Simulation and implementation of power electronics for educational purposes: with SEPIC converter for MPPT

Dissertação de mestrado em Industrial Electronics and Computer EngineeringNowadays, the importance and investments in electricity and renewable energy sources is significantly growing, so that the development and prosperity level of nations are measured accordingly with the strength and the efficiency of the power sector in the country. Every day, the importance of renewable energy sources in the world is increasing to compensate the growing demand of energy in the future, especially with the global rise in oil prices and the environmental pollution. Therefore, renewable energy sources, such as wind, sun, biomass, waves and tides, will be the energy providers for our planet in the future. Renewable energy sources are closely linked with power electronics, so that it is not possible to obtain the required electrical power without using semiconductor electronic elements, which have the capability to convert electrical power (for example, rectifiers can convert electrical power from AC to DC and the inverters do exactly the opposite). These elements give sufficient flexibility to control and convert the voltages according to our application, and in function of the load needs. All of the above indicates the importance of power electronics area in the present time. Therefore, as a part of this project, a tutorial document on power electronics has been written for students and non-specialists who want to learn power electronics and know the basics of this area of Electrical Engineering. This document has an organizing strategy and arrangement in order to facilitate and give motivation for students to study power electronics, trying to provide, as much as possible, simple explanations and figures. Every circuit in this document was simulated by using the programs PSIM and MATLAB, which gives the possibility for students to change the circuit parameters, then monitoring the new results (with this document is made available a CD with the simulations models of the circuits). In addition, it contains worked examples with the most important ideas that must be known for every example. All figures and results of circuits are drawn to facilitate and clarify the figures as much as possible, using a plotting program named KST. As a practical part of this Master thesis work, which also aims to merge renewable energy sources and power electronics applications, a battery charging system with MPPT circuit was implemented, to be used with a micro wind turbine, which can be employed in a boat in the future. This work used a micro wind turbine with a permanent magnet synchronous generator which converts mechanical energy into electrical energy. The generator produces AC three-phase voltages that are rectified with an uncontrolled rectifier, PD3, which is then connected to a DC-DC converter (coupled inductor SEPIC converter), used here to increase or decrease the DC voltage value. In the output of the rectifier is used a capacitor to filter the DC voltage. The implemented control method uses a Maximum Power Point Tracker (MPPT), with perturbation and observation algorithm. This algorithm is ideal to use with intermittent wind energy resources. To operate at the optimal power point, the algorithm has to change the duty cycle of the SEPIC. This control was implemented in a microcontroller ARDUINO ATMEGA UNO 328P. All the developed system for energy production was simulated using PSIM program. This allowed to observe the behavior of the system when was used a passive load (resistive load) and an active load (battery). Finally, with this work I hope to create benefits to my homeland Syria and to my second country, Portugal.Hoje em dia, a importância e o investimento na energia elétrica e em fontes de energia renováveis tem uma grande preponderância nas nossas vidas. O grau de prosperidade e o desenvolvimento das nações pode ser aferido através do grau de importância do setor energético no país. A cada dia que passa, a importância das fontes de energia renováveis aumenta, uma vez que existe uma procura cada vez maior de energia, isto tendo em conta o aumento mundial dos preços de combustível e a poluição ambiental. Tendo em conta isto, as fontes de energia renováveis, tais como o vento, o sol, a biomassa, as ondas e as marés, serão os fornecedores de energia para o nosso planeta num futuro próximo. As fontes de energia renováveis estão intimamente ligadas com a eletrónica de potência, e não é possível obter a energia elétrica desejada sem usar elementos eletrónicos semicondutores, os quais têm a capacidade de realizar conversões (por exemplo os retificados podem converter tensão CA para CC, e os inversores o oposto). Estes elementos dão flexibilidade suficiente para controlar e converter as tensões de acordo com a nossa aplicação, e conforme a carga. Tudo o que é referido acima indica a importância da eletrónica de potência nos tempos atuais. Desta forma, como parte deste trabalho de Dissertação de Mestrado, foi escrito um tutorial de eletrónica de potência destinado aos estudantes e aos não-especialistas que querem aprender eletrónica de potência e perceber as bases desta área da Engenharia Eletrotécnica. Este documento apresenta uma certa estratégia e organização facilitadoras e motivadoras para que os alunos venham a estudar eletrónica de potência, contendo, dentro do possível, explicações e figuras simples. Cada circuito apresentado neste documento foi simulado usando os softwares PSIM e MATLAB, sendo oferecida a possibilidade aos estudantes para alterar os parâmetros dos circuitos e observarem os resultados (o documento é acompanhado de um CD com os modelos de simulação). Além disto, o documento contém exemplos trabalhados mostrando os conceitos mais importantes de cada circuito. Todas as figuras e resultados dos circuitos foram desenhados de forma a facilitar a sua compreensão, utilizando um programa designado KST. Como parte prática deste trabalho, e envolvendo a fusão entre a eletrónica de potência e as aplicações de energias renováveis, foi implementado um circuito carregador de baterias com circuito MPPT, a ser usado com uma turbina micro-eólica, e que poderá ser empregado em barcos, no futuro. Neste projeto foi usada uma micro-turbina com um gerador síncrono de ímanes permanentes que converte a energia mecânica do vento em energia elétrica. O gerador produz tensões CA que necessitam de ser retificadas, e para isso é usado um retificador não controlado, PD3, ligado a um conversor DC-DC (conversor SEPIC com indutância de acoplamento mútuo). O conversor serve para aumentar ou diminuir a tensão de saída. Além disto, o retificador tem na sua saída um condensador de forma a filtrar a tensão. O método de controlo implementado foi um seguidor do ponto de máxima potência (Maximum Power Point Tracker - MPPT). O algoritmo do MPPT usado foi o da perturbação-observação. Este algoritmo é o ideal para utilizar com as fontes de energia intermitentes, como é o caso do vento. Para operar no ponto de máxima potência, o algoritmo tem que mudar constantemente o duty-cycle do conversor SEPIC. Este controlo foi implementado numa placa de desenvolvimento ARDUINO ATMEGA UNO 328P. O sistema para produção de energia desenvolvido foi todo simulado usando o software PSIM. Isto permitiu observar o comportamento desse sistema quando foi colocada na sua saída uma carga passiva (carga resistiva) e uma carga ativa (bateria). Finalmente, com este trabalho, espero poder trazer benefícios ao meu país natal, a Síria, e ao meu segundo país, Portugal

Rail power conditioner based on indirect AC/DC/AC modular multilevel converter using a three-phase V/V power transformer

This paper presents a rail power conditioner (RPC) system based on an indirect AC/DC/AC modular multilevel converter (MMC) where a V/V power transformer is used to feed the main catenary line and the locomotives. The proposed control strategy for this system has been introduced to guarantee a good compensating performance of negative sequence currents (NSCs) and harmonics on the public grid side. This control strategy has also the ability to achieve balanced and equal voltage between the MMC’s submodules (SMs) capacitors. Simulation results for this RPC based on an indirect MMC are presented in this paper to show the main advantages of using this topology. The results show how the proposed system is able to compensate NSCs and harmonics on the public grid side when the V/V power transformer feeds two unequal load sections.Fundação para a Ciência e Tecnologia (FCT)info:eu-repo/semantics/publishedVersio

Opportunities and challenges of power electronics systems in future railway electrification

With the continuous expansion of the railway power systems, the integration of high speed locomotives and the need to increase the overhead catenary line power capacity, the main shortcomings of the conventional railway feeding system are becoming more evident. In order to overcome these drawbacks and to contribute to the technological evolution with innovative and electrically more efficient systems, several solutions have been proposed and implemented. In this context, this paper briefly presents a study of different railway power systems, highlighting emerging concepts, such as regenerative braking, energy storage systems, the inclusion of renewable energy sources, bidirectional power flow and wireless power transfer. Some of these concepts can be implemented in short to medium term, or in the long term. Following these concepts, an overview of the power electronics challenges for the implementation of these emerging concepts is presented and discussed.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 QUALITY4POWER PTDC/EEI-EEE/28813/2017. Mr. Luis A. M. Barros is supported by the doctoral scholarship PD/BD/143006/2018 granted by the Portuguese FCT foundation. Mr. Mohamed Tanta was supported by FCT PhD grant with a reference PD/BD/127815/2016

Modular multilevel converter in electrified railway systems: applications of rail static frequency converters and rail power conditioners

The Modular Multilevel Converter (MMC) has become the most preferable multilevel converter topology for medium and high-power systems, due to the MMC's high reliability and redundancy. This paper focuses on MMC applications in electrified railway traction grids, namely, applications of rail static frequency converters and rail power conditioners. These applications provide a higher railway traction grid capacity and improve the power quality of the three-phase power grid. Simulation results of a case study are presented to show the features when using the MMC in electrified railway grids.This work has been supported by the Portuguese Foundation of Science and Technology (FCT), within the R&D Units Project Scope: UIDB/00319/2020 and PTDC/EEIEEE/28813/2017. The first author Mohamed Tanta is supported by FCT Ph.D. grant with a reference PD/BD/127815/2016

New multifunctional isolated microinverter with integrated energy storage system for PV applications

This paper proposes a novel multifunctional isolated microinverter which is able to extract the maximum available power from a solar photovoltaic module and inject it into the power grid, while simultaneously charging a battery energy storage system (BESS). The proposed microinverter integrates a novel DC–DC power converter and a conventional DC–AC power converter. The DC–DC power converter is able to send electrical energy to the secondary side of a high-frequency transformer and to the BESS, using only two power switches. Throughout this paper, the converter topology, the operation modes, the control algorithms, and the development of a laboratory prototype of the proposed microinverter are described in detail. Moreover, simulation and experimental results are presented to demonstrate the feasibility of the proposed solution.This work has been supported by FCT—Fundação para a Ciência e Tecnologia within the R&DUnits Project Scope: UIDB/00319/2020. This work has been supported by the FCT Project QUALITY4POWERPTDC/EEI-EEE/28813/2017. Luis A. M. Barros is supported by the doctoral scholarship PD/BD/143006/2018 granted by the Portuguese FCT foundation. Mohamed Tanta was supported by FCT PhD grant with a reference PD/BD/127815/2016 granted by the Portuguese FCT agency. Tiago J. C. Sousa is supported by the doctoralscholarship SFRH/BD/134353/2017 granted by the Portuguese FCT agency

Active power conditioner based on a voltage source converter for harmonics and negative sequence components compensation in electrified railway systems

The electrification of railway systems has always presented major challenges to the public electrical power systems. Electric locomotives are usually supplied by a single phase AC catenary, causing unbalance and the appearance of negative sequence components (NSCs) in the three phase electrical power grids. In addition, the traction power system of the electric locomotive is usually comprised by uncontrolled rectifiers to convert AC voltage to DC voltage, which produces high levels of current harmonics. Consequently, the operation of electric locomotives causes serious power quality problems to the public electrical power systems. This paper evaluates the use of Shunt Active Power Conditioners (SAPCs) to compensate power quality problems in single phase 25 kV, 50 Hz railway traction substations, when using the conventional V/V or the Scott traction power transformer between the catenary and the public electrical power systems.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 H2020 EU project 777515 - IN2STEMPO. Mohamed Tanta was supported by FCT PhD grant with the reference PD/BD/127815/2016.info:eu-repo/semantics/publishedVersio

Cost estimation of rail power conditioner topologies based on indirect modular multilevel converter in v/v and scott power transformers

This paper presents a cost estimation study for several rail power conditioner (RPC) topologies based on an indirect modular multilevel converter (MMC), in which these topologies are combined with V/V or Scott power transformers. The RPC topologies under interest in this paper are: the RPC based on a full-bridge MMC (RPC based on MMC4), the RPC based on two-phase three-wire MMC (RPC based on MMC3), and the RPC based on a half-bridge MMC (RPC based on MMC2). These RPC systems operate at medium voltage levels in the interconnection to 25 kV-50 Hz catenary sections to solve power quality problems, such as the current harmonics and the negative sequence components (NSCs) of currents. Along the paper are described the V/V and the Scott power transformers, the RPC main architectures, and the estimated cost of implementation for each RPC topology considering V/V or Scott implementations. As main contribution, the presented results could help in the selection procedure of the RPC topology, giving the best economical solution according to the used power transformer (V/V or Scott).This work has been supported by FCT – Fundação para a Ciência 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. Mohamed Tanta is supported by the doctoral scholarship with a reference PD/BD/127815/2016 granted by the Portuguese FCT agency

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

Comprehensive analysis and cost estimation of five-level bidirectional converters for electric vehicles operation in smart cities context

A comprehensive analysis, comparison and cost estimation of five-level bidirectional converters for the electric vehicle (EV) operation in smart cities context is presented in this paper. Nowadays, five-level converters are widely used with success to interface between the power grid and renewable energy sources, as well as, to operate as motor drivers. Therefore, with the EV introduction into the power grids arises a new opportunity to use such five-level converters as interface between the power grid and the EV batteries, i.e., in on-board charger applications. Moreover, considering the future scenarios of smart grids and smart cities, the five-level bidirectional converters will be essential for the operation modes grid-to-vehicle (G2V, charging the batteries from the power grid) and vehicle-to-grid (V2G, returning energy from the batteries to the power grid). In this context, this paper presents an aggregation of the most important five-level bidirectional converter topologies that can be applied for on-board EV chargers in smart cities context. Along the paper it is presented a detailed description of the hardware and control algorithms of the five-level converters, and are also presented and explained simulation results performed under realistic operating conditions. Finally, it is presented the cost estimation for a real application considering the hardware requirements for each one of the converters.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 and 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 Ǧ Fundação para a Ciência e a Tecnologia, within project SAICTPAC/0004/2015-POCI-01-0145-FEDER-016434.info:eu-repo/semantics/publishedVersio

A proposed single-phase five-level PFC rectifier for smart grid applications: an experimental evaluation

The use of PFC rectifiers has assumed an increasingly preponderance, contributing in a decisive way to improve the power quality indices, since they allow to operate with sinusoidal current on the ac side and with controlled voltage on the dc side. In this paper is proposed a novel PFC rectifier that allows five levels of voltage. As noted in the paper, it presents a number of interesting advantages when compared to the conventional five level PFC rectifier, mainly because it requires less passive and active semiconductors to produce the different voltage levels and requires less hardware resources to implement the gate driver circuits. The proposed five level PFC (5L PFC) rectifier operates in boost mode and has a single dc link (although with a midpoint to achieve the various levels), being an important feature for applications in smart grids (e.g., smart electrical appliances and electric mobility chargers). The key topics of the 5L PFC rectifier are addressed and discussed based on the analysis of the principle of operation. As current control strategy it was adopted the model predictive control. Experimental results in steady and transient state were considered for an effective validation of the 5L PFC rectifier, verifying the operation with: sinusoidal current on the ac side; multi level operation with five levels; controlled dc link voltage.FCT - Fundação para a Ciência e Tecnologia within the Project Scope: UID/CEC/00319/2019. This work has been supported by FCT Project newERA4GRIDs PTDC/EEI-EEE/30283/2017 and by 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. Mr. Tanta was supported by FCT PhD grant with a reference PD/BD/127815/2016