Flexible Ac Transmission Systems (Facts) - Full Paper Presentation - Eeerulez.blogspot

FLEXIBLE AC TRANSMISSION SYSTEMS ( FACTS )

WHAT IS FACTS ?

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IEEE definition : “AC transmission systems incorporating power electronic based and other static controllers to enhance availability and to increase power transfer capabilities” 

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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

COMBINED SERIES SERIES CONTROLLER 

 Inline power flow control

COMBINED SERIES SHUNT CONTROLLER 

  Unified power flow

controller

(B) CLASSIFICATION BASED ON COMMUTATION   Forced Commutation : GTO 

Natural commutation : SCR 

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(C) CLASSIFICATION BASED ON SWITCHING FRQUENCY   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) CONVERTER(VSC)

VOLTAGE SOURCE

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Ø

C o n sists o f a vo lta g e Consists of impedances so u rce Supplies or absorbs reactive C o m p a ct  C a n su p p ly a ctive a n d power re a ctive p o w e r No voltage source 

Eg: SVC, TCSC, TCPST etc.

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E g : S TA TC O M , S S S C , U P FC e tc .

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-LFZES-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-HFCES-DC  For supplying reactive power  Active power control is  possible  Quick response  Less space 

STATIC SYNCHRONOUS SERIES COMPENSATOR (SSSC)

Classification string: 1S-FC-HFCES-DC 

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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-HFCES-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 etchave 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

REFERENCES W.N. Chang and C.J. Wu, “Developing static

reactive power compensator in a power system”, IEEE Trans. on Power Systems K.R. Padiyar and R.K. Varma, “Damping torque analysis of static VAR system controllers”, IEEE Trans. on Power Systems, N.G.. Hingorani, “Flexible ac transmission”, IEEE Spectrum, pp. 40–45 Power Semiconductor Devices and Circuits, Brown Boveri symposia series, Baden Datettwil

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