Parameter sensitivity of indirect universal field oriented controllers

The universal field-oriented (UFO) controller was developed to decouple flux and torque in an arbitrary synchronous flux reference frame, realizing a high degree of generality which makes the UFO controller compatible with all existing field-oriented controllers, including indirect and direct field orientation. This compatibility is useful for realizing induction motor drives over a wide speed range using both direct UFO (DUFO) control and indirect UFO (IUFO). Robust, torque control is obtained with the direct field orientation at high inverter frequencies. Generalized torque and flux expressions are derived analytically for detuned operation of the IUFO controller in an arbitrary reference frame. For a given machine, determined by its leakage factor, the expressions can be graphically represented, using only three parameters as functions of the input commands ratio. With these graphs the steady-state performance of all indirect field-oriented controllers, controlling rotor flux, airgap flux, or stator flux can be readily evaluated