Research On Direct Torque Control For Permanent Magnet Synchronous Motor

The application of permanent magnet synchronous motor (PMSM) can save energy to promote energy-saving goals. The direct torque control on PMSM has the advantages of novel and simple ideas, torque response quickly, and has high static and dynamic performance, but the torque and flux pulsation are great. It not only increases the cost but also reduces the reliability of the system that uses speed sensor in the control system. The application of speed sensorless control technology can estimate the position and speed of the rotor, thereby eliminating sensor. In view of the above problems, this paper mainly focuses on the following aspects of the work.The principle of PMSM is introduced, the mathematical model is set up and the principle on direct torque control is described. The direct torque control makes torque control more directly and system response more quickly, but reduces the precision of the torque control.The hysteresis comparison of direct torque control simulation diagram is based on. The control performance of direct torque control is verified in four cases which are the sudden load, step load, speed switching and low magnetic. Direct torque control system response is very fast, but the flux and the torque pulsation is greater.The principle and the realization method of the space vector pulse width modulation (SVPWM) are analyzed. Through the simulation analysis, It is verificated that the system of the PMSM direct torque control on SVPWM basically maintained a rapid response characteristic. The control method improves the steady performance of the system, the flux and the torque ripple got certain inhibition and the anti-jamming of the system and the speed following are better.The principle of sliding mode control is introduced and the sliding mode observer is applied to estimate PMSM speed. Through the simulation analysis, it can meet the requirement of the direct torque control that using sliding mode observer estimates the motor speed, the system keeps fast system response and the system has good static and dynamic performance.