Equipment Development Of Power Quality Control Decice For High Power And Temperature Resistance Furnace

This paper is based on the project of "the power quality improvement of car temperature carbon graphite heat treatment high temperature electric furnace in the single heating zone and energy saving" of a Technology Group in the city ofChangsha,Hunan province.Concerning the low electrical energy utilization rate and poor power quality in the working process of the high-power high temperature electric furnace,this paper puts forward power supply hierarchical control technology for the improvement of utilization rate of electric energy;a shunt hybrid active power filter applicable to 380V low-voltage network is designed,and the harmonic source in industrial manufacture is managed on the spot.In this paper,a detailed data research is made on the pollution of harmonic wave and power factor of a working high power high temperature electric furnace at different working stage.As the reasons for the power quality issues been analyzed,the scheme of making harmonic suppression and reactive compensation for the power quality issues of high power high temperature electric furnace by the combination of active and passive treatment is proposed.In this paper,as the reasons for the low electrical energy utilization and deficiency of high power high temperature electric furnaceat high temperature caused by the difference among resistance values of graphiteelectrode in different temperature phases in its working process been analyzed,the power supply hierarchical control technology is proposed.The power is provided by large or small power sources respectively in different temperature phases,and analysis are made on the feasibility and the process of automatic switching and transition.And the validity and efficiency of the scheme is verified through simulation.Designs are made on control system and sampling circuit and the actuator,the PLC ladder diagram is compiled.In this paper,the topological structure of shunt hybrid active power filter is introduced.An equivalent circuit between passive filter and active filter is established.This paper analyses its filter theory theoretically,and makes parameter design on passive filter.The method of deadbeat voltage prediction control is proposed to stabilize dc side voltage;the principle of deadbeat control for inner current control is deduced,and the control strategy flow chart of voltage loop and inner current control is established,and the validity of the proposed control strategy is verified through simulation.Modular design is made on the active filter,and designs are made on the main circuit and control circuits respectively;heat loss calculation is carried outon the modular active current filter,and the modular APF designed after the calculation can meet the demand of heat dissipation,the relevant program design is made on the active filter.In this paper,the hybrid shunt active filter installation which is applicable to 380V low-voltage network is developed and the management of harmonic source in industrial load is carried out on the spot,and the equipment is put into operation successfully in a Technology Group in Hunan province.Site operation of the equipment demonstrates that the application of power supply hierarchical control technology and hybrid shunt active power filters can remarkably enhance the electric energy utilization rate of the high-power industrial furnace when operated under different temperature conditions.Harmoniccurrent and power factor,which used to be higher than that of official standard,now are low by international standards,thus bringing about enormous economical andsocial benefits.