03-05-2011, 03:20 PM
Study of Evaluated a STATCOM Application for Voltage Stability by Dynamic PV Curves and Time Simulations
Abstract:
In this paper; voltage stability is evaluated by both
dynamic PV curves and titne-domain simiilations. considering the
combined a'ynamic contsol effects of a static compensator
(Sl:4TCOA.I) and transfosnier on-load-taps (OLT). The studied
system is heavily loaded at hvo locations and an 80 Mvar
SPITCOM is connected to impsore the voltage stability of entire
system for a contingency of a three-tesminal line outage. The
results presented in this paper: (a) show that a STATCOM can
gseatly improve the voltage stability of a heavily loaded system,
(b) qirantrJL the combined impacts of STATCOM and OLT
control: © illiistsate that the masgin of stability can be easily
urd effectively evaluated by PV ciiives: (d) corselate timedomain
simiilations and P V curves for a system with a STATCOM
and OLT dynamic control.
Keywords: FACTS, STATCOM. Voltage Stability, PV Curve,
Stability Margin, Voltage" Control
I . INTRODUCTION
With the ongoing deregulation of the electric utility industry.
numerous changes are continuously being introduced to a once
predictable business. With electricity increasingly being
considered as a commodity, transmission systems are being
pushed closer to their stability and thermal limits while the focus
on the quality of power delivered is greater than ever. In
addition, dynamic reactive power support is becoming more
important. especially in urban areas where local (i.e.. at the load)
generation is being reduced or eliminated. In the deregulated
utility environment, financial and market forces will demand a
more optimal and profitable operation of the power system with
respect to generation, transmission, and distribution. Now, more
than ever, advanced technologies are paramount for the reliable
and secure operation of power systems. Power electronic based
equipment. such as FACTS controllers, with their capability to
rapidly respond to system events, increase power transfer limits,
and improve the quality of power delivered. constitute one of the
most-promising technical advancements to address the new
operating challenges being presented today [ I , 2. 121.
This paper ~OGUSGSo n one such FACTS controller for voltage
support as a dynamic reactive power (var) source, namely the
static compensator (STATCOM). Typically. the first step in
0-7803-5935-6/00/$10.00 © 2000 IEEE
providing voltagehar support in a power system is with the
application of shunt capacitors, shunt reactors, and transformer
on-load-taps (OLT). Therefore. combined control of this
discrete-acting existing equipment with a continuously controlled
dynamic device, such as a STATCOM. becomes important for the
overall technical and economic operation of the system [ 111.
Typically. time-domain simulations are employed to analyze
the performance of power systems containing both conventional
equipment and FACTS controllers for voltagdvar support. This
approach, however, usually requires a large number of study
cases at different system operating conditions and contingencies
to evaluate the relationship between system and control
parameters and voltage stability.
The application of PV curves also provides a means to
evaluate the voltage stability of a power system for various
conditions and contingencies [3, 4, 51. Evaluations of voltage
stability for an AC/DC hybrid system and for a system with
FACTS controllers were reported in [6, 7. 81. However.
performance of conventional equipment for voltage regulation,
(e.g., shunt capacitors, shunt reactors. OLTs) has not always been
considered. Furthermore, combined control of conventional
equipment and FACTS controllers should be considered for
various operation conditions from light load to heavy load, not
just around peak point of PV C U N ~ .
In this paper, power system performance is evaluated
considering both OLT and STATCOM applications for
voltagelvar support. Both PV curves and time-domain
simulations are camed out and compared to verify the agreement
between two study methods. In addition. an index value. namely
"Margin of Stability.'' is applied. It is shown that this index value
is an effective means in which to evaluate the impacts of the
system and control parameters on voltage stability.
2. MODELING AND TEST SYSTEM FOR ANALYSIS
2.1 Modeling of the STATCOM
Figure 1 shows a stability model for a STATCOM. For the
simulations contained in this paper, the STATCOM is applied for
voltage regulation with a slope reactance (i.e.. droop) of 3%. The
time constant of the STATCOM control is 50 milliseconds. Thc
STATCOM is modeled as a current source, based on its inherent
characteristics
DOWNLOAD FULL REPORT
http://meppiService/PSES/Documents/Statcom%20Voltage%20Stability.pdf
