Research On Permanent Magnet Synchronous Motors Sensorless Vector Control System

PMSM(Permanent Magnet Synchronous Motor) has the advantages of small size, simple structure, high efficiency and strong adaptability to the environment. These advantages make PMSM widely used in all kinds of high-performance drive system. The sensorless control technology of PMSM can reduce system costs, increase system reliability, so it becomes a hot topic in the field of motor control research.Firstly, the current situation and prospect of PMSM sensorless control system is introduced, and the emphasis is three-level inverter technology and sliding mode observer. Secondly, based on the analysis of the structure and characteristics of PMSM, the mathematical models of the motor in three different coordinate system are established. Then, vector control technology is introduced as a control strategy according to the requirements of speed control system. Thirdly, the theory of three-level and space vector which are produced by three-level inverter will be introduced, after that, a new space vector pulse width modulation in60°coordinate system on the basis of the principle of the traditional SVPWM control algorithm will be studied. Fourthly the extend state sliding mode observer is established on the basis of sliding mode control theory, stator voltage equation and rotor flux variation in PMSM stationary coordinate system. On the basis of the linear sliding mode presented above, high order terminal sliding mode is introduced in order to establish the second-order nonsingular terminal sliding mode, so that the problems of chattering and approaching in linear sliding mode are resolved. Finally, based on the results researched above, the PMSM sensorless vector control system, which is double closed loop, is contrusted, and the switch of the system state is accomplished fast and smoothly with the help of a new self-start strategy.The simulations of SVPWM improved algorithm, sliding mode observer, sensorless control system are accomplished on the simulation platform called MATLAB. By analyzing and comparing the graphs, the accuracy of the theory can be verified.