1,721,037 research outputs found
Metodo e Dispositivo per controllare la tensionegenerata da un generatore elettrico asincrono
No full textLa soluzione proposta prevede di controllare la corrente di magnetizzazione del generatore e quindi la tensione erogata tramite un convertitore elettronico (inverter trifase). Questo è un dispositivo con un elevato rendimento e con una dinamica di intervento pressoché istantanea se riferita alla frequenza industriale.Il convertitore sarà inserito nel sistema di cogenerazione secondo la figura 3. Lo schema di controllo misurerà e ricostruirà il vettore rappresentativo del flusso al traferro del generatore e lo userà come riferimento di fase. A questo punto due anelli di controllo delle correnti saranno in grado di erogare od assorbire con continuità (entro i limiti fisici dell’inverter) correnti rispettivamente in fase o in quadratura con il flusso. Compito del controllo sarà mantenere la tensione del generatore al valore nominale manipolando opportunamente la corrente di magnetizzazione che risulta essere la corrente in fase col flusso. La figura 4 mostra su di un diagramma vettoriale il meccanismo con cui risulta possibile mantenere la tensione generata al valore voluto compensando l’effetto dei carichi sul flusso del generatore
A Five-Level Single-Phase Grid-Connected Converter for Renewable Distributed Systems
No full textIn low-power renewable systems a single-phase grid-connected converter is usually adopted. This paper deals with a novel five-level converter topology that follows this trend. A review of the state of the art of the five-level topologies and a theoretical power loss comparison with the proposed solution is realized. The proposed converter architecture is based on a full-bridge topology with two additional power switches and two diodes connected to the midpoint of the DC Link. Since the two added levels are obtained by the discharge of the two capacitors of the DC Link, the balancing of the midpoint voltage is obtained with a specific PWM strategy. Simulation and experimental results show the effectiveness of the proposed solution
METODO E DISPOSITIVO PER CONTROLLARE LA TENSIONE GENERATA DA UN GENERATORE ELETTRICO ASINCRONO
No full textUnipolar PWM for transformerless grid-connected converters in photovoltaic plants
No full textIn domestic grid connected PV applications a single phase converter is usually used. In such a low power plants it is possible to adopt converter topology with no galvanic isolation between the photovoltaic panels and the grid. The absence of a high or low frequency transformer permits to reduce power losses, cost and size of the converter. On the other side in presence of a galvanic connection a large leakage ground current could arise due to parasitic PV panel capacitance. This leakage current causes electric safety problems, an increase of EMI and a reduction of the power quality. This paper presents a converter topology based on unipolar PWM modulation able to minimize the leakage ground current locking the common output voltage to VDC/2 as the converters topology based on bipolar modulation do. Simulation results show the effectiveness of the proposed topology. Eventually a comparison of the power losses of the proposed architecture with respect to some established topologies is presented
3boost: A High-Power Three-Phase Step-Up Full-Bridge Converter for Automotive Applications
No full textThis paper describes a simple dc-dc step-up converter topology for switch-mode dc power supplies. The proposed configuration is well suited for high-power applications with battery supply. In the automotive framework, the push-pull architecture is the most widespread. However, as power increases, the use of a full-bridge architecture is mandatory. This paper presents a full-bridge architecture where the traditional single-phase transformer is replaced by a three-phase transformer. A prototype was realized and tested for the power supply of automotive devices. In this environment, one of the most important requirements is the ability to provide a burst of power during short-duration events, together with high-efficiency and high-quality output voltage. The latter constraints can be achieved by only using closed-loop switch-mode dc-dc converters at high switching frequency, thus reducing converter efficiency and creating electromagnetic-compatibility (EMC) problems. In this paper, the aforementioned issues were tackled relying on an open-loop topology. Open-loop converters are feasible if the output resistance of the converter is as low as possible, and a possible solution is the minimization of power losses. The solution is the use of a three-phase transformer with a delta-wye connection within a full-bridge converter topology. The configuration will be referred to as 3boost power supply. The three-phase transformer replaces the common single-phase transformer, and it is driven by a three-phase full-bridge inverter operating in six-step modulation. At secondary, a three-phase full wave diode rectifier is used to obtain the output dc voltage level. Therefore, a unitary transformer utilization factor is achieved. A simple theoretical comparison between the three types of converters-push-pull, conventional full bridge, and 3boost is shown. A low-power version of the converter was realized. Experiments confirm that this topology allows to achieve a high efficiency, a low- er ripple factor, and a good EMC behavior
DC-AC converter, in particular for providing power supply from a solar panel to a mains power supply
No full textA DC-AC converter, in particular for providing
electric energy from a solar panel to an electric network,
comprising: an input section (10) for receiving a substantially
direct voltage; an H-bridge (20) adapted to receive
said substantially direct current through said input section
(10) and designed to output a substantially alternating
voltage, said H-bridge (20) being drivable at least in the
following conditions: at least one operating condition, at
which electric energy is supplied to said electric network
(2); a first and a second recirculation condition, at which
a current flows through at least part of said H-bridge (20),
and no electric energy is supplied to said electric network
(2). The converter (1) further comprises: an output section
(40) to supply said substantially alternating current
to said electric network (2); an uncoupling module (50)
operatively interposed between said input section (10)
and said H-bridge (20) and configured for uncoupling said
input section (10) from said H-bridge (20) at said first and
second recirculation conditions of said H-bridge (20)
Convertitore DC/DC trifase
No full textUn convertitore DC/DC trifase è ottenuto sostituendo il trasformatore monofase di un tradizionale amplificatore tipo switching, con un trasformatore trifase (1). Grazie alle intrinseche caratteristiche del sistema trifase, si ottiene una riduzione della distorsione armonica del segnale continuo in uscita dall’alimentatore
3boost a High Power Three Phase Step-up Full-bridge Converter for Automotive Applications
No full textThis paper presents a simple and original DC-DCstep-up converter topology for switchmode DC powersupplies. The proposed architecture is well suited for highpower applications with battery supply.A prototype was realized and tested for the power supply ofautomotive devices. In this environment signals arecharacterized by high dynamic variations, thus ihey can beoperated only relying on power supplies with high dynamiccapabiliiies. The latter constraint can be SChieVed only usingdosed-loop switch-mode DUDC converters at high switchingfrequency. So doing converter efficiency is reduced, and EMCproblems arise. In summary power supply efficiency andsupply voltage quality are key Ceatures of the converler design.In lhis paper the above mentioned issued were tackledrelying on an open loop topology. The original solution is theadoption of a three-phase transformer with delta-wyeconnection within a full-bridge converter topology. Theproposed architecture will be referred to as 3boost powersupply. The three-phase transformer replaces the commonsingle-phase transformer and it is supplied at primary by threesquare waves, produced by a three-phase full bridge inverter.At secondary a three-phase full wave diode rectiller is used toobtain the output DC voltage level.The proposed architecture is patent pending.This paper presents a simple and original DC/DC step-up converter topology for switch-mode DC power supplies. The proposed architecture is well suited for high power applications with battery supply. A prototype was realized and tested for the power supply of automotive devices. In this environment signals are characterized by high dynamic variations, thus they can be operated only relying on power supplies with high dynamic capabilities. The latter constraint can be achieved only using closed-loop switch-mode DC/DC converters at high switching frequency. So doing converter efficiency is reduced, and EMC problems arise. In summary power supply efficiency and supply voltage quality are key features of the converter design. In this paper the above mentioned issued were tackled relying on an open loop topology. The original solution is the adoption of a three-phase transformer with delta-wye connection within a full-bridge converter topology. The proposed architecture will be referred to as 3boost power supply. The three-phase transformer replaces the common single-phase transformer and it is supplied at primary by three square waves, produced by a three-phase full bridge inverter. At secondary a three-phase full wave diode rectifier is used to obtain the output DC voltage level. Experimental results confirm that this topology, with respect to a single-phase push-pull converter, allows to achieve higher efficiency, a lower ripple factor, and a unitary transformer utilization factor. The proposed architecture is patent pending. © 2004 IEEE
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