28 research outputs found
Calibração experimental de uma câmara digital
Apresenta-se um método prático de obtenção da resposta do sensor de uma máquina fotográfica digital comum, com base numa imagem de referência produzida em qualquer loja de impressão de fotografia. O grande objectivo é poder caracterizar a qualidade da luz emitida por lâmpadas de baixo consumo sem recorrer a dispositivos especiais.Fundação para a Ciência e a Tecnologia (FCT
Experimental comparison of single-phase active rectifiers for EV battery chargers
An experimental comparison of single-phase active rectifiers for electric vehicle (EV) battery chargers is
presented and discussed. Active rectifiers are used in on-board EV battery chargers as front-end converters
to interface the power grid aiming to preserve the power quality. In this paper, four topologies of active
rectifiers are compared: traditional power-factor-correction; symmetrical bridgeless; asymmetrical
bridgeless; and full-bridge full-controlled. Such comparison is established in terms of the requirements for
the hardware structure, the complexity of the digital control system, and the power quality issues, mainly the
grid current total harmonic distortion and the power factor. Along the paper these comparisons are presented
and verified through experimental results. A reconfigurable laboratorial prototype of an on-board EV
battery charger connected to the power grid was used to obtain the experimental results.This work has been supported by COMPETE: POCI-01-0145-FEDER-007043 and FCT – Fundação para a Ciência e Tecnologia within the Project Scope: UID/CEC/00319/2013. This work is financed by the ERDF – European Regional Development Fund through the Operational Programme for Competitiveness and Internationalisation - COMPETE 2020 Programme, and by National Funds through the Portuguese funding agency, FCT - Fundação para a Ciência e a Tecnologia, within project SAICTPAC/0004/2015- POCI- 01-0145-FEDER-016434.info:eu-repo/semantics/publishedVersio
Review of a disruptive vision of future power grids: a new path based on hybrid AC/DC grids and solid-state transformers
Power grids are evolving with the aim to guarantee sustainability and higher levels of power quality for universal access to electricity. More specifically, over the last two decades, power grids have been targeted for significant changes, including migration from centralized to decentralized paradigms as a corollary of intensive integration of novel electrical technologies and the availability of derived equipment. This paper addresses a review of a disruptive vision of future power grids, mainly focusing on the use of hybrid AC/DC grids and solid-state transformers technologies. Regarding hybrid AC/DC grids in particular, they are analyzed in detail in the context of unipolar and bipolar DC grids (i.e., two-wire or three-wire DC grids), as well as the different structures concerning coupled and decoupled AC configurations with low-frequency or high-frequency isolation. The contextualization of the possible configurations of solid-state transformers and the different configurations of hybrid transformers (in the perspective of offering benefits for increasing power quality in terms of currents or voltages) is also analyzed within the perspective of the smart transformers. Additionally, the paper also presents unified multi-port systems used to interface various technologies with hybrid AC/DC grids, which are also foreseen to play an important role in future power grids (e.g., the unified interface of renewable energy sources and energy storage systems), including an analysis concerning unified multi-port systems for AC or DC grids. Throughout the paper, these topics are presented and discussed in the context of future power grids. An exhaustive description of these technologies is made, covering the most relevant and recent structures and features that can be developed, as well as the challenges for the future power grids. Several scenarios are presented, encompassing the mentioned technologies, and unveiling a progressive evolution that culminates in the cooperative scope of such technologies for a disruptive vision of future power grids.This work has been supported by FCT—Fundação para a Ciência e Tecnologia within
the R&D Units Project Scope: UIDB/00319/2020. This work has been supported by the FCT
Project newERA4GRIDs PTDC/EEI-EEE/30283/2017, and by the FCT Project DAIPESEV PTDC/EEIEEE/30382/2017
New opportunities and perspectives for the electric vehicle operation in smart grids and smart homes scenarios
New perspectives for the electric vehicle (EV) operation in smart grids and smart homes context are
presented. Nowadays, plugged-in EVs are equipped with on-board battery chargers just to perform the
charging process from the electrical power grid (G2V – grid-to-vehicle mode). Although this is the main
goal of such battery chargers, maintaining the main hardware structure and changing the digital control
algorithm, the on-board battery chargers can also be used to perform additional operation modes. Such
operation modes are related with returning energy from the batteries to the power grid (V2G- vehicle-to-grid
mode), constraints of the electrical installation where the EV is plugged-in (iG2V – improved grid-tovehicle
mode), interface of renewables, and contributions to improve the power quality in the electrical
installation. Besides the contributions of the EV to reduce oil consumption and greenhouse gas emissions
associated to the transportation sector, through these additional operation modes, the EV also represents an
important contribution for the smart grids and smart homes paradigms. Experimental results introducing the
EV through the aforementioned interfaces and operation modes are presented. An on-board EV battery
charger prototype was used connected to the power grid for a maximum power of 3.6 kW.This work has been supported by COMPETE: POCI-01-0145-FEDER-007043 and FCT – Fundação para a Ciência e Tecnologia within the Project Scope: UID/CEC/00319/2013. This work is financed by the ERDF – European Regional Development Fund through the Operational Programme for Competitiveness and Internationalisation Ǧ COMPETE 2020 Programme, and by National Funds through the Portuguese funding agency, FCT - Fundação para a Ciência e a Tecnologia, within project SAICTPAC/0004/2015- POCI- 01-0145-FEDER-016434.info:eu-repo/semantics/publishedVersio
Evaluation of the introduction of electric vehicles in the power grid – a study for the island of Maio in Cape Verde
Serie: Lecture notes in electrical engineering, vol. 402This paper presents an evaluation of the introduction of electric vehi-cles (EVs) in an electrical power grid. The main contribution is the control analysis of the power quality considering simultaneous battery charging pro-cesses. The methodology used can be applied to any known power grid; howev-er, it was considered the case of the island of Maio, in Cape Verde, in continua-tion of previous works concerning that power grid. Two commercial different types of battery chargers were considered: a traditional model with highly dis-torted current consumption (that causes distortion in the power grid voltage), and another with almost sinusoidal current consumption. Considering simulta-neous battery charging processes, it can be concluded that the power grid struc-ture (composed by three medium voltage branches) with the current power de-mands of the consumers of the island of Maio have a potential integration for 300 EVs if battery chargers with almost sinusoidal current consumption are used, i.e., 152 for the first medium voltage branch, 35 for the second branch, and 113 for the third branch. Moreover, the results show that the first medium voltage branch of the distribution system, which has the capability to support the integration of 152 EVs if the battery chargers have sinusoidal current con-sumption (presenting a maximum value of THDv% in the power grid voltage of 1.8%), only can support 27 EVs if are used traditional battery chargers, with highly distorted current consumption (considering a maximum THDv% of 5%).COMPETE: POCI-01-0145-FEDER-007043Fundação para a Ciência e Tecnologia (FCT) - UID/CEC/00319/2013Fundação para a Ciência e Tecnologia (FCT) - SFRH/BD/80155/201
A novel architecture of a bidirectional bridgeless interleaved converter for EV battery chargers
This paper presents a novel architecture of a
bidirectional bridgeless interleaved converter for battery
chargers of electric vehicles (EVs). The proposed converter is
composed by two power stages: an ac-dc converter that is used to
interface the power grid and the dc-link, and a dc-dc converter
that is used to interface the dc-link and the batteries. The ac-dc
converter is an interleaved bridgeless bidirectional boost-type
converter and the dc-dc converter is a bidirectional
buck-boost-type converter. The proposed converter works with
sinusoidal grid current and with high power factor for all
operating power levels, and in both grid-to-vehicle (G2V) and
vehicle-to-grid (V2G) operation modes. In the paper is described
in detail the proposed converter for EV battery chargers: the
circuit topology, the principle of operation, the power control
theory, and the current control strategy. Several simulation
results for both G2V and V2G operation modes are presented.Fundação para a Ciência e Tecnologia (FCT
A novel control strategy based on predictive control for a bidirectional interleaved three-phase converter
An experimental confirmation of predictive control
applied to a bidirectional interleaved three-phase (BIT) converter
is presented. The BIT converter is a powerful solution for
numerous applications, mainly, renewables interface, motor
drivers, active rectifiers, and active power filters. However, a
precise and robust digital control strategy is required,
maintaining a low computational effort. In this paper, a
predictive control based on continuous control set is proposed as
a new control scheme for the BIT converter, permitting the
control of the ac side current with fixed switching frequency and
with a faster response. The predictive control scheme applied to
the BIT converter is defined along the paper, evidencing in detail
the digital employment aspects according to the discrete-time
model of the BIT converter. An explicit experimental validation
under realistic operating conditions is presented using a
developed laboratorial prototype, highlighting the convenience of
the control applied to the BIT converter.This work has been supported by FCT – Fundação para a
Ciência e Tecnologia in the scope of the project: PEstUID/CEC/00319/2013.
This work has been supported by
COMPETE: POCI-01-0145-FEDER-007043 and FCT –
Fundação para a Ciência e Tecnologia within the Project
Scope: UID/CEC/00319/2013. This work is financed by the
ERDF – European Regional Development Fund through the
Operational Programme for Competitiveness and
Internationalisation < COMPETE 2020 Programme, and by
National Funds through the Portuguese funding agency, FCT <
Fundação para a Ciência e a Tecnologia, within project
SAICTPAC/0004/2015< POCI< 01<0145<FEDER<016434. Mr.
Tiago Sousa is supported by the doctoral scholarship
SFRH/BD/134353/2017 granted by the Portuguese FCT
agency.info:eu-repo/semantics/publishedVersio
A novel single-phase bidirectional nine-level converter employing four quadrant switches
A novel bidirectional ac-dc multilevel converter
based on four quadrant switches is proposed. This new
converter can establish nine voltage levels downstream the
coupling filter used to interface with the power grid, and,
comparing with conventional two- or three-level converters, it
operates with improved ac-side current, both for operation as
active rectifier (on-grid), grid-tied inverter (on-grid) or voltage
inverter (off-grid). A detailed description of the converter is
exhibited, highlighting its main advantages according to the
applications where it can be employed in smart grid scenarios.
In order to confirm its viability, a considerable set of results is
presented and discussed, establishing an overall comparison
with conventional converters. Moreover, the proposed
converter is validated operating as active rectifier, as grid-tied
inverter, and as voltage inverter, controlled in closed-loop by
current or voltage. The details of the proposed power converter
hardware and the implementation of the digital algorithm,
based on a fixed switching frequency structure, are clarified and
discussed throughout the paper.This work has been supported by COMPETE: POCI-010145-FEDER-007043 and FCT – Fundação para a Ciência e Tecnologia within the Project Scope: UID/CEC/00319/2013. This work is financed by the ERDF – European Regional Development Fund through the Operational Programme for Competitiveness and Internationalisation – COMPETE 2020 Programme, and by National Funds through the Portuguese funding agency FCT within project SAICTPAC/0004/2015 – POCI – 01–0145–FEDER–016434. Mr. Tiago Sousa is supported by the doctoral scholarship SFRH/BD/134353/2017 granted by of the FCT project 0302836 NORTE-01-0145-FEDER-030283.info:eu-repo/semantics/publishedVersio
A novel fixed switching frequency control strategy applied to an improved five-level active rectifier
A novel fixed switching frequency control
strategy applied to an improved five-level active rectifier
(iFLAR) is proposed. The operation with fixed switching
frequency represents a powerful advantage, since the range of
the produced harmonics is well identified, and it is possible to
design passive filters to mitigate such harmonics. The
experimental validation shows that the control strategy allows
attaining an ac-side current with reduced total harmonic
distortion and high power factor, which is an attractive
influence for grid-connected electrical appliances. This
contribution is even more relevant with the new paradigm of
smart grids where higher levels of power quality are required.
A theoretical analysis of the control strategy and the details of
its implementation in a digital signal processor are presented.
The control scheme and the developed iFLAR were
experimentally confirmed using a laboratorial prototype,
showing its benefits in terms of accuracy, reduced total
harmonic distortion and high power factor.This work has been supported by COMPETE: POCI-010145-FEDER-007043 and FCT – Fundação para a Ciência e Tecnologia within the Project Scope: UID/CEC/00319/2013. This work is financed by the ERDF – European Regional Development Fund through the Operational Programme for Competitiveness and Internationalisation – COMPETE 2020 Programme, and by National Funds through the Portuguese funding agency, FCT – Fundação para a Ciência e a Tecnologia, within project SAICTPAC/0004/2015 – POCI – 01–0145–FEDER–016434. Mr. Tiago Sousa is supported by the doctoral scholarship SFRH/BD/134353/2017 granted by the Portuguese FCT agency. This work is part of the FCT project 0302836 NORTE-01-0145-FEDER-030283.info:eu-repo/semantics/publishedVersio
Comprehensive analysis and comparison of digital current control techniques for active rectifiers
This paper presents a comprehensive analysis and comparison of digital current control techniques for active rectifiers. These rectifiers are connect-ed to the power grid and are controlled aiming to obtain sinusoidal grid currents and unitary power factor. In this context this paper presents the principle of operation of a full-bridge full-controlled active rectifier, which is controlled by different digital current control techniques, namely, proportional-integral (PI) in stationary frame, PI in synchronous frame, PI sinewave (PIS), feedforward, sliding mode, and predictive. These digital current control techniques are explained in detail and is established a comparison in terms of their current errors in steady-state, as well as in terms of their digital implementation using the digital signal processor (DSP) TMS320F28335 from Texas Instruments.FCTCOMPETE: POCI-01-0145-FEDER-00704