Multi-criteria contingency ranking method for voltage stability

The objective of this paper is to propose a fast, accurate, and robust method for ranking contingencies according to their severities as far as voltage stability is concerned. In general terms, the proposed procedure consists of obtaining the operating state and computing performance indices for each contingency of a predefined list. The contingencies are then ranked according to their performance indices. The proposed method can be used as a real time operation tool, since its computational effort is very small. The proposed method is able to pick most of the severe contingencies, resulting in very good capture ratios. Simulation results are shown for small test and large realistic power systems.     

Calculation of weighting factors of static security indices used in contingency ranking of power systems based on fuzzy logic and analytical hierarchy process

Contingency screening and ranking is one of the most important issues for security assessment in the field of power system operation. The objective of contingency ranking is to quickly and accurately select a short list of critical contingencies from a large list of potential contingencies and rank them according to their severity. Then suitable preventive actions can be implemented considering these contingencies that are likely to affect the power system performance. In this paper a novel approach is presented for contingency ranking based on static security assessment. This method employs weighted performance index with the application of fuzzy logic based analytical hierarchy process in order to select appropriate weighting factors to be imposed. The proposed method is applied to IEEE 30 bus system and the results are presented.     

电力系统在线偶然事故排序的一种新方法

将偶然事故排序中通常采用的系统行为指标同系统的可靠性与经济性指标相结合,形成偶然事故对系统影响的期望值,以此对偶然事故进行排序,使得对偶然事故的选择更具有合理性.最后对一给定的系统进行试算,并进行分析,证明这种方法是合理的.     

A novel collapse prediction index for voltage stability analysis and contingency ranking in power systems

Voltage instability is a serious phenomenon that can occur in a power system because of critical or stressed conditions. To prevent voltage collapse caused by such instability, accurate voltage collapse prediction is necessary for power system planning and operation. This paper proposes a novel collapse prediction index (NCPI) to assess the voltage stability conditions of the power system and the critical conditions of lines. The effectiveness and applicability of the proposed index are investigated on the IEEE 30-bus and IEEE 118-bus systems and compared with the well-known existing indices (Lmn, FVSI, LQP, NLSI, and VSLI) under several power system operations to validate its practicability and versatility. The study also presents the sensitivity assumptions of existing indices and analyzes their impact on voltage collapse prediction. The application results under intensive case studies prove that the proposed index NCPI adapts to several operating power conditions. The results show the superiority of the proposed index in accurately estimating the maximum load-ability and predicting the critical lines, weak buses, and weak areas in medium and large networks during various power load operations and contingencies. A line interruption or generation unit outage in a power system can also lead to voltage collapse, and this is a contingency in the power system. Line and generation unit outage contingencies are examined to identify the lines and generators that significantly impact system stability in the event of an outage. The contingencies are also ranked to identify the most severe outages that significantly cause voltage collapse because of the outage of line or generator.     

一种新的故障筛选和排序的方法

为了避免在故障筛选与排序中忽略严重故障而导致大停电的发生,提出了一种比较精确的新的故障筛选和排序方法。以动态安全域的求解为基础,在故障筛选时运用解析法求动态安全域,进而求解失稳度。以故障的失稳度作为故障筛选的指标,快速选出严重的故障,形成故障筛选集。在故障排序时对于筛选集中的故障线路运用BP神经网络求解动态安全域,从而求解概率不安全指标,以故障的概率不安全指标作为故障排序的指标,得到精确的故障排序。通过IEEE10机39节点系统算例验证了该方法能够快速、全面、准确地实现故障的筛选与排序,同时通过IEEE4机11节点系统验证了BP神经网络求解动态安全域的可行性,误差为0.0608,满足要求。     

基于静态电压稳定的事故筛选和排序算法综述

由于负荷的快速增长以及市场机制下电力系统运行方式的频繁调整使得电网可能接近稳定极限运行,这使得电网的电压稳定问题变得越来越严重.如何在事故扰动情况下快速而准确地评估电网的电压稳定性具有重要的意义.阐述了事故筛选和排序的基本概念和评估的指标类型,对现有的各种事故筛选和排序方法进行了总结与述评,并指出了此领域研究存在的问题.     

基于静态电压稳定的事故筛选和排序算法综述

由于负荷的快速增长以及市场机制下电力系统运行方式的频繁调整使得电网可能接近稳定极限运行,这使得电网的电压稳定问题变得越来越严重。如何在事故扰动情况下快速而准确地评估电网的电压稳定性具有重要的意义。阐述了事故筛选和排序的基本概念和评估的指标类型,对现有的各种事故筛选和排序方法进行了总结与述评,并指出了此领域研究存在的问题。     

Effect of line contingency on static voltage stability and maximum loadability in large multi bus power system

Voltage instability is the phenomena associated with heavily loaded power systems. It is normally aggravated due to large disturbance. Due to deregulation of power system, the system has to cater for the load bids in open access. This may cause the increased transaction level leading to more stress on the power system. It has become an urgent need of today to address the voltage stability problems to keep the voltage profile under control. Several incidences of voltage instability have occurred worldwide recently. In the event of contingency, the most serious threat to operation and control of power system is insecurity. The estimation of the power system state under contingency is an essential task for the power system engineers. The contingency analysis technique is a prerequisite to predict the effects of various contingencies like failure of transformers, transmission lines, etc. It helps to initiate necessary control actions to maintain power system security, reliability and stability. In the present work, two kinds of performance indices viz. active power performance index and reactive power performance index are computed for a large power system using a special code written in MATLAB environment. Furthermore, a novel idea of static voltage stability analysis by incrementing the load in proportion to the original load on load buses along with the most vulnerable line outage using Newton Raphson (N–R) load flow is presented.     

一种三级协调的配电网预想故障筛选与排序方法

为了提高配电网预想故障集筛选和排序的快速性、准确性,文章以配电网历史故障数据和运行数据为基础,提出一种三级协调的配电网预想故障筛选与排序方法。采用层次云理论计算故障情况下电压、短路电流、有功功率、无功功率损耗和功率因数之间的权重关系,并通过预处理构建支路参数筛选指标,对预想故障集进行预筛选以缩小故障筛选范围。利用π型支路模型,提出基于同步相量测量装置(Phasor Measurement Unit,PMU)的负荷裕度筛选指标和基于PMU的电压稳定排序指标,实现对严重故障的快速筛选与排序。实例分析表明:该方法能全面、准确、高效地实现系统预想故障集筛选与排序。     

A new contingency analysis approach for voltage collapse assessment

Voltage collapse analysis in power systems has been the subject of concern of many researchers. Recently, a new technique based on tangent vector behavior has shown to be attractive, because of the accuracy and the low computational effort required. In this paper, tangent vector is employed for contingency analysis. The idea consists of monitoring tangent vector norm associated with each contingency, identifying the most critical ones. The method is tested with the help of the IEEE-118 bus and the Southeastern Brazilian power systems, considering the generators reactive power limits.     

特高压输电线路用绝缘子的展望

对我国输电线路目前所采用的瓷、钢化玻璃和复合材料三种绝缘子的运行情况进行了全面分析,并对世界各国绝缘子的研制及使用情况作了介绍。在此基础上,对我国特高压线路用绝缘子的研制方向提出了一些建议。     

Impact of distributed generation on distribution contingency analysis

Alternative energy sources are becoming more cost effective, and many utilities are now providing incentives for alternative power. Placing these alternative energy sources, as well as other smaller traditional energy sources, on the distribution power system, allows the development of a new paradigm related to distributed generation (DG). The size and site of the DG will have an effect on the voltages and operations of the distribution power system in the future. This paper discusses a procedure for evaluating the impact of site and size on both the original distribution power system as well as a reconfigured power system after a fault. Validation of this work is done using the IEEE 37 node distribution feeder and the results and trends are presented.     

输变电工程建设单位的安全管理

对输变电工程建设单位在安全管理中出现的问题进行详细分析，并提出相应的解决方法。     

An online power system static security assessment module using multi-layer perceptron and radial basis function network

Efficient contingency screening and ranking method has gained importance in modern power systems for its secure operation. This paper proposes two artificial neural networks namely multi-layer feed forward neural network (MFNN) and radial basis function network (RBFN) to realize the online power system static security assessment (PSSSA) module. To assess the severity of the system, two indices have been used, namely active power performance index and voltage performance index, which are computed using Newton–Raphson load flow (NRLF) analysis for variable loading conditions under N − 1 line outage contingencies. The proposed MFNN and RBFN models based PSSSA module, are fed with power system operating states, load conditions and N − 1 line outage contingencies as input features to train the neural network models, to predict the performance indices for unseen network conditions and rank them in descending order based on performance indices for security assessment. The proposed approaches are tested on standard IEEE 30-bus test system, where the simulation results prove its performance and robustness for power system static security assessment. The comparison of severity obtained by the neural network models and the NRLF analysis in terms of time and accuracy, signifies that the proposed model is quick, accurate and robust for power system static security evaluation for unseen network conditions. Thus, the proposed PSSSA module implemented using MFNN and RBFN models are found to be feasible for online implementation.     

基于小范围动态安全域的故障筛选与排序

事故筛选排序是电力系统概率安全分析中尤为重要的组成部分。为了使电力系统的安全评估能够实时监测和在线应用,提出了一种兼顾准确性和实时性的新故障筛选排序模型。为同时满足精度与速度的要求,采用改进的小范围解析法求得相对于概率不安全指标精度敏感的小范围动态安全域。采用稳定判据将故障分类,各类故障采用不同策略并行排序。致命性故障按照概率不安全指标排序后,立即输出。一般性故障,定义了基于小范围安全域的最易失稳距离,优化了故障损失威胁模型,按照失稳距离初步筛选,再按损失威胁进行排序。该故障筛选与排序模型针对每个故障只需计算一次动态安全域,对致命性故障排序一次,对一般性故障筛选和排序各一次。IEEE10机39节点系统仿真结果表明,该模型可以迅速可靠地完成故障筛选与排序,对系统运行方案具有较强指导性。     

全局输配电网电压稳定故障筛选与排序的分布式计算方法

随着传统配电网向含大量分布式电源的主动配电网转变,输电网、配电网电压稳定评估已不再适宜各自独立计算。基于输电网、配电网分属于不同控制中心调控,提出一种全局输配电网电压稳定故障筛选与排序的分布式计算方法。该方法分为两阶段：阶段1中采用输配电网主从分裂分布式潮流工具在系统要求最小负荷裕度值的工况下进行各预想故障的潮流计算,采用最优乘子法筛选出潮流不可解的严重故障;阶段2中采用基于输配电网分布式连续潮流的步长加速二次曲线拟合方法计算严重故障的负荷裕度并进行排序。由1个IEEE 118节点输电网和2个IEEE 33节点配电网组成的全局输配系统的仿真算例表明所提方法能够快速可靠地实现全局输配电网电压稳定故障筛选与排序。     

1000MW水轮发电机定子股线环流损耗分析计算

定子线棒换位技术是1 000 MW水轮发电机设计中的关键技术之一,合适的换位方式有利于更好的减小定子股线间的环流损耗,提高电机效率.对水轮发电机常用的360°全换位、0°/360°/0°加槽部空换位段换位、不足360°换位、0°/360°/0°延长换位等4种换位方式进行讨论,采用漏感电势法分别计算4种换位方式下1000...     

基于引导传播和流形排序的协同显著性检测方法

提出一种基于图像间显著性引导传播和图像内流形排序的两阶段引导方法,充分挖掘单幅图像显著性引导传播机理,提高面向群组图像协同显著性检测算法的精确度和实时性。对N张群组图像中的任意一幅图像,第一价段借助单幅图像显著性探索其与组内其他图像两两间的共同相似性属性,获取N-1张初始协同显著性图。为了有效抑制非相似区域的背景干扰,在第二阶段中,通过流形排序(EMR)算法,计算N-1张前景显著性图每个像素点的排序值,以更新之前的显著性检测结果,恢复出第一阶段中误检为背景的相似性区域。最后在基于贝叶斯理论的融合算法框架下实现最终协同显著性图的获取。基于iCoseg和MSRC数据库进行评测,所提算法在综合指标F值和受试者工作特征(ROC)曲线下面积(AUC)等评价指标方面一致优于现有5种协同显著性检测算法。基于真实场景的实验结果从普遍适用性角度对本文算法做了进一步验证。     

A power fluctuation evaluation method of PV plants based on RankBoost ranking

Fluctuation evaluation is an important task in promoting the accommodation of photovoltaic (PV) power generation. This paper proposes an evaluation method to quantify the power fluctuation of PV plants. This consists of an index system and a ranking method based on the RankBoost algorithm. Eleven indices are devised and included in the index system to fully cover diverse fluctuation features. By handling missing and invalid data effectively, the ranking method fuses multiple indices automatically and provides a systematic and comprehensive comparison of power fluctuation. Simulation results based on power data from six PV plants indicate that the evaluation list obtained by the RankBoost ranking method is better represented and more comprehensive than that derived by the equal weight method.     

基于期望损失指标的电力系统故障筛选和排序

为了避免在故障筛选与排序中只考虑故障的严重程度,提出了一种新的故障筛选和排序的方法。它是以动态安全域的求解为基础,以故障的期望损失作为筛选和排序的指标,同时考虑故障发生时电力系统的经济性与随机性两个方面,更符合实际情况。首先,根据经验故障集,用小范围解析法计算电力系统发生故障时的动态安全域,从而求解发生故障时的改进的概率不安全指标和期望损失,根据故障在故障集中的比例筛选出期望损失比较大的故障线路,将其放入筛选集中。然后,根据误差比例控制曲线,控制计算动态安全域的精度,重新计算筛选集中电力系统发生故障时的动态安全域、期望损失和它们所占的比例,依据此比例进行排序。通过IEEE10机39节点系统算例验证了该方法能够快速、全面、准确地实现故障的筛选与排序。