18-10-2012, 04:01 PM
FUEL CELL BASED BATTERY-LESS UPS SYSTEM
FUEL CELL BASED BATTERY-LESS UPS SYSTEM.pdf (Size: 1.79 MB / Downloads: 108)
Introduction
In the present day, every application ranging from those used at home and small
offices to hospitals, banks and huge call centers are dependent on electricity. Any power
disturbance such as power outage or voltage sag/swell can result in malfunctioning of
the equipment, loss in productivity and data and in the case of health care, loss of lives is
also possible. Hence, power quality and power continuity are important factors that need
to be ensured for critical applications. There exists an intrinsic relationship between the
load performance and the electric power quality. Power outages and other power
disturbances cannot be avoided but a system can be developed to ensure that the load
does not see these power disturbances.
Power quality disturbances
The study of the different power quality disturbances, their effects on the
equipment and the frequency of occurrence is important for arriving at the most
appropriate and optimized solution for these disturbances. The common power quality
disturbances faced are voltage surges, spikes and sags and harmonics (or noise) in the
power line. These disturbances have been explained below [2]:
1. Surges: Surge is a rapid short-term increase in voltage. Surges are often
caused when high power demand devices such as air conditioners turn off
and the extra voltage is dissipated through the power line. Since sensitive
electronic devices require a constant voltage, surges stress delicate
components and cause premature failure.
Possible solutions for power quality disturbances
The most common solutions for the above mentioned power quality disturbances
are surge suppressors, stabilizers and UPS (Uninterruptible Power Supply) systems.
A surge suppressor is an electronic device that limits the damaging effect of
power surges on electronic equipment from commercial power plants, generators, and
electrical storms. A surge protector passes the electrical current along from the outlet to
a number of electrical and electronic devices plugged in to the power strip. In case of
voltage surge or spike, the surge protector attempts to regulate the voltage either by
blocking or shorting to ground voltages above a safe threshold.
Overview of UPS systems
An UPS system basically has three components – rectifier, inverter and back up
power system. The backup energy system can be batteries, flywheel, engine generator,
fuel cells and/or supercapacitors.
Depending on the design approach and the performance characteristics, there are
four common types of UPS systems [3]-[5]: