Transcript Luis Layo (SP) Session 4 – Block 3

Barcelona 12-15 May 2003
Analysis of the effects of wind
farms dynamic behaviour on
distribution networks
DFIM Wind Farms Voltage Control
CIRED Barcelona 12-15 May 2003
Luis Layo (SP) Session 4 - Block 3
IBERDROLA
Luis Layo (SP) Session 4 – Block 3 – Selected Paper - Question 6
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Barcelona 12-15 May 2003
Index
• Voltage control strategy on DFIM Wind Farms
• Models developed for simulations
• Reactive power control tests of a wind farm
from a distribution control centre
• Voltage control operation procedure
• Question 6: Are there now cost effective
solutions for all the voltage control challenges
of renewable generators?
Luis Layo (SP) Session 4 – Block 3 – Selected Paper - Question 6
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Barcelona 12-15 May 2003
Introduction
• Wind energy has turned out to be one of the most
important and promising sources of renewable energy
• This energy source will represent a significant
proportion of total installed power in the Spanish
power system
• The expected amount of wind power establishes
important challenges to distribution and transmission
network planning and operation
• Problems related to reactive power management in
wind farms and to their connection to the electric
network
Luis Layo (SP) Session 4 – Block 3 – Selected Paper - Question 6
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DFIM Model
Switch Gear
Asynchronous
Generator
G
Network
DFIM
Rotor
AC
DC
DC
AC
Doubly Fed
Induction
Machine
• This kind of wound rotor machine has to be fed both from stator
and rotor sides
• Asynchronous generator which behaves as a synchronous with
variable speed. Varying rotor input signal:
– Amplitude: reactive power control
– Phase: active power control
– Frequency: rotor speed control
Luis Layo (SP) Session 4 – Block 3 – Selected Paper - Question 6
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Control strategy: general features
• Reactive power can be controlled while maintaining
active power generation
• Distributes the required reactive power of the farm in a
proportional way among all the operative generators:
qi 
Qref
n
q
i 1
* qimax
imax
– Each machine will work with a different power factor
– Machines tend to reach the saturation state at the same time
Luis Layo (SP) Session 4 – Block 3 – Selected Paper - Question 6
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Control strategy: model
q1sp
q2sp
Wind Farm
Control
Centre
q1 max
Pe1
q3sp
Qmax  qimax
q isp 
q3 max
q2 max
Pe2
Distribution Network
Control Centre
qnsp
Pe3
Q ref
q
Qmax . imax
qn max
Pen
Qref
Luis Layo (SP) Session 4 – Block 3 – Selected Paper - Question 6
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Barcelona 12-15 May 2003
Control strategy: requirements
• Wind generators
– Control loop changes to receive local set point
• Wind Farm Control Centre:
– Active power of each machine
– P-Q capacity curve
• Distribution network Control Centre
– OPF: maximum reactive power available
– Communications
• Cost-effective
– Take advantage of exiting control capacity
Luis Layo (SP) Session 4 – Block 3 – Selected Paper - Question 6
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Barcelona 12-15 May 2003
Security Control: voltage monitoring
V
Vmax trigger
Control trigger off
Vmax admisible
Qe emergency control
Vmax normal
Qe free control
Qe
Qe free control
Qe=0 , V= 1 P.U.
Vmin normal
Qe emergency control
Control trigger off
Vmin admisible
Vmin trigger
Luis Layo (SP) Session 4 – Block 3 – Selected Paper - Question 6
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Barcelona 12-15 May 2003
Reactive Power Control Simulations
Evolución
de
las
potencias
activas
por
máquina
Evolución
de
las
potencias
reactivas
por
máquina
Evolución
la s Potencia
s Re activas
des cada
Máquina
Evolución
de la sdePotencias
Activas
Gene rada
por cada
Máquina
Comportamiento
del Sistema de Control de cosj
Comportamie nto del Sistema de Control de cos(phi)
42 00 00
300
0 .9 7 5
1
Induc tivo
Inductivo
0 .9 7 5
0 .9 5 0
0 .9 2 5
P otencia
R eactiva
kVAR]
P otencia
A ctiva [[kW]
0 .9 5 0
kW
enkVAR
activaen
Potencia
reactiva
Potencia
C apacitivo
Capacitivo
0 .9 2 5
0
200
100
-2 0 0
0
-4 0 0
-1 0 0
-2 0 0
-6 0 0
-3 0 0
-8 0 0
-4
0 .9 0 0
0
5
10
15
20
25
0
Power factor performance of the
wind farm
5
1100
1155
2200
2255
Tiempo
Tiempo [se
[seg]
g]
Tiempo [se g]
Reactive
Active
power
power
performance
performance
of
each
of
each
generator
generator
(wind gusts)
Luis Layo (SP) Session 4 – Block 3 – Selected Paper - Question 6
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Barcelona 12-15 May 2003
Salajones Wind Farm data
Control Centre OPF -> Q set point
• 23 MW: 35 wind generators
• In service since 1999
• Doubly fed induction
generators DFIM
• 660 kW machines
• 66 kV network connection
• Wind farm -> generators:
radio link
• Control centre -> wind farm:
optical fibre link
Luis Layo (SP) Session 4 – Block 3 – Selected Paper - Question 6
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Q control test in a real Wind Farm
Luis Layo (SP) Session 4 – Block 3 – Selected Paper - Question 6
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Voltage control secondary service
• P.O. 7.4: establishes power factor limits (Q
generation and absorption bands) in the
transmission-distribution border points
Power Factor
Transmission Network
P
Q
Transmission Network
0………1
Q+Q’
P-P’
Q
tg =
P
P’
Q’

Distribution Network
Wind Farm
Q+Q’
tg’ =
P-P’
Luis Layo (SP) Session 4 – Block 3 – Selected Paper - Question 6
Distribution Network
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Voltage Control Proposal
• Required service as normal generators
• Softer conditions in distribution networks
• Perform the voltage control service based in
power factor bands according to the periods
of the day
– Peak: reactive power generation
– Off-peak: reactive power absorption
– Medium: power factor of unity
Luis Layo (SP) Session 4 – Block 3 – Selected Paper - Question 6
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Conclusions
• Wind farms made up with DFIMs constitute an
important tool from the voltage regulation point of view
• DFIMs are strongly recommended for the new wind
farms from the power system viewpoint, especially in
areas with a large wind generation concentration
• Wind farms with voltage control capacity will have a
better position to be accepted in the system, in terms of
planning, installation and operation
• The DFIM technology allows to perform voltage control
in a very cost-effective way
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