A Direct Torque Controlled Surface Mounted PMSM Drive with Initial Rotor Position Estimation Based on Structural and Saturation Saliencies

For a practical direct torque controlled (DTC) permanent magnet synchronous motor (PMSM) drive system, the information of the initial rotor position, which is usually obtained by a mechanical position sensor, is essential for starting under the full load. In order to avoid the disadvantages of using mechanical position sensors, great efforts have been made on the development of sensorless control schemes. This paper presents an initial rotor position estimation scheme for a DTC PMSM drive based on a nonlinear model of PMSM incorporating both structural and saturation saliencies. Firstly, the performance of the estimation scheme is simulated within Matlab/Simulink environment. Based on the simulation results, the estimation scheme has been investigated. Experiments have also been carried out to identify the initial rotor position of a surface mounted PMSM (SPMSM). In the experiment, specially designed high voltage pulses are applied to amplify the saturation saliencies. The peak currents corresponding to the voltage pulses are used, in combination with the inductance patterns, to determine the d-axis position and the polarity of the rotor. Finally, the presented initial rotor position identification strategy has been implemented in a sensorless DTC drive for an SPMSM. Experiments are conducted to confirm the effectiveness of the method and the performance of the drive system.