直流电弧炉电弧等离子体射流的数值模拟

数值模拟是研究直流电弧炉中电弧等离子体射流特性的有效方法,它可为理解和优化电弧炉冶炼过程提供参考依据。本文对直流电弧炉冶炼过程建立了电弧等离子体的二维稳态轴对称磁流体力学模型,采用大型商业软件PHOENICS对电弧流场和温度场进行了计算,仿真结果与文献报导的实际测量结果吻合良好。     

用于高效冶炼氧化镁的双电极直流电弧炉的仿真与实验

将一台3 000k V·A的三相交流氧化镁冶炼电弧炉改造成相同容量的双电极直流电弧炉。揭示了在不同冶炼电流下,输出电压与最大弧长之间的关系。同时,采用三维有限元法对氧化镁熔池的温度场分布进行仿真分析,得出熔池温度场的分布规律。利用改造后的电弧炉制得高纯度的氧化镁晶体,且冶炼得到的氧化镁熔坨的形貌近似椭圆形横截面的拉伸体,与仿真结果一致。最后,比较采用直流电弧炉和交流电弧炉冶炼氧化镁的生产数据,结果表明双电极直流电弧炉冶炼氧化镁的工艺,在单吨能耗、电极损耗以及晶体纯度等方面,均优于传统的三相交流电弧炉。本文工作为采用双电极直流电弧炉生产氧化镁提供了理论指导和依据。     

基于测量数据的电弧炉随机模型及谐波电流计算

文章介绍了一种用于电弧炉谐波分析的时域模型。该模型基于交流电弧的伏安特性,在实测数据的基础上利用统计技术得到电弧伏安特性曲线的有关参数,并采用分段线性化方法模拟电弧炉的伏安特性,在此基础上进行电弧炉的电流计算及谐波分析。在计算中将影响电弧炉工作状态的主要随机因素考虑进来,建立了电弧炉随机分析模型。对某钢厂的12500kVA电弧炉进行了分析研究,分析结果与实测数据有很好的一致性。     

基于实测数据的电弧炉实时数字仿真模型及其实现

提出了一种基于现场实测数据建立电弧炉实时仿真模型的方法。该模型将电弧炉等效为受现场实测数据控制的电流源,采用锁相技术实现了实测数据与实时仿真系统的同步,从而使得长时间实时仿真成为可能。在此基础上,本文还根据实际电弧炉配电系统,搭建了用于静止无功补偿(SVC)系统控制和保护设备闭环测试的实时仿真系统(RTDS)并进行了控制器闭环测试。仿真和测试结果表明,本文提出的电弧炉建模方法是可行和有效的,该模型能够全面而真实地再现实际电弧炉引起的诸如电压波动与闪变、谐波、三相不平衡等电能质量问题,所建立的RTDS实时仿真测试系统可以用于SVC控制系统的闭环测试。     

用于电能质量研究的新型交流电弧炉混沌模型

提出一种用于电能质量研究的新型交流电弧炉混沌模型。首先,基于电弧炉负载U-i特性曲线的分段线性化,依据负载实际消耗的有功功率,得到能精确反映电弧炉稳态特性的静态模型,该模型适用于电弧炉引起的谐波问题研究。然后,用基于不对称非线性电阻蔡氏电路产生的低频混沌信号对静态电弧电压进行调制,模拟电弧炉运行的动态过程, 得到电弧炉负载的动态模型,该模型特别适用于研究电弧炉引起的电压波动与闪变问题。在Matlab下,对电弧炉静态、动态模型进行仿真研究。仿真结果与实际测量数据相比较,显示该模型能够精确描述电弧炉引起的谐波和电压波动等电能质量问题。模型有效且易于使用,它的提出为电能质量治理措施研究奠定了基础。     

The effect of electrode-holding arms on the electrical parameters of the bus-tube section of current lead in an arc steel furnace

The essence of the electromagnetic effect of metalware located near current-carrying elements has been shown. Aftereffects, such as heating of metalware, additional active losses of power supply, perturbation in the magnetic field, and consequent changes in the active resistance and inductive reactance of the equivalent circuit of a furnace have also been considered. The existing technique of taking into account the influence of metalware located near current-carrying elements on the electrical parameters of the current lead of high-power technological equipment has been examined, with its drawbacks being revealed. A method for increasing the accuracy and range of applicability of the technique has been suggested. To do this, a more universal coefficient of neighboring metalware (CNM) has been introduced. The coefficient allows us to take into account the influence of metallic structures on the resistance and magnetic reactance of the furnace circuit. The results of numerical simulations for a bus-tube section of current lead in a 100-t arc steel furnace (ASF) have been presented. The results of simulations were compared with the experimental data obtained by physical modeling of current lead of a 100-t ASF. A numerical model validated by such a way was used to obtain the dependences of active resistance and inductive reactance and CNM on the geometry of the investigated section and the properties of electrode-holding arms. The obtained dependences are the basis for an engineering technique intended to design current leads for an arc steel furnace.     

交流电弧炉的间谐波检测及状态判断

针对交流电弧炉不同工况的状态判断问题,文中将能量平衡关系推导出的交流电弧炉时变电阻,与经典非线性电阻模型相叠加,创新地加入弧长随机变化模型,形成了新的可模拟电弧炉不同工况状态的时变电阻模型。应用Matlab/Simulink软件仿真验证了模型的准确性。对仿真出的电弧炉在熔化期、精炼期中的电压电流,用总体平均经验模态分解(EEMD)方法分别进行分解,得到了电弧炉不同时期下全然不同的间谐波特征。实验结果表明,EEMD可消除经验模态分解(EMD)遇到的模态混叠问题,保证了提取出的两个时期电压电流中间谐波信息的准确性与有效性。基于此结果,提出了一种依据不同工况下间谐波特征对电弧炉进行状态判断的方法。     

Electrical Power Quality of Iron and Steel Industry in Turkey

The iron and steel industry has been growing increasingly in Turkey in the last decade. Today, its electricity demand is nearly one tenth of the installed generation capability of 40 GW in the country. In this paper, power quality (PQ) investigations based on the arc furnace installations of the iron and steel plants using field measurements according to the international standard IEC 61000-4-30 are documented. Interharmonics and voltage flicker problems occurring both at the common-coupling points of those plants and at the arc furnace and static var compensator (SVC) systems of the plants themselves are determined with the use of GPS receiver synchronization modules attached to the mobile PQ measurement systems. It has been observed that flicker and interharmonic problems are dominant at the points of common couplings where arc furnace installations are supplied. Based on the field measurements obtained with collaborative work of five arc furnace plants, it is possible to say that contemporary SVC systems cause interharmonic amplification problems around the second harmonic, and novel methods are required to solve this problem.      

Curve-fitting-based method for modeling voltage–current characteristic of an ac electric arc furnace

Field measurements of voltage and current are the most effective way for characterizing the electric response of an ac electric arc furnace that describes its nonlinear behavior. Sufficient measured information can be adopted to determine the background harmonic level in a power system, to characterize specific sources of harmonics, and to develop an appropriate nonlinear voltage–current characteristic. In this paper, a curve-fitting-based method called cubic spline interpolation is proposed to model the voltage–current characteristic of an ac electric arc furnace in the steady state. Meanwhile, the actual measured data are collected for modeling use. Two classic methods, harmonic current injections and equivalent harmonic voltage sources, for modeling the electric arc furnace load are reviewed and used to evaluate the performance of proposed model. Results obtained from the measured data and computer simulations of the three electric arc furnace models are then compared according to the voltage and current waveforms, as well as the voltage–current characteristic. It is shown that the proposed model is more accurate than the two classic approaches for harmonic assessment of electric arc furnaces and can be used for modeling similar types of nonlinear loads in the harmonic penetration study.     

电弧炉电极调节器对电网电压波动影响的仿真研究

针对电弧炉电极调节器性能对电网电压波动的影响进行了仿真研究。利用Matlab/Simulink提供的基本模块库和电力系统专用模块库相结合,搭建交流电弧炉系统的仿真模型。整个仿真模型可分为两部分,即电弧炉主电路和电弧炉电极调节系统,两部分结合构成一个闭环系统。根据电弧炉的工作特点,在仿真时,考虑分别加入两种类型的弧长扰动,即短路扰动和低频正弦扰动。在每种扰动下,通过改变电极调节器的性能参数,研究电网电压的波动。仿真结果表明在电极调节器性能参数设计不合理的情况下,电网电压波动剧烈,在性能参数理想的情况下,电网电压的波动幅值会大大地减小。     

直流电弧炉用混沌理论和神经网络建模及预测

根据直流电弧炉电弧电压信号所具有的混沌特性,使用相空间重构理论和径向基函数神经网络对直流电弧炉进行了建模和预测研究。先计算了电弧电压时间序列的最大Lyapunov指数来验证电弧电压信号的混沌特性,后对所测得的电弧电压信号进行相空间重构,根据所求得的嵌入维数和延迟时间,使用径向基函数神经网络对电弧电压信号建模和预测。分析表明:该法用于直流电弧炉电气特性的建模研究,且进一步提高了预测的准确性。同时,多步预测结果可为直流电弧炉电弧电压的有效控制提供理论上的参考依据。     

用于谐波分析研究的电弧炉系统的模型和仿真

为电弧炉系统谐波分析提供了一种新思路,在理论上作了研究,并用实例证明了它的可行性。首先根据电弧电阻的随机性公式,用Matlab仿真得出电弧电阻随时间变化曲线,再用对实际电弧炉系统进行仿真和谐波分析,最终得到电弧炉系统的各次谐波含量,与实际数据比较,误差较小,因此认为此方法是可行的。     

Analysis of characteristics of electric arc furnaces as control objects

Small-scale analysis of the operating modes of electric arc furnaces (EAFs) has been performed under conditions of basic control and disturbing effects. The influence of the nonlinearity of the current-carrying conductor on the power-transmission coefficients has been investigated for different melting-process stages. The study of the adjusting characteristics of the furnace has shown that power-transmission coefficients have a sign-alternating character during movements of electrodes with transition through zero at maximum power, which makes such a control action ineffective under the above conditions. The nonlinearity of the current-carrying conductor weakly affects the current value at the maximum power, but it reduces the arc voltage and length. The values of power-transmission coefficients comparable in arc length and current in the working range of the operating conditions show an equivalence of the controllers that stabilize the current or the arc length (arc voltage) in terms of the accuracy of controlling the arc power. It has been shown that the current-transmission coefficient during the melting stage reaches considerable values, which causes pronounced changes in the furnace conditions and occurrence of the flicker. It has been established that, to mitigate the adverse effect of the supply-voltage disturbance, it is reasonable to apply current controllers.     

Simulation of Arc Furnace Power Systems

An electronic arc model has been developed which simplifies the study of harmonic phenomena in are furnace power systems on a transient network analyzer (TNA). The model helps insure the proper magnitude and phase relationship of the harmonies at each loading condition. The simulation procedures and arc model characteristics are described. Also, some examples of typical study results are given.     

Nonlinear properties of voltage and current transfer ratios for electric arc furnaces

A method of arc voltage gradient calculation for an electric arc furnace (EAF) is presented. The arc voltage gradient is the basic characteristic in study and simulation of an automatic power control system of an EAF. This characteristic is a strongly nonlinear multifactorial function that depends on electrical parameters of a power supply system, thermal conditions, and processes of arc heat exchange in an EAF melting bath. The method of arc voltage gradient calculation considers the relation between the electric and thermal conditions of an EAF in order to describe feasible nonlinear properties and to improve expressions for voltage and current transfer ratios as nonlinear multifactorial functions in particular. An EAF is regarded as a subject of control. Multifactorial properties are defined by the parameters of an equivalent electrical circuit of a furnace and by variable conditions of arc heat exchange in a melting chamber during steel melting. The method is effective for overcoming the uncertainty of the arc length in simulation of an EAR power controller. The unstable behavior of the furnace at a high impedance was explained using the obtained functions of the arc current and the arc voltage for various electrodes and the arc length. The minimum allowed arc current was found. The automatic power controller becomes unstable and the arc is extinguished under this value.     

递阶智能控制在电弧炉控制系统中的应用

由于电弧炉铅锌冶炼过程是一个极其复杂的物理化学过程，具有较强的非线性、不确定性、事变性和强耦合等。对于这样一个复杂过程，要建立它的精确数学模型是非常困难的，甚至是不可能的。根据大量的冶炼经验和统计数据，本文提出了一种基于专家控制系统的递阶智能控制的控制策略，这种方法已成功应用于广东韶冶的铅锌冶炼之中，且该方法对于其他的复杂生产过程控制也具有一定的指导意义。     

电弧炉电气系统谐波分析的频域方法研究

文中对电弧炉电气系统谐波分析的频域方法进行了研究。首先对电弧电压波形进行了傅立叶分析，接着讨论了电弧炉系统谐波分析的思路。从替代定理和叠加原理出发，将三相对称及不对称电弧炉系统简化为单相系统进行求解。经过电路分析，导出了电弧炉系统主电路谐波、注入电网谐波、流过电容器谐波的解析计算公式。分析表明：电弧炉系统的主电路谐波的大小与系统的谐波阻抗、电弧电压波形和电弧炉的平均功率因数有关，电弧炉注入电网的谐波主要为低次谐波。当电弧炉电气系统在串联谐振点和并联谐振点附近时，均会出较大谐波电流，而串联谐振对系统的影响更大一些。     

Power Usage and Electrical Circuit Analysis for Electric Arc Furnaces

Power usage in ultrahigh-powered electric arc furnaces requires considerably more investigation into system parameters, furnace secondary circuit analysis, and operating characteristics than previously given to normal powered electric arc furnaces. The power input must be analyzed from the infinite electric utility bus to the arc at the electrode. All interested parties must participate in the analysis to assure a mutual understanding of each other's problems. Various high-voltage systems are compared along with power factor correction applications. An 18-ft (5.5-m) 80-ton (72.6-metric tons (MT)) furnace has been selected for detailed analysis with a 50-MVA furnace transformer. In addition to electrical considerations, the power melting profile and associated refractory erosion is also subjected to analysis in this review. The analysis indicates that with proper application, ultrahigh-powered electric arc furnaces will provide increased production with reasonable refractory erosion.     

交流电弧炉SVC装置2次滤波支路设计校核新方法

交流电弧炉不仅属于典型的谐波污染源、闪变发生源,而且交流电弧炉冶炼过程在2次附近产生较大的间谐波分量。基于某实际钢铁公司交流电弧炉谐波发生量和SVC装置参数的定量分析及仿真研究,得到交流电弧炉必须设置2次C型滤波器,保证将电弧炉2次左右的谐波和间谐波放大控制在一定范围内的研究结论。在此基础上给出2次滤波支路的设计方法,提出了2次滤波支路安全校核新方法,指导交流电弧炉滤波装置工程设计。     

An adaptive arc furnace model

This paper presents an adaptive arc furnace model. The integrated model is divided into three parts, the supply system model, the nonlinear load model and the controller model. First, the supply system is represented by a set of linear differential equations. Simulation is achieved by a numerical method and the measurements are taken as the control input. Secondly, based on the arc melting process and typical arc furnace V-I characteristic, the arc furnace load is described as a current-controlled nonlinear resistance. The pattern of nonlinear resistance is controlled by the average arc length, which reflects the arc furnace operating condition. Finally, the rectangular approximation of arc voltage is adopted by the controller to generate the arc power-arc length and the arc current-arc length curves. This information combined with the arc furnace operation and measurement information is used for the control scheme to determine the arc length and arc furnace transformer tap. Thus, the proposed adaptive arc furnace model is suitable for different operating conditions. This model is also compared prith the existing arc furnace models, which provides its validity. The effect of arc furnace load on the power system is also studied through the proposed model