Research On Nonlinear Load Harmonic Sources And Suppression Methods For Large Scale Iron And Steel Enterprises

As the implementation of national policies on energy saving and emission reduction,the smaller converter and blast furnace which were used in large steel and iron enterprises have been eliminated gradually,meanwhile,more and more electric-arc furnaces,medium frequency furnaces and rolling mills,all of which are large capacity and higher-power.However,these devices generate a great deal of harmonics when they are used.The power system harmonic is becoming more and more serious and has posed a serious threat to the safe and economic operation of power system.In actual production,in order to meet the national standards on power quality harmonic caused by non-linear load in the large steel and iron enterprises should be studied and corresponding solutions would be put forward in a next step,both of the study and solution are of great practical significance to the harmonious development between the steel mills and the power industries.In this paper,Working Principles of electric-arc furnaces,medium frequency furnaces and rolling mills which are used in large steel and iron enterprises and the harm of harmonics to power system which are generated during the working process of these devices are introduced and analyzed firstly.Then corresponding mathematical model and circuit model are developed.Finally,the effectiveness of the model is validated by simulation which is achieved by professional simulation software PSCAD/EMTDC used in power system.In this paper,an actual power supply system which is for a steel enterprise in Qing Yuan city and the nearby areas is selected as research background,the power supply models of different nonlinear loads in which a large arc furnace,a intermediate frequency furnace and a rolling mill are included,the harmonic current value which flow to the power system at peak load point is calculated.The practicality of the model is verified by comparing the simulation results with the measured value of the model.At the end,a comprehensive treatment scheme of SVC(static var compensator)is proposed after overall consideration.The effects after treatment are analyzed by calculation to ensure safe and stabilized operation of distribution power supply system used in large steel and iron enterprises.The results of harmonic suppression are clearly after adapting a treatment to compensate harmonics,thus the economic and the feasibility of the method is validated.Meanwhile,building and simulating the nonlinear models with different characters in large steel and iron enterprises are studied in this paper,which is of practical significance to power system harmonic analysis,harmonic prediction,harmonic suppression,etc.