Research And Application Of Key Technologies For Power Quality Control Of AC Electric Arc Furnace

At present,the ratio of electric furnace steel production in China is far below the global average.Under the guidance of the national sustainable development policy,electric furnace steelmaking has gradually risen to a hot spot.However,as an important equipment for sustainable development of steel industry,the AC electric arc furnace is more and more invested in the power grid.The power quality problems caused by its special electrical properties are becoming more and more serious,affecting the safe and stable economic operation of the power grid.Therefore,the research on the power quality control technology of AC electric arc furnace is of great significance.Firstly,this paper introduces AC electric arc furnace and its power supply and distribution system,and based on the measured grid-connected data,the power quality emission characteristics of typical AC electric arc furnace are carried out from four aspects:harmonic,interharmonic,negative sequence and reactive power impact.The research results show that the AC electric arc furnace is a non-linear load with both impact and three-phase asymmetry,which lays a foundation for the power quality control of AC electric arc furnace.Secondly,in view of the current situation that the influence of electric arc furnace transformer magnetizing inrush current is not considered in the power quality treatment of AC electric arc furnace,this paper analyzes the influence of electric arc furnace magnetizing inrush current on the power quality control device from three aspects:theoretical analysis,measured data and simulation modeling.The research results show that the effect of magnetizing inrush current must be considered in the design of secondary filter branch.After that,aiming at the problems existing in the four key technologies of power quality limit calculation,interference generation calculation,passive filter design and TCR capacity allocation in AC electric arc furnace power treatment,the power quality limit calculation system and interference generation calculation method are improved.The calculation method of the amount of occurrence,the passive filter design and safety check method considering the magnetizing inrush current of electric arc furnace transformer and the characteristics of electric arc furnace are proposed,and the TCR capacity allocation method is given based on the Steinmetz compensation theory.Finally,the above-mentioned contents are applied to the AC electric arc furnace power supply and distribution system of a steel plant,which verifies the feasibility of the proposed scheme.Based on a large number of measured grid-connected data of AC electrics arc furnace,this paper reveals the power quality emission characteristics of AC electric arc furnaces and proposes a method for designing and checking filter parameters that takes into account the influence of magnetizing inrush current and gives an effective method for allocating TCR capacity.The above methods have achieved good results in practical projects and is of great significance to the planning and design,safe operation and power quality improvement of AC electric arc furnace power supply and distribution system.