Acionamento de máquina assíncrona orientada indiretamente pelo campo com controle adaptativo MRAC e sem medição de velocidade.

Abstract

The appearance of the field oriented control strategies (indirect-IFOC or direct-DFOC) has increased the interest for electric driving using assynchronous machines. In this work, the indirect field orientation control - IFOC is studied, i n which i t is very useful for systems operating w i t h high performance. This method is based on decoupled control of rotor flux and electromagnetic torque, for which i t is necessary to know the rotor flux vector frequency. This frequency is thus determined by adding the machine speed and the slipping frequency. IFOC is essentially a feedforward scheme and presents as desadvantages the use of a speed sensor and the dependency of machine parameters. Nowadays, several works have proposed a better performance for this strategy, using adaptatives models for compensating the parametric variations. I n this study, the reference model adaptative techniques are adopted for estimating directly the machine speed, only using stator variables. The proposed scheme permits that IFOC may be implemented without speed sensor and the IFOC may be tuned, despite of the rotor time constant changes. I n this work, the influence of rotor time constant in IFOC control is analysed and an extensive bibliography review concerning compensation techniques of rotor time constant and sensorless speed strategies is presented. It is also addressed different reference models types to be used in the adaptation scheme. The simulation and experimental results are also presented.