10 research outputs found
PRMA-ISA protocol for multiple access of mixed voice and data traffic
No full textA combined multiple access protocol is investigated, based on the ISA algorithm, which was first introduced for a slotted unframed channel, and later modified to fit a cellular wireless network with distributed handoff [13, 14]. ISA manages the access rights at the beginning of each slot in order to maximize the success probability (one step throughput), based on an independence assumption on the presence of packets at the stations. We extend this concept in the context of a framed channel that has the same basic structure as Packet Reservation Multiple Access (PRMA) [1]. In this case, it is possible to see the frame as a whole bunch of 'parallel channels', over which the overall success probability must be maximized at the beginning of the frame for all free slots. The combined PRMA-ISA algorithm has been developed and investigated by means of simulations, using models previously proposed for data and voice (phone calls) traffic
Optimization of Harmonic Performances in Multilevel Converter Structures
No full textIn recent years, multilevel power converters have been gaining more and more interest in high voltage and high power conversion. Within this scenario, a very interesting approach lies in the use of semiconductors with different voltage ratings and different switching characteristics. For this aim both GTOs and IGBTs could be employed, but a better technological solution surely lies in the use of IGBTs only, with different voltage ratings. Optimized multilevel converter structures, based on the Multi-Point-Clamped (MPC) concept or on the series connection of H-bridge inverter could then be developed, exploiting the possibilities arising from the use of different voltage levels. The authors have developed an optimal modulation strategy that uses the redundant switching configurations of the MPC converter structure to achieve an increment of the output voltage levels number. The novel approach, that is here proposed, permits a reduction of the harmonic content of the voltage/current waveforms and an interesting optimization of the switching stresses of the power semiconductor devices
Modeling, simulation and experimental validation of a generation system for medium-voltage DC integrated power systems
No full textIn this paper, a demonstrative technological implementation of a shipboard 2.15 MVA generation system is described along with its modeling, numeric simulation and some factory tests. The system, named Naval Package (NP), is part of a demonstrative program commissioned by Italian Navy for preliminary evaluations of Medium-Voltage DC (MVDC) supply technologies aimed at equipping its future vessels. The NP is made by a dual-star alternator, whose two stator three-phase windings feed two diode-rectifier full-bridges respectively. The alternator (rated speed 6300 rpm) is designed to be moved by a 22000 rpm gas turbine through a gearbox. This paper will present NP innovative issues, with reference to design solutions, operative requirements, dynamic modeling under normal and faulty conditions, and some factory tests
Sviluppo e utilizzo di architetture di controllo digitale per sistemi elettronici di potenza ed azionamenti elettrici
No full textDottorato di ricerca in ingegneria elettrica. 10. ciclo. Docente di riferimento M. MazzucchelliConsiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7, Rome; Biblioteca Nazionale Centrale - P.za Cavalleggeri, 1, Florence / CNR - Consiglio Nazionale delle RichercheSIGLEITItal
Combined ZVS-ZCS topology for high-current direct current hybrid switches: Design aspects and first measurements
No full textElectrical Engineering, Mathematics and Computer Scienc
Exploitation of low-cost microcontroller potentialities to develop fully digital rotor flux oriented induction motor drives
No full text
