Research On Direct Torque Control Of Electric Traction Drive System

2016 national railway planning from the "four vertical and four horizontal" jumped to "eight vertical and eight horizontal","13th Five-Year" period China will continue to promote the railway construction,the use of asynchronous motor-driven electric locomotives and EMU will remain the main railway power.As the key technology of electric locomotive / high speed EMU,the control performance of electric traction AC drive directly determines the traction performance of the whole vehicle.The asynchronous traction motor as the main power source of electric traction drive system,its control strategy is an important part of electric drive system research.Direct torque control is one of the high performance control strategies applied in asynchronous motor AC speed control system.The strategy can respond to the emergencies in operation,and can effectively play traction.It has the characteristics of fast dynamic response and simple system structure.However,there is a problem that the torque ripple is easy to cause the idle slip and the low switching frequency limit causes the stator current harmonics to interfere with the traction power supply network.Therefore,the analysis and improvement of the torque ripple and current harmonic problem,and then improve the electric traction system direct torque control performance,will help China's railway industry technology development.In this paper,the asynchronous traction motor is used as the control object.Firstly,the mathematical model of the asynchronous motor and the working principle of the two-level inverter are introduced.The basic principle of the direct torque control system and the speed region of the traction motor control strategy,including the circular,octadecagon,hexagonal and weak magnetic flux trajectory control of the basic principles and implementation methods.Secondly,based on the low speed torque ripple and harmonic current of traction motor direct torque control system are analyzed,using 3 kinds of low velocity zone optimization scheme,were given twelve direct torque control sector,indirect stator quantities control with time delay compensation based on a finite set of model predictive direct torque control for improved traction low speed control performance of power system area.Finally,this paper uses Matlab / Simulink software to construct a direct torque control system for each speed region of a traction motor for a motor vehicle,and 3 kinds control schemes for the low speed zone.Through the analysis of the simulation results,the model predicts the direct torque control strategy with delay compensation is verified.At the same time,it can achieve the characteristics of suppressing the torque ripple and reducing the harmonic content of the current with fast dynamic response and simple system structure.effect.Based on the above analysis results,the direct torque control scheme of the electric traction drive system is designed.The simulation results show that the direct torque control and the full torque domain direct torque control method with delay compensation are proved by the simulation experiment.In the electric traction system effectiveness.