Wind Generator Modelling for Fault RideThrough Studies Dr.-Ing. Markus Pöller

Wind Generator Modelling General Concepts

DIgSILENT Seminar: Wind Power Integration, Melbourne/Australia, 2007

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Wind Generator Modelling – General Concepts Main functional blocks of a wind generator: • • • • • • • •

Generator AC/DC converters with electrical controllers. Converter protection Other protection (over-/undervoltage, overspeed, over-/under-frequency etc.) Speed controller. Mechanical drive train Aerodynamic turbine characteristic Pitch controller

Required accuracy for stability studies: • Generator/converter/controllers/protection: high • Mechanical drive train: medium • Speed controller/Pitch controller/Aerodynamics: low DIgSILENT Seminar: Wind Power Integration, Melbourne/Australia, 2007

Doubly-Fed Induction Generator

DIgSILENT Seminar: Wind Power Integration, Melbourne/Australia, 2007

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Doubly-Fed Induction Generator

is

rs

xs

us

1: e

jωr t

xr

rr

ir

ur

xm

u s = rs i s +

ωref dΨs +j Ψ ωn dt ωn s

u r = rr i r +

ω ref − ω g d Ψr +j Ψr ω n dt ωn

DIgSILENT Seminar: Wind Power Integration, Melbourne/Australia, 2007

DFIG with Crow Bar Inserted

1:e

u s = rs i s +

jωr t

ωref dΨs +j Ψs ωn ωn dt

0 = (rr + rc )i r +

ωref − ω g d Ψr +j Ψr ωn dt ωn

DIgSILENT Seminar: Wind Power Integration, Melbourne/Australia, 2007

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Model Reduction •

Neglecting stator transients (3rd order model):

u s = rs i s + j

ω ref − ω g dΨr +j Ψr ω n dt ωn

u r = rr i r + •

ω ref Ψ ωn s

Neglecting rotor transients (1st order model):

ω ref Ψ ωn s ω ref − ω g u r = rr i r + j Ψr ωn u s = rs i s + j

DIgSILENT Seminar: Wind Power Integration, Melbourne/Australia, 2007

DFIG-Control

Pref

Qref

Vref

Qref

Ptot V

P-I

Qtot

idref

iqref

Q

P-I

idref

iqref id

id iq

P-I

P-I

md

mq

rotor-side converter

md

iq

mq

grid-side converter

DIgSILENT Seminar: Wind Power Integration, Melbourne/Australia, 2007

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Protection of Rotor-Side Converter Pref

Qref

Vref

Qref

Ptot V

P-I

Qtot

idref

iqref

Q

P-I

idref

iqref id

id

md

Crow-bar

P-I

P-I

iq

rotor-side converter

mq

md

Chopper

iq

mq

grid-side converter

Blocking DIgSILENT Seminar: Wind Power Integration, Melbourne/Australia, 2007

Converter Protection •

Protection against: – High DC-voltages – High rotor currents

•

Chopper resistance -> protects against high DC-voltages

•

Crow-bar -> protects against high DC-voltages and/or high rotor currents

DIgSILENT Seminar: Wind Power Integration, Melbourne/Australia, 2007

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DIgSILENT

Example: symmetrical Voltage Dip, 80% 1.05 1.00

Modell 3. Ordnung

0.95 0.90 0.85 0.80 0.75 0.000

0.125

0.250

0.375

[s]

0.500

HV: Spannung in p.u. MV: Spannung in p.u. MV: Voltage, Magnitude in p.u.

75.00 50.00 Modell 3. Ordnung

25.00 0.00 -25.00

Modell 3. Ordnung

-50.00 0.000

0.125

0.250

0.375

[s]

0.500

0.125

0.250

0.375

[s]

0.500

0.125

0.250

0.375

[s]

0.500

Cub_1\PCC PQ: Wirkleistung in MW Cub_1\PCC PQ: Blindleistung in Mvar Cub_1\PCC PQ: Wirkleistung in MW Cub_1\PCC PQ: Blindleistung in Mvar

1.50 1.00 0.50 0.00 -0.50 -1.00 -1.50 0.000 Current Measurement: Läuferstrom, Phase L1 in kA Current Measurement: Läuferstrom, Phase L1 in kA

1.25 1.00 0.75 0.50 0.25 0.00 0.000 Current Measurement: Läuferstrom, Betrag des Raumzeigers in kA Current Measurement: Läuferstrom, Betrag des Raumzeigers in kA

DFIG

DIGSILENT

DFIG-WEA

Comparison of Model of 3rd and 5th order

Voltage sag 80%

Date: 6/19/2007 Annex: 1 /1

DIgSILENT Seminar: Wind Power Integration, Melbourne/Australia, 2007

DIgSILENT

Example: symmetrical Voltage Dip, 80% 1.50 1.00 0.50 0.00 -0.50 -1.00 -1.50 0.000

0.125

0.250

0.375

[s]

0.500

0.125

0.250

0.375

[s]

0.500

0.125

0.250

0.375

[s]

0.500

Current Measurement: Läuferstrom, Phase L1 in kA Current Measurement: Läuferstrom, Phase L1 in kA

1.25

1.00

0.75

0.50

0.25

0.00 0.000 Current Measurement: Läuferstrom, Betrag des Raumzeigers in kA Current Measurement: Läuferstrom, Betrag des Raumzeigers in kA

1.0375 1.0250 1.0125 1.0000 0.9875 0.9750 0.9625 0.000 GS-G1: Voltage Phasor, Magnitude in p.u. GS-G1: Voltage, Magnitude in p.u.

DIGSILENT

DFIG Comparison of Model of 3rd and 5th order

DFIG Läufer Voltage sag 80%

Date: 6/19/2007 Annex: 1 /2

DIgSILENT Seminar: Wind Power Integration, Melbourne/Australia, 2007

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DIgSILENT

Example: symmetrical Voltage Dip, 20% 1.20 1.00 0.80 0.60 0.40 0.20 0.00 0.000

0.125

0.250

0.375

[s]

0.500

0.125

0.250

0.375

[s]

0.500

0.125

0.250

0.375

[s]

0.500

0.250

0.375

HV: Spannung in p.u. MV: Spannung in p.u. MV: Voltage, Magnitude in p.u.

80.00

Modell 3. Ordnung

40.00 0.00 -40.00 -80.00

Modell 3. Ordnung

-120.00 0.000 Cub_1\PCC PQ: Wirkleistung in MW Cub_1\PCC PQ: Blindleistung in Mvar Cub_1\PCC PQ: Wirkleistung in MW Cub_1\PCC PQ: Blindleistung in Mvar

3.00 2.00 1.00 0.00 -1.00 -2.00 0.000 Current Measurement: Läuferstrom, Phase L1 in kA Current Measurement: Läuferstrom, Phase L1 in kA

3.00 2.00 1.00 0.00 -1.00 0.000

0.125

[s]

0.500

Current Measurement: Läuferstrom, Betrag des Raumzeigers in kA Current Measurement: Läuferstrom, Betrag des Raumzeigers in kA

DFIG Model

DIGSILENT

DFIG-WEA

Comparison of models 3rd and 5th order

Voltage sag 20%

Date: 6/19/2007 Annex: 1 /1

DIgSILENT Seminar: Wind Power Integration, Melbourne/Australia, 2007

DIgSILENT

Example: symmetrical Voltage Dip, 20% 3.00

2.00

1.00

0.00

-1.00

-2.00 0.000

0.125

0.250

0.375

[s]

0.500

0.125

0.250

0.375

[s]

0.500

Current Measurement: Läuferstrom, Phase L1 in kA Current Measurement: Läuferstrom, Phase L1 in kA

3.00

2.00

1.00

0.00

-1.00 0.000

Current Measurement: Läuferstrom, Betrag des Raumzeigers in kA Current Measurement: Läuferstrom, Betrag des Raumzeigers in kA

1.15

1.10

0.017 s 0.004 s

0.172 s 0.162 s

Y = 1.070 p.u.

1.05

1.00

0.95

0.90 0.000

0.125

0.250

0.375

[s]

0.500

GS-G1: Voltage Phasor, Magnitude in p.u. GS-G1: Voltage, Magnitude in p.u.

DIGSILENT

DFIG Model Comparison of models 3rd and 5th order

DFIG Läufer Voltage sag 20%

Date: 6/19/2007 Annex: 1 /2

DIgSILENT Seminar: Wind Power Integration, Melbourne/Australia, 2007

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DIgSILENT

Example: 2-phase fault 1.25 1.00 0.75 0.50 0.25 0.00 -0.25 0.000

0.125

0.250

0.375

[s]

0.500

0.125

0.250

0.375

[s]

0.500

0.125

0.250

0.375

[s]

0.500

0.250

0.375

[s]

0.500

HV: Spannung in p.u. MV: Spannung in p.u. MV: Line-Ground Positive-Sequence Voltage, Magnitude in p.u.

200.00 100.00

Modell 3. Ordnung

0.00 Modell 3. Ordnung

-100.00 0.000

Cub_1\PCC PQ: Wirkleistung in MW Cub_1\PCC PQ: Blindleistung in Mvar Cub_1\PCC PQ: Wirkleistung in MW Cub_1\PCC PQ: Blindleistung in Mvar

3.75 2.50 1.25 0.00 -1.25 -2.50 0.000

Current Measurement: Läuferstrom, Phase L1 in kA Current Measurement: Läuferstrom, Phase L1 in kA

3.00 2.00 1.00 0.00 -1.00 0.000

0.125 Current Measurement: Läuferstrom, Betrag des Raumzeigers in kA Current Measurement: Läuferstrom, Betrag des Raumzeigers in kA

DFIG Model

DIGSILENT

Comparison of model 3rd and 5th ofrder

DFIG-WEA 2-phase fault

Date: 6/19/2007 Annex: 1 /1

DIgSILENT Seminar: Wind Power Integration, Melbourne/Australia, 2007

DIgSILENT

Example: 2-phase fault 3.75

2.50

1.25

0.00

-1.25

-2.50 0.000

0.125

0.250

0.375

[s]

0.500

0.250

0.375

[s]

0.500

Current Measurement: Läuferstrom, Phase L1 in kA Current Measurement: Läuferstrom, Phase L1 in kA

3.00

2.00

1.00

0.00

-1.00 0.000

0.125 Current Measurement: Läuferstrom, Betrag des Raumzeigers in kA Current Measurement: Läuferstrom, Betrag des Raumzeigers in kA

1.20 1.15 1.10

0.023 s 0.010 s

0.136 s 0.129 s 0.122 s

Y = 1.070 p.u.

1.05 1.00 0.95 0.90 0.000

0.125

0.250

0.375

[s]

0.500

GS-G1: Voltage Phasor, Magnitude in p.u. GS-G1: Line-Ground Positive-Sequence Voltage, Magnitude in p.u.

DIGSILENT

DFIG Model Comparison of model 3rd and 5th ofrder

DFIG Läufer 2-phase fault

Date: 6/19/2007 Annex: 1 /2

DIgSILENT Seminar: Wind Power Integration, Melbourne/Australia, 2007

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Discussion

•

“Stability model” (model of 3rd order) produces results with sufficient accuracy if rotor converter protection doesn’t trigger.

•

But: “Stability model” (model of 3rd order) is not able to predict max. rotor currents and max. DC-voltage correctly, hence it cannot predict rotor protection action.

•

Crow-bar insertion has substantial influence on voltage support during fault and hence on fault ride-through capability of a wind farm.

DIgSILENT Seminar: Wind Power Integration, Melbourne/Australia, 2007

Conclusion •

For analysing fault ride through capability of DFIGs, detailed EMT models are required.

•

PowerFactory allows modelling a wind farm by an EMT model (typical step-size 0,1 ms) and the rest of the system (e.g. NEM-system) by a stability (RMS)-model (typical step size 10ms)

•

Approach has successfully been applied in wind farm integration studies in Australia (e.g. Cape Bridgewater)

•

For stability impact studies, studying large number of wind-farms, simplified “stability model” is sufficient.

DIgSILENT Seminar: Wind Power Integration, Melbourne/Australia, 2007

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