地区电网低频减负荷控制系统的初步探讨

低频减负荷装置作为保证电网安全稳定运行的第三道防线无疑成为抑制系统频率下降的有效方法.提出了一种基于线性规划的地区电网低频减负荷最优化方法,并引入频率变化率作为控制判据.仿真结果证明,该方法是可行的.     

适应新能源高占比系统的低频减载优化方法

该文介绍考虑低频减载反馈环节的改进频率响应模型,分析了传统低频减载方案在新能源高占比电力系统中的不足,提出一种基于频率变化率的多次加速减载的优化方法。在Matlab/Simulink中进行仿真,结果证明了优化方法的有效性。与传统低频减载方案相比,优化方案减载量更少,系统频率恢复更加快速稳定,在新能源高占比系统中具有更强的经济性和适应性。     

电网自动减载监控管理系统设计

为确保电力系统安全稳定运行,低频减载是低频紧急控制最为有效的一种措施,针对低频减载方案制定响应速度慢、编制工作量大、缺乏系统管理的状况,对电网自动低频减载监控管理系统进行了合理设计,以提高省、地、县级调度第三道防线管理水平。采用"基于全网拓扑的电力需求平衡能力在线评估方法",实现低频减载动态监控,通过在线和离线方案策略研究,动态模拟方案执行过程,自动生成模拟分析报告及各种报表,规范专业管理,使工作流程更加顺畅,提高了工作效率,实现电力平衡评估决策的标准化、系统化、条理化和高效化。     

互联电网第三道安全防线

国内电力系统为防止电网稳定破坏,广泛采用了低频减载（UFLS）、低压减载（UVLS）、振荡（失步）解列、高周切机和过载联切装置以构成第三道防线。这些装置的应用为提高系统的安全性和动态电能质量发挥了重要作用。但是这些装置的配置和参数的整定还缺乏理论依据和实用化算法,随着省级电网的扩大和内外部联系的加强,省级电阿的安全稳定特性越来越受到外部电网的影响,变得越来越复杂,如果省级电网内部的故障处理不当。很可能给外部电网带来安全稳定隐患。近年来国内外发生的电网事故充分说明,如果第三道防线配置和整定不当,电网运行将时刻受到大面积停电的威胁。     

传统减负荷判据在互联电网中的适应性研究

指出了现代互联电网中加强第三道防线的重要意义。对传统低频低压减负荷判据的动作原理和内在不足进行了深入阐述,并通过对IEEE 39节点系统和中国某实际电网的时域仿真加以验证。得出需以全局、动态、交互的观点和手段对传统减负荷判据加以改进,确保互联系统在严重故障后的安全稳定。     

发电机模型的选取对低频减载分析计算的影响

针对频率变化的不同处理方式,分析了发电机模型的选取对低频减载分析计算结果的影响,表明发电机转子运动方程和定子绕组电压平衡方程都不及计频率变化的影响使低频减载分析计算结果偏于保守,发电机转子运动方程和定子绕组电压平衡方程都及计频率变化的影响使低频减载分析计算结果偏于乐观。通过在实际电网中比较不同发电机模型下的频率安全裕度和低频减载动作情况,证实了分析结论的正确性。     

750kV同塔双回交流输变电工程防雷保护研究

针对频率变化的不同处理方式,分析了发电机模型的选取对低频减载分析计算结果的影响,表明发电机转子运动方程和定子绕组电压平衡方程都不及计频率变化的影响使低频减载分析计算结果偏于保守,发电机转子运动方程和定子绕组电压平衡方程都及计频率变化的影响使低频减载分析计算结果偏于乐观.通过在实际电网中比较不同发电机模型下的频率安全裕度和低频减载动作情况,证实了分析结论的正确性.     

基于BPA的电力系统低压减载的研究

低压减载作为电力系统的第三道防线,是维持电力系统安全稳定和经济运行,并保证电能质量的重要措施.依工程实际需求,在电力系统分析软件BPA的基础上,参考国内外现有研究成果,针对分散型低压减载方案,提出基于电压-无功灵敏度减负荷的方法确定低压减载量.采用连续潮流算法,确定薄弱区域的电压-无功灵敏度,最后通过时域仿真分析对所配置的方案进行校验.以河北南网2007年夏季高峰数据为例,验证了该方法具有很好的工程参考价值.     

一种集中协调-实时分布控制的低频低压减载方法

低频低压减载是一种能有效防止电网电压崩溃的紧急措施。提出一种预先集中协调,实时分布控制的低频低压减载方案。基于独立低频低压减载装置构建分布式低频低压减载方案架构;采用负荷分层分区控制决定负荷切除量,实现站间、站内负荷的协调控制。通过仿真将低频低压减载方案与传统减载方案进行对比。结果表明,该方法能够提高切负荷精度,实现精准的负荷控制,降低稳控措施代价影响,加强电网的稳定性。     

计及负荷响应的电力系统低频低压联合减载方案

传统的逐轮次低压减载和低频减载相互独立,减载时未计及负荷的频率电压特性以及频率电压之间的相互影响,在严重扰动下可能因为欠切或者过切负荷而导致系统失稳。提出了一种基于响应的电力系统低压、低频联合减载方案,该方案将负荷有功的动态响应解耦为负荷母线频率和负荷电压的动态响应,依据实测得到的负荷电压响应与频率响应来计算低压减载量,再计及离线计算的低频减载量从而构成综合减载量。IEEE 39节点系统的仿真结果说明,该方法与传统逐轮次减载方法相比,能使受扰系统的频率和电压恢复得更好,有效地保障了电力系统的电压和频率稳定性。     

光伏电站快速频率响应技术研究及应用

随着大容量高比例的新能源集中接入电网,电源结构发生较大变化,电网可用的快速频率响应资源逐步减少,同时大规模新能源基地通过特高压直流外送规模不断扩大,若出现大功率直流闭锁将对电网频率安全造成严重威胁,电网的调频压力及安全运行风险不断增大,亟需新能源参与电网快速频率响应,提升大电网频率风险防控水平。介绍了新能源电站快速频率响应性能要求,面向已有或新建的光伏电站,提出了快速频率响应典型方案,开发了新能源电站一体化控制系统,并在光伏电站开展了示范应用,实现了电站AGC/AVC和快速频率响应功能的集成,达到了光伏电站对电网频率和电压主动支撑的目的。     

Enhancement of transient stability of an industrial cogeneration system with superconducting magnetic energy storage unit

This paper has developed the coordination of load shedding scheme and superconducting magnetic energy storage (SMES) unit to enhance the transient stability of a large industry cogeneration facility. The load-shedding scheme and the tie line tripping strategy by using the frequency relays have been designed to prevent the power system from collapse when an external fault of utility power system occurs. An actual external fault case and a simulated internal fault case have been selected to verify the accuracy of the load shedding scheme by executing the transient stability analysis. To improve the frequency and voltage responses, an SMES unit with various control modes has been installed in the cogeneration system. The sensitivity analysis of the SMES unit with different parameters is applied to achieve better system responses. Besides, an SMES unit with active power deviation as feedback signal is also considered to improve the electric power fluctuation of the study plant with rolling mills. It is found that the SMES system will enhance the electric power quality and minimize the economic losses of the cogeneration facility due to unnecessary load shedding.     

Load shedding scheme for an interconnected hydro-thermal hybrid system with SMES

The frequency of the power system varies based on the load pattern of the consumers. With continuous increase in the load, the frequency of the system keeps decreasing and may reach its minimum allowable limits. Further increase in the load will result in more frequency drop leading to the need of load shedding, if excess generation is not available to cater the need. This paper proposed a methodology in a hybrid thermal-hydro system for finding the required amount of load to be shed for setting the frequency of the system within its minimum allowable limits. The load shedding steps were obtained based on the rate of change of frequency with the increase in the load in both areas. The impact of superconducting magnetic energy storage (SMES) was obtained on load shedding scheme. The comparison of the results was presented on the two-area system.     

1 000 MW超超临界机组凝结水泵变频优化试验及应用

为了进一步降低凝结水泵运行的厂用电率占比，解决超超临界机组参与电网深度调峰工况下凝结水泵变频控制节能效果受限的问题，通过在1 000 MW超超临界机组上开展现场试验并获取特性数据，针对当前运行现状提出一种适合深度调峰且机组热力系统安全的凝结水泵变频控制策略，并加以实施和变工况验证。优化运行结果表明：该控制策略在保证机组安全稳定运行的前提下，能有效降低凝结水泵的功耗，凝结水泵耗电率由0.218%下降至0.152%;在低负荷阶段节能效果更为显著，在500 MW工况下，凝结水泵功耗由1 057 kW下降至633 kW,下降了40.1%;在400 MW工况下，凝结水泵功耗由1 035 kW下降至512 kW,下降了50.5%。     

集群光伏电站一次调频参数经济优化设计方法

针对集群光伏电站参与电网一次调频,提出一种可实现光伏电站经济性最优的一次调频下垂参数优化设计方法.通过模拟同步发电机一次调频的下垂控制,设计考虑减载率与左右下垂系数3个参数的光伏集群参与一次调频的控制方案.在建立单一光伏电站调频参数优化模型的基础上,通过K均值聚类实现光伏集群规模化一次调频参数的降维优化设计.最后,以5...     

海上风电多端柔性直流并网系统频率支持研究

针对海上风电多端柔性直流（VSC-MTDC）并网系统,重点研究风电VSC-MTDC对岸上电网调频功能。通过建立详细风电场、换流站和电网模型,提出一种适用于海上风电VSC-MTDC并网系统动态频率调节方法,即改进斜率控制。整个海上风电场VSC-MTDC加入改进斜率控制后,可使有功功率在若干岸上换流站之间合理分配,从而确保相应岸上电网有功功率平衡,实现VSC-MTDC对于岸上电网频率调节,提升电网频率稳定性。同时给出风电VSC-MTDC对于电网调频的量化指标,即参与调频贡献指数和参与调频能力指数,分别反映VSC-MTDC参与电网调频贡献的能量和瞬时调频能力。在PSCAD/EMTDC仿真平台下搭建一个四端海上风电VSC-MTDC并网系统的仿真模型,并进行动态仿真,其中一个岸上电网发生负荷变化、频率偏移时,风电VSC-MTDC系统实现电网调频控制,仿真结果验证所提并控制方法可为电网频率稳定提供帮助。     

Prospect of new pumped-storage power station

In this paper, a new type of pumped-storage power station with faster response speed, wider regulation range, and better stability is proposed. The operational flexible of the traditional pumped-storage power station can be improved with variable-speed pumped-storage technology. Combined with chemical energy storage, the failure to achieve second-order response speed and the insufficient safety and reliability of pumped-storage power units could be solved. With the better solar energy and site resources, the integrated performance can be improved by an optical storage system installed in future pumped-storage stations. Through the characteristics analysis of the new type of pumped-storage power station, three types of optimal station locations are proposed, namely, the load concentration area, new energy concentration area, and ultra- high-voltage direct current receiver area. Taking the new pumped-storage power station as an example, the advantages of multi-energy cooperation and joint operation are analyzed. It can be predicted that the frequency and load regulation of the power grid will be more flexible, and the service capacity to the main power grid will be much stronger in the future.     

Impact of wind power generating system integration on frequency stabilization in multi-area power system with fuzzy logic controller in deregulated environment

Among the available options for renewable energy integration in existing power system, wind power is being considered as one of the suited options for future electrical power generation. The major constraint of wind power generating system (WPGS) is that it does not provide inertial support because of power electronic converters between the grid and the WPGS to facilitate frequency stabilization. The proposed control strategy suggests a substantial contribution to system inertia in terms of short-term active power support in a two area restructured power system. The control scheme uses fuzzy logic based design and takes frequency deviation as input to provide quick active power support, which balances the drop in frequency and tie-line power during transient conditions. This paper presents a comprehensive study of the wind power impact with increasing wind power penetration on frequency stabilization in restructured power system scenario. Variation of load conditions are also analyzed in simulation studies for the same power system model with the proposed control scheme. Simulation results advocates the justification of control scheme over other schemes.     

Capacity configuration of battery energy storage as an alternative to thermal power units for frequency regulation

传统调频机组因其固有特性而不易实现实际出力与理论计算值相吻合,并且工作在经济运行区内,难以应对电力系统快速发展,新能源发电并入等引起的频率稳定问题.电池储能系统(battery energy storage system,BESS)具有快速,精确的功率响应能力等优势,从而成为新的辅助调频手段的关注热点.在探讨BESS参与电网一,二次调频的实现方法基础上,对与火电机组具备同等调频能力的BESS功率与容量进行配置,并提出了储能容量控制策略建议.示例计算和对比分析,验证了该配置方案的可行性和储能系统参与电网调频的可靠性,为新调频手段的选取与分析提供了借鉴.