Study And Design Of Mine Electric Locomotive's Variable-Frequency Adjustable-Speed System Based On DSP

Mine electric locomotive is an important conveyance in coal production. It has always been driven by DC motor. It has some disadvantage such as the maintenance of brush and the spark of commutator, which making high operating costs, low operational reliability, high maintenance cost. With the development of power electronics technology, the AC drive system based on power electronic converters can be realized. Especially after the realization of LSI and Computer Controling, the performance of AC variale speed has been improved a lot. AC motor has a lot of advantages over DC motor. These characters include its higher power and efficiency, brushc and commutator, the lower cost of maintenance. So it is an inevitable trend that the DC motor will be replaced by DC motor to be used on mine electric locomotive.In this paper, I analyze the deficiency of mine electric locomotive and compare the advantages and disadvantages of some adjustable-speed method. Then a new scheme is raised. In this scheme, the DC motor is replaced by AC asynchronous motor and the vector control is used to improve the system performance. The inverters based on space-vector PWM technique have many good qualities, such as less pulsating torque, higher usage of DC bus voltage, less switching loss, better high-speed regulation performance, so it is applicable for the high-performance motor control system. So the locomotive is improved by adopting the vector control based on SVPWM. Based on the dynamic mathematical model of AC asynchronous motor, the principle of the vector control is discussed, and the implementation method of SVPWM is rasied. Then the simulation model of the whole system is set up by using Matlab/simulink, and the feasibility of the system is verified by analysising the simulation result.Then I designed the hardware circuit and software program of the vector control system based on SVPWM. Because the caltulation work of the vector control is huge, the TMS320F2812 chip is used to realize the vector control and make the SVPWM. The design uses IPM as the inverter device. The using of TMS320F2812 and IPM greatly simplifies the system design. IPM which is controlled by the SVPWM generates 3-phase voltage for AC motor. The system detectes the current and the speed to send them to DSP, then DSP analyzes and calculates these signal according to the vector control algorithm to generate the SVPWM signal. At last the experiment to validate this design was made in lab. The experiment testified the system has a better adjustable-speed performance. The system meets the requirements of pratical applications.