Investigating the Impact of Removing the Undervoltage Protection for Wind Turbines Presented by KHALED ALGHADHBAN Chalmers University of Technology School of Electric Power Engineering Göteborg, Sweden 2003 NORPIE 2004 Trondheim, Norway

OUTLINEConclusion Case Studies Introduction Generator Protection Overview

Introduction background  The standard size has increased from 20 kW to 2 MW.  The production cost: wind =coal based on condensation

Introduction background

 24 GW of wind turbines in Europe make utilities concerned about voltage dips  It is required and essential to disconnect the wind turbine for serious grid faults  whenever possible, the turbine should stay online

Introduction background  The wind turbine undervoltage setting up to now in Sweden is 85% for 0.5 seconds.  ok for few turbines, serious if 100 MW of wind production is lost, then could lead to voltage collapse.

Introduction Purpose of Paper  Not tripping for undervoltage does not damage the wind turbine generator in itself, an idea is to trip only for overcurrent and overspeed.  The purpose of this paper is to study the impact on a small grid as well as for the wind turbines if the undervoltage protection is removed and the protection function is taken over by overspeed and overcurrent protections.

Generator Protection Overview Protection Function Trip Value (setting) Frequency Low= 47.5 Hz High= 51 Hz Overvoltage High1= 110% High2= 125% 110% of nominal speed Undervoltage Low1= seconds delay Low2= seconds delay

Generator Protection Overview Overcurrent (Inverse time)

Case Studies using SIMPOW®  First Case: 70% Voltage Dip on Utility Bus with 600ms Duration  Second Case: Different Voltage Dips with Different Durations

Case Studies First Case (Voltage Dip at Utility bus) Measurements

Case Studies First Case (High Wind) Existing Settings (with undervoltage protection)

Case Studies First Case (High Wind) New Settings (Without Undervoltage protection)

Case Studies First Case (Low Wind) Existing Settings (with Undervoltage Protection)

Case Studies First Case (Low Wind) New Settings (without Undervoltage Protection)

Case Studies Second Case  Different Voltage Dips with Different Durations  High Wind Speed  Low Wind Speed

Case Studies Second Case (High Wind) ms TRIPPYYYYNNNNN Peak Q w= ms TRIPPYYYYYNNNN W= ms TRIPPYYYYYNNNN W= ms TRIPPYYYYYYNNN W=

Case Studies Second Case (High Wind)

Case Studies Second Case (Low Wind) ms TRIPPNNNNNNNNN Peak Q Max P ms TRIPPNNNNNNNNN Peak Q Max P ms TRIPPNNNNNNNNN Peak Q Max P ms TRIPPNNNNNNNNN Peak Q Max P

Conclusion  Tripping for undervoltage for a wind turbine can be safely avoided and thus unnecessary loss of wind power production can be avoided.  Overcurrent and overspeed protection can take over the undervoltage function.  At low wind speeds hardly any dips caused the turbine to trip if the undervoltage protection was removed. For high wind speeds, the overcurrent protection tripped the turbine for dips lower than 40-60% depending on the dip magnitude. Using a 10% overspeed limit, generally made the overcurrent to trip before the overspeed.

QUESTIONS Presented by KHALED ALGHADHBAN Investigating the Impact of Removing the Undervoltage Protection for Wind Turbines