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
AEP/ Unified Power Flow Controller /100 MVA/ EPRI
NYPA/ Convertible Static Compensator/ 200 MVA
Vermont Electric/ STATCOM/ 130 MVA/ Mitsubishi
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. How is Vinj created? + b1 a2 a1 b2 c1 c2

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

18. Sine-triangle PWM