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.     

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.     

基于连续潮流的配电网供电能力评估

随着非全相运行的分布式电源大量接入配电网,配电网固有的三相不平衡特征更加突出,传统配电网供电能力评估因忽略配电网三相不平衡特征导致结果不准确。为了准确分析三相不平衡特征对配电网最大供电能力评估的影响,建立了以配电网供电负荷参数最大为目标函数,考虑了支路热约束和节点电压等状态变量和分布式电源的有功和无功功率等控制变量的含分布式电源三相不平衡配电网供电能力评估模型。选择电压跌落情况最严重的相作为连续参数,确保预测-校正过程的的连续潮流法求解的结果更加精确。最后,采用拓展的IEEE33节点配电系统进行仿真验证,表明文中所提的模型和求解方法是有效的。     

基于连续潮流的输电网可用输电能力计算

提出一种基于连续潮流的线性迭代法计算输电网可用输电能力ATC(AvailableTransferCa鄄pability),详细推导了该算法的数学模型,并给出计算方法及流程,将算法应用到IEEE-30节点系统,结果表明该方法具有一定的实用性、可靠性和有效性。同时,将基于连续潮流法与直流灵敏度法的计算精度进行比较,结果表明该方法精度高;此外讨论了负荷参数λ取固定增长步长与变增长步长两种情况下的计算精度与计算速度,结果表明两者计算精度差不多,但后者计算速度快一些。     

基于线性化最优潮流的电网可用输电能力计算

可用输电能力(ATC)是评价互联电网运行安全稳定裕度的重要测度指标。针对交流最优潮流(OPF)模型计算ATC时在收敛性方面的不足,提出一种计及电压和网损的线性潮流方程,在此基础上构造用于ATC计算的OPF计算模型,并通过先估计网损、再求解优化问题的2步求解策略得到ATC的计算结果。IEEE 39节点系统的算例分析验证了所提方法的正确性和有效性。     

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。     

An evaluation method for power transfer capability enhanced by lightning countermeasures

Various countermeasures are taken against lightning faults in power transmission lines to decrease their occurrence and improve transmission reliability. However, how much they enhance the power transfer capability has not yet been quantitatively evaluated. The conventional deterministic approach, which is widely used in power system planning methodology, is inadequate to deal with this issue. This paper proposes a new method for numerically defining the power transfer capability enhanced by countermeasures against lightning. The proposed method is based on a probabilistic approach in which several fault patterns are taken into consideration with their occurrence frequency and maximum transferable power. This paper also gives an example application of the proposed method to a model trunk transmission system. The effect of a third overhead ground wire on the increase of transfer capability of a 500 kV transmission line has been quantitatively evaluated.     

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。     

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。     

地区电网备自投在线投退控制策略(二)考虑备用电源侧可用供电能力的备自投控制策略

由于投入备自投装置时,没有充分考虑备用电源侧元件热稳定极限的影响或其他相关母线的电压越限情况,导致连锁故障发生,会使故障进一步扩大.在考虑备用电源所在电网的网架结构、运行方式以及负荷水平的条件下,建立了备用电源侧可用输电能力实时在线评估数学模型,并应用重复潮流法,对该模型进行了求解,将所得结果作为备自投装置动作与否的决...     

含有风电发电机组可用输电能力新算法的研究

阐述了含有风电发电机组的潮流计算模型,提出将改进蚁群算法、变邻域搜索算法和差分进化算法相结合应用到可用输电能力研究中,该算法克服了陷入局部最优解的缺点,并提高了寻优的效率、全局的寻优能力和结果 的稳定性.以IEEE30节点标准系统作为算例对输电网可用输电能力进行仿真计算,计算结果表明本文提出的算法具有合理性和可靠性.     

基于连续潮流法的交直流系统可利用传输能力的计算

提出并建立了交直流系统可利用传输能力(ATC)模型.该模型采用两端直流混合系统,考虑电压稳定性、节点电压水平、热稳定、N-1故障等安全约束条件.应用连续潮流法求解过程中,将交流和直流系统方程分解计算,通过直流网络状态量与换流器交流母线电压和给定直流控制量之间关系方程组来简捷地计及交直流系统间耦合关系.对IEEE30节点系统进行的仿真计算证明了所提出模型和算法的有效性.     

Determination of transfer capability region using boundary tracing method

In electricity markets, transfer capability is a parameter showing the potential of a considered source–sink pair to transfer power. This paper enhances transfer capability monitoring by proposing a method to determine this parameter with respect to a region referred to as the ‘transfer capability region’ (TCR). The boundary of a TCR is traced by using the modified predictor–corrector process on a plane of real and reactive powers. The TCR shows a set of feasible loading points at the sink area. Moreover, the shape of TCR always changes according to the system parameters. This paper also defines the outermost boundary of the TCR when the considered parameters are set to be free. We apply the proposed method to test systems, and then compare to the maximum loading points obtained by the conventional transfer capability calculation. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

考虑电压和热稳定约束的可利用传输能力的快速算法

在现代电力市场环境,可利用传输能力(ATC)需要尽快提供给使用方。而在计算中要考虑的所有N-1故障因素导致了ATC计算任务非常繁重。基于此,提出了一种应用故障过滤与排序技术的ATC快速计算方法。首先,采用迭代线性潮流法(ILPF)对电网的N-1故障进行排序以筛选出热稳定极限和电压幅值约束条件下最严重的故障情况;然后,应用原始-对偶内点法对最严重故障情况进行ATC的计算,解决了ATC计算的耗时问题。算法的有效性通过IEEE30母线系统的仿真得到了验证。     

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。     

Decomposition-coordination strategy to improve power transfer capability of interconnected systems

The maximum power transfer across critical corridors or interfaces is limited by various system constraints such as thermal, voltage, and stability limits. In an open transmission access environment, these constraints would be deeply influenced by the interactions among the path flows in different control areas. In particular, small signal stability, commonly in the form of low frequency oscillations, is considered a crucial factor since it limits the power transfer capability of transmission paths in interconnected multi-area systems. Based on such considerations, the focal point of this paper will be a new approach to coordinating the path transfers across multiple control areas, giving exclusive attention to the small signal stability. The differential eigenvalue method is used to derive the damping ratio constraints for satisfying the small signal stability criteria which are linear inequality constraints expressed in terms of the control parameter. Using Bender’s decomposition, the proposed methodology is formulated as a master problem and a set of sub-problems, each associated with one area motivated by the improvement of the overall computational efficiency via parallel processing. The performance of the decomposition-coordination method is illustrated with a 68-bus system from which it might be deduced that inter-area transfer margin could be improved by reasonable rescheduling of the neighboring tie-line flows.     

Continuation power flow considering area net interchange constraint

Interconnected power systems not only allow to the areas to provide mutual assistance, but also import or export energy with respect to optimize energy resources assessment where, a cost reduction involved in the generation of power required to meet its demand. To determine the required control actions, in the planning and operation stages, it is important to verify the loading margins for both the normal operation and the different conditions of contingencies that may eventually occur. In this paper a continuation power flow that allows obtaining the loading margin and maximum active power transfer considering the area interchange control is proposed. From the results of the IEEE systems (9 and 118 buses), a difference of up to twelve percent in the active power transfer capacity is verified compared to the cases without area interchange control. The method also highlights the effects of the loop flow which occur as a consequence of the existence of parallel paths in the interconnected network.     

基于功率传输转移分布因子的简化电网潮流计算方法

为了减少大型电力系统的潮流计算时间,研究简化电网的潮流计算方法具有重要意义。现有方法将传统Ward等值技术用于电网简化后,简化电网却产生与原始电网不同的潮流结果。针对这种情况,提出了一种改进的简化电网的直流潮流计算方法。在已有研究的基础上,给出了基于功率转移分布因子的直流潮流算法以及使用Ward技术对电网的简化方法。结合上述两部分,给出了基于功率转移分布因子的简化电网潮流计算方法。通过仿真算例表明,所得的结果具有较高的精度,可用于简化大型电网的潮流计算、潮流预报等应用中。     

电力企业危机管理能力的模糊评价

通过对危机管理能力的研究,建立电力企业危机管理能力的评价指标体系,包括信息标准、决策标准、管理标准三类.构造电力企业危机管理能力的三级结构.采用模糊评价法将电力企业的危机管理能力分为5个等级,通过模拟数据对电力企业危机管理能力进行评价,可以得到该企业的危机管理能力.     

基于转移潮流反应灵敏度的新型距离保护算法

非故障过流引起的距离3段保护连锁跳闸是导致大停电事故的主要原因,判断与故障线路相连接的线路上产生过流的原因进而闭锁由非自身故障造成的保护动作,是避免此类大停电事故的关键。提出了一种基于转移潮流反应灵敏度的新型距离保护算法。通过比较故障时线路上的实测潮流和由故障前线路潮流及转移潮流反应灵敏度计算而来的故障潮流的近似程度,而区分转移潮流过流和真实故障过流,进而阻止由于非故障过流造成的距离3段保护误动作。在Matlab/Simulink软件环境下,对互连6母线系统在不同工况下进行了实例仿真计算,结果表明该方法具有较高的准确性和实用性。