulation, the PWM is generated by comparing a DC level and a Single
Triangular Wave; hence a rectangular pulse is acquired. It provides a reasonable
efficiency
Multiple Pulse Width Modulation
It is generated by comparing a DC level and MultipleTriangular Waves. We get
many rectangular pulses. It is improved version of the single level PWM, the order
of harmonics is same as of single-pulse modulation, and distortion factor is
reduced however due to larger switching of transistors in this, switching losses
increase.
Page | 26
Sinusoidal Pulse Width Modulation
It is generated by comparing a Reference Sine Wave with relatively high frequency
Triangular wave. It is better than above methods but has low fundamental
harmonic and the more switching a cycle increases the losses and the power is
lost in heating.
FIGURE 2.13(Sinusoidal PWM)
2.5PROTECTION SYSTEM
Temperature controller
A temperature controller basically senses the temperature value, and if the
temperature increases beyond a particular set point, it turns on the cooling system
(e.g.) cooling fan to maintain the temperature and when the temperature goes
below that set point, the cooling systems turn off.
Over voltage protection
Over voltage protection system, protects the system from over voltage.
Whenever system voltage increased from certain level it shut down the
system to avoid system damage.
Page | 27
PART 2
DESIGN AND IMPLEMENTATION
Page | 28
CHAPTER 3
BUCK REGULATOR MODULE
3.1. Overview
One of the biggest problems of renewable energy systems is the voltage
regulation. As the atmospheric conditions keep on changing, so does the output
voltage of these atmospheric dependent sources. To maintain a particular DC
output, DC regulators are used to regulate these unregulated voltages. DC
regulators not only regulate the voltages but also step-up or step-down the voltage
levels according to requirements.
In the case of our project, we have an 80 Watt Solar panel which gives output
voltages of 21.2 Volts in no load condition and about 17 Volts in load condition. We
are using this panel to charge a battery of 12V, 65Ah. Thus we have stepped down
these 17 volts into 12 volts by implementing a buck converter module, which not
only steps down the voltages but also steps up the current.
The buck converter module is divided into the following two parts
1) Pulse Width Modulation circuit.
2) Buck circuit.
These circuits are described in detail in the subsequent articles.
3.2. Pulse Width Modulation circuit
The working of the PWM circuit is described below.
3.2.1 Working
Signal comes from pin 3 of 555 (50% duty cycle)output of pin 6 which is common
with pin 2 generates a triangular waveform. The RC filter connected to the pin6 of
Page | 29
the IC controls the Ƭ of the square wave signal coming from pin 3. The square
wave is compared with the triangle wave to generate PWM. The transistor Q1
connected in common-emitter biased configuration to amplify the signal. This
signal is given to the buck circuit.
Circuit diagram of the PWM circuit is given below
FIGURE 3.1 (PWM circuit)
3.2.2 Observations
The thing we observed in this circuit is that we can change the PWM duty cycle by
varying the variable resistor RV1 and achieve a PWM of desired duty cycle. If the
duty cycle is increased the charging also increases as the system is on for more
time. Likewise if the PWM is decreased, the charging decreases.
The output waveform obtained by this circuit is shown in the figure below
Page | 30
FIGURE 3.2 (PWM output)
3.3. Buck Circuit
The PWM from the circuit is given to the input of both p and n-channel MOSFETs
simultaneously. In the buck converter, n-channel MOSFET works as a diode while
p-channel works as a switching device. The inductor is used for removing the
ripples of current which is controlled by switching frequency. The C stabilizes the
required voltages at the output, which is controlled by Pulse width of the given
input at the gates.
The MOSFETs turn on alternatively. Here p-channel MOSFET works on a 0V
topology which means it turns on at zero-volt and the n-channel MOSFET turns on
at high voltage signal. The p-channel topology is set by connecting the drain of the
MOSFET to the ground and its source at the given input.
The circuit diagram is shown below,
Page | 31
FIGURE 3.3(Buck circuit)
FIGURE 3.4 (Buck output)
3.4. Calculations for Buck Converter
Calculations of buck circuit are shown as under,
Vs = 9V
Vo = Va= 13V
L=270 µH
Page | 32
RBATTERY =10 mΩ
F=8 KHz
T1= K.T
So, K=
T2= (1-K).T
For output voltages
Va=
= K.Vs
K=
) =
)
K= 0.69………….. (i)
T2= 1-0.69 = 0.31sec, T1= 0 sec
Pulse Width=K= T2-T1= 0.31-0= 0.31
K= 31%
ΔI=
=
ΔI= 2A……………. (ii)
ΔVc=
∫ (
)
ΔVC= ⁄ = 31.25 mV…………….. (iii)
Now, for efficiency,
ŋ = POutput/ PInput
Vin=17 V
Iin= 4A
Vo=13V
Iomax=4.5A
Page | 33
POutput= 58.5 watt
PInput =68 watt
Ŋ= 86.01%
Page | 34
CHAPTER 4
SYSTEM SWITCHING MODULE
The switching module is an important module of the Hybrid energy system. It works
automatically and controls charging, inverting, switching and the comparing of
different voltages with thepre-defined reference voltages by using LM357 and a
relay. The working of the module is detailed in the following topic.
4.1 Working
Solar and wind energy systems areonly available when they are producing 12V at
their respective outputs. When in any source, the generated voltages are 12V, they
start charging the battery. Voltages are compared by using LM358 as a comparator
on which 6V are given through battery as a reference using voltage divider circuit.
At the negative input of IC, solar or wind generated voltages are given and
compared with the reference voltages. If the voltages exceed from 6V on the
negative input, the charging turns on. This is the case for both sources. If voltages
drop down from 6V, than charging automatically stops.
We also used a comparator to compare the voltages of the battery with 12V
external supply, if the voltages in the battery drop from 9V, the charging starts and
it automatically stop when the battery is fully charged.
External supply has been used to activate the relay either to use the system as
backup (UPS). When the utility electric supply is available, the relay turns on the
charging system and when the mains are off (utility electricity is not available), the
relay automatically switches to normally closed position and connects to the
inverter.
Given below is the circuit diagram of the relay module
Page | 35
FIGURE 4.1 (Switching Circuit module)
FIGURE 4.2(Relay switch)
To operate all relays, BC547 is used in common-emitter configuration to switch
them for different logics.Respective calculations of the transistor are given below.
4.2 Calculations
Relay Coil Resistance=Rc= 400Ω
Current through relay= 30mA
β=313
RL1G2R-14-DC12B1
12V
SW1
SW-SPDT
D1LED-BIGY
R1 22K
Q1BC547
Using Relay as a Switch
Page | 36
Ic=BIb Ic=Ie
Ib=30x10-3/313
Ib=96x10-6A…………. (i)
Rb=12-30x10-3x400)- 0.7/96x10-6
Rb=22kohm ………… (ii)
Page | 37
CHAPTER 5
INVERTER MODULE
5.1 Overview
To convert the DC voltage into AC, inverters are used. A converted signal of any
desired voltage or frequency can be achieved by using appropriate transformers
and switching devices. The Alternating DC power (coming from the Bridge circuit)
is connected to a transformer through the center tap of the primary winding. This
alternation of the direction of current in the primary winding of the transformer
produces AC in the secondary.
There are many types of inverters as discussed in the chapter 2 of this report.
Three of which are mainly used in house hold UPS systems. The square wave,
Modified-sine wave, and the Pure-sine wave inverter.
Originally we planned to use a pure-sine wave inverter with our Hybrid system. We
worked on it but we weren‟t quite successful in achieving the desired output of
220V, then we worked on modified sine wave inverter in which we successfully
achieved the desired output. Thus, we have worked on both the sine wave and the
modified sine wave inverter. In this project and the details of both of these types
are given in the subsequent topics.
5.2 Design and Development of Pure Sine Wave Inverter
Pure sine wave inverter gives a sine wave as an output. It provides an output
which is quite the same as the natural sine-wave. As the electrical and electronic
equipment are designed in such a way that they efficiently work on a sine-signal,
thus any other type of signal be it square of modified sine reduces the performance
and the life of the equipment.
The modules of our sine wave explained in the subsequent topics.
Page | 38
5.2.1 Modules of Pure Sine-Wave Inverter
Our sine wave inverter consist of a microcontroller unit which generates a
switching signal of 15 KHz, an H-bridge circuit to convert the signal into AC, a low
pass LC filter circuit to block the high frequency components and the transformer
unit to step-up the voltages.
Block diagram of our sine wave circuit is given below
FIGURE 5.1 (Block diagram of pure sine wave inverter)
5.2.2 AVR Micro-Controller Unit
Microcontroller unit is a multi-purpose control unit which can handle multiple tasks
simultaneously. We have used it just to generate a switching signal of 15 KHz. We
have used AVR micro-controller unit in our inverter.AVR microcontroller is a
modern type of microcontroller and is better than the PIC micro-controller in many
ways.
5.2.2.1 Advantages of AVR
Some benefits of AVR are given below:
Cost: At the moment, the very lowest-price microcontroller available from
any manufacturer. Atmel AVR ATtiny11 6 MHz FLASH.
Speed: Not only are most AVRs capable of 20MHz. the PIC chips are at a
higher price (for example, PIC16F88) only run at 5 MHz with a 20 MHz
oscillator frequency. In addition, with the better addressing modes and
registers of the AVRs, most operation can be done in only one instruction,
where it often takes more than one instruction to do the same thing on a
PIC.
Peripherals: Many Atmel AVR micro controllers, like many Microchip PIC
micro controllers, have a built-in 10 bit ADC. Some have LCD or USB
drivers.
Fast PWM: AVR has a fast PWM port unlike PIC microcontroller.
Page | 39
5.2.2.2 Technical specifications
The high-performance, low-power Atmel 8-bit AVR RISC-based microcontroller
combines 16KB of programmable flash memory, 1KB SRAM, 512B EEPROM, an
8-channel 10-bit A/D converter, and a JTAG interface for on-chip debugging. The
device supports throughput of 16 MIPS at 16 MHz and operates between 4.5-5.5
volts.
By executing instructions in a single clock cycle, the device achieves throughputs
approaching 1 MIPS per MHz, balancing power consumption and processing
speed.
5.2.2.3 Code and Explanation for PWM in AVR
Explanation:
Below is the program for atmega16 microcontroller with a clock frequency of 8 MHz
(Fcpu = 8MHz). We have worked on a compiler named AVR GCC.
Initially we included AVR libraries,then we initialized sine table in which the
values of a complete sine wave are stored (we generated a sin table in
range 0-359 degrees whereas, zero of sine wave is set at decimal 128(0x80
in Hex).
Then in the next chunk of the code, we used timer0 (8-bit) which starts from
0 and peaks to 255 (it gives a saw tooth output).
The constant float step = (2*180)/256 = 1.40625
For i=0;
s = sin (0*1.40625) = 0
For i = 255
s = sin (255*1.40625) = 358.5937 = 359deg approx.
This is how the sine wave is generated from 0-359deg. When timer reaches 255
then interrupt over flow is generated (Refer the sine wave code, at the end).
The next part of the code shows that we have used the clock select bits as
pre-scalar.
TIMSK| = (1<<TOIE0) means we are enabling timer overflow interrupt enable 0.
Page | 40
3 2
1
8 4
U1
:A
LM
358
N
5 6
7
8 4
U1
:B
LM
358
N
B1
12V
AM
FM
+ -
B3
12V
AM
FM
+ -
C1
22
00u
C2
22
00u
Q1
IRF
52
10
Q2
IRF
52
10
Q3
IRF
32
05
Q4
IRF
32
05
L1 80
0u
L2 80
0uT
R1
TR
AN
-2P
2S
L3 80V
C3
10u
A B C D
The last part of the code is the most important part of pure sine wave
generator.
OCR0 is output compare register for timer 0 and it continuously compares timer0
values i.e. 0, 1, 2.......255, and for each value of timer the value from sine wave
table is computed then sample++increases the pointer of sine wave table to the
next i.e. the value at the second index of sine table and that is computed for the
output until samples equals to 255. Then we used the command sample = 0the
cycle is repeated again and again.
CODE:
#include <stdlib.h>
#include <avr/io.h>
#include <util/delay.h>
#include <avr/interrupt.h>
#include <avr/sleep.h>
#include <math.h>
#include <stdio.h>
0x80, 0x83, 0x86, 0x89, 0x8C, 0x90, 0x93, 0x96,
0x99, 0x9C, 0x9F, 0xA2, 0xA5, 0xA8, 0xAB, 0xAE,
0xB1, 0xB3, 0xB6, 0xB9, 0xBC, 0xBF, 0xC1, 0xC4,
0xC7, 0xC9, 0xCC, 0xCE, 0xD1, 0xD3, 0xD5, 0xD8,
0xDA, 0xDC, 0xDE, 0xE0, 0xE2, 0xE4, 0xE6, 0xE8,
0xEA, 0xEB, 0xED, 0xEF, 0xF0, 0xF1, 0xF3, 0xF4,
0xF5, 0xF6, 0xF8, 0xF9, 0xFA, 0xFA, 0xFB, 0xFC,
0xFD, 0xFD, 0xFE, 0xFE, 0xFE, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xFF, 0xFF, 0xFE, 0xFE, 0xFE, 0xFD,
0xFD, 0xFC, 0xFB, 0xFA, 0xFA, 0xF9, 0xF8, 0xF6,
Page | 41
0xF5, 0xF4, 0xF3, 0xF1, 0xF0, 0xEF, 0xED, 0xEB,
0xEA, 0xE8, 0xE6, 0xE4, 0xE2, 0xE0, 0xDE, 0xDC,
0xDA, 0xD8, 0xD5, 0xD3, 0xD1, 0xCE, 0xCC, 0xC9,
0xC7, 0xC4, 0xC1, 0xBF, 0xBC, 0xB9, 0xB6, 0xB3,
0xB1, 0xAE, 0xAB, 0xA8, 0xA5, 0xA2, 0x9F, 0x9C,
0x99, 0x96, 0x93, 0x90, 0x8C, 0x89, 0x86, 0x83,
0x80, 0x7D, 0x7A, 0x77, 0x74, 0x70, 0x6D, 0x6A,
0x67, 0x64, 0x61, 0x5E, 0x5B, 0x58, 0x55, 0x52,
0x4F, 0x4D, 0x4A, 0x47, 0x44, 0x41, 0x3F, 0x3C,
0x39, 0x37, 0x34, 0x32, 0x2F, 0x2D, 0x2B, 0x28,
0x26, 0x24, 0x22, 0x20, 0x1E, 0x1C, 0x1A, 0x18,
0x16, 0x15, 0x13, 0x11, 0x10, 0x0F, 0x0D, 0x0C,
0x0B, 0x0A, 0x08, 0x07, 0x06, 0x06, 0x05, 0x04,
0x03, 0x03, 0x02, 0x02, 0x02, 0x01, 0x01, 0x01,
0x01, 0x01, 0x01, 0x01, 0x02, 0x02, 0x02, 0x03,
0x03, 0x04, 0x05, 0x06, 0x06, 0x07, 0x08, 0x0A,
0x0B, 0x0C, 0x0D, 0x0F, 0x10, 0x11, 0x13, 0x15,
0x16, 0x18, 0x1A, 0x1C, 0x1E, 0x20, 0x22, 0x24,
0x26, 0x28, 0x2B, 0x2D, 0x2F, 0x32, 0x34, 0x37,
0x39, 0x3C, 0x3F, 0x41, 0x44, 0x47, 0x4A, 0x4D,
0x4F, 0x52, 0x55, 0x58, 0x5B, 0x5E, 0x61, 0x64,
0x67, 0x6A, 0x6D, 0x70, 0x74, 0x77, 0x7A, 0x7D
void InitSinTable()
Page | 42
//sin period is 2*Pi
const float step = (2*M_PI)/(float)256;
float s;
float zero = 128.0;
//in radians
for(int i=0;i<256;i++)
s = sin( i * step );
//calculate OCR value (in range 0-255, timer0 is 8 bit)
wave[i] = (uint8_t) round(zero + (s*127.0));
void InitPWM()
/*
TCCR0 - Timer Counter Control Register (TIMER0)
-----------------------------------------------
BITS DESCRIPTION
NO: NAME DESCRIPTION
--------------------------
BIT 7 : FOC0 Force Output Compare
BIT 6: WGM00 Wave form generartion mode [SET to 1]
BIT 5: COM01 Compare Output Mode [SET to 1]
BIT 4: COM00 Compare Output Mode [SET to 0]
BIT 3: WGM01 Wave form generation mode [SET to 1]
Page | 43
BIT 2: CS02 Clock Select [SET to 0]
BIT 1: CS01 Clock Select [SET to 0]
BIT 0: CS00 Clock Select [SET to 1]
Timer Clock = CPU Clock (No Pre-scaling)
Mode = Fast PWM
PWM Output = Non Inverted
*/
TCCR0|=(1<<WGM00)|(1<<WGM01)|(1<<COM01)|(1<<CS00);
TIMSK|=(1<<TOIE0);
//Set OC0 PIN as output. It is PB3 on ATmega16 ATmega32
DDRB|=(1<<PB3);
ISR(TIMER0_OVF_vect)
OCR0 = wave[sample];
sample++;
if( sample >= 255 )
sample = 0;
5.2.3 H-Bridge Circuit
H-bridge circuit is basically enables a voltage to be applied across a load in either
direction. In inverters, it is used to amplify the input square wave coming from the
micro-controller.
We are giving modulated square wave at the input of the H-bridge because if we
give sine wave to the MOSFET or any other switching device like the BJT or IGBT,
very high switching losses occur. This is because when we give sinusoidal
Page | 44
waveform to any of these devices, they start operating in the linear region, and
power loss occurs in devices operating in linear region. When we give a square
waveform to them, they operate on either saturation or cut-off regions thus having
minimum power loss.
We used IRF5305 and IRFP150 MOSFETs. These are high power MOSFETs with
maximum current rating of 31 Amp and 42 Amp respectively. IFR5305 is a P-
channel MOSFET whereas IRFP150 is an N-channel MOSFET. Their datasheets
are given at the end of this report.
The circuit configuration of H-bridge is given below
FIGURE 5.2 (H-Bridge Circuit)
5.2.3.1 Working of H-Bridge
Working of an H-bridge can be divided into two modes.
In Mode1, the input signal at the gate of M1 is high and at the gate of M4 it is low.
This causes conduction from M1-M4 and we achieve a +12V signal at the output.
In Mode2, the input signal at the gate of M3 is high and at the gate of M2 it is low.
This causes conduction from M3-M2 and we achieve a -12V signal at the output.
And thus we obtain a 24Vpeak-peak signal at the output.
Page | 45
The working of H-Bridge in both conduction modes can be easily understood by
the following figure 5.3.
(A)
(B)
FIGURE 5.3 (H-Bridge Conduction Modes)
Page | 46
5.2.3.2 Results
Due to the conduction of half part of the bridge at +ve half cycle and the other half
part of the bridge at –ve half cycle, we obtain a square waveform of 24 Vpeak-peak at
the output.
In figure below is the Proteus simulation showing the waveform output of bridge
circuit during each conduction cycle.
FIGURE 5.4(Wave-forms of H-bridge conduction cycle)
5.3.3.3 Observations
In the H-bridge circuit we have observed that input signal‟s frequency does not
change at the output that means the frequency remains un-altered. Only the power
of the signal increase in terms of current.
5.3.3.4 Problems
Initially we used all the MOSFETs of same type (i-e. n-channel MOSFETs). This
caused the shorting of the MOSFETs during the conduction mode. This
phenomenon is known as shooting over of the MOSFET. Despite the duration of
this shooting over was quite small, it caused loading on the MOSFETs. The
MOSFETs started heating up due to this, and eventually they burned out.
Page | 47
Another problem occurred while using the MOSFETs of same channel was that the
upper MOSFETs (M1 and M3) did not turn on properly. After studying, we learned
that they required 18V to turn on thus; we needed a MOSFET driver that was
IR2110. We worked on it but it did not working properly too, because according to
the formula for bootstrap capacitor given in datasheet, the driver must have given
18V output but it was not working so we had to search for an alternate.Then after
extended study we came to know that replacing the upper two n channel
MOSFETs with p channel MOSFET is the solution. We applied this technique and
it worked.
Using this technique also solved the problem of MOSFET shooting over by
inducing a dead time/delay in the MOSFET switching.
5.3.4 LC Filter
We have determined inductance of the inductor using LC resonant band stop filter
as LC meters were not available in the lab.
FIGURE5.5 (LC filter)
5.3.4.1 Working
The method to determine L or C is simple. Suppose we are required to determine
the inductance, then by above circuit,
V1=1Vrms square wave from signal generator.
R1= 500ohm
C1=10uf
L1=unknown
Page | 48
Rload= 1Kohm
V1 signal from function generator is set to 1Vrms using multi-meter.
At resonance frequency the LC combination will have very low impedance so it will
short out the signal and will drop across resistor R1 and prevents the signal to
reach the load.
Using this principle we have varied signal frequency from function generator and
we are detecting output voltage at load using multi-meter. At resonance frequency
multi-meter will show ideally zero volts.
So by using formula we have,
Fc=1/2pi*sqrt(LC)
L=1/(2*pi*f.)2 *C
5.3.4.2 Problems
First we designed an RC circuit but we observed that the Resistance R in the
circuit acts as a load and dissipates power. After studying, we decided to use an
LC filter.
The main problem with the LC filter was the designing of the inductor as the
inductor of desired value was not available in the market, thus we had to make it by
hand. LC meter was not available also thus we had to repeatedly calculate the
inductance value mathematically.
5.3.5 Working of Sine Wave Inverter
A 50Hz sin wave is generated with the help of a lookup table within the AVR
microcontroller and is modulated over a switching frequency signal of 15KHz. As
this signal has very weak current, so it is amplified by a BC 547 transistor. The
amplified signal is given at the gates of M1 and M2 MOSFETs. The output of the
microcontroller is given to another BC 547 which is working as an inverting
amplifier. By this, the signal from the microcontroller gets inverted as well as
amplified. This signal is given at the gates of M3 and M4 MOSFETs.
Now what happens is that, when the input signal at the gate of M1 of the H-bridge
is high and at the gate of M4 of the H-bridge is low, conduction from M1-M4 occurs
and we achieve a +12V signal. When the input signal at the gate of M3 goes high
and at the gate of M2 goes low, conduction from M3-M2 occurs and we achieve a -
12V signal. Thus at the output we receive a waveform of 12Vpeak or 24Vpeak-peak.
Page | 49
The output of the H-bridge is then fed into a low pass LC filter which filters the high
frequency components of 15 KHz and gives the 50 Hz sine output. This output is
then fed into a transformer which steps up this 12 Volts AC waveform into 220Volts
AC.
5.4 Design and Development of Modified Sine Wave Inverter: Modified sine wave inverter gives an output which is intermediate between the
square wave and pure sine wave. Is has much lower efficiency than the pure sine
wave.
The circuit diagram of a modified sine wave inverter is shown below
FIGURE 5.6(Modified Sine wave circuit)
FIGURE 5.7 (Practical Delay circuit)
Page | 50
5.4.1 Explanation.
For a modified sine wave inverter we need two inverted square waves signal to
switch the MOSFETs. Two generate these signals we use HEF4047 multi-vibrator
IC. We use it in a-stable mode. It gives a buffered output so there is no need for
impedance matching between TTL based ICs and CMOS based ICs. In a-stable
mode it generates square wave of exactly 50% duty cycle at its pin 10 and gives its
inverted signal on pin 11. It also generates frequency double to that of pin 10 at pin
13. It can be done by using 0.2µF capacitor and a 7.6KΩ resistor as mentioned in
its datasheet to generate frequency of 500Hz at pin 13.
From pin 13 we give a signal to HCF4017 IC as a clock. HCF 4017 is a decade
counter with 12 outputs. It is used to generate a 50Hz signal with controlled delay
at both positive and negative edge. Pins 1, 5, 6, 9 and pins 2, 4, 7 are used as
output. All other outputs are grounded as CMOS ICs are very sensitive and even a
small stray signal can burn them out.
The output of HCF4047 is about 1v, which cannot be used to drive MOSFETs so
the signal is amplified by using BC-547 as an amplifier (connected in common
emitter biased configuration. This signal is again amplified and inverted. The signal
obtained is a controlled PWM which we now give at the MOSFET gates.
The block diagram of the modified sine wave inverter module is given below.
FIGURE 5.8(Block diagram of modified sine wave inverter)
Page | 51
5.4.2 Working
We gave a PWM signal to the pair of MOSFET connected in a push pull
configuration. When M1 MOSFET is turned on by a high input (Q), the M2 MOSFET
turns off at that time because on its input we had given an inverted signal (Q ) with
some delay. This delay is used so that one of the MOSFETs gets time to turn off
before second one turns on. In this mode, the current flows from source to
MOSFET M1 as shown in figure. When Q1 goes low Q becomes high and M2 turns
on, resulting in a current flowing from source as shown in diagram by I2. Thus, we
get a bipolar high voltage output at the transformers secondary.
The 22kΩ resistor from Gate to the source as shown in the diagram is important
because when the input signal goes to zero, the MOSFETs may not completely
turn off because of the capacitance between gate and source so this resistance
makes sure that signal is fully grounded.
The threshold voltage to turn on a MOSFET is approximately 4V. We are driving
MOSFETs with 12v signal so that MOSFETs is completely turned on otherwise it
will result in power dissipation.
5.4.3 Results
FIGURE 5.9(Delayed inverted output)
5.4.4Problems
In power inverter, shoot through current is a major problem and needs to be
solved. It is a short circuit current, and as described in the previous topic, occurs
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when both MOSFETs are on. This happens for a very short time i.e. for some
Nano-seconds. But eventually it results in a short circuit current, which causes
loading and thus it may damage the MOSFETs.
This situation can be avoided by introducing a dead time between the two signals
both at rise and fall edge. If the dead time is increased too much, the output
voltages drop because MOSFETs are turned ON for a very short time.
Finally impedance matching is an important factor. Transformers output impedance
(Secondary) should be low so that minimum voltage drop occurs when we connect
any load to with it.
5.5 Transformer Design
Core of a transformer is vital for its operation. There are three types of cores
available in the market for making a transformer. Silicon core, Soft iron core, and
Radio metal core. Standard transformers use 3% silicon steel cores. In our project
we have chosen shell type radio metal core as it has better permeability and it has
low I2R losses.
5.6.1 Calculations
The parameters and calculations of the transformer design are given below.
Iron losses in silicon core = 0.1 watt/sq.Inch
Width = 1.75”
Length = 1.25”
Thickness = 0.35-0.4mm
Cross-section area= Length x Width
Transformer Wattage = (cross-section area x 5.6)2
= (1.75 x 1.25 x 5.6)2
= (12.25)2 =150VA ………. (i)
Turn Ratio/volt = 6/cross-section area (for radio metal core)
= 2.74 V / turns …………. (ii)
Input wire gauge = 0.22mm
Diameter of wire = 0.028‟‟
Page | 53
Resistance/1000yards=38.99Ω
Length/pound (yards) = 140.6 yards
Turns/ inch = 33.0 turns
Current in Amp calculation = 2400Amp/sq. inch
Primary turns= 24V/2.74
= 8.75 or 9 turns approx. …….. (iii)
Secondary turns = 230/2.74
=84 turns……. (iv)
Secondary voltage = 230 V
Secondary current = 1.53 A
Maximum current that can flow,
Primary voltage=24 V
Current I1=I2 (V2/V1)
I1 = (230 x 1.53)/24= 14.66A…………. (v)
5.6.3 Problems Faced
We faced many problems with the design of our transformer. Voltage drop due to
impedance mismatching was the main problem for which we had to redesign our
transformer 3 times. First we designed a transformer of 500VA. It gave an output of
130Volts AC instead of 220Volts. We changed our filter components by trying
different value inductors and capacitors. It did help a bit and our output increased
to 165Volts AC, but it helped no further. Then we designed a transformer of
150VA. Voltage drops also occur in this transformer but these drops are a bit
acceptable keeping in view our project.
Page | 54
FIGURE 5.10(Proteus Circuit of pure sine wave inverter)
5.7 RESULTS
FIGURE 5.11(Simulated Output of Pure-Sine wave inverter)
Page | 55
CHAPTER 6
AUTOMATIC TEMPERATURE
CONTROLLER
All semi-conductor devices heat up due to large current conduction. In elevated
temperatures, the semiconductors do not perform well thus they need to be cooled
by removing the heat continuously. This task is achieved by heat sinks, which
conduct the heat to the external environment. Automatic cooling fans also known
as the temperature controllers control the ambient temperature of the circuit by
allowing cool air from outside to flow across the circuit, removing heat from the
circuit environment. This removal of heat from the environment allows better
conduction of heat by the heat sink, keeping the electronic device working properly.
In our inverter module, the high frequency switching of the MOSFETs produces a
lot of heat, thus we have designed an automatic temperature controller which
consists of following main components.
LM 35 temperature sensor.
LM 358, LM 741 Operational-Amplifiers.
12v DC fan.
BC547 transistor.
The temperature is controlled by the help of a 12v DC fan which starts operating
when the temperature rises above 31°C. Working and the design of this module
are detailed in subsequent topics, whereas the technical specifications of the
sensor and the Op-Amps are given below.
6.1. MAIN COMPONENTS USED
i) LM-35 TEMPERATURE SENSOR
The LM35 series are precision integrated-circuit temperature sensors, whose
output voltage is linearly proportional to the Celsius (Centigrade) temperature. The
Page | 56
LM35 thus has an advantage over linear temperature sensors calibrated in °
Kelvin, as the user is not required to subtract a large constant voltage from its
output to obtain convenient Centigrade scaling. The LM35 does not require any
external calibration or trimming to provide typical accuracies of ±1⁄4°C at room
temperature and ±3⁄4°C, over a full −55 to +150°C temperature range. Low cost is
assured by trimming and calibration at the wafer level. The LM35‟s low output
impedance, linear output, and precise inherent calibration make interfacing to
readout or control circuitry especially easy. It can be used with single power
supplies, or with plus and minus supplies. As it draws only 60 μA from its supply, it
has very low self-heating, less than 0.1°C in still air. The LM35 is rated to operate
over a −55° to +150°C temperature range, while the LM35C is rated for a −40° to
+110°C range (−10° with improved accuracy). The LM35 series is available
packaged in hermetic TO-46 transistor packages, while the LM35C, LM35CA, and
LM35D are also available in the plastic TO-92 transistor package. The LM35D is
also available in an 8-lead surface mount small outline package and a plastic TO-
220 package.
ii) OPERATION AMPLIFIERS
We have used two types of operational amplifiers in our temperature controller.
There is no difference in the working of these Op-Amps and we could have used
the same types of Op-Amps.
a) LM 358
It consists of two independent, high gain and internally frequency compensated op-
ampswhich were designed specifically to operate from a singlepower supply over a
wide range of voltages. Application areas of LM 358 include transducer amplifiers,
dc gainblocks and all the conventional op-amp circuits. It can be directlyoperated
off of the standard +5V power supply voltage whichis used in digital systems and
can easily provide the requiredinterface electronics without requiring the additional
±15Vpower supplies. The LM358is available in a chip sized package using
National semiconductor‟s micro SMD packagetechnology.
b) LM741
The LM741 is a general purpose operational amplifierwhich features improved
performance over industry standardslike the LM709. The LM-741 series amplifiers
offer many features which make their application nearly foolproof (e-g) they have
overload protection on the input andoutput, there is no latch-up when the common
mode range is exceeded, and they have freedom from oscillations.
Page | 57
The LM741C of the LM741seried is identical to the LM741 and LM741A except
that, the LM741C has its performance guaranteed over a 0°C to+70°C temperature
range, instead of −55°C to +125°C.
6.2. BLOCK DIAGRAM
Below is a simple block diagram for easy understanding of the working of the
designed module.
FIGURE 6.1 (Block diagram of Fan control circuit)
6.3. CIRCUIT DIAGRAM
Given below is the circuit diagram of the temperature control circuit.
FIGURE 6.2 (Temperature based fan controller)
6.4. WORKING
The LM 35 is a linear temperature sensing device whose output is 10mV/°C. This
means that at 1°C, 10 milli Volts are given at the output. As this output is very low,
thus we have amplified it by a factor of 10 by using LM 358 as a non-inverting
amplifier.
Page | 58
We have set 33.4°C as reference temperature, so whenever the temperature rises
from this reference, the fan turns on and whenever it falls from the reference, the
fan turns off. To achieve this set-point of 33.4°C, we first calculated the voltages at
this temperature, which came out to be 3.65Volts. Then we set these reference
voltages at the non-inverting pin (pin 3) of the LM741 by the help of a
potentiometer and fed the output of the LM358 into the inverting pin (pin2) of the
LM741.
Now what happens is that when the temperature rises above 33.4°C, the sensor
gives its output accordingly to the amplifier, which amplifies this output and feeds it
to the inverting pin of the comparator. The comparator compares this value with the
reference and gives an output to the base of the BC-547 transistor. Voltages at the
base allow the 12V at the collector to drop across the fan, thus turning the fan on.
6.5. CALCULATIONS
1. Calculations for setting the gain are as under
As we know thatV=(
) 0
At 33.4°C, the output voltages would be
Where, Rf = 100KΩ
AndRi = 10.2 KΩ
So, V = (1+
)x0.334
V = 3.655 Volts
2. Calculations for BJT being used as a switch are as under
β = 313
Vcc = 12V
Ie = 65.6 mA
Re = 102.2 Ω
Now, as we know that Ie = (β+1) xIb
Page | 59
So, Ib= (
)
Ib = 206 µA
Now, Vcc = IbRb + Vbe +IeRe
Rb= –
)
Rb= –
)
Rb = 22.3 kΩ
For Collector-Emitter voltage,
Vce = Vcc - IeRe
Vce = 12-(65.6mA )
Vce = 5.3 volts
Page | 60
VG
R4
DC7
Q3
GND1
VCC8
TR2
TH6
CV5
U1 555
B1 12V
C1 12pF
D1 10BQ
015
33%
RV1
500k
D2 10BQ
015
R1 10K
R2 470
Q1 BC54
7
R3 1k
VIN
20V
L1 270u
H
C1 2200
uF
VDIO
UT
C2 100u
F
ILVS
Id
Q1 IRF5
305
+88.8
Volts
Q2 IRFZ
44n
B3 12V
Sour
ce B
attry
26%
RV1
100k
24%
RV2
100k
wind
fix vo
ltage
s3 2
1
8 4
U1:A
LM35
8
5 6
7
8 4
U1:B
LM35
8
0%
RV3
100k
sola
r var
ayin
g
9%
RV4
100k
wind
vara
ying
R1
22K R2 22K
Q1 BC54
7
Q2 BC54
7
RV1(
3)
RV2(
3)
RV3(
3)
U1:B
(-IP)
RL1
G2R-
14-D
C12
sola
r cha
rgin
g rel
ay
RL2
G2R-
14-D
C12
wind
char
ging
rela
y
D1 LED-
BIBY D2 LE
D-BI
BY
RL3
G2R-
14-D
C12
tota
l cha
rgin
g con
trol
B4 12V
R3 22K
SW1
SW-S
PDT
Q3 BC54
7D3 LED-
BIBY
RL4
G2R-
14-D
C12
Char
ging
/Inve
rter
3 2
1
8 4
U2:A
LM35
8
71%
RV5
100k
82%
RV6
100k
U2:A
(+IP
)
U2:A
(-IP)
CLK
14
E13
MR
15CO
12
Q03
Q12
Q24
Q37
Q410
Q51
Q65
Q76
Q89
Q911
U1 74HC
4017
R4
DC7
Q3
GND1
VCC8
TR2
TH6
CV5
U2 555
B1 12v
R2 2k2
C1 0.1u
87%
RV1
100K
Q1 BC54
7
R5 470
B2 12V
Q2 BC54
7
R1
470O
hm
Q5 BC54
7
R4 470O
hm
Q7 BC54
7
R6 470O
hm
R3 470 R7 470
Q9 IRFP
150N
Q10
IRFP
150N
TR1
TRAN
-2P3
S
+88.8
AC V
olts
R8 22k
R9 22k
L1 220V
Tem
pera
ture
bas
ed F
an C
ontro
l Circ
uit
31.0 3
1 VOUT
2U2 LM35
3 2
1
8 4
U1:A
LM35
8
R2 100K
R1 10.2K
78%
RV1
10k
3 2
6
7 4
1 5
U3 LM74
1
R3 22K
Q1 BC54
7 +88.8
kRPM
D1 1N40
07
R3(1)
U3(+IP)
U1:A(OP)
3 2
1
8 4
U1:A
LM35
8
55%
RV1
10k
R1 10k D1 1N
751A
R2 22k
Q1 BC54
7
B2 12V
BUZ1
BUZZ
ER
RL1
9V
Switc
hing
Con
trol C
ircui
t
Mod
ified
Sin
e W
ave
Inve
rter
Q1 2N30
55
R1 470
D1 1N47
43A
C1 4700
u
C2 10u
+88.8
Volts
SOLA
R PA
NEL
WIN
D TU
RBIN
EVOLT
AGE
REG
ULAT
OR
BUCK
CO
NVER
TER
PWM
CO
NTRO
LLER
BUZZ
ER C
IRCU
IT
FIGURE 6.4 (Complete
Circuit Layout of
the Project)
Page | 61
CHAPTER 7
CONCLUSION AND SCOPE
We have concluded that our hybrid energy system is a reliable source of
energy and the efficiency of the system can be further increased by using
renewable energy systems which are capable of giving higher power output. We
can increase the storage of the system by using a rechargeable battery bank. The
initial costs of the project are very high but the running costs and maintenance
costs of the system are very low.
The future scope of this project is very vast as this project demonstrates the
latest technique of producing renewable energy in an efficient and cost effective
manner. Hybrid energy systems are being deployed in many third world countries
like Ethiopia, Ghana and Palestine etc. under United Nation‟s clean energy
program. This concept of clean and cheap energy is slowly infiltrating the market
and many international projects are underway.
In Pakistan Hybrid energy can be very useful in lower Punjab region and
especially in the underdeveloped areas like Cholistan and the Thar Desert. Thus
projects like these should be funded by the government and private investors for
the revenue generation and the betterment of the nation.
Page | 62
Future Recommendations
Due to lack of time and funds, this project is modeled as a basic concept of
the hybrid renewable energy system. Being a basic system, much work
needs to be done to improve this project.
Our recommendationsinclude that the power rating of the system should be
increased. Instead of a single battery, a battery bank should be used to
increase the energy storage capacity of the system.
Instead of buck regulator, buck-boost regulator should be used. Transformer
should be designed carefully as problems with the impedance mismatching
occur, resulting in low efficiency.
A solar tracking system should be attached with the solar panels so that the
efficiency of the source increases.
Page | 63
CHAPTER 8
REFERENCES
i) Muhammad H. Rashid. “Power Electronics, Circuits, Devices and
Applications”.
ii) Robert Boylestad and Louis Nashelsky, “Electronic devices and circuit
theory”.
iii) Gary D. Burch, “Hybrid Renewable Energy Systems”. U.S. DOE
Renewable Energy Workshop, August 21, 2001
iv) Ian F. Crowley and Ho Fong Leung, “PWM Techniques: A Pure Sine
Wave Inverter”4/27/2011.
v) Katsunori Taniguchi, YasumasaOgino, and HisaichiIrie,”PWM Technique
for Power MOSFET Inverter”.IEEE transactions on Power Electronics.
Volume 3. No 3. July 1988.
vi) Information from the internet (Blogs, Wikipedia, howstuffworks.com
(etc.))
Page | 64
CHAPTER 9
APPENDIX
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