Harmonic Reduction of Arc Furnaces Using D-Statcom

This paper presents simulation studies of an electric arc furnace (EAF) model in the MATLAB/SIMULINK environment. EAF was modeled as a current source controlled by a non-linear resistance. Voltage flicker, a phenomenon of annoying light intensity fluctuation, caused by EAF, has been a major power quality concern for both power companies and customers. A model was developed for the electric arc furnace and it was applied in the simulation studies of distribution static synchronous compensator (DSTATCOM) for voltage flicker mitigation. The controller for DSTATCOM was designed based on DQ-model for the reactive power management which helps in the mitigation of the flicker. With the validated EAF and STATCOM model, simulations are conducted to study the fast response of the compensator in the distribution systems.

The stochastic and nonlinear characteristics of electric arc furnaces (EAFs) lead to power quality challenges in the power system. In studying EAF behaviors, having optimized characteristics/models, selecting a suitable and optimum model that adapts to the actual characteristics of EAFs, and investigating simulation software’s capability for implementing EAF models are essential. However, the literature shows a research gap in investigating EAF simulations in various software products based on different models. This paper studies several time-domain models, such as piece-wise linear, modified piece-wise linear, hyperbolic, exponential, and exponential-hyperbolic models, for EAF modeling and simulation. The optimal estimation of parameters for the introduced models is necessary to adapt actual EAF characteristics. Thus, one of the studies taken in this paper is optimizing the EAF model’s characteristics. The proposed optimization problem is solved using the genetic algorithm (GA) and particle swarm optimization (PSO). Moreover, the optimized models are simulated in DIgSILENT and EMTP-RV to investigate different EAF models from the viewpoint of accuracy and efficiency. The optimization of different EAF models’ characteristics and comparison of EMTP-RV and DIgSILENT in simulating EAF behavior are the contributions of this paper. The proposed method is validated based on the actual data of a realistic EAF-based steel company in Iran. The obtained results show that the modified piece-wise linear model has the most accuracy in identifying the EAF behavior. The test results based on DIgSILENT and EMTP-RV simulations imply that the EAF could be simulated with high accuracy using modified piece-wise linear and piece-wise linear models. In general, EMTP-RV has expressed more accuracy in simulating different EAF models, and the simulation execution speed of EMTP-RV is around 2.5 times faster than DIgSILENT. In contrast, DIgSILENT is more suitable to facilitate the power system studies of EAF according to its extensive study tools and library.

The electric arc furnace can cause voltage flicker and produce harmonics that can impact the power system. This is due to the characteristics of electric arc furnace as a nonlinear load. Designing an electric arc furnace model is intended to study the characteristics of the electric arc furnace and its impact to the power system. The voltage flicker model of Chua's Chaotic Circuit and differential equations of the arc length will be used in the modeling of the electric arc furnace. In accordance with the purposes of this study, the model of electric arc furnace will be applied to the design and placement plan in the power system. Before applying the electric arc furnace model to the power system, the v-i characteristic of electric arc furnace, harmonics, flicker, and other preinstallation requirements will be studied as mentioned in the grid code.

Problem statement: The Electric Arc Furnace (EAF) is a non-linear load and creates power quality related problem. Therefore, accurate modeling of the EAF is essential. Approach: In this study, an optimal model for EAF in time domain called exponential-hyperbolic, was proposed to describe the behavior of the EAF for all of the operating conditions and it does not need the initial conditions as they needed for the existing methods of modeling of the EAF. Then, the behavior of the proposed model of EAF on the power system was studied using the PSCAD software. In order to analyze the proposed method, several characteristics for different operating conditions were investigated. Results: In the simulation, the parameters were taken from the EAF of the Mobarakeh Steel Making Company (Isfahan-Iran). The results of the simulation accurately showed the behavior of the EAF of the company. Conclusion: The finding of this study showed that the proposed exponential-hyperbolic model was capable in modeling of EAF for different operating conditions.

Electric arc furnaces have intense non-linear, time variant, and uncertain characteristics bringing about voltage and current harmonics, unbalances, and voltage flicker. In this article, a new three-phase dynamic and intelligent arc furnace in time domain based on adaptive neuro-fuzzy inference system is proposed. In this approach, the adaptive neuro-fuzzy inference system is trained by several actual electric arc furnace operations, and a pattern detection based on the modified chain code method is presented. Hence, electric arc furnace performance is analyzed by applying a preprocessing stage using low-pass average filters and chain code method that recognizes the defects in different patterns such as pulses, impulses, similar and inverse profiles, steps, etc. A chain code is a lossless compression algorithm for detecting the behavior of different data. The adaptive neuro-fuzzy inference system is simultaneously trained by electric arc furnace operation at each stage by means of the patterns. For data collection, a power quality analyzer and oscilloscope are connected to different actual electric arc furnaces. Finally, the electric arc furnace model is presented as a voltage source depending on a current similar to a non-linear black box. This model has no linearity in arc characteristic and can show an actual arc.

Voltage flicker and harmonics are the power quality problems which are introduced to the power system as a result of nonlinear and stochastic behavior of the arc furnace operation. To analyze harmonic and flicker generated by an arc furnace, accur ate arc furnace models are needed. In this paper, different arc furnace models with different level of complexity are reviewed. In the first part of this paper a new developed time domain static model based on a piece-wise linear approximation of the V-I characteristics of the arc furnace is presented. While static arc models are useful for harmonic studies, dynamic models are useful for power quality studies specially the study of voltage flicker. In the second part of the paper, dynamic model for an arc furnace us ing MATLAB (Simulink) is presented. In addition to this, the novelty of this simulation technique lies in the fact that the variation of power transmitted to the load by the arc furnace during the cycle of operation is considered, thus making the proposed model more accurate and dependent on the operating conditions of the load. Finally recommendations are made for the application of some of these models and the accuracy of the presented model to other models from the practical point of view by using MATLAB is shown.

Electric arc furnaces (EAFs) are nonlinear and time-variant loads that cause severe fluctuations of current, voltage, and current harmonics, voltage flicker, frequency changes, etc. The requirement is to present an accurate model to analyze the function of these types of loads. In this paper, a new model based on hidden Markov model theory is presented for an electric arc. For this purpose, the characteristic of the arc voltage-current is divided into four regions. Then, on the basis of actual measured samples of an electric arc in several functioning cycles of EAF, different operating points are generated in the form of statistical probability, corresponding to hidden Markov theory in the aforementioned four regions. The arc model is designed in the form of a current-dependent voltage source. Therefore, the proposed model is without linear approximation and corresponds to the actual state. Also, in order to be accurate in flicker modeling, a voltage is randomly considered for the arc model. After designing the aforementioned model, the effects resulting from this electric load in the power system are studied and analyzed. The simulation results are compared with the measured arc to show the accuracy and soundness of the model.

Electric Arc Furnace (EAF) with nonlinear characteristic and often causes various power quality (PQ) problems is the common seen smelting equipment in the industrial power system. Electricity users and utilities continuously seek the useful solutions for the improvements of these PQ problems. In recent years, the applications of using solar photovoltaic (PV) technology for PQ controls are become more and more because of the increasing installations of solar PV power generations. Purpose for this study aims to design a multi-mode PV-STATCOM system for the mitigation of voltage fluctuation that caused by EAF in the steel plant system. Performance of proposed PV-STATCOM design is tested and verified by MATLAB/Simulink simulations under a real 11.4 kV electric feeder with a 45 ton AC EAF load. Results show the proposed system has a well performance than that in general PV-STATCOM that only using unique control mode.

The chapter covers general issues related to power quality in Electric Arc Furnaces. The use of electric arc furnaces (EAF) for steelmaking has grown dramatically in the last decade. Of the steel made today 36% is produced by the electric arc furnace route and this share will increase to 50 by 2030. The electric arc furnaces are used for melting and refining metals, mainly iron in the steel production. AC and DC arc furnaces represent one of the most intensive disturbing loads in the sub-transmission or transmission electric power systems; they are characterized by rapid changes in absorbed powers that occur especially in the initial stage of melting, during which the critical condition of a broken arc may become a short circuit or an open circuit. In the particular case of the DC arc furnaces, the presence of the AC/DC static converters and the random motion of the electric arc, whose nonlinear and time-varying nature is well known, are responsible for dangerous perturbations such as waveform distortions and voltage fluctuations. Nowadays, arc furnaces are designed for very large power input ratings and due to the nature of both, the electrical arc and the melt down process, these devices can cause large power quality problems on the electrical net, mainly harmonics, inter-harmonics, flicker and voltage imbalances. The Voltage-Current characteristic of the arc is non-linear, what can cause harmonic currents. These currents, when circulating by the electric net can produce harmonic voltages, which can affect to other users. In evaluation and limitation, there are some definitions and standards to quantify the disturbance levels, such as (***IEC, 1999), (***IEEE 1995), and (***IEEE, 1996). and. The total harmonic distortion (THD), short-term voltage flicker severity (Pst), and long-term voltage flicker severity (Plt) are used. However, sometimes it is desired to record voltage and current waveforms in the specified duration to track the disturbance levels.

La operación de los hornos de arco eléctrico (EAF) causa variaciones en las variables eléctricas, como son: potencia activa, reactiva, voltaje y frecuencia. Estas variaciones se deben al funcionamiento propio del EAF que produce un consumo altamente intermitente, lo que lo hace una carga especial. Este trabajo presenta una metodología para el análisis e interpretación de los datos registrados por el sistema SCADA/EMS y el sistema de monitoreo de área extendida WAMS, durante la operación de un EAF conectado al sistema eléctrico de potencia (SEP) de Ecuador. El propósito de este análisis es caracterizar las perturbaciones a través de las variables eléctricas frecuencia, voltaje, potencia activa y reactiva, medidas en la Subestación más sensible a la operación del EAF. Para esto, se realiza un análisis de datos multivariantes basado en Funciones Empíricas Ortogonales EOF, junto con clasificadores inteligentes. Adicionalmente, se propone un modelo de EAF para simulación de transitorios electromecánicos, el cual se basa en un tren de pulsos de ancho modulado (Pulse-width modulation PWM), afectado por una señal de ruido de frecuencia parametrizable. Tanto la propuesta metodología para caracterización de la actuación del EAF a través de registros, como el modelo propuesto muestran prometedores resultados respecto de la evaluación post-operativa y de planeamiento operativo del impacto de la operación de un EAF en el SEP.

This companion paper to that presented at the 2009 IEEE IAS Annual Meeting describes new differential protection solutions for electric arc furnace (EAF) power systems that use Rogowski Coils as current sensors. These novel solutions provide multiple protection zones, covering the entire EAF electric supply system. The protection philosophy includes multiple differential zones of protection such as cables serving the EAF vault, series reactors, EAF transformers (including all power apparatus in the protection zones), and busbars.

Problem. Electrical distribution networks are plagued by power quality problems, which have a negative impact on sensitive electrical loads. These problems include reactive current, low power factor on the load side, and voltage harmonics, voltage sags and voltage swells on the grid voltage side. To address these issues, a unified power quality conditioner (UPQC) that combines shunt and series compensators is suggested. The goal of the work is to implement a UPQC integrated with a photovoltaic (PV) system to mitigate power quality problems in the power system, and boosting the grid supply through power injection from the PV system. Methodology. One of the less complex and effective ways to improve the grid’s voltage quality is by using the unit vector template generation (UVTG) strategy as the composition technique (UPQC-P) through the UPQC series compensator. The synchronous reference frame (SRF) strategy through the UPQC shunt compensator to improve the current quality on the load side is used. To further optimize the SRF strategy, it is used the snake optimization (SO) to find the optimal values for the PI controller’s parameters. Results. The UPQC-PV is used to mitigation the power quality issues in the grid and loads by UVTG and SRF techniques in series and shunt compensators, respectively. Scientific novelty. The composition technique (UPQC-P) through a series compensator and uses the SO for tuning the PI controller in the shunt compensator. Practical value. This study reduces the total harmonic distortion (THD) in the load voltage to 0.57 %, while the THD in the grid voltage remains at 10 %. It restores the load voltage to its reference value of 230 V during voltage sags (down to 161 V) and swells (up to 300 V) in the grid. Additionally, it mitigates the low power factor on the load side (0.707 lagging) to achieve a unity power factor in grid current, balances the unbalanced load current to a balanced grid current, and enhances grid stability by injecting power from the PV system into the grid. References 33, table 3, figures 7.

Arc furnaces are known to cause voltage flicker and to inject harmonics into the power system. Utilities and customers are concerned about these effects and try to take precautions to minimize them. Simulation is a powerful means of testing and verifying proposed solutions to this end. Developing an arc furnace model that can duplicate its erratic operation has been a challenging task for several researchers in the past. Two classes of approaches have been proposed for the modeling problem: stochastic and chaotic. Both methods have their advantages and shortfalls as shown in related publications. In this paper, the authors present the results of a study, where an arc furnace is modeled using both chaotic and deterministic elements. The flicker effect, which is the manifestation of voltage fluctuations, is captured using the well studied Chua's chaotic circuit, whereas a dynamic model in the form of a differential equation is used for the electric arc. The resulting model produces both effects and the resulting harmonic spectrum of the simulated arc furnace voltage is used as an illustration.

Due to the proliferation of non-linear modern power electronics, currents and voltages produced by non-linear loads have lead to the deterioration and distortion of the output sine wave forms of the source currents and voltages. These distortions have resulted in the power quality problems. The non-linear load draws reactive power and harmonics from the ac source in the fundamental current. The harmonics in power system caused by non-linear loads such as, arc furnaces, switch mode power supply, fluorescent lamps rectifiers etc all are the main sources of harmonics, as a result of these non-linear loads the supply system lead to overheating of cables and conductors, electromagnetic interference to nearby communication facilities etc. Therefore, as a result of theses harmonics, a traditional passive filters are used to suppressed the integer multiple fundamental frequencies, but due to the passive filter draws back in producing series or parallel impedance with the supply impedance and heavy in sized, its limitations in service becomes an old scheme. The application of shunt active power filter in mitigating these harmonics problems supersedes the used of passive filter. This paper, presents the modeling and simulation of single-phase shunt active power filter controlled with fuzzy logic controller (FLC) to mitigate the harmonics drawn by non-linear loads. The proposed scheme is performed by using MATLAB fuzzy tool box environment. Simulation results obtained by the proposed control algorithm found to be satisfied and within the recommended imposed IEEE 519-1992 harmonic standard limit.

철강 소비가 늘어나고, 전기아크로 운영기술의 발전에 따라 아크로의 사용이 증가하고 있다. 그러나 전기아크로의 사용이 늘어날수록 계통에는 악영향을 미치게 된다. 즉, 전력품질 문제인 전압 및 전류 고조파, 상 불평형, 역률저하, 전압 플리커 등의 문제가 발생하고 있다. 여기서는 시변 특성과 비선형 특성을 갖는 고조파에 대하여 해석하였다. 우선 전기 아크로가 포함된 전력계통 모델을 만들고, 전기 아크로의 다양한 운전 조건에 따라 발생된 고조파가 계통에 미치는 영향을 분석하였다. 또한 고조파 저감 대책으로 고조파 필터를 설계하여 그 영향을 검토하였다.