| Permanent magnet synchronous machine with its simple structure, high efficiency, wide speed range, are widely applied in many fields, such as machining operation, aerospace, electric traction etc., and direct torque control is a new type of high-performance AC driving system after vector control technique, as a result, the research of direct torque control of permanent magnet synchronous machine has become a focus. Therefore, this thesis take studies of the direct torque control system of permanent magnet synchronous machine as a goal; it has important theoretical and practical significance.After consulted many literatures, the thesis introduced the structure of permanent magnet synchronous machine, and then analyzed the status and trend of permanent magnet synchronous machine's direct torque control system. Based on space vector principle, the three kinds of coordinate systems as well as the transformation of them which usually used in motor's speed control system are introduced, then, the mathematic models on different coordinate systems are derived. After that, the theory of DTC is studied deeply and traditional control system based on Bang-Bang mode is researched. The effects of space voltage vectors towards to stator flux and electromagnetic torque are also analyzed. Due to existent disadvantages of traditional DTC mode, Space Vector Pulse Width Modulation is brought into PMSM DTC system in order to resolve the problems such as remarkable fluctuations of flux and torque. Moreover, the improved algorithm is given for the harmonious control of stator flux and electromagenic torque.With Matlab/Simulink the subsystems of traditional DTC system and SVPWM DTC system for PMSM are modeled and designed. Then the simulation models of the above two control strategies are also established. Simulation research is conducted and the experimental results are corresponding with theory analysis:the improved system has good dynamic and static performance, less flux and torque ripple. |
PDF Full Text Request