Sensorless vector control of interior permanent magnet synchronous motor drives at very low speed without signal injection

In recent years, sensorless control of interior permanent magnet synchronous motors (IPMSMs) has been a research area of significant interest. A multitude of solutions have been proposed for sensorless operation but most of them fail to deliver satisfactory performance in the low speed region. This study describes the active flux concept, which is used to design a rotor position and speed observer. The proposed observer does not require any speed adaptation. Hence, speed estimation errors especially in the low speed region do not affect the performance of the observer. An online stator resistance estimator is proposed to further enhance the low speed operation of the observer. The proposed observer is capable of delivering accurate state estimation at very low speeds including standstill without signal injection. Simulation and experimental results at 0 and 5 rpm confirm the effectiveness of the proposed sensorless approach.