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Transformer Fleet Optimal Maintenance with Risk Considerations

ELECTRIC POWER COMPONENTS AND SYSTEMS 2019年第16-17期47卷 1551-1561页

作者： Alves da Silva, Alexandre P. Ducharme, Christian Ferreira, Vitor H. Vale SA Strategy & Technol Div Av Praia Botafogo 186 Tone Oscar Niemeyer 16 BR-22250040 Rio De Janeiro RJ Brazil Elect Energy Res Ctr CEPEL Rio De Janeiro Brazil Fluminense Fed Univ UFF Engn Sch Niteroi RJ Brazil

This paper aims at proposing an optimization model for high voltage transformers' maintenance scheduling to minimize operational cost and risk. The focus of the paper is on the transformer fleet management, and not on a single transformer maintenance procedure or the evaluation of a single transformer failure risk. The proposed methodology takes as inputs the importance (e.g., based on the expected energy not supplied) and failure risk of each transformer (e.g., based on on-line Dissolved Gas Analysis), and the maintenance cost for each transformer. It also considers the main practical constraints in field interventions. As output, the proposed methodology provides the best timing for the maintenance of each transformer from the fleet of interest. The problem has been modeled as mixed-integer linear programming. Eleven months of real data from the Brazilian transmission system are used for setting up the recent history of outages. The following year data are employed to test the effectiveness of the optimization model. The output of the proposed fleet maintenance scheduling tool is the optimum viable intervention calendar for a power transformer fleet within a 52-week horizon. This proposal represents an innovative and robust solution, which can support the operational planning experts' decision-making process.

关键词： asset performance management maintenance scheduling maintenance planning reliability centered maintenance risk analysis reliability optimization mixed-integer linear programming power transformers dissolved gas analysis

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Double-layer optimization of home energy management systems with volt-watt functions

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IEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING 2019年第5期14卷 705-715页

作者： Van Tu Dao Ishii, Hideo Hayashi, Yasuhiro Waseda Univ ACROSS Shinjuku Ku 1-104 Totsukamachi Tokyo 1698050 Japan

The increasing number of rooftop solar panels and home-scale batteries in residential areas enables an emerging energy market for homeowners to take part in. By optimizing the energy usage at home, the surplus amount can be exported to the grid for selling to intermediaries like aggregators at a higher price than a feed-in tariff set by the government. Though not trading with the power utility, the resulting reverse power flow may cause the service voltage to increase and violate the set upper limit. To avoid this problem, the utility asks all grid-connected inverters to reduce the reverse power by installing volt-watt functions. Unfortunately, this kind of function may reduce the profits of the homeowners since the exported energy cannot match the amount committed to the aggregator. Our research addresses this issue by proposing a double-layer optimization for each home energy management system. The first layer optimizes the one-day home energy usage with consideration of uncertainty in the predicted data of load and solar irradiance to estimate the highest home profit as possible. Then, the second layer tries to reduce the high reverse power with minimal impact on the profit found in the first layer. A simulation of a distribution system shows that the proposed method is able to flatten the power profile flowing reversely to the grid and reduce the drawbacks of volt-watt functions. Homeowners are recommended to practice the proposed method when trading the surplus energy. (c) 2018 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

关键词： active power curtailment home energy management system mixed-integer linear programming stochastic programming volt-watt functions

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Economic and environmental benefits of recovery networks for WEEE in Europe

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JOURNAL OF CLEANER PRODUCTION 2019年 222卷 655-668页

作者： Messmann, Lukas Helbig, Christoph Thorenz, Andrea Tuma, Axel Univ Augsburg Resource Lab Univ Str 16 D-86159 Augsburg Germany

The EU directive on Waste Electrical and Electronic Equipment (WEEE) imposes the obligation to collect a large share of the end-of-life products on electronics manufacturers. Environmental aspects, however, are often considered only rudimentarily. Based on previous research and real-world data, a mixed integer linear programming (MILP) model of a European reverse network for WEEE is developed, including collection, high-value recovery, or third-party collection and recycling. The results comprise optimal network decisions and corresponding opportunity costs for economic and 21 environmental categories (18 midpoints, 3 endpoints). The evaluation of the environmental impact is based on data from the ecoinvent database, characterized using the ReCiPe 2016 Life Cycle Impact Assessment (LCIA) method. The results unveil conflicts and congruencies between the objectives. Collection and high-value recovery are preferable in up to six countries for economically optimal networks and in up to 15 countries with optimal benefit for global warming and fossil resource depletion. Discrepancies in objective values are larger between economic and most of the environmental solutions than in between most of the environmental ones. The dimensions land use and freshwater eutrophication show the least conflicts with the economic rationale. Solutions for mineral resource depletion prefer third-party collection and recycling. Conflicts between solutions are resolved by the e-constraint method. Sensitivity analyses show the robustness of key findings. This study emphasizes the importance of a broad assessment of environmental impacts as well as mutual economic and environmental opportunity costs in large-scale recovery networks for WEEE. (C) 2019 Elsevier Ltd. All rights reserved.

关键词： Reverse network design Life Cycle Impact Assessment WEEE mixed-integer linear programming

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Optimization model for long-distance integrated transmission of wind farms and pumped-storage hydropower plants

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APPLIED ENERGY 2019年 242卷 285-293页

作者： Su, Chengguo Cheng, Chuntian Wang, Peilin Shen, Jianjian Wu, Xinyu Dalian Univ Technol Inst Hydropower & Hydroinformat Dalian 116024 Peoples R China Yellow River Conservancy Tech Inst Sch Hydraul Engn Kaifeng 475004 Peoples R China

Long-distance and large-capacity wind power transmission from western and northern China to load centers through ultra-high voltage (UHV) transmission lines is an important and effective measure for large-scale wind power accommodation in China. This paper proposes a novel practical integrated transmission mode for a wind farm (WF) and a pumped-storage hydropower plant (PSHP). In order to cope with additional imbalance costs caused by deviations from the submitted day-ahead schedule and increase the total operational profit, an optimization model for the integrated transmission of a WF and a PSHP has been formulated. The forecast errors for wind power generation are modeled by a scenario analysis technique. Hydraulic constraints and the head effect on the performance of each pumped-storage hydropower unit (PSHU) in both generating and pumping modes have been considered. Through incorporating the nonlinearities, including constraints on the operation status of units and turbine performance curves, the model is converted into a mixed-integer linear programming (MILP) formulation using piecewise linear approximation techniques. Case studies demonstrate that the integrated transmission of the WF and PHSP can efficiently alleviate the negative effect of wind power fluctuations and significantly increase profit. Sensitivity analyses have been carried out to evaluate the effect of the penalty factor for energy imbalance and the electricity price mechanism in the receiving-end power grid on the overall performance of the WF-PSHP union.

关键词： Integrated transmission Wind farm Pumped-storage hydropower plant Wind power forecast errors mixed-integer linear programming

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Optimal mathematical programming for the warehouse location problem with Euclidean distance linearization

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COMPUTERS & INDUSTRIAL ENGINEERING 2019年 136卷 70-79页

作者： You, Meng Xiao, Yiyong Zhang, Siyue Yang, Pei Zhou, Shenghan Beihang Univ Sch Reliabil & Syst Engn Beijing 100191 Peoples R China

The warehouse location problem (WLP) involves determining one (or multiple) locations as the materials/products collecting/distributing centers for serving a group of customers scattered geographically in a region, at a minimum total transportation cost. The most conventional and widely used approach for solving the WLP is the weighted k-means algorithm. However, this is not a global approach, because it always traps into local optima and is sensitive to the initial settings. Our numeric examples demonstrated that the solutions obtained by the weighted k-means could depart from the optimal values by as much as 16.8% on average. In this paper, we present an optimal programming approach based on mixed-integer linear programming (MILP) for the WLP, which is irrelative to the initial solution and can be optimally solved by commercial solvers. For large-sized datasets, we developed an MILP-based dynamic iterative partial optimization (MILP-DIPO) to search for the near-optimal results with controllable computational time. Experiments on 14 datasets, including 6 small-sized synthesized datasets and 8 variants of the known benchmark datasets in the UEF repository, were performed to validate the proposed model and heuristics. The computational results confirm that improvements with the proposed method could be as great as -22.9% (-14.0% on average) for small-sized datasets. For the eight benchmark datasets, the MILP-DIPO algorithm delivered near-optimal solutions in a reasonable computational time, with up to - 8.0% (- 2.6% on average) improvement compared to the results obtained by the conventional weighted k-means algorithm.

关键词： Warehouse location problem mixed-integer linear programming Clustering Optimization

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A multi-stage supply chain network design problem with in-house production and partial product outsourcing

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APPLIED MATHEMATICAL MODELLING 2019年 70卷 572-594页

作者： Cortinhal, M. J. Lopes, M. J. Melo, M. T. Univ Inst Lisbon ISCTE IUL Av Forcas Armadas P-1649026 Lisbon Portugal Univ Lisbon Fac Ciencias CMAF CIO P-1749016 Campo Grande Portugal Saarland Univ Appl Sci Business Sch Waldhausweg 14 D-66123 Saarbrucken Germany

We propose a mixed-integer linear programming model for a novel multi-stage supply chain network design problem. Our model integrates location and capacity choices for plants and warehouses with supplier and transportation mode selection, and the distribution of multiple products through the network. The aim is to identify the network configuration with the least total cost subject to side constraints related to resource availability, technological conditions, and customer service level requirements. In addition to in-house manufacturing, end products may also be purchased from external sources and consolidated in warehouses. Therefore, our model identifies the best mix between in-house production and product outsourcing. To measure the impact of this strategy, we further present two additional formulations for alternative network design approaches that do not include partial product outsourcing. Several classes of valid inequalities tailored to the problems at hand are also proposed. We test our models on randomly generated instances and analyze the trade-offs achieved by integrating partial outsourcing into the design of a supply chain network against a pure in-house manufacturing strategy, and the extent to which it may not be economically attractive to provide full demand coverage. (C) 2019 Elsevier Inc. All rights reserved.

关键词： Supply chain network design In-house production Product outsourcing Transportation mode selection Single-assignment mixed-integer linear programming

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Increased utilisation of renewable energies through demand response in the water supply sector - A case study

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ENERGY 2019年 175卷 810-817页

作者： Meschede, Henning Univ Kassel Dept Sustainable Prod & Proc Kassel Germany

Renewable energy systems (RES) play a key role in sustainable energy supply systems. Due to the volatile nature of RES, storage capacities and demand shifting strategies must be implemented. In remote areas like islands, the water supply sector mainly consisting of desalination plants and wells has a significant impact on the energy system. The objective of this paper is the evaluation of the demand shifting potential within this sector with respect to its robustness against probabilistic influencing variables. mixed integer linear programming is used to simulate the optimised dispatch. Compared to the total annual electricity demand of the island, the study shows that up to 2.1% (1.5 GWh) positive and 5.0% (3.6 GWh) negative demand shifting potential can be assumed if only existing plants are used. Utilisation of micro pumped hydro storage can increase these potentials to 5.5% (4.2 GWh) in positive and 10.3% (7.9 GWh) in negative direction. Furthermore, probabilistic solar radiation has no significant influence on the DR potential while for wind power a saturation of the DR potential for higher degrees of self-sufficiency can be found. Nevertheless, the absolute highest degrees of self-sufficiency come along with the utilisation of both photovoltaic (PV) and wind. (C) 2019 Elsevier Ltd. All rights reserved.

关键词： Demand response Water supply Sector coupling mixed-integer linear programming Island energy system Smart energy system

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Scheduling ships movements within a canal harbor

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SOFT COMPUTING 2019年第9期23卷 2923-2936页

作者： Pellegrini, Paola di Tollo, Giacomo Pesenti, Raffaele Univ Lille Nord de France IFSTTAR COSYS LEOST 20 Rue Elisee ReclusBP 70317 F-59666 Villeneuve Dascq France Ca Foscari Univ Venice Dept Management Cannaregio 873 I-30121 Venice Italy

In this paper we propose a model for the in-port ship scheduling problem that consists in scheduling the movement of ships inside a canal harbor. Our model, which we name RECIP-MILP, is inspired by a model for scheduling trains, to exploit the analogies between a canal harbor and a single track railway network. Moreover, we show how to translate spatial safety constraints into time ones. We apply our model to instances representing ship movements in the Port of Venice. We test the performance of both the exact RECIP-MILP model and a heuristic solution algorithm based on it. We show that we can exactly solve most instances in few minutes.

关键词： In-port ship scheduling problem Ship scheduling mixed-integer linear programming Venice

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Surgical case scheduling with sterilising activity constraints

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INTERNATIONAL JOURNAL OF PRODUCTION RESEARCH 2019年第10期57卷 2984-3002页

作者： Al Hasan, Hasan Gueret, Christelle Lemoine, David Rivreau, David Univ Angers LARIS Angers France IMT Atlantique LS2N Nantes France Univ Catholique Ouest LARIS Angers France

In this paper, we study a real scheduling problem which consists in scheduling a set of elective surgical cases requiring surgical instruments and tools in several operating rooms. The objectives are to minimise the overtime of the surgical unit staff, the number of operating rooms used and the number of instruments processed in emergency in the sterilising unit while respecting the current level of service represented by the total number of patients operated per month at the orthopaedic surgery unit. This research was performed in collaboration with the University Hospital of Angers in France (CHU Angers), which has also provided historical data for the experiments. We propose a mixed integer linear programming model for the problem which is solved in a lexicographic fashion. We also propose a robust formulation to deal with the uncertain surgery durations. Both the deterministic and robust formulations are then compared over a set of instances provided by the CHU. The solutions obtained are competitive in terms of number of operating rooms and significantly improve those implemented operationally at the CHU in terms of overtime and emergencies at the sterilising unit.

关键词： operating rooms in health services elective surgeries planning sterilisation unit scheduling mixed-integer linear programming robust optimisation

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Flexible feeder interconnections for increased penetration of renewables and improved volt/VAr control in distribution networks

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IET GENERATION TRANSMISSION & DISTRIBUTION 2019年第21期13卷 4861-4869页

作者： Baghban-Novin, Salar Golshannavaz, Sajjad Nazarpour, Daryoush Hamidi, Amir Urmia Univ Elect Engn Dept Orumiyeh Iran

In this study, a daily distribution management system (DMS) is developed, which utilises the potential of soft open points (SOPs) to enhance the renewable share in power provision task. The active and reactive power contributions of SOPs, as a flexible interconnection, amend the voltage security issues due to high penetration of photovoltaics (PVs). A complete model for SOP is developed to address the conduction and switching losses that affect the technical and economic operation indices. The optimal scheduling framework of DMS is linearly modelled within mixed-integer linear programming to lower the computational burden of the problem. Case studies are carried out on IEEE 33-node system to illustrate and verify the effectiveness of the proposed model. The comparative analysis shows a lower operation cost besides the improved voltage profile and the reduced losses of the whole system. The effective collaboration of PVs and dispatchable distributed generations (DDGs) assisted by the SOPs power processes causes higher penetration of PVs and enhanced the exploitation of DDGs results in a 9.8% increment of PV power exploitation and improved power factor of DDGs operation.

关键词： integer programming scheduling distributed power generation photovoltaic power systems reactive power linear programming optimisation reactive power control voltage control power distribution control power system security distribution networks renewable share power provision task active power contributions reactive power contributions SOP flexible interconnection voltage security issues switching losses technical operation indices economic operation indices optimal scheduling framework DMS mixed-integer linear programming computational burden IEEE 33-node system lower operation cost improved voltage profile reduced losses dispatchable distributed generations SOPs power processes higher penetration PV power exploitation power factor DDGs operation flexible feeder interconnections distribution networks daily distribution management system soft open points

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