A short term hydrothermal scheduling approach for dominantly hydrosystems

A short-term hydrothermal scheduling approach is presented for predominantly hydroelectric systems. The model takes into account both the operating hydroelectric system and the electric transmission network constraints. The model consists of a simulation of the hydraulic system with the discharge decisions given by an optimal DC power flow algorithm. The release targets of the reservoirs, established by long-term operational planning, are enforced by a dual Lagrangean approach that fixes a penalty for the use of water in the reservoirs. Two illustrative examples have been solved in order to evaluate the efficiency of the approach     

Impact of hybrid wind and hydroelectric power generation on the operational performance of isolated power systems

In recent years, electric power systems are adopting new technologies in their structure in order to achieve better performance and efficiency in the electricity production, transmission and distribution. This fact together with additional financial incentives being developed in many countries have increased considerably the number of power generating units using renewable energy sources. However, a major drawback of these units is their dependency on unexpected weather conditions such as the wind speed and the rainfalls in the respective hydrologic areas. The purpose of this paper is to investigate the impact of wind parks and hydroelectric power plants on the reliability and operational performance of isolated power systems. A probabilistic methodology has been developed for simulating more efficiently and realistically the reliability and operational performance of these power systems. This is an effective computational methodology that is based on the Monte-Carlo sequential simulation approach and it evaluates the reliability and operational indices of the conventional thermal and hydroelectric power plants, the wind parks and the overall indices of the system. An appropriate model based on the power system of a Greek island is used and the obtained results are presented for a number of case studies representing various planning and operating schemes in order to deduce the optimal one.     

多类型分布式电源接入下的低压交流与直流配电网运行经济性对比

配电网运行经济性是配电网经济评估的重要组成部分,直接影响着用户用电效益。随着直流配电网的快速发展以及多类型分布式电源接入低压配电网,如何定量评估低压交流与直流配电网运行损耗,进而对比二者运行经济性,对于未来低压配电系统的规划和运行具有重要指导意义。根据含有多类型分布式电源接入的低压交流与直流配电系统典型拓扑结构,建立了基于系统全环节功率损耗的交直流运行经济性对比评估模型,并以运行经济性为优化目标建立考虑储能充放电状态的配网运行策略优化模型。最后基于深圳中美中心低压直流配网示范工程实际数据对系统典型运行日的功率损耗进行分类统计,对比了交流与直流配网运行经济性的差异以及储能接入的影响。结果表明,在多类型分布式电源接入下,系统功率损耗呈现明显的时空分布差异性,且长期运行下低压直流配电网运行经济性具有一定优势。     

考虑网损分摊的潮流跟踪方法

潮流跟踪算法是输电成本分摊的重要方法。传统算法在实际工程计算中要对线路净潮流进行近似,且把网损分摊和潮流跟踪独立开来。据此,提出考虑网损分摊的潮流跟踪方法。算例表明该算法的正确性和有效性。     

“十二五”期间云南季节性水电的消纳方案

"十二五"期间云南水电比重较大,负荷特性与水电特性不匹配使得云南电网丰水期存在大量的水电季节性电量,若不能充分利用将产生大量的弃水。测算了云南季节性电能规模,研究了云南季节性电能的可外送规模和消纳方案,提出了通过在西电东送协议基础上,丰水期云南增送广东季节性电力与电量,贵州相应减送广东同样规模电力与电量的方法,实现云南季节性电能在贵州的消纳。研究结果表明,云南2014年可以外送贵州3 GW季节性电能,外送弃水电量约4.8 TWh;2015年可以外送贵州2 GW季节性电能,外送弃水电量约4.4 TWh;由此能够产生约12.6亿元的经济效益。     

Selection of objectives in minimum loss power flow in hydrothermal electric power systems

Two formulations of the optimal minimum loss hydrothermal power flow problem in electric power systems are discussed. The formulations — one based on Kron's loss objective function and the other a network-based loss formulation — are treated in detail and the results of the two approaches are compared using two standard test systems. For the systems investigated, Kron's loss minimization schedules higher thermal generation than that required by the network loss minimization during lower demand. Kron's loss minimization involves lower active power transmission losses than those involved by the network-based loss minimization during low demand, and higher active power transmission losses than those required by the network-based loss minimization during higher demand. The total energy loss involved in the outcome of the Kron's loss minimization results is higher than that due to the network-based loss minimization schedule. There is a negligible difference in voltage magnitudes. Reactive power generation results favour the network-based loss approach. On the basis of the experiments, it is concluded that a network-based loss model is preferable in this application.     

Non-uniform composite representation hydroelectric systems forlong-term hydrothermal scheduling

This paper presents a nonuniform composite representation of hydroelectric power systems for use in long-term hydrothermal generation scheduling. This representation was developed from reservoir operational rules based on optimal reservoir trajectories obtained with a deterministic hydrothermal scheduling algorithm. A test system consisting of 7 large hydroelectric power plants of the Southeast Brazilian power system with 12572 MW of installed power capacity was selected for a case study. Operational cost comparisons with the classical uniform composite representation reveal significant savings     

基于电能成本效益分析的微电网水光协调优化运行方法

微电网为包括水力发电在内的可再生能源发电提供了可靠的并网与管理平台,其优化运行是一门重要课题。基于机会成本概念,以当前时段水力发电的最大化机会成本为目标建立优化模型,建立水力发电功率的成本效益模型作为优化运行模型的基础。接着以经济运行成本和环境折算成本建立模型目标函数,计及功率平衡约束,分布式发电运行约束,储能运行约束等必要约束条件建立微电网优化运行模型。最后基于萤火虫算法设计所建立模型的求解流程。最后通过设置离网模式和并网模式分别采用所建立的模型制定系统优化运行计划并进行指标对比,验证了所建立模型的有效性。     

Optimal reconfiguration of distribution systems with representation of uncertainties through interval analysis

The present work presents an approach for optimal reconfiguration of electrical distribution systems (EDS) to minimize energy losses considering uncertainties in the load demand and in the wind based distributed generation (DG). The optimization algorithm applied to solve the reconfiguration problem is based on the bio-inspired metaheuristic Artificial Immune Systems (AIS). An interval power flow model is used to obtain an interval energy loss from the representation of the uncertainties. The interval loss is used to guide the AIS algorithm through the search space. Network and operational constraints as the radiality and connectivity of the network as well as different load levels are considered. Well-known test systems are used to assess the impact of the uncertainties representation in the reconfiguration problem.     

基于失负荷期望的河北南部电网重要输电线路可用输电能力

研究和评估输电线路的可用输电能力,对于确定电网的合理运行方式和优化配置电网资源具有重要意义,为此,将失负荷期望概率应用于可用输电能力计算,以河北南网重要输电线路为研究对象,基于重要输电线路的典型潮流对河北南网进行地理分区,分析了典型运行方式下各分区的失负荷期望概率。最后确定了使河北南网各分区失负荷期望概率小于0.1 d/a的廉彭双回、清沧和辛沧两线的可用输电能力。研究结果可为确定线路输送功率和减小电网失负荷期望概率的措施提供参考。     

特高压风火打捆送电与江苏电网协调运行研究

研究了一种反映特高压风火打捆送电特性的建模方法。通过对直流送端出力特性现状和调度运行特性的调研,建立了风火打捆送电在电力系统运行模拟中的模型,再结合受端电网的负荷特性,提出了该模型在受端电网负荷高峰月和非高峰月的参数设定方法,解决了特高压风火打捆送电在电力系统生产模拟中的建模问题,具有降低受端电网能耗和运行成本的效果。算例表明,将该风火打捆模型应用到江苏电网场景中,可以提升江苏电网运行效率,同时合理控制风火打捆送电的弃风比例。     

柔性交流输电系统潮流计算中改进的遗传算法

阐述了一种在具有柔性交流输电装置的电力系统中求解最潮流问题的改进的遗传算法对两种柔性交流输电装置进行了研究,用于潮流控制的晶闸管控制相器和晶闸管控制的串顺在求解过程中结合最佳交流潮流,用遗传算法通过选择最佳调节状态使总发电成本最低,且使潮流保持在安全极限内,。用ＩＥＥＥ１４节点系统进行了测试,证实了其可行性和有效性。     

南方电网直流输电损耗分析及基于降损的交直流潮流优化探讨

直流输电损耗是直流输电的重要技术和经济指标,主要包括换流站损耗、直流线路损耗和接地极系统损耗。分析了南方电网直流输电损耗系数k,认为双极平衡方式下k值最小,输送功率对直流输电损耗有直接影响,并探讨了南方电网西电东送交直流输电通道功率优化分配方法,以降低输电总损耗。     

华东电网2007年电力供需基本情况和2008年电力供需形势分析

介绍了华东电网2007年电力供需基本情况,包括用电负荷、发电情况及区外来电;新增发电机组及变电、送电线路的建设;并网电厂运行情况及各类故障事件的统计。对2008年电力供需形势进行了预测,指出各省、市今年夏季可能的缺电情况,提出了具体的应对措施。     

含有电力弹簧的主动配电网优化运行

电力弹簧作为一种新型负荷侧调节设备,与具有宽电压范围的非关键负载串联形成智能负载,自动调节用电量与发电量匹配,以实现配电网运行优化。研究了含有电力弹簧的主动配电网最优潮流模型,提出了一种基于果蝇优化算法的智能负载优化方法,松弛法被用于推导最优潮流的二阶锥规划公式。结果表明,智能负载的主动调节可以优化配电网电压水平,降低有功网损,降低配电网的运行成本。所提多目标优化模型在一个改进的IEEE-33节点模型中求解,仿真结果验证了其正确性和有效性。     

低碳电力规划的调度模拟技术研究

对电力规划方案进行低碳化模拟计算是实现电力行业低碳发展的重要措施。基于电力系统运行模拟和评估的思想,利用机组检修信息、机组碳排放信息、负荷预测结果、区外功率交换数据和机组启停信息,建立了以日运行为基础的调度模拟模型,模拟低碳化电力规划下的全网运行,制定发电出力计划,最终实现全网最优低碳运行的目标。并以湖北电网为例进行了算例分析,验证了方法的有效性。     

A three-phase SSVS model for power flow studies in unbalanced transmission networks

The goal of this paper is to develop a steady-state mathematical model of the new generation of power electronic-based plant components presently emerging as a result of the concept of flexible AC transmission systems (FACTS), namely the series synchronous voltage source (SSVS) controller. The modelling is carried out in the phase co-ordinate frame of reference to study the SSVS power flow control performance in three-phase transmission networks. In this context, the controller power flow equations are integrated into an existing three-phase Newton–Raphson power flow program. Guidelines and methods for implementing the proposed model are described for highly robust and unified iterative solutions. The validity of this model is verified by a numerical example. The paper concludes with an example of power flow control in a network operating under unbalanced conditions.     

Affine Arithmetic-based DC Power Flow for Automatic Contingency Selection with Consideration of Load and Generation Uncertainties

Power systems operate under uncertainties from variations of loads and generation with time. Power flow in a power system becomes increasingly uncertain, especially when renewable energy, such as wind and photovoltaic generation, is integrated. In this article, a DC power flow approach based on affine arithmetic is proposed to quantify risks due to uncertainties. The proposed method has been applied to the automatic contingency selection under uncertainties. Numerical studies on IEEE test systems (30, 57, and 118 buses) have proved that the DC power flow approach based on affine arithmetic is a fast and reliable method for power system planning and operation when considering uncertainty. Test cases have shown that the proposed method is as fast as the conventional DC power flow while it is much more efficient than the Monte Carlo method. Thus, the DC power flow approach based on affine arithmetic serves as a new and effective decision support tool for planners and operators to cope with high levels of renewable energy penetration, electric vehicle load integration, and other uncertain scenarios.     

Quasi-Newton method for optimal load-flow solution under emergency mode of operation

Power systems in developing countries periodically experience a shortage of reserve capacity and imbalance between generation, transmission and distribution facilities. This results in the emergency operation of power systems. The solution of load flows under emergency operating conditions is used to decide on appropriate control action so as to prevent the spread of an emergency or to bring the system back to a normal state. This paper presents a method for optimal load-flow solution under the emergency mode of operation. The load flow is viewed as an optimization problem in which ‘inconvenience’ experienced by customers, owing to variation in supply voltage and load curtailment, is minimized subject to the network constraints and operational limits of the system. The problem is decomposed into two sub-problem is decomposed into two sub-problems exploiting the P-Q decoupling technique. An algorithm is given for the minimization of the sub-problems. The solution of the problem is based on recurring factorization of the Hessian matrices. For large systems the time required to compute the Hessian matrices is considerable. It is shown that the time can be reduced by approximating the Hessian matrices using a quasi-Newton method. Two versions of updating the Hessian matrix are given and their comparative advantages are discussed. The method is illustrated using the IEEE 14 bus and 30 bus test systems. Improvements in the method have been suggested and test results are presented.     

风电场对发输电系统可靠性影响的评估

建立了基于蒙特卡罗仿真的含风电场的发输电系统可靠性分析模型,该模型不仅考虑了风速的随机性、风电机组强迫停运率及其与气候的相关性,而且计及了输电网络故障率和输电线路有功功率限制.将该模型应用于含风电场的电力系统仿真,按照在满足系统安全约束条件的前提下充分利用风电的原则,对系统进行模拟调度,计算出能反映风电价值的可靠性指标,为风电场的规划与运行提供了重要的参考价值.