Ppt

Flexible AC Transmission Systems: Placement, Control, and Interaction

EPRI/NSF Workshop on Global Dynamic Optimization


Flexible AC Transmission Systems

Alternating current transmission systems incorporating power electronics-based and other static controllers to enhance controllability and increase power transfer capability

EPRI/NSF Workshop on Global Dynamic Optimizationer

Flexible ac transmission system composed of a static equipment. The Flexible Alternative current transmission is used for AC Transmission of electrical energy and increase the power transfer capability. FACT is define by IEEE as a power electronics based system and it is provide one or more ac transmission system are control and increase power transfer capability.


FACTS Controllers• Static VAR Compensator - SVC• Thyristor Controlled Series Compensator - TCSC• Thyristor Controlled Phase Angle Regulator - TCPAR• Static Synchronous Compensator - StatCom• Solid State Series Compensator - SSSC• Unified Power Flow Controller - UPFC


SVC


StatCom

• shunt device• lower rated components since only carry a fraction of

the line current• impacts bus voltage and reactive power support


SSSC

• series device• must have higher rated transformer and devices• impacts active power flow


UPFC

• combination of StatCom and SSSC• may control voltage, impedance, and angle• impacts active and reactive power flow in line

UPFC Topology



Series compensationIn series compensation, the FACTS is connected in series with the power system. It works as a controllable voltage source. Shunt compensationIn shunt compensation, power system is connected in Shunt (parallel) with the FACTS. It works as a controllable Current source


Steady-State Power Flow Control

• UPFC

• SSSC

• TCSC

These devices can affect active power flow


Useable Transmission Capacity• Dynamic:

– Transient stability– dynamic stability– Dynamic overvoltage and under voltages

Power flow in ac transmission line


tt

gt

t

b ijg

ijb


• Conventional eigenvalue analysis cannot predict the high frequency self-modes of the several FACTS devices in a large power system network.

• High frequency control interactions among the several FACTS devices must be checked using an EMTP-type program

• A promising technique is based on the use of high frequency eigenvalue calculation using the different FACTS


Series controllers

• low loop impedance - the series controllers may experience a very strong interaction, and therefore these controllers must be designed in a coordinated way - the main linking variable among the series controllers is the ac current

• high loop impedance - no control interactions may be expected among series controllers


Dynamic Control

• transient stability improvement

• inter-area oscillation damping

• subsynchronous resonance


HVDC

• HVDC converters in a large network will not experience control interactions if the transference impedances between their commutation busbars are high. This means that, in this case, the dc control design of each station can be based exclusively on the Short-Circuit Ratio (SCR) at its ac connection point.

Any Queries ? ? ?

THANK YOU…!!!

&

Ppt

Engineering

Transcript of Ppt