Download Wind Power Generation Power Flow and Dynamic Modeling

Wind Power Generation
Power Flow and Dynamic Modeling
Vadim Zheglov
EnerNex, Tennessee
[email protected]
Eduard Muljadi
NREL, Golden CO
[email protected]
UWIG-EnerNex
Modeling Workshop
Albany, NY
July 5-6, 2011
NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC
Background
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Conventional vs.
Wind Power Plant
Load
Load
Other Conv.
Generator
POI or PointPOI
of or
connection
Interconnection
to the grid
Interconnection
Interconnection
Transmission
Line
Transmission
Line
GSU
Xfmr
Large
Synchronous
Generator
Collector
Collector
System System
Station
Station
Prime
Mover
Individual
WTGs
Individual
WTGs
Feeders and Laterals (overhead
Feeders and Laterals (overhead
and/or underground)
and/or underground)
NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC
Power Generation
Conventional vs Wind Power Plant
•
Single or multiple large (100 MW)
generators.
•
Many (hundreds) of wind turbines (1 MW – 5
MW each)
•
Prime mover: steam, combustion engine
– non-renewable fuel affected by fuel
cost, politics, and pollution restrictions.
•
Prime mover: wind (wind turbine) –renewable
(free, natural, pollution free)
•
Controllability: adjustable up to max limit
and down to min limit.
•
Controllability: curtailment
•
Predictability: preplanned generation
based on load forecasting, influenced by
human operation based on optimum
operation (scheduled operation).
•
Predictability: wind variability based on wind
forecasting, influenced more by nature (wind)
than human, based on maximizing energy
production (unscheduled operation).
•
Located relatively close to the load
center.
•
Located at wind resource, it may be far from
the load center.
•
Generator: synchronous generator
•
Generator: Four different types (fixed speed,
variable slip, variable speed, full converter) –
non synchronous generation
•
Fixed speed – no slip: flux is controlled
via exciter winding. Flux and rotor rotate
synchronously.
•
Type 3 & 4: variable speed with flux oriented
controller (FOC) via power converter. Rotor
does not have to rotate synchronously.
NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC
Power Generation
Types of Wind Turbine Generator
Four basic topologies based on grid interface:
– Type 1 – conventional induction generator
– Type 2 – wound-rotor induction generator with variable rotor
resistance
– Type 3 – doubly-fed induction generator
– Type 4 – full converter interface
Type 1
Type 2
Type 3
Pla nt
Fee ders
Plant
Feeders
gene rator
generator
PF control
capacitor s
Slip power
as heat loss
Plant
Feeders
gene rator
ac
to
dc
PF control
capacitor s
Type 4
Plant
Feeders
generator
ac
to
dc
dc
to
ac
ac
to
dc
dc
to
ac
full power
partial power
NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC
Power Flow Modeling
Wind Turbine Generator
NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC
WPP Representation
POI or
connection
to the grid
Collector System
Station
Interconnection
Transmission Line
Individual WTGs
Collector System Equivalent
Feeders and Laterals (overhead
and/or underground)
Req
Beq/2
jXeq
Beq/2
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Equivalencing
NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC
Equivalencing
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Pad-Mounted
Transformer
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Reactive
Compensations
Represented by
Separate Model
Type 1 and 2 WTGs are induction machines:
• Several stages of capacitors banks at the WTG terminals are normally applied . Net power factor at bus 5 ~ 1.0
• In power flow:
• modeled as fixed shunt devices
• WTG of type 1 is approximately PF=0.9 therefore the capacitor need is about to be ½ of the power output.
• example, for a 100 MW WPP at full output, Qmin = Qmax = -50 Mvar
• and add a 50 Mvar shunt capacitor at the WTG terminals.
• Plant level reactive compensation may still be installed to meet interconnection requirements and should be
explicitly represented in power flow.
NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC
Reactive
Compensations
Type 3 and Type 4 WTGs (an estimate to start depending on the terminal voltage)
• These WTGs are capable of adjusting power factor to a desired value within the rating of the
generator and converter. They are also capable of voltage control at the interconnection point or at its
terminals.
• External reactive power compensation is often required to meet interconnection requirements
• If these WTGs do not participate in voltage control, the equivalent generator should be assigned a
fixed power factor, typically unity. (i.e., Qmin = Qmax = 0).
• If the WTGs do participate in voltage control, then the equivalent generator should be assigned a
reactive capability approximately equal to the aggregate WTG reactive power range (i.e., Qmin = Srated tan(cos-1(0.90); and Qmax = Srated tan(cos-1(0.95)) ).
• For example, consider a 100 MW WPP that employs Type 4 WTGs with specified power factor
range +/-0.95 at full output. In this example, Qmin should be set to -33 Mvar and Qmax should be set
to +33 Mvar. At an output level below rated, the reactive limits should be adjusted according to the
WTG capability curve.
NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC
Reactive Power
Flow
I
+
jI X
+
jI X
VB
VA
A
A = B
VA = VB
QA =QB= 0.5 I2X
A
B
B
I
jI X
QB =I2X ; QA= 0
QA =I2X ; QB= 0
VA
VA
VA’
VA”
VA= 1.0
I
I
I
I
VB = 1.0 V < V ;  = 0 VB = 1.0
VA > VB ; B = 0
A
B
A
-
-
All Q comes from B
VA
All Q comes from A
VA
jI X
VB = 1.0
Equal Q (VAR) contribution
I’ VB = 1.0
Overexcited
I”
VB”= 1.1
VA’ > VA ; QA =I’2X ; QB< 0
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Reactive
Compensations
POI or
connection
to the grid
Turbine close to substation
Collector System
Station
Interconnection
Transmission Line
Turbine far from substation
Individual WTGs
Feeders and Laterals (overhead
and/or underground)
X100 > X1
IX100 > IX1
NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC
Practical Limit of
Reactive Power Output
• Due to collector system effects, some WTGs in the WPP will actually reach terminal
voltage limits before reaching the nameplate reactive power limits.
• The net effect is that actual reactive power capability could be less than the nameplate.
• The reactive power capability can be determined by field test or careful observation of WPP
performance during abnormally high or low system voltage.
• For example, Figure 7 shows the results of field tests to determine the practical reactive
limits of a 200 MW WPP.
• All measurements were made at the interconnection point. Taking into account the effect of
transformer and collector system impedances, the reactive power limits of the equivalent
WTG can be established.
• Currently, there are no industry standard guidelines for testing WPP steady-state reactive
limits.
NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC
Practical Limit of
Reactive Power Output
+95 and
VPOI
VA
Vinf
I
reactor
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Practical Limit of
Reactive Power Output
VPOI
VA
Vinf
I
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Validation
Detailed Vs. Single-Machine Representations
0.435
QWT =
3-phase fault, all WTGs at 12 m/sec
0
-0.435
P34.5 kV
Q34.5 kV
From « Validation of the WECC Single-Machine Equivalent Power Plant », Presented DPWPG-WG Meeting at IEEE
PSCE, March 2009 - Jacques Brochu, Richard Gagnon, Christian Larose, Hydro Quebec
NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC
Validation
Detailed Vs. Single-Machine Representations
QWT =
0.435
3-phase fault, different wind speed for each feeder
0
-0.435
1 and 2 feeders
P34.5 kV
4 feeders = Typical
2 and 4 feeders = Typical
Q34.5 kV
1 feeder
From « Validation of the WECC Single-Machine Equivalent Power Plant », Presented DPWPG-WG Meeting at IEEE
PSCE, March 2009 - Jacques Brochu, Richard Gagnon, Christian Larose, Hydro Quebec
NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC
Wind Power Plant
Network
34.4/230 kV station transformer
230 kV Line 1
Infinite Bus
R1, X1, B1
Rt, Xt.
0.6/34.4kV equivalent GSU transformer
34.5 kV collector
system equivalent
Re, Xe, Be
Rte, Xte
Gen
Ideal Gen
4
1
230 kV Line 2
R2, X2, B2
2
3
Station‐level shunt compensation 5
Turbine‐level shunt compensation
100 MW equivalent
wind turbine
generator
NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC
Power Flow
Power Flow
• Prepare the network (line branches, transformers, generators, and the loads).
• Set the level of the loads and generations.
• For wind turbine generator:
• Type 1 and 2 – set the level of real power and reactive power, set the maximum and
minimum limits of the real and reactive power. set the level of capacitor compensation.
• Type 3 and 4 – set the level of real power and reactive power, and set the maximum and
minimum limits of real and reactive power
• Run the power flow program
• Observe the abnormal operation (over load lines, over/under voltage buses and make
adjustments as necessary.
• Repeat the process for different scenarios: load change, generation change, line disconnected
NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC
Power Flow
Data
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Power Flow
Assessment
Pre‐fault Condition Fault Event
230 kV Line 1
Infinite Bus
34.4/230 kV station transformer
R1, X1, B1
Rt, Xt.
0.6/34.4kV equivalent GSU transformer
34.5 kV collector
system equivalent
Re, Xe, Be
Rte, Xte
Ideal Gen
Gen
4
1
230 kV Line 2
R2, X2, B2
2
Station‐level shunt compensation 34.4/230 kV station transformer
230 kV Line 1
Infinite Bus
3
R1, X1, B1
Rt, Xt.
100 MW equivalent
wind turbine generator
5
Turbine‐level shunt compensation
0.6/34.4kV equivalent GSU transformer
34.5 kV collector
system equivalent
Re, Xe, Be
Rte, Xte
Ideal Gen
Gen
4
1
230 kV Line 2
R2, X2, B2
2
3
Station‐level shunt compensation 5
100 MW equivalent
wind turbine generator
Turbine‐level shunt compensation
Post‐fault Condition NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC
Power Flow
Assessment
Pre‐fault Condition Post‐fault Condition NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC
Dynamic Modeling
Wind Turbine Generator
NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC
Dynamic Modeling
Needs
G2

Dynamic models are needed to study the
dynamic behavior of power system.
Users include system planners and
operators, generation developers,
equipment manufacturers, researchers,
and consultants.

Wind Power Plant (WPP) models are
needed to study the impact of proposed
or existing wind power plants on power
system and vice versa (i.e. to keep
voltage and frequency within acceptable
limits).

Models need to reproduce WPP behavior
during transient events such as
faults/clear events, generation/load
tripping, etc.
G1
Short
Circuit
loss
of
line
new
line
Resizing
WTG
wind turbine generator
G3
NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC
Dynamic Modeling
Check List
Check List:
• Prepare the power flow model and run the power flow to ensure that the pre-fault and
post-fault condition results are acceptable and makes sense.
• For wind turbine generator:
• Prepare the wind turbine dynamic model to be represented
• If the wind turbine parameters (of the WECC generic models) are not available
from the turbine manufacturers, use the default data provided by the generic
models available from the WECC website
• If the wind turbine parameters (of the WECC generic models) of the turbines to
be simulated are available from the turbine manufacturers, use the latest model
parameters provided.
• Prepare the dynamic script of the scenario of interests and run the dynamic simulation
for the contingencies fault, loss of lines, etc.) to be investigated.
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Dynamic Modeling
Time Scale
Switching Transients
Subsynchronous Resonance
Transient Stability
Oscillatory Stability
Long-term Dynamics
10-6
10-5
10-4
.001
.01
.1
1 cycle
Source: Dynamic Simulation Applications
Using PSLF – Short Course Note – GE Energy
1
10
100
1 minute
1000
104
1 hour
TIME (seconds)
NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC
Dynamic Models
WECC Generic Models
Generic model development in PSSE/PSLF
– Complete suite of prototype models implemented
PSLF
PSSE
Model Type
Generator
Excitation / Controller
Turbine
Pitch Controller
Type 1
wt1g
Type 2
wt2g
wt2e
wt2t
wt2p
Type 3
wt3g
wt3e
wt3t
wt3p
Type 4
wt4g
wt4e
wt4t
wt4p
Generic model
Generator
El. Controller
Turbine/shaft
Pitch control
Pseudo Gov/: aerodynamics
WT1
WT1G
WT3
WT3G
WT3E
WT3T
WT3P
WT4
WT4G
WT4E
WT12T
WT2
WT2G
WT2E
WT12T
WT12A
WT12A
wt1t
wt1p
Current focus
– Model validation & refinement (e.g., freq. response)
– Identification of generic model parameters for different
manufacturers (at NREL)
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Dynamic Models
WTG Type 1 and 2
Pla nt
Fee ders
Plant
Feeders
Type 1 WTG
gene rator
Type 2 WTG
gene rator
PF control
capacitor s
Slip power
as heat loss
ac
to
dc
PF control
capacitor s
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Dynamic Models
WTG Type 3 and 4
Plant
Feeders
Type 3 WTG
Plant
Feede rs
Type 4 WTG
generator
ac
to
dc
dc
to
ac
genera tor
ac
to
dc
dc
to
ac
full power
partial power
NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC
Single Turbine
Representation
Major components of WPP Equivalent Representation:
•
•
•
•
Wind Turbine Generator (WTG) Equivalent and power factor correction (PFC) caps
Plant level reactive power compensation if applicable
Pad-mounted Transformer Equivalent
Collector System Equivalent branch.
Interconnection
Transmission Line
Station
Transformer(s)
Collector
System
Equivalent
Pad-mounted
Transformer
Equivalent
W
POI or Connection to
the Transmission
System
Plant-level
Reactive
Compensation
Wind Turbine
Generator
Equivalent
PF Correction
Shunt Capacitors
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Multiple Turbine
Representation
In some cases, multiple turbine representation may be appropriate, for example:
• To represent groups of turbines from different types or manufacturers
• To represent a group of turbines connected to a long line within the wind plant
• To represent a group turbines with different control algorithms.
Collector System Equivalent #1 considered to
be a long/weak line feeder
Pad-mounted
Transformer
Equivalent #1
WTG Equivalent #1
of Type 3 Voltage
controlled
W
Interconnection
Transmission Line
21 MW
Station
Transformer(s)
Collector System
Equivalent #2
Pad-mounted
Transformer
Equivalent #2
34 MW
W
POI or Connection to
the Transmission
System
WTG Equivalent
#2 Type 1
PF Correction
Shunt Capacitors
Pad-mounted
Transformer
Equivalent #3
Total
Output
100 MW
WTG Equivalent #3
of Type 3 PF=1
W
Collector System
Equivalent #3
45 MW
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Dynamic Model
Validation
•Prepare the simulation carefully (i.e. the correct information must be used): type of WTG,
collector system impedance, transformers, power system network, input parameters to
dynamic models, control flags settings set-up, reactive power compensation at the turbine
level or at the plant level.
•Initialize the simulation based on pre-fault condition (check v, i, p, q, f, if available).
•Recreate the nature of the faults if possible, otherwise use the recorded data to drive the
simulation and compare the measured output to the simulated output (pre-fault, during the
fault, post-fault).
•Represent the events for the duration of observation (any changes in wind, how many
turbine were taken offline due to the fault?).
•Prepare the data measured to match the designed frequency range of the software used.
•Field data is expensive to monitor, public domain data is limited, difficult to get, and quality
of data needs to be scrutinized
–
–
Anticipate errors in the measurement and make the necessary correction
The location of simulation should be measured at the corresponding monitored data.
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Dynamic Model
Validation Example
Example of Dynamic Model
Simulation versus Field Data (Type 3)
Interconnection
Transmission Line
Station
Transformer(s)
Collector
System
Equivalent
POI or Connection to
the Transmission
System
Two Turbine Representation
Pad-mounted
Transformer
Equivalent
W
91% WTGs stays “on”
after the fault.
W
9% WTGs were
dropped of line during
the fault.
Complete Representation (136 turbines)
Interconnection
Transmission Line
Station
Transformer(s)
136 WTGs were
represented
POI or Connection to
the Transmission
System
9% WTGs were
dropped of line during
the fault.
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Dynamic Model
Validation Example
Real Power Comparison
V and f
1.2
140
1.15
Q-sim-1wtg (MVAR)
Q-measured (MVAR)
Q-sim-136WTG
60
1.07
0.6
1.03
0.4
100
R e a l P o w e r (M W )
0.8
R e a c tiv e P o w e r (M V A R )
1.11
F re q u e n c y (p .u .)
V o lta g e (p .u .)
80
P-sim-1wtg (MW)
P-measured (MW)
P-sim-136WTG
120
1
Reactive Power Comparison
80
60
40
40
20
0
0
0.5
1
1.5
2
2.5
3
-20
0.99
20
V
f
0.2
0
0.95
0
0.5
1
1.5
-40
-60
0
2
0.5
1
1.5
2
2.5
3
3.5
4
Time (s)
Time (s)
Time (s)
Compare P&Q measured to P&Q
simulated
V and f
System
Generator
A
C
B
W
Input
V and f
Wind Turbine
Generator
Equivalent
Regulated
Bus
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3.5
4
Dynamic Model
Validation
Comparison against other model (Benchmarking)
•Another method to validate new model is to use another model that has been
validated against field measurement as a benchmark model.
•Several transient fault scenarios can be performed using both models, and the
results can be compared.
•Parameter Tuning
– The new model and the benchmark model may have some differences in
implementation, we may have to perform parameter tuning to match the output of
the benchmark model.
– However, one should realize that the model may not be able to match the output of
the benchmark model in all transient events.
•Parameter Sensitivity
– In order to limit the number of parameters that should be tuned, parameter
sensitivity analysis may need to be performed.
– In general important parameters are varied one by one and the sensitive
parameters can be tuned to match the bench mark model.
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Dynamic Model
Validation Example
Example of Model to Model Comparison (Type 2 “Detailed” Model vs Generic Model)
Terminal Voltage
Reactive Power
Real Power
Turbine Speed
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NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC