Position Sensorless Direct Torque Control for Low-Speed Operation of Permanent Magnet Compressors

In sensorless drives of permanent magnet compressors under low-speed conditions, sensitivity to measurement noise remains a critical challenge. This paper presents a novel position sensorless direct torque control (DTC) strategy for low-speed operation, aimed at enhanced noise immunity and robustness. An adaptive state observer is presented to observe stator currents. Then Lyapunov-based adaptation law is employed to dynamically estimate the rotor speed and position, while the speed-dependent observer gains are incorporated to adaptively reduce the impact of measurement noise and enhance stability. Experimental results verify the effectiveness of the proposed strategy.