Polynomial loss models for economic dispatch and error estimation

Polynomial loss models are introduced for the economic dispatch problem. The models are based on interpolations of load flow solutions. An approximate error estimation method for the loss models is also presented. The effect of approximate loss models on the economic dispatch is evaluated according to the deterioration of total generation cost in addition to the relative values of the coefficients of the loss formula. Case study shows that loss expressions have characteristics which have not been considered previously. Comparisons between the proposed models and the generalized generation distribution factor (GGDF) based models show the advantages of the proposed models     

江苏电网节能发电调度分析与对策

节能发电调度通过对机组发电负荷的优化分配,使得平均煤耗降低,实现节能减排的目标。详细分析了机组启停、机组调节能力、时段耦合、网损、替代发电、电厂安全生产对节能发电调度的影响,并提出了对应的改进策略。江苏电网节能发电调度的实际结果表明:与三公调度模式相比,节能发电调度能够有效降低平均煤耗,在"节能、减排、降耗"等方面存在巨大潜力。同时,还详细分析了节能发电调度带来的江苏电网潮流分布问题,通过与浙江电网"有序调停"的对比,突出了江苏电网节能发电的特色。     

分布式光伏并网下基于调温启停混合控制方式的空调负荷双层优化调度策略

为解决分布式光伏剩余功率注入配电网导致的电压抬升和线路过载问题,利用配电网中空调负荷良好的热储能特性,提出了一种基于调温启停混合控制方式的空调负荷双层优化调度策略,建立了包含电力公司、负荷聚合商（load aggregators,LA）和用户的双层优化调度架构。首先电力公司以网损损失成本和需求响应成本之和最小为目标向负荷聚合商下达调度指令,其次,负荷聚合商以利润最大为目标,选择不同用户的控制方式。相比于传统控制方法,此调度策略改善了聚合空调功率在响应跃迁处的响应效果,更快地达到了调度指令的要求,同时聚合功率保持稳定,促进了分布式光伏的消纳,使节点电压和线路传输功率保持在安全运行范围内。最后,采用基于改进的IEEE33节点进行分析,仿真结果验证了所提调度策略的可行性和有效性。     

考虑电能交互的冷热电多微网系统日前优化经济调度

多个冷热电联供型微网接入同一区域配电网,形成以配电网为核心的冷热电联供型多微网系统。当冷热电联供型多微网间通过联络线进行电能交互时,给传统的多微网系统优化调度问题带来了挑战。在分析典型冷热电联供型微网供能结构的基础上,研究供用储设备间的冷热电能流动关系和设备的数学模型,建立考虑微网间电能交互的冷热电联供型多微网系统优化经济调度模型。通过天津中新生态城算例,分析各个冷热电联供型微网中设备出力和冷热电负荷平衡情况,与多微网间不存在电能交互时的优化调度进行经济成本、CO₂排放量和各微网与电网交易电功率值的比较,与传统冷热电联供系统“以热定电”和“以电定热”运行方式下多微网系统的总运行成本进行对比,验证所提模型的经济性、环保性和有效性,并对微网间交易电价的制定做进一步研究。     

基于自适应粒子群算法的负荷最优分配

在传统经济负荷分配模型的基础上,结合节能调度的宗旨,建立了综合考虑系统有功网损最小和机组发电耗煤量最小的多目标负荷分配模型,该模型能对系统进行整体节能优化.引入了自适应权重和因子的概念,采用了一种用于多目标负荷最优分配的自适应粒子群算法,并对IEEE 57节点系统进行了仿真计算.结果表明,该方法能降低系统网损和减少机组煤耗,从而有效地节约能源,同时满足系统的安全约束.     

A modified power flow analysis to remove a slack bus with a sense of economic load dispatch

This paper attempts to a basic concept for a modified power flow analysis with a sense of the economic load dispatch to remove the concentrated burden of the slack bus. The power flow calculation in the proposed method is incorporated into the economic load dispatch (ELD). Furthermore, the proposed method eliminates not only the burden of a slack bus, but also maintains ‘an equal incremental cost’ in the economic load dispatch sense in this paper. Both the IEEE 14-bus and IEEE 39-bus systems are used to verify the usefulness of the proposed technique.     

Application of linear programming redispatch technique to dynamicgeneration allocation

Consideration is given to dispatch problems that involve the allocation of system generation optimally among generating units while tracking a load curve and observing the power rate limits of the units, system spinning reserve requirements, and other security constraints. Two methods are used in the solution of the problem. The first method is a quadratic programming technique combined with a linear programming redispatch technique. The latter utilizes a linear programming formulation of the dynamic dispatch problem about the base case static economic dispatch solution. The second method is based on the Dantzig-Wolfe decomposition technique. Tests and computer results of four systems of different combinations of units and intervals are given to show the advantages of the techniques proposed     

一种安全约束经济调度的广义网络流规划算法

本文分析了一般网络流规划算法在潮流分布、网络损失与安全约束等方面所存在的问题,提出了一种安全约束经济负荷分配的广义网络流规划模型与算法。并讨论了广义网络流规划的模型与非线性解法。对例题进行计算,验证了本文方法的有效性。     

Risk assessment and bi‐level optimization dispatch of virtual power plants considering renewable energy uncertainty

Aiming at the effective management of distributed energy resources (DERs ), we propose a bi‐level optimization dispatch model which consists of a virtual power plant (VPP ) and an independent system operator (ISO ) in order to achieve a coordinated dispatch between the upper level objective function of minimizing system's operation cost and the lower level objective function of maximizing the VPP 's net profit. However, the VPP 's dispatch strategy is variable due to the threat from unavoidable uncertainties including unit outage, load forecast deviation, and renewable energy forecasting error. In order to evaluate the influences of these risks on VPP 's dispatch strategy, a proper definition of expected energy not supplied (EENS ) and its relationship with VPP 's reserve capacity are provided. Also, chance‐constrained programming (CCP ) is adopted during the analysis. By including VPP 's risk cost into the dispatch model, VPP 's dispatch strategy is able to keep a balance between the potential risk and economic profit. In addition, a further discussion regarding the risk cost is conducted in view of renewable energy capacity proportion and the VPP capacity proportion. Based on the analysis results of the case study provided, the proposed model serves as a foundation for VPP 's economic and risk‐balanced dispatch.     

基于异质能源多时间尺度互补的动态经济调度策略

大规模新能源并网给电力系统的经济调度带来了巨大的挑战,构建互补系统联合运行可有效地提升电网对新能源的消纳能力,但是目前单一的互补系统日前调度模型没有考虑互补系统实际的互补及平抑效果。为此,提出了一种基于风光水火多时间尺度互补的动态调度策略。利用异质能源之间的互补特性将风、光、水打捆成虚拟电源(VP),并定义负荷跟踪指标表征VP对负荷的跟踪能力,使VP出力能很好地追踪负荷曲线。建立含日前24 h计划、日内4 h滚动计划以及实时15 min计划在内的多时间尺度互补协同调度模型,设置滚动修正的弃风弃光约束,使前一尺度调度计划中弃风、弃光量更大的时段在下一尺度调度计划中具有更大的弃风、弃光上调裕度,利用不断更新的预测数据,滚动修正日前调度计划,从而始终保证VP对负荷的良好追踪,实现互补效果的最大化。通过算例验证了所提调度策略能够有效地提升互补系统实际的互补和平抑效果、减轻调度压力并且降低发电费用。     

计及用户电池损耗的电动汽车分布式两阶段调度策略

规模化电动汽车(Electric Vehicle,EV)的无序充电行为给电网造成了压力,因此研究EV有序调度策略对保证电网的安全运行具有重要意义.为此,文中提出一种计及用户电池损耗的分布式两阶段调度策略.在调度前定性分析调度意愿和调度能力以筛选可调度车辆,并在第一阶段提出了平均充电率指标,结合最小充电成本完善用户侧优化...     

基于相变储能系统主动响应能力挖掘的配电网经济调度

为了解决配电网面临的供电电压不合格和潮流分布欠优等问题,提出基于相变储能系统(PCMTESS)需求响应的配电网经济调度策略。介绍PCMTESS的构造和工作机理,分析热力侧的能耗规律,建立计及热耗散的热力侧和计及无功调节能力的电力侧封装模型。在此基础上,考虑潮流分布约束和分布式新能源出力特性,以配电网的购电成本最小化为目标,在综合考虑光伏、风机、负荷不确定性的条件下,建立统一的配电网调度模型。提出主、子问题交互迭代的求解策略,实现优化模型的高效求解。基于IEEE 41节点配电网的仿真结果表明,所提PCMTESS在维持室温舒适的前提下,能够优化配电网的潮流分布和改善电网的电能质量;所提调度模型为配电网的安全经济调度和综合能源消纳问题的解决提供了一个崭新的视角。     

A novel approach to computationally efficient algorithms for transmission loss and line flow formulations

This paper presents a novel approach to powerful, effective and computationally efficient algorithms for formulation and evaluation of transmission loss and line flow through efficient loss coefficients and distribution factors, respectively which are uniquely suitable for real term application. These loss coefficients and distribution factors are generated extremely elegantly and efficiently from the hidden treasures of an available load flow solution with trivial computational burden. Results on few IEEE Test systems are extremely exciting which reveal that the loss coefficients evaluated at the normal operating conditions are quite robust and for all practical purposes need not be re-evaluated for wide changes in system operating conditions for evaluation of transmission loss or economic load dispatch solution.     

A framework for uncertainty quantification and economic dispatch model with wind–solar energy

More and more renewable energy generations are being connected to power system, such as wind power, solar power, together with the load forecasting deviation, so there is a growing need to study impacts of multiple different uncertainties on system. It is important that operators understand how these stochastic characteristics of uncertainties affect the stable operation of power system. In this paper, the combinations of uncertainties that are power fluctuation due to forecasting deviation of wind speed, solar radiation and load. Framework is established including joint probabilistic models of several uncertainties and the risk models of load shed under two different scenarios. An economic dispatch model considering unit commitment is proposed to minimize the generation cost and operational cost and starting-up cost of conventional power units, combined heat and power (CHP) units and heat-only units. However, high/low risk of load shed does not represent large/small of load loss in fact, thus the load loss is defined as multiplying of load shed risk and load loss amount, which is described by methodology of α-superquantile. Effectiveness of proposed model is examined by case studies and the numerical results are presented.     

Analytical solution for combined economic and emissions dispatch

Due to the environmental concerns that evolve from the emissions produced by fossil-fuelled power plants, the economic dispatch that minimises only the total fuel cost can no longer be considered single-handed. This paper proposes an analytical strategy based on mathematical modelling to solve economic, emission, and combined economic and emission dispatch problems by a single equivalent objective function. The proposed strategy has been applied to dissimilar realistic systems at different load conditions and the outcome of one such realistic system is presented here.     

电能量市场下负荷聚合商参与负荷削减投标策略

针对负荷聚合商(LA)在电能量市场下参与负荷削减投标(LCB)时面临负荷与价格的不确定性问题,文中提出一种可使LA代理成本最小的LCB参与策略。首先,将LA的购电申报、LCB申报与可调节负荷的控制问题统一描述为混合整数线性规划问题。其次,利用双层规划模型处理负荷功率的不确定性,利用历史场景法结合场景缩减处理市场价格的不确定性。最后,基于宾夕法尼亚州-新泽西州-马里兰州(PJM)电力市场数据,针对所提策略及其在测试场景集中的表现进行分析。测试结果表明,所提策略及场景缩减方法能够降低聚合商4%以上的代理成本与10%以上的风险损失,可提高最多17.8%的履约率,为LA在不确定问题下的投标提供技术支撑。     

互联电网安全约束经济调度场景构建方法

安全约束经济调度在省级电网调度控制中应用较为成熟。为实现大范围内资源优化配置,有必要研究互联电网安全约束经济调度技术。针对在实际生产运行中遇到的困难,提炼了优化目标设计、系统平衡、联络线调整、基础数据整合五个关键问题,并对每个问题给出多种解决策略。建立了基于策略组合的互联电网安全约束经济调度场景构建方法,分析了不同场景的适应性及对应模型特点。最后通过实际电网算例验证了策略组合的合理性和准确性。以实际需求为导向,构建不同的应用场景和经济调度模型,能提升互联电网安全约束经济调度技术的实用性和适应性。     

计及源荷不确定性及需求响应的离网型微电网两阶段日前经济调度

离网型微电网在远洋海岛、偏远地区等有举足轻重的作用,但源荷不确定性对其稳定运行具有一定负面影响。为减轻日内调度压力,提出了一种适用于离网型微电网的两阶段日前调度模型。利用混沌相空间重构、多目标粒子群、数据驱动及线性规划等方法,通过灵活资源调控降低源荷不确定性所带来的弃风和失负荷等负面影响,可在降低调度成本的基础上,兼顾系统高效性及可靠性。第一阶段以微电网综合运行成本最低,可再生能源就地利用率最高及系统失负荷率最小为目标,建立了计及需求响应的离网型微电网多目标经济调度模型。第二阶段针对第一阶段调度后产生的弃风与失负荷,采用极限学习机(Extreme Learning Machine, ELM)及XGBoost构建了蓄电池消纳弃风模型和调频电源调度模型。最后通过仿真算例的对比表明,需求响应对于系统高效性的增强是以增加调度成本和降低负荷可靠性为代价的,相比之下,所提两阶段日前调度方法可在降低调度成本的基础上,同时兼顾系统高效性及可靠性,为偏远地区和海岛等地区的离网型微电网运行提供参考。     

Interchange costing and wheeling loss evaluation by means ofincrementals [electricity]

The authors consider the incremental pricing concepts and incremental loss concepts for use in real-time operations involving interchange evaluation and wheeling loss evaluation. They provide an overview of methods to evaluate the cost of electrical energy for purchases and sales using incrementals (i.e. derivatives of energy costs and energy losses). Since incrementals are directly available from economic dispatch, the methods are well suited for rapid on-line costing. The authors extend the incremental methods to calculate on-line losses associated with three-party or wheeling type transactions. The accuracy of the method of calculating wheeling losses is verified by a load flow comparison. The potential impacts to the production cost for such transactions are also evaluated using a large system model. Finally, it is pointed out that the overall production cost of the wheeling utility may increase or decrease, even though the wheeling losses are completely accounted for, due to the change in generation profile which results from adjustments in the economic dispatch     

基于变量降维的大电网经济调度优化方法

随着电网规模扩大,经济调度问题因变量增多,维度巨大,造成求解困难。文中利用Benders分解法,将大电网安全约束经济调度问题分解为无安全约束的优化主问题和网络潮流安全约束子问题,将子问题安全约束返回主问题进行模型重构,通过主子问题协调最终实现问题求解。优化问题求解过程中,根据当前运行信息,对机组调整价值进行甄别,将其中对安全和经济贡献小的机组进行集中处理,同时根据重要断面潮流负荷变化的物理特征对研究时段进行检验,将非重点关注的相邻时段进行简化合并,实现压缩机组变量和时段数量、降低求解维度的目的。最后,算例验证表明基于变量降维的优化方法可以减少大电网优化时间,同时保持较高的求解精度,满足工程化计算要求。