1421_ABDULRAHIMBINJUSOH2011

8/3/2019 1421_ABDULRAHIMBINJUSOH2011

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UNIVERSITI TEKNOLOGI MALAYSIA

NOTES : * If the thesis is CONFIDENTIAL or RESTRICTED, please attach with the

letter from the organisation with period and reasons forconfidentiality or restriction.

PSZ 19:16 (Pind. 1/07)

DECLARATION OF THESIS / UNDERGRADUATE PROJECT PAPER AND

COPYRIGHT

Authors full name : ABDUL RAHIM BIN JUSOH

Date of birth : JULY 31ST 1989

Title : CHARGE CONTROLLER DESIGN FOR MAXIMUM POWER

POINT TRACKING APPLICATION

Academic Session : 2010/2011

I declare that this thesis is classified as :

I acknowledged that Universiti Teknologi Malaysia reserves the right as follows :

1. The thesis is the property of Universiti Teknologi Malaysia.2. The Library of Universiti Teknologi Malaysia has the right to make copies

for the purpose of research only.

3. The Library has the right to make copies of the thesis for academicexchange.

Certified by:

SIGNATURE SIGNATURE OF SUPERVISOR

890731-11-5467 PROF DR ZAINAL BIN SALAM

(NEW IC NO. /PASSPORT NO.) NAME OF SUPERVISOR

Date : 15th MAY 2011 Date : 15th MAY 2011

CONFIDENTIAL (Contains confidential information under the

Official Secret Act 1972)*

RESTRICTED (Contains restricted information as specified bythe organisation where research was done)*

OPEN ACCESS I agree that my thesis to be published as onlineopen access (full text)


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I hereby declare that I have read this thesis and in my opinion this thesis is

sufficient in terms of scope and quality for the award of the degree of

Bachelor of Engineering (Electrical)

Signature : ....................................................

Name of Supervisor : Prof Dr Zainal bin Salam

Date : 15th

May 2011


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CHARGE CONTROLLER DESIGN FOR MAXIMUM POWER

POINT TRACKING APPLICATION

ABDUL RAHIM BIN JUSOH

A report submitted in partial fulfillment of the

requirements for the award of the degree of

Bachelor of Engineering

(Electrical)

Faculty of Electrical Engineering

Universiti Teknologi Malaysia

MAY 2011


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I declare that this thesis entitled Charge controller design for maximum power point

tracking application is the result of my own research except as cited in the references.

The thesis has not been accepted for any degree and is not concurrently submitted in

candidature of any other degree.

Signature : ....................................................

Name : Prof Dr Zainal bin Salam

Date : 15th

May 2011


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Dedicated, in thankful appreciation for support, encouragement and understanding to my

beloved mother, father, brothers and sisters, lecturers and friends.


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ACKNOWLEDGEMENT

In preparing this thesis, I was in contact with many people, researchers,

academicians, and practitioners. They have contributed towards my understanding and

thoughts. First and foremost, I would like to express my heartily gratitude to my

supervisor, Prof. Dr Zainal bin Salam for his proposal, guidance and enthusiasm given

throughout the progress of this project. I also very thankful to Dr David C. Hamill for

spare his time replying my email, giving comments and motivations for me to complete

this study. Without their continued support and interest, this thesis would not have been

the same as presented here.

My appreciation also goes to my family who has been so tolerant and supports

me all these years. Thanks for their encouragement, love and emotional support that they

had given to me.

My fellow postgraduate students should also be recognised for their support.

My sincere appreciation also extends to all my colleagues and others who have

provided assistance at various occasions. Their views and tips are useful indeed.

Unfortunately, it is not possible to list all of them in this limited space. I am grateful to

all my family members.


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ABSTRACT

Photovoltaic (PV) power generation has raise attention around the world as the

best electric source to replace the conventional energy source. It has growing fast due to

green energy demand as people now are become more concern about environment

especially on global warming issue. Because of this, manufacturers, scientists and

engineers are working hard to make the use of photovoltaic system to become more

efficient. One of big initiative is the introduction to maximum power point tracking

(MPPT) circuit to enhance the operating power used on photovoltaic circuit. There were

various inventions and designs for maximum power point tracking circuit being

introduced to make the MPPT to be simpler, faster and cheaper. One of the MPPT

circuit is the circuit proposed by David C. Hamill and Yan Hong Lim in their article

Simple maximum power point tracker for photovoltaic arrays. The maximum power

point tracker used is simple fast and has been proving efficient to track the maximum

power point. The components used in the circuit is just simple analogue and digital

device connecting with logic gate which make it cheaper compared to other maximum

power point tracker circuit. The purpose of this study is analyse and simulate the MPPT

circuit to prove the ability of the referred circuit. The analyzing process will cover the

MPPT parameters, mathematical algorithm involved and the components used in the

design. The simulation then will be done using Casdence Orcad Capture. From the

simulation, several waveforms can be observed and compared to result in the article. The

discussion on waveforms obtained is done next to prove the design and the

recommendation to improve this study was proposed.


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ABSTRAK

Penjanaan tenaga elektrik menggunakan melalui photovoltaik sebagai sumber

tenaga baru bagi menggantikan sumber tenga konvensional telah menarik perhatian

dunia. Ia berkembang pantas berikutan permintaan terhadap sumber bersih kerana

masyarakat mula mengambil berat terhadap alam sekitar terutama terhadap isu

pemanasan global. Oleh sebab itu juga, para saintis, jurutera dan pengeluar berusaha

untuk membolehkan penggunaan system photovoltaic yang lebih efisien. Salah satu dari

usaha adalah penggunaan litar pengesan titik kuasa maksimum (MPPT). Terdapat

pelbagai rekaan dan ciptaan telah diperkenalkan untuk menjadikan litar MPPT ini

berfungsi dengan lebih senang, pantas dan murah. Salah satunya ialah litar yang

diperkenalkan oleh David C. Hamill dan Yan Hong Lim dalam artikel mereka Simple

maximum power point tracker for photovoltaic arrays. Komponen yang digunakan

dalam litar ini adalah peranti asas analog dan digital yang disambung dengan get logik.

Kajian ini dilakukan adalah untuk menganalisa dan menjalankan simulasi terhadap litar

tersebut. Proses analisa melibatkan persamaan matematik yang terlibat dan komponen-

komponen yang digunakan dalam litar. Proses pula dijalankan dengan dengan

menggunakan Casdence Orcad Capture. Daripada proses simulasi itu, beberapa bentuk

gelombang akan dapat dilihat dan dibandingkan dengan hasil simulasi dari artikel.

Perbincangan terhadap gelombang yang diperoleh kemudiannya dijalankan dan

beberapa cadangan untuk menjadikan kajian ini lebih baik juga diusulkan.


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TABLE OF CONTENTS

CHAPTER TITLE PAGE

DECLARATION ii

DEDICATION iii

ACKNOWLEDGEMENTS iv

ABSTRACT v

ABSTRAK vi

TABLE OF CONTENTS vii

LIST OF TABLES x

LIST OF FIGURES xi

LIST OF ABBREVATIONS xiii

1 INTRODUCTION

1.1 OVERVIEW 1

1.2 OBJECTIVES 2

1.3 SCOPE OF STUDY 2

1.4 METHODOLOGY 3

2 LITERATURE REVIEW

2.1 PHOTOVOLTAIC

2.1.1 INTRODUCTION 52.1.2 PHOTOVOLTAIC GENERATION 6

2.1.3 PV CELL EQUIVALENT CIRCUIT 9

2.2 MAXIMUM POWER POINT TRACKING

2.2.1 INTRODUCTION 11


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2.2.2 MPPT CHARGE CONTROLLER 11

2.2.3 PARAMETERS IN MPPT 13

3 MPPT CHARGE CONTROLLER CIRCUIT

3.1 INTRODUCTION 15

3.2 CONTROL EQUATION 15

3.3 CIRCUITS COMPONENT AND FUNCTION

3.3.1 INTRODUCTION 20

3.3.2 SOLAR ARRAY 21

3.3.3 CONTROLLER

3.3.3.1 VOLTAGE FOLLOWER 22

3.3.3.2 VOLTAGE INVERTER 25

3.3.3.3 ANALOG MULTIPLIER 27

3.3.3.4 DIFFERENTIATIORS 29

3.3.3.5 VOLTAGE COMPARATORS 31

3.3.3.6 XOR GATE 32

3.3.3.7 D FLIP-FLOP 33

3.3.4 POWER STAGE

3.3.4.1 INTRODUCTION 35

3.3.4.2 BLOCKING DIODE 35

3.3.4.3 CHARGING/DISCHARGING

CAPACITOR

36

3.3.4.4 BUCK CONVERTER 36

3.4 CIRCUIT OPERATION 38

4 SIMULATION RESULT AND DISCUSSION

4.1 INTRODUCTION 41

4.2 ORCAD CAPTURE 41

4.3 ORCAD CAPTURE SIMULATION 42

4.3.1 SCHEMATIC CIRCUIT 42

4.3.2 SIMULATION RESULT 43


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4.3.3 SIMULATION RESULT ANALYSIS 45

5 CONCLUSION AND RECOMMENDATION

5.1 CONCLUSION 48

5.2 RECOMMENDATION 49

REFERRENCES 50

APPENDICES 52


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x

LIST OF TABLES

TABLE NUMBER TITLE PAGE

1 CONTROL EQUATION 19

2 XOR TRUTH TABLE 33

3 D FLIP-FLOP TRUTH TABLE 33

4 PRE AND CLEAR FUNCTION TABLE 35

5 SIMPLIFIED CIRCUIT OPERATION 40


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LIST OF FIGURES

FIGURE

NUMBER

TITLE PAGE

1 METHODOLOGY FLOWCHART 4

2 SOLAR ARRAY 7

3 CURRENTVOLTAGE CURVE AND POWER

VOLTAGE CURVE FOR A TYPICAL SOLAR

ARRAY

7

4 SOLAR CELL IV CURVE VARYING SUNLIGHT 8

5 PV ARRAY EQUIVALENT CIRCUIT 9

6 P-V CURVE AND I-V CURVE FOR A TYPICAL

75W PV MODULE 12

7 SOLAR CELL I-V CURVE 13

8 SOLAR ARRAY P-V CURVE 14

9 SIGNUM FUNCTION GRAPH 17

10 MPPT CHARGE CONTROLLER CIRCUIT 21

11 OP-AMP EQUIVALENT CIRCUIT 22


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12 VOLTAGE FOLLOWER CONNECTION 24

13 INVERTING OP-AMP CONNECTION 26

14 AD633 SCHEMATIC DIAGRAM 28

15 AD633 ANALOG MULTIPLIER CONNECTION 28

16 VOLTAGE AND POWER DIFFERENTIATOR

CONNECTION

30

17 POWER AND VOLTAGE COMPARATORS 31

18 XOR CONNECTION 32

19 74HC74 D-FLIP FLOP CONNECTION 34

20 BUCK CONVERTER CIRCUIT 36

21 BUCK CONVERTER CIRCUIT WHEN SWITCH

CLOSED 37

22 BUCK CONVERTER CIRCUIT WHEN SWITCH

OPENED 37

23 CIRCUIT OPERATION FLOWCHART 39

24 CIRCUIT OPERATION GRAPH 39

25 SIMULATION SCHEMATIC CIRCUIT 43


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26 SIMULATION ARRAY VOLTAGE WAVEFORM 44

27 ARRAY POWER WAVEFORM 44

28 SIMULATION POWERVOLTAGE CURVE 45

29 THEORETICAL ARRAY VOLTAGE

WAVEFORM

46

30 THEORETICAL ARRAY POWER WAVEFORM 46

31 THEORETICAL P-V CURVE 47


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xiv

LIST OF ABBREVIATIONS

MPP - MAXIMUM POWER POINT

MPPT - MAXIMUM POWER POINT TRACKING

P &O - PERTURB AND ORDER

PV - PHOTOVOLTAIC

ISC - SHORT CIRCUIT CURRENT

I-V CURVE - CURRENTVOLTAGE CURVE

P-V CURVE - POWER - VOLTAGE CURVE

VMPP - VOLTAGE AT MAXIMUM POWER POINT

VOC - OPEN CIRCUIT VOLTAGE

- DERIVATIVES OF VOLTAGE OVER TIME

- DERIVATIVES OF POWER OVER TIME

sign - SIGNUM FUNCTION

VARRAY - ARRAY VOLTAGE


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IARRAY - ARRAY CURRENT

PARRAY - ARRAY POWER

XOR - EXCLUSIVE OR


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CHAPTER 1

INTRODUCTION

1.1 Overview

The power output of a solar panel varies significantly with varying load

conditions given constant illumination on the panels surface. Under full sunlight, a 75W

solar panel can deliver the 75W power to an ideal load. An ideal load is a load that will

not push or pull the solar panel below or above the voltage at maximum power point

(MPP). For example, solar panels are connected to a battery load to charging or

discharging the battery. The solar panels will be forced to operate at the battery voltage,

which is not the ideal voltage to produce their maximum power. However, this problem

can be avoided by connecting the solar panels to a maximum power point tracker

(MPPT) charge controller rather than simply connecting the module to the battery. By

using the MPPT charge controller, the power at the loads, will be the same to the solar

panels power.


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Basically, there were two kinds of maximum power point tracker, which mechanical

where the solar panels move tracking the sunlight (beyond the scope of this thesis) and

electrical that varies the electrical operating point of the modules are able to deliver

maximum power available. Most of electrical MPPT are based on perturb and order

approach (P&O), implemented by a hill climbing algorithm on a microcontroller [1].

This approach is complex and can be slow, when MPP varied rapidly, because a

microcontroller used sequential approach. Then new approach was introduced by

replacing the microcontroller with analog component and basic logic circuit. This

approach was extremely simple and robust and efficiently proved by many articles. This

approach concept will be deeply discussed later in the other part of this thesis.

1.2 Objectives

The objective of this project is to analyse and simulate a charge controller circuit

for Maximum Power Point Tracker (MPPT) a pplication based on Simple maximum

power point tracker for photovoltaic arrays article in IEEE electronic letter. The article

was written by David C. Hamill and Yan Hong Lim focusing on new technique for

tracking MPP of photovoltaic (PV) array using basic analog components and logic gate.

1.3 Scope of study

The study will be limited to photovoltaic and the maximum power point tracking

application. It will fully focus on charge controller for maximum power point tracking

based on referred electronic letter. It will cover the control equations, circuit algorithms,

circuit operations and the circuit simulations that will be discussed and analysed later in

other chapter. The simulation work will be done using Casdence Orcad Capture Family

Release 9.2.


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1.4 Methodology

This subtopic discussed the design methodology adopted for this study. The

design methodology is important because it determines the quality of end product

(study). In this study there were some particulars phase being followed begins withstudy the basic of photovoltaic system. Next it follows with research on the fundamental

of maximum power point tracking and its operation. After that, it was continued with

analyzing the circuit which covers the the circuit algorithm, every component of the

circuit and its operation. Finally the circuit was simulated using Orcad Capture Family

Release version 9.2 to verify the circuit. The simulation result then was compared to the

result in electronic letter which referred as theoretical results.


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The methodology process is simplified in the flowchart below;

Figure 1: Methodology flowchart

Study the basic ofphotovoltaic system

Study the fundamental of

maximum power point

tracking and its' operation

Study the circuit algorithm

Study the circuit operation

Simulation using Orcad

capture


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CHAPTER 2

LITERATURE REVIEW

2.1 Photovoltaic

2.1.1 Introduction

Photovoltaic is known as a method of converting energy from the sun into

electrical energy [13]. Photovoltaic has been discussed all around the world as a new

energy source to replace current energy source. This method of electricity generation is

growing fast due to free energy source and contributes less effect to the environment.

This is because people are now become more concern about the environment and want a

clean energy source or widely known as Green Energy. Due to high energy demand,

manufacturers and engineers are working to make the PV used to become more efficient.

A simple, fast and cheap MPPT is one of initiative to improve PV energy used.


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2.1.2 Photovoltaic Generation

Photovoltaic (PV) is a method of generating electrical power by converting solar

radiation into direct current electricity using semiconductors that exhibit the

photovoltaic effect[13]. Those materials that exhibit photovoltaic effect cause them to

absorb photons of light and release electrons. The free electrons are captured, an electric

current result that can be used as electricity. Those material that exhibit photovoltaic was

called solar cell is reserved for devices designed specifically to capture energy from

sunlight while the term photovoltaic cell is used when the light source is unspecified.

Modules are then interconnected, in series or parallel, or both, to create an array with the

desired peak DC voltage and current. Typically, a solar array is designed to operate at

specified power.

In the PV cells, a thin semiconductor layer is specially treated to form an electric

field, positive terminal on one side and negative terminal on the other side. When the

light strikes the PV array, electrons are knocked loose from the atoms in the

semiconductor material. If an electrical conductor is attached to both positive and

negative side, forming an electrical circuit, the electrons can be captured in form of

electric current [14]. In order to generate useful power, it is necessary to connect a

number of cells together to form a solar panel (PV arrays). The electrical output of a cell

is proportional to the amount of solar radiation on it and it is highest in condition of

direct sun. Below is the diagram of typical solar array;


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Figure 2: Solar Array

The graph below showed the current-voltage curve and power-voltage curve for

a typical PV array.

Figure 3: Current-Voltage and power-voltage curves for a typical solar array


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The current of the array depends on three parameters [5],

a) Quantity of light falling on the solar array. The graph of solar cell I-V curve invarying sunlight is shown below;

Figure 4: Solar cell I-V curve for varying sunlight

From the graph above, when more sunlight falling on the array, higher ISC

produced by the solar array. The orange line was current-voltage curve for the

highest sunlight falling on the array, while the red line was current-voltage curve

for lowest sunlight falling on the array.

b) The size of array surface area;The bigger surface array surface area use, the array will receive more sunlight.

c) The voltage that the array is operating;The operating voltage for the solar array was depended the load of the solar arrayand types semiconductor used and its connection.


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2.1.3 PV Cell Equivalent Circuit

Ideally a PV cell can model with a dc current source connected parallel with a

diode [17]. Then the total current produced is current generated by PV effect, IL minus

the current through the diode.

However to make it more practical the diode is connected to a shunt resistor, RSH

and a series resistor, RS. The equivalent circuit for a PV array is shown below;

Figure 5: PV array equivalent circuit

= (1)

= 1 1 +

(2)

IL is the current generated by PV effect

ID is the current through the diode


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ISH is current through shunt resistor

RSH is shunt resistor

RS is series resistor

I is the PV output current

V is the PV output voltage

IO is saturation current of the diode

Q is elementary charge 1.6x10-19

K is constant value 1.38x10-23J/K

T is the cell temperature in Kelvin

n is diode ideality factor (typically between 1 and 2)


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2.2 Maximum Power Point Tracking

2.2.1 Introduction

Maximum power point tracking are operations to track the point at which current

and voltage of the PV array operate at maximum power it capable. There were two basic

ways to track the maximum power point. First one is the mechanical ways where solar

arrays moving in the direction of sunlight that may led the array to operate at maximum

power point. Next, the electrical approach which will be discussed in this study. There

were various method proposed to track the maximum power point electrically. It can be

divided to two methods which is using microcontroller and not using microcontroller.

Only the method not using the microcontroller approach will be discussed in this study

which the controller circuit is based on an electronic letter written by David C. Hamill

and Yan Hong Lim entitled Simple maximum power point tracking for PV arrays. The

approach used by David C. Hamill and Yan Hong Lim enable tracking process used is to

be simpler, faster and cheaper.

2.2.2 MPPT Charge Controller

To understand the operation of MPPT, let consider the operation of charge

controller without MPPT (conventional) and then compared it with the charge controller

with MPPT. The graphs below show I-V curve and P-V curve for a typical 75W PV

module at standard test condition.


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Figure 6: P-V Curve and I-V curve for a typical 75W PV Module

When a conventional charge controller was used to charge a battery, the charge

controller is simply connected directly to the battery. This forces the PV module to

operate at the battery voltage. In the graph above, a conventional charge controller was

used to charge a 12V battery and then forces to the 75W PV modules to operate at 12V.

The PV module was limited the power production to around 53W.

Rather than simply connecting directly the charge controller and the battery, the

charge controller is connected to a MPPT system to allow the PV module operates at

maximum power available. In the graph above, Solar Boost MPPT (a MPP Tracking

Device) allow the PV module to operate at maximum power which is 75W. The module

now operates at 17V which is the VMPP of the PV module. The operating current at this

point is 4.45A and the battery charge current is;

= (3)


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I = 17 4.4512

= 6.3An increased of 1.85A of charge current was obtained by using the MPPT charge

controller.

2.2.3 Parameters in MPPT

Maximum Power Point (MPP) is a point at which the arrays operate under

voltage and current at maximum power it capable of. Figure below show the current and

voltage curve (I-V curve) o f a PV cells.

Figure 7: Solar cell I-V curve

In the current-voltage curve (IV curve), MPP is the point which current and

voltage of the array produce maximum array power. The value of the power (P) PV cells


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is obtain by multiplying the current (I) and voltage (V). The current-voltage curve (I-V

curve) shows that current has exponential relationship with the voltage. The maximum

power point (MPP) of the cell occurs at the knee point the exponential curve. At this

point the differentiation of voltage over time (dv/dt) is zero. The enable the solar cells

operate at maximum power point, the solar cells must operate at VMPP which is the

voltage at maximum power point. The current passing through at this point is labeled as

IMPP in the curve. Resultant of multiplying both VMPP and IMPP is MPP. VOC is the open

circuit voltage which occurs when there is no load attach to the solar cells. It can be seen

VOC is the maximum value of voltage in the I-V curve. At this point, there is no current

flow through the cell. ISC is the short circuit current correspond to short circuit condition

when the impedance is low and is calculated when voltage equals to zero. Isc is the

maximum value for solar cells current in the I-V curve. In the Power-Voltage curve (PV

curve), MPP is the peak point of the curve where at that point the power is maximum.

PV curve labeled with MPP is shown below;

Figure 8: Solar array P-V Curve


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CHAPTER 3

MPPT CHARGE CONTROLLER CIRCUIT

3.1 Introduction

In this chapter, the maximum power point tracking charge controller circuit for

photovoltaic array application proposed for the study will be discussed. The circuit will

be fully based on electronic letter entitled Simple maximum power point tracker for

photovoltaic arrays written by David C. Hamill and Yan Hong Lim. The circuit study

will cover the circuit control equation, the component of each component in the circuit,

the algorithm for each component in the circuit and the circuit operation.

3.2 Control Equation

This part of study deduces control strategy to obtain a control equation. The main

purpose of the control equation is to have a control equation for tracking the maximum


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power point. Referring back to the PV curve drawn from solar cell in figure 8 Chapter 2

part 2.23, the maximum power point (MPP) is located at dp/dv=0. Through the graph, a

general equation for dp/dv, also been deduced [2];

= > 0 < = 0 = < 0 > (4)

The control strategy that will be followed is, if V0. So the V (array voltage) will be increased so that P moving towards MPP. If

V>VMPP it can be deduce dp/dv 0 < = 0 = < 0 > (5)

From equation (4) and (5), we can deduce an equation (7);

= kdp

dv

dp

dv=

k (6)

dp

dv=

dp

dt

dt

dv=

=

k

= k

(7)


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But based on the electronic letter by D.C Hamill and Yan Hong Lim, there were

problems with the equation, first appears on both side of the equation and this would

manifest itself in practice as a high frequency oscillation. Second, the referred circuit

used many analog component and analog dividers are undesirable components since

they have many imperfections. Lastly, when V=Vmpp, =0, then there would be

division by 0. This whole issued can be solved using signum function [21].

The graph for signum function is shown below;

Figure 9: Signum function graph

The general equation for signum function is;

=

1 < 0

0

= 0

1 > 0(8)

Where denotes the assignment of information held by RHS to LHS of the equation

1

-1


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The equation is still not satisfactory since RHS can be zero and there is still used

of analog divider. The problems were solved by modified the signum function which

never have zero value and introducing new control equation that not used division [2].

The signum modified to, if


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Sgn() Sgn() Sgn()Sgn() Sgn() v action


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The last condition is the point at V is still V >V MPP but now moving towards the

MPP. It means 0 and


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Figure 10: MPPT Charge Controller Circuit

3.3.2 Solar Array

As been discussed in Chapter 2, a solar array equivalent circuit can be drawn by

connecting a DC current source, ISC parallel with diode string, nS. The parameter setting

for both DC current source and the number of diodes, n will be used for the diode string.

The type of diodes that will be used for Orcad Capture simulation is 120NQ045.


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3.3.3 Controller

The controller circuit consists of a voltage follower, an analog inverter, a

multiplier, two differentiators, two comparators, a XOR gate and a flip-flop.

3.3.3.1 Voltage Follower

The voltage follower was achieved by using op-amp as shown in the figure10.

Op-amp is a DC-coupled high gain electronic voltages amplifier with a differential

inputs and usually single-ended output. The function of op-amp is to amplify the input

voltages to produce larger output.

Equivalent circuit of an op-amp

Figure 11: Op-amp equivalent circuit

V+ = non inverting input

V- = inverting input

Vs+ and Vs- = positive and negative supply

VO = output voltage

Resistance Ri was very high, then Ri was assumed opened circuit while resistance RO

was very low, so RO assumed closed circuit.


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+ = = 0+ =

Op-amp Operation

=(+ ) (11)

AOL = op-amp open loop gain. Then value usually very high hence the output voltage

was very high.

In the referred circuit, the array was connected to a voltage divider before fed to

the voltage follower. LM318 op-amp was used as the op-amp for voltage follower. The

significant used of 51 ohm and 200ohm voltage divider in this circuit is have high

impedances input at multiplier as the voltage follower is then connected as input of the

multiplier. The supply voltages to the op-amp were set to V+ = 5V and V= -5V. The

figure below shows the connection at the voltage divider.


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Figure 12: Voltage Follower connection

The output voltage of the voltage follower;

+ = 22 + 3

+ =200

200 + 251


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+ = 0.7968

=

=

+ = 0.7968

(12)

3.3.3.2 Voltage Inverter

Another application of op-amp was inverting the voltage of fed into the op-amp.

The current array of was measured in term of voltage connecting the array with small

resistor (0.47). The input into the voltage inverter is negative of array current multiply,

-IARRAY with the value sensing resistor, Rs. The output voltage, VOUT of will be to

positive value multiplying with resistance R4 and R6 connecting the op-amp. Then

output voltage waveform of the will be the same as the input waveform shape but the

value is invert from negative to positive and also based on value of R 4 and R6. The op-

amp being used in the circuit is LM318. The connection of voltage inverter op-amp is

shown below in figure 13.


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Figure 13: Inverting Op-amp connection

The output voltage of LM318 voltage inverter is;

4 = 6

= 0

= 6 4


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= 36 0.47 1

= 2.868 (13)

The output voltage of inverting op-amp is then fed into the multiplier. The

current of the op-amp was inverted for reason to have positive value of Power at the

multiplier.

3.3.3.3 Analog Multiplier

Analog multiplier is an electronic device that evaluates the product of two analog

signals which its output [20]. In this circuit, the analog multiplier is use to calculate the

power of the array by multiplying the array voltage and array current. The analog

multiplier being used in circuit proposed by David C. Hamill and Yan Hong Lim was

AD633. The AD633 is a functionally complete, four-quadrant, analog multiplier. It

includes high impedance, differential X and Y inputs, and a high impedance summing

input (Z) [12]. The output of AD633 is pin7 (W). This analog multiplier was built using

2 differential op-amps, a multiplier and a voltage follower. Figure 14 shows the

schematic diagram AD633.


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Figure 14: AD633 Schematic diagram

In the referred circuit, pin 1(X1) of AD633 analog multiplier was fed with array voltage

while pin 3(Y1) was fed with the array current. Pin 2(X2), pin 4(Y2) and 6(Z2) was

connected to ground. The voltage source to for AD633 was set to V+ = 5V and

V- = -5V. The product of multiplication which is the array power is measure at pin

7(W). The connection to AD633 analog multiplier is shows below.

Figure 15: AD633 Analog Multiplier Connection


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The output of the AD633 is;

= 1 21 210

+

= 0.7968 0(2.868 0)10

+ 0

= 0.2285

= 0.2285 (14)

3.3.3.4 Differentiators

Another application of op-amp is to differentiate the voltage fed into the op-amp.

This application was achieve connect a capacitor in series with the op-amp and a resistor

at the feedback. In the MPPT circuit referred, the measured power and voltage of the

array is approximately differentiated using high pass filter. A first order high pass filters

with true time constant T yields an approximation T to its true derivative for the array

power while it yields an approximation T to its derivative for the array voltage [1].

The op-amp used as in differentiator circuit is LM318. The connection for power and

voltage differentiator is shown below. It can be seen that the parameter of capacitors,

and resistors used in the differentiator circuit is same. The differentiated value power

and voltage of array is measured as the value is needed to evaluate to track the MPP.


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30

= (15)

T

= (16)

Figure 16: Voltage and Power Differentiator Connection


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3.3.3.5 Voltage Comparators

An electronic device that compares two voltages or currents, and switches its

output to indicate which one is larger [19]. In the referred circuit, the output of

differentiators, dV/dt and dP/dt was fed into comparator. At the comparators both the

differentiated voltage and array was compared to ground. The op-amp being used as the

comparators were LM311. Although an ordinary op-amp can be used as comparator,

theres special integrated circuit intended for use as comparators. LM311 chips are

designed for very fast response and arent in the same league as other op-amp [7]. The

connection at the comparators is shows below in figure 17.

Figure 17: Power and Voltage Comparators

dP/dt

0

0

dV/dt

Xp

-5V

-5V

R12

1G

5V

R11

1G

5V

Xv

U6

LM311

7

2

3 1

8

4

6

5

OUT

+

- G

V+

V-

B/SB

0

U7

LM311

7

2

3 1

8

4

6

5

OUT

+

- G

V

+

V-

B/SB

0


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The comparators will produce output 1 if the input value is greater than zero while it

produce zero if the input value is lower than zero.

= 1 > 00 0 (17)

= 1 > 00 0 . .(18)

3.3.3.6 XOR gate

In the referred MPPT charge controller circuit, both output of comparators to the

XOR gate. There is pull-out resistors connected parallel in between the comparators and

XOR gates. This connection is to provide additional power to drive the XOR gate. In the

pull-out resistor, 4.7k ohm resistor connected in series with 5V voltage source and

shunted in between comparators and XOR gate. The XOR being used in the circuit was

CD4030. The connection at XOR gate is shown below.

Figure 18: XOR connection

U8A

CD4030A

2

3

1

5V

R13

4.7k

Xv

5V

Xc

Switch

R14

4.7k


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Since there were two inputs to the XOR gate, then there will be 4 conditions. The

truth table of the XOR gate showing the output of each condition is shown below in

Table 2.

Xv Xp Output

0 0 0

0 1 1

1 0 1

1 1 0

Table 2: XOR truth table

3.3.3.7 D flip-flop

Flip-flop is an electronic circuit that has two stable states and thereby is capable

of serving one bit of memory [9]. It usually controlled by one or two signals and/or a

gate or clock signal. The output of D-flip-flop, Q looks a delay of input D. The output of

D flip-flop takes on the state of the input, D at the moment of positive edge at clock pin.

The truth table of D flip-flop is shown below in table Table 3.

Clock D Qn+1

X Qn

0 0

1 1

Table 3: D flip-flop truth table


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In the referred circuit, the D flip flop that being used is 74HC74 D flip-flop. The

connection to flip-flop is shown below in figure19

Figure 19: 74HC74 D-Flip Flop connection

PRE and CLR must be connected high logic (1) to enable the flip-flop to operate

where output was determined by input, D [9]. According to table 4, flip-flop will operate

if PRE and CLR are set to high logic. The XOR output was sampled by D flip-flop latch

clocked at constant frequency 1/TS. (In referred circuit Ts = 50s).


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Table 4: PRE and CLR functions table

According to electronic paper written by David C. Hamill and Yan Hong Lim,

the output of XOR is connected to flip-flop before fed to switch because to prevent high

frequency switching chattering and to minimize the unavoidable interference generate

by the buck converters switching action. This interference occurs immediately after the

clock transition and is over before the next, so latch never samples it.

3.3.4 Power stage

3.3.4.1 Introduction

The power stage components can be divided into three parts which is the

blocking diode, charging/discharging and buck converter.

3.3.4.2 Blocking Diode

Diode, DB is blocking diode which is connected in series with the solar array to

prevent reverse terminal current [1]. In the referred circuit, the diode was assumed ideal.

The type of diode that will be used in the simulation is the same as the diodes used in

PRE CLR Operation

0 0 Block

0 1 Set

1 0 Clear

1 1 Flip-flop operate


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solar array which is 120NQ045. The cathode pin of the diode was connected to the

voltage follower.

3.3.4.3 Charging /Discharging Capacitor

The capacitor, C was used to control the voltage of the array [1]. When the

operating voltage was smaller than voltage at the maximum power point, VMPP

(VVMPP), by discharging to

decrease the array voltage. The capacitor actions, was controlled by the switch by

opening and closing the switch.

The value that was set to the capacitor is 470F.

3.3.4.4 Buck Converter

Buck converter is a step down DC-DC converter [10]. The DC input voltage or

current can be regulated to desired DC output. The output of buck converter was smaller

than the input voltage.

Circuit of a buck converter

Figure 20: Buck converter circuit


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Circuit of a buck converter when switch is closed

Figure 21: Buck converter circuit when switch closed

=

=

= (19)

Figure 22: Buck Converter circuit when switch opened


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=

= (20)

By the controlling the switches, we can control the voltage of output load. In the

referred circuit, load was a 4V battery while the voltage produced by the array was

bigger; buck converter was used to control the voltage by controlling the switch, S. The

inductor use in buck converter is large enough (1.5mH) to enable it to operate in

continuous current mode. The state equations of the conductor were;

= (21)

=

(22)

Where S = 0 or 1 indicate switch open or closed, respectively.

3.4 Circuit Operation

This part of study will discuss how the circuit operates to track the MPP. The

circuit operation is based on the array voltage and the circuit operates by changing the

array voltage to track voltage at MPP. The circuit operation was simplified using

flowchart below in figure 23.


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Figure 23: Circuit Operation flowchart

Figure 24: Circuit Operation graph

Point A, V


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b) V now increases towards VMPP, dv/dt is positive and dp/dt is also positivewhile p is increasing toward MPP. Switch opens and capacitor charging to

increase V toward VMPP.

Point B, V>VMPPT

a) dv/dt is positive and dp/dt is negative while p retreating from MPP. Switchwas closed and capacitor discharging resulting V decreasing towards VMPP.

b) V now decreases towards VMPP, dv/dt is negative, dp/dt is positive while pis increasing toward MPP. Switch was closed and capacitor discharging

resulting in V decreasing towards VMPP.

All the operations were simplified to table 5 below.

Condition

Comparator output

S Switch VoltageXv Xp

vVmpp >0 >0 1 1 0 opens increases

vVmpp 0 0 0 0 0 opens increases

v>Vmpp 0 >0 0 1 1 closes decreases

v>Vmpp >0 0 1 0 1 closes decreases

Table 5: Simplified Circuit Operation


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CHAPTER 4

SIMULATION RESULT AND DISCUSSION

4.1 Introduction

This chapter will cover Orcad Simulation setting used, simulation result andanalysis of the result obtained from the result.

4.2 Orcad Capture

OrCAD Capture provides fast and intuitive schematic design entry for PCB

development or analog simulation using PSpice. The component information system

(CIS) integrates with it to automatically synchronize and validate externally sourced part

data [16].


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Orcad Capture provides various libraries which many components like LM311, LM318,

AD633 and many more were set up in the library. Each component was set up their

parameters and setting the same as practical component.

Orcad Capture provides simulation application as the waveform at any part of the circuitcan be obtained. Besides that provides voltage, current and power dissipation bias value

display of each component.

4.3 Orcad Capture Simulations

4.3.1 Schematic circuit

After the all components of the have connected, the simulation test is done.

Figure below shows schematic circuit in Orcad Capture Simulation. This circuit was

fully based on circuit proposed by David C Hamill and Yan Hong Lim.


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Figure 25: Simulation schematic circuit

4.3.2 Simulation Result

For the simulation, the DC current source was set to 25A while the number of

diodes used is 12. The simulation was run for 0.1s. Three parameters were taken to be

compared with theoretical result obtained from electronic letter written by David C

Hamill and Yan Hong Lim. The first parameter is array voltage waveform. Figure 26

below shows array voltage waveform obtained from the simulation.

0

J2

BC264A

D7

1

2

0

CLK

DSTM1

OFFTIME = 25uS

ONTIME = 25uS

DELAY = 100uS

STARTVAL = 1

OPPVAL = 0

D14

120NQ0451

2

5V

0

0

D5

1

2

R8

1k-5V

D6

1

2

R4

1k

0

0

C7

100n

R6

36k

0

R7

1k

12V

5V

V1

4Vdc

R3

200k

-12V

U2

LM318

3

2

7

4

6

8

5

1+

-

V+

V-

OUTC2

C3

C1

U7

LM311

7

2

3 1

8

4

6

5

OUT

+

- G

V+

V-

B/SB

R12

1G

5V

0

U9A

74HC74

3

1

2

4

5

6CLKCLR

D

PREQ

Q

R14

4.7k

HI

U6

LM311

7

2

3 1

8

4

6

5

OUT

+

- G

V+

V-

B/SB

D13

1 2

R11

1G

-5V

HI

D10

1

2

D12

1

2

-5V

R2

51k

L1

1.5mH

1 2

U8A

CD4030A

2

3

1

0

D11

1

2

5V

U5

LM318

3

2

7

4

6

8

5

1+

-

V+

V-

OUT

C2C3

C1

R13

4.7k

R9

100k

C5

470u

0

5V

I1

0.25Adc

R1

0.47

0

D1

1

2

D3

1

2

5V

D4

1

2

U1

LM318

3

2

7

4

6

8

5

1+

-

V+

V-

OUT

C2C3

C1

D2

1

2

5V

D8

1

2

-5V C6

100n

D9

1

2

0

5V

R10

100k

R5

1k

U3

AD633/AD

1

2

3

4

6

7

8

5

X1

X2

Y1

Y2

Z

W

V+

V-

U4

LM318

3

2

7

4

6

8

5

1+

-

V+

V-

OUT

C2C3

C1

0


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Figure 26: Simulation Array Voltage Waveform

The second parameter was the array power waveform. This waveform was

obtained by multiplying array voltage and array current which also is 0.2285 of array

power.

Figure 27: Array Power waveform


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The last parameter that will be discussed is the Power-Voltage Curve

which is obtained by setting the array power as Y-axis and array voltage as X-axis.

Figure 28: Simulation PowerVoltage Curve

4.3.3 Simulation result analysis

The array voltage waveform obtained from the simulation is obviously different

compared to the theoretical array voltage waveform obtained from the electronic letter.

The theoretical array voltage waveform is shown in figure 29 below.


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Figure 29: Theoretical array voltage waveform

Since the array voltage was totally wrong from the theoretical (figure 30), the

array power waveform obtained was totally wrong too. It is because the array power is

based on array voltage, P=IV.

Figure 30: Theoretical array power waveform

The P-V curve obtained from simulation was wrong too because it is also based on the

array voltage waveform obtained. The theoretical P-V curve is shows below in figure 31.


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Figure 31: Theoretical P-V curve

Some problems were from simulation were found. The array voltage obtained

from is gradually decreasing because the act of capacitor discharging it. From thesimulation, it is also been found that the switch is always open since the signal from pin

Q of the flip-flop is always low. These problems occur because both of input to XOR

gate is always high. The inputs into XOR gate are always high because the input to

comparators is always greater than 0. All this chain problem was rooted from array

voltage and array power fed into the differentiator. From the simulation, it has been

found that, the array voltage and array power into the differentiator is same. This

situation shouldnt be happen because array power is result of multiplying array voltage

with array current unless the array value is one. In the simulation, the output of the

multiplier does not provide the value of array power obtained by multiplying the array

current and array voltage. The effort to use ABM mult (another multiplier in Orcad

library) manage to multiply its inputs but it give another effect on the voltage follower

output as the output become negative even the input is positive.


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CHAPTER 5

CONCLUSION AND RECOMMENDATION

5.1 Conclusion

From analysation done on reffered MPP circuit, theoretically the circuit willsuccessfully work in tracking the maximum power point. This was proved by algorithm

of the circuit which the operating voltage will oscillate around the V MPP. Hence, the

operating power is oscillate around the maximum power point within narrow margin.

The analysation on each components used and its connection also provide the

prove that the circuit is able to work as maximum power point controller circuit. It was

verify by the operation of controller circuit providing signal to switch to varies the


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Unfortunately, the simulation result fail to provide desired result that been

proven in the article that the circuit was successfully simulated and verify the theoretical

approach proposed. The array voltage, array power and P-V curve obtain from the

simulation were obviously differ from the theoretical waveform as several problems

occurred to the circuit.

5.2 Recommendation

The first thing of progress that should make this study better to obtain desired

result which the theoretical result from the electronic letter referred either using

simulation or experimental. After all these problems have been encountered, the next

progress is the analysation of the dynamic effectiveness of the MPPT charge controller

circuit by changing the parameters used in the circuit. The parameters like illumination

of the arrays can be varied by changing the DC current sources parameter and the

temperatures affecting the array voltages also can be varied by changing the numbers of

diodes used in the diode string. The dynamic effectiveness analysis can be made by

looking into the time taken by the circuit to adapt when there were changes in

parameters.


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REFERRENCES

1. Y. H. Lim and D. Hamill,Simple maximum power point tracker for photovoltaicarrays, Electronics Letters, vol. 36, pp. 997999, May 2000.

2. Y. H. Lim and D. C. Hamill,Synthesis, simulation and experimental verificationof a maximum power point tracker from nonlinear dynamics, Power Electronics

Specialists Conference, 2001. PESC. 2001 IEEE 32nd Annual, vol. 1, pp. 199

204, 2001.

3. M. Savenkov and R. Gobey,A Simple Power Point Tracker Utilizing the RippleCorrelation Control Technique, International Solar Energy Society Conference-

Asia pacific region, November 2008.

4. R. A. Cullen, What is maximum power point tracking (MPPT) and How does itwork, Solar Boost Blue Sky Energy article.

5. F. Antony, C. Durschner and K. Remmers, Photovoltaics for Professionals: SolarElectric Systems Marketing, Design and Installation, SolarPraxis, 2007.

6. D. W. Hart, Introduction to power electronics, Prentic-Hall International Inc,1997.

7.

Paul Horowitz, The art of electronics, second edition, Cambridge University

Press, 1989.

8. Siti Hawa Ruslan, Puspa Inayat Khalid and Ismawati Abd Ghani, ModulPengajaran Elektronik 2 Edisi 3, Universiti Teknologi Malaysia, 2004.


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9. En. Zulkifli, Modul Pengajaran Elektronik Digit, Universiti TeknologiMalaysia, 2007.

10.Dr Zainal Salam and Dr Awang Jusoh Chopper Lecture Note, UniversitiTeknologi Malaysia.

11.T. Bazouni, Competition Electronic - Easymax solar power enhancer,Competition Electronics article.

12.LM318, AD633, LM311, CD4030 and 74HC74 datasheet.

13.http://en.wikipedia.org/wiki/Photovoltaics 14.http://science.nasa.gov/science-news/science-at-nasa/2002/solarcells/

15.http://en.wikipedia.org/wiki/Maximum_power_point_tracking/

16.http://www.cadence.com/products/orcad/orcad_capture

17.http://zone.ni.com/devzone/cda/tut/p/id/7229 solartutor2/

18.http://www.electronics-tutorials.ws/filter/filter_6.html/

19.http://en.wikipedia.org/wiki/Comparator/

20.http://en.wikipedia.org/wiki/Analog_multiplier/

21.http://en.wikipedia.org/wiki/Sign_function/
http://en.wikipedia.org/wiki/Photovoltaicshttp://en.wikipedia.org/wiki/Photovoltaicshttp://en.wikipedia.org/wiki/Photovoltaicshttp://science.nasa.gov/science-news/science-at-nasa/2002/solarcells/http://science.nasa.gov/science-news/science-at-nasa/2002/solarcells/http://science.nasa.gov/science-news/science-at-nasa/2002/solarcells/http://en.wikipedia.org/wiki/Maximum_power_point_tracking/http://en.wikipedia.org/wiki/Maximum_power_point_tracking/http://en.wikipedia.org/wiki/Maximum_power_point_tracking/http://www.cadence.com/products/orcad/orcad_capturehttp://www.cadence.com/products/orcad/orcad_capturehttp://www.cadence.com/products/orcad/orcad_capturehttp://zone.ni.com/devzone/cda/tut/p/id/7229%20solartutor2/http://zone.ni.com/devzone/cda/tut/p/id/7229%20solartutor2/http://zone.ni.com/devzone/cda/tut/p/id/7229%20solartutor2/http://www.electronics-tutorials.ws/filter/filter_6.html/http://www.electronics-tutorials.ws/filter/filter_6.html/http://www.electronics-tutorials.ws/filter/filter_6.html/http://en.wikipedia.org/wiki/Comparator/http://en.wikipedia.org/wiki/Comparator/http://en.wikipedia.org/wiki/Comparator/http://en.wikipedia.org/wiki/Analog_multiplier/http://en.wikipedia.org/wiki/Analog_multiplier/http://en.wikipedia.org/wiki/Analog_multiplier/http://en.wikipedia.org/wiki/Sign_function/http://en.wikipedia.org/wiki/Sign_function/http://en.wikipedia.org/wiki/Sign_function/http://en.wikipedia.org/wiki/Sign_function/http://en.wikipedia.org/wiki/Analog_multiplier/http://en.wikipedia.org/wiki/Comparator/http://www.electronics-tutorials.ws/filter/filter_6.html/http://zone.ni.com/devzone/cda/tut/p/id/7229%20solartutor2/http://www.cadence.com/products/orcad/orcad_capturehttp://en.wikipedia.org/wiki/Maximum_power_point_tracking/http://science.nasa.gov/science-news/science-at-nasa/2002/solarcells/http://en.wikipedia.org/wiki/Photovoltaics


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APPENDIX

APPENDIX A


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APPENDIX B

1421_ABDULRAHIMBINJUSOH2011

Documents

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