Research On Speed Sensorless Vector Controlsystem For AC Motor

In modern industrial production, various production processes are mostly realized byproduction machinery driven by motors, in which electricity usage of AC motors accounts forabout85%of the total volume, showing the breadth of its application and its important role in thenational economy. Therefore, improving the performance of AC speed control system has becomea research focus.For high dynamic performance, we should start from the dynamic model of AC motors.Vector control theory achieves decoupling between the AC motor stator current excitation andmagnetic vectors by coordinates transformation, and the component and the torque component canbe independently controlled so that AC Control of the motor is equivalent to DC motor controlprocess. Sensorless technique does not rely on the detection of speed sensor rotational speed, butthe speed information indirectly acquired through other non-obtaining speed information. It gainsconsiderable control, while improves the exchange control System reliability and reduces costs atthe same time.AC motors are divided into two major categories: induction motors and synchronous motors.This paper studies the system of sensorless control of asynchronous AC motors and permanentmagnet Synchronous motor based on Basic speed sensor vector control system. Althoughstructures are different, they are both suitable for vector control. Firstly, the article gave asummary of AC variable speed technique development and sensorless control technique status,and listed the pros and cons of every method. Secondly, the article introduces the coordinatetransformation theory, and gives analysis of Its mathematical model under three coordinatessystems in order to lead to vector control theory, and elaborates on mathematical model of therotor flux oriented vector control system, the basic equations and system architecture, as well as two PWM control technology. Subsequently, based on above theories, the article analyzed themathematical models of magnet synchronous motors under three different coordinate systems, andgave its press rotor flux oriented vector control in-depth study. All of above studies providefoundations of Further research ofAC motor speed sensorless vector control system.On the above basis, this paper introduces the basic theory of self-adaptive model reference,and its application of parameter identification is described in details. The article established ACmotor speed identification system, and designed a self-adaptive Model reference speedidentification algorithm using the AC motor stator voltage and current equation estimated speedmode. Finally, I simulated speed sensorless vector control system based on asynchronous motorsand permanent magnet synchronous motor respectively using MATLAB tools under differentworking conditions, and provided analysis comparison of final simulation results.Simulation results show that vector control system based on adaptive model reference is suitable for asynchronous motor and permanent-magnet synchronous motor.Two speed sensorlessvector control system is effective, with satisfying identification precision and dynamicperformance, which tells PWM method through voltage space-vector is better than the methodthrough current hysteresis tracking.