The Research On Sensorless Control For PMSM Based On DTC-SVM

Direct Torque Control (DTC) becomes a very high performance AC motor control technique after vector control in recent years. The speed sensorless technique which can simplify the hardware structure and reduce the system cost is a very hotspot of current research. The combination of these two theories is one of the directions in the development of motor control technique.This thesis compares two different DTC methods: ST-DTC and DTC-SVM, based on the platform of Surface Permanent Magnet Synchronous Machine. According to the matlab simulation results, DTC-SVM is more advanced both in dynamic performance and torque chattering restraint. Moreover, the author points out that the PI controller in the torque control loop would be less efficient in the existing DTC-SVM methods. It could deteriorate the dynamic performance. This thesis proposes a new method which introduces an additional speed feedback into the torque control loop. The simulation results show that this method can make the PI controller work more efficient, and improve the system dynamic performance.After that, this thesis discusses how to realize the sensorless control with a Sliding Mode Observer (SMO). The author constructs a 4-order SMO for the speed estimation. In addition, the sign function has been changed in order to solve the chattering problem. The simulation results show that this SMO can track the varying speed, and can realize close loop control. With the modified sign function, the chattering problem can be well solved.Finally, this thesis provides principle schemes of hardware design with the TMS320F28335 chip.