Study In Variable-frequency Adjustable-speed System Of Mine Electric Locomotive Based On Direct Torque Control

Mine electric locomotive with storage battery is an important conveyance of coal mine. Now it has still used a DC adjustable-speed control method based on DC series motor. This adjustable-speed control mode is discontinuous and a large numbers of electric energy is consumed on resistance in series. So the storage battery is frequently charged so that time and energy is wasted and the efficiency is reduced, and the storage battery is easily damaged and its life-span is shorter. AC asynchronous motor can run under abominable operating condition because of its simple structure, high efficiency and small maintenance. Therefore it is a good choice to use it as traction motor of mine electric locomotive.So,it must be change into the AC adjustable-speed system.This article has conducted some research and discussion just in view of this problem.A advanced technology of frequency conversion is putted forward in the paper : The technology of direct torque control(DTC) which control directly stator flux and electromagnetic torque of asynchronous motor. Its control frame is very simple since it needs not complicated coordinate transform and parameter operation.At first, the simulation models of approximate circle flux control system are presented based on the application of MATLAB/Simulink by the author.The feasibility and correctness of this method are testified in theory and the correlative waves which can explain the advantage of system are captured too. Then, the author applies the theory of DTC into the AC adjustable-speed system of mine electric locomotive, and its Variable-frequency adjustable-speed system is built on DSP TMS320LF2407. The author has done the experiments of the approximate circle flux control system using the DSP test-bed, and has completed the design and study in lab phase of DTC system. Some valuable waves in experiment are captured and has analyzed the results of experiments at last. The experiment testified that AC drive electric locomotive have greater traction force, smaller starting current and less energy loss than DC drive's.