▁bla de ▁pitch ▁is ▁typically ▁held ▁at ▁the ▁constant ▁angle ▁that ▁capt ures ▁the ▁most ▁power , ▁fairly ▁flat ▁to ▁the ▁wind . ▁A bove ▁r ated ▁wind ▁speed , ▁the ▁generator ▁tor que ▁is ▁typically ▁held ▁constant ▁while ▁the ▁bla de ▁pitch ▁is ▁active . ▁ ▁One ▁technique ▁to ▁control ▁a ▁permanent ▁magnet ▁synchron ous ▁motor ▁is ▁Field ▁Ori ented ▁Control . ▁Field ▁Ori ented ▁Control ▁is ▁a ▁closed ▁loop ▁strategy ▁composed ▁of ▁two ▁current ▁controllers ▁( an ▁inner ▁loop ▁and ▁outer ▁loop ▁cas cade ▁design ) ▁necessary ▁for ▁cont rolling ▁the ▁tor que , ▁and ▁one ▁speed ▁controller . ▁ ▁Constant ▁tor que ▁angle ▁control ▁ ▁In ▁this ▁control ▁strategy ▁the ▁d ▁axis ▁current ▁is ▁kept ▁zero , ▁while ▁the ▁vector ▁current ▁is ▁align ▁with ▁the ▁q ▁axis ▁in ▁order ▁to ▁maintain ▁the ▁tor que ▁angle ▁equal ▁with ▁ 9 0 o . ▁This ▁is ▁one ▁of ▁the ▁most ▁used ▁control ▁strategy ▁because ▁of ▁the ▁simplicity , ▁by ▁cont rolling ▁only ▁the ▁I q s ▁current . ▁So , ▁now ▁the ▁elect romagnet ic ▁tor que ▁equation ▁of ▁the ▁permanent ▁magnet ▁synchron ous ▁generator ▁is ▁simply ▁a ▁linear ▁equation ▁depend ▁on ▁the ▁I q s ▁current ▁only . ▁ ▁So , ▁the ▁elect romagnet ic ▁tor que ▁for ▁Id s ▁= ▁ 0 ▁( we ▁can ▁achieve ▁that ▁with ▁the ▁d - axis ▁controller ) ▁is ▁now : ▁ ▁Te = ▁ 3 / 2 ▁p ▁( λ pm ▁I q s ▁+ ▁( L ds - L q s )