Research And Design Of Rotor Field Oriented Control System Based On Three-Level Inverter

The AC drive system composed by induction motor has a simple structure, reliable operation, low costs and is easy to capacity expansion. The rotor field oriented control system can achieve high performance at a low cost. Compared with the two-level inverter, the output of three-level inverter has low voltage change rates and harmonics, so the research on rotor field oriented control system based on three-level inverter has important practical significance.The thesis focuses on the rotor field oriented control, which is based on the diode-clamped three-level inverter and takes induction motor as control objects. Firstly, the implementation method of SVPWM modulation is presented after deeply analysing the diode-clamped three-level inverter topology, and then the thesis verifies the correctness of SVPWM modulation method through the Simulink. Besides, according to the mathematical model under the three-phase stationary coordinate, this thesis establishes the asynchronous motors’mathematical model under the two-phase stationary coordinate and the rotating coordinate, and the basic principle of rotor field oriented control is introduced. After comparing the advantages and disadvantages of several normal flux observer models, an improved all speed ranges flux observer model is given. And then the model of speed estimate based on MARS is designed. Then, the overall structure of the system is designed, in which the robustness of the system is enhanced by using the bias decoupling method during the process of the stator voltage decoupling. Simulink simulation shows that the system has good steady states and dynamic performance, and proves the feasibility of the speed sensor-less system.Finally, the core hardware control circuit is designed based on FPGA TMS320F28335 and CPLD EPM570. No-load and load mutations experimental study is carried out on the experimental platform and the experimental results show a good dynamic and static performance, which prove that the system has high practical application value.