The universal field oriented controller

This paper synthesizes and develops a universal field oriented (UFO) controller for induction machines. The UFO controller decouples flux and torque in an arbitrary flux reference frame. Due to its high degree of generality the UFO controller lends itself to be fully compatible with all existing field oriented controllers, indirect as well as direct field orientation. As a consequence, the digital implementation of the UFO scheme is identical for all induction motor drives enabling the usage of identical hardware and software. Examples of UFO control block diagrams for different field oriented controllers are presented. The execution time of the UFO algorithm is compared with the classical rotor flux field orientation method when using a high speed digital signal processor. Further, this paper indicates that the flexibility of changing the flux reference frame can extend the stability region of the drive especially at high speed during flux weakening. Detuning problems in field orientation are handled in an optimal manner for each field oriented controller by proper selection of the model of the induction machine and its reference frame.