In-depth research on direct torque control of permanent magnet synchronous motor

The direct torque control theory has achieved great success in the control of induction motor. However, in the DTC drive system of permanent magnet synchronous machine (PMSM) proposed a few years ago, there are many basic theoretical problems that must be clarified. This paper describes an investigation about the effect of the zero voltage space vectors in the DTC system of PMSM and points out that if using the zero voltage space vectors rationally, not only the DTC system can be driven successfully but torque ripple is reduced and performance of the system is improved. This paper also studies the sensorless technique in the DTC system of PMSM and configures the DTC system of PMSM with sensorless technique including zero voltage space vectors. Numerical simulations and experimental tests have proved the theory correct. In the sensorless condition, the DTC system of PMSM is wide-ranged speed adjusting, and the ratio of speed adjustment is 1:100.