01-03-2013, 03:42 PM
Power Quality Improvement with Static Compensator on Grid Integration of Wind Energy System
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Abstract
The generated power from renewable energy
source is always fluctuating due to environmental
conditions. In the same way, wind power injection into
an electric grid affects the power quality due to the
fluctuation nature of the wind and the comparatively
new types of its generators. On the basis of
measurements and norms followed according to the
guidelines specified in IEC-61400 (International
Electro-technical Commission) standard, the
performance of the wind turbine and thereby power
quality are determined. The power arising out of the
wind turbine when connected to a grid system
concerning the power quality measurements, are:
active power, reactive power, voltage sag, voltage swell,
flicker, harmonics, and electrical behavior of switching
operation. These are measured according to
national/international guidelines.
INTRODUCTION
O have sustainable growth and social progress, it
is necessary to meet the energy need by utilizing
the renewable energy resources like wind, biomass,
hydro, co-generation, etc. In sustainable energy
system, energy conservation and the use of
renewable source are the key paradigm. The need tointegrate the renewable energy like wind energy into
power system is to make it possible to minimize the
environmental impact on conventional plant [1].
The integration of wind energy into existing power
system presents technical challenges and that
requires consideration of voltage regulation,
stability, power quality problems. The power quality
is an essential customer-focused measure and is
greatly affected by the operation of a distribution and
transmission network. The issue of power quality is
of great importance to the wind turbine [2]. There
has been an extensive growth and quick development
in the exploitation of wind energy in recent years.
GRID COORDINATION RULE
The American Wind Energy Association (AWEA)
led the effort in the United States for adoption of the
grid code for the interconnection of the wind plants
to the utility system. The first grid code was focused
on the distribution level, after the blackout in the
United State in August 2003. The United State wind
energy industry took a stand in developing its own
grid code for contributing to a stable grid operation.
The rules for realization of grid operation of wind
generating system at the distribution network are
defined as-per IEC- 61400-21. The grid quality
characteristics and limits are given for references
that the customer and the utility grid may expect.
GRID CODE REQUIREMENTS FOR GRID
CONNECTION
The voltage regulation in power systems is
directly related to the control of reactive power. The
recent grid codes require that the wind farms should
provide reactive power control capabilities in
response to the power system voltage in a manner
similar to conventional power plants. The reactive
power control requirements are related to the
characteristics of each network. Reactive power
control is an important issue for wind farms, because
not all wind turbine technologies have the same
capabilities, whereas wind farms are often installed
in remote areas and therefore reactive power has to
be transported over long distances resulting in power
losses. The nominal voltages are 380, 220, 110 kV
for onshore wind farms and 155 kV for offshore
wind farms in Germany and 400, 275 kV for Great
Britain. The British code refers to wind farms with
rated power above 50 MW.
STATIC COMPENSATOR (STATCOM)
The STATCOM is a shunt-connected reactive
power compensation device that is capable of
generating and/or absorbing reactive power and in
which the output can be varied to control the specific
parameters of an electric power system. It is in
general a solid-state switching converter capable of
generating or absorbing independently controllable
real and reactive power at its output terminals when
it is fed from an energy source or energy-storage
device at its input terminals. A STATCOM is a
controlled reactive power source. It provides the
desired reactive power generation and absorption
entirely by means of electronic processing of the
voltage and current waveforms in a voltage source
converter (VSC).
CONCLUSION
In this paper we present the FACTS device
(STATCOM) -based control scheme for power
quality improvement in grid connected wind
generating system. Flexible AC Transmission
System (FACTS) device such as Static Compensator
―STATCOM‖ is power electronic based switch is
used to control the reactive power and therefore bus
voltages. Results are presented to show that the
voltage at bus 25 drops to very low value of .91 pu
due to insufficient reactive power but this bus voltage
gets improved to 0.98when STATCOM is
incorporated in the system. Thus the voltage and
hence Power Quality Improvement With Static
Compensator on Grid Integration of Wind Energy
System is improved.