power systems

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2. Increase in population and industrial growth, insufficient
energy resources to generate or transmit the power in power
system, increase in load causes power demand in the electrical
power system.
These power demand leads to voltage instability, increase the
losses, reduces the power transfer capability and stability of
the power system.
FACTS devices are optimally located in the power system to
examine the stability of the system.
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3. IEEE defines FACTS as "a power electronic based system
and other static equipment that provide control of one or
more AC transmission system parameters to enhance
controllability and increase power transfer capability”.
FACTS stands for Flexible AC Transmission System.
In a power system, FACTS devices enable control of active
and reactive power flow. Using the devices opens up the
potential of reducing power losses of a transmission line.
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4. Power flows (real and reactive) are functions of three
parameters, namely, (i) voltage, (ii) phase angle difference
and (iii) reactance of the transmission lines.
FACTS devices allow the dynamic control of power systems.
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5. FEATURE OF FACTS
The objectives of FACTS include:
(i) To increase the transmission capabilities while
maintaining the stability of power systems,
(ii) to control power so that if flows on the desired routes,
(iii) to increase loading capacity of transmission lines,
blackouts.
The design of FACTS devices is based on the combination of
traditional power system components (such as inductors,
capacitors, transformers, and, switches) and power electronics
elements (such a transistors and thyristors).
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7.  Depending on the power electronic devices used in the control, the FACTS controllers can be
classified as
(A) Variable impedance type
(B) Voltage Source Converter (VSC) based
A. The variable impedance type controllers
i. Static Var Compensator (SVC), (shunt connected)
ii. Thyristor Controlled Series Capacitor or compensator (TCSC), (series connected)
iii. Thyristor Controlled Phase Shifting Transformer (TCPST) of Static PST (combined shunt
and series)
B. The VSC based FACTS controllers
i. Static synchronous Compensator (STATCOM) (shunt connected)
ii. Static Synchronous Series Compensator (SSSC) (series connected)
iii. Interline Power Flow Controller (IPFC) (combined series-series)
iv. Unified Power Flow Controller (UPFC) (combined shunt-series)
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8. Some special purpose FACTS controllers are
(a) Thyristor Controller Braking Resistor (TCBR)
(b) Thyristor Controlled Voltage Limiter (TCVL)
(c) Thyristor Controlled Voltage Regulator (TCVR)
(d) Interphase Power Controller (IPC)
(e) NGH-SSR damping
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10. SERIES CONTROLLER
 The series controller is used to introduce or inject voltage in series with the line
voltage. It consists of a capacitor or reactor. It is used to supply or consume variable
reactive power.
 When the load on the transmission line is higher, it needs extra reactive power. In
this condition, it is used to supply reactive power with the help of a capacitor.
In most cases, the capacitors are installed at the end of the line to compensate demand
of reactive power. Example:- Thyristor controlled series capacitor (TCSC), Static
synchronous series capacitor (SSSC) etc.
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11. It consists of a series compensating capacitor shunted by a thyristor controlled reactor
(TCR). Its elementary use of the TCSC is to offer a perpetually variable capacitance by
largely dropping the variable remunerating capacitance by the TCR. The TCR at the
essential frequency may be a variable reactance. Impedance, affected by delay angle
(alpha), steady-state reactance of TCSC is the parallel of LC circuit, comprising of
mounted capacitive reactance, XC and a variable reactance inductive reactance XL. The
TCSC may be a tunable parallel LC circuit to the line that’s a gradual work current
supply
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12.  It is voltage source device based mostly of compensator referred to as static
synchronous series compensator (SSSC), within which the steady state
management of transmission line will be made up of the series compensator given
by a synchronous AC voltage supply (SVS), whose yield voltage coordinate voltage
of the series condenser.
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13. S
N
FACTS device Parameter controlled
1 Static VAR Compensator (SVC) – 1st
generation
Voltage
2 Thyristor Controlled Series
Compensator (TCSC)-1st generation
Reactance (and hence
active power flow)
3 Thyristor Controlled Phase Shifter
(TCPS) – 1st generation
Angle
4 Static Synchronous Compensator
(STATCOM) – 2nd generation
Voltage
5 Static Synchronous Series Controller
(SSSC) – 2nd generation
Reactance
6 Unified Power Flow Controller
(UPFC) – 2nd generation
Reactance
7 Convertible Series Compensator
(CSC)
Reactance
8 Interphase Power Flow Controller
(IPFC)
Angle
FACTS DEVICES - FOR DYNAMIC CONTROLS
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14. Conventional Equipment - for static controls
SN Conventional equipment Parameter controlled
1 Series capacitor Reactance (hence active
power flow)
2 Shunt capacitor and reactor Voltage
3 Transformer LTC (online tap changer) Voltage
4 Phase shifting transformer Angle
5 Synchronous condenser Voltage
6 Others (reconductoring, addition of
new lines, etc.)
Reactance and voltage
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15.  N. G. Hingorani and L. Gyugyi, Understanding FACTS:
Concepts and Technology of Flexible AC Transmission
Sysytems. Wiley- IEEE, 1999.
 P. Moore and P. Ashmole, “Flexible AC Transmission Systems,”
Power Engineering Journal, December 1995, pp. 282-286
 M. Bocovich et al., “Overview of series connected flexible AC
transmission systems (FACTS), North American Power
Symposium, September 2013
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