AI and OR in management of operations: history and trends

The last decade has seen a considerable growth in the use of Artificial Intelligence (AI) for operations management with the aim of finding solutions to problems that are increasing in complexity and scale. This paper begins by setting the context for the survey through a historical perspective of OR and AI. An extensive survey of applications of AI techniques for operations management, covering a total of over 1200 papers published from 1995 to 2004 is then presented. The survey utilizes Elsevier's ScienceDirect database as a source. Hence, the survey may not cover all the relevant journals but includes a sufficiently wide range of publications to make it representative of the research in the field. The papers are categorized into four areas of operations management: (a) design, (b) scheduling, (c) process planning and control and (d) quality, maintenance and fault diagnosis. Each of the four areas is categorized in terms of the AI techniques used: genetic algorithms, case-based reasoning, knowledge-based systems, fuzzy logic and hybrid techniques. The trends over the last decade are identified, discussed with respect to expected trends and directions for future work suggested

Power Quality in Electrified Transportation Systems

"Power Quality in Electrified Transportation Systems" has covered interesting horizontal topics over diversified transportation technologies, ranging from railways to electric vehicles and ships. Although the attention is chiefly focused on typical railway issues such as harmonics, resonances and reactive power flow compensation, the integration of electric vehicles plays a significant role. The book is completed by some additional significant contributions, focusing on the interpretation of Power Quality phenomena propagation in railways using the fundamentals of electromagnetic theory and on electric ships in the light of the latest standardization efforts

Solid-state transformers in locomotives fed through AC lines: A review and future developments

One of the most important innovation expectation in railway electrical equipment is the replacement of the on-board transformer with a high power converter. Since the transformer operates at line-frequency (i.e., 50 Hz or 16 2/3 Hz), it represents a critical component from weight point of view and, moreover, it is characterized by quite poor efficiency. High power converters for this application are characterized by a medium frequency inductive coupling and are commonly referred as Power Electronic Transformers (PET), Medium Frequency Topologies or Solid-State Transformers (SST). Many studies were carried out and various prototypes were realized until now, however, the realization of such a system has some difficulties, mainly related to the high input voltage (i.e., 25 kV for 50 Hz lines and 15 kV for 16 2/3 Hz lines) and the limited performance of available power electronic switches. The aim of this study is to present a survey on the main solutions proposed in the technical literature and, analyzing pros and cons of these studies, to introduce new possible circuit topologies for this application

Connection and Control Strategy of PV Converter Integrated into Railway Traction Power Supply System

In order to supply the single-phase locomotive load and mitigate the negative sequence current, this paper develops a V/V transformer-based connection and control strategy of three-phase photovoltaic (PV) converters integrated into railway traction power supply systems. In this V/V transformer-based connection, the two-phase traction voltage is converted into the three-phase voltage. This approach can offer a common low voltage AC bus, which is more convenient for more access to three-phase PV converters. Based on this V/V transformer-based connection, an individual phase current control strategy with the hybrid current reference is fully designed. In this control strategy, the current reference, containing two parts, is generated. One is the asymmetrical part for powering the single-phase locomotive load and mitigating the negative sequence current. The other is the symmetrical part for feeding the surplus power back to the utility grid. Then, each phase current replaces the dual-sequence current to be controlled to track the corresponding phase current reference. Consequently, PV converters can flexibly inject the symmetrical and asymmetrical currents without the dual-sequence extraction for a simpler implementation. Finally, the effectiveness of the developed connection and control strategy is validated by the simulation studies

Intervenções básicas do sistema de tração

Trains and railways are influence our lives in a variety of ways we may not always realize. Passengers traveling across country get their destination safely and quickly with the use of trains and railway systems. Urban cities came up with importance of railways and railway stations in particular. Moreover, unlike other industries which become modern over a period of time, railways changed technology at a much faster scale. It bought distant towns closer to mainstream cities and helped big time in commerce. Railways were the first form of rapid land transportation and had an effective monopoly on passenger traffic until the development of the motor car and airliners in the early-mid 20th century. In addition to that, mankind nowadays largely depending on railways mainly because it offers more safe, comfortable and cheaper transportation. The main aim of this project is, to give detailed information about present-day railway systems as well as the reason behind the paradigm shift from Diesel Locomotive to Energy Traction system. Along with, the involvement of power equipment for transferring energy from the National Grid to the Pantograph (Mechanical Part of Train, which ensures the connection between Contact Wire and the Train), followed by, the Maintenance actions taking to account to keep Portugal Railway system more functional, then describes the main case studies associated with this electrically operated railway system and the developed solutions based on the requirements of the company

Smart power conditioners for electric railway power grids

Programa doutoral em Engenharia Eletrónica e de Computadores (especialidade de Eletrónica de Potência e Energia)Railway transport presents itself as one of the greatest economic and social drivers of several nations in the world. Furthermore, it is considered the safest means of land transport, with the electric rail system being efficient and environmentally friendly. However, for the inclusion of more and larger electric locomotives, it is necessary to increase the capacity of the railway supply systems. This doctoral thesis intends to contribute to the development of power electronics solutions capable of increasing the capacity of railway supply systems. As such, a power electronics converter connected in a neutral section located between two traction power substations (TPS) is proposed. The proposed algorithm makes it possible to dynamically balance the average active powers of the two substations, mitigating overload problems. In the event of deceleration or braking of a locomotive on one side, it is possible to use the energy from this regenerative braking to assist another locomotive on the other side of the neutral section. Moreover, the proposed solution still presents the interface with a photovoltaic solar system and an energy storage system. In this way, it is possible to minimize energy dependence on the power grid, as well as to include renewable energy sources. The storage system also makes it possible to store surplus production or energy from regenerative braking for later use. The proposed solution is validated with the help of computer simulations considering a real implementation scale. The simulation model is based on cascaded multilevel modular converters, with each submodule also featuring solid-state transformers. Considering a reduced-scale prototype developed in the laboratory, computer simulations of the prototype are also presented and discussed. The document also presents a chapter that portrays all the steps taken for the implementation of the reduced-scale sectioning post-Rail Power Conditioner (sp-RPC) laboratory prototype. Once its implementation was completed, its experimental validation was carried out, proving the correct functioning of the system based on the proposed algorithm.O transporte ferroviário apresenta-se como um dos maiores impulsionadores económicos e sociais de várias nações do mundo. Para além disso, é considerado como o meio de transporte terrestre mais seguro, sendo o sistema ferroviário elétrico eficiente e amigo do ambiente. Contudo, para a inclusão de mais e maiores locomotivas elétricas é necessário aumentar a capacidade dos sistemas de alimentação ferroviários. Esta tese de doutoramento pretende contribuir com o desenvolvimento de soluções de eletrónica de potência capazes de aumentar a capacidade dos sistemas de alimentação ferroviários. Como tal, é proposto um conversor de eletrónica de potência conectado numa secção neutra que se encontra entre duas subestações de tração de energia. A algoritmia proposta permite equilibrar as potências ativas médias das duas subestações de forma dinâmica, mitigando os problemas de sobrecarga. Na ocorrência de uma desaceleração ou travagem de uma locomotiva num dos lados, é possível utilizar a energia proveniente desta travagem regenerativa para o auxílio de marcha de outra locomotiva existente no outro lado da secção neutra. Não obstante, a solução proposta apresenta ainda a interface com um sistema solar fotovoltaico e um sistema de armazenamento de energia. Desta forma, é possível minimizar a dependência energética da rede elétrica, bem como incluir fontes de energia renovável. O sistema de armazenamento permite ainda armazenar o excedente de produção ou a energia proveniente de uma travagem regenerativa para posterior utilização. O conceito proposto é estudado com auxílio de simulações computacionais considerando uma escala de implementação real. O modelo de simulação é baseado em conversores modulares multinível em cascata, sendo que cada sub-módulo apresenta ainda transformadores de estado sólido. Considerando um protótipo de pequena escala desenvolvido em laboratório, simulações computacionais do protótipo são igualmente apresentadas e validadas. O documento apresenta ainda um capítulo que retrata todos os passos realizados para a implementação do protótipo laboratorial do sectioning post-Rail Power Conditioner (sp-RPC) de pequena escala. Uma vez finalizada a sua implementação, procedeu-se à sua validação experimental, comprovando o correto funcionamento do sistema com base na algoritmia proposta.This work has been supported by FCT — Fundação para a Ciência e Tecnologia, within the R&D Units Project Scope UIDB/00319/2020. Mr. Luis A. M. Barros is supported by the doctoral scholarship PD/BD/143006/2018, granted by the Portuguese FCT foundation

DC railway power supply system reliability evaluation and optimal operation plan

With the continuous and rapid development of the economy and the acceleration of urbanisation, public transport in cities has entered a period of rapid development. Urban rail transit is characterised by high speed, large traffic volume, safety, reliability and punctuality, which are incomparable with those of other forms of public transport. The traction power supply system (TPSS) is an important part of an electrified railway, and its safety issues are increasingly prominent. Different from the substation in a general power system, the load of a TPSS has a great impact on the traction transformer; moreover, in order to ensure normal operation of the train in case of failure, the traction substation must be able to access a cross-district power supply, as it has a high demand for reliable operation. The safe and reliable operation of DC TPSSs is the basis of the whole urban railway transit system. Previous studies have investigated the reliability of the TPSS main electrical wiring system. However, the impact of traction load and the actual operation of trains on system reliability has not been considered when designing a DC railway power supply system. The purpose of the research for this thesis is to find an optimal system operation plan for urban railways, considering load characteristics. This thesis begins with a review of the main arrangements of DC railway power supply systems and the literature on railway reliability studies. A model of single train simulation and a power supply system is established in MATLAB. The developed simulator is then integrated with a TPSS reliability model to evaluate the energy and reliability performance of DC railway power systems. Based on the train traction load model and train schedule, a comprehensive method for evaluating a DC TPSS considering traction load is proposed. Through simulation of the actual operation of the train group, the system energy consumption and substation life loss generated under different train operation diagrams and schedules are compared to provide a reference for the reasonable design of the timetable. Taking the life loss and energy consumption of the whole TPSS as the objective function, a genetic algorithm is used to optimise the train speed, coasting velocity, station dwell time and headway to find the optimal operation strategy. This is illustrated with a case study of the Singapore East–West metro line. The study has addressed the following issues: development of a multi-train power simulator, evaluation of reliability performance, and finally the search for an optimal operation plan. The train running diagram and timetable are optimised jointly. This can help railway operators make decisions for an optimal operation plan and reduce the operation risk of the power system

Infrastructure Design, Signalling and Security in Railway

Railway transportation has become one of the main technological advances of our society. Since the first railway used to carry coal from a mine in Shropshire (England, 1600), a lot of efforts have been made to improve this transportation concept. One of its milestones was the invention and development of the steam locomotive, but commercial rail travels became practical two hundred years later. From these first attempts, railway infrastructures, signalling and security have evolved and become more complex than those performed in its earlier stages. This book will provide readers a comprehensive technical guide, covering these topics and presenting a brief overview of selected railway systems in the world. The objective of the book is to serve as a valuable reference for students, educators, scientists, faculty members, researchers, and engineers