Research And Application Of The Qian' Gang AC Frequency Conversion Control System In Hot Strip Milling

Shougang Co.Ltd.Qian'an Iron&Steel Co.hot strip milling introduced the main and auxiliary drive frequency conversion device from Toshiba Mitsubishi-Electric Industry Systems Corporation in Japan.The device provides power for the main rolling mill and roller motor.This drive equipment has the advantages of high performance and reliability,high speed control accuracy,high power factor,good stability and simple maintenance and so forth.lt has been generally recognized in the market.Especially,the main drive equipment using AC-DC-AC frequency control mode in the high power AC synchronous main rolling mill control system and using full digital vector control system to meet the high precision speed control and the transition state of the flux and torque control,satisfied the demands of different load torque and process.The object of this paper is the AC frequency conversion device in hot strip rolling line of Qian'an Iron&Steel Co.The research and application of AC frequency control system is the purpose of digesting foreign advanced technology of speed-adjusting system with frequency conversion,analysising on control strategy and optimizing of the control system,upgrading of equipment defects,etc.In this paper,according to the characteristics of AC frequency conversion control system in hot rolling mill,firstly,analyses the development of AC drive technology,and then introduces the basic configuration and structure principle in the main drive system of hot rolling.According the structure characteristics and operational principle of the three level PWM(Pulse Width Modulation)in the main drive system of hot rolling,this paper designs the bipolar triangular carrier wave simulation circuit and neutral point clamped type three-level inverter circuit simulation.In this paper,the image of the power components of the lead time sequence and the output voltage waveform in inverter is demonstrated,easy to understand and master.In this paper,the method of internal control for converter and inverter is analyzed.According the problem of speed detection in AC synchronous motor,the positioning method of the rotor is proposed.Aiming at a series of problems caused by the distortion of speed detection,this paper analyzes the problem of the resolver installation,and with the equipment modificating in precision control,the accuracy of the system is improved greatly.Paper for AC drive control system in actual production application:master and slave control,the load balance control and dynamic speed drop control,combining with the characteristics of production and process requirements,and with the functional development and optimization of the adjustment,it produces a good running effect.In addition,according the failure of main drive power unit,by the upgrading of its protective circuit and shortening the inspection cycle,it effectively reduced the probability of the occurrence in such problems.The research conclusion of this paper has been verified in the actual production process,the relevant technical indexes have been improved obviously.The research results make the stability and efficient operation in drive system,and provide a reliable technical basis for the stable production of enterprises.