Study On Three-phase AC Permanent-Magnet Synchronous Motors Of Servo System For Flux-Weakening Control

With the features of small size, high efficiency and power density, PMSM have widely used in some fields which need high-precision control and high reliability. For example, aerospace, military, robots, processing center, computer peripherals, electric vehicles, CNC machine tools, household appliances. In order to get high-precision control, wide speed range, large output torque, stable system, strong anti-jamming capability, the advanced and reliable control system is needed. So studying on control method about speed control system of PMSM is a hot issue.When PMSM run above a certain speed in the actual system, with supply voltage limit and current controller saturation of control system, it will be very difficult to continue to increase speed. To widen the speed range, then we must take flux-weakening control to reduce flux. However, PMSM is rotor permanent magnet excitation, the flux size of it can’t be adjustable. The frequently used method is that changing the stator current vector can get the same effect. And most of the studies about flux-weakening control are changing the size of stator current.Works done by this thesis are as follows. At first it describes the motor structure of PMSM, analysis mathematical model under the three-phase coordinate system and dq coordinate system, and makes a deeply description of vector control, introduces the principles and program implementation of SVPWM. Then it elaborates principles of servo-vector system control and id=0control of PMSM, and simulates the double closed-loop servo system of PMSM by MATLAB. At last it analysis the principle of flux-weakening control and related theory deeply, introduces the basic structure of flux-weakening control. It adds the flux-weakening control part to double closed-loop servo system of SMPMSM. Simulations of the above control system show that it achieves the flux-weakening control of SMPMSM.