Research On The Sensorless Operation For Direct Torque Control Of PMSM Based On DSP

With high power density, high efficiency and without excitation current, Permanent magnet synchronous motors has been widely used in AC drive system. In order to measure the speed and position of motors, rotor shaft speed sensor needs to be installed in a highly performed motor speed control system. However, there are some disadvantages of sensors, such as difficulties in installation, high costs, less reliability and not easy to maintain. In order to resolve these problems, the sensorless drive of PMSM has become a trend. PMSM control methods mainly include vector control and direct torque control. Compared with vector control, direct torque control worked directly on the electromagnetic torque, and it can form a close loop, without rotation transformation. In addition, the simple structure, dynamic torque response also constitutes the superiority of direct torque control. This paper introduces the current speed estimation scheme for PMSM, and compares the advantages and disadvantages of each scheme with thoughts of the characteristics of direct torque control, and puts forward a direct torque control system based on rotor flux speed estimation.First, mathematical models of PMSM are set up in different coordinate systems in this paper. We also introduces the theory of PMSM direct torque control and traditional pulsation problem, then a PMSM DTC system based on the expected voltage space vector modulation is proposed. Secondly, introduces the principle of the estimated speed based on the rotor flux vector angle and voltage vector modulation technology. And completed simulation study based on Matlab/simulink. The result shows that the speed estimated based on the rotor flux vector angle is correct and feasible. At the same time, the torque ripple is decreased compared with traditional DTC by producing expected voltage space vector.Finally, using TMS320F2812DSP of TI company as the main controller, the hardware of the whole system and the main software has been designed. Based on the designing results of the system, we did the experiment and analysed the experimental results which agrees with the theoretical results.