Fast real power contingency ranking using counter propagation network: feature selection by neuro-fuzzy model

In deregulated operating regime power system security is an issue that needs due consideration from researchers in view of unbundling of generation and transmission. Real power contingency ranking is an integral part of security assessment. The objective of contingency screening and ranking is to quickly and accurately shortlist critical contingencies from a large list of credible contingencies and rank them according to their severity for further rigorous analysis. In the present work, modified counter propagation network (CPN) with neuro-fuzzy (NF) feature selector is used for real power contingency ranking of the transmission system. The CPN is trained to estimate the severity of a series of contingencies for given pre-contingencies line-flows. But for larger size system it becomes rather difficult to cope with the increased size of input pattern and network as well. And it adversely affected the performance of the network and computational overhead. The proposed NF feature selector prunes the size of input pattern by exploring the individual power of features to characterize/discriminate different clusters. The reduced set of discriminating inputs not only ensures saving in training time but also improves estimation accuracy and execution time and these are the deciding parameters in evaluating the performance of particular contingency ranking technique. The effectiveness of proposed approach is demonstrated on IEEE 30-bus test system and practical 75-bus Indian system.     

基于PMU技术的电压稳定研究

电压失稳是一个动态的强非线性过程,需要采用动态方法来研究,而常规的动态电压稳定分析方法(如时域仿真法)的最大缺点是计算速度慢、耗费时间长,不能满足电压稳定在线研究的需要。本文利用PMU实测数据,在网损灵敏度理论的基础上,构造了一个二阶指标—综合网损灵敏度指标(Integrated Loss Sensitivity Index,ILSI),同目前电压稳定分析常用的一阶指标相比,具有线性度好,准确度高的优点,在电压失稳过程中有比较均匀的变化趋势,这样不仅可以让运行人员清楚地了解系统的稳定状况,而且还可以预测稳定极限。提出的算法物理意义明确、算法结构简单,在IEEE9节点系统的仿真结果表明,该指标在系统电压恶化的过程中显示良好的线性度,可以很好地表征目前系统的电压水平。     

基于Fisher Score特征选择的电力系统暂态稳定评估方法

针对不同电气输入特征与电力系统暂态稳定关联程度不同以及当输入特征受到干扰时评估准确率明显下降的问题,提出一种基于Fisher Score特征选择的电力系统暂态稳定评估方法。设计一种面向电力系统暂态稳定评估二分类问题的样本特征Fisher Score值计算方案;通过Fisher Score值排序有效区分重要特征与冗余特征、噪声特征与非噪声特征;将选择的电气特征输入不同机器学习模型中进行训练和评估。新英格兰39节点系统和IEEE 145节点系统的仿真结果表明,所提特征选择方案能有效筛选电力系统暂态稳定评估中重要度高的特征,提升了评估模型的预测性能。     

Line outage ranking for voltage limit violations with corrective rescheduling avoiding masking

This paper describes a technique for ranking line outages causing voltage limit violations taking into account the post-outage correctability of the network during contingency selection process. Due to the choice of large even powered of performance index (PI): (i) masking is avoided; and (ii) complete potential of correctability of power network is utilised. Fletcher and Reeves conjugate gradient method is used for optimisation. Use of newly derived compensated voltage shift factor has been made. To restrict the reactive power limit violations at generation buses, use of newly derived reactive power compensated shift factor has been made. Control corrections have been optimised for each line outage in the same base case pre-outage condition itself. This allows the use of same set of pre-outage sensitivity coefficients and line outage distribution factors. It is to be stressed here that the control corrections have been obtained for each line outage in pre-contingency condition mainly for computational convenience. But actually these corrections are applied in respective post-outage conditions. The algorithm is tested on IEEE 25-bus, 30-bus and 91-bus test systems.     

电力系统动态仿真中参数不确定性影响的评估

电力信息化是指信息技术在电力工业中的应用,是电力工业在信息技术的驱动下由传统工业向高度集约化、高度知识化、高度技术化转变的过程。文中以构建面向水电厂的综合数据分析平台为主要解决方案,基于“数据抽取”策略和IEC 61850标准,实现综合数据源集成和信息建模,并探索更加符合数据多个异构信息系统数据处理的分析构架,保障综合数据分析平台“安全分析”,进而提高水电厂海量数据的综合分析和有效处理水平,为实现行业管理、安全生产、经济运行等业务辅助决策创造条件。     

电压稳定分析中支路型故障筛选及排序算法研究

提出了一种用于电压稳定性分析的支路型故障筛选和排序的快速算法，该方法分为4个阶段：①依据正常运行状态下的潮流解从所有预想事故中筛选出严重事故；②通过分析线路被置换后系统雅克比矩阵的最小奇异值，从所筛选出的事故中再次筛选出更严重的事故；③在指定的负荷水平下解潮流方程，从第二次筛选出的事故中再次筛选出最严重的事故；④对每个最严重的事故进行1次潮流计算，估计其最大负荷能力。通过New-England 39节点系统和IEEE 118节点系统算例表明，此算法计算量少，简单有效，易于实现。     

Electricity market equilibrium of nonlinear power systems with reactive power control

The impact of reactive power control on the electricity market equilibrium is investigated. The effects of limitations on the reactive power generation and absorption, and load power factor adjustments, are examined using a novel electricity market equilibrium model that solves large-scale nonlinear power systems with asymmetric strategic firms. The algorithm implemented employs the linear supply function theory for bid-based pool markets. AC power flow analysis is used to represent the electricity network, incorporating variable price-responsive active and reactive load demands. The significance of the reactive power modeling in the electricity market equilibrium is demonstrated using the IEEE 14-bus and IEEE 118-bus systems. It is shown that variations on the reactive power in the system result in different market outcomes, as incentives are given to the strategic generating firms to alter their bidding strategies. The convergence characteristics of the IEEE 118-bus system are graphically presented and discussed to demonstrate the superior computational performance of the proposed algorithm in producing results under strict binding constraints and heavy transmission congestion conditions.     

基于简化预测—校正内点法的拟直流最优潮流

在大规模电力系统最优潮流的在线计算应用中,传统直流最优潮流算法虽然有着很高的计算效率,但是由于其完全忽略了电压和无功功率的影响,计算结果精度偏低。文中通过引入无功功率来修正有功功率平衡方程,提出了基于拟直流模型的最优潮流算法。为进一步提高计算效率,提出了一种简化预测—校正内点算法,该算法通过对最优潮流模型中不等式约束进行简化处理,形成只含上限约束的广义不等式约束,大大简化了程序的编写。通过对IEEE 30,118,300节点系统以及Polish 2 736,3 120节点系统的仿真测试,验证了算法的可行性和有效性。     

Fast contingency selection through a pattern analysis approach

This paper presents a method for automatic contingency selection and static security evaluation of electrical power systems. The method employs multi-layer perceptron neural networks whose inputs are power flows and injections, while the outputs compute performance indexes associated with post-contingency scenarios. Contingency ranking and selection are performed based on the artificial neural networks responses. Classifications of system operating state with respect to static security are also provided. The performance of the method is evaluated for different operating conditions using the IEEE 24-bus test system.     

IMPROVED CONTINGENCY SELECTION ALGORITHM FOR VOLTAGE SECURITY ANALYSIS

ABSTRACT

A simple and efficient method for optimal selection of weights, along with higher order performance indices for voltage contingency selection, has been suggested in this paper. Some of the existing performance indices for voltage contingency selection has been critically reviewed. The proposed performance indices are able to eliminate misranking and masking effects. The post-outage quantities have been computed, using a new set of distribution factors, defined in terms of pre-outage real and reactive power flows in transmission lines/ outputs of generators. The proposed algorithm has been tested on IEEE 14-bus system and a practical 75-bus Indian system.     

Voltage magnitude contingency screening by constrained optimization method

Generation and transmission unit outages cause MW line overloading and bus voltage magnitude violation problems in the remaining part of the system. This paper presents a new method for bus voltage magnitude screening for transmission line and transformer outages. Classification and ranking errors of sensitivity-based methods are overcome by imposing a non-linear constrained optimization module on the well-known linear feed-forward computational algorithms. Genetic algorithms are preferred as computation tool because of its implementation simplicity as well as for its parallel processing advantage in future computers. Accuracy of the method is tested on IEEE 57-bus test system and IEEE 118-bus test system. The results are compared with those of the full load flow to verify the strength of the method proposed in this paper.     

Optimal Location of Thyristor-controlled Series Capacitor to Enhance Power Transfer Capability Using Firefly Algorithm

Abstract—The optimal power flow problem seeks to find an optimal profile of active and reactive power generations along with voltage magnitudes in such a manner as to minimize the total operating costs of a power system while satisfying network security constraints. This article presents a firefly algorithm to solve the optimal power flow problem incorporating a thyristor-controlled series capacitor. A thyristor-controlled series capacitor is considered to find the optimal location in transmission lines to enhance the power transfer capability of the transmission line. To assess the effectiveness of the proposed algorithm, it was tested on a 5-bus test system, an IEEE 14-bus system, and a modified IEEE 30-bus system, and it was compared with the genetic algorithm and differential evolution with and without a thyristor-controlled series capacitor. It has also been observed that the proposed algorithm can be applied to larger systems and does not suffer with computational difficulties. The results show that the firefly algorithm produces better results than others and has fast computing time for solving the optimal power flow problem with a thyristor-controlled series capacitor.     

基于矢量化运算模式的电力系统潮流计算

通过把电力系统潮流方程的求解转化为一个新的非线性规划模型的求解,解决了病态系统潮流计算发散的问题,为给定条件下的潮流计算是否有解提供了一个新的判断途径。利用牛顿法获得具有对称不定系数矩阵的修正方程后,采用AMD算法对系数矩阵进行排序,并采用LDLT算法进行求解,提高了修正方程的求解速度。整个潮流计算模型以矢量化形式表达,简化了程序复杂度,提高了代码的通用性和易维护性。对节点数从118到703共3个测试系统进行了仿真计算,结果验证了文中所提方法的正确性。     

基于电力系统支路切割的潮流并行协调算法

在研究基于支路切割的网络分块方法的基础上,提出了一种通过切割支路实现网络分块的新算法。该算法将切割支路的潮流以虚拟负荷的形式作为协调变量对子网络之间的耦合影响进行处理,并有效地将大规模电力系统的潮流计算问题转化为若干个子网络的潮流计算问题,是一种基于电力系统潮流调度概念的准并行算法,可以方便地在PC机群上实现。该算法在IEEE 14节点、IEEE 30节点和IEEE 118 节点网络上的验算结果表明:应用该算法获得的潮流计算结果正确,切割支路的选择对算法性能存在一定影响,划分网络的具体技术措施还有待深入研究。     

Differential search algorithm for solving multi-objective optimal power flow problem

In this paper, a simple and efficient nature inspired search method based on differential search algorithm (DSA) has been presented and used for optimal power flow (OPF) problem in power systems. By using the proposed DSA method, the power system parameters such as real power generations, bus voltages, load tap changer ratios and shunt capacitance values are optimized for the certain objective functions. Different types of single-objective and multi-objective functions on IEEE 9-bus, IEEE 30-bus and IEEE 57-bus power systems are used to test and verify the efficiency of the proposed DSA method. By comparing with several optimization methods, the results obtained by using the proposed DSA method are presented in detail. The results achieved in this work illustrate that the DSA method can successfully be used to solve the non-linear and non-convex problems related to power systems.     

Optimal Power Flow Using Differential Search Algorithm

—In this article, a new nature-inspired metaheuristic technique called the differential search algorithm is proposed to solve the optimal power flow problem. The proposed differential search algorithm has been developed and tested under normal and contingency power system conditions. To show the effectiveness of the proposed method, it has been demonstrated on the standard IEEE 30-bus and IEEE 118-bus test systems with different objectives that reflect performance indices of the power system. Obtained results using the proposed technique indicate that the proposed differential search algorithm provides an effective, a robust, and a high-quality solution for the optimal power flow problem. The comparisons of the proposed differential search algorithm results with those reported in the literature reveal the potential and superiority of the proposed algorithm in terms of the optimal solution quality and robustness.     

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。     

航海家优化算法在电力系统最优潮流计算中的应用

受15、16世纪地理大发现中航海家探险行为的启发,提出了一种新型元启发式智能算法——航海家优化算法(navigator optimization algorithm,NOA)来求解电力系统的最优潮流。新算法中定义了搜寻周期的概念,通过较好地平衡迭代过程中"搜索"和"利用"的程度,可以实现更好的寻优性能。将所提出算法用于IEEE 30和IEEE 118节点系统的最优潮流计算,并与现存的其他智能算法进行比较,验证了所提出算法的优越性。该算法对于实际电力系统的规划和运行具有一定的参考意义。     

Fuel restricted short term economic dispatch using evolutionary programming for utility system

The objective of the paper is to minimize the production cost of the thermal power generation. An elegant approach is presented in order to obtain the equivalent cost function of the participating non-fuel restricted units and the Economic Dispatch Calculations (EDC) are carried out along with fuel restricted units. The Evolutionary Programming (EP) technique is used for real power optimization with fuel restricted units. The optimal solution is obtained neglecting losses. The Fast Decoupled Load Flow (FDLF) analysis is conducted to find the losses by substituting the generation values. Then the loss is participated among all generating units using participation factor method. The load flow is conducted again and the voltage limit violation is checked. The Algorithm is tested on IEEE 6-bus system IEEE 30-bus system and a 66-bus utility system. The results obtained by this new approach are compared with those obtained using classical method. It is observed that the proposed method is more reliable and efficient.     

计及不确定性的预想事故自动选择区间方法

由于发电机出力和负荷需求具有不确定性,引入区间分析方法来处理电力系统静态安全分析中的不确定性问题.利用对区间线性方程组求解的区间直流潮流算法来计算发电机和支路开断后的潮流;提出一种新的改进的对区间进行大小比较的可信度量度函数.在此基础上,提出和实现了计及不确定性的电力系统预想事故自动选择的区间方法.采用5母线算例系统、IEEE 14母线算例系统和中国某省调电网实际系统对算法进行了验证,将文中算法与不计不确定性的传统分析方法以及概率方法相比较,证实了在静态安全分析中计及不确定性的必要性和文中方法的有效性及应用价值.