Study On Direct Torque Control For Permanent Magnet Synchronous Motor Based On Sensorless Technology

Direct Torque Control (DTC) is a novel technology of frequency conversion after the vector control in the field of AC drive systems. Conventional DTC has some advantages, such as easy implementation and fast response, so a better dynamic performance can be obtained, but some large ripples of torque also exist. Aiming at the shortcomings of conventional DTC, a novel direct torque control system based on Space-voltage Vector Pulse Width Modulation (SVPWM) is proposed in this dissertation. The SVPWM can restrain the torque ripples.In conventional motion control systems of Permanent Magnet Synchronous Motor (PMSM), optical encoders or rotary transformer are used for this purpose. However, these additional sensors increase the costs of the system and reduce the reliability. With this background, the research based on the abolishment of these sensors to increase the reliability and decrease the costs is becoming popular.The basic theory of the PMSM DTC is systematically described in this dissertation, and the simulation system based on SVPWM is establishesd to research for PMSM DTC. To research the sensorless technology of PMSM DTC, this dissertation selects Model Reference Adaptive System (MRAS) as the observer of the rotor speed and position. Simulation results show that using MRAS to estimate the speed and position of rotor has good control effects.To design the control system, the digital signal processor TMS320F2812 produced in TI Company is used as kernel control chip, and plentiful experimental tests have been done. The simulation and the experiment results show that the PMSM DTC system designed in this dissertation not only can preserve the fast response performance of DTC, but also it can decrease the ripples of torque effectively.