Enhancement sensorless control system for PMSM drives using square-wave signal injection

This paper enhances a very recent sensorless control method in wide-speed range including zero speed, which is based on a square wave voltage injected in d axis and the measurement of corresponding induced stator current variations in the middle of sampling period. This method realizes a high bandwidth control by eliminating the usual LPFs employed in specific signal processing, it uses only two current sensors and is very robust to parameter variations. The contributions of this paper are focused to improve the rotor position estimation for fast dynamic variation of the stator currents, e.g., in cases of step load torque or step speed reference. Also, a simple but efficient method to filter the feedback currents is introduced. The simulations results prove the enhanced sensorless control method in wide speed range, with step load torque.