Research On Voltage Fluctuation And Flicker Suppressor Of Electric Arc Furnace Based On Fault Current Limiter

As a clean secondary energy,electric power is widely used in all fields of life,There is a problem with the quality of power,which may affect the normal production and life,which may cause fluctuations in the power grid and even cause the power grid to be disassembled,and occurrence of major accident.Therefore,power quality problems are attracting more and more attention.Furthermore,with the development of social economy,The demands for steel and steel quality are increasing,and the capacity of large steelmaking equipment represented by ac arc furnace is also increasing.The power quality problems caused by high-order harmonics,voltage fluctuations and flicker,and three-phase unbalance caused by electric arc furnace have brought great harm to the power grid.Among them,voltage fluctuation and flicker problems are the most difficult to control,and it is also the focus and hotspot in the research of electric power quality control of electric arc furnace.This paper abandons the traditional reactive power compensation method of post-passive compensation and innovatively proposed a new method of unified compensation after active suppression.This new method is based on the basic principle of the current limiter,and takes advantage of its property that the inductance can be switched on and off instantaneously without additional control.Compared with the traditional method,a series of operations such as monitoring,analysis and switching action are saved,so that zero delay and instantaneous action are mostly achieved.Since no additional control is required,it is highly reliable and effectively inhibit voltage fluctuation and flicker under any circumstance in the working condition.Starting with the definition of voltage fluctuation and flicker,this paper analyzes the basic concepts of voltage fluctuation and flicker,and presents the calculation method of voltage fluctuation and flicker.Moreover,this paper also analyzes the causes of voltage fluctuation and flicker resulting from by electric arc furnace.By the comparison between the traditional device compensation method of reactive power compensation and the new method of suppression before compensation proposed in this paper,the innovation and advantages of the new method are highlighted.Based on the analysis of the working principle and operating characteristics of the electric arc furnace,a new simulation model suitable for the voltage fluctuation and flicker of the electric arc furnace is proposed.The model integrates the ideas of various electric arc furnace modeling to arc voltammetry.The characteristic is the breakthrough point.An arc model with a single arc length is established.Finally,it is regarded as a function of the arc length as needed,and the external electrical characteristics of the electric arc furnace are changed by controlling the change of the arc length.At the same time,two kinds of arc furnace models with varying laws are given—the sinusoidal law change and the white noise law change,and the advantages and disadvantages of the two models are compared.Since the novel flick suppressor proposed in this paper does not require control and can act in real time,the random change load and the sinusoidal regular change load have no difference to the flicker suppressor,in order to better verify the flicker suppressor.The validity of the model is finally selected as the simulation model of the sinusoidal law model simulating the worst case.The key of the new flicker suppressor proposed is a current limiter.This method abandons the suppression strategy of traditional SVC and STATCOM passive compensation.The current limiter can actively suppress the characteristics of current change,first suppress the fluctuation and limit the fluctuation to allow.After the range,the fixed capacitor is used for uniform compensation to raise the voltage level of the common connection point.In this paper,a new type of bridge cross-connected current limiter is applied.By analyzing its basic principle,the mechanism of the current limiter applied to the arc furnace voltage fluctuation and flicker suppression is introduced,and the magnetic circuit model of the current limiter is carried out.Through the analysis of the magnetic circuit model,it is explained that the essence of the suppressor is to replace the various types of switching devices in the traditional sense in the form of a magnetic switch.It can control the current limiting inductor instantaneously and instantaneously without external control.The switching has improved the reliability and responsiveness of the device.In addition,by analyzing the transient characteristics of the current limiter,the effect of the variable arc furnace load is explained.In order to make the suppressor effectively suppress voltage fluctuation and flicker,reducing the loss and the adverse effect on the efficiency and quality of EAF smelting as much as possible,this paper gives the suppressor related performance under the condition of electric arc furnace.The design method of parameters and body parameters,at the same time,the DC current,current limiting inductance and installation position are simulated and optimized,and the optimal solution that satisfies the suppression effect and the lowest loss is obtained.Corresponding design guidelines are provided for practical applications in engineering.Finally,the design of the 220V/30 A prototype was tested to verify the effectiveness of the device.