Sharif Digital Repository

For steel industries optimum operation with high efficiency is of the first importance. On the other hand, extra investments in the supply side of electric arc furnaces may have been seen as redundant cost. Therefore, to improve the system efficiency, devices such as SVCs or STATCOMs can be employed. In this paper, the benefits of dynamic shunt reactive compensation by SVCs in steel industries are investigated. It is shown that this operation leads to optimization in steel production process and is completely beneficial from economic point of view. Supply system of a typical arc furnace is simulated using MATLAB software and the effects of a compensator on the operating characteristics of an... 

This paper presents a new time domain model for electric arc furnaces using MATLAB, The model can simulate both nonlinear and time varying nature of such loads, which create flicker, harmonics, and voltage/current unbalance. In this model, Cassie and Mayr equations are used in three-phase mode and the effects of arc furnace transformer tap changer and flexible cables mutual inductances are considered. The proposed model takes into account the system inter-relation of parameters and arcing conditions as well  

This paper presents a newr control strategy for the shunt active filter in three-phase three-wire svstems with zero sequence voltages. An extended method based on instantaneous power theory in a rotating reference frame is developed for extracting the compensating signals for highlv/randomly varying loads. Since voltages at the point of common coupling contain low frequency interharmonics, conventional methods can not be used for dc voltage regulation. Therefore, a new method is introduced for this purpose. A three-phase electric arc furnace model is used to showT power quality improvement through reactive power and harmonic compensation by a shunt active fi'lter using the proposed method.... 

This paper presents an electric arc furnace (EAF) optimization framework intended to define optimal control profiles for the EAF, in order to increase its efficiency and thus reduce the energy consumption. The framework aims to minimize controllable losses and to maximize energy transfer to the bath and, consequently, minimize the operational costs. This is achieved through improved actuation of the EAF inputs, i.e., transformer power, oxygen lancing, and carbon addition. To achieve maximal energy transfer to the bath and to reduce the heat losses from the arcs, proper properties of the slag, such as foaminess and basicity, are a subject of considerable attention. The framework is designed... 

The ability of static VAr compensators (SVC) to reduce the flicker caused by electric arc furnaces and other variable VAr loads depends on their speed, which is limited by delays in reactive power measurement and thyristor ignition. In this paper, a predictive method is proposed to compensate the delay time and, hence, to improve the SVC performance. Previous samples of the load reactive power are used to predict its future values. Predicted VAr is then applied as a reference for reactive power compensation. © 2006 IEEE  

In this study main reactive power calculation methods are evaluated and compared. Furthermore, a novel simple method that can be used for calculation of reactive power in electric arc furnace (EAF) plants is proposed. The focus here is on their application in the control system of static VAr compensators (SVCs). SVC can compensate only the fundamental harmonic component. So the reactive power signal used in the control system should be sensitive only to the main harmonic component. In addition, the reactive power calculation should be fast enough that SVC can follow the quick changes of the load to mitigate the flicker efficiently. To compare various reactive power calculation methods and to... 

The paper presents a conceptual study on modification of the electric arc furnace (EAF) slag doors in order to allow removal of the excess slag from the EAF. The idea behind additional slag doors is to allow deslagging of the bath in certain unfavorable cases when the slag height is too great. Slags which exceed the optimal height cause unnecessary refractory corrosion and additional energy losses. The study proposes symmetric slag doors comprised of two hatches, i.e. upper and lower. The upper hatch is intended to decrease the slag height to the optimal level, while the lower hatch can be used to completely deslag the EAF at tapping. In this manner, tilting of the EAF is not necessary. A... 

This paper presents a new compensating system, which consists of a shunt active filter and passive components for mitigating voltage and current disturbances arising from an Electric Arc Furnace (EAF). A novel control strategy is presented for the shunt active filter. An extended method based on instantaneous power theory in a rotating reference frame is developed for extraction of compensating signals. Since voltages at the Point of Common Coupling (PCC) contain low frequency interharmonics, conventional methods cannot be used for dc voltage regulation. Therefore, a new method is introduced for this purpose. The passive components limit the fast variations of load currents and mitigate... 

The paper studies the effects of solid and liquid steel properties on the heat transfer coefficient (HTC) in electric arc furnaces (EAFs). Mathematically speaking, the HTC is a function of solid and liquid steel properties. Different velocities of the bath cause different flow paths around the solid particles and therefore different HTCs - a computational issue that has not been addressed yet. Therefore, a simplified calculation model is proposed, intended for HTC estimation according to the EAF conditions. Although many studies investigated this topic, most of them either assume unconventional conditions for the EAF operation, are computationally complex or focus on a specific case; and... 

In this paper, a conceptual study and quantification of using a thermophotovoltaic system (TPV) to convert incident radiation on furnace panels to electrical energy is presented. In typical electric arc furnaces (EAF), a considerable amount of energy is wasted during the melting process, that is, steel enthalpy, off-gas extraction, vessel cooling, slag enthalpy, and others. Although a remarkable share of the energy is wasted in circulating water, the contained exergy is simply too low to be considered for heat recovery (under 0.5% of input exergy) in comparison to energy content of the extracted gasses and slag. In the performed study, a TPV power output is calculated as a function of arc... 

Electric arc furnaces are used to make steel from scrap iron in steel industry. Nowadays, the aim of more researches in this area is to increase yield of furnace and it's compatibility with environment. One of the methods to achieve these purposes is to control the off-gas system as relative pressure in furnace would be kept negative. Because the combustion gases inside the furnace must not leak into the plant environment. However for preventing of loss of energy, the amount of this negative number must be small. In this paper, new intelligent control method named fuzzy emotional control, applied to off- gas system to control the relative pressure in the furnace and its result is compared to... 

The nonlinear and time varying nature of electric arc furnaces (EAFs) create flicker, harmonics, and voltage/current unbalances. Nowadays to improve the performance of EAFs and the power quality problems of electrical systems around them high speed compensators like STATCOM are needed. This paper uses a time domain model for electric arc furnaces and a new model of STATCOM respectively for creating and improving mentioned power quality problems. In this paper, first we investigate and simulate electric arc furnace and STATCOM using SIMULINK/PSB. Second, we simulate a network including them completely. The proposed models take into account arcing conditions and associated effects improvement... 

AC electric arc furnaces (EAFs) highly reduce power quality of the network by generating disturbances such as flicker and harmonics. These disturbances are due to the nonlinear electromagnetic and thermal field behaviors of the AC arcs. Analysis of these nonlinear behaviors is required for improving power quality in the network. This paper presents a three-dimensional finite element modeling of the electromagnetic fields in an AC three-phase electric arc furnace. The model includes the electrodes, arcs and molten bath. Current density, voltage and magnetic field intensity in the arcs, molten bath and electrodes are predicted as a result of applying the three-phase AC voltages to the EAF.... 

This paper discusses the application of unified power quality conditioner (UPQC) for improving power quality of a system supplying an electric arc furnace (EAF). The UPQC includes combined series and shunt active filters sharing a common DC link. It is used to mitigate voltage disturbances and compensate for reactive power, harmonics and interharmonics. A novel control strategy for the UPQC is presented. As voltages at the point of common coupling contain low-frequency interharmonics, conventional methods cannot be used for extracting voltage reference signals. In the proposed method, voltage references are extracted using a phase-locked loop to generate sinusoidal waveforms. Current...