Download Abstract - PG Embedded systems

Dynamic voltage restorer
Abstract
Voltage deviations, often in the form of voltage sags, can cause severe process disruptions and
result in substantial economic loss. The Dynamic Voltage Restorer (DVR) has been proposed to protect
sensitive loads from the effects of voltage sags on the distribution feeder. The compensation capability of a
DVR depends primarily on the maximum voltage injection ability and the amount of stored energy
available within the restorer. In this paper a new phase advance compensation (PAC) strategy for the DVR
is proposed in order to enhance the voltage restoration property of the device. The scheme requires only an
optimum amount of energy injection from the DVR to correct a given voltage sag. Using the proposed
method it can be shown that a particular disturbance can be corrected with less amount of storage energy
compared to that of existing in-phase boosting method. In the end a closed-loop controller that consists of
an inner current loop and an outer voltage loop is also incorporated into the DVR system.
BLOCK DIAGRAM:
BOOSTER
TRANSFORMAR
SENDING END
ZERO CROSSING
DETECTOR
FILTER
OPTOCOUPLER
MICROCONTROLLER
RECEIVING END
OPTOCOUPLER
An optical coupler or optocoupler is a passive device for branching or coupling an optical signal. An optocoupler is a
combination of a light source and a photosensitive detector. In the optocoupler, or photon coupled pair, the coupling is
achieved by light being generated on one side of a transparent insulating gap and being detected on the other side of the
gap without an electrical connection between the two sides (except for a minor amount of coupling capacitance).
FILTER
Another practical application of filter circuits is in the “conditioning” of non-sinusoidal voltage waveforms in power circuits.
Some electronic devices are sensitive to the presence of harmonics in the power supply voltage, and so require power
conditioning for proper operation. If a distorted sine-wave voltage behaves like a series of harmonic waveforms added to
the fundamental frequency, then it should be possible to construct a filter circuit that only allows the fundamental
waveform frequency to pass through, blocking all (higher-frequency) harmonics.
Zero-crossing detector is an applied form of comparator. Either of the op-amp basic comparator circuits
discussed can be employed as the zero-crossing detector provided the reference voltage Vref is made zero. Zerocrossing detector using inverting op-amp comparator is depicted in figure. The output voltage waveform shown in
figure indicates when and in what direction an input signal vin crosses zero volt. In some applications the input
signal may be low frequency one (i.e. input may be a slowly changing waveform). In such a case output voltage
vOUT may not switch quickly from one saturation state to the other. Because of the noise at the input terminals of the
op-amp, there may be fluctuation in output voltage between two saturation states (+ Vsat and – Vsat voltages). Thus
zero crossings may be detected for noise voltages as well as input signal vin. Both of these problems can be
overcome, if we use regenerative or positive feeding causing the output voltage vout to change faster and eliminating
the false output transitions that may be caused due to noise at the input of the op-amp.
Booster Transformer
Normally used in public address systems, where the audio have to travel long distances and have to drive more than
one speaker then a booster transformer is inserted in the audio line, also called audio transformer
PIC 16F877A MICROCONTROLLER:
High Performance RISC CPU:
• Only 35 single word instructions to learn
• All single cycle instructions except for program branches, which are two-cycle
• Operating speed: DC - 20 MHz clock input
DC - 200 ns instruction cycle
• 2K x 14 words of Program Memory, 128 x 8 bytes of Data Memory (RAM)
• Pin out compatible to PIC16C72/72A and PIC16F872
• Interrupt capability
• Eight-level deep hardware stack
• Direct, Indirect and Relative Addressing modes
Peripheral Features:
• High Sink/Source Current: 25 mA
• Timer0: 8-bit timer/counter with 8-bit prescaler
• Timer1: 16-bit timer/counter with prescaler, can be incremented during SLEEP via external
• Timer2: 8-bit timer/counter with 8-bit period register, prescaler and postscaler
crystal/clock
• Capture, Compare, PWM (CCP) module
- Capture is 16-bit, max. resolution is 12.5 ns
- Compare is 16-bit, max. resolution is 200 ns
- PWM max. resolution is 10-bit
• 8-bit, 5-channel analog-to-digital converter
• Synchronous Serial Port (SSP) with SPI™ (Master/Slave) and I2C™ (Slave)
• Brown-out detection circuitry for Brown-out Reset (BOR)
CMOS Technology:
• Low power, high speed CMOS FLASH technology
• Fully static design
• Wide operating voltage range: 2.0V to 5.5V
• Industrial temperature range
• Low power consumption:
- < 0.6 mA typical @ 3V, 4 MHz
- 20
-<1
PIN DIAGRAM