Design And Research Of Electrical Control System For Port Downward Belt Conveyor System

Belt conveyor is an important loading and unloading equipment in port bulk material transportation because of its advantages of continuous transportation and strong transport capacity.Because of the terrain,downward belt conveyor is used when material needs to be transported downward.Under the condition of heavy load or overload,how to rationally utilize the regenerative energy generated and implement effective braking to avoid stall is the key point of downward belt conveyor system.Therefore,the study of an electrical control system which can reliably brake downward belt conveyor and complete its braking energy recovery and utilization will be conducive to the safe operation and energy saving of the port.Based on the design project of downward belt conveyor system for bulk material transportation in Chongqing Orchard Port,this thesis designs the electrical control system of downward belt conveyor system,establishes the simulation model of threephase AC asynchronous motor frequency conversion speed regulation and its energy feedback system,simulates the frequency conversion braking of downward belt conveyor under several different working conditions,and gives feedback in power generation braking.The waveform analysis of the power to the grid is carried out to verify the effectiveness of the energy feedback system.The main contents of this paper are as follows:(1)Electrical control system design and energy feedback research of downward belt conveyor system.According to the actual operating environment characteristics of downward belt conveyor system,the design requirements and objectives of the system are analyzed,and the electrical control system design of downward belt conveyor system is completed.It mainly includes hardware equipment selection,frequency converter schematic design,system communication scheme design and so on.On this basis,based on the force analysis of bulk materials on the downward belt conveyor,combined with the operation characteristics of different working conditions,the working principle,energy conversion and regenerative power feedback conditions of the belt conveyor are studied.(2)The simulation model of slip flux open-loop vector control system of threephase asynchronous motor is established and simulated.The theory of vector control speed regulation system of three-phase asynchronous motor is studied.An open-loop vector control model oriented by rotor flux is established.The stator current is completely decoupled.The specific parameters of current PI controller and speed PI controller are tuned in engineering respectively.The control accuracy of the system is further improved by adding feed-forward decoupling.The working principle of gridside and motor-side converters SVPWM is deduced and analyzed in detail,and the corresponding simulation models are established to verify the results.(3)Based on the system schematic diagram and the theoretical analysis of double SVPWM working principle,according to the actual operation parameters of downward belt conveyor in orchard operation area of Chongqing Port,the Simulink simulation models of motor-side and grid-side converters are established respectively.The bilateral and cooperative control strategies based on PI regulation algorithm are proposed,and the complete simulation model of energy feedback traction system is built.Frequency conversion speed regulation experiments under various operating conditions are carried out on the machine side and the simulation curves are recorded.The harmonic analysis of the voltage and current waveforms fed back to the power grid on the network side and the frequency spectrum are recorded.The effectiveness of the control algorithm is verified by the simulation results.