dr. slavomir seman, abb drives, wind ac, finland slavomir ... · need for confidentiality. a...

© ABB Group June 13, 2011 | Slide 1

Need for confidentiality. A converter manufacturer's view

Dr. Slavomir Seman, ABB Drives, Wind AC, Finland

[email protected]

Wind Integration Symposium, 16-17 June 2011, Frankfurt / Main


ABB’s discrete automation and motionDrives business unit

� Dedicated to the manufacturing and marketing of low voltage AC and DC drives, wind turbine converters and solar inverters.

� Wind turbine converters from 0.6 to 6 MW, for both doubly-fed and full converter turbine concepts (16% market share).

� Wind Turbine Converters are manufactured in Finland (Helsinki), Estonia (Jüri), China (Beijing), USA (New Berlin, WI), India (Bangalore) .


© ABB Group June 13, 2011 | Slide 3© ABB Inc. June 13, 2011 | Slide 3

� 1. Wind turbine models – definitions and purpose of study

� 2. Detailed Models – EMT – example Type 3 (DFIG)

� 3. Generic Models – RMS – example Type 4 (Full converter)

� 4. How to validate? – Model acceptance (Examples)

� 5. Summary and Conclusions

Resolving the conflict between realistic validated models & manufacturer's confidentiality


Simulation models of WT and WPP� Definition EMT model RMS models

RMS models – primarily for power system stability studies

� Standardized

� Ts typicaly ¼ cycle or shorter

� Generic

� Open source and well documented

� Not vendor specific

� Tool independent (not related to particular simulation SW)

EMT models – detail studies

� Detailed

� Ts typicaly at microsecond level

� Vendor specific

� Tool dependent

� Documented in general

� Could include ”black box” part


WT Standardized models – example IEC ongoing standardization

SOURCE IEC T88 -27 WG disseminated presentation

Reference to wind turbine terminals (part 1 - POC)

� Fundamental frequency positive sequence response as a minimum

� Is not� intended for long-term stability analysis

� intended for studies of wind speed variability

� covering power quality aspects

� for short-circuit calculations

� applicable to studies of islanded or extremely weak systems

� including wind power plant level controls and additional

� equipment (models will be defined in part 2 - PCC).


WT Standardized models – IEC standardization Models should be developed with the following specifications in mind -

continued

� Span at least the existing four categories of wind turbine technologies

� To be used primarily for power system stability studies

� - faults (balanced and unbalanced ) in the transmission grid

� - grid frequency disturbances (~ ±6% from 50/60 Hz) (discussed)

� - set-point changes

� Numerical capability to handle phase jumps

� Initialise to a steady state from power flow solutions in the full power

� range [and for voltage deviations ~ ±10%]

� Valid for dynamic voltages ~ 0…130%.

� Typical simulation time frame of interest (10…30 seconds)

� Typical integration time step not smaller than ¼ cycle


WT Standardized models – IEC standardization

Models should be developed with the following specifications in mind -continued

� Constant wind speed

� External conditions such as wind speed must be taken into account in those instances where it may significantly influence power swings

� Over-/underfrequency, overcurrent and over-/undervoltage protection included

� Turbine-generator inertia and first shaft torsional mode

� Numerically sound in both high and low (~2.5) short-circuit systems

� Independent of any provider of simulation tools

� Modular in nature

� Generic models for protection and control systems should be easily parameterized to represent any manufacturer-specific systems

� Possibility of replacing the generic control and protection system blocks with manufacturer-specific blocks

� Reactive power capability of the wind turbine


Doubly fed asynchronous generator – EMT model

10...24 kV, f = 50 Hzor 60 Hz

line coupling transformer

generatorsideconverter

grid sideconverter

gearbox

brake

pitch drive

rotor bearing

main circuit breaker for protection

converter control

wind turbine control

medium voltageswitchgear

frequency converter

main contactor for normal on-off operation

Activecrowbarprotection

asynchronous generator with slip rings1500 rpm ±30%


Black box model - DFAG

X2

X1

Sk, Xnet

132 kV/20kV 20kV/690V

DFIG WTGrid

Wind park network

ZWP

ITrpra

ITrprb

ITrprc

Upra

Uprb

Uprc

Grid + WF network

Upra

Uprb

Uprc

ITpra

ITprb

ITprc

DFIG Wind Turbine (drive train not included)


Generic model of WT 3 type model – DFAG•Generator and converter represented as controlled current source. Fits well for Full converter concept

•Can be also applied for steady state and quasi-steady state of Type 3 DFAG

•However, it is not suitable for transient analyses of DFAG under severe balanced and especially unbalanced fault!

•DFAG is directly coupled with power grid and therefore dynamic behavior of electromechanical system is to be represented by more detailed model or optionally reduced (generic) model shall be extended by additional protection logic that would represent operation of crowbar and transient behavior during unbalance

Generator/Converter model

Generator usually reduced to first order model

© ABB Group June 13, 2011 | Slide 11© ABB Inc. June 13, 2011 | Slide 11

Model validation by site test – example DFAG

Type test of a single wind turbine – typically performed by so-called “container test”.

Wind power plant compliance assessment – performed by simulation.

Tester

Photo: E2Q


DFAG – Detailed model 3-phase fault 0% Un, 180 ms

4900 5000 5100 5200 5300 5400 5500 56000

50

100

150

200

250

300

350

400

450

500

Time [ms]

Urm

s[V

]MEASURED INSTANTANEOUS VALUES AT LV SIDE OF TR

uurmsgrid

[V]

uvrmsgrid [V]

uwrmsgrid [V]


DFAG – Detailed model 3-phase fault 0% Un, 180 ms

4900 5000 5100 5200 5300 5400 5500 5600-6000

-4000

-2000

0

2000

4000

6000

8000

t [ms]

i s [A

]

comparison of measured and simulated LV TR currents

simulatedmeasured


� Full power test at 2 MW DFAG Turbine equipped by ABB converter – measurement performed at 20kV terminals by certificated test laboratory during grid code validation in Nov. 2006 vs. simulated results by DFAG RMS model.

Validation – DFAG generic model simulation vs. measurement

RMS Models � Full power test at 2 MW DFIG at 20kV terminals

� 20% Un 3 phase Voltage Dip, Full power dip lasts for 500 ms

� Voltage support starts within 1,5 - 2 cycles (30-40 ms)


� Full power test at 2 MW DFAG Turbine equipped by ABB converter – measurement performed at 20kV terminals by certificated test laboratory during grid code validation in Nov. 2006 vs. simulated results by DFAG RMS model.

RMS models � Full power test at 2 MW DFIG at 20kV terminals

� 20%Un 3 phase Voltage Dip, Full power, dip lasts for 500 ms

� Q supply starts within 2 cycles (40 ms) and required value is supplied within 150 ms

Validation – DFAG generic model vs. measurement


� 2 MW DFAG WT drive fed from ABB laboratory network under symmetrical voltage dip with 35% Un remaining voltage performed in 03/2008

Present status of advanced ABB DFAG technology performance

38 ms !

� 100% of reactive current is provided within 40 ms –comparable with Full –Scale concept

� Crowbar operates 0.5 -1 cycle (10-20 ms)!!!


Conclusions - DFAG WT model validation

� DFAG detailed EMT model can represent dynamic behavior of WT accuratelly. However, EMT model is not suitable for most of the power system stability studies and runs with very short time steps (microseconds).

� Usually EMT model is not open - source – proprietary

� Simplification (obtaining realistic RMS model) is challenging mainly due to:

�Diversity of technologies used for FRT (representation of crowbar, chopper etc.)

�DFAG is directly connected to the grid therefore oversimplification of generator and converter model may lead to unrealistic simulation model performance especially during severe grid fault simulations.

�RMS (usually positive sequence) model has limited ability to represent behavior of concept under severe unbalanced fault– possibly tripping WT or entire WF.

� DFAG Generic RMS model that represents typical performance of the wide range technologies available in the market and connected to power system is still under under development and discussion.


Full power converter concept with IG

© ABB Group June 13, 2011 | Slide 19�© ABB Inc.

�June 13, 2011 | Slide 19

Full converter detailed and generic simulation model

test.v_wind

v_wind

v_wind

Pref_max

dip_flag

ext_dip_flag

Tel

Uabc_lg_grid

flux_ref

Pref_dyn

Cselect

Uac-Q_ref

n_gen

Wind Turbine rev1_1(Aero+mech+wtc)

Scope20

RT

RT

test.Pref_max

Pref_max

Tel

Pref_dyn

n_gen

Tel_out

Initialization/Tel

flux_ref

Pref_dyn

Cselect

Uac-Q_ref

n_gen

Uabc_lg_grid

dip_flag

ext_dip_flag

Tel

Grid+Trafo+Conv+Gen

Generator/Converter model

Electrical Control Model

Q

P

Generic model “open source” (RMS) of WT 4 type model – Full power converterDetailed model “black box” (EMT) of WT

4 type model – Full power converter

© ABB Group June 13, 2011 | Slide 20�© ABB Inc.

�June 13, 2011 | Slide 20

Simulation Models – Validation of full converter WT drive by factory test


Generic WT 4 type model against full power test – Results2,5 MW, Full converter WTD under 3-ph dip, Generic model Ts = 5 ms

0 0.2 0.4 0 .6 0 .8 1 1 .2 1 .4 1 .6 1 .8 20

0 .1

0 .2

0 .3

0 .4

0 .5

0 .6

0 .7

0 .8

0 .9

1

Tim e

Vol

tage

G rid V o ltage

G eneric M ode lM eas ured va lues

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 20

0.2

0.4

0.6

0.8

1

1.2

1.4

Tim e

Cur

rent

Converter Total Current

G eneric M odelM eas ured values

0 0.2 0.4 0 .6 0 .8 1 1 .2 1.4 1 .6 1 .8 20

0.2

0.4

0 .6

0 .8

1

1.2

1.4

Tim e

Cur

rent

C onverte r A c t ive C u rren t

G eneric M ode lM eas ured va lues

0 0 .2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2-0.2

0

0.2

0.4

0.6

0.8

1

1.2

Tim e

Cur

rent

Converter Reac t ive Current

G eneric M odelM eas ured va lues

© ABB Group June 13, 2011 | Slide 22© ABB Group June 13, 2011 | Slide 22

Validation of WT 4 type model – German valid. Procedure TR4

2.5 MW, Full-converter WTD under 3-ph dip, Generic model Ts = 5 ms

0.5 1 1.5 2-0.5

0

0.5

1

1.5

2

VALIDATION ACCORDING TO GERMAN VALIDATION STANDARD FGW TR4 Terminal voltage

A B1 B2 C1 C2

measurementsimulation

© ABB Group June 13, 2011 | Slide 23© ABB Group June 13, 2011 | Slide 23

Reactive current – validation (TR4)

2.5 MW Full-converter WTD under 3-ph dip, Generic model Ts = 5 ms

0.5 1 1.5 2-0.5

0

0.5

1

1.5

2

VALIDATION ACCORDING TO GERMAN VALIDATION STANDARD FGW TR4 Reactive Current

A B1 B2 C1 C2

Time[p.u.]

Vol

tage

[p.u

.]

measurementsimulation

0.5 1 1.5 2

0

1

2


Mea

sure

d R

eact

ive

Cur

rent

A B1 B2 C1 C2

positive sequenceaverage

0.5 1 1.5 2

0

1

2

Sim

ulat

ed R

eact

ive

Cur

rent

Time [s]

A B1 B2 C1 C2

positive sequenceaverage

0.5 1 1.5 2-0.5

0

0.5


Diff

eren

ce o

f ave

rage

s (p

u)

A B1 B2 C1 C2

0.5 1 1.5 2

-1

0

1

Diff

eren

ce o

f pos

itive

seq

uenc

es (p

u)

A B1 B2 C1 C2

Time [s]

Averages difference

Area Actual Limit


Validation WT4 generic model - FRT test according TR4 RMS values comparison

Transient mode too short – definitions

Good Fit


Validation WT4 generic model - FRT test according to TR4 error evaluation

Almost not passed !


Validation WT4 generic model - FRT test according Spanish PVVC - Comparison and error evaluation


Generic model implementation Simulink vs. DigSilent PF

� Model is tool independent !

2 2.5 3 3.5 40

0.5

1

1.5

Time

Vol

tage

Terminal Voltage

Terminal Voltage, SimulinkTerminal Voltage, DigSilent

2 2.5 3 3.5 40

0.5

1

1.5

Time

Vol

tage

Reactive Power

Reactive Power, SimulinkReactive Power, DigSilent

2 2.5 3 3.5 40

0.5

1

1.5

Time

Cur

rent

Active Current

Active Current, SimulinkActive Current, DigSilent

2 2.5 3 3.5 40

0.5

1

1.5

Time

Cur

rent

Reactive Current

Reactive Current, SimulinkReactive Current, DigSilent


Conclusions - generic full-Power WT model validation

� ABB generic model based on modified WECC Type 4 model was validated - Generic model presented assumes: DC bus voltage controlled to be mantained within the limits during transients (e.g. Break chopper).

� Usually WT4 model is reduced into model of WT Network converter and simplified generator. However, different full power WT concept may bring necessity to model whole drive train.

� Model is tool independent and not vendor specific.

� Generator and converter represented as controlled current source -valid for full converter concept.

� Successfully validated against measurements following German and Spanish guideline.


Summary and conclusions� We need proper classification of WT models

� EMT – Models are vendor specific and usually tool dependent – detailed Black Box

� RMS – Generic, structure shall not be vendor specific and simulation tool independent Model definitions still ongoing – for power system stability studies, have limitations (e.g. short-circuit calculation – WT3, power quality)

� RMS - WT Standardized Models – IEC standardization ongoing (T88 -27 WG)

- based on work performed by the

- WECC Wind Generator Modeling Group

- IEEE Dynamic Performance of Wind Power Generation Working Group

� Issues under Discussion:

� Type 4 model might be tunable for types 3-4??

� - “common” LVFRT profile is emerging - (grid code definitions influence).

� - except for sustained crowbar action (type 3)?

� Validation - How to validate? Engeneer’s judgement or detailed validation (e.g. TR4) ?

� Proper validation = validation of model against measurement from full scale set-up (site or factory test).

dr. slavomir seman, abb drives, wind ac, finland slavomir ... · need for confidentiality. a...

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