Research Of Three-Level Control System Based On Flux Orientation

The thesis focuses on vector control for induction motor based on flux orientation with the diode-clamped three-level topology as the platform. The theory analysis of the induction motor operation model, simulation study of the control system, and experiment verification are done as the main parts of the research.Firstly, the thesis introduces topology of diode clamped three-level inverter and the theory of three-level SVPWM algorithm, analysises diode-clamped three-level inverter switching state and switching vector, decides the sectors of reference voltage and calculate the switching vector duration by selecting the switching vectors. The three-level SVPWM algorithm is verified using Matlab/Simulink. After that, the model of induction motor on the three-phase stationary reference frame is introduced. The model of induction motor based on rotor flux orientation and the model of induction motor based on stator flux orientation are derived and then the thesis introduces the theory of flux orientation. Followed by the analysis of induction motor mathematical model, full order observer is set up and matrix of observer feedback gains is designed to estimate the induction motor speed. After that, the control system simulation model based on rotor flux orientation and model based on stator flux orientation are set up using Matlab/Simulink. Furthermore, the sensor-less vector control simulation system model is also set up with the same tool. The results of simulation indicate that the vector control system has a quick dynamic response and high steady state accuracy. And the simulation results of different flux orientation are analyzed. The results of sensor-less vector control simulation system model shows speed estimation has a good tracking performance and a good robustness to the load variation. Finally, it introduces the hardware circuit design of the three-level inverter control system based on TMS320F28335and EPM570and verifies the corresponding algorithm based on the three-level inverter experimental platform as above. System simulation and experimental results are analyzed and summarized. Suggestion and prospect are proposed for the future work.