Direct Torque Control Of Permanent Magnet Synchronous Motor Based On The Fast Terminal Sliding Mode

The permanent magnet synchronous motor (PMSM) with simple structure, reliable operation, torque\weight is high and a significant loss of small and other characteristics, is being more and more attention, in high-precision and high reliability requirements of high-profile occasions. Since 1996, the Swedish ABB has developerd the first direct torque control using frequency converter technology. The direct torque control technique is becoming the new generation of inverter technology representatives. Direct torque control is often applied for PMSM drives due to its fast responses and superior dynamics. However, large flux and torque ripple, difficulty to accurately control at very low speed and unconstant switching frequency exist in the torque control.To solve the above problems, sliding mode control which is strongly robust to system parameters variations, low accuracy requires of model and external disturbances,has a desirable perspective in PMSM control field. Existing research to sliding mode variable structure control application in permanent magnet synchronous motor direct torque control have been found, linear sliding is used in the system state control. The error between the system state and the given trajectory is gradually convergence in the index the form of asymptotic, but never be able to reach a given trajectory. The chatter free fast terminal sliding mode control was introduced into the PMSM DTC. The proposed control scheme can drive system converge to the equilibrium point in finite time based on Parameter Adjustmen of Lyapunov theorem, reduced steady state error of linear sliding, has stronger robust to motor parameter and disturbance, attenuated the chatter and resolve large flux and torque ripple, unconstant switching frequency of traditional PMSM-DTC.Speed-loop control are commonly used PI controller, which has simple structure, easy to realize, but there is overshoot, dependence on the system parameters. Two order sliding mode speed control is proposed to place the traditional PI control. It can drive torque ripple to converge to the equilibrium point in finite time, and has stronger robust to motor parameter and disturbance, and attenuated the chatter, the whole control effect is improved greatly.Direct torque control system model of ermanent magnet synchronous motor has been established in Matlab\Simulink simulation platform based on the theoretical analysis. The result of simulation show that strategy has very good torque performance, and has very strong robustness again load disturbances, parameters varieties and the other uncertainties.