Fault ridethrough testing of wind turbines

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Fault ride-through testing of wind turbines

• Presented by Olve Mo
• Paper co-authors John Olav Tande
• Leif Warland
• Kjell Ljøkelsøy
• SINTEF Energy Research, Norway

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Background

• Grid codes now require wind farms to ride-through
  temporarily grid voltage dips (faults).
• Full scale tests against different grid codes is
  not practical
• IEC 61400-21 ed2 (CD 2006) presents a
  standardized test for characterizing the wind
  turbine response to a voltage dip
• The result of the standardized tests can be used
  to validate a numerical simulation model of the
  wind turbine.
• The validated simulation model can then to be
  used to check compliance to different grid codes

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Scope

• Can numerical simulations models be used to
  accurately predict ride-through capabilities of a
  fixed speed, direct connected induction
  generators?
• Will the results of the new standardized test
  provide useful results for validation of such
  models?

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IEC 61400-21 ed2 (CD 2006)
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Laboratory test setup
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Short circuit emulator only (IG discon.)
Small dip setup
Large dip setup
Instantaneous voltage
Fundamental positive sequence voltage
90
55
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Numerical simulation model

• Model of laboratory set-up
• PSCAD/EMTDC Simulation tool (Instantaneous value,
  time domain simulation tool)
• Standard PSCAD induction machine model used (7th
  order model)

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Comparison (small dip, ride through succeeded)
--- Measured --- Simulated
Active power
Voltage
Fundamental positive sequence
Reactive power
Current
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Comparison (large dip, ride through failed)
Active power
Voltage
--- Measured --- Simulated
Fundamental positive sequence
Reactive power
Current
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Determination of ride-through limit

• Reapplied large voltage dip with successively
  reduced torque setting until the generator was
  able to ride-through the voltage dip
• Very promising result for the use of simulations
  to assess fault ride through capabilities !

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Large dip, 86 torque (ride through succeeded)
Large dip, 87.5 torque (ride through failed)
--- Measured --- Simulated
Voltage
Voltage
Fundamental positive sequence
Current
Current
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Conclusions

• Simulations and laboratory measurements shows
  excellent agreement
• Validated simulation models can accurately
  predict fault ride-through capability of direct
  grid connected induction generators
• Test results from a standard test will be useful
  for model validation provided detailed data of
  both wind turbine and test equivalent are found
  in the test report.
• More advanced wind turbines may be more
  challenging (doubly fed induction generator,
  power electronic converter control, fast pitch
  systems, fast acting digital protection systems)
• Is it possible to get desired accuracy using
  simpler phasor type models ?? (e.g. PSSE)

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Small voltage dip measurements
Current
Voltage
Instantaneous
Fundamental positive sequence
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Large voltage dip measurements
Current
Voltage
Instantaneous
Fundamental positive sequence
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Work experiences

• Voltage and current dynamics is very sensitive to
  grid / short circuit impedance parameters (R and
  X) and not only the generator model parameters
• Saturation effects in the generator causes
  deviations between measurements and simulations
  (due to high current)
• AC current transformers saturated. Had to be
  replaced by DC current sensors