Sensorless PMSM Speed Observer with Stator Resistance Estimation

The sensorless method presented in this paper is implemented using a modified back Electromotive Force (EMF) observer connected in cascade with a flux/current Sliding Mode Observer (SMO). Both observers are considered in an estimated γ-δ rotating reference frame instead of α-β stationary reference frame. Permanent Magnet Synchronous Motor (PMSM) stator voltages and current errors are used in flux/current observer to detect the modified back EMF errors. In sliding mode phase rotor position information is derived from these errors by means of the back EMF observer without initial rotor position knowledge. An adaptation scheme for the stator resistance is developed to improve the estimation accuracy. Simulation results show good properties of the proposed estimation approach.