Research On Sensorless Control Of Induction Motor Based On Voltage Model Flux Observer

Vector control technology promotes the development of ac drive, contributing to break the monopoly of dc drive in speed adjustable system. In past decades, induction motor is more and more widely used in industrial application, agricultural production and social life for its advantages of simple manufacture, low cost and high reliability. Compared with the speed-sensor control in induction motor drive, sensorless control has advantages in cost and reliability, and attracts increased attention both in industry and academia for induction motor drive. In this dissertation, the key technologies of induction motor drive, which include vector control and observation of flux and speed, are studied based on the stator flux orientation. The model structure of induction motor under the orientation of stator flux is constructed, and a deeper research on voltage model flux observer is taken.Firstly, according to the investigation and analysis of the mathematical model of the induction motor, the dynamical induction motor model in stator flux reference frame is configured. The design of the control loop parameters in stator flux reference frame is made based on the model decouple analysis. Besides, the simulation platform in Matlab/Simulink and experimental platform with dSPACE control board are set up to confirm the validity of the designed control loop parameters. The designed control system established the foundation for the following sections.Secondly, a kind of voltage model flux observer with good performance at low speed, which is presented by J.Holtz, was studied. Based on the linearized theory, a small signal model was established. Then the relationship between the feedback factor and the observer’s performance was obtained. Besides, the influence of the input error on the flux observation was analyzed. Considering various aspects of the observers’performance, a new self-adaptive design method of the feedback factor in the observer was developed. A series of simulations and experiments verified the validity and effectiveness of the theoretical analysis. The experiment results show that the flux observer with the self-adaptive feedback factor can achieve good performance in both high and low speed area.Finally, the induction motor speed sensorless vector control system in stator flux reference frame is developed based on the designed voltage observer. The parameter sensitivity of the voltage observer is analyzed based on aforementioned configuration, which is confirmed by simulation and experimental results. Based on the parameter sensitivity analysis, conclusions are drawn that only the stator resistance influences the flux observer and the variation of the mutual inductance has little impact in the speed estimation.