A Comparative Study on Operating Characteristics of PMSM Based on Direct Torque Control in Low Speed Region

This paper compares sensorless drive characteristics of a permanent magnet synchronous motor (PMSM) in low speed region. The sensorless drive is based on direct torque control (DTC) and in order to reduce the error of speed estimation, two methods are evaluated. The first one to introduce the change rate of torque angle as compensation for speed estimation and the second one uses high frequency injection to estimate the speed and position of rotor. Simulation using MATLAB/Simulink shows the effectiveness of these two methods and experiment results also prove the practicality of these two methods.