995 research outputs found
Development of bidirectional dc-dc converters for hybrid power sources - Final Report
No full textA Bidirectional Isolated Full-Bridge Converter was designed, prototyped and tested. The device is intended to interface a Bank of Supercapacitors with a battery-powered bus, in order to boost the capability of supplying large power peaks. The converter was based on the Isolated Dual Active Bridge configuration. When driven by an external control voltage, it is capable of generating in both directions a train of current pulses, with 2kW peak power, for any battery voltage in the range 24-32V and for any supercapacitor voltage in the range 35-70V. Worst-case battery current was 70A. Pulse duration was 100ms with 50% duty cycle and 1 ms rise time
Energy Policies and Sustainable Management of Energy Sources
No full textSustainability of current energy policies and known mid-term policies are analised in their multiple facets. First an overview is given about the trend of global energy demand and energy production, analysing the share of energy sources and the geographic distribution of demand, on the basis of statistics and projections published by major agencies. The issue of sustainability of the energy cycle is finally addressed, with specific reference to systems with high share of renewable energy and storage capability, highlighting some promising energy sources and storage approaches.</jats:p
Energy needs and sustainable management of the energy cycle
No full textThe issue of sustainability of the energy policies is analised in its manifold facets. An overview is given about the trend of global energy needs and energy production, analysing the geographic distribution of consumptions and the share of energy sources, on the basis of the statistics and projections published by major agencies. The issue of sustainability of the energy cycle is finally addressed, highlighting how the use of biomasses as an energy source and of hydrogen as an energy carrier are among the most promising approaches
Predictive dead time controller for GaN-based boost converters
No full textA dynamic dead time controller is presented, specifically intended to operate in synchronous boost converters based on GaN field-effect transistor switches. These transistors have a reduced stored charge with respect to silicon metal-oxide-semiconductor field-effect transistors with similar breakdown voltage and series resistance, and can operate at higher frequencies with reduced switching losses. On the other hand, the voltage drop in reverse conduction is typically more than doubled with respect to silicon devices resulting in relevant power losses during the free-wheeling phases. Therefore, dynamic control of dead time can be profitably applied even in converters operating in the tens of volts range. The device presented in this study controls the switching delays taking into account both variations of the fall/rise times and of the turn-off/on delays, in order to keep dead time within a range of a few nanoseconds above its minimum value. A discrete-component prototype was designed, built in a synchronous boost converter and extensively tested at 1-2MHz switching frequency, in a range of operating parameters corresponding to significant variations of the switching times (currents in the 1-6A range, output voltage up to 50V). The prototype demonstrated the capability to match dead time to actual operating conditions with a smooth and fast transient response
A Florentine family in crisis: the Strozzi in the fifteenth century.
No full textPhDIn 1434 the Strozzi lineage had held a leading position in
Florentine society and government for at least one hundred and fifty
years, and was one of the largest and wealthiest of the city's
patrician lineages. The records of the catasto of 1427 and of the
scrutiny of 1433 are used to give a profile of the dominant social,
economic and political position of the Strozzi before the advent of
Medicean dominance. Their record of electoral success, and the
political and cultural leadership of influential and respected men
such as Palla di Nofri and Matteo di Simone, with other factors, put
the Strozzi amongst the greatest enemies of the victorious Medicean
regime of late 1434. The effects of political opposition and exile
on the lineage are examined both directly, through records of office-holding,
and indirectly through such indicators as marriage alliances
and household wealth. The two most prominent lines of the Strozzi
were exiled after 1434. Palla di Nofri's life and preoccupations in
his Paduan exile are examined, together with the lives of his sons;
none of these Strozzi ever returned to Florence, pursued as they were
by the enmity of the Medicean regime. The very different careers of
Filippo di Matteo and his brother Lorenzo are also examined: how they
succeeded in founding a lucrative bank in Naples, and in returning to
Florence to 'rebuild' (rifare) the position of the Strozzi lineage
there. The final decades of the century saw the Strozzi in an
economically more secure position, due substantially to the efforts
of Filippo. Except for a very small number of its members admitted
into the regime, most of the lineage is here shown to have remained
excluded from significant political office until after the fall of
the Medici regime in 1494
Design, implementation and experimental results of an inductive power transfer system for electric bicycle wireless charging
No full textThe use of renewable energy and the transformation of transport mode are crucial items for achieving an efficient and clean electrical mobility that allow being competitive on the market. In this context the interface between the power system and the Electric Vehicles (EVs) assumes a strategic role. Specifically, wireless energy transmission, based on Inductive Power Transfer (IPT), is an attractive solution for EVs charging. Moreover, the use of electric bicycles or kick scooters as mode of urban transport is continuously growing because they are lightweight, sustainable, easily parking, flexible and efficient transport devices. Owing to its benefits, the wireless power transfer can be considered suitable for those devices. In fact, IPT can also be exploited for Vehicle-To-Grid (V2G), where the wireless power flow can occur from battery to power grid as well. For E-bike applications, bicycle-to-grid or bicycle-to-bicycle energy transfer are viable solutions by means of a Bi-Directional Inductive Power Transfer (BDIPT). In this paper, a 300 W IPT wireless charger prototype for E-bikes is proposed. Modelling, design, simulation and experimental results of this prototype are provided. Open-loop and closed-loop tests have been performed, focusing on system behaviour for different cases of load, distance and misalignment between the coils
Highly Efficient Capacitive Galvanic Isolation for EV Charging Stations
No full textThis paper proposes an isolated Switched Capacitor (SC) power converter which provides galvanic isolation through Capacitive Power Transfer (CPT). The combination of these two technologies might answer for electrical and power requirements in different electrical mobility application fields, such as battery charging. Accordingly, due to the low conversion losses the combination of these two technologies can provide, compact, cost effective and highly efficient power converters can be derived, thus potentially answering the scalability requirements for the Electric Vehicles (EV) market. To assess the operation of the proposed circuital solution, a Full Bridge (FB) CPT isolated interfacing converter prototype has been designed and built. Since GaN switches were used for the primary bridge, by taking advantage of their low input capacitance and gate charge, a 500 kHz switching frequency was set, thus deriving a compact power converter. The prototype has been designed for applications up to 12 kW (600 V, 20 A), and tested close to 3 kW (up to 400 V or 15 A) for the purpose of this work to demonstrate its functionality. The measurements assessed a conversion efficiency above 90% with a peak of almost 95%
An Approach for Maximum Power Point Tracking in Satellite Photovoltaic Arrays
No full textA technique for managing power generation in a spacecraft power bus is introduced. The proposed technique is based on a sectional MPPT approach, where the solar array is split into several sections, interfaced to the power bus by dedicated Array Power Regulators. The dc-dc converter inside each of them is enslaved to a multimode controller, capable of selecting either MMPT or regulation mode or standby. The operating mode is managed in such a way that the rough regulation is achieved by sequentially increasing/decreasing the number of converters in MPPT according to the fluctuations of the power absorption on the bus, while the fine regulation is performed by a single converter in the regulation mode. Some possible configurations of the system are analyzed. Simulations of the algorithm and experimental results are provided
SMPT: a sequential MPPT approach for power bus management in space vehicles
No full textA technique for managing power generation in a
spacecraft power bus is introduced. SMPT is based on a
sectional MPPT approach, where the solar array is split into
several sections, interfaced to the power bus by dedicated Array
Power Regulators. The dc-dc converter inside each of them is
enslaved to a multimode controller, capable of selecting either
MMPT or regulation mode or standby. The operating mode is
managed in such a way that the rough regulation is achieved by
sequentially increasing/decreasing the number of converters in
MPPT according to the fluctuations of the power absorption on
the bus, while the fine regulation is performed by a single
converter in the regulation mode. Some possible configurations
of the system are analyzed. Simulations of the algorithm and
experimental results are provided
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