李生虎(1974),男,博士,教授,博士生导师,研究方向为电力系统建模与可靠性分析、风电并网电力系统分析与控制、特高压直流和柔性交流输电(E-mail:
周慧敏(1998),女,硕士在读,研究方向为特高压直流和稳定控制系统可靠性
颜云松(1981),男,博士在读,高级工程师,从事电力系统安全稳定控制相关工作
安全稳定控制系统(SSCS)扁平化设计可实现各控制子站间、各分区电网间的信息交互,有利于减小SSCS层数,提高可靠性,但是增加了控制路径搜索和薄弱环节辨识的难度。文中在树状SSCS中增加双向/环状通道以减少中间站点,根据邻接矩阵搜索从顶层站点到底层站点的所有路径; 计及元件可用率和底层站点可控容量,量化扁平化SSCS对底层资源的控制能力; 定义站点平均控制能力和平均关联路径数指标,评价扁平化对各站点控制能力的影响; 提出扁平化SSCS控制能力对元件可用度的灵敏度的解析算法,以确定SSCS薄弱环节。算例表明:扁平化设计减少了层级和中间站点,同时提高了SSCS控制能力; 站点所经路径越多、层数越少、路径可控容量越大,对SSCS控制能力影响越大。
The flat design of security and stability control system (SSCS) can realize the information interaction between each control sub-station and each sub-grid, which is conducive to reducing the number of SSCS layers and improving its reliability, thus increasing the difficulty of searching the control paths and differentiating the vulnerable components. The bidirectional/loop communication channels are added to the tree-shape SSCS to reduce the intermediate stations and find all the paths from the top to bottom stations based on the adjacent matrix. Considering availability of components and controllable capacity of underlying stations, the control capability of the flat SSCS is newly quantified. Average control ability and average associated path number are defined to evaluate the influence of flattening on the control ability of each station. Analytical sensitivity model of the control capability of flat SSCS with respect to the components′ availability is proposed to determine the vulnerable components. The numerical analysis shows that the flat design reduces levels and intermediate stations, and improves the controllability of the SSCS. The impact on the controllability of the SSCS increases by the number of paths and controllable power, but decreases by the number of layers.
安全稳定控制系统(security and stability control system, SSCS)由通信通道和控制站点组成,主要用于维护电网频率和功角稳定[
SSCS可基于动态数据参数,也可由严重事件直接驱动。低频减载属于前者,启动须等待几个摇摆周期,时间长达数秒。在此过程中可能发生机组停运和大面积停电,恶化电网暂态过程。因此,在电网发生重大事件(如特高压直流受端单极或双极闭锁)时,可立即启动SCCS,快速增加有功出力或减少有功缺额,加快频率恢复过程。
我国能源基地和负荷中心不重叠,有必要采取大容量、远距离交/直流输电[
SSCS一般采用树状结构[
SSCS结构设计需要考虑经济成本、控制复杂性、可靠性等因素。对于SSCS可靠性,现有研究方法包括状态空间[
文中在树状SSCS中增加双向/环状通信通道,实现扁平化设计。搜索顶层至底层站点间有向路径,计及元件可用率和可控容量,量化SSCS的控制能力; 定义站点平均控制能力指标和站点平均关联路径数指标,量化扁平化设计效果; 提出SSCS控制能力对站点和通道可用率的灵敏度的解析表达,以确定扁平化SSCS薄弱环节; 通过算例分析验证了所提算法的正确性。
SSCS A的结构
Configuration of SSCS A
对于
SSCS A扁平化设计
Flat design of SSCS A
从分区电网互联角度出发,
3个分区电网SSCS互联
Integration of SSCS of three regional systems
实际跨区电网SSCS扁平化设计,还须考虑以下因素:
(1) 跨区电网SSCS设计主要针对有功平衡和频率稳定,很少考虑无功/电压,因为无功很少进行大容量、远距离传输。
(2) 扁平化设计须兼顾站点功能和重要性、通道建设和维护成本等。有些站点位于枢纽变电站、大机组、负荷中心附近,扁平化设计过程中这些站点必须保留。
(3) 扁平化淡化了站点间层级关系,可能会增加控制复杂程度,实际系统不可能也没必要全部采用环网,只要对部分薄弱站点或通道扁平化,因此薄弱环节辨识对扁平化设计非常重要。薄弱环节辨识取决于控制路径可用率和控制容量。
定义从顶层站点到底层站点的任意通路为控制路径。对树状系统,通过观察可以确定所有路径,如
从拓扑结构来说,可以视站点为顶点,通道为边,用邻接矩阵
站点重新编号后的SSCS A
SSCS A with renumbering to stations
以
(1) 从
(2) 对第
(3) 为避免在双向或环状通道中循环,在记录站点和通道时,需要避免搜索路径的重复。
按照上述原则,S1指向S2和S3。S2指向底层站点S6、S7、S8,因此得到3条控制路径,如
控制路径的拓扑搜索
Topology search to control path
增加横向联系后,SSCS可能出现环路,这在变电站通信和电网稳定控制系统中都可能存在。文中在建立连接矩阵时,已经避免环路重复搜索。和树状网络一样,环路控制也须明确上下级关系,只是前者上下级关系静态不变而后者动态变化。
控制路径所关联元件成串联关系,因此第
路径中关联元件包括站点和通道。假设站点
式中:
实际通道如专用光纤复合架空地线(optical fiber composite overhead ground wire, OPGW)的可靠性包括电气、机械、光学等方面,任一方面性能下降都可能导致通信功能失效。文献[
各控制路径间为并联关系,资源
路径可用率越高、可调容量越大,SSCS控制能力越强。因此定义系统对资源
SSCS的控制能力为对各资源控制能力之和
联立式(4)、式(5)和式(7)可得
扁平化对SSCS的影响是增加了光纤成本和控制路径,提升了控制能力,减少了站点和层级数。为量化扁平化正面效果,定义站点平均控制能力
定义SSCS站点平均关联路径数为
扁平化增加了确定薄弱环节的难度,可以每次断开一条通道或一个站点,比较断开前、后的
式中:
类似可推导系统控制能力对通道可用率的灵敏度。对灵敏度较大的通道,需要降低故障率、减少修复时间,或者加强扁平化设计。
SSCS站点可靠性参数参考文献[
计算树状结构、底层备用、中间备用和扁平化结构下SSCS对各控制资源的控制能力,见
树状SSCS控制能力
Controllability of SSCS with tree structure
站点 | 不同结构SSCS控制能力 | |||
树状 | 底层备用 | 中间备用 | 扁平化 | |
R1 | 287.73 | 299.50 | 299.50 | 299.98 |
R2 | 191.82 | 191.82 | 199.67 | 199.99 |
R3 | 95.91 | 95.19 | 99.83 | 99.99 |
R4 | 95.91 | 99.83 | 99.83 | 99.79 |
R5 | 47.96 | 47.96 | 49.92 | 49.90 |
R6 | 95.91 | 95.91 | 99.83 | 99.79 |
针对电网A,
不同结构下分区SSCS的
不同结构下SSCS的
SSCS控制能力对站点可用率的灵敏度见
Sensitivity of
SSCS控制能力对通道可用率的灵敏度见
Sensitivity of
Sensitivity of
通道编号 | 控制资源 | ||
R4 | R5 | R6 | |
4 | 2.442 | 2.442 | 3.883 |
5 | 1.941 | 1.941 | 4.885 |
7 | 8.768 | 0 | 0 |
9 | 0 | 0 | 8.768 |
文中针对电网SSCS扁平化需求,搜索顶层/底层站点间所有路径,量化扁平化SSCS控制能力及评估指标,提出灵敏度模型以确定薄弱环节,得到以下结论:
(1) SSCS控制能力与控制路径的可用率和可控容量有关。路径可用率越高,可控容量越大,系统控制能力越好。可以通过增加可用率或路径以提高系统控制能力。
(2) 增加备用或采用扁平化结构能增加SSCS的控制路径。优先增加层级较高站点备用。相比于增加备用,扁平化设计对提高SSCS控制能力的效果更明显。
(3) 站点或通道所关联的路径越多,路径控制容量越大,站点或通道越薄弱,故障影响越大。在SSCS设计中,应优先考虑这些薄弱元件。
文中SSCS扁平化设计考虑了系统可靠性和控制能力。实际扁平化设计还须考虑控制难度和光纤成本等因素,有待进一步研究。
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