铸钢用9MVA交流电弧炉炼钢过程电气运行特性研究

大型重型机器制造企业使用交流电弧炉炼钢提供钢液,制造锻造用钢锭和铸钢件。使用电气监测仪表,对鞍钢重型机械有限责任公司1~#交流电弧炉炼钢过程中的电力参数进行了实测,得到72668个有效数据。分析表明,在1挡电压下电弧炉变压器利用率仅为67.79%。研究以二次侧工作电流为自变量,建立该电弧炉炼钢过程电气运行的非线性电抗模型,绘制电气运行特性曲线。研究结果表明,变压器在1,2,5挡电压下运行,工作电流提高至额定电流,输出的有功功率可分别提高35.6%,16.7%,21.3%。     

三相电弧炉不对称电路计算法

分析三相电弧炉电流不对称对等效电阻、等效电抗的影响,在此基础上,对三相电弧炉在电源电压、短网参数、工作电流皆不对称的情况下,给出了计算公式。实例表明,在计算时,应充分考虑三相电路不对称所造成的影响。     

电弧炉运行电抗与合理供电研究

首先对运行电抗及其影响因素作了描述并介绍了国外有关运行电抗的研究结果,然后通过理论分析与实测结果,得到了既简单又精度高的描述电弧炉运行电抗的关系式。最后,作为实例,将研究结果应用于某１００ｔ钢包精炼炉,可节电３．８％。     

电力变压器短路电抗在线测量方法研究

电力变压器的短路电抗是设计及运行过程中表征变压器本体抗短路电流冲击能力的重要参数。本文分析了基于电气量特征的短路电抗在线测量方法及对变压器运行状态进行实时监测的可行性,研究了基于变压器励磁电流补偿法和消去法的两种短路电抗在线测量方法的原理,推导了计算公式。动模实验在线测量结果与离线短路实验结果的比较表明了两种方法的正确性和有效性。     

电力变压器短路电抗在线测量方法研究

电力变压器的短路电抗是设计及运行过程中表征变压器本体抗短路电流冲击能力的重要参数.本文分析了基于电气量特征的短路电抗在线测量方法及对变压器运行状态进行实时监测的可行性,研究了基于变压器励磁电流补偿法和消去法的两种短路电抗在线测量方法的原理,推导了计算公式.动模实验在线测量结果与离线短路实验结果的比较表明了两种方法的正确性和有效性.     

高压直流接地极的设计标准

电力变压器的短路电抗是设计及运行过程中表征变压器本体抗短路电流冲击能力的重要参数.本文分析了基于电气量特征的短路电抗在线测量方法及对变压器运行状态进行实时监测的可行性,研究了基于变压器励磁电流补偿法和消去法的两种短路电抗在线测量方法的原理,推导了计算公式.动模实验在线测量结果与离线短路实验结果的比较表明了两种方法的正确性和有效性.     

高阻抗电弧炉的电弧稳定性

近年来,随着高阻抗电弧炉长弧操作的运行和泡沫渣的实践,关于电弧稳定性的研究工作显得越来越重要了.影响电弧稳定的最重要因素是运行电抗,因此定量地讨论了运行电抗有关问题.介绍了提高电弧稳定性的主要措施.最后,给出了电弧稳定性判据.     

基于对称分量法的电弧炉无功补偿技术

电弧炉具有低电压、大电流而且负荷非线性的特点,在其运行过程中产生大量的负序电流,导致电网不稳定。通过对称分量法提取出负序分量,进而应用单片机控制投切补偿电纳,进行无功功率补偿,从而有效地抑制了负序电流,使电网稳定运行。计算机仿真表明,提出的无功补偿技术可以有效地补偿负序电流,使电弧炉运行在三相对称状态。     

一种精确计算电弧炉短网电抗的混合计算方法

短网是电弧炉非常重要的设备,其电气参数的优劣直接影响到电弧炉的运行性能和使用寿命。短网结构复杂、计算困难,传统的基于解析近似计算方法已不能满足工程应用的需要。利用工频磁场数值仿真在计算电气回路电感方面的优势,通过在短网首尾端构造虚构导体形成回路,应用磁场数值仿真计算回路电感和解析算法计算首尾端虚构件电感,并通过推导混合算法获得交流电弧炉短网三相电抗,避免通过解析近似算法计算短网各相自感和相间互感,其准确性在国内实际工程中得到验证。     

电弧炉PID神经网络解耦控制器

结合电弧炉主电路系统,推导出电弧炉电气系统状态方程,在此基础上分析了电弧炉三相电流的耦合关系.使用PID神经元网络控制器对电弧炉电极系统进行解耦控制.给出了PID神经元网络控制器的权值初始化规则,其权值更新采用经典的BP算法.分别对于控制器的解耦性、抗干扰性和鲁棒性进行仿真,结果表明PID神经网络控制器具有很好的动态性...     

炼钢电弧炉工艺过程的动态模拟

基于物料平衡和热平衡以及化学反应的热、动力学,结合相关的参数建立了电弧炉冶炼过程的动态模型。该模型可动态地模拟电弧炉冶炼过程中的废钢量、炉温、渣量、钢液成分、炉渣组成的炉气成分的变化。文中以某100t交流电弧炉冶炼的操作参数为例进行了仿真计算,并与现场数据作了对比。结果表明模型可与实际结果吻合得很好。完善后的模型可望对生产全过程作出动态的预报,并可综合评估电弧炉冶炼的能耗、物耗、生产效率等技术经济指标,从而为电弧炉工艺改进、生产操作与控制提供指导。     

Hydropower Development in Southwestern China

A simple expression is derived to obtain the direct axis synchronous reactance (x/sub d/) of synchronous machines from operating conditions. This method is suitable for obtaining this parameter where original data are lost and no other information is accessible.     

A new method for determining the armature leakage reactance ofsynchronous machines

A method for determining the armature leakage reactance of synchronous machines is presented. In this method, the terminal voltage/armature current characteristic with the machine unloaded and unexcited is needed, together with the open-circuit characteristic of the machine. The armature leakage reactance is derived from these two curves using an iterative technique. The armature leakage reactances of five synchronous machines of different designs are obtained using this method. Their values are compared with those of the Potier reactance of these machines measured at various terminal voltages     

Performance of a three-phase AC generator with inset NdFeB permanent-magnet rotor

This paper presents the analysis and performance of a three-phase AC generator with an inset, neodymium-iron-boron (NdFeB) permanent-magnet (PM) rotor. Such a rotor construction gives rise to an inverse saliency effect (i.e., the direct-axis synchronous reactance is less than the quadrature-axis synchronous reactance). This feature results in an improvement in the voltage regulation characteristics when the generator supplies an isolated, unity-power-factor load. By solving the equations derived from the two-axis theory, it is found that there exists, in general, two values of load current at which zero voltage regulation is obtained. The relationship between armature resistance, inverse saliency ratio, and the operating speed to give zero voltage regulation is investigated. The finite-element method (FEM) is used for computing the pertinent generator parameters for performance evaluation, namely the no-load voltage and the synchronous reactances. Flux plots are presented to confirm the origin of inverse saliency in the inset PM rotor. The theoretical analysis is validated by experiments carried out on a 2.5-kVA prototype generator.     

基于TCR_TSC的电弧炉无功补偿仿真研究

由于电弧炉在运行过程中的功率因数低,无功功率波动急剧,负载变化大,产生大量的高次谐波电流,电压畸变,对电网产生不利影响,严重影响电能质量,造成大量的能量消耗,同时影响工业产量和质量。通过对电弧炉运行时的电气特性进行分析,采用TCR_TSC型SVC协调控制的补偿方法对无功进行补偿,滤除谐波。MATLAB/ Simulink仿真结果表明该装置滤波效果良好。     

带限流模式直流断路器在柔性直流输电系统中的应用

直流断路器的设计与研发是直流系统实际应用中的难点。对此,提出了一种具备故障限流模式的混合式直流断路器,该断路器具有正常运行、限流运行和故障隔离三种工作状态,通过三种状态之间的相互转换可实现正常工作时以低电抗方式运行、故障时进入限流状态以高电抗方式运行限制故障电流,最终隔离故障,可起到保护系统设备的作用,并对该断路器进行了闸组内的电压、电流应力分析。最后通过在PSCAD/EMTDC上搭建的仿真模型验证了该断路器的可行性和有效性。     

Capacitor effects on induction motors fed by quasi-rectangularcurrent sources

Analytical and experimental studies of the capacitor effects on the steep rising and falling voltage spikes and the current harmonics in induction motors fed by quasi-rectangular current sources were conducted for the case of a motor fed with a six-pulse current source. The phase current of the motor fed by the six-pulse current source goes through various regions of harmonic current and voltage variations. The analytical and experimental results showed that as the value of the capacitor reactance is reduced gradually toward the motor magnetizing reactance, the motor encounters the higher-frequency current amplifications first, and, subsequently, the seventh-harmonic amplification and then the fifth-harmonic amplifications. The analytical results also show that it is possible to encounter a severe fundamental-frequency current amplification when the capacitor reactance is less than the motor magnetizing reactance     

Line-to-line short-circuit-based finite-element performance and parameter predictions of large hydrogenerators

A two-dimensional (2-D), time-stepped finite-element (FE) method is used to model and successfully replicate saturated line-to-line and three-phase short-circuit test responses recorded on a 40-pole 13.75 MVA hydrogenerator at Hydro-Quebec's Rapides-des-Quinze generating station. Three levels of line-to-line and sudden three-phase short-circuit tests (0.13, 0.25, and 0.48 p.u.) are simulated numerically using the FE-based model. While symmetrical faults are only used for parameter determination, the computed line-to-line waveforms are thoroughly compared to real data, with special attention given to field current responses. According to IEEE Std.-115-1995, the d-axis dynamic reactances and time-constants are computed from three-phase short-circuit tests while the negative-sequence reactance is derived from the line-to-line short-circuit test resulting in a rated armature current. The obtained simulated tests responses and parameter values, from both symmetrical and asymmetrical faults, support the effectiveness of the proposed FE-based model in incorporating the saturation phenomenon, large number of poles, and detailed damper representation to achieve an accurate dynamic performance assessment together with negative-sequence reactance and dynamic constants prediction.