186 research outputs found
Diode-Clamped Multilevel Converters: a practicable way to balance dc-link voltages
No full textThe converter topologies identified as Diode Clamped
Multilevel (DCM) or, equivalently as Multi Point Clamped
(MPC), are rarely used in industrial applications, owing to
some serious drawbacks involving mainly the stacked-bank
of capacitors that constitutes their multilevel DC-link. The
balance of the capacitor voltages is not possible in all
operating conditions when the MPC converter
possesses a passive front-end. On the other hand,
in AC/DC/AC power conversion, the back-to-back
connection of a multilevel rectifier with a multilevel
inverter allows the balance of the DC-link capacitor
voltages and, at the same time, it offers the
Power Factor Correction capability at the mains
AC input. An effective balancing strategy suitable
for MPC conversion systems with any number of
DC-link capacitors is presented here. The strategy
has been carefully studied to optimize the converter
efficiency. The simulation results related to a high
power conversion system (up to 10 MW) characterized
by four intermediate DC-link capacitors are shown
GaN E-HEMT based High Flatness Broadband Power Noise Source for Dynamic Identification of Mechatronic Systems and Batteries
No full textStill today the dynamic identification of mechatronic systems - in particular electrical machines - is often based on stimulating them with deterministic signals, being single sinusoidal tones, single steps or periodical pulse trains of fixed frequency the most common ones. Such methodologies were the most, when not the only, practicable ones when the instrumentation was limited to low frequency generators and analog oscilloscopes, at most. The modern metrological scenario allows to concretize way more sophisticated approaches nowadays, which can bring to Mechatronics more holistic and easily executable identification methods; like those based on flat noise sources traditionally used in Radio Frequency (RF). More in general, the adoption of SiC and GaN fully controllable switches demands that also Power Electronics become eventually permeated with the very different way of thinking peculiar of RF. Within the framework of such cultural and methodological evolution that Power Electronics must embrace, the paper describes the unconventional use of converters based on GaN switches as powerful high-flatness noise sources for broadband dynamic identification, here tailored for modern electrical machines and battery technologies. Indeed, owing to the much shorter raise and fall times, as well as much higher switching frequencies enabled by GaN, it is possible to greatly extend the upper boundaries of the frequency bands where desired spectra can be synthesized by commutating such fully controllable switches according to proper time-based patterns. The authors illustrate the use of a randomly PWM-modulated H-bridge employing GaN E-HEMTs as high-flatness noise source up to at least 200 kHz thanks to 1 MHz PWM carrier. Various selected experimental results from identifications of BLDC Motors and Lithium-Iron-Phosphate (LiFePo4) cells are shown. The details in the figures are fully visible by magnifying the electronic version of the paper, which represents the same approach when Microfilms were widely used
Tenca inedito fra Leopardi e Petrarca
No full textSi tratta della ricostruzione filologica di importanti carte saggistiche inedite (fra le quali spiccano quelle più tarde, del 1880, sull' "Appressamento della morte" del Leopardi e sul "De vita solitaria" del Petrarca) del critico e patriota milanese Carlo Tenca (1816-1883), a cui lo studioso ha dedicato un trentennio di lavoro: pubblicandone, fra l'altro, per la Commissione bolognese per i Testi di Lingua, le edd. critiche dei "Versi editi e inediti" (1979), nonché dei "Racconti ed abbozzi editi e inediti" (2003); per Liguori, i saggi 1845-59 sull'editoria popolare, "Delle strenne e degli almanacchi" (1995); per la Clueb, gli "Scritti d'arte", 1838-59 (I ed. 1998, 2010, ristampa riveduta e corretta
An optimal controller for voltage balance and power losses reduction in MPC AC/DCAC converters
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Investire in alternative investments: attori e business model innovativi nell’ecosistema delle start-up
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INTRODUCING AN ACCESSIBLE TASK-BASED LEARNING (ATBL) APPROACH TO INCLUSIVE ENGLISH LANGUAGE TEACHING (IELT) AT THE UNIVERSITY OF VERONA
No full textNow that the pandemic is slowly abating, it is time to focus on a learner-centred curriculum design for the future. The OECD report [1] on curriculum design for their 2030 project, underlines the fact that there may be “wide gaps” (p. 17) between the intentions behind curriculum design and the actual learner experience of such curricula. Over the past few years of Emergency Remote Teaching (ERT), in fact, the focus has not been on either content or learners, but rather on digital tools and the mechanics of implementing them in online learning [2]. The Covid pandemic and the adoption of ERT, an ad hoc solution to an unexpected problem, was conceived of as an emergency measure with no long-term guarantees of success. It has, however, confirmed that the process of integrating digital tools in education may only be effective on the plane of inclusion and equity if adopted in a principled manner, and most importantly, if a learner-centred approach is adopted [2]. One framework which seeks to cater for the needs of inclusion from the viewpoint of diverse students in diverse learning contexts, regardless of access to technology, is the Universal Design for Learning (UDL), and its three macro areas, i.e. the what (content) the how (formative aspects such as goal setting) and the why (motivation) of learning, it provides a transferable approach that still enables autonomy and flexibility in its implementation [3]. This presentation illustrates concrete ways in which these three central tenets of UDL are being implemented in the design of an experimental, accessible, task-based learning (ATBL) approach to Inclusive English Language Teaching (IELT) at the Verona University language centre. The course is part of an ongoing research project which aims to develop an effective model for this type of teaching. The learning design stems from the findings analysed qualitatively in a series of interviews conducted with key stakeholders in our study (teachers, tutors and students). The 40-hour course blends synchronous onsite/ online sessions with asynchronous activities provided for autonomous study on the e-learning platform. The participants are mixed-abilities, including special needs learners. An ATBL approach was created for this learning design because of its focus on meaningful tasks in realistic contexts that put the needs of the learners at the centre of the process. The interactive use of language in real-life tasks may also promote increased learner agency and engagement. This, in turn, may also impact performance gain, while leading to learner perceptions of autonomy, motivation, and a growing self-awareness that contribute both to more effective learning and competence. References: [1] A. Schleicher, Curriculum (Re)design. A Series of Thematic Reports from the OECD Education 2030 Project, 2020. Retrieved from https://www.oecd.org/education/2030-project/contact/brochure-thematic-reports-on-curriculum-redesign.pdf [2] J. Xiao, “Decoding new normal in education for the post-COVID-19 world: Beyond the digital solution,” Asian Journal of Distance Education, vol. 16, issue 1, pp. 141-155, 2021. Retrieved from http://asianjde.com/ojs/index.php/AsianJDE/article/view/558. [3] Center for Applied Language Technology, “The UDL Guidelines”, CAST, 2022. Retrieved from https://udlguidelines.cast.org/?utm_source=castsite&utm_medium=web&utm_campaign=none&utm_content=footer. Keywords: Universal Design for Learning, Task-Based Learning, English Language Teaching, Accessibility, Inclusion, Emergency Remote Teaching
Voltage regulation of AC/DC converters for railway applications: a comparison among control strategies
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