Study On Optimization Of Permanent Magnet Synchronous Motor Direct Torque Control

Abstract:Permanent magnet synchronous motor is a simple structure, reliable operation, small size, light weight, low loss and a high efficiency machine. it was applied in various fields of our daily life and production. But because it is an object with a multi-variable, non-linear, strong coupling, and always changed with the time, so how to control it effectively is a key problem we need to face. Nowadays, there is variety of control strategies has been proposed, among them direct torque control strategy is widely used in the control system, but the control accuracy has yet to be further improved. Therefore, this thesis aim at optimizing of control problem for permanent magnet synchronous motor direct torque control. The main research work and innovations are as follows:Aiming at the torque ripple in direct torque control system and the problem of switching of inverter is inconstant, using matrix converter instead of the structure of the voltage source inverter, in order to reach further reduce the torque ripple purpose. On the base of the in conventional matrix converter modulation strategy of the foundation, proposed an optimized direct torque control method, that is, the method using input smaller amplitude space voltage vector applied to the direct torque control, by optimizing the hysteretic loop comparator for a more precise distinction between the torque error, focus on optimizing direct torque control switching table. By comparing the simulation experiment to prove the feasibility and effectiveness of the improved method.In this thesis, aiming at the buffeting problem exist on sliding surface of the sliding mode observer for direct torque control, combined with the advantages of terminal sliding mode and non-singular sliding mode, propose a sliding mode observer optimal design method, and compared with improved methods and conventional sliding mode variable structure observer method by simulation. The results show that the proposed method can effectively suppress the chattering problem, and achieve the purpose of motor control performance.