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Transient circuit simulation of arc-free current breaking by resistance rise
Dareer Bin Khalid, Michael Rock, Luigi Piegari, 2021, original scientific article

Abstract: There has been intensive research and development in the field of Circuit breakers, whether DC and AC, or low voltage and high voltage. The result of this has led to the production of highly reliable circuit breakers that accompany a built-in arc extinguishing system. However, the purpose of this study is to give the basics for arc-free current breaking with fast interruption of fault currents, e.g., in surge protective devices (SPD) for AC and DC systems, by means of a time-dependent resistor with fast rising resistance. This investigation shall illustrate how the current can be driven almost to zero with a steadily time increasing resistance, and interrupted completely without an electric arc. The basic aim of the conducted transient circuit simulations is to determine suitable time functions for the current or resistance and necessary initial and final resistances. This paper will discuss the "optimisation conditions", a switching time as short as possible, small switch-off overvoltage, and possibly an energy conversion in the resistor as low as possible is set using ATP-EMTP and analytical calculations.
Keywords: current breaking, ATP-EMTP, time-dependent resistance, optimisation, concave functions, convex functions
Published in DKUM: 13.11.2023; Views: 247; Downloads: 3
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The use of differential evolution to determine maximum generation and load values in the distribution network
Eva Tratnik, Janez Ribič, Matej Pintarič, Miran Rošer, Gorazd Štumberger, Miloš Beković, 2022, original scientific article

Abstract: By integrating renewable energy sources into the existing distribution network, the characteristics and local stability of the network is highly impacted. The network, which was built with the goal of a directed energy flow from large conventional sources connected to the transmission network via the distribution network to consumers, can change the direction of the energy flow. The adoption of environmental commitments and directives encourages the integration of local dispersed energy sources, which can worsen voltage conditions in the distribution network. To avoid excessive local production, distribution network operators must limit the installation of new generati on units, as it is necessary to take into account the quality of power supply by monitoring its network parameters, such as the appropriate voltage profi le and the rati o between acti ve and reacti ve power. On the other hand, excessive loads due to the mass transiti on of household heati ng and transport towards electricity can also pose a problem for high-quality electricity supply due to the excessive voltage drop. The arti cle presents an algorithm for determining the maximum size of unit producti on and the maximum load at a node in the distributi on network. Also demonstrated is the use of variable tap transformer technology, which adjusts the tap of the transformer to provide an appropriate voltage profi le in the network. The enti re analysis was performed on a model of a real medium-voltage network, in which solar and hydropower plants are already included. The model was verifi ed by comparing its calculated values with actual measurements. The goal was to determine the size of the unit’s maximum producti on, as well as the size of the maximum load, by using the diff erenti al evoluti on algorithm, while keeping voltage profi les within the permissible limits. The results of the analysis are presented in the article.
Keywords: distribution network, renewable energy sources, optimisation method, voltage profile
Published in DKUM: 30.10.2023; Views: 232; Downloads: 9
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Energy consumption and grid interaction analysis of electric vehicles based on particle swarm optimisation method
Klemen Deželak, Klemen Sredenšek, Sebastijan Seme, 2023, original scientific article

Abstract: The widespread adoption of electric vehicles poses certain challenges to the distribution grid, which refers to the network of power lines, transformers, and other infrastructure that delivers electricity from power plants to consumers. This higher demand can strain the distribution grid, particularly in areas with a high concentration of electric vehicles. Grid operators need to ensure that the grid infrastructure can handle this additional load and prevent overloading and consequences in terms of additional losses. As part of the task, a methodology was developed for the assessment of the electricity consumption of battery electric vehicles in Slovenia. The approach used for the calculation includes the number of electric cars, average consumption, distance travelled and efficiency of the system. Additionally, the results of the modelling approach for an integrated distribution grid model in terms of steady-state simulations are presented. The regular situation of the power losses within the distribution grid is managed together with an optimal result. In this sense, an application of the particle swarm optimisation-based strategy is suggested to minimise reliance on grid systems.
Keywords: electric vehicles, distribution grid, optimisation, power losses
Published in DKUM: 10.10.2023; Views: 223; Downloads: 16
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Editorial: combined water and heat integration in the process industries
Elvis Ahmetović, Ignacio E. Grossmann, Zdravko Kravanja, François Marechal, Jiri Klemeš, Luciana E. Savulescu, Dong Hongguang, 2022, preface, editorial, afterword

Abstract: Water and energy are resources that are used in large quantities in different sectors (domestic, agricultural, and industrial). Based on data on global water and energy consumption in the world over the recent past, as well as forecasts for the coming years, a continuous trend of increasing water and energy consumption can be observed. ...
Keywords: water integration, heat integration, systematic methods, pinch analysis, mathematical programming, heat-integrated water networks, optimisation, process industry
Published in DKUM: 18.08.2023; Views: 230; Downloads: 18
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Simulated global empty containers repositioning using agent-based modelling
Alaa Abdelshafie, Bojan Rupnik, Tomaž Kramberger, 2023, original scientific article

Abstract: Due to an ever-increasing movement of containers across the globe in line with the economic boom, the trade imbalance and issues related to empty containers have become inevitable. Empty containers accumulated at specific ports cannot only generate profit but also increase the environmental footprint. This research proposes a Maritime Empty Container Reposition Modelling Framework by integrating the agent-based modelling (ABM) paradigm to model the global movements of empty containers. An agent-based maritime logistic empty container redistribution model was developed to help minimize the total relevant costs for empty container movement in the planning horizon. In the system, ports, shipping companies, customers, and empty containers were identified as critical agents. Using simulated annealing (SA), shipping line agents were able to optimise empty container repositioning to determine the best sequence for moving containers. The model was applied to the Asia–Middle East region to simulate global empty containers repositioning in the region. The results comparison shows that the proposed optimised empty container repositioning framework can significantly reduce the shipping line’s costs and make full use of empty containers
Keywords: maritime industry, empty containers, repositioning, agent-based modelling, simulation, optimisation
Published in DKUM: 02.08.2023; Views: 211; Downloads: 20
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Considering IT trends for modelling investments in supply chains by prioritising digital twins
Milena Kajba, Borut Jereb, Matevž Obrecht, 2023, original scientific article

Abstract: Supply chain disruptions and challenges have and will always exist, but preparing in advance and improving resilience for the upcoming consequences should be the utmost important goal. This paper explores trends that affect innovation in the technological sphere of supply chain systems. More precisely, the research is focused on Digital Twin technology applicability through other logistics IT trends and aims to research the pressing issue of ensuring the visibility and resilience of future supply chain systems. The paper’s objective is to produce a conceptual model enabling the investment assessment of the necessary IT resources. Initially, a theoretical confirmation of logistics IT trends’ relevance to supply chain systems was established. After, propositions of Digital Twin technology applications to other logistics IT trends were made, which were divided into corresponding constant multitudes of supply chain systems. Lastly, the conceptual model for the investment assessment of the necessary IT resources was derived in the form of a matrix. It considers 16 parameters for investment assessment and applicability to all companies, regardless of their specifics. It also supports the notion of digital IT competencies’ fundamental importance to the continuous operation of supply chain systems.
Keywords: supply chain management, logistics, process optimisation, visibility, resilience, Digital Twin
Published in DKUM: 03.04.2023; Views: 393; Downloads: 48
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Management and logistics : selected topics
Borut Jereb, Mimo Drašković, Irena Gorenak, Sanja Bauk, Maja Fošner, Bojan Rosi, Drago Pupavac, Darja Topolšek, Oleksandr Dorokhov, Uroš Kramar, Željko Ivanović, Marjan Sternad, Matjaž Knez, Sonja Mlaker Kač, Ludmila Malyaretz, Matevž Obrecht, Tina Cvahte Ojsteršek, 2016, scientific monograph

Abstract: The scientific monograph titled Logistics and Management – selected topics is the result of a bilateral project, lasting from 2013 to 2015 and titled “Preparation of a joint scientific monograph in the field of logistics and management issued at the Faculty of Logistics in Celje and the Maritime Faculty of Kotor”. The project was managed by Professor Maja Fošner, PhD, from the Faculty of Logistics at the University of Maribor, and Professor Veselin Draskovic, PdD, from the Maritime Faculty of Kotor, Montenegro. The main goal of the monograph is to give a comprehensive account of selected areas from the field of logistics and challenges in the development of logistics, such as risk management and supply chains, transport cost, competences in logistics, urban logistics, green logistics, seaport cooperation, logistics network optimisation, logistics in tourism, logistics in performance management, systemic logistics providers and solutions to problems of transportation task. Wishing to offer a comprehensive presentation of various areas in the field of logistics, the authors of the monograph contributions, who participated on the project (Maja Fošner, Bojan Rosi, Borut Jereb, Marjan Sternad, Veselin Draskovic (ed.), Mimo Draskovic, Sanja Bauk, Senka Sekulac-Ivosevic), invited to cooperation also other researchers from the Faculty of Logistics and the Maritime Faculty of Kotor (Irena Gorenak, Matjaž Knez, Matevž Obrecht, Sonja Mlaker Kač, Tina Cvahte, Darja Topolsek, Drago Pupavac, Zeljko Ivanovic, Oleksandr Dorokhov, and Ludmila Malyaretz) who enriched the present monograph with their contributions. The monograph is aimed at professional public and anyone interested in the field of logistics. It should also serve as a useful aid in the study of logistics.
Keywords: logistics, management, risk management, supply chains, transport cost, urban logistics, green logistics, seaport cooperation, logistics network, optimisation, logistics in tourism, logistics in performance management, systemic logistics providers
Published in DKUM: 08.05.2018; Views: 1482; Downloads: 229
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This document is also a collection of 14 documents!

Multi-objective synthesis of company’s supply-networks based on integration of renewable resources
Annamaria Vujanović, 2017, doctoral dissertation

Abstract: The aim of this doctoral dissertation was to develop a general methodology for sustainable integration of company's supply networks into nearby regional networks by i) integrating renewables, thereby increasing company's energy self-sufficiency, ii) by performing multi-objective synthesis in order to obtain economically efficient and yet environmentally benign or even unburdening solutions, and iii) to perform dynamic and stochastic synthesis under uncertainties in dynamically changing market conditions in order to obtain more reliable and realistic solutions. The research work is directly interlinked with a large-scale European meat producing company Perutnina Ptuj d.d., which is located in the heart of Slovenia. The aim of the first part was to integrate renewables into companies’ supply-networks at regional level in order to maximize the self-sufficiencies of their energy supplies. This concerns companies’ activities from the use of natural resources to supplying their final products to the customers being interlinked with their regional networks. A Mixed-Integer Linear Programming (MILP) model has been developed for the integration of both the companies’ and surrounding regional supply-networks and the utilization of different types of renewables as sources for the companies’ energy supplies. The potential renewable energy sources, which are located within companies surrounding region are solar, biomass, organic and animal wastes. The result indicates that by sufficient integration of renewables into companies’ supply networks, profitable and yet energy self-sufficient solutions can be obtained. The second part presents the multi-objective synthesis of a company’s supply-network by integrating renewables and accounting for several environmental footprints. A previously developed model for achieving energy self-sufficiency by integrating renewables into companies’ supply-networks has been extended for the evaluation of environmental impacts, such as energy, carbon, nitrogen, and water footprints. The achievement of an energy self-sufficient supply-network has been considered whilst significantly reducing environmental impacts. Direct (burdening) and indirect (unburdening) effects that form total effects on the environment are considered for the evaluation of environmental footprints. This approach identifies those alternative energy production technologies that are more profitable and environmentally more benign with significant unburdening capabilities. The results showed significant unburdening of the environment in terms of carbon and nitrogen footprints; however, higher burdening in terms of the water footprint. The third part presents a multi-objective MILP synthesis of a dynamic supply-network under uncertainty applied to the company. The previously-developed multi-objective model for achieving energy self-sufficiency by integrating renewables into companies’ supply-networks has now been extended to account for the dynamic consideration of variable supply and demand over the year, for uncertainties related to products’ demand and sun radiation, and for multi-objective optimisation, in order to obtain the most sustainable company’s supply-network. The sustainable synthesis of a company’s network is performed regarding the integration of the renewables such as biomass and other wastes, and solar energy. The obtained solutions are those reflecting maximal profit, reflecting constantly-changing dynamic market conditions, accounting for several uncertain parameters, and protecting the environment.
Keywords: Company's supply network, Renewables, Environmental Impacts, Dynamic synthesis, Flexibility, Multi-objective optimisation, Uncertainty
Published in DKUM: 21.07.2017; Views: 1531; Downloads: 165
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Multicriteria optimisation in logistics forwarder activities
Tanja Poletan, Alen Jugović, Ratko Zelenika, 2007, original scientific article

Abstract: Logistics forwarder, as organizer and planner of coordination and integration of all the transport and logistics chains elements, uses adequate ways and methods in the process of planning and decision-making. One of these methods analysed in this paper, which could be used in optimisation of transport and logistics processes and activities of logistics forwarder, is the multicriteria optimisation method. Using that method, in this paper is suggested model of multicriteria optimisation of logistics forwarder activities. The suggested model of optimisation is justified in keeping with method principles of multicriteria optimization, which is included in operation research methods and it represents the process of multicriteria optimization of variants. Among many different processes of multicriteria optimization, PROMETHEE (Preference Ranking OrganizationMethod for Enrichment Evaluations) and Promcalc& Gaia V. 3.2., computer program of multicriteria programming, which is based on the mentioned process, were used.
Keywords: traffic, transport, forwarding, logistic chain, planning, optimisation, PROMETHEE
Published in DKUM: 05.06.2017; Views: 1008; Downloads: 146
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