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Study on Variable Speed Wind Turbines’ Capabilities for Frequency Response. Germán Claudio Tarnowski - Technical University of Denmark & Vestas Wind Systems A/S Jacob Østergaard - Technical University of Denmark Poul E. Sørensen - Risø National Laboratory, Denmark - PowerPoint PPT Presentation
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Study on Variable Speed Wind
Turbines’ Capabilities for
Frequency Response
Germán Claudio Tarnowski - Technical University of Denmark & Vestas Wind Systems A/S
Jacob Østergaard - Technical University of Denmark
Poul E. Sørensen - Risø National Laboratory, Denmark
Philip C. Kjær - Vestas Wind Systems A/S, Denmark
2
Outline
1. Introduction: variable speed wind turbine frequency
response for grid frequency stability.2. Simulation set-up
Small/low inertia power system with wind power Models
3. Simulation cases: generation tripa) Conventional generation only (Base Case)b) Wind power Without inertia responsec) Wind power + Inertia responsed) Wind power + Inertia response + Primary frequency
control
4. Conclusions & remarks
3
Introduction
Grid frequency variations Imbalance between generation and
consumption
Wind Turbine Frequency Response:
Change in the wind turbine active power output as response to a
change in the grid frequency
Inertia response (power from rotating kinetic energy)
Primary frequency control (power from wind reserve)
Study on capabilities of WT-DFIG for providing Study on capabilities of WT-DFIG for providing controlledcontrolled frequency frequency
response during frequency drop in a small/low inertia power system, response during frequency drop in a small/low inertia power system,
combining inertia response and primary frequency controlcombining inertia response and primary frequency control
4
Simulation set-up: WT-DFIG model
Drive train
3rd order DFIG
Converter control: active and reactive power.
Pitch control: rotational speed
Aerodynamics
CP (,)
0 5 10 15 200
0.1
0.2
0.3
0.4
0.5
C
P ( ,
)
= 0
= 10
= 0
= 10
5
Wind turbine frequency response
puR
fPDROOP
)1(100
AVRR PFP
pudt
dffH(f)P tIE 2
WT control block PDROOP(+)
f (-)
PowerInertia
Emulation
ConverterPower
Reference
1
RateLimiter
Max , Min
WT FrequencyResponse Block
GridFrequency
2
WT PowerReference
1
Power
Change (f)P(f)PDeltaP DROOPIEe
Inertia response (inertia emulation)
Primary frequency control (Droop)
Plant power reserve (reserve factor)
6
Simulation set-up: Power system
Capacity Inertia Type
ST1 100 MVA H = 3.5 Reheat steam turbineST2 150 MVA H = 6 Reheat steam turbineHT 50 MVA H = 5 Hydro turbine
Tripped 50 MW - -Load 250 MW - active
50 MW Generation Loss (20%)
1ST 2ST HT Tripped
loadP
WF2ST HT Tripped
loadP
Wind Farm replacing ST1
30% Wind Power Penetration
Conventional generators
Capacity Type
WF 100 MVA Wind Farm
7
Simulation set-up: Conventional generatorsmodel
Model for Steam Power Plant and Hydro Power Plant
Power fromInertia Reaction
Power fromFrequency Control
Power fromDispatch
P electric1
Inertia
.Freq Ref
.Governor
+ Prime Mover
1/Droop
P dispatch3
gridfrequency
2
gridfrequencyderivative
1
8
Simulation cases: Inertia response from wind turbine
1. Grid with conventional generators
2. Grid without inertia response from WT
3. Grid with inertia response from WTGen.Unit
R % FR
PR
MWHeq (s)
Base case
ST1 6 0.3 30
5ST2 5 0.3 30
HT 5 0.33 50
Case 2 WF Without inertia response 3.8
Case 3 WF Inertia response 5
50 MW Generation Loss (20%)
9
0 5 10 15 20 25 3048
48.2
48.4
48.6
48.8
49
49.2
49.4
49.6
49.8
50
seconds
Grid
fre
quen
cy [
Hz]
Conventional GenerationWPG - No inertia responseWPG - With inertia response
Results: Grid frequency
1. Conventional generators case
2. WT without inertia response case
3. WT with inertia response case
-0.2 0 0.2 0.4 0.6 0.8 1
49
49.2
49.4
49.6
49.8
50
seconds
Grid Frequency
[Hz]
Frequency gradient
10
Results: Power plants electric power output
1. Conventional generators
2. Wind power without inertia response
3. Inertia response from wind power
WF2ST HT Tripped
loadP 0 5 10 15 20 25 30
20
40
60
80
100
120
140
160
seconds
Pow
er [
MW
]
Power [MW]Steam turbine ST2
Steam turbine ST1
Wind turbine
Hydro turbine
11
WT inertia response
0 5 10 15 20 25 30
1.06
1.08
1.1
Ro
tatio
na
l sp
ee
d [
pu
]
0 5 10 15 20 25 300
0.5
1
1.5
2
Pitch
an
gle
[D
eg
]
seconds
0 5 10 15 20 25 300.65
0.7
0.75
0.8
Pow
er [
pu]
Mechanical power WTElectrical power WT
0 5 10 15 20 25 300.6
0.7
0.8T
orqu
e [p
u]
Torque generator shaftTorque Blades
Powers [pu]
Torques [pu]
Rotational speed [pu]
Pitch angle [deg]
12
Simulation cases: inertia response + primary frequency control
4. Droop 16% + Inertia response
5. Droop 10% + Inertia response
6.6. Droop 9% + Inertia response Droop 9% + Inertia response (Instability)(Instability)
Gen.Unit
R % FR
PR
MWHeq (s)
Case 4
WF
16 0.1 8
5Case 5 10 0.15 12
Case 6 9 0.15 12
50 MW Generation Loss (20%)
13
Results: Grid frequency
1. Conventional generators
4. WT Droop 16% + Inertia response
5. WT Droop 10% + Inertia response
0 5 10 15 20 25 3048
48.2
48.4
48.6
48.8
49
49.2
49.4
49.6
49.8
50
seconds
Grid
fre
quen
cy [
Hz]
Conventional GenerationWPG: Inertia + Droop R = 16%WPG: Inertia + Droop R = 10%
0 0.2 0.4 0.6 0.8 1
49.2
49.3
49.4
49.5
49.6
49.7
49.8
49.9
50
seconds
Grid Frequency
[Hz]
Frequency gradient
14
Results: Power plants electric power output
1. Conventional generators
2. Droop 16% + Inertia response
3. Droop 10% + Inertia response
WF2ST HT Tripped
loadP 0 5 10 15 20 25 30
20
40
60
80
100
120
140
160
seconds
Pow
er [
MW
]
Power [MW]Steam turbine ST2
Steam turbine ST1
Wind turbine
Hydro turbine
15
Turbine droop 10% + inertia response
0 10 20 30 40 50 60 70 80 90
0.7
0.8
0.9
1
Pow
er [
pu]
Mechanical power WTElectrical power WT
0 10 20 30 40 50 60 70 80 900.6
0.7
0.8
0.9T
orqu
e [p
u]
Torque generator shaftTorque Blades
PAVAILABLE
0 10 20 30 40 50 60 70 80 901
1.05
1.1
1.15
Rota
tional speed [
pu]
0 10 20 30 40 50 60 70 80 900
2
4
Pitch a
ngle
[D
eg]
seconds
Powers [pu]
Torques [pu]
Rotational speed [pu]
Pitch angle [deg]
16
Turbine droop 9% + inertia response. Turbine droop 9% + inertia response. Instability.Instability.
0 10 20 30 40 50 60 70 80 90
0.6
0.8
1
Ro
tatio
na
l sp
ee
d [
pu
]
0 10 20 30 40 50 60 70 80 9048.5
49
49.5
50
Fre
qu
en
cy [
Hz]
seconds
Powers [pu]
Torques [pu]
Rotational speed [pu]
Grid Frequency [Hz]
0 10 20 30 40 50 60 70 80 90
0.6
0.8
1
Pow
er
[pu]
Mechanical power bladesElectric power wind turbine
0 10 20 30 40 50 60 70 80 900
0.5
1
1.5
To
rqu
e [
pu
]
Torque generator shaftTorque Blades
PAVAILABLE
17
Conclusions & remarks
Variable speed WTs’ capabilities for inertia response and primary frequency control was studied
Suitable control systems for variable speed WTs need to be developed for integrating high amounts of wind power in the grid
Grid frequency stability can be improved combining WT inertia response and primary frequency control
Instability in wind turbines with bad settings of primary control and inertia response: Capability depends on the combination of droop value, power reserve and inertia emulation.
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