Direct Torque Control Sensorless on Three-Level Inverter Permanent Magnet Synchronous Motor Based on Sliding Mode Observer

The direct torque control (DTC) is a novel technology of frequency conversion after the vector control in the field of AC drive systems, which is receiving increasing attention due to the important advantages as fast torque response, simple structure and robustness against motor parameter variation when compared with other motor control techniques. Aiming at the drawbacks of high torque and stator linkage magnetic flux ripples and stator voltage and, stator current harmonic contents result in conventional direct torque controlled drive, a three-level neutral-point-clamped (NPC) inverter based on space-voltage vector pulse width modulation (SVPWM) is used to feed the permanent magnet synchronous motor (PMSM) in this paper, showing low air-gap flux and torque ripples and reduced stator current and stator voltage harmonic distortion. At the same time, a sliding mode observer (SMO) for permanent magnet synchronous motor speed and rotor position is used to realize sensorless control.