Study On Dtc For Pmsm Based On Speed-Sensorless

Permanent magnet synchronous motors (PMSM) have many advantages of small size, low noise and high efficiency, etc., which have been applied widely with the rapid development of the power electronics technology and modern control theory. Direct torque control (DTC) technique has traits of simple control structure, fast torque dynamic response, less dependence on motor parameters and so on, which has become a popular issue of academic research. With basing on the traditional DTC theory and combining with the space vector pulse width modulation (SVPWM) technology, the design of PMSM DTC speed-sensorless system based on sliding mode control (SMC) is deeply researched in the article, and the corresponding simulation analysis and discussion of results are done.The followings are the main contents and innovations of this article.1. The problem of PMSM traditional DTC system is researched. The mathematical models of PMSM in different coordinate systems are given on the basis of the principle of coordinate transformation, and as the breakthrough point of the stator voltage space vector, each module Matlab/Simulink modeling of the PMSM DTC system based on the traditional DTC principle is described in detail. Finally, it was took simulation research for the system, being analyzed and discussed the existing problems in the simulation results.2. PMSM DTC system based on SVPWM is designed. The traditional DTC adopt hysteresis loop comparator and switching voltage vector selection table, which leads to the flux and torque ripple. As a breakthrough point of SVPWM technology, the modeling method of SVPWM model is introduced in detail, and the simulation analysis and research for the SVPWM model are given; Combining with DTC principle, the simulation model of PMSM DTC system based on SVPWM is designed, which solves these problems existing in the traditional DTC system through comparing the simulation analysis. 3. PMSM SVPWM-DTC system based on SMC is designed. The speed loop PI controller of PMSM DTC system based on SVPWM is adopted presently, which does not meet the high-permance control requirements when the control system is disturbed by external disturbance or internal parameters. On the basic theoretics of SMC, a novel reaching law is proposed in the paper, which is different from the index reaching law, and switching function is not included in the novel reaching law, while the terminal attractor and the system state are used to construct a novel reaching law. More, a novel sliding mode speed controller is designed, which is applied to the PMSM SVPWM-DTC system. At last, the control system is verified to better robustness by comparing the simulation analysis.4. On EKF theory, combining with SVPWM technology, PMSM DTC speed-sensorless system based on SMC is designed. The problems which lie on increase in cost, reducing the reliability of the system and it is not easy to install make the speed-sensorless algorithm research become inevitable. EKF algorithm is derived from the basis of Kalman Filter (KF) theory. The EKF mathematical model of PMSM is derived from the mathematical model of PMSM in the a(3coordinate system and the linear theory of nonlinear systems, enabling the observation of its rotational speed, angle, torque and flux trajectory. Finally, EKF algorithm combines with PMSM SVPWM-DTC system based on SMC, which achieve speed-sensorless algorithm.