Submitted By:A.Pradeep

(11B71A0244)

Seminar Title

DETECTING POWER GRID SYNCHRONISATION FAILURE ON SENSING

BAD VOLTAGE OR FREQUENCY

ABSTRACTThis paper presents the development of a microcontroller based

islanding detection for grid connected inverter with very simple

under/over voltage and under/over frequency islanding detection

algorithms.

The microcontroller monitors the under/over voltage and under/over

frequency from utility grid and the processed value of voltage and

frequency for turning ON/OFF the relay between a grid connected

inverter and the utility grid.

The project would alternatively use a variable frequency generator

using 555timer for changing the frequency while a standard variac

shall be used to vary the input voltage for achieving the test

conditions as stated above.

HARDWARE REQUIREMENTS

POWER SUPPLY BLOCK

MICROCONTROLLER (AT89S52/AT89C51)

555 TIMER

LM358

LM339

RELAYS

BC547(NPN TRANSISTOR)

LIQUID CRYSTAL DISPLAY

LED

IN4007

RESISTORS

CAPACITORS

POWER SUPPLY

230 V AC 50 Hz

5VDC

230/12V step down transformer

Filter(470µf)

5v RegulatorBridge rectifier

MICROCONTROLLER

• It is a smaller computer

• Has on-chip RAM, ROM, I/O ports...

Pin Description

555 TIMERThe 555 Timer IC is an integrated circuit (chip) implementing a variety of timer and multivibrator applications

The 555 has three operating modes:

•Monostable mode: in this mode, the 555 functions as a "one-

shot". Applications include timers, missing pulse detection,

switches, touch switches, frequency divider, capacitance

measurement, pulse-width modulation (PWM) etc.

•Astable - free running mode: the 555 can operate as an

oscillator. Uses include LED and lamp flashers, pulse

generation, logic clocks, tone generation, security alarms,

pulse position modulation, etc.

•Bistable mode or Schmitt trigger: the 555 can operate as a

flip-flop, if the DIS pin is not connected and no capacitor is

used. Uses include bounce free latched switches, etc.

LM358 (DUAL OPERATIONAL AMPLIFIER)

The LM358 series consists of two independent, high gain; internally

frequency compensated operational amplifiers which were designed

specifically to operate from a single power supply over a wide range of

voltages

Operation from split power supplies is also possible and the low

power supply current drain is independent of the magnitude of the power

supply voltage.

Pin description

1 ) Output 1 2 )Inverting input

3 ) Non-inverting input 4 )VCC-

5 )Non-inverting input 2

6 ) Inverting input 2

7 ) Output 2 8 ) VCC+

LM339( COMPARATOR)

The LM339 consists of four independent precision voltage comparators.

The LM339 series was designed to

directly interface with TTL and CMOS.

When operated from both plus and

minus power supplies, the LM339 series

will directly interface with MOS logic

where their low power drain is a distinct

advantage over standard comparators.

RELAY

IT IS A ELECTRO MAGNETIC SWITCH

USED TO CONTROL THE ELECTRICAL DEVICES

COPPER CORE MAGNETIC FLUX PLAYS MAIN ROLE HERE

BLOCK DIAGRAM

Islanding of grid is connected to inverter which is basically managing two

parameters voltage and frequency

In the program it is so written that the output from 555 timer which is fed to

the MC goes to be low 48KHz or above 52Hz. The corresponding outputs of MC

will go high and which will result in switching “ON or OFF” a load to indicate

that the islanding has taken place. (for frequency concerned).

As per the voltage is concerned we have taken 2 comparators. Both the

comparators are given to i.e., one for inverting input and other for non-

inverting input which are given at a particular voltage.

This program is that in either of these cases whether the few is low / high (or)

it could be either in high / low condition the duration will be 50, 49, 48 06

greater than 52.

Working of project

Advantages

The advantage of this project is, it’s secured the Power of the Grid i.e., Power Plants should supply power to the grid rather than drawing the power from the grid.

DISADVANTAGE

The disadvantage of this project is, it’s available in

single phase supply where power Grid is of Three

Phase supply.

Applications

This project is applicable for Solar Power Plant

where frequency varies; frequency and voltage

parameters should match with the Power grid.

THANK YOU