A Single-Stage Asymmetrical Half-Bridge Flyback Converter with Resonant Operation -Chung-Yi Ting , Yi-Chieh Hsu -Department of Electronic and Computer Engineering, National Taiwan University of Science and Technology

A Single-Stage Asymmetrical Half-Bridge Flyback Converter with Resonant Operation Chung-Yi Ting , Yi-Chieh Hsu , Jing-Yuan Lin ,and Chung-Ping Chen Department of Electronic and Computer Engineering, National Taiwan University of Science and Technology.

 Abstract: This paper proposes a single-stage asymmetrical half-bridge fly-back (AHBF) converter with resonant mode using dual-mode control. The presented converter has an integrated boost converter and asymmetrical half-bridge fly-back converter and operates in resonant mode. The boost-cell always operates in discontinuous conduction mode (DCM) to achieve high power factor. The presented converter operates simultaneously using a variable-frequency-controller (VFC) and pulse-width-modulation (PWM) controller. Unlike the conventional single-stage design, the intermediate bus voltage of this controller can be regulated depending on the main power switch duty ratio. The asymmetrical half-bridge fly-back converter utilizes a variable switching frequency controller to achieve the output voltage regulation. The asymmetrical half-bridge fly-back converter can achieve zero-voltage-switching (ZVS) operation and significantly reduce the switching losses. Detailed analysis and design of this single-stage asymmetrical half-bridge fly-back converter with resonant mode is described. A wide AC input voltage ranging from 90 to 264 Vrms and output 19 V/ 120 W prototype converter was built to verify the theoretical analysis and performance of the presented converter.
Keywords: fly-back converter; zero-voltage-switching (ZVS); Variable-frequency-controller (VFC); single-stage
LINK:  https://www.preprints.org/manuscript/201805.0140/v1

Essential & Practical Circuit Analysis: Part 1- DC Circuits-Solid State Workshop

Circuit theory (F parameter, Prof. Sang-Yeol Lee)-회로이론(F파라미터, 이상열 교수님)- KIM NAM NAM ENGINEERING INSTITUTE

Electronic Engineering (Constant Voltage Circuit)-Prof.Kim Gi-Nam- Institute of Engineering-전자공학(정전압회로) - 김기남공학원 제공(방송기술직, 공기업 공채전문 학원)-SOUTH KOREA

Electronic Engineering (Constant Voltage Circuit)-Provided by Kim Gi-Nam Institute of Engineering

Fully-Integrated LED Drivers Using Digital Control Techniques by Kichang Jang Department of Electrical and Computer Engineering The Graduate School of the University of Seoul

Fully-Integrated LED Drivers Using Digital Control Techniques by Kichang Jang A
 Ph.D. Dissertation submitted to the Department of Electrical and Computer Engineering at the Graduate School of the University of Seoul 
in partial fulfillment of the requirements for the degree of Doctor of Philosophy June 2016 Approved by Joongho Choi Advisor

 ABSTRACTS
Most LED-lighting applications are constructed through the connection of a number of LEDs in parallel or in a series for the attainment of sufficient light. If LEDs are connected in parallel, however, an issue regarding the current-matching properties of the LEDs may arise; furthermore, if the LEDs are connected in a series, a high-voltage issue and an instability problem regarding the presence of a single open-circuit LED may also occur. Although the supply voltage varies due to the varying load condition, the current regulator maintains a constant LED current, while the employment of a switching converter can drive the LEDs for the improvement of the operating efficiency. LED drivers are still hampered by a poor operating efficiency, though, due to a voltage drop that is caused by the pass-transistor and the resistor of the current regulator. In this thesis, LED drivers that have been designed for flash-LED and LED-lighting applications are introduced; furthermore, a novel flash-LED current regulator is presented. To obtain a higher efficiency and a smaller area, the proposed regulator is operated without a resistor unlike the conventional current-regulator design. The designed flash-LED driver for which the proposed current regulator is used consists of a boost converter, an analog-to-digital converter (ADC), and a digital-to-analog converter (DAC). The boost-converter output voltage is set by an adaptive-voltage control for which the ADC and the DAC are used, and this control ensures the provision of a high-precision LED current; here, the use of the proposed LED-driver-control method provides only a 2 % current error at an LED current of 0.5 A. A higher efficiency and a smaller area are achieved through the use of a 0.13 μm-BCD process for the implementation of the flash-LED driver. A primary-side-regulated flyback converter for an LED-lighting application is also presented in this thesis. The proposed mid-current sensing circuit is introduced for the attainment of a precise outputcurrent regulation with respect to both the discontinuous-conduction mode (DCM) and the continuous-conduction mode (CCM); furthermore, a current error that is derived from an on-time propagation delay that is due to circuit imperfections is also analyzed A novel adaptive on-time-delay compensation circuit is therefore proposed for the attainment of a precise output-current regulation. The proposed compensation circuit is fully integrated for the delayerror factor; also, unlike a number of the other existing circuits, external components are not required for the proposed circuit. The LED-lighting flyback converter is implemented using a 0.35 μm- BCD process. The use of the proposed method provides only a 4 % current error regardless of the LED current that is applied
 Keywords: LED driver, adaptive voltage control, boost converter, current regulator, primary-side regulation flyback converter, mid-current sensing circuit
LINK: https://www.mediafire.com/file/c3s26xyq7fhv59w/Fully-Integrated_LED_Drivers.pdf/file

LABORATORIOS E PROJETOS DA COORDENAÇÃO DE CIENCIAS ESPACIAIS -CEA-INPE-INSTITUTO NACIONAL DE PESQUISAS ESPACIAIS -BRASIL

LINK https://youtu.be/HHztrhZvJ64

New China-Brazil earth resource satellite sent into space-CBERS-4A launch-PARCERIA BRASIL CHINA

CBERS-4A LAUNCH 

Etapa Final de Testes do Satélite Sino-Brasileiro - CBERS-4A
PROGRAMA BRASIL COM CIENCIA HISTORIA DE 30 ANOS DE PARCERIA BRASIL CHINA EM DESENVOLVIMENTO DE SATELITES
TAIYUAN, Dec. 20 (Xinhua) -- A new satellite, jointly developed by China and Brazil, was sent into space on Friday, pushing forward the aerospace cooperation between the two countries, according to the China National Space Administration (CNSA).

 The China-Brazil Earth Resource Satellite-4A (CBERS-4A) was launched on a Long March-4B carrier rocket at 11:22 a.m. Friday Beijing Time from the Taiyuan Satellite Launch Center in north China's Shanxi Province.

 The satellite is the sixth satellite under the earth resource satellite cooperation program between the two countries. It will obtain global optical remote-sensing data and support the Brazilian government's monitoring of the Amazon rainforest and the country's environmental changes.

 The CBERS-4A will replace CBERS-4, which was launched in 2014, to improve the resolution of the remote-sensing data, said CNSA. It is equipped with three optical payloads: a wide-range panchromatic multispectral camera developed by China, and a multispectral camera and a wide-field imager developed by Brazil. It has a better imaging capacity and higher positioning accuracy than CBERS-4, and can better meet the urgent needs of both countries in land and resources exploration, land classification, environmental protection monitoring, climate change research, disaster prevention and mitigation, crop classification and yield estimation, according to CNSA. It can also provide services for Asian, African and Latin American countries. In July 1988, China and Brazil signed the agreement establishing the joint research and production of the earth research satellites. The first such satellite was launched from China in 1999. Brazilian Minister of Science, Technology, Innovation and Communications Marcos Cesar Pontes said the cooperation between China and Brazil has contributed to international economic and social development. He said the new satellite will be used in fields such as earth resource monitoring, agriculture, meteorology, environmental protection, surveying and mapping, and serve Brazil and more developing countries.

Low Cost Drive Circuit and Control IC Design for AC-Direct LED Lamps-Doctoral Thesis Yoo-Chae Chung (정 유 채) Department of Electrical Engineering Pohang University of Science and Technology

Low Cost Drive Circuit and Control IC Design for AC-Direct LED Lamps-Doctoral Thesis Yoo-Chae Chung (정 유 채) Department of Electrical Engineering Pohang University of Science and Technology

 Abstract
This paper proposes a drive circuit for ac-direct LED lamps and its custom IC design. The proposed circuit consists only of a line filter, an LED bridge, a load inductor, a bi-directional switch, and a switch-control circuit. The switch connects the LED bridge to the power line directly. Each leg of the LED bridge consists of LEDs and a protection diode, all connected in series. The load inductor limits the bridge current. The switch operates at a zero current switching condition, so the circuit has high power efficiency PE. The circuit can operate at a free-volt input condition (85 < Vin,rms < 265 V). For all input voltage conditions the circuit had PE > 89%, luminous efficiency ~ 90 lm/W, power factor > 0.9 and 120 Hz flicker index ~ 0.3. The circuit satisfies the IEC 61000-3-2 Class C and the EN 55015 regulations. The proposed LED driver is wellsuited for use in household LED lamps.
LINK
https://www.mediafire.com/file/9g9cnq4x5nsm7ch/Low_Cost_Drive_Circuit_and_Control_IC_Design_for_AC-Direct_LED.pdf/file

Two-stage Active Gate Driver for SiC MOSFET by Abhay Negi Faculty of North Carolina State University Thesis Master of Science Electrical Engineering

Two-stage Active Gate Driver for SiC MOSFET by Abhay Negi 

A thesis submitted to the Graduate Faculty of North Carolina State University in partial fulfillment of the requirements for the degree of Master of Science Electrical Engineering
Raleigh, North Carolina 2017

ABSTRACT
NEGI, ABHAY. Two-stage Active Gate driver for SiC MOSFET. (Under the direction of Dr. Subhashish Bhattacharya).

Wide-band gap devices have rejuvenated the research in field of power electronics due to their superior properties over Silicon (Si) such as low on-resistance, high breakdown voltage, low switching losses and high temperature operation. However, SiC MOSFETs and GaN devices pose varied challenges due to high dv/dt and di/dt switching which creates issues related EMI, common mode current, high voltage overshoot, cross-talk, etc. In phase-leg configuration, due to high turn-on dv/dt of SiC MOSFET, a positive spurious voltage is induced on the gate to source voltage (Vgs) of the complementary MOSFET. This reduces signal to noise margin on the Vgs of the complementary MOSFET making it susceptible to spurious turn-on in the phase-leg. This can be reduced by using higher turn-on gate resistance for lower dv/dt but it will lead to higher switching loss. This thesis explores the twostage turn-on active gating for SiC MOSFETs to control turn-on dv/dt and di/dt independently. A two-stage active gate driver is designed which uses lower gate resistance in first stage to increase rate of current rise and higher gate resistance in second stage for lower turn-on dv/dt. A low-inductance DC bus PCB is designed to minimize voltage overshoots and ringing associated with high loop inductance. Switching losses are measured with and without active gating by double-pulse testing of 1200V/ 300A ROHM SiC half-bridge module BSM300D12P2E001 for comparison.

LINK:https://research.ece.ncsu.edu/bhattacharya/wp-content/uploads/2019/07/etd29.pdf

ENGENHEIRA TELECOMUNICAÇÕES GERALDIDE FRANCIA GANHADORA DO PROJETO PAPEATEC CONCURSO GENTE BRILHANTE TELEFONICA PERU

GERALDINE FRANCIA La tecnología es una herramienta que cambia vidas y Geraldine es prueba de ello. Esta ingeniera de telecomunicaciones promueve el aumento de la presencia femenina en este rubro porque sabe que traería grandes beneficios.

PROYECTO “Papeatec” – Yauyos, Lima El proyecto consiste en acercar la tecnología a estudiantes de una comunidad agrícola de Yauyos mediante talleres formativos en programación y electrónica aplicada a Internet. Los conocimientos adquiridos les servirán para desarrollar una red de sensores que miden las características de los suelos agrícolas y elegir el más adecuado para cada tipo de sembrío. Los conocimientos a brindar favorecerán a que los estudiantes descubran cómo la tecnología puede mejorar sus vidas, a través de diversos ejemplos de tecnología aplicada a agricultura, ganadería y acuicultura.

FUENTE ORIGINAL:
https://elcomercio.pe/especial/comprometidosconlaeducacion/temporada-2/geraldine-francia-noticia-1994800?utm_source=ElComercio&utm_medium=Portada-Principal&utm_campaign=fundacion-telefonica

A Non-isolated ZVZCS Resonant PWM DC-DC Converter for High Step-up and High Power Applications Author Jung,Byoung Kil Dept.of Control and Instrumentation Eng. Graduate School of Industry and Engineering Seoul National University of Science and Technology

Abstract
 A Non-isolated ZVZCS Resonant PWM DC-DC Converter for High Step-up and High Power Applications Jung,ByoungKil (SupervisorChoi,SeWan) Dept.of Control and Instrumentation Eng. Graduate School of Industry and Engineering Seoul National University of Science and Technology

 The demand of non-isolated high step-up DC-DC converters is gradually increasing in many applications such as dc back-up energy systems for UPS, photovoltaic and fuel cell systems and hybrid electric vehicles.This paper proposes non-isolated step-up DC-DC converters with an improved switching method.The proposed converter shows ZVS turn-on of the switches in CCM as well as reduced turn-off switching losses owing to the switching method that utilizes Lr-Cr resonance in the auxiliary circuit.Also,owing to the proposed switching method the switching losses associated with diode reverse recovery become negligible even in the small dutycycle.The capacitance in the auxiliary circuit is significantly reduced compared to PWM method.The duty cycle loss is further reduced resulting in increased step-up ratio. Experimental results from a 2kW prototype of two-phase interleaved version are also provided to validate the proposed concept.

 LINK FULL TEXT:https://www.mediafire.com/file/47c75j6rsx645de/A_Non-isolated_ZVZCS_Resonant_PWM_DC-DC_Converter.pdf/file

UNIFIED POWER QUALITY CONDITIONER: DESIGN, SIMULATION AND EXPERIMENTAL ANALYSIS Author Ahmet TEKE PhD THESIS DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING-UNIVERSITY OF ÇUKUROVA INSTITUTE OF NATURAL AND APPLIED SCIENCE

UNIFIED POWER QUALITY CONDITIONER: DESIGN, SIMULATION AND EXPERIMENTAL ANALYSIS AUTHOR Ahmet TEKE PhD THESIS

DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING UNIVERSITY OF ÇUKUROVA INSTITUTE OF NATURAL AND APPLIED SCIENCE
 ABSTRACT
 Power quality (PQ) problem can be defined as the deviations of the voltage and/or current from the nominal sine wave. PQ problems generally concern with voltage sags/swells and harmonic currents. Custom Power (CP) devices that mitigate these power quality problems have gained more attention in the recent decades. Unified Power Quality Conditioner (UPQC) is one of the CP devices and it mitigates both load current and supply voltage problems, simultaneously. In this study, UPQC and a new topology of UPQC namely OPEN UPQC are designed, modeled and setup experimentally to mitigate voltage sag/swells and harmonic currents. UPQC consists of Dynamic Voltage Restorer (DVR) and Active Power Filter (APF). An improved voltage compensation controller and new sag/swell detection method based on Enhanced Phase Locked Loop (E-PLL) are presented for DVR. Traditional Instantaneous Reactive Power Theory (IRPT) is optimized for APF control algorithm to compensate harmonic load current under unbalanced and distorted supply voltages. Digital Signal Processor based 6 kVA, 230Vline-lineUPQC and OPEN UPQC prototypes have been developed for laboratory tests. UPQC and OPEN UPQC with proposed controller algorithms effectively compensates the sag/swell in supply voltage by keeping the load voltage amplitude at 0.9-1 per unit and eliminates the load current harmonics by keeping supply current at 5%

LINK
 https://www.mediafire.com/file/emmt5nhaj82tk1r/TEKE-CONDICIONADOR_POTENCIA.pdf/file

Ambientalismo: A grande farsa da humanidade e o grande atraso do Brasil PHD LUIZ CARLOS BALDICERO MOLION

Ambientalismo: A grande farsa da humanidade e o grande atraso do Brasil 

 LUIZ CARLOS BALDICERO MOLION, paulistano, 72 anos. Possui graduação em Física pela Universidade de São Paulo (1969), PhD em Meteorologia, University of Wisconsin, Madison (1975), pós-doutorado em Hidrologia de Florestas, Institute of Hydrology, Wallingford, UK (1982) e foi fellow do Wissenschaftskolleg zu Berlin, Alemanha (1989-1990). Foi por muitos anos pesquisador do Instituto Nacional de Pesquisas Espaciais, diretor da área de ciências espaciais e atmosféricas em 1985 e diretor associado em 1986, ano em que co-coordenou um projeto de pesquisa sobre a Amazônia em parceria com cientistas da NASA. Foi diretor da Fundação para Estudos Avançados no Trópico Úmido em Manaus, professor palestrante convidado da Western Michigan University de 15 a 30 de janeiro de 2001, e delegado do Brasil na 15ª reunião da Comissão de Climatologia da Organização Meteorológica Mundial em 2010.

CAD and Graphics2 Hanyang University Jin Kook Lee, PhD Assistant Professor, Space and Design IT Lab. Department of Interior Architecture Design, Hanyang University

LINK:http://www.kocw.net/home/search/kemView.do?kemId=1176197

Unicamp testa modelo de inteligência artificial em pacientes com doenças cardíacas crônicas-Pesquisa foi premiada pela Sociedade Brasileira de Cardiologia e pelo Congresso Europeu de Inovação-BRASIL

Uma pesquisa conduzida no Laboratório Aterolab da Faculdade de Ciências Médicas (FCM) da Unicamp testou o uso da inteligência artificial para identificar pacientes com doenças coronarianas crônicas e classificá-los com maior ou menor risco a eventos clínicos adversos. O modelo – baseado em algoritmos – permitiu ainda estimar os custos desses pacientes para o Sistema Único de Saúde (SUS). A finalidade do estudo, de acordo com os pesquisadores da Unicamp, é aumentar a precisão da alta hospitalar e ajudar nas decisões médicas.

 “Quando o médico atende um paciente grave com doença coronariana aguda, ele precisa decidir se o paciente pode ter alta, se precisa de outro tipo de intervenção ou de cuidados de alto custo, se pode ir para um hospital da rede pública ou ficar em hospital de alta complexidade. Para facilitar essa decisão, criamos alguns algoritmos sofisticados baseados em equações a partir da soma de características dos pacientes”, explicou o cardiologista Andrei Sposito, coordenador do Aterolab e orientador da pesquisa.

 Usando dados de prontuários de pacientes atendidos em hospitais públicos e privados, os pesquisadores analisaram 1.089 indivíduos com síndromes coronarianas agudas entre 2006 e 2018 e modelaram 29 variáveis clínicas possíveis para pacientes cardíacos. Essas variáveis incluíram sinais vitais, dados coronarográficos, diagnósticos e dados laboratoriais. Para as análises de custos, os pesquisadores consideraram a possibilidade de nova revascularização, mortes cardiovasculares e não cardiovasculares, tratamento dialítico crônico, hospitalizações e acidentes vasculares cerebrais (AVC).

 Após a captura das informações coletadas dos prontuários em papel ou eletrônico, os dados foram inseridos no sistema e o computador foi “treinado” para simular os possíveis cenários para o paciente com doença coronariana crônica. Depois, a cada novo dado coletado durante o atendimento clínico ou ambulatorial e inserido no sistema, o computador se recalibra.

 “O computador aprende com cada resultado e informa ao médico a melhor conduta clínica para o paciente. A partir desse trabalho, conseguimos prever 92% dos eventos clínicos que um paciente pode vir a ter. Identificamos, ainda, pacientes de alto risco para síndromes coronarianas agudas cujo custo foi quase cinco vezes maior. A aplicação da inteligência artificial para esses pacientes pode representar uma economia de quase R$ 50 milhões por ano para os hospitais brasileiros. Além disso, teremos certeza que os pacientes mais graves estarão recebendo um tratamento mais exato”, disse o cardiologista Luiz Sérgio F. de Carvalho, pesquisador do Aterolab e autor principal do estudo.


Os resultados da pesquisa intitulada "Inteligência artificial prediz o risco de novos eventos após síndromes coronarianas agudas, identifica indivíduos de alto custo e aqueles com elevada carga de fatores de risco não controlados" foi apresentada durante o 74º Congresso Brasileiro de Cardiologia, ocorrido em setembro em Porto Alegre e ganhou o prêmio de melhor tema livre. O estudo contou ainda com a participação de Silvio Gioppato, Marta Duran Fernandez, Bernardo Carvalho Trindade, José Carlos Quináglia e Silva e Sandra Ávila.
 Após a apresentação da pesquisa durante o Congresso, a Sociedade Brasileira de Cardiologia (SBC) convidou os pesquisadores do Aterolab da FCM para criarem, dentro da SBC, uma comissão para desenvolver um projeto de inteligência artificial com as mesmas características desenvolvidas na Unicamp e distribuí-lo, nacionalmente, para os hospitais públicos nos próximos dois anos.
 “Nosso estudo mostrou que a utilização da inteligência artificial aprimora a eficácia do atendimento. Conseguimos identificar quem tem mais chance de morrer, de voltar para o hospital ou de custar mais caro. Conseguimos identificar 10% dos pacientes que consomem mais de 30% dos recursos gastos. Podemos prevenir que tudo isso aconteça usando essa nova tecnologia”, reforçou Luiz Sérgio.
 A pesquisa foi apresentada no início de novembro durante o International Society for Pharmacoeconomics and Outcomes Research (ISPOR) Europe 2019, na Dinamarca, e ficou em primeiro lugar como melhor trabalho. O ISPOR é o mais importante congresso europeu de inovação. “Os Estados Unidos estão fazendo um incentivo aos hospitais que adotam prontuários eletrônicos que façam interface com o sistema de inteligência artificial. Em pouco tempo, eles estarão rodando isso de forma perfeita. No Brasil, alguns hospitais privados estão atrás disso. Quem lida com gestão médica entendeu que não tem saída. Essa é a melhor forma de trabalhar. Para o paciente é um sistema seguro. Para o hospital é mais barato, pois otimiza as ações. É o futuro que chegou”, conclui Sposito.
LINK ORIGINAL:
https://www.unicamp.br/unicamp/ju/noticias/2019/11/11/unicamp-testa-modelo-de-inteligencia-artificial-em-pacientes-com-doencas-0

TÉCNICA DE MODULAÇÃO PARA REDUÇÃO DA DHT DE CORRENTE APLICADA A RETIFICADOR BOOST BRIDGELESS EM MODO CONDUÇÃO DESCONTINUA Caio G. da S. Moraes, Mateo D. Roig G., Telles B. Lazzarin Instituto de Eletrônica de Potência - INEP, Universidade Federal de Santa Catarina - UFSC, Brasil

TÉCNICA DE MODULAÇÃO PARA REDUÇÃO DA DHT DE CORRENTE APLICADA A RETIFICADOR BOOST BRIDGELESS EM MCD
 Caio G. da S. Moraes, Mateo D. Roig G., Telles B. Lazzarin Instituto de Eletrônica de Potência - INEP, Universidade Federal de Santa Catarina - UFSC, Florianópolis - SC, Brasil 

 Resumo – Tradicionalmente, os retificadores do tipo Boost operando no modo de condução descontínua (MCD) não usam controle de corrente e operam com razão cíclica constante, mas apresentam uma distorção harmônica significativa devido à presença de uma componente de 3ª harmônica. O presente artigo equaciona matematicamente o problema e propõe o uso de uma técnica de modulação que corrige a razão cíclica durante o período da rede e, assim, elimina significativamente a distorção harmônica da corrente, sem adicionar sensores de corrente. A técnica de modulação utilizada já foi apresentada na literatura, no entanto, este artigo demonstra um maior detalhamento matemático da estratégia e propõe uma metodologia para determinar o índice de modulação ótimo. Adicionalmente, propõese também uma alternativa para tornar a técnica menos susceptível às variações da tensão de entrada. De modo a validar o estudo teórico, construiu-se um protótipo de 500 W do retificador Boost bridgeless modificado, com tensão eficaz de entrada de 220 V, tensão de saída de 450 V e frequência de comutação de 58,6 kHz. Resultados experimentais apresentaram uma melhoria na distorção harmônica total de 22,17% para 4,88% e no fator de potência de 0,977 para 0,996, ambos em carga nominal. Palavras-chave – Condução Descontínua, Correção do Fator de Potência, Redução da Distorção Harmônica, Retificador Boost Brigeless Modificado, Técnica de Modulação.
LINK: https://sobraep.org.br/site/uploads/2019/09/rvol24no03-13-0023-345-355.pdf

STRATEGIES TO DEAL WITH GROUND FAULTS IN GRID-CONNECTED TRANSFORMERLESS PHOTOVOLTAIC CONVERTERS WITH BATTERY ENERGY STORAGE SYSTEM Lucas V. Bellinaso, Ricardo S. Figueredo, Marcelo P. Almeida, Ricardo J. F. Bortolini, Leandro Michels, Ildo Bet, Roberto Zilles Power Electronics and Control Group of the Federal University of Santa Maria, PHB Eletrônica LTDA, Universidade de São Paulo - USP,Brazil

STRATEGIES TO DEAL WITH GROUND FAULTS IN GRID-CONNECTED TRANSFORMERLESS PHOTOVOLTAIC CONVERTERS WITH BATTERY ENERGY STORAGE SYSTEM
 Lucas V. Bellinaso, Ricardo S. Figueredo, Marcelo P. Almeida, Ricardo J. F. Bortolini, Leandro Michels, Ildo Bet, Roberto Zilles
Power Electronics and Control Group of the Federal University of Santa Maria,
PHB Eletrônica LTDA,
Universidade de São Paulo - USP,Brazil

 Abstract – Grid-connected photovoltaic systems with energy storage, also called PV hybrid mini-grid system (PVHMS), operate in both grid-tied and stand-alone modes and are expected to play an important role in distributed generation. Transformerless photovoltaic converters are most preferred for these systems due to their higher conversion efficiency in comparison to insulated converters, increasing autonomy of the battery energy storage system (BESS). Safety in transformerless photovoltaic converters is a critical issue due to parasitic capacitance between PV modules and ground that could result in high leakage current. Existing safety requirements for grid-tied PV inverters may not be sufficient for PVHMS converters since they have multiple leakage current paths. This study analyzes some leakagecurrent- related faults on transformerless PVHMS converters, and proposes relay opening sequences to avoid unnecessary interruptions of power supply for the local loads. The following situations are analyzed: i) fault at dc side, ii) fault at ac load side, and iii) commutation between on-grid and off-grid operation modes. These faults have been studied for a transformerless PVHMS converter with a single dc-ac stage. Experimental results are presented to validate the proposed schemes and a table summarizing the proposals is presented. Keywords – Electric shock, Photovoltaic power systems, Power electronics, Protective relaying, Uninterruptible power systems.
LINK:https://sobraep.org.br/site/uploads/2019/09/rvol24no03-10-0015-314-322.pdf

Várias comitivas de universidades internacionais visitaram a Unicamp em novembro-SÃO PAULO BRASIL

A Unicamp recebeu durante o mês de novembro várias visitas internacionais como parte da sua política de ampliação de cooperação com importantes universidades do mundo. No dia 7, representantes da Leibniz University Hannover, na Alemanha esteve na Universidade com o objetivo de explorar oportunidades de intercâmbio e discutir critérios de intercâmbio cultural baseados nos antecedentes da Cooperação BRICS. No encontro, participaram os professores Celso Kazuyuki Morooka, assessor do Escritório Internacional da Unicamp e Bruno de Conti, diretor do Instituto Unicamp Confúcio, além do senhor Qinxiang Gao, Diretor da BJTU para o Instituto Unicamp Confúcio. No dia 14, representantes das universidades de Lund (Suécia) e Norwegian University of Science and Technology foram recebidos pela administração central da Unicamp. Com a Universidade de Lund discutiu-se possibilidades de colaboração e participaram do encontro os professores Rafael Dias, assessor do Escritório Internacional da Unicamp; Mario Maróstica, da Faculdade de Engenharia de Alimento e Juscelino Tovar, da universidade sueca. A visita da comitiva da Norwegian University of Science and Technology teve como foco estreitar as relações entre as instituições, bem como, ampliar as possibilidades de parcerias. Os representantes noruegueses foram recebidos pela coordenadora geral da Universidade, Teresa Dib Zambon Atvars. A universidade americana Emory University esteve representada no dia 19 pelos professores Tye Tavaras, Eric Weeks, Michael A. Elliott, Philip Wainwright e Jeffrey Lesser. Na Unicamp, foram acompanhados pelo professor Rafael Dias, assessor do Escritório Internacional da Unicamp, em um campus tour pela Universidade.

 Dia 25 mais duas visitas de universidades da América Latina estiveram na Unicamp. A Universidad Adolfo Ibañez (Chile) foi recebida pelo reitor Marcelo Knobel e pelos professores Mariano Laplane, diretor executivo da Deri e Marco Aurélio Pinheiro Lima, diretor executivo de Planejamento Integrado (Depi). A comitiva chilena foi composta pelos professores Carlos Jerez, Josefina Poupin e Jocelyn Olivari. O encontro teve como ponto principal promover colaborações futuras.

 A Unversidad Nacional de Jaén (Peru), representada por Abner Barzola Cárdenas e Zadith Garrido Campaña, acompanhados por seis alunos, foram recebidos pelos professores Mariano Laplane e Hugo Enrique Hernandez Figueroa, da Faculdade Engenharia Elétrica e de Computação da Unicamp.

LINK ORIGINAL:
https://www.unicamp.br/unicamp/noticias/2019/11/26/varias-comitivas-de-universidades-internacionais-visitaram-unicamp-em-novembro

Master's Thesis Multi-powered UPS Department of Electrical Engineering Graduate School, Chonnam National University AUTHOR KIM Jongcheol

Master's Thesis Multi-powered UPS Department of Electrical Engineering Graduate School, Chonnam National University KIM Jongcheol

 (Abstract) 

As the society develops, load sensitive to power environment such as medical equipment, communication equipment, FA (factory automation) system and data center server is widely used, and reliability and stable supply of power system becomes more important. In particular, electrical equipment used for military purposes is not expected to have any problems in the power supply system during exhibition or operation, so it is becoming necessary to secure a reserve energy source, to duplicate the system or to make surplus system. Even if the reliability of the power supply system is high, momentary power failure due to an accident or a lightning can not be avoided, and there is also a momentary voltage drop (Sag) or a voltage rise (swell) of the power supply. Table 1 below is a definition of the power anomaly phenomenon that appears in the commercial power source shown in IEEE Std 1159TM-2009. In case of power-sensitive load, it is necessary to prepare for system failure because it can cause fatal damage even in short-term system failure. Therefore, there is a need for an uninterruptible power supply (UPS) [1] [2] to compensate for instantaneous voltage fluctuations as well as for blackout situations. Automotive UPS systems typically consist of a single module, such as a battery, bi-directional inverter, high-speed switch, and the UPS module is connected to the vehicle generator and critical loads. If the existing UPS system is composed of a single power source and the UPS system is composed of only one power source, it is difficult to cope with the demand of the main load in the long term only by the output of the UPS when the power source is out of power. To solve this problem, connecting several power sources to a load leads to a large increase in cost due to the connection of UPS to each power source. It is an off-line UPS system that is commonly used. The advantage of the off-line method is that when the input power is normal, there is less generation of electromagnetic waves and noise, and the power consumption is low due to high energy efficiency. In addition, it has a simple circuit configuration, high durability, low cost, and miniaturization compared to on-line. The disadvantage of off-line is that momentary power cut-off occurs in the case of power failure, and the output changes according to the input voltage change during non-operation, making it difficult to adjust the voltage and therefore it is not suitable for high-precision load. In the case of Figure 1, it is composed of a single power source, and if the UPS system consists of only one power source, it is difficult to cope with the demand of the main load in the long term only by the output of the UPS when the power source is outage. In particular, in a system having a purpose for use in a command communication terminal of a military, it is difficult to supply stable power because there are many variables in power supply. In this paper, we propose a multi - power applied UPS system that eliminates the disadvantages of the parallel - connected power supply and has a fast switching time. The UPS system operates in the battery charging mode when the system is in normal operation and operates in the UPS mode, which is the battery discharge mode, in the event of a system failure. In such a mode switching, the follow up of the command voltage should be performed within the shortest time. Since the UPS must supply the same voltage to the load within 4ms in case of a system fault, the switching time and return time must be short when controlling the output voltage and current of the UPS, and the power failure detection time is also important. In addition, since the main loads of the UPS system are mostly time-varying and non-linear loads, it is also necessary to be able to control non-linear loads. Conventionally, a proportional integral (PI) controller has been used as a control method of such a UPS system. The PI controller has a very stable output characteristic in the steady state, but it takes a long time to reach the steady state at the time of mode change or load change due to slow acceleration. Therefore, due to the limit of the transient response characteristic of the controller, it is difficult to perform stable power supply within a short time in the case of a system fault. Also, since the gain of the PI controller affects the response characteristics, response characteristics may be slow or overshoot may occur depending on the gain value selection of the controller. Therefore, in this paper, to compensate the limitation of the proportional integral controller, the controller using the DFT with fast electrostatic sensing characteristics is applied. The control using DFT has an advantage that it can perform fast power failure detection by comparing grid voltage waveform and voltage waveform created by DFT using Schmitt trigger. Therefore, stable power supply is possible when using only PI control in mode switching in UPS system. The multi-power applied UPS system proposed in this paper is finally designed to satisfy the following conditions. In case of system fault, detection method using fast DFT is applied to the electrostatic detection in order to supply stable power to the load in a shorter time than the conventional PI control method. At this time, the switching time of mode switching was set to be less than 4 ms, which is 1/4 of the system cycle, according to KS C 4310 regulation of the uninterruptible power supply in the industry standard council. A 10kW UPS system, in which commercial voltage, vehicle generator, and auxiliary diesel generator can be connected to the proposed switchgear, was tested and validated.

LINK
https://www.mediafire.com/file/6xt8y2r9j7fz25c/Multi-powered_UPS.pdf/file