▁is ▁corrected ▁by ▁the ▁actu ator . ▁The ▁reference ▁pitch ▁angle , ▁which ▁comes ▁from ▁the ▁P I ▁controller , ▁goes ▁through ▁a ▁lim iter . ▁Rest rict ions ▁on ▁limits ▁are ▁very ▁important ▁to ▁maintain ▁the ▁pitch ▁angle ▁in ▁real ▁term . ▁Lim iting ▁the ▁rate ▁of ▁change ▁is ▁very ▁important ▁especially ▁during ▁fault s ▁in ▁the ▁network . ▁The ▁importance ▁is ▁due ▁to ▁the ▁fact ▁that ▁the ▁controller ▁dec ides ▁how ▁quickly ▁it ▁can ▁reduce ▁the ▁aer od ynamic ▁energy ▁to ▁avoid ▁acceleration ▁during ▁errors . ▁ ▁Other ▁controls ▁ ▁Gener ator ▁tor que ▁ ▁Modern ▁large ▁wind ▁tur b ines ▁are ▁variable - speed ▁machines . ▁When ▁the ▁wind ▁speed ▁is ▁below ▁r ated , ▁generator ▁tor que ▁is ▁used ▁to ▁control ▁the ▁rot or ▁speed ▁in ▁order ▁to ▁capture ▁as ▁much ▁power ▁as ▁possible . ▁The ▁most ▁power ▁is ▁captured ▁when ▁the ▁tip ▁speed ▁ratio ▁is ▁held ▁constant ▁at ▁its ▁optim um ▁value ▁( typ ically ▁ 6 ▁or ▁ 7 ). ▁This ▁means ▁that ▁as ▁wind ▁speed ▁increases , ▁rot or ▁speed ▁should ▁increase ▁proportion ally . ▁The ▁difference ▁between ▁the ▁aer od ynamic ▁tor que ▁captured ▁by ▁the ▁bl ades ▁and ▁the ▁applied ▁generator ▁tor que ▁controls ▁the ▁rot or ▁speed . ▁If ▁the ▁generator ▁tor que ▁is ▁lower , ▁the ▁rot or ▁acceler ates , ▁and ▁if ▁the ▁generator ▁tor que ▁is ▁higher , ▁the ▁rot or ▁slow s ▁down . ▁Below ▁r ated ▁wind ▁speed , ▁the ▁generator ▁tor que ▁control ▁is ▁active ▁while ▁the