t 12 wind turbine

8/9/2019 t 12 Wind Turbine

1/24

[email protected]

http://www.powerworld.com

2001 South First Street

Champaign, Illinois 61820

+1 (217) 384.6330

2001 South First Street

Champaign, Illinois 61820

+1 (217) 384.6330

Transient Stability Analysis

with PowerWorld Simulator

T12: Wind Turbine Modeling


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2© 2012 PowerWorld CorporationT12: Wind Turbine

• Over the last decadewind turbine capacityhas grown to the pointwhere they need to beexplicitly considered in

system-wide transientstability studies

Need for Wind Turbine Models

http://www.awea.org/publications/reports/AWEA-Annual-Wind-Report-2009.pdf

Growth in US Wind Capacity


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• A wind farm usually consists of many small turbines in acollector system

• Each turbine’s voltage is usually less than 1 kV (usually 600V) with a step-up transformer (usually to 34.5 kV)

• Usually, the wind farm is modeled in aggregate, but howaccurate such aggregate models are is an open question

• PowerWorld Simulator provides support of each of the fourmajor types of wind turbine models used in transientstability studies

– Type 1: Induction generator with fixed rotor resistance – Type 2: Induction generators with variable rotor resistance

– Type 3: Doubly-fed induction generators

– Type 4: Full converter generators

• New wind turbines are either Type 3 or Type 4

Wind Turbine Modeling


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• Wind turbines are represented as generators in

the power flow

– Type 1 and 2 units operate at fixed real/reactive

power with the unit supplying real power andconsuming reactive power; usually there are

compensating capacitors

– Type 3 and 4 are treated as regular PV buses

Wind Turbine Modeling:

Power Flow Solution


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• Wind Turbines do not have an “exciter”, “governor”, or“stabilizer”

• However, modeling is very analogous – Wind Machine Model = Machine Model

– Wind Electrical Model = Exciter – Wind Mechanical Model = Governor

– Wind Pitch Control = Stabilizer

– Wind Aerodynamic Model = Stabilizer

• Simulator will show wind models listed as though theyare Exciters, Governors, and Stabilizers – Obviously you should not use a synchronous machine

exciter in combination with a wind machine model and windgovernor!

Wind Generator Models


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• Old Type 1 models as induction machine – MOTOR1, GENIND

– CIMTR1, CIMTR2, CIMTR3, CIMTR4

• GE-specific Type 2 wind turbine model – GENWRI, EXWTG1, WNDTRB

• GE-specific Type 3 wind turbine model – GEWTG, EXWTGE, WNDTGE

– Detailed model for GE 1.5, 1.6 and 3.5 MW turbines

Generic Wind Turbine Models

Type 1 Type 2 Type 3 Type 4GE DYD PSS/E DYR GE DYD PSS/E DYR GE DYD PSS/E DYR GE DYD PSS/E DYR

Machine WT1G WT1G1 WT2G WT2G1 WT3G WT3G1,

WT3G2

WT4G WT4G1

“Exciter” WT2E WT2E1 WT3E WT3E1 WT4E WT4E1

“Governor” WT1T WT12T1 WT1T WT12T1 WT3T WT3T1 WT4T

“Stabilizer” WT1P W12A1 WT1P WT12A1 WT3P WT3P1


7/247© 2012 PowerWorld CorporationT12: Wind Turbine

• Voltage control of wind turbines depends on the type

• Type 1 squirrel cage induction machines- no directvoltage control

• Type 2- wound rotor induction machines with variableexternal resistance, no direct voltage control, butexternal resistance system usually modeled as an exciter

• Type 3 and Type 4- have the ability to perform voltageor reactive power control, similar to synchronousmachines. Common control modes are constant powerfactor control, coordinated control across a wind farm tomaintain a constant interconnection point voltage, andconstant reactive power control

Wind Turbine Voltage Control

Glover, Sarma, Overbye, Power System Analysis and Design



• Types 1 and 2- Induction machine models, stator windings areconnected to the rest of the network, rotor currents areinduced by the relative motion between the rotating magneticfield due to the stator currents and the rotor

• Slip is the difference between the synchronous speed and the

rotor speed, defined using motor convention as

Wind Turbine Modeling

s r

s

n nS

n

−=

• Synchronous speed is ns an rotor speed is nr , per unit

Ra jXa

+

-

Vt

I jXm

jX1

R1/S

Equivalent

circuit for asingle cage

induction

machine




Type 1 Wind Model- WT1G Power

Speed Curve

Type 1 generators usually operate with a small negative slip since thewind turbine causes the machine to spin slightly faster than

synchronous speed

Real Pow er

Real Pow er

Slip

10.950.90.850.80.750.70.650.60.550.50.450.40.350.30.250.20.150.10.050-0.05-0.1-0.15-0.2-0.25-0.3-0.35-0.4-0.45-0.5-0.55-0.6-0.65-0.7-0.75-0.8-0.85-0.9-0.95

R e a l P o w e r

2.8

2.6

2.4

2.2

2

1.8

1.6

1.4

1.2

1

0.8

0.6

0.4

0.2

0

-0.2

-0.4

-0.6

-0.8

-1

-1.2

-1.4

-1.6

-1.8

-2

-2.2

-2.4

-2.6

-2.8

Values are

calculated

between

a Slip of -1 and 1



• Type 2 models augment Type 1 by allowing for variable rotor

resistance control in the wound rotor induction generator

• By using turbine speed and electrical power output as inputs to the

control system, the wind turbine can provide a more steady power

output during wind variation

Type 2 Wind Models

Real Pow er

Real Pow er

Slip

10.950.90.850.80.750.70.650.60.550.50.450.40.350.30.250.20.150.10.050-0.05-0.1-0.15-0.2-0.25-0.3-0.35-0.4-0.45-0.5-0.55-0.6-0.65-0.7-0.75-0.8-0.85-0.9-0.95

R

e a l P o w e r

1.6

1.4

1.2

1

0.8

0.6

0.4

0.2

0

-0.2

-0.4

-0.6

-0.8

-1

-1.2

-1.4

-1.6

Real Pow er

Real Pow er

Slip

10.950.90.850.80.750.70.650.60.550.50.450.40.350.30.250.20.150.10.050-0.05-0.1-0.15-0.2-0.25-0.3-0.35-0.4-0.45-0.5-0.55-0.6-0.65-0.7-0.75-0.8-0.85-0.9-0.95

R e a l P o w e r

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0

-0.1

-0.2

-0.3

-0.4

-0.5

-0.6

-0.7

-0.8

-0.9

external

resistance = 0.05external resistance

= 0.99 pu



• Models Doubly-Fed Asynchronous Generators (DFAGs) orDoubly-Fed Induction Generators (DFIGs)

• In addition to the stator windings, rotor windings are connectedto the AC network through a converter

• Allows separate control of both real and reactive power

• Allows a much wider speed range• No electrical coupling with the turbine dynamics

• The DFAG dynamics are well approximated as a voltage-sourceconverter (VSC)

Type 3 Wind Models

V θ ∠

jX eq

High/LowVoltage

Management

1

eq X

−

Isorc

Iq

I p

E q

I

Type 3 DFAG Model, Voltage Source Converter (VSC)

Output from

reactive powercontrol system

Network



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• Physically, these models usually consist of a wound rotorinduction machine coupled with a voltage-source converterAC excitation system

• Electrical performance is dominated by the converter whichacts on a much faster time scale than transient stability level

dynamics – Machine model consists of a synthesized voltage behind a

reactance

– Rotor dynamics are not important electrically

• Modeling – Represents the generator by a machine model

– Reactive power control by an exciter model

– Mechanical control by a governor model

– Blade pitch control by a stabilizer model

Type 3 Wind Models


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• Generator 3 will be modeled using a GEWTGmachine, which models a 85 MW aggregationof GE 1.5 MW DFIGs

• Exciter model EXWTGE will be used to modelthe reactive power control of the wind turbine

• Governor model WNTDGE will be used tomodel the inertia of the wind turbine and itspitch control

• Generators 1 and 2 remain unchanged

• Open the case which has these settings,wscc_9bus_Type3WTG.pwb

Type 3 Wind Model Example

wscc_9bus_Type3WTG


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States of Exciter\EField_Gen Bus1 #1 States of Exciter\Sensed Vt_Gen Bus1 #1States of Exciter\VR_Gen Bus1 #1 States of Exciter\VF_Gen Bus1 #1

20191817161514131211109876543210

2.5

2.4

2.3

2.2

2.1

2

1.9

1.8

1.7

1.6

1.5

1.4

1.3

1.2

1.1

1

0.9

Mech Input_Gen Bus1 #1 MW Terminal_Gen Bus1 #1 Mech Input_Gen Bus 3 #1MW Terminal_Gen Bus 3 #1 Mech Input_Gen Bus 2 #1 MW Terminal_Gen Bus 2 #1

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90

85

80

75

70

65

60

55

50

45

40

35

30

25

20

15

10

5

0

V (pu)_Bus Bus1 V (pu)_Bus Bus 2 V (pu)_Bus Bus 3V (pu)_Bus Bus 4 V (pu)_Bus Bus 5 V (pu)_Bus Bus 6V (pu)_Bus Bus 7 V (pu)_Bus Bus 8 V (pu)_Bus Bus 9

20191817161514131211109876543210

1.05

1

0.95

0.9

0.85

0.8

0.75

0.7

0.65

0.6

0.55

0.5

0.45

0.4

0.35

0.3

0.25

0.2

0.15

0.1

0.05

0

• Set up Plot Definitions as desired• Click “Run transient Stability”


Wind turbine MW

Mechanical input and

terminal outputVoltage recovery

Generator 3EXWTGE states

wscc_9bus_Type3WTG


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States of Governor\Pitch_Gen '3' '1'States of Governor\Pitch Control_Gen '3' '1'States of Governor\Pitch Compensation_Gen '3' '1'States of Governor\Mech Speed_Gen '3' '1'

20191817161514131211109876543210

3

2.8

2.6

2.4

2.2

2

1.8

1.6

1.4

1.2

1

0.8

0.6

0.4

0.2

0

• During the fault the wind turbine terminal bus voltage will be quitelow. This will cause the turbine’s Low Voltage Power Logic (LVPL) toreduce the real power current to zero.


• This will cause the wind turbine pitchcontrol system to begin to pitch the blades

to reduce the mechanical power into therotor. This pitch control occurs slowly.

States of Governor\Turbine Power, Gen '1' '1'

20191817161514131211109876543210

0.158

0.156

0.154

0.152

0.15

0.148

0.146

0.144

0.142

0.14

0.138

0.136

0.134

0.132

0.13

0.128

0.126

0.124

0.122

0.12

• Once the fault is cleared, this currentis ramped back up, subject to a rate

limit.

Generator 1

Turbine Power

Pitch

wscc_9bus_Type3WTG


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• The way load dynamics are modeled often has a significant impacton the results of transient stability studies

• So far, we have mostly been looking at generator models, but manyload models are also available in Simulator

• The default (global) models are specified on the Options, Power

System Model page as constant impedance loads – Used when no other model is specified – Discussed in the Transient Stability Basics section

• Simulator makes it very easy to add complex load models

• More detailed models are added by selecting “Stability Case Info”

from the ribbon, then Case Information, Load Characteristics Models.• Models can be specified for the entire case (system), or individual

areas, zones, owners, buses or loads.

• To insert a load model, right-click and select “Insert”to display the Load Characteristic Information dialog.

Example: Impact of a Complex Load


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• Add a CLOD model to the system – Go to the Load Characteristic page

in Model Explorer

– Right-click and choose “insert” toopen the Load Characteristicinformation dialog

• In the dialog, click “System” in theElement Type box to apply theload model to all buses in thesystem

• Click “Insert” to select the modeltype. Use CLOD (see [1]), whichmodels the load as a combination oflarge and small induction motors,constant power and dischargelighting loads

Complex Load Example

Applies at the system level

Insert a CLOD model

[1] J.A. Diaz de Leon II, B. Kehrli, “The Modeling Requirements for Short-Term Voltage Stability Studies,” Power Systems

Conference and Exposition (PSCE), Atlanta, GA, October, 2006, pp. 582-588.


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• The case with these settings is wscc_9bus_Type3WTG_CLOD

• Run the simulation

• Compare the plots obtained with and without the CLOD loadmodel


States of Governor \Turbine Pow er_Gen '1' '1'

20191817161514131211109876543210

0.1510.151

0.15

0.15

0.149

0.149

0.148

0.148

0.147

0.147

0.146

0.146

0.145

0.145

0.144

0.144

0.143

0.143

0.142

0.142

0.141

0.141

0.14

0.14

0.139

V (pu)_Bus '1' V (pu)_Bus '2' V (pu)_Bus '3' V (pu)_Bus '4'V (pu)_Bus '5' V (pu)_Bus '6' V (pu)_Bus '7' V (pu)_Bus '8'V (pu)_Bus '9'

20191817161514131211109876543210

1.05

1

0.95

0.9

0.85

0.8

0.75

0.7

0.65

0.6

0.55

0.5

0.45

0.4

0.35

0.3

0.25

0.2

0.15

0.1

0.05

0

Plots after inserting system-level CLOD model

wscc_9bus_Type3WTG_CLOD


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20191817161514131211109876543210

1.1

1

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0

• On the Simulation page, increase the timefor when the line is opened from 1.12seconds to 1.155 seconds

• Open the Events tab on the Results page

• The Transient Contingency events are

there, but there are also under voltageload trip events present




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Mech Input_Gen Bus 2 #1 Mech Input_Gen Bus 3 #1 Mech Input_Gen Bus1 #1

Time (Seconds)20191817161514131211109876543210

M e c h a n i c a l P o w e r ( M W

)

160

140

120

100

80

60

40

20

0

Mech Input_Gen Bus 2 #1 Mech Input_Gen Bus 3 #1 Mech Input_Gen Bus1 #1

Time (Seconds)20191817161514131211109876543210

M e c h a n i c a l P o w e r ( M W

)

160

150

140130

120

110

100

90

80

70

60

50

40

30

20

• In the PowerWorld CLOD model, under-voltage motor tripping may beset by the following parameters – Vi = voltage at which trip will occur (default = 0.75 pu)

– Ti (cycles) = length of time voltage needs to be below Vi before trip will occur

• In the example, under voltage trips occurred at bus 5 and bus 8 when

the fault clearing time was increased to 1.155• Verify that increasing the clearing time further to 1.2 causes additional

under-voltage trips of loads at buses 6, and an over-frequency trip ofGenerator 2


cleared at 1.2 secondsGeneratorPmechcleared at 1.155 seconds



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States of Exciter\EField_Gen Bus1 #1 States of Exciter\Sensed Vt_Gen Bus1 #1States of Exciter\VR_Gen Bus1 #1 States of Exciter\VF_Gen Bus1 #1

20191817161514131211109876543210

3

2.8

2.6

2.4

2.2

2

1.8

1.6

1.4

1.2

1

0.8

0.6

0.4

0.2

0

-0.2


20191817161514131211109876543210

1.2

1.1

1

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0


Voltages

Generator

exciter states

Plots when fault is cleared at 1.2seconds

Large and Small Induction Motor Loads

experience under voltage trips at buses 5,6,

and 8 at about 2 seconds after the line opens

Generator 2 opens due to overfrequency at 4.2 seconds after the line

recloses



22/24


• CLOD model under-voltage tripping can be turned off by setting itsparameter Vi to zero

• Re-open the CLOD dialog, and set Vi to zero


• Run the simulation, clearingthe fault at 1.2 seconds

• Compare the plots

Voltages with under-

voltage tripping turned

OFF

Voltages with under-

voltage tripping turned

ON (default)



20191817161514131211109876543210

1.1

1

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0


20191817161514131211109876543210

1.2

1.1

1

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0

Set to zero to turn off

under-voltage tripping

Mech Input_Gen Bus 2 #1 Mech Input_Gen Bus 3 #1Mech Input_Gen Bus1 #1

Time (Seconds)20191817161514131211109876543210

M e c h a n i c a l P o w e r ( M W )

160

150

140

130

120

110100

90

80

70

60

50

40

30

20

10

0

-10


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• Completely asynchronous by design, called a “full convertermodel”

• The wind turbine’s output is completely decoupled from thenetwork using an AC-DC-AC converter

• This decoupling allows considerable freedom in selectingwhat type of electric machine is used – Machine could be a conventional synchronous generator,

permanent magnet synchronous generator, or squirrel cageinduction machine

– No electrical coupling with the turbine dynamics

• Represented as a VSC, like Type 3, but with Ip and Iq as directcontrol variables and without effective reactance

• Modeled – Machine/Exciter combination WT4G1/WT4E1 (PSSE)

– Machine/Exciter/Governor WT4G, WT4E, and WT4T (PSLF)

Type 4 Wind Models


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t 12 wind turbine

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