Speed Sensorless Control of Induction Motors with All-Pass Filters Considering the Negative Operating Frequency

Abstract

This paper proposes all-pass filters (APFs) to enable the reversal operation for the speed sensorless control of induction motors.

Thus far, various speed sensorless control methods that employ voltage and current models have been proposed. However, the accuracy of speed estimation in the low-speed range decreases because of the use of a quasi-integrator for flux estimation. This paper employs APFs to realize highly accurate flux estimation, which is a correction method of position estimation designed for permanent magnet synchronous motors, and indicates that the conventional APF approach fails to realize the reversal operation because it is designed under the condition of positive frequency.

This paper proposes a novel APF structure and its switching strategy for the reversal operation considering negative and positive frequencies. In addition, the effectiveness of the proposed method for the speed sensorless control of induction motors is demonstrated experimentally.