| China s coal future reserve of 5.5 billion ton,its proven reserve have 1.2 billion ton,ranked third in the world.In its proven reserves of primary energy,coal of occupsed 94%.Such energy structure determines that it is difficult to change the coal-based energy structure.According to relevant agencies prediction, coal energy consumption in the country will still be in a fifty percent by the year 2050.As is known to us,coal mining enterprise is large and power-consumption enterprise,what s more,power electricity is also wased seriously.Along with the coal resources integration and enterprises mergers and restructuring,coal enterprise is developing toward large-scale enterprise,mining electrical equcpment is bounding to develop into large-capacity and high-power equipment.If no effective measures,coal waste of electricity will be even more severe.Belt conveyor transportation system is the main link in production in coal mine, Due to its uneven introduced.in the quantity, very easy to failure. At present, most still adopts hydraulic coupler coal to solve it, because the startup problem of the bad environment, hydraulic coupling still exist many problems. And the use of frequency conversion technology reconstruction to the coal mine production equipment, can not only minimize the failure, improve the production efficiency can achieve the purpose of saving energy While at present domestic mining medium-voltage high-power inverter is not mature, most rely on imports. Therefore, the mine medium-voltage high-power inverter is urgently needed. This paper first introduces in detail the development situation of mine-used inverter, the development of several frequency control strategy and the development situation of three-level inverter, and points out the current problems existed in the mine belt conveyor, compared the frequency conversion with hydraulic coupler. The research significance of topic is drawed.Then this paper from the following several aspects:1,Introduced the direct torque control system of basic content: Asynchronous motor mathematic models, inverter and voltage space vector. Set up two phase static coordinate mathematical model, analyses the motor inverter and the relationship between the voltage space vector of stator voltage space vector and the flux and the torque influence. For the next part of the three-level direct torque control system and lay the foundation of the further research.2,Analysis the working principle of three level, based on the three-level inverter mathematical model. And expounds tri-level direct torque system problems, Focuses on analyzing the midpoint potential fluctuation, and puts forward the cause of vector method to suppress fixed synthesis midpoint potential fluctuation; In Matlab established based on multi-level hysteresis three level direct torque control system, and simulation research and analysis. 3,According to the application of medium voltage inverter mine-used research-belt conveyor.On the analysis of the dynamic characteristics of the conveyor belt, determine its viscoelastic model was established on the basis of belt conveyor discrete model of dynamic equation; Combining the chapter tri-level direct torque control system, established in Matlab variable frequency drive for mine belt conveyor, and the model of no-load and full load simulation research and analysis.Finally, based on the above analysis and research, combining engineering practice to engineering test, the test result indicated that:the medium-voltage converter basic can meet the basic requirement for mine motor speed. Provides a theory basis for mine medium-voltage high-power design. |
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