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.     

输电系统可用传输能力的研究

针对电力工业市场化改革的需求，综述了在电力市场环境下，输电网可用输电能力ATC（Available Transfer Capability)计算问题的研究现状及发展方向，介绍了ATC的定义，分析限影响ATC准确计算的各种不确定因素，针对ATC在线计算和离线计算的特点，提出了ATC计算的确定性模型和概率性模型，分析比较了目前ATC计算的几种算法的优,缺点，最后，展望了输电网可用输电能力计算中有价值的研究方向。     

Evaluation of available transfer capability using fuzzy multi-objective contingency-constrained optimal power flow

In trying to determine the available transfer capability (ATC), this paper primarily sets out to develop a fuzzy logic approach to parallelizing contingency-constrained optimal power flow (CCOPF). This algorithm may be used by utilities to optimize economy interchange for severe contingencies analyzed without disclosing details of their operating costs to competitors. In fact, the ultimate objective of fuzzy multi-objective CCOPF (FMCCOPF) is to carry out the minimization of both the base case (pre-contingency) operating cost and the post-contingency correction times as conflicting but fuzzy goals. Besides, the Benders decomposition is applied to partition the fuzzy formulation with contingency constraints, which allows for post-contingency corrective rescheduling, motivated by the improvement of computational efficiency using parallel processing. The feasibility of the proposed method is comprehensively realized by a comparison with the conventional optimal power flow (OPF) and the CCOPF with respect to the same array of transactions, base case, and generator/line outages for the IEEE-30 bus system and the IEEE-118 bus system.     

Probabilistic approach to available transfer capability calculation

This paper suggests a probabilistic approach to calculate available transfer capability in the interconnected network. Calculation of available transfer capability is complicated because it involves determination of total transfer capability, transmission reliability margin and capacity benefit margin.In the suggested available transfer capability quantification method, total transfer capability is determined by the continuation power flow process. Transmission reliability margin and capacity benefit margin are evaluated by probabilistic load flow and Monte Carlo simulation, respectively.Proposed method is applied to a modified IEEE 72-bus 3-area system to calculate available transfer capability on two different time spans. Results of the case study show that suggested probabilistic approach can offer operational flexibility for system operators to consider system and market uncertainties.     

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)     

Assessment of oscillatory stability constrained available transfer capability

This paper utilizes a bifurcation approach to compute oscillatory stability constrained available transfer capability (ATC) in an electricity market having bilateral as well as multilateral transactions. Oscillatory instability in non-linear systems can be related to Hopf bifurcation. At the Hopf bifurcation, one pair of the critical eigenvalues of the system Jacobian reaches imaginary axis. A new optimization formulation, including Hopf bifurcation conditions, has been developed in this paper to obtain the dynamic ATC. An oscillatory stability based contingency screening index, which takes into account the impact of transactions on severity of contingency, has been utilized to identify critical contingencies to be considered in determining ATC. The proposed method has been applied for dynamic ATC determination on a 39-bus New England system and a practical 75-bus Indian system considering composite static load as well as dynamic load models.     

用随机规划法计算可用传输容量

该文提出了一种新颖的方法,来计算互联系统中通过预定界面的ATC(Availab1e Transfer Capability)值.它把电力系统中的不确定因素:发电机开断、线路开断和负荷预测误差,处理为随机变量,用基于随机规划法的混合方法,二阶段求索随机规划法和机会约束规划法求解.经过算例检验,此方法是有效的.     

用随机规划法计算可用传输容量

该文提出了一种新颖的方法,来计算互联系统中通过预定界面的ATC(AvailableTransferCapability)值。它把电力系统中的不确定因素:发电机开断、线路开断和负荷预测误差,处理为随机变量,用基于随机规划法的混合方法,二阶段求索随机规划法和机会约束规划法求解。经过算例检验,此方法是有效的。     

计算电网可用输电能力的方法述评

在电力市场环境下,电网可用输电能力(ATC)是反映输电系统可用于传输电力的剩余容量的重要指标。文中根据国际公认的NERC关于ATC的定义,讨论了TRM和CBM两种裕度的含义及几种计算方法;详述了现有的多种ATC的计算方法,包括线性分布因子法、重复潮流法、连续潮流法、最优潮流法和灵敏度分析法,并分析比较了各种方法的优缺点。最后对我国电力市场环境下大型互联电网之间的ATC计算提出了一些建议。     

计算电网可用输电能力的方法述评

在电力市场环境下,电网可用输电能力(ATC)是反映输电系统可用于传输电力的剩余容量的重要指标.文中根据国际公认的NERC关于ATC的定义,讨论了TRM和CBM两种裕度的含义及几种计算方法;详述了现有的多种ATC的计算方法,包括线性分布因子法、重复潮流法、连续潮流法、最优潮流法和灵敏度分析法,并分析比较了各种方法的优缺点.最后对我国电力市场环境下大型互联电网之间的ATC计算提出了一些建议.     

暂态稳定约束的可用输电能力计算

提出了一种基于暂态约束的最大可用传输容量的发电计划调整方法,利用单机等面积定则原理(SGEAC)对预想事故快速扫描、找出严重故障,并计算出临界机组的功率转移量的估计值,进而提出发电计划调整策略.该方法既具有时域仿真方法的精确性与良好的适应性,又能获得单机稳定裕度.与其他能量函数相比,该方法不必进行失稳模式的判别,避免了穷尽式搜索,能够适应多重故障、多摆失稳场景和不同的失稳模式.同时,该算法对所有严重故障集同时处理,满足了实时预防控制的要求.通过对不同失步模式的实例分析验证了所提方法的有效性.     

考虑暂态稳定约束的可用输电能力的计算

基于传统的最优潮流模型及多机电力系统的经典数学模型,利用隐式梯形积分法,将电力系统中所有发电机转子摇摆方程差分化为等式约束、发电机转子相对摇摆角稳定极限作为不等式约束,将其作为暂态稳定条件加入最优潮流的等式约束和不等式约束方程中,提出了一种考虑暂态稳定约束的可用输电能力计算的计算方法,用原始-对偶内点法求解该模型,并通过引入一个非线性互补函数改进原对偶内点法中的互补松弛变量在每次迭代中都必须保持正向的缺点,使优化问题的求解效率得到提高。14节点系统计算为例说明了该方法的有效性。     

考虑暂态稳定约束的可用输电能力的计算

基于传统的最优潮流模型及多机电力系统的经典数学模型,利用隐式梯形积分法,将电力系统中所有发电机转子摇摆方程差分化为等式约束、发电机转子相对摇摆角稳定极限作为不等式约束,将其作为暂态稳定条件加入最优潮流的等式约束和不等式约束方程中,提出了一种考虑暂态稳定约束的可用输电能力计算的计算方法,用原始-对偶内点法求解该模型,并通过引入一个非线性互补函数改进原对偶内点法中的互补松弛变量在每次迭代中都必须保持正向的缺点,使优化问题的求解效率得到提高.14节点系统计算为例说明了该方法的有效性.     

静态条件下可用输电能力决策研究

在对可用输电能力范围(ATC) 问题研究现状分析的基础上,指出该问题不应只局限于刚性优化方面,还应进一步向柔性决策方向发展.在电力系统运行调度层面,从产义的角度探讨静态条件下 ATC 决策问题.从裕度与风险评估、调度方式与输电能力间关系以及不 ATC 决策3方面分析了该问题研究现状,指     

Application of dynamic rating to increase the available transfer capability

As the deregulated environment of power systems has spread worldwide, it is essential to operate power systems efficiently and economically. With the advance of communication technologies and sensors, so‐called dynamic rating is now to be realized. Dynamic rating is a method which determines accurate ratings by utilizing real‐time information such as conductor temperatures, ambient temperatures, and wind speeds. The dynamic rating is considered to increase the thermal capacities of overhead transmission lines and therefore take on importance in the deregulated electric power industry. The importance of the dynamic rating lies mainly in the area of Available Transfer Capability (ATC) improvement. In this paper, the validity of the proposed dynamic rating application is shown from the viewpoint of ATC, especially ATC with thermal constraints. In addition, the possibilities of ATC estimations using sensitivities are verified for the purpose of reducing calculation time, considering the importance of real‐time simulation of ATC. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 166(4): 40–47, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20537     

考虑复杂天气风险源的电力系统可用输电能力评估

引入越限惩罚型变权熵理论,建立能够综合考虑雷电、降雨、风、气温、相对湿度等多种天气因素的复杂天气风险源模型,利用该模型计算相应的综合气象因子;基于电气设备的健康指数模型,提出天气风险源修正架空线路故障率的方法;采用非序贯蒙特卡罗仿真,对考虑复杂天气风险源的电力系统可用输电能力进行评估。采集我国南方沿海地区实际气象数据,并在IEEE 118节点系统进行仿真,结果表明所提方法是有效的。     

Determination of available transfer capability using multi-objective contingency constrained optimal power flow with post-contingency corrective rescheduling

In a new competitive electricity market, accurate information should be shared to provide nondiscriminatory access to all participants. Key information to determine how much power can be shipped through the network is dubbed available transfer capability (ATC). This paper presents a methodology for the calculation of ATC, which is performed through a fuzzy logic approach to parallelizing contingency constrained optimal power flow (CCOPF). This algorithm may be used by utilities to optimize economy interchange for severe contingencies analyzed without disclosing details of their operating cost to competitors. In fact, the main objective of fuzzy multi-objective CCOPF is to determine the minimization of both the base-case (pre-contingency) operating cost and the post-contingency correction times as conflicting but fuzzy goals. Also, Benders decomposition is adopted to partition the fuzzy formulation with contingency constraints, which allows for post-contingency corrective rescheduling, motivated by the improvement of the computational efficiency using parallel processing. The IEEE-30 bus system is employed to test the proposed algorithm and the results are comprehensively demonstrated by a distinct comparison between the conventional optimal power flow and the CCOPF with respect to the same array of transactions, base-case, and generation/line outages.     

风电并网系统区域间概率可用输电能力计算

为了准确评估风电场接入电网对系统可用输电能力(Available Transfer Capability,ATC)的影响,针对风电并网系统的概率可用输电能力计算展开研究,详细分析不同风电并网情况下ATC的变化规律。首先基于风速Weibull分布,建立了大型风电场输出功率数学模型;进而采用原-对偶内点法完成风电并网系统可用输电能力单一样板值的求解。在此基础上,采用蒙特卡罗仿真法从广义角度对风电并网系统的ATC进行概率评估。仿真结果表明,所提算法能够有效评估风电这种波动性电源对ATC的影响。研究成果可为风电并网系统安全经济性能评估提供有效参考信息,对未来电网规划扩建具有指导意义。     

交直流系统可利用传输能力的评估

提出了一种基于内点法的适用于交直流系统求解可利用传输能力的新方法。由交直流网络间的耦合关系和换流器转换方程, 推导出直角坐标系交直流系统的Jacobi、Hessian 矩阵, 进而用原始-对偶内点法求解计及电压幅值和热稳定约束的交直流系统ATC。针对静态电压稳定约束下交直流系统直流控制方式会发生调整的情况, 提出分段求解交直流系统ATC的方法, 该方法能方便考虑直流变量约束及运行方式的调整。经算例验证该算法在交直流系统ATC计算中对初始值选择要求不高, 收敛迅速。     

交直流系统可利用传输能力的评估

提出了一种基于内点法的适用于交直流系统求解可利用传输能力的新方法.由交直流网络间的耦合关系和换流器转换方程,推导出直角坐标系交直流系统的Jacobi、Hessian矩阵,进而用原始-对偶内点法求解计及电压幅值和热稳定约束的交直流系统ATC.针对静态电压稳定约束下交直流系统直流控制方式会发生调整的情况,提出分段求解交直流系统ATC的方法,该方法能方便考虑直流变量约束及运行方式的调整.经算例验证该算法在交直流系统ATC计算中对初始值选择要求不高,收敛迅速.