Direct Torque Control System Of Permanent Magnet Synchronous Motor Based On Segmented Modulation Strategy

Permanent magnet synchronous motor (PMSM) is characterized by small volume, high efficiency, simple structure and so on and it has been widely used in fields which require high control accuracy and reliability, such as aerospace, digital control machine tools, radar and a variety of military weapon systems and robotics, it also occupies a pivotal position in modern AC motor.The structure and characteristics of PMSM are analyzed firstly in this paper, the mathematical models of PMSM in different coordinate systems are given. The paper deeply studies theories of direct torque control (DTC) based on PMSM, analyses the control actions of voltage vectors to electromagnetic torque and motor flux. According to the mentioned theories, the paper gives the block diagram of direct torque control principle for PMSM.To solve the problems of the torque and the flux ripples in the DTC system, this paper presents a direct torque control scheme based on segmental modulation method, after analyzing DTC strategies using space vector modulation and sliding mode. The scheme takes advantages of the features of sliding mode that it is insensitive to system parameter variations and load disturbances, as well as good robustness and fast response, to overcome defects of flux observation based on voltage model. The proposed control strategy is simulated by tools of Matlab and Simulink, and the simulation results agree with theoretical analysis, verifying that the theory is correct.Finally, the system hardware design, which uses DSP as control core, rectifier and intelligent power module as main circuit, is given, so do the flow charts of each module of system software.