Research Of Permanent Magnet Synchronous Motor Direct Torque Control Based On Fuzzy Logic

With the development of high performance permanent-magnet material, power electronic technique, large scale integrated-circuit and computer technology, the permanent magnet synchronous motor (PMSM) is widely used because of its small volume, high power density, high efficiency and power factor. Direct torque control (DTC) was put forward aiming at induction motor in the 1980s, it is another high performance control strategy for ac motor after vector control. With the solving of DTC strategy's theoretical foundation in PMSM, the direct torque control of permanent magnet synchronous motor was concerned more and more.In this paper, the principle of coordinate transformation was introduced at first, and then the basic theory of PMSM DTC was discussed and the space voltage vector switching table of traditional DTC strategy was derived according to the model of PMSM. Improved vector switching table of traditional DTC and introduced zero-voltage vector, which made torque keeping invariant, decreased action frequency of switching devices and improved control performance of system. Aiming at the fault of traditional DTC easily produced torque pulsation, the model of PMSM DTC based spaced vector modulation was given according to the foundation of space voltage vector modulation. Then the basic principle of fuzzy logic is introduced to the PMSM DTC. According to the feature that the flux hysteresis and torque hysteresis are fuzzy themselves, they can be fuzzified and the repository can be organized classically to complete the choice of space voltage vector.On the premise of theory analysis above, the simulation modules of flux and torque calculator, electromagnetic torque hysteresis, stator flux linkage hysteresis, sector choice and fuzzy controller of PMSM have been set up under the MATLAB/Simulink. The simulation of DTC control strategy with space vector modulation and fuzzy control are presented which demonstrate the fundamental theory of DTC control strategy for PMSM. The DTC of fuzzy control strategy and traditional control strategy are compared, the simulation results shows that fuzzy control strategy can decrease torque pulsation, improve dynamic and static performance of systems.On the basic of theoretical derivation and simulation verification, the hardware and software are designed for the digital signal processor (DSP)-based system. Furthermore, the DTC control system platform for PMSM is constructed. The hardware system of this paper includes main circuits, control circuits, drive circuits and measurement circuits. Then a driving experiment based SPWM and SVPWM is completed with drive board, to lay a foundation for further improvement.