摘要:
In spatial vector control of a pulse width modulation (PWM) inverter (40) adapted for variable speed drive of an induction motor (50), a difference vector ( ẽ(n)) between magnetic flux vectors (φ̃ (n), φ̃ (n-1 ))occurring during adjacent sampling periods is generated by synthesizing a zero vector (V 0 , Ṽ 7 ) and voltage vectors ( Ṽ 1 - Ṽ 6 ) in such a manner that a resultant voltage vector always includes as component a minimum unit of zero vector or voltage vector, whereby even when the angular speed of rotation of the magnetic flux changes, the switching frequency of the PWM inverter is prevented from decreasing and the current ripple is reduced.