Reserch And Design On Induction Motor Vector Control System Based On Three-Level Inverter

In recent years, with the development of power electronic technology, large scale integrated circuit and computer control technology, coupled with the application of modern control theory, ac variable speed has been widely used in various industrial fields, and become the main direction of electric drive control field. Especially, vector control can make the torque and flux decoupling so that induction motor can achieve similar dynamic effects of DC motor. Therefore, Induction motor vector control is widely applied. Multi-level inverter can achieve high voltage high power, low output voltage harmonic content, small electromagnetic interference, so that it has been widely used in the the high power field. Three-level inverter is a most representative kind of multi-level inverter. Therefore, the research of induction motor rotor field-oriented control system based on three-level inverter has practical significance.In this thesis, topology and basic working principle of the diode clamped three-level inverter are presented firstly, and space vector pulse width modulation (SVPWM) control strategy and specific steps are discussed, including vector composition, vector effect time calculation, vector sequence and alloction of vector time. Secondly, the coordination transformation principle and the mathematical model of induction motor are presented. In the two-phase synchronous rotating coordinate system, the magnetic component and the torque component of current achieve complete decoupling, so that induction motor can achieve high performace control, the torque and flux of which can be controlled apart like DC motor. This is the basis for achieving vector control. Thirdly, the vector control theory of induction motor is presented, and the rotor field-oriented control system is designed, in which the rotor flux observer and reference voltage feedforward compensation are presented. Fourthly, the influence of the field oriented and system performance due to parameter variations is analyzed. Make used of model reference adaptive theory to identify motor parameters and compensate rotor time constant. The rotor time constant identification based on MRAS utilizing reactive power model is proposed and compared with rotot flux model. Fifthly, the simulation results are presented by MATLAB/Simulink, and the results verify correctness and feasibility of theory.Finally, the hardware and software of induction motor field oriented control system based on three-level inverter are designed, and this system is debugged. The experimental results indicate that this system has good dynamic performance and robustness.