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An iterative two-stage PSCOPF method considering line fault uncertainty under typhoon influence

IET RENEWABLE POWER GENERATION 2024年第0期

作者： Zhou, Ke Wu, Lifang Mo, Zhiyue Zhang, Biyun China Southern Power Grid Guangxi Power Grid Co Lt Elect Power Sci Res Inst Nanning Peoples R China

Typhoon weather poses a significant threat to the security and stability of the power system, as it can potentially lead to the disconnection of transmission lines. Concurrently, there exists substantial uncertainty regarding which specific lines may become disconnected under such weather conditions. The preventive security constrained optimal power flow (PSCOPF) is one of the main methods to address this issue. However, the current PSCOPF exhibits low computational efficiency due to the requirement of analysing all line faults through the N-1 check. Therefore, this paper proposes a PSCOPF method based on two-stage optimization. Firstly, the concentric relaxation method is employed to screen and obtain the critical line faults, thereby reducing the total quantity of security constraints associated with N-1 line fault scenarios. Secondly, the incorporation of scenario transition constraints is introduced to decompose the PSCOPF model into OPF (optimal power flow) models under N-0 scenarios and N-1 critical line fault scenarios, then solve iteratively to achieve multi-scenario decoupling. Finally, the proposed method was validated on the IEEE30 test system to demonstrate its capability to ensure economics in the N-0 scenario and security in N-1 scenarios. Typhoon weather poses a significant threat to the security and stability of the power system, as it can potentially lead to the disconnection of transmission lines. Concurrently, there exists substantial uncertainty regarding which specific lines may become disconnected under such weather conditions. Therefore, an iterative PSCOPF solution method based on two-stage optimization is proposed to address the problem of low efficiency in the existing PSCOPF method. image

关键词： computational complexity constraint handling disasters load flow non-linear programming power system economics power system security power transmission faults transmission networks uncertain systems

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Single-vendor single-buyer multi-product economic production quantity problem with stochastic constraints: a modified generalized elimination method

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JOURNAL OF THE OPERATIONAL RESEARCH SOCIETY 2024年

作者： Gharaei, Abolfazl Amjadian, Alireza Sebt, Mohammad Vahid Tirkolaee, Erfan Babaee Univ Toronto Toronto ON Canada Kharazmi Univ Tehran Iran Istinye Univ Istanbul Turkiye Yuan Ze Univ Taoyuan Taiwan Western Caspian Univ Baku Azerbaijan Dalhousie Univ Dept Ind Engn Halifax NS Canada

This study designs a single-buyer single-vendor multi-product Economic Production Quantity (EPQ) model to optimize the total cost in an inventory system. To do so, a non-linear programming (NLP) model is developed considering a set of stochastic constraints on space or warehouse capacity, backordering cost, procurement, ordering, and obtainable budget. A modified Generalized Elimination Method (GEM) is then offered to treat the complexity of the model wherein the variables are eliminated by adding two equations. The developed method generates much more high-quality solutions compared with the classic GEM, while the number of iterations slightly increases. Three problem instances in different scales are then taken into account to assess the efficiency of the modified GEM in terms of optimality criteria. The results demonstrate that the modified GEM has an excellent performance with respect to optimal solutions, infeasibility, number of iterations, complementarity, and errors of optimality. Finally, the behavior of the objective function is analyzed against order quantity fluctuations to draw out practical implications.

关键词： Economic production quantity non-linear programming inventory management backordering generalized elimination method

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Optimal power flow with security operation region

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INTERNATIONAL JOURNAL OF ELECTRICAL POWER & ENERGY SYSTEMS 2021年 124卷 106272-106272页

作者： Ferreira, Jhonatan S. de Oliveira, Edimar J. de Paula, Arthur N. de Oliveira, Leonardo W. Passos Filho, Joao A. Fed Univ Juiz De Fora UFJF Juiz De Fora Brazil

This paper presents an approach to include security constraints in the Optimal Power Flow (OPF) problem aiming at providing a power system operation in safe region. The proposed operating region is formed by elliptical wraps that enclose historical and safe system operative states, which include wind power generation and demand scenarios. The wraps are obtained through a proposed non-linear programming (NLP) problem that defines the ellipse's shape by using nodal voltages at buses of interest. In addition, the proposed approach can determine the operational risk, that is, the risk of an operative state leaving the safety region, by applying a relaxation method. The proposed methodology is tested in the 39-bus New England system and 118-bus IEEE test system. The results show that the elliptical wraps are effective to enclose the secure operational states and maintain the system within a safe region.

关键词： Secure operation region Optimal power flow non-linear programming Security constraints Elliptical wraps

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On Minimisation of Earthing System Touch Voltages

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ENERGIES 2019年第20期12卷 3838页

作者： Vycital, Vaclav Ptacek, Michal Topolanek, David Toman, Petr Brno Univ Technol Fac Elect Engn & Commun Dept Elect Power Engn Brno 60190 Czech Republic

Finding cost efficient earthing system design with acceptable level of safety might be quite tedious work. Thus, many earthing system engineers try to find the most suitable design either by employing only their best experience or taking advantage of some more complex optimisation programs. Although both approaches might work well under certain circumstances, they might fail either due to counter-intuitiveness of the specific situation or by misunderstanding of the applied optimisation method, its limitations etc. Thus, in this paper, the earthing system design optimisation problem was addressed by analysing optimisation simulation results together with conducted sensitivity analysis. In the paper, a simple double ring earthing system was optimised while using five different optimisation methods. The earthing system was placed in different horizontally stratified soil models and the earthing system was optimised by minimising touch voltages instead of commonly minimised earth potential rise. The earthing system was modelled by Ansys Maxwell software. Apart from using Ansys Maxwell built-in optimisers, the possible solution space has also been mapped by performing sensitivity analysis with changing the earthing system design dimensions and the results of optimisation were compared and validated. It was found out that the Sequential non-linear programming Optimisation technique was quite superior to the other techniques. Additionally, in most cases, the Ansys Maxwell optimiser was able to found optimal solution;however, in some cases, based on the initial conditions, it might get stuck in local minima or the results might be influenced by the solution noise. Additionally, some quite non intuitive dependencies of earthing system electrodes positions had been found when different spatial dimensions constraints are used.

关键词： earthing earthing system optimisation Ansys Maxwell sensitivity analysis touch voltage non-linear programming

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Analysis of Numerical Methods to Include Dynamic Constraints in an Optimal Power Flow Model

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ENERGIES 2019年第5期12卷 885-885页

作者： Arredondo, Francisco Daniel Castronuovo, Edgardo Ledesma, Pablo Leonowicz, Zbigniew Univ Carlos III Madrid Dept Elect Engn Av Univ 30 Leganes 28911 Spain Wroclaw Univ Sci & Technol Fac Elect Engn PL-50370 Wroclaw Poland

The optimization of the operation of power systems including steady state and dynamic constraints is efficiently solved by Transient Stability Constrained Optimal Power Flow (TSCOPF) models. TSCOPF studies extend well-known optimal power flow models by introducing the electromechanical oscillations of synchronous machines. One of the main approaches in TSCOPF studies includes the discretized differential equations that represent the dynamics of the system in the optimization model. This paper analyzes the impact of different implicit and explicit numerical integration methods on the solution of a TSCOPF model and the effect of the integration time step. In particular, it studies the effect on the power dispatch, the total cost of generation, the accuracy of the calculation of electromechanical oscillations between machines, the size of the optimization problem and the computational time.

关键词： power system transient stability economic dispatch numerical integration methods non-linear programming optimal power flow

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Optimal Design of Heat-Integrated Water Allocation Networks

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ENERGIES 2019年第11期12卷 2174页

作者： Kermani, Maziar Kantor, Ivan D. Marechal, Francois EPFL Valais Wallis IPESE Grp CH-1951 Sion Switzerland

Industrial operations consume energy and water in large quantities without accounting for potential economic and environmental burdens on future generations. Consumption of energy (mainly in the form of high pressure steam) and water (in the form of process water and cooling water) are essential to all processes and are strongly correlated, which requires development of systematic methodologies to address their interconnectivity. To this end, the subject of heat-integrated water allocation network design has received considerable attention within the research community in recent decades while further growth is expected due to imposed national and global regulations within the context of sustainable development. The overall mathematical model of these networks has a mixed-integer nonlinear programming formulation. As discussed in this work, proposed models in the literature have two main difficulties dealing with heat-water specificities, which result in complex formulations. These difficulties are addressed in this work through proposition of a novel nonlinear hyperstructure and a sequential solution strategy. The solution strategy is to solve three sub-problems sequentially and iteratively generate a set of potential solutions through the implementation of integer cut constraints. The novel mathematical approach also lends itself to an additional innovation for proposing multiple solutions balancing various performance indicators. This is exemplified with both a literature test case and an industrial-scale problem. The proposed solutions address a variety of performance indicators which guides decision-makers toward selecting the most appropriate configuration(s) among a large number of potential possibilities. Results exhibit that despite having a sequential solution strategy, better performance can be reached compared to previous approaches with the additional benefit of providing many potential solutions for further consideration by decision-makers to select the

关键词： mathematical programming superstructure optimization solution strategy heat-integrated water allocation network non-linear programming non-isothermal mixing industrial application

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Workforce and task optimization to guarantee oxygen bottling under a COVID-19 pandemic scenario: A Chilean case study

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INTERNATIONAL JOURNAL OF PRODUCTION ECONOMICS 2024年 271卷

作者： Severino, Gonzalo Rivera, Jose Parot, Roberto Otaegui, Ernesto Fuentes, Andres Reszka, Pedro Univ Tecn Federico Santa Maria Dept Ind Valparaiso Chile Univ Calif Berkeley Dept Mech Engn Berkeley CA 94720 USA Air Liquide Chile Santiago Chile Univ Adolfo Ibanez Fac Engn & Sci Santiago Chile

This work describes an optimization model to analyze the response of a Chilean oxygen-bottling plant to disruptions induced by large external events such as the COVID-19 pandemic. The model addresses employee shift scheduling, machine scheduling with setup times, production scheduling and inventory management, thus being non-linear, although resolved in reasonable computation times. The workers are assumed to have the same training and skills for a specific task, and to behave homogeneously from the psychological and physical perspectives. The objective function minimizes the cost of bottling oxygen, using monthly average of deaths as a proxy variable to model oxygen demand. The results obtained with this model suggest optimizing task assignments as a short-term solution to satisfy an increased oxygen demand representative of a pandemic scenario, while an additional long-term solution is installing a second cryogenic tank. Considering the latter solution, the model allows to quantify the number of workers necessary to operate an enlarged plant. An updated qualifications matrix coupled with an optimized schedule shows that the number of workers required under these conditions does not have to be doubled, but would have to be increased by only one worker.

关键词： Staff scheduling Production Workforce planning COVID-19 non-linear programming

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A single machine EPQ inventory model for a multi-product imperfect production system with rework process and auction

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International Journal of Advanced Logistics 2016年第3-4期5卷 141-152页

In this paper, a multi-product Economic Production Quantity (EPQ) inventory model for a defective production system by a single machine is considered. The faulty produced products are reworked or are put on auction as they are. The aim of this research is to determine the optimal cycle length and the percentage of reworking every fault product such that the total inventory cost, including setup, production, holding, reworking, and lost profit, is minimized. We have proved that this problem is a convex non-linear programming method. Therefore, we came up with the exact algorithm based on differentiation to solve it. Finally, a sensitivity analysis is performed to evaluate the effect of changes in different parameters of the problem.

关键词： EPQ model imperfect production system non-linear programming lost profit

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Optimization and Control in Automated Design

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IFAC Proceedings Volumes 1996年第1期29卷 1134-1139页

作者： Haroutiun A. Terzian Doctor of Sciences Professor Member of National Academy of Sciences vice-president of State Engineering University of Armenia

The statement and features of design problem are considered, and methods for search optimization are discussed. A comparative analysis of certain methods for optimization is given based on the results of more than 80 thousand numerical experiments. The problems of optimization methods adaptation to mathematical models of the systems under design are elucidated.

关键词： non-linear programming search methods optimization design control

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A Relaxation Type Two-Level Method for State Constrained Dynamic Optimization Problems

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IFAC Proceedings Volumes 1978年第1期11卷 2041-2047页

作者： Juhani Hirvonen Lauri Hakkala Helsinki University of Technology Systems Theory Laboratory 02150 Espoo 15 Finland

A new relaxation type two-level method for solving state space constrained dynamic optimization problems is suggested. The method is closely related to the hierarchical approach and on the other hand it can be viewed as an application of the Hestenes-Powell method of multipliers. The state space constrained original problem is transformed into a control constrained first level problem by using the multiplier method. As in the hierarchical approach the first level problem is dependent on certain Lagrange multiplier type parameters which are determined at the second level. A coordination type iteration process between the two levels results in the solution of the original state constrained, optimization problem. The convergence properties of the method are studied via numerical experiments; analytical convergence results are not available so far.

关键词： Optimal control constrained optimization non-linear programming two-level methods multiplier methods iterative methods

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