基于极限场景分析的电力系统有功功率和备用协调调度

针对电力系统有功备用在调用过程中因线路传输容量不足而无法投入使用的问题,提出一种基于极限场景分析的有功功率和备用协调调度方法。首先,建立考虑备用可用性的优化调度模型。然后,基于连续贪婪算法,提出计及备用调用时机组出力调整范围的极限场景生成方法。最后,将模型分解为预测场景下的备用经济性分配主问题和若干极限场景下的备用可行性校核子问题,进行迭代求解。通过在新英格兰10机39节点系统的测试结果表明,所提方法不仅可以有效解决备用可用性问题,还可以识别影响备用可用性的关键线路和时段。     

Blackstart capability planning for power system restoration

Blackstart capability is essential for power system restoration following a blackout. System restoration planners determine the restoration sequences to provide cranking power from blackstart units (BSUs) to non-blackstart units (NBSUs), pick up critical loads, and energize the necessary transmission paths. This paper proposes a new algorithm for optimization of the restoration actions. An optimal search algorithm is proposed to determine the plan to crank NBSUs through the selected paths of transmission lines. Assuming that the generation capability of a BSU is constant, the method is used to optimize the overall system MWHr generation capabilities from NBSUs. To reduce the computational complexity of system restoration planning, a new generator model is proposed that results in a linear integer programming (IP) formulation. Linearity of the IP problem formulation ensures that the global optimality is achieved. The optimal power flow (OPF) is used to examine the feasibility of planned restoration actions. Test cases from the IEEE 39-bus system, ISO New England system, and Duke-Indiana system are used to validate the proposed algorithm. Numerical simulations demonstrate that the proposed method is computationally efficient for real-world power system cases.     

Generation scheduling with thermal stress constraints

This paper describes a scheduling method for representing the thermal stress of turbine shafts as ramp rate constraints in the thermal commitment and dispatch of generating units. The paper uses Lagrangian relaxation for optimal generation scheduling. In applying the unit commitment, thermal stress over the elastic limit is used for calculating the ramping cost. The thermal stress contribution to generation cost requires the calculation of a set that includes thermal stress at the end of each time step; this requirement presents a complicated problem which cannot be solved by an ordinary optimization method such as dynamic programming. The paper uses an improved simulated annealing method to determine the optimal trajectory of each generating unit. Furthermore, the paper uses linear programming for economic dispatch in which thermal stress limits are incorporated in place of fixed ramp rate limits. The paper illustrates the economics of frequently ramping up/down of low cost generating units versus the cost of replacement of their turbine rotors with a shorter life span. The experimental results for a practical system demonstrate the effectiveness of the proposed method in optimizing the power system generation scheduling.     

Optimal Scheduling of Spinning Reserve with Transmission Constraints

An effective method is proposed to schedule spinning reserve optimally. The method considers the transmission constraint in the whole scheduling process. To get the feasible solution faster, transmission line limits are first relaxed using the Lagrangian Relaxation technique. In the economic dispatch, after unit generation and spinning reserve are allocated among the committed units to satisfy the system andunit constraints, the schedule is then modified by a linear programming algorithm to avoid line overloads. The schedule is then updated by a probabilistic reserve assessment to meet a given risk index. The optimal value of the risk index is selected via a cost/benefit analysis based on the tradeoff between the total Unit Commitment (UC) schedule cost and the expected cost of energy not served. Finally, a unit decommitment technique is incorporated to solve the problem of reserve over-commitment in the Lagrangian Relaxation–based UC. The results of reserve scheduling with the transmission constraint are shown by the simulation runs performed on the IEEE reliability test system.     

电力工业可持续发展的统一规划模型

尝试建立电力工业持续发展的统一规划优化模型,协调考虑国家能源政策、一次能源开采能力与运输限制、环保问题、合理装机容量、电源结构优化、系统调峰问题、电源布局优化、电源电网协调发展以及电力投资决策对后续发展的影响,为寻求科学的、经济的、可持续的电力发展方案提供决策支持。模型以电厂、电网投资决策矩阵为优化对象,机组、线路状态矩阵由此构造而得,从而构成了以电源电网投资决策、规划各年份典型日各节点各类型机组开机容量、典型时段的出力等为决策变量的混合整数规划问题,使得投资决策模块和生产模拟模块融为一体,并可以一次性对规划期各年份进行优化。整个模型已经在江苏省2020年电力发展规划研究中得到验证。     

计及需求侧管理的电—气集成能源系统协同规划

随着电转气技术的发展,电力系统与天然气系统间的耦合程度不断增强,传统电力系统与天然气系统独立规划的模式已不能满足电—气集成能源系统(IEGES)的需要。另一方面,实施需求侧管理可以优化电力负荷轮廓、实现削峰填谷、提升消纳间歇性可再生能源发电的能力,有利于整个IEGES的安全与经济运行。在此背景下,对计及需求侧管理的IEGES的协同规划问题进行了探讨。首先,基于用户满意度对需求侧管理建模,并以包括投资成本、运行成本和需求侧管理补偿费用的总成本最小为优化目标,建立IEGES中燃气机组、电转气设备、输电线路和天然气管道选址规划的混合整数非线性规划模型。然后,为加快求解速度,对模型中的非线性部分进行线性化处理,将原混合整数非线性规划问题转化为混合整数线性规划问题,并采用AMPL/CPLEX商业求解器求解。最后,以由修改的IEEE 39节点电力系统与比利时20节点天然气系统耦合形成的IEGES为例,对所构造的模型和采用的方法进行说明,并考察了其在节约成本和消纳风电方面的影响。     

A Practical Model for Generator Maintenance Scheduling with Transmission Constraints

In this paper an optimal maintenance scheduling of generating units in a power system has been developed with transmission network representation. Here a DC load flow has been embedded in the maintenance model to include network constraints resulting in a more practical maintenance schedule. The model developed here uses the minimization of system cost (production cost plus the unserved energy cost) as the objective criterion, whereas the reliability objective function used is the minimization of unserved energy. The optimization is achieved by integer linear programming. The incorporation of transmission network adds significant complexity to maintenance scheduling. The proposed model enables almost all practical maintenance scheduling constraints to be handled easily. The optimization has been carried out to minimize the cost function considering different cases (i.e., with and without incorporation of the transmission network). The effectiveness of the proposed method has been demonstrated by obtaining numerical results on sample and real scale test systems. A comparison of the cost objective function clearly indicates that the maintenance schedule obtained from the simple generation model alone is more expensive than the one with transmission, and that there is a considerable degree of suboptimality in the former case.     

基于机会约束规划的最优旋转备用容量确定

在机会约束规划的框架下,研究了在兼顾系统运行的可靠性和经济性时,如何考虑发电机组的故障停运和负荷预测误差等不确定性因素,以便确定系统所需的最优旋转备用容量。在以最小化旋转备用的购买成本为目标、以系统的安全性要求为机会约束的条件下,构造了确定系统所需的最优旋转备用容量的数学模型,并采用基于蒙特卡洛仿真的遗传算法进行求解。最后以包含18台机组的电力系统为例对所提出的模型与方法进行了说明。     

考虑风电降载的电力系统鲁棒备用调度模型

风电主动控制可抑制风电出力的波动,有效缓解系统备用压力。文中提出了一种考虑风电降载的电力系统鲁棒备用调度模型,考虑风电场和负荷功率预测误差的不确定性,引入风电降载比定量描述风电备用持有水平,建立风电场备用、旋转备用等鲁棒约束条件,同时根据对偶原理将鲁棒优化模型转化为确定性的数学规划问题,利用线性松弛技术和空间分支定界法寻找模型的全局最优解。最后,采用改进的IEEE 39节点算例验证模型的有效性。     

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     

Optimal Spinning Reserve for a Wind-Thermal Power System Using EIPSO

This paper presents an evolutionary iteration particle swarm optimization (EIPSO) algorithm to solve the nonlinear optimal scheduling problem. A new index called iteration best is incorporated into particle swarm optimization (PSO) to improve the solution quality. The new PSO, named iteration PSO (IPSO), is embedded into evolutionary programming (EP) to further improve the computational efficiency. The EIPSO is then applied to solve the optimal spinning reserve for a wind-thermal power system (OSRWT). Results are used to evaluate the effects of wind generation on the spinning reserve selection of a power system. The OSRWT program considers the outage cost as well as the total operation cost of thermal units to evaluate the level of spinning reserve. The up spinning reserve (USR) and down spinning reserve (DSR) are also introduced into the OSRWT problem. The optimal scheduling of spinning reserve was reached while minimizing the sum of total operation cost and outage cost. Two practical power systems are used as numerical examples to test the new algorithm. The feasibility of the new algorithm is demonstrated by the numerical example, and EIPSO solution quality and computational efficiency are compared to those of other algorithms.     

Clonal selection algorithm for power generators maintenance scheduling

This paper introduces a technique based on the one of the artificial immune system (AIS) technique known as the clonal selection algorithm (CSA) to obtain the optimal maintenance schedule outage of generating units. Based on a weekly load profile, the proposed technique provides the optimal maintenance window and calculates the optimal output power from each generator over a one year horizon. The maintenance scheduling problem is decoupled into two interrelated sub-problems namely, the maintenance scheduling and the power system sub-problems. The CSA is used to solve the maintenance scheduling subproblem to obtain the optimal maintenance outage of each unit. Based on the schedule generated by the CSA, the economic dispatch iterative lambda technique is used to find the optimal output power from each unit. Due to the search nature of the CSA, infeasible solutions may be introduced during the solution process. Therefore, a local search technique is used to watch the feasibility of the new solutions. The paper reports test results of the proposed algorithm to find the optimal maintenance schedule of the IEEE 30 bus system with 6 generating units and the IEEE 118 bus system with 33 generating units. Results are compared against the results obtained by complementary decision variables structure (CDV) and the evolutionary programming based techniques. Results are encouraging and indicate the viability of the proposed CSA technique.     

基于直流潮流的发输电系统区间负荷N-K事故计算

从严格数学角度研究了基于直流潮流的发输电系统区间负荷K个元件事故评估。区间负荷N-K事故场景非常多,首先从优化角度建立了区间负荷N-K最好状态和最坏状态最小切负荷模型,其中最坏状态模型是典型的双层优化模型,上层决策变量是机组、线路和负荷状态,下层模型是直流潮流的最小切负荷模型。然后,使用强对偶理论和数学等效化简方法,把系统N-K区间负荷最坏状态最小切负荷双层优化模型转化为混合整数线性规划模型,该模型可使用成熟优化软件求解。最后,使用IEEE标准算例,测试了考虑区间负荷、机组和线路（或变压器）故障的区间负荷N-K事故最坏状态评估模型,测试结果显示了本文所提方法的有效性和可行性。     

基于线性潮流的电力系统长时间尺度快速时序仿真方法

电力系统长时间尺度时序仿真和生产模拟是可再生能源和电网规划设计阶段的重要依据,也是检验规划设计方案科学性的有效工具.首先,为了提高大规模电力系统长时间尺度时序仿真效率,针对输电网的特点,提出了一种输电网潮流线性化方法,并基于IEEE标准算例对线性潮流的精度及计算效率进行检验和对比,结果表明该方法不仅具有较高的计算精度,...     

考虑自适应传输备用的含风电电力系统双层随机调度方法

大规模风电接入增加了电网发生输电阻塞的概率.为克服确定性阻塞管理方法在应对系统随机扰动上的不足,基于考虑阻塞风险的机会约束规划条件,提出一种计及风电不确定性的传输备用自适应量化方法,构建了包含自适应传输备用的双层随机调度模型.该模型将线路传输备用纳入上层的机组组合模型中,针对下层的经济再调度问题,采用改进点估计法求得线路实时潮流的统计分布特性,并将结果返回上层模型以动态调整备用需求大小.同时,基于下层模型的Karush-Kuhn-Tucher最优条件,将双层优化结构合并为单层,并最终转化为便于求解的混合整数规划问题.最后,通过IEEE RTS-24节点测试算例验证了所提模型和方法能够有效缓解传输阻塞,提高风电消纳和备用可用性.     

考虑电转气设备和风电场协同扩建的气电互联综合能源系统规划

随着电转气技术的发展和燃气机组占比的日益提高,电力、天然气系统间的耦合程度逐渐加深。在此背景下,对气电互联综合能源系统扩建规划时,考虑投建发电机组、输电线路、天然气气井、输气管道、风电场、电转气设备,并探究电转气设备和风电场协同扩建对系统扩建方案、风电消纳和经济性的影响。在计及电力、天然气系统相关运行约束的前提下,建立以系统投资运行总成本之和最小为目标的气电互联综合能源系统长期协调规划扩建模型;通过分段线性法将该模型转化为混合整数规划模型进行求解;通过IEEE 24节点的电力系统和12节点的天然气系统组成的算例系统验证所提模型的有效性,结果表明合理的电转气设备和风电场协同投建可以减少输电线路阻塞和输电线路的过度投建,提高系统经济性和运行安全性。     

A numerical integration method for long-term power system dynamic simulation

Large power system frequency/voltage fluctuations due to severe faults in trunk transmission lines or major generating units may trip-off other facilities and result in large-scale power system blackout. To prevent such blackout, development of an accurate and fast long-term power system dynamic simulation tool is required. With respect to the development stage, selection of a numerical integration method available for step-size adjustment, and the development of a scheme for the adjustment are principal subjects. The trapezoidal and the second-order Gear methods were selected as possible candidates for the step-size adjustment from the viewpoint of numerical stability. The trapezoidal method is selected from the viewpoint of accuracy and applicability to power system dynamic simulations. A new scheme for the automatic step-size adjustment is proposed for the trapezoidal method to achieve fast simulation of the long-term power system dynamics. The validity of the proposed scheme is verified through simulation studies on a single-machine-to-infinite bus system.     

Evaluation of the operating reserve in hydrothermal generation systems

The demand for an accurate evaluation of power reserves has become very important especially since the installation of large generating units such as nuclear power plants. The features of the power reserve and its partition into non-spinning and spinning components are discussed. Attention is paid to the regulating margin of the generating units and to the problem of evaluating the magnitude and duration of the operating reserve in a hydrothermal generating system under uncertain conditions.Practical examples are given to illustrate evaluation of the fast and slow operating reserves for the hydro and thermal subsystems of the Egyptian Unified Power System. The relation between the uncertainty in the amount of the required operating reserve on the one hand, and the amount of statistical data and size of added generating units on the other are discussed.     

Transmission network expansion planning considering repowering and reconfiguration

Transmission expansion planning (TEP) is a classic problem in electric power systems. In current optimization models used to approach the TEP problem, new transmission lines and two-winding transformers are commonly used as the only candidate solutions. However, in practice, planners have resorted to non-conventional solutions such as network reconfiguration and/or repowering of existing network assets (lines or transformers). These types of non-conventional solutions are currently not included in the classic mathematical models of the TEP problem. This paper presents the modeling of necessary equations, using linear expressions, in order to include non-conventional candidate solutions in the disjunctive linear model of the TEP problem. The resulting model is a mixed integer linear programming problem, which guarantees convergence to the optimal solution by means of available classical optimization tools. The proposed model is implemented in the AMPL modeling language and is solved using CPLEX optimizer. The Garver test system, IEEE 24-busbar system, and a Colombian system are used to demonstrate that the utilization of non-conventional candidate solutions can reduce investment costs of the TEP problem.     

风-火-水-储-气联合优化调度策略

针对电力系统因调节能力不足而造成弃风等问题,构建多源并存的电力系统内风-火-水-储-气联合优化调度模型,并给出模型的求解方法。该模型将常规机组中的灵活电源包括燃气、水电与储能系统进行联合建模,考虑联合运行后不同机组间的相互影响,对联合运行时系统消纳清洁能源的能力提升的内在机理进行分析。为求解提出的联合调度模型,对模型线性化之后采用CPLEX调用内点法进行计算。最后用改进的7机39节点系统进行仿真,结果验证了所提模型对于提高系统调节能力、促进风电消纳、优化系统工况的作用。联合调度策略结合实际电力系统中多源并存的现状为应对风电接入问题提供了一种实际可行的调度方案。