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Incorporating Service Quality Regulation in Distribution System Maintenance Strategy

IEEE TRANSACTIONS ON POWER DELIVERY 2011年第4期26卷 2495-2504页

作者： Mohammadnezhad-Shourkaei, Hosein Abiri-Jahromi, Amir Fotuhi-Firuzabad, Mahmud Sharif Univ Technol Dept Elect Engn Ctr Excellence Power Syst Control & Management Tehran 113659363 Iran

The concerns of regulatory authority for the cost efficiency and service quality of distribution utilities has led them to implement monetary schemes, such as penalty/reward mechanism (PRM). PRM provides explicit financial incentives for distribution system operators (DSO) to maintain or improve their efficiency and quality of service. Although the effectiveness of the PRM is proven, analytical tools that can handle the complex decision-making process faced by decision makers to respond to PRM are scarce. This paper presents an approach for distribution system maintenance management in the presence of the PRM. The proposed approach tailors the maintenance plans by taking into account the equipment condition in terms of failure rate, cost of planned and unplanned outage, as well as labor and material cost in conjunction with the incentives provided by PRM. New insights are also gained regarding the effects of PRM on the process of decision making by DSO.

关键词： Distribution system operators (DSO) maintenance management mixed-integer linear programming penalty/reward mechanism (PRM)

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An optimization approach for managing fresh food quality throughout the supply chain

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INTERNATIONAL JOURNAL OF PRODUCTION ECONOMICS 2011年第1期131卷 421-429页

作者： Rong, Aiying Akkerman, Renzo Grunow, Martin Tech Univ Denmark Dept Engn Management DK-2800 Copenhagen Denmark Univ Turku Dept Informat Technol Turku 20014 Finland Univ Tecn Lisboa Ctr Appl Math & Econ ISEG P-1200781 Lisbon Portugal

One of the most challenging tasks in today's food industry is controlling the product quality throughout the food supply chain. In this paper, we integrate food quality in decision-making on production and distribution in a food supply chain. We provide a methodology to model food quality degradation in such a way that it can be integrated in a mixed-integer linear programming model used for production and distribution planning. The resulting model is applied in an illustrative case study, and can be used to design and operate food distribution systems, using both food quality and cost criteria. (C) 2009 Elsevier B.V. All rights reserved.

关键词： Supply chain management mixed-integer linear programming Food industry Quality modelling

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Optimal scheduling of continuous plants with energy constraints

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COMPUTERS & CHEMICAL ENGINEERING 2011年第2期35卷 372-387页

作者： Castro, Pedro M. Harjunkoski, Iiro Grossmann, Ignacio E. Lab Nacl Energia & Geol Unidade Modelacao & Optimizacao Sistemas Energet P-1649038 Lisbon Portugal ABB Corp Res Ctr D-68526 Ladenburg Germany Carnegie Mellon Univ Dept Chem Engn Pittsburgh PA 15213 USA

This work addresses the scheduling of continuous single stage multiproduct plants with parallel units and shared storage tanks. Processing tasks are energy intensive and we consider time-dependent electricity pricing and availability together with multiple intermediate due dates, handled as hard constraints. A new discrete-time aggregate formulation is proposed to rapidly plan the production levels. It is combined with a continuous-time model for detailed scheduling as the essential part of a rolling-horizon algorithm. Their computational performance is compared to traditional discrete and continuous-time full-space formulations with all models relying on the Resource-Task Network (RTN) process representation. The results show that the new models and algorithm can generate global optimal schedules much more efficiently than their counterparts in problems involving unlimited power availability. Under restricted power, the aggregate model underestimates the electricity cost, which may cause the rolling-horizon approach to converge to a suboptimal solution, becoming the discrete-time model a better approach. (c) 2010 Elsevier Ltd. All rights reserved.

关键词： Production planning mixed-integer linear programming Non-uniform time grid Continuous-time model Resource-Task Network

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Offering Strategy Via Robust Optimization

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IEEE TRANSACTIONS ON POWER SYSTEMS 2011年第3期26卷 1418-1425页

作者： Baringo, Luis Conejo, Antonio J. Univ Castilla La Mancha E-13071 Ciudad Real Spain

This paper provides a technique to build hourly offering curves for a price-taker producer participating in a pool. The technique relies on solving a sequence of robust mixed-integer linear programming problems. Instead of using price predictions as input data, price confidence intervals are considered. These intervals are successively divided into a sequence of nested subintervals, which allow formulating a collection of meaningful and easy-to-solve robust mixed-integer linear programming problems. The solutions of these problems provide adequate information to build hourly offering curves.

关键词： mixed-integer linear programming optimal offering pool price-taker producer robust optimization

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New Models for Commercial Territory Design

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NETWORKS & SPATIAL ECONOMICS 2011年第3期11卷 487-507页

作者： Angelica Salazar-Aguilar, Maria Rios-Mercado, Roger Z. Cabrera-Rios, Mauricio Univ Autonoma Nuevo Leon Grad Program Syst Engn San Nicolas De Los Garza 66450 NL Mexico Univ Puerto Rico Dept Ind Engn Mayaguez PR 00681 USA

In this work, a series of novel formulations for a commercial territory design problem motivated by a real-world case are proposed. The problem consists on determining a partition of a set of units located in a territory that meets multiple criteria such as compactness, connectivity, and balance in terms of customers and product demand. Thus far, different versions of this problem have been approached with heuristics due to its NP-completeness. The proposed formulations are integer quadratic programming models that involve a smaller number of variables than heretofore required. These models have also enabled the development of an exact solution framework, the first ever derived for this problem, that is based on branch and bound and a cut generation strategy. The proposed method is empirically evaluated using several instances of the new quadratic models as well as of the existing linear models. The results show that the quadratic models allow solving larger instances than the linear counterparts. The former were also observed to require fewer iterations of the exact method to converge. Based on these results the combination of the quadratic formulation and the exact method are recommended to approach problem instances associated with medium-sized cities.

关键词： mixed-integer linear programming integer quadratic programming Territory design Location Valid inequalities

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Assessing the Yearly Impact of Wind Power Through a New Hybrid Deterministic/Stochastic Unit Commitment

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IEEE TRANSACTIONS ON POWER SYSTEMS 2011年第1期26卷 401-410页

作者： Restrepo, Jose F. Galiana, Francisco D. McGill Univ Dept Elect & Comp Engn Montreal PQ H3A 2A7 Canada

This paper proposes a new unit commitment (UC) formulation for a power system with significant levels of wind generation. The proposed scheme departs from existing unit commitments in that it explicitly models the day-ahead predicted residual demand probability density function (PDF) including the effect of wind power curtailment. This PDF is then used to define a constraint on the probability of the residual demand exceeding the scheduled reserve, which is imposed in addition to the standard N-1 deterministic security criterion. This hybrid probabilistic/deterministic form maintains the mixed-integer linear structure that makes the proposed UC compatible with highly efficient commercially available solvers. Numerical examples illustrate the economical and technical benefits obtained by systematically including wind curtailment as decisions variables in the UC. In addition, the paper computes the hourly day-ahead UC schedule over the course of one year for a typical power system to illustrate the impact of wind power penetration on measures such as operation costs, incremental costs, emission levels, on/off unit switching operations, and reserve levels.

关键词： mixed-integer linear programming probabilistic security reserve unit commitment wind power

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Predicting Metabolic Fluxes Using Gene Expression Differences As Constraints

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IEEE-ACM TRANSACTIONS ON COMPUTATIONAL BIOLOGY AND BIOINFORMATICS 2011年第1期8卷 206-216页

作者： van Berlo, Rogier J. P. de Ridder, Dick Daran, Jean-Marc Daran-Lapujade, Pascale A. S. Teusink, Bas Reinders, Marcel J. T. Delft Univ Technol Fac Elect Engn Math & Comp Sci Delft Bioinformat Lab NL-2628 CD Delft Netherlands Kluyver Ctr Genom Ind Fermentat NL-2628 BC Delft Netherlands Delft Univ Technol Ind Microbiol Grp Dept Biotechnol NL-2628 CD Delft Netherlands Vrije Univ Amsterdam Fac Earth & Life Sci Syst Bioinformat IBIVU NL-1081 HV Amsterdam Netherlands

A standard approach to estimate intracellular fluxes on a genome-wide scale is flux-balance analysis (FBA), which optimizes an objective function subject to constraints on (relations between) fluxes. The performance of FBA models heavily depends on the relevance of the formulated objective function and the completeness of the defined constraints. Previous studies indicated that FBA predictions can be improved by adding regulatory on/off constraints. These constraints were imposed based on either absolute [21], [3] or relative [20] gene expression values. We provide a new algorithm that directly uses regulatory up/down constraints based on gene expression data in FBA optimization (tFBA). Our assumption is that if the activity of a gene drastically changes from one condition to the other, the flux through the reaction controlled by that gene will change accordingly. We allow these constraints to be violated, to account for posttranscriptional control and noise in the data. These up/down constraints are less stringent than the on/off constraints as previously proposed. Nevertheless, we obtain promising predictions, since many up/down constraints can be enforced. The potential of the proposed method, tFBA, is demonstrated through the analysis of fluxes in yeast under nine different cultivation conditions, between which approximately 5,000 regulatory up/down constraints can be defined. We show that changes in gene expression are predictive for changes in fluxes. Additionally, we illustrate that flux distributions obtained with tFBA better fit transcriptomics data than previous methods. Finally, we compare tFBA and FBA predictions to show that our approach yields more biologically relevant results.

关键词： Gene expression data mixed-integer linear programming optimization function FBA

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Using the analytic center in the feasibility pump

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OPERATIONS RESEARCH LETTERS 2011年第5期39卷 310-317页

作者： Baena, Daniel Castro, Jordi Univ Politecn Cataluna Dept Stat & Operat Res ES-08034 Barcelona Catalonia Spain

The feasibility pump (FP) has proved to be a successful heuristic for finding feasible solutions of mixed integer linear problems. Briefly. FP alternates between two sequences of points: one of feasible solutions for the relaxed problem, and another of integer points. This short paper extends FP, such that the integer point is obtained by rounding a point on the (feasible) segment between the computed feasible point and the analytic center for the relaxed linear problem. (C) 2011 Elsevier B.V. All rights reserved.

关键词： Analytic center Interior-point methods mixed-integer linear programming Feasibility problem Primal heuristics

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Time representations and mathematical models for process scheduling problems

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COMPUTERS & CHEMICAL ENGINEERING 2011年第6期35卷 1038-1063页

作者： Mouret, Sylvain Grossmann, Ignacio E. Pestiaux, Pierre Carnegie Mellon Univ Dept Chem Engn Pittsburgh PA 15213 USA Total Refining & Mkt Res Div F-76700 Harfleur France

During the last 15 years, many mathematical models have been developed in order to solve process operation scheduling problems, using discrete or continuous-time representations. In this paper, we present a unified representation and modeling approach for process scheduling problems. Four different time representations are presented with corresponding strengthened formulations that rely on exploiting the non-overlapping graph structure of these problems through maximum cliques and bicliques. These formulations are compared, and applied to single-stage and multi-stage batch scheduling problems, as well as crude-oil operations scheduling problems. We introduce three solution methods that can be used to achieve global optimality or obtain near-optimal solutions depending on the stopping criterion used. Computational results show that the multi-operation sequencing time representation is superior to the others as it allows efficient symmetry-breaking and requires fewer priority-slots, thus leading to smaller model sizes. (C) 2010 Elsevier Ltd. All rights reserved.

关键词： Time representations Batch scheduling Crude-oil scheduling mixed-integer linear programming

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A model for optimization of process integration investments under uncertainty

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ENERGY 2011年第5期36卷 2733-2746页

作者： Svensson, Elin Stromberg, Ann-Brith Patriksson, Michael Chalmers Univ Technol Environm & Energy Dept SE-41296 Gothenburg Sweden Univ Gothenburg Dept Math Sci SE-41296 Gothenburg Sweden Chalmers Univ Technol Dept Math Sci SE-41296 Gothenburg Sweden

The long-term economic outcome of energy-related industrial investment projects is difficult to evaluate because of uncertain energy market conditions. In this article, a general, multistage, stochastic programming model for the optimization of investments in process integration and industrial energy technologies is proposed. The problem is formulated as a mixed-binary linear programming model where uncertainties are modelled using a scenario-based approach. The objective is to maximize the expected net present value of the investments which enables heat savings and decreased energy imports or increased energy exports at an industrial plant. The proposed modelling approach enables a long-term planning of industrial, energy-related investments through the simultaneous optimization of immediate and later decisions. The stochastic programming approach is also suitable for modelling what is possibly complex process integration constraints. The general model formulation presented here is a suitable basis for more specialized case studies dealing with optimization of investments in energy efficiency. (C) 2011 Elsevier Ltd. All rights reserved.

关键词： Process integration Multistage stochastic programming mixed-integer linear programming Scenario-based modelling Decision support Investment planning

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