The document discusses several types of FACTS devices used in power systems, including static VAR compensators (SVC), thyristor controlled series capacitors (TCSC), static synchronous compensators (STATCOM), and static synchronous series compensators (SSSC). It provides details on their operating principles and how they can be used to control reactive power flow and voltage in transmission lines.

1. FACTs Devices

2. Some Important FACTs Devices
 Static VAR Compensator (SVC)
 Thyristor Controlled Reactor (TCR)
 Thyristor Switched Capacitor (TSC)
 TSC – TCR Combined Configuration
 Thyristor Controlled Series Capacitor (TCSC)
 STATic COMPensator (STATCOM)
 Static Synchronous Series compensator (SSSC)
 Unified Power-Flow Controller (UPFC)

3. Static VAR Compensators (SVC)
 Thyristor Controlled Reactor (TCR)
 Thyristor Switched Capacitor (TSC)
 TSC – TCR Configuration

4. Thyristor Controlled Reactor (TCR)

5. Thyristor Controlled Reactor (TCR)
 The controllable range of the TCR firing angle, α,
extends from 90º to 180º.
 A firing angle of 90º results in full thyristor conduction
with a continuous sinusoidal current flow in the TCR.
 As the firing angle is varied from 90º to close to 180º,
the current flows in the form of discontinuous pulses
symmetrically located in the positive and negative
half-cycles

6. Thyristor Controlled Reactor (TCR)

7. Thyristor Controlled Reactor (TCR)

8. Thyristor Controlled Reactor (TCR)

9. Thyristor Switched Capacitor (TSC)

10. Thyristor Switched Capacitor (TSC)

11. Thyristor Controlled Series Capacitor (TCSC)

12. Thyristor Controlled Series Capacitor (TCSC)
 the principle of variable-series compensation is
simply to change the fundamental-frequency voltage
across an fixed capacitor in a series compensated
line through appropriate variation of the firing angle
 This changed voltage changes the effective value of
the series-capacitive reactance.

13. Thyristor Controlled Series Capacitor (TCSC)

14. STATic COMpensator (STATCOM)

15. STATic COMpensator (STATCOM)
 It is in general a solid-state switching converter
capable of generating or absorbing independently
controllable real and reactive power at its output
terminals when it is fed from an energy source or
energy-storage device at its input terminals.
 It provides the desired reactive-power generation
and absorption entirely by means of electronic
processing of the voltage and current waveforms in
a voltage-source converter (VSC).
 The exchange of reactive power between the
converter and the ac system can be controlled by
varying the amplitude of the 3-phase output
voltage, Es, of the converter.

16. STATic COMpensator (STATCOM)
 If the amplitude of the output voltage is
increased above that of the utility bus voltage,
Et, then a current flows through the reactance
from the converter to the ac system and the
converter generates capacitive-reactive power
for the ac system.
 If the amplitude of the output voltage is
decreased below the utility bus voltage, then the
current flows from the ac system to the converter
and the converter absorbs inductive-reactive
power from the ac system.

17. STATic COMpensator (STATCOM)

18. STATic COMpensator (STATCOM)
 Adjusting the phase shift between the converter-
output voltage and the ac system voltage can
similarly control real-power exchange between
the converter and the ac system.
 The converter can supply real power to the ac
system from its dc energy storage if the
converter-output voltage is made to lead the ac-
system voltage.
 it can absorb real power from the ac system for
the dc system if its voltage lags behind the ac-
system voltage.

19. STATic COMpensator (STATCOM)
 Because the reactive power at zero frequency
(dc) is by definition zero, the dc source supplies
no reactive power as input to the converter and
thus clearly plays no part in the generation of
reactive-output power by the converter.
 The converter simply interconnects the three
output terminals so that the reactive-output
currents can flow freely among them. i.e. the
converter establishes a circulating reactive-
power exchange among the phases.

20. STATic COMpensator (STATCOM)
 The real power that the converter exchanges at
its ac terminals with the ac system is supplied to
or absorbed from its dc terminals by the dc
capacitor.
 However, the main function of the capacitor is to
provide a circulating-current path as well as a
voltage source for the converter operation for
reactive power compensation.

21. Static Synchronous Series compensator
(SSSC)

22. SSSC
 SSSC injects a quadrature voltage, VC, in
proportion to the line current but is lagging in
phase.
 This voltage acts in opposition to the leading
voltage appearing across the transmission-line
inductance, which has a net effect of reducing
the line inductance.

23. SSSC
 Normally, the SSSC output voltage lags behind
the line current by 90º to provide effective series
compensation.
 In addition, the SSSC can be gated to produce
an output voltage that leads the line current by
90º, which provides additional inductive
reactance in the line.
 This feature can be used for damping power
swings and, if the converter has adequate rating,
for limiting short-circuit currents.

24. SSSC