Advanced SVC models for newton-raphson load flow and ... - ITCJ

116 IEEE TRANSACTIONS ON POWER SYSTEMS, VOL 15. NO. I. PEBRUARY 2000
by the variable susceptance representation. As expected, both
representations have a minimum impact on network losses, but
at the point of SVC connection differences can be observed in
the voltage profile and in the reactive power contributed by both
models.
As discussed in Section 111, the compound generator-constunt
susceptance representation provides an accurate load flow
represetitation of SVC's for the complete range of operation.
However, inefficiencies may be observed owing to the need to
reorder and to redimension the linearized systems of equations.
In the OPF formulation, further complications may arise with
this compound representation. The multiplier method, which
has shown to be very effective in enforcing variables outside
limits, may have difficulties in checking whether or not a SVC
is operating within limits when represented as a constant susceptancc.
VIII. CONCLUSIONS
Comprehensive SVC models suitable for conventional
and optimal power flow analysis have been presented in
this paper, namely SVC total suscepiance model and SVC
firing angle model. In contrast to SVC models reported in
the open literature, the proposed models do not make use
of the generafor concept normally employed for the SVC
representation. Instead, they use the variable shunt susceptance
concept. Arguably, this has the advantage of representing actual
SVC operation more realistically. Moreover, since SVC shunt
susceptance models only make use of one node to represent
SVC's operating inside and outside ranges then Newton based
power flow solutions become more efficient, compared to cases
when generafor based models of SVC's are used in Newton
algorithms. An SVC model which uses the thyristor firing angle
as the state variable has shown to provide fuller information
that existing SVC models. The firing angle required to achieve
a specified level of compensation becomes readily available
from the power flow solution, as well as the fundamental
frequency, internal SVC resonant points. A Newton-Raphson
load flow and a Newton's OPF algorithms have been upgraded
to incorporate the new SVC models. A real-life, bulk transmission
system has been used as the test case. Conventional and
optimal solutions were obtained in less than 6 iterations.
ACKNOWLEDGMENT
H. Ambriz-PBrez would like to thank Comisi6n Federal de
Electricidad, MBxico for granting him study leave to carry out
Ph.D. studies at the University of Glasgow, Scotland, UK.
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It. Aeha was horn in Mexico. He graduated from University of Michoilcdn
in 1979 and rcceiverl the Ph.D. degrcc from the University of Canterbury,
Christchurch, New Zealand, in 1988, He was a postdoctoral Fellow at the
University of Toronto, Cantidti and the Univcrsity of Durham, England. He
is currently n Senior Lecturer ut the University 01 Glasgow, Scotland, wherc
hc lectures and conducts mseilrcli on power systems analysis i~nd power
electronics applications. His research interests arc in the aceus of FACTS,
custom power, and real-time modeling and iinalysis.
C. R. Focrte-Esqaivel was barii in Mexico in 1964. He received the B.Eng. degree
(Hans) from Institute Tecnol6gicn de March, Mexico in 1990, the MSc.
degree 1wm lnstiluto Politecnico Naciunal, Mexico in 1993, and thc Ph.D degree
from the University dGlasgaw, Scotland, UK, in lY97. He is currently :NI
Assistant Professor at thc Institute TecnolOgico de March His main research
interests lie oil the dynamic and steady-state analysis of FACTS, custom power,
and real-time modeling and analysis.