Design Of Flux And Speed Observer In IM Vector Control And Its Schemes Implementation

Induction motor has the advantage of simple structure, convenient control, reliable operation and low price, is widely used in industrial and agricultural production. As the adoption of the modern motor control technology represented by vector control, the performance of ac motion control system is greatly increased, close to or even more than a dc motor. Classic vector control is also known as field oriented control.In order to achieve the field orientation,the flux position information is needed. However,the flux information is obtained indirectly by sensors or observer technology. In addition, in recent years, considering the factors such as the cost and installation of the speed sensor, part of the vector control of ac motor systems haveno longer used speed sensor. So, the speed observer is a good method to solve the problem.Aiming at these problems, in this paper, on the basis of reading a large amount of literature, the flux observer and speed observer of induction motor have been study comprehensively. The main content is as follows:(1) For small signal integral problems of voltage model, the improved voltage model is proposed. Aiming to eliminate the influence of the dc offset, replacing the pure integral by a LPF, the method improve the performance of voltage model at low-speed.(2)Neither voltage model or current model canestimate rotor flux accurately at all speed.So the closed-loop hybrid model is put forward. In order to give full play to the high speed performance of voltage model and low speed performance of current model, the model adopts the cascade method to combine voltage model and current model, thus to realize rotor flux estimation at all speed.(3) For the issue of flux observer sensitive to the motor parameter and the need of sensorless control, the speed adaptive full order flux observer is put forward. Because of the robustness, based on Luenberger observer and Lyapunov stability theory, flux observer and speed adaptive mechanism is designed respectively. In addition, speed adaptive mechanism also meet the requirements of sensorless control.(4) For the issue of flux observer sensitive to the motor parameter and the need of sensorless control, the sliding mode flux observer is put forward. The most prominent advantage of the observer is that it is hardly affected by interference and motor parameters under steady state. In addition, based on the relationship of the flux and current, the speed estimation is obtained, achieving the control without speed sensor.