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Flexible AC Transmission System Overview

Flexible AC Transmission System Overview. Flexible AC Transmission System. Alternating current transmission systems incorporating power electronics-based and other static controllers to enhance controllability and increase power transfer capability. Constraints on Useable Transmission Capacity.

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Flexible AC Transmission System Overview

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  1. Flexible AC Transmission System Overview

  2. Flexible AC Transmission System Alternating current transmission systems incorporating power electronics-based and other static controllers to enhance controllability and increase power transfer capability

  3. Constraints on Useable Transmission Capacity • Dynamic: • Transient and dynamic stability • Subsynchronous oscillations • Dynamic overvoltages and undervoltages • Voltage collapse • Frequency collapse

  4. Steady-State: • Uneven power flow • Excess reactive power flows • Voltage capability • Thermal capability

  5. 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

  6. US FACTS Installations Vermont Electric/ STATCOM/ 130 MVA/ Mitsubishi NYPA/ Convertible Static Compensator/ 200 MVA AEP/ Unified Power Flow Controller /100 MVA/ EPRI San Diego G&E/ STATCOM/100 MVA Mitsubishi Northeast Utilities/ STATCOM/ 150 MVA/ Areva (Alstom) TVA STATCOM/ 100MVA EPRI Eagle Pass (Texas) Back-to-back HVDC 37 MVA/ ABB Austin Energy STATCOM/ 100MVA ABB CSWS (Texas) STATCOM/ 150 MVA / W-Siemens

  7. Power Flow Control • Power transfer between areas can be affected by adjusting the net series impedance. • Transmission line capability can be increased by installing a series capacitor which reduces the net series impedance.

  8. UPFC

  9. UPFC • may control voltage, impedance, and angle • impacts active and reactive power flow in line

  10. Basic Operation

  11. UPFC Capabilities • Increase transmission line capacity • Direct power flow along selected lines • Powerful system oscillation damping • Voltage support and regulation • Control of active and reactive power flow at both sending- and receiving-end

  12. Operation • Reactive power is generated or absorbed by the shunt inverter to control bus voltage • Reactive power is generated or absorbed by the series inverter to control the real and/or reactive power flow on the transmission line

  13. Cont’d • A portion of the real power flow on the transmission line is drawn from the bus by the shunt inverter to charge the DC capacitor. • Real power is inserted into the line through the series inverter.

  14. Power flow in a transmission line and To increase PSR, increase

  15. - + - +

  16. + a1 b1 c1 a2 b2 c2 How is Vinj created?

  17. + a1 b1 c1 a1 on, b1 on, c1 off Vab=0, Vbc=V, Vca = -V b2 a2 c2 + a1 b1 c1 a1 on, b1 off, c1 off a2 b2 c2 Vab=V, Vbc=0, Vca = -V + a1 b1 c1 a1 on, b1 off, c1 on Vab=V, Vbc=-V, Vca = 0 a2 b2 c2

  18. Sine-triangle PWM

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