Fuzzy logic Based maximum Power Point tracking for Solar Panel

FUZZY LOGIC BASED MAXIMUM POWER POINT TRACKING FOR SOLAR ARRAY

                                               

                  A  PROJECT REPORT

                                                          Submitted by

           ASHWIN KARTHI.P                                                       50507105005

           JANARTHARNAN.V                                                       50507105304

           KARTHIKEYAN.S                                                           50507105305

                   In partial fulfillment for the award of the degree

                                                          of

                                      BACHELOR OF ENGINEERING

                                                          in

ELECTRICAL AND ELECTRONICS ENGINEERING

                  

C.ABDUL HAKEEM COLLEGE OF ENGINEERING AND TECHNOLOGY MELVISHRAM, VELLORE

ANNA UNIVERSITY: CHENNAI 600 025

APRIL 2011

ANNA UNIVERSITY: CHENNAI 600 025

BONAFIDE CERTIFICATE

Certified that this project report “FUZZY LOGIC BASED MAXIMUM POWER POINT TRACKING FOR SOLAR ARRAY” is the bonafide  work of “ASHWIN KARTHI.P, JANATHARNAN.V AND KARTHIKEYAN.S” who carried out the project work under my supervision.

SIGNATURE                                               SIGNATURE

                                                                                                       

HEAD OF THE DEPARTMENT                 Mr. P.Mohanavel M.E.,Ph.D..,

                                                                      SUPERVISOR .                                                                                                Lecturer/EEE

Department of Electrical & Electronics        Department of Electrical & Electronics                                                               Engineering                                                   Engineering

C.Abdul Hakeem College of                         C.Abdul Hakeem College of Engineering                                                   Engineering                                         

and Technology, Melvisharam,                  and Technology, melvisharam,       

Vellore-632509.                                             Vellore-632509.                                                                                                                                    

Submitted to the viva-voce examination held on__________________

INTERNAL EXAMINER                                           EXTERNAL EXAMINER

ACKNOWLEDGEMENT

We profoundly thank our chairman Haji Janab MR.S.Ziauddin Sahed B.A and our beloved correspondent Janab V.M.Abdul latheef shhed B.E., for providing adequate facilities.

We are greatly inbedted to our guide Mr.P.Mohanavel M.E., PhD, lecturer, Deportment of Electrical and Electronics Engineering for his precious guidance, suggestions about innovative ideas, and encouragement.

          We also thank Mrs. J. Hemamalini M.Tech., HOD, Dept of Electrical and Electronics Engineering amd Mr. M. R. Khan Galib B.Tech., Sr. Lectuerer, department of Electrical and Electronics Engineering for their kind support, advice, and encouragement. We specially thank Mr.kumar M.E and Mr.VASUDHAVAN M.E…, mechanical dept for his encouragement and support to our project.

We want to convey our special thank our dept. Staffs Mr. S. Selvaganapathy M.E., Mr.C.Boobalan M.Tech., Mr.S.Deepa Prasath M.E., Mr.S.Sengottaian M.E., Mr. K.Shafeeque Ahamed, M.E., Mr. Ravi Chandaran , Mr.G.Syed  Zabiyullah M.E., Ms.L.Mehboobjan M.E., Ph.D Ms.Susmitha M.E., and Ms.. T.Farheen Fathima B.E., MBA., for their kind support and suggestion regarding our project work.

          We also thank Mr.W.N.Khalid ahamed B.C.A., for facilitating system arrangements for our project work. We want to say thanks to Mr.B.V.Papanna Rao DEEE., Mr.S.Nasir Ahmed DEEE., Mr.M.H.Mubeenur Rahman DEEE., Mr.Anes DEEE.,  for their great support and help regarding PCB preparation and soldering work. We specially want convey our thank to Mr.R.Rajamoorthy ITI., Mr.S.Ganadharan ITI., Mr.T.Elango ITI., Mr.A.Duraimurugan ITI., Mr.G.Venkatesen ITI.., and Mr.R.Thesinguraja ITI., for their help in preparation of base mechanical works and PCB cutting and drilling work.   

ABSTRACT

The main objective of our project is to develop of an Automatic Solar radiation tracker . Fossil fuels are a relatively short-term energy source; consequently, the uses of alternative sources such as solar energy are becoming more wide spread.

To make solar energy more viable, the efficiency of solar array systems must be maximized.

A feasible approach to maximizing the efficiency of solar array systems is sun tracking. In this project were propose a control based system the movement of a solar array so that it is constantly aligned towards the direction of the sun.

Solar modules are devices that cleanly convert sunlight into electricity and offer a practical solution to the problem of power generation in remote areas.

The solar tracker designed and constructed in this project offers a reliable and affordable method of aligning a solar module with the sun in order to maximize its energy output.

Automatic Sun Tracking System is a hybrid hardware/software prototype, which automatically provides best alignment of solar panel with the sun, to get maximum output (electricity).

TABLE OF CONTENTS

CHAPTER                                      TITLE                                                      PAGE

     NO                                                                                                          NO

ABSTRACT                                                                                   IV

LIST OF THE TABLE                                                                  X      

LIST OF FIGURES                                                                       XI    

LIST OF SYMBOLS                                                                      XII

1             INTRODUCTION

1.1         GENERAL                                                                       1

1.2          LITERATURE SURVEY                                                 1

1.3          NEED OF SUN TRACKER                                             6

1.4          ORGANIZATION OF work                                         7

1.5          Solar Energy                                                                  7       

1.6          ORGANZIATION OF THE REPORT                               8

2             SOLAR TRACKING

2.1            INTRODUCTION                                                             10

2.2             RELEVANCE OF SOLAR TRACKING                           10

2.3             MATERIAL AND EFFICENCY                                       11

2.3.1 single crystal                                                                 12

2.3.2 Poly or multi crystalline                                                12

2.3.3 Ribbon silicon                                                                 12

2.3.4 Amorphous silicon films                                                   12

2.4             PHOTOVOLTAIC CELL                                                  13

2.5             PHOTOVOLTAIC MODULE                                             14

2.6             SOLAR TRACKER FUNDAMENTAL                                15

2.7             OVERVIEW OF CURRENT TRACKER DRIVER TYPES  16

TABLE OF CONTENTS

 CHAPTER                                     TITLE                                                   PAGE

     NO                                                                                                                NO

2.7.1 Gas Trackers (Passive Trackers)                                          16

2.7.2 Active Trackers                                                                   16

2.7.3 Open Loop Trackers                                                              17

2.8    TYPES OF SOLAR TRACKERS                                              17

2.8.1 Single Axis Trackers                                                            17

2.8.2 Dual Axis Trackers                                                              18

2.9    TRACKER MOUNT TYPES                                                     18

2.9.1    polar axle                                                                         18

2.9.2    Horizontal Axle                                                               19

2.9.3    VERTICLE AXLE                                                           20

2.9.4     Altitude Azimuth                                                            21

3             STEPPER MOTOR

3.1             INTRODUCTION                                                                  22

3.2             BIPOLAR V/S UNIPOLAR STEPPER MOTOR                   23

3.3UNIPOLAR STEPPER MOTOR                                                24

3.4       STEPPER MOTOR ADVANTAGE AND

DISADVANTAGE                                                                    25     

3.5       OPEN LOOP OPERATION                                                  26

3.6       STEPPER MOTOR TYPE                                                       26

3.6.1    Variable-reluctance (VR)                                             26

3.6.2    Permanent Magnet (PM)                                             27

3.6.3    Hybrid (HB)                                                               28

3.7   APPLICATION OF STEPPER MOTOR                                    28

TABLE OF CONTENTS

CHAPTER                                    TITLE                                                   PAGE

     NO                                                                                                               NO

3.8      THE ROTATING MAGNETIC FIELD                                     29

3.9      TORQUE GENERATION                                                         29

4             FUZZY LOGIC

4.1    INTRODUCTION                                                            31

4.2    FUZZY LOGIC                                                                32

4.3    FL DIFFERENCE FROM CONVENTIONAL  

CONTROL METHODS                                                    32

4.4    FL WORKING                                                                 33

4.5   benefits                                                                        33

4.6    HE RULE MATRIX                                                         34

4.7   SOLAR  fuzzy ControlleR                                     35

4.7.1    Membership Functions                                            35

4.7.2    FuzzificatioN                                                        36

4.7.3    Fuzzy rule base                                                    36

4.8   Inference Engine                                                     37

4.9   Defuzzification                                                        37

5             HARDWARE DESCRIPTION

5.1   SOLAR CHARGING CIRCUIT                                                 38

5.2   Block Diagram of the hardware design    38

5.2.1    Control algorithm (DISPLAY)                 39

5.2.2     CONTROLLER (PIC16F877A)                                      39

5.2.3    motor terminal identification             40

 TABLE OF CONTENTS

CHAPTER                                    TITLE                                                   PAGE

     NO                                                                                                               NO

5.3    DRIVER CIRUIT                                                             40

5.4   LCD DISPLAY circuit                                                 41

5.4.1 LCD DISPLAY                                                       41   5.5 Stepper motor driver                                               43

circuit l297 to l298

5.6 dsi307 RTC                                                                     44

6             RESULT AND DISCUSSION

6.1 CONSOLIDATED TABLE                                               45

7      CONCULION

7.1 GENERAL                                                                        46

7.2 CONCLUSION                                                                  46

7.3 Scope for Future Work                                        46

APPENDIX 1                                                                                             51

List of tables

Table                         name of the table                                 page

    No                                                                                                                   no

3.1: Sequence of giving pulses to motor                                                 25

4.1  FAM table for SOLAR Fuzzy Logic Controller                               35

    6.1 CONSOLIDATED TABLE                                                              44

                        

LIST OF FIGURES

FIGURE                               NAME OF THE FIGURE                           PAGE

    NO                                                                                                               NO 

         

    2.1 Equivalent Circuit of Solar Cell                                                                 11

2.2 The Schematic Symbol of Solar Cell                                                 11

 2.3 Photovoltaic cell                                                                                15

2.4 Single axis solar tracker                                                                    17

 2.5 Dual axis solar tracker                                                                      18

    2.6 Horizontal Mount                                                                               20

2.7 Vertical  Mount                                                                                20

 2.8 Two Axis Mount                                                                               21

 3.1 Stepper motor                                                                                   22

3.2 A 2- phase (winding) unipolar Stepper Schematic                                 23         

3.3 A two phase (winding) bipolar stepper motor                                       23

3.4 Cross section of a variable reluctance motor                                        27

3.5 Principle of a PM type stepper motor                                     `             27

3.6 Cross section of hybrid stepper motor                                                  28

3.7 Magnetic field rotation in Stepper Motor                                              29

4.1 Schematic diagram of Fuzzy Logic Controller                                    35

4.2  Input and output Membership function and linguistic Variables            36

5.1 Solar Charging circuit                                                                       38

5.2 Block Diagram of the hardware design                                             38

5.3 DRIVER CIRUIT                                                                             40

5.4 LCD DISPLAY CIRCUIT                                                                 41

CHAPTER 1

INTRODUCTION

1.1            GENERAL

As the range of applications for solar energy increases, so does the need for improved that materials and methods used to harness this power source..There are several factors affect the efficiency of the collection process. Major influences on overall efficiency include solar cell efficiency, intensity of source radiation and storage techniques..The materials used in solar cell manufacturing limit the efficiency of a solar cell..

This makes it particular difficult to make consider able improvements in the performance of the cell, and hence restricts the efficiency of the overall collection process..

Therefore, the most attainable method of improving the performance of solar power collection is to increase the mean intensity of radiation received from the source..There are three major approaches for maximizing power extraction in medium and large scale systems..They are sun tracking, maximum power point (MPP) tracking or both.

1.2            LITERATURE SURVEY

Daniel A. Pritchard had given the design, development, and evaluation of a microcomputer-based solar tracking and control system (TACS) in 1983. It was capable of maintaining the peak power position of a photovoltaic (PV) array by adjusting the load on the array for maximum efficiency and changed the position of the array relative to the sun. At large PV array system installations, inverters were used to convert the dc electrical output to ac for power grid compatibility. Adjustment of the inverter or load for maximum array output was one function performed by the tracking and control system. Another important function of the system was the tracking of the sun, often a necessity for concentrating arrays.

The TACS also minimized several other problems associated with conventional shadow-band sun trackers such as their susceptibility to dust and dirt that might cause drift in solar alignment. It also minimized effects of structural war page or sag to which large arrays might be subjected during the day.

Array positioning was controlled by Q single-board computer used with a specially designed input output board. An orderly method of stepped movements and the finding of new peak power points was implemented. This maximum power positioning concept was tested using a small two-axis tracking concentrator array. A real-time profile of the TACS activity was produced and the data analysis showed a deviation in maximum power of less than 1% during the day after accounting for other variations [Daniel A. Pritchard, 1983].  

Ashok Kumar Saxena and V. Dutta had designed a versatile microprocessor based controller for solar tracking in 1990 .Controller had the capability of acquiring photovoltaic and metereological data from a photovoltaic system and controlled the battery /load. These features were useful in autonomous PV systems that were installed for system control as well as monitoring in remote areas .Solar tracking was achieved in both open loop as well as closed loop modes. The controller was totally automatic and did not require any operator interference unless needed [Ashok Kumar Saxena and V.Dutta,[1990]..

A.Konar and A.K. Mandal had given a microprocessor based automatic position control scheme in 1991. They had designed for controlling the azimuth angle of an optimally tilted photovoltaic flat type solar panel or a cylindrical parabolic reflector to get the illuminating surface appropriately positioned for the collection of maximum solar irradiance. The proposed system resulted in saving of energy .It was designed as a pseudo tracker in which step tracking scheme had been used to keep the motor idle to save energy .The tracking system was not constrained by the geographical location of installation of the solar panel since it was designed for searching the MSI in the whole azimuth angle of 360” during the locking cycle. Temporal variations in environmental parameters caused by fog, rain etc., at a distance from the location where panel was mounted, did not affect proper direction finding [A. Konar and A.K Mandal, 1991]

A. Zeroual et al. had designed an automatic sun-tracker system for optimum solar energy collection in 1997. They used electro-optical sensors for sun finding and a microprocessor controller unit for data processing and for control of the mechanical drive system. This system allowed solar energy collectors to follow the sun position for optimum efficiency. It had a modular structure which facilitates its application to different systems without great modifications. The system had been applied to control a water heating parabolic solar system for domestic uses. Many parameters had been controlled for system security such as temperature, pressure and wind velocity. The system had been tested for a long period in variable illumination. The result showed that it operated satisfactorily with high accuracy [A.Zeroual et al., 1997].

F. Huang et al. had designed a microcontroller based automatic sun tracker combined with a new solar energy conversion unit in 1998 .The automatic sun tracker was implemented with a dc motor and a dc motor controller. The solar energy conversion unit consisted of an array of solar panels, a step-up chopper, a single-phase inverter, an ac mains power source and a microcontroller based control unit. High efficiency was achieved through the automatic sun tracker and the MPP detector. In this system, the MPP detection and the power conversion were realized by using the same hardware circuit. In the existed MPP detectors, the detection of the MPP was achieved by using analog computing, comparing, and holding. In contrast to the existed ones, in the new system, the MPP was detected by software which was embedded in a microcontroller [F. Huang et al., 1998].

Hasan A. Yousef had given the design and Implementation of a fuzzy logic computer controlled sun tracking system to enhance the power output of photo-voltaic (PV) solar panels in 1999. The tracking system was driven by two permanent magnet DC motors to provide motion of the PV panels in two axes. A PC based fuzzy logic control algorithm utilizing the knowledge of the system behaviour was designed in order to achieve the control objectives because the control of the dual axis tracking system was not an easy task due to nonlinear dynamics and unavailability of the model parameters. The implementation of such a controller was realized by building an interfacing card consisting of sensor data acquisition, motor driving circuits, signal conditioning circuits and serial communication with the PC. The developed fuzzy logic controller algorithm had a simple structure, in fact it was of P-type like controller [ Hasan A. Yousef , 1999].

Chee-Yee Chong et al. had given the process architectures for track fusion in 2000. They used the concept of multiple targets tracking because it had shown that tracking with multiple sensors can provide better performance than using a single sensor. One approach to multiple targets tracking with multiple sensors was to first perform single sensor tracking and then fused the tracks from the different sensors. Two processing architectures for track fusion were presented: sensor to sensor track fusion, and sensor to system track fusion. They presented different approaches for fusing track state estimates, and compared their performance through theoretical analysis and simulations [Chee-Yee Chong et al., 2000].  

Eftichios Koutroulis et al. had given the microcontroller based photovoltaic maximum power point tracking control system in 2001. Maximum power point tracking (MPPT) was used in photovoltaic (PV) systems to maximize the photovoltaic array output power, irrespective of the temperature and irradiation conditions and of the load electrical characteristics. A new MPPT system had developed, consisting of a Buck-type dc/dc converter, which was controlled by a microcontroller-based unit. The PV array output power delivered to a load was maximized using MPPT control systems, which consisted of a power conditioner to interface the PV output to the load, and a control unit, which drove the power conditioner such that it extracted themaximum power from a PV array. It was used to directly control the dc/dc converter, thus reducing the complexity of the system.The resulting system had high-efficiency lower-cost[Eftichios Koutroulis et al.2001].

Yeong Chau Kuo et al. proposed a novel maximum power point tracking (MPPT) controller for a photovoltaic (PV) energy conversion system in 2001. They used the slope of power versus voltage of a PV array, the proposed MPPT controller allowed the conversion system to track the maximum power point very rapidly. As opposed to conventional two-stage designs, a single stage configuration was implemented, resulted in size and weight reduction and increased efficiency. The proposed system acted as a solar generator on sunny days, in addition to working as an active power line conditioner on rainy days. Finally, computer simulations and experimental results demonstrated the superior performance of the proposed technique [Yeong ChauKuo et al., 2001]

K. K. Tse et al. had presented a novel technique for efficiently extracting maximum power from photovoltaic (PV) panels in 2002. The power conversion stage, which was connected between a PV panel and a load or bus, was a SEPIC or converter or their derived circuits operated in discontinuous inductor–current or capacitor– voltage mode. Method of locating the maximum power point (MPP) was based on injecting a small-signal sinusoidal perturbation into the switching frequency and compared the ac component and the average value of the panel terminal voltage. Apart from not requiring any sophisticated digital computation of the panel power, the proposed technique did not approximate the panel characteristics and could even locate the MPP under wide insolation conditions. They had verified tracking capability experimentally with a 10 W solar panel under a controlled experimental setup [K.K.Tse et al., 2002].

1.3 Need of Sun Tracker:

Each day, the sun rises in the east, moves across the sky, and sets in the west. Whenever the sun is shining on us, it is sending energy in our direction. We can feel the heat from the sun, and we can see objects that are illuminated by the light from the sun as it moves across the sky. However, if we could get a solar cell to turn and look at the sun all day, then it would be receiving the maximum amount of sunlight possible and converting it into the more useful energy form electricity. If we are located in the tropics, we see that the sun appears to follow a path that is nearly directly overhead. However, for locations north or south of the tropics (e.g., latitudes greater than 23.5 degr12ees), the sun never reaches a position that is directly overhead. Instead, it follows a path across the southern or the northern part of the sky

1.4 Objective of Work

If we could configure a solar cell so that it faces the sun continually as it moves across the sky from east to west, we could get the most electrical energy possible. One way to do this, of course, is by hand. However, keeping a solar cell facing the sun throughout the day is not a very efficient use of a person’s time. Going outside to a solar cell every hour to turn it toward the sun might be possible, but this would still not be an efficient method. A photo sensor is employed to control the solar cell tracking system. For example, if the photo sensor is not aligned with sun rays, then it could turn on the motor until it is once again aligned. If the motor is attached to the frame holding the solar cell, then the solar cell could be moved to face the sun. As long as the photo sensor is in alignment with the sun, nothing happens. However, when the sun moves across the sky and is not in proper alignment with the photo sensor, then a motor moves the frame until the photo sensor is in the sun once more. This could have the effect of keeping the solar cell facing the sun as it moves across the required human attention. So we need a tracking system that would automatically keep the solar cell facing the sun throughout the day. We have to build an automated system of our own, using a single motor. The system includes a frame on which a solar cell could be mounted. The frame is to move so that it faces the sun as it travels across the sky during the day. The frame could be driven by an electric motor that turns on and off in response to the movement of the sky. Here in this thesis work, panel itself work as a sensor.

1.5 Solar Energy

One of the most important problems facing the world today is the energy problem. This problem is resulted from the increase of demand for electrical energy and high cost of fuel. The solution was in finding another renewable energy sources such as solar energy, wind energy, potential energy...etc. Nowadays, solar energy has been widely used in our life, and it's expected to grow up in the next years. Solar energy has many advantages:

1.Need no fuel

2.Has no moving parts to wear out

3.Non-polluting & quick responding

4.Adaptable for on-site installation

5.Easy maintenance

6. Can be integrated with other renewable energy source

7.Simple & efficient

Tracking systems try to collect the largest amount of solar radiation and convert it into usable form of electrical energy (DC voltage) and  store this energy into batteries for different types of applications. The sun tracking systems can collect more energy than what a fixed panel system collects.

1.6 ORGANZIATION OF THE REPORT

          The report consists of five chapters, CHAPTER 2 deals with introduction of SOLAR TRACKING and its various types. It also discusses about the SOLAR ARRAYS and its power production. This also discusses about solar mount types

         

CHAPTER 3 deals with STEPPER MOTOR and its various types. Along with this it also explains about the excitation of stepper motors

CHAPTER 4 explains the logic behind the project. The logic that we use in this project is FUZZY LOGIC.   

CHAPTER 5 In this project is a chapter that consists details about the HARDWARE MODULES of this project

CHAPTER 6 This is the chapter that analysis the RESULTS of the project. It also gives some discussion about the obtained results

  

CHAPTER 7 of this report consists of CONCLUSION and the FUTURE ENCHANCEMENT for our project

Chapter 2

solar tracking

2.1 introduction

There are several forms of tracking currently available; these vary mainly in the method of implementing the designs. The two general forms of tracking used are fixed control algorithms and dynamic tracking. The inherent difference between the two methods is the manner in which the path of the sun is determined. In the fixed control algorithm systems, the path of the sun is determined by referencing an algorithm that calculates the position of the sun for each time period. That is, the control system does not actively find the sun's position but works it out  given the current time,  day,  month, and year.  The dynamic tracking system, on the other  hand, actively searches for the sun's position at any time of day (or night).Common to both forms o f tracking is the control system. This system consists of so me method of direction control, such as DC motors, stepper motors, and servo motors, which are directed by a control circuit, either digital or analog.

2.2 Relevance of Solar Trackers

 For people living in remote communities, often in third world countries, access to grid-connected electricity is not always possible. Often the nearest utility is a long distance from  homes and the cost o f developing the infrastructure that would allow for access to the grid  is prohibitive. Remote communities in third world countries are of course not the only ones  that suffer this dilemma. Australia is a large country with many farmers and communities  that are remote from the local grid and in these cases alternative sources of electrical  power must be obtained.

Equivalent Circuit of a Solar Cell  

                

Fig.2.1

Fig, 2.2 The Schematic Symbol of Solar Cell

To understand the electronic behavior of a solar cell, it is useful to create a model which is electrically equivalent, and is based o n discrete electrical components whose behavior is well know. An ideal solar cell may be modeled by a current source  in parallel with a diode. In practice no solar cell is ideal, so a shunt resistance and a series resistance component are added to the model. The result is the "equivalent circuit of a solar cell" as shown above. The other figure is the schematic representation of a solar cell for use in circuit diagrams

2.3 Materials and Efficiency

Various materials have been investigated for solar cells. There are two main criteria - efficiency and cost. Efficiency is a ratio of the electric power output to the light power input. Ideally, near the equator at noon on a clear day; the solar radiation is approximately 1000 W/m². So a 10% efficient module of 1 square meter can power a 100 W light bulb. Costs and efficiencies of the materials vary greatly. By far the most common material for solar cells (and all other semiconductor devices) is crystalline silicon. Crystalline silicon solar cells come in three primary categories1

2.3.1 Single crystal or monocrystalline wafers. Most commercial monocrystalline cells have efficiencies on the order of 14%; the sun power cells have high efficiencies around 20%. Single crystal cells tend to be expensive, and because they are cut from cylindrical ingots, they cannot completely cover a module without a substantial waste of refined silicon. Most monocrystalline panels have uncovered gaps at the corners of four cells.

2.3.2  Poly or multi crystalline made from cast ingots - large crucibles of molten silicon carefully cooled and solidified. These cells are cheaper than single crystal cells, but also somewhat less efficient. However, they can easily be formed into square shapes that cover a greater fraction of a panel than monocrystalline cells, and this compensates for their lower efficiencies.

2.3.3   Ribbon silicon formed by drawing flat thin films from molten silicon and has a multi crystalline structure. These cells are typically the least efficient, but there is a cost savings since there is very little silicon waste and this approach does not require sawing from ingots. These technologies are wafer based manufacturing. In other words, in each of the above approaches, self supporting wafers of approximate 300 micro metres thick are fabricated and then soldered together to form a module. Thin film approaches are module based. The entire module substrate is coated with the desired layers and a laser scribe is then used to delineate individual cells. Two main thin film approaches are amorphous silicon and CIS:

2.3.4   Amorphous silicon films are fabricated using chemical vapor deposition techniques, typically plasma enhanced (PE-CVD). These cells have low efficiencies around 8%.CIS stands for general chalcogenide films of Cu. While these films can achieve 11% efficiency, their costs are still too high.

2.4 Photovoltaic Cell

A solar electric module (also known as a ‘panel’) is made up of many PV cells that are wired together in a series to achieve the desired voltage. The thin wires on the front of the module pick up the free electrons from the PV cell

A solar cell or a photovoltaic cell, converts sunlight directly into electricity at the atomic level by absorbing light and releasing electrons. This behavior is a demonstration of the photoelectric effect, a property of certain materials that produce small amounts of electric current when exposed to light.

 A typical solar cell has two slightly different layers of silicon in contact with each other. When the sun shines on these layers, it causes electrons to move across the junction between the layers, creating an electric current

The top silicon layer in a solar cell is very thin. It includes as a deliberate impurity some atoms of an element that has more electrons than silicon, such as phosphorus. These impurity atoms are called donors, because they can donate or release their extra electrons into the silicon layer as free electrons.

The bottom silicon layer in a solar cell is much thicker than the top layer. It has as an impurity some atoms of an element such as boron that has fewer electrons than silicon atoms. These impurity atoms are called acceptors, because relative to the silicon atoms they have “holes” where electrons can be accepted.

At the junction where these two layers come together, the donors next to the junction give up their electrons, which migrate across the junction to the adjacent acceptors. This gives the top layer with the donors a net positive charge (because they gave up their excess electrons), and the bottom layer a net negative charge (because the acceptors have their “holes” filled with the excess electrons).

When light shines on the layers, atoms in the bottom layer absorb the light and release electrons in accordance with the photoelectric effect. These electrons then migrate to the positively charged top layer. This movement of electrons creates the electrical current from a solar cell that can flow through a circuit with contacts at the two layers.

During the central part of the day, the output of the solar cell will be at or near its maximum because the sunlight is arriving at a more direct angle. At the beginning and at the end of the day, the output will fall off regardless of the orientation of the solar cell, mainly because the sunlight has to travel obliquely through the atmosphere at these times, arriving at a low angle. This decreases the intensity of the sunlight.

Due to the designing, a solar cell will develop a voltage that is fairly constant. However, the higher the intensity of the sunlight falling on the cell, the more electrical current is produced. This is why a voltmeter connected to a solar cell will have just about the same reading from midmorning to mid afternoon, while a motor connected to the solar cell will run faster during the middle of the day, when the output current is a maximum.

Figure 2.3 photovoltaic cell

2.5 Photovoltaic Module

Photovoltaic (PV) modules are devices that cleanly convert sunlight into electricity and offer a practical solution to the problem of power generation in remote areas. They are especially useful in situations where the demand for electrical power is relatively low and can be catered for using a low number of modules. Running lights, a refrigerator and a television in a small home or the powering of water pumps on a remote farming property are examples of tasks that a small array of solar modules can cope with. It has high purchase cost and to keep the number of modules required to a minimum, it is important that the modules produce as much electricity during the hours that they are exposed to sunlight as possible.

2.6 Solar Tracker Fundamentals

A solar tracker is a device that is used to align a single P.V module or an array of modules with the sun. Although trackers are not a necessary part of a P.V system, their implementation can dramatically improve a systems power output by keeping the sun in focus throughout the day. Efficiency is particularly improved in the morning and afternoon hours where a fixed panel will be facing well away from the suns rays. P.V modules are expensive and in most cases the cost of the modules themselves will outweigh the cost of the tracker system. Additionally a well designed system which utilizes a tracker will need fewer panels due to increased efficiency, resulting in a reduction of initial implementation costs.

2.7 OVERVIEW of Current Tracker Drive Types

Solar trackers can be divided into three main types depending on the type of drive and sensing or positioning system that they incorporate. Passive trackers use the sun’s radiation to heat gases that move the tracker across the sky. Active trackers use electric or hydraulic drives and some type of gearing or actuator to move the tracker. Open loop trackers use no sensing but instead determine the position of the sun through prerecorded data for a particular site.

2.7.1 Gas Trackers (Passive Trackers)

Passive trackers use a compressed gas fluid as a means of tilting the panel. A canister on the sun side of the tracker is heated causing gas pressure to increase and liquid to be pushed from one side of the tracker to the other. This affects the balance of the tracker and caused it to tilt. This system is very reliable and needs little maintenance.

Although reliable and almost maintenance free, the passive gas tracker will very rarely point the solar modules directly towards the sun. This is due to the fact that temperature varies from day to day and the system can not take into account this variable. Overcast days are also a problem when the sun appears and disappears behind clouds causing the gas in the liquid in the holding cylinders to expand and contract resulting in erratic movement of the device. Passive trackers are however an effective and relatively low cost way of increasing the power output of a solar array.

2.7.2 Active Trackers

Active trackers measure the light intensity from the sun to determine where the solar modules should be pointing. Light sensors are positioned on the tracker at various locations or in specially shaped holders. If the sun is not facing the tracker directly there will be a difference in light intensity on one light sensor compared to another and this difference can be used to determine in which direction the tracker has to tilt in order to be facing the sun.

2.7.3 Open Loop Trackers

Open loop trackers determine the position of the sun using computer controlled algorithms or simple timing systems.

2.8 Types of Solar Trackers

There are many different types of solar tracker which can be grouped into single axis and double axis models..

2.8.1 Single Axis Trackers:

Single axis solar trackers can either have a horizontal or a vertical axle. The horizontal type is used in tropical regions where the sun gets very high at noon, but the days are short. The vertical type is used in high latitudes (such as in UK) where the sun does not get very high, but summer days can be very long. These have a manually adjustable tilt angle of 0 - 45 °and automatic tracking of the sun from East to West. They use the PV modules themselves as light sensor to avoid unnecessary tracking movement and for reliability. At night the trackers take up a horizontal position.

Figure 2.4 single axis solar tracker

2.8.2 Dual Axis Trackers

Double axis solar trackers have both a horizontal and a vertical axle and so can track the Sun's apparent motion exactly anywhere in the world. This type of system is used to control astronomical telescopes, and so there is plenty of software available to automatically predict and track the motion of the sun across the sky. Dual axis trackers track the sun both East to West and North to South for added power output (approx 40% gain) and convenience.

 Figure 2.5 dual axis solar tracker

2.9 Tracker Mount Types 

Solar trackers may be active or passive and may be single axis or dual axis. Single axis trackers usually use a polar mount for maximum solar efficiency. Single axis trackers will usually have a manual elevation (axis tilt) adjustment on a second axis which is adjusted on regular intervals throughout the year. There are two types of dual axis trackers, polar and altitude-azimuth.

2.9.1 POLAR AXLE

Polar trackers have one axis aligned close to the axis of the rotation of the earth hence the name polar .By this, only high accuracy astronomical telescope mounts rotate on an axis parallel to the earth’s axis .For solar trackers ,so called “polar” trackers have their axis aligned perpendicular to the ‘ecliptic”(an imaginary disc containing the apparent path of the sun).

Simple solar trackers are manually adjusted to compensate for the shift of the ecliptic through the seasons. Adjustment is usually at least twice a year at the equinoxes; once to establish a position for autmn and winter and a second adjustment for spring and summer .Such trackers are also referred to as “single axis” because only one drive mechanism is needed for daily operation. This reduces the cost and allows the use of passive tracking methods.

2.9.2 Horizontal Axle

Single axis horizontal trackers may be oriented by either passive or active mechanisms .In these, a long horizontal tube is supported on bearings mounted upon pylons or frames .The axis of the tube is on a north-south line. Panels are mounted upon the tube, and the tube will rotate on its axis to track the apparent motion of the sun through the day. Since these do not tilt toward the equator they are not especially effective during winter midday(unless located near the equator),but add a substantial amount of productivity during the spring and summer seasons when the solar path is high in the sky. These devices are less effective at higher latitudes .The principal advantage is the inherent robustness of the supporting structure and the simplicity of the mechanism. Since the panels are horizontal, they can be compactly placed on the axle tube without danger of self-shading and are also readily accessible for cleaning. For active mechanisms, a single control and motor may be used to actuate multiple rows of panels.

Figure 2.6 horizontal mount

2.9.3 Vertical Axle

A single axis tracker may be constructed that pivots only about a verticle axle , with the panels either vertical or at a fixed elevation angle. Such trackers are suitable for high latitudes, where the apparent solar path is not especially high ,but which leads to long days in summer, with the sun travelling through a long arc. This method has been used in the construction of a cylindrical house in austria (latitude above 45 degrees north) that rotates in its entirety to track the sun, with vertical panels mounted on one side of the building . The solar panels rotate independently, allowing control of the natural heating from the sun.

                                     

Figure 2.7 Vertical Axle Mount

2.9.4 Altitude Azimuth

Two –axis mount

Point focus parabolic dish with sterling system. The horizontally rotating azimuth table mounts the vertical frames on each side which hold the elevation triunions for the dish and its integral engine/generator mount.

Restricted to active trackers, this mount is also becoming popular as a large telescope mount owing to its structural simplicity and compact dimensions .One axis is a vertical pivot shaft or horizontal ring mount that allows the device to be swung to a compass point. The second axis is a horizontal elevation pivot mounted upon the azimuth platform. By using combinations of the two axis, any location in the upward hemisphere may be pointed. Such systems may be operated under computer control according to the expected solar orientation, or may use a tracking sensor to control motor drives that orient the panels toward the sun. This type of mount is also used to orient parabolic reflectors that mount a sterling engine to produce electricity at the device.

                           

                                            Figure 2.8: Two Axis Mount

CHAPTER 3

STEPPER MOTOR

3.1 INTRODUCTION

The stepper motor is an electromagnetic device that converts digital pulses into mechanical shaft rotation. The shaft or spindle of a stepper motor rotates in discrete step increments when electrical command pulses are applied to it in the proper sequence. The sequence of the applied pulses is directly related to the direction of motor shafts rotation. The speed of the motor shafts rotation is directly related to the frequency of the input pulses and the length of rotation is directly related to the number of input pulses applied. Many advantages are achieved using this kind of motors, such as higher simplicity, since no brushes or contacts are present, low cost, high reliability, high torque at low speeds, and high accuracy of motion. Many systems with stepper motors need to control the acceleration/ deceleration when changing the speed.  

Figure 3.1 stepper motor

3.2 Bipolar v/s. Unipolar Stepper Motors

The two common types of stepper motors are the bipolar motor and the unipolar motor. The bipolar and unipolar motors are similar, except that the unipolar has a center tap on each winding. The bipolar motor needs current to be driven in both directions through the windings, and a full bridge driver is needed .The center tap on the unipolar motor allows a simpler driving circuit, limiting the current flow to one direction. The main drawback with the unipolar motor is the limited capability to energize all windings at any time, resulting in a lower torque compared to the bipolar  motor. The unipolar stepper motor can be used as a bipolar motor by disconnecting the center tap. In unipolar there are 5 wires.One common wire and four wires to which power supply has to be given in a serial order to make it drive. Bipolar can have 6 wires and a pair of wires are given supply at a time to drive it in steps.

                                                                                       

Figure 3.2: A 2- phase (winding) unipolar Stepper Schematic.

 Figure 3.3: A two phase (winding) bipolar stepper motor.

3.3 Unipolar Stepper Motor:

In the construction of unipolar stepper motor there are four coils. One end of each coil is tide together and it gives common terminal which is always connected with positive terminal of supply. The other ends of each coil are given for interface. Specific colour code may also be given. Like in this motor orange is first coil (L1), brown is second (L2), yellow is third (L3), black is fourth (L4) and red for common terminal.

By means of controlling a stepper motor operation we can

1.     Increase or decrease the RPM (speed) of it

2.     Increase or decrease number of revolutions of it

3.     Change its direction means rotate it clockwise or anticlockwise

To vary the RPM of motor we have to vary the PRF (Pulse Repetition Frequency). Number of applied pulses will vary number of rotations and last to change direction we have to change pulse sequence. So, all these three things just depend on applied pulses. Now there are three different modes to rotate this motor

1. Single coil excitation

2. Double coil excitation

3. Half step excitation

In half step excitation mode motor will rotate at half the specified given step resolution. Means if step resolution is 1.8 degree then in this mode it will be 0.9 degree. Step resolution means on receiving on 1 pulse motor will rotate that much degree. If step resolution is 1.8 degree then it will take 200 pulses for motor to compete 1 revolution (360 degree). Specification of the stepper motor: Max rated current per coil: 0.75 Ampere, unipolar, 6 wires

The motors rotation has several direct relationships to these applied input pulses. The sequence of the applied pulses is directly related to the direction of motor shafts rotation.

The speed of the motor shafts rotation is directly related to the frequency of the input pulses and the length of rotation is directly related to the number of input pulses applied

                                   Table 3.1: Sequence of giving pulses to motor

.

3.4 Stepper Motor Advantages and Disadvantages

Advantages:

1. The rotation angle of the motor is proportional to the input pulse.

2. The motor has full torque at standstill (if the windings are energized)

3. Precise positioning and repeatability of movement since good stepper motors have an accuracy of 3 – 5% of a step and this error is non cumulative from one step to the next.

4. Excellent response to starting/ stopping/reversing.

5. Very reliable since there are no contact brushes in the motor. Therefore, the life of the motor is simply dependant on the life of the bearing.

6. The motors response to digital input pulses provides open-loop control, making the motor simpler and less costly to control.

7. It is possible to achieve very low speed synchronous rotation with a load that is directly coupled to the shaft.

8. A wide range of rotational speeds can be realized as the speed is proportional to the frequency of the input pulses.

Disadvantages:

1. Resonances can occur if not properly controlled.

2. Not easy to operate at extremely high speeds.

3.5 Open Loop Operation

One of the most significant advantages of a stepper motor is its ability to be accurately controlled in an open loop system. Open loop control means no feedback information about position is needed. This type of control eliminates the need for expensive sensing and feedback devices such as optical encoders. Position of stepper motor is known simply by keeping track of the input step pulses.

3.6 Stepper Motor Types

There are three basic stepper motor types. They are:

1.     Variable-reluctance

2.     Permanent-magnet

3.     Hybrid

3.6.1 Variable-reluctance (VR)

This type of stepper motor has been around for a long time. It is probably the easiest to understand from a structural point of view. This type of motor consists of a soft iron multi-toothed rotor and a wound stator. When the stator windings are energized with DC current the poles become magnetized. Rotation occurs when the rotor teeth are attracted to the energized stator poles.

Figure 3.4: Cross section of a variable reluctance motor.

3.6.2 Permanent Magnet (PM)

Often referred to as a “tin can” or “canstock” motor the permanent magnet step motor is a low cost and low resolution type motor with typical step angles of 7.5° to 15°. (48 – 24 steps/revolution) PM motors as the motor name implies have permanent magnets added to the motor structure. The rotor no longer has teeth as with the VR motor. Instead the rotor is magnetized with alternating north and south poles situated in a straight line parallel to the rotor shaft. These magnetized rotor poles provide an increased magnetic flux intensity and because of this the PM motor exhibits improved torque characteristics when compared with the VR type.

Figure 3.5: Principle of a PM type stepper motor.

3.6.3 Hybrid (HB)

The hybrid stepper motor is more expensive than the PM stepper motor but provides better performance with respect to step resolution, torque and speed. Typical step angles for the hybrid stepper motor, range from 3.6° to 0.9° (100 – 400 steps per revolution). The hybrid stepper motor combines the best features of both the PM and VR type stepper motors. The rotor is multi-toothed like the VR motor and contains an axially magnetized concentric magnet around its shaft. The teeth on the rotor provide an even better path which helps guide the magnetic flux to preferred locations in the airgap. This further increases the detent, holding and dynamic torque characteristics of the motor when compared with both the VR and PM types.

Figure 3.6: Cross section of hybrid stepper motor

.

3.7 Applications of Stepper Motor

A stepper motor can be a good choice whenever controlled movement is required. They can be used to advantage in applications where you need to control rotation angle, speed, position and synchronism. Because of the inherent advantages listed previously, stepper motors have found their place in many different applications. Some of these include printers, plotters, high end office equipment, hard disk drives, medical equipment, fax machines, automotive and many more.

3.8 The Rotating Magnetic Field

Figure 3.7: Magnetic field rotation in Stepper Motor

When a phase winding of a stepper motor is energized with current a magnetic flux is developed in the stator. The direction of this flux is determined by the “Right Hand Rule” which states: “If the coil is grasped in the right hand with the fingers pointing in the direction of the current in the winding (the thumb is extended at a 90° angle to the fingers), then the thumb will point in the direction of the magnetic field. The rotor then aligns itself so that the flux opposition is minimized. In this case the motor would rotate clockwise so that its south pole aligns with the north pole of the stator and its north pole aligns with the south pole of stator. To get the motor to rotate we must provide a sequence of energizing the stator windings in such a fashion that provides a rotating magnetic flux field which the rotor follows due to magnetic attraction.

3.9 Torque Generation

The torque produced by a stepper motor depends on several factors:

1.     The step rate

2.     The drive current in the windings

3.     The drive design or type

In a stepper motor a torque is developed when the magnetic fluxes of the rotor and stator are displaced from each other. The stator is made up of a high permeability magnetic material. The presence of this high permeability material causes the magnetic flux to be confined for the most part to the paths defined by the stator structure in the same fashion that currents are confined to the conductors of an electronic circuit. This serves to concentrate the flux at the stator poles. The torque output produced by the motor is proportional to the intensity of the magnetic flux generated when the winding is energized. The basic relationship which defines the intensity of the magnetic flux is defined by: H = (N * i) / l

Where:

N = Number of winding turns

i = Current

H = Magnetic field intensity

l = Magnetic flux path length

This relationship shows that the magnetic flux intensity and consequently the torque is proportional to the number of winding turns and the current and inversely proportional to the length of the magnetic flux path. It has been seen that the same frame size stepper motor could have very different torque output capabilities simply by changing the winding parameters.

CHAPTER 4

FUZZY LOGIC

4.1 INTRODUCTION

Fuzzy Logic was initiated in 1965, by Lotfi A. Zadeh , professor for computer science at the University of California in Berkeley. Basically, Fuzzy Logic (FL) is a multivalve logic, that allows intermediate values to be defined between conventional evaluations like true/false, yes/no, high/low, etc. Notions like rather tall or very fast can be formulated mathematically and processed by computers, in order to apply a more human-like way of thinking in the programming of computers. Fuzzy systems is an alternative to traditional notions of set membership and logic that has its origins in ancient Greek philosophy.

The precision of mathematics owes its success in large part to the efforts of Aristotle and the philosophers who preceded him. In their efforts to devise a concise theory of logic, and later mathematics, the so-called ”Laws of Thought” were posited . One of these, the ”Law of the Excluded Middle,” states that every proposition must either be True or False. Even when Parmenides proposed the first version of this law (around 400 B.C.) there were strong and immediate objections: for example, Heraclitus proposed that things could be simultaneously True and not True.

It was Plato who laid the foundation for what would become fuzzy logic, indicating that there was a third region (beyond True and False) where these opposites ”tumbled about.” Other, more modern philosophers echoed his sentiments, notably Hegel, Marx, and Engels. But it was Lukasiewicz who first proposed a systematic alternative to the bi–valued logic of Aristotle. Even in the present time some Greeks are still outstanding examples for fussiness and fuzziness, (note: the connection to logic got lost somewhere during the last 2 millenniums.

Fuzzy Logic has emerged as a a profitable tool for the controlling and steering of systems and complex industrial processes, as well as for household and entertainment electronics, as well as for other expert systems and certain other complex applications

4.2 FUZZY LOGIC

In this context, FL is a problem-solving control system methodology that lends itself to implementation in systems ranging from simple, small, embedded micro-controllers to large, networked, multi-channel PC or workstation-based data acquisition and control systems. It can be implemented in hardware, software, or a combination of both. FL provides a simple way to arrive at a definite conclusion based upon vague, ambiguous, imprecise, noisy, or missing input information. FL's approach to control problems mimics how a person would make decisions, only much faster.

4.3 FL DIFFERENCE FROM CONVENTIONAL CONTROL METHODS

FL incorporates a simple, rule-based IF X AND Y THEN Z approach to a solving control problem rather than attempting to model a system mathematically. The FL model is empirically based, relying on an operator's experience rather than their technical understanding of the system. For example, rather than dealing with temperature control in terms such as "SP =500F", "T <1000F", or "210C <TEMP <220C", terms like "IF (process is too cool) AND (process is getting colder) THEN (add heat to the process)" or "IF (process is too hot) AND (process is heating rapidly) THEN (cool the process quickly)" are used. These terms are imprecise and yet very descriptive of what must actually happen. Consider what you do in the shower if the temperature is too cold: you will make the water comfortable very quickly with little trouble. FL is capable of mimicking this type of behavior but at very high rate.

4.4 FL WORKING

FL requires some numerical parameters in order to operate such as what is considered significant error and significant rate-of-change-of-error, but exact values of these numbers are usually not critical unless very responsive performance is required in which case empirical tuning would determine them. For example, a simple temperature control system could use a single temperature feedback sensor whose data is subtracted from the command signal to compute "error" and then time-differentiated to yield the error slope or rate-of-change-of-error, hereafter called "error-dot". Error might have units of degs F and a small error considered to be 2F while a large error is 5F. The "error-dot" might then have units of degs/min with a small error-dot being 5F/min and a large one being 15F/min. These values don't have to be symmetrical and can be "tweaked" once the system is operating in order to optimize performance. Generally, FL is so forgiving that the system will probably work the first time without any tweaking.

4.5 benefits

FL offers several unique features that make it a particularly good choice for many control problems.

1) It is inherently robust since it does not require precise, noise-free inputs and can be programmed to fail safely if a feedback sensor quits or is destroyed. The output control is a smooth control function despite a wide range of input variations.

2) Since the FL controller processes user-defined rules governing the target control system, it can be modified and tweaked easily to improve or drastically alter system performance. New sensors can easily be incorporated into the system simply by generating appropriate governing rules.

3) FL is not limited to a few feedback inputs and one or two control outputs, nor is it necessary to measure or compute rate-of-change parameters in order for it to be implemented. Any sensor data that provides some indication of a system's actions and reactions is sufficient. This allows the sensors to be inexpensive and

imprecise thus keeping the overall system cost and complexity low.

4) Because of the rule-based operation, any reasonable number of inputs can be processed (1-8 or more) and numerous outputs (1-4 or more) generated, although defining the rulebase quickly becomes complex if too many inputs and outputs are chosen for a single implementation since rules defining their interrelations must also be defined. It would be better to break the control system into smaller chunks and use several smaller FL controllers distributed on the system, each with more limited responsibilities.

5) FL can control nonlinear systems that would be difficult or impossible to model mathematically. This opens doors for control systems that would normally be deemed unfeasible for automation.

4.6 THE RULE MATRIX

The fuzzy parameters of error (command-feedback) and error-dot (rate-of change-of-error) were modified by the adjectives "negative", "zero", and "positive". To picture this, imagine the simplest practical implementation, a 3-by-3 matrix. The columns represent "negative error", "zero error", and "positive error" inputs from left to right. The rows represent "negative", "zero", and "positive" "error-dot" input from top to bottom.

This planar construct is called a rule matrix. It has two input conditions, "error" and "error-dot", and one output response conclusion (at the intersection of each row and column). In this case there are nine possible logical product (AND) output response conclusions.

Although not absolutely necessary, rule matrices usually have an odd number of rows and columns to accommodate a "zero" center row and column region. This may not be needed as long as the functions on either side of the center overlap somewhat and continuous dithering of the output is acceptable since the "zero" regions correspond to "no change" output responses the lack of this region will cause the system to continually hunt for "zero". It is also possible to have a different number of rows than columns. This occurs when numerous degrees of inputs are needed.

The maximum number of possible rules is simply the product of the number of rows and columns, but definition of all of these rules may not be necessary since some input conditions may never occur in practical operation. The primary objective of this construct is to map out the universe of possible inputs while keeping the system sufficiently under control.

4.7 SOLAR fuzzy Controller    

The primary reason for choosing the fuzzy logic controller in this study is that the flexibility offered by it. In which the control strategy is represented by a set of rules and it doesn’t require the exact set of equations to represent the system. This allows the design to change the basic characteristics of the controller with a minimal efforts ie., simply by redefining  the rules. The block diagram of the fuzzy logic controller is shown in Fig. 4.5.

Figure 4.1 : Schematic diagram of Fuzzy Logic Controller

4.7.1 Membership Functions               

The present design utilizes three types of membership functions ( Γ, Ί & D). The input variables are partitioned into seven linguistic variables while the output variables are assigned form the any of the linguistic variables. The input and output membership functions with associated linguistic variables are shown in Fig. 6.

Figure 4.2 Input and output Membership function and linguistic Variables

4.7.2 Fuzzification

Fuzzification process convents the physical variables to fuzzy set variables. The crisp variables of the inputs are mapped into the fuzzy plane with the associated membership functions. It gives each input variable a membership function relating to the fuzzy set.

4.7.3 Fuzzy rule base

Each input variables are assigned to seven linguistics variables, therefore 49 rules are formulated. These rules are formulated with a simple IF-THEN structure. They map the inputs states into 49 output conditions. The fuzzy rules will take up the general form.

The rule base can be represented by the fuzzy associative memory (FAM) table shown in Table 1.

Table 4.1  FAM table for UPFC Fuzzy Logic Controller

Pe/dPe	VLN	LN	SN	Z	SP	LP	VLP
VLN	VVS	VS	S	SM	VSM	VVSM	M
LN	VS	S	SM	VSM	VVSM	M	VVLM
SN	S	SM	VSM	VVSM	M	VVLM	VLM
Z	SM	VSM	VVSM	M	VVLM	VLM	LM
SP	VSM	VVSM	M	VVLM	VLM	LM	L
LP	VVSM	M	VVLM	VLM	LM	L	VL
VLP	M	VVLM	VLM	LM	L	VL	VVL

4.8 Inference Engine

The Fuzzy logic controller discussed in this paper incorporates Mamdani’s implication method of inference. This implication has a simple min-max structure. It involves two phase of operations. In the first phase the two input variables are involved with min-operation, hence the antecedent pair in the rule structure are constructed by logical AND. Then all the rules are aggregated by using max operation.

4.9 Defuzzification 

Defuzzification is the process by which fuzzy linguistic variables are converted to real control variables. Different defuzzification techniques have been introduced depending on the complexity of the system. The weighted average method is adopted in this study.

CHAPTER 5

HARDWARE DESCRIPTION

5.1 Solar Charging circuit

An electronic circuit is designed, built and tested. This circuit regulates the process of photovoltaic solar panel battery charging process. The circuit is cheep and can be easily constructed from discrete electronic components. The circuit operation is based on matching the solar cell terminal load voltage to battery unit to be charged depending on the solar light intensity condition.  The use of this circuit may increase the overall charging current.

          This solar charging circuit may reduce the demand for electricity by making use of the collected and stored energy from the sunlight.

           The construction and the design of the solar charger is clearly explained in this report

5.2 Block Diagram of the hardware design

5.2.1 Control algorithm (DISPLAY)

1. Measure in circuit current.

2. If current is <dark value (It indicates onset of night) the tracker resets itself to reset position (extreme east) and sleeps for 10 hours, then it goes to step1.

3. If current <threshold value (minimal daylight current), wait for 15 minutes and go to step1.

4. Turn panel forward by 15◦and measure current again after a pause of 1 minute. If current increases, continue with rotation. If it decreases, then revert back by 15◦. If it remains constant, stop rotating, wait for 15 minutes and go to step 1. Using PIC 16F877A, in circuit current is being monitored as and when indicated in above algorithm and depend on the control strategy command is given to stepper motor to turn forward to backward .The monitored current is displayed on LCD panel . Here we use small stepper motor just for making the working model. We can use big motor of higher rating with proper gear arrangement to give automatic rotation to tracker.

5.2.2 CONTROLLER (PIC16F877A)

This pins rb0-rb7, and rd0-rd7 are digital i/o pins. The pins ccp1 and ccp2, which locations with rc1and rc2, can be used for a pwm signal (see DC motor tutorial). The pins an0-an7 are for analog i/o (see photoresistor tutorial). TX and RX are debugging i/o (see output message to computer tutotial).The remaining pins deal with power/ground, the clock signal, and programmer i/o.

A PIC is made of several “ports” each port is designated with a letter, rbo-rb7 are a port. rc0-rc7 and rd0-rd7 are a Port as well ra0-ra5 and re0-re2 are also ports, but with fewer pins. Some of these pins have special purposes, but most can be used as basic input/output pins

5.2.2 motor terminal identification

our motor terminals are

white, black-----common        

red            -----coil 1

green                 -----coil 2

red white   -----coil 3

green white--- –coil 4

The terminals are found using the measurement of resistance between the terminals.

5.3  DRIVER CIRUIT

5.4  LCD DISPLAY CIRCUIT

5.4.1 LCD DISPLAY

LCD is used in our proposed scheme to display the values of in-circuit current. For simulation purpose, we can use LCD in a 4-bit Mode. For that, we require only four data lines to be connected to the four port pins of PIC and three control signals to control the data flow and display..

Data can be displayed using following instructions:

Lcd_Config

Prototype – void Lcd_Config(unsigned short *port, unsigned short RS, unsigned short

EN, unsigned short WR, unsigned short D7, unsigned short D6, unsigned short D5, unsigned short D4).

Description - Initializes LCD at port with pin settings you specify: parameters RS,

EN, WR and D7. D4 need to be a combination of values 0–7 (e.g. 3, 6, 0, 7, 2, 1, 4).

Lcd_Init

Prototype – void Lcd _ Init (unsigned short *port)

Description- Initializes LCD at port with default pin settings

D7 → port.7

D6 → port.6

D5 → port.5

D4 → port.4

E → port.3

RS → port.2

Example - Lcd_Init (&PORTB);

RW → port.0

Lcd_Out

Prototype- void Lcd_Out_Cp(char *text);

Description - Prints text on LCD at specified row and column (parameters row and

col). Both string variables and literals can be passed as text.

Lcd_Out_Cp

Prototype- void Lcd _Out_Cp(char *text);

Description - Prints text on LCD at current cursor position. Both string variables and

literals can be passed as text.

Lcd_Chr

Prototype – void Lcd_Chr (unsigned short row, unsigned short col, char character);

Description - Prints character on LCD at specified row and column (parameters row

and col). Both variables and literals can be passed as character.

Lcd_Chr_Cp

Prototype – void Lcd_Chr_Cp(char character);

Description - Prints character on LCD at current cursor position. Both variables and

literals can be passed as character.

Lcd_Cmd

Prototype – void Lcd_Cmd(unsigned short command);

Description - Sends command to LCD. You can pass one of the predefined constants to the function.

5.5 Stepper motor driver circuit l297 to l298

This Step motor controller uses the L297 and L298N driver combination; it can be used as stand alone or controlled by microcontroller. It is designed to accept step pulses at up to 25,000 per second. An on-board step pulse generator can be used if desired (40-650 pps range). Single supply operation is standard All eight

fig 5.5 Stepper motor driver circuit l297 to l298

5.6 ds1307 rtc

A real time clock is basically just like a watch - it runs on a battery and keeps time for you even when there is a power outage! Using an RTC, you can keep track of long timelines, even if you reprogram your microcontroller or disconnect it from USB or a power plug.

Most microcontrollers, including the Arduino have a built-in timekeeper called millis() and theres also timers built into the chip that can keep track of longer time periods like minutes or days. So why would you want to have a seperate RTC chip? Well, the biggest reason is that millis() only keeps track of time since the Arduino was last powered -that means that when the power is turned on, the millisecond timer is set back to 0. The Arduino doesnt know its 'Tuesday' or 'March 8th' all it can tell is 'Its been 14,000 milliseconds since I was last turned on'. OK so what if you wanted to set the time on the Arduino? You'd have to program in the date and time and you could have it count from that point on. But if it lost power, you'd have to reset the time. Much like very cheap alarm clocks: every time they lose power they blink 12:00

While this sort of basic timekeeping is OK for some projects, some projects such as data-loggers, clocks, etc will need to have consistant timekeeping that doesnt reset when the Arduino battery dies or is reprogrammed. Thus, we include a seperate RTC! The RTC chip is a specialized chip that just keeps track of time. It can count leap-years and knows how many days are in a month, but it doesn't take care of Daylight Savings Time (because it changes from place to place

Chapter 6

Result and discussion

6.1 CONSOLIDATED TABLE 

date	02/03/2011		05/03/2011		07/03/2011		09/03/2011		10/03/2011
time	deg	watt	deg	watt	deg	watt	deg	watt	deg	watt
10.00am	0	13.7198	50	22.2707	30	16.3325	50	19.254	50	22.9969
10.30am	70	13.1535	50	26.7465	50	17.138	80	19.5539	70	24.7159
11.00am	80	13.4435	70	25.7123	40	18.35	90	26.7712	70	24.4696
11.30am	100	13.9111	80	22.6325	50	16.7041	80	15.4179	80	24.9001
12.00pm	90	14.7425	100	19.058	90	16.99	120	24.4807	80	25.8172
12.30pm	60	13.4736	100	27.7504	90	17.2516	120	28.888	90	24.9318
1.00 pm	90	13.7135	90	16.4340	90	17.443	100	16.055	90	25.7936
1.30 pm	100	13.8015	100	17.556	100	17.392	100	23.9554	100	23.6397
2.00 pm	100	13.899	120	16.5271	120	17.38	110	20.8272	110	25.1025
2.30 pm	110	13.5649	110	16.6854	100	17.633	130	19.2713	130	21.7499
3.00 pm	110	13.4844	120	17.7197	120	18.404	120	19.3962	150	21.6789
3.30 pm	150	15.3956	110	17.7052	120	17.9427	120	20.4098	140	20.0944
4.00 pm	140	13.3593	130	17.3944	140	17.13	140	16.0364	160	18.3355

CHAPTER 7

CONCLUSION & SCOPE FOR FUTURE WORK

7.1 generaL

This chapter presents the review of work done, results obtained in this solar of the project

7.2 CONCLUSION

In this thesis, the sun tracking system was implemented which is based on PIC microcontroller. After examining the information obtained in the data analysis section, it can be said that the proposed sun tracking solar array system is a feasible method of maximizing the energy received from solar radiation. The controller circuit used to implement this system has been designed with a minimal number of components and has been integrated onto a single PCB for simple assembly.

The use of stepper motors enables accurate tracking of the sun while keeping track of the array's current position in relation to its initial position. The automatic solar radiation tracker is an efficient system for solar energy collection. It has been shown that the sun tracking systems can collect about 8% more energy than what a fixed panel system collects and thus high efficiency is achieved through this tracker. 8% increase in efficiency is not the most significant figure; it can be more prominent in concentrating type reflectors.

7.2 Scope for Future Work

To improve the sun tracking, a stand alone sun tracker can be designed using 18 series

PIC microcontroller. In 18 series PIC microcontroller, data can be stored periodically in MMC card .We need not to do it manually (no need of rotation). In this proposed area, we took 45 degree as standard alignment during results which had been taken in April, 2008. Alignment can be varied changing with season. Moreover, concentrating type collectors are more efficient than flat plate collectors. We can make use of that to increase efficiency.

REFERENCES

[Aliman et al., 2007] Omar Aliman, Ismail Daut, Muzamir Isa and Mohd Rafi Adzman, “Simplification of Sun Tracking Mode to Gain High Concentration Solar Energy” American Journal of Applied Sciences, 2007, Page(s):171-175.

[Aliman and Daut , 2007] Omar Aliman, Ismail Daut, “Rotation-Elevation of Sun Tracking Mode to Gain High Concentration Solar Energy”, IEEE Conference, 12-14 April 2007, Page(s):551 – 555

[Armstrong and Hurley, 2005] S. Armstrong and W.G Hurley “Investigating the Effectiveness of Maximum Power Point Tracking for a Solar System”, IEEE Conference on Power Electronics, 2005 Page(s):204 – 209.

[Chong et al., 2000], Chee-Yee Chong, Mori, S. Barker, W.H and Kuo-Chu Chang, “Architectures and Algorithms for Track Association and Fusion”, IEEE Transaction, Volume15, Issue 1, Jan.2000, Page(s):5- 13.

[Chung et al., 2003] Henry Shu-Hung Chung, K.K Tse, S.Y. Ron Hui, C.M. Mok, M.T. Ho, “A novel maximum power point tracking technique for solar panels using a SEPIC or Cuk converter”, IEEE Transactions on Power Electronics, Volume 18, Issue 3, May 2003 Page(s):717 – 724.

[Hua and Shen, 1998] Chihchiang Hua and Chihming Shen, “Comparative study of peak power tracking techniques for solar storage system”, APEC proceedings on Applied Power Electronics, Volume2, 15-19Feb.1998, Page(s):679-685.

[Huang.F. et al.,1998] F. Huang, D.Tien and James Or, “A microcontroller based automatic sun tracker combined with a new solar energy conversion unit” IEEE Proceedings on Power Electronic Drives and Energy Systems for Industrial Growth, Volume 1, 1-3 Dec. 1998, Page(s):488 - 492 .

[Kobayashi Kimiyashi et al., 2004] Kimiyoshi Kobayashi, Hirofumi Matsuo and Yutaka Sekine, “A novel optimum operating point tracker of the solar cell power supply system” ,IEEE Conference on Power Electronics, Volume 3, 20-25 June 2004,Page(s):2147 - 2151 Vol.3. [Konar and Mandal, 1991] A.Konar and A.K Mandal, “Microprocessor based Sun

Tracker”, IEEE Proceedings-A, Vol. 138, No.4, July 1991, Page(s):237-241. [Koutroulis et al., 2001] Koutroulis, E.Kalaitzakis, K. Voulgaris and N.C., “Development of a microcontroller-based, photovoltaic maximum power point tracking control system” IEEE Transactions on Power Electronics, Volume 16, Issue 1, Jan. 2001 Page(s):46 – 54    

[Kuo et al., 2001] Yeong-Chau Kuo, Tsorng-Juu Liang and Jiann-Fuh Chen, “Novel Maximum-Power-Point-Tracking Controller for Photovoltaic Energy Conversion System” IEEE Transactions on Industrial Electronics, Volume 48, Issue 3, June 2001 Page(s):594 – 601. [Pritchard, 1983] Daniel A. Pritchard, “Sun Tracking by Peak Power Positioning for Photovoltaic Concentrator Arrays” IEEE Transactions on Control System, Volume 3, Issue3, Aug1983,Page(s):2-8.

[Saxena and Dutta, 1990] Ashok Kumar Saxena and V.K Dutta, “A Versatile Microprocessor based Controller for Solar Tracking”, IEEE Conference, Vol. 2, 21 – 25May, 1990, Page(s):1105-1109.

[Shanmugam and Christraj, 2005], S.Shanmugam and W.Christraj, “The Tracking of the Sun for Solar Paraboloidal Dish Concentrators”, ASME Transactions, Vol.127, February 2005, Page(s):156-160.

[Tse et al., 2002] K.K Tse, M.T. Ho, Henry S.H Chung and S.Y Hui, “A novel Maximum Power Point Tracker for PV Panels using Switching Frequency Modulation”, IEEE Transactions on Power Electronics, Volume 17, Issue 6, Nov. 2002,Page(s):980–989.

Zeroual .A et al., 1997] A. Zeroual, M. Raoufi , M. Ankrim and A.J. Wilkinson, “Design and construction of a closed loop Sun Tracker with Microprocessor Management” , International Journal on Solar Energy, Vol. 19, 1998, Page(s): 263- 274.

[Sungur Cemil, 2007] Cemil Sungur “Sun –Tracking System with PLC Control for Photo-Voltaic Panels” International Journal of Green Energy, Vol.4, 2007, Page(s): 635–643.

[Tse et al., 2002] K.K Tse, M.T. Ho, Henry S.H Chung and S.Y Hui, “A novel

Maximum Power Point Tracker for PV Panels using Switching Frequency Modulation”, IEEE Transactions on Power Electronics, Volume 17, Issue 6, Nov.

2002,Page(s):980–989.

[Wai and Wang Wen-Hung, 2008] Rong-Jong Wai and Wen-Hung Wang, “Grid- Connected Photovoltaic Generation System”, IEEE Transactions on Circuits and Systems I: Fundamental Theory and Applications , Volume 55, Issue 3, April 2008, Page(s):953 - 964

[Wai et al., 2006] Rong-Jong Wai, Wen-Hung Wang, Lin and Jun-You, “Grid- Connected Photovoltaic Generation System with Adaptive Step-Perturbation Method

and Active Sun Tracking Scheme”, IEEE Transactions on Industrial Electronics, Nov.

2006, Page(s):224 - 228

[Yousef, 1999] Hasan A Yousef , “Design and implementation of a fuzzy logic computer-controlled sun tracking system” , Proceedings of the IEEE International Symposium on Industrial Electronics, Volume 3, 12-16 July 1999, Page(s):1030 –

1034.

[Zeroual .A et al., 1997] A. Zeroual, M. Raoufi , M. Ankrim and A.J. Wilkinson,

“Design and construction of a closed loop Sun Tracker with Microprocessor Management” , International Journal on Solar Energy, Vol. 19, 1998, Page(s): 263-

274.

[http:PIC] “PIC 16F877 microcontroller” available at www.eng.uwi.tt/depts/elec /staff/feisal/ ee25m/resources/ee25m-lect2.pdf

[http:mikroC] “mikro C user manual” available at www.mikroe.com/pdf/ mikroc/mikroc_manual.pdf [http:motor] “Stepper motor Basics” available at www.solarbotics.net/library /pdflib/pdf/motorbas.pdf

We collected stepper motor details from this www.reuk.co.uk/examining-a-steppermotor.htm 

APPENDIX I

16F877A

High-Performance RISC CPU

1.     Only 35 single-word instruction to learn.

2.     All single-cycle instruction except for program branches, which are two-cycle.

3.     Operating speed :dc-20MZ clock input DC-200 ns instruction cycle

4.     Up to  8K x 14 words of flash program memory ,up to 368 * 8 bytes of data memory (RAM), up to 256 * 8 bytes of EEPROM Data Memory

5.     Pinout compatible to other 40-pin PIC16FXXX icrocontrollers

PERPHERAL FERTURES  

1.     TIMER 0 : 8-bit timer/counter with 8-bit prescaler.

2.     TIMER 1: 16bit timer/counter with prescaler can be incremented during sleep via exterbal crystal/clock.

3.     TIMER 2: 8-bit timer/counter with 8-bit period register,prescaler and postscaler

4.     Two  capture, compare,PWM modules – capture is 16-bit ,nax .resolution is 200 ns-PWM max. Resolution is 10-bit

5.     Synchrous serial port(SSP) with SPItm(MASTER MODE) and 12Ctm (MASTER/SLAVE).

6.     Universal Synchronous Asynchronous Receiver Transmitter (USART/SCI)with 9-bit address detection

7.     Parallel Slave Port (PSP) -8 bits wide with external RD,WR andCS Controls(40/44-pin only)

8.     Brown-out detection circuitry for brown-out Reset (BOR)

Analog features

1.     10-bit ,up to *-channel Analog – to –Digital Converter (A/D)

2.     Brown–out Reset (BOR)

3.     Analog Comparator m\Module with

a.     Two analog comparator

b.     Programmable on-chip voltage reference (VREF) module.

c.      Programmable input multiplexing from devices inputs and internal voltage reference

d.    Comparator outputs are externally accessible.

Special Microcontroller Fertures

1.     100,000erase/write cycle Enhanced Flash program memory typical.

2.     1,000,000 erase/write cycle Data EEPROM memory typical

3.     Data EEPROM Retention > 40 years

4.     Self-reprogrammable under software control

5.     In circuit Serial Programming (ICSPtm)via two pins

6.     Singlee-supply 5V In- Circuit serial programming

7.     Watchdog Timer(WDT) with its own on-chip RC oscillator for reliable operation

8.     Programmable code protection

9.     Power saving Sleep mode

10.                        Selectable oscillator options

11.                        In –Circuit Debug(ICD) via two pins.

CMOS technology

1.     Low-power,high-speed flash /EEPROM technology

2.     Fully static design

3.     Wide operating voltage range(2.0 V to 5.5 V)

4.     Commercial and industrial temperature ranges

5.     Low-power consumption.