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Il cambiamento climatico in atto ci spinge ad intervenire rapidamente con azioni efficaci e durature nel tempo. Tra i principali settori inquinanti, l'energia utilizzata negli edifici, nelle industrie e nei trasporti è causa della gran parte delle emissioni di gas serra a livello mondiale. L'elettrificazione di questi settori è una delle soluzioni ottimali per il processo di decarbonizzazione supportando le politiche della transizione energetica in corso. La produzione di energia elettrica da fonti rinnovabili e la crescita esponenziale del mercato dei veicoli elettrici a livello mondiale sono la chiave per un futuro sostenibile. Tuttavia, nonostante il loro potenziale, portano l'attenzione sulla loro reciproca integrazione al fine di comprendere a fondo i reali vantaggi dal punto di vista energetico, economico ed ambientale. Inoltre, la possibilità di scambio energetico bidirezionale grazie all'avvento della tecnologia Vehicle-to-Grid (V2G) definisce nuove opportunità di integrazione e supporto alla rete elettrica. In questo lavoro, vengono studiate la gestione energetica e il controllo ottimizzato per l'integrazione dei veicoli elettrici con la rete elettrica e i sistemi di generazione rinnovabile distribuita. Nella prima parte viene introdotto il problema delle emissioni, l'elettrificazione dei trasporti e le definizioni di alcuni concetti chiave. Successivamente, l'integrazione dei veicoli elettrici viene studiata da due diversi punti di vista. Il primo, in parte in collaborazione con la Christian-Albrechts-Universität (CAU) a Kiel, si focalizza su aspetti legati all'elettronica di potenza e al controllo di basso livello, mostrando un confronto tra diverse topologie di convertitori DC-DC (DAB), un'analisi sull'efficienza totale di ricarica del veicolo e la simulazione di un sistema V2G sperimentale per la fornitura di servizi ancillari. Il secondo invece si concentra maggiormente sulla gestione ed il controllo predittivo dei flussi energetici per l'integrazione dei veicoli elettrici con microreti, focalizzando l'attenzione su aspetti economici ed ambientali. In particolare, viene mostrata l'implementazione e la validazione sperimentale di un sistema di controllo real-time per una stazione di ricarica fotovoltaica installata presso l'Università di Trieste, un sistema V2G integrato all'interno di uno ski-resort Alpino ed infine, uno studio relativo ad una microrete condominiale che mostra i vantaggi legati ad un gruppo di autoconsumatori che agiscono collettivamente. Ongoing climate change is driving the need for rapid action with effective and long-term impacts. Among the major polluting sectors, energy used in buildings, industries, and transportation accounts for most of the world's greenhouse gas emissions. Electrification of these sectors is one of the optimal solutions for the decarbonization process by supporting the ongoing energy transition policies. Electricity generation from renewable sources and the exponential growth of the global electric vehicle market are the key to a sustainable future. However, despite their potential, they bear attention to their mutual integration in order to fully understand the real benefits from energy, economic and environmental perspectives. In addition, the possibility of two-way energy exchange through the advent of Vehicle-to-Grid (V2G) technology defines new opportunities for integration and support to the power grid. In the present work, optimized energy management and control for the integration of electric vehicles with the power grid and distributed renewable generation systems are studied. In the first part, the emission problem, electrification of transportation and definitions of some key concepts are introduced. Next, the integration of electric vehicles is studied from two different perspectives. The first, partially in collaboration with the Christian-Albrechts-Universität (CAU) in Kiel, focuses on aspects related to power electronics and low-level control, showing a comparison of different DC-DC converter (DAB) topologies, an analysis of total vehicle charging efficiency, and a simulation of an experimental V2G system for providing ancillary services. The second focuses more on the management and predictive control of energy flows for the integration of electric vehicles with microgrids, focusing on economic and environmental aspects. In particular, it shows the implementation and experimental validations of a real-time control system for a photovoltaic charging station installed at the University of Trieste, an integrated V2G system within an Alpine ski-resort, and finally, a study related to a condominium microgrid showing the benefits related to a group of jointly acting renewables self-consumers.

One of the most common failures or breakdowns that can occur in high-voltage (HV) equipment is due to partial discharges (PDs). This occurs as a result of inadequate insulation, aging, harsh environmental effects, or manufacturing flaws. PD detection and recognition methods have gained growing attention and have seen great progress in the past decades. Radiometric methods are one of the most investigated detection approaches due to their immunity to electromagnetic interference (EMI) and their capabilities to detect and locate PD activities in different applications such as transformers, cables, etc. Several review articles have been published to classify and categorize these works. Nonetheless, some concepts are missing, and some improvement techniques, such as PD detection at high-frequency (HF) and very high-frequency (VHF), have been overlooked. We present in this paper an exhaustive review study of state-of-the-art PD detection based on radiometric methods at different usable radiofrequency bands (i.e., HF, VHF, and UHF). Accordingly, we propose a new generic categorization approach based on the detected electromagnetic wave component (magnetic or electric fields) and pick-up location, either from free space or ground cable.

Questa tesi riassume il lavoro svolto durante il triennio di dottorato nel periodo compreso tra il 2019 e il 2022. Come è ben noto nella comunità scientifica, l'ambiziosissimo progetto di fusione nucleare ha richiesto e richiede notevoli risorse ed investimenti; La tabella di marcia per la generazione di energia da fusione nucleare su larga scala comprende missioni impegnative. I progetti ITER e DEMO, essendo progetti internazionali, richiedono la collaborazione (sia dal punto di vista economico che tecnico) di diversi Paesi a livello europeo ed extraeuropeo; per questo motivo i vari aspetti tecnologici, che verranno poi implementati e applicati nei reattori a fusione finali, vengono prima analizzati, simulati e gestiti da vari enti degli stati membri del progetto (compresa l'Italia). Una delle strutture di ricerca più importanti per questi progetti si trova presso la sede ENEA di Frascati (RM) ed è denominata DTT (divertor tokamak test facility). La struttura DTT è progettata per esplorare tutte le linee di regimi operativi del plasma rilevanti per ITER e DEMO; In particolare sarà possibile dimostrare la fattibilità fisica e tecnologica di varie configurazioni di divertore. In questo modo sarà possibile integrare le conoscenze su concetti di divertori alternativi già sperimentati su macchine esistenti. Poiché l'energia magnetica immagazzinata nei magneti superconduttori è dell'ordine di 2GJ-4GJ (per DTT), in caso di guasto o quench deve esserci la possibilità di estrarla molto velocemente per salvaguardare l'integrità del Tokamak e dei superconduttori. In questo caso intervengono i cosiddetti sistemi FDU (Fast Discharge Unit), costituiti essenzialmente da resistenze per consentire la scarica e la rapida dissipazione dell'energia. La protezione viene realizzata collegando una resistenza di scarica in serie ad ogni blocco di magneti suddivisi in vari gruppi a seconda della loro configurazione elettrica. L'obiettivo principale di questa tesi è quindi quello di riportare tutti i modelli, le simulazioni ei risultati elaborati per l'intera durata del corso di studio nell'ambito dello sviluppo di Fast Discharge Units (FDU). This thesis summarizes the work carried out during the 3-year PhD course in the period between 2019 and 2022. As is well known in the scientific community, the very ambitious nuclear fusion project has required and still requires considerable resources and investments; The roadmap for large-scale nuclear fusion power generation is comprised of challenging missions. The ITER and DEMO projects, being international projects, require the collaboration (both from an economic and technical point of view) of different countries at European and non-European level; for this reason, the various technological aspects, which will then be implemented and applied in the final fusion reactors, are first analyzed, simulated, and managed by various bodies of the project member states (including Italy). One of the most important research facilities for these projects is located at the ENEA headquarters in Frascati (RM) and is called DTT (divertor tokamak test facility). The DTT structure is designed to explore all lines of plasma operating regimes relevant to ITER and DEMO; In particular, it will be possible to demonstrate the physical and technological feasibility of various divertor configurations. In this way it will be possible to integrate knowledge on alternative divertor concepts already tested on existing machines. Since the magnetic energy stored in superconducting magnets is of the order of 2GJ-4GJ (for DTT), in the event of a failure or quench there must be the possibility to extract it very quickly to safeguard the integrity of the Tokamak and superconductors. In this case, the so-called FDU systems (fast discharge unit) intervene, which basically consist of resistors to allow discharge and fast dissipation of energy. Protection is carried out by connecting a discharge resistor in series to each block of magnets divided into various groups depending on their electrical configuration. The main objective of this thesis so is to report all the models, simulations and results processed for the entire duration of the course of study as part of the development of Fast Discharge Units (FDU).

The objective of this paper is to illustrate an alternative control algorithm for power converters which have the task of introducing the energy generated by systems based on the use of renewable sources such as, photovoltaic or wind power, in to small-sized networks, microgrids. Virtual Synchronous Generator can operate both in parallel to the main network as well as in isolated and autonomous conditions (islanding-mode). The contribute of this work is to drive a consolidate approach, made in time domain, in a more flexible and less time-consuming approach based on Park transformation.

The paper investigates the role of the space charge accumulation phenomena in the inception of Partial Discharges (PD) in a defect within the bulk of the dielectrics of a High Voltage Direct Current (HVDC) cable. It is widespread accepted that the number of PD occurring in an HVDC cable during its lifetime is largely less than that under AC voltage stress. This is essentially due to higher values of the voltage between the conductor and the screen needed to trigger PD under a steady DC voltage than the same value under AC stress. Nevertheless, due to the dependency of the electrical conductivity of the insulation on the electric field and temperature, PD in HVDC cables is strongly influenced by the temperature distribution and, consequently, on the load current. Thus, the main goal of this research is to evaluate the main parameters of the PD occurring in an HVDC cable during a load transient. Numerical simulations by using Comsol Multlphysics® are validated by the results obtained with an ad hoc experimental setup. A model DC cable, subjected to transient phenomena due to a current step and with an air void defect in the insulation material, is simulated and setup. On the other hand, an experimental setup is used to carry out PD measurements on the same case study. The results of this research show the strong dependency of the PD parameters on the temperature distribution varying over time during a load transient.

This paper is focused on the measurement of partial discharges in the Silicon Carbide MOSFET. The latter represents a recent developed power electronics device, which has improved characteristics compared to the traditional Silicon MOSFET. The new technology has been conceived in order to satisfy the new market needs. With the ever-increasing development of the electric mobility sector, the need for ever more performing electronic power devices grows. The main features provided by the Silicon Carbide device were found in literature and concern a great thermal conductivity, wide bandgap, high power and high working temperature. However, considering the high voltage at which these devices work, also taking into account their small geometric dimensions, it is essential to evaluate the behavior from the partial discharges point of view. Based on the above, the aim of the present work is the measurement of partial discharges in ten different Silicon Carbide MOSFET devices in order to evaluate the electrical performances of the new proposed material as well as the quality of their manufacturing process. Experimental tests have been carried out by taking into account the Standard CEI EN 60270 for the realization of the measurement setup and the Standard CEI EN 61287 for the measurement procedure. In particular, the latter Standard provides the guidelines for the applied voltage waveform. Measurement results showed that no partial discharge phenomena occur in all the specimens under tests. Therefore, the SiC MOSFET passed the partial discharge test successfully.

The Phase-Resolved-Partial-Discharge pattern (PRPD) is a conventional technique used for the evaluation of partial discharges (PD) phenomena in High-Voltage-Alternating-Current (HVAC) systems. This map is constructed by plotting the peak of each detected pulses as a function of the phase angle of the supply voltage. Therefore it is obvious that this technique cannot be used for the analysis of data from PD mesaurement under different supply voltage condition (DC). The aim of this paper is to evaluate the application of the Time-Frequency map (TF map) for the analysis of a dataset obtained from PD measurement under DC voltage. A density-based clustering algorithm was also used to gain more insight from the collected data. The results show that, with this approach, it's possible to perform a noise rejection and identify PD pulses.

This paper presents a simple, practical and low-cost implementation of a power losses minimization algorithm for three-phase induction motors taking also into account both iron core losses and magnetic saturation. The algorithm evaluates, in real-time, the optimal direct axis magnetizing flux component for efficiency enhancement of the drive. A further advantage of the proposed technique is represented by a flexible and low-cost implementation by means of an ATMEL ATSAM3X8E microcontroller. The power loss minimization algorithm is tested preliminarily by means of several simulations, then, experimentally validated by applying the proposed control strategy on a 5.5 kW Field Oriented Control (FOC) induction motor drive. Significant results in terms of efficiency enhancement are presented and discussed, demonstrating that the proposed online control can significantly decrease the power losses of the drive.

To date, there are several methods for calculating the electric field distribution within a dielectric layer subjected to HVDC voltage. However, experimental techniques for evaluating the accuracy of models for calculating the electric field, such as space charge measurement, are often not precise enough to be used for this purpose. At the same time, the knowledge of Partial Discharge (PD) phenomenon occurring under HVDC stress is also not as developed as that of PD under HVAC voltage. The main goal of this research is to study the effectiveness of dielectric conductivity models to forecast the inception condition for PD under load and HVDC voltage stress. This study has been carried out by means of comparison between computer simulation and experimental results. The simulations have been carried out by means of a dielectric conductivity model implemented in the FEM software Comsol Multiphysics. The experimental setup consist of a model cable insulated with XLPE with an artificial defect created at the outer surface of the dielectric layer. Although the definition of the electric field inside a cavity is affected by several parameters which are also mutually dependent, the analysis performed demonstrates the predictability of the PD activity within certain voltage and temperature ranges.

Electric scalar potential estimation is a key step for non-invasive investigations of brain activity with high time resolutions. The neural sources can be reconstructed by solving a typical inverse problem based on a forward problem formulated as a set of boundary value problems coupled by interface conditions. In this paper, we propose a Shepard multinode method to numerically estimate electric scalar potentials via collocation. The method is based on a special kind of inverse distance weighting partition of unity method to increase polynomial precision, approximation order, and accuracy of the classical Shepard approximation. The barycentric form, through the use of cardinal basis function, is adopted to generate Shepard interpolants with high polynomial reproduction order. Comparisons with the analytic solution and the standard Shepard method are provided to assess the proposed approach.

The Divertor Tokamak Test (DTT) is an experimental nuclear fusion reactor currently under construction at the ENEA research center in Frascati and whose first plasma is expected in 2025. The present article shows the conceptual philosophy and the guidelines behind the design of the grounding system of the DTT. The article focuses on the main target of the grounding system and on the main technical standards to refer to for the design.

This paper presents a detailed analysis of the use of a novel Harmonic Mitigation algorithm for Cascaded H-Bridge Multilevel Inverter in electrical drives for the transportation field. For this purpose, an enhanced mathematical model of Interior Permanent Magnet Synchronous Motor (IPMSM), that takes into account simultaneously saturation, cross-coupling, spatial harmonics, and iron loss effects, has been used. In detail, this model allows estimating accurately the efficiency and the torque ripple of the IPMSM, crucial parameters for transportation applications. Moreover, two traditional pulse width modulation strategies, Sinusoidal Phase-Shifted and Switching Frequency Optimal Phase-Shifted have been considered for comparison purposes with an optimized harmonic mitigation algorithm. Thus, this work provides a deep analysis of IPMSM drive performance fed by CHBMI, paying attention to various aspects such as the IPMSM efficiency, torque ripple, current, and voltage total harmonic distortion (THD). Finally, experimental investigations have been carried out to validate the analysis conducted.

In this paper, the description of a series of quasi-static pushing tests and dynamic snap-back tests is proposed, involving the base-isolated emergency building of the Palermo university hospital. The base isolation system is characterized by a set of double-curved friction pendulum isolators placed on the top of the columns of the underground level, characteristics that cannot be found in the experimental studies available in the literature. The aim of the work was to investigate the static and dynamic properties of the building in question and comparing the in-situ results with the characteristics assigned during the design process and to assess the level of agreement. Static lateral pushing tests were aimed at identifying the main mechanical properties of the whole isolation level (e.g. friction forces and stiffness). Moreover, dynamic snap-back tests were carried out for different levels of displacement to characterize the dynamics of the building and the re-centering capacity of the isolation system. The design of the field testing, comprising the thrust mechanical device and the reaction RC wall, is described along the paper followed by the description of the in-situ testing and its main results. Then, the role of the in situ tests in proving the structural reliability and how to choose/use them in the case of friction pendulum base-isolated structures are discussed.

In this paper, we propose the design of a dual circular-polarized antenna for L-band applications (1.1-1.6 GHz). The designed antenna has been developed by considering crossed-dipoles on top of which a circular patch has been placed to properly act on the mutual coupling between the dipoles. The dual circular polarization is achieved by feeding dipoles in quadrature. Moreover, to increase the antenna gain and polarization purity at high elevation angles, a fence of passive monopoles has been added. The proposed antenna can profitably used as primary feed of a low-frequency parabolic reflector.

Partial discharge (PD) detection can be considered one of the most useful tools for assessing the insulation conditions of the power apparatus in high-voltage systems. Under AC conditions, this analysis is widely employed in online and offline tests, such as type tests or commissioning, and can be carried out by applying the phase-resolved PD (PRPD) method, since the patterns can give information about the defect classification. Under DC voltages, the classic pattern recognition method cannot be performed, and the measurements show complexities related to the nature of the phenomena. For this reason, to date, a standard for PD measurements under DC does not exist. In previous papers, a new method for PD detection under DC stress voltages has been proposed by the authors. It is based on the application of a direct current periodic (DCP) waveform useful in obtaining PRPD patterns. The dependence of partial discharge inception voltage (PDIV) and PD repetition rate (PDRR) on the δ shape parameter of the DCP for different materials, as well as the capability to recognize different discharge phenomena, provided valid indications on the behavior of PD in the transition from AC to DC. The aim of this paper is to evaluate the time dependence of PD occurring in a dielectric by applying the DCP waveform. In our previous studies, the investigations were focused on the PD behavior under different values of the DC voltage periodic part. In another work, the DCP waveform with both positive and negative polarity was applied to several dielectric materials. In the proposed work, instead, the DCP waveform is applied for a long time in order to observe its effect on the PD behavior for 72 h. In this way, due to the space charge accumulation phenomenon, the aging effect, also due to the space charge accumulation phenomenon, is evaluated. The methodological approach was to acquire PRPD patterns over time and evaluate their trends in comparison with the sinusoidal case. The experimental results show that, with a DCP waveform having δ = 0.6, the aging effect similar to that provided by pure DC stress is observed, while the acquired PRPD patterns are easily interpretated, as in the AC case.

Recently, sensor networks effectively provide many applications in different fields. The deployment of mobile sensors, unmanned aerial vehicles is to reduce the burden of energy consumption for sensor nodes. However, saving energy in such networks is still a critical issue. This paper investigates the performance of a hybrid RF-Solar harvesting circuit for remote sensing devices. The harvesting circuit can simultaneously harvest power from solar and radio frequency (RF) sources readily available in the surrounding environment. The proposed work builds RF and solar harvester circuits to create hybrid harvesting circuits for all elements in the combined sensing networks. The stand-alone RF harvester circuit is a dual-band multi-stage harvester that is designed to work at 2.4GHz, Wi-Fi/WLAN bands. The standalone solar harvester circuit comprises a solar panel with a maximum power point tracking (MPPT) algorithm. The whole hybrid system can produce a maximum power of up to 133.25W with a boost current element in the charging system. Since each node is equipped with a rechargeable battery, all the batteries are charged by the harvested power from the proposed circuits. This approach supports the operation of the networks safe and continuous even when a shortage of harvested power happens due to bad conditions such as cloudy or rainy days. This work shows promise and is applicable.

Cascaded H-Bridges Multilevel Inverter (CHBMI) is a fascinating solution for optimization purposes in several application fields. The CHBMI performance optimization can be reached both with hardware and software solutions. In detail, the CHBMI performances are a function of the modulation strategy adopted and its parameters such as modulation index, switching frequency, and dead time. This paper presents performance experimental analysis on dead time effects on CHBMI performance in terms of harmonic distortion and conversion efficiency. In this analysis, two different modulation strategies have been considered and implemented. The paper focuses on modulation strategies implemented, the test bench set-up, experimental investigations, and the results comparative analysis.

The paper is focused on the electromagnetic analysis of the Toroidal Field (TF) superconducting coils of the Divertor Tokamak Test facility (DTT) when electrical transients occur in the TF coils system: for example, during the operations of the Fast Discharge Units (FDUs) and considering also, the simultaneous occurrence of a fault condition. During the FDU intervention, a transient voltage excitation lasting few microseconds occurs at the TF coil terminals and it electrically stresses the insulations of TF coils itsef. To investigate the voltage distribution across, inside and between different Double Pancakes (DPs) of each TF coil, a lumped parameters circuital model has been developed and implemented in Ansys Simplorer simulation environment. This model includes both the detailed sub-model of each TF coil and FDU. The transient analyses have been carried out for two different scenarios: a reference one and a failure scenario, considering three different fault resistance values and also two different values of the resistance connecting the TF case to ground. In order to verify the correct sizing of the coil insulation and the TF case-to-ground resistance value inserted in the circuit of each TF coil, the voltages of each TF coil (terminal-to-terminal, terminal-to-ground, across of adjacent DPs and so) were computed in the time domain (in the range of milliseconds) for both scenarios. An overview of calculations and simulation results is presented and discussed, pointing out a high sensitivity of fault conditions and of overvoltage values and addressing mitigation strategies.

Partial discharge (PD) diagnosis tests, including detecting, locating, and identifying, are used to trace defects or faults and assess the degree of aging in order to monitor the insulation condition of medium- and high-voltage power cables. In this context, an experimental evaluation of three different printed circuit board (PCB)-based inductive sensor topologies, with spiral, non-spiral, and meander shapes, is performed. The aim is to assess their capabilities for PD detection along a transmission power cable. First, simulation and experimental characterization are carried out to determine the equivalent electrical circuit and the quality factor of the three sensors. PD activity was studied in the lab on a 10-m-long defective MVAC cable. The three PCB-based sensors were tested in three different positions: directly on the defective cable (P1), at a separation distance of 10 cm to 3 m (P2), and on the ground line (P3). For the three positions, all sensors’ outputs present a damped sine wave signal with similar frequencies and durations. Experimental results showed that the best sensitivity was given by the non-spiral inductor, with a peak voltage of around 500 mV in P1, 428 mV in P2, and 45 mV in P3, while the meander sensor had the lowest values, which were approximately 80 mV in P1. The frequency spectrum bandwidth of all sensors was between 10 MHz and 45 MHz. The high sensitivity of the non-spiral inductor could be associated with its interesting properties in terms of quality factor and SFR, which are due to its very low resistivity. To benchmark the performance of the designed three-loop sensors, a comparison with a commercial high-frequency current transformer (HFCT) is also made.

Sensing networks have recently proven to be useful in a variety of disciplines. The use of mobile sensing robots and unmanned aerial vehicles (UAVs) is intended to lessen the burden of sensor node energy consumption. However, conserving energy in the networks remains a major concern. In this work, a design of a hybrid RF-Solar harvesting system to support sensing devices is investigated. The harvesting circuits may collect energy from both solar and radio frequency (RF) resources that are commonly available in ambient environments. This approach creates hybrid harvesting circuits for all elements in the combined sensor networks by combining RF and solar harvester circuits. The RF harvester circuit is a dual-band multi-stage harvester for the 2.4GHz Wi-Fi/WLAN spectrum. In the solo solar harvester circuit, a solar panel with a maximum power point tracking (MPPT) algorithm is employed. The hybrid system can offer a maximum power of up to 136.5W due to a boost current element in the charging system. Because each node has a rechargeable battery, the gathered power from the proposed circuits is used to charge all of the batteries. This strategy allows networks to run safely and continuously even when there is a scarcity of gathered electricity due to severe weather, as cloudy or rainy days. This work is both promising and practical.

This paper presents an experimental investigation of two different printed circuit board (PCB) inductive sensors, with meander and non-spiral shapes, to assess their capabilities and best orientation for corona partial discharge (PD) detection. First, simulations with the Ansys HFSS software are performed in order to evaluate the equivalent electrical circuit of the two sensors and their 2d radiation patterns. The meander sensors presented a resonant frequency of 600 MHz, while it was around 1.1 GHz for the non-spiral. The 2d radiation pattern showed that better sensitivity is achieved when the inductive sensor is oriented 90 degrees with respect to the PD source. Experimental tests showed a peak-to-peak voltage of the PD signal detected by both sensors of around 14 mV when the orientation was 90 degrees with a main frequency around 35 MHz. The peak-to-peak voltage dropped to about 5.4 mV and 6.9 mV for the meander and the non-spiral sensors, respectively, with a main frequency of about 33.5 MHz, when the orientation was 0 degrees. The obtained PRPD patterns and the PD signal shapes were quite similar to those provided by a High-Frequency Current Transformer (HFCT) commercial sensor.

This paper presents the test results of an electrically small loop antenna sensor towards detecting the radiated magnetic field due to partial discharge (PD) activities. The loop antenna prototype was printed on an FR-4 substrate with a thickness of 1.6 mm, featuring a compact size of 20 mm times20 mm times1.7 mm. The proposed sensor, initially simulated with Ansys HFSS software, has a resonant frequency of about 100 MHz. Its detection capability for three types of partial discharges (i.e., corona, surface and internal PDs) has been evaluated. Laboratory experiments showed that the evaluated loop spiral antenna is appropriate for the detection of the three types of PDs. Indeed, the results show a peak-to-peak voltage equal to 22.87 mV, 74.8 mV, and 79.72 mV, respectively, for corona, surface, and internal PDs, with a frequency spectrum showing a maximum at 42.19 MHz, 16.41 MHz, and 35.1 MHz, respectively. Lastly, the performance of the proposed small loop sensor was compared to that of the commercial HFT sensor. The results show that the two sensors present comparative sensitivity for the three types of PD.

The space charge accumulation phenomenon represents one of the main degradation factors for the dielectrics employed in the field of the HVDC transmission. For this reason, the recommendation IEEE Std 1732-2017 has been proposed. In that standard, due to the importance attributed at the space charge phenomenon, the experts suggest the introduction of the space charge measurement in HVDC cables during the prequalification or type tests, by means of the PEA method. However, despite for tests in flat specimens the PEA technique is well consolidated, for cable specimens difficulties are still present. In particular, the PEA cell output signal is strongly conditioned by the arranged measurement setup, such as the connection between the components and ground, the length of the cable specimens under test, the position and the width of the pulse voltage electrodes. Based on the above, the aim of the present work was to arranged a PEA measurement setup in order to obtain a clear charge profile. In addition, considering that the above mentioned standard requires the space charge measurement also under temperature gradient, in our work this has also been made.

The occurrence of Partial Discharge (PD) inside a cavity subjected to HVDC voltage can be considered as one of the most likely sources of insulation ageing and failure. In practical applications, the recognition of PD under HVDC is more difficult than under AC stress because of the lower repetition rates and the impossibility to obtain a PD pattern synchronized with the waveform of the applied voltage. In this paper, the relationship between conduction phenomena in dielectrics and the occurrence of PD is investigated by means of a novel experimental setup. A couple of dielectric cells connected in series is subjected to various HVDC stress levels. The applied voltage is divided between the two cells by subjecting them to a temperature difference. The PD activity inside an air void defect existing within one of the two dielectric cell is measured by means of a PRY-CAM®. This setup reproduces, to the extreme, the effect of the distribution of the electric field in an HVDC cable on PD activity when it is exposed to a thermal gradient across the insulation. In addition, an equivalent circuit model has been developed to evaluate the PD Inception Voltage (PDIV) across the cavity. The comparison between the experimental and model results demonstrates the capability of the macroscopic conduction model to reproduce the inception of PD phenomena in solid dielectrics under HVDC stress and temperature gradient.

In recent years, the growing concern for air quality has led to the development of sustainable vehicles to replace conventional internal combustion engine (ICE) vehicles. Currently, the most widespread technology in Europe and Portugal is that of Battery Electric Vehicles (BEV) or plug‐in HEV (PHEV) electric cars, but hydrogen‐based transport has also shown significant growth in the commercialization of Fuel Cell Electric Vehicles (FCEV) and in the development of new infrastructural schemes. In the current panorama of EV, particular attention should be paid to hydrogen technology, i.e., FCEVs, which is potentially a valid alternative to BEVs and can also be hybrid (FCHEV) and plug‐in hybrid (FCPHEV). Several sources cited show a positive trend of hydrogen in the transport sector, identifying a growing trend in the expansion of hydrogen infrastructure, although at this time, it is still at an early stage of development. At the moment, the cost of building the infrastructure is still high, but on the basis of medium/long‐term scenarios it is clear that investments in hydrogen refueling stations will be profitable if the number of Fuel Cell vehicles increases. Conversely, the Fuel Cell vehicle market is hampered if there is no adequate infrastructure for hydrogen development. The opportunity to use Fuel Cells to store electrical energy is quite fascinating and bypasses some obstacles encountered with BEVs. The advantages are clear, since the charging times are reduced, compared to charging from an electric charging post, and the long‐distance voyage is made easier, as the autonomy is much larger, i.e., the psychosociological anxiety is avoided. Therefore, the first part of the paper provides an overview of the current state of electric mobility in Portugal and the strategies adopted by the country. This is necessary to have a clear vision of how a new technology is accepted by the population and develops on the territory, that is the propensity of citizens to technological change. Subsequently, using current data on EV development and comparing information from recent years, this work aims to investigate the future prospects of FCEVs in Portugal by adopting a dynamic model called SERA (Scenario Evaluation and Regionalization Analysis), with which it is possible to identify the Portuguese districts and cities where an FC charging infrastructure is expected to be most beneficial. From the results obtained, the districts of Lisbon, Porto and Aveiro seem to be the most interested in adopting FC technology. This analysis aims to ensure a measured view of the credible development of this market segment. © 2021 by the authors

Wireless sensor networks (WSNs) are usually deployed to different areas of interest to sense phenomena, process sensed data, and take actions accordingly. The networks are integrated with many advanced technologies to be able to fulfill their tasks that is becoming more and more complicated. These networks tend to connect to multimedia networks and to process huge data over long distances. Due to the limited resources of static sensor nodes, WSNs need to cooperate with mobile robots such as unmanned ground vehicles (UGVs), or unmanned aerial vehicles (UAVs) in their developments. The mobile devices show their maneuverability, computational and energy-storage abilities to support WSNs in multimedia networks. This paper addresses a comprehensive survey of almost scenarios utilizing UAVs and UGVs with strogly emphasising on UAVs for data collection in WSNs. Either UGVs or UAVs can collect data from static sensor nodes in the monitoring fields. UAVs can either work alone to collect data or can cooperate with other UAVs to increase their coverage in their working fields. Different techniques to support the UAVs are addressed in this survey. Communication links, control algorithms, network structures and different mechanisms are provided and compared. Energy consumption or transportation cost for such scenarios are considered. Opening issues and challenges are provided and suggested for the future developments.

The focus of this work is the transient modelling of the DC-arc voltage on a Hybrid Switch (a mechanical switch in parallel with a static switch) of a key protection component called Fast Discharge Unit (FDU) in the Divertor Tokamak Test (DTT). The DTT facility is an experimental tokamak in advanced design and realization phase, which will be built in the ENEA Research Centre in Frascati (Italy). The FDU allows the safe discharge of the Toroidal Field (TF) superconducting magnets when a quench is detected or a failure occurs in the power supply or in the cryogenic system. In this work, the arc conductance of the mechanical By-Pass Switch (BPS) of the Hybrid Switch is modelled using the well-known Mayr-Cassie equations and the Paukert arc parameters. The simulations show a good agreement with the expected results in terms of voltage and current transient from the mechanical switch to the static switch.

This paper deals with optimum design and development of a thermionic electron gun to meet specified beam requirements within defined electric and geometric constraints for a Ka -band traveling wave tube (TWT) for space applications. The electron gun design is based on the Pierce method and carried out according to the iterative process indicated by Vaughan. The design of a periodic permanent magnet (PPM) beam focusing system for the stability of the beam is also required. A sensitivity analysis, by varying electric parameters and geometric parameters, is presented and taken into account as a fundamental role to the aim of optimizing the design of the Pierce gun. A cathode current value of 550 mA at a cathode voltage value of 20 KV with a beam diameter value of less than 0.55 mm, as a result of the analysis, is imposed as a goal design parameter, to obtain a TWT output power value more than 500 W. The simulated results show very good agreement with the beam tester experimental results. The body current measured value, in excellent agreement with the simulated one, shows the effectiveness of the design procedure. Data from the experimental beam tester demonstrate 98% beam transmission to the collector.

this paper deals with the design, realization and test of a Microwave Monolithic Integrated Circuit (MMIC) power amplifier (PA) for next generation Q-band high throughput satellite systems. The MMIC, based on a four-stage architecture, was realized on a commercial 100 nm gate length Gallium Nitride on Silicon (GaN-Si) process. Accounting for the peculiarities of the selected technology, especially the lossy substrate and the relevant thermal resistance, particular care was devoted to identify effective circuital solutions able to mitigate the insertion loss of the matching networks and the temperature increase in the active devices. Experimental results carried out directly on-wafer show that the PA can achieve a saturated output power of roughly 36dBm with a gain and a power added efficiency higher than 20 dB and 23%, respectively, in the operative band from 37.5 GHz to 42.5 GHz. The chip area is 3.54 × 3.5 mm2. Such results are close to others state-of-art PAs realized in more expensive GaN processes based on Silicon Carbide, thus demonstrating that high resistivity Silicon substrate can be efficiently adopted also in such a peculiar application.

According to the electricity tariff recently issued by the Italian government for the domestic heating systems fed with heat pumps (HP), an energy and economic analysis was carried out with the aim of investigating the effectiveness of the air-to-air heat pump systems (HPS) as an alternative to the traditional heating using domestic gas boilers systems (GBS). For the purpose of this study, the apartments of three residential buildings were examined. The hourly heating loads were calculated with the ASHRAE radiant time series and the coefficient of performance (COP) of the HPs was evaluated for each operating condition. The costs for the heating system installation and electricity and/or gas bills were combined with the benefits, related to the current promoting tax credit program. The study turned out that the time when the GBS convenience surpasses the HPS mainly depends on the amount of thermal energy consumed in the year, although other important features, such as the domestic electricity consumption and the kind of energy used to supply the domestic hot water system and the cookers, play a relevant role in making the best choice between HPS and GBS.