Quasi-Newton method for optimal power flows

A prototype procedure for solving the optimal power flow problem with a quasi-Newton (variable metric) method is described. The method was developed by Powell and later extended by Berna, Locke and Westerberg. It is attractive for three reasons. First, it can accommodate optimal power flow constraints in a straightforward manner. Second, it is robust and will home in on a solution even from infeasible starting points. Third, it promises to be very fast. The adaptation of the method to the optimal power flow is discussed and illustrated with the results from tests on two small power systems.     

Utility-cogenerator game for pricing power sales and wheeling fees

The authors have studied an extensive game model of an electricity market where a cogenerator sells excess electricity to an electric utility or to an end user. They found that a buy-back system (the utility purchases cogenerated power) is as efficient as a cogenerator-customer wheeling system and that these two systems are more desirable than a monopoly system for the regulator. The buy-back rate should be equal to (LP bargaining solution) or less than (Nash bargaining solution) the marginal cost of the electric utility. They also conducted an analysis of a two-period electricity market in which they found that the cogenerator that can supply excess power during peak period obtains the market advantage     

Real-time optimal power flow in automatic generation control

The authors describe the concept, mathematical formulation, and solution of a real-time OPF (optimal power flow) in an energy management system. The real-time OPF replaces a classical real-time economic dispatch whenever a network flow violation occurs. To meet performance requirements (solution speed and frequency of execution) a two-stage approach is proposed. A full OPF is first executed in a nontime-critical mode and the critical branch flows are determined. Then, a constrained economic dispatch is executed based on the critical constraint set determined during the first stage. The execution frequency of the second stage is the same as the execution frequency of a standard real-time economic dispatch     

Development of a voltage sag detection method for nonutility generation systems

This paper deals with a new detection method based on three‐phase vector operation for voltage sag. The detection method is applicable to a protection system using a high‐speed interruption system which protects distributed generators and critical loads in a customer's facility. The algorithm and merits of this method are explained in detail. The detection characteristics are then analyzed using the ATP (Alternative Transients Program) and are confirmed using a real‐time digital simulator, and it is shown that the method is useful for detecting voltage sag. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 152(4): 34–41, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20117     

A new model for optimal generation scheduling of power system considering generation units availability

The objective of the short-term combined economic–environmental dispatch is to obtain the optimal power outputs of all generating units in the system given simultaneous minimization of the corresponding fuel cost and the release of gaseous pollutants in the environment. In this paper the classical model of the dynamic combined economic–environmental power dispatch is upgraded considering the availability of the generating units present in the system. The unavailability of power generation is defined as risk index and is considered to be a function of the generating units power level. An efficient multi-objective based genetic algorithm is applied for optimization purposes. Combined hydro-thermal power system is used as a case study system. The results show increase of the availability of power generation followed by small increase of the fuel cost and the gaseous emission.     

考虑分布式电源出力不确定性的城市电网模糊最优潮流分析

针对风力发电、太阳能发电等分布式电源出力的不确定性,引入模糊数学理论将不确定性的发电出力用模糊数表示,将梯形模糊数与最优潮流结合建立城市电网模糊最优潮流模型.依据模糊数的比较规则,通过加权位移法将模糊目标函数和模糊约束转化为确定性目标函数与约束,并采用原对偶内点法进行求解.对一24节点城市电网进行仿真分析,结果表明在某些出力不确定情况下所得优化结果是平均最优值.     

基于共同代理机制的发电商激励契约设计

共同代理是市场中普遍存在的一种现象。在电力市场中,设计合理的共同代理机制可以为梯级水电进入市场等问题提供一种新的解决思路。将共同代理理论应用于电力市场中,提出了电力市场环境下多个发电商委托同一个代理人的内生型共同代理模型,在代理人具有私人信息情况下,推导了发电商具有二次成本函数时委托人最优激励契约应满足的条件。并通过算例分析,对比了考虑和不考虑代理人参与约束两种情况的均衡解,验证了该激励契约的有效性,获得了一些有意义的结论。     

基于共同代理机制的发电商激励契约设计

共同代理是市场中普遍存在的一种现象.在电力市场中,设计合理的共同代理机制可以为梯级水电进入市场等问题提供一种新的解决思路.将共同代理理论应用于电力市场中,提出了电力市场环境下多个发电商委托同一个代理人的内生型共同代理模型,在代理人具有私人信息情况下,推导了发电商具有二次成本函数时委托人最优激励契约应满足的条件.并通过算例分析,对比了考虑和不考虑代理人参与约束两种情况的均衡解,验证了该激励契约的有效性,获得了一些有意义的结论.     

分布式电源对配网可靠性的影响及优化配置

基于配电网供电可靠性分析分布式电源(DG)的选址与定容。在配电网发生故障时由故障前的实际运行情况动态地生成优化孤岛方案,并结合DG出力模型计算各负荷点的可靠性,得到系统电量不足指标;在此基础上,为克服粒子群优化(PSO)算法所存在的早熟问题以及人工鱼群算法(AFSA)的收敛速度过慢缺陷,对粒子人工鱼群混合优化算法进行适应性改进,有效提高了配电网中DG选址与定容优化的计算效率。通过对IEEE-RBTS Bus6系统主馈线F4进行分析,验证了所提方法的有效性和正确性。     

利用最佳相似日的光伏电站短期出力预测

提出一种基于最佳相似日的光伏电站短期出力预测方法。该方法利用密度指标确定初始聚类中心优化K-means聚类算法,采用加权欧式距离法获得历史样本的出力水平相似日集,采用相关系数法获得历史样本的曲线形状相似日集,确定预测日出力水平相似日集和曲线形状相似日集,选取两集合的交集样本作为最佳相似日。建立BP神经网络出力预测模型,采用光伏电站的实测数据训练预测模型,对比不同类型天气的预测结果与实测数据,表明论文的预测方法具有较高的预测精度。     

Impact of the penetration of distributed generation on optimal reactive power dispatch

Optimal reactive power dispatch (ORPD) is a complex and non-linear problem, and is one of the sub-problems of optimal power flow (OPF) in a power system. ORPD is formulated as a single-objective problem to minimize the active power loss in a transmission system. In this work, power from distributed generation (DG) is integrated into a conventional power system and the ORPD problem is solved to minimize transmission line power loss. It proves that the application of DG not only contributes to power loss minimization and improvement of system stability but also reduces energy consumption from the conventional sources. A recently proposed meta-heuristic algorithm known as the JAYA algorithm is applied to the standard IEEE 14, 30, 57 and 118 bus systems to solve the newly developed ORPD problem with the incorporation of DG. The simulation results prove the superiority of the JAYA algorithm over others. The respective optimal values of DG power that should be injected into the four IEEE test systems to obtain the minimum transmission line power losses are also provided.     

Secure and optimal operation of a power generation and transmissionsystem-application to the Moroccan system

This article presents a new method for solving the “optimal power flow” problem in electric power systems. The method is fast and accurate. It has been implemented through two separate optimization models: MODINOP-the initial optimization model-which finds quickly a near optimal solution; and MODFINOP-the final optimization model-which leads to the optimal solution from the initial solution. The initial optimization model uses the principal component of the branch power flows as control variables. The network losses are computed at each optimization step and attached to the branch extremity buses as additional loads. The final optimization model improves the accuracy. It uses the state variable changes as control variables and incorporates the losses in the objective function. The resulting optimization models are solved using linear programming which is easy to implement and provides a fast solution. The utilization of these models with actual data of the Moroccan transmission network operation yield quickly, in a few seconds on a VAX 11/780, accurate results consistent with the real time data and compatible with the results provided by other models     

基于高斯混合模型的海洋能发电资源优化配置研究

针对海洋能资源丰富的海岛电网,提出了以消纳率最优为目标的海洋能发电资源优化配置方法。首先,采用高斯混合模型描述海洋能发电的随机波动性,并生成出力场景;然后以海洋能消纳率最优为目标构建了海岛电网的海洋能发电资源优化配置模型;最后,对渗透率、消纳率及源荷匹配度三个指标进行综合分析,获得最优配置方案。基于实际海岛负荷、波浪和潮流数据构建了海洋能发电资源优化配置算例,并重点分析了资源优化配置过程中渗透率约束的取值范围。结果表明,在不同的渗透率约束下,源荷匹配度呈现先升后降的趋势。因此,可以根据最大的源荷匹配度,确定资源优化配置模型中的渗透率约束取值范围。此外,在最优渗透率约束取值范围内,高斯混合模型出力场景与实测数据场景的优化配置结果相差不大且趋势一致,验证了高斯混合模型生成海洋能出力场景的有效性。     

超(超)临界燃煤发电技术发展与展望

高效燃煤发电技术一直是能源高效利用的先锋。当前主流的超（超）临界燃煤发电技术发展经历了3个阶段,技术在全球范围内逐渐成熟;在材料工业发展的支持下,朝着700 ℃等级先进超超临界技术的方向发展;并已逐步解决商业化应用的关键技术难题,迈向第 4个重要发展阶段。受制于如钢材和加工等基础工业领域的薄弱条件,中国在高效燃煤发电技术研发方面长期落后于发达国家;但经过长期追赶,当前已逐渐接近世界先进水平,且在700 ℃等级先进超超临界技术研发方面,也取得了可喜成绩。在高效燃煤发电技术应用等方面,中国近40年来发展迅猛,当前中国的煤电机组煤耗水平已达到欧洲诸国的先进水平。进一步发展材料等基础工业,从主机设备、系统布置等方面进行设计创新,仍然是高效燃煤发电技术发展的关键。     

发电侧峰谷分时电价设计及电量分配优化模型

构建发电侧与售电侧峰谷分时电价联动机制有利于平衡发电公司和供电公司之间的利益,但必须建立在定制出合理的上网定价机制的基础上,因此有必要研究发电侧分时电价问题。从发电成本的角度考虑,采用两部制电价对发电侧峰谷分时电价进行研究。应用会计成本法计算发电侧容量成本,并根据发电容量确定峰谷分时容量电价;根据发电厂煤耗等变动成本确定发电侧峰谷分时电量电价,从而得到发电侧峰谷分时电价;构建各时段各发电厂的电量分配优化模型。通过算例分析证明所提出的发电侧峰谷分时电价设计机制及电量分配优化模型是可行的。     

水库发电优化调度模型的快速求解算法及应用

针对水库"以水定电"优化调度数学模型求解方法中,传统动态规划方法易陷入"维数灾",而现代智能算法搜索效率低且易陷入局部最优解等不足。本文基于水库在高水头运行时耗水率小的特点,提出了水电站水库"以水定电"调度模型的快速求解方法——浮子算法。该方法在水电站满足保证出力和最小下泄流量等要求的前提下,尽可能提高水库调度期的运行水位以达到直接寻找优化调度解的目的。通过案例分析并与离散微分动态规划(DDDP)方法求解结果比较,本算法结果与DDDP算法十分接近,计算时间约为后者的50%。与其他算法联合使用,可在提高优化效果的同时缩短模型的求解时间,为水电站水库"以水定电"调度计划的制定和快速决策提供技术支持。     

Cost analysis of a power system using probabilistic optimal power flow with energy storage integration and wind generation

This paper examines the storage application and its optimal placement for the social cost and transmission congestion relief of wind integration. Probability density functions (PDFs) are used to characterize the uncertainties of wind speed and load. A probabilistic optimal power flow (POPF) is developed using two-point estimation which incorporates the storage system either as a variable load or as a variable generator. Storage systems are optimally placed and adequately sized using a particle swarm optimization (PSO) to minimize the sum of operation and congestion costs over a scheduling period. A technical assessment framework is developed to enhance the efficiency of wind integration and evaluate the economics of storage technologies and conventional gas-fired alternatives. The proposed method is used to carry out a cost-benefit analysis for the IEEE 24-bus system and determine the most economical technology. Optimal storage distribution and its potential to relieve the transmission congestion are evaluated for higher wind penetration levels.     

计及可再生电源不确定性的配电网鲁棒最优潮流

主动配电网中可再生分布式电源出力的不确定性影响系统安全运行。基于鲁棒优化方法,首先建立考虑可再生分布式电源出力不确定性的主动配电网鲁棒最优潮流模型,该模型考虑了能改善其解保守性的价格型需求侧响应。对模型中的不确定集进行凸转换,采用凸优化方法对模型进行求解。IEEE 13节点和IEEE 123节点系统的仿真测试结果表明,相比于传统确定性模型,采用所提鲁棒优化模型获得的优化结果能同时兼顾安全性和经济性。