The Research On Permanent Magnet Synchronous Motor Direct Torque Control System

Due to the permanent magnet synchronous motor has the advantages of simple structure, high efficiency, high power factor,small volume, easy heat dissipation and maintenance and a series of excellent characteristics, so it is widely used in digital machine tools, robots, aviation, aerospace, machining centers and other occasions. In the permanent magnet synchronous motor (PMSM) control method, direct torque control (DTC) because of its novel control method, system has simple structure, dynamic, static characteristics such as high performance and received the universal attention, but still existing flux observation error is large, the problem of high torque ripple, therefore, study on PMSM DTC strategy has very important significance. Around the PMSM DTC system, the main contents are as follows:(1) This paper establishes the mathematical model of PMSM and introduces the PMSM coordinate and matrix transformation in different coordinate system, and derives the PMSM the mathematical model in different system, then elaborates the basic principle of it(2) Introduction of PMSM DTC overall block diagram and various components, and implementation way. Including the flux model and torque model, flux partition and switch table determines, in view of the traditional direct torque control stator flux linkage error, such as DC drift problem, emphatically introduces four different stator flux integrator.(3) Respectively combined with pure integrator, integrator with a saturable feedback and integrator with an amplitude on the DTC system simulation, and the results were compared to three, and change speed to maintain other given value invariable situation, we find application integrator with an amplitude of direct torque control system for speed ripple greatly, aiming at this phenomenon, this paper puts forward a kind of according to the permanent magnet synchronous motor state equation to obtain the magnitude of the stator flux, the system is no longer subject to external given value influence.(4) For two level inverters, the paper puts forward a method based on three level inverter direct torque control system, and on the three level inverter principle, topology structure, control principle, and the control strategy are analyzed in detail, proposed one kind based on the fixed synthesizing vectors three level DTC method, based on fixed vector synthesis method for three level DTC simulation, verification based on neutral point clamped three level inverter DTC is based on two level inverter DTC has better characteristics.(5) At the end of the work of this paper are summarized, and the future research work in the analysis and prospect.