1,721,324 research outputs found
SPERIMENTAZIONE PRELIMINARE DI UN SISTEMA DI CONVERSIONE MULTIFASE MULTILIVELLO “QUAD INVERTER”
No full textL’attività di ricerca inerente i convertitori multifase-multilivello, già intrapresa da alcuni anni presso l’Unità di Bologna, è stata recentemente integrata con la la realizzazione sperimentale di un prototipo di sistema di conversione esafase a 9 livelli. 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 ’affidabilità dell’azionamento che, in caso di guasto, può operare correttamente anche con 5, 4 o 3 fasi, se pur a ridotta potenza.
Per maggior semplicità e sicurezza operativa, nella prime verifiche sperimentali è stato utilizzato un carico passivo esafase equilibrato (a morsetti aperti) in luogo del motore. La realizzazione finale prevede l’impiego di un motore ad induzione a doppio statore trifase asimmetrico, ottenuto mediante la modifica dell’avvolgimento di un motore trifase standard. Per quanto riguarda la tecnica di modulazione, si è dapprima adottato un semplice controllo PWM sui singoli inverter trifase, senza ottimizzazione della forma d’onda di uscita. Le prime verifiche sperimentali hanno riguardato sia il funzionamento simmetrico sia quello asimmetrico del convertitore, per verificare la possibilità di ripartizione della potenza in uscita tra i 4 inverter. I risultati ottenuti sono in buon accordo con quelli derivanti dalle simulazioni numeriche, già presentati e discussi nel corso del precedente anno
Transient Analysis and Control Strategies for a Quad-Inverter Multiphase Multilevel Motor Drive in Faulty Conditions
No full textIn this paper, post-fault-tolerant control strategies for quad-inverter multiphase-multilevel induction motor drives are investigated. More specifically, four standard two-level three-phase VSIs (voltage source inverters) supplying the open-end windings of a dual three-phase induction motor is considered, quadrupling the power capability of a single VSI with given voltage and current ratings. In healthy conditions, the control al gorithm is able to generate multi-level voltage waveforms, equivalent to the ones of a three-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 unit 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, and the effectiven ess of the proposed control strategies under healthy and post-fault operating conditions have been proved
Configurazione “quad-inverter” per la propulsione elettrica a bassa tensione e/o alta potenza
No full textNel corso dell’ultimo anno è stata ulteriormente sviluppata l’attività inerente i convertitori multifase-multilivello, conseguente alla combinazione di due attività già intraprese da alcuni anni dall’Unità di Bologna: la ricerca sui sistemi multifase (n > 3) e lo studio dei convertitori multilivello. L’obiettivo della ricerca è quello di studiare ed implementare nuove tecniche di modulazione per sistemi di conversione in grado di alimentare motori elettrici di relativamente
grande potenza (decine o centinaia di kW) con tensioni di alimentazione relativamente basse (fino a 100V), utilizzando componentistica elettronica discreta, quindi con basso costo, alta efficienza ed elevata affidabilità. La configurazione proposta 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. La tecnica di modulazione proposta è in grado di provvedere a forme d’onda di tensione multilivello ed allo stesso tempo di regolare la ripartizione di potenza media tra i quattro inverter all’interno di ciascun ciclo di modulazione. Le tecniche di modulazione proposte sono state testate e validate numericamente con il programma PLECS in ambiente Simulink/Matlab. Il prototipo dell’intero sistema di conversione è attualmente in fase avanzata di realizzazione presso il laboratorio del Dipartimento di Ingegneria Elettrica dell’Università di Bologna
Preliminary hardware implementation of a six-phase quad-inverter induction motor drive
No full textA hardware implementation of a quad-inverter configuration for multi-phase multi-level induction motor drives is presented in this paper. The scheme is based on four conventional 2-level three-phase voltage source inverters, able to supply the open-end windings of a dual three-phase motor (asymmetric six-phase machine), quadrupling the power capability of a single VSI with given voltage and current ratings. By a proper control algorithm the proposed converter is able to generate multi-level voltage waveforms, equivalent to the ones of a 3-level inverter, and to share the total motor power among
the four dc sources within each switching period. A full-scale prototype of the whole power system has been realized utilizing six balanced impedances as six-phase load. A complete set of experimental results is given with reference to both balanced and unbalanced operating conditions
Simulation of Processes in Dual Three-Phase System on the Base of Four Inverters with Synchronized Modulation
No full textNovel method of space-vector-based pulse-width modulation (PWM) has been disseminated for synchronous control of four inverters feeding six-phase drive on the base of asymmetrical induction motor which has two sets of windings spatially shifted by 30 electrical degrees. Basic schemes of synchronized PWM, applied for control of four separate voltage-source inverters, allow both continuous phase voltages synchronization in the system and required power sharing between DC sources. Detailed MATLAB-based simulations show a behavior of six-phase system with continuous and discontinuous versions of synchronized PWM.</jats:p
High-Voltage High-Frequency Arbitrary Waveform Multilevel Generator for DBD Plasma Actuators
No full textA high-voltage high-frequency single-phase arbitrary waveform voltage generator able to supply a wide range of plasma reactors is proposed in this paper. The generator structure is based on the cascaded H-bridge multilevel topology, including 24 H-bridge basic modules with the capability of 49 output voltage levels. The individual H-bridge dc supply (600V) is provided by a flyback converter fed by a low-voltage (12V) dc battery. In this way, the input isolation of the ±14.4kV maximum output voltage is realized in a simple and effective manner, and a portable device is obtained. The multilevel generator has been tested by supplying a dielectric barrier discharge (DBD) fluid-dynamic plasma actuator with different voltage waveforms, pointing out a wide and interesting set of results in terms of output plasma currents, and a first comparison has been carried out with respect to a conventional AC sinusoidal generator. A simplified circuit model has been introduced for the DBD plasma actuator, and the whole system has been numerically implemented by Simulink of Matlab. The simulation results are in good agreement with the experiments
Quad-Inverter Configuration for Multi-Phase Multi-Level AC Motor Drives
No full textA novel quad-inverter configuration for multiphase multi-level ac motor drives is analyzed in this paper. The proposed scheme is based on four conventional 2-level three-phase voltage source inverters (VSIs) supplying the open-end windings of a dual three-phase motor (asymmetric six-phase machine), quadrupling the power capability of a single VSI with given voltage and current ratings. The proposed control algorithm is able to generate multi-level voltage waveforms, equivalent to the ones of a 3-level inverter, and to share the total motor power among the four dc sources within each switching period. The whole ac motor drive has been numerically implemented and a complete set of simulation results is given
Investigation on the Development of a Sliding Mode Controller for Constant Power Loads in Microgrids
Full text linkTo implement renewable energy resources, microgrid systems have been adopted and developed into the technology of choice to assure mass electrification in the next decade. Microgrid systems have a number of advantages over conventional utility grid systems, however, they face severe instability issues due to the continually increasing constant power loads. To improve the stability of the entire system, the load side compensation technique is chosen because of its robustness and cost effectiveness. In this particular occasion, a sliding mode controller is developed for a microgrid system in the presence of constant power loads to assure a certain control objective of keeping the output voltage constant at 480 V. After that, a robustness analysis of the sliding mode controller against parametric uncertainties was performed and the sliding mode controller’s robustness against parametric uncertainties, frequency variations, and additive white Gaussian noise (AWGN) are presented. Later, the performance of the proportional integral derivative (PID) and sliding mode controller are compared in the case of nonlinearity, parameter uncertainties, and noise rejection to justify the selection of the sliding mode controller over the PID controller. All the necessary calculations are reckoned mathematically and results are verified in a virtual platform such as MATLAB/Simulink with a positive outcome
Multi-Phase Multi-Level AC Motor Drive Based on Four Three-Phase Two-Level Inverters
No full textA novel multi-phase multi-level ac motor drive is analyzed in this paper. The proposed scheme is based on four conventional 2-level three-phase voltage source inverters (VSIs) supplying the open-end windings of a dual threephase motor (asymmetric six-phase machine), quadrupling the power capability of a single VSI with given voltage and current ratings. The proposed control algorithm is able to generate multi-level voltage waveforms, equivalent to the ones of a 3-level inverter, and to share the total motor power among the four dc sources within each switching period. The proposed ac motor drive has been numerically implemented and a complete set of simulation results is given to prove the effectiveness of the whole scheme
Real-time forecasting of EV charging station scheduling for smart energy systems
No full textThe enormous growth in the penetration of electric vehicles (EVs), has laid the path to advancements in the charging infrastructure. Connectivity between charging stations is an essential prerequisite for future EV adoption to alleviate user's "range anxiety". The existing charging stations fail to adopt power provision, allocation and scheduling management. To improve the existing charging infrastructure, data based on real-time information and availability of reserves at charging stations could be uploaded to the users to help them locate the nearest charging station for an EV. This research article focuses on an a interactive user application developed through SQL and PHP platform to allocate the charging slots based on estimated battery parameters, which uses data communication with charging stations to receive the slot availability information. The proposed server-based real-time forecast charging infrastructure avoids waiting times and its scheduling management efficiently prevents the EV from halting on the road due to battery drain out. The proposed model is implemented using a low-cost microcontroller and the system etiquette tested
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