Research And Realization Of PMSM Control System Using NPC Three-level Inverter

With the increasing consumption of electrical energy in our country. At present, our country was promoting the energy conservation and emission reduction. The frequency control system has been spread as an important way of energy-saving and emission-reduction. Multi-level inverter has been extensively used in high power frequency control area due to high voltage, low output harmonic, the small EMI. The NPC (Neutral Point Clamped) three level inverter topology structure is the most widely used. PMSM has been widely applied in the field of ac servo and frequency control system because of simple structure, high efficiency, the advantages of control performance.The thesis was based on structural features of neutral point clamped three-level inverter and PMSM, according to the mathematical model and theoretical basis of the aspects, The study introduced some basic control methods about the PMSM. The thesis was based on Direct Torque Control (DTC) method of neutral point clamped three-level inverter about PMSM as well as brought out two improvements and simulation research. The main work is as follows:The research of DTC control method based on improved operation vector fixed synthesizing vectors, There esists many problems in NPC inverter such as the fluctuant neutral point voltage, the high change rate output voltage, high switching loss and so on. It comes up with the fixed synthesizing vectors method which is based on the these inherent existing questions. The fixed synthesizing vector is composed of different space vectors based on the least pulsation of neutral point voltage. But it also conquers the high change rate of output voltage and high switching loss problems, It establishes the Matlab/Simulink simulation system model based on fixed synthesizing vectors method. The analysis through results indicates that the method can restrain imbalance of neutral point voltage, high change rate output voltage, high switching loss effectively.The research of DTC control method based on improvements fixed synthesizing vectors, In order to control the stator flux linkage and electromagnetic torque accurately based on twelve fixed synthesizing vectors, increasing the quantity of fixed synthesizing vectors to twenty-four, dividing the whole vector space into twenty-four active areas. The algorithm can further decrease harmonic content of output voltage and current, at the same time, it can also solve the inherent problems of neutral point clamped three-level inverter. In this way, the algorithm can reduce high-frequency pulse ripples of motor stator flux and electromagnetic torque.Finally, The thesis builts the hardware experiment system of NPC three-level inverter control system of PMSM. The hardware platform mainly includes controling circuit, driving circuit, detecting and regulating circuit, protecting circuit and so on. Software design is completed in Integrated Development Environment(IDE) CCS3.3. Experiment results demonstrates the validity and feasibility of the system.