06-08-2011, 03:40 PM
FACT new.pptx (Size: 700.97 KB / Downloads: 150)
FLEXIBLE AC TRANSMISSION SYSTEMS (FACTS)
WHAT IS FACTS ?
IEEE definition : “AC transmission systems incorporating power electronic based and other static controllers to enhance availability and to increase power transfer capabilities”
FACTS CONTROLLER
Power electronic based system or other equipment that provides control of one or more AC transmission system.
They can be inserted in series or shunt and in some cases a combination of both
SERIES CONTROLLER
Variable impedance or variable source
Injects voltage in series with the line
More powerful controller
For active power control
Improve transient stability of power system
SHUNT CONTROLLERS
Injects current into a line
Variable impedance or source connected to the line
Improve dynamic stability
Inline power flow control
COMBINED SERIES SHUNT CONTROLLER
Unified power flow controller
(B) CLASSIFICATION BASED ON COMMUTATION
Forced Commutation : GTO
Natural commutation : SCR
© CLASSIFICATION BASED ON SWITCHING FRQUENC
low frequency (50 – 60 Hz)
Medium frequency switching (100 – 500 Hz)
High frequency switching ( > 500 Hz)
(D) CLASSIFICATION BASED ON TYPE OF PE DEVCIE USED
VARIABLE IMPEDENCE TYPE(VIT) VOLTAGE SOURCE CONVERTER(VSC)
Consists of impedances
Supplies or absorbs reactive
power
No voltage source
Eg: SVC, TCSC, TCPST etc.
IMPORTANT FACTS CONTROLLERS
SVC (Static var compensator)
STATCOM (Static Compensator)
SSSC (Static Synchronous Series Compensator)
UPFC (Unified Power Flow Controller)
STATIC VAR COMPENSATOR (SVC)
Classification string: 1P-NC-LF-ZES-NDC
PF correction
Provides fast acting reactive power
Stabilization of bus bar voltage
Improve damping of dynamic oscillation
STATIC VAR COMPENSATOR (SVC)
Transformer
Switchgear
Reactor
Thyristor valves
Capacitor bank
Cooling system
Control and protection
STATIC SYNCHRONOUS COMPENSATOR(SSC) OR STATCOM
Classification string: 1P-FC-HF-CES-DC
For supplying reactive power
Active power control is
possible
Quick response
Less space
STATIC SYNCHRONOUS SERIES COMPENSATOR (SSSC)
Classification string: 1S-FC-HF-CES-DC
Exchange both active and reactive power
Compensate drop due to reactive and resistance losses
Maintains constant X/R ratio
UNIFIED POWER FLOW CONTROLLER (UPFC)
Classification string: 2-FC-HF-CES-DC
Combination of STATCOM and SSSC
Control both active and reactive power
Provides high flexibility
Terminal voltage control
Phase angle regulation
Series line compensation
ADVANTAGES OF FACTS
Power transmission capability
System stability
Power quality
Environmental impact
Transmission losses
Dynamic and reactive power support and voltage control
Dynamic oscillation in power system
CONCLUSION
FACTS is an application of power electronics in transmission system
FACTS controllers makes a system ‘flexible’
FACTS controllers are classified based on connection, commutation etc.
SVC, STATCOM, UPFC etc have a number of applications in power systems
FACTS has an important role in active and reactive power control
FACTS helps to improve the capacity of an existing system
FACTS controllers improve the power quality and stability