| Minning electric locomotive is the primary vehicle in the coal mine.At present, DCadjustable-speed drive is still widely used in those cases. DC motor has many disadvantages,such as low-reliability, much maintenance, high cost, and large energy is wasted by use of DCdrive. With the fast development of the coal industry, DC drive system with low performancecan’t meet production requirements. Therefore, it is absolutely necessarily to replace DC drivewith AC drive.This paper analyses the commonly used AC drive methods, such as variable voltagevariable frequency, vector control, direct torque control, and designs a variable-frequencyadjustable-speed system for mining electric locomotive based on direct torque control. Theprinciple of direct torque control, hexagonal and circular flux trajectory control method, and thealgorithm of non-speed sensor technology are introduced in detail. The traditional direct torquecontrol output torque ripple seriously, which is obvious in the low speed. According to slidingmode variable structure theory, this paper uses the sliding mode variable structure controllerinstead of traditional hysteresis comparison controller, and puts forward the sliding modelvariable structure direct torque control variable frequency adjustable-speed system. Thesimulation results show that the improved direct torque control system has good dynamic andstatic performance, reducing the torque pulsation, and maintains switch device frequencyconstant.Finally,the paper designs the system hardware circuit and software programming. Throughbuilding mining electric locomotive variable frequency adjustable-speed control systemexperimental platform, the temperature rising test and traction performance test is carried on.The experimental results show that the system has many advantages, such as good heatperformance, large starting torque, quick torque response, adjustable-speed smoothly etc, andmeets the demand for practical production. |
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