Railway interference management: TLM modelling in railway applications

This thesis deals with the application of analytical and numerical tools to Electromagnetic Compatibility (EMC) management in railways. Analytical and numerical tools are applied to study the electromagnetic coupling from an alternating current (AC) electrified railway line, and to study the electrical properties of concrete structure - a widely used component within the railway infrastructure. An electrified railway system is a complex distributed system consisting of several sub-systems, with different voltage and current levels, co-located in a small area. An analytical method, based on transmissions line theory, is developed to investigate railway electromagnetic coupling. The method is used to study an electrified railway line in which the running rails and earth comprise the current retum path. The model is then modified to include the presence of booster transformers. The analytical model can be used to study the railway current distribution, earth potential and electromagnetic coupling - inductive and conductive coupling - to nearby metallic structures. The limiting factor of the analytical model is the increasing difficulty in resolving the analytical equation as the complexity of the railway model increases. A large scale railway numerical model is implemented in Transmission Line Matrix (TLM) and the electromagnetic fields propagated from the railway model is studied. As this work focuses on the direct application of TLM in railway EMC management, a commercially available TIM software package is used. The limitation of the numerical model relates to the increased computation resource and simulation time required as the complexity of the railway model increases. The second part of this thesis deals with the investigation of the electrical properties of concrete and the development of a dispersive material model that can be implemented in numerical simulators such as TIM. Concrete is widely used in the railway as structural components in the construction of signalling equipment room, operation control centres etc. It is equally used as sleepers in the railway to hold the rails in place or as concrete slabs on which the whole rail lines are installed. It is thus important to understand the contribution of concrete structures to the propagation of electromagnetic wave and its impact in railway applications. An analytical model, based on transmission line theory, is developed for the evaluation of shielding effectiveness of a concrete slab; the analytical model is extended to deal with reinforced concrete slab and conductive concrete. The usefulness and limitation of the model is discussed. A numerical model for concrete is developed for the evaluation of the effectiveness of concrete as a shield. Initially, concrete is modelled as a simple dielectric material, using the available dielectric material functionality within TLM. It is noted that the simple dielectric model is not adequate to characterise the behaviour of concrete over the frequency range of interest. Better agreement is obtained with concrete modelled as a dispersive material having material properties similar to that exhibited by materials obeying Debye equation. The limitations of the dispersive material model are equally discussed. The design of conductive concrete is discussed, these have application in the railway industry where old existing structures are to be converted to functional rooms to house sensitive electronic system. A layer of conductive concrete can be applied to the facade to enhance the global shielding of the structure

Metrology Infrastructure for Energy and Power Quality in DC Railway Systems

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Passenger Exposure to Magnetic Fields in Electric Vehicles

In electric vehicles, passengers sit very close to an electric system of significant power, usually for a considerable amount of time. The relatively high currents achieved in these systems and the short distances between the power devices and the passengers mean that the latter could be exposed to relevant magnetic fields. This implies that it becomes necessary to evaluate the electromagnetic environment in the interior of these vehicles before releasing them in the market. Moreover, the hazards of magnetic field exposure must be taken into account when designing electric vehicles and their components. For this purpose, estimation tools based on finite element simulations can prove to be very useful. With appropriate design guidelines, it might be possible to make electric vehicles safe from the electromagnetic radiation point of view

Modern Applications in Optics and Photonics: From Sensing and Analytics to Communication

Optics and photonics are among the key technologies of the 21st century, and offer potential for novel applications in areas such as sensing and spectroscopy, analytics, monitoring, biomedical imaging/diagnostics, and optical communication technology. The high degree of control over light fields, together with the capabilities of modern processing and integration technology, enables new optical measurement systems with enhanced functionality and sensitivity. They are attractive for a range of applications that were previously inaccessible. This Special Issue aims to provide an overview of some of the most advanced application areas in optics and photonics and indicate the broad potential for the future

A review on power electronics technologies for electric mobility

Concerns about greenhouse gas emissions are a key topic addressed by modern societies worldwide. As a contribution to mitigate such effects caused by the transportation sector, the full adoption of electric mobility is increasingly being seen as the main alternative to conventional internal combustion engine (ICE) vehicles, which is supported by positive industry indicators, despite some identified hurdles. For such objective, power electronics technologies play an essential role and can be contextualized in different purposes to support the full adoption of electric mobility, including on-board and off-board battery charging systems, inductive wireless charging systems, unified traction and charging systems, new topologies with innovative operation modes for supporting the electrical power grid, and innovative solutions for electrified railways. Embracing all of these aspects, this paper presents a review on power electronics technologies for electric mobility where some of the main technologies and power electronics topologies are presented and explained. In order to address a broad scope of technologies, this paper covers road vehicles, lightweight vehicles and railway vehicles, among other electric vehicles.This work has been supported by FCT – Fundação para a Ciência e Tecnologia with-in the Project Scope: UID/CEC/00319/2020. This work has been supported by the FCT Project DAIPESEV PTDC/EEI-EEE/30382/2017, and by the FCT Project new ERA4GRIDs PTDC/EEI-EEE/30283/2017. Tiago Sousa is supported by the doctoral scholarship SFRH/BD/134353/2017 granted by FCT

Propagation and Effects of Vibrations in Densely Populated Urban Environments

Environmental vibration generated by sources such as rail lines, road traffic and construction work is a serious concern, especially in the urban environment. It leads to annoyance of the exposed population, creating uncomfortable living and working spaces. Thus, prediction and mitigation of these effects is an important research area, investigated by an increasing number of engineers and researchers. In this regard, computational models are especially useful. They enable the prediction of environmental vibration levels in the planning stages of a new project, reducing or, ideally, completely removing the need for in-situ investigations. Currently available numerical approaches are highly capable and can be used to model the complex cases encountered in the urban environment. However, the largest drawback of these approaches is the long computational times needed to obtain the solution, thus limiting their usage for real applications. The thesis aims to create environmental vibration prediction tools, with particular interest in their computational efficiency. This way, the created methodologies could be easier applicable to a wider audience. Modelling of the vibration propagation through soil, in most cases, is the most time consuming task. Thus, the thesis mostly focuses on this part of the system. A semi-analytical soil modelling approach was chosen to model the soil, using a Thomson-Haskell transfer matrix method. The method is advantageous, due to the analytical formulation of the soil, which does not require the discretization of the full soil domain and incorporates the infinite nature of the soil. The semi-analytical method is coupled to the finite element method, where the soil is accounted for using the semi-analytical approach, while the external structures can be modelled with finite elements. This way, the computational efficiency of the semi-analytical approach is combined with the modelling freedom of the finite elements method, allowing the application of the created model for a wide range of application cases. The thesis investigates a number of modelling cases that are commonly encountered when analysing dynamic soil–structure interaction and vibration propagation through soil. A railway bridge structure is analysed using lumped-parameter models to obtain a solution in the time domain. The work presents a novel lumped-parameter model fitting technique that is needed to obtain a numerically stable solution. Further, the semi-analytical soil model is used to analyse cases commonly encountered in the urban environment. For that purpose, various configurations of soil interacting with structure are tested, such as: rigid blocks, pile foundations, railway tracks, embedded structures, and cavities inside the soil. The proposed modelling methods are validated by comparison with other numerical methods. Very good agreement is found, demonstrating the high accuracy and the reduced computational effort of the proposed modelling approaches. A novel numerical method for predicting railway-induced vibrations is also proposed. The method utilizes the semi-analytical soil model formulated in both moving and fixed frames of reference. This way, it is possible to model the railway track and the vehicle in a moving frame of reference, while the nearby structures are formulated in a fixed frame of reference. The approach offers a flexible and numerically stable approach of modelling the full vibration propagation path, using a single-step solution procedure