Flexible AC Transmission

gilamonsterbirdsElectronics - Devices

Nov 24, 2013 (3 years and 8 months ago)

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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


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

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

Austin Energy

STATCOM/ 100MVA

ABB

AEP/ Unified Power
Flow Controller
/100 MVA/ EPRI

TVA

STATCOM/ 100MVA

EPRI

Northeast Utilities/
STATCOM/ 150 MVA/
Areva (Alstom)

NYPA/ Convertible
Static Compensator/
200 MVA

Vermont Electric/
STATCOM/ 130
MVA/ Mitsubishi


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.

Power Flow Control

UPFC

UPFC


may control voltage, impedance, and angle


impacts active and reactive power flow in line

Basic Operation

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

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.

jX
S
V
R
V
SR
P
sin
S R
SR
V V
P
X


Power flow in a transmission line


To increase
P
SR
, increase

and

R S
V V jXI
 
jXI
S
V
R
V

A
V
B
V
inj
V
-

+

A
V
inj
V
B
V

jX
S
V
R
V
SR
P
R
V

inj
V
-

+



sin
S R
SR
V V
P
X
 


 
jXI
inj
V
S
V
R
V



How is V
inj

created?

V
+

b
1

a
2

a
1

b
2

c
1

c
2

V
+

b
1

a
2

a
1

b
2

c
1

c
2

a
1

on, b
1

on, c
1
off

V
ab
=0, V
bc
=V, V
ca
=
-
V

a
1

on, b
1

off, c
1
off

V
ab
=V, V
bc
=0, V
ca
=
-
V

V
+

a
1

b
1

c
1

c
2

b
2

a
2

V
+

a
1

b
1

c
1

c
2

b
2

a
2

a
1

on, b
1

off, c
1
on

V
ab
=V, V
bc
=
-
V, V
ca
= 0

Sine
-
triangle PWM

0
100
200
300
400
500
600
700
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
0
100
200
300
400
500
600
700
0
0.5
1
V
a
0
100
200
300
400
500
600
700
0
0.5
1
V
b
0
100
200
300
400
500
600
700
-1
0
1
V
ab