Study On The Control Strategy Of Permanent Magnet Direct-drive System For Scraper Conveyor

As a traditional energy,coal still plays an indispensable role in thermal power generation,metallurgy and other industrial fields.Scraper conveyer has a decisive role in material transportation with its advantages of stable operation,low unit freight and continuous transport of large quantities of coal resources.This paper takes the permanent magnet direct drive system of Henan Pingmei Shenma Group coal mine as the platform,and makes researches of the scraper conveyor permanent magnet direct drive system from three aspects: the deadbeat direct torque control,the power balance control of multi motors and the sensorless control.Firstly,the basic structure of PMSM is introduced and its mathematical model is deduced.The basic principle of DTC of PMSM is briefly described and the corresponding simulation verification is made,which lays the foundation for the following research contentsSecondly,aiming at the problems of large pulsation and unfixed switching frequency in traditional DTC,the space vector modulation algorithm is used to improve it and the deadbeat control of electromagnetic torque and stator flux linkage is realized through mathematical derivation.The torque ripple of traditional DTC can be reduced and the switching frequency can be fixed by space vector modulation.The dynamic response performance of DTC can be further improved through the deadbeat control algorithm,so as to improve the performance of DB-DTFC system.To solve the problem of power imbalance in the coordinated operation of the scraper conveyer’s multiple motors,the master-slave control strategy is adopted to carry out the coordinated control of the double PMSM of the head.Meanwhile,the circular cross-coupling strategy is adopted to solve the problem that the master-slave control is not suitable for the flexible connection of the head-tail motor.In addition,the starting acceleration curve of the scraper conveyor is designed as "S" type to reduce the starting impulse current,thus improving the reliability and safety of the scraper conveyor.In order to solve the chattering problem and narrow speed domain problem in the sensorless control of the traditional first-order sliding mode observer method,the super-twsting algorithm is combined with the sliding mode observer to form a second-order sliding mode observer,which can effectively reduce the chattering of the sliding mode observer.Furthermore,the coefficients of the second-order sliding mode observer are designed to be related to the motor speed,which can effectively expand the stable speed domain of the sensorless algorithm.Finally,the effective convergence of the second-order sliding mode observer is verified by Lyapunov stability criterion.Finally,the direct drive system of PMSM in Henan Pingmei Shenma Group Coal Mine is used as the experimental platform to verify the algorithm,which has practical engineering significance.