1,721,078 research outputs found
Multiphase-Multilevel Inverter for Open-Winding Loads
No full textThis research book focused towards a novel multiphase-multilevel ac motor drive system much suitable for low-voltage high-current power applications. In specific, six-phase asymmetrical induction motor with open-end stator winding configuration, fed from four standard two-level three-phase voltage source inverters (VSIs). Proposed synchronous reference frame control algorithm shares the total dc source power among the 4 VSIs in each switching cycle with three degree of freedom. Precisely, first degree of freedom concerns with the current sharing between two three-phase stator windings. Based on modified multilevel space vector pulse width modulation shares the voltage between each single VSIs of two three-phase stator windings with second and third degree of freedom, having proper multilevel output waveforms. Complete model of whole ac motor drive based on three-phase space vector decomposition approach was developed in PLECS - numerical simulation software working in MATLAB environment. Proposed synchronous reference control algorithm was framed in MATLAB with modified multilevel space vector pulse width modulator. The effectiveness of the entire ac motor drives system was tested. Simulation results are given in detail to show symmetrical and asymmetrical, power sharing conditions. Furthermore, the three degree of freedom are exploited to investigate fault tolerant capabilities in post-fault conditions. Complete set of simulation results are provided when one, two and three VSIs are faulty. Hardware prototype model of quad-inverter was implemented with two passive three-phase open-winding loads using two TMS320F2812 DSP controllers. Developed McBSP (multi-channel buffered serial port) communication algorithm able to control the four VSIs for PWM communication and synchronization. Open-loop control scheme based on inverse three-phase decomposition approach was developed to control entire quad-inverter configuration and tested with balanced and unbalanced operating conditions with simplified PWM techniques. Both simulation and experimental results are always in good agreement with theoretical developments
Struttura di conversione multifase-multilivello per applicazioni di trazione elettrica
No full textCombinando lo schema multilivello con lo schema multifase si ottiene la configurazione multifase-multilivello proposta. Tale configurazione prevede l’utilizzo di 4 inverter trifase standard e di un motore esafase asimmetrico (a doppio avvolgimento trifase). In pratica, questo schema consente di quadruplicare la potenza del motore rispetto a quella che sarebbe ottenibile con uno dei quattro inverter che lo alimentano, con l’ulteriore vantaggio di forme d’onda di tensione multilivello su ciascuna delle sei fasi. Inoltre, la presenza di più fasi consente di aumentare l’affidabilità dell’azionamento che, in caso di guasto, può operare correttamente anche con 5, 4 o 3 fasi, se pur a ridotta potenza
Tecniche di modulazione per convertitori a quadruplo inverter trifase in condizioni di guasto
No full textL’attività di ricerca nel settore degli inverter multifase multilivello, già intrapresa dall’Unità di Bologna alcuni anni or sono, è stata ulteriormente sviluppata estendendo l’analisi alle problematiche della sincronizzazione delle tecniche di modulazione ed al funzionamento in caso di guasto di una o più unità del sistema di conversione.
Per quanto riguarda la sincronizzazione della modulazione, finalizzata essenzialmente alla riduzione o eliminazione delle sub-armoniche nella tensione di uscita, sono state sviluppate alcune tecniche di modulazione per la configurazione multifase multilivello a quadruplo inverter [1]-[2], in collaborazione con il Gruppo di Ricerca del Dr. V. Oleshuk del Institute of Power Engineering, Academy of Sciences of Moldova.
Per quanto riguarda l’analisi della configurazione a quadruplo inverter in caso di guasto, sono state esaminate le casistiche di malfunzionamento di uno, due e tre inverter, prevedendo per ciascuna di queste una modalità di funzionamento post-guasto a prestazioni ridotte [3].
L’analisi è basata sulla considerazione che il guasto, se pur limitato ad un solo componente di un singolo inverter trifase, compromette tipicamente il funzionamento dell'intero inverter. Per consentire al convertitore a quadruplo inverter di poter operare anche in caso di guasto, è quindi necessario isolare dal sistema l’intera unità trifase avariata. Con riferimento alla situazione più comune di un solo inverter guasto, sono state introdotte tecniche di modulazione tali da ripartire uniformemente la potenza sui tre inverter attivi (stessa potenza sulle alimentazioni) o di ripartire egualmente la potenza tra i due sistemi trifase di uscita (minimizzazione delle perdite di inverter e motore) [4]. Lo studio ha riguardato l’analisi teorica, la verifica con simulazioni numeriche in ambiente Matlab/PLECS, ed alcune verifiche speri- mentali sul prototipo di convertitore realizzato presso il Laboratorio del DIE
Future developments in vehicle-to-grid technologies
No full textThe concept of smart city is a multifarious of seven fundamental features: smart policies, smart governance, smart people, smart science and technology, smart environment, smart living, and smart built environment. Within the concepts of smart science and technology, smart environment, and smart built environment, the vehicle-to-grid (V2G) technology can be categorized. Since these characteristics of a smart city include subcategories, which consider Sci-Tec research and development, sustainable and safe transport systems, inter/national connectivity infrastructure, sustainable resources management, sustainable/green energy resources, Hi-Tec construction technology, and advance building technology. The smart city, status, and goals depend on each particular case, and each particular city features. These goals are measured by means of indicators, which are based on existing urban and building infrastructure, resources, codes, standards, and regulations. The smart-city model, proposed in PAS 182:2014, is intended to create a data-driven city, integrating city systems, with operational independence and operational efficiency. The modern infrastructure should be versatile, diversified, normalized, and its physical components may vary. In such way, there should be a clear strategy of balancing the development of existing and emerging or planned infrastructure. In order to achieve the goals and objectives of the smart-city planning, multidisciplinary teams should work together (engineers, architects, politicians, planning authorities, etc.), which final outcome should be an integrated economics, urban planning, architectural design, and sustainable construction. The main focus of this chapter is to put in context the previous developments made in V2G technologies as well as their considerations, constrains, and advantages—to take them as a starting point for future research topics related to the methods, simulations, and analysis presented in this document
Influence of Electric Vehicles on Improvements in the Electric Distribution Grid
No full textThis chapter analyses the improvements that will be required and challenges that the distribution system will probably face for upcoming years in the mission to modify the existing electricity grid towards a modern system which can tackle and automatically resolve problems. It will include a detailed examination of the evolution of the distribution grid, a thorough analysis of electric mobility, and a survey of state-of-the-art charging infrastructure for electric vehicles
Fault-Tolerant Control Strategies for Quad Inverter Induction Motor Drives with One Failed Inverter
No full textIn this paper post-fault-tolerant control strategies
for quad-inverter multiphase-multilevel induction motor
drives are investigated. More specifically, four standard 2-
level three-phase voltage source inverters (VSIs) supplying the
open-end windings of a dual three-phase induction motor
(asymmetric six-phase machine) is considered, quadrupling
the power capability of a single VSI with given voltage and
current ratings. In healthy conditions, the control algorithm is
able to generate multilevel voltage waveforms, equivalent to
the ones of a 3-level inverter and to share the total motor
power among the four dc sources in each switching period.
This sharing capability is investigated under post-fault
operating conditions, when one VSI must be completely
insulated due to a severe failure on it. In this case, the
conversion power units can operate with a reduced power
rating by a proper modulation of the remaining three VSIs.
The whole ac motor drive has been numerically implemented
to verify the effectiveness of the proposed control strategies
under healthy and post-fault operating conditions
Experimental Investigation of Fault-Tolerant Control Strategies for Quad-Inverter Converters
No full textFault-tolerant control strategies for quad-inverter based multiphase-multilevel converters are proposed and experimentally verified in this paper. Explicitly, the conversion scheme consists of four standard 2-level three-phase voltage source inverters (VSIs), able to supply a dual three-phase induction motor in open-end stator winding configuration (asymmetric six-phase machine), quadrupling the utility power of a single VSI within given voltage and current ratings. The developed modulation scheme has the capability to generate multilevel output voltage waveforms in healthy conditions, equivalent to the one of a 3-level VSI, and to share the total motor power among the four dc sources in each switching cycle. This sharing potentiality is investigated under post-fault operating conditions, when one VSI completely insulated due to a severe failure on it. In such circumstances, the quad-inverter system can perform with reduced power rating by a proper modulation of the remaining three healthy VSIs. The complete multiphase-multilevel conversion system with the proposed control algorithm under healthy and post-fault operating conditions has been verified by experimental implementation in open-loop control aspect using two dsp TMS320-F2812 processors with two three-phase passive loads in openend configuration
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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