Research On Direct Torque Control Method Of Traction Motor For Harmonious Electric Locomotive

Asynchronous motors have the characteristics of simple mechanical structure,low manufacturing cost,good durability,easy maintenance,etc,and have been widely used in the field of rail transit.In the research of variable voltage and variable frequency speed regulation of asynchronous motors,Direct Torque Control(DTC)technology has become a current research because of its simple research ideas,direct controlled objects and good robustness.Hot spot.The traditional six-zone DTC system has unstable regulation of the stator flux linkage,and the torque pulsation generated is large,which has great limitations in the actual application process.In order to obtain better control performance,this dissertation is based on the Harmony Electric Locomotive Traction Motor—JD160A traction motor.Aiming at the deficiencies of the DTC system in flux and torque control,an improved DTC control scheme is designed,and through theoretical analysis and Simulink Simulation,conducted in-depth research on the asynchronous motor DTC system.First of all,the idea of Clark transformation in the process of over DTC control was used,the two-level voltage source inverter model and the motor mathematical model in different coordinate systems were established,and the theoretical knowledge of the DTC control strategy was explained.the inverter output was analyzed and obtained The relationship between signal,flux linkage and torque.Secondly,based on the control process of the hexagonal DSC system and the traditional six sectors DTC system,to obtain the optimal voltage vector as the goal,the flux linkage,torque adjustment and interval judgment were studied,and the optimal space voltage vector switch selection table was obtained.At the same time,the problems of the traditional method of stator flux trajectory irregularity and torque ripple were described.Thirdly,in view of the shortcomings of the traditional six sectors DTC system,a twelve sectors direct torque control and torque grading adjustment twelve-zone direct torque control optimization scheme was designed,and the original 60° sector was improved to a re-divided30° Sector,torque control adopts a hierarchical adjustment method.There are three non-zero voltage vectors in the same sector to choose from,which optimizes the effect of voltage vector.Finally,on the simulation platform,model the hexagonal DSC system,the six-division DTC system,the 12-division DTC system,and the twelve-division DTC system of torque hierarchical adjustment to obtain the stator current and stator flux linkage of different schemes.The trajectory,electromagnetic torque and speed response and sector graphics were compared and analyzed.The results show that the improved control scheme has better control performance,its speed fluctuation is small,the flux linkage is smoother,the current waveform changes sinusoidally,and the torque ripple can be effectively reduced.