Study Of AC Asynchronous Speed Sensor-less Control System

Induction Motor VVVF speed control system commonly referred to as variable speed system.As the deterioration in speed when the power does not change with the speed, the speed range is wide, either the speed is high or low, the efficiency is high.In certain technical measures taken to achieve high dynamic performance, comparable with the DC drive system.Direct torque control has a rapid development after Vector control, It is a new high-performance AC drive system.All the research of direct torque control is in the stator coordinate system of the mathematical model of AC motor, without the need for rotation transformation, it only needs the stator flux. Direct torque control not only control torque, but also control stator flux.Control structure is simple and directly with high dynamic and static performance.In this paper, first we analysis the AC induction motor dynamic mathematical model,the coordinate transformation and the transformation matrix. Introduce the basic principles and structure of direct control system,after that, simulate the system and improve the system when the speed is low.Sensor-less speed estimation is an important research direction of modern AC drive, in order to get a good speed performance, must be the introduction of speed feedback. This paper introduces the slip angular frequency calculations, focusing on ultra-Popov stability theory based on Model reference adaptive speed estimation and correction in the low speed rotor flux voltage model to improve the accuracy of speed estimation.Finally use TMS320LF2812 to complete the design of both hardware and software for AC asynchronous speed sensor-less.