Research On Dual Drive Design Of Belt Conveyor Based On Combined Frequency Conversion

In the coal mine project,belt conveyor was widely used in underground transportation system.With the rapid development of society,the demand for energy was increasing.The belt conveyor of underground coal handling equipment was an important part of improving coal production efficiency in coal mines.The belt conveyor must have the characteristics of large capacity,high-speed and long distance.In order to achieve large capacity,high-speed and long distance functions of belt conveyor,dual drive system had been widely applied.Variable frequency drive mode had the advantages of soft starting,poleless speed-adjusting,power balance,energy saving and environmental protection.Most of the driving mode at home and abroad was inclined to choose frequency conversion as the driving mode of belt conveyor.Aiming at the characteristics of bad environment and narrow space in coal mine,and improving the cost performance of the double machine drive equipment of belt conveyor,a double machine driving method based on one rectifier and two inverter combined frequency conversion was proposed.This method had a high degree of integration relative to the traditional two frequency converter drive mode.It had the advantages of less electrical equipment,small size,convenient transportation and installation,low equipment cost and so on.The key technical problem was to solve the problem of overcurrent in the starting and accelerating process,the problem of system stability,the synchronous speed of the double machine and the balance of output power,the key technical problem was to use the combined frequency conversion to drive the double machine system of belt conveyor.In order to solve these problems,the key was the combined frequency conversion control mode and control algorithm.Usually,there were four ways of frequency conversion control,such as constant V/f control,slip frequency control,vector control and direct torque control.The first two kinds of control methods belonged to open loop control,and the error of speed precision was large,which was not conducive to the synchronous same speed control of the dual system.Although the vector control method can ensure the speed precision,but it can not actively distribute electromagnetic torque and was bad to power balance control.Although the traditional direct torque control method can be used to achieve power balance and dual synchronous control,there was a large current fluctuation in the process of starting and frequency conversion.In order to further improve the performance of the traditional direct torque control and reduce the current fluctuation,the traditional direct torque control method was improved.The method was simulated by MATLAB/SIMULINK,the simulation results showed that the improved method can improve the control performance and reduce the current fluctuation.Aiming at the problem of synchronous motor speed synchronization,power balance and system stability of belt conveyor drive system based on combined frequency conversion,the reasons of the power imbalance of the system was analyzed,and the power balance control method of the belt conveyor was put forward.The simulation of this method was carried out by SIMULINK,and the feasibility of the method was verified theoretically.It was proved that whether this way was feasible,whether the speed of two motors for belt conveyor was synchronous,and whether the system can resume stable operation again if the speed and the load of the drive system were changed.After solving the key technical problems of the combined frequency conversion and confirming the feasibility of the method,we need to design the double drive system of the belt conveyor.In this paper,the hardware circuit and software of dual drive belt conveyor control system were designed.At last,the experiment of the combined frequency conversion double drive system of belt conveyor had been carried out,and the feasibility of the combined frequency conversion drive method was confirmed.The dual machine drive system of the belt conveyor was able to work steadily,realized the function of poleless speed-adjusting,and balanced the output power of the motor.