Optimal load shedding study of naval-ship power system using the Everett optimization technique

This paper reports an application of the Everett optimization technique for value-based load shedding in naval-ship power system with network constraints and application of reliability constraints. A new congestion analysis index—expected contingency margin (ECM), which considers the probability of disturbance, and reliability indices loss of load probability (LOLP) and expected unserved energy (EUE) are presented to filter the critical outage and congestion cases. The optimal load shedding scheme carried out using the Everett optimization technique uses a utility function, which addresses the cost of allocating pay-off while satisfying the network and reliability constraints and generation capacity limits. The algorithm search for the optimal λ to form a fair pricing mechanism, which produces maximum pay-off and minimum load shedding while, satisfying system constraints. The proposed approach is examined on naval-ship power system and detailed results are shown.     

A Framework to Implement Supply and Demand Side Contingency Management in Reliability Assessment of Restructured Power Systems

This paper presents a framework to implement supply and demand side contingency management in the reliability assessment of hybrid power markets. A model for the independent system operator (ISO) to coordinate reserve and load curtailment bids for contingency states is introduced to balance reliability worth and reliability cost. The load curtailments and generation re-dispatch for a contingency state are determined based on minimizing the market interruption cost using an optimization technique. A nonsequential Monte Carlo simulation technique based on this framework has been proposed to evaluate the customer reliability of restructured power systems with the hybrid market model. The modified IEEE Reliability Test System (RTS) is used to illustrate the proposed technique     

Reliability/cost evaluation of a wind power delivery system

When the geographical locations with good wind resources are not close to the main load centers, it becomes extremely important to assess adequate transmission facility to deliver wind power to the power grid. A probabilistic method is presented to evaluate the contribution of a wind power delivery system to the overall system reliability. The basic model incorporates transmission line connecting a remotely located large wind farm to a conventional grid system. The classical generation system adequacy evaluation model is extended to incorporate limited transmission system. The mean Capacity Outage Probability Table (mean-COPT) concept is used to increase the computational efficiency as it allows determination of EUE (expected unserved energy) and LOLE (loss of load expectation) simultaneously in calculation of reliability indices of the generating system. The wind farm generation model is obtained by superimposing simulated wind speed, obtained from developed ARMA time series model, on power curve of WTG. An apportioning method has been used to reduce the number of states in the resulting model, obtaining an equivalent reduced 5-state model. Applying transmission line constraints result in wind generation model ranging from 2- to 5-state models. The study recognizes benefits from fuel offset by wind power, reliability worth and environmental improvement and determines appropriate transmission line capacity based on its contribution to the overall system risk and associated transmission system cost. The paper illustrates results using a real wind farm. The presented methods and discussions should be useful to power system planners and policy makers.     

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.     

基于潮流估计和分块负荷削减的配电网可靠性评估算法

基于中压配电网闭环设计、开环运行的特点,以及元件电压降落、功率损耗及树状网络潮流分布的特点,推导出了节点电压、支路传输功率与支路阻抗的关系。在节点负荷矩基础上推导出了计算和修正节点负荷矩的等值阻抗和等值功率计算公式;提出了配电网故障解析中负荷转移后的电压估计模型、送端馈线潮流估计模型和受端馈线潮流估计模型,提高了可靠性评估中元件故障状态下潮流计算的效率。以分块链表简化配电网的结构并给出分块负荷削减的模型,实现了计及潮流约束的配电网可靠性评估。IEEE 33节点系统和工程算例仿真表明,文中提出的负荷削减模型与潮流估算模型相结合可快速、准确地实现中压配电网的可靠性计算,具有较高的工程实用价值。     

热电联产系统的随机生产模拟

随机生产模拟是电力市场中进行电价预测和发电管理的有力工具,但传统的随机生产模拟方法对于热电联产系统并不适用。文中对传统的随机生产模拟和目前的联产系统的生产模拟进行了改进,提出了一套针对热电联产进行随机生产模拟的新方法。对机组模型、热电联合等效概率密度函数进行简要介绍,给出了运行指标、系统可靠性指标的计算方法,以及处理机组最小技术出力即机组分段运行情况的方法和如何确定机组带负荷顺序的方法。最后通过一个算例对上述方法进行了验证。     

市场环境下电力系统安全可靠性措施的经济当量

在竞争的电力市场中，由于各发电公司、电网公司、供电公司分属不同的经济实体，从而导致在系统运行和规划设计中对系统安全可靠性因素的考虑与传统电力系统存在巨大的区别。该文针对市场环境下电力系统的安全可靠性问题，从电网运行、电网规划、辅助服务等几方面进行了探讨。文中指出：电力系统中的安全可靠性将融入经济性中，传统的安全可靠性指标将不再单独存在，而只是作为可能给相应公司带来经济利益的一种措施：安全可靠性措施的经济当量是指实施某一项安全性措施所能带来的经济利益与其实施成本之差，即安全性措施的实施效益；传统电力系统中的某一安全可靠性指标在市场环境下是否会得到执行、执行到何种程度将取决于其经济当量值，只有当其经济当量值大于零，该安全可靠性校验措施的执行才是可行的。在对各类安全性校验措施实施后所导致的后果分析的基础上，文中提出了电力系统运行和电力系统规划设计中安全可靠性措施经济当量的计算模型。经济当量的提出为市场环境下电力系统安全可靠性的经济化实现提供了新的思路。     

基于PC机群的发输电系统可靠性评估

为提高发输电系统可靠性评估的计算速度，提出了一种可靠性评估并行交流潮流法。该方法的核心是基于大规模电网分解协调原理的粗粒度空间并行快速解耦潮流模型和算法。其特点是：把系统划分为几个子网络；用LU分解法计算子网络和边界节点的交流潮流；根据进程间交换的潮流违限消息进行校正控制；最后计算可靠性指标。提出的方法在用个人计算机和1000M以太网构建的计算平台上实现了大电力系统充裕度评估交流潮流法的并行计算。通过对IEEE-118、IEEE-RTS96系统和一个实际电力系统进行的计算分析，验证了方法的正确性、可行性和有效性。     

Scenario selection in composite reliability assessment of deregulated power systems

Power market analysis should be incorporated in reliability assessments of deregulated power systems. For the Nordic power system, this is done by using The Multi-area Power-market Simulator (EMPS) for long-term power market analysis, where EMPS finds the optimal socio-economic dispatch on a weekly basis, with respect to, e.g., hydro reservoir levels. The EMPS analysis results in a set of load and generation scenarios, and these scenarios are interpreted as a sample of future power market behaviour, and is used as basis for a reliability assessment. These load and generation scenarios are referred to as power market scenarios.The power market analysis produces a large number of power market scenarios, and to include all these scenarios in a reliability assessment results in excessive computation time. The scenario selection method is presented and discussed. Scenario selection is used to pick out a subset of the generated power market scenarios, to only use this subset of scenarios as a basis for the reliability assessment. The paper provides some general guidelines for application of the scenario selection method. It is shown that the scenario selection method can reduce the scenario set by about 90%, with little loss of accuracy in the reliability assessment.     

基于网流规划的发输电组合系统可靠性评估模型研究

发输电组合系统的可靠性评估主要采用解析法和蒙特卡洛模拟法。这两个方法各有优点，但在可靠性评估过程中都要反复进行潮流计算，以判断是否违反运行约束，从而确定系统是否处于故障状态，并计算恢复策略实施过程中的负荷削减量，这将花费大量的计算时间。为改善发输电组合系统可靠性评估的计算效率，缩短评估时间，适应实时在线评估的需要，该文提出基于网流规划(NFP)的评估算法。计算结果表明，此算法是高效和合理的。     

Distribution network expansion planning and DG placement in the presence of uncertainties

Distribution network expansion planning (DNEP) is one of the most important tools to deal with the demand growth in a system. DNEP is usually carried out through reinforcement or installation of new components. In this paper, a new and combined methodology is used to consider several practical aspects in DNEP such as uncertainty, distributed generation (DG), load growth, electricity market and multi stage dynamic expansion are included in the planning. So that DNEP is addressed in the presence of distributed generation (DG), considering load and price uncertainties under electricity market environment. The proposed planning aims at minimizing investment and operational costs simultaneously. Since DNEP in coordination with DG planning leads to reduce planning cost; therefore, the coordinated DNEP and DG planning are presented in this paper. The proposed planning is implemented by the particle swarm optimization (PSO) technique. Besides, the uncertainties are modeled as the probability distribution function (PDF) and Monte-Carlo simulation (MCS) is used to insert the uncertainties into the programming. The proposed planning is carried out based on the 9-bus as well as Kianpars–Ahvaz test systems (Kianpars–Ahvaz is a practical network in Ahvaz province, Iran). The simulation results demonstrate the ability and effectiveness of the proposed planning to deal with uncertainties under electricity market environment.     

一种基于VB编程的配电网可靠性评估算法

提出了一种网络分层和递归算法相结合的复杂配电网可靠性评估算法.该算法首先通过对网络的分层处理,将其等效为树状目录结构,然后通过对此结构的递归遍历,计算网络中各等效节点的可靠性参数和配电网可靠性指标.该算法用VB语言编程,并采用了可视化界面,使评估方法更加便捷,评估效率更高.实例计算表明了该方法的有效性.     

面向综合负荷的并网光伏发电系统等效建模

基于MATLAB/Simulink和光伏电池自身的物理机理搭建了并网光伏发电的仿真系统,研究了其对配电网综合负荷特性的影响因素,分析比较了已有光伏发电系统等效模型的优劣。在此基础上构建了光伏发电系统传递函数等效模型,该模型具有结构简单、参数少、能有效描述光伏发电系统的出力极限等优点,同时易于在电力系统仿真软件中实现。采用所提出的等效模型与传统综合负荷模型并联,构建广义综合负荷模型,对含光伏发电系统的综合负荷进行建模,仿真实践表明此广义综合负荷模型具有良好的泛化能力,辨识参数稳定,能够满足工程仿真的需要。     

电力系统概率充分性和概率稳定性的综合评估

采用概率方法对组合电力系统的充分性和稳定性进行综合评估，涉及内容包括元件运行状态模拟，网络拓扑分析，潮流计算，暂态稳定计算，有功发电再调度，无功电压校正等的数学建模，多种紧急控制措施和发电再调度的模拟，文中给出了组合电力系统概率充分性和概率稳定性的综合评估算法流程和指标体系，并对IEEE测试系统的计算结果进行了分析，其结果证明了概率综合评估算法的必要性和可行性。     

计及高渗透率光伏的配电网广义负荷一体化等值建模

计及光伏等新能源电源的配电网广义负荷模型,通常是在传统综合负荷模型的基础上并联新能源电源的等值模型,其结构庞大,模型阶数较高,使得参数难以辨识。提出一种计及光伏的配电网广义负荷一体化等值建模方法,其简化了模型结构,且无需依赖光伏发电系统的出力数据。基于光伏发电系统动态特性的理论和仿真分析,提出光伏发电系统的多项式等值模型;建立光伏发电系统和配电网静态负荷的一体化模型,扩展参数取值范围,并采用改进遗传算法对模型参数进行辨识。基于DIgSILENT-MATLAB联合仿真平台的仿真结果表明,所提一体化等值模型能够较为准确地描述计及光伏发电系统的配电网广义负荷的动态特性。     

Evaluating the integration of wind power into distribution networks by using Monte Carlo simulation

This paper provides a probabilistic method to assess the impact of wind turbines (WTs) integration into distribution networks within a market environment. Combined Monte Carlo simulation (MCS) technique and market-based optimal power flow (OPF) are used to maximize the social welfare by integrating demand side management (DSM) scheme considering different combinations of wind generation and load demand over a year. MCS is used to model the uncertainties related to the stochastic variations of wind power generation and load demand. The market-based OPF is solved by using step-controlled primal dual interior point method considering network constraints. The method is conceived for distribution network operators (DNOs) in order to evaluate the effect of WTs integration into the network. The effectiveness of the proposed method is demonstrated with an 84-bus 11.4 kV radial distribution system.     

考虑光伏出力与负荷相关性的光伏电站容量可信度评估

光伏发电容量可信度是衡量光伏发电对电力系统可靠性贡献的重要标准。提出一种计及光伏出力与负荷相关性的光伏发电容量可信度的计算方法。首先,根据光伏发电昼夜特性,建立白天、黑夜分时段出力模型;其次,采用离散联合概率分布构造刻画光伏出力与电网负荷相关特性的联合多状态模型;最后,利用非序贯蒙特卡洛模拟方法计算得到系统可靠性指标和光伏发电容量可信度。基于等LOLE和等LOEE准则,计算了RBTS系统增加光伏电站后的光伏发电容量可信度,结果表明所提出方法的正确性和实用性。     

电力市场下可靠性电价与可靠性市场的研究

着重研究了系统的备用容量与发电可靠性和用电可靠性之间的关系以及不同发电可靠性条件下的发电可靠性电价和不同用电可靠性条件下的用电可靠性电价的确定。提出了满足个性化可靠性需求的交易模式,即由电网公司根据负荷的预计分布规律与备用市场价格确定在不同备用与供电可靠性条件下的备用电源计划安排,从而得到备用电源的费用及单位负荷功率的可靠性电价;电力用户根据自身的用电负荷特征及电网公司公布的可靠性电价申报供电可靠性要求;电网公司根据发电厂机组的可靠性水平确定系统需要增加的备用容量,进而确定发电厂的可靠性电价。     

基于供需双方竞标的辅助服务交易新机制

在竞争的电力市场中,各发电公司、电网公司和供电公司分属不同的经济实体,这导致在系统运行、规划和设计中对于系统安全可靠性因素的考虑与传统电力系统存在着巨大的区别。市场环境下的电力交易应由供需双方共同确定,基于这一原则,作者通过求取辅助服务所导致各节点供(用)电可靠性增加值及用户乐于为该可靠性增加值所支付的费用,在电网安全性供给方与电网安全性需求方(即辅助服务提供商与对电网安全性提出要求的用户)之间建立了一种等价关系,使得用户对电网使用的安全可靠性和提供辅助服务之间具有了可比性。以此为基础,在电力系统运行中提出了一种基于供需双方竞标的辅助服务交易新机制。最后,以IEEE32机24节点可靠性测试系统为例,检测了所提模型的合理性及算法的可行性。     

考虑源网荷储协调互动的配电网无功优化

无功电压控制是保障电网安全稳定运行的基础,高比例新能源发电是新型电力系统的主要特征,挖掘新能源发电、储能以及柔性负荷等柔性可控资源的无功电压潜力能有效保障新型电力系统安全稳定运行。文中提出了一种考虑源网荷储互动的配电网无功电压控制方法,从负荷需求侧响应出发基于市场实时电价信息以负荷转移成本和用户购电成本为基础实现价格驱动需求响应的负荷平移策略;利用储能系统协调新能源发电出力和负荷平移规则,构建综合考虑源网荷储互动的配电网无功优化模型。通过调节无功补偿设备、储能充放电策略协调新能源出力,在满足负荷需求侧响应需求的基础上达到系统无功电压的最优控制。通过改进的IEEE33节点系统仿真分析,实验结果表明通过源网荷储的充分互动能够有效提高系统无功电压调节能力,实现配电网安全、经济运行。