Graduation Project _Final Version_Mus'Ab Samarah

Qatar University Third Generation Zero-CO2 footprint Solar Isam Akil Samara

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Qatar University

College of Engineering

Department of Electrical Engineering

A Graduation Project Report

Qatar University Third Generation Zero-CO2 footprint Solar Car

By

Ahmed Issam

Mahmoud Akil

Musa’b Samara

Supervised By:

Prof. MohieddineBenammar

Dr.FaridTouati

May 2013


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-Student Statement-

We, the undersigned students, confirm that the work submitted in this project report is entirely

our own and has not been copied from any other source. Any material that has been used from

other sources has been properly cited and acknowledged in the report.

We are fully aware that any copying or improper citation of references/sources used in this report

will be considered plagiarism, which is a clear violation of the Code of Ethics of Qatar

University.

In addition, we have read and understood the legal consequences of committing any violation of

the Qatar University’s Code of Ethics.

Student Name Student ID Signature Date 1 Musa’bFawzi Samara 200600742 30-5-2013

2 Ahmed Isam 200501566 30-5-2013

3 Mahmoud Nabil Akil 200801939 30-5-2013


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ACKNOWLEDGMENT

We would like to take the opportunity to thank out supervisors Prof.Mohieddine Benammar

and Dr.Farid Touati for their continuous supervision and commitment. Our acknowledgments

and appreciation go to Dr. Ahmed Massoud and Prof. Lazhar Ben-Brahim for their support.

We don’t forget our appreciation and special thanks for our families and friends who

supported us throughout the semester .

We would like also to thank Eng.Mazen Faiterand Eng. Ayman Ammar for their technical

support and commitment.

A special thanks goes tothe mechanical team mates, goes to my team mates , Nour Allam

, Ajad Hussain and Abdulkader Sakil for their valuable help in assembling, designing and

implementing all the mechanical components of the car .

We would like also to expand our thanks and appreciation to Shell Oil Company and Qatar

National Research Fund (QNRF) for funding our project via the Undergraduate Research

Experience Program(UREP 12-065-2-028 ).

Ahmed Issam

Mahmoud Akil

Musa’b Samara


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ABSTRACT

The purpose of this project is to build an efficient third generation zero-CO2 footprint

solar vehicle and participate in the 2013 Shell Eco-marathon Competition. Hence, this project is

dedicated to improve power efficiency of the Gernas I and Gernas II cars and to obtain a higher

rank in the “Battery –Electric Prototype “category in the competition. By following up the rules

and regulations of the Shell Eco-marathon competition .The need for renewable energy was the

main motivation for this project. This project discusses how important is the renewable energy in

modern cars and that it can make a huge impact in the cars technology. In this report the solar

system will be the source of energy which will be discussed in details with the Matlab/Simulink

simulation. In order to extract the maximum power from the PV modules the boost, DC-DC

converters will be used along with the maximum power point tracking (MPPT) Algorithm to

achieve that aim and it will also be simulated and tested by PROTEUs simulation and Multisim

software.


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TABLE OF CONTENT

ACKNOWLEDGMENT ...........................................................................................................3

ABSTRACT...............................................................................................................................4

TABLE OF CONTENT ..........................................................................................................5

LIST OF FIGURES .................................................................................................................8

LIST OF TABLES ................................................................................................................ 11

CHAPTER I:INTRODUCTION ................................................................................................ 12

1.1Motivation: ....................................................................................................................... 12

1.2 General Problem Statement: ............................................................................................ 13

1.3 Project Objective: ............................................................................................................ 14

1.4 Design Constraints: ..................................................................................................... 14

CHAPTER 2: SYSTEMOVERVIEW ....................................................................................... 16

2.1 Introduction: .................................................................................................................... 16

2.2 Mechanical Design: ......................................................................................................... 16

2.2.1 Gernas I Car Design:................................................................................................. 16

2.2.2 Gernas III Car Design (Improvements) : ................................................................... 17

2.2.2.1 Body Shell: ............................................................................................................ 17

2.2.2.2Chassis and Steering: .......................................................................................... 18

2.2.2.3 Braking System: ................................................................................................. 19

2.3 Energy System ................................................................................................................ 21

2.3.1 Battery: ..................................................................................................................... 22

2.3.2 Solar Arrays:............................................................................................................. 23

2.3.3 Boost Converter: ....................................................................................................... 24

CHAPTER 3: ENERGY SYSTEM ........................................................................................... 25

3.1 Introduction ..................................................................................................................... 25

3.2 Motor .............................................................................................................................. 26

3.3 Battery: ........................................................................................................................... 29

3.3.1Battery management system: ..................................................................................... 30

3.4 Photovoltaic power frame ................................................................................................ 33


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3.5 Photovoltaic cells modeling ............................................................................................. 38

CHAPTER 4:DESIGN OF DC-DC CONVERTER ................................................................... 41

4.1 DC-DC converter ............................................................................................................ 41

4.1.1 Background information: .......................................................................................... 41

4.1.2 Analysis and Calculations: ........................................................................................ 42

4.1.2.1 The Values of Lmin and Cmin : ......................................................................... 42

4.1.2.2 Proof equations (4.1) and (4.2): .......................................................................... 43

4.1.3 Boost converter simulation using MULTISIM .......................................................... 44

4.1.3.1Multisim-Simulation : ......................................................................................... 44

4.1.3.2 Schematic circuit:............................................................................................... 44

4.1.3.3Design components: ............................................................................................ 45

4.1.3.4Switchtype : ........................................................................................................ 45

4.1.3.4Results : .............................................................................................................. 46

CHAPTER 5: ENERGIZING SYSTEM IMPLEMENTATION , TESTING and VALIDATION

................................................................................................................................................. 47

5.1 Practical implementation of the electrical system ............................................................. 47

5.1.1 First stage of implementation: ................................................................................... 47

5.1.2. Second Stage of implementation: ............................................................................. 49

5.1.3 The Third stage of implementation (PCB Stage): ................................................. 50

5.2 Testing : ...................................................................................................................... 52

5.2.1 Designed boost converter VS Commercial boost converter: ...................................... 55

5.3 Validations: ................................................................................................................. 57

CHAPTER 6: CONCLUSION AND RECOMMENDATIONS ................................................. 67

6.1Conclusion ....................................................................................................................... 67

6.2 Future work and Recommendations ................................................................................. 67

REFFRENCES.......................................................................................................................... 68

Appendix .................................................................................................................................. 70

Appendix A............................................................................................................................... 70

Appendix B ............................................................................................................................... 74

Appendix C ............................................................................................................................... 75

Appendix D............................................................................................................................... 76


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Appendix E ............................................................................................................................... 77

Appendix F ............................................................................................................................... 79


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LIST OF FIGURES

Figure1. 1Energy demands between 1970 and 2040 [1] ............................................................. 12

Figure 2.1 The Gernas I solar car [3] ......................................................................................... 17

Figure 2.2Gernas III Body Shell. ............................................................................................... 18

Figure 2.3The Steering in Gernas II and the braking systems . ................................................... 19

Figure 2.4The hand break for front wheel in Gernas II .............................................................. 20

Figure 2.5The Wheel used in GernasII . .................................................................................... 20

Figure 2. 6 The oveall system components ................................................................................ 21

Figure 2. 7 TURNIGYNANO-TECH lithium polymer battery................................................... 22

Figure 2.8Sepang International Circuit in Kuala Lumpur [18] ................................................... 23

Figure 2.9The Solar Cells .......................................................................................................... 23

Figure 2. 10 The DC-DC boost converter topology.................................................................... 24

Figure 3. 1 BMS circuit diagram ............................................................................................... 33

Figure 3. 2 Perturb and Observe algorithm ................................................................................ 35

Figure 3. 3 MPPT circuit diagram ............................................................................................. 37

Figure 3. 4 The generated PWM signal from the MCU .............................................................. 37

Figure 3. 5 MPPT charging current ........................................................................................... 38

Figure 3. 6 PV Panel system ...................................................................................................... 39

Figure 3. 7 I-V Curve with different irradiations........................................................................ 40

Figure 3. 8 P-V curve with different irradiations........................................................................ 40

Figure4. 1Schematic circuit design using Multisim software ..................................................... 44

Figure4. 2PWM generated by using Bipolar voltage source ....................................................... 46

Figure 5.1practical implementation ........................................................................................... 47

Figure 5.2. PWM signal from the Microcontroller .................................................................... 48

Figure 5.3 1) The Upper level of the designed prototype boost converter is the boost converter

circuit. 2) The lower level of the prototype is the microcontroller circuit. .................................. 49


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Figure 5.4 Printed circuit board abbreviated PCB ...................................................................... 50

Figure 5.5control circuit for MPPT PCB ................................................................................... 51

Figure 5.6Power circuit of the MPT system PCB ...................................................................... 51

Figure 5.7phase two of testing ................................................................................................... 52

Figure 5.8Phase two of the testing process ................................................................................ 53

Figure 5.9phase two results ....................................................................................................... 53

Figure 5.10 Testing the finalized version of the system ............................................................. 54

Figure 5.11 (1) The first reading shows the output current from the charging system where it has

been taken nearly at 3 pm. (2) The 2nd

reading shows different output and input currents were the

time was nearly 4 pm. (3) The 3rd

and the last reading shows an output and input currents taken

at nearly 5 pm. .......................................................................................................................... 55

Figure 5. 12 the driver and the team will be provided by the walkie talkies................................ 58

Figure 5. 13 The Horn is installed and positioned on front of the car, so the sound of it will be

very clear and load for the others in case of overtaking or for different needing. ........................ 58

Figure 5. 14 The car is provided by two side mirrors to enable the driver to have a full vision on

the road and in case of overtaking as well .................................................................................. 59

Figure 5. 15 Braking system is provided in the car to allow the driver to stop or to decelerate in

any needed case ........................................................................................................................ 59

Figure 5. 16 The car was weighted to be 36 kg (without the driver) ........................................... 59

Figure 5. 17 Helmets are available for both the driver and the reserve driver. ............................ 60

Figure 5. 18ventilation system is provided in the car to have an comfort area for the driver ....... 60

Figure 5. 19 The suite and the cloves for the driver for the safety of the driver .......................... 61

Figure 5. 20 The car is provide with a fire extinguisher which is usable and valid to use by the

driver in case of emergency. ...................................................................................................... 61

Figure 5. 21 Seat built is provide with the seat to be used by the driver while racing ................. 61

Figure 5. 22 1) 2 Wheels in front side. 2) 1 Wheel in Back side ................................................. 62

Figure 5. 23 The car was tested many times and in different situations in order to have the best

stability of the body in order to get the best body stability on the road. ...................................... 62

Figure 5. 24. Energy compartment that contains the Battery, Motor and the charger is very easy

to access by a hard doormade from plastic sheet. ....................................................................... 63

Figure 5. 25 the Chassis of the car body which is made of Aluminum bars and coulumns and it

is very hard and strong enough to protect the driver in case of accidents .................................... 63

Figure 5.26 The Electrical Energy system compartment, Includes The Motor, Batteries , charger

and the electrical conections ...................................................................................................... 63

Figure 5. 27 A door made of a plastic transparent sheet with a dimensions of ( X ) makes the way

easy for the driver to access and exit from the vehicle in both normal and emergency situations 64

Figure 5. 28 Two bottoms for emergency shut-down which can be used by the driver or any

assistor in the emergency cases ................................................................................................. 64

Figure 5. 29The car is provided by a two separated braking systems 1) Braking system for the

rear wheels and 2) another braking system for the front wheel ................................................... 65


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Figure 5. 30 The out put voltage is within the margin given by the rules of the competition, the

system output is tested to be about 24v ...................................................................................... 65

Figure 5. 31 The Battery used in the system of the car energizing is Lithium-polymer based with

a BMS system provided in case of emergency . ......................................................................... 65

Figure 5. 32 The solar panels used in the car to recharge the batteries are within the size of 0.17

m2 ............................................................................................................................................. 65

Figure 5. 33 One motor of 22V rated voltage has been used in the car ....................................... 66


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LIST OF TABLES

Table 2. 1 Gernas I VS Gernas III specifications ....................................................................... 21

Table 3.1Motor specification ..................................................................................................... 28

Table 3.2Battery Specifications ................................................................................................. 29

Table 3.3CKSR 50NP specifications ......................................................................................... 31

Table 3.4LM35 specifications ................................................................................................... 31

Table 3.5PV panel specification ................................................................................................ 34

Table4. 1 Proof of the equations (4.1) and (4.2) ......................................................................... 43

Table 5.1Comparison between The designed boost converter and a commercial boot converter

product ...................................................................................................................................... 56

Table 5.2Comparing the Shell Eco-Marathon rules to the designed car ( Gernas 2 ) [15] ........... 57


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CHAPTER I:INTRODUCTION

1.1Motivation:

There are different significant aims that make the use of renewable energy for different

applications a very important of our life and future. Everyone should invest in the renewable

energy field since it is cleaner, healthier, environmentally friendly and it is renewable

.Renewable energy is playing a major role these days and it is trending among all of other fossil

fuel sources as can be seen in figure 1 which shows that in the next coming years up to 2040

renewable energy will gain shares and will be one of the most energy sources used compared to

other energy sources.

Figure1. 1Energy demands between 1970 and 2040 [1]

Hence, we have been motivated to work on an application that mainly uses one of the renewable

energy sources which is solar energy. This graduation project aims to contribute to the strategic

goal of participations of the department of Electrical Engineering in the shell Eco-Marathon

competition.

Ultimately, the reason that motivate us to work hard on this project is the theme of the

competition itself. The goal of the Shell Eco-marathon competition is to build the most energy


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efficient environmentally friendly prototype vehicle possible. Our ability to participate in such a

competition, and contribute in developing, designing, building and optimizing the future

environmentally friendly vehicle was the biggest motivation to achieve this project.The project

will be mainly a continuation development of previous Gernas I solar car. At the end of this

project, we would’ve our energy energy-efficient green car.

1.2 General Problem Statement:

Shell Eco marathon competition started in 1939 when some employees of Shell Company in the

USA had created a friendly wager which could move to the furthest distance using the same

amount of fuel[2].After that it has been expanded to other countries in different continents .

Starting byAmerica, Europe and then Asia by adding more energy types such as solar electric

cars and biofuel cars.

Shell-Eco-marathon is a unique competition that encourages students to design, build and drive

the most energy-efficient car. There are about three events around the world where hundreds of

team participate in this competition. The goal of the competition is just simple, each team will

design a car that will travel the furthest on the least amount of energy .The Eco-Marathon is held

around the world with events in Finland, France, Germany, Holland, Japan,Malaysiaand the

USA. [2]

Each year’s competition Shell Company provides participants with publications of all rules and

regulations that should be followed in order to be allowed to be in the competition. Every design

constraint should be referred to these rules before any implementing take place. For more

information about rules and regulations of Shell Eco marathon competition, you can refer to

appendix A.

Different vehicle design groups are available for Shell Eco marathon competition such General

design group,Urbanconcept Group and prototype group . We have been enrolled in the prototype

group design . Where we have to design and implementa second generation solar powered car by

improving the first-generation solar called GernasI.Improving the car’s power efficiency and

making it lighter in weight are one of our challenges in this project. Thus, the car will use solar


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cells to charge the batteries that will power the motor and run the car. The car should be ready

for shipping to Malaysia by 3rd

of June, 2013 in order to participate in the Shell Eco Marathon

competition in July, 2013.

1.3 Project Objective:

This main purpose of this project is to design a solar powered car that shall participate

in the Shell Eco-marathon Asia , July 2013.Our main tasks in this project is rounded

by the designing and implementing the power generation system for the car .Where

other three students of electrical engineering will take the mechanical design in

consideration .

1.4 Design Constraints:

The following constrains are based on the shell Eco-Marathon rules and limitations and to

another internal constrains.

The total surface area of solar cells will be restricted to 0.17 𝑚2

The maximum voltage on the car shall not go beyond 48 Volts nominal and 60 Volts

maximum, this includes batteries, super capacitors and solar cells .

The electrical system of the car should be isolated so that there must be a key in order to

be immediately turn system off in case of danger .

This car will pass several safety and technical performance tests, Hence, It should be

ready to pass all this tests successfully.

The maximum vehicle weight, without the Driver is 140 kg.

Vehicles must be equipped with two independently activated brakes or braking systems.

There are two 12 V batteries allowed .One should be equipped for the horn and the other

one to power all other electrical components such as motor .

Only one battery should power the electric motor without any combinations with other

components .This will add a constraint on the weight of the car and other components .

The current relay in the Battery Management System will trip once the value of the

current detected exceeds the 80 % of the battery discharge rate.

The race should be completed within specified time, maximum :25 minutes which will

affect the power output .


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All Batteries must be placed outside the driver’s compartment behind the bulkhead and

securely mounted.

The time limitation was considered as one of the most important factors which was taken

into consideration to have the project done in the specified time and to have the car

shipped in the specified time in order to follow the rules which states that the car have to

be shipped before the competition by the beginning of June.

One of the internal constrains that we faced on this project is to create the PCBs of the

power electronics part of the project where the designed boost converter was done

manually and homemade which is much more difficult than using the automatic machine

to have a double PCB sides which also considered as one of the most important

constrains in the project.


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CHAPTER 2: SYSTEMOVERVIEW

2.1 Introduction:

The purpose of this chapter to get an overview of the system that we had designed throughout

our academic year with help of the mechanical team . This includes all the improvements that

have been made compared to Gernas I and Gernas II cars. This will be explained briefly taking in

consideration the mechanical design, energy system and the overall of body shell of the car.

Major part of this project contains designing mechanical components such as the steering system,

braking system and last the frame of the vehicle which will be the chassis. However, our main

focus was on the energy system which will be explained briefly in the following sections. In fact,

our project is chosen based on the a prototype group which means the vehicle has to be designed

and implemented using the best available components to insure an efficient charging of car’s

battery through the MPPT and methods that shall meet the Shell Eco marathon rules and

regulations. In the following sections, we are going to present an overview of the mechanical and

electrical systems of Gernas III

2.2 Mechanical Design:

2.2.1 Gernas I Car Design:

In 2010,Gernas I team which consists of three electrical students have designed and built a

prototype car. Their design was built to be solar powered car using an electric brushless dcmotor

to be ready to participate in Shell Eco marathon 2010 in Germany. The vehicle has six main

components: body shell, chassis, steering/wheel system, braking system, wheels, and energy

System.

Figure 2.1 shows the body shell of the prototype vehicle in which the Gernas I team has

designed. In building the body shell, carbon fiberwas used .Next, .Gernas I chose a metal frame

for chassis because it makes it safer for the driver according to their design . The Gernas I car

features a wheel arrangement of two wheels at the front and one in the rear .Moreover, toimprove

the aerodynamics, Gernas I team has placed the rear wheel inside of the shell, therefore this may

reduce the drag created by the wheel. The steering system was designed based on an ordinary

wheel steering as shown in figure 2.1. In fact, the wheels were brought from a bicycle and came


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with two foot braking; one for the rear wheel and one for the front wheels. Moreover, It is good

to mention that Gernas I vehicle was designed to have a gear with two stages .For the solar panels

,they had decided to choose a mono-crystalline silicon cells named as 100 & 80Watts semi-flexible

Solar Panel for 12V, from Sunflex company[3].

Figure 2.1 The Gernas I solar car [3]

Speaking about the battery specification, the high capacity Lithium-Polymer Battery rated as

36V/16AH was used as power storage component in the car. Its weight was more than 4 kg

.Furthermore; they used a brushless DC motor connected to drive the rear wheel.

2.2.2 Gernas III Car Design (Improvements) :

Although the Gernas I team’s design was fairly a good design. A lot of improvements can be

done to have a competitive car that can challenger all other competitors in the Shell Eco

Marathon competition. These improvements are based on weight, shell weight, and type of frame

used in the chassis, and the efficiency of the energy system. In this section, all the major

improvements that were done on Gernas I will be mentioned in terms of body shell, chassis,

steering and braking system.

2.2.2.1 Body Shell:

Figure 2.2 shows the body shell of the prototype vehicle in which we designed for Gernas III

vehicle. In building the body shell, polycarbonate plastic was used to shape the vehicle shell.

Polycarbonate plastic has great features such as it is very lightweight compared to other material

choices, It does not conduct electricity and makes a great insulation ,It is easy to work with via


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cutting , drilling and It is transparent which gives a great vision for the driver [4]. The strength

of the material is not very important because the vehicle will not be used with any big loads.

Figure 2.2Gernas III Body Shell.

2.2.2.2Chassis and Steering:

The frame of the chassis used in Gernas III vehicle was made of Aluminum material. Aluminum

frame. The aim of using the aluminum material is that it is lighter than steel and cheaper. The

great benefits of this Aluminum structure are combined by its strength to tolerate greater crashes

and it is great to mention that it is easy to fabricate.

As shown figure 2.3 the steering has been replaced with aluminum one , instead of the steel that

was used in Gernas I . We can notice the difference between the two types of steering .In Gernas

I ,they used a wheel driving steering ,on the other hand ,we are using a light Aluminum bike

steering which gives the driver the ability to control and drive safely without any troubles on the

track .


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Figure 2.3The Steering in Gernas II and the braking systems .

2.2.2.3 Braking System:

In the vehicle that was designed by the mechanical team, there are two independently brakes.

Where each brake consisting of a single command control. It works in a way such that one brake

must operate front wheels and the other one is responsible for the rear wheels. Having the

breaking system embedded with the steering will allow the driver to use the brake with any

trouble or a need to remove his hands from the steering. It is important to mention that braking

systems will be inspected for effectiveness by assigning the vehicle on an incline with a 20 %

slope according to Shell Eco Marathon constraints.

Finally , the gear that have been placed in our vehicle was based on slightly improving velocity

ratio and reducing the energy consumption by reducing the amount of revolutions that the

brushless DC electric motor has to rotate in order to generate enough torque to move the vehicle

at an optimum speed. This was verified by testing the car where we had a maximum speed of

32km/hr . Figure 2.5 shows the front wheel of Gernas III which is approximately the same used

for GernasI .


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Figure 2.4The hand break for front wheel in Gernas II

Figure 2.5The Wheel used in GernasII .


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Comparing Gernas I and Gernas II, the following table 2.1 will show the main differences

between the two cars :

Gernas I Gernas III

Weight 50 kg 36 kg

Chassis Metal Alamunium

Braking system Foot braking system Hand braking system

Steering system Steering wheel Bicycle steering

Motor 2000 – 6000 rpm 189 rpm

Battery Lithium-polymer (36V/16AH) Lithium-polymer

(22.2V/5000mAH)

Gear box Not Applicable Applicable Table 2. 1 Gernas I VS Gernas III specifications

2.3 Energy System

Figure 2.6 shows that our overall system contains of different major stages of implementing for

the energy system .It starts by the solar panels which is basically designed to allow the solar

radiation energy goes in and recharge the battery once it got empty . It is considered as the main

unit of the system is the solar cell. Followed by a MPPT that shall be used for delivering the

energy from the solar cells to the batteries. This action will be accomplished with the support of

a Maximum Power Point Tracker algorithm through generation of microcontrollers PWM.

Furthermore, at the beginning of the race the battery will be fully charged and the solar cells will

recharge the battery via the MPPT . Hence we got the system working together which will makes

the motor works accordingly. In the following sections, the system will be describes by the

design of each block in the figure (2.6).

Figure 2. 6 The oveall system components


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2.3.1 Battery:

Li-Po batteries are one of the most well-known types of rechargeable batteries that are capable to

work with planes, radio-controller and helicopters. Here are some of the advantages of the Li-Po

batteries:

Li-Po batteries are light weight and can be made in almost any shape and size.

They have large capacities, meaning they hold lots of power in a small package.

They have high discharge rates to power the most demanding electric motors.

They provide high energy storage to weight ratios in an endless variety of shapes and

sizes.[5]

The battery is an important component of our car power generation system. Generally, batteries

are classified based on their weight, dimensions, and weight and amp hours. According to Shell

Eco-Marathon rules, the battery that was selected to our power generation system will have a

voltage value of 22.2 V. In our design , we assured that our battery will kept fully charged until

the car covers around 11.2 km of the competition circuit by going in four laps of 2.8 km each of

the Sepang International circuit as shown in figure 2.8.

In this project, we have selected TURNIGYnano-tech lithium polymer battery which is built with

anLiConano-technology substrate complex greatly improving power transfer making the

oxidation/reduction reaction more efficient, this helps electrons pass more freely from anode to

cathode with less internal impedance.

Figure 2. 7 TURNIGYNANO-TECH lithium polymer battery


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Figure 2.8Sepang International Circuit in Kuala Lumpur [18]

2.3.2 Solar Arrays:

The transforming of radiations of the sun into electrical energy are done by the solar array

.Hence, it is a significant component in the solar car. It consists of several solar cells which are

arranged to provide an output voltage or power to recharge the battery of the solar car. Solar

array system is designed to allow the solar radiation energy goes in and generate electrical power

that will recharge the battery once it got empty .The main unit of the system is the solar cell.

There are two configurations for the solar array, either, parallel or series configuration of solar

cells. Figure 2.9 explains the configurations we set in our design which is in series.

Figure 2.9The Solar Cells


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2.3.3 Boost Converter:

The DC-DC boost converter along with the maximum power point tracking algorithm will be

able to extract the maximum power from the PV panels. This topology of DC-DC boost

converter is summarized in the figure 2.10 .

Figure 2. 10 The DC-DC boost converter topology.

SolarArray

LDiode

C R


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CHAPTER 3: ENERGY SYSTEM DESIGN

3.1 Introduction

The energy system of this car mainly depends on converting the photons energy

that hits the surface of the PV panels into electric energy, and this particular job is achieved by

the solar panels that will charge the batteries, which will power the motor of the car on the other

side, because with the nonlinear characteristic of the PV panels we cannot connect the PV panels

directly to the load, this is will be inefficient way, even if there a PV array that its voltage

matches with the rated voltage of the motor, in addition to that the battery existence is highly

required or otherwise the car cannot be driven at night, and even if the car is not moving the

battery will store the converted energy for later use. Furthermore PV panel’s main problem for

such a dynamic application is that the power from the PV panel might be zero sometimes due to

the shading effect, in this case the battery will deliver the required energy.

Batteries technology plays a vital role in the electric cars futures, because the energy

system of these kinds of cars mainly depends on the batteries, because the main issues that keep

blocking the development of the electric car is the batteries, and the development the batteries

technologies will lead to a great development in the electric car field, because the main concerns

is the how much mileage the car can do with installed battery in the car and how much time does

the battery need to get from being fully drained to full charged, in addition to that the energy

density of the battery itself is a big headache, which is the energy per unit mass, furthermore the

life cycle of the battery itself.

Motor is also a very important component in the system, because in fact the whole design

of the energy system will depend upon the selection of the type of the electric motor and the

rating of the motor. Electric motors are widely known by their high efficiency compared to

internal combustion engines, and it does not require frequent maintains like the internal

combustion engine. However there is server types of electric motors each type has its own

advantages and disadvantages, and each type fit for a certain application, in the this application

brushless DC motor fit perfectly, which is also known as the electrically commuted motor, it’s

asynchrouns motor that is powered by DC source via an internal inverter which is impeded

inside the motor, the main aim of the inverter is to convert the DC signal to an AC signal.


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3.2 Motor

In the design process its always advisable to start from the load till the source, in order to

create harmony between the energy system component, to avoid the failure of the system in the

future and to avoid to overloading your component above the withstand point of the component

that it’s have been designed for. In this case the determination of the torque load of the car is

required in order to determine the motor that should be used, to make sure that this motor can

handle such a weight , the motor can accelerate smoothly without any problem and the motor

shaft won’t broke due to overloading. On the other hand the circular motion of the motor is

usually governed by the following equation

𝑇𝑚 −𝑇𝐿 = 𝐽𝑑𝜔𝑚

𝑑𝑡 (3.1)

Where,

𝑇𝑚: Is the motor torque (newton Meter).

𝑇𝐿: Is the load torque.

𝐽 ∶ Is the equivalent inertia of the motor plus the load.

𝜔𝑚: is the angular speed (radian per second).

As the equation states that in the transient there will be acceleration, this acceleration

amount will depend upon the inertia of both the motor and the load until the motor torque equals

the load torque then the motor will stop accelerating and the system will enter the steady state

interval, in the Shell Eco-Marathon acceleration is not a big issue, but the power consumption is

the biggest issue, which is measuring the power from getting from my PV panels and the power

that the motor is using, however the rules stated that there is a fixed time if the car should cross

the finish line within this time, but this can be achieved using gears in order to get higher top

speeds, and this configuration will give the advantage of getting high torque from the motor

since its running in low speeds if we used higher gear ratio according to the following equation

𝑃 = 𝑇𝑚 ∗ 𝑊𝑚 (WATT) (3.2)


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Where,

P: is the output power from the motor

Computing the torque load for the car will lead to the prober selection for the motor, in

order to calculate the load torque of the car requires calculating some factors that will influence

the performance of the car during the race like the rolling resistance, grade resistance and the

acceleration force.

In the computation of the rolling resistance force of the car, first the rolling resistance

which is the constant that depends on the surface friction in 0.017 for poor asphalt surface, also

the weight of the car plus the driver must be determined.

𝑅𝑅 = 𝑣𝑤 ∗ 𝑅 (𝑙𝑏)[6] (3.3)

Where

RR rolling resistance of the vehicle (lb)

vw the vehicle plus the driver weigh (lb)

R rolling resistance coefficient (dimensionless)

𝑅𝑅 = 198.416 ∗ 0.017 = 3.373 𝑙𝑏

The grade resistance (GR) is the amount of force that the vehicle needs in order to be

able to move on a road with a slope[6].for the incline angle or the slope of the road the maximum

angle found after studying the race track in 3D is 3 degree.

𝐺𝑅 = 𝑣𝑤 ∗ sin ∝ (𝑙𝑏)[6] (3.4)

Where

GR is the grade resistance

Alpha is the incline angle (degree)

𝐺𝑅 = 198.416 ∗ sin 3 = 10.2930 𝑙𝑏

The acceleration force is the amount of force that the vehicle needs to accelerate from

stop to maximum speed in a certain time.


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𝐹𝐴 = 𝑣𝑤 ∗ 𝑉𝑚𝑎𝑥

32∗𝑡𝑎 (𝑙𝑏)[6] (3.5)

Where

Vmax is the maximum speed (ft/second)

Ta is the required time to accelerate to the maximum speed

𝐹𝐴 = 198.416 ∗ (41.010

32∗300)=0.8476lb

𝑇𝐿 = 𝐺𝑅 + 𝑅𝑅 + 𝐹𝐴 ∗ 𝑟 ∗ 𝑅𝑓 (𝑙𝑏. 𝑖𝑛) (3.6)

𝑇𝐿=(0.847 + 10.293 + 3.373) ∗ 14.685 = 202𝑙𝑏. 𝑖𝑛 = 22.1𝑁.𝑀

According to the previously mentioned facts the selection was a 23556 MN.M BLCD

motor that has the following specifications and has a rated torque which more than the torque

load of the car.

Table 3.1Motor specification

Rated voltage 24 volts

Rated current 17 AMPS

Rated power 210 watt

Rated speed 189 rpm

The manufacturer provided the user with some important data in a form of table in order

for the user to see the performance of the motor under different conditions, and here are the plots

of these data.


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3.3 Battery:

The battery element is a very important element in this energy system, since PV panels

cannot always supply the power to the system due the shading effect or the weather is cloudy,

according to that the battery should be fully charged in case the PV panels won’t charge it during

the race, and it should contain an enough energy inside it to make the car cross the finish line.in

the other hand the motor inside the system might require a burst of energy, which means that the

energy inside the battery might be extracted in hurry, according to that a high discharge rate

battery is required, because drawing a high current from some batteries might cause an

overheating for some batteries, also how much energy is contained in one unit mass is important

since this will cause an overweight in the car, which will lead to more power consumption, since

the aim of the rice is measure how much energy the PV panel delivered and how much energy

the motor consumed.

The crown goes to the lithium polymer batteries abbreviated li-pol technology among the

other technologies, for a lot of reasons like the watt-hour per kilogram, which means there is a

lot energy stored in a small weight, the high discharge rate, its safe unlike lithium ion batteries

when it contains a lot of energy it might explode, however li-pol might explode if it overcharged,

and it has a greater life cycle degradation rate compared to lithium ion batteries. The voltage of a

single li-pol cell in the range 2.7 volt to 4.23 volts, 4.23 volts will indicate that the battery is fully

charged, and it should be disconnected from the load if the voltage drops to 2.7 volts, because it

cannot be recharged again. However our selected battery has the following specifications.

Table 3.2Battery Specifications

Capacity 5000mAH

Voltage 22.2 V

Discharge rate 35C constant 70C burst

Weight 786 g


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Dimensions 154x50x49mm

As the motor manufacturer implied that the motor will consume a maximum current of

16A, and the battery can deliver a current of 175 A for an hour ten it will be fully drained, and by

consuming a current of 16 the battery can last for 10 hours. As the C rate is a measure of the rate

at which the battery is discharged relative to its maximum capacity.

𝐴𝑀𝑃𝑚𝑎𝑥 = 𝐶𝑟𝑎𝑡𝑒 ∗ 𝑐𝑎𝑝𝑎𝑐𝑖𝑡𝑦

AMPmaxis the maximum current that can be drawn from the battery within hour then it will be

fully drained.

3.3.1Battery Management System:

In order to protect the driver of the car and to prevent the battery from exploding a

battery management system BMS is highly required in this system, and also a critical

requirement for Shell Eco Marathon completion. The BMS mainly consist of over under voltage

protection, overcurrent protection and discharge temperature. Overcharge protection is not

needed because the maximum current the PV panel can supply is 0.6 A which is less than the

number that most manufacturers specify 0.5C [6].

The overcurrent protection will make sure that the discharge rate of the battery is less

than 80% of its rated discharge rate as recommended by the manufacturer to increase the life

time of the module. In order to achieve that the presence of current sensor is necessary in order

to monitor the current of the battery along with comparator, so the comparator changes its state

from low to high as the current exceeds 80%. The current transducer CKSR 50NP is a good fit

for this system because it has a measuring range of -150 to 150A and it should be operated from

a 5 volts source, and has the following parameters.


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Table 3.3CKSR 50NP specifications

Current measuring range ±150 A

Supply voltage 5 V

Sensitivity 12.5 mV/A

Electric offset voltage 0.7mv

The under voltage protection will make sure that if the terminal voltage of the battery

drops below the cut-off voltage then the circuit should trip, because if the battery is drained

further it won’t accept recharging again, for this purpose a voltage divider is used in order to

sense the voltage of the battery, which is connected to a comparator.

The discharge temperature protection will make sure that the battery will work under the

rated temperature; if the temperature is higher the circuit should trip. For this task also a

temperature sensor with a comparator will be used. The temperature sensor LM35 has the

following specification.

Table 3.4LM35 specifications

Precision Centigrade Temperature Sensors

Low impedance output 0.1Ωfor 1 mA load

Low self-heating 0.08 C in still air

Rated for full −55 to +150 C range

The output of all of the above circuits will be connect to an AND gate which controls the

gate of a MOSFET transistor, which will energize the coil of the relay if one of these circuits


32 | P a g e

detect a violations in the rated values. As figure 3.1 shows the circuit diagram of the BMS the

output of each protection circuit is connected to an AND gate which controls the gate of the

MOSFET. If the output of the AND gate is high then the MOSFET will conduct and the relay

will trip the motor. Furthermore the positive terminal of the battery is connected to the normally

connected terminal of the relay (NC) and a small light emitting diode (LED) with a small current

limiter resistor are connected in series with the normally open terminal of the relay (NO) in order

to indicate that the relay trips. The relay in order to operate its needs a 12 voltage source, and by

measuring the coil resistance will be able how much current the relay needs in order to energize

the coil and trip. The freewheeling diode is needed to protect the MOSFET and its impeded with

the MOSFET’s internal architecture.

The BMS board is supplied by a 12 voltage battery according to the Shell Eco-Marathon

completion rules, which is connected to a 5 volt regulator in order to operate the analogue and

the digital IC,s in the board, and they are three potentiometer in order to adjust the threshold

values of the current ,temperature and voltage of the battery. And the used OP-Amps care single

supply OP-AMPS, which requires only 5 Volts as a supply voltage.


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Figure 3. 1 BMS circuit diagram

3.4 Photovoltaic power frame

Photovoltaic cells or solar cells are electric devices that convert the energy contained in

the light into electric energy [6], the used photovoltaic array will charge the battery during the

race, according to the rules the PV system should occupy an area of a 0.17 m2(10 cells of 5*5

inches), the selection was a two modules which are connected in series in order to rise the


34 | P a g e

voltage to be able to charge the battery with a good amount of current even if the panels are

partially shaded. Table 3.5 shows the panel’s specification.

Table 3.5PV panel specification

Open circuit voltage 21.24 V

Short circuit current 0.61 A

Maximum power current 0.56A

Maximum power voltage 18 V

Maximum power 10 W

Connecting two of these PV panels in series will give the system a power of 18 watts and

a voltage of 36 volts. Furthermore connecting them in parallel will assure that the maximum

power voltage of the panels will be slightly higher than the battery voltage, which will allow the

current transfer from the panels to the battery, but if the connection was made in series then the

voltage of the maximum power will be for sure less than or equal to 18 volt, which is less than

the battery voltage and in this case no power transfer will occur from the panels to the battery.

Since the power obtained from the PV system depends on the irradiance, temperature and

the current drawn from the cells. Maximum power point tracker MPPT is needed in order to

extract the maximum power from the PV panel. There are many techniques for maximum power

point tracker, Perturb and observe technique is mainly used for dynamic system, but this

technique require microcontroller in order to implement it. Figure 3.2 shows the maximum

power point tracking algorithm.


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Figure 3. 2 Perturb and Observe algorithm

The microcontroller will be used along with the DC-DC converter in order to implement

the maximum power point tracker; by changing the duty cycle of the boost converter the voltage

and the current of the PV array will be varied, sensing the variation in the current and the voltage

PV panel with the microcontroller will enable the system to detect the point where the maximum

power lies.

The code for the MPPT algorithm was written using C language, and the communication

between the computer and the microcontroller was done using AVR programmer, and the clock

frequency of the microcontroller was raised from 8 MHZ to 20 MHZ using external RC crystal

oscillator in order for the system response faster while the car is moving, so if the old point

where the maximum power occur the system will find the new point so fast. For the analogue to

digital converter ADC the internal 1.1 volts reference was used along with LC filter in order to


36 | P a g e

regulate the reference voltage, and two small capacitor fitters was used in the input of each

channel to reduce the noise in each channel.

The microcontroller offers several techniques for pulse width modulation, however the

best techniques that sweets these application is called the past PWM mode, in this mode the

timer counter counts from the bottom value to the top value each time, and by changing the

values of the top register will be able to change the frequency of the PWM , when the 16 bit

timer reaches the value that is stored in the compare match register it will either set or clear the

output, so by changing the value of the compare match register we will be able to change the

duty cycle.in addition to that this PWM mode allow us to have high frequency unlike other

modes that are limited to a very low range of frequency.

For the 8 bit ADC two channels has been used in order to sense the voltage and the

current of the PV panel, in order to compute the power we have to first sense the current and then

wait till the conversion process end then we sense the voltage and wait till the process finish. The

simulation for the MPPT was done using PROTEUS because it allow us to test the code of the

MPPT, because this code will allow the user to install the hex file which is generated by the

AVR studio in the microcontroller and test the code, in this case the PV system was represented

using a fixed DC source, however the code does not allow you to specify the power of the DC

source, but the system was able to extract more than 1K A in order to charge the battery as the

simulation result will show, and in this case since the source voltage source is constant the

MPPT system will just seeks more current because more current means more power, in addition

to that the same schematic will be used in the PCB design, since the library of this code is reach

with most of the footprint packages of most of the popular electric devices. And here is the

schematic of the MPPT system.


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Figure 3. 3 MPPT circuit diagram

Figure 3. 4 The generated PWM signal from the MCU


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As the above graph shows that the PWM signal from the microcontroller is varying in

order to search the point of the maximum power from the DC source.

Figure 3. 5 MPPT charging current

In the above graph the maximum charging current is 1.0606 KA, which is clearly indicate

that the system is maximizing the charging current since the DC voltage is constant unlike the

PV panel voltage which may change due to irradiance, temperature and shading effect [8].

3.5 Photovoltaic cells modeling

Modeling the PV panels is very important in this project, because most of the parameters

in the solar cell datasheet is with irradiance of 1kw/m^2, and knowing the change in the behavior

or the response of the system during different conditions is very important, also to make sure that

the energy system will be able to deliver the power to the load. The selected temperature for the

simulation will be 25 C according to the weather forecasting in the eco Marathon’s hosting

country which is Malaysia, where the competition will be held in May. [9]


39 | P a g e

The Model of the PV panels has been parameterized by using the short circuit current and

the open circuit voltage of each cell, this has been done by taking a sample cell form the module

and then test it using the multi-meter to obtain the short circuit current and the open circuit

voltage, then a variable resistor with a ramp function in the control input of the block will control

the resistance in ohm of the block, in order to obtain the I-V and the P-V characteristic of the PV

panels.

By using the X-Y scopes , the output I-V and P-V curves were obtained after the simulation has

been run four times, each time the irradiation has been changed in order to obtain I-V and P-V

curves under different irradiations depending on Malaysia irradiation nature during the eco

marathon shell competition which will be held in May [10].

Figure 3. 6 PV Panel system


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Figure 3. 7 I-V Curve with different irradiations

Figure 3. 8 P-V curve with different irradiations

0 5 10 15 20 25 30 35 400

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Voltage ( V)

Curr

ent

(A)

1 KW/m2

0.8KW/m2

0.6 KW/m2

0.5 KW/m2

0 5 10 15 20 25 30 35

2

4

6

8

10

12

14

16

18

20

Voltage (V)

Pow

er

(W)

1KW/m2

0.8KW/m2

0.6KW/m2

0.5KW/m2


41 | P a g e

CHAPTER 4:DESIGN OF DC-DC CONVERTER

4.1 DC-DC converter

DC-DC converters divides mainly into two types, linear regulators and switched-mode

converters, where linear regulators can only output at lower voltages from the input, but the

problem is that this type of DC-DC converters are inefficient when the voltage drop is large

where this inefficiency wastes power and needs more expensive and larger components. While

switched-mode DC-DC converters are converters which converts unregulated dc input voltage

into a controlled dc output at a desired voltage level.

4.1.1 Background information:

DC-DC converters have mainly three types, each type has different characteristics, modeling

and outputs, where each type can be used in different applications depends on the purpose of the

user[11].

1- Buck converter ( Step-down converter ): Converts dc input voltage from high voltage

level to a lower voltage level, it has some widely use applications (Example: In regulated

dc power supplies and dc motor speed control).

2- Boost Converter ( Step-up converter ): Converts dc input voltage form low voltage level

to a higher voltage level, this type of converters has some useful applications (Example:

In Regulated dc power supplies and the regenerative braking of dc motors).

3- Buck-Boost Converters (Step-down/Step-up): Converters which is structured by

combining both buck and boost converters, where this type of dc converters, converts a

dc input voltage from one level to another depending on the desired voltage output level,

whether step-up or step-down, an applications for the Buck-Boost converters are:

(Regulated dc power supplies).

As we are looking for a suitable DC-DC converter to our charging system for the battery of the

solar car, we are going to choose the boost converters, because I-V Characteristics of the PV

panel its highly non-linear and it depends on the radiation and temperature, so we need to vary

voltage of the PV panel in order to get the maximum power from the PV panel by varying the

voltage which can be varied by varying the duty cycle[12].


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4.1.2 Analysis and Calculations:

Boost Converter has two states that will be analyzed and studied to get all the equations of the

boost converter, that will be used in the design of the boost converter , simulation and the the

implementation.

4.1.2.1 design parameters :

In order to get less harmonic noise than other switching converters, the best way to operate in the

CCM (continues current mode )[13], then to obtain Lmin and Cmin:

To find Lmin :

𝐿𝑚𝑖𝑛 = (1−𝐷)2𝐷𝑅

2𝑓 (4.1)

To find Cmin :

𝐶𝑚𝑖𝑛 = 𝐷

𝑅𝑓 ∆𝑉𝑜𝑉𝑜

(4.2)


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4.1.2.2 Proof equations (4.1) and (4.2):

Table4. 1 Proof of the equations (4.1) and (4.2)

Lmin Proof , equation (4.1) Cmin Proof , equation (4.2)

𝐼𝐿𝑚𝑖𝑛 = 𝐼𝐿 −∆𝑖𝐿

2 (4.3)

𝐼𝐿 = Is (4.4)

Vs Is = Vo Io (4.5) , since (𝐼𝐿 = Is )

Vs𝐼𝐿 = Vo Io (4.6)

IL= 𝑉𝑜2

𝑅 𝑉𝑠(4.7)

IL =

𝑉𝑠

(1−𝐷)2𝑅(4.8)

∆𝑖𝐿 = 𝑉𝑙

𝐿∆t (4.9)

𝐼𝐿𝑚𝑖𝑛 = 𝐼𝐿 −∆𝑖𝐿

2 (4.10)

𝐼𝐿𝑚𝑖𝑛 = 𝑉𝑠

(1−𝐷)2𝑅 -

𝑉𝑠

2𝐿∆T (4.11)

For CCM , 𝐼𝐿𝑚𝑖𝑛 >= 0

Then ,

∆Q= 𝑖𝑑𝑡 (4.12)

∆𝑄 = 𝐼𝑜∆T = 𝑉𝑜

𝑅𝐶∆T (4.13)

∆𝑉𝑜

𝑉𝑜=

𝐷

𝐶𝑅𝑓 (4.14)

Then,

𝐿𝑚𝑖𝑛 = (1 −𝐷)2𝐷𝑅

2𝑓

Cmin = D

Rf ∆𝑉𝑜

𝑉𝑜


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4.1.3 Boost converter simulation using MULTISIM

The designed boost converter was simulated by using the Multisim software with the same

values was found and calculated in the design part.

4.1.3.1Multisim-Simulation :

Boost converter was simulated using Multisim software in order to get results and compare them

with the results of the Protues software simulation, to ensure that the results are reasonable and

they make sense , where this sensitivity is based surely on the calculations made for the

designed boost converter design.

4.1.3.2 Schematic circuit:

Figure 2.1. shows the designed boost converter were simulated using Multisim, the figure

shows the schematic circuit developed in order to simulate it and get the output voltage and

current needed according to our design which is based on the load requirements that will charge

the battery in a specific time.

Figure4. 1Schematic circuit design using Multisim software

V1

11 V

L1

20.6µH

C1

302.6µF

R1

2Ω

V2

25 V

D1

1N4001G

Q1

IRF1010N

V3

5V -0V10kHz

XMM1

XSC1

A B

Ext Trig+

+

_

_ + _

XMM2

XMM3

XMM4


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4.1.3.3Design components:

The design of the DC-DC boost converter was done to maximize the output voltage in order to

have larger voltage output than the battery voltage , were the cases of full shading or partially

shading on the PV panels was taken into considerations to have that larger voltage than the

battery voltage even in these case.

- Capacitor : 302.6 uf

- Inductor : 20.6 uH

- Transistor : IRF1010N

- Diode : 1N4001G

- Resistors : 2 ohm

4.1.3.4Switchtype :

Switches are very important in this project, because they are used in DC-DC converters

in order to change the level of the output voltage and current, which is very important in reaching

the point where the maximum power can be extracted from the PV panels, and this point has a

corresponding voltage and current. In power electronics systems we are mostly concerned about

the efficiency, so the job of passing a current and voltage dropping is mostly achieved by

switches, manly ideal switches introduce zero voltage drop when the switch is on, which means

zero resistance, and doesn’t pass any current when the switch is off, in other words zero

conductance, and when we operate the switch on both modes ON and OFF, it will act like a

resistance that’s manly depends on the duty cycle[14].

MOSFET is the popular for most of the power electronics application for low power

application and for high frequency application. It’s basically a three terminal device drain, source

and gate, the gate and the source terminals are the control terminals, also the drain and source

terminals are the power terminals. The gate terminal is insulated from the rest of the device;

hence it does not draw no steady state current. So when the gate terminal of the MOSFET is

charged to a specific voltage with respect to the source it will start conduction by creating a

channel between the source and drain. The type of MOSFET used in most power electronics


46 | P a g e

application is the enhancement type, which means that the device will start conduction when the

voltage across the gate and the source is more than the thread hold voltage of the MOSFET that

specified in the data sheet (Vth), and the device will operate in the cut of region when the gate to

source voltage is zero. [14].

4.1.3.4Results :

Using Multisim software in order to simulate the designed boost converter design and get results

and as the boost converter is considered as a switched mode converter, figure 4.2 shows how

PWM generation done by using the Multisim software it was easy to generate PWM for the

transistor switch, by using Bipolar voltage source which can generate PWM for the switch gate.

Figure4. 2PWM generated by using Bipolar voltage source


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CHAPTER 5: ENERGIZING SYSTEM IMPLEMENTATION , TESTING

and VALIDATION

5.1 Practical implementation of the electrical system

Implementing the desired system which was shown by design and theory in the previous

sections is the main target of this part, in which the implementation of the system practically will

verify all the results and theories that has been considered and also to get a results as well for the

whole system.

5.1.1 First stage of implementation:

In this stage the system were tested in order to charge the 22.2 LI-PO battery and we

successfully got a charging current of 0.5A which is almost the MPPT current.

Figure 5.1practical implementation


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In this stage of implementation , the system was ready to test manually , where the duty cycle of

the MPPT were varied manually as the current and voltage sensing still not applicable in the

system notifying from the above picture the Multi-meter to the right reads the charging current

which is 0.547 A, and also the multi-meter to the left outputs the output voltage of the boost

converter, which is the voltage that will be imposed across the battery in order to charge the

battery. And the board to right is the control circuit that contains the MC and the board to the left

contains the power circuit that contains the boost converter. In this implantation the duty cycle

was varied using a potentiometer as mentioned previously , in other words the MPPT was

tracked manually. And the following picture contains the PWM signal from the microcontroller.

Figure 5.2. PWM signal from the Microcontroller


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5.1.2. Second Stage of implementation:

The 2nd

stage of the system implementation was done by creating a prototype for the boost

converter and its microcontroller (MC), by designing and building the boost converter in the

upper level and the microcontroller in the lower level of the prototype. The Upper level includes

all the components needed to build the boost converter circuit which is made up from the same

components used and calculated in the first stage of the implementation. The lower part of the

prototype represent the microcontroller circuit which generates PWM to the gate drive of the

boost converter and also it has been made up from the same components calculated and used in

the first stage of implementation.

Figure 5.3 1) The Upper level of the designed prototype boost converter is the boost converter circuit. 2) The lower level

of the prototype is the microcontroller circuit.


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5.1.3 The Third stage of implementation (PCB Stage):

Printed circuit board abbreviated PCB is electrically connected electronic components using the

copper pathways inside the copper, and it’s very essential for the circuit establishment, all of the

boards in this project have been done in PCB, because bread boards cannot be used because it

cannot withstand high currents, and using the striped boards in the prototype causes the

connections to get loose with time. The program that has been used to make the PCB’s was

PROTEUS ARES. The control circuit and the power circuit for the MPPT circuit has been done

in two separate boards, because doing them in one board means double side board, which is very

difficult when using the old method by using laser printer with photo resist.

Figure 5.4 Printed circuit board abbreviated PCB

The control board contains the 5 volts supply that will power the MCU and even the

analogue IC’s in the power circuit board, furthermore the traces was done on the bottom copper

side of the board, and the bottom copper surface with used also as a ground for the hole board, to

make the PCB possible to be done in one side board, because of too many connections. The

original pads of the components has been modified because they are very small, so instead of

using the circular pads a DIL type pads was used, because it will also give a lot of area around

the pad itself which will allow nesting.


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Figure 5.5control circuit for MPPT PCB

In the power circuit of the MPPT also the bottom copper used also as ground, and anew

package has been made for the inductor, current sensor and the capacitors. Since this power

circuit will handle a current of 0.65 A which is the short circuit of the PV system the traces width

should be very high.

Figure 5.6Power circuit of the MPT system PCB


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5.2 Testing :

Testing the system has passed through different stages, for instant in order to fully make

sure that the MPPT code a special circuit has been designed in order to make sure that the code is

fully functioning, and the final stages was the comparison between the commercial device for the

MPPT. Most of the test for the MPPT system has been done when the panels are static, while

using multi-meters for measurement.

The first stage was to test the system without making the MPPT system fully automatic,

in other words the change in the duty cycle in the MPPT algorithm was done manually by using

a potentiometer with the microcontroller, the microcontroller will read the voltage across the

potentiometer and it will send the duty cycle of the PWM signal proportional to the voltage, in

other words the tracking of the maximum power form the PV was done manually.

Figure 5.7phase two of testing

The second stage was to make sure that the MPPT algorithm is fully functioning, this

testing has been done by connecting two potentiometers to the ADC channels of the MCU, these


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two potentiometers will act like the current sensor and the voltage sensor from the PV panel side,

so by changing the values of the current and the voltage the change in the duty cycle was

observed.

Figure 5.8Phase two of the testing process

Figure 5.9phase two results

The oscilloscope was divided into three areas, the first area reads the voltage of the first

potentiometer which represents the current, the second area reads the output of the second

potentiometer which represent the voltage of the PV and the third channel was for the PWM


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signal, any change in the potentiometer voltage will lead to a change in the duty cycle, if the

change is positive then the duty cycle will increase and vice versa, except when one of the output

of the potentiometers is zero then varying the other one won’t change the duty cycle because in

this case the power is zero. However this test was very important because what has been noticed

is that sometimes the duty cycle might increase more that the frequency of the PWM signal

itself, so accordingly an if statement was added to the code in order to prevent that from

happening.

The final stage of testing was done on the PV panels, and to observe how much the

MPPT was able to extract form the panel, and the commercial MPPT also was tested in the same

conditions in order compare between both systems. The results were taken in different timings to

have a different outputs and under different irradiation situations, were the testing was between 3

pm and 5 pm.

Figure 5.10 Testing the finalized version of the system


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The Results of testing the system was taken in different timings and under different sun

irradiations in order to have different outputs and to get an idea about the system effeciency

through out testing the system and get outputs from different situations that may vary from best

condition of sun irradiation were the sun is clear and providing the PV pannels perfectely, to

another situation where the sun maybe shaded by a certain surrounding objects or even by

clouds. The next figure (5.11) will show these diferent readings on different timings as

mentioned prevousely, and by that test the readings was showing that the output power taken

from the designed system was 19W by the time of 3 pm having an output current of 0.528 and an

output voltage of 36V.

Figure 5.11 (1) The first reading shows the output current from the charging system where it has been taken nearly at 3

pm. (2) The 2nd

reading shows different output and input currents were the time was nearly 4 pm. (3) The 3rd

and the last reading shows an output and input currents taken at nearly 5 pm.

5.2.1 Designed boost converter VS Commercial boost converter:

The results of the implemented boost converter was compared with another commercial boost

converter in order to have an idea about the effciency of the designed and implemented boost

converter by comparing its results with a commecial product that can deliver the same required

output voltage and current.


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Table 5.1Comparison between The designed boost converter and a commercial boot converter product

The designed boost converter

product

Commercial boost converter

product

Current (A) 0.528 0.601

Voltage (V) 36 36

Power (W) 19.008 21.636

As the results in the table 5.1 shows a preference for the commercial boost converter at

the expense of the designed boost converter, where the commercial one gives an output power of

21.636W and the designed boost converter gives 19.008W, and this variation refers to some

factors that can affect the output of each product, one of the reasons that can make this slight

deviation is the factor of irradiation, where not exactly the same sun irradiation is applied in both

cases and not the exact timing of testing was done which is surely affected the output of the

product. Also the selection of the design components can make a difference in the output power

of each product.


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5.3 Validations:

During designing , Implementing and testing , the rules of the Shell Eco-Marathon were

taken into considerations to produce a valid output that can meet these rules and limitations , and

the following table (5.1) will review some of these limitations and how the design and the

implementation met these rules of the competition , where these rules and limitations varies

between some critical points and from different perspectives , the main rules are for the

competition centred around three main subjects. The first subject and the most important thing in

the competition is the safety, and under the slogan of “ Safety First “ as this subject is the main

import thing ever and always, not only during the race but all the time as this subject saves both

individuals and surrounding areas, the organisers and the sponsors of the Shell Eco-Marathon put

a very strict rules for the safety. The design also was limited by some rules which will be shown

in the following table (5.1) where some of these rules goes under the rules of safety. Finally, one

of the most important rules that were taken into calculations during car designing , are the

energizing rules , which limits the type of energy source and the electric propulsion. All of these

rule and limitations will be compared to Qatar’s University 2nd

generation solar car ( Gernas 2 )

design in the next table (5.2) :

Table 5.2Comparing the Shell Eco-Marathon rules to the designed car ( Gernas 2 ) [15]

Shell Eco-Marathon rules

No. Subject Application

a. Safety Rules :


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1. Radio Communication : The

communication between the driver and the

team organizers are allowed as long as the

communication tool is “ hands-free “.

Figure 5. 12 the driver and the team will be provided by the

walkie talkies

2.

Horn :Horn is very important to install in

the car and to be used by the driver while

overtaking during the race.

Figure 5. 13 The Horn is installed and positioned on front of

the car, so the sound of it will be very clear and load for the

others in case of overtaking or for different needing.


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3.

Side-view mirrors : Driver must have a

full vision on the road and have to use the

side-view mirrors that can allow him get

better view while overtaking.

Figure 5. 14 The car is provided by two side mirrors to enable

the driver to have a full vision on the road and in case of

overtaking as well

4.

Breaks : Breaking is one of the most

important tools that have to be installed in

terms of safety and as one of the main

tools in any normal vehicle, so that it can

be used in case of emergency or to slow

down.

Figure 5. 15 Braking system is provided in the car to allow the

driver to stop or to decelerate in any needed case

5.

Car weight : The car weight must not

exceeds 140 kg ( not including the driver )

Figure 5. 16 The car was weighted to be 36 kg (without the

driver)


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6.

Helmet and safety goggles: Driver safety

is taken very highly required and strictly

needed to be exist, and that was notified

by putting a rule that states that the full-

face and three quarter style helmets and

safety goggles are required for both driver

and reserve driver.

Figure 5. 17 Helmets are available for both the driver and the

reserve driver.

7.

Diver clothing and comfort: Racing suite

(fire retardant) , gloves and shoes are

very highly recommended to be

provided for both driver and the reserve

driver. Also a ventilation system have to

be installed inside the car to provide the

driver with a good surrounding

temperature inside the car and to avoid any

heat stress for the driver.

Figure 5. 18ventilation system is provided in the car to have

an comfort area for the driver


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Figure 5. 19 The suite and the cloves for the driver for the

safety of the driver

8. Fire extinguisher: The car must

beprovided with a fire extinguisher of type

(ABC or BC type) and the driver have to

be trained on how to use it in case of

emergency.

Figure 5. 20 The car is provide with a fire extinguisher which

is usable and valid to use by the driver in case of emergency.

9. Seat built :The seat built of the drive must

be installed with a seat built for the driver

safety that can protect the drive in case of

emergency and it is very essential and

important to use it during the race.

Figure 5. 21 Seat built is provide with the seat to be used by


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the driver while racing

b. Vehicle Design:

1.

3 or 4 Wheels vehicle:According to design

limitations of the competition, the vehicle

must be designed to be with 3 or 4 wheels

only.

Figure 5. 22 1) 2 Wheels in front side. 2) 1 Wheel in Back side

2.

Body Stability :The body of the car must

be stable and not to be affected by any

weather changing like wind and rain for

example, so that it will not be dangerous

to other Team members.

Figure 5. 23 The car was tested many times and in different

situations in order to have the best stability of the body in

order to get the best body stability on the road.


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3.

Cover of the energy compartment: Easy

access to any energy compartment

(Battery ,Mottor , Charger , ect.) have to

be applied in the car for any inspection or

maintenance.

Figure 5. 24. Energy compartment that contains the Battery,

Motor and the charger is very easy to access by a hard

doormade from plastic sheet.

4. Chassis solidity :The Chassis must be very

strong and hard to protect the driver in

case of accidents.

Figure 5. 25 the Chassis of the car body which is made of

Aluminum bars and coulumns and it is very hard and strong

enough to protect the driver in case of accidents

5.

The isolation of the Energy storage

system:any component of the Energy

storage system must be isolated

completely from the driver’s

compartment, for example ( Batteries,

Charger, Motor and the Electrical

connections ).

Figure 5.26 The Electrical Energy system compartment,

Includes The Motor, Batteries , charger and the electrical

conections


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6. Vehicle access : The car must have an

easy way to access and also to exit, so the

driver can access and vacate the car within

10 seconds.

Figure 5. 27 A door made of a plastic transparent sheet with a

dimensions of ( X ) makes the way easy for the driver to

access and exit from the vehicle in both normal and

emergency situations

7. Emergency shut-down: An Emergency

system provides a bottoms from both

interior and exterior sides of the vehicle

that can be pressed in cases of emergency

by the driver or by the assistance team to

shut-down the system.

Figure 5. 28 Two bottoms for emergency shut-down which

can be used by the driver or any assistor in the emergency

cases

8. Braking :The vehicle must be provided by

an activated braking system with

independently activated brakes one for

the front side wheels and the other for

the rear side wheels.


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Figure 5. 29The car is provided by a two separated braking

systems 1) Braking system for the rear wheels and 2) another

braking system for the front wheel

c. Energy Sources:

1.

Vehicle Electrical system: The rules put a

safety margin to the output voltage of the

vehicles, so that the maximum voltage on

board of the vehicle must be below 48v

nominal and 60v maximum.

Figure 5. 30 The out put voltage is within the margin given by

the rules of the competition, the system output is tested to be

about 24v

2.

Battery: Batteries must be Lithium-

polymer based batteries with a battery

management system (BMS) in order to

shut-down in case of overvoltage , over

current and over temperature.

Figure 5. 31 The Battery used in the system of the car

energizing is Lithium-polymer based with a BMS system

provided in case of emergency .

3.

Solar cells: The solar cells must a surface

area less than 0.17 m2 ( 10 cells of 5X5

inches. )

Figure 5. 32 The solar panels used in the car to recharge the


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batteries are within the size of 0.17 m2

4. Motor : it is allowed to use up to 2 electric

motors with a controller.

Figure 5. 33 One motor of 22V rated voltage has been used in

the car


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CHAPTER 6: CONCLUSION AND RECOMMENDATIONS

6.1Conclusion

At the end of this report, during the implementation of the system that is needed for our

application for shell Eco marathon car .Implementing the first stage for our system was a

challenge for us .However, with our hard work we had done it successfully .The system has

been simulated by different software’s such as Proteus Software andMultism .We have got

different responses to the boost converter . Moreover, we have implemented our system on the

breadboard, prototype model and PCB, where it has been connected it to the real solar panels

where we had noticed the boost converter working successfully and then it was compared to

another commercial boost converter and we have got a results from the test and it was validated

as well. The system was simulated and implemented based on the Shell Eco-Marathon rules and

limitations, were these rules and limitations were taken into considerations and calculations from

the first moment of this project and till the end of it. The implementation of the project was

divided into two main parts, where the team was divided into two sections, the first team was

working on the energy and electrical system implementation and to provide the car with the best

efficient system that could be done, which was the main part of the senior design project. And

the second team was mainly responsible for building the mechanical part of the car, where the

body design and implementation should be done. However this division of two teams didn’t

mean a full separation of work, where the two parts of work could not be done without the other

and the interference and collaboration in work was a must to end the project in the best way and

to get the best output needed.

6.2 Future work and Recommendations

An improvements on the car can be done in future, where more technology items can be

added to it, by putting some LCDs which can display some details of the car and the race, like

the consumed power, the battery charging level, the motor speed and a GPS system. Also the

weight of the car can be reduced by having a different material for the body of it and by selecting

lighter components, like the motor, battery and the PV cells, which can be very effectively on the

subject of efficiency improving, where lighter weight can offer less friction.


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REFFRENCES

[1] ExxonMobil. (2013) The Outlook for Energy 2013: The View to 2040. [Online].

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http://www.shell.com/global/environment-society/ecomarathon/about/history.html

[3] Samer Sai,Sami Al-Shurman,Ahmad Ibrahimi, A. AbdulaAziz,M.Hellabi,Farid Touwti

Alnunu, ""Design of Qatar University's First Solar Car for Shell Eco-Marathon Competition

," in First International Conference on Renewable Enegeies and Vehicular Tech., Doha,

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[4] Steel City Robotics. ( 2013, May) Mechanical Considerations. [Online].

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content/uploads/2011/05/mechanical_considerations.pdf

[5] RCHELICOPTERFUN. (2008) RCHELICOPTERFUN. [Online].

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[6] (2009, may) rovingnetworks. [Online]. www.rovingnetworks.com

[7] MIT students. (2008, December ) mit.edu. [Online].

mit.edu/evt/summary_battery_specifications.pdf‎

[8] Dave Freeman. (2010, november) texasinsturment. [Online].

http://www.ti.com/lit/an/slva446/slva446.pdf

[9] (2008) climatemps. [Online]. http://www.malaysia.climatemps.com/

[10] Solar Radiation Map. [Online]. http://161.142.139.60/solar/menu.html

[11] M., Tore , U., & William , R. Ned, "switch-mode DC-DC Converters," in Power

electronics. United States of America: John Wiley and sons, Inc., 2009.

[12] A., & Salimi, M. Zakipour, "On backstepping controller design in buck/boost dc-dc

converter," in International conference on electrical, electronics and civil engineering,

2011.

[13] Linear Technology Magazine Circuit Collection, Volume IV. [Online].

http://cds.linear.com/docs/Application%20Note/an84f.pdf

http://www.exxonmobil.com/corporate/files/news_pub_eo2013.pdf

http://www.shell.com/global/environment-society/ecomarathon/about/history.html

http://www.steelcityrobotics.org/wp-content/uploads/2011/05/mechanical_considerations.pdf

http://www.steelcityrobotics.org/wp-content/uploads/2011/05/mechanical_considerations.pdf

http://www.rchelicopterfun.com/rc-lipo-batteries.html

www.rovingnetworks.com

mit.edu/evt/summary_battery_specifications.pdf?

http://www.ti.com/lit/an/slva446/slva446.pdf

http://www.malaysia.climatemps.com/

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[14] V Ramanarayanan. (2005, Nov.) Course Material On Switched Mode Power Conversion.

[15] Norman Koch, "Official Rules 2013," Shell Eco-marathon®, p. 37, 2013.

[16] (2011, Dec) “Photovoltaics”. [Online]. http://en.wikipedia.org/wiki/Photovoltaics

[17] (2011, Nov.) Detailed design review report of Solar car for American Solar challenge.

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http://eng.fsu.edu/me/senior_design/prev.html


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Appendix

Appendix A

Shell Eco-marathon®

Official Rules 2013 CHAPTER I


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Appendix A




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Appendix A




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Appendix A




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Appendix B


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Appendix C


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Appendix D

The code using C :

#include<avr/io.h> #include<avr/delay.h> voidPWM_in() TCCR1A|=(1<<COM1A1)|(1<<COM1B1)|(1<<WGM11); TCCR1B|=(1<<WGM13)|(1<<WGM12)|(1<<CS10); ICR1=1599;// frequency of oscillation OCR1A=800;// initall duty cycle DDRB=(1<<PB1);// output of the PWM DDRD=0xff; PORTD=0xff;// led on voidADC_int(void) ADCSRA|=(1<<ADPS2)|(1<<ADPS1)|(1<<ADPS0);// Set ADC prescalar to 128 - 125KHz sample rate @ 16MHz ADCSRA|=(1<<ADEN);// Enable ADC uint8_tADC_Start(uint8_tchannel) DIDR0=0x00; ADMUX=(ADMUX)&0x10; if(channel<=0x07) ADMUX=(ADMUX)|channel;//choose channel number ADMUX|=(1<<REFS0);// Set ADC reference to AVCC ADMUX|=(1<<ADLAR);// Left adjust ADC result to allow easy 8 bit readin if(ADSC!=1) ADCSRA|=(1<<ADSC);// Start A2D Conversions while((ADCSRA&0x10)!=0x10) DIDR0=0xff; returnADCH; intmain(void) uint8_tvoltage; int8_tcurrent; uint16_tpower; uint16_toldpower; PWM_in(); ADC_int(); oldpower=0; while(1) current=(-1*ADC_Start(4));// current sensor is connected to channel zero voltage=ADC_Start(5);//voltage sensor is connected to channel 1 power=current*voltage; if(power>oldpower) if(OCR1A<=1599) OCR1A=OCR1A+100; elseif(power<oldpower) if(OCR1A!=0) OCR1A=OCR1A-100; oldpower=power;


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Appendix E


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Appendix E


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Appendix F

Documents

Graduation Project _Final Version_Mus'Ab Samarah