FACTS Flexible AC Transmission System.ppt

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TECHNICAL PRESENTATION
FLEXIBLE AC TRANSMISSION SYSTEMS
SUDHA M R
Assistant Engineer
220kV S/S,SHORNUR

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FLEXIBLE AC TRANSMISSION SYSTEM
 FACTS is a static equipment used for
the AC transmission of electrical energy.
 It is meant to enhance controllability
and increase power transfer capability.
It is generally a power electronics-
based device.

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 The operation of the AC power transmission
network is generally constrained by limitations
even though plant in other parallel transmission
lines may have adequate capacity to carry
additional amounts of power.
 This is a consequence of free flow mode of
operation of AC power transmission network.
Introduction

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This free flow mode of transmission network operation
can be contrasted with a vision of controlled power flow
mode of operation,
where the power flow through one or more transmission
lines is controlled in a predetermined manner.
This vision can be achieved and the natural behavior of
the network modified through the application of power
flow devices at strategic locations. The use of such
devices could reduce the need for additional network
facilities by improving the utilization and performance of
the existing facilities.
Introduction

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 The philosophy of FACTS is to use power
electronics controlled device to controlled devices
to control power flows in transmission network ,
there by allowing the transmission line to be
loaded to its full capacity.
FACTS

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FACTS devices are based on the solid state control
are capable of control actions at far higher speed.
 The three parameters that control the transmission
line power flow are line impedance and magnitude
and phase of receiving end voltages.
Conventional control of these parameters, although
adequate during steady state and slowly changing
load conditions, cannot be achieved quickly enough
to handle dynamic system conditions. The use of
FACTS technology will change this situation.

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S T R
POWER FLOW CONTROL

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 If we consider the flow of power from bus S to bus R
 There is no way of individually setting the power flow
through each circuit , either directly from S to R , or
via T.
 The load sharing is entirely governed by the line
impedances ,which is inflexible.
 If the impedances are dissimilar, one circuit may
never realize its full thermal capacity when operating
with the other circuit.

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One possible way of controlling the load sharing between
the circuits is by use of HVDC schemes as shown in fig.
HVDC link
S T R
HVDC LINK CONTROLING PARREL POWER FLOWS

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 The power flowing through along the HVDC
path can be electronically controlled by
adjusting the converter firing angle. It is thus
possible to load each circuit separately.
 The use HVDC schemes is unlikely to be an
economic solution to the problem of improving
the circuit utilization since it requires the
installation of costly converter equipment on
one circuit and rebuilding of the overhead lines
or cables.

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 Use of FACTS technology is a more attractive
option since FACTS devices can be fitted
retrospectively to existing AC transmission
routes thus providing an economic solution.
 FACTS device is fitted in the circuit and provides
control over system electrical parameters

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S T R
POWER FLOW CONTROL USING FACTS
FACTS
device

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 FACTS control of AC transmission is effective not only
during steady state conditions ,but also during system
transient conditions , such as caused by unexpected
line outages, where it may be important for the
stability of the system to control the power flow
through a critical circuit in the power system
 Additionally, the use of FACTS devices for controlling
power flows in networks independent of transmission
plant impedances has other benefits, such as contract
path procedure .

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With FACTS , power can be routed over
the path or prevented from flowing along
undesirable alternative paths.

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Line reactance X
S R
δ
Vs
V r
P= Vs Vr Sin δ
X
STABILITY CONSTRAINT OVER MAXIMUM TRANSMISSION LINE LOADING

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 The main factor limiting the steady state power flow
is the question of stability .
 This often has the effect of constraining maximum
circuit loading to a level well below the maximum
thermal capacity.
 Thus most transmission lines are effectively under
utilized.
 This problem also occurs in most part of the world
and is a function of the topology of the power
system. It is especially prevalent in systems where
major generation and load centers are separated by
large distance.

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REACTIVE POWER CONSTRAIT OF MAXIMUM
TRANSMISSION LINE LOADING
Thus the line will absorb reactive power QL given by
QL = V2
SR
X
Where
VSR= equal to the difference between the receiving end voltages

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REACTIVE POWER CONSTRAIT OF MAXIMUM
 The line shunt
capacitance will generate
reactive power according
to the equation,
 QC = V2
S ωC/X

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REACTIVE POWER CONSTRAIN OF MAXIMUM
 This equation is load dependent.
Greater line loading leads to grater
reactive power absorption.
 The reactive power must be supplied
from the network.
 If the reactive power is not available
to offset the reactive power absorbed
by the line, then the line loading is
constrained.

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 Thus lightly loaded lines generate reactive
power.
 Under heavy loading conditions, the reactive
power absorbed by the line reactance will be
greater than the reactive power generated by
the shunt capacitance , the line will absorb
reactive power.
 Hence under changing loading conditions, there
is a changing requirement for reactive power.
 In general, where longer transmission distances
are involved some form of reactive
compensation is needed to ensure that the
reactive power balance is met and that the line
loading is not adversely constrained.

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 There are FACTS devices to provide
reactive compensation ,which allow the
line to behave as though it is always
naturally loaded.
 The use of reactive compensation by no
means new, however , the advantage that
FACTS provide is firstly that the
compensation can be infinitely varied as
opposed to merely switching reactors in
and out and secondly that the
compensation can be varied at high speed
thus giving the stability advantages.

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FACTS CONTROLLERS
 There are two different approaches to
realization of power electronics based FACTS
controllers.
 first group employs,
 STATIC VAR COMPENSATOR(SVC)
 THYRISTOR CONTROLLED SERIES CAPACITOR(TCC)
 THYRISTOR CONTROLLED PHASE SHIFTING
TRANSFORMER(TCPST)

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FACTS CONTROLLERS
 The second group use self commutated static
converters as controlled voltage sources.
 Second group includes,
 STATIC SYNCHRONOUS COMPENSATOR
 SERIES COMPENSATOR
 UNIFIED POWER FLOW CONTROLLER
 INTER LINE POWER FLOW CONTROLLER

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STATIC VAR COMPENSATOR(SVC)
 It is 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 electric system(typically bus voltage).
 Thyristor controlled or thyristor switched reactor for absorbing reactive
power and thyristor switched capacitor for supplying reactive power.
 This compensator is normally used to regulate the voltage of the
transmission system at a selected terminal.
 They are also employed for transient and dynamic stability improvement.
FACTS CONTROLLERS

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THYRISTOR CONTROLLED SERIES CAPACITOR (TCSC)
 It is a capacitive reactance compensator which consists of
a series capacitor bank shunted by a thyristor controlled
reactor in order to provide a smoothly variable capacitive
reactance.
The variable series capacitive compensation is useful in
steady state control of power flow, transient stability
improvement ,power oscillation damping and balancing
power flow in parallel lines.
FACTS CONTROLLERS

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FACTS CONTROLLERS
THYRISTOR CONTROLLED PHASE SHIFTING
TRANSFORMER (TCPST)
 The TCPST can be used to regulate the
transmission angle to maintain the balanced power
flow in multiple transmission paths or to control so
as to increase the transient and dynamic stability of
the power system.

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FACTS CONTROLLERS
STATIC SYNCHRONOUS COMPENSATOR (STATCOM)
 SATCOM is static synchronous generator operated as a
shunt connected static VAR compensator whose capacitive
or inductive output current can be controlled independent
of the system voltage.
 The ability of the STATCOM to produce the current at low
system voltage make it more effective than
 The ability of the STATCOM to generate and absorb
reactive power make it suitable for power oscillation
damping.

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FACTS CONTROLLERS
STATIC SYNCHRONOUS SERIESCOMPENSATOR
(SSSC)
 It is a static synchronous generator operated as
a series compensator
 output voltage is controllable independently of
the line current for the purpose of increasing or
decreasing the overall reactive voltage drop
across the line and there by controlling
transmitted electric power.

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FACTS CONTROLLERS
UNIFIED POWER FLOW CONTROLLER ( UPFC)
 Using a unified power flow controller all the three line
parameters, the voltage ,impedance and phase angle can
be controlled to influence the real and reactive power flow
in AC line.
 The control of voltage impedance and phase angle can be
carried out concurrently or selectively. It may also provide
independently controllable shunt reactive compensation.
 It is a complete controller for controlling active and
reactive power control through the line as well as line
voltage control.

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FACTS CONTROLLERS
INTERLINE POWER FLOW CONTROLLER ( IPFC )
 It is a recently introduced controller.
 IPFC is a combination of two or more static synchronous
series compensators which are which are coupled via a
common DC link to facilitate bidirectional flow of real
power between the AC terminals of the SSSC(static
synchronous series compensator)s and are controlled to
provide independent reactive compensation for the
adjustment of real power flow in each line and maintain
the desired distribution of reactive flow among the line.

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FACTS CONTROLLERS
 Using the advanced solid state technology, FACTS
controllers offer flexibility of the system operation
trough fast and reliable control.
 They enable better utilization of existing power
generation and transmission facilities without
compromising system availability and security.
 The system planner has to select a controller out of
the set of FACTS controllers for improving the
system operation based on cost benefit analysis.

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COST :
Due to the high capital cost of transmission plant , cost
consideration frequently outweigh all other considerations.
Compared to the alternative methods of transmission loading
problems FACTS technology is often the most economic
alternatives.
CONVENIENCE
All FACTS devices can be retrofitted to existing AC transmission
path with varying degrees of ease. Compared to HVDC and
six phase transmission system solutions can be provided without
wide scale system disruption within a reasonable time scale.
MAJOR BENEFITS OF FACTS

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MAJOR BENEFITS OF FACTS
ENVIRONMENTAL IMPACT :
 In order to provide new transmission path to supply an ever
increasing worldwide demand for increasing electric power, it is
necessary to acquire the right to convey electrical energy to a
given route.
 It is common for environmental opposition to frustrate attempt to
establish new transmission route.
 FACTS technology , however allows greater throughput over
existing route thus meeting consumer demand without the
construction of new transmission lines.
 However , the environmental impact of the FACTS device itself
may be considerable. In particular, series compensation units can
be visually obtrusive with large items of transmission equipment
placed on top of high voltage insulated platforms.

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Thank you for your kind attention

FACTS Flexible AC Transmission System.ppt

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