FLEXIBLE AC FLEXIBLE AC TRANSMISSION SYSTEMS TRANSMISSION SYSTEMS - PowerPoint PPT Presentation

FLEXIBLE AC FLEXIBLE AC TRANSMISSION SYSTEMS TRANSMISSION SYSTEMS FACTS 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”  

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 COMBINED COMBINED SERIES COMBINED SERIES  SERIES SERIES SERIES SERIES SHUNT CONTROLLER SHUNT CONTROLLER CONTROLLER CONTROLLER      Inline power flow  Unified power flow control controller

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

(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) VOL TAGE SOURCE CONVERTER(VSC) Ø  C onsi sts of a vol tage  Consists of impedances source  Supplies or absorbs reactive C om pact C an suppl y acti ve and  power reacti ve pow er  No voltage source Eg STATC O M SSSC U PFC etc  : , , .  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  T erminal 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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