This project develops a microcontroller-based system for detecting islanding of a grid-connected inverter by monitoring voltage and frequency from the utility grid. The microcontroller triggers a relay to disconnect the inverter from the grid if voltage or frequency go outside predetermined ranges. A 555 timer circuit is used to vary the test frequency, while a variac adjusts the voltage. Hardware components include a microcontroller, 555 timer, comparators, relays and other supporting electronics. The system displays islanding detection on an LCD screen. It can be applied to solar power plants for grid security by ensuring power is supplied rather than drawn during abnormalities.

1. DEVELOPING ISLANDING ARRANGEMENT
AUTOMATICALLY FOR GRID ON SENSING
BAD VOLTAGE OR FREQUENCY
Under the Guidance of
Submitted by
Project Title

2. ABSTRACT
This 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.

3. BLOCK DIAGRAM

4. HARDWARE REQUIREMENTS
 POWER SUPPLY
 MICROCONTROLLER (AT89S52/AT89C51)
 555 TIMER
 LM358
 LM339
 RELAYS
 BC547
 LIQUID CRYSTAL DISPLAY
 LED
 IN4007
 RESISTORS
 CAPACITORS

5. 230 V AC
50 Hz
5V
DC
12V step down
transformer
Filter(470µf)
5v RegulatorBridge rectifier

6.  It is a smaller computer
 Has on-chip RAM, ROM, I/O ports...
RAM ROM
I/O
Port
Timer
Serial
COM
Port
Microcontroller
CPU
A single chip

7. CPU
On-chip
RAM
On-chip
ROM for
program
code
4 I/O Ports
Timer 0
Serial
Port
OSC
Interrup
t
Control
External interrupts
Timer 1
Timer/Counter
Bus
Control
TxD RxDP0 P1 P2 P3
Address/Data
Counter
Inputs

8.  Compatible with MCS®-51 Products
 8K Bytes of In-System Programmable (ISP) Flash Memory
 Endurance: 10,000 Write/Erase Cycles
 4.0V to 5.5V Operating Range
 Fully Static Operation: 0 Hz to 33 MHz
 256 x 8-bit Internal RAM
 32 Programmable I/O Lines
 Three 16-bit Timer/Counters
 Eight Interrupt Sources
 Full Duplex UART Serial Channel
 Interrupt Recovery from Power-down Mode
 Watchdog Timer
 Dual Data Pointer

10. 555 TIMER
The 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.

11. Pin Name Purpose
1 GND Ground, low level (0 V)
2 TRIG OUT rises, and interval starts, when this input falls below 1/3 VCC.
3 OUT This output is driven to +VCC or GND.
4 RESET A timing interval may be interrupted by driving this input to GND.
5 CTRL "Control" access to the internal voltage divider (by default, 2/3 VCC).
6 THR The interval ends when the voltage at THR is greater than at CTRL.
7 DIS Open collector output; may discharge a capacitor between intervals.
8 V+, VCC Positive supply voltage is usually between 3 and 15 V.
Internal architecture of 555 timer

12. 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

13. 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.

14. FEATURES
•Wide single supply voltage range 2.0VDC TO
36VDC or dural supplies ±1.0VDC to ±18VDC
● Very low supply current drain (0.8 ㎃ )
independent
of supply voltage (1.0 ㎽ /comparator at 5.0VDC)
● Low input biasing current 25 ㎁
● Low input offset current ±5 ㎁ and offset voltage
● Input common-mode voltage range includes
ground
● Differential input voltage range equal to the power
supply voltage
● Low output 250 ㎷ at 4 ㎃ saturation voltage
● Output voltage compatible with TTL, DTL, ECL,
MOS and CMOS logic system

15. IT IS A ELECTRO MAGNETIC SWITCH
USED TO CONTROL THE ELECTRICAL DEVICES
COPPER CORE MAGNETIC FLUX PLAYS MAIN ROLE HERE

16. The relay's switch connections are usually labeled COM, NC and
NO:
COM = Common, always connect to this; it is the moving part of
the itch.
NC = Normally Closed, COM is connected to this when the relay
coil is off.
NO = Normally Open, COM is connected to this when the relay
coil is on

17. BC547 (NPN –Transistor)
The BC547 transistor is an NPN Epitaxial
Silicon Transistor.
It is used in general-purpose switching and
amplification BC847/BC547 series 45 V, 100
mA NPN general-purpose transistors.
The ratio of two currents (Ic/Ib) is called the DC Current Gain of
the device and is given the symbol of hfe or nowadays Beta, (β).

18. The current gain from the emitter to the collector
terminal, Ic/Ie, is called Alpha, (α), and is a function of the
transistor itself

19. LIQUID CRYSTAL DISPLAY (LCD)
Most common LCDs connected to the microcontrollers are
16x2 and 20x2 displays.
This means 16 characters per line by 2 lines and 20
characters per line by 2 lines, respectively.
The standard is referred to as HD44780U, which refers to
the controller chip which receives data from an external
source (and communicates directly with the LCD.

20. LCD BACKGROUND
If an 8-bit data bus is used the LCD will require 11 data lines
(3 control lines plus the 8 lines for the data bus)
The three control lines are referred to as EN, RS, and RW
EN=Enable (used to tell the LCD that you are sending it data)
RS=Register Select (When RS is low (0), data is treated as a command)
(When RS is High(1), data being sent is text data )
R/W=Read/Write (When RW is low (0), the data written to the LCD)
(When RW is low (0), the data reading to the LCD)

21. 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.
All these 3 condition’s are taken by the MC and displayed in LCD
Working of project

22.  Keil an ARM Company makes C compilers, macro assemblers, real-
time kernels, debuggers, simulators, integrated environments,
evaluation boards, and emulators for ARM7/ARM9/Cortex-M3,
XC16x/C16x/ST10, 251, and 8051 MCU families.
 Compilers are programs used to convert a High Level Language to
object code. Desktop compilers produce an output object code for the
underlying microprocessor, but not for other microprocessors.

23.  i.e the programs written in one of the HLL like ‘C’ will compile
the code to run on the system for a particular processor like x86
(underlying microprocessor in the computer).
 For example compilers for Dos platform is different from the
Compilers for Unix platform So if one wants to define a compiler
then compiler is a program that translates source code into object
code.

24. This project is applicable for Solar Power Plant
where frequency varies; frequency and voltage
parameters should match with the Power grid.

25. 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.

26. The disadvantage of this project is, it’s available in
single phase supply where power Grid is of Three
Phase supply.

27.  “The 8051 Microcontroller and Embedded systems” by
Muhammad Ali Mazidi and Janice Gillispie Mazidi , Pearson
Education.
 ATMEL 89S52 Data Sheets.
 www.atmel.com
 www.beyondlogic.org
 www.wikipedia.org
 www.howstuffworks.com
 www.alldatasheets.com

28. QUERIES ?

29. THANKYOU