Prediction of Instability Separation Modes and Its Application in Practical Dynamic Security Region

The transient critical boundary of dynamic security region (DSR) can be approximated by a few hyper planes correlated with instability separation modes. A method to fast predict instability separation modes is proposed for DSR calculation in power injection space. The method identifies coherent generation groups by the developed K-medoids algorithm, taking a similarity matrix derived from the reachability Grammian as the index. As an experimental result, reachability Grammian matrices under local injections are approximately invariant. It indicates that the generator coherency identifications are nearly consistent for different injections. Then instability separation modes can be predicted at the normal operating point, while average initial acceleration is considered as the measure of the critical generator group to amend the error. Moreover, based on these predicted instability separation modes, a critical point search strategy for DSR calculation is illustrated in the reduced injection space of the critical generators. The proposed method was evaluated using New England Test System, and the computation accuracy and speed in determining the practical DSR were improved.

Quantitative analysis of the dynamic change and spatial differences of the ecological security: a case study of Loess Plateau in northern Shaanxi Province

Using the theory and method of the ecological footprint, and combining the changes of regional land use, resource environment, population, society and economy, this paper calculated the ecological footprint, ecological carrying capacity and ecological surplus/loss in 1986-2002 on the Loess Plateau in northern Shaanxi Province. What is more, this paper has put forward the concept of ecological pressure index, set up ecological pressure index models, and ecological security grading systems, and the prediction models of different ecological footprints, ecological carrying capacity, ecological surplus and ecological safety change, and also has assessed the ecological footprint demands of 10,000 yuan GDE The results of this study are as follows： （1） the ecological carrying capacity in northern Shaanxi shows a decreasing trend, the difference of reducing range is the fastest; （2） the ecological footprint appears an increasing trend; （3） ecological pressure index rose to 0.91 from 0.44 during 1986-2002 on the Loess Plateau of northern Shaanxi with an increase of 47%; and （4） the ecological security in the study area is in a critical state, and the ecological oressure index has been increasing rapidlv.

Theory and Method of Power System Integrated Security Region Irrelevant to Operation States:An Introduction

How to comprehensively consider the power flow constraints and various stability constraints in a series of power system optimization problems without affecting the calculation speed is always a problem.The computational burden of probabilistic security assessment is even more unimaginable.In order to solve such problems,a security region(SR)methodology is proposed,which is a brand-new methodology developed on the basis of the classical point-wise method.Tianjin University has been studying the SR methodology since the 1980s,and has achieved a series of original breakthroughs that are described in this paper.The integrated SR introduced in this paper is mainly defined in the power injection space,and includes SRs to ensure steady-state security,transient stability,static voltage stability,and smalldisturbance stability.These SRs are uniquely determined for a given network topology(as well as location and clearing process for transient faults)and given system component parameters,and are irrelevant to operation states.This paper presents 11 facts and related remarks to introduce the basic concepts,composition,dynamics nature,and topological and geometric characteristics of SRs.It also provides a practical mathematical description of SR boundaries and fast calculation methods to determine them in a concise and systematic way.Thus,this article provides support for the systematic understanding,future research,and applications of SRs.The most critical finding on the topological and geometric characteristics of SRs is that,within the scope of engineering concern,the practical boundaries of SRs in the power injection space can be approximated by one or a few hyperplanes.Based on this finding,the calculation time for power system probabilistic security assessment(i.e.,risk analysis)and power system optimization with security constraints can be decreased by orders of magnitude.

A new transient stability margin based on dynamic security region and its applications

A new transient stability margin is proposed based on a new expression of dynamic security region (DSR) which is developed from the existing expression of DSR. Applications of the DSR based transient stability margin to contingency ranking and screening are discussed. Simulations in the 10-machine 39-bus New England system are performed to show the effectiveness of the proposed DSR based tran-sient stability margin.

Dynamic security risk assessment and optimization of power transmission system

The paper presents a practical dynamic security region (PDSR) based dynamic security risk assessment and optimization model for power transmission system. The cost of comprehensive security control and the influence of uncertainties of power injections are considered in the model of dynamic security risk assessment. The transient stability constraints and uncertainties of power injections can be considered easily by PDSR in form of hyper-box. A method to define and classify contingency set is presented, and a risk control optimization model is given which takes total dynamic insecurity risk as the objective function for a dominant con-tingency set. An optimal solution of dynamic insecurity risk is obtained by opti-mizing preventive and emergency control cost and contingency set decomposition. The effectiveness of this model has been proved by test results on the New Eng-land 10-genarator 39-bus system.

面向燃气机组调峰的天然气管网动态安全域

燃气机组调峰的灵活性有助于提升可再生能源消纳水平,但所造成的管道压力剧烈波动却为天然气管网引入新的安全风险。该文提出一种面向燃气机组调峰的天然气管网动态安全域,以表征满足动态管流安全的燃气机组有功调整量的集合。首先,分析以时域连续的气负荷质量流率作为注入空间的天然气管网动态安全域难以实用化的原因。为此,提出将燃气机组进气口质量流率转化为有功调整量的函数,定义以初始运行点为基准、以各燃气机组有功调整量为注入空间的天然气管网动态安全域。为兼顾计算精度和效率,基于时空正交配置法对管网连续变量进行近似离散,建立安全域边界搜索优化模型。并进一步揭示天然气管网稳态安全域可通过松弛该优化模型中部分约束条件求解得到,为动态安全域的一种退化形式。算例结果表明,所提方法克服天然气管网稳态安全域对于日内安全分析过于乐观的局限性,有助于增强电力-天然气耦合系统的协同态势感知能力。

Security region based real and reactive power pricing of power system

This paper develops a novel model and an algorithm of security region based real and reactive power pricing of power systems.In the proposed model,the reactive power production cost is represented as the opportunity cost.The static voltage stability region in the cut set power space(CVSR) and the practical dynamic security region(PDSR) in the injection power space are used to represent the constraints of voltage stability and transient stability,so that the consideration of this kind of constraints in the optimization becomes very easy.In the proposed algorithm,a decoupled optimization and iteration method of active power production cost and reactive power production cost is suggested.According to the K-T optimality conditions,the prices of active power and reactive power,and the different components corresponding to the concerned security constraints are derived.The components of spot prices can reflect the influence of different node power injections on each kind of security constraints,so that through the node price all of the participants in power market can be stimulated to take an active part in maintaining the system security.An illustrative example on the New England 10-genetator 39-bus System is used to demonstrate the proposed method.

能源安全保障的驱动路径与实践策略:基于地方财政自主度的视角

基于2015—2021年我国30个省份(不含港澳台及西藏)的面板数据,构建能源安全评估框架,考察其区域差异和动态演变状况,分析财政保障能源安全的驱动路径及实践策略。研究发现:观测期内能源安全指数随时间呈波动上升趋势,指数相对大小表现出东部地区>西部地区>中部地区特点。从区域差异来看:我国能源安全的泰尔指数呈现出区域间变化不大、区域内波动下降的态势,且区域差异主要来源于区域内部的差异;核密度估计曲线分布具有“高度变高,宽度变窄”特点,即区域内部差异随时间稍有变小;能源安全指数符合σ和β收敛性质。财政自主度对能源安全有显著促进作用,该正向作用可通过缓解地方政府财政压力、增加政府总储蓄的途径发挥。财政自主度对能源安全的正向影响呈现出“西部地区>东部地区>中部地区”的特点。财政自主度是所有影响能源安全的显性因素中的最重要因素。根据研究结果,为我国统筹能源安全与发展提出相关的财政政策和产业政策建议。

Autonomous-synergic Voltage Security Regions in Bulk Power Systems

Determining security/stability boundaries is a common and critical means of preventing cascading failures induced by voltage-related issues,which represents one of the major challenges in bulk power systems.However,traditional approaches suffer from conservative issues and heavy computational burdens.To address these challenges,the concept of an autonomous-synergic voltage security region(AS-VSR)and the corresponding dynamic constraint coefficient pruning(DCCP)computation method,which fully consider the volt/var characteristics of bulk power systems,are proposed in this letter.Both linearized and nonlinearized robust optimization problems are introduced to obtain accurate results.The computational accuracy,time cost,and advantages of autonomous-synergic control are observed in the simulation results.

基于实用动态安全域的电力系统安全成本优化

基于实用动态安全域(PDSR)提出一种电力市场环境下的电力系统安全成本优化(最优安全控制)模型及算法。该模型计及了暂态稳定性约束、事故发生概率及系统失稳损失。独立系统运行员(ISO)依该模型能确定安全成本最低的系统安全水平,即确定系统安全性和经济性的平衡点。安全成本由备用成本、再调度成本和期望失稳损失组成。而且所提算法计算速度快、易于实现。另外,该文提出的模型及算法也可方便的应用于传统垂直统一管理模式下的电力系统,只要分别用发电机备用成本曲线和边际成本曲线替换发电商向ISO呈报的备用容量价格曲线和再调度功率价格曲线即可。最后以新英格兰10机39节点系统为例,检验了所提模型的合理性及算法的可行性。

基于实用动态安全域的输电系统概率动态安全评估

提出一种基于实用动态安全域的输电系统概率动态安全评估模型。该模型计及了负荷和发电节点注入功率的不确定性、预想事故的不确定性、事故发生地点、故障切除时间及负荷中感应电动机负荷比例的不确定性。安全域的数学描述使注入功率不确定性和电动机负荷比例不确定性的计及变得简便。概率安全性评估的结果能够指导运行人员进行预防控制。以NewEngland10机39节点系统为例验证了所提出的数学模型,并用Monte-Carlo方法加以检验。

计及负载率和临界滑差的改进感应电动机加权聚合

在暂态稳定仿真中所用的等值感应电动机的模型参数对仿真精度的影响很大。为了获取这些参数,大多采用基于容量加权的模型参数聚合法。感应电动机群中的各电动机初始滑差不同对聚合结果有重要影响,而该初始滑差由负载率和临界滑差联合决定。文中据此提出了利用负载率和临界滑差来修正的感应电动机加权聚合法。算例表明,依据该方法所聚合出的等值感应电动机能更好地模拟原感应电动机群对暂态稳定性的影响。研究还表明,由于实际系统中参与聚合的感应电动机个数很多,且其负载率分布具有随机性,用统计综合法得到的等值感应电动机模型参数基本可用。

含双馈风机电力系统的动态安全域

计算了含双馈风机电力系统的动态安全域,并通过时域仿真对其边界的准确性进行了验证。经过大量仿真发现,在工程关心的范围内,接入双馈风机后,注入功率空间上电力系统动态安全域的边界仍可以用超平面进行拟合;分析了双馈风机接入对电力系统动态安全域的影响,发现双馈风机接入后引起动态安全域的外扩,并对其机理进行了探讨。

基于安全域的电力系统有功及无功优化(英文)

提出了一种同时计及电力系统有功及无功的新型优化潮流模型与算法。在构建优化潮流(OPF)的数学模型时借助了3种电力系统安全域的概念与方法,它们分别是:满足系统潮流约束(母线电压约束、支路热稳定极限以及发电机出力限制)的“静态安全域”、“静态电压稳定域”以及针对既定的网络结构和既定的网络结构变化过程的保证系统暂态稳定性的“动态安全域”。在此基础上,利用电力系统的有功功率与支路角之间、无功功率与节点电压幅值之间的仿射关系,建立了通过二次规划来求解优化潮流(OPF)的算法。文中最后在新英格兰10机39节点系统中演示了所提出算法的有效性。

电力系统动态安全域线性近似方法比较

分析比较了网络约化模型下电力系统动态安全域的3种线性近似方法的综合效能,分别为: 基于稳定域二次近似的动态安全域线性近似(Q线性近似)、基于稳定域线性近似的动态安全域线性近似(L线性近似)和基于稳定域边界法向量恒定假设的动态安全域近似(L0线性近似)。其共同之处为在事先搜索而得的处于动态安全域边界的临界点处应用相应的近似刻画方法。文中以最小二乘拟合搜索得到的临界点所获得的线性近似为基准,分析比较了上述3种线性近似对安全域边界刻画的准确程度;特别是对于低维的动态安全域,以搜索获得的真实动态安全域为基准,采用图示方法直接比较不同线性近似的近似程度。仿真分析表明:在具有事先搜索的临界点时,3种线性近似方法均能准确地近似动态安全域的局部边界;同时,L0线性近似和L线性近似计算量小,更适用于大型电力系统。

电力系统功率注入空间的动态安全域

本文根据电力系统结构保留模型和微分拓扑理论,阐述了用一组超平面近似描述动态安全域边界的理论依据,给出了决定这些超平面的解析表达式,并用算例作了验证。

基于改进解析法的小范围动态安全域搜索方法

由于目前动态安全域搜索方法用于概率安全指标计算结果会存在一定的误差,基于正态分布函数的快速衰减特性,提出了动态安全域(DSR)的小范围搜索方法。首先搜索DSR边界超平面的估计值,据此确定一个搜索的小范围,然后在这个小范围内利用改进解析法计算DSR边界的近似超平面。新英格兰10机39节点系统上的算例误差为4.5%,说明所提方法是合理可行的。

用动态安全域法决定暂态稳定紧急控制措施初探

动态安全域(DSR)法是动态安全分析与控制的一种新方法,它具有时域仿真法与直接法所不具备的“域”的特点。采用DSR法来确定暂态稳定紧急控制措施。在定义了相应的测度之后,根据测度给出了两类算法棗最少控制点法与综合控制法,由这些算法可以快速确定切机或切负荷量的大小。算例验证了算法的有效性。

基于动态安全域的电力系统安全概率评估模型

针对电力系统安全性问题特性,提出一种基于动态安全域的安全概率评估模型。模型核心是不安全概率指标,并通过该指标来表征各电力元件以及整个电力系统的安全性状况。概率方法的引入,使得模型不仅计及系统中各种主要的不确定性因素,而且对系统的安全状况进行了定量的描述。动态安全域理论大大降低了安全概率评估的计算量,使得该模型具有实用性。评估结果可以用于指导运行人员在安全控制中制定正确的决策。用新英格兰10机39节点系统(New England 10-generator 39-bussystem)对该模型做了验证。

计及连锁故障的暂态稳定概率评估方法

动态安全域的一系列研究成果为解析法在暂态稳定概率评估的应用提供了便利条件。针对负载较重的电网,提出了一种基于动态安全域的计及连锁故障引起系统失稳的暂态稳定概率评估方法,对系统安全影响较大的线路发生初始故障,交替求解暂态稳定和潮流分布,考虑了失稳以及过载保护动作的概率特性,得到对系统安全影响较大的线路最可能引发的连锁故障路径,进而求得考虑连锁故障引发系统失稳在内的线路不安全概率指标。以IEEE 10机39节点系统为例,验证了该方法的可行性和合理性。