Research And Design Of The Speed Sensorless Direct Torque Control System

Direct Torque Control (DTC) becomes a very high performance AC motor control technique after vector control in recent years, which has been widely applied because of its simple structure, robust characteristics and excellent dynamic response. The speed sensorless technique which can simply the hardware structure of the variable speed system and reduce the system cost is a very hotspot of current research works. The combination of these two theories is one of the directions of the development of motor control technique.This paper builds a mathematic model for asynehronous motor and tells the basic principle of direct torque control. According to the afults of traditional direct torque control and the requirement of anasynehlonous motol’s control strategy, this paper brings forward a novel DTC system based on SVPWM in the base of traditional DTC. This novel DTC system makes SVPWM and DTC into a good combination. The motor and PWM inverter are seemed as one controlled objeet, so that the motor can obtain a constant magnetic field similar to the ideal circle and at last, solving the problems of torque, current, flux linkage ripple and inconstant switching frequency.In order to simplify the structure of alternating current speed adjusting of system, reduce the cost, and improve the system performance, the speed estimation without speed sensor is an important trend of modern AC drive. This thesis has diseussed several primary algorithm of speed estimation and emphasized on the algorithm of speed estimate based on model reference adaptive system (MRAS), and designed the algorithm of speed estimate based on model reference adaptive system.Finally, the direct torque system without speed senor is designed using digital signal proeessor (DSP).