Continuous control set model predictive control of a bridgeless-boost three-level active rectifier

Over the past few decades, active rectifiers have assumed an important preponderance for numerous applications that propose to minimize power quality problems. Consequently, digital control algorithms are following this trend by contributing with a significant set of advantages. This paper presents the use of a continuous control set model predictive control (CCS-MPC) for a bridgeless-boost three-level (BB3L) active rectifier. The BB3L has a set of advantages when confronted with traditional solutions to improve power quality, where the possibility to operate with three voltage levels, sinusoidal current and unitary power factor, while using few switching devices, are the main features. Considering the multiplicity of applications for the BB3L active rectifier, the CCS-MPC is applied to obtain a robust current tracking. The BB3L is presented in detail throughout the paper and based on its mathematical model, the digital control equations are formulated, highlighting that the possibility of operating with a fixed switching frequency is the main characteristic. The results are achieved for many operating conditions, covering steady-state and transient-state, validating the accurate application of the CCS-MPC.This work has been supported by FCT – Fundação para a Ciência e Tecnologia within the R&D Units Project Scope: UIDB/00319/2020. This work has been supported by the FCT Project newERA4GRIDs PTDC/EEI-EEE/30283/2017. Tiago J. C. Sousa is supported by the doctoral scholarship SFRH/BD/134353/2017 granted by FCT

Innovative off-board EV home charging station as a smart home enabler: Present and proposed perspectives

This paper presents an innovative off-board electric vehicle home charging station (EV-HCS) operating as a smart home (SH) enabler. The present status and the proposed perspectives in terms of operation modes are comprehensively addressed along the paper showing the contextualization of the addressed research topic. Comparing with the existing solution, the main motivations and advantages of the off-board EV-HCS are: (a) Off-board dc EV charger, faster than a classical on-board EV charger; (b) Flexible operating power value, aiming an optimized power management in the home; (c) Operation as an active conditioner for the home or the grid, with or without an EV plugged-in, which represents an attractive functionality for enhancing the operation of SHs and smart grids; (d) Bidirectional operation with an EV. The methods used to describe these advantages are validated using computer simulations. The control algorithm is succinctly described, demonstrating its adaptability to the power electronics topology presented for the EV-HCS hardware. The obtained results demonstrate that the proposed EV-HCS presents attractive functionalities for enhancing the EV integration into SHs and smart grids.ERDF – European Regional Development Fund through the Operational Programme for Competitiveness and Internationalisation – COMPETE 2020 Programme, and by National Funds through the Portuguese funding agency, FCT – Fundação para a Ciência e a Tecnologia, within project SAICTPAC/0004/2015 – POCI – 01–0145–FEDER–016434. Mr. Tiago Sousa is supported by the doctoral scholarship SFRH/BD/134353/2017 granted by the Portuguese FCT agency; Fundação para a Ciência e Tecnologia (FCT)info:eu-repo/semantics/publishedVersio

Selective harmonic measurement and compensation using smart inverters in a microgrid with distributed generation

This paper presents a frequency domain selective harmonic measurement and compensation using smart inverters (SIs) applied to a microgrid with distributed generation. The compensation current is calculated by a main processing unit (MPU), which controls the compensation action of each distributed generation unit (DGU) connected to the microgrid. A single fast Fourier transform (FFT) is implemented to obtain the frequency spectra of the power grid voltages and the currents consumed by the connected loads. Based on the calculated compensation currents and the availability of the DGUs, the MPU establishes the harmonic orders that each DGU should compensate, aiming to equalize the rms current values among the different DGUs. The proposed approach intends to optimize the DGUs efficiency in the microgrid and, additionally, it allows the connection of the converters to the power grid without the need for a synchronization algorithm. A comprehensive description of the implemented FFT algorithm is performed and, finally, the operation of the proposed scheme is verified by simulation results.COMPETE: POCI-01-0145–FEDER–007043 and FCT – Fundação para a Ciência e Tecnologia within the Project Scope: UID/CEC/00319/2013. This work is financed by the ERDF – European Regional Development Fund through the Operational Programme for Competitiveness and Internationalisation – COMPETE 2020 Programme, and by National Funds through the Portuguese funding agency, FCT – Fundação para a Ciência e a Tecnologia, within project SAICTPAC/0004/2015 – POCI – 01–0145– FEDER–016434. SFRH/BD/134353/2017 granted by the Portuguese FCT agencyinfo:eu-repo/semantics/publishedVersio

The role of the electric vehicle in smart homes: Assessment and future perspectives

The wide spreading of electric mobility is imposing the application of new technologies of hardware and software for supporting new operation paradigms, not only in the perspective of improving smart grids, but also each time more in the perspective of boosting the preponderance of smart homes. Concretely, nowadays it is clear that the emergent technologies for smart homes, targeting power quality and a more efficient power management, are also altering the conventional electrical power grids toward smart grids. In this panorama, by relating the strategic pillars of electric mobility and smart homes, this paper has as main objective the characterization of the role of the electric vehicle (EV) in smart homes, presenting a broad assessment based on the state of the art, as well as creating a link with upcoming advanced operations. From the smart home point of view, since it should be equipped to deal with the requirements of the EV, the assessment of both on-board and off-board EV battery charging systems are considered along the paper. Furthermore, the presence of technologies such as energy storage systems, renewable energy sources and dc electrical appliances in smart homes towards sustainability is also reflected in this paper, but framed from the point of view of an off-board EV battery charging system, since it is more convenient for enabling the interface of these mentioned technologies. Looking the paper as a whole, a relevant contribution is the discussion of future operations for the EV in smart homes, also envisioning the opportunity for ac, dc, or hybrid power grids. Illustrative and strategic results are shown, covering all these features with specific details, not only based on numerical simulations, but also based on experimental results, which were obtained with a proof-of-concept laboratory prototype.FCT -Fundação para a Ciência e a Tecnologia(DAIPESEV PTDC/EEI-EEE/30382/2017

Rate effect in inclined fibre pull-out for smooth and hooked-end fibres: a numerical study

Based on a numerical model to simulate the static behaviour of a smooth fibre extracted from a cementitious matrix, a rate dependent friction law, widely used in earthquake engineering for steady-state slip phenomena, is proposed to capture the rate effect observed in dynamic pull-out tests for both smooth and hooked-end fibres. After calibrating the friction coefficients with the experimental results of smooth fibres, the model is subsequently applied to predict the pullout behaviour of both smooth and hooked-end fibres at different inclination angles (0∘, 30∘ and 60∘) loaded at three different velocities (0.01, 0.1 and 1 mm/s). The global tendency of all the pull-out curves was captured, fibre’s cross sectional deformations were also reproduced remarkably well. Moreover, the developed model helps to cast light on the different mechanisms related to the pull-out process.Ministerio de Ciencia, Innovación y Universidades, Spain, through the projects BIA2015-68678-C2-1-R and RTC-2017-6736-3, is acknowledged. Elisa Poveda appreciates the funding from the International Campus of Excellence CYTEMA, as well as, the University of Castilla-La Mancha, throughout Ayudas para estancias en universidades en el extranjero en 2019 en el ámbito del plan propio de investigación susceptibles de co-financiación por el Fondo FEDER, Programa 010100021 to fund her stay in the University of Minho during 2018 and 2019, respectively. Manuel Tarifa acknowledges the financial support from the Department of Applied Mechanics and Project Engineering, UCLM (2018), and from the Programa propio de I+D+i de la Universidad Politécnica de Madrid para realizar estancias de investigación internacional igual o superior a un mes (2019), with the same purpose. The last two authors acknowledge the support provided by the project ICoSyTec (POCI-01-0145-FEDER-027990) financed by FCT and co-funded by FEDER through the Operational Competitiveness and Internationalization Programme (POCI). The authors thank BEKAERT for the supply of fibre

Betão de alta resistência reforçado com fibras exposto a elevadas temperaturas

Atualmente, a utilização de betões de elevada resistência tem vindo a aumentar, nomeadamente, em aplicações com requisitos especiais, tais como arranha-céus, torres eólicas, centrais nucleares, etc. No entanto, com o aumento significativo da resistência, este tipo de material desenvolve um comportamento significativamente mais frágil. Adicionalmente, quando expostos a elevadas temperaturas, como no caso de incêndio, dependendo da temperatura e tempo de exposição poder-se-á verificar uma diminuição significativa da resistência à compressão, fissuração bem como uma rotura explosiva. Neste trabalho apresentam-se e discutem-se os resultados do estudo da influência da temperatura no comportamento mecânico de microbetão de alta resistência reforçado com fibras de aço. Diversos provetes de betão de elevada resistência foram expostos a distintas temperaturas durante um período superior a uma hora, designadamente, 400, 500, 600 e 700 ºC. O comportamento mecânico, após exposição às diferentes temperaturas, foi avaliado através de ensaios de compressão, flexão e tração uniaxial e posteriormente comparado com o betão de referência (exposto à temperatura ambiente). Na generalidade, as propriedades mecânicas do betão de alta resistência diminuíram com o aumento da temperatura. Verificou-se um decréscimo mais acentuado da resistência à compressão, tração uniaxial e tração em flexão para temperaturas superiores a 400ºC.PTDC/ECM-EST/2635/2014, SFRH/BSAB/114302/2016.info:eu-repo/semantics/publishedVersio

Earth-based render of tabique walls – an experimental work contribution

A research work focused on studying earth render for tabique application purposes is presented. Initially, a brief description of the tabique building technique is provided. The relevance of the application of this traditional building technique is also highlighted. Different compositions of earth render are experimentally analysed and the respective performance is evaluated. Flexural and compressive strengths, workability, drying shrinkage cracking and water resistance are the material properties assessed. A simple earth render is selected as being adequate for tabique building applications and it is applied on the manufacturing of a tabique wall sample. This wall sample is monitored in terms of thermal insulation ability and its thermal transmission coefficient is estimated. Taking into account that there is still a lack of published technical information related to this topic, this paper may contribute to solve this limitation and to give some guidance in future repairing processes of tabique construction. The technological benefit of adding lime or cement with earth is researched. Real tabique timber structure samples are applied in order to validate the obtained experimental results.info:eu-repo/semantics/publishedVersio

New Perspectives for Vehicle-to-Vehicle (V2V) Power Transfer

This paper presents a comparison between different possibilities for the vehicle-to-vehicle (V2V) power transfer between two electric vehicles (EVs). The traditional V2V operation mode is performed through a common energy aggregator, such as the electrical power grid, consisting of a combination of the vehicle-to-grid (V2G) and grid-to-vehicle (G2V) operation modes. The traditional V2V power transfer is based on four power conversions, since each on-board EV battery charger is comprised by two power converters (dc-dc and dc-ac). In this context, this paper proposes new perspectives for the V2V power transfer, both in ac and dc, focusing in the V2V power transfer using dc power (dcV2V). The proposed methods discard the need for an energy aggregator connection, being possible to directly connect two EVs, charging one EV from the other. Furthermore, the proposed dcV2V method allows the reduction of four power conversions to a single one, allowing to increase the overall efficiency of the power transfer between EVs, An efficiency-based evaluation of the different V2V methods is performed, supporting the benefits of dcV2V.This work has been supported by COMPETE: POCI-01-0145–FEDER–007043 and FCT –Fundação para a Ciência e Tecnologia within the Project Scope: UID/CEC/00319/2013. This work is financed by the ERDF – European Regional Development Fund through the Operational Programme for Competitiveness and Internationalisation –COMPETE 2020 Programme, and by National Funds through the Portuguese funding agency, FCT –Fundação para a Ciência e a Tecnologia, within project SAICTPAC/0004/2015 –POCI –01–0145–FEDER–016434.Mr. Tiago Sousa is supported by the doctoral scholarship SFRH/BD/134353/2017 granted by the Portuguese FCT agency

Vehicle electrification: technologies, challenges and a global perspective for smart grids

Nowadays, due to economic and climate concerns, the private transportation sector is shifting for the vehicle electrification, mainly supported by electric and hybrid plug-in vehicles. For this new reality, new challenges about operation modes are emerging, demanding a cooperative and dynamic operation with the electrical power grid, guaranteeing a stable integration without omitting the power quality for the grid-side and for the vehicle-side. Besides the operation modes, new attractive and complementary technologies are offered by the vehicle electrification in the context of smart grids, which are valid for both on-board and off-board systems. In this perspective, this book chapter presents a global perspective and deals with challenges for the vehicle electrification, covering the key technologies toward a sustainable future. Among others, the flowing topics are covered: (1) Overview of power electronics structures for battery charging systems, including on-board and off-board systems; (2) State-of-the-art of communication technologies for application in the context of vehicular electrification, smart grids and smart homes; (3) Challenges and opportunities concerning wireless power transfer with bidirectional interface to the electrical grid; (4) Future perspectives about bidirectional power transfer between electric vehicles (vehicle-to-vehicle operation mode); (5) Unified technologies, allowing to combine functionalities of a bidirectional interface with the electrical grid and motor driver based on a single system; and (6) Smart grids and smart homes scenarios and accessible opportunities about operation modes.Fundação para a Ciência e Tecnologia (FCT

Bond-Slip Mechanisms of Hooked-End Steel Fibers in Self-Compacting Concrete

Abstract. The experimental results of hooked-end steel fibers pullout tests on a self-compacting concrete medium are presented and discussed in this work. The influence of fiber embedment length on the fiber pullout behavior is studied. The role of the end hook of the fiber on the overall pullout behavior is also investigated by carrying out tests with fibers without its end hook, in order to separate the contribution of the frictional bond component from those derived from the mechanisms provided by the end hook of the fiber. Finally, the experimental bond-slip relationships are modeled by an analytical model