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

The optimal flux-searching algorithms of an induction machine have reached a stage of development permitting maximum torque operation over an entire flux-weakening region. In the high-speed region, however, the sensitivity to parameter errors of an induction machine still remains a problem. This paper presents an approach that ensures maximum torque operation maintaining robustness to parameter error in the flux-weakening region. To guarantee the performance in the high speed region, the machine leakage inductance is adapted on line, based on the injection of sinusoidal current. Also, the detuned effect on machine inductance is thoroughly analyzed to relate the sensitivity of parameters to the performance of the flux-weakening region. Experimental results demonstrate that the proposed adaptation scheme effectively selects the optimal flux level regardless of variation of leakage inductance.