含暂态能量裕度约束多故障最优潮流计算

借助暂态能量裕度对发电机有功和无功出力的解析灵敏度，将暂态能量裕度约束直接加入最优潮流模型中，建立含暂态能量裕度约束多故障最优潮流逐次线性规划模型，采用单纯形法求解，取得了较好的效果。此外，还提出了根据大步长单故障最优潮流近似计算获得的暂态能量裕度进行故障扫描方法，并寻找到同一失稳模式下影响系统稳定的关键故障，验证了满足关键故障稳定性要求的最优潮流解可以同时满足同失稳模式下的其它故障的稳定约束。新英格兰10机39节点系统的最优潮流及暂态稳定计算验证了所提方法的有效性。所有优化结果均用一个在电力系统中广泛使用的暂态稳定仿真程序进行了验证。     

Two approaches to transient stability-constrained optimal power flow

Formulation of transient stability-constrained optimal power flow (TSC-OPF) and finding a practical solution for the problem have gained much attention recently. In this paper, two approaches to include transient stability constraints in the OPF problem considering detailed dynamic models for generators and their controls are introduced. The first method is based on the maximum relative rotor angle deviation (MRRAD) of generators which suits systems that have specific requirements on MRRAD. The second method represents the transient stability margin of the system based on generators output power (GOP) and hence does not rely on MRRADs. The transient stability boundary can be represented by a nonlinear function of GOP. The Artificial Neural Network (ANN) curve-fitting tool is used to derive a mathematical formulation for the transient stability boundary (TSB). The closed form representation of the TSB is then inserted in the OPF problem as a new constraint. The proposed method is examined using the WSCC 9-bus, the New England 39-bus and the IEEE 300-bus test systems. The results indicate that the proposed methods lead to lower computational time in solving TSC-OPF which has been a serious challenge for this problem.     

一种用于电-气互联系统运行优化的动态收缩凸松弛算法

提出了一种动态收缩凸松弛算法来解决电-气互联系统的运行优化问题.模型建立中,考虑了新能源与储能元件接入以及管存和气流方向等运行约束.所提算法利用了二阶锥松弛和凸包松弛的方法将非凸约束转换为凸约束,并通过动态收缩求解算法将电-气互联系统的运行优化问题转化为精确松弛域内的混合整数二阶规划问题加以求解.算例测试中,分别以修改...     

考虑暂态稳定约束的联络线最大传输功率计算

由于确定电力系统联络线最大功率时要考虑其故障时对系统暂态稳定的影响,故提出了一种基于能量函数灵敏度的考虑暂态稳定约束的联络线最大传输功率计算方法。该法首先确定网络在临界或失稳情况下的能量裕度及能量裕度对各发电机有功出力的灵敏度,再用等步长法和二分法按各发电机能量裕度灵敏度的大小调整有功出力,结合时域仿真法的判稳校验求出考虑暂态稳定约束的联络线极限传输功率。该法计算简单、快速,较好的解决了考虑暂态稳定约束后计算负担过重和直接法偏于保守的问题。2个算例仿真测试证实了该法的有效性。     

Solution of optimal reactive power dispatch of power systems using hybrid particle swarm optimization and imperialist competitive algorithms

Management of reactive power resources is essential for secure and stable operation of power systems in the standpoint of voltage stability. In power systems, the purpose of optimal reactive power dispatch (ORPD) problem is to identify optimal values of control variables to minimize the objective function considering the constraints. The most popular objective functions in ORPD problem are the total transmission line loss and total voltage deviation (TVD). This paper proposes a hybrid approach based on imperialist competitive algorithm (ICA) and particle swarm optimization (PSO) to find the solution of optimal reactive power dispatch (ORPD) of power systems. The proposed hybrid method is implemented on standard IEEE 57-bus and IEEE 118-bus test systems. The obtained results show that the proposed hybrid approach is more effective and has higher capability in finding better solutions in comparison to ICA and PSO methods.     

Optimal reactive power dispatch using ant colony optimization algorithm

This paper proposed a procedure to solve the optimal reactive power dispatch (ORPD) problem using ant colony optimization (ACO) algorithm. The objective of the ORPD problem is to minimize the transmission power losses under control and dependent variable constraints. Proposed sensitivity parameters of reactive power at generation and switchable sources are derived based on a modified model of fast decoupled power flow. The proposed ACO-based algorithm is applied to the IEEE standard 14-bus, 30-bus systems, and a real power system at West Delta Network as a part of the Unified Egyptian Network. The obtained simulation results are compared with those of conventional linear programming, genetic algorithm, and particle swarm optimization technique. Simulation results show the capability of the proposed ACO-based algorithm for solving the ORPD problem, especially with increasing the system size.     

Artificial bee colony algorithm for solving multi-objective optimal power flow problem

This paper presents a new and efficient method for solving optimal power flow (OPF) problem in electric power systems. In the proposed approach, artificial bee colony (ABC) algorithm is employed as the main optimizer for optimal adjustments of the power system control variables of the OPF problem. The control variables involve both continuous and discrete variables. Different objective functions such as convex and non-convex fuel costs, total active power loss, voltage profile improvement, voltage stability enhancement and total emission cost are chosen for this highly constrained nonlinear non-convex optimization problem. The validity and effectiveness of the proposed method is tested with the IEEE 9-bus system, IEEE 30-bus system and IEEE 57-bus system, and the test results are compared with the results found by other heuristic methods reported in the literature recently. The simulation results obtained show that the proposed ABC algorithm provides accurate solutions for any type of the objective functions.     

暂态稳定约束下期望收益最大的断面输电极限

基于机会约束规划理论,提出了暂态稳定约束下断面输电极限计算的随机模型。对给定的置信水平,模型中概率暂态稳定约束被转化为最小临界切除时间代数约束,结合泛函最优控制原理,上述随机模型被变换为线性不等式约束的数学规划模型。最后应用风险决策中的期望值准则,对不同置信水平下系统的收益损失进行综合评估,得到了系统在暂态稳定约束下期望收益最大的运行方案。39节点新英格兰系统上的仿真结果说明了所提方法的有效性和实用性。     

基于轨迹灵敏度的暂态稳定约束最优潮流计算

为将暂态稳定约束最优潮流问题转化为最优潮流和暂态稳定两个子问题,根据暂态稳定计算结果求出发电机转角及转速相对于机械输入功率的轨迹灵敏度。基于轨迹灵敏度,计算出在最领先发电机和最落后发电机之间转移的有功功率,据此修改其在最优潮流模型中的有功功率上下限,从而实现两个子问题的交替求解。并且推导出准确的轨迹灵敏度及初值计算公式,利用上述公式,得更小的转移功率值,从而使功率转移后系统的优化程度更高。同时在惯性中心坐标下采用最大转角判据找出最领先机和最落后机,并以3机9节点和10机39节点系统为例,验证了该方法的可行性。     

考虑暂态稳定约束的可用功率交换能力计算的研究

建立了计及暂态稳定约束的计算电力系统可用功率交换能力(ATC)的数学模型,采用转子角约束作为暂态稳定约束,利用梯形法将表示暂态稳定约束的微分方程离散化为差分方程,从而将这一问题转化为只含有代数约束方程的非线性规划问题,并利用高效的原一对偶内点法求解。7节点和36节点系统的计算结果表明了本所建立模型及所用方法的有效性。     

基于灵敏度分析和时域仿真的暂态稳定预防控制优化方法

根据临界切除时间灵敏度将暂态稳定约束条件线性化,简化了考虑暂态稳定约束的最优潮流(TSCOPF)问题的求解过程,为暂态稳定预防控制优化问题提供了一种新的解决方案。针对大系统临界切除时间灵敏度计算费时的实际问题,采用线路有功功率灵敏度筛选待调发电机的方法和并行计算技术以提高计算效率。WSCC 9节点系统标准算例和SGCC 9 177节点电网算例的仿真结果表明,所提方法具备良好的优化效果和工程实用性。     

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.     

Transient stability constrained optimal power flow using oppositional krill herd algorithm

Transient stability constrained optimal power flow (TSCOPF) is becoming an effective tool for many problems in power systems since it simultaneously considers economy and dynamic stability of system operations. It is increasingly important because modern power systems tend to operate closer to the stability boundaries due to the rapid increase of electricity demand and the deregulation in power sector. TSCOPF is, however, a nonlinear optimization problem with both algebraic and differential equations which is difficult to solve even for small power network. In order to solve the TSCOPF problem efficiently, a relatively new optimization technique, named as krill herd algorithm (KHA), is employed in this paper. KHA simulates the herding behavior of krill swarms in response to specific biological and environmental processes to solve multi-dimensional, linear and nonlinear problems with appreciable efficiency. To accelerate the convergence speed and to improve the simulation results, opposition based learning (OBL) is also incorporated in the basic KHA method. The simulation results, obtained by the basic KHA method and the proposed oppositional KHA (OKHA) algorithm, are compared to those obtained by using some other recently developed methods available in the literature. In this paper, case studies conducted on 10 generator New England 39-bus system and 17 generator 162-bus system indicate that the proposed OKHA approach is much more, computationally, efficient than the other reported popular state-of-the-art algorithms including the basic KHA and the proposed method is found to be a promising tool to solve the TSCOPF problem of power systems.     

基于交叠概率的暂态电压稳定评估特征选择

针对电力系统的高维特征量,提出了一种能有效降低维数的特征选择方法.该方法以最小概率落入类别间的不可判别区域为原则选取特征组合.算法核心在于特征组合过滤判据的确定,判据的形成基于样本点落入类别间交叠区域的概率,方法简易直观.针对系统的暂态电压稳定评估问题,首先构建了一组暂态电压稳定评估的原始特征属性集,将经特征选择降维后的特征组合作为决策树的输入,并用10倍交叉验证方法对评估结果进行验证.2个标准系统的算例表明,通过该方法对暂态电压稳定评估进行特征选择得到的特征属性组合在电压稳定评估的应用上具有更高的准确率     

暂态稳定约束下收益最佳TTC评估方法

传统的考虑暂态稳定约束的极限传输容量(TTC)研究采用确定性分析方法。由于忽略了不同故障发生的概率,确定性方法的计算结果难以充分发挥输电网络的经济效益。基于风险决策中的期望值准则,提出了暂态稳定约束下收益最佳的TTC评估方法。该方法考虑了不同故障暂态失稳的概率和代价,避免了运行人员依靠经验指定风险门槛值的问题,因此能够使得电力系统在运行的经济性和安全性之间达到最佳平衡。10机39节点新英格兰典型系统的仿真算例表明了方法的有效性和实用性。     

Optimal bidding strategies in oligopoly markets considering bilateral contracts and transmission constraints

In electricity industry with transmission constraints and limited number of producers, Generation Companies (GenCos) are facing an oligopoly market rather than a perfect competition one. Under oligopoly market environment, each GenCo may increase its own profit through a favorable bidding strategy. This paper investigates the problem of developing optimal bidding strategies of GenCos, considering bilateral contracts and transmission constraints. The problem is modeled with a bi-level optimization algorithm, where in the first level each GenCo maximizes its payoff and in the second level a system dispatch will be accomplished through an OPF problem in which transmission constraints are taken into account. It is assumed that each GenCo has information about initial bidding strategies of other competitors. Impacts of exercising market power due to transmission constraints as well as irrational biddings of the some generators are studied and the interactions of different bidding strategies on participants’ corresponding payoffs are presented. Furthermore, a risk management-based method to obtain GenCos’ optimal bilateral contracts is proposed and the impacts of these contracts on GenCos’ optimal biddings and obtained payoffs are investigated. At the end, IEEE 30-bus test system is used for the case study in order to demonstrate the simulation results and support the effectiveness of the proposed model.     

基于暂态稳定裕度指标的最优潮流求解

基于一种新型暂态稳定裕度指标,提出了求解含暂态稳定约束的最优潮流（SCOPF）新方法。该方法利用暂态稳定裕度指标及其灵敏度组成的不等式代替暂态稳定约束,将针对预想故障的优化潮流问题转化为常规非线性规划问题。所用的暂态稳定裕度指标基于故障后电力系统稳定域边界隐式方程,可由稳定域二次近似获得其近似估计。所提出的SCOPF求解方法易于实现,可处理多个预想故障,算法具有良好的收敛性和合理的计算时间。在新英格兰10机39节点系统中进行的仿真验证了该方法的有效性。     

基于最优潮流并计及静态电压稳定性约束的区域间可用输电能力计算

可用输电能力(ATC)是衡量电力系统在安全稳定运行的前提下区域间功率交换能力的指标。文中基于最优潮流(OPF)方法，建立起符合电力市场交易机制的ATC计算模型，其中考虑到输电线路故障对系统静态电压稳定性的影响，加入线路N-1故障时广义参数化形式的潮流方程及相应的不等式约束条件，使系统在故障时仍有负荷裕度，以保持电压稳定；以支路功率和系统负荷裕度之间的灵敏度指标进行预想故障选择，并用原对偶内点法计算得到输电线路N-1安全约束下的区域间可用输电能力。IEEE30和IEEE118节点系统算例表明该模型和算法的正确性与有效性。     

针对暂态电压稳定问题的自动电压控制系统与切负荷协调控制策略

建立了暂态电压稳定分析的微分代数方程组,并提出了应对暂态电压稳定问题的自动电压控制(automatic voltage control,AVC)体系下二级电压紧急控制与切负荷协调控制策略。该协调控制策略把低压切负荷作为与AVC体系下二级电压紧急控制并行的一种控制手段,在这种协调控制的过程中优先考虑采用二级电压紧急控制,当计算发现仅依靠二级电压紧急控制不能使系统保持暂态电压稳定的时候再采用切负荷控制。在PSAT仿真环境下建立了含AVC体系下二级电压紧急控制和切负荷控制的电力系统暂态电压稳定仿真模型,对广东电网748节点系统进行仿真,验证了所提出的控制策略和模型的正确性和有效性。     

Power system with multi-type FACTS devices states estimation based on predictor–corrector interior point algorithm

This paper addresses a state estimation problem of power systems incorporating various flexible alternating current transmission system (FACTS) devices. Static var compensators, thyristor controlled series compensators, and unified power flow controllers are considered since they represent various kinds of FACTS devices. By considering constraints of system buses and devices, the estimation problem can be formulated as a nonlinear optimization with constraints. An algorithm based on predictor–corrector interior point is applied to solve the problem. The IEEE 14- and 118-bus systems modified by incorporating FACTS devices are used as test systems to verify and demonstrate the effectiveness of the proposed algorithm. Numerical results indicate that the proposed algorithm performs better than the primal dual interior point based method even the presence of bad measurement data.