Experimental validation of a novel architecture based on a dual-stage converter for off-board fast battery chargers of electric vehicles

The experimental validation of a novel architecture of an off-board, three-phase fast battery charger for electric vehicles (EVs) with innovative operation modes is presented in this paper. The proposed EV fast battery charger is based on a dual-stage power converter (ac-dc and dc-dc) sharing the same dc link. The ac-dc stage is used as an interface between the power grid and the dc link. It is composed of the parallel association of two full-bridge voltage-source converters, and allows control of the grid current and of the dc-link voltage. The dc-dc stage is used as an interface between the dc link and the batteries. It is constituted by a bidirectional three-level asymmetrical voltage-source converter, and controls the flux of current during the EV battery charging process. Compared with the traditional solutions used for EV fast battery chargers, the proposed architecture operates as an interleaved converter, facilitating the reduction of the passive filters size, and the grid current harmonic distortion for the same switching frequency. Throughout the paper, the ac-dc and dc-dc stages, and the digital control algorithms are described in detail. The experimental validation was performed in a laboratory using a developed EV fast battery charger prototype, operating through the grid-to-vehicle and the proposed charger-to-grid modes, exchanging active, and reactive power with the power grid.ERDF - European Regional Development Fund()info:eu-repo/semantics/publishedVersio

Vehicle-to-anything: a power transfer perspective for vehicle electrification

The concept of vehicle-to-anything (V2X) is mainly focused on the bidirectional communication between any technology of vehicle and any external system that can contribute for its operation. However, prospecting the vehicle electrification, this concept can also be associated with the power transfer between an electric vehicle (EV) and any external system, where bidirectional communication is absolutely fundamental. Within the power transfer, the possibility of exchanging active power between an EV and the power grid is considered as a promising operation mode, especially considering the possibility of selling demand response services for the electrical power grid. Contemplating the vehicle electrification context, in addition to the latent possibility of interaction between EVs and the power grid for active power exchange, other possibilities of interaction can also be considered, providing advantageous services for the power grid. Thus, this article approaches the V2X concept for off-board systems in the power transfer perspective for vehicle electrification, aggregating new contributions related with the interaction between an EV and any external electrical system (operating as source or load), and both from on-grid or off-grid point of view. Contributions are meticulously presented, recognizing their advantages and disadvantages in a real-scenario of operation. A comparison in terms of cost of implementation and in terms of efficiency is presented considering the various solutions of the vehicle electrification in a smart grid perspective.This work has been supported by FCT – Fundação para a Ciência e Tecnologia within the Project Scope: UID/CEC/00319/2019. 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 POCI-01-0145-FEDER-030283

Efficiency comparison of a dc-dc interleaved converter based on SiC-MOSFET and Si-IGBT devices for EV chargers

The charging process is one of the main factors for the widespread dissemination of electric mobility, therefore, the use of optimized power electronics converters is of utmost importance. In addition to innovative topologies, the use of emerging technologies of semiconductors is also crucial. In this context, using a three-phase interleaved dc-dc topology, a comparison between the use of SiC-MOSFET and Si-IGBT is presented in this paper, mainly in terms of operating efficiency. Two cases have been presented: 1) with the same inductor, where only power device losses have been considered; 2) with the same inductor current ripple, where different inductors have been considered and the analysis included also the inductor design and losses. The simulations were carried out in LTspice simulation tool on realistic dynamic models of power switch modules obtained from the manufacturer’s experimental tests. The results validate the use of SiC-MOSFET for the three-phase interleaved dc-dc topology showing lower losses for both the power devices and inductor and, most important, prove the advantages of its use in terms of efficiency for a wide range of operating powers.This work has been supported by FCT - Fundacao para a Ciencia e Tecnologia with-in the Project Scope: UID/CEC/00319/2019, and by the FCT Project newERA4GRIDs PTDC/EEI-EEE/30283/2017

A multilevel bidirectional Four-Port DC-DC converter to create a DC-Grid in Solid-State transformers with hybrid AC/DC grids

Smart grids are incessantly contemplating new challenges about power electronics technologies, and this paper focuses on the application of solid-state transformers (SSTs) and the forthcoming perspective of hybrid AC/DC grids. In such perspective, a multilevel bidirectional four-port (MB4P) DC-DC converter is proposed to be integrated in a three-phase SST. It interfaces the SST through three independently ports, corresponding to the three-phases, and the other port is used to create a DC grid. The proposed MB4P DC-DC converter has as main features a multilevel operation with seven voltage levels as function of the voltages on both DC sides, as well as the interleaved operation, where the controlled variables have a ripple with a frequency six times higher than the switching frequency. Furthermore, it can operate in buck or boost modes, and with current or voltage control. Besides the voltage and current control, specific attention is given to the proposed PWM. The advanced attributes of the MB4P DC-DC converter are proven by computer simulations and by analytical description, both exploring steady-state and transient-state distinctive requirements.FCT -Fundação para a Ciência e a Tecnologia(DAIPESEV PTDC/EEI-EEE/30382/2017

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

A novel topology of modular multilevel bidirectional non-isolated dc-dc converter

The paradigm of smart grids has been continuously addressing new challenges in terms of power electronics converters, for instance, to deal with technologies like renewables, electric mobility, energy storage, and hybrid power grids. Allied with this context, a novel topology of modular multilevel bidirectional (MMB) non-isolated dc-dc converter is proposed in this paper. Taking into consideration the nature of the proposed MMB dc-dc converter, it is appropriated to operate as back-end converter linked to front-end ac-dc converters based on cascade structures, i.e., with more than one dc-link. As distinctive features, the proposed MMB dc-dc converter can operate with five-voltage levels, allowing to reduce the voltage stress in each semiconductor, and it is controlled based on the interleaved principle of operation, although it is not an interleaved converter. A dedicated pulse-width modulation, as well as voltage and current control strategies, are proposed and clearly explained along the paper. The claimed distinctive features of the proposed MMB dc-dc converter are supported by analytic description and by computer simulation validation, considering steady-state and transient-state operations in relevant conditions of the dc interfaces.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/EEI-EEE/30382/2017. Tiago Sousa is supported by the doctoral scholarship SFRH/BD/134353/2017 granted by FCT

Model predictive control of a single-phase five-level VIENNA rectifier

Power converters and control strategies are very vital for the increasing sustainability of the power grid targeting smart grids. In these circumstances, it is proposed a novel single-phase five-level (SP5L) VIENNA rectifier digitally controlled by a model predictive control (MPC) with fixed switching frequency, which can be useful for a variety of applications with a robust current tracking. The proposed SP5L VIENNA rectifier is an advancement of the classical three-level VIENNA rectifier, also contributing to preserve power quality, and exhibiting the advantage of operating with more voltage levels at the expense of few additional switching devices. The proposed topology is introduced and correlated with the classical solutions of active rectifiers. The operation principle is introduced and used to describe the MPC, which is given in detail, as well as the necessary modulation strategy. The results were obtained for a set of various operating conditions, both in terms of reference of current and grid-side voltage, as well as in steady-state and transient-state, proving the benefits of the proposed SP5L VIENNA rectifier and the accurate and precise use of the MPC to control the grid-side current.This work has been supported by FCT -Fundacao para a Ciencia 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/EEI-EEE/30382/2017. Tiago Sousa is supported by the doctoral scholarship SFRH/BD/134353/2017 granted by FCT

Innovative off-board EV home charging station as a smart home enabler: Present and proposed perspectives

This paper presents an innovative off-board electric vehicle home charging station (EV-HCS) operating as a smart home (SH) enabler. The present status and the proposed perspectives in terms of operation modes are comprehensively addressed along the paper showing the contextualization of the addressed research topic. Comparing with the existing solution, the main motivations and advantages of the off-board EV-HCS are: (a) Off-board dc EV charger, faster than a classical on-board EV charger; (b) Flexible operating power value, aiming an optimized power management in the home; (c) Operation as an active conditioner for the home or the grid, with or without an EV plugged-in, which represents an attractive functionality for enhancing the operation of SHs and smart grids; (d) Bidirectional operation with an EV. The methods used to describe these advantages are validated using computer simulations. The control algorithm is succinctly described, demonstrating its adaptability to the power electronics topology presented for the EV-HCS hardware. The obtained results demonstrate that the proposed EV-HCS presents attractive functionalities for enhancing the EV integration into SHs and smart grids.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; Fundação para a Ciência e Tecnologia (FCT)info:eu-repo/semantics/publishedVersio

A novel topology of multilevel bidirectional and symmetrical split-Pi converter

The paradigm of smart grids has encouraged new developments of power electronics converters, for instance, in the perspective of renewables and electric mobility applications. Aligned with this perspective, this paper proposes a novel topology of a multilevel bidirectional and symmetrical (MBS) split-pi dc-dc converter. As a central distinguishing feature, it operates with three voltage levels in both dc sides (0, vdc/2, vdc), meaning that the voltage stress in each semiconductor is reduced when compared with the conventional split-pi converters, and it operates with controlled variables (voltage and current) based on the interleaved principle of operation, although it is not an interleaved split-pi converter. As demonstrated along the paper, the MBS split-pi converter can be controlled with current or voltage feedback in any of the dc interfaces, while the common dc-link voltage is controlled by the dc interface where the source is connected. The adopted current and voltage control schemes, as well as the pulse-width modulation, are presented and comprehensively explained. The validation is presented for the main operation modes, where it is possible to verify the claimed distinguishing features of the proposed MBS split-pi converter.Fundação para a Ciência e Tecnologia (FCT