Parameter Sensitivity in Sensorless Induction Motor Drives With the Adaptive Full-Order Observer

Parameter mismatches seriously impact the stability and the rotor-speed accuracy in sensorless induction motor drives, particularly in low speed. To deal with the parameter sensitivity of the drive system with an adaptive full-order observer (AFO), this paper proposes a new unified parameter-sensitive equation that could accurately show the estimated rotor-speed error caused by all four kinds of parameter mismatches-rotor resistance, stator resistance, mutual inductance, and leakage inductance-with arbitrary feedback gains. With the proposed equation, the parameter sensitivity in the full operating region can be directly calculated, avoiding lots of simulations or experiments usually used in traditional analysis. Thus, the equation contributes to select a suitable feedback gains for a robust AFO. Moreover, based on steady-state operating point analysis, a feasible condition is proposed for judging the drive system´s stability when parameter mismatches exist. The validity of the proposed analysis will be confirmed by simulation study and experimental results.