Renewable energy sources are key enablers to decrease greenhouse gas emissions and to cope with the anthropogenic global warming. Their intermittent behaviour and limited storage capabilities present challenges to power system operators in maintaining the high level of power quality and reliability. However, the increased availability of advanced automation and communication technologies has provided new intelligent solutions to face these challenges. Previous work has presented various new methods to operate highly interconnected power grids with corresponding components in a more effective way. As a consequence of these developments the traditional power system is transformed into a cyber-physical system, a smart grid.Previous and ongoing research activities have mainly focused on validating certain aspects of smart grids, but until now no integrated approach for analysing and evaluating complex configurations in a cyber-physical systems manner is available. This paper tackles this issue and addresses system validation approaches for smart grids. Different approaches for different stages in the design, development, and roll-out phase of smart grid solutions and components are discussed. Finally, future research directions are analysed.Keywords: smart grid; simulation; hardware-in-the-loop; research; infrastructure; education; training IntroductionEnergy efficiency and low-carbon technologies are key enablers to mitigate the increasing emission of green-house gases still resulting in a global warming trend [1]. The efforts to reduce greenhouse gas emissions also strongly affect the power system. Renewable sources, storage systems and flexible loads provide enhanced possibilities but power system operators and utilities have to cope with their fluctuating nature, limited storage capabilities and the typically higher complexity of the whole infrastructure with a growing amount of heterogeneous components [2]. Additionally, due to changing framework conditions, like the liberalization of the energy markets and new regulatory rules, as well as technology developments (e.g., new components), approaches for design, planning, and operation of the future electric energy system have to be restructured. Sophisticated component design methods, intelligent information and communication architectures, automation and control concepts as well as proper standards are necessary in order to manage the higher complexity of such intelligent power systems (i.e., smart grids) [3][4][5]. Besides technical challenges also economic, ecological and social issues have to be addressed in smart grid research and innovation, too.During the last decade-especially in the past framework programs of the European Commission (i.e., FP6 and FP7)-a growing number of research and technology development activities have already been carried out in this area. Their main attempt was to fulfil the challenging goals and needs of the Strategic Energy Technology Plan (SET-Plan) of the European Commission for a sustainable environment and to foster the inno...

In this letter, a very low-profile planar horn antenna is proposed. It consists of a subwavelength aperture placed into a "Bull's Eye" concentric periodic corrugated conducting plate that produces good return losses and a narrow radiated beam. The antenna is excited by means of a waveguide whose flange has been properly mechanized in the rear part of the structure. The mechanism explaining this phenomenon is similar to the enhanced transmission observed at optical wavelengths in similar structures. In this work, the circularly corrugated structure has been scaled into the microwave frequency range and, moreover, the plane wave excitation has been replaced by a subwavelength aperture excited by a conventional closed metallic waveguide. This transforms the original focusing structure into a new concept of a very low-profile feeder with potential applications.Index Terms-Bull eye, concentric periodic corrugated plate, metamaterials, subwavelength aperture, very low-profile feeder.

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In this letter, very low profile planar horn antenna feeders are designed and measured. Using previous results of antennas consisting of a narrow slot on a metallic plane and flanked by two grooves, a further step is given here by reducing the thickness of the prototype. A key factor in the approach is the operation in the transversal slot resonance instead of the usual longitudinal slot resonance. Moreover, by inserting a dielectric material of relative permittivity r 1, the thickness can be further reduced, maintaining and even improving the radiation features of the prototype. Reducing the metallic plate thickness has important consequences in the weight and profile of the antennas, making them easy to handle and to fit into different structures. In addition, in ranges where the wavelength is of the order of centimeters, a thick metallic plate can be a serious drawback due to mechanical restrictions. In these cases the design following the rules given in this letter can alleviate this constraint.Index Terms-Corrugated plate, subwavelength aperture, very low profile feeder.

A dual-operating-band planar horn antenna having very low profile is presented in this paper. By opening a subwavelength aperture into a corrugated conducting plate, good return losses and a narrow radiated beam in each of the two desired operating frequency bands can be measured. This behavior is very similar to that observed in optical wavelengths where enhanced transmission was measured through apertures etched in metallic corrugated plates. Here, the double-corrugated structure has been scaled into the microwave frequency range and the excitation has been done by a conventional closed metallic waveguide placed in the rear part of the structure. In this way, a new concept of a very low profile feeder is proposed with potential wireless applications.Index Terms-Double-periodic corrugated plate, dual-band, subwavelength aperture, very low profile feeder.

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In the Master's of Telecommunication Engineering program at the University of Deusto, Spain, courses in communication circuit design, electronic instrumentation, advanced systems for signal processing and radiocommunication systems allow students to acquire concepts crucial to the fields of electronics and communication. During the educational project presented in this paper, students build a continuous-wave frequency-modulation (CWFM) Doppler radar system from components as simple as ordinary cocoa cans and common electronics components placed on a breadboard without any soldering. One of the goals of the project is to stimulate students' interest in building an entire, completely functional communication system that integrates the knowledge acquired in the various courses and whose functioning they can check in real scenarios. This paper describes this learning project and the ways in which it helps students understand and connect all the concepts that underlie a fully operative communications system, thus meeting the competencies and learning outcomes of the courses involved in the project.

This study is intended to show the future voltage control strategy designed in the framework of the ELECTRA Integrated Research Programme (IRP) project for the web-of-cells (WoC) concept. This scheme, called post-primary voltage control, aims to keep the node voltages at any time within the bands defined by the regulations and to minimise the power losses in the system by calculating the optimal voltage set-points for the different nodes. The reactive power will mainly be used to restore the voltages but also active power could be delivered in some cells depending on their voltage levels. Different operating modes of the voltage control will be discussed taking both planning and the real-time operation phases into account. The application of the voltage control strategy to one test grid considered as representative of the WoC structure will also be shown in this study.