Session 14: Generic Renewable Plant
Model Development & Validation
Variable Generation in Power Systems: A Short Course on the Integration and
Interconnection of Variable Generation Plants into Electric Power Systems
June 17-20, 2014
World Trade Center Portland
Portland OR
Robert M. Zavadil
Vice-President & Principal Consultant
620 Mabry Hood Road, Suite 300
Knoxville, Tennessee 37932
Tel: (865) 218-4600 ext. 6149
bobz@enernex.com
www.enernex.com
Role of Models in Bulk Power System Planning

Adequate simulation models are indispensable for maintaining
grid reliability
– Identify and address impact of new generator, transmission equipment
additions
– Perform planning studies to ensure system reliability at the local and
regional level

Modeling focus for grid studies
– Steady-state: power flow for voltage and reactive compensation assessment,
contingency evaluation
– Dynamic: behavior of system and individual elements during and immediately
after major system disruptions (e.g., short-circuits, loss of major generators, etc.)

Model requirements addressed in existing (and future) NERC
standards
UVIG Short Course on the
Integration and Interconnection of Variable Generation into Electric Power Systems
June 17-20, 2014
Slide 2
Context for Renewable Generation


Emphasis is on very specific models for bulk electric system
impact studies, not “models” generally
Behavior of turbines/plant under defined range conditions
– Large-signal, short-duration variations of voltage and/or frequency
– Events of BES origin, not resource-driven

Renewable plants vs. conventional generators
– Conventional generators -> synch. Machine + exciter + governor
– Wind plants comprised of many (exotic) machines, and lots of other
stuff
– Solar PV employs modern static power conversion
– “Plant” vs. “Generator” validation

Large signal validation likely necessary
UVIG Short Course on the
Integration and Interconnection of Variable Generation into Electric Power Systems
June 17-20, 2014
Slide 3
Energy Conversion Technology for Wind
Generation
1.0E-005
Wind turbine technology
Idc
VRCC OvervoltageProtection
DF
DC
DD
2
S1
Wind plant technology
– Substantial influence on behavior
as seen by the grid
»
»
»
Turbine terminal characteristics – PF
compensation, control
Distributed reactive power compensation
Reactive losses (I*I*X) within plant
Va
TL
Line-Side Power
Converter
(dc to variable-frequency and
possible variable-magnitude ac)
(dc to fixed frequency and
magnitude ac)
Ib1
C
Ic1
A
B
#2
C
#1
0.69
1.03
A
1.85 [MVA]
12.47
B
C
N
ac
dc
ac
B
Cpf
Machine-Side Power
Converter
Ia1
A
IM
Te
JB = Rotational Inertia of Blades

Tap
a b c
wg
Cpf
W
Ibr
Iar
Multimass
( IndM/c)
Te Wpu
+
282.0
TL
& other low-speed components
referred to high-speed base (kgm2)
0.66
0.66
B
Crowbar
====================
V729
Cpf
DA
0.66
Ecap
+
DB
0.7
5.0
DV733
0.001
– Conventional induction machines
– Induction machines w/ static
power converter control
– more exotic technology (e.g., direct
drive, PM synchronous generators)
– Unconventional prime mover and
mechanical system, control
Comparator
+
DC
V730
A
Ecap
dc
to
Grid
K = torsional constant
of shaft referred to high-speed
base
(Nm/rad)
Generator
(SCIM, PMSG, Low-speed PM
Generator, etc.)
TM
TE
Gearbox
P, Q (stator)
750 kW woundrotor induction
generator
JG = Rotational Inertia of Generator
and Gearbox (kg-m2
– Turbine technology is but one
aspect of model for grid studies
Shaft Speed 
Blades
P (rotor/converter)
Power
Converter
(line side)
Power
Converter
(machine side)
Switch
Control
Pgen ,Qgen

iabc(rotor)
i*abc(rotor)
Rotor Current
Computation
T*
Torque
Computation

Lookup Table
(T vs. )
UVIG Short Course on the
Integration and Interconnection of Variable Generation into Electric Power Systems
June 17-20, 2014
Slide 4
Wind Plant Components
42.8+j0
50.3
1
-2.31
Charlie
F3-12
#75014
1.01 @ 41.45
46.35
16.56
47.19
17.98
F5-8
#75026
0.97 @ 28.5
F4-8
#75020
0.966 @ 35.34
48.13
14.46
25.63
7.95
F4-10
#75021
0.969 @ 41.05
26.2
5.81
F4-12
#75022
0.971 @ 42.96
62.27
10.87
F5-10
#75027
0.97 @ 33.23
F3-15
#75018
1.025 @ 47.25
Delta
22.5-j6.51
j2.25
F4-6
#75019
0.966 @ 31.55
Substation-based
reactive compensation
Turbine-based
reactive compensation
26.2-j5.81
j2.24
F3-10
#75013
1.003 @ 37.93
47.19
13.42
-56.2
20.6
3
F3-8
#75012
0.997 @ 34.6
58.12
57.14
17.79 21.58
j2.36
59.13
58.12
16.17 20.04
F3-6
#75011
0.992 @ 31.08
60.16
59.13
14.46 18.41
j2.25
F5-2
#75025
0.975 @ 24.36
F4-4
#75017
0.969 @ 27.82
61.74
60.16
10.65 16.69
48.3
47.68
6
-5.36 8.11
j2.45
F3-4
#75010
0.987 @ 27.56
F4-2
#75016
0.974 @ 24.15
10.5+j5
F1-11
#75004
1.081 @ 35.13
49.0
9
-4.83
Plant-based
reactive compensation
j2.42
49.09
7.28
42.
8
0
j2.39
j4.55
61.74
12.91
j2.36
F3-2
#75009
0.982 @ 23.26
27.75-j4
F2-6
#75007
0.995 @ 28.11
57.14
17.03
44.92
7.58
45.4
4
-5.5
j2.34
47.6
46.98
8
8.59
-5.72
F2-4
#75006
0.99 @ 25.5
46.9
46.28
8
9.06
-6.23
46.2
45.44
8
-6.72 10.13
j4.63
48.36
7.78
F2-2
#75005
0.986 @ 23.56
PIPES TN7
#1629
1.011 @ 12.73
108.2
21.46
108.
2
-17.8
31.6
5
-8.62
j2.38
108.2
21.46
j21.99
30.91
10.17
F1-6
#75003
1.02 @ 26.71
j2.35
32.1
31.65
5
-9.92 10.95
F1-4
#75002
1.01 @ 25.04
j2.33
32.83
32.15
10.85 12.28
F1-2
#75001
0.996 @ 23.13
32.83
13.23
j2.5
39.9
39.43
6
4.53
-3.42
j2.45
39.96
5.92
j2.38
39.4
38.82
3
-2.08 3.35
38.8
2
-0.97
38.02
2.65
BUFFRIDG9
#75000
0.978 @ 20.58
P&Q
LKY NKT N7
#1625
1.031 @ 9.99
87.39
18
BUFFRID7
#1797
1.023 @ 18.7
108. 89.9
2 3
-17.8 -10.4
126.4
7
-32.52
121.1
50.16
Echo
Foxtrot
Alpha
36.8-j5
Bravo
23+j0
F4-17
#75023
0.97 @ 45.41
11.15
0.23
11.
2
0
F4-20
#75024
0.974 @ 46.57
MV OH or UG collector lines
Electrotek Concepts, Inc.
408 North Cedar Bluff Road, Suite 500
Knoxville, Tennessee 37923
1998 SUMMER PEAK LOAD MAPP MODEL
41.2-j13.4
F3-18
#75015
1.044 @ 49.37
Golf
11.2+j0
Groups of wind turbines
36.
8
-5
j2.25
F2-17
#75008
1.044 @ 42.32
Contingencies:
MAX_GEN1.DBR
UVIG Short Course on the
Integration and Interconnection of Variable Generation into Electric Power Systems
June 17-20, 2014
Slide 5
Drivers for Generic Modeling

Wind generation is no longer “invisible”; solar PV coming on
quickly
– 60+ GW of wind generation capacity installed in US
– Some areas are experiencing high saturation levels
– Continuing growth

Adequate simulation models are indispensable
– Identify and address impact of new generator additions
– Perform planning studies to maintain system reliability at the local and
regional level

The Status Quo is not sustainable or acceptable
– One-of-a-kind and proprietary models are incompatible with the current
system modeling practice in the NERC Regional Entities (Res)
– WECC launched initiative in 2005 to explore generic models for wind
generation
June 17-20, 2014
UVIG Short Course on the
Integration and Interconnection of Variable Generation into Electric Power Systems
Slide 6
WECC Generic Model Initiative


Convened by Modeling & Validation Work Group (MVWG) in
July, 2005
Original Mission Statement:
– Invest best efforts to accomplish the following:
» Develop a set of generic (non-vendor specific), non-proprietary,
positive-sequence power flow and dynamic models suitable for
representation of all commercial, utility-scale WTG technologies,
and
» Develop a set of best practices to represent wind plants using
generic models as basic building blocks
– Coordinate directly with wind manufacturers and other stakeholder
groups outside WECC
UVIG Short Course on the
Integration and Interconnection of Variable Generation into Electric Power Systems
June 17-20, 2014
Slide 7
Proposed standard models

Based on characteristics of grid interface and generator
topology
–
–
–
–
Type I – conventional induction generator
Type II – wound rotor induction generator with variable rotor resistance
Type III – doubly-fed induction generator
Type IV – full converter interface
Type I
Type II
Plant
Feeders
generator
Type III
Pla nt
Fee ders
gene rator
PF control
capacitor s
Slip power
as heat loss
Type IV
Plant
Feeders
generator
ac
to
dc
PF control
capacitor s
Plant
Feeders
generator
ac
to
dc
dc
to
ac
ac
to
dc
dc
to
ac
full power
partial power
UVIG Short Course on the
Integration and Interconnection of Variable Generation into Electric Power Systems
June 17-20, 2014
Slide 8
Technical challenges
 Wind
generator modeling versus wind plant modeling
– Wind plant “equivalencing” is required to reduce data and
computational burden
– WGMG will first concentrate on development of generic
WTG dynamic models
 Grid
versus wind disturbances
– Performance in response to grid disturbances can be
modeled reasonably well using generic models
– Performance in response to wind disturbances could
introduce complications – but note that this is less
importance in the planning environment
UVIG Short Course on the
Integration and Interconnection of Variable Generation into Electric Power Systems
June 17-20, 2014
Slide 9
Technical challenges
 Single and
multiple generator “equivalencing”
Main
station Xfm
Equivalent feeder impedance
and shunt admittance
Equivalent generator with appropriate VAR
range, depending on Pgen (*)
System
P.O.I.
Equivalent pad-mounted
transformer
Equivalent low-voltage shunt
compensation, if any
Explicit plant-level shunt
compensation, if any
System
P.O.I.
UVIG Short Course on the
Integration and Interconnection of Variable Generation into Electric Power Systems
June 17-20, 2014
Slide 10
Technical challenges
A
fundamental assumption is that a simplified
representation of the aerodynamics is required to
develop generic, non-proprietary models
 Initial investigation showed encouraging results
– For variable speed WTGs, the relationship between Pmech
and pitch angle is nearly linear over a wide range of
operating conditions
– For fixed speed WTGs, the relationship between Cp and pitch
angle is nearly linear over a wide range of operating
conditions
– WGMG is currently evaluating approaches to implement
these observations inUVIGaShort
dynamic
simulation environment
June 17-20, 2014
Course on the
Integration and Interconnection of Variable Generation into Electric Power Systems
Slide 11
Technical challenges
 Simplification
of aerodynamic characteristics
– The mechanical power (Pmech) applied to the generator is a
function of the performance factor (Cp)
Pmech = ½ × (air density) × (swept area) × Cp × (wind speed)3
– Cp is a function of blade pitch and tip-speed ratio (or just
rotor speed, if wind speed is assumed constant)
– During a typical dynamic simulation, blade pitch and tip
speed ratio vary, thus Cp and Pmech will also vary
– Cp is modeled using a look-up table or Cp matrix specific to
each WTG provided by the manufacturer usually on a
confidentiality basis
UVIG Short Course on the
Integration and Interconnection of Variable Generation into Electric Power Systems
June 17-20, 2014
Slide 12
Technical challenges
 Example
– Typical Cp curve (left) for a fixed-speed induction WTG
– The dashed magenta line shows operating points that
correspond to the steady-state power curve (right)
Pitch AngleTrajectory for
Increasing Wind Speed
Coefficient of Performance
(Cp)
Pitch Angle )
Tip-Speed Ratio ) UVIG Short Course on the
Integration and Interconnection of Variable Generation into Electric Power Systems
June 17-20, 2014
Slide 13
Generic Model Development Timeline

1st version of generic models incorporated into planning
software
– PSS/E (Siemens-PTI), PSLF (GE), Powerworld – dynamic model
libraries
– 2008 time frame




Issues, inadequacies uncovered and investigated
Effort launched to developed 2nd generation
Completed late 2013
“Approved” by WECC REMTF/MVWG in early 2014
UVIG Short Course on the
Integration and Interconnection of Variable Generation into Electric Power Systems
June 17-20, 2014
Slide 14
Generic Model Overview
UVIG Short Course on the
Integration and Interconnection of Variable Generation into Electric Power Systems
June 17-20, 2014
Slide 15
Technical Spec’s for WECC Generic Models





The models shall be non-proprietary and accessible to transmission planners
and grid operators without the need for non-disclosure agreements.
The models are expected to provide a reasonably good representation of
dynamic electrical performance of wind power plant at the point of
interconnection with the utility grid, not inside the wind power plant.
Studies of interest to be performed using the generic models are electrical
disturbances, not wind disturbances. Electrical disturbances of interest are
primarily balanced transmission grid faults, not internal to the wind power
plant, typically of 3 - 6 cycles duration. Other transient events such as
capacitor switching and loss of generation can also be simulated.
The accuracy of generic models during unbalanced events needs further
research and development. At the present time, there is no standard
guideline.
Manufacturers and model users (with guidance from the manufacturers)
shall have the ability to represent differences among generators with the
same topology by selecting appropriate model parameters.
UVIG Short Course on the
Integration and Interconnection of Variable Generation into Electric Power Systems
June 17-20, 2014
Slide 16
Tech Specs (2)






Simulations performed using these models typically cover a 20-30 second
time frame, with a ¼ cycle integration time step. Wind speed is assumed to
be constant.
The generic models shall be functional models suitable for the analysis and
simulation of large-scale power systems. Their frequency range of validity is
from dc to approximately 10 Hz.
A generic model shall include the means for external modules to be
connected to the model, e.g., protection functions.
The models shall be initialized based on the power-flow power dispatch. For
power less than rated, blade pitch will be set at minimum and wind speed at
an appropriate (constant) value. For rated power, a user-specified wind
speed (greater than or equal to rated speed) will be held constant and used
to determine initial conditions.
For type 2 WTG, a look-up table of power versus slip shall be provided.
For converter-based WTG (Type 3 and Type 4) appropriate limits for the
converter power and current shall be modeled.
UVIG Short Course on the
Integration and Interconnection of Variable Generation into Electric Power Systems
June 17-20, 2014
Slide 17
Tech Specs (3)



Power level of interest shall be primarily 100% of rated power, with wind
speed in the range of 100% to 130% of rated wind speed. However,
performance should be correct, within a reasonable tolerance, for the
variables of interest (current, active power, reactive power and power
factor), within a range of 25% to 100% of rated power.
In addition to the overall machine inertia, the first shaft torsional mode
characteristics shall be user-specified in terms of frequency, turbine inertia,
and damping factor, with calculations performed internally to determine
appropriate torsional model parameters to match the modal frequency. The
model should be able to represent one or two masses.
The models shall be applicable to strong and weak systems with a short
circuit ratio of 2 and higher at the point of interconnection. The models
should not behave erratically when the SCR is low.
UVIG Short Course on the
Integration and Interconnection of Variable Generation into Electric Power Systems
June 17-20, 2014
Slide 18
Tech Specs (4)



Aerodynamic characteristics shall be represented with an approximate
performance model that can simulate blade pitching, assuming constant
wind speed, without the need for traditional CP curves.
Shunt capacitors and any other reactive support equipment shall be modeled
separately with existing standard models.
The models shall have provision to detect voltage dip conditions and switch
to alternative control modes as necessary.
UVIG Short Course on the
Integration and Interconnection of Variable Generation into Electric Power Systems
June 17-20, 2014
Slide 19
Type I and II Generic Models*




WT1G and WT2G modules, used to represent the generator in Type 1 and
Type 2 WTGs, respectively. A standard induction machine model is used.
WT1T and WT2T modules, used to represent the turbine in Type 1 and Type
2 WTGs, respectively.
WT1P and WT2P modules, used to represent the aerodynamic (pitch)
controls for Type 1 and Type 2 WTGs, respectively. These modules were
modified to more accurately reflect pitch control action during and shortly
after a fault.
WT2E module, used to represent the rotor resistance control for Type 2
WTGs.
*from WECC Wind Power Plant Dynamic Modeling Guide, March 2014
UVIG Short Course on the
Integration and Interconnection of Variable Generation into Electric Power Systems
June 17-20, 2014
Slide 20
Type III & IV Generic Models*







REGC_A module, used to represent the generator/converter. It processes the real and
reactive current commands, and outputs real and reactive current injection into the
grid model.
REEC_A module, used to represent the WTG electrical controls. It acts on the active
and reactive power reference from the REPC_A module, with feedback of terminal
voltage and generator power output, and provides real and reactive current
commands to the REGC_A module.
REPC_A modules, used to represent the plant controller. It processes voltage and
reactive power output to emulate volt/var control at the plant level. It also processes
frequency and active power output to emulate active power control. This module
provides active reactive power command to the REEC_A module.
WTGT_A module, used to represent the turbine.
WTGAR_A module, used to represent the aerodynamic conversion (Type 3 only).
WTGPT_A module, used to represent the pitch controller (Type 3 only).
WTGTQ_A module, used to represent the torque controller (Type 3 only).
*from WECC Wind Power Plant Dynamic Modeling Guide, March 2014
UVIG Short Course on the
Integration and Interconnection of Variable Generation into Electric Power Systems
June 17-20, 2014
Slide 21
Wind Turbine Electro-mechanical Model


Allows explicit
representation of
rotating mass formed
by generator, turbine
blades (inertia, turbine
speed)
2nd-order model
includes high/low
speed shaft
connecting generator
to hub
UVIG Short Course on the
Integration and Interconnection of Variable Generation into Electric Power Systems
June 17-20, 2014
Slide 22
WT1P and WT2A – Pseudo-governor Model
for Type 1 and Type 2 WTG

Later commercial
versions of these
turbines incorporated
blade pitch control
– “Active Stall”
– Fast response to grid
disturbances


Achievable reduction in
mechanical power input
during grid disturbances
can be important for
ride-through
Neglecting pitch control
is a conservative
approach
UVIG Short Course on the
Integration and Interconnection of Variable Generation into Electric Power Systems
June 17-20, 2014
Slide 23
WT1/WT2 Pitch Control Model

Good results compared to two major Type 1 WTG vendorspecific PSCAD models
Source: Zavadil
Source: Zavadil
P-I block: Gain=1, Time Constant=0.1s
Lag Filter: Gain=2, Time Constant=3 s
Rate Limiter: Up(pitch back)=1.5, Dn(restore)=0.5
P-I block: Gain=1, Time Constant=0.001s
Lag Filter: Gain=1, Time Constant=0.01 s
Rate Limiter: Up(pitch back)=0.5, Dn(restore)=0.5
UVIG Short Course on the
Integration and Interconnection of Variable Generation into Electric Power Systems
June 17-20, 2014
Slide 24
WT1/WT2 Pitch Control Model
Good validation against MWT1000A manufacturer model
Reactive power [pu] Active power [pu]
WTG terminal voltage [pu]

200
100
Detail
Generic
0
0
1
2
3
4
5
6
7
8
9
10
200
100
Detail
Generic
0
-100
0
1
2
3
4
5
6
7
8
9
10
1.5
1
Detail
Generic
0.5
0
0
1
2
3
4
5
6
7
UVIG Short Course on the
Time [s]
Integration and Interconnection of Variable Generation into Electric Power Systems
8
9
10
June 17-20, 2014
Slide 25
WT1/WT2 Pitch Control Model
Partial success with validation against V82-AGO

0
0
Pitch
Pitch
-0.2
-0.2
-0.4
-0.4
-0.6
-0.6
-0.8
-0.8
-1
-1
-1.2
-1.2
50% output
40% voltage dip
-1.4
-1.6
-1.6
-1.8
-2
50% output
80% voltage dip
-1.4
-1.8
0
1
2
3
4
5
6
7
8
9
10
-2
0
1
2
3
4
5
6
7
8
9
10
-4
-4
Pitch
Pitch
-4.2
-4.5
-4.4
Proposed model
structure would not
capture this
behavior
-4.6
-5
-4.8
-5
-5.5
-5.2
-6
100% output
40% voltage dip
-5.4
-5.6
-6.5
100 % output
80% voltage dip
-5.8
-6
0
1
2
3
4
UVIG Short Course on the
-7
0 into Electric
1
2 Power
3 Systems
4
Integration and Interconnection of Variable Generation
5
6
7
8
9
10
5
6
7
8
June 17-20, 2014
Slide 26
9
10
WT2E – Rotor Resistance Control Model
for the Type 2 WTG



Type 1
Control of effective external
rotor resistance in WR
induction machine provides
gene rator
for limited variable speed
operation
Topology popularized by
Vestas, then Suzlon (e.g. V47,
V80, S88)
Few if any of these machines
Type 3
currently sold; many in fleet,
however.
Type 2
Pla nt
Fee ders
Plant
Feeders
gene rator
PF control
capacitor s
Slip power
as heat loss
Type 4
Plant
Feeders
gene rator
Plant
Feede rs
genera tor
ac
to
dc
PF control
capacitor s
ac
to
dc
dc
to
ac
UVIG Short Course on the
partia
l power
Integration and Interconnection of
Variable
Generation into Electric Power Systems
ac
to
dc
dc
to
ac
full power
June 17-20, 2014
Slide 27
REGC_A – Renewable Energy
Generator/Converter Model



Serves as interface to the
electrical network
Represents WR induction
machine + rotor (and
stator) side converter in
Type III, power converter
only in Type IV
Fundamentally a current
source, with some bells
and whistles
UVIG Short Course on the
Integration and Interconnection of Variable Generation into Electric Power Systems
June 17-20, 2014
Slide 28
REEC_A – Renewable Energy Electrical
Control Model for Type III and Type IV



Ultimately calculates
desired real and reactive
current
Complexity was necessary
to allow mapping of
vendor control strategies
to single model
Default parameters or
manufacturer guidance
UVIG Short Course on the
Integration and Interconnection of Variable Generation into Electric Power Systems
June 17-20, 2014
Slide 29
WTGAR_A and WTGPT_A



WTGAR_A: Aero-dynamic
Model
WTGPT_A: Pitch Control Model
These models are necessary to
capture some specific behaviors
of some commercial turbines
– e.g. active drive train damping for
mechanical oscillations
– More accurate representation of
blade pitch control during grid
disturbances

Probably not required in most
grid interconnection studies
UVIG Short Course on the
Integration and Interconnection of Variable Generation into Electric Power Systems
June 17-20, 2014
Slide 30
WTGTRQ_A – Torque Control Model

For Type III turbine
modeling, where
– operation over wide
range of or below-rated
speed is of interest
– Nuances of power control
– e.g. drive train damping
– is thought to be
important

Greatly increases model
complexity
UVIG Short Course on the
Integration and Interconnection of Variable Generation into Electric Power Systems
June 17-20, 2014
Slide 31
REPC_A –
Renewable Energy Plant Control Model

Optional model
provides for plant-level
control of real and
reactive power
– Closed-loop voltage
regulation
– Closed-loop reactive
power control
– Closed-loop real power
control (frequency
deviations)

Many large renewable
plants have auxiliary
equipment for reactive
power management
UVIG Short Course on the
Integration and Interconnection of Variable Generation into Electric Power Systems
June 17-20, 2014
Slide 32
Summary – Type I and Type II

Type 1 - Fixed-speed, induction generators
–
–
–
–

The WT1 modeling package includes 3 main models as follows:
Generator model WT1G
Drive-train model WTGT_A
Pseudo turbine-governor model WT1P
Type 2 – Induction generators with variable rotor
resistance
–
–
–
–
–
The WT2 modeling package includes 4 main models as follows:
Generator model WT2G
Rotor resistance control model WT2E
Drive-train model WTGT_A
Pseudo-governor model WT2A
UVIG Short Course on the
Integration and Interconnection of Variable Generation into Electric Power Systems
June 17-20, 2014
Slide 33
Summary – Type III and Type IV

Type 3 - Doubly-fed asynchronous generators with rotor-side
converter
–
–
–
–
–
–
–

Generator/Converter Model – REGC_A
Converter Control Model for the Generic Wind Model – REEC_A
Drive-train Model – WTGT_A
Aero-dynamics Model – WTGAR_A
Pitch-controller Model – WTGPT_A
Torque Control Model – WTGTRQ_A
Wind Power Plant Controller Model – REPC_A
Type 4 - Variable speed generators with full converter interface.
–
–
–
–
Generator/Converter Model – REGC_A
Converter Control Model for the Generic Wind Model – REEC_A
Drive-train Model – WTGT_A
Wind Power Plant Controller Model – REPC_A
UVIG Short Course on the
Integration and Interconnection of Variable Generation into Electric Power Systems
June 17-20, 2014
Slide 34
Generic PV Plant Models




Photovoltaics burst onto
scene after generic model
development for wind was
well underway
Same concepts extended to
cover PV
Some aspects of the
technology very similar (e.g.
power conversion
technology)
Still some nuances for PV,
though (e.g. prime mover)
UVIG Short Course on the
Integration and Interconnection of Variable Generation into Electric Power Systems
June 17-20, 2014
Slide 35
Built from selected wind models…



REGC_A module, used to represent the Generator/Converter
(inverter) interface with the grid.
REEC_B module, used to represent the Electrical Controls of the
inverters.
REPC_A module, used to represent the Plant Controller.
Vt
REPC_A
Vreg
Vref
Qref
Qbranch
Pref
Pbranch
Freq_ref
Freg
Plant Level
V/ Q Cont rol
Qext
Plant Level
P Cont rol
Pref
Q Cont rol
P Cont rol
Vt REGC_A
REEC_B
Iqcmd’
Ipcmd’
Iqcmd
Current
Limit
Logic
Ipcmd
Iq
Generat or
Model
Ip
Net work
Solut ion
Pqf lag
UVIG Short Course on the
Integration and Interconnection of Variable Generation into Electric Power Systems
June 17-20, 2014
Slide 36
WECC Generic Model for
Distributed and Small PV Plants

Small and distributed PV present
special challenges for modeling:
– Not directly connected to bulk
system
– Aggregate behavior of many small
plants is important to bulk system
(like wind)
– Aggregate behavior is complicated
by intermingling with industrial,
commercial, and residential loads


Bulk system tools not generally
used for distribution analysis,
and vice-versa
New dynamic aggregate “net
load” model is needed; under
exploration
UVIG Short Course on the
Integration and Interconnection of Variable Generation into Electric Power Systems
June 17-20, 2014
Slide 37
FERC Order 764



Standard, valid, generic, non-confidential, and public
power flow and stability models (variable generation) are
needed and must be developed, enabling planners to
maintain bulk power system reliability.
Make recommendations and identify changes needed to
NERC’s MOD Standards
Status:
– Report issued in May 2010; approved by NERC in June 2010
– Recommendations discussed and communicated to NERC SDTs
UVIG Short Course on the
Integration and Interconnection of Variable Generation into Electric Power Systems
June 17-20, 2014
Slide 38
FERC Order 796


Generator Verification Reliability Standards; Issued March 20, 2014
Includes NERC Standards:
– MOD-025-2 Verification and Data Reporting of Generator Real and Reactive
Power Capability and Synchronous Condenser Reactive Power Capability
– MOD-026-1 Verification of Models and Data for Generator Excitation Control
System or Plant Volt/VAr Control Functions
– MOD-027-1Verification of Models and Data for Turbine/Governor and Load
Control or Active Power/Frequency Control Functions
– PRC-019-1 Coordination of Generating Unit or Plant Capabilities, Voltage
Regulating Controls, and Protection
– PRC-024-1 Generator Frequency and Voltage Protective Relay Settings
“The generator verification Reliability Standards help ensure that verified data is
available for power system planning and operational studies by requiring the
verification of generator equipment and capability needed to support BulkPower System reliability and promoting the coordination of important protection
system settings”
UVIG Short Course on the
Integration and Interconnection of Variable Generation into Electric Power Systems
June 17-20, 2014
Slide 39
Highlights of Recommendations –
Model Validation

MOD 26 - Verification of Models and Data for Generator Excitation System Functions
(and MOD 27)
– Unit/Plant Size for Validation
– Validation of various technologies in a single plant
» Uniform VG plant (i.e. all units same technology) a single aggregate generator model
» Diverse VG plant, the plant should be represented by multiple aggregated unit models
– Validation of different control layers
– Modeling and Model Validation:
» Models should state clearly the type and the range of events they have been designed
to simulated, and the limitation of the model should be defined.
» Best approach to model validation is to use field (or test bench) measurement of
various disturbances that exercise the different control functions
» A model is valid if its dynamic behavior is close enough to reality – perfect curve
fitting is not necessary
– Future functionality
– Modeling of protection
– Issues related to the fuel source for variable generation
June 17-20, 2014
UVIG Short Course on the
– Revalidation
Integration and Interconnection of Variable Generation into Electric Power Systems
Slide 40
Approaches for Model Validation


Various methods can and have been used
All have advantages and disadvantages
UVIG Short Course on the
Integration and Interconnection of Variable Generation into Electric Power Systems
June 17-20, 2014
Slide 41
New WT3 Model – Single Turbine

Initial validation with two vendors – good news
Vestas
ABB
Source: Pourbeik
UVIG Short Course on the
Integration and Interconnection of Variable Generation into Electric Power Systems
June 17-20, 2014
Slide 42
WT4 Validation – Single Turbine

Good results for multiple manufacturers
– Differences in controls approach drove model options
Siemens
Vestas
ABB
Source: Pourbeik
UVIG Short Course on the
Integration and Interconnection of Variable Generation into Electric Power Systems
June 17-20, 2014
Slide 43
PMU Data appears ideal for validation…

First-principle quantities (i.e. voltage, grid injection
current phasors) at cycle-by-cycle resolution
– Response of wind plant to large-signal disturbances on grid
» Voltage (short-circuits)
» Frequency excursions
– PMU resolution is consistent with bandwidth of dynamic
simulations in major bulk system analysis tools (PSS/E, PSLF)

Monitoring at wind plant interconnection to BES would
provide sufficient data for characterizing performance
– Voltages and currents
– Other important quantities can be derived
UVIG Short Course on the
Integration and Interconnection of Variable Generation into Electric Power Systems
June 17-20, 2014
Slide 44
Data For Model Validation
Real Power
Terminal
Voltage
Reactive
Power
Generator
Speed
Dashed: Vendor-specific detailed
model.
Solid: WT1 model
UVIG Short Course
on the
Integration and Interconnection of Variable Generation into Electric Power Systems
June 17-20, 2014
Slide 45
…but

A specific event may be hard to replicate via simulation
– Plant model complexities
– Initial conditions/system state
– Origin and nature of system disturbance

Actual events will be asymmetrical
– PSS/E, PSLF models are positive sequence only
– Unbalanced events model very approximately
– 3-phase faults are extremely rare

Events are infrequent
– With just a few monitored locations, appropriate data for validate may be
long in coming
– Can be partially remedied by monitoring at many locations

Large number of commercial turbines to validate (60+ GW installed
capacity; ~500 plants)
UVIG Short Course on the
Integration and Interconnection of Variable Generation into Electric Power Systems
June 17-20, 2014
Slide 46
What about short-circuit contributions?


Most of the modeling focus has been on dynamic behavior in
response to large-signal disturbances
Short-circuit current contribution is an aspect of dynamic behavior
very relevant to system protection
– The effect of wind plant and interconnection on transmission line protection
schemes must be assessed
– Short circuit analysis is important part of System Impact and/or Facilities studies


Wind turbines and plants are difficult to characterize with
conventional short-circuit methods and tools
Conventional utility or industrial practice (i.e. IEEE Brown Book) does
not necessarily apply
UVIG Short Course on the
Integration and Interconnection of Variable Generation into Electric Power Systems
June 17-20, 2014
Slide 47
Challenges


(Synchronous) Generators
represented as “V-behind-Z”
for conventional short-circuit
calculations
Wind turbine technology does
not fit model
– Induction generators
– Power electronics control


–
–

–

General behavior like conventional induction
machine
Fast control of external rotor resistance may affect
even initial contribution
Doubly Fed Asynchronous Generators (Type III)
–
–

Can contribute significant fault current
Contribution decays with time (depends on network
conditions)
Induction generators with controllable rotor
resistance (Type II)
–
Wind plant characteristics
– Large number of small sources
– Extensive MV collector system
(may influence turbine shortcircuit contribution)
Squirrel-cage induction generators (Type I)
Rotor power converter will limit stator currents to
near rated value,
But, if rotor power converter is “crowbarred”,
turbine will contribute like conventional induction
machine
Full Power Conversion (Type IV)
–
–
Converter control will insure that terminal currents
stay close to rated
No “shoot-through” currents with modern converter
technology
UVIG Short Course on the
Integration and Interconnection of Variable Generation into Electric Power Systems
June 17-20, 2014
Slide 48
Some Guidance



IEEE PES working group on short-circuit contributions from wind
plants
Papers presented at IEEE GM 2012 (Detroit)
Provides initial recommendations for working around inherent
challenges
UVIG Short Course on the
Integration and Interconnection of Variable Generation into Electric Power Systems
June 17-20, 2014
Slide 49
Some help, if you are interested…

UVIG wiki for renewable
plant modeling and
more…
UVIG Short Course on the
Integration and Interconnection of Variable Generation into Electric Power Systems
June 17-20, 2014
Slide 50
Some References
1)
2)
3)
4)
5)
6)
7)
8)
9)
10)
11)
12)
13)
14)
P. Kundur, N. Balu, and M. Lauby, Power system stability and control. McGraw-Hill Professional, 1994.
P. Ledesma, J. Usaola, and J. Rodriguez, “Transient stability of a fixed speed wind farm,” Renewable Energy, vol. 28, no. 9, pp. 1341–1355,
2003.
D. Trudnowski, A. Gentile, J. Khan, and E. Petritz, “Fixed-speed wind generator and wind-park modeling for transient stability studies,” IEEE
Transactions on Power Systems, vol. 19, no. 4, pp. 1911–1917, 2004.
V. Akhmatov, H. Knudsen, A. Hejde Nielsen, J. Kaas Pedersen, and N. Kjølstad Poulsen, “Modelling and transient stability of large wind farms,”
International Journal of Electrical Power and Energy Systems, vol. 25, no. 2, pp. 123–144, 2003.
E. Muljadi, C. Butterfield, B. Parsons, and A. Ellis, “Effect of variable speed wind turbine generator on stability of a weak grid,” IEEE Transactions
on Energy Conversion, vol. 22, no. 1, pp. 29–36, 2007.
Erlich, J. Kretschmann, J. Fortmann, S. Mueller-Engelhardt, and H. Wrede, “Modeling of wind turbines based on doubly-fed induction
generators for power system stability studies,” IEEE Transactions on Power Systems, vol. 22, no. 3, pp. 909–919, 2007.
V. Akhmatov, Analysis of dynamic behaviour of electric power systems with large amount of wind power. PhD thesis, Electric Power
Engineering, Oersted-DTU, Technical University of Denmark, 2003. Available at
http://www.studenterpraest.dtu.dk/upload/centre/cet/projekter/05-va-thesis.pdf.
J. Slootweg, H. Polinder, and W. Kling, “Dynamic modelling of a wind turbine with doubly fed induction generator,” in IEEE Power Engineering
Society Summer Meeting, vol. 1, pp. 644–649 vol.1, 2001.
T. Ackermann, Wind power in power systems. John Wiley Chichester, West Sussex, England, 2005.
Manitoba HVDC Research Centre, EMTDC: Transient Analysis for PSCAD Power System Simulation, 4.2 ed., April 2005. Available at
https://pscad.com/resource/File/PSCADV421Student/EMTDC_Users_Guide_V4.2.pdf.
E. Muljadi and A. Ellis, “Validation of wind power plant models,” in 2008 IEEE Power and Energy Society General Meeting-Conversion and
Delivery of Electrical Energy in the 21st Century, pp. 1–7, 2008.
M. Behnke, A. Ellis, Y. Kazachkov, T. McCoy, E. Muljadi, W. Price, and J. Sanchez-Gasca, “Development and validation of WECC variable speed
wind turbine dynamic models for grid integration studies,” in AWEA WindPower Conference, 2007.
M. Singh and S. Santoso, “Electromechanical and Time-Domain Modeling of Wind Generators,” in IEEE Power Engineering Society General
Meeting, (Tampa, FL), June 2007.
S. Santoso, M. Singh, D. Burnham, and E. Muljadi, “Dynamic modeling of wind turbines,” tech. rep., University of Texas at Austin and National
Renewable Energy Laboratory, 2009.
UVIG Short Course on the
Integration and Interconnection of Variable Generation into Electric Power Systems
June 17-20, 2014
Slide 51
Some More References
15)
16)
17)
18)
19)
20)
21)
22)
23)
24)
25)
26)
M. Singh, K. Faria, S. Santoso, and E. Muljadi, “Validation and analysis of wind power plant models using short-circuit field measurement data,”
in IEEE Power and Energy Society General Meeting, (Calgary, AB), July 2009.
S. Santoso, M. Singh, E. Muljadi, and V. Gevorgian, “Dynamic model of full-converter PMSG wind turbine with frequency response controls,”
tech. rep., University of Texas at Austin and National Renewable Energy Laboratory, 2011.
M. Singh, M. Vyas, and S. Santoso, “Using generic wind turbine models to compare inertial response of wind turbine technologies,” in IEEE
Power and Energy Society General Meeting, (Minneapolis, MN), July 2010.
J. Slootweg and W. Kling, “Aggregated modeling of wind parks in power system dynamics simulations,” in IEEE Power Tech. Conference,
(Bologna, Italy), June 2003.
S.-K. Kim, E.-S. Kim, J.-Y. Yoon, and H.-Y. Kim, “PSCAD/EMTDC based dynamic modeling and analysis of a variable speed wind turbine,” in IEEE
Power Engineering Society General Meeting, (Denver, CO), pp. 1735 –1741, Vol.2, june 2004.
R. Gagnon, G. Sybille, S. Bernard, D. Pare, S. Casoria, and C. Larose, “Modeling and Real-Time Simulation of a doubly-fed induction generator
driven by a wind turbine,” in Proceedings of the International Conference on Power systems Transients (IPST ’05), (Montreal, QC), pp. 19–23,
2005.
R. Delmerico, N. Miller, W. Price, and J. Sanchez-Gasca, “Dynamic Modeling of GE 1.5 and 3.6 MW Wind Turbine-Generators for Stability
Simulations,” in IEEE Power Engineering Society General Meeting, (Toronto, ON), pp. 13–17, 2003.
D. Burnham, S. Santoso, and E. Muljadi, “Variable rotor-resistance control of wind turbine generators,” in IEEE Power & Energy Society General
Meeting, (Calgary, AB), pp. 1–6, July 2009.
Y. Lei, A. Mullane, G. Lightbody, and R. Yacamini, “Modeling of the wind turbine with a doubly fed induction generator for grid integration
studies,” IEEE Transactions on Energy Conversion, vol. 21, no. 1, pp. 257–264, 2006.
J. Tande, J. Eek, E. Muljadi, O. Carlson, J. Pierik, J. Morren, A. Estanqueiro, P. Sørensen, M. OMalley, A.Mullane, O. Anaya-Lara, B. Lemstrom,
and S. Uski-Joutsenvuo, “IEAWIND Annex XXI Final Technical Report: Dynamic models of wind farms for power system studies,” tech. rep., IEA
Wind, 2007. Available at http://www.ieawind.org/wnd_info/Publications_Tasks/IEA_Wind_Task_21_wind_farm_models_final%20report. pdf.
D. Hansen and G. Michalke, “Fault ride-through capability of DFIG wind turbines,” Renewable Energy, vol. 32, no. 9, pp. 1594 – 1610, 2007.
Perdana and O. Carlson, “Aggregated Models of a Large Wind Farm Consisting of Variable Speed Wind Turbines for Power System Stability
Studies,” in Proceedings of 8th International Workshop on Large-Scale Integration of Wind Power into Power Systems as well as on
Transmission Networks for Offshore Wind Farms, (Bremen, Germany), October 2009.
UVIG Short Course on the
Integration and Interconnection of Variable Generation into Electric Power Systems
June 17-20, 2014
Slide 52