IEEE Transactions on Power Delivery, Vol. 12, No. 4,October 1997
1848
Paper prepared by the FACTS Terms & Definitions Task Force
of the DC and FACTS Subcommittee
A-A. Edris, Chair
Task Force Members:
Adapa, M. H. Baker, L. Bohmann K. Clark, K.
J. Lemay, A. S . Mehraban, A. K. yers, J. Reeve, F. Sener,
.
Abstract - FACTS is an acronym which
stands for Flexible AC Transmission System.
FACTS is an evolving technology-based
solution envisioned to help the utility
industry to deal with changes in the power
delivery business. This paper presents results
of Task Force 3 of the IEEE’s FACTS Working
Group of the DC and FACTS Subcommittee
which had the assignment to establish
appropriate definitions of FACTS-related
terminology. These definitions will be
included in the IEEE Dictionary.
Keywords- Terms, Definitions, Power
Transmission, Stability, Flexibility,
Alternating Current System
of the Institute of Electrical and Electronic
Engineers (IEEE) to embrace development
and application of new concepts in the
transmission and distribution arena, the
and FACTS Subcommittee has created a
Working Group for FACTS with Task Forces
to work on FACTS Applications and FACTS
Standard Terms & Definitions.
The Membership of the Task Force (TF) for
FACTS Standard Terms & Definitions
represented
a
cross
section
of,
manufacturers, electric utility industries and
university researchers. The TF members
together with a constant dialogue with
CIGRE Working Groups have provided z
balanced input for the development of the
definitions which are presented in this paper.
Since the introduction of the Flexible AC This paper is intended to provide the
Transmission System (FACTS) concept i n developed definitions of the FACTS standard
1990 [l], [2], [3], the technology has been terms. These definitions are proposed to be
moving ahead at an increasing pace. Very included in the
EE Dictionary.
The
significant long-term benefits of FACTS proposed Terms & Definitions were
technology are now recognized on a developed with the following objectives:
worldwide basis since FACTS, along with
advanced control center technology and 0 To fit into the historically established and
commonly used terms identifying related
overall automation, represent a new era for
concepts and functions.
transmission systems. Since it is within the
scope of the Power Engineering Society (PES) 0 To develop a consistent set of terms,
compatible with existing IEEE and CIG
[13], [14] definitions and non-conflicting
PE-681-PWRD-0-11-1996 A paper recommended and approved
by the IEEE Transmission and Distribution Committee of the IEEE
with technical language used in the USA,
Power Engineering Society for publication in the IEEE Transactions
Europe or elsewhere.
on Power Delivery. Manuscript submitted January 12, 1996; made
available for printing November 25, 1996.
0
To exclude adjectives reflecting temporary
values and ambiguous meanings.
0885-8977/97/$10.00 0 1997 IEEE
1849
2. FACTS TERMS AND DEFINITIONS
The definitions presented in the following
are divided into basic definitions and
definitions of Controllers that serve specific
function(s). The given categorization is the
result
of
extensive
discussions and
compromises.
2.1 Basic Definitions
Flexibility of Electric Power Transmission
The ability to accommodate changes in the
electric transmission system or operating
conditions while maintaining sufficient
steady state and transient margins.
Flexible AC Transmission System
(FACTS)
Alternating current transmission systems
incorporating power electronic-based and
other
static controllers
to
enhance
controllability and increase power transfer
capability.
FACTS Controller
A power electronic-based system and other
static equipment that provide control of one
or more AC transmission system parameters.
2.2 FACTS Controllers Definitions
The definitions presented in the following
are organized according to their respective
connection to the controlled ac transmission
system.
2.2.1 Shunt Connected Controllers
Battery Energy Storage System (BESS)
A chemical-based energy storage system
using shunt connected, voltage sourced
converters capable of rapidly adjusting the
amount of energy which is supplied to or
absorbed from an ac system.
Static Synchronous Compensator (SSC or
STATCOM)
A static synchronous generator operated as a
shunt-connected static v ar compensator
whose capacitive or inductive output current
can be controlled independent of the ac
system voltage.
Static Condenser (STATCON)
This term is deprecated in favor of the Static
Synchronous
Compensator
(SSC
or
STATCOM).
Static Synchronous Generator (SSG)
A static, self-commutated switching power
converter supplied from an appropriate
electric energy source and operated to
produce a set of adjustable multi-phase
output voltages, which may be coupled to an
ac power system for the purpose of
exchanging independently controllable real
and reactive power.
0
Static Var Compensator (SVC)
A shunt-connected static var generator or
absorber whose output is adjusted to
exchange capacitive or inductive current so
as to maintain or control specific parameters
of the electrical power system (typically bus
voltage).
Static Var Generator or Absorber (SVG)
A static electrical device, equipment, or
system that is capable of drawing controlled
capacitive and/or inductive current from an
electrical power system and thereby
generating or absorbing reactive power.
Generally considered to consist of shuntconnected, thyristor-controlled reactor(s)
and/or thyristor-switched capacitors.
Static Var System (SVS)
A combination of different static and
mechanically-switched var compensators
whose outputs are coordinated.
Superconducting Magnetic Energy
Storage (SMES)
A Superconducting electromagnetic energy
storage
device
containing
electronic
0
1850
converters that rapidly injects and/or absorbs include transiently rated energy storage or
real and/or reactive power or dynamically energy absorbing devices to enhance the
dynamic behavior of the power system by
controls power flow in an ac system.
additional
temporary
real
power
Thyristor Controlled Braking Resistor
compensation, to increase or decrease
(TCBR)
momentarily, the overall real (resistive)
A
shunt-connected,
thyristor-switched voltage drop across the line.
resistor, which is controlled to aid
stabilization of a power system or to 0 Thyristor controlled Series Capacitor
minimize power acceleration of a generating
(TCSC)
unit during a disturbance.
A capacitive reactance compensator which
consists of a series capacitor bank shunted by
thyristor controlled reactor in order to
Thyristor Controlled Reactor (TCR)
A shunt-connected,
thyristor-controlled provide a smoothly variable series capacitive
inductor whose effective reactance is varied reactance.
in a continuous manner by partialThyristor Controlled Series
conduction control of the thyristor valve.
Compensation
An
impedance compensator which is applied
Thyristor Switched Capacitor (TSC)
A
shunt-connected,
thyristor-switched in series on an ac transmission system to
capacitor whose effective reactance is varied provide smooth control of series reactance.
in a stepwise manner by full- or zeroconduction operation of the thyristor valve.
Thyristor Switched Reactor (TSR)
A
shunt-connected,
thyristor-switched
inductor whose effective reactance is varied
in a stepwise manner by full- or zeroconduction operation of the thyristor valve.
Var Compensating System (VCS)
A combination of different static and rotating
var compensators whose outputs are
coordinated.
0
2.2.2 Series Connected Controllers
Static Synchronous Series Compensator
(SSSC or S ~ C )
A static, synchronous generator operated
without an external electric energy source
as a series compensator whose output
voltage is in quadrature with, and
controllable
independently of, the line
current for the purpose of increasing or
decreasing the overall reactive voltage drop
across the line and thereby controlling the
transmitted electric power . The S3C may
Thyristor Controlled Series Reactor
(TCSR)
An inductive reactance compensator which
consists of a series reactor shunted by a
thyristor controlled reactor in order to
provide a smoothly variable series inductive
reactance.
Thyristor Switched Series Capacit
(TSSC)
A capacitive reactance compensator which
consists of a series capacitor bank shunted by
a thyristor switched reactor to provide a stepwise control of series capacitive reactance.
Thyristor Switched Series Com
An impedance compensator which is applied
in series on an ac transmission system to
provide a step-wise control of
series
reactance.
0
Thyristor Switched Series Reactor (TS
An inductive reactance compensator which
consists of series reactor shunted by thyristor
1851
switched reactor in order to provide a step- 2.2.4 Other Controllers
Thyristor Controlled Voltage Limiter
wise control of series inductive reactance.
(TCVL)
A
thyristor-switched metal-oxide varistor
2.2.3 Combined Shunt and Series
(MOV) used to limit the voltage across its
Connected Controllers
terminals
during transient conditions.
Interphase Power Controller (IPC)
A series-connected controller of active and
reactive power consisting ,in each phase ,of
3. PRESENT APE’LICATION STATUS OF
inductive and capacitive branches subjected
FACTS CONTROLLERS
to separately phase-shifted voltages. The
active and reactive power can be set FACTS Controllers are currently in various
independently by adjusting the phase shifts stages of maturity. Some, such as SVCs,
and/or the branch impedances, using STATCOM and TCSCs, are commercially
Others are either in the
mechanical or electronic switches. In the available.
particular case where the inductive and development or demonstration stages.
capacitive impedances form a conjugate pair, 3.1 Commercially Available
each terminal of the IPC is a passive current
FACTS Controllers
source dependent on the voltage at the other
The
FACTS Controllers
for which
terminal.
commercial or demonstration projects exist
Thyristor Controlled Phase Shifting
include:
Transformer (TCPST)
Static Var Compensator (SVC)
A phase-shifting transformer, adjusted by
thyristor switches to provide a rapidly SVCs have been in use since the early 1960s.
variable phase angle.
The SVC application for transmission
voltage control began in the late 1970s. Since
Unified Power Flow Controller (UPFC)
that time, many SVCs have been applied
A combination of a static synchronous worldwide for voltage control and, in some
compensator (STATCOM) and a static cases for stability enhancement.
synchronous series compensator (S3C) which
Thyristor SwitchedKontrolled Series
are coupled via a common dc link, to allow
Capacitor (TSSCECSC)
bi-directional flow of real power between the
series output terminals of the S3C and the Since 1991 there have been three
shunt output terminals of the STATCOM, installations, in the United States of America
and are controlled to provide concurrent real (USA), using thyristor switches to obtain a
and reactive series line compensation controllable series capacitive compensation.
without an external electric energy source.
The UPFC, by
means of angularly The first installation [4] was essentially
unconstrained series voltage injection, is experimental in nature, testing the hardware
able to control, concurrently or selectively, of thyristor switched series capacitor (TSSC).
the transmission line voltage, impedance, A thyristor valve was applied across one
and angle or, alternatively, the real and phase of a capacitor module on a series
reactive power flow in the line. The UPFC capacitive compensated 345 kV transmission
may also provide independently controllable line Kanawa River - Matt Funk line at
Kanawa River Substation in West Virginia.
shunt reactive compensation.
The second installation [5] was a thyristor
controlled series capacitor (TCSC). It consists
1852
of a fixed capacitor shunted by a thyristor provide phase shifting and/or series
controlled reactor, providing continuously compensation. Both the STATCOM and
controlled series capacitive compensation. It series subsystem will consist of a 160 MVA
was installed in a 300 km, 230 kV voltage sourced, multi-pulse, harmonic
transmission line at the Kayenta Substation neutralized GTO inverter and magnetic
in Arizona. The functions of this installation interface. The UPFC will be installed on 138
are to increase power transfers to the line’s kV transmission line at Inez substation i n
thermal limit and evaluate the TCSC ability Kentucky. The installation is planned to be
to control power flow, line impedance, completed by the end of 1997.
damp electromechanical power oscillations,
and mitigate Subsynchronous Resonance 3.3 Future FACTS Contro
(SSR).
FACTS Controllers which are expected to be
available in the foreseeable future include:
The third installation, at the Slatt substation
in Oregon, is also a TCSC [6]. The Slatt TCSC 0 Thyristor Controlled Phase Shifting
Transformers (TCPST) [lo]
is comprised of six identical thyristorcontrolled capacitor modules connected i n 0 Static Synchronous Series Compensator
series.
(SSSC or ~3 C) ~111
e Interphase Power Controller (IPC) [12]
0
Static Synchronous Com
4. CONCLUSIONS
This paper presents proposed Terms &
Definitions of FACTS. The proposed
definitions were developed with the
following objectives:
To fit into the historically established and
commonly
used terms identifying related
In operation the 100 Mvar STATCOM will
concepts and functions.
provide voltage control to the 161 kV bus
voltage during daily buildup to minimize 0 To develop a consistent set of terms,
compatible with existing IEEE and CIGRE
the activation of the on load tap changer of
definitions and non-conflicting with
the 500 kV / 161 kV transformer.
Furthermore, the STATCOM will provide
technical language used in the USA,
adequate voltage support to the 161 kV and
Europe or elsewhere.
500 kV buses during light and peak load 0 To exclude adjectives reflecting temporary
conditions.
values and ambiguous meanings.
These definitions will be included in the
3.2 FACTS Controllers Currently Under
IEEE Dictionary.
Development
0
Unified Power Flow Controller (UPFC) [8] The paper has also presented the present
status of FACTS Controllers, commercially
The first large-scale UPFC will consist of a available, currently under development, and
shunt voltage sourced inverter (STATCOM) those to be developed in the future.
rated at 2 160 MVA to provide 2 150 Mvar
5.
CES
reactive power support and 50 MW real
power through the DC link required in full
1. N. G. Hingorani, “High Power Electronics
UPFC mode of operation. The series voltage
and Flexible AC Transmission System”, Joint
sourced inverter is rated
160 MVA to
The most recent STATCOM installation is a
+ 100 Mvar STATCOM [7l which is installed
in November 1995 at Sullivan (500 kV / 161
kV) substation in Johnson City, Tennessee.
In 1991 an
80 Mvar was installed at the
Inuyama Switching Station in Japan [9].
1853
APC/IEEE Luncheon Speech, April 1988 at
the American Power Conference 50th
Annual Meeting in Chicago, Printed I€€€
Power Engineering, July 1988.
2. N. G. Hingorani, "Power Electronics i n
Electric Utilities: Role of Power Electronics i n
Future Power Systems", Invited Paper,
Proceedings of the IEEE Special Issue, Vol. 76,
No. 4, April 1988.
3. L. Gyugyi, "Dynamic Compensation of AC
Transmission
Lines
by
solid-state
Synchronous
Voltage
Sources," IEEE
Transactions on Power Delivery, Vol. 9, No.
2, pp. 904-911, April 1994.
4. A.J. F. Kari, R.A. Byron, B. J. War, A.S.
Mehhraban, M, Chamia, P. Halvarsson, L.
Angquist, "Improving Transmission System
Performance
Using Controlled
Series
Capacitors, CIGRE Paper 14/37/3&07, Paris,
France, 1992.
5. N. Christl, R. Hedin, P.E. Kraucs, P.
Luetzelberger, S.M. McKenna,
A.H.
Montoya, K. Sadek, D. R. Torgerson,
"Advanced Series Compensation (ASC) with
Thyristor Controlled Impedance," CIGRE
Paper 14/37/38-07, Paris, France, 1992.
6. J. Urbanek, R.J. Piwko, E.V. Larsen, B.L.
Damsky, B.C. Furumasu, W. Mittlelstadt, J.D.
Eden,
Thyristor Controlled Series
Compensation- Prototype Installation at Slatt
500 kV Substation," I€€€ Transactions o n
Power Delivery, pp. 1460-1469, July 1993.
7. C.D. Schauder, M. Gernhardt, E. Stacy,
T.W. Cease, A. Edris, "Development of 100
Mvar Static Condenser for Voltage Control of
Transmission Systems," I€€€ Transact ions
on Power Delivery, Vol. 10, No. 3, pp. 14681496, July 1995.
8. L. Gyugyi, C.D. Schauder, S.L. Williams,
T.R. Reitman, D.R. Torgerson, A. Edris, "The
Unified Power Flow Controller: A New
Approach to Power Transmission Control,"
I€€E Transactions on Power delivery, Vol.
10, No .2, pp. 1085-1097, April 1995
9. S. Mori, K. Matsuno, M. Takeda, and M.
Seto," Development of Large Static Var
Generator Using Self-Commutated Inverters
for Improving Power System Stability," Paper
NO. 92 WM 165-1 PWRS, I€€E/PES 2992
Winter Meeting, New York, New York,
January 26-30,1992.
10. S. Nyatti, M.E. Eitzmann, J. Kappenman,
D. Van House, N. Mohan, A. Edris, Design
Issues for a Single-Core Transformer
Thyristor
Controlled
Phase
Angle
Regulator," I€€€ Transactions on Power
Delivery, Vol. 10, No. 4, pp. 2013-2019,
October 1995.
11. L. Gyugyi, C.D. Schauder, K. K. Sen,"
Static Synchronous Series Compensator: A
Solid-state Approach to the
Series
Compensation of Transmission Lines," Paper
to be presented at IEEE/PES Winter Power
Meeting, Baltimore, MD, January '8996
12. J. Brochu, P. Pelletier, Beauregard, G.
Morin,
"Interphase Power Controller
Adapted to the Operating Conditions of
Networks ,I1 I€€€ Transactions on Power
Delivery, Vol. 10, No. 2, pp. 961-969, April
1995.
13. Static Var Compensators, CIGRE Working
Group 38-01, Task Force No. 2 on SVC, Cigre,
Paris, 1986, Edited by I. A. Erinmez
14. "FACTS Overview", published by CIGRE
and IEEE PES, 1995, Reference IEEE 95 TP 108.