Research On Long Cable Power Supply Technology Of High Power Inverter For Mining

At present,the coal industry is still the pillar of China’s energy industry.With the continuous increase of the productivity of coal mines,the automation and high power of production equipment in coal mines have been continuously improved.Therefore,high-power mine frequency converter is widely used in coal mines,because it has the remarkable advantages of energy saving,controlling the smooth operation of mechanical and electrical equipment,reducing production costs and so on.Due to the limitation of the actual mining environment in underground coal mine,the distance between the frequency conversion speed regulating device and the production equipment is far,so the transmission between the high-power frequency converter and the production equipment needs to use a long cable.These situations also produce a series of negative problems,such as the use of long cables for long-distance transmission of electromechanical equipment caused by the motor end of the phenomenon of harmonic pollution generated in high-power frequency converters.Therefore,this thesis will study the phenomenon of overvoltage at the motor end and high power frequency converter harmonics and other problems as the focus,and put forward the corresponding solutions.Firstly,based on the basic theory of transmission line,this thesis studies the transmission characteristics of the long cable,and establishes the PWM long line drive single-phase equivalent circuit to study the nature of the over-voltage at the motor end.The single-phase equivalent model of long wire drive is established.By changing the rise time of PWM pulse,the length of cable,characteristic parameters(resistance,capacitance,inductance)and load impedance,the changes of overvoltage under different conditions are simulated,and the relationship between the changes of different parameters and overvoltage is obtained.Secondly,the harmonic generation and the harm caused by the harmonic are analyzed,and the simulation model of high-power frequency conversion is established to verify that the harmonic mainly comes from the rectifier side of the converter.And analyzes the active and passive measures to restrain the harmonics of the frequency converter.Aiming at the phenomenon of overvoltage,based on the PWM long-line variable frequency drive equivalent model,this thesis analyzes the parameters of the RC filter at the motor end and the RLC filter at the inverter end by using the transfer function,and verifies the inhibition effect of the two kinds of filters through simulation.Then the parameter range of LC sinusoidal filter which can suppress harmonic effectively is designed,which provides a reference for the parameter selection of filter in practical application.