An Improved Sensorless Control Scheme for PMSM, with Online Parameter Estimation

This paper proposes an improved sliding mode observer based on super-twisting algorithm (STA-SMO) for sensorless control scheme of permanent magnet synchronous motors. An alpha-beta axis stator current observer is built according to the back electromotive force (EMF) model after the back EMF error signal is obtained. The chattering phenomenon inherent in the traditional STA-SMO is eliminated by restricting the equivalent disturbance term to a small range, the coefficient of observer can be kept constant with speed variations. Meanwhile, because the mismatch between actual and set resistance associated with stator temperature may lead to a large estimated error and even system instability, a parallel stator resistance online estimation scheme is presented based on modified SMO. The stability of the online stator resistance estimator is proved by Lyapunov function. Compared with the traditional STASMO, the improved STA-SMO not only improves the accuracy of rotor position observation, but also effectively avoids chattering. Finally, the effectiveness of the proposed improved sensorless control scheme is verified by computer simulation.