Optimization-based sale transactions and hydrothermal scheduling

Selling and purchasing power are important activities for electric utilities because of potential savings. When a selling utility presents an offer including prices, power levels and durations, a purchasing utility selects power levels and durations within the offered range subject to relevant constraints. The decision making process is complicated because transactions are coupled with system demand and reserve, therefore decisions have to be made in conjunction with the commitment and dispatching of units. Furthermore, transaction decisions have to be made in almost real time in view of the competitiveness of the power market caused by deregulation. In this paper, transactions are analyzed from a selling utility's viewpoint for a system consisting of thermal, hydro and pumped-storage units. To effectively solve the problem, linear sale revenues are approximated by nonlinear functions, and nonprofitable options are identified and eliminated from consideration. The multipliers are then updated at the high level by using a modified subgradient method to obtain near optimal solutions quickly. Testing results show that the algorithm produces good sale offers efficiently     

水火电力系统短期发电计划优化方法综述

水火电力系统的短期发电计划问题在电力系统的安全可靠和经济运行中发挥着越来越重要的作用，由于其本身的复杂性，很难从理论上找到全局最优解。深入探讨各种优化算法，并加以分类，详细综述各种优化方法在水火电力系统短期发电计划问题中所取得的研究成果和存在的不足之处。     

Scheduling of hydrothermal power systems

The authors present a method for scheduling hydrothermal power systems based on the Lagrangian relaxation technique. By using Lagrange multipliers to relax system-wide demand and reserve requirements, the problem is decomposed and converted into a two-level optimization problem. Given the sets of Lagrange multipliers, a hydro unit subproblem is solved by a merit order allocation method, and a thermal unit subproblem is solved by using dynamic programming without discretizing generation levels. A subgradient algorithm is used to update the Lagrange multipliers. Numerical results based on Northeast Utilities data show that this algorithm is efficient, and near-optimal solutions are obtained. Compared with previous work where thermal units were scheduled by using the Lagrangian relaxation technique and hydro units by heuristics, the new coordinated hydro and thermal scheduling generates lower total costs and requires less computation time     

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     

独立发电企业水火协调优化运行研究综述

介绍了在电力市场环境中,当独立发电企业同时拥有水电和火电的情况下,国内外关于研究合理安排水火电发电计划的理论和方法,从而使发电企业运行总成本最少。同时,详细阐述了各种方法取得的进展和以后的研究方向。     

Differential evolution technique-based short-term economic generation scheduling of hydrothermal systems

This paper presents differential evolution (DE)-based optimization technique for solving short-term economic generation scheduling of hydrothermal systems. A multi-reservoir cascaded hydrothermal system with non-linear relationship between water discharge rate, power generation and net head is considered here. The water transport delay between the connected reservoirs is also taken into account. Several equality and non-equality constraints on thermal units as well as hydro units and the effect of valve-point loading are also included in the problem formulation. The effectiveness of the proposed method is demonstrated on two test systems comprising of hydro and thermal units. Convergence characteristic of the proposed technique has been found to be quite satisfactory. The results obtained by the proposed technique are compared with other evolutionary methods. It is seen that the proposed technique is capable of producing encouraging solutions.     

独立发电企业水火协调优化运行研究综述

介绍了在电力市场环境中,当独立发电企业同时拥有水电和火电的情况下,国内外关于研究合理安排水火电发电计划的理论和方法,从而使发电企业运行总成本最少.同时,详细阐述了各种方法取得的进展和以后的研究方向.     

Long-term expansion planning for hydrothermal electric power systems

This paper shows some aspects of the applicability of mixed integer programming (MIP) in expansion planning for regional electric utility systems, considering both power plants and the transmission network. The hydrothermal generation system may include significant run-of-river and reservoir power stations, and also pumped storage stations. Some essential elements of the model are explained to demonstrate the MIP modelling. The application of the model to the long-term expansion planning problem of a hydrothermal power system is also described.     

Market power assessment and mitigation in hydrothermal systems

The objective of this work is to investigate market power issues in bid-based hydrothermal scheduling. Initially, market power is simulated with a single stage Nash-Cournot equilibrium model. Market power assessment for multiple stages is then carried through a stochastic dynamic programming scheme. The decision in each stage and state is the equilibrium of a multi-agent game. Thereafter, mitigation measures, especially bilateral contracts, are investigated. Case studies with data taken from the Brazilian system are presented and discussed     

Reliability analysis for hydrothermal generating systems includingthe effect of maintenance scheduling

Usually, power system reliability indicators are obtained for one year periods, and must take into account maintenance requirements for thermal generating units. This paper describes an efficient method for the calculation of the two most common power system reliability indicators: LOLE (loss of load expectation) and EENS (expected value of energy not served), in the case of electric systems including generation units with limits on energy generation (hydropower plants with a variable amount of available water). The method is based on transforming the initial load curve into a thermal load curve, which enables one to separate completely the hydrothermal and the thermal power systems, thereby facilitating both reliability evaluations and maintenance scheduling     

风力发电机组控制系统的研究分析

对目前流行的风力发电机组控制系统进行对比分析.在简述风力机特性的基础上,介绍了定桨距和变桨距发电机组的特点,重点分析了基于双馈发电机的变速恒频发电系统及桨叶节距角控制系统.讨论了未来风力发电控制技术的发展趋势和应用前景.     

三角旋回算法及其在短期水火协调优化中的应用

提出一种新的全局优化方法--三角旋回算法(Triangle Gyration Algorithm,简称TGA),认为该算法具有结构简单、鲁棒性强和快速收敛的特点.算法的寻优过程采用历史最优目标函数值进行指导,利用三角变换进行迭代使其能够快速收敛到全局最优.用一个典型的算例对三角旋回算法进行了性能分析,且将该算法应用在水火电力系统短期(日前现货市场)协调优化调度中,得出的结论是该算法综合性能优越,在优化方法领域具有广阔的应用前景.     

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.     

Improvement of process closed-loop control systems for power units

We describe the results of activities carried out at ZAO Interavtomatika (Interautomatika AG) on the development and putting into use of improved systems for closed-loop control of the main process values of Russian power units equipped with once-through boilers. We also consider a general approach for improving control systems and describe specific technical solutions taken for furnishing the main technological items of coal-and gas-and-oil-fired power units with closed-loop control systems.     

A coordinated dispatch method withpumped-storage and battery-storage forcompensating the variation of wind power

Growing penetration of wind power challenges to power system security, since the conventional generators may not have sufficient capacity to compensate wind power fluctuation plus the reverse peak regulation. In this paper, the high-capacity pumped-storage and fast-response battery-storage are coordinated to compensate the variation of both wind power and load, aiming at shifting peak load, responding to wind power ramping, reducing the curtailment of wind and stabilizing the output of thermal units. A practical framework is designed for optimizing the operation of the hybrid system consisting of the wind, pumped-storage, and battery storage, which can take full advantages of pumped-storage and battery-storage. The detailed mathematical formulations of the pumpedstorage and battery-storage are built. Three cases are studied to demonstrate the advantages of the proposed coordination method.     

大规模新能源并网下火电机组深度调峰优化调度

当前,火电机组亟须进行深度调峰改造来提高电网大规模新能源消纳能力。文中对大规模新能源并网下火电机组深度调峰优化调度进行研究。首先,分析火电机组深度调峰成本,建立火电机组深度调峰的能耗成本、运行补偿收益以及备用容量成本的数学模型;然后,以综合运行成本最低为目标函数,建立考虑火电机组运行约束的深度调峰调度模型,并使用分支定界法求解调度模型;最后,以8台火电机组、1个风电场和1个光伏电站构成测试系统,分别从调峰深度、新能源消纳量、火电企业收益等方面对大规模新能源并网下火电机组深度调峰优化调度进行分析。算例结果表明：在文中所建优化调度模型中,火电机组深度调峰能显著提高新能源消纳量,但火电机组单位发电成本提高,火电机组效益明显下降。在当前深度调峰补偿标准下,火电机组深度调峰效益低于基本调峰。     

水火电力系统多目标环境经济调度模型及其求解算法研究

通过综合考虑发电费用最小及污染气体排放量最小这两个调度目标建立了水火电力系统多目标环境经济调度模型,并提出一种混合多目标差分进化算法对模型进行求解.该算法针对多目标优化问题的特点对差分进化算法的算子进行了修正,并基于混沌序列提出一种参数自适应调整策略以克服算法参数率定的难题.设计了一种二次变异算子来防止算法陷入局部最优.针对不同类型约束特性提出一种约束处理方法.实例计算结果及对比分析验证了所提方法的可行性和有效性,为实现水火电力系统实现经济与减排双目标均衡优化提供了一条崭新途径.     

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.     

火电机组年合同电量的编制与分解算法研究

在传统调度、完全市场、限量竞价三种模式下,提出了火电机组年合同电量的编制与分解算法。算法从兼顾电网调度公平性和经济性的角度出发,以发电-负荷平衡、最大/最小发电量、机组检修计划等条件为约束,对火电机组的年合同电量进行编制和分解。算法通过调整各种模式下交易电量的市场份额以适应市场交易机制的变化,并对不同机制下的年合同电量提出了相应不同的编制与分解算法,具有较强的适用性和适度的前瞻性。某地方电网算例验证了该算法的实用性和有效性。