04-04-2011, 03:36 PM
Presented by:
R.Padamaja
G.Mamatha Reddy
A DSP based on on-line UPS sc.ppt (Size: 315.5 KB / Downloads: 194)
INTRODUCTION:
Un-interruptible power supplies (UPS) play an important role in interfacing critical loads such as computers, tele-communicationlinks, data-processing systems, life supporting systems and industrial controls,e.t.c.
Among the various UPS topologies, on –line UPSs provides maximum protection to such loads against any utility power problem, as it protects against power blackout.
Because of multiple power conversion stages, online UPSs have been the most complex and expensive type of systems.
Today’s low cost, high performance Digital Signal Processors (DSPs) provide an improved and cost- effective solution for online UPS design.
Online UPS design, making them software controllable, adding some facilities like remote configuration and monitoring and other network management facilities.
Typical On-Line UPS:
A typical UPS consists of a rectifier supplied battery bank & a static inverter-filter system to convert a dc voltage to a sinusoidal an output Modern UPS systems minimize the harmonic content of the inverter output voltage through the use of complex filtering schemes employing large passive components.
Need for Pulse Width Modulation:
Online UPSs have been the most complex and expensive type of systems voltage.
Pulses are generated whenever a carrier signal & modulating signal crosses eachother.
These pulses are given to thyristors and pulsating output is generated.
Depending on the number of output pulses generated, switching frequency of inverter is determined
General PWM techniques for UPS:
1. Using Analog devices:
Analog PWM uses natural sampling technique, which compares a sinusoidal modulating wave form with a triangular wave
2. Using Microprocessors:
A digital PWM signal generator is interfaced with a microprocessor. It calculates the pulse width at every sampling instant. According to this calculated width, the pulse generator generates the pulses with a constant switching frequency.