ECN publication
Transient stability of wind farms with different electrical concepts - UpWind report, Work Package 9, Task 3.1., Deliverable D9.4.1
Published by: Publication date:
ECN Wind Energy 17-2-2011
ECN report number: Document type:
ECN-E--11-003 ECN publication
Number of pages: Full text:
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As part of the EU 6th FP project "UpWind" Work Package 9.3 the dynamic response of two different electrical designs of offshore wind farms has been evaluated for symmetrical onshore grid faults. The first design uses an HVDC connection to shore based on voltage source converters and the second design uses an HVAC connection. In both cases the wind farm consists of variable speed turbines, with a with permanent magnet generator and full-power voltage source converter, grouped into 5 feeders connected to a single bus.
The simulation results of a 3-phase fault in the onshore grid have been compared for different minimum grid voltages, for different wind speeds and for different power ratings of the dc-link braking resistor.
In all cases the HVAC and HVDC connected wind farms did ride-through the 3-phase onshore grid fault while supporting the grid voltage during and shortly after the fault. The applied method of active power reduction of the HVDC connected wind farm by a fast decrease of the ac-voltage in the wind farm showed to be effective. Also it does not rely on communication links and also the WT converter control is very similar as in the HVAC connected wind farm. On theWT generator side the response to the applied faults was similar in the HVAC connected WF and in the HVDC connected WF as the full-rated WT converter effectivly decoupled the generator side from the WF grid side. The drive-train oscillations only depend a little on the operating conditions and are rapidly damped during the ramp up of the active power.
Due to the limitations of the models several aspects are not or not accurately represented in the results, such as harmonics, unbalance and the response of protection systems. However, the models can be used to design evaulate wind farm configurations and wind farm control systems. In order to make the models better applicable they should be validated with measurements or with other models.

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