Speed convergence rate-based feedback gains design of adaptive full-order observer in sensorless induction motor drives

The convergence rate of speed estimation is an important criterion to evaluate the performance of the adaptive full-order observer (AFO) in speed-sensorless induction motor drives. Based on the analysis of the speed convergence rate, the AFO with different feedback gains has corresponding shortcomings in specific operating regions. Thus, a new proposed design strategy that adopts a different set of feedback gains in different operating regions is more appropriate. In this study, the AFO below rated speed uses two optional sets of feedback gains. In the low-speed regenerative mode, a novel set of feedback gains is proposed to enhance the stability and provide a faster convergence rate of the speed estimation. In the other operating region, the traditional set of feedback gains with zero parameters is selected. The validity of the proposed method is confirmed by simulation study and experimental results. Good sensorless experimental operation, containing zero speed, is implemented.