The Research On Direct Torque Control Of Asynchronous Motor

Direct torque control system has a wide range of regulating speed, high precision of speed stabilizing, fast dynamic response, etc,now it is a novel control algorithm in area of AC variable speed. Direct torque control technology uses the space vector analysis method, directly to calculate and control the torque and flux of AC motor in the stator coordinate system, the calculated torque and flux respectively produced a pulse signal with schmitt moderating for a given value, then process optimal control of inverter switching status to obtain high dynamic performance of torque.This paper, from mathematical model of asynchronous motor, it systematically described the direct torque control basic theory of asynchronous motor, and detailed analysis of the relationship of space voltage vector and stator flux,motor torque. Aim at the characteristics of asynchronous motor, it analyzed and discussed the direct torque control with the space vector modulation and implement methods, including the generation of reference vector and modulation technique of space voltage vector.Based on the simulation software—Matlab / Simulink, direct torque control mathematical model of asynchronous motor is established, each modules of asynchronous motor's direct torque control system is detailed simulation analysed,simulation results show the quick response of motor torque and speed of direct torque control system, which is fully reflects the advantage of fast response of direct torque control system, and verify the feasibility of the program in theory.In order to verify the feasibility of direct torque control of asynchronous motor in practical applications,the experiment of direct torque control is researched. The system hardware adopt digital signal processor (DSP) as a controller, use highly integrated intelligent power module as inverting process, current and voltage detection respectively adopt Yaohua LEM current sensors and LEM voltage sensors, it improve accuracy of the system sampling. TMS320F2812 Asynchronous Motor direct torque control software using C programming language, the program including the AD sampling, magnetic chain torque calculation, hysteresis comparison, the flux linkage interval judgments as well as the PWM waveform generator. Finally, the program is debugged basing on the prepared platform .