The Research Of Fast Torque Control System For AC Traction Drive

Direct torque control system which was developed after vector controlsystem is a high performance control scheme, some problems in the vectorcontrol system were largely solved, such as the variation of motorparameters sensitivity, a large amount of calculation, the complex structureand so on. However, in the conventional direct torque control scheme, theactual torque must exist pulsation due to the Bang-Bang control. At lowspeeds, the torque pulsation will be greater,and also there will be adeviation in the stator flux observations. Another point is the switchingfrequency of the inverter are also will affect the values of torquepulsation.However, with the development of the power electronic devices,the indirect torque control scheme can be extended to full speed zone andthe speed range was more and more wide. This paper mainly focuses on thefollowing aspects:First, a brief analysis of the Exchange velocity modulationdevelopment and Several main control scheme. Described a mathematicalmodel of the induction motor and inverter, and four flux observer ofasynchronous motor. A detailed analysis of the voltage space vectorconcept, and build the simulation model to analyze the simulation results.laid the foundation for the further study.Second, for the lack of direct torque control strategy, this paper studiesthe fast torque control strategy. The control strategy is based on thein-depth study of indirect torque control, and making further derivation forthe mathematical relationships and physical meaning. Fast torque responsecan be achieved by introducing a dynamic weak magnetic, and also thecontrol system’s dynamic performance has also been improved.Finally, establishment of simulation model for the fast torque controlstrategy based on Matlab/simulink, and compared with traditional directtorque control of the simulation results to verify the feasibility andsuperiority of the control scheme. In experimental platform based onTMS320LF2812, the hardware and software are designed for fast torquecontrol system, and analysis of experimental results. Through the simulation and experimental results can be seen that thestator flux is the movement in accordance with the circular path，the torqueripple is smaller, speed range is wider, steady state and dynamicperformance is excellent. And it can effectively improve the current andmagnetic flux waveform. Torque response speed has been significantlyimproved due to the introduction of dynamic field weakening.