Os sistemas fotovoltaicos conectados à rede convertem diretamente a energia solar em energia elétrica entregando à rede elétrica de distribuição uma energia limpa e renovável. Esses sistemas são formados basicamente por um conjunto de módulos fotovoltaicos e inversores que são responsáveis por converterem energia elétrica em corrente contínua em energia elétrica em corrente alternada. Esta Tese apresenta um estudo de características elétricas e térmicas de inversores utilizados em sistemas conectados à rede a partir de uma análise teórica e experimental. Os ensaios de inversores foram realizados em duas etapas: a primeira etapa foi desenvolvida no Laboratório de Energia Solar (Labsol) da Universidade Federal do Rio Grande do Sul (UFRGS) onde foi utilizado um sistema fotovoltaico de 4,8 kWP e dez modelos de inversores de diferentes fabricantes. As características elétricas de inversores que foram medidas e analisadas são: eficiência de conversão de corrente contínua em corrente alternada, eficiência do seguidor do ponto de máxima potência, fator de potência e distorção harmônica na corrente e na tensão. Ensaios térmicos de inversores também foram realizados e os resultados apresentados e analisados. A segunda etapa dos ensaios foi desenvolvida no Laboratório de Energia Solar Fotovoltaica do Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT) na Espanha onde foi utilizado um sistema fotovoltaico de 3 kWP e sete modelos de inversores de diferentes fabricantes. Os inversores ensaiados são monofásicos de potência até 5 kW e de diferentes topologias (transformador de alta freqüência, baixa freqüência e sem transformador). A influência da tensão CC de entrada no comportamento da eficiência CC/CA e do fator de potência foi analisada. Os resultados obtidos nos ensaios permitiram o desenvolvimento de modelos matemáticos que descrevem o comportamento elétrico e térmico de inversores. Os modelos matemáticos propostos foram inseridos em um programa de simulação computacional desenvolvido no Labsol da UFRGS, denominado FVConect. A evolução dos resultados da simulação comparada valida plenamente os modelos utilizados. A análise dos resultados do comportamento de inversores amplia o conhecimento sobre o funcionamento desses equipamentos e a sua interação dinâmica com os demais componentes de sistemas fotovoltaicos conectados à rede. / Grid-connected photovoltaic systems directly convert solar energy into electrical energy delivering to the distribution grid a clean and renewable energy. These systems are basically formed by an array of photovoltaic modules and inverters. The inverters are responsible for converting direct current to alternating current. This Thesis presents a study of electrical and thermal characteristics of inverters used in grid-connected photovoltaic systems from a theoretical and experimental analysis. The inverters tests were carried out in two stages: the first stage was performed at Solar Energy Laboratory at Federal University of Rio Grande do Sul where it was used a 4,8 KWP grid-connected photovoltaic system and ten inverters of different manufacturers. The proposed mathematical models were inserted into computer simulation software developed at UFRGS named FVConect. The evolution of the simulation results compared to the experimental results validates the proposed models. The analysis of the behavior of the inverters improves the understanding of the operating of such equipment and their dynamic interaction with other grid-connected photovoltaic system components.

Este trabalho apresenta abordagens para a avaliação do fenômeno da Degradação Induzida pelo Potencial (PID do inglês Potential Induced Degradation) em módulos e instalações fotovoltaicas de c-Si. Nos ensaios em laboratório, a IEC TS 62804-1:2015 foi aplicada e ações adicionais são sugeridas como forma de adaptação da especificação técnica para o acompanhamento da degradação durante o ensaio e para melhor indicar a propensão do equipamento a se recuperar das consequências da aparição de PID. Nos ensaios em campo, avaliou-se a solução convencional do mercado de reverter a degradação através de circuitos anti-PID, além de apresentar a aplicação de técnicas de detecção do fenômeno em sistemas operacionais. A abordagem teórica e os resultados práticos mostram que o procedimento de aferição de tensões individuais de operação é um método útil para detectar PID. Os estudos de caso apresentados indicam que esta metodologia é eficaz inclusive na detecção precoce do fenômeno para diferentes topologias de células fotovoltaicas de c-Si. / This work presents approaches to assess the Potential Induced Degradation (PID) on c-Si photovoltaic modules and installations. The IEC TS 62804-1:2015 was applied to the laboratory tests and some additional actions are suggested. The adaptation of the technical specification aims to monitor the degradation rates during the tests and also to consider the capacity of the photovoltaic modules to recover from the degradation. In the field detection methodologies are presented and anti-PID circuits were also tested. The theoretical approach reveals that individual voltage measurements are useful to detect PID even in its early stage, as can be seen on the case studies presented.

Os sistemas fotovoltaicos conectados à rede convertem diretamente a energia solar em energia elétrica entregando à rede elétrica de distribuição uma energia limpa e renovável. Esses sistemas são formados basicamente por um conjunto de módulos fotovoltaicos e inversores que são responsáveis por converterem energia elétrica em corrente contínua em energia elétrica em corrente alternada. Esta Tese apresenta um estudo de características elétricas e térmicas de inversores utilizados em sistemas conectados à rede a partir de uma análise teórica e experimental. Os ensaios de inversores foram realizados em duas etapas: a primeira etapa foi desenvolvida no Laboratório de Energia Solar (Labsol) da Universidade Federal do Rio Grande do Sul (UFRGS) onde foi utilizado um sistema fotovoltaico de 4,8 kWP e dez modelos de inversores de diferentes fabricantes. As características elétricas de inversores que foram medidas e analisadas são: eficiência de conversão de corrente contínua em corrente alternada, eficiência do seguidor do ponto de máxima potência, fator de potência e distorção harmônica na corrente e na tensão. Ensaios térmicos de inversores também foram realizados e os resultados apresentados e analisados. A segunda etapa dos ensaios foi desenvolvida no Laboratório de Energia Solar Fotovoltaica do Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT) na Espanha onde foi utilizado um sistema fotovoltaico de 3 kWP e sete modelos de inversores de diferentes fabricantes. Os inversores ensaiados são monofásicos de potência até 5 kW e de diferentes topologias (transformador de alta freqüência, baixa freqüência e sem transformador). A influência da tensão CC de entrada no comportamento da eficiência CC/CA e do fator de potência foi analisada. Os resultados obtidos nos ensaios permitiram o desenvolvimento de modelos matemáticos que descrevem o comportamento elétrico e térmico de inversores. Os modelos matemáticos propostos foram inseridos em um programa de simulação computacional desenvolvido no Labsol da UFRGS, denominado FVConect. A evolução dos resultados da simulação comparada valida plenamente os modelos utilizados. A análise dos resultados do comportamento de inversores amplia o conhecimento sobre o funcionamento desses equipamentos e a sua interação dinâmica com os demais componentes de sistemas fotovoltaicos conectados à rede. / Grid-connected photovoltaic systems directly convert solar energy into electrical energy delivering to the distribution grid a clean and renewable energy. These systems are basically formed by an array of photovoltaic modules and inverters. The inverters are responsible for converting direct current to alternating current. This Thesis presents a study of electrical and thermal characteristics of inverters used in grid-connected photovoltaic systems from a theoretical and experimental analysis. The inverters tests were carried out in two stages: the first stage was performed at Solar Energy Laboratory at Federal University of Rio Grande do Sul where it was used a 4,8 KWP grid-connected photovoltaic system and ten inverters of different manufacturers. The proposed mathematical models were inserted into computer simulation software developed at UFRGS named FVConect. The evolution of the simulation results compared to the experimental results validates the proposed models. The analysis of the behavior of the inverters improves the understanding of the operating of such equipment and their dynamic interaction with other grid-connected photovoltaic system components.

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / A necessidade de obter uma matriz energÃtica menos poluente e em harmonia com o meio ambiente à um tÃpico muito importante no sÃculo XXI. Este trabalho apresenta um conversor cc-ca de dois estÃgios para injetar a energia de um arranjo de painÃis fotovoltaicos à rede elÃtrica. O primeiro estÃgio à um conversor elevador, isolado, baseado na CÃlula de ComutaÃÃo de TrÃs Estados (CCTE), responsÃvel por elevar a tensÃo dos painÃis fotovoltaicos de 48 Vcc para 400 Vcc e de extrair a mÃxima potÃncia disponÃvel deles. O segundo estÃgio consiste em um conversor monofÃsico cc-ca, ponte completa, responsÃvel por injetar a energia na rede elÃtrica de baixa tensÃo (220 Vca, 60 Hz). SÃo apresentados estudos teÃricos e exemplos de projeto dos circuitos de potÃncia e controle para ambos os estÃgios e, com o objetivo de validar a anÃlise, sÃo apresentados resultados de simulaÃÃo computacional, complementados com resultados experimentais, correspondentes a um protÃtipo de laboratÃrio de 850 W. O rendimento global obtido experimentalmente à aproximadamente 86,5% enquanto que a distorÃÃo harmÃnica total da corrente entregue à rede elÃtrica obtida via simulaÃÃo computacional à 3,8% a plena carga. / In the 21st century, the need of a more clean and environment friendly power matrix has become a very important issue. Therefore this work presents a two stage cc-ac converter for connecting a photovoltaic array to the electrical grid. The 1st stage itâs an isolated boost converter, based in the Three Stage Switching Cell (TSSC), in charge of boosting the photovoltaic array voltage from 48 Vcc to 400 Vcc and to track its maximum power point. The 2nd stage is a single-phase cc-ac Full-Bridge converter responsible of injecting the photovoltaic power into the low voltage power grid (220 Vac, 60 Hz). Both, theoretical analysis and designs examples of power and control circuits are presented for the two stages and, in order to validate the analysis, simulation results complemented with experimental results from an 850 W laboratory prototype are presented. The overall efficiency obtained from the prototype was 86.5% while the total harmonic distortion of the current obtained via simulation was 3.8% at full load.

Submitted by Erika Demachki (erikademachki@gmail.com) on 2016-10-18T20:19:54Z No. of bitstreams: 2 Dissertação - Gabriel Mendonça de Paiva - 2016.pdf: 3565340 bytes, checksum: 6df5384c34ed001061350c147d523756 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Erika Demachki (erikademachki@gmail.com) on 2016-10-19T16:18:31Z (GMT) No. of bitstreams: 2 Dissertação - Gabriel Mendonça de Paiva - 2016.pdf: 3565340 bytes, checksum: 6df5384c34ed001061350c147d523756 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2016-10-19T16:18:31Z (GMT). No. of bitstreams: 2 Dissertação - Gabriel Mendonça de Paiva - 2016.pdf: 3565340 bytes, checksum: 6df5384c34ed001061350c147d523756 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2016-06-03 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / This study aimed to evaluate the design of a grid-connected photovoltaic (PV) system according to the positioning of the modules which compose the generator depending on tilt and azimuth angles in Goiânia, Goiás. In that purpose, a review of the literature was carried out concerning the main methods of inverter sizing ratio analysis applied to grid-connected PV systems. Starting from an hourly average climate measurement database from Goiania, an algorithm was developed to search for the ideal local inverter sizing ratio, considering the use of polycrystalline module technology. The parameters used in the analysis were provided by the manufacturers of the componentes used in the grid-connected PV system in installation at the Electrical, Mechanical and Computational Engineering School (EMC) from Federal University of Goias (UFG), which nominal power is 33.84 kWp. An inverter sizing ratio band of 0.54 to 0.77 was obtained for a -90° to +90° azimuth angle variation and 0° to 90° tilt angle variation. The potential of financial indicators improvement was verified and it was estimated a potential reduction in the levelized cost of energy above 10% comparing the inverter sizing ratio improved system to an unitary inverter sizing ratio system. / Este estudo tem como objetivo avaliar o dimensionamento de um sistema fotovoltaico conectado à rede (SFCR) de acordo com o posicionamento dos módulos que compõem o gerador quanto ao ângulo de inclinação e ao ângulo azimutal em Goiânia, Goiás. Para isso foi realizada uma revisão da literatura quanto às principais metodologias de análise do fator de dimensionamento do inversor (FDI) aplicado a SFCRs. A partir de uma base de dados em intervalos horários de medições climáticas de Goiânia desenvolveu-se um algoritmo para busca do FDI ideal para a localidade, considerando o uso de módulos de silício policristalino (p-Si). Os parâmetros utilizados na análise foram os parâmetros fornecidos pelos fabricantes dos componentes utilizados no SFCR em instalação da Escola de Engenharia Elétrica, Mecânica e de Computação (EMC) da Universidade Federal de Goiás (UFG), cuja potência nominal é de 33,84 kWp. Os métodos de análise do FDI foram comparados e foi considerado mais adequado neste estudo o método das perdas máximas anuais por limitação de potência no inversor. A faixa de FDI obtida para uma variação de -90° a +90° no ângulo azimutal e de 0° a 90° no ângulo de inclinação foi da ordem de 0,54 a 0,77. O potencial de aprimoramento de indicadores financeiros por meio do FDI foi verificado e foi estimada uma potencial redução acima de 10% do custo da energia produzida comparando o aperfeiçoamento do FDI com um FDI unitário.

The grid-connected photo-voltaic (PV) system is one of the most promising renewable energy solutions which offers many benefits to both the end user and the utility network and thus it has gained the popularity over the last few decades. However, due to the very nature of its invariability and weather dependencies, the large scale integration of this type of distributed generation has created challenges for the network operator while maintaining the quality of the power supply and also for reliable and safe operations of the grids. In this study, the behavioral impact of large scale PV system integration which are both steady and dynamic in nature was studied.  An aggregate PV model suited to study the impacts was built using MATLAB/Simulink.  The integration impacts of PV power to existing grids were studied with focus on the low voltage residential distribution grids of Mälarenergi Elnät AB (10/0.4 kV). The steady state impacts were related to voltage profile, network loss. It was found that the PV generation at the load end undisputedly improves the voltage profile of the grid especially for the load buses which are situated at farther end of the grid. Further, with regard to the overvoltage issue, which is generally a concern during the low load demand period it was concluded that, at a 50% PV penetration level, the voltage level for the load buses is within the limit of 103% as prescribed by the regulator excepting for few load buses. The voltage level for load buses which deviate from the regulatory requirement are located at distance of 1200 meter or further away from the substation. The dynamic impact studied were for voltage unbalancing in the grid, which was found to have greater impact at the load buses which is located farther compared to a bus located nearer to the substation. With respect to impact study related to introduction of harmonics to the grid due to PV system integration, it was found that amount of harmonic content which was measured as total harmonic distortion (THD) multiplies with integration of more number of PV system. For a 50 % penetration level of PV, the introduced harmonics into the representative network is very minimal. Also, it was observed from the simulation study that THD content are be less when the grid operates at low load condition with high solar irradiance compared to lower irradiance and high load condition.

Power distribution facilities all over the world have been committed towards making the grids smarter in order to reduce the risks of grid failures and provide an affordable, reliable, and sustainable supply of electricity to the end consumers. The smart grid concept involves incorporation of monitoring, analysis and control functions into the existing power distribution infrastructure. One of the foremost steps in realizing the smart grid concept is the integration of information and communication technologies with power system engineering. Various communication technologies are available, out of which Powerline Communication (PLC) has been found to be most suitable owing to its least intensiveness on additional infrastructure. Existing methods use PLC as a separate communication physical layer to establish com- munication between components in a micro/sub-micro grid. However, these methods poses the problems of a separate physical layer requirement to establish communication between inverters, attenuation of the information signal by the EMI filters present in various loads and equipments connected to the micro grid, requirement of signal repeaters at regular distance intervals and requirement of a separate server for monitoring and control. In order to simultaneously utilize the incorporation of front end inverters into the grid and achieve inter-inverter communication, a PLC method for the grid connected inverters based on a harmonic injection into the grid current is proposed in this thesis. The harmonic injection is accomplished by considering the grid current as a composite vector with components rotating at different speeds. The lower harmonic spectrum space can be chosen to avoid the attenuation problems associated with the EMI filters. In the proposed method, as the choice of the harmonic space is flexible, it is possible to even adopt a dynamically changing harmonic space to optimize THD. The advantage of the method is that it simultaneously achieves communication along with grid interfacing of DGs without any requirement of extra hardware. Also, since the principle of information exchange amongst inverters is the same as that of the power transfer, there is no added complexity involved in the inverter control system due to the proposed PLC method. The principle of the Composite Space Vector on which the proposed PLC method is based upon has been explained in detail along with the frame transformation equations. The control scheme to achieve the power transfer and the information exchange for the grid connected inverters is explained. The design procedure for various circuit elements and the control loop parameters has been explained. The thesis also discusses the various factors affecting the choice of the modulating signal and the speed of communication achievable in the proposed PLC method. For both the three phase and single phase systems, simulation results have been presented for the proposed PLC method under different grid conditions and different harmonics as the modulating signals. The simulations have been performed using the MATLAB SIMULINK SimPowerSystems toolbox. The simulation results have been experimentally verified through a laboratory prototype. The laboratory prototype consists of individual IGBT based inverters controlled through the Texas Instruments TMS320F2812 DSP based digital controller.

This thesis is concerned with the generation control in small isolated power systems consisting of inverter interfaced generation systems. First the components of an individual distributed generation system (DGS) as well as the corresponding control schemes for active and reactive power flow are discussed and implemented. Then the contribution of multiple DGS to meet the requirement of the loads in both gridconnected and island operations are discussed. Having evaluated the performance of each developed model such as voltage source inverter, PQ and PV controlled as well as reference DGS, the impact of voltage degradation on power load control in isolated systems is analyzed. Finally a new method for generation control in a small power system based on power sharing between multiple DGS with voltage degradation consideration as the last alternative for sustaining the system is proposed and implemented.-11D

Considering the long term target set by the Swedish government of having an energy system basedexclusively on renewable sources, the potential for different renewable sources need to beinvestigated. When analyzing the sources used for electricity production in Sweden today, solarPV represents a very small share. This relatively small share also mainly consists of grid-connecteddistributed PV systems, and to analyze the possibilities of making solar energy a larger share inthe electricity production in Sweden this study will focus on grid-connected centralized PV farms.The main purpose of the study is to identify the potential for grid-connected centralized PVsystems for large scale production in Sweden. This will include an identification of the mostimportant key factors influencing the profitability, an investment calculation to be aware of theprofitability, a prediction of the future development of the PV industry in Sweden and lastly themain challenges that the PV industry is facing.To conduct this study a collaboration with Vattenfall Vind AB has been made, where a case studybased on three specific locations has been implemented when analyzing both the profitability andthe key factors. These three cases are based on places where Vattenfall has existing wind farms orhas assigned for upcoming ones. These areas could be seen as a potential benefit since the companyalready has started to inspect the land area, and that wind and PV farms might be able to sharenecessities such as infrastructure.The results of the study mainly indicate that the PV industry most likely will continue develop andgrow, but the profitability of investing in grid-connected centralized PV farms does not lookpromising today or in the next coming years. This mainly due to low prices for electricity anduncertainties in the future development of the financial support policy. The location is also veryimportant for this type of installation. There are places in southern Sweden with enough insolation,but these areas can be seen as limited. To make solar energy a larger share of the electricityproduction in Sweden in a profitable way today, more investments should be made in gridconnecteddistributed PV systems rather than grid-connected centralized PV farms. PV farms forlarge scale production might though be more profitable in the future when the prices for modulesand inverters will decrease further and when the spot price increases.

The present thesis deals with fault impact mitigation in grid connected converters used for High Voltage Direct Current transmission. Certain critical fault cases require additional obstructing protection actions to ease the impact on the converter valves. DC sided faults drives high fault currents through the converters. Single phase to ground faults at the converter AC bus results in overvoltages across the converter valve arms. The phenomenon of these faults are described both for symmetric and asymmetric configurations. Different available solutions are explained and evaluated. Simulations in PSCAD/EMTDC show the impact of the protection measures. A three phase short circuit introduced on the tertiary winding of the transformer is an effective temporary measure against the destructive fault cases. It is shown in this report that a tertiary shortcircuit will greatly reduce the overvoltages after converter bus faults and redirect a large part of the fault currents after DC faults. With the lower voltage on the tertiary winding, it is a suitable connection point for short circuit devices.