Optimal flux selection for maximum torque operation of an induction machine in the flux weakening region

This paper presents a new approach to select the optimal flux of a saturated induction machine for torque maximization over the entire flux weakening region. Considering the bounded constraints on both current and voltage, the optimal flux values which maximize the torque are obtained by solving a first-order differential equation of the rotor flux. These results provide a significant increase in the available torque compared with any other conventional methods. Also the detuning effect of mutual inductance is thoroughly analyzed to relate the parameter sensitivity to the operation of the flux weakening region. As a result of the analysis, it is shown that the proposed control scheme has an inherent self-compensating property for detuned condition of mutual inductance. To reduce the detuning effect on the stator transient leakage inductance, a simple on-line algorithm to identify the stator transient leakage inductance is presented.