Analyzing the specific features of structural transformations and generalizing the results of restorative thermal treatment of cast shell parts and valves carried out in different modes under industrial conditions

The results obtained from subjecting shell parts of PT-60-130 and T-100-130 turbines to restorative thermal treatment in different modes under industrial conditions are analyzed by way of comparison and generalized. Specific features relating to structural transformations occurring in different modes of restorative thermal treatment are revealed.     

Specific features of the stressed state and estimation of the lifetime of stamped-and-welded elbows used in hot reheat steam lines of 500-MW power units

Results obtained from calculations of the stressed and strained state of stamped-and-welded elbows having geometrical peculiarities in the zone of weld joints are presented. It is shown that relatively low calculated stresses in weld joints correspond to the actual degree of microdamage in elbows that have been in operation for 164000 h. Recommendations for extending the service life of elbows are given.     

Restorative thermal treatment of thermal and mechanical equipment: An important power supply reserve

We present results obtained from long-term operation of metal and subsequent investigation of its properties and structure after it had passed restorative thermal treatment. We also give proposals for extending the application field of this method for prolonging the term of reliable service of thermal power stations equipment the metal of which operates under creep conditions.     

Scheduling of generation in deficit power systems

Scheduling studies are carried out on a deficit hydrothermal power system. The problem is formulated as one of minimizing the severity of power cuts. The maintenance schedule of the thermal plants is selected by minimizing its deviation from an ideal, unrealizable schedule. The thermal plants are production-scheduled on the basis of their maintenance schedule. The influence of the stochastic nature of the load and the hydro inflows on the scheduling is evaluated. The hydro plants are scheduled through the extension of the techniques of the surplus case. Illustrative studies on an actual deficit hydro-thermal system are described     

Thermal and chemical tests of the steam generator of unit 3 at the Kalinin nuclear power station

The results obtained from combined thermal and chemical tests of the steam generator of Unit 3 at the Kalinin nuclear power station are summarized. The obtained data are compared with the results of thermal and chemical tests carried out on steam generators at other nuclear power stations equipped with VVER-1000 reactors, and recommendations on selecting the steam-generator blowdown schedule are given.     

Operational planning for pumped storage power station using heuristic techniques

A computer algorithm is described that coordinates, economically, the operation of a large pumped storage scheme with an existing thermal generation system. It uses heuristic techniques to establish a system model for operation, based largely on the manual merit order method, and in incorporates several operating constraints, including generator maximum and minimum generation levels, minimum shutdown times and loading and unloading rates. Designed specifically as an operational planning tool, the algorithm produces a unit commitment and load schedule for every half-hour interval of any load curve supplied. By costing this schedule with and without the pumped storage scheme, a pumping cost is obtained that can then be compared with other methods of frequency control. Finally, by extending the schedule to include hydrogeneration, the economic benefit of using the scheme in this mode may also be evaluated.     

Sensitivity analysis of an optimal short term hydro-thermalschedule

The authors deal with the sensitivity analysis of an optimal short term hydro-thermal schedule. Methodological and practical aspects of the system economy loss (SEL) calculation caused by incorrect input data are investigated. It was shown and checked by numerical simulations that errors in the hydro plant characteristics can be studied through errors in the short term load forecasting. In a special case when differentiability conditions are satisfied (economic dispatching problem) analytical formulas for the SEL are developed. Some of the important results of sensitivity calculations concerning relevant errors in thermal cost coefficients, hydro plant characteristics, forecasted water inflows and forecasted system demands are presented. The critical input data have been selected and their tolerance margins established to preserve the beneficial effects of an optimal short term schedule     

A solution to the unit commitment problem considering LNG fuel constraints

In this paper, an algorithm is proposed for finding a quasi-optimal schedule for the short-term thermal unit commitment problem taking LNG fuel constraints into account. In recent years, LNG fuel has been used increasingly. As a result, LNG fuel constraints should be considered in making a unit commitment schedule. Generally, unit commitment is a nonlinear combinatorial problem including discrete variables. To solve the problem, a two-step algorithm is developed using mathematical programming methods. First a linear programming problem is solved to determine the amount of LNG fuel to be consumed by each LNG unit, then a Lagrangian relaxation approach is used to obtain a unit commitment schedule. This two-step algorithm simplifies the problem and thus has good convergence characteristics. To test the effectiveness of the proposed algorithm, a numerical simulation was carried out on a 46-unit thermal system over a 24-hour period. A result with a dual gap of 0.00546 was obtained. © 1998 Scripta Technica, Electr Eng Jpn, 125(3): 22–30, 1998     

ZG2Cr12NiMo1W1V钢铸造导叶片工艺及性能试验研究

主要简述了ZG2Cr12NiMo1W1V材料的热加工工艺试验及材料性能的研究。通过熔炼、热处理、焊接热加工工艺试验分析,确定了ZG2Cr12NiMo1W1V的热加工工艺参数,同时提出了建议性的材料性能验收指标,为今后同类材质产品的生产提供了技术参考。     

A genetic algorithm solution to the optimal short-term hydrothermal scheduling

This paper presents an algorithm for solving the hydrothermal scheduling through the application of genetic algorithm (GA). The hydro subproblem is solved using GA and the thermal subproblem is solved using lambda iteration technique. Hydro and thermal subproblems are solved alternatively. GA based optimal power flow (OPF) including line losses and line flow constraints are applied for the best hydrothermal schedule obtained from GA. A 9-bus system with four thermal plants and three hydro plants and a 66-bus system with 12 thermal plants and 11 hydro plants are taken for investigation. This proposed GA reduces the complexity, computation time and also gives near global optimum solution.     

A Joint Smart Generation Scheduling Approach for Wind Thermal Pumped Storage Systems

Abstract

Energy storage plays a crucial role in the development of smart grids with high wind power penetration. Pumped storage is an effective solution for smoothing wind power fluctuation and reducing the operating cost for a wind thermal power system. The joint generation scheduling of power systems with mixed wind power, pumped storage, and thermal power is a challenging problem. This article proposes a novel two-stage generation scheduling approach for this problem in the contexts of smart grids. Through optimization, a day-ahead thermal unit commitment and pumped storage schedule are provided; then, in real time, the pumped storage schedule is updated to mitigate the wind power forecasting error and hence avoid the curtailment of wind power generation. The proposed model aims to reduce the total operating cost, accommodate uncertain wind power as much as possible, and smooth the output fluctuation faced by thermal units, while making the system operate in a relatively reliable way. A binary particle swarm optimization algorithm for solving the proposed model and the pumped storage schedule update algorithm are also presented. The model and algorithm are tested on a ten-generator test system.     

A recursive economic dispatch algorithm for assessing the costs ofthermal generator schedules

The authors develop an efficient, recursive algorithm for determining the economic power dispatch of thermal generators within the unit commitment environment. The algorithm uses the equal incremental fuel cost criterion as its basis. In the algorithm, the fuel cost functions of the thermal generators are modeled by quadratic polynomials and the transmission losses are discounted. A method for incorporating the operation limits of the online generators and limits due to ramping generators is developed. The algorithm is amenable to computer implementation using the artificial intelligence programming language Prolog. The performance, of the algorithm was demonstrated through its application to the evaluation of the costs of dispatching 13 thermal generators within a generator schedule in a 24-h schedule horizon     

Unit commitment using Lagrangian relaxation and particle swarm optimization

Unit commitment (UC) is a NP-hard nonlinear mixed-integer optimization problem. This paper proposes ELRPSO, an algorithm to solve the UC problem using Lagrangian relaxation (LR) and particle swarm optimization (PSO). ELRPSO employs a state-of-the-art powerful PSO variant called comprehensive learning PSO to find a feasible near-optimal UC schedule. Each particle represents Lagrangian multipliers. The PSO uses a low level LR procedure, a reserve repairing heuristic, a unit decommitment heuristic, and an economic dispatch heuristic to obtain a feasible UC schedule for each particle. The reserve repairing heuristic addresses the spinning reserve and minimum up/down time constraints simultaneously. Moreover, the reserve repairing and unit decommitment heuristics consider committing/decommitting a unit for a consecutive period of hours at a time in order to reduce the total startup cost. Each particle is initialized using the Lagrangian multipliers obtained from a LR that iteratively updates the multipliers through an adaptive subgradient heuristic, because the multipliers obtained from the LR tend to be close to the optimal multipliers and have a high potential to lead to a feasible near-optimal UC schedule. Numerical results on test thermal power systems of 10, 20, 40, 60, 80, and 100 units demonstrate that ELRPSO is able to find a low-cost UC schedule in a short time and is robust in performance.     

Unit commitment problem in deregulated environment

This paper addresses the self-scheduling problem of generation companies owning thermal power units considering bilateral contracts and day-ahead market. This approach allows precise modelling of variable costs, start-up costs and comprehensive system of constraints. The self-scheduling model is formulated as deterministic optimization problem in which expected profit is maximized by 0/1 mixed-integer linear programming technique. Solution is achieved using the homogeneous and self-dual interior point method for linear programming, with a branch and bound optimizer for integer programming. The effectiveness of the proposed model for optimizing the thermal generation schedule is demonstrated through the case study with detailed discussion.     

A linear programming method for the scheduling of pumped-storageunits with oscillatory stability constraints

Scheduling of pumped-storage units at the Taiwan Power Company (TPC) is investigated in this work. In addition to economic considerations, oscillatory stability of the power system as affected by the operation of pumped-storage units is of major concern. To achieve a secure as well as economical dispatching schedule for the pumped-storage units, differential dynamic programming is first employed to reach a preliminary schedule in which total fuel cost of the thermal units over the study period is minimized. Oscillatory stability analysis of the power system under the preliminary schedule is then performed by computing the eigenvalues and eigenvectors for all electromechanical modes. Sensitivities of the eigenvalues for the poorly-damped inter-area mode with respect to individual generator outputs are evaluated. Then a systematic approach based on linear programming is presented to refine the preliminary schedule in order to improve the damping for the inter-area mode. The effectiveness of the proposed approach is demonstrated by short term operational planning of the Taiwan power system     

基于“三公”调度的年度滚动发电计划与机组组合优化模型

“三公”调度是我国目前普遍采用的调度模式。负荷预测及水电计划是火电发电计划编制的基础,一般具有时间越近、精度越高的特点,实际应用中一般通过滚动预测及修正以提高发电计划的可用性。基于“三公”调度提出了年度滚动发电计划与机组组合优化模型,在优先保障“三公”调度目标的同时,优化机组的启停计划,提高火电机组的平均负荷率,并减少机组启停次数,以提高电网运行的经济性。所提模型为混合整数线性规划问题,能够采用CPLEX等商业软件求解。广西电网的仿真分析验证了所提模型的正确性及有效性。     

A solution method using neural networks for the generator commitment problem

This paper studies the feasibility of applying the Hopfield-type neural network to unit commitment problems in a large power system. The unit commitment problem is to determine an optimal schedule of what thermal generation units must be started or shut off to meet the anticipated demand; it can be formulated as a complicated mixed integer programming problem with a number of equality and inequality constraints. In our approach, the neural network gives the on/off states of thermal units at each period and then the output power of each unit is adjusted to meet the total demand. Another feature of our approach is that an ad hoc neural network is installed to satisfy inequality constraints which take into account standby reserve constraints and minimum up/down time constraints. The proposed neural network approach has been applied to solve a generator scheduling problem involving 30 units and 24 time periods; results obtained were close to those obtained using the Lagrange relaxation method.     

节能发电调度发电计划编制算法

在发电计划的编制过程中,如何实现机组发电序位表是体现节能发电要求的关键所在,为此,提出了发电计划编制核心算法。该算法基本原理为:根据全网负荷、分区负荷预测以及节能发电序位表,确定机组开机方式,然后采用等微增率法分配机组发电量;通过引入设备利用率系数分配机组发电曲线以满足系统安全运行和调峰要求,并修正机组发电曲线以满足运行约束条件,最终得到机组发电曲线。结合江苏电网以火电机组为主的特点,利用该算法进行节能调度发电试验日发电计划编制,验证了算法的合理性。     

定子吊装系统的结构设计及使用

火电厂发电机定子是火电机组单件最重的设备,它的吊装就位具有施工空间狭小、周围架构及设备密集、对项目工期影响大及施工难度大等特点。文章设计了一套能应用于300~1 000 MW火电机组发电机定子的吊装系统,该系统借用汽机房天车主梁结构强度和大车行走机构,利用专用架构和液压提升装置吊装发电机定子,具有所需空间小、施工工艺简单、安全可靠、对汽机房内的架构和其他设备安装要求底等特点。