Inverter Nonlinear Error Compensation Using Feedback Gains and Self-Tuning Estimated Current Error in Adaptive Full-Order Observer

The performance of a speed-sensorless induction motor drive is poor at low-speed range. This is because the inverter nonlinear error, such as inaccurate motor parameters, deadtime, turn on/off delay, and on-state voltage drop of power switches, has strong influence on the speed estimation at low-speed range. In this paper, the feedback gains of an adaptive full-order observer are designed to guarantee the stability of speed estimation and to reduce the influence of the inverter nonlinear error on the speed estimation. In addition, the estimated current error caused by the inverter nonlinear error is identified offline. It is stored in the lookup table to compensate for the influence of the inverter nonlinear error on the speed estimation. The feasibility of the proposed method is verified by experiments.