Research on sensorless DTC of PMSM based on non-singular terminal-sliding-mode observer

A non-singular terminal-sliding-mode (NTSM) observer which contains a high-order sliding mode is introduced into a direct torque control (DTC) system of permanent magnet synchronous motor (PMSM). The proposed system uses the non-singular terminal-sliding-mode observer to obtain the back electromotive force which is used to estimate the rotor position and speed of PMSM for sensorless DTC system. Compared with the conventional sliding mode observer, NTSM observer without the low-pass filter can avoid the problem of speed estimation lag and phase lag, and contains the integral element, decreases ripple, reduces static errors. The numerous simulation results proved that the proposed algorithm improves the speed estimation precision and dynamic performance of system.