02-02-2013, 11:07 AM
A NEW CONFIGURATION FOR UNINTERRUPTED POWER IN ISOLATED
LOCATIONS: WIND TURBINE – ELECTRIC GENERATOR – BATTERY BANK
(WT-UPS)
1A NEW CONFIGURATION.pdf (Size: 301.41 KB / Downloads: 63)
ABSTRACT
A new configuration is presented to investigate the use of
renewable energy sources, such as wind energy, an
auxiliary thermo-electric generator and a battery bank, to
feed critical loads in isolated locations in less developed
areas, where no electric supply is available. Where
possible standard off-the-shelf car parts such as
alternators and AVR are used. This configuration, called
Wind Turbine Uninterruptible Power Supply (WT-UPS) is
a modular system that offers a number of advantages over
the classic hybrid systems. Initial experimental results
show the system works as predicted.
INTRODUCTION
Uninterruptible power supply systems combine different
independent energy sources to ensure continued operation
of critical loads. In the system presented in this work, a
Wind Turbine Uninterruptible Power Supply (WT-UPS),
two primary energy sources, one renewable (a wind
turbine driven electric generator) and one traditional (an
internal combustion driven electric generator) are used, in
combination with a temporary storage system (a battery
bank), to provide AC electric power to a critical load
SYSTEM DESCRIPTION
Figure 1 shows a complete block diagram of the proposed
WT-UPS system. The main building blocks are the wind
generator, the solid state power conversion block, the
battery bank, the auxiliary electric generator and the
regulation and control circuits controlling the operation of
the various energy sources as an uninterrupted AC
power supply.
In normal operation the wind drives the WT-UPS main
generator, which is a car alternator. The main generator
output is connected to an uncontrolled three-phase
rectifier and an LC filter, providing a low-ripple dc
output. The alternator AVR (automatic voltage
regulator) ensures that the dc level is constant when the
wind turbine is operational.
The filtered dc output is fed to a DC/DC converter with
a 79 V dc output level. This stage is included in order to
optimize both the battery bank and the output inverter
design. It also gives a degree of flexibility to the overall
design, since it allows for the use of alternators of
different output voltages.
INITIAL EXPERIMENTAL SET-UP
SIMPLIFICATION
For laboratory testing purposes, the wind turbine
generator is replaced by an inverter-fed AC motor
driving a synchronous AC motor. This set is controlled
to emulate car alternators of up to 42V output driven by
different wind patterns [5]-[9]. Also, to avoid
unnecessary noise and exhaust management problems in
the electronics laboratory, the AC internal combustion
motor-generator set has being replaced with a AC source
derived from the main supply. These changes do not
reduce the validity of the experimental set-up for testing
the different electronic blocks, but greatly reduce overall
testing cost and mechanical complexity.
RESULTS
Figure 4 shows WT-UPS output connected to an
inductive load. Both current and voltage waveforms are
sinusoidal, and their quality is confirmed by the spectral
analysis presented in figure 5.
CONCLUSIONS
The preliminary results obtained with the experimental
set up using the complete electronic circuitry (power
electronic converters and control electronics) prove that
the overall concept is correct, that each of the electronic
component blocks work as required and that the modular
design strategy using different and complementary
energy sources, both renewable and traditional, achieve
the design aims. The design can be easily adjusted to the
use of 12, 24 and 42 V car alternators according to
whatever the local supply offers. The use of off-the shell
automotive parts widely available in less developed
countries in the construction of relatively sophisticated
uninterrupted power supplies for critical loads operating
in isolated locations is particularly important since it
reduces technological dependence and offers equipment
that can be locally produced and maintained.