The Solaris Power

 

 

SOLARIS POWER BE (ELECTRONICS) PROJECT REPORT Prepared By TAIMUR MUSHARRAF

05B-001-EE

HARIS IDREES

05B-003-EE

BABAR KHAN

05B-030-EE

SHOUKAT ALI IZHAR

05B-033-EE

BATCH -2005(B) Project Advisor Associate Prof. RAZA JAFRI DEPARTMENT OF ELECTRONICS ENGINEERING USMAN INSTITUTE OF TECHNOLOGY HAMDARD UNIVERSITY

 

We dedicate this book to our parents...

 

“A pessimist sees the difficulty in every opportunity; An optimist sees the opportunity in every difficulty”. Winston Churchill

 

ACKNOWLEDGEMENT

We would like to thank Mr. Musharraf H. Javed (CEO – TIE Hi-Tech) for his tremendous motivation, support and technical assistance without this project would not have been possible. We would also like to express our gratitude to Mr. Raza Jafri (Associate Professor & Internal Advisor) for his help and guidance throughout the project. In addition we would also like to acknowledge the help of Mr. Waseem Zeeshan (Assistant Professor) for his help in the initial distribution and the phase division of the project, Ms. Tabassum Waheed (Assistant Professor) for her help in the literary support and Mr. Salman Jafri (Assistant Professor) for his guidance in programming.

 

TABLE OF CONTENTS CHAPTER 1: Introduction .......................................................................................................1 Solaris Power ...............................................................................................................................2 Solar Power Plants…...………………………………………………………………………….3 Objective & Feasibility...……..…………………………………………………………………6 1.1 Block Diagram & Description ...........................................................................................8

CHAPTER 2: Project Design & Implementation ..............................................................11 Module Explanation ...................................................................................................................12 2.1 Tracker .............................................................................................................................12 2.2 Charge Controller Board ..................................................................................................14 2.2.1 Modified Charge Controller Board ...........................................................................17 2.2.2 PV Regulator .............................................................................................................23 2.2.3 AC Charger ...............................................................................................................27 2.3 Inverter .............................................................................................................................28 2.3.1 Methodology ............................................................................................................. 30 2.3.2 Block Diagram ..........................................................................................................30 2.3.3 PWM Control Circuit ................................................................................................32 2.3.4 H-Bridge....................................................................................................................38 2.3.5 Half Bridge Converter ...............................................................................................40 2.3.5.3 Ferrite Core Transformer ...................................................................................46 2.3.6 Modified Sine-wave Inverter ....................................................................................54

CHAPTER 3: Accessories .......................................................................................................58 3.1 Battery ..............................................................................................................................59 3.2 Photo Voltaic Cells ..........................................................................................................61 3.3 Display Panel ...................................................................................................................63 3.4 PIC Microcontroller .........................................................................................................64

CHAPTER 4: Fabrication & Performance Evaluation ...................................................67 Summary & Summation.............................................................................................................68 4.1 Final Designs & Pictures..................................................................................................59 4.2 Performance Charts ..........................................................................................................70 4.2.1 Tracker ......................................................................................................................70 4.2.2 PV Regulator .............................................................................................................70 4.2.3 Battery Charge Monitoring Board.............................................................................70 4.2.4 Inverter ......................................................................................................................71

  4.3 Conclusion .......................................................................................................................71 4.4 Cost Analysis ...................................................................................................................72

APPENDIX A: Firmware ........................................................................................................73 APPENDIX B: Transformer Core Datasheets ...................................................................80 APPENDIX C: Test Points & Troubleshooting .................................................................86 APPENDIX D: Software and Instruments ..........................................................................87 APPENDIX E: References ......................................................................................................88

CHAPTER: 1 

INTRODUCTION    

 

• Overview of Solar Energy  •  Current projects of the world  • Objective of the Solaris Power  • General description 

-2- 

CHAPTER 1 Solaris Power Based on the current scenario presented by the rise in global energy consumption, we have to face the fact that there is not enough oil in this world left to continue to support our needs...eventually, our supply will stop and following it, the grinding halt of the world's economy. Fossil fuels are becoming costly and people are worried as our nation is so dependent on everyone else, but ourselves. Solar energy is becoming more and more common as a means to power things that normally run off of electricity. Alternative energy is starting to become more prominent now, and environmental concern is no longer for the environmental conservationists. People are starting to wake up and see that our planet is slowly being destroyed by pollution and lack of responsibility. Prime examples are the introduction of the fuel cell, solar energy generators, hybrid cars etc.

Future Uses of Solar Energy:

The sun holds a very prominent place in the history of human development, numerous examples of its precedence in the minds of those before us is evidence of it, even today this is proving to be the case as of all the sources of renewable energy available to mankind in its pursuit of a sustainable future, solar power is a pivotal one. Plentiful, free and absolutely clean, the main challenge to fully tap its huge potential is to harness and distribute it. We have made considerable progress with solar power, but future uses of solar energy will be spawned by innovations still to come. At present, solar power is used in three main ways, that is, to heat air, water and space. Photovoltaic cells are also one of the most popular forms whereby sun energy is converted into power. According to the U.S. Department of Energy’s Energy Efficiency and Renewable Energy arm, there will be more breakthroughs in new materials, cell designs, and novel approaches to product development in photovoltaic research and development. Future uses of solar energy could

-3-  include our mode of transportation and even clothing, which will be equipped to produce clean, safe electric power.

In the future, use of solar energy will be ubiquitous because concentrating solar power will be fully competitive with conventional power-generating technologies within a decade. “Concentrating solar power, or solar thermal electricity, could harness enough of the sun's energy to provide large-scale, domestically secure, and environmentally friendly electricity”.

Solar Power Plants:

There are several solar power plants in the Mojave Desert in the US, which supply power to the electricity grid. Solar Energy Generating Systems (SEGS) is the name given to nine solar power plants in the Mojave Desert which were built in the 1980s. These plants have a combined capacity of 354 megawatts (MW) making them the largest solar power installation in the world. Solar One and Solar Two (Solar Towers):  

Solar towers use many large, computer controlled, sun tracking mirrors (heliostats) to focus the suns energy on a receiver located at the top of a tower. A heat transfer fluid, usually molten nitrate salt, is heated in the receiver and used either to drive a turbine/generator to produce electricity or to provide high temperature thermal heat. The molten salt can be used to store the thermal energy for producing electricity at night or during cloudy weather. The U.S. Department of Energy, and a consortium of U.S. utilities and industry, built the first two large-scale, demonstration solar power towers in the desert near Barstow, CA.

-4-  Solar One operated successfully 1982

to

from 1988,

proving that power towers

perform

efficiently to produce utility-scale

power

from sunlight. The Solar One plant used water/steam as the heat-transfer fluid in the receiver; this presented several problems in terms of storage and continuous turbine operation. To address these problems, Solar One was upgraded to Solar Two, which operated from 1996 to 1999. Both systems had the capacity to produce 10 MW of power.

The unique feature of Solar Two was its use of molten salt to capture and store the sun's heat. The very hot salt was stored and used when needed to produce steam to drive a turbine/generator that produces electricity. The system operated smoothly through intermittent clouds and continued generating electricity long into the night.

Solar Electricity Generating Systems:

The

trough

systems

predominate

among

today's

commercial solar power plants. Nine trough power plants, called Solar Energy Generating Systems (SEGS), were built in the 1980s in the Mojave Desert near Barstow by the Israeli company Luz Industries. These plants have a combined capacity of 354 MW making them the largest solar power installation in the world. Today they generate enough electricity to meet the power needs of approximately 500,000 people.

-5- 

Sketch of a Parabolic Trough Collector system Trough systems convert the heat from the sun into electricity. Because of their parabolic shape, trough collectors can focus the sun at 30-60 times its normal intensity on a receiver pipe located along the focal line of the trough. Synthetic oil circulates through the pipe and captures this heat, reaching temperatures of 390 °C (735 °F). The hot oil is pumped to a generating station and routed through a heat exchanger to produce steam. Finally, electricity is produced in a conventional steam turbine. The SEGS plants are configured as hybrids to operate on natural gas on cloudy days or after dark, and natural gas provides 25% of the total output.

Solar Technology in Pakistan: Although solar technology has been in operation since the 1980’s however, it has only come to light in Pakistan in recent years. Even now its use is only limited to Solar Heaters and DC to DC power generation.

-6-  Objective: This project has aimed to utilize all available technologies regarding the implementation of solar power as well as those applied in inverters to produce a fully autonomous electrical charging system catering to the energy consumption requirements of industries as well as homes. The implementation of this project was sought because the current technology available in Pakistan is Solar DC to DC power conversion whose primary limitation is the alteration of the appliances operating on AC power. The vendors have designed the new equipment for the utilization of this converted DC to DC energy. Therefore, our goal was to devise a system which does not require the alteration of the appliances installed. Another subsequent advantage of our project is that no such system exists in Pakistan. Feasibility:

It provides electricity when and where power is most limited and most expensive, which is a highly valuable and strategic contribution. Solar electricity mitigates the risk of fuelprice volatility and improves grid reliability.

While many of the costs of fossil fuels are well known, others (pollution related health problems, environmental degradation, the impact on national security from relying on foreign energy sources) are indirect and difficult to calculate. These are traditionally external to the pricing system, and are thus often referred to as externalities. A corrective pricing mechanism, such as a carbon tax, could lead to renewable energy, such as solar thermal power, becoming cheaper to the consumer than fossil fuel based energy.

-7-   Also solarr thermal poower plants can generallly be built in a few yeears becausee solar plantts are built almost a entiirely with modular, m reeadily availlable materrials. In con ntrast, manny types of conventiona c al power prrojects, especially coal and nucleear plants, require lonng lead timess.

The feasibbility of suuch a system m in Pakistan is apprropriate as displayed by b statisticaal survey shoown below:

n share of solar energ gy in poweer From the above pi-cchart one caan see thatt there is no generationn sector of Pakistan. P

-8-  1.1 Block Diagram:

Figure 1.1 3D CAD Layout of the system:

Figure 1.2

-9-   A descripttion of the critical c compponents of the t project is i provided below:

1.1.1 Photto-Voltaic Array: A Thhe photovooltaic (PV)) power technologyy uses semiconduuctor cells (Wafers),, generally y several square centimeterrs in size. From the solid-state physics pooint of view, the cell is basiccally a largee area p-n diode d with the t junctionn positioned d close to thhe top surface. The cell converts thhe sunlight into direct current elecctricity. Num merous cellls are assembbled in a module to generaate required power.

1.1.2 Traccker: It perform ms the solar tracking t of PV modulee to increasee the efficienncy of the system. s

1.1.3 Safeety & Comb biner Circu uit: Thhe pure DC electricity from the ph hoto-voltaicc panels is fed into the combiiner circuitt which ass the nam me implies combines all of the photo-voltaicc electricity y. It also connsists on a safety circcuit which safeguards from f overloaad and overr current pottential cond ditions.

1.1.4 Charge Controoller: Thhe charge coontroller orr regulator is a significcant piece of equipm ment utilizedd in this prooject; it is needed n to prevent p the overcharging of the batteries which w can be hazarddous. Also

-10-  proper chaarging preveents any dam mage to thee batteries annd hence inncreases the battery lifee. There are two typess of chargee controllerrs being used in this project aree: (a) DC-D DC charger (PV ( Regulaator), used when w electrricity from the PV pannels is availlable. (b) AC-D DC chargeer, used when w photto-voltaic energy e is unavailablle (due to atmospheric a c conditionss), in the case of whichh AC mainss supply will be used. 1.1.5 Batttery Bank: Thhe battery baank consistts of severall batteries, depending d on the typpe of voltagge and curreent ratings will be useed to store DC energyy. Also theey will suppply this storred DC pow wer to the inverter. 1.1.6 Inveerter: Thhe power inverter i is the heart of this syystem. It consists onn a DC-AC C converter circuit whiich convertss the DC voltages supplied s byy the batterries into AC electricitty which will be utiilizable for the electriccal appliancces. And forr this projecct the Invertter would be b capable off providing output loadd up to 1KV VA.

1.1.7 Disp play Panel: Thhe display panel consists on a liquid cryystal displaay, showing meters, m charrging source selection,, and overlooad and undder load condditions. Thiss board alsoo contains the t safety elements e suuch as circuit breakers, b fuuses and em mergency shu utdown buttton.

     

 

CHAPTER: 2 

PROJECT DESIGN &  IMPLEMENTATION    

• Design & Circuit Layouts  • Module Operation  • Testing and Simulation  • Troubleshooting 

       

-12- 

CHAPTE ER 2 Module Explanation E n PHOTO SENSORS

ker: 2.1 Track

A A 

The trackeer here is being b used to increasee light gathhering

B

capability of the systtem. This is i accompliished by ussing a pair of seensors for horizontal h a verticall tracking of and o the sun. [3]

2.1.1 Circcuit Explan nation: It takes innput from thhe 2 sensorrs (LDR) & then takees decision to move th he panel in a direction with w greaterr sunlight inntensity.

Figu ure 2.1

•

Here thhe scan ratee has been set s at 30 min nutes.

•

The traacker is impplemented using u PIC12 2F675 8-bit microcontro m oller unit. [8]

   

-13-  2.1.2 Circcuit Implem mentation Problem Statement: S : •

T was rarely deteecting a balance condiition i.e. it was eitherr moving thhe The Tracker panel right r or left. It was not stopping th he motor.

•

We found that it was w very diifficult to achieve the same s Outpuut directly from f the tw wo sensorrs.

•

Even when w almosst the same intensity i off light was falling f over the 2 sensors, there waas a veryy small diffeerence in thhe output vo oltage (in millivolts) m thhe internal ADC of thhe microccontroller with w 10bits output & a resolutionn of (Vdd – Vss)/2n = (5-0)/210 = 4.8mvv was sharp enough to detect d this tiiny variation.

 

Solution n:  

In order too remove thhe stated problems wee decided too take an innternal refeerence ratheer than compparing the output o of thee two LDR Rs. In this way w the trackker checks if one of thhe two sensors is facingg sufficient light l intensiity it movess the panel in that direection so thaat the other sensor alsoo faces suffi ficient inten nsity. When both sensoors are facin ng sufficiennt intensity a balanced condition c is achieved. LDR R Voltage Reference R C Circuit

 

Figu ure 2.2 * Reference [55], [6]

-14-  Implemen nted PCB of o the Circu uit:

ure 2.3 Figu

2.2 Chargge Controlller Board:

 

Figu ure 2.4    

Thhe circuit foor a Chargee Controllerr is rated 6A and batteery (i.e. to be chargedd) voltage raating is 12V V (variablee range up to 14V). Inn the abovve figure, PV P Panels & Battery Unnit will be connected c too their respeective juncttions with prroper polariities. Diiode D4 is a schottkyy diode useed for dischharge preveention. It iss one of thhe typical appplications of o a schottky diode. Schottky S D Diodes are m metal to n--type Silicoon Diode andd are differeent from Sillicon Diodes. Advantagges of Schoottky Diode over Silicoon Diodes aree Small Revverse Recovvery Period d, Faster andd have smalll forward voltage v dropp.

-15-  Disadvantage of Schottky diode is that their reverse voltage is very small as compared to Silicon Diodes which makes them unsuitable for high power applications. 80SQ035/80SQ045 has a breakdown voltage of 50V it means that D4 will withstand a potential of 50V which is large enough to prevent Batteries from discharging through the PV panel. This is necessary so that the PV panel does not get damaged. Transistor T3 turns on when the PV panel voltage is large enough to cross the potential Vbe of T3 which is typically 0.7V, voltage drop across R9 & the 12V drop across D6. Here D6 ensures that T3 does not turn on at a voltage below 12V, R9 limits current through the B-E junction. IC3 is a 5V voltage regulator which ensures a constant voltage of 5V at its output. Capacitors C6 & C7 are used to filter the input and output. VR1 is a potentiometer used to change the Float Voltage Setting i.e. the Depth of Charging. The Temperature Sensor TM1 (thermistor) modulates the float voltage setting slightly, the full voltage set point rises in colder temperatures & falls at hot temperatures. Shorting the equalize terminals J1 causes the circuit to stay in the charging state, this is useful for occasionally overcharging (equalizing) a battery. IC1 has been split up into IC1a & IC1b just to make the schematic clear. Otherwise both are part of the same IC. IC1a & IC1b are Op-Amps operating as Comparator. Each Op-Amp produces an output which is the counterpart of the other for driving the bipolar LED. Battery Voltages are compared to the float voltage setting by the Op-Amp IC1a & IC1b. If the battery voltage is less than the float voltage setting then the Red light turns on and the battery gets charging. Once Battery voltages become equal to the Float Voltage Setting Green LED glows indicating the battery voltage has reached the floating

-16-  voltage, then the circuit starts oscillating above and below the Float voltage and RED & GREEN LED glows alternatively. The opto-coupler OC1 provides electrical isolation to the Output of IC1a & the Gate of MOSFET T1. It provides optical coupling, & switches on or off depending on the input. As a signal passes through the pin 1 & pin 2 of OC1 i.e. when the battery is charging & RED led is glowing the opto-coupler turns on. As soon as the signal through pin 1 & pin 2 fades away OC1 turns off. T1 is an Enhancement-Type N-MOS which modulates the Charging Current of the battery. When there is no input at its gate (OC1 is off due to IC1a output low) minimum current flows through T1. As the output of IC1a goes high this turns OC1 on & transistor T1 resistance decreases (Enhancement Mode of MOSFET) causing greater amount of charging current. F1 is a 6.0A Fuse to provide protection to the circuit. It breaks if the current goes above 6.0A. D5 is a Crowbar Diode for safety purpose. If the Battery is inserted in the reverse position by mistake, i.e. the polarities are not proper then the diode D5 provides a short part through itself & a 6.0A fuse. Thus prevents other parts of the circuit from damage. The current Rating of the Diode must be greater than 6.0A so that it does not burn before the fuse breaks.

Implemented PCB of the Circuit:

Figure 2.5

-17-  2.2.1 Mod dified Charrge Controlller Board::

S : Problem Statement: •

We trried to sim mulate the test t circuit of the chaarge controoller based on discrette compoonents on a simulation software, however due to cerrtain circum mstances thhe desiredd result couuld not be acchieved.

•

Also we w encounttered a prooblem with the 6A Scchottky Dioode which is currentlly unavaiilable in thee Market, soo we have decided to usse a combinnation of Scchottkys.

Solution n: A microcoontroller bassed charge controlling c device is more m in tune with our reequirementss.

Figu ure 2.6

* Reference [55], [6], [7]

-18-  Descriptioon:

Thhe schematiic is divideed in two main parts the 'brain', thee PIC micrrocontroller and the otther part iss for checking voltages through resistors r bridges. b L LOW reference is i centered on P1; HIG GH referencee is centeredd on P2. Both resistor r briddges are pow wered by reegulated 5V Volts and thereffore indepeendent from m the batterry voltage. The last bridgee is dedicateed to the batttery voltag ge. The PIC will convert thhese three voltages and a compaare the batttery voltage too the two references. The PIC will then take actions.

The differrent tasks too be perform med by the program p in the t PIC are quite simplle and do noot require a lot l of code space, s the taasks preform med by the program p aree: •

Iniitialize the controller c (vvariables, po orts,…)

•

Reead the uppeer limit (P1 on GP0)

•

Reead the loweer limit (P2 on GP1)

•

Reead the actuaal voltage of o the battery y (on GP2)

•

Chheck if TEST T is High inn order to ch hoose the addjustment rooutine or no ot. o

Do acttions ÆIs thhe battery voltage v too low? l

Adjustmeent:

Too set the dessired HIGH voltage refference, a teest mode is used. Why y? because in i normal opperation moode, the PIC C performss actions with w delays. Modifying g the batterry voltage creates an interaction aroound the 'sw witching' point. Moreovver, it helps to lower thhe intrinsic coonsumptionn of the moddule.

-19-  This delay process makes the adjustment process a bit difficult. By putting the TEST point at +5volt, we inform the PIC to run the adjustment routine, means without delays.

To adjust the reference values: •

Set Test point to HIGH to enter adjustment mode.

•

Use an adjustable power supply ; Connect it in place of the battery.

•

Set power supply to 10.8 volts. Adjust P1 to get a LOW level on GPIO.4 (pin 3).

•

Set power supply to 13.8 volts. Adjust P2 to get a LOW level on GPIO.5 (pin 2).This means that the 'Solar Panel' is disconnected above 13.8 volts (or other reference suitable for our needs)

•

By varying the power supply voltage, check that :

•

Between 10.8 and 13.8, GPIO.5 is HIGH and GPIO.4 is HIGH (Solar Panel and Load connected)

•

Above 13.8, GPIO.5 is LOW and GPIO.4 is HIGH (Solar Panel disconnected)

When this has been achieved, disconnect test point (TP) from +5 volts to go back to Normal Mode.

2.2.1.1 Problem Faced in Programming: Problem Statement: At this step we were unable to achieve the desired output from the controller. The output of the microcontroller was unpredictable even though we had programmed it.

Observation: We realized that, there was some problem with the configuration registers. The HEX file for the source code generated by Microchip was incorrect.

-20-  MPLAB o Major problem is to configure the registers. o It changes the register variables after every step, i.e. it reset the values in certian file registers while in a delay loop. o Also encountered ADC initializing problem o If you leave the simulator continue running it does’nt update the variables. o There are different types of PIC and each uses a different compiler. o For the PIC12/16 you need a different compiler compared to PIC18,PIC24/30. After wasting too much of our time on MPLAB we switch to the new tool i.e. MikroC of Mikroelektronica. MikroC Most excellent Features: o MikroC uses high level approach. o MikroC covers PIC12/16 and 18. o MikroC is supposed to have a decent library. o MikroC provide 'built in functions' which we have no access in MPLAB. For our programming requirement we finally opted for MikroC [9]. 2.2.1.2 Final Charge Controller Design:

For the final design we shifted from the 12F675 having 6 I/O pins to the 16F877A which has 33 I/O pins. Here the decision will be made according to the Present Battery Level. We also added the Source Selection feature to the design & finally the decisions taken by the Charge Controller depending on the present conditions (input) is as follows.

-21-  •

Read battery level and check whether it is in the nominal range i.e. Sufficient enough to drive the inverter.

•

If battery level is sufficient enough (present level falls within the nominal range) then there is no need to charge the battery.

•

If battery level is insufficient then check which of the source is available for charging & give the indication for available sources.

•

Decides whether PV is to be selected for charging or AC from the wall outlet is to be used for charging depending upon the user input.

•

Charge the battery until it saturates. But don’t over charger it!!!

Charge controller disconnects the charger from battery when the battery voltages become constant (does not increase further) indicating saturation is achieved & thus prevents overcharging & extends battery life.

Modifications in Initial Design: Initially the idea was to have hardware controlled limits; however when using software controlled limits to control charging, this modification freed up more pins of controller & enhanced charge controller efficiency.

We merged the AC Charge Controller & DC Charge Controller into a single microcontroller for a more efficient and compact design; this is also a slight modification from the initial design.

The battery voltage drops after the charging is turned off & it took some time for the battery to go back to its new holding voltage, thus we introduced a delay in the code so that the controller waits for sometime after switching off charging, so that the battery

-22-  voltage stabilizes & then reads the present battery level to make Charging Decision i.e. either Continue Charging, Indicate Battery Full or Indicate Battery Error.

CIRCUIT SCHEMATIC

Figure 2.7

PCB LAYOUT

* Reference [5], [6], [7]

-23- 

3D LAYOUT & CIRCUIT

Figure 2.8 2.2.2 PV Regulator: The voltage levels being obtained from the solar panel are unregulated; to stabilize the voltages we designed a PV regulator circuit [4]. The block diagram is as follows:

Figure 2.9 Configuration •

Q1, Q2 & Q5, Q6 are wired in a Darlington pair arrangement.

•

Q3 & Q4 forms the control circuit. These two transistors are wired in parallel & the charging current for the battery flows equally through this parallel combination of transistors.

The amount of current that can pass through the Darlington pair can be calculated by:

-24-  Input current * gain of transistor 1 (hFE1)* current gain of

OUTPUT = DESIRED OUTPUT •

When no modulation is needed, i.e. the output voltage is equal to input voltage & there is no error.

•

The sensing circuit remains OFF, therefore entire current flows though the Q1 & Q2.

•

Q1 & Q2 conducts max current & drives Q3 & Q4 into full conduction so that Vce is closer to Vce(sat) for Q3 & Q4 both.

•

Thus the output voltage is almost equal to input voltage. OUTPUT > DESIRED OUTPUT

•

Once Q5 & Q6 detects error then the current that drives Q1 & Q2, conducts through Q5 & Q6 too. Thus the entire current is divided between transistors Q1, Q2 & Q5, Q6.

•

Thus Q1 & Q2 moves towards cutoff region (away from saturation) as their input current is decreased.

•

Which in turn moves Q3 & Q4 away from saturation (towards cutoff), as a consequence Vce increases & thus output decreases until it becomes equal to desired voltage setting.

-25-  •

Thherefore Q5 & Q6 keepp monitoring g the outputt and maintaain output at a the desired voltage settingg.

•

R Ouutput voltagge setting caan be changeed through R6. OUT TPUT < DE ESIRED OU UTPUT

•

Onnce Q5 & Q6 Q detect errror then the Q5 & Q6 moves m towarrds cutoff, thus t the enttire current flows throuugh Q1& Q2 2.

•

Ass a result Q11 & Q2 movves towardss saturation region (awaay from cutoff) as theirr inpput current is i increasedd.

•

Thhis in turn moves m Q3 & Q4 away from fr cutoff region (tow wards saturattion), as a connsequence Vce V decreasses & thus output o increeases until itt become eq qual to dessired voltagge setting.

•

Thhus Q5 & Q6 keeps moonitoring outtput and maaintains outpput at desireed voltage settting

•

Deesired Outpuut voltage setting can be b changed through t R6. 

Schematicc Diagram:

Figu ure 2.10

-26-  Implemen nted PCB of o the Circu uit:

Figu ure 2.11 Testing th he PV Regu ulator:

First we provided the PV regulator r circuit

v voltages

transformeer,

usedd

from to

an

autosimulate

unregulateed voltages from a PV panel. p

Secondlyy

we

coonnected

the

chargge

controlleer board with the PV regulator, in i order to test the coontrolling capability c o of the reguulator as w well as th he controlleer board.

-27-  C 2.2.3 AC Charger: Here the main m supplyy source willl be from KESC. K The primary p purrpose of thee AC chargeer is to proviide charging when thee sunlight iss unavailablle. Current requiremen nt is adjusteed accordinglly with the size of the battery [13]. The charginng ON/OFF F time and voltages v wiill be controlled and monnitored by the t microco ontroller.

The blockk diagram is as follows:: 220 VAC  50Hz

RECTTIFIER

Circuit Diagram:

Figu ure 2.12

Simulatioon Result:

CONTROL  CIRCUIT

BATTTERY

-28- 

Figure 2.13 2.3 Inverter: Power inverters are devices which can convert electrical energy of DC form into AC. [14] They come in all shapes and sizes, from low power functions such as powering a car radio to that of backing up a building in case of power outage. Inverters can come in many different varieties, differing in price, power, efficiency and purpose. The purpose of a DC/AC power inverter is typically to take DC power supplied by a battery, such as a 12 volt car battery, and transform it into a 220 volt AC power source operating at 60Hz, emulating the power available at an ordinary household electrical outlet.

Figure provides an idea of what a small power inverter looks like. Power inverters are used today for many tasks like powering appliances in a car such as cell phones, radios and televisions. They also come in handy for consumers who own camping vehicles, boats and at construction sites where an electric grid may not be as accessible to hook

-29-  into. Inverters allow the user to provide AC power in areas where only batteries can be made available, allowing portability and freeing the user of long power cords.

On the market today are two different types of power inverters, modified sine wave and pure sine wave generators. These inverters differ in their outputs, providing varying levels of efficiency and distortion that can affect electronic devices in different ways.

A modified sine wave is similar to a square wave but instead has a “stepping” look to it that relates more in shape to a sine wave. This can be seen in Figure 2.14, which displays how a modified sine wave tries to emulate the sine wave itself. The waveform is easy to produce because it is just the product of switching between 3 values at set frequencies, thereby leaving out the more complicated circuitry needed for a pure sine wave. The modified sine wave inverter provides a cheap and easy solution to powering devices that need AC power. It does have some drawbacks as not all devices work properly on a modified sine wave, products such as computers and medical equipment are not resistant to the distortion of the signal and must be run on a pure sine wave power source.

Figure 2.14

-30-  2.3.1 Methodology

The construction of the pure sine wave inverter can be complex when thought of as a whole but when broken up into smaller projects and divisions it becomes a much easier to manage project. The following sections detail each specific part of the project as well as how each section is constructed and interacts with other blocks to result in the production of a 220 volt pure sine wave power inverter [16].

2.3.2 Block Diagram

Analog circuitry, as well as discrete components, a MOSFET drive integrated circuit and a low pass filter is all that is necessary to generate a 60Hz, 220V AC sine wave across a load. The block diagram shown in figure shows the varying parts of the project that will be addressed. The control circuit is comprised of three basic blocks, the 6.0V reference, sine wave generator and triangle wave generator; when these blocks are implemented with comparators and other small analog circuitry they control the PWM signals that the two MOSFET drivers will send. The PWM signals are fed into these MOSFET drivers that perform level translation to drive four N-Channel MOSFETs in an H-Bridge configuration. From here the signal is sent through a low pass LC filter so that the output delivers a pure sine wave. The specific operation, construction, and resulting output waveforms for each block will be discussed in detail in the following sections.

-31-  The blockk diagram is as follows::

PWM M & SIGNALLLING 

OUTPUT DRIIVER 

Figu ure 2.15

2.3.2.1 Floow Diagram m

12 VDC INPUT FRO OM BATTERY

DC‐DC  CO ONVERTER R PWM CONTROL  CIRCUIT

DC‐AC  INVERTER R HALF BRIDG GE  CONVERTER R

SINE‐PW WM  CONTROLLLER  CIRCUIT

HIGH  FREQUENCYY  TRANSFORMER

FULL BRID DGE  INVERTEER

LOW PASS FFILTER

220 VAC 6 60Hz  OUTPUT

Figurre 2.16

-32-  M Control Circuit 2.3.3 PWM

     

Figu ure 2.17

Thhe top pictuure shows the t input reeference waaveform, annd the geneerated PWM M signal oveerlaid. The bottom b pictuure shows the t signals which w are passed into a comparatoor to achievee the PWM M waveform m. The sinee reference is includedd to show the t result of o modifyingg the trianglle wave. If these waveeforms are passed intoo a comparaator, we will obtain:

-33-  PWM H-BRIDGE CONTROL SIGNAL Now,

using

an

H-Bridge

MOSFET

configuration, and utilizing both the above PWM signal and the square wave generated, we can obtain: This is the final signal if filtered the Sine Output will arrive.

Sine Wave Generator: The first step to creating an accurate pulse width modulation signal using analog circuitry is to construct an accurate representation of the signal. Therefore an oscillator was needed to produce a stable 60Hz sine wave that had little distortion so that the output could be as accurate as possible. A “Bubba” oscillator was chosen as the means to produce this signal because of its ability to produce a stable sine wave that contains very little distortion. The circuitry and values chosen are shown in Figure and the

[10]

op-amp

chip chosen to complete the task was an LM348 as it is an inexpensive part and meets all the requirements of creating this sine wave.

Figure 2.18

-34-  Results:

60Hz Sine wave was achieved. Carrier Wave Generator:

Generating a sine wave at 60Hz requires both the reference sine wave and a carrier wave at the switching speed of the power supply. Carrier waves can be either saw-tooth or triangular signals; in this case, a triangular wave is used. The generation of the triangular carrier wave has been done with analog components. The circuit for the construction of the triangle wave generator consists of a square wave generator and integrator shown in Figure 2.19.

Figure 2.19

[10]

, as

-35-  The above circuit will oscillate at a frequency of 1/4RtC, and the amplitude can be controlled by the amplitude of R1 and R2. Rt =150K VR, R1=8.2K & R2=1.5M VR, and C=0.1uF, this circuit generates square and triangle waves.

Results:

Problem Statement: Difficulties with this circuit were mainly caused by the operational amplifier selected in its design. The square and triangle waves may be skewed due to the op-amp’s inability to reach output rails. Also, if the frequency is too high for the op-amp to handle, the square wave will be skewed and the triangle wave will be noticeably clipped or distorted. We have used 9 ICs for generating the required signals. The behavior of discrete component is sometimes unpredictable and again in the PWM output we get the result as show in the oscilloscope output. The output signals are not very clean PWM pulses; this is due to the op-amp behavior towards high frequency.

-36- 

Solution: (Figuree 2.20)

As the remedy of previous work we have h to convvert the Op-amp based b circuits to the

XR R-2206

Fuunction

generator IC. Now afterr implementting the circuit beelow we acchieved the pulsess which woould be driving thee MOSFET T Driver IC IR-2110. I  

 

P Previous outtput from Opp-Amps.

Output of XR R-2206 based PWM.

-37-  Complete circuit of PWM:

-38-  2.3.4 H-Bridge Generating a sine wave centered on zero volts requires both a positive and negative voltage across the load, for the positive and negative parts of the wave, respectively. This can be achieved from a single source through the use of four MOSFET switches arranged in an H-Bridge configuration. To minimize power losses and utilize higher switching speeds, N-Channel MOSFETs were chosen as switches in the bridge. Level translation between PWM signals and voltages required to forward bias high side N-Channel MOSFETS, the IR2110 MOSFET driver integrated circuit was chosen. A diagram of the H-Bridge circuit with MOSFETS and drivers is shown in the figure below:

Figure 2.21 The IR2110 High and Low Side Drive device exceeds all requirements for driving the MOSFETs in the bridge. It is capable of up to 500V at a current rating of 2A at fast switching speeds. This device is required to drive the high side MOSFETS in the circuit designated HO, due to the fact that the gate to source voltage must be higher than the drain to source voltage, which is the highest voltage in the system. This device utilizes a bootstrapping capacitor to maintain a voltage difference of approximately 10V above the drain to source voltage. With a full bridge configuration, two of these devices are utilized, as shown in the above figure. A typical connection of a single IR2110 device is shown in Figure.

-39- 

Operation of the IR2110 device will be controlled through generated PWM signals. The PWM signals will be fed to the HIN and LIN pins simultaneously. If the internal logic detects a logic high, the HO pin will be driven; if a logic low is detected, the LO pin will be driven. The SD pin controls shut down of the device and will be unused and tied to the ground. Additional pins that require external connections are the Vss pin which will also be tied to the ground, the Vcc pin which will be tied to 12V, pins requiring connections to Boot-strapping components and outputs to the MOSFETS.

Driving four MOSFETs in an H-Bridge configuration allows +350, 350, or 0 volts across the load at any time. To utilize PWM signals and this technology, the left and right sides of the bridge will be driven by different signals. The MOSFET driver on the left side of the bridge will receive a square wave of 60Hz, and the right side will receive the 50KHz PWM signal. The 60Hz square wave will control the polarity of the output sine wave, while the PWM signal will control the amplitude. The MOSFETs to be used in the design are the IRFB20N50KPbF (IRF740) Hexfet Power MOSFET, rated for 500V at 20A with an Rds of 0.21ohm.

-40-  The implemented PCB:

Overall Circuit diagram of PWM & Output Control Circuit:

Figure 2.22

2.3.5 Half Bridge Converter: A schematic of the half-bridge converter is shown in Figure 2.23. The major components of the half-bridge converter are the two transistors, which are illustrated in the figure. The purpose of the half-bridge converter is to chop up the 12 VDC supplied by a battery so that an alternating current is seen by the transformer. The red and blue paths have been added to figure to illustrate the switching technique used to create and alternating current

-41-  from direcct current. T The red pathh shows thaat current iss forced acrross the prim mary side of o the transfoormer whenn the upper transistor t is open and thhe lower traansistor is closed. When thee transistorrs are toggled,

the

curreent

is

forced in the directiion of the

blue

producingg

path,

thus

an

AC

waveform m. Since the pulses that contrrol the trannsistors are compplimentary, both half-bridge transistorrs will never be on at the same

Figu ure 2.23

time and thhe process repeats r 1000,000 times per p second. The transiistors selectted for the half-bridge h Z44 by International Rectifier. R Thhe were IRFZ IRFZ44 diissipated thee least amouunt of heat for long durrations of ooperation.

Why to usse Push-Pu ull techniqu ue?

* Reference [15]

-42- 

2.3.5.1 Half Bridge Converter Implementation: The TL494 was selected; a short description of the IC is given below: 

  The schematic diagram of circuit is given below:

Figure 2.24

-43-  Now the TL494 circuit was interfaced with transformer of rating; Input = 15+0+15 Volt AC, Output=220VAC and current of 2A.

The results:

-44-  Problem Statement: From the above oscilloscope output we can see the output is not pure Square output, although the amplitude was about 155VAC.

2.3.5.2 Solution for the TL494 Circuit: Now we used the SG3525 module; the short description of IC is as follows:

Figure 2.25

-45- 

MODIFIED  CIRCUIT 

Figure 2.26

AMPLITUDE  ≈ 300 Vpp 

      

Now we got the 60Hz (16.67msec) Square outputs with an rms value of 211VAC. Problem Statement:

The output was about 190VAC on load; however  the  shape  of  the  output  waveform  was  neither 

 

-46-  Sine  nor  Square.  It  has  a  peak  value  for  few  microseconds  and  then  it  decrease  with  many dumping signals.  Observation: From  above  simulation  we  noticed  that  the  core  gets  saturated  after  30‐40  minutes.  And the voltage starts decreasing by 3‐5 volts per minute. 

Conclusion: Therefore, we decided to wind a Ferrite-Core transformer to rectify the load current problem.

2.3.5.3 Ferrite Core Transformer The term ferrite core may refer to a core used to build an electric transformer; there are two kinds of core (nucleous) applications following the size and frequencies, one for signal transformers and the other for power transformers.

The ferrite cores used for power transformers are working in the range of low frequencies (1 to 50KHz usually) and are quiet big size, can either be toroidal, shell or C shaped and are useful in all kind of switching electronic device (especially power supplies from 1W to 100W maximum because usually powerful applications are out of range of ferritic single core and require grain oriented lamination cores).

The ferrite cores used for signal have a range of applications from 1KHz to many MHz perhaps up to 300, and found its main application in electronics.

Ferrite is a class of ceramic material with useful electromagnetic properties and an interesting history. Ferrite is rigid and brittle. Like other ceramics, ferrite can chip and break if handled roughly. Luckily it is not as fragile as porcelain and often such chips and cracks will be merely cosmetic. Ferrite varies from silver gray to black in color. The

-47-  electromagnetic properties of ferrite materials can be affected by operating conditions such as temperature, pressure, field strength, frequency and time.

There are basically two varieties of ferrite: soft and hard. This is not a tactile quality but rather a magnetic characteristic. 'Soft ferrite' does not retain significant magnetization whereas 'hard ferrite' magnetization is considered permanent. Fair-Rite ferrite materials are of the 'soft' variety.

Ferrite has a cubic crystalline structure with the chemical formula MO.Fe2O3 where Fe2O3 is iron oxide and MO refers to a combination of two or more divalent metal (i.e: zinc, nickel, manganese and copper) oxides. The addition of such metal oxides in various amounts allows the creation of many different materials whose properties can be tailored for a variety of uses.

Ferrite components are pressed from a powdered precursor and then sintered (fired) in a kiln. The mechanical and electromagnetic properties of the ferrite are heavily affected by the sintering process which is time-temperature-atmosphere dependent.

Ferrite shrinks when sintered. Depending on the specific ferrite, this shrinkage can range from 10% to 17% in each dimension. Thus the unfired component's volume may be as much as 60% larger than the sintered value. Maintaining correct dimensional tolerances as well as the prevention of cracking related to this shrinkage are fundamental concerns of the manufacturing process.

* Reference [17], [18], [19], [20]

-48-  Types of Ferrite Cores: Magnetics cores can be divided into

many

types

of

categories. This discussion will divide magnetic cores into two major categories, structure (shape) and material. These major core categories will then be sub-divided into additional categories. This includes; various standard types of “core with bobbin” structures (E, EP, EFD, EC, ETD, PQ, POT, U and others), toroids, and some custom designs.

Transformer Formulae & Calculations:

ETD-49:

  

 

2.11

2.71

 5.72

10

 

2314.2135   

10

0.101

-49-  10  

1   

 

10

50

           

4

/ 1.5

   

 

1

100

1 

 

  1000

211

2.11

271

2.71

900    Input Winding

10 4

= 16# AWG

Output Winding = 14# AWG  

10 4

0.3,

80% 5.71

1

  10  

1 10 1 10

1 

900 244 10 1 10

900    1 

For Details of Symbols & Constants, Refer to the Appendix B – Page # 73

-50-  ETD-44:

25 213      

 

2.13

173

1.73

 2.13

1.73

10

 

 

1

 3.684

10 4

; 

10

 ; 

 

5.07 10 450 0.3 

  80%  ? 3.684

3.684

450 5.07 10  

0.22 10 4 0.8 25 4 

10 4 0.3

0.8 248.82

 14.2

248.82 

 

25

0.3

-51- 

For Details of Symbols S & Constantss, Refer to the t Append dix B – Pag ge # 70

Designingg a Transfoormer Baseed on Calcu ulations: The first problem p in making m the ferrite coree transformer is the core. Unfortu unately in thhe market there is no data d availabble for the ferrite corees, also it iis very diffficult to finnd ferrite-corres in Pakisttan. Now ouur first challlenge was to search thhe whole market m for thhe ferrite-corres, and finaally after maany days off searching, we finally got two sizzes of ferriteecores, how wever these were withoout any speccifications or o data. We browsed th hrough manny core manuufacturer’s websites, w annd we dow wnloaded thee datasheetss of their manufacture m ed cores, dow wnloaded thhe pictures and we co ompared thee features oof cores thaat we boughht with the mechanical m d data. The coores we hav ve now are ETD-44 E andd ETD-49.

                   

 

-52- 

ding Resultts: The Wind

  Figu ure 2.27 Now from m the datasheeets and cattalog charts the Core ETD-49 E valuues are: WA=2.71ccm2, B=9000 Gauss, Vin=12V,

f=100KHzz,

Vout=4400V

From our calculation we got: Turns/voltt=0.1173,

Primary Turns= T 1.45T T,

As compaared with thee results froom an onlinee calculatorr:

It is now confirmed c thhat our calcculations aree on cue.

Seconndary Turns= = 56T.

-53- 

Testing the design:

Figure 2.28 AC voltage at the output are varying due to the output frequency of 4.51 KHz, however, the digital meters that we have are operating at a less approximation speed. We rectified the output and measured the DC voltage for first three transformers using an analog meter, and the results were very shocking. The DC voltages were more than 800VDC. As for the forth one, which was designed for 400V we got 300VDC as shown in the above picture. And the output waveform is on the right picture. Problem Statement: Output of transformer in terms of voltage is ok but when a capacitor is connected to smooth the output, the transformer starts to generate noise and voltage drops to 2030VDC. While searching through different forums on the internet we found that for primary side Strip wire of the same width of the Bobbin is used for winding however, this is unavailable in Pakistan, so we tried to use copper sheet of same thickness but still failed to achieve the desired output. And one more critical factor of Ferrite core winding is the type of core, of which three types are available namely, F-Type, R-Type and PType. The component vendors in Pakistan do not have any data related to the type of materials being used.

-54-  Conclusioon: After workking for 3 weeks w on thhis part of our o project, we were uunable to geet the desireed output. Annd after seeeking the advice a of our o internall advisor w we shifted our o attentioon towards thhe square wave inverrter based on the connventional iron core transformerr. However, the theme of implemeenting the sq quare wavee inverter w was to modiffy the outpuut as near as possible to the Sine waave using LC L Filters att the output of inverter..

2.3.6 Mod dified Sine--wave Inverrter Now for teest bases wee implemennted SG3525 5 based inveerter circuitt operating at a 60Hz.

Figu ure 2.29 The Result: The no looad voltagess were 238VAC and when the a load of 2000W was applied the voltaage droppeed to about

1 188VAC.

happened,,

becausee

This the

current off the transfformer was insuffficient to drive this amounnt of load. Hence H the voltage v decreases as a result. [21]

-55-  2.3.6.1 Im mplementing the Inverrter using PIC P Microccontroller: The reasonn of using a PIC microocontroller was w to conttrol the circuit more effficiently annd to set the parameterss according to our requ uirements. The T up-dow wn pulses are a generateed by the miccrocontrolleer to drive the t Push-Pu ull MOSFET Ts. Circuit also holds the overloaad cutoff conndition [11] for fo the safetyy of the sysstem. And thhe transform mer used heere has ratinng as followss; Input 12 + 0 + 12 VA AC, Output 220 + 240 + 260 VAC C at current of o 7A.

Figu ure 2.30 The Filterr Design: The outpuut low-pass LC Filter was w design ned using onnline calcullator and th he calculateed values are as follows::

-56-  The P-Spiice Simulattion of Filteer:

ure 2.31 Figu The violett line indicaates the squuare output from f the traansformer aand the greeen line is thhe resulting waveform w a after passinng through the t low-passs LC Filterr. And the amplitude is i also increaased due to the energizzing of the in nductor coills.

     

 

CHAPTER: 3 

ACCESSORIES   

• Battery   •  PV Panel  • 16 X 2 LCD Module  • PIC Microcontroller 

       

-59- 

CHAPTE ER 3 Acceessories

3.1 Batterry The batterry in our project p is basically thee heart of our o backup system. Itt is fed witth constant 12VDC from m the chargee controller, and it provvides input tto the inverrter. General Sizes S of Avaailable Battteries:

  Tab ble 3.1 Chargingg Rate: The charging rate is determined d b the follo by owing formuula, Hourrs of Chargee = (Ah Ratting x % of Charge Neeeded x 1.25) / Charger Setting

The chargge algorithm m for lead-acid batteriies is similar to lithiuum-ion but differs from m nickel-bassed chemisttries in that voltage ratther than cuurrent limitiing is used.. The chargge time of a sealed lead-acid batteery is 12-16 hours (uup to 36 hoours for larrger capacitty batteries). With higheer charge cuurrents and d multi-stagee charge m methods, the charge tim me can be redduced to 10 hours or lesss. Lead-aciid cannot bee fully chargged as quick kly as nickeel or lithium--based systeems. It takes abbout 5 timess as long too recharge a lead-acid battery b to thhe same lev vel as it doees to dischargge. On nickkel-based baatteries, this ratio is 1:1, and roughhly 1:2 on lithium-ion.

-60-  Battery raatings: 12VDC, 85Ah 8 ,18Plaate Phoenixx Brand Leaad Acid Batttery is usedd in the systeem. With suffiicient rest and a stable teemperature,, voltage measurementts provide an a amazinglly accurate SoC S estimattion for leadd acid batteeries. It is im mportant thhat the batteery is free of o polarizatioon. If conneected in a system, such h as in a caar, there aree steady aux xiliary loadss, not to menntion frequeent starting and a driving g. BCI Stand dard for SoC estimation  of a 12V lead acid carr battery. 

Tab ble 3.2 Do and doon’t batteryy table: Each batteery has uniqque needs that t must bee met to obbtain reliablle service and a long lifee. The Do annd don’t baattery table summarizees these neeeds and advvises properr handling of o each battery type. Used in

Charging

Nickel-ca admium (NiC Cd)

Nickel-meta alhydride (NiM MH)

Two-way ra adios, power tools s, medical. Do run the battery fully down once per month; try to use up all energy before b charging.

Similar application as N NiCd; higher de ensity.

Cell phones, laptops s, video cameras.

Motorcy ycles, cars, wheelch hairs, UPS.

Do run the batte D ery fu ully down once ev very 3 months s. O Over-cycling is not advised.

Do ch harge the batte ery often.. The battery la asts longer with partial ratherr than full discha arges.

Do not leav ve battery in charger for more s because than 2 days of memory.

Do not leave ba D attery in n charger for more m th han 2 days bec cause off memory.

Do no ot use if pack g gets hot du uring charge. Check k also charger.

Do charrge the battery y immediately after ad-acid must use. Lea always be kept in a charged d condition. The batttery lasts longer with w partial rather than t full discharg ges. Overcycling is not advised..

Avoid getting battery too o hot during charrge.

Avoid getting ba A attery to oo hot during ch harge.

Charge methods: urrent, Constant cu followed by y trickle charge whe en full. Fast-charge e preferred over o slow charge. Slow charge = 16h Rapid charg ge = 3h Fast charge e = 1h+

Charge methods C s: C Constant curren nt, fo ollowed by trick kle ch harge when full. Slow charge nott re ecommended. Battery will get w warm towards full f ch harge. R Rapid charge = 3h Fa ast charge = 1h+ 1

Lithium-ion (Li-ion)

Charg ge methods: Consttant voltage to 4.20V V/cell (typical). No trickle e-charge when full. Li-ion L may rema ain in the e charger (no memo ory). Battery m must remain cool. No fasttcharge possible.

Le ead-acid (Seale ed or flooded) )

Charge methods: Constan nt voltage to 2.40/ce ell (typical), followed d by float held at 2.25V V/cell. Battery must remain cool. Fa ast charge not possible e; can remain on floatt charge.

Rapid charge = 3h Slow ch harge = 14h Rapid charge = 10h

-61-  Discharging g

Full cycle does d not harm NiCd.. NiCd is one e of the most hardy y and durable che emistries.

Avoid too many A y full cy ycles because of w wear. Use 80% depth-of-discharge. N NiMH has higher en nergy density than N NiCd at the expense off shorter cycle life.

Avoid full cycle becau use of wear. 80 0% depth-of-discharge recom mmended. Recharge more often. Avoid full discharge.. Low voltage v may cut off safety circuit

Service needs

Discharge to t 1V/cell every 1 to 2 months to prevent memory. Do not disc charge before each h charge. Best to store at 40% charge in a cool place. Open n terminal voltage can nnot determine state-ofcharge. 5 years y and longer storage possible. Prrime battery if stored longer than n6 months. Do not disp pose; contains to oxic metals; mu ust be recycled.

Discharge to 1V D V/cell ev very 3 months s to prevent memory y. D not discharg Do ge before each cha arge Store at 40% ch harge in n a cool place. Open te erminal voltage e ca annot determin ne sttate-of-charge. Prime battery iff sttored longer th han 6 m months.

No ma aintenance neede ed. Loses capac city due to o aging whethe er used or o not.

Should be recyc cled. Lo ow volume household NiMH H may be disposed.

Should be recycled. Low volume v household Li-ion may be dispos sed

Storage

Disposal

Store at 40% charge e in a cooll place (40% state--of-charge read ds 3.75-3.80V/cell at open terminal. Do no ot store at full charge and at warm m tempe eratures becau use of acc celerated aging g.

Avoid fu ull cycle because e of wear. Use 80% de epth-ofdischarg ge. Recharge more offten or use larger battery. b Low ene ergy density limits le ead-acid to wheeled d applications Apply to opping charge every 6 months. Occasio onal discharge// charge may improve perform mance. Store always at a full state-off-charge. Do not storre below 2.10V/c cell; apply topping charge every 6 month hs.

Do not dispose; must be recycled.

Tab ble 3.3 3.2 Photo Voltaic Ceells A solar ceell, made froom a monoocrystalline silicon waffer. A solar cell or photovolltaic cell is a device th hat convertss light energy innto electricaal energy by b the pho otovoltaic effect. e Photovoltaaic is the field of technnology and research reelated to the appplication of solar cells c as so olar energyy.

[1]

Sometimees the term solar cell is reserved d for devicees intended specifically y to capturre energy froom sunlighht, while thhe term ph hotovoltaic cell is useed when th he source is i unspecifieed.

Assembliees of cells are used too make solaar moduless, which maay in turn be b linked in i photovoltaaic arrays.

Solar cellss have manyy applicatioons. Individ dual cells arre used for ppowering sm mall devicees such as electronic calculators. Photovolttaic arrays generate a form off renewablle electricity, particularrly useful in i situation ns where electrical e poower from the grid is i unavailablle such as in remote area powerr systems, Earth-orbiti E ing satellitees and spacce

-62-  probes, remote radiottelephones and water pumping p appplications. Photovoltaaic electricitty is also incrreasingly deeployed in grid-tied g eleectrical systtems.

PV panel ratings:

* Reference [22]

-63-  3.3 Displaay Panel The displlay panel consists c of Liquid Crrystal Display modules of o 16 x 2 linnes.

16 x 2 Alp phanumeric LCD Module Featu ures •

Inttelligent,

w with

builtt-in

Hitach hi

HD447780

com mpatible LC CD controlller and RAM M providingg simple intterfacing •

61 x 15.8 mm m viewing arrea

•

5 x 7 dot matrrix format for fo 2.96 x 5.56 mm charracters, pluss cursor linee

•

Caan display 224 differentt symbols

•

Loow power coonsumptionn (1 mA typiical)

•

Poowerful com mmand set annd user-pro oduced charaacters

•

TT TL and CMO OS compatiible

•

Coonnector forr standard 0.1-pitch pin n headers

The displaay outputs are a as follow ws: MO ODE SELECTTION INVERTER . ON N

OFF

CHARGIN . NG PV

AC

-64-  3.4 PIC Microcontroller

Introduction: The microcontroller is a very common component in modern electronic systems. Its use is so widespread that it is almost impossible to work in electronics without coming across it. Microcontrollers are used in a wide number of electronic systems such as: •

Engine management systems in automobiles.

•

Keyboard of a PC.

•

Electronic measurement instruments (such as digital multimeters, frequency synthesizers, and oscilloscopes)

•

Printers.

•

Mobile phones.

•

Televisions, radios, CD players, tape recording equipment.

•

Hearing aids.

•

Security alarm systems, fire alarm systems, and building services systems.

What is a microprocessor?

The microprocessor is the integration of a number of useful functions into a single IC package. These functions are: •

The ability to execute a stored set of instructions to carry out user defined tasks.

•

The ability to be able to access external memory chips to both read and write data from and to the memory.

-65-  What is a microcontroller?

Basically, a microcontroller is a device which integrates a number of the components of a microprocessor system onto a single microchip.

The PIC Microcontroller: PIC stands for – “Peripheral Interface Controller”. The original PIC was designed to be a Peripheral Interface Controller for 6502 microcontroller from Rockwell late 70’s.

Why did we choose Microchip PIC Family of Microcontrollers? • Free development softwares MPLAB IDE and Mikro C. • Low cost development hardware. • Devices are easy to obtain through distributors and can be sampled. • A wide range of devices are available with varying feature sets. • Microchip is in continuous development of new PIC devices. • Has a large Internet based development community (piclist.com).

-66-  The Architecture of 16F877:

The architecture of 16F877 has wide range of built-in modules so that no need for external hardware components.

Figure 3.1 Supporting Hardware:

PIC Test bench for code checking.

PIC Programmer.

     

 

CHAPTER: 4 

FABRICATION &  PERFORMANCE  EVALUATION    

• System Wiring Diagrams  •  Modular Performance Charts  • Cost Analysis  • Conclusion 

        

-68- 

CHAPTER 4 Fabrication & Performance Evaluation 4.1 Final Designs & Pictures

Complete wiring layout between various modules of the system.

Figure 4.1

The true scaled CAD layout based on the above wiring diagram:

-69-  Finished Modules M

            

-70-  4.2 Performance Charts 4.2.1 Tracker Name

Design Constraints

Results

Pass / Fail

Tracking

Horizontal Tracking

Pass

Scan rate

30 minutes

Controlled Tracking Designed Programmable Approx 50mV sensitivity >95%

Sensitivity Efficiency

Tracker should be stable & parallel to Sun >90%

Pass Pass Pass

Table 4.1 4.2.2 PV Regulator Name

Design Constraints

Results

Pass / Fail

Up to 36 Volts

Achieved

Pass

Desired level (Set Externally)

O/P deflection is only 400mV

Pass

Provide constant 6A

Designed for 10A

Pass

>90%

Achieved

Pass

Temperature

Not more than 50oC

Size

Should be compact

Operating temperature is 45 oC 97mm * 100mm

Variable Input Regulated Output Charging Current Regulation Efficiency

Pass Pass

Table 4.2 4.2.3 Battery Charge Monitoring Board Name Controller Based Indications Modes Cutoff Status Size Efficiency

Design Constraints Intelligent Charging Display all conditions User defined Low & full battery conditions Should be compact >90%

Results PIC based monitored charging 8 Status LEDs Multiple source selection

Pass / Fail Pass Pass Pass

Limits achieved

Pass

110mm * 130mm >95%

Pass Pass

Table 4.3

-71-  4.2.4 Inverter Name Voltage Power Waveform Output Stage Control Circuit Transformer Size

Design Constraints

Results

Pass / Fail

Convert 12VDC to 220VAC Provide 850VA continuous power Pure 50Hz Sine wave

12VDC to 220VAC 50Hz

Pass

> 900VA

Pass

Modified Sine

Fail

MOSFET based

Achieved

Pass

Microcontroller based

PIC microcontroller

Pass

Iron core transformer used Ferrite Core due to unavailability of ferrite core. Should be compact 115mm * 200mm Table 4.4

-Pass

4.3 Conclusion: As you can see from the information above most of the more important design constraints were met. The packaged product did convert 12VDC to a 220VAC, 50 Hz. Some of the more aggressive constraints were however not met. We were unable to produce a pure sine wave. Even though, we have designed the PWM circuitry for the Sine wave generation, however for the failure of the ferrite core transformer phase of the project, we feel that this constraint was set pretty aggressively without enough knowledge of the availability of the data and the categorized core itself. We feel that while this constraint was a failure that it is an acceptable failure. The packaged unit size was efficiently controlled by using the CAD tools. The overall efficiency of the entire system is 85% which is appreciable on the research and testing level. In the end our project stands as a fully functional finished product ready to be marketed.

Future Improvement: With the proper implementation of ferrite core transformers the efficiency, weight reduction and the pure sine wave output can be achieved. If one is able to find the respective data and specifications of the ferrite core and its materials.

-72-  4.4 Cost Analysis

Part Name

Cost (Rs.)

Tracker i. PV Panel ii. Drive & Mechanical Stand iii. Circuit Charge Controller i. BCM Circuit ii. PV Regulator iii. AC Charger Battery Box Inverter i. Ferrite Cores ii. Winding Wires iii. Circuit iv. Transformer (Iron Core) v. MOSFETS Miscellaneous i. Development Boards ii. Programmer iii. LCD iv. Heat Sinks v. Fans vi. Relays vii. Function Generator ICs viii. Mix ICs ix. PCBs a) Tracker b) PV Regulator c) Display Board d) BCM e) Inverter f) Relay Control Board x. Connectors xi. Wires xii. Switches & Fuses xiii. Components Damaged During Testing a) MOSFETS b) ICs Total Cost

20,000 10,000 150 200 650 850 5,500 2,000 500 750 350 1,500 450 120 50 230 400 600 450 900 600 70 150 100 200 250 150 300 700 650

900 230 49,950

Table 4.5 Our estimated cost was Rs.75,000; however we have been able to complete the project in under Rs.50,000, this cost reduction has been quite an achievement for us.

     

 

  

APPENDICES   

• Firmware  •  Transformer Core Datasheets  • List of Test Points ‐ Troubleshooting  • Software & Instruments  • References 

       

-74- 

APPENDIX A: FIRMWARE BATTERY MONITORING BOARD void Bfcheck(); //Checks whether Battery is full or needs to be charged void SrcCheck(); //Checks Available Source & give Indication on LED void CC(); //DC Charger void BC(); //AC Charger int batt=0, bn=0, pv=0, i=0, j=0; void main() { OPTION_REG = 2; //Prescaler 1:8 ADCON0 = 1; ADCON0.0 = ADON = 1; ADCON1 = 132; //AN0 to AN4 Analog, AN5 to AN7 Digital, ADC Clock = Fosc/2, Right Justified TRISA = 0xFF; //PortA/RA = Input TRISB = 0; PORTB/RB = Output; PORTB = 0; //Reset PORTB TRISC = 0; //PORTC/RC = Output PORTC = 0; //Reset PORTC Bfcheck(); //Indicates if battery is full or needa to be charged SrcCheck(); //Indicates Available Sources PORTB.f4 = 1; //Indicates Source Selection Input Needed delay_ms(2000); //Wait for input PORTB.f4 = 0; //Reset Source Selection Indication if(PORTA.f5==0) //If Switch Pressed { //Switch Debouncing delay_ms(1000); if(PORTA.f5==0) { PORTB.f2 = 1; //Indicates DC Charger PORTB.f3 = 0; //Indicates AC Charger Jumps to DC Charger; } else if(PORTA.f5==1) { PORTB.f2 = 0; //Indicates DC Charger PORTB.f3 = 1; //Indicates AC Charger BC(); Jumps to AC Charger;; } } void bfcheck() { batt = ADC_Read(1); if(batt >= 690) { hang: PORTB.f7 = 1; goto hang; } else

//Read Battery //If Battery is in //Nominal Range then //INDICATE BATTERY FULL //LOOP BACK (HANG)

-75-  PORTB.f7 = 0; fully charged } void SrcCheck() { pv = ADC_Read(0); if(pv >= 700) sufficient { PORTB.f5 = 1; } else { PORTB.f5 = 0; }

//Indicates Battery not

//Read PV //If PV = 3.42v is

//PV Available Indication

//PV not available

void CC() { OPTION_REG = 2; //Prescaler 1:8 ADCON0 = 1; //ADCON0.0 = ADON = 1 ADCON1 = 130; //AN0 to AN4 Analog, AN5 to AN7 Digital, ADC Clock = Fosc/2, Right Justified TRISA = 0xFF; //PortA/RA = Input TRISB = 0; //PortB/RB = Output TRISC = 0; //PortB/RB = Output PORTC = 0; //Reset Output Port batt = ADC_Read(1); delay_ms(1); //Acquisition Time pv = ADC_Read(0); delay_ms(1); while (pv > 700) { PORTB.f7 = 1; //Battery Full Indication while(batt < 690) //If battery is not in nominal range { charge1: PORTB.f7 = 0; //Battery not full PORTC.f0 = 1; //Turn DC Charger RELAY ON PORTB.f1 = 1; //Charging INDICATION for(i=0; i<600 ; i++) //Wait for 30 minutes { delay_ms(3000); } PORTB.f1 = 0; //Charging INDICATION OFF PORTC.f0 = 0; //DC Charger RELAY OFF for(j=0; j<60 ; j--) //wait for 3 minutes { //so that battery voltage stabilise delay_ms(300); } bn = ADC_Read(1); //Read Battery level after being charged for "i" minutes delay_ms(1); if(batt < bn) //if battery voltage rises { batt = bn; //store new battery level

-76-  goto charge1; } else

//loop back //if battery voltage not

rising if(bn > 685)

//if battery is in nominal

range { goto bfull1; } else

//battery full //battery not in nominal

range { goto error1; } bfull1:

error1:

PORTB.f7 = PORTC.f0 = while(1); PORTB.f7 = PORTC.f0 = PORTB.f0 = while(1); }

1; 0; 0; 0; 1;

//error indication //BATTERY FULL LED //DC CHARGER RELAY OFF //HANG INDEFINITELY //BATTERY FULL LED //DC CHARGER RELAY OFF //ERROR LED //HANG INDEFINITELY

} void BC() { OPTION_REG = 2; //Prescaler 1:8 ADCON0 = 1; //ADCON0.0 = ADON = 1 ADCON1 = 130; //AN0 to AN4 Analog, AN5 to AN7 Digital, ADC Clock = Fosc/2, Right Justified TRISA = 0xFF; //PortA/RA = Input TRISB = 0; //PortB/RB = Output batt = ADC_Read(10); delay_Us(2000); PORTA.f7 = 1; //BATTERY FULL while(batt < 690) 645 = 3.068volt == 11.19v; { charge: PORTB.f7 = 0; //BATTERY FULL PORTC.f1 = 1; //AC CHARGER RELAY PORTB.f1 = 1; //CHARGING INDICATION for(i=0; i<600 ; i++) //WAIT FOR 30minutes { delay_ms(3000); } PORTB.f1 = 0; //CHARGING LED PORTC.f1 = 0; //AC CHARGER RELAY for(j=0; j<60 ; j++) //WAIT 3minutes { delay_ms(3000); } bn = ADC_Read(1); delay_ms(1); if(batt < bn) //IF BATTERY VOLTAGE RISING { batt = bn; //UPDATE CURRENT BATTERY LEVEL goto charge; //LOOP BACK }

-77-  else

bfull:

error:

if(bn > 685) 3.34volts == 0; { goto bfull; //JUMP TO BATTERY FULL } else { error; //JUMP TO ERROR } PORTB.f7 = 1; //BATTERY FULL PORTC.f1 = 0; //AC CHARGER RELAY OFF while(1); PORTB.f7 = 0; //BATTERY FULL PORTC.f1 = 0; //AC CHARGER RELAY OFF PORTB.f0 = 1; //ERROR LED while(1); }

}

TRACKER int left,right; void main() { OPTION_REG = 2; Prescaler 1:8; ADCON0 = 1; ADCON0.0 = ADON = 1; ADCON1 = 128; //AN0 to AN4 Analog, AN5 to AN7 Digital, ADC Clock = Fosc/2, Right Justified TRISA = 0xFF; //PortA/RA = Input TRISB = 0; PORTB/RB = Output; PORTB = 0; //Reset PORTB while(1) { left = ADC_Read(0); Delay_ms(100); right = ADC_Read(1); Delay_ms(100); if (left > 500 && right < 500) { PORTB.f7 = 1; // LEFT PIN PORTB.f6 = 0; // RIGHT PIN PORTB.f5 = 0; Delay_ms(5000); PORTB.f7 = 0; } else if(right > 500 && left < 500) { PORTB.f7 = 0; // LEFT PIN PORTB.f6 = 1; // RIGHT PIN PORTB.f5 = 0; Delay_ms(5000); PORTB.f6 = 0; } else { PORTB.f7 = 0; // LEFT PIN PORTB.f6 = 0; // RIGHT PIN PORTB.f5 = 1;

-78-  delay_ms(20000); PORTB.f5 = 0; } }

DISPLAY BOARD DEVICE : PIC16F877A CLOCK : 12MHz HS RS = C.4 , R/W = C.5 , En = C.6 , Data Bus = D.7 to D.0 Lcd8_Init(*portctrl, *portdata); E ? ctrlport.6 RS ? ctrlport.4 R/W ? ctrlport.5 D7 D6 D5 D4 D3 D2 D1 D0 void main() { int inp,m,bfull; Input) m = 0; selection TRISA = 63; TRISB = 0; TRISC = 0; TRISD = 0; // TRISE = 7; ADCON1= 7; PORTC = 0; PORTD = 0; Lcd8_Init(&PORTC, &PORTD); PORTD Lcd8_Out(1, 7, "TIE"); Lcd8_Out(2, 5, "SOLARIS"); m: Delay_ms(2000); Lcd8_Cmd(LCD_TURN_OFF); Delay_ms(200); Lcd8_Cmd(LCD_TURN_ON); PORTB = 0; bfull = PORTA.f0; Lcd8_Cmd(LCD_CLEAR); if(bfull==1)

? ? ? ? ? ? ? ?

dataport.7 dataport.6 dataport.5 dataport.4 dataport.3 dataport.2 dataport.1 dataport.0

//inp Stores the value at PORTE (Sw //m stores the current mode //Digital Inputs //LED //PORTC is output (Ctrl Port - LCD) //PORTD is output (Data Bus - LCD) //PORTE is input (Keypad) //All inputs are Digital //Reset PORTC //Reset PORTD // Initialize LCD at PORTC and // Print text on LCD

PORTB.f4 = 1; PORTB.f3 = 0; Lcd8_Cmd(LCD_CLEAR); Lcd8_Out(1, 7, "INV?"); Lcd8_Out(2, 5, "Press YES"); Lcd8_Cmd(LCD_BLINK_CURSOR_ON);

-79-  b1:

Delay_ms(1000); inp = PORTA.f5; if(inp==1) { PORTB.f7 = 1; goto invr; } else goto b1; else

{ PORTB.f4 = 0; PORTB.f3 = 1; Lcd8_Cmd(LCD_CLEAR); Lcd8_Out(1,7, "CHRG?"); Lcd8_Out(2,5, "Press YES"); Lcd8_Cmd(LCD_BLINK_CURSOR_ON); b2: Delay_ms(1000); inp = PORTA.f5; if(inp==1) { PORTB.f0 = 1; goto chrg; } else goto b2; } invr:Lcd8_Cmd(LCD_CLEAR); Lcd8_Cmd(LCD_TURN_OFF); Delay_ms(200); Lcd8_Cmd(LCD_TURN_ON); Lcd8_Out(1,6, "INV-ON"); while(bfull==1) bfull = PORTA.f0; Delay_ms(3000); PORTB.f7 = 0; Lcd8_Out(1,6, "INV-OFF"); PORTB.f3 = 1; //Battery Low Indication PORTB.f4 = 0; goto m; chrg:Lcd8_Cmd(LCD_CLEAR); Lcd8_Cmd(LCD_TURN_OFF); Delay_ms(200); Lcd8_Cmd(LCD_TURN_ON); Lcd8_Out(1,6, "CHRG-ON"); while(bfull==0) bfull = PORTA.f0; Delay_ms(3000); PORTB.f0 = 0; Lcd8_Out(1,6, "CHRG-OFF"); PORTB.f4 = 1; //Battery Full Indication PORTB.f3 = 0; goto m; }

-86- 

APPENDIX C: LIST OF TEST POINTS - TROUBLESHOOTING

Sr #

TOPIC

PAGE #

1.

Tracker – Voltage Reference Circuit

13

2.

Charge Controller Board (12F675)

17

3.

Programming Issues

19

4.

Battery Charge Monitor

22

5.

PV Regulator

26

6.

AC Charger

28

7.

Sine Wave Bubba Oscillator

33

8.

Carrier Wave Generator

34

9.

TL494 Based Half-Bridge Converter

42

10.

SG3525 Based Half-Bridge Converter

44

11.

Ferrite Core Transformer Testing

46

12.

SG3525 Based Mod-Sine Inverter

54

13.

PIC Inverter

56

-80- 

APPENDIX B: TRANSFORMER DATASHEETS

 

-81- 

 

-82- 

 

-83- 

 

-84- 

 

-85- 

-87- 

APPENDIX D: SOFTWARE & INSTRUMENTS SOFTWARES: o o o o o o o o o

PIC Simulator IDE MPLab IDE Mikro C Win Prog AutoCad OrCad 9.2 Circuit Design Suite Target 3001 PCB Artist

EQUIPMENTS:

TEKTRONIX 2213

SUNWA CD-800

DMM - 3302

YF-150 CAPACITANCE METER

FUNCTION GENERATOR 4415

TEKTRONIX 2445B

ALL-11 UNIVERSAL PROGRAMMER

LODESTAR FREQUENCY COUNTER

LODESTAR AVO METER

XELTEX SUPER PRO L+

TEKTRONIX TAS 465

SOLDERING STATION

-88- 

APPENDIX E: REFERENCES Books & Research Papers

[1] Home Power Magazines, 2007 Feb, June & November + 2008 August. [2] Single Phase Grid connected PV System Mr. Chainon Chaisook, 2002. [3] Solar Tracker EC476, Spring 2005 by Toby Peterson & Jeff Valane. [4] Introduction to Power Electronics by Denis Fewson, Chapter 2 & 4. [5] PIC Microcontroller Datasheets from www.microchip.com. [6] IEEE Workshop on PIC microcontroller presented by Andrew & Tim, 16 Jan, 2000. [7] Microchip Embedded control handbook updated 2000. [8] Microchip tips & tricks 8-bit flash microcontroller, 2003. [9] Mikro C user manual, 2006. [10]

AN106, Op-Amp Applications – Analog Devices by James Wong.

[11]

Current overload protection for inverter, USS4410935 Oct 18, 1983.

[12]

MCU-based non-inverting buck-boost converter for battery chargers.AN2389 ST.

[13]

Single Stage battery charger with PFC by Ningliang Mi – Curtis Instruments Inc.

[14]

DC-AC Isolated battery inverter. Application note AN9611 Feb, 2003.

[15]

NI – LM5030 Push-Pull Converter Design Notes by Michele Sclocchi.

[16]

NASA Technical Notes – PWM Static Inverter by Francis Gourash Feb, 1970.

[17]

HF Power inductor design by Dr. Ray Ridley, Ridley Engineering March 2007.

[18]

Wurth Elektronik – Transformer Cookbook.

[19]

Magnetics – Power Design, Section 4.0. www.magnetics.com

[20]

Designing Coil & transformer by M.C.Sharma Ch#14 Page:193.

[21]

Losses in transformer winding by Llyod H. Dixon.

-89- 

Websites

o www.precision-inc.com o www.wa4dsy.net/filter o www.piclist.com o www.mikroelektronika.com o www.irf.com o www.semikron.com o www.datasheetcatalog.com o www.educypedia.be o www.aaroncake.net o www.pdfcoke.com