Research On Direct Torque Control Method Of Permanent Magnet Synchronous Motor

Permanent magnet synchronous motors are widely used in industrial control and social life thanks to the advantages of simple structure and high efficiency.Compared with vector control,direct torque control(DTC)technology selects the appropriate space voltage vector directly aiming at the electromagnetic torque,without complex rotation coordinate transformation,and has excellent dynamic and static performance.Therefore,direct torque control has become a hot research issue in the field of high performance control of permanent magnet synchronous motors.First of all,this paper establishes mathematical models of permanent magnet synchronous motors in different coordinate systems,and analyzes the basic principles of traditional DTC.It provides the foundation for further research and improvement of DTC system.Secondly,by analyzing the existing DTC mathematical model of the permanent magnet synchronous motor and mathematically deriving the torque formula,it is pointed out that the stator flux and the torque angle are both controllable variables in traditional DTC.And the torque is controlled by the quadrature axis component of the stator flux.Based on this,a DTC control method without linkage loop for non-salient permanent magnet synchronous motors is presented.Different from the traditional double closed loop structure of torque and flux linkage,this method takes the motor torque as the priority control quantity to achieve the direct control of torque.Based on theoretical analysis,the effectiveness of the method is verified by simulation and experiments.Next,this paper combines direct torque control technology and flux weakening algorithm to expand the speed range of the motor.In analyzing the electromagnetic constraint conditions of the motor during flux weakening,the operation process of the motor is divided into different working areas,a flux weakening switching method is designed.And combined with the characteristics of direct torque control,this chapter proposes a given scheme of flux linkage and torque during flux weakening.The results of simulation and experiments verify the proposed method.Finally,experimental platform is established to verify the performance of the control strategy,and the hardware circuit and system software are designed.The experimental results show that the motor control platform designed in this paper is reliable.