| The closed-loop of speed is essential in the high-performance direct torque control system.These sensors such as the photoelectric pulse encoder had been used for the feedback of speed signal in the traditional DCT system. However, installing the speed sensor brought about series of problems such as lower reliability,bigger volume and higher cost. The direct torque control technology based on speed sensorless had become the current researching hotspot of AC drive.A new kind of speed identification method which was based on a stator magnetic field oriented and neurons theory in the DTC system was presented in this dissertation against the deficiencies of the prevenient speed identification method. Asynchronous motor mathematical model was established in statorα-βcoordinate system according to the new method based on DTC theory, and stator current equation of state could be gained according to this model and transformed into neurons with five input nodes—one output node, an adaptive identification modules driverred by stator current was derivated. According to speed identification formula, speed could be estimated fleetly and transferred back to adjust model whose parameters could be modified, and the adjustment made them approximate to the real value. The simulation results compared with the conventional speed identification method based on neurons in the matlab/sinulink using parameters of 37kW asynchronous motors showed the identified speed could accurately track the actual speed, perform good dynamic response,eliminate the speed settlement of the traditional methods and the stator flux is rounder. In particular, when the parameters of system changed suddenly, the system was of great robustness and easy to application.A digital system for speed sensorless DTC system had been designed based on TMS320F2812 digital processor which is produced by the TI company. The improved speed-identification algorithm was implemented in this system against the traditional DTC system. There was a introduction to the hardware and software of the system and some programs. |
