Transcript 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
• Dynamic:
– Transient and dynamic stability
– Subsynchronous oscillations
– Dynamic overvoltages and undervoltages
– Voltage collapse
– Frequency collapse
• Steady-State:
– Uneven power flow
– Excess reactive power flows
– Voltage capability
– Thermal capability
FACTS Controllers
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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
US FACTS Installations
AEP/ Unified Power
Flow Controller
/100 MVA/ EPRI
San Diego G&E/
STATCOM/100 MVA
Mitsubishi
Eagle Pass (Texas)
Back-to-back HVDC
37 MVA/ ABB
CSWS (Texas)
STATCOM/ 150 MVA
/ W-Siemens
Vermont Electric/
STATCOM/ 130
MVA/ Mitsubishi
NYPA/ Convertible
Static Compensator/
200 MVA
Northeast Utilities/
STATCOM/ 150 MVA/
Areva (Alstom)
TVA
STATCOM/ 100MVA
EPRI
Austin Energy
STATCOM/ 100MVA
ABB
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.
UPFC
UPFC
• may control voltage, impedance, and angle
• impacts active and reactive power flow in line
Basic Operation
UPFC Capabilities
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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
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
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.
Power flow in a transmission line
VS
jX
PSR
VR
VSVR
PSR 
sin 
X
and V  V  jXI
R
S
VR

VS
To increase PSR, increase 
jXI
VA
- Vinj +
VB
VB

Vinj
VA
VS
jX
VR
- Vinj +
VSVR
PSR 
sin    
X
VR
VR
PSR
Vinj

jXI

VS
How is Vinj created?
a1
b1
c1
+
V
a2
b2
c2
a1
a1 on, b1 on, c1 off
Vab=0, Vbc=V, Vca = -V
a1 on, b1 off, c1 on
Vab=V, Vbc=-V, Vca = 0
c1
+
V
a2
a1
a1 on, b1 off, c1 off
Vab=V, Vbc=0, Vca = -V
b1
b2
b1
c2
c1
+
V
a2
b2
c2
a1
b1
c1
+
V
a2
b2
c2
Sine-triangle PWM
1
1
V
a
0.8
0.5
0.6
0
0.4
0
100
200
300
400
500
600
700
0
100
200
300
400
500
600
700
0
100
200
300
400
500
600
700
1
b
0.2
V
0
-0.2
0.5
0
-0.4
1
V
ab
-0.6
-0.8
-1
0
-1
0
100
200
300
400
500
600
700