An In-Depth Study of Complex Power System Dynamic Behavior Characteristics for Chinese UHV Power Grid Security

In this paper,a series of major policy decisions used to improve the power grid reliability,reduce the risk and losses of major power outages,and realize the modernization of 21st century power grid are discussed. These decisions were adopted by American government and would also be helpful for the strategic development of Chinese power grid. It is proposed that China should take precaution,carry out security research on the overall dynamic behaviour characteristics of the UHV grid using the complexity theory,and finally provide safeguard for the Chinese UHV grid. It is also pointed out that,due to the lack of matured approaches to controll a cascading failure,the primary duty of a system operator is to work as a "watchdog" for the grid operation security,eliminate the cumulative effect and reduce the risk and losses of major cascading outages with the help of EMS and WAMS.

Contribution of UHV Grid to United National Power Market

Power market construction is an important part of the marketization reform in China's electric power industry and an essential part of the economic system reform in China. With the social and economic development, the contradiction between distribution of energy resources and development of regional economies gets increasingly noticeable, and a united national power market is consequentially required to optimize the allocation of energy resources over the whole country. Analyses indicate that the development of UHV grid will provide a strong material support for the united national power market by expanding market coverage, lowering load fluctuation and promoting diversif ication of power resources.

Influence and hazard of disastrous space weather on power grid in China

Based on the measured data of geomagnetically induced currents(GIC) in Guangdong Ling'ao 500 kV power networks during several magnetic storms at the peak years of 23rd Solar Cycle,the GIC calculation results of 750 kV planning power grid in Shanxi,Gansu,Qinghai and Ningxia,the structure and characteristics of power networks from 500 kV to 1 000 kV,and super magnetic storm in 1859 are analyzed in this paper. Through the analysis,the possible impacts of extreme space weather on the future ultra-high voltage(UHV) grid,the security of large-scale power system in China are expounded,and the research suggestions coping with the strong solar storms are proposed.

China Needs Prompt Construction of a Strong National Power Grid (Excerption)

China needs to develop a strong national power grid which takes ultra-high-voltage (UHV) transmission systems as its core. The grid is expected to adopt 1000-kV-class AC and ± 800-kV DC transmission systems. In view of significant achievements in technological research and considerable progress in UHV manufacturing technology, China is capable of developing UHV systems. In order to promote the construction of UHV systems,China Electric Power Research Institute and other institutions have initiated first-phase research activities of UHV transmission technologies. The main contents involve research on UHV transmission technology and its economy,developing and manufacturing abilities on UHV equipment, prospective of UHV network frame and selection of demonstration projects, etc.

Influencing Factors of the Power Fluctuation on the Ultra High Voltage Transmission Line Caused by Faults at the Remote Ends of the Interconnected Grid

After the North China grid and the Central China grid get into connection with the UHVAC demonstration, a new phenomenon is discovered according to some simulations. That is, the faults at the remote end of the UHV interconnected grid will result in significant power fluctuation and voltage drop on the UHV transmission line and even system splitting. But the faults near the UHV line only have marginal effects. Further, the simulation results also indicate that the short-circuit current of the buses near the UHV line is larger than that of the buses far away from the UHV line. This phenomenon is divergent from the traditional view. In this paper, the detail will be introduced, and the factors influencing the system stability after faults are presented and analyzed. The results indicate that transmission power of the UHV line and of the lines between the remote end and the major grid influence the fluctuation on UHV line. The load model and the grid structure of the remote end also have effect on it. Finally, corresponding control scheme is presented to improve the operation conditions of the UHV interconnected grid and ensure its security and stability.

Component Analysis and Calculation for Social Benefits of UHV Assessment

With the rapid development of the UHV power grid, evaluation of the economic and social benefits of the UHV power grid is conducive to guiding the planning and construction of UHV power grid. At present economic benefit evaluation system of the UHV power grid is driving to maturity stage on the whole at home and abroad, but it invariably tends to regard social benefits as part of economic benefits, without evaluating social benefit separately. The social benefit evaluation model of UHV power grid is built in case of sufficient investigation. The differentials between social benefit and social cost are calculated respectively by three kinds of solutions according to the constructed social cost evaluation index system and social benefits evaluation index system, conclusion that UHV power grid transmission has better social benefits can be reached by contrastively analyzing the social three kinds of solutions corresponding to benefits. At last, the evaluation model and method are verified and analyzed through the analysis of engineering projects.

特高压直流接地极选址及受端电网结构偏磁电流抑制策略研究

常规的特高压直流接地极选址及受端电网结构偏磁电流抑制方法主要使用CDEGS软件确定电流抑制修正关系,易受接地极电位差变化影响,导致不同测点的偏磁电流过高,因此需设计一种特高压直流接地极选址及受端电网结构偏磁电流抑制策略。根据地质构造及断裂关系生成特高压直流接地极选址流程,设计受端电网结构偏磁电流抑制算法,从而完成特高压直流接地极选址及受端电网结构偏磁电流抑制。实验结果显示设计的直流接地极选址及电网结构偏磁电流抑制策略的各个测点的偏磁电流较小,表明该策略抑制效果较好、可靠性高,有一定的应用价值。

基于Unity3D的施工方案模拟平台在特高压工程的应用研究

三维施工方案仿真模拟平台旨在充分发挥已有三维设计成果的效用,将三维成果价值延伸至施工阶段,辅助开展重大风险作业施工方案的模拟推演和评审交底,加强工艺质量管控,提升风险防范意识。平台基于Unity3D引擎开发,采用相似性算法对GIM模型进行了轻量化处理,借助高清渲染管线实现了对全工作流的支持,通过TaskCore实现了对高自由度任务流程的管理。平台采用模块化设计,已实现对7类施工方案的模拟,并在雅中—江西±800 kV直流输电工程进行了应用,通过工艺、工序管理等功能,满足了现场对培训、演练、考核等场景的应用需求。平台的应用有效提升了施工作业人员的专业技能和安全意识,对于进一步探索如何借助信息化手段提升电网工程建设管理水平具有积极意义。

考虑断面耦合控制的特高压复杂大电网最大供电能力优化方法

最大供电能力计算是特高压复杂大电网优化运行的重要问题,随着高比例可再生能源大量接入电网,电力电量平衡问题愈发突出。计及考虑稳定旋备约束、耦合断面约束、机组调节能力约束后,最大供电能力计算问题呈现高维特征,难以对其建模及求解。对此,首先根据传输断面限制和特高压复杂大电网分区运行的特点,搭建了考虑断面耦合控制的特高压复杂大电网最大供电能力优化调度模型,然后分别应用单纯形法(SM)、内点法(IP)、模拟退化算法(SA)、白鲸优化算法(BWO)和蜂群算法(ABC)求解模型,计算大电网在日内未来15 min最大供电能力,并提出各类型电源和备用的协调优化方案。最后以某省网为例进行模型及求解方法验证。仿真结果显示,因为电力系统规模庞大和断面间耦合关系复杂,启发式智能优化算法存在运行时间较长、收敛速度较慢、搜索精度不高的问题,而内点法收敛迅速、鲁棒性强、对初值的选择不敏感,具有更好的稳定性和计算效率,可为复杂特高压电网电力保供和电力平衡提供有效实用支撑。

电网工程基建现场风险全状态感知系统在“两交一直”特高压工程中的应用

为降低电网工程建设中的施工风险,本文在研究分析电网工程基建现场安全风险作业的基础上,基于移动互联、物联网、人工智能等技术,构建了一种基建现场人、机、物状态信息的电网工程基建现场风险全状态感知系统,并在以雅中-江西±800 kV特高压直流输电线路工程为代表的“两交一直”特高压工程建设中进行了应用。实践表明,该系统通过安全风险管理、人员设备管控、视频智能分析告警、物联状态感知,有效提升了风险作业现场的数据采集及智能感知水平,有助于加强风险作业的数据分析及智能管控水平,进而为基建现场精细化管理提供了有效的智能化手段,进一步提高了电力工程建设综合管理能力。

特高压潇湘站500kV母线分母运行对湖南电网影响分析

1000kV潇湘—赣江特高压交流双回线路投运后,省间交流通道无功支撑能力提升,系统稳定性得到增强,但也导致系统短路电流的增大。为保障湖南电网暂态电压稳定,需要对省内机组的开机与旋转备用提出要求,因此限制了电网供电能力和运行灵活性。针对此问题,对湖南电网500kV网架结构进行优化研究,提出特高压潇湘站500kV母线分母运行优化方案,降低近区短路故障对系统的冲击,提高电网暂态电压稳定水平,提升电网供电能力,为湖南电网安全稳定运行提供技术支撑。

特高压电网社会效益分析及评价方法

引入全寿命周期成本和影子价格理论,识别特高压电网成本和社会经济效益组成;并基于与效益相关的各元素影子价格估算公式,深入分析除售电收益外特高压电网所带来的巨大的社会效益。编制投入产出效益流量表,建立基于全寿命周期成本的特高压电网社会效益评价指标;结合灵敏度分析理论,形成适用于特高压电网的社会效益评价方法。以我国某特高压同步大电网2020年规划方案为算例,对比分析了在传统财务成本和考虑全寿命周期成本计算方式下的社会效益评价结果,验证了所提方法的有效性和可行性。

国网“十三五”规划电网面临的安全稳定问题及对策

中国能源资源与生产力逆向分布,能源基地距离负荷中心1 000~4 000 km,必须实施能源大范围优化配置,才能保障能源供应。"十三五"期间,特高压步入加速发展的快车道,国家电网(不含南网)将形成"三送端(西北、东北、西南)、一受端(华北—华中—华东)"的规划电网格局,将出现交直流并列运行、多直流集中馈入受端等特征。直流输送容量的提升和大容量特高压变压器的应用使电网安全稳定性面临新的挑战,多回直流集中送电"三华"负荷中心也对送端电网的频率稳定水平提出了更高的要求。依托国家电网仿真中心,从短路电流、静态安全性、暂态稳定性、动态稳定性、电压稳定性等方面进行安全校核,结果表明,通过构建"强交强直"电网格局、采用交直流协调控制策略、适时解开1 000/500 k V电磁环网等对策,可有效解决国网"十三五"规划电网面临的主要安全稳定问题。

华北—华中—华东特高压同步电网构建和安全性分析

总结了国内外电网的发展趋势和经验。结合中国电源和负荷的分布特点,提出了中国同步电网受端规模、电压等级、输电方式和华北—华中—华东特高压(ultra high voltage,UHV)同步电网的安全构建原则。分析了大规模同步电网的安全稳定特性和大电网停电机制,论证了规划中的华北—华中—华东特高压同步电网的安全性。

特高压同步电网安全性论证

根据《电力系统安全稳定导则》,从短路电流、静态安全性、暂态稳定性、动态稳定性等方面,校核了特高压同步电网方案的安全稳定性;根据《电力安全事故应急处置和调查处理条例》要求,校核了可能发生的自然灾害导致的电网严重故障下,特高压同步电网的承受能力及可采取的措施;根据第3道防线的设置原则和要求,分析了由低频减载、低压减载和解列控制构成的第3道防线在特高压同步电网的适应性。结果表明,特高压同步电网安全性满足《电力系统安全稳定导则》的要求,承受严重故障能力强,第3道防线可有效控制事故范围,避免出现大停电;采用基于广域同步量测信息的自适应解列、交直流协调控制等技术可以进一步提高系统的安全性。

磁暴对我国特高压电网的影响研究

随着我国长距离输电的发展,江苏、广东等地曾多次发现磁暴在电网中产生了较大幅度的地磁感应电流(geomagnetically induced current,GIC),有可能对电网造成危害。文章通过对电网GIC监测数据和地磁数据进行分析,指出除磁暴强度外,大地电性结构、电网结构与参数也是影响GIC水平的重要因素;借助磁暴产生GIC的物理模型并根据特高压电网线路电阻小、输电距离长、采用单相变压器等特点预测未来特高压系统中的GIC干扰问题将更加严重;根据2010年我国特高压规划建立了电网的等效模型,利用典型磁暴感应出地面电场的数值初步估算了各变电站的GIC水平;最后对目前研究中有待解决的关键问题进行了总结,并结合我国国情提出了解决方案。

特高压输电线路雷电过电压的分类识别方法

特高压交流输电以输送容量大和功耗小等优点成为了我国电网发展的方向。但由于输送距离长,线路走廊和离地高度大等原因,线路遭受雷击的概率大,因此雷击过电压将是影响特高压电网运行安全的重要原因之一。根据1000 kV电网的线路和杆塔特点,用ATP-EMTP软件对线路上出现的感应雷、反击和绕击雷过电压进行了仿真,并分析了这3种过电压的波形差别:发生感应雷击时,过电压同时作用于三相中,且相间电压的相似度大;发生直击雷时,相间电压的相似度小于感应雷过电压,且反击和绕击过电压的初始行波差异较大。根据这些特征,引入小波能谱矩阵相似度的概念,依此系数的大小识别感应雷过电压和直击雷过电压;在此基础上,对电压初始行波进行小波变换,根据模极大值的极性以及避雷器的持续放电时间识别反击与绕击过电压。该方法的理论基础比较直观,大量的暂态仿真结果和实测波形验证了该方法在识别不同故障条件下的雷击过电压时的可靠性和有效性。

特高压交/直流电网仿真技术研究

电力系统的规模日趋扩大,复杂程度不断增加,迫切需要建立与特高压电网发展形势相适应的特高压电网仿真系统。首先分析了各种仿真系统的特点及其适用范围,然后结合我国特高压电网研究对仿真系统的要求,讨论了可用来对大规模交/直流电网的机电暂态与电磁暂态现象进行实时仿真的全数字实时仿真系统与数模混合仿真系统的原理、功能、特点、发展现状及适用范围,指出了其现存的局限性,提出了改进与完善的思路。

基于相位角原理的特高压电网失步解列改进方案

传统的基于相位角原理的失步解列判据是通过判断装置安装处电流和电压的相位角变化轨迹来区分短路故障和失步振荡的。由于1 000kV交流特高压线路一次时间常数较大,因此在某些三相短路故障情况下易造成基于相位角原理的失步解列装置误动。针对上述现象,在深入分析发生短路故障和失步振荡情况时特高压输电线路电流和电压特性的基础上,提出了一种失步解列改进方案。最后,根据国家电网公司企业标准中推荐的1 000kV长距离、短距离线路典型接线方案建立了实时数字仿真(RTDS)模型,并利用该模型对改进方案的有效性进行了实验验证。

交流特高压近区电网自动电压控制研究与实践

特高压接入给其近区电网的无功电压运行和控制带来挑战。结合工程实践,文中研究了面向特高压近区电网的自动电压控制方法。分析了特高压近区电网的无功电压运行控制特点,针对特高压有功潮流变化对近区电网母线电压影响大,电网电压波动大,多电厂、多变电站紧密耦合等运行特性,提出并实现了考虑特高压线路运行方式变化的敏捷电压优化控制技术,同时兼顾特高压近区电网内紧密耦合的多电厂之间、多变电站之间、电厂与变电站之间的协同,在保证电压安全的基础上,减少不合理的无功功率流动,避免不必要的电容电抗器等离散设备投切。所提出的方法已经在实际现场投入闭环运行,运行效果证明了其有效性和可行性。