Stator-flux-based vector control of induction machines in magnetic saturation

In many variable-torque applications of induction machines, it is desirable to operate the machine in magnetic saturation, thus allowing the machine to produce higher torques. Stator-flux-based control schemes have been developed as a possible alternative method of control of induction machines. Stator-flux-based control schemes need not depend on the magnetic characteristics of the machine, and hence are potentially more robust and easier to implement in magnetic saturation than rotor-flux-based control. The authors analyze the induction machine in saturation using a nonlinear /spl pi/-model of the machine's magnetics, and develop a control scheme in the stator flux reference frame that is independent of magnetics. Experiments carried out on a 3 hp, 1800 RPM wound rotor induction machine show smooth operation of the control scheme at torque levels up to at least 4 times rated torque.