19-08-2013, 04:34 PM
DEVELOPING ISLANDING ARRANGEMENT AUTOMATICALLY FOR GRID ON SENSING BAD VOLTAGE OR FREQUENCY
DEVELOPING ISLANDING.ppt (Size: 1.84 MB / Downloads: 43)
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.
HARDWARE REQUIREMENTS
POWER SUPPLY
MICROCONTROLLER (AT89S52/AT89C51)
555 TIMER
LM358
LM339
RELAYS
BC547
LIQUID CRYSTAL DISPLAY
LED
IN4007
RESISTORS
CAPACITORS
555 TIMER
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.
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.
Working of project
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