“Sixty years ago I knew everything; now I know nothing; education is a progressive discovery of our own ignorance. Will Durant”



sábado, 20 de janeiro de 2018

High Frequency Isolated Power Conversion from Medium Voltage AC to Low Voltage DC Shishuo Zhao - Virginia Polytechnic Institute and State

High Frequency Isolated Power Conversion from Medium Voltage AC to Low Voltage DC 
Shishuo Zhao - Virginia Polytechnic Institute and State 

 Modern data center power architecture developing trend is analyzed, efficiency improvement method is also discussed. Literature survey of high frequency isolated power conversion system which is also called solid state transformer is given including application, topology, device and magnetic transformer. Then developing trend of this research area is clearly shown following by research target. State of art wide band gap device including silicon carbide (SiC) and gallium nitride (GaN) devices are characterized and compared, final selection is made based on comparison result. Mostly used high frequency high power DC/DC converter topology dual active bridge (DAB) is introduced and compared with novel CLLC resonant converter in terms of switching loss and conduction loss point of view. CLLC holds ZVS capability over all load range and smaller turn off current value. This is beneficial for high frequency operation and taken as our candidate. Device loss breakdown of CLLC converter is also given in the end. Medium voltage high frequency transformer is the key element in terms of insulation safety, power density and efficiency. Firstly, two mostly used transformer structures are compared. Then transformer insulation requirement is referred for 4160 V application according to IEEE standard. Solid insulation material are also compared and selected. Material thickness and insulation distance are also determined. Insulation capability is preliminary verified in FEA electric field simulation. Thirdly two transformer magnetic loss model are introduced including core loss model and litz wire winding loss model. Transformer turn number is determined based on core loss and winding loss trade-off. Different core loss density and working frequency impact is carefully analyzed. Different materials show their best performance among different frequency range. Transformer prototype is developed following designed parameter. We test the developed 15 kW 500 kHz transformer under 4160 V dry type transformer IEEE Std. C57.12.01 standard, including basic lightning test, applied voltage test, partial discharge test. 500 kHz 15 kW CLLC converter gate drive is our design challenge in terms of symmetry propagation delay, cross talk phenomenon elimination and shoot through protection. Gate drive IC is carefully selected to achieve symmetrical propagation delay and high common mode dv/dt immunity. Zero turn off resistor is achieved with minimized gate loop inductance to prevent cross talk phenomenon. Desaturation protection is also employed to provide shoot through protection. Finally 15 kW 500 kHz CLLC resonant converter is developed based on 4160V 500 kHz transformer and tested up to full power level with 98% peak efficiency.

 LINK WEB : https://vtechworks.lib.vt.edu/bitstream/handle/10919/74969/Zhao_S_T_2017.pdf?sequence=1

terça-feira, 16 de janeiro de 2018

Small-Signal Modeling and Controller Design of a Grid-Connected Inverter for Solid State Transformer-Bo-Gyeong Kim Department of Electrical and Computer Engineering ULSAN NATIONAL INSTITUTE OF SCIENCE AND TECHNOLOGY

Design of a Grid-Connected Inverter for Solid State Transformer -Bo-Gyeong Kim 
Department of Electrical and Computer Engineering ULSAN NATIONAL INSTITUTE OF SCIENCE AND TECHNOLOGY 

 A single-phase grid-connected inverter for solid state transformer (SST) is presented. This work is aimed at the modeling and the design of control schemes for the inverter. In this thesis, a small-signal model for the grid-connected inverter with modified bipolar pulse width modulation method is developed. Small-signal analysis allows to predict the stability and dynamics of the inverter. Based on theoretical analysis, controllers are designed to improve dynamics and to guarantee stability of the system. A high power factor and low harmonics are desirable in transmission system to improve the efficiency of the utility line. The current controller of the single-phase grid-connected inverter has sinusoidal reference to achieve power factor correction (PFC) and harmonics suppression. Proportional-integral (PI) scheme is widely used to control the power converter. The PI controller has the infinite gain at dc so it is suitable to track the dc reference. However, it is not good for tracking sinusoidal reference due to its finite gain at ac. The proportional-resonant (PR) controller which introduces large gain at specific frequency can track the sinusoidal reference without steady-state error but the error remains in step input response. The proportional-integral-resonant (PIR) controller has the advantage of both tracking the sinusoidal reference and removing the steady-state error for the step input. In this thesis, PIR controller is proposed for current control and design procedure for the PIR controller is presented. In addition, the voltage controller is needed to regulate the dc link voltage. The voltage controller is designed to improve the audio-susceptibility and the output impedance characteristics. The dynamics and stability of the inverter system is analyzed. The proposed small-signal model and controllers are verified by PSIM simulation and experiments.



domingo, 14 de janeiro de 2018


 Esta disciplina tem por objetivo o estudo de circuitos eletrônicos, como sejam amplificadores a transistores, circuitos com amplificadores operacionais, realimentação, resposta freqüência, etc. No final da disciplina os alunos devem ser capazes de dimensionar, projetar e implementar circuitos eletrônicos baseados nos circuitos estudados na cadeira.

 Pré-Requisitos: EE410 EE530/ EE530 F589. Os alunos devem ter conhecimentos sólidos dos seguintes tópicos: componentes eletrônicos básicos (resistências, condesadores e bobinas), semicondutores (diodos, transistores TBJ e FET), modelos de transistores bipolares e MOSFET, análise básica de circuitos (Lei das Malhas, lei dos nós, etc.) e transformada de Laplace.

 Para uma melhor visualização do andamento desta disciplina mostramos abaixo, com maior detalhe, os assuntos abordados, com as respectivas horas e referência bibliográfica. Tópicos NºHoras Bib.
 1)Revisão dos Modelos Diodos, transistores BJT e FET 4 [2]
 2)Análise de circuitos com um transistor (BJT) e FET Polarização DC e Análise em Configurações Básicas 8 [2]
 3)Análise de circuitos com dois transistores (BJT) e FET Conexões em cascata, Cascode, Darlinton, Quasi-Darlington, Par realimentado, Par Diferencial, Espelho de corrente. 8 [2]
 4)Resposta em freqüência Resposta em freqüência de um amp. de um estágio, Resposta em freqüência de um amp. de múltiplos estágios. 8 [4]
 5)Amplificadores Operacionais Tipos de Opamp, Estrutura básica de um Opamp FV, Opamp básicos, Opamp ideal e real, Característica de Opamp., Modelos. 10 [4]
 6)Circuitos com Amplificadores Operacionais Amp. não Inversor, Amp. Inversor, Amp. Diferença, Amp Somador, Integrador, Diferenciador, Aplicações não Lineares. 6 [4]
 7)Realimentação Equação da realimentação ideal, Efeitos da realimentação, Configurações, Configurações práticas e efeito de carregamento, Realimentação em um simples estágio. 8 [4]
 8)Circuitos Integrados Processos básicos em fabricação de CI, fabricação de circuitos em tecnologia bipolar, Dispositivos ativos em tecnologia bipolar, componentes passivos em tecnologia bipolar, fabricação de circuitos em tecnologia MOS, Dispositivos ativos em tecnologia MOS, componentes passivos em tecnologia MOS.


Aula 1Aula 2Aula 3Aula 4
Aula 5Aula 6Aula 7Aula 8
Aula 9Aula 10Aula 11Aula 12
Aula 13Aula 14Aula 15Aula 16
Aula 17Aula 18Aula 19Aula 20
Aula 21Aula 22Aula 23Aula 24*

Physics, UFC, 1981, MSc. In Electrical Engineering, UNICAMP, 1984. Ph.D. In Electrical Engineering, UNICAMP, 1991. Livre Docência In Electronic Instrumentation, UNICAMP, 2001. Professor since 1985 in Microelectronics and Electronic Department -DEMIC. Responsible for Department's Laboratory of Sensors and Instrumentation.


sábado, 6 de janeiro de 2018

High Efficiency Power Converter for Low Voltage High Power Applications - Morten Nymand - DTU Electrical Engineering Technical University of Denmark

Nymand High Efficiency Power Converter for Low Voltage High Power Applications 
Author:Morten Nymand
Supervisor:Michael A. E. Andersen
 DTU Electrical Engineering Technical University of Denmark Ørsteds Plads Building 349 DK-2800 Kgs. Lyngby Denmark
 Publishing date: January 2010
Classification: Public Edition: 1st Edition
Note: This thesis is submitted in partial fulfillment of the requirements for obtaining the PhD degree at the Technical University of Denmark. Copyright: Morten Nymand, 2010

The topic of this thesis is the design of high efficiency power electronic dc-to-dc converters for high-power, low-input-voltage to high-output-voltage applications. These converters are increasingly required for emerging sustainable energy systems such as fuel cell, battery or photo voltaic based energy systems.

Applications include systems for emergency power back-up (UPS), de-centralized combined heat and power systems, traction applications such as hybrid electrical vehicles, forklift trucks and special applications such as low emission power generation for truck and ship containers, and remote power generation for light towers, camper vans, boats, beacons, and buoys etc.
In chapter 2, a review of current state-of-the-art is presented. The best performing converters achieve moderately high peak efficiencies at high input voltage and medium power level. However, system dimensioning and cost are often determined by the performance at the system worst case operating point which is usually at minimum input voltage and maximum power. Except for the non-regulating V6 converters, all published solutions exhibit a very significant drop in conversion efficiency at minimum input voltage and maximum output power.
 In chapter 3, a detailed analysis of dominant loss factors in high power converters for low voltage applications is presented. The analysis concludes that:
 Power transformers for low voltage high power, if properly designed, will have extremely low leakage inductance.
  If optimally designed, boost converters will be much more efficient than comparable buck type converters for high power low voltage applications.  The use of voltage clamp circuits to protect primary switches in boost converters is no longer needed for device protection. On the other hand, they will dramatically increase power losses. Moreover, if a converter is properly designed, primary side voltage clamp circuits will not even work in low voltage high power converters.
  Very high conversion efficiency can be achieved. Peak efficiency of 98% and worst case minimum efficiency of 96.8% are demonstrated on a 1.5 kW converter.

 In chapter 4, the ability to - and challenges involved in - scaling of power converters for low voltage applications in the power range of 1-10 kW are analyzed. The analysis concludes that power MOSFETs needs to be paralleled extensively to scale power level to 10 kW. Maintaining fast current switching and reliable current sharing is essential. Further, the high ac-current carrying loop on the converter primary side will become increasingly difficult to scale due to fundamental issues such as physical size of components and penetration depth in copper.
Finally in chapter 5, a new method for partial paralleling of multiple primary power stages in isolated boost converters is presented. Maximum benefit of scaling in terms of higher efficiency and lower cost is preserved by only paralleling primary switches and the critical high ac-current loop. Dynamic current sharing is inherently guaranteed between parallel power stages. The principle can be applied to all isolated boost type converters and, in principle, an unlimited number of power stages can be paralleled. Feasibility and operation of the new topology are demonstrated on a dual 3 kW and a quad 10 kW prototype converter. Measured peak efficiency is 98.2% and worst case minimum efficiency is between 96.5% and 96.9%.


segunda-feira, 1 de janeiro de 2018

Laboratório de Microrredes Inteligentes na UNIVERSIDADE FEDERAL DE SANTA CATARINA-BRASIL (uGridLab)




sexta-feira, 29 de dezembro de 2017

Linhas de Transmisão - Apresentação da Obra LT CC 800kV XINGU - ESTREITO (BMTE)-BRASIL

Linha de Transmissão (LT) Corrente Contínua (CC) +800 kV Xing/Estreito e de suas Instalações Associadas. Esta LT, com extensão de 2.086,9 km, interceptará quatro estados – Pará, Tocantins, Goiás e Minas Gerais. A LT terá início na Subestação (SE) Xingu, localizada a aproximadamente 17 km da UHE Belo Monte, no município de Anapu-PA, seguindo até a SE Estreito, localizada no município de Ibiraci-MG. Considerando a extensão e importância do empreendimento e buscando otimizar o planejamento e a execução das obras, a LT (CC) +800 kV Xingu/Estreito foi dividida em 8 trechos, cada um com aproximadamente 260 km. Um grupo de quatro construtoras (EPCistas) será responsável pelos respectivos trechos contratados, possibilitando, dessa forma, um maior controle por parte da equipe da SPE S.A. Um dos Eletrodos será instalado no município de Altinópolis, SP, e será interligado à Estação Conversora (EC) Estreito por meio da Linha de Eletrodo, que interceptará 5 municípios: Ibiraci e Claraval, no Estado de Minas Gerais, e Franca, Patrocínio Paulista e Altinópolis, no Estado de São Paulo. Já o Eletrodo que interligará a EC Xingu será instalado em Anapu, PA, com a Linha de Eletrodo sendo instalada apenas neste município.

O Mapa de Localização apresenta a localização geográfica do empreendimento, nos Estados de Pará, Tocantins, Goiás, Minas Gerais e São Paulo.

OBJETIVOS E JUSTIFICATIVAS DO EMPREENDIMENTO A Usina Hidrelétrica de Belo Monte, em construção na região de Altamira e Vitória do Xingu, no Pará, na sua configuração final, terá capacidade instalada de 11.233 MW, sendo 11.000 MW na casa de força principal e 233 MW na casa de força secundária. Por se tratar de uma usina hidrelétrica com grande capacidade instalada, com potencial para gerar muita energia, parte da produção durante os meses chuvosos será enviada para os estados das regiões Sudeste e Nordeste, principais consumidores do país. A fim de facilitar e otimizar o escoamento da energia produzida, foram comparadas diversas tecnologias existentes. Por fim, optou-se pelo sistema de Corrente Contínua de ±800 kV para reforço à interligação Norte – Sudeste, além de um sistema em corrente alternada de 500 kV como reforço às interligações Norte - Nordeste – Sudeste. As Instalações Associadas da LT (CC) +800 kV Xingu/Estreito incluem as Estações Conversoras (EC) Xingu e Estreito, dois Eletrodos de Terra, com suas respectivas Linhas de Eletrodo, com extensões de aproximadamente 46 km (Linha de Eletrodo Xingu) e 74 km (Linha de Eletrodo Estreito), para interligação desses eletrodos às ECs, e sete Estações Repetidoras (ERs).


quinta-feira, 28 de dezembro de 2017


SEPOC 2017 is the 10th edition of the Seminar on Power Electronics and Control and this year the conference will be held with the IEEE seal. The meeting will take place at the Technology Center of the Federal University of Santa Maria and is organized by the IEEE Chapters and Student Branch.

The seminar’s objective is to provide interaction among academia and industry to discuss the latest cutting-edge technologies on Power Electronics and Control and their applications. In 2017, the conference is themed on distributed power generation.

Plenary Session 03: Reliability of Power Electronic Systems – Challenges and State-of-the-Art 

 Speaker: Huai Wang - Aalborg University, Denmark Huai Wang is currently an Associate Professor and a Research Thrust Leader with the Center of Reliable Power Electronics (CORPE), Aalborg University, Denmark. 

His research addresses the fundamental challenges in modelling and validation of power electronic component failure mechanisms, and application issues in system-level predictability, condition monitoring, circuit architecture, and robustness design. Prof. Wang is a lecturer of a 2-day industry/PhD course on Capacitors in Power Electronics Applications, and a 3-day industry/PhD course on Reliability of Power Electronic Systems held annually at Aalborg University. He is an invited speaker at the European Center for Power Electronics (ECPE) workshops, and a tutorial lecturer at leading power electronics conferences (ECCE, APEC, EPE, PCIM, IECON, etc.). He has co-edited a book on Reliability of Power Electronic Converter Systems in 2015, filed four patents in capacitive DC-link inventions, and contributed a few concept papers in the area of power electronics reliability. Prof. Wang received his PhD degree from the City University of Hong Kong, Hong Kong, and Bachelor degree from Huazhong University of Science and Technology, Wuhan, China. He was a visiting scientist with the ETH Zurich, Switzerland, from August to September 2014, and with the Massachusetts Institute of Technology (MIT), Cambridge, MA, USA, from September to November 2013. He was with the ABB Corporate Research Center, Baden, Switzerland, in 2009. He received the IEEE PELS Richard M. Bass Outstanding Young Power Electronics Engineer Award, in 2016, for the contribution to the reliability of power electronic conversion systems. He serves as an Associate Editor of IEEE Journal of Emerging and Selected Topics in Power Electronics and IEEE Transactions on Power Electronics.

LINK  : http://farol.ufsm.br/transmissao/transmissao-ao-vivo-sepoc-24102017-09h

quarta-feira, 27 de dezembro de 2017

Single phase transformerless inverter topologies for grid-tied photovoltaic system: A review - Monirul Islam a,Saad Mekhilef ,Mahamudul Hasan

Single phase transformerless inverter topologies for grid-tied photovoltaic system: A review Monirul Islam a,Saad Mekhilef ,Mahamudul Hasan 

 Power Electronics and Renewable Energy Research Laboratory (PEARL), Department of Electrical Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur 50603, Malaysia 
Department of Mechanical Engineering, University of Malaya, Kuala Lumpur 50603, Malaysia

 Abstract :
Grid-tied inverters are the key components of distributed generation system because of their function as an effective interface between renewable energy sources and utility. Recently, there has been an increasing interest in the use of transformerless inverter for low-voltage single-phase grid-tied photovoltaic (PV) system due to higher efficiency, lower cost, smaller size and weight when compared to the ones with transformer. However, the leakage current issues of transformerless inverter, which depends on the topology structure and modulation scheme, have to be addressed very carefully. This review focuses on the transformerless topologies, which are classified into three basic groups based on the decoupling method and leakage current characteristics. Different topologies under the three classes are presented, compared and evaluated based on leakage current, component ratings, advantages, and disadvantages. An examination of demand for the inverter, the utility grid, and the PV module are presented. A performance comparison in MATLAB/Simulink environment is done among different topologies. Also an analysis has been presented to select a better topology. Finally, based on the analysis and simulation results, a comparison table has been presented. Furthermore, some important experimental parameters have been summarized.

sábado, 23 de dezembro de 2017

H6-type transformerless single-phase inverter for grid-tied photovoltaic system -Monirul Islam, Saad Mekhilef ✉ Power Electronics and Renewable Energy Research Laboratory (PEARL), Department of Electrical Engineering, University of Malaya.

H6-type transformerless single-phase inverter for grid-tied photovoltaic system ISSN 1755-4535
Received on 20th April 2014 Accepted on 7th October 2014 doi: 10.1049/iet-pel.2014.0251
Monirul Islam, Saad Mekhilef ✉ Power Electronics and Renewable Energy Research Laboratory (PEARL), Department of Electrical Engineering, University of Malaya, Kuala Lumpur 50603, Malaysia ✉ E-mail: saad@um.edu.my

There has been an increasing interest in transformerless inverter for grid-tied photovoltaic (PV) system because of the benefits of lower cost, smaller volume as well as higher efficiency compared with the ones with transformer. However, one of the technical challenges of the transformerless inverter is the safety issue of leakage current which needs to be addressed carefully. In addition, according to the international regulations, transformerless inverter should be capable of handling a certain amount of reactive power. In this study, a new H6-type transformerless inverter for grid-tied PV system is proposed that can eliminate the threat of leakage current. The proposed topology has also the capability to inject reactive power into the utility grid. Three-level output voltage employing unipolar sinusoidal pulsewidth modulation can be achieved with the proposed topology. The proposed topology structure and detail operation principle with reactive power control are investigated. The relationship among the existing topologies and their reactive power control capability are also discussed. The proposed topology is simulated in MATLAB/Simulink software to initially verify the accuracy of theoretical explanations. Finally, a universal prototype rated 1 kW has been built and tested. The experimental results validate the theoretical analysis and simulation results.

domingo, 10 de dezembro de 2017

High-Frequency Transformer Design for Solid- State Transformers in Electric Power Distribution Systems Roderick Javier Garcia Montoya University of Arkansas, Fayetteville

High-Frequency Transformer Design for Solid-State Transformers in Electric Power Distribution Systems
A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Electrical Engineering by Roderick Javier Garcia Montoya Universidad Tecnológica de Panamá Bachelor of Science in Electromechanical Engineering, 2011
December 2015 University of Arkansas This thesis is approved for recommendation to the Graduate Council. ABSTRACT The objective of this thesis is to present a high- or medium-frequency transformer design methodology for Solid-State Transformer (SST) applications. SSTs have been proposed as a replacement of the traditional 50/60 Hz transformer in applications demanding high-power density. Moreover, due to the high penetration of distributed generation, DC grids, energy storage systems, and sensitive loads, SSTs have been considered as an enabling technology for envisioned future energy systems. These applications demand additional functionalities that may not be achieved with traditional transformers. For example, active power flow control, harmonic suppression, voltage regulation, voltage sag compensation, and reduced size and volume. In this thesis, SST topologies are evaluated in order to determine their impact upon the transformer design. In addition, design considerations for core and wire selections, isolation requirements, and different transformer structures are investigated. As a result, the proposed transformer design methodology accounts for leakage inductance requirements for optimal power transfer, high-frequency effects in the transformer core and windings, and a flux density optimization to maximize transformer’s efficiency. The design procedure has been implemented in MATLAB® as an interactive tool for designing high-frequency transformers.