A Project Report on Three Phase Voltage Regulation Using SCR & Micro-Controller

A Project Report on Three Phase Voltage Regulation using SCR & Micro-Controller.

ACKNOWLEDGEMENT

Our Quest for practical knowledge led us in to the esteemed Organization Automatic Electric Co.(Lonavla), which is a hall of fame. If words are considered as symbols of approved and tokens of acknowledges, then let Words play the heralding role of expressing our gratitude. We profusely thank our director Sri. Mr.Pramod Kale and our university Coordinator Dr.D.Shaligram for their encouragement and support through out the project.

We extend our heartiest thanks to our respected Project coordinator, Mrs. Preeti Salunkhe, who is always a constant source of inspiration for us and for her motivations in making this project completion.

We are very thankful to our beloved guideMs. JyutikaNalawade, for her valuable and patient guidance throughout our endeavor. We remember With Regards and respect the assistance and encouragement given by her. We are very much indebted to our beloved parents who have given this opportunity to join in this course and are great source of encouragement for us. Above all, the GRACE OF GOD of all creations led us to complete our project successfully.

EXECUTIVE SUMMERY

In our day to day life we use a lot many devices to satisfy our needs or to make our life comfortable and luxurious. Every device needs a power supply, to work on. And for the optimum functioning of the device it is necessary that the supply should be reliable. That is, it should provide a constant voltage.

But this is not possible always. There are many reasons due to which there is a fluctuation in the supply voltage. This change in the supply voltage may cause the device to damage or make it work in an undesired way, which no one would desire.

Hence the best alternative is to regulate the supply voltage. This is what we have tried to achieve here. Our project is supply voltage regulation, using controller and SCR.

In our project we provide the load with a constant voltage of 240 V ac., in spite of any variation in the input voltage. The voltage regulation is achieved by controlling the firing angle of the SCR so precisely that the load receives a constant supply. The voltage across the load is stepped down and provided to ADC. ADC will produce a digital signal corresponding to the input analog signal. This digital signal from ADC is then processed by the controller and generates a firing pulse for SCR, hence controlling the load current.

INDEX

INTRODUCTION .……………………………………………….4

AIM & OBJECTIVES ....………………………………………...7

PROJECT PLANNING .………………………………………….9

BLOCK DIAGRAM ...………..…………………………………12

BLOCK DIAGRAM DESCRIPTION.……….…………………14

COMPONENT SEPECIFICATIONS.………………………….18

CIRCUIT DIAGRAM.………………………………………….47

FUNCTIONALITY.…………………………………………….49

SOFTWARE FLOW CHART.………………………………….51

RESULTS & CONCLUSION.………………………………….58

BIBLIOGRAPHY.……………………………………………...60

CHAPTER 1

Introduction

INTRODUCTION

Hence the best alternative is to regulate the supply voltage. This is what we have tried to achieve here. Our project is supply voltage regulation, using controller and SCR.

Silicon Controlled Rectifiers also called Thyristors controller, employing novel technology,which is designed to provide a price effective solution for applications that require power, current or voltage regulation with some power factor correction and a smother process control. Traditional phase-angle control causes lots of harmonic current distortion on the main power supply. This in turn creates voltage distortion which affects power quality. There is no simple accessory available for reducing this problem.

However, when simple voltage or current regulation is required often phase-angle control is the most cost effective solution.

Thyristors and triacs are switched on by using a gate. They automatically switch off again when the conducted current reaches zero.

Therefore, these devices can be used in power regulators and by switching at a predetermined position on the AC sine wave (the phase-angle) the effective voltage can be reduced or increased.This can be used to regulate voltage or power to a load.

CHAPTER 2

Aim & Objective

AIM & OBJECTIVE

AIM:-

To develop a systemforcontrolling fluctuation in thethree phase Voltage supply using SCR and Controller.

OBJECTIVE:-

To upgrade the existing three phase analog regulatory system, to a three phase, microcontroller based SCR drive system. So that if any fluctuation comes in threephase voltage supply, controller will Sense that fluctuation and accordingly give triggering pulses to the SCR to get controlled regulated output at the load.

CHAPTER 3

Project planning

PROJECT PLANNING

Exactly what was planned in the project?

To design hardware for voltage regulation by using SCR bridge
To sense fluctuation in the single phase voltage supply.
To sense zero crossing of the input sine wave.
To get correct firing angle of SCR for getting correct control voltage.
To calculate the correct delay time for giving trigger pulse to SCR.
To trigger SCR depending upon calculated data and get the regulated

output.

To implement the same for three phase voltage supply.

What is achieved?

We designed hardware for voltage regulation by using SCR bridge
We sensed fluctuation in the single phase voltage supply.
We sensed zero crossing of the input sine wave.
We got correct firing angle of SCR for getting correct controlvoltage.
We calculated the correct delay time for giving trigger pulse to SCR.

TIME SCHEDULING

S.no / Schedule / days
1 / Understanding project details / 2
2 / Finalizing project modules / 3
3 / Data collection / 7
4 / Selection of Microcontroller and its peripherals / 4
5 / Component search / 11
6 / Circuit Design / 5
7 / Hardware assembly / 7
8 / Hardware testing and debugging / 7
9 / Software coding (for calculating correct delay for different angle) / 2
10 / Preparing look up table for different ADC values / 1
11 / Software coding(for voltage fluctuation) / 3
12 / Testing code on hardware / 8
13 / Project report & presentation / 3

CHAPTER 4

Block Diagram

BLOCK DIAGRAM

CHAPTER 5

Block Diagram Description

BLOCK DIAGRAM DESCRIPTION

POWER SUPPLY

This is the first block of our system. We have used a step-down centre tap transformer, with the voltage rating of 240V ac as primary voltage and 24-0-24V ac as the secondary voltage. The current rating of the transformer is 500mA.

The stepped-down ac signal is supplied to the rectifier & regulator. It consists of a simple rectifier diode bridge network along with some filtering circuit, for smoothing out the input signal. This filtered and rectified signal is then regulated using a positive voltage regulator, to the desired value (say 5 V dc & 15 V dc) and also negative voltage regulator to the desired value (say -15 V dc).For these purpose; we are using three regulator chips.

LM7805 (+5V DC)

MC7815C (+15V DC)

L7915 (-15V DC)

The basic input requirement of the two regulators 7815 & 7915 is 23v dc. i.e. it needs at lest this voltage to provide a constant +/-15V. This is why we have selected the center-tap transformer of 24V dc. But the input voltage requirement of 7805 is just about 13v dc; hence we have reduced the voltage of the transformer to 13V through a resistor in series.

The input of the regulator is provided with a filter capacitor of 10uF, 50v. and the output with 0.01uf, forming a pie filter for better signal to noise ratio.

ZERO CROSSING DETECTOR

This circuit is containing of OP-AMP UA 741.This is mainly used to detectthe zero crossing of the input sine wave so that we can get Synchronization.

The output of ZCD is given to the PORT pin 2.5 of the Microcontroller. Here ZCD is used so that we can give trigger angle to the SCR at Correct time.

The op-amp in the ZCD is just a sine to square wave generator. It converts in the input 24V ac signal to the square wave of 5 V and of the same frequency as that of the sine wave. Op-amp UA 741 is provided with a dual supply, obtained from the positive and negative regulators (+15V & -15V dc).

The output pin of the ZCD is provided with a rectifying diode which restricts the negative signal from reaching the controller pin to avoid any damage to it.

SCR BRIDGE NETWORK

This block consists of a pair of SCR & diodes. Input to the SCRBridge circuit is fluctuated Single phase voltage supply, which is given to anode of both the SCRs and cathode of both the diodes. Cathode of both the SCRs and Anode of both the diodes are provided to the load. We have assumed a resistive load of 10K ohm. From this load resistor one voltage signal will go to the Potential divider for feedback purpose. This will act as the input signal to the ADC.

The gate of the SCR is connected to the PORT2.0 and PORT2.1. A specific triggering pulse is provided to the gate of the SCR of sufficient time delay so as to keep the load voltage constant.

POTENTIAL DIVIDER

To get controlled output we need to give feedback signal from the SCR bridge circuit to ADC. But here feed back signal is nearer of 240V.So, we required to step it down to the +5V.

Because of this, here we have used potential divider network. From this potential divider network we will get voltage signal around +5V. To obtain the voltage of 5V ac from 240Vac we have used the network ratio of 59:1. The upper 59K resistor is fix while the lower 1K is a pot of 10k. Then after this voltage signal is given to ADC0808.

ANALOG TO DIGITAL CONVERTER (ADC 0808)

Here we get input from potential divider network which is around +5V. Then this analog value is converted to digital data and is given to Microcontroller. ADC 0808 has four channels but we need only one, hence we have selected channel 0 for input. The 8 bit digital output of ADC is provided to the port 1 of controller.

MICROCONTROLLER 89C51RD2

This block is the only decision making block, which decides whether any fluctuation in the supply line has occurred or not. It continuously compares the signal with the reference described in the software. If there is no change then SCR will be fired by it at phase angle 0 deg. But if it finds some fluctuation, then it will generate the pulse at a measured time delay to provide the firing angle of the SCR (through gate) such that the fluctuations will be nullified, and the supply to the load remains unaffected, in-spite the fluctuations.

CHAPTER 6

Components Specification

COMPONENT SPECIFICATION

POWER SUPPLY

SPECIFICATION OF IC LM7805:-

_ 3-Terminal Regulators

_ Output Current up to 1.5 A

_ Internal Thermal-Overload Protection

_ High Power-Dissipation Capability

_ Internal Short-Circuit Current Limiting

_ Output Transistor Safe-Area Compensation

Description information

This series of fixed-voltage integrated-circuit voltage regulators is designed for a wide range of applications. These applications include on-card regulation for elimination of noise and distribution problems associated with single-point regulation. Each of these regulators can deliver up to 1.5 A of output current. The internal current-limiting and thermal-shutdown features of these regulators essentially make them immune to overload. In addition to use as fixed-voltage regulators, these devices can be used with external components to obtain adjustable output voltages and currents.

Absolute maximum ratings over virtual junction temperature range (unless otherwise noted)

Input voltage, VI: A7824C 40 V)

All others 35 V

Operating virtual junction temperature, TJ 150C

Lead temperature 1,6 mm (1/16 inch) from case for 10 seconds 260C

Storage temperature range, Tst -65C to 150C

The LM7805 series of three terminal regulators are available with several fixed output voltages. The voltages available allow regulators to be used in logic systems, instrumentations, Hi-Fi and other solid state electronics equipment without any external feedback components.

These ICs are designed as fixed voltage regulator and with adequate heat sinking can deliver output currents in excess of 1A.The input capacitor Ci=0.33µF is used, if regulator is located far from the power supply filter capacitor. It filters out the effect of stray inductance of wire, ceramic or tantalum capacitor may be used. To improve the transient response of regulator capacitor of 0.1µF is connected at output. It utilizes common ground fir input and output and has dropout voltage (Vin – Vo) of 2 V.

Device type with input voltages / Output voltage
(V) / Output current / Quiescent
Current
(mA) / Line regulation
(mV) / Load regulation
(mV) / Ripple rejection
(dB)
78XXC
(35) / 5
12
15 / 1A / 8 / 25
60
75 / 50
120
150 / 80
72
70
78LXXAC
(35) / 5
12
15 / 100Ma / 3 to 5
3 to5
3.1 to 5 / 10
20
25 / 5
10
12 / 62
54
51
78LXXC
(35) / 5
12
15 / 100mA / 3 to 6
3 to 6.5
3.1 to 6.5 / 10
20
25 / 5
10
12 / 60
52
49
78MXX (35) / 5
12
15 / 0.5A / 4 to 10
4 to 10
4 to 10 / 50
120
150 / 100
240
300 / 78
71
69

SPECIFICATION OF MC7815 (+15V REGULATOR)

These voltage regulators are monolithic integrated circuits designed asfixed–voltage regulators for a wide variety of applications including local,on–card regulation. These regulators employ internal current limiting,thermal shutdown, and safe–area compensation. With adequate heat sinkingthey can deliver output currents in excess of 1.0 A. Although designedprimarily as a fixed voltage regulator, these devices can be used withexternal components to obtain adjustable voltages and currents.

• Output Current in Excess of 1.0 A

• No External Components Required

• Internal Thermal Overload Protection

• Internal Short Circuit Current Limiting

• Output Transistor Safe–Area Compensation

• Output Voltage Offered in 2% and 4% Tolerance

• Available in Surface MountD2PAK and Standard 3–Lead TransistorPackages

• Previous Commercial Temperature Range has been extended to aJunction

TemperatureRange of –40°C to +125°C.

SPECIFICATION OF L7915 (-15V REGULATOR)

OUTPUT CURRENT UP TO 1.5A
OUTPUT VOLTAGES OF -5; -6; -8; -12; -15;-18; -20; -24V
THERMAL OVERLOAD PROTECTION
SHORT CIRCUIT PROTECTION
OUTPUT TRANSITION SOA PROTECTION

The L7900 series of three-terminal negativeregulators is available in TO-220, TO-220FP,TO-3 and D2PAK packages and several fixedoutput voltages, making it useful in a wide range ofapplications. These regulators can provide localon-card regulation, eliminating the distributionproblems associated with single point regulation;furthermore, having the same voltage option asthe L7800 positive standard series, they areparticularly suited for split power supplies. Ifadequate heat sinking is provided, they candeliver over 1.5A output current.Although designed primarily as fixed voltageregulators, these devices can be used withexternal components to obtain adjustable voltagesand currents.

SPECIFICATION OF 1N4007 DIODE

• Low forward voltage drop.

• High surge current capability.

ZERO CROSSING DETECTOR

SPECIFICATION OF UA741(OP-AMP)

LARGE INPUTVOLTAGERANGE
NO LATCH-UP
HIGH GAIN
SHORT-CIRCUIT PROTECTION
NO FREQUENCY COMPENSATION
SAME PIN CONFIGURATION AS THE UA709

The UA741 is a high performance monolithic operational amplifier constructed on a single siliconchip. It is intended for a wide range of analog applications.

-Summing amplifier

- Voltage follower

- Integrator

- Active filter

- Function generator

The high gain and wide range of operating voltages provide superior performances in integrator,summing amplifier and general feedback applications.The internal compensation network (6dB/octave) insures stability in closed loop circuits.

PIN CONNECTIONS

MICROCONTROLLER

SPECIFICATION OF MICROCONTROLLER 89C51RD2

The 89C51RB2/RC2/RD2 device contains a non-volatile 16kB/32kB/64kB Flash
Program memory that is both parallel programmable and serial In-System and In-Application Programmable. In-System Programming (ISP) allows the user to download new code while the microcontroller sits in the application. In-Application Programming (IAP) means that the microcontroller fetches new program code and reprograms itself while in the system. This allows for remote programming over a modem link. A default serial loader (boot loader) program in ROM allows serial In-System programming of the Flash memory via the UART without the need for a loader in the Flash code. For In-Application Programming, the user program erases and reprograms the Flash memory by use of standard routines contained in ROM. This device executes one machine cycle in 6 clock cycles, hence providing twice the speed of a conventional 80C51. An OTPconfiguration bit lets the user select conventional 12 clock timing if desired. This device is a Single-Chip 8-Bit Microcontroller manufactured in advanced CMOS process and is a derivative of the 80C51 microcontroller family. The instruction set is 100% compatible with the 80C51 instruction set. The device also has four 8-bit I/O ports, three 16-bit timer/event counters, a multi-source, four-priority-level, nested interrupt structure, an enhanced UART and on-chip oscillator and timing circuits. The added features of the P89C51RB2/RC2/RD2 make it a powerful microcontroller for applications that require pulse width modulation, high-speed I/O and up/down counting capabilities such as motor control.

FEATURES

80C51 Central Processing Unit.
On-chip Flash Program Memory with In-System Programming (ISP) and In-Application Programming (IAP) capability.
Boot ROM contains low level Flash programming routines for downloading via the UART.
Can be programmed by the end-user application (IAP)
6 clocks per machine cycle operation (standard)
12 clocks per machine cycle operation (optional)
Speed up to 20 MHz with 6 clock cycles per machine cycle(40 MHz equivalent performance); up to 33 MHz with 12 clocks per machine cycle
Fully static operation
RAM expandable externally to 64 kB
4 level priority interrupt
8 interrupt sources
Four 8-bit I/O ports
Full-duplex enhanced UART

- Framing error detection

- Automatic address recognition

Power control modes

- Clock can be stopped and resumed

- Idle mode

- Power down mode

Programmable clock out
Second DPTR register
Asynchronous port reset
Low EMI (inhibit ALE)
Programmable Counter Array (PCA)
PWM
Capture/compare

BLOCK DIAGRAM