【作者】 李伟；

【导师】 尹项根； 张哲；

【作者基本信息】 华中科技大学 ， 电力系统及其自动化， 2011， 博士

【摘要】 随着计算机技术、自动控制技术和网络通信等科学技术的飞速发展,电力系统设备的自动化程度不断提高。本世纪初,欧美国家相继提出了“智能电网”的概念和发展计划,我国的国家电网公司也于2009年启动了智能电网的建设工作。智能电网的研究和实践日益得到政府高度重视和全社会的关注,它将是现代电力系统的发展趋势。数字化变电站是智能电网的关键节点,电子式互感器作为数字化变电站重要的基础性设备,其工作方式与常规变电站的互感器有着本质的不同,它对稳态电流和暂态电流的刻画能力以及它与站内其他二次设备的通信接口,是电子式互感器在数字化变电站中应用成败的关键性问题。对电子式互感器开展深入研究,对大规模推广应用电子式互感器,以及数字化变电站乃至智能电网的安全稳定运行,有着不言而喻的重要意义。本文以目前获得广泛关注的有源型电子式电流互感器(简称ECT)为课题对象开展了相关研究。文章在国内外相关研究的基础上,深入研究了ECT的暂态测量特性和信号处理技术,探索了ECT合并单元(简称MU)的信息模型以及数字化风电场风力发电机的信息模型构建方法。目前关于ECT的研究主要是针对稳态测量情况下,探讨提高测量精度的各种方法和措施。但实践发现,ECT信号处理电路中的积分器电路对互感器的暂态特性有着决定性的影响。本文建立了ECT传感头的数学模型,通过数字仿真手段对比分析了不同积分器和参数配置对互感器暂态性能的影响,并提出了一种确定传感头积分器参数的方法。根据研究结果,文章设计了一套具有合适积分器的ECT传感头,实验表明该传感头有着良好的稳态性能和暂态性能,完全可以也十分有必要应用于比实际继电保护装置对互感器暂态特性要求更苛刻的动模实验研究中。针对改善ECT暂态性能,提高抗干扰能力以及为了更好地解决采样同步问题,文章发明了一种基于压频变换的模数混合积分器方法,并深入探讨了实现该方法的若干关键性技术。该方法通过巧妙的计数技术,将理想积分和模数变换在压频变换过程中完成,使传感头既具有良好的暂态特性,也免去了一般ECT所需的采样同步信号光纤,简化了电路结构,提高了ECT可靠性,也极大地增强了ECT的抗干扰能力。动态模拟实验是开展继电保护特性研究和电气设备暂态模型研究的重要手段。采用传统的电磁式电流互感器(简称MCT)测量电流可能会破坏模拟系统参数,影响实验结果,使得研究结论无法适用于真实情况。而且MCT由于磁饱和问题,导致输出波形畸变,使研究工作所依据的波形根本不是研究对象产生的一次电流波形,这严重干扰了对研究对象本身的研究,甚至可能会使研究工作误入歧途。本文以ECT为基本测量工具建立了整套的动模实验的测量系统,并在此基础上开展了发电机内部故障研究和变压器和应涌流研究。文章对比了ECT和MCT对动模实验结果的影响,结果表明,采用ECT作为测量手段,可充分发挥其微功耗、无饱和的独特优点,对研究工作的开展有着MCT无法替代的重要作用。风电作为一种实用化程度较高的可再生能源,近年来获得了迅猛的发展。数字化变电站作为风电场与电力网唯一接口,其安全稳定运行对于提高风电场发电效率有着决定性作用。MU是电子式互感器应用于数字化变电站的关键性接口装置,它承担着向二次设备及时提供电流电压采样值的重任。目前投入试运行的MU大多数基于IEC61850-9-1标准研制,或者实现了IEC61850-9-2标准的部分功能,都只能单向发送采样值。本文从数字化变电站应用的角度对MU进行了深入的需求分析,重点开展了基于IEC61850-9-2标准的MU信息建模和信息交换服务建模,使MU可以完成全双工通信,具备接受在线调整和控制的能力。这可缩短变电站的调试时问,也为运行人员在变电站连续运行中对MU的监视与控制提供了手段,有利于加强风电场安全稳定运行。目前风电场监控通信系统及通信协议多由风机厂家自行规定,这给风电场的建设和运行管理造成了极大的不便。本文借鉴计算机软件工程“自顶向下”的设计思想,利用研究合并单元建模的方法,首次建立了完整的基于IEC61400-25标准的风力发电机模型,这对于开展数字化风电场研究与建设具有较强的参考作用。最后,论文总结了主要研究成果,并指出了要进一步研究的内容。更多还原

【Abstract】 With the great advances of computer technology, automatic technology and network communications, power system becomes more automatic than ever. At the beginning of this century, European countries and USA put forward the concept of "smart grid". The State Grid Corporation of China also started construction of the smart grid in 2009. The government and society pay more attention to the smart grid, and the smart grid is the development trend of power system. Digital substation is an important part in smart grid。Electronic transformer is very important and necessary to digital substation, whose characteristics and operation are quite different from conventional current transformer of voltage transformer. For the safe and steady operation of digital substation and smart grid, it is of great significance to make more intensive research on electronic transformer.This thesis carries out some related studies about the active Electronic Current Transformer (abbr. ECT) which has caused widespread concern. Based on plenty of references from home and abroad, the thesis makes thorough study on the transient characteristics and signal processing circuit of ECT. Then the thesis explores the modeling method of ECT’s merging unit information model and wind generator information model in digital wind farm.The present study about ECT focuses on steady state performance. People explore all ways to improve the measurement accuracy. However, practical application implies that the integrator in ECT’s signal processing circuit could infect the transient performance significantly. This thesis establishes mathematical model of the ECT’s sensor, and analyses the influences of the integrator structure and parameter on ECT’s transient performance by way of digital simulation. The thesis advances a method to find appropriate integrator parameters. Based on the result, the thesis designs a set of sensor with integrator. Experiments demonstrate that the sensor has excellent steady performance and transient performance, which means that the sensor can be applied in power system dynamic simulation research.Aiming at improving ECT transient performance and anti-interference ability, and also aiming at find better ways to solve the sampling synchronization, the thesis invents a new signal process method for Rogowski-coil based ECT. The thesis also discusses thoroughly some essential technologies to implement the new method. By means of artful counting, the method merges ideal integrator and analog-digital converter in VFC process, which makes the sensor acquire excellent transient performance and cancel the fiber for sampling synchronization. The method can simplify the sensor circuit and improve the sensor reliability.Dynamic simulation experiment (abbr. PSE) is very important for relay research and electric transient modeling. Applying magnetic current transformer (abbr. MCT) in PSE may affect simulation parameter, thus the research result can’t be applied to active environment. Because of MCT’s saturation, distorted waveform used in research isn’t the true wave produced by electric equipment, which may make the research more difficult. The thesis build up a set of measure system comprised of ECT for PSE, and some experiments has been carried on. The thesis compares the waveforms produced by MCT and ECT, and result suggests that ECT is very suitable and important to PSE.As a kind of good practical renewable energy, wind power develops rapidly in recent years. Wind farm’s digital substation is the only interface to power utility, whose operation is important to wind farm’s operation. Merging unit is a key device for transmitting samples, which is very important for applying ECT in power system. Most merging units in trial operation are developed according to IEC61850-9-1 or part of IEC61850-9-2, which means that the merging unit can only transmit samples and can’t receive commands. In the view of digital substation, the thesis analysis requirements for merging unit. Then the thesis focuses on establishing information model and information exchanging model of merging unit, which makes merging unit acquire the ability of full-duplex communication. In this way, the merging unit can online receive commands from other devices.Most supervisory and control system for wind farm are developed by wind generator manufacturer separately. It brings inconvenience to the wind farm construction and operation management. Referencing the "top-down" concept in computer software engineering, and according to IEC61400-25 standard, the thesis establishes a integrated information model of wind generator. The thesis also studies the merits and shortcomings of five SCSM defined in IEC61400-25. Involving the SCSM-MMS defined in IEC61850 standard, wind farm supervisory and control system can communicate with substation SCADA system seamlessly, which is the trend for future wind farm.All research results are summarized finally and the direction of further research are pointed out.更多还原