Filtro ativo de potência paralelo monofásico com conversor CC-CC bidirecional para operação como UPS

Dissertação de mestrado em Engenharia Eletrónica Industrial e de ComputadoresAtualmente, a utilização de cargas não-lineares na rede elétrica é uma constante. Este tipo de cargas leva a uma degradação da Qualidade de Energia Elétrica, uma vez que consome harmónicos de corrente, prejudicando o transporte e a distribuição de energia e o funcionamento da maioria dos equipamentos ligados à rede elétrica. Para além disso, em determinados sistemas há cargas que necessitam de ser alimentadas ininterruptamente, tais como controladores de processos industriais, computadores, equipamentos médico e sistemas de comunicação de dados, pelo que estas cargas não podem depender exclusivamente da rede elétrica, uma vez que, sendo esta suscetível a falhas, terá de ser complementada por geradores de emergência ou UPSs (Uninterruptible Power Supplies – fontes de alimentação ininterruptas). Deste modo, torna-se necessário o desenvolvimento e a utilização de equipamentos capazes de mitigar os problemas acima referidos. No Grupo de Eletrónica de Potência e Energia (GEPE) da Universidade do Minho têm sido desenvolvidos Filtros Ativos de Potência para compensar problemas de Qualidade de Energia. Assim sendo, neste trabalho de Mestrado foi proposto o desenvolvimento de um Filtro Ativo Paralelo Monofásico com operação como UPS. Este equipamento é capaz de compensar o fator de potência e os harmónicos de corrente em condições normais de funcionamento da rede elétrica e é também capaz de alimentar, de forma isolada, um conjunto de cargas prioritárias perante eventuais falhas na rede. Para além disso, foi também desenvolvido um conversor CC-CC bidirecional isolado com o intuito de carregar as baterias a partir da rede elétrica, através do barramento CC do Filtro Ativo Paralelo, bem como injetar energia na rede elétrica isolada proveniente das mesmas. Pretendeu-se que o equipamento desenvolvido fosse leve, compacto e com operação silenciosa, de modo a poder ser instalado no quadro elétrico de uma habitação. Deste modo, alguns procedimentos foram tomados aquando do projeto da solução apresentada, tais como a escolha dos semicondutores de potência e dos elementos magnéticos a utilizar. No final, foi efetuado um levantamento de custos da solução obtida de modo a analisar a sua viabilidade comercial.Nowadays, the use of nonlinear loads connected to the electrical power grid is unceasing. This kind of electrical loads leads to Power Quality declining, since it consumes harmonic currents, worsening power transmission and distribution and the proper operation of a vast amount of power grid connected equipment. Furthermore, there are loads connected to several power systems that need incessant power supplying, such as industrial process controllers, computers, medical equipment and datacenters, whereby these loads cannot depend exclusively upon the power grid, since it is vulnerable to power outages, and therefore must be complemented by emergency generators or UPSs (Uninterruptible Power Supplies). Therefore, the development and use of equipment capable of mitigating these issues is needed. The Group of Energy and Power Electronics (GEPE) of the University of Minho has been developing Active Power Filters to compensate for Power Quality problems. Thus, the development of a Single-Phase Shunt Active Power Filter with UPS operation was proposed in this Master's thesis work. This equipment is capable of compensating for power factor and harmonic currents during normal operation of the power grid, and is also able to supply with isolation a set of priority electrical loads towards eventual power outages. Besides that, a bidirectional isolated DC-DC converter was developed in order to charge the battery pack from the power grid, through the Shunt Active Power Filter DC-link, as well as to provide energy stored in the batteries to the isolated electrical power grid. It was intended for the equipment to be weightless, compact and silent in order to be installed in a domestic electrical switchboard. Consequently, several procedures were taken during the solution’s development, such as the power semiconductors and the magnetic elements selection. In the end, it was performed the costing of the obtained solution with the purpose of evaluating its commercial feasibility

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

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

Selective harmonic measurement and compensation using smart inverters in a microgrid with distributed generation

This paper presents a frequency domain selective harmonic measurement and compensation using smart inverters (SIs) applied to a microgrid with distributed generation. The compensation current is calculated by a main processing unit (MPU), which controls the compensation action of each distributed generation unit (DGU) connected to the microgrid. A single fast Fourier transform (FFT) is implemented to obtain the frequency spectra of the power grid voltages and the currents consumed by the connected loads. Based on the calculated compensation currents and the availability of the DGUs, the MPU establishes the harmonic orders that each DGU should compensate, aiming to equalize the rms current values among the different DGUs. The proposed approach intends to optimize the DGUs efficiency in the microgrid and, additionally, it allows the connection of the converters to the power grid without the need for a synchronization algorithm. A comprehensive description of the implemented FFT algorithm is performed and, finally, the operation of the proposed scheme is verified by simulation results.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. SFRH/BD/134353/2017 granted by the Portuguese FCT agencyinfo:eu-repo/semantics/publishedVersio

Continuous control set model predictive control of a bridgeless-boost three-level active rectifier

Over the past few decades, active rectifiers have assumed an important preponderance for numerous applications that propose to minimize power quality problems. Consequently, digital control algorithms are following this trend by contributing with a significant set of advantages. This paper presents the use of a continuous control set model predictive control (CCS-MPC) for a bridgeless-boost three-level (BB3L) active rectifier. The BB3L has a set of advantages when confronted with traditional solutions to improve power quality, where the possibility to operate with three voltage levels, sinusoidal current and unitary power factor, while using few switching devices, are the main features. Considering the multiplicity of applications for the BB3L active rectifier, the CCS-MPC is applied to obtain a robust current tracking. The BB3L is presented in detail throughout the paper and based on its mathematical model, the digital control equations are formulated, highlighting that the possibility of operating with a fixed switching frequency is the main characteristic. The results are achieved for many operating conditions, covering steady-state and transient-state, validating the accurate application of the CCS-MPC.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. Tiago J. C. Sousa is supported by the doctoral scholarship SFRH/BD/134353/2017 granted by FCT

On the viability of dc homes: an economic perspective from domestic electrical appliances

The past few years witnessed a growing acclaim for dc power systems, which is mainly justified by the increasing use of energy storage systems and renewable energy sources based mainly on solar photovoltaic technologies. However, there is also a motivation from the point of view of domestic electrical appliances. Since the vast majority of these appliances is comprised by an ac-dc converter, it can be convenient to shift the domestic power supply from ac to dc. In this context, this paper presents an economic assessment of dc homes from the energy consumption perspective and its comparison with traditional homes supplied by ac electrical power grids. In order to perform such assessment, the main type of electronic loads is powered both by ac voltage and by dc voltage, comparing the efficiency and estimated energy cost for each case. The removal of the ac-dc converter present in these loads is also analyzed and compared with the two previously referred cases, supporting the supply of dc power to this type of loads. The analysis is performed by means of experimental results obtained with a laboratorial setup, aiming to validate the feasibility of dc homes under realistic operating conditions of the loads.This work has been supported by FCT - Fundacao para a Ciencia e Tecnologia within the Project Scope: UID/CEC/00319/2019. This work has been supported by FCT within the Project Scope DAIPESEV -Development of Advanced Integrated Power Electronic Systems for Electric Vehicles: PTDC/EEI-EEE/30382/2017. This work is part of the FCT project 0302836 NORTE-01-0145-FEDER-030283. Mr. Tiago Sousa is supported by the doctoral scholarship SFRH/BD/134353/2017 granted by the Portuguese FCT agency

A review on integrated battery chargers for electric vehicles

Electric vehicles (EVs) contain two main power electronics systems, namely, the traction system and the battery charging system, which are not used simultaneously since traction occurs when the EV is travelling and battery charging when the EV is parked. By taking advantage of this interchangeability, a single set of power converters that can perform the functions of both traction and battery charging can be assembled, classified in the literature as integrated battery chargers (IBCs). Several IBC topologies have been proposed in the literature, and the aim of this paper is to present a literature review of IBCs for EVs. In order to better organize the information presented in this paper, the analyzed topologies are divided into classical IBCs, IBCs for switched reluctance machines (SRMs), IBCs with galvanic isolation, IBCs based on multiple traction converters and IBCs based on multiphase machines. A comparison between all these IBCs is subsequently presented, based on both requirements and possible functionalities.This work has been supported by FCT - Fundação para a Ciência e Tecnologia within the R&D Units Project Scope: UIDB/00319/2020. T.J.C.S. is supported by the FCT scholarships SFRH/BD/134353/2017 and COVID/BD/151993/2021

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

Performance comparison of a typical nonlinear load connected to Ac and Dc power grids

This paper presents a performance comparison of a typical nonlinear load used in domestic appliances (electronic load), when supplied by an ac and a dc voltage of the same rms value. The performance of the nonlinear load towards its connection to ac and dc power grids is accomplished in terms of the waveforms which are registered in the consumed current, internal dc-link voltage and output voltage. A simulation model was developed using realistic database models of the power semiconductors comprising a nonlinear load with input ac-dc converter, so that the efficiency can be calculated and compared for three distinct cases: (1) load supplied by an ac voltage; (2) load supplied by a dc voltage; (3) load without the input ac-dc converter supplied by a dc voltage. Thus, besides the comparison between the ac and dc power grids supplying the same nonlinear load (cases 1 and 2), a third case is considered, which consists of removing the input ac-dc converter (eliminating needless components of the nonlinear load when supplied by a dc voltage). The obtained results show that supplying nonlinear loads with dc power grids is advantageous in relation to the ac power grid, and therefore it can be beneficial to adapt nonlinear loads to be powered by dc power grids.This work has been supported by COMPETE: POCI-01-0145–FEDER–007043 and FCT –Fundação para a Ciência eTecnologia within the Project Scope: UID/CEC/00319/2013. This work is financed by the ERDF –European Regional De-velopment Fund through the Operational Programme for Competitiveness and Interna-tionalisation –COMPETE 2020 Programme, and by National Funds through the Por-tuguese funding agency, FCT –Fundação para a Ciência e a Tecnologia,within project SAICTPAC/0004/2015 –POCI –01–0145–FEDER–016434. Mr. Tiago Sousa is sup-ported by the doctoral scholarship SFRH/BD/134353/2017 granted by the Portuguese FCT agency

Performance comparison of a typical nonlinear load supplied by ac and dc voltages

This paper presents a performance comparison of a typical nonlinear load when supplied by ac or dc voltages with the same rms value. The performance of the nonlinear load towards its connection to ac and dc power grids is accomplished in terms of the waveforms and efficiency. A simulation model was developed using realistic database models of the power semiconductors comprising the load, and an experimental setup was assembled, so that the efficiency can be determined and compared for simulation and real operating conditions. Three distinct cases were considered for this study: (1) Load supplied by ac voltage; (2) Load supplied by dc voltage; and (3) Load without the input ac-dc converter supplied by dc voltage. The obtained results show that supplying nonlinear loads with dc power grids is advantageous in relation to the ac power grid, and therefore it can be beneficial to adapt nonlinear loads to be powered by dc power grids.This work has been supported by COMPETE: POCI-01-0145–FEDER–007043 and FCT –Fundação para a Ciência e Tecnologiawithin 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 thePortuguese 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 agenc