1. SINTEF Energy Research 1 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

2. SINTEF Energy Research 2 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

3. SINTEF Energy Research 3 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?

4. SINTEF Energy Research 4 IEC 61400-21 ed2 (CD 2006)

5. SINTEF Energy Research 5 Laboratory test setup Generator Motor

6. SINTEF Energy Research 6 Short circuit emulator only (IG discon.) Instantaneous voltage Fundamental positive sequence voltage Small dip setup Large dip setup 55% 90%

7. SINTEF Energy Research 7 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)

8. SINTEF Energy Research 8 Comparison (small dip, ride through succeeded) Fundamental positive sequence Voltage Current Active power Reactive power --- Measured --- Simulated

9. SINTEF Energy Research 9 Comparison (large dip, ride through failed) Fundamental positive sequence Voltage Current Active power Reactive power --- Measured --- Simulated

10. SINTEF Energy Research 10 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 !

11. SINTEF Energy Research 11 Large dip, 86% torque (ride through succeeded) Large dip, 87.5% torque (ride through failed) Fundamental positive sequence Current Voltage --- Measured --- Simulated Voltage Current

12. SINTEF Energy Research 12 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)

13. SINTEF Energy Research 13 Small voltage dip measurements Voltage Current Instantaneous Fundamental positive sequence

14. SINTEF Energy Research 14 Large voltage dip measurements Voltage Current Instantaneous Fundamental positive sequence

15. SINTEF Energy Research 15 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