330 MW发电机无刷励磁系统运行分析

从运行人员的角度出发,紧密结合现场实际,论述了蒲电二期汽轮发电机组无刷励磁系统及其附属系统的工作原理。分析比较了发电机无刷励磁系统与传统励磁系统,结果表明,发电机无刷励磁系统运行可靠性高,技术和经济性能优越。提出了蒲电二期发电机自并励励磁系统在设计方面存在的问题：监测旋转二极管运行情况的霍尔效应传感器易发生故障;发电机的励磁电流、励磁电压难以监视等。     

笼型异步发电机在小风电系统中的励磁运用

针对小型永磁同步发电机输出电压随风速变化而同趋势变化,无法自我调节等不足．提出了一种全新的集电力电子技术、控制技术及鼠笼异步发电机于一体的动态励磁方法,即经济可靠的笼型异步发电机结合应用SVG（静止无功发生器）技术的方法。结合物理实验与算例,对笼型异步发电机在离网运行时的励磁特点进行了分析,并通过与永磁同步发电机在有效风速工作范围和整体效率等方面的对比．得出了在小型离网风力发电系统中应用笼型异步发电机,相对永磁同步发电机有诸多优点,有着很好的应用前景。     

汽轮发电机轴电流报警原因分析及处理

针对某电厂3号汽轮发电机自商运并网后频繁出现轴电流高一段报警问题,根据轴电流产生的机理以及轴电流波形特性,采用模拟对比的分析方法,分析造成该次频发轴电流高报警的直接原因为发电机励端大轴存有随机、不稳定性接地故障。为进一步确认故障位置,通过对发电机励端绝缘结构分析,在停机大修解体期间,对发电机励端所有绝缘部件进行检查,发现了励端外油档绝缘层失效及高压油管安装不规范引起轴瓦绝缘失效为造成机组在运行期间产生轴电流高报警的根本原因。在大修回装时,采取对励端部件进行有效绝缘控制和对高压油管增加热缩套绝缘防护方案后,彻底解决了本次轴电流高报警的问题。     

双馈风电机组传动系统高频轴电压抑制技术开发及应用

针对双馈风电机组高频轴电压的特点,本文概述分析了高频轴电压产生的原理和造成的危害,详述了对高频轴电压的抑制措施,并在风电场推广应用,实践验证了高频轴电压综合抑制技术的有效性。     

基于自适应反演算法的电力系统发电机励磁绕组协调控制研究

为解决电力系统发电机励磁绕组受突加负载与突卸负载影响而容易出现协调控制效果较差的问题,提出基于自适应反演算法的电力系统发电机励磁绕组协调控制研究。依据电力系统发电机励磁绕组结构,在系统空载状态下对励磁进行补偿控制。采用自适应反演算法,获取协调控制实际输入控制率,并设计电力系统控制原则。确定机组整体模型中相应参数,实现电力系统发电机励磁绕组协调控制。实验结果表明,该控制方法在突加负载和突卸负载影响下电压保持平稳,为电力系统稳定运行奠定了基础。     

自并励磁发电机机组励磁变故障的应急方法

静止式自并励磁系统励磁变出现故障,在短时间内无法修复,必然使发电机组停运造成巨大损失.是否可以采用与励磁电压等级相同的市电作为励磁电源,以替代故障的励磁变,使发电机组能正常投运.通过分析以及实例证明,用相同的电压等组的市电是可以替代故间的励磁变的.     

660MW级双水内冷汽轮发电机水系统的研发和验证

双水内冷汽轮发电机技术是我国首创并具有完全自主知识产权的技术.在分析双水内冷汽轮发电机水系统运行中存在的主要问题的基础上,研发了660 MW级双水内冷汽轮发电机水系统,简述了660MW级双水内冷汽轮发电机水系统的技术规范、设计原则、组成,分析了660MW级双水内冷汽轮发电机水系统特点.型式试验结果表明,所研发的660MW级双水内冷汽轮发电机水系统的性能达到了设计要求,能保证660 MW级双水内冷汽轮发电机的安全可靠运行,为660 MW级双水内冷汽轮发电机的研制和投运奠定了基础.     

储能系统逆变器虚拟同步机控制算法研究

由于风力发电机等分布式电源的渗透率逐渐提高,对电力系统的无功平衡、电压质量和电压稳定性等因素也产生越来越多的负面影响。为提高电力系统稳定性和电压质量,以储能系统为后备支持,提出了基于虚拟同步发电机(VSG)控制的储能系统控制方法。该方法包括同步发电机(SG)的电气部分、励磁部分和机械部分,使变换器具有同步发电机的特性,可精确控制储能系统输出的有功和无功功率。最后通过Matlab/Simulink仿真模型验证了该控制方法的可行性。研究成果可为新能源并网系统安全控制提供参考。     

兆瓦级风力发电机轴电压现场测量与分析

阐述了风力发电机轴电压产生的原因以及危害。结合兆瓦级风力发电机的现场实际安装,设计了相应的试验测量方案,并实测了轴电压和轴电流波形。采用专业软件对实测波形进行分析,通过比较其有效值、峰峰值以及FFT波形,结果显示出在不同接地方式下轴电压和轴电流存在差异;发电机转轴2侧接地电刷均接地时轴电压最小,电刷均不接地时轴电压最大;且轴电流在1 000 Hz和2 000 Hz处有明显的电流分量。在风力发电机运行期间,保证发电机的总体绝缘状况良好和转轴2侧的接地电刷可靠接地,以确保发电机正常可靠运行     

自并励静止励磁系统在燃气轮发电机的应用

介绍了沙口发电厂燃气轮发电机自交励静止励磁系统的组成，性能及其特点，总结了运行和维护经验，指出了该系统存在的薄弱环节以及改进意见。     

Multi channel voltage control for fuel cells

Cell voltage control is a safe method to evaluate the operation of the single cells even though large efforts are being made to stabilise the behaviour of the fuel cells over the whole operating range. For fully developed systems only voltage control of single cells is necessary, whereas in test benches it is necessary to record data of the voltages during operation. Normally, a lot of cells are combined to a stack so that higher total voltages can be reached. Higher voltages make possible a high efficient transformation from direct current of the stack to alternate current of the public network. Sometimes more than 100 cells are connected together whereby the open circuit voltage of a single cell amounts to approximately 1 V. Therefore, the signal processing chips show a high supply maximum rating or the resolution of the values has to be reduced.This paper presents an economically priced multi channel voltage control for single cells of a PEM-fuel cell in combination with a microprocessor control and was developed at the Chair for Electric Power Networks and Renewable Energy Sources. The developed system can transfer the data of up to 32 single cells in serial connection. The resolution amounts to 10 bits per channel. The module has its own microprocessor, which is responsible for the intermediate storage of the collected data and the transfer to the RS-232 interface. Optionally, the module can be equipped with an LCD-display of 20 × 4 letters where different menus of the measured and calculated values can be indicated. The module is designed for a voltage of 1 V per channel and can be supplied with a direct voltage of between 6 and 24 V from the fuel cell stack.     

大型发电机转子轴系横振评判标准分析

为了保证大容量汽轮发电机组转子轴系在电厂的长期安全运行,其横振特性在设计及运行阶段均须满足相应的评判标准.总结了国内外标准及行业标准中对于发电机组转子轴系横振特性的评判要求,运用Riccati轴系传递矩阵法分别计算了600 MW、1 000 MW等级大型发电机组轴系临界转速,并结合权威测试机构对机组的现场升降速试验数据进行了调研,将多组计算和试验得到的转子轴系临界转速与相关标准进行了对比.分析结果表明,现行横振评判标准具有较好的适用性,并建议可将频率、响应、敏感度等指标结合,以评判发电机组横振特性的优劣,进一步提高标准的适用性,从而提高大型汽轮发电机组轴系设计的可实现性.     

Enhancement of static excitation system performance for generatorsnear electric arc furnace loads

The tuning of static excitation systems (SESs) to enhance the performance of six gas turbine (GT) generators near an electric arc furnace (EAF) feeder has been successfully accomplished. The operation of these EAFs causes severe and long duration voltage fluctuations at the generator bus. Frequent generator tripping was reported when the adjacent EAFs were in operation. Preliminary field measurements and computer simulations indicated that the SESs did not have sufficient damping under this type of voltage fluctuation. By the adjustment of the SES gains and time constants according to the guideline set by the IEEE Standard 421.2, the SES damping can be greatly improved. This has been verified by additional field tests on six GT generation units. Now these generators can be operated very well although the EAFs still cause voltage fluctuation     

基于静态安全约束的风电场穿透功率极限计算

风电场穿透功率极限的计算是风电场规划阶段的重要内容.以电压稳定为约束条件,分别从静态稳态分析和动态分析两方面进行考虑,确定了既能满足静态稳态运行要求,又动态不失稳的风电场穿透功率极限.静态安全约束指标是线路潮流不过载、节点电压不越限(波动范围5%).暂态稳定的判据是系统中发电机最大功角差第一摆和第二摆衰减震荡,中枢节点电压恢复稳定,各节点电压偏差在额定值的5%之内.     

Implementation of an electrolysis system with DC/DC synchronous buck converter

A synchronous buck DC–DC converter that can be used to produce hydrogen through electrolysis by using the energy generated from renewable energy sources has been designed and implemented. The reason for selecting this topology is that the voltage level at the output of renewable sources, such as solar cells and storage batteries, is about 12 V DC, and the voltage level required for electrolysis is about 2 V DC. Traditional buck converters have low efficiencies at low output voltages since the voltage drops on the components are comparable to the output voltage. The converter has been designed and tested at 25 A output current. Two different electrodes were used for electrolysis and the effect of electrode opening on the operation was observed. In addition, the stability analysis of non-linear electrolysis system load has been performed.     

A solid state direct on line starter for medium voltage inductionmotors with minimized current and torque pulsations

This paper describes a thyristorized static switch which is designed and implemented specifically for frequent direct-on-line starting of medium voltage large induction motors. The circuit configuration chosen utilizes back-to-back connected series thyristor strings on two of the supply lines. Both the starting current and the torque pulsations of the induction motor are minimized by a controlled, nonsimultaneous switching of motor phases to the supply. This reduces the electrical stresses on the power system and the mechanical stresses on the shaft as compared to conventional switching elements. The optimum switching strategy is found by the use of a hybrid mathematical model in ABC/dqO form. The validity of the results obtained for medium voltage, squirrel-cage induction machine are verified by the use of a physical simulator consisting of a low voltage, small induction machine and a shaft torque measuring system. The system has been in operation successfully in an iron and steel plant since 1991     

考虑暂态电压稳定性的电力系统多目标无功备用优化

鉴于目前电力系统无功备用优化方法较少涉及暂态电压稳定性,提出一种同时提高电力系统静态/暂态电压稳定性的无功备用优化模型,该模型首先基于数据密度提出一种无功电压控制分区方法,分别在静态/暂态电压的薄弱区域内定义静态/暂态无功备用,然后结合所建立的两个目标建立多目标无功备用优化模型,最后提出一种基于多阶段的多目标优化求解方法。通过求解所建模型,获得能够同时提升系统静态/暂态电压稳定性的无功备用配置方案。对IEEE 39节点系统的仿真分析证明了所提方法的有效性。     

Relating cyclic voltammetry and impedance analysis in a viologen electrochromic device

Viologens are electrochromic materials that have a wide range of coloration depending on the radical substituents. The results for a new blue viologen-based device, that has recently been patented, with an active area of 8.5 cm² is presented in this paper. The characterization techniques used are based on optical measurements, chronoamperometry, cyclic voltammetry, and impedance spectroscopy analysis. A study of the results obtained from these measurements provides both an overview of the reactions taking place and has allowed an equivalent circuit to be developed which relates the different electrochemical parameters. The transmittance is observed to change from 80% to 15% in 600 nm for input voltages ranging from 0 to 2.5 V. However, increasing voltage beyond 1.8 V shows no optical change, thus, maintaining the voltage below this level optimizes the use of electrical current. Voltages and charges used for each redox reaction have been computed and are seen to be linearly related. The equivalent circuit generated to mimic the process has included parameters based on Warburg diffusion and double-layer capacitances. Results from this model are consistent with measurements for up to 1.8 V. Saturation of reduced species has been deduced for input voltages beyond this level.     

Water distribution and performance variation in a transparent PEMFC with large active area

Water management is a key factor affecting the performance and lifetime of proton exchange membrane fuel cells. A transparent single fuel cell with an active area of 100 cm² was designed in this paper to characterize the water distribution. High-strength transparent borosilicate glass was used as the end plate to ensure uniform clamping forces, and a water-cooling chamber was adopted for the uniform temperature distribution. The effects of temperature, humidity, flow rate and pressure on the cell performance were investigated. It was found that in a certain range, a large cathode flow resulted in a relatively stable power output and a low level of water distribution. However, a better cell performance and higher level of water distribution can be observed with lower temperature, higher operation pressure and higher humidity. The actual voltage was determined by a compensatory calculation through the voltage changes caused by all of the influencing factors, and the compensatory voltages were quite close to each other. The results showed that under 40 °C and 60 °C, 0 Bar and 1.5 Bar, and 50 RH% and 100 RH%, the compensated voltages were 0.873 V and 0.864 V, 0.869 V and 0.855 V, and 0.843 V and 0.844 V, respectively.     

Comparison of efficiencies of low, mean and high temperature fuel cell Systems

Fuel cell systems are always said to show high electrical efficiency. The results achieved up to now, however, differ considerably, especially between the various fuel cell types all using natural gas as fuel. With the presented study the reasons for the different results and general potentials for fuel cell systems are highlighted. For that purpose several system lay-out concepts were elaborated for PEFC, PAFC and SOFC.The performed energy balance calculations for eight different plant concepts (three PEFC, two PAFC and three SOFC) for steady state operation with methane revealed that because of external reforming PEFC and PAFC systems are limited to about 67% and 70%, respectively, for the fuel utilisation. High temperature fuel cells can achieve at least 80% because of the possibility of internal reforming, or even over 90% in case of anode off-gas recycling. In combination with a cell voltage which is about 100 mV lower than that of MCFC and planar SOFC, PEFC can only achieve 38% of electrical net efficiency, PAFC 42% and tubular SOFC 54%. The latter is similar to MCFC, which is operated at higher cell voltage but lower fuel utilisation. The highest efficiency with up to 63% can be achieved with planar SOFC systems, because this concept allows high fuel utilisation together with high cell voltages.