Impact of Shaft Stiffness on Inertial Response of Fixed Speed Wind Turbines

Futurepowersystemfacesseveralchallenges，oneofthemisthehighpenetrationlevelofintermittentwindpowergeneration，providingsmallorevennoinertialresponseandbeingnotcontributingtothefrequencystability.Theeffectofshaftstiffnessoninertialresponseoffixedspeedwindturbinesispresented.Fourdifferentdrive-trainmodelsbasedonthemulti-bodysystemaredeveloped.Thesmall-signalanalysisdemonstratesnosignificantdifferencesbetweenmodelsintermsofelectro-mechanicaleigen-valuesforincreasingshaftstiffness.Thenaturalresonancefrequencyofdrive-traintorsionmodesshowsslightlydifferentvaluesbetweendampedandundampedmodels，butnosignificantdifferencesarefoundinthenumber-massmodels.Time-domainsimulationsshowthechangesintheactivepowercontributionofawindfarmbasedonafixedspeedwindturbineduringthesystemfrequencydisturbance.Thechangesinthekineticenergyduringthedynamicprocessarecalculatedandtheircontributiontotheinertiaconstantissmallandeffective.Thelargestcontributionofthekineticenergyisprovidedatthebeginningofthesystemfrequencydisturbancetoreducetherateofthefrequencychange，itispositiveforthefrequencystability.