The concept of FACTS (Flexible Alternating Current Transmission System) refers to a family of power electronics-based devices able to enhance AC system controllability and stability and to increase power transfer capability.
3. Introduction
• The concept of FACTS (Flexible Alternating Current
Transmission System) refers to a family of power electronics-
based devices able to enhance AC system controllability and
stability and to increase power transfer capability.
• The design of the different schemes and configurations of
FACTS devices is based on the combination of traditional
power system components (such as transformers, reactors,
switches, and capacitors) with power electronics elements
(such as various types of transistors and thyristors)
4. Benefits of FACTS
• To increase the power transfer capability of transmission
networks.
• To provide direct control of power flow over designated
transmission routes.
• Control of power flow as ordered so that it follows on the
prescribed transmission corridors.
• Increase the loading capability of lines to their thermal
capabilities
5. FACTS CONTROLLERS
SHUNT
• Static Var Compensator
• Static Synchronous Compensator
• STATCOM
SERIES
• Thyristor Controlled Series Compensator (TCSC)
• Static Synchronous Series Compensator
• Fault Current Limiter (SC+FPD)
HYBRID
• Dynamic Power Flow Controller (DFC)
• HVDC Light/HVDCLightB2B/UPFC
6. Shunt Connected Controllers
• In shunt compensation, power system is connected
in shunt (parallel) with the FACTS. It works as a
controllable current source. Shunt compensation is of two
types:
• Shunt capacitive compensation
This method is used to improve the power factor.
Whenever an inductive load is connected to the transmission
line, power factor lags because of lagging load current.
To compensate, a shunt capacitor is connected which draws
current leading the source voltage.
The net result is improvement in power factor.
7. Contd….
• Shunt inductive compensation:
This method is used either when charging the transmission
line, or, when there is very low load at the receiving end.
Due to very low, or no load – very low current flows through
the transmission line.
Shunt capacitance in the transmission line causes voltage
amplification (Ferranti effect).
The receiving end voltage may become double the sending end
voltage (generally in case of very long transmission lines).
To compensate, shunt inductors are connected across the
transmission line.
9. Contd….
• Static VAR compensator (SVC)
The SVC is an excellent tool for achieving dynamic voltage
control of power systems. Increased efficiency in power
systems
• Most common SVCs are:
– Thyristor-controlled reactor (TCR):
Reactor is connected in series with a bidirectional thyristor
valve.
The thyristor valve is phase-controlled.
10. Contd….
– Thyristor-switched reactor (TSR):
Same as TCR but thyristor is either in zero- or full-
conduction.
Equivalent reactance is varied in stepwise manner.
– Thyristor-switched capacitor (TSC):
capacitor is connected in series with a bidirectional
thyristor valve.
Thyristor is either in zero- or full- conduction.
Equivalent reactance is varied in stepwise manner.
11. Contd….
– Mechanically-switched capacitor (MSC):
Capacitor is switched by circuit-breaker.
It aims at compensating steady state reactive power. It is
switched only a few times a day.
12. Series Connected Controller
FACTS for series compensation modify line impedance.
Examples:
Thyristor-controlled series capacitor (TCSC): a
series capacitor bank is shunted by a thyristor-
controlled reactor
Thyristor-controlled series reactor (TCSR): a series reactor
bank is shunted by a thyristor-controlled reactor
Thyristor-switched series capacitor (TSSC): a series
capacitor bank is shunted by a thyristor-switched reactor
Thyristor-switched series reactor (TSSR): a series reactor
bank is shunted by a thyristor-switched reactor.
15. Contd….
It could be a combination of separate series & shunt
controllers or unified power flow controller.
Inject current into the system with the shunt controller and
voltage in series with the line with series controller.
When the controllers are unified, exchange real power between
series and shunt controllers via power link.
16. Conclusion
The above discussion reflects various work and philophies are
covered in the area of FACTS. The potential role that FACT
may play towards the development of the future Indian
transmission system. In fact, FACT elements may provide
Indian TSOs with effective solutions to the several criticalities
they encounter. Finally, it has to be noted that in a highly
meshed network, as the Indian FACTS become extensively
deployed, they will deliver real benefits only when subjected
to a coordinated and hierarchical control.