The Research On DTC System Of AC Motor Based On The Key Parameter Identification

With the high speed development of power electronics and computer technology, AC electricity transmission systems are replacing DC ones step by step. The typical technology for AC motor control has VVVF, VSVF, VC and DTC etc. Direct Torque Control (DTC) of asynchronous motors, which has been developed in the recent decades, is a power control method for motor drives. Following the vector control technique,the quick development of DTC makes itself a new high-powered AC driving technique paralleling to the vector control.In this paper, DTC of asynchronous motor was introduced based on analyzing AC motor mathematic model, and discussed the methods to observation of flux linkage, proposed measures to improve the u-i integral model. Analyzing the limitation of method to observe the stator flux linkage of traditional DTC, indicated the key approach to achieve improvement for DTC preferment is to observe the flux linkage accurately. To achieve it the author established a new observer, which substitutes one order low-pass filter for pure integration unit and adopts PI close-loop calibration unit to compensate the DC drift error of stator flux observer, the results show that it improves the performances of DTC system.The speed estimation with speed sensorless is an important trend of modern AC drive. This thesis has discussed the primary algorithm of speed estimation. On this foundation, fix the reference frame on the stator current vector and rotate synchronously(stator current orientation). The stator flux equation doesn't use integrator including stator resistance, the speed estimation arithmetic has the characteristics of small account and high estimation precision. It improves the sensorless system of AC motor.The paper reseaches the simulation model of the flux and speed identification, with the background of narrow gauge mine locomotive, experimental verifications for the control strategy and intelligent technology are given, some data have been selected. the results of simulation and experiment show the feasibility and effectiveness of the method, which are shown in this paper.