Determination of Transmission Reliability Margin Using Parametric Bootstrap Technique

The determination of available transfer capability (ATC) must accommodate a reasonable range of transmission reliability margin (TRM) so that the transmission network is secure from uncertainty of transfer capability that may occur during a power transfer. This paper presents a computationally accurate method in determining the TRM with large amount of transfer capability uncertainty using the parametric bootstrap technique. The parametric bootstrap technique is used to randomly generate a bootstrap sample of ATCs with large uncertainty selected at a certain percentage of bootstrap confidence interval. The bootstrap sample of ATCs in a day is used to determine the TRM at every time interval. The TRM value at a particular time interval is selected based on a certain percentage of normal cumulative distribution function (CDF). Then, a new value of ATC at the current time interval is calculated by considering the TRM at the same time interval. The effectiveness of the proposed TRM method in providing new ATC value is validated on the Malaysian power system. The results show that the proposed method provides accurate estimation of TRM in which it is relatively similar to the TRM result obtained by the standard deviation of uncertainty which is incorporated in the Monte Carlo simulation technique. Further comparisons in terms of accuracy and total computational time in estimating the TRM is made between the parametric and nonparametric bootstrap techniques.      

基于马尔可夫链和故障枚举法的可用输电能力计算

可用输电能力(ATC)是电力市场中指导电网输电交易的重要指标,也是电网调度部门调整阻塞的重要参考。电力系统是一个动态时变系统,存在大量的不确定性和随机性,考虑这些不确定性因素对ATC的影响是准确计算ATC的一个难点。马尔可夫链能根据系统的初始状态和可能状态之间的转移概率预测系统未来的发展趋势,该文引入马尔可夫链对电力系统状态进行预测,并采用故障枚举法对各时刻的可能状态进行枚举,通过概率方法求取ATC的期望值,并能得到ATC随时间变化的曲线。IEEE14节点系统的计算结果表明,所提出的模型及算法是正确有效的,能给出更准确的ATC信息。     

基于主从递阶决策模型的TRM评估

市场化环境下的电能交易可能引起系统潮流的频繁变化,系统运行不确定性增大,支路过负荷、节点电压越限等故障发生的可能性更大,因此对评估电网功率传输能力提出了更高要求,特别是如何有效评估输电可靠性裕度(TRM),对于电力市场的安全、可靠、经济运行具有重要意义.文中引入至少输电容量的概念,综合考虑了系统中的不确定因素,构建了基于主从递阶决策的TRM双层优化模型,并给出了求解该模型的一种简便、实用的方法.最后通过对IEEE118节点系统进行数据仿真,说明了该模型的合理性和有效性.     

Fast evaluation of available transfer capability using cubic-spline interpolation technique

This paper presents a new computationally fast and accurate method for evaluating available transfer capability (ATC) based on a curve fitting technique so-called as the cubic-spline interpolation technique. The advantage of the technique used in the computation of ATC is that it has the ability to reduce the time consuming ac power flow computations. The cubic-spline interpolation technique traces the curves of voltage magnitude and power flow variations with respect to the increase of real power transfer. ATC is then determined at the point where the voltage or power flow limits intersect the curves. Prior to the ATC evaluation, contingency ranking and selection techniques are used to define the critical lines in a system that can adversely affect the transfer capability assessment. The effectiveness of the proposed method is verified by illustrating the ATC evaluation on a practical test system. ATC results obtained from the proposed cubic-spline interpolation technique prove that the method is satisfactorily accurate and it is faster than the ATC method using the recursive ac power flow computations.     

Assessment of available transfer capability of transmission systems

The available transfer capability (ATC) of a transmission system is a measure of unutilized capability of the system at a given time and depends on a number of factors such as the system generation dispatch, system load level, load distribution in the network, power transfers between areas, network topology, and the limits imposed on the transmission network due to thermal, voltage and stability considerations. This paper describes a method for determining the ATC between any two locations in a transmission system (single-area or multiarea) under a given set of system operating conditions. The method also provides ATCs for selected transmission paths between the two locations in the system and identifies the most limiting facilities in determining the network's ATC. In addition, the method can be used to compute multiple ATCs between more than one pair of locations. The proposed method is illustrated using the IEEE reliability test system (RTS)     

Stochastic-Algebraic Calculation of Available Transfer Capability

Power systems are stochastic in nature due to uncertainty in bus loading and transmission system asset status. The available transfer capability (ATC) is a measure of "available capacity" in a power transmission system beyond already committed uses, i.e., beyond base case loading. To render the ATC as a more realistic measure of transmission availability, a stochastic calculation of ATC is proposed. A stochastic power flow algorithm can be used to help quantify and evaluate the uncertainty of the ATC. The limitations considered in the stochastic ATC calculation algorithm are: transmission thermal rating limits; bus voltage magnitude limits; and transmission circuit outages. The stochastic-algebraic calculation of ATC is described and tested using a reduced order WECC 179 bus system     

考虑新能源出力不确定性的可用输电能力在线评估方法

准确、高效地在线计算新能源送出断面的可用输电能力(ATC)对于在维持系统安全稳定运行的前提下提高新能源消纳能力具有重要意义提出一种考虑新能源出力不确定性的ATC在线评估方法,在各新能源电厂出力区间概率的基础上进行概率潮流计算,获得关键输电断面的功率区间及其概率;评估断面功率区间故障后新能源机组脱网和受端负荷损失情况,获得运行风险;以收益与运行风险差值最大化为目标获得断面的ATC值。某实际电网算例验证了所提方法的有效性.     

基于区间规划的可用传输容量计算方法

区域间可用传输容量是保障系统安全的指标之一.在电力市场环境下,发电机报价的不确定性将给电网可用传输容量计算带来很大偏差.文中基于区间数理论,引入了广义报价的新理念,详细分析了广义报价作用下的发电序位决策方法,构建了不确定性的电网可用传输容量计算新方法.该方法可方便地求解不同市场购电期望水平下不确定性的电网可用传输容量,...     

计及可用输电能力的含大规模风电的输电系统规划

大容量风力发电基地的快速发展给电力系统安全与经济运行带来了新的问题,对输电系统进行规划时,既要考虑具备足够的可用输电能力（available transfer capability, ATC）以容纳大规模风电并网, 又要避免输电容量过分冗余造成投资浪费。在此背景下, 针对含有大容量风力发电的电力系统, 提出了一种计及ATC的输电系统规划随机优化模型, 主要内容包括:（1）在考虑风速和负荷等随机变量之间相关性以及线路和发电机故障概率的基础上, 构造了ATC概率模型;（2）采用拉丁超立方采样和灵敏度分析相结合的方法求解ATC概率模型;（3）构建以输电线路投资成本最小和ATC期望值最大为目标的优化模型, 将输电系统规划的经济性和运行风险进行有机结合。采用遗传算法求解所建立的输电系统规划优化模型, 并用18节点和46节点算例系统说明所发展模型和方法的基本特征。     

计及源网荷交互影响的区域电网热稳安全供电区间计算方法

新能源和负荷的不确定性与输电通道的潮流转移存在交互影响,区域电网供电能力呈现出强不确定性的特点。提出一种计及源网荷交互影响的区域电网热稳安全供电区间计算模型及其求解方法。采用安全供电区间来描述区域电网供电能力的分布范围,考虑新能源和负荷的不确定性,建立区域电网热稳安全供电区间的线性化模型。在输电通道安全运行约束中考虑可中断负荷参与调控的影响,挖掘区域电网的供电能力。实际电网的算例结果表明,不同源荷分布下的供电能力分布在一个较宽的范围,可中断负荷的分布和容量均对供电能力影响较大,验证了所提模型的正确性。     

考虑新能源发电不确定性的可用输电能力风险效益评估

随着新能源发电的迅速发展,其功率输出的间歇性、随机性将对可用输电能力(ATC)产生显著影响。利用蒙特卡洛仿真法模拟新能源发电出力间歇性、随机性和负荷波动以及系统设备状态的不确定性,通过最优潮流求解特定系统状态和参数下的ATC;利用概率统计理论确定ATC样本值的概率密度,基于此建立ATC的风险效益模型,通过数值分析技术确定综合效益最大的ATC。从发电设备位置、功率输出不确定性、穿透率等方面研究新能源发电对ATC的影响。用包含风电、光伏电源的改进IEEE 118系统验证了方法的有效性。     

应用粒子群优化算法求解可用输电能力

在电力市场环境下,诸多问题(例如实时电价、网络阻塞等)都需要最优潮流作为理想的工具.本文以最优潮流为基础,应用一种简单有效、且收敛性很好的演化计算算法--粒子群优化算法(PSO)进行可用输电能力(ATC)问题的求解.根据约束条件的越限量大小,动态地调整罚函数,在保证全局搜索能力的基础上改进了收敛速度.应用此算法对IEEE-30节点系统进行了可用输电能力计算,并与传统的最优潮流算法进行了比较,结果表明该算法的有效性,具有实用意义.     

Chronological simulation for transmission reliability margin evaluation with time varying loads

This paper has as objective to assess the chronological variations in the Available Transfer Capability (ATC) caused by uncertainties associated with hourly load fluctuations and equipment availabilities. The system states resulting from these uncertainties are generated using the Monte Carlo Method with Sequential Simulation (MCMSS). The ATC for each generated state is evaluated through a linear optimal power flow based on the Interior-Point Method. These ATC values have been used to generate the probability distribution of the hourly ATC. This probability distribution enabled to estimate the Transmission Reliability Margin (TRM) for a specified risk level. The results, with a modified version of the IEEE Reliability test System, demonstrate that the time dependent uncertainties have a significant impact on the TRM.     

Consideration of multiple uncertainties for evaluation of available transfer capability using fuzzy continuation power flow

In today’s electric power industry, accurate and flexible information is needed to provide nondiscriminatory access to all market participants. This paper primarily purports to determine available transfer capability (ATC) based on the fuzzy set theory for continuation power flow (CPF), thereby capturing uncertainty. Assuming that uncertainties involved in the ATC calculation are estimated or measured, a fuzzy model is formulated in which major uncertainty parameters affecting the ATC are regarded as fuzzy variables subject to their possibility distributions. The purpose of this paper is to elaborate main features of the fuzzy continuation power flow (FCPF) algorithm that can handle uncertainties in load parameters and bus injections as well. As such, the robust solution will assist in providing additional information on the actual ability of the network to a system operator. In other respects, it poses a significant influence on the potential curtailment of power trades from which the reinforcement strategy can be set by the system operator. The viability of the proposed method would be verified through a stark contrast with the ones obtained from the conventional CPF and the fuzzy power flow (FPF) in the IEEE-24 RTS bus system and in the IEEE-118 bus system.     

基于直流灵敏度法的可用传输容量输电费用评估

在竞争性的电力市场环境下,输电网的可用传输容量(Available Transfer Capability,ATC)输电费用是一个亟待解决的问题。提出了ATC传输费用的概念,阐述了直流潮流灵敏度法的ATC的传输费用算法,该方法利用直流潮流灵敏度的变化来分析电力市场环境下可用传输容量的问题,并利用潮流跟踪法将可用传输容量输电费用公平分摊到各个交易的参与者,最后使用所提算法以及常规最优潮流法对WSCC-9节点输电系统某时段的电力交易进行了仿真计算。结果表明,此方法计算速度快、迭代次数少,能有效地跟踪电力市场的变化,能够满足电力市场实时交易的要求,具有一定的经济实用价值。     

Computation of TCSC reactance and suggesting criterion of its location for ATC improvement

Deregulation of power system has brought major changes in the system operation and control. When open access is made available to the market players, one or more lines in the transmission network could be overloaded, thereby causing congestion. Congestion management can be achieved by improving available transfer capability (ATC) of the network. FACTS devices such as TCSC and UPFC have proven their utility for ATC improvement. The active power flow control can be done more effectively by these devices. Their design and installation need the determination of changes in parameters for maintaining the desired power flow in the line causing congestion. This paper proposes a new approach for determination of changes in the reactance of TCSC, required for achieving the desired transfer capability. Sensitivity analysis is used for computing the changes in line flow of the lines with and without TCSC. Also a suitable criterion with a mathematical model for computation of reactance is proposed for selection of a line for the installation of TCSC. Through the results, it is shown that ATC is improved to a specified value by the installation of TCSC in the selected line which has the reactance as computed by the proposed method.     

考虑经济性收益最大的可用输电能力计算

电力系统区域间电网的可用输电能力(ATC)是所有电力市场参与者进行交易活动所必须了解的一项重要参数。文中将基于可靠性分析技术的枚举法和基于序列二次规划的最优潮流算法相结合,用于求解电力系统不同区域间的最大输电能力(TTC)及其概率分布。提出了一种考虑经济性收益最大的ATC统计计算模型,并利用二分法作统计优化搜索,提高了ATC统计计算的速度。计算机测试结果表明了该方法的有效性。     

快速计算电网可用输电能力的改进直流法

可用输电容量（ATC）指一定方向上,在满足系统各种约束的情况下区域间的最大传输能力。非线性方法可以算出比较准确的ATC,但计算速度难以达到在线计算的要求。直流灵敏度算法由于计算速度快,得到了广泛的在线应用,但对无功的忽略,有时又会产生比较大的误差。为了提高直流灵敏度算法的准确性,提出了改进直流法,方法在传统直流灵敏度算法的基础上考虑了无功和电压的影响,将直流算法和交流算法相结合,从而在保证计算速度的同时,显著减小误差。     

计及风光出力时变相关特性的输电可靠性裕度评估

风-光并网背景下,为准确评估风-光相关性出力及系统输电可靠性裕度(transmission reliability margin,TRM),提出了一种计及风-光出力时变相关特性的TRM评估方法。首先,计及风-光出力存在的时变相关特性和季节特性,提出了基于时变Copula函数的风-光24 h联合出力场景生成方法,所生成的场景为准确评估TRM提供基础。然后,在考虑TRM时间尺度特性的同时,引入GlueVaR度量系统存在的传输能力缺额风险,进而构建了区分决策者不同风险偏好的TRM期望净收益模型。最后,以风-光场景集为基础,利用序贯蒙特卡洛模拟方法生成系统时序运行场景集,结合IEEE-RTS系统利用优化算法求解模型。与以往方法相比,所提评估方法不仅提高了风-光出力场景生成的精度,而且保障了系统的可靠经济运行,实现了TRM的差异化评估。     

电力市场下电网的可传输容量

电网的可传输容量（ATC）是在电力市场前提下产生和发展的，它反映出输电网对电力市场还可提供的最大传输容量，并随着电力市场运营的深入，双边交易的剧增，而受到了广泛关注，介绍了ATC的概念；阐述了ATC的计算方法：连续潮流法、最优潮流法和灵敏度分析法，总结了各种方法的优缺点和适用范围；并通过分析目前ATC在美国的实际应用情况，对ATC的应用和研究工作提出了一些建议。