Traction system for electric vehicles based on synchronous reluctance permanent magnet machine

Electric vehicles (EVs) integrate two main power electronics systems, namely, the battery charging system and the traction system. In this study, we aimed to complement and deepen the study of the latter, more specifically, focusing on a traction system based on a synchronous reluctance permanent magnet (SRPM) machine, since this is an emerging electric machine in the EV paradigm. The developed prototype integrates bidirectional ac-dc and dc-dc converters, allowing for regenerative braking, and the SRPM machine is controlled using a maximum torque per ampere (MTPA) algorithm. Computer simulations and the experimental results for the traction system are presented in this paper. The dynamic characteristics of the SRPM machine proved to be relevant for EV applications, with effective results obtained during load and speed changes. The effective behavior of the SRPM machine was partially rooted in the use of the MTPA algorithm, which has proven itself to be an effective algorithm for the electric machines of EVs.This work has been supported by FCT—Fundação para a Ciência e Tecnologia within the R&D Units Project Scope: UIDB/00319/2020

A novel front-end multilevel converter for renewable energy systems in smart grids

The integration of renewable energy systems into smart grids requires dc-to-ac power electronics converters for adapting the voltage levels of both sides. In this context, a novel topology of front-end multilevel dc-to-ac converter is proposed in order to enhance the integration of renewable energy systems into smart grids, preventing power quality problems. The proposed converter is designed to operate as a grid-tied inverter, imposing controlled sinusoidal grid currents in phase opposition with the power grid voltage, and establishing five distinct voltage levels to improve the current waveform. The dc side is suitable to be connected directly to a set of photovoltaic solar panels with an appropriated voltage level, or to an external dc-to-dc intermediary converter used to interface other renewable energy sources. An entire analysis of the hardware design and the operation principle is presented, including the adopted control strategy for the proposed front-end converter in conditions of current control. An accurate computational validation under realistic operating conditions for a significant operating power range is presented using a dedicated power electronics simulation software, where the obtained results show the advantages and the convenience of the proposed front-end converter in detriment of the classical solutions.Fundação para a Ciência e Tecnologia (FCT); 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–016434info:eu-repo/semantics/publishedVersio

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

Unified architecture of single-phase active power filter with battery interface for UPS operation

This paper presents a shunt active power filter with battery interface for uninterruptible power supply (UPS) operation. The proposed unified architecture is composed by a single-phase ac-dc converter from the power grid side and by a bidirectional isolated dc-dc converter to interface the batteries, allowing the operation in three distinct modes: (1) Shunt active power filter; (2) Off-line UPS to supply a set of priority loads during power outages; (3) Energy storage system to support the power grid. The proposed architecture and the developed control algorithms were validated with a reduced-scale laboratorial prototype in all the three different operation modes. The presented experimental results highlight the benefits of the proposed architecture.Fundação para a Ciência e Tecnologia (FCT)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

Single-phase shunt active power filter with UPS operation using a bidirectional Dc-Dc converter for energy storage interface

This paper presents a single-phase shunt active power filter (SAPF) with bidirectional dc-dc converter for uninterruptible power supply (UPS) operation. The proposed system comprises two power converters, namely a dc-ac converter to interface the power grid and a bidirectional isolated dc-dc converter connected to a battery pack, with both converters sharing the same dc-link. The arrangement of the converters allows the operation of the system in three different modes: (1) As SAPF, during normal operation; (2) As off-line UPS, in case of power grid outages; (3) As battery charging system, combined with the operation as SAPF. Simulation results of these three modes are presented in the paper to prove the operation feasibility of the proposed system. A reduced-scale prototype was developed, and the main parameters of the control stage, as well as the implemented control algorithms and power structure, are described in the paper. The experimental results obtained highlight the main benefits of the developed prototype.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

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 two-switch three-level active rectifier for grid-connected electrical appliances in smart grids

A novel topology of two-switch three-level active rectifier (TSTL-AR) is proposed in order to connect electrical appliances to smart grids considering power quality aspects. The proposed active rectifier is presented as a powerful solution to mitigate the negative effects of current harmonic distortion of the diode-bridge rectifiers, besides the ability of operating with unitary power factor. These aspects are particularly relevant considering the new paradigm of smart grids, where almost all the electrical appliances should be controlled in order to comply normative impositions of power quality. In addition, active rectifiers are also fundamental devices regarding the electric vehicle battery chargers, which are a new and significant class of electrical appliances for smart grids. In this paper, a comprehensive and detailed description of the novel topology of TSTL-AR is presented and compared with the classical power factor correction topology. Along the paper, it is discussed in detailed a digital current control structure based on finite control set model predictive control, permitting an accurate, robust, and faster control of the grid current. A laboratory prototype was developed and experimental tests were performed, verifying the precise operation, and demonstrating the importance of the proposed active rectifier for electrical appliances in smart grids. The results show a low level of current THD, a unitary power factor, and a regulated dc-link voltage.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

A novel converter topology for applications in smart grids: technical and economical evaluation

Technological advances in smart grids significantly contribute to an energy sustainability paradigm, assisting to diminish harms associated with global warming. Some of the key challenges in smart grids are linked with power electronics applications for renewable energy sources (RES), electric mobility (EM), energy storage systems (ESS) and power quality (PQ). These applications for smart grids have a common feature: the requirement to use the full-controlled grid-side power converters. Thereby, this paper aims to contribute with a technical and economical evaluation about a novel topology of the grid-side power converter for applications in smart grids. In terms of technical features, the proposed converter is classified as: (a) Bidirectional, allowing a bidirectional power flow with the electrical grid; (b) Symmetrical, allowing the operation with two distinct applications in the dc-side (e.g., RES, ESS, or EM); (c) Multilevel with nine levels, allowing high levels of PQ for the grid-side. With the objective to establish an accurate case-study, throughout the paper, the technical and economical evaluation is also performed based on the comparison between the proposed topology and the conventional ones. Considering an economical evaluation, the paper presents a cost estimation study concerning the implementation costs of the proposed topology, assuming realistic conditions of operation for applications in smart grids. Based on the entire evaluation for a real operating power range, the obtained results show the operational convenience of the topology in accordance with different applications in smart grids.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

Performance evaluation of a proportional integral with proportional derivative feedforward voltage control for UPSs

This paper presents a performance evaluation of a proportional-integral (PI) with proportional-derivative (PD) feedforward control for the output voltage of a single-phase off-line uninterruptible power supply (UPS) without using additional sensors. The control system is explained and simulation results are presented to analyze the steady state and transient response of the implemented voltage control. A laboratorial prototype was developed, and acquired experimental results considering linear and nonlinear loads are presented and discussed, corroborating the obtained simulation results.SFRH/BD/134353/2017info:eu-repo/semantics/publishedVersio