sistema de exc. vs estabilidad
TRANSCRIPT
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Impact of excitation system on power system stability
ABBABB Industrie AG
1.INTRODUCTION
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Impact of excitation system on power system stability
HV SYSTEM
THE POWER STATIONSTEP UP
CONTROL ROOM
TRANSFORMER LV SWITCHGEAR
HV- BREAKERAC & DC
AUXILIARYSYSTEMS
GOVERNOR
1GENERATOR
BREAKER
AUX.TRANSF
.
PROTECTION
1
CONTROLSYSTEMS
SYNCHRONIZING
PTs&CTs
TURBINESYNCHRONOUS
GENERATOR
EXCITATIONSYSTEM
STARPOINT
CUBICLEEXCITATION
TRANSFORMER
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If Synchronous Ug
Machine
ExcitationSystem
Grid
Controller
The automatic voltage control system
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~=
SM E ~SM =
1 a 200 A
Rotating exciter100 a 10000
A
Static excitation
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Basic Requirements Excitation Current up to 10000 amps
Input frequency range from 16 Hz to 400 Hz
Adaptable to different redundancy requirements for controls andconverters
State of the art man machine interface
Compatibility with most applied power plant control systems
Remote diagnostics
Comfortable commissioning tools
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Operational Application
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Main Components of an UNITROL 5000 System
AVR
ABB Industrie AG
ABB
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Measuring
System overview
AVR 2
AVR 1
Protection
Monitoring
AVR + FCR
Logic Control
CONVERTER N
CONVERTER 2
CONVERTER 1
Converter
Control
Field flashing
Field suppressionFieldbreaker
AVR = Autom. Voltage Reg.
FCR = Field Current Reg. ABB
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MeasuringandA/D
conversion
Min.
/max.value
priorityQ
Main Functions of the AVR
with Field Current Controller
UG, I
G
UG
UG, I
G, I
f
UG, I
G, I
f
UG, IG
If
AVR Setpoint-V/Hz limiter
- Soft start _- I Compensation
- IP
Compensation
+
Underexcit. limiter-Q=F(P,U,UG)
-Stator current lead
-Min. field current
Overexcit. limiter-Max field current
-Stator current lag
Power System
Stabilizer PSS
Man setpoint _
+
PID
PI
To pulse
generation
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Impact of excitation system on power system stability
2. IMPACT ON POWER SYSTEM STABILITY
Voltage Control Dynamics ( controller, power stage and power source)
Limiters
Power System Stabilizer
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Impact of excitation system on power system stability
2.1 Voltage Control Dynamics ( controller, power stage and power source)
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Parameter Description Unit Range
TR Measuring filter time constant s 0.020
Ts Gate control unit and converter time constant s 0.004
KIR Reactive power compensation factor p.u. -0.20...+0.20
KIA active power compensation factor p.u. -0.20...+0.20
KR Steady state gain p.u. 10...1000
Kc Voltage drop to commutations andimpedances p.u. Acc. Transf.
TB1 Controller first lag time constant s TB1 TB2TB2 Controller second lag time constant s 0
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IR UR
IDR
UT
ITIDT
If Uf
IDS
IS
US
Synchronous machinethree-phase representation ABB
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IQ2
IQ1
D axisra
Idd Ud
Stator
dD
rdD
IdD
rf f
Uf If Q1
Q2
q Q axis
rQ1 rQ2ra
IqRotor
Uq
d
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decompositionABB
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Torque TM =
TE =
PM
speed
US Ep sin
Xq +
TM
XT +XE
Motion equation:
0o 45o 180o
TM TE = 2Hd
dt
The characteristic Dynamic Equation
ABB
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IEEE 421.1
UF ceiling
NR
c
b
UF nominald
AVR - Voltage control dynamic
System type (Static excitation, Brush-less, DC Exciter)
Settings of control algorithm
Response time
Ceiling capabilitiesExcitation system nominal
response
=c e -ao
(ao)(oe)
a
oe=0.5s
ABB
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Comparison of Excitation System Types
Mechanical
-Conversion of
mech. to electr.
Energy
- Size of exciter
- Sliprings
Electrical
- Rectifier
- Directmeasuring
of field current
- Fast field
suppression
DC-Exciter
yes
power and speed
yes
not required
possible
possible
AC-Exciter
stat. diodes
yes
power and speed
yes
static external
possible
possible
AC-Exciter
rot. diodes
yes
power and speed
no
static rotary
not possible
not possible
Stat. Exciter
stat. thyristors
main machine
power
yes
static
possible
possible
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Comparison of Exciter Characteristics
Dynamic
Performance
- Major time
constant of control circuit
- Ceiling factor
- Negative fieldcurrent
Reliability (MTBF)
- Machine, Transformer
- Converter
Maintenance
- Machine, Transf.
- Converter
DC-Exciter
TdL+TE
limited
possible
good
good
at standstill
at standstill
AC-Exciterstat. diodes
TdL+TE
not limited
not possible
good
better
at standstill
duringoperation
AC-Exciterrot. diodes
TdL+TE
limited
not possible
good
better
at standstill
at standstill
Stat. Exciterstat. thyristors
TdL
not limited
possible
better
better
at standstill
duringoperation
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Ceiling limit
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Impact of excitation system on power system stability
ABBABB Industrie AG
2.2 LIMITERS
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Impact of excitation system on power system stability
Setpoint building
Automatic
channel
-Setpoint
Follow up
Automatic
Ug
ACTransducer
and filter
-Soft start
-V/Hz limiter
-Q influence
-P influence
Ug actual
effective setpoint
+
-
Powersystem
stabilizer
(PSS)
HVGate
Gain
+ DC
Gain
Ucmax
HF gain
+
UcAVRUnderexcitation
limiters (UEL)
Overexcitation
limiters (OEL)
LV +
Gate
+
UcP gain
1/TA 1/TB
Ucmin Ucmax
IFTransducer
-
and filter
+
Gain
DC
Gain
P gain
Uc FCR
Manual set point
Follow up
Automatic
Follow up Manual
Follow upcontrol
UcAVR
Uc FCR
Ucmin
1/TA 1/TB AVR
FCR
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Theorectical stability
limit
Practical
stability
limit
P [p.u.]
Declared rated
operation point
ofgenerating
unit
Turbine
ouputpowerlimit
Thermal limit
of stator
LEADING
(underexcited
)
n
LAGGING(overexcited
)
Thermal
limit of
rotor
-1.0 p.u. U2
Xq
U2
Xd
Minimum
Field current
limitSafe operationrange
1.0 Q [p.u.]
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The Power Chart of a solid polesynchronous machine
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Synchronous machine operation Limits
Max.Max. fieldfield currentcurrent limiterlimiter
Min.Min. fieldfield currentcurrent limiterlimiter
StatorStatorcurrentcurrent limiterlimiter
UnderUnderexcitationexcitation P,QP,Q limiterlimiterP
Theoreticalstability limit
-Q 1/Xd +Q
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Main duty of the limiters:
Keep the synchronous machine operating withinthe safe and stable operation limits, avoidingthe action of protection devices that may tripthe unit.
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VOLTAGE REGULATOR WITH LIMITERS
ABB
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LOWERVAL.GATE
Voltagesetpoint
Supply
~ - +
=-
Ifth setpoint
Ifact-
+
IfmaxI2dt max
= / ~
=
+ I2
dt
COMP
/ #
SM =
~
THE OPERATING PHILOSOPHY OF Ifmax LIMITER
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Fieldcurrent
xIFN
Ceiling limit
thermal limit
setpoint
switch time
Time [s]
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Machine
frequencyfT [p.u]
Machineterminalvoltage
UT [p.u]
Machine field
1
1+ sTR
V / Hz Limiter
x yy=KVHZ.x+U_fn-KVHZ
-KVHZ
U_fn +
x>0
T_V_Hz
Delay
UTMAX
UTMAX
0
U_V/HZ
Volt/Hz
influence
signal
toAVR
[p.u.]current
IF [p.u.]1
1+ sTR
Max. field current limiter-
KIFmax+
x2
-KCF
+
EmaxFy
Setpoint 2 forIF max limiter
(option)
Stator
IFth1
IFth2
KHF
x>0 0IFmax1
IFmax2
1s
xx>y
LV
Gate
Current
IT [p.u.]1
1+ sTR
Stator current limiter
+
-KCS
EmaxSy
- KITind
+
To OEL limiter
gate ofAVRKHS
x>0
1s
0
xx>y
ITth
ITmaxTo UEL limiter
gate ofAVR
-+
KITcap
Min. field current limiter+
KIFmin
-
HV
Gate
Generatorreactivepower
1 P/Q limiter
IFmin
QT[p.u.]
1+ sTRGeneratorterminal
voltageUT [p.u.]
x2
1
le
- KPQ
+
ABB
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Generator
active powerPT [p.u.]
1+ sTR Look-upTab
yn
= f(xn)
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2.3 Power system Stabilizer
ABB
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Impact of excitation system on power system stability
IXq(s) XT XE
Ep UG
Ep
XT+XE
US
InfiniteBus
Ep-S = I. Xq
Ep
H
UG
=I.Xq
X q ( s ) = X q 1 + s Tq '
1 + s Tq ' '
= I. (XE+XT)
US
1 + sT q o ' 1 + s T q o ' '
Stationary and transient air gap voltages ABB
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Pe E
p U G US
90o
phasorrotation
Transient behavior ofand PEPE
ABB
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2
A) HXT+XE
Infinite Bus
B)H1 H2 Equivalent Inertia Heq =
XT+XE
H1 H2
H1+H2
TM TE = 2 H d TM TE Hd
taking dt = 2
dt2
For small oscillations keeping the drivingtorque constant the dynamic equationlinearized can be written as: 2 H
n
d2
dt2
+ D d
n dt +K1=0
Inertia. Ang. Acc. Dampingtorque
SynchronizingTorque
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Dynamic equation of synchronousmachine+grid for small oscillations ABB
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Oscillation frequency
phasorrotation K1
n
2 H
rad/s
Negative Damping(Unstable Region)
UG
D/ws*
Torque
Positive Damping(Stable Region)
Damping axis
K1=synchronizing coefficient
operating point
K1 =slope =T
=E p ' . Us
coso'Te=K1.
ResultingTorque
Xq'+XE +XT
Synchronizing Axis 0o o 90o
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Phasor diagram of machine+gridfor small oscillations ( without AVR) ABB
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Impact of excitation system on power system stability
2H n
d2
dt2
+D
d
n dt+K1
+K2 Ep'=0
Inertia.Ang. Acc. Dampingtorque
Synchron.Torque
Add .Torquefrom exc. system
Negative Damping(Unstable Region)
K2.Ep
UGD/ws*
-UG
phasorrotation
Positive Damping(Stable Region)
Resulting torque componentwithou t excitation system
Te=K1.Resulting torque componentwit h excitation system
ABB Industrie AG
Synchronizing Axis
Phasor diagram of machine+grid+excitation systemfor small oscillations ABB
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AVR
FINAL
CTRLELEMENT
~
ALTERNATIVE
PSS
UG
M
P,Q
Fig3: PSS in the excitation system
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Main Target of PSS:
It provides an additional torque component in order to get:
1) A positive resulting torque component on damping axis, even for thehighest possible rotor oscillation frequency.
2) A positive torque component on synchronizing axis for partialcompensation of generator terminal voltage variations even forthe highest possible oscillation frequency
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PSS2A acc. IEEE 421.5 1992PM
1 + s.2.H
+ N+
PA
1 + s.2.H VSTmax VSTmax
s.TW1 s.TW2 (1 + s
T 8)
1+s.T1 1+s.T3 VST
1 + s.TW1 1 + s.TW2 (1+
s
T9)M
+ Ks1
-
1+s.T2 1+s.T4
Ks3
VSTmin VSTmin
PE s.TW3
1 + s.TW3
s.TW4
1 + s.TW4
Ks2
1 + s.T7
PE
1 + s.2.H
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Adaptive PSS (APSS) Alternative to PSS2A
Driving Power Pa
UG , IGUref +
+ -
AVR+
Uf
+
Synchronous
Generator
UG
Measurement
P
GRID
APSS3rd Order System Model
Filter
P
Estimator
White
noise+ Regulator
+
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+
Multi Band PSS (MBPSS)
FB1(s)
+ K b-
FI1(s)
+
K i
-FI2(s)
Limit To
AVR
+
FH1(s)
+
K h-