| Belt conveyor,the most important equipment for bulk material transportation and the most inexpensive units shipping rates,is widely used in coal mines,power plants,ports,chemical plants,environmental plants,warehouses and other areas.In this dissertation,the motor drive system for mining belt conveyor system is studied.Based on the three-level high-power explosion-proof inverter drive,the sensorless vector control method of permanent magnet synchronous motor is adopted.The main design goal is high efficiency,high reliability and low switching loss.Aiming at high efficiency,high reliability and low switching loss,the mathematical model of mine belt conveyor speed regulation system,thermal analysis and heat loss optimization of high-power three-level explosion-proof converter pulse-width modulation(PWM)and full speed sensorless control of high-power permanent magnet synchronous motor are deeply studied.The scheme design of the speed adjustment system of the mine belt conveyor is given and verified by experiments.This dissertation establishes the mathematical model of speed regulation system of mine belt conveyor,analyses the operation characteristics of mine belt conveyor and the starting mode of S-curve,studies the topology,and working principle of three-level explosion-proof frequency converter,establishes the mathematical model of permanent magnet synchronous motor,and analyses the constraints and operating curve of permanent magnet synchronous motor in operation.The main circuit of high-power three-level explosion-proof inverter is in a closed environment,and the optimization of thermal loss of power switching devices becomes the key to the reliable operation of the system.According to the commutation circuit,the loss model of power switching device of high-power three-level explosion-proof converter is analyzed in detail.The heat loss optimization PWM(HLO-PWM)of high-power three-level explosion-proof converter is studied.Aiming at the problem that the conventional method can not achieve global optimization because of its complexity and switching loss,the HLO-PWM can minimize switching loss at any power factor and modulation index by injecting zero sequence component into three-phase sinusoidal modulation wave and locating the non-switching clamp region of reference signal according to load power factor.According to the operation condition of mine belt conveyor,an initial position detection method based on pulse voltage injection method is studied.Accurate initial rotor position estimation can be realized with the salient pole and saturation effect of IPMSM.Aiming at the problems of inaccurate starting torque control,slow starting speed and large energy consumption in traditional I/F starting control,a starting control method of mine belt conveyor based on high frequency pulsating voltage injection method is studied.By making full use of the position information of motor rotor,high performance starting control of mine belt conveyor is realized.Aiming at the problem of phase delay and inherent chattering caused by low-pass filter in traditional sliding mode observer-based PMSM Position-free control system,the sensorless control method of PMSM based on second-order sliding mode observer is studied,which can effectively reduce system chattering and eliminate filter phase delay.Aiming at the problem that the stability condition of the second-order sliding mode observer changes with the operation condition of the motor,a parameter adaptive rate is designed to realize on-line self-regulation of the sliding mode gain.Combined with the application situation of mine flameproof belt conveyor,according to the relevant national standards,based on the optimization of PWM modulation strategy based on heat loss and full speed sensorless control strategy of permanent magnet synchronous motor,the prototype trial production and related performance experiments were completed.There are 76 figures,8 tables and 103 references in this dissertation. |
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