Dissertations / Theses on the topic 'Grid connected photovoltaic power generation system'

Dissertation (DTech(Electrical Engineering))--Cape Peninsula University of Technology, 2012<br>The confluence of the limited resources of fossil fuels (e.g. coal, oil and natural gas), environmental degradations leading to climate change, security of supplies and fossil fuels high costs have demanded a tremendous efforts on humanity to seek for a sustainable and unlimited natural energy sources. Amongst these renewable energy sources stands out solar energy because of its ubiquitousness. Solar energy is converted to DC electricity by the photovoltaic effect. Photovoltaic (PV) power systems installed in commercial and industrial buildings are a good example of distributed power generation. Here the energy consumption and production match and thus electricity taken from the grid during daytime peak hours can be reduced. This is beneficial as the transmission losses in the grid are avoided and also transmission need is reduced. The cost effectiveness of a solar energy system has hindered its wide adoption and deployment in terms of the initial capital cost even though it has a zero energy cost and very minimal operating and maintenance costs. Different governments have instituted many financial incentives for fast adoption of PV systems for both residential and commercial applications. However, all these incentives are not sustainable in the longer term forecast. For PV system to attain grid parity requires more than unsustainable approach of many governments providing time limited subsidies. The technical solution to the problem is to reduce the overall system cost through technical innovations. One such method is the adoption of transformerless inverter technology as the grid interface system. Transformerless inverter topology provides galvanic isolation through innovative inverter topology and switching strategies that eliminates problems created by not employing the service of transformer.

Submitted by Maicon Juliano Schmidt (maicons) on 2015-07-13T18:32:37Z No. of bitstreams: 1 Miguel Francisco da Silveira.pdf: 1561110 bytes, checksum: dcb1486a17c6616e1fcf6803ce1272ec (MD5)<br>Made available in DSpace on 2015-07-13T18:32:37Z (GMT). No. of bitstreams: 1 Miguel Francisco da Silveira.pdf: 1561110 bytes, checksum: dcb1486a17c6616e1fcf6803ce1272ec (MD5) Previous issue date: 2013-01-31<br>Milton Valente<br>UNISINOS - Universidade do Vale do Rio dos Sinos<br>Muito tem se falado sobre o uso de fontes alternativas de energia e do uso de pequenas fontes em geração distribuída (GD), especialmente com a nova legislação brasileira que agora considera esta possibilidade. O aproveitamento da energia solar vem crescendo ao longo dos últimos anos, tanto através de seu uso como fonte térmica, quanto através da geração fotovoltaica, baseado no baixo impacto ambiental desta fonte de energia. Este trabalho tem por objetivo estudar o impacto da geração distribuída no sistema de distribuição de energia elétrica pelo uso de geradores fotovoltaicos conectados diretamente à rede de distribuição. O estudo é realizado em regime permanente, sob o ponto de vista elétrico, em um alimentador específico, considerando curvas típicas propostas para dias ensolarados e encobertos. Para esta análise foi utilizada uma base de dados de um ano, com dados de irradiância e de temperatura do ar ambiente coletados na cidade de Porto Alegre - RS entre Julho de 2004 e Junho de 2005. Esta base de dados serviu para estabelecer as curvas típicas de geração de um dia ensolarado e de um dia encoberto, através de uma metodologia desenvolvida. Com o uso destas curvas típicas foi definido o padrão de geração fotovoltaica em um dia ensolarado e em um dia encoberto. Após a definição deste padrão de geração foi possível analisar o impacto em um alimentador específico, localizado na cidade de Viamão - RS. A análise do impacto na rede considerou a influência que a geração distribuída ocasiona nos níveis de tensão nos diferentes nós ao longo do alimentador. Foi considerada uma penetração de 20% de GD, em dois diferentes horários para um dia ensolarado e para um dia encoberto. A potência gerada foi normalizada em relação à potência consumida nos diferentes pontos do alimentador. Os impactos observados na rede de distribuição não foram relevantes, entretanto a geração fotovoltaica contribuiu levemente para a melhora em alguns níveis de tensão que estavam na faixa crítica, em alguns cenários analisados.<br>Alternative sources of energy and distributed generation (DG) are current subjects, especially in Brazil where the regulations had just changed and now the possibility of DG and compensation of energy can be considered. The use of solar energy has been increased along the last years, thus as a heat source or as photovoltaic (PV) generation, based mainly on the low environmental impact of this energy source. This essay aims to study the impact of distributed generation in the electrical energy distribution system caused by the use of photovoltaic generators connected straight to the distribution grid. The study is done in steady state condition, in a specific feeder, considering typical curves proposed for sunny and cloudy days. A data base of irradiance and temperature of air ambient of one year had been used for this analysis. The data had been collected in the city of Porto Alegre – RS – Brazil, from July 2004 to June 2005. This data base was used to establish the generation typical curves of sunny and cloudy days through a methodology developed. The photovoltaic generation standards for sunny and cloud days had been defined by the use of these typical curves. With these standards were possible to analysis the impact in a specific feeder, located in the city of Viamão – RS – Brazil. The analysis of the impact in the grid considered the influence of distributed generation could cause on voltage levels at different bars along the feeder. It had been considered a penetration of DG of 20%, in two different hourly times for each day, sunny and cloudy typical curves. The power generated had been normalized related to the power consumed in different points of the feeder. The impact observed in the distribution grid is not relevant. However, the distribution generation did contribute to slightly raise some voltage levels that are already among the critical zone, in some of the sets analysed.

No Brasil, quando uma unidade consumidora (UC) sob regime de microgeração ou de minigeração distribuída tem parte ou a totalidade da sua demanda por potência ativa suprida pela planta geradora, mas sua demanda por potência reativa é atendida exclusivamente pela rede elétrica, verifica-se uma aparente deterioração do fator de potência dessa UC, sob a ótica da concessionária. Esse efeito decorre do fato de que o fator de potência, de acordo com a regulamentação vigente, é determinado apenas a partir das medições dos fluxos de potência ativa e reativa trocados entre a UC e a rede elétrica e não também entre a planta geradora e UC. Para consumidores do Grupo A (tensão de fornecimento igual ou superior a 2,3 kV) nessa situação, de acordo com o perfil da carga, pode haver cobrança por excedentes de reativos, constituindo-se assim uma barreira. Especificamente no caso de sistemas fotovoltaicos conectados à rede, existe a possibilidade de se utilizar os próprios inversores c.c.-c.a para suprir a demanda de reativos da UC e, dessa forma, minimizar o problema apresentado. Com o objetivo de se avaliar essa alternativa no contexto brasileiro, tendo-se em vista condições reais de operação e os limites normativos de injeção de potência reativa para inversores de sistemas fotovoltaicos, foi realizado um estudo de caso de uma planta fotovoltaica instalada no telhado do prédio da Administração do Instituto de Energia e Ambiente da Universidade de São Paulo. O estudo mostrou que a compensação realizada por meio do inversor selecionado evitou a cobrança de excedentes de reativos sem afetar de forma significativa a produtividade do sistema fotovoltaico. Do ponto de vista elétrico, verificou-se que a injeção de reativos pelo inversor não provocou variações significativas de tensão no ponto de acoplamento ou no alimentador e, ainda, se verificou considerável liberação de capacidade do sistema supridor da concessionária. Dessa forma, a análise dos resultados indica uma tendência a se considerar a compensação de reativos proporcionada pelo próprio inversor a opção mais viável para se lidar com os excedentes de reativos, comparativamente a métodos convencionais de compensação ou à situação em que nenhuma ação compensatória seja implementada.<br>In Brazil, when a consumer unit (CU) under a distributed microgeneration or minigeneration scheme has part or all of its demand for active power supplied by the generating plant, but its demand for reactive power is served exclusively by the grid, the power factor of this CU appears deteriorated, from the perspective of the utility. This effect is due to the fact the power factor, according to the current regulations, is determined only from measurements of the flows of active and reactive power exchanged between the UC and the grid and not also between the generating plant and UC. Users of group A (supply voltage equal to or greater than 2.3 kV) in this situation, according to the CU load profile, may be charged due the reactive power excess, thus constituting a barrier. Specifically in the case of grid-connected photovoltaic systems, there is the possibility of using the d.c.- a.c. inverters to suply the CU reactive power demand and, thus, minimizing the presented problem. In order to evaluate this alternative in the Brazilian context, keeping in view real operating conditions and regulatory limits for the reactive power injection for photovoltaic inverters, we conducted a case study with a photovoltaic plant installed on the roof of the University of São Paulo Institute for Energy and Environment administration building. The study showed that the compensation performed by the selected inverter prevented the reactive power excess charging without affecting significantly the photovoltaic system productivity. From an electrical point of view, it was found that the injection of reactive power by the inverter did not cause significant voltage variations at the coupling point or at the transformer and, additionally, there was a significant release in the utility suply system capacity. Thus, the analysis results indicates a tendency to consider the compensation provided by the inverter itself the most viable option for dealing with the surplus of reactive power compared to conventional compensation methods or to the situation in which no compensatory action is implemented.

A matriz energética mundial é composta por várias fontes primárias, dentre as quais os combustíveis fósseis, como o petróleo, prevalecem sobre as demais. No entanto, devido ao crescimento populacional e ao desenvolvimento tecnológico e industrial, haverá um conseqüente aumento na demanda de energia e devido à preocupação ambiental, será necessária a busca por outras fontes energéticas. Dentre essas, destaca-se a energia solar fotovoltaica, por possibilitar a geração de forma limpa e descentralizada. O Brasil tem a vantagem de estar localizado na zona inter-tropical, registrando altos índices de irradiação solar durante todo o ano, em comparação com outros países do mundo que já fazem uso desta tecnologia. Neste trabalho, foi estudada a inserção de sistemas fotovoltaicos conectados à rede elétrica pública e integrados em edificações residenciais urbanas. Para tanto, foram dimensionados sistemas para três residências situadas em diferentes regiões brasileiras, e que possuem as mesmas características construtivas e o mesmo consumo médio mensal de energia elétrica. Uma das premissas consideradas foi a autossuficiência energética das edificações apenas utilizando o recurso solar como fonte de geração. As cidades escolhidas para a análise foram Porto União/SC, São Carlos/SP e Petrolina/PE por possuírem diferenças significativas nos níveis de irradiação solar, representando desta forma os extremos encontrados no território brasileiro. A partir do dimensionamento foram estimadas a geração de energia elétrica anual para cada localidade e as curvas de geração foram confrontadas com as curvas de demanda diária média das regiões Sul, Sudeste e Nordeste, representando respectivamente, as três cidades escolhidas. Foram estimados os custos de instalação dos três sistemas, sendo feita ainda uma análise econômica simplificada para a verificação do impacto gerado pela inserção da tecnologia solar fotovoltaica como fonte alternativa na geração de energia elétrica em edificações residenciais urbanas. Para a avaliação econômica foi considerada a adoção do Sistema de Compensação Energética e um Período de Retorno Simples, que é a relação obtida entre o investimento feito inicialmente para a instalação de um sistema fotovoltaico e a economia anual proporcionada por essa instalação. Considerando um período de vida útil de um sistema fotovoltaico como sendo estimado em 25 anos, os resultados demonstraram que todos os sistemas seriam pagos antes desse período. A partir dos dimensionamentos, foi possível concluir ainda que a área requerida para a instalação de sistemas fotovoltaicos em residências é muito pequena e possui elevado potencial de aproveitamento, viabilizando desse modo a sua inserção no ambiente urbano.<br>The world\'s energy matrix is made up of several primary sources among which fossil fuels, mainly oil, prevail. Nevertheless, given population growth coupled with technological and industrial development, there will consequently be an increase in energy demands and, due to environmental concerns, looking for other energy sources is necessary. Among those, photovoltaic solar energy stands out for providing clean, decentralized energy generation. Brazil has the advantage of being located within the intertropical zone, registering higher levels of solar irradiation throughout the year compared to other countries that already use such technology. In this thesis, we studied the insertion of photovoltaic systems into the public grid and integrated to urban residential buildings. For such, we sized systems for three home environments situated in different Brazilian regions with similar building characteristics and same average monthly consumption. One of the premises considered was the buildings energy self-sufficiency based on solar resources alone. The cities chosen for the experiment were Porto União/SC, São Carlos/SP and Petrolina/PE given their significantly different exposure to solar irradiation, thus representing the extremes found in the Brazilian territory. From the initial sizing up the annual electricity demand for each location was estimated and generation curves were confronted with the daily demand curves from the South, Southeast and Northeast regions representing, respectively, the three chosen cities. Implementation costs were estimated for the three systems along with a simplified economic analysis in order to verify the impact caused by the insertion of photovoltaic solar energy as an alternative source of power generation in urban residential buildings. For the economic evaluation was considered the use of the Compensation System Energy and a Simple Payback Period, which is the ratio between the initial investment for the installation of a photovoltaic system and the annual savings provided by this facility. Considering a life cycle of a photovoltaic system as estimated at 25 years, the results showed that all systems would be paid before that period. From the sizing was still possible to conclude that the area required for the installation of photovoltaic systems in residences is very small and has a high potential for use, thereby enabling their integration into the urban environment

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior<br>Este trabalho apresenta o estudo, desenvolvimento e aplicação de novas técnicas de controle aos sistemas de geração de energia fotovoltaica, conectados à rede elétrica monofásica, visando a melhoria da eficiência destes sistemas em relação aos métodos de controle tipicamente utilizados. O trabalho é dividido em duas partes principais, as quais estão relacionadas ao rastreamento do ponto de máxima potência (Maximum Power Point Tracking – MPPT) e, depois, ao controlador interno dos conversores boost-quadrático – lado dos painéis fotovoltaicos – assim como aos controladores do inversor de tensão, no lado da rede elétrica monofásica. A primeira parte do trabalho consiste no desenvolvimento de um algoritmo de meta heurística para o MPPT, o qual é baseado no método do recozimento simulado (Simulated Annealing - SA) e tem como objetivo a determinação do ponto de máximo global, buscando soluções fora de uma vizinhança próxima, de modo a evitar o atracamento em máximos locais da curva de potência de saída do arranjo de painéis fotovoltaicos, melhorando, assim, o aproveitamento da energia em situações de sombreamento parcial. A segunda parte do trabalho apresenta o projeto de controladores baseados no modelo interno (Internal Model Control – IMC) com 1 grau de liberdade (1 Degree of Freedom – 1 DOF) aplicados, primeiramente, ao conversor CC-CC Boost Quadrático, utilizado para o MPPT, e, posteriormente, a um inversor de tensão com filtro LCL, conectado à rede elétrica monofásica, operando no modo de injeção de corrente. É apresentada a modelagem matemática de ambos os conversores e analisada a compensação da realimentação interna ao sistema do inversor de tensão, correspondente ao desacoplamento da tensão da rede, através da estratégia de alimentação à frente (Feedforward). Visando-se uma base de comparação, para a análise de desempenho do conversor IMC – 1DOF, também é aplicado ao sistema de injeção de corrente, o controlador Proporcional-Ressonante (P+Res). São apresentados resultados de simulação computacional e experimentais de ambos os 8 controladores, os quais permitem verificar o desempenho do sistema em situação de rede fraca e carga local não-linear.<br>This paper presents the study, development and application of new control techniques for photovoltaic power generation systems, connected to single-phase power grid in order to improve the efficiency of these systems in relation to control methods typically used. The work is divided into two main parts, which are related to tracking the maximum power point (Maximum Power Point Tracking - MPPT) and then the internal controller of boost quadratic converters - side of the photovoltaic panels - as well as the controllers the voltage inverter, the side of the single-phase mains. The first part of the work is the development of a heuristic goal algorithm for MPPT, which is based on the method of simulated annealing (Simulated Annealing - SA) and aims at determining the overall maximum point, seeking out solutions in a close vicinity, so as to prevent the docking local maxima in the curve of power output of the photovoltaic array, thereby improving the utilization of energy in partial shading situations. The second part presents the design of controllers based on internal model (Internal Model Control - IMC) with 1 degree of freedom (1 Degree of Freedom - 1 DOF) applied, first, the DC-DC Boost Quadratic converter, used for MPPT, and thereafter, a voltage inverter with LCL filter connected to the single phase power supply operating in current injection mode. A mathematical modeling of both converters and analyzed the compensation of internal feedback to the voltage inverter system corresponding to the disconnection of the mains voltage through the power strategy a head (feedforward). A basis of comparison for the performance analysis of IMC-1DOF converter is aiming at, is also applied to the current injection system, Proportional-Resonant Controller (P + Res). They are presented computer simulation and experimental results of both controllers, which allow you to check the system performance in low and non-linear local load network situation.<br>Tese (Doutorado)

In recent years there has been a growing interest in moving away from large centralized power generation toward distributed energy resources. Solar energy generation presents several benefits for use as a distributed energy resource, especially as a peaking power source. One drawback of solar energy sources is the need for energy storage for the system to be utilized for a significant percentage of the day. One way of avoiding adding energy storage to a solar generation system while still maintaining high system utilization is to design the power conversion subsystem to also provide harmonic and reactive compensation. When the sun is unavailable for generation, the system hardware can still be utilized to correct for harmonic and reactive currents on the distribution system. This system's dual-purpose operation solves both the power generation need, and helps to improve the growing problem of harmonic and reactive pollution of the distribution system. A control method is proposed for a system that provides approximately 1 kW of solar generation as well as up to 10 kVA of harmonic and reactive compensation simultaneously. The current control for the active was implemented with the synchronous reference frame method. The system and controller was designed and simulated. The harmonic and reactive compensation part of the system was built and tested experimentally. Due to the delay inherent in the control system from the sensors, calculation time, and power stage dynamics, the system was unable to correct for higher order harmonics. To allow the system to correct for all of the harmonics of concern, a hybrid passive - active approach was investigated by placing a set of inductors in series with the AC side of the load. A procedure was developed for properly sizing the inductors based on the harmonic residuals with the compensator in operation.<br>Master of Science

Made available in DSpace on 2016-12-12T20:27:38Z (GMT). No. of bitstreams: 1 Camila Bianka Silva Bastos.pdf: 1963598 bytes, checksum: bee88eacc3f6e3c327425297316a691d (MD5) Previous issue date: 2015-02-27<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior<br>This dissertation presents a study of the operation of two different three-phase grid-connected test-grids with the connection of a 1MWp photovoltaic system. Two analysis methods are used to evaluate the impacts of this photovoltaic systeM, these methods being conventional static analysis and the analysis known as Quasi-Static Time-Series Analysis. Despite the fact that all grids have unique characteristics, it is important to use test-grids, which simulate the real grid characteristics, to analyze the kinds of problems that can occur and then look for alternatives, if necessary. The impacts evaluated are related to the system losses, minimized with the allocation study of the generation on the grid, voltage profile and tap position curve, when automatic load tap changers are used. It was verified that the photovoltaic system interconnection point is the most influenced one after its connection to the grid. The Quasi-Static Time-Series Analysis allow the correct evaluation of the load-generation interaction, running the time series power flow through estimated data for the load and irradiance curves during 168 hours. The conventional static analysis only considers critical operation conditions, like minimum and maximum load, and no generation or maximum generation, and does not evaluate different case scenarios that occur in reality. The photovoltaic systems can bring many advantages to the electric systems, like the improvement on the final consumer voltage profile, line losses reduction, and also environmental impacts reduction. However, with the increase of distributed photovoltaic generation on the electrical grid, it s necessary to be aware of the impacts that this may cause by performing interconnection studies.<br>Esta dissertação apresenta um estudo da operação de uma rede teste trifásica de média tensão com a interligação de um sistema fotovoltaico de 1,0 MWp. Dois métodos de análise são utilizados para avaliar os impactos deste sistema fotovoltaico, sendo estes métodos as análises estáticas convencionais eas análises conhecidas como Quasi-Static Time-Series Analysis. Apesar de cada rede elétrica apresentar características únicas, é importante a utilização de sistemas testes, que simulam as características de sistemas reais, para analisar que tipos problemas podem surgir e então buscar alternativas, se necessário. Os impactos avaliados se referem às perdas no sistema, minimizadas com a correta alocação da geração, perfil de tensão e curva de posição do tap, no caso de transformador com comutação automática de tap. Contata-se que o ponto de conexão do sistema fotovoltaico é o mais influenciado pela sua conexão à rede. As análises QSTS possibilitam avaliar corretamente a iteração entre carga e geração, efetuando o fluxo de potência consecutivo através de dados estimados para as curvas de carga e de irradiância solar ao longo de 168 horas. Já as análises convencionais consideram apenas condições críticas de operação, como por exemplo, carga leve ou nominal e geração nula ou máxima, não avaliando então diferentes cenários de operação que ocorrem na prática. Os sistemas fotovoltaicos podem trazer muitos benefícios aos sistemas elétricos, como melhoria do perfil de tensão de atendimento ao consumidor, redução de perdas nas linhas, além da redução nos impactos ambientais. Entretanto, com o aumento de geração fotovoltaica distribuída na rede, é necessário estar atento aos impactos que isto pode causar através de estudos de interconexão.

The increasing penetration of distributed energy resources, in particular Photovoltaic (PV) production units, and the ever-growing use of power electronics-based equipment has led to specific concern about Power Quality (PQ) in the Low-Voltage (LV) grid. These include high- and low-order current harmonics as well as voltage distortion at the point of common coupling. Solutions to overcome these issues, meeting international grid codes, are being proposed in the context of smart energy management schemes.This work proposes a novel three-phase topology for a PV system with enhanced PQ mitigation functionality, tackling the corresponding control challenges.First, a single-stage current-source inverter PV system with active filtering capability is preferred to the more common two-stage voltage-source inverter topology with additional voltage-step-up converter. The system also guarantees a nearly unitary displacement power factor in the connection to the grid and allows for Maximum Power Point Tracking (MPPT) with direct control of the PV array power. The grid-synchronised dq-axis grid current references are generated for the mitigation of nonlinear load low-order current harmonics, without the need for additional measurements. Active damping is used to minimise grid-side filter losses and reduce high-order harmonics resulting from the converter switching.Results on a 500W laboratory prototype confirm that active damping reduces the switching harmonics in the grid currents and active filtering properly mitigates the low-order current harmonics. The MPPT algorithm works effectively for various irradiance variations. Second, a PV system with a novel Indirect Matrix Converter (IMC)-based unified power quality conditioner topology is developed for enhanced current and voltage compensation capability, with compactness and reliability advantages. PQ issues such as current harmonics, and voltage sags, swells, undervoltage and overvoltage are mitigated by the shunt and series converters, respectively.The more common Space Vector Modulation (SVM) method used in IMCs is developed for this specific topology. In particular, a new shunt converter modulation method is proposed to additionally control the PV array current with zero switching vectors, resulting in a specific switching sequence.A direct sliding mode control method is also studied separately for the shunt and series converters, so that the zero-vector modulation method of the shunt converter can be used, with no sensitive synchronisation of the switching signals; this contrasts with the SVM method. A new dc link voltage modulation method with 12 voltage zones, instead of 6, is proposed to help overcome the limitation in the choice of shunt converter switching vectors due to the positive dc link voltage constraint.Results are obtained for the direct method on a 1 kW laboratory prototype with optimised IMC dc link connection and alternative shunt converter switching transitions to guarantee a positive dc link voltage. Current and voltage compensation capabilities are confirmed by tests in various operating conditions.<br>Doctorat en Sciences de l'ingénieur et technologie<br>info:eu-repo/semantics/nonPublished

Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2015.<br>From the electric power generation perspective, the last three decades have been characterized by sustained growth in the amount of Distributed Power Generation (DPG) systems integrated into the electric grid. This trend is anticipated to continue, especially in light of the widespread acceptance of the many benefits envisaged in the increase of renewable-based power generation. The potential for grid-integrated DPG systems to significantly contribute to electric power supply reliability has consistently attracted extensive research in recent times, although concerns continue to be raised over their adverse impact on the normal grid operation at high penetration levels. These concerns largely stem from the limited controllability of most DPG systems, which tend to exhibit large output impedance variation, and non-deterministic power output characteristics. There has therefore also been a growing need to develop effective control strategies that can enhance the overall impact of the DPG systems on the grid operation, thus improving their synergistic properties, and probably also enabling an even higher penetration level into the utility grid. In line with this identified need, this thesis discusses the modeling and controller design for an inverter-based DPG system with the capability to effectively operate both in grid-connected and autonomous (i.e. independent of the utility grid) operational modes. The dual-mode operation of the DPG is made possible by incorporating into the inverter interface control scheme the means to ensure seamless transition of the DPG between the grid-connected and autonomous modes of operation. The intention is to have a grid-integrated inverter-based DPG system whose operation approximates that of an online Uninterruptible Power Supply (UPS) system, in that it is able to sustain power supply to the local load in the absence of the grid supply, which would be desirable for critical loads, for which the level of power supply reliability guaranteed by the grid often falls short of the requirements. The work developed in this thesis considers three of the aspects associated with grid-integrated DPG systems that are equipped with autonomous-mode operation capability.

Aujourd'hui, les systèmes photovoltaïques connectés au réseau sont de plus en plus utilisés parmi les systèmes à énergies renouvelables. L’élément clé du système de conversion de puissance est le convertisseur statique connecté au réseau. Pour les applications de faible puissance, le convertisseur monophasé est le meilleur compromis. Les structures de conversion mono-étage permettent d’avoir un rendement plus élevé ainsi qu'un coût et une taille réduits. Cependant, dans des conditions de faible irradiation la tension PV chute, ce qui entraîne l'arrêt de l'onduleur et la perte totale de puissance injectée. Par conséquent, les systèmes à un étage de conversion souffrent d'une plage de fonctionnement réduite. Dans ce travail, nous proposons des solutions pour améliorer le rendement et la fiabilité des systèmes mono-étage connectés au réseau. Pour cela, dans la première partie, un contrôleur basé sur le mode glissant terminal rapide est combiné à un contrôle direct de la puissance. Il est associé à un algorithme de suivi du point de puissance maximale. Les simulations et les résultats expérimentaux sur un banc d'essai de 1kW montrent l'efficacité de la proposition en termes de performance dynamique, de faible distorsion harmonique totale et de robustesse aux variations d'irradiance. Les systèmes mono-étage sont également confrontés à une ondulation de puissance sur le bus continu à la fréquence double de celle du réseau. Ces ondulations de puissance sont néfastes à la durée de vie des panneaux solaires. Ainsi, la deuxième partie de ce travail propose de développer un dispositif qui simultanément réduit les ondulations de puissance et compense la chute de tension. Le dispositif est constitué de deux convertisseurs statiques : un flyback à faible puissance et un pont complet (H-bridge). Le compensateur hybride augmente la plage de fonctionnement de l'onduleur, empêchant son arrêt. Il contribue aussi à augmenter la fiabilité du système. Un banc expérimental de 1kW a été dimensionné et réalisé. Il a permis d’évaluer le dispositif sur plusieurs points de fonctionnement. Les résultats en régime permanent montrent que le compensateur hybride peut simultanément réaliser une atténuation de 85% des ondulations de puissance et une compensation de 20% de la chute de tension. Le dispositif a également de bonnes performances en régime transitoire. Dans la troisième partie de ce travail, la surveillance des modules PV est abordée afin d'augmenter la fiabilité. La méthode proposée est basée sur la spectroscopie d'impédance. Elle ne nécessite pas d’équipement supplémentaire car elle utilise le circuit qui permet d’atténuer les ondulations de puissance. De plus elle ne nécessite pas d'interrompre la production d'électricité. Les résultats de simulation, à l'aide de MATLAB-Simulink®, montrent une réduction de plus de 80% de l'amplitude des ondulations de la tension aux bornes des modules PV. Les résultats montrent que la spectroscopie d'impédance permet d’estimer les paramètres de l'impédance du module PV avec une erreur relative inférieure à 5%. L’évolution de ces paramètres en cours de fonctionnement devrait permettre de surveiller l’état de santé du panneau<br>Today, grid-connected photovoltaic systems are becoming an increasingly important part of renewable energy. The power conversion system's heart is the grid-connected interface converter based on power electronics. The single-phase inverter is the best compromise for low power applications as an interface for power conversion. Single-stage systems offer higher efficiency and lower cost and size. However, the PV voltage drops under low irradiance conditions, leading to inverter shut down and the total injected power loss.As a consequence, single-stage systems suffer from a low operating range. This work addresses the critical issues of the single-stage single-phase grid-connected PV system, including reliability and efficiency. A fast terminal sliding mode combined with direct power control is proposed in the first part. It is associated with a maximum power point tracking algorithm with power output. Simulations and experimental results on a 1kW test bench show the proposal's effectiveness in terms of dynamic performance, low total harmonic distortion and robustness to irradiance variations. Single-phase power systems also face pulsating power at twice the mains frequency on the DC bus. This pulsating power should not be transferred to the PV side as it reduces the efficiency of the solar panel. Thus, the second part of this work proposes a dual-function decoupling circuit: it mitigates pulsating power and compensates for the voltage drop. Thanks to the following additional power converters, these objectives are fulfilled: a low power flyback and an H-bridge. The hybrid compensator increases the inverter's operating range, prevents its shutdown, and increases the system reliability. A 1kW experimental bench has been designed to evaluate the proposal for several operating points. The steady-state results show that the hybrid compensator can simultaneously achieve 85% compensation of the pulsating power and 20% compensation of the voltage drop. The circuit also shows good transient responses. In the third part of this work, monitoring and fault diagnosis of PV modules are addressed to increase system reliability, efficiency, and safety. The proposed fault diagnosis method is based on online PV impedance spectroscopy without additional equipment. It does not require interrupting the power production and uses the pulsating power decoupling circuit as an impedance spectroscopy tool. The simulation results, using MATLAB-Simulink®, show a reduction of more than 80% ripples amplitude of the PV modules terminal voltage. The results also show that impedance spectroscopy can estimate the PV module impedance parameters with a lower than 5% relative error. The evolution of these parameters during operation should make it possible to monitor the health of the panel

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico<br>This work proposes study and implementation of a DC/DC Z-source converter operating in continuous conduction mode (CCM); It is applied to a photovoltaic system connected to a DC microgrid; aiming to inject the electricity supplied from PV array; To this end; the PV array is connected to the input of Z-source converter; which rises from 167V to 400V and injects the output current at the DC bus; using maximum power point tracking techniques (MPPT); The prototype implemented in the laboratory was developed for 1;38 kW output power; with the possibility to be fed either by a DC current source or DC voltage source; which does not happen with traditional converters (Buck; Boost; etc); The average efficiency achieved yield of 94%; As for the electric power processing from renewable sources; two heuristic methods were tested: Perturbe and Observe (P&O) and Conductance Incremental (IC); The average efficiency of the prototype; using the P&O technique in tracking maximum power was 79;9%; while using the second technique (IC) the average efficiency was a 82;5% ;<br>O presente trabalho propÃe o estudo e a implementaÃÃo de um conversor CC/CC Z-source; operando em modo de conduÃÃo contÃnuo (MCC); O mesmo à aplicado em um sistema fotovoltaico interligado a uma microrede CC; objetivando injetar a energia elÃtrica fornecida a partir de arranjo fotovoltaico;Para tal; o arranjo fotovoltaico à conectado na entrada do conversor Z-source; que a eleva de 167V para 400V e injeta a corrente de saÃda no barramento CC de 400V; utilizando tÃcnicas de rastreamento do ponto de mÃxima potÃncia (MPPT); O protÃtipo implementado em laboratÃrio foi desenvolvido para uma potÃncia nominal de saÃda de 1;38 kW com possibilidade de ser alimentado tanto por uma fonte CC de corrente ou uma fonte CC de tensÃo; diferenciando-se dos conversores tradicionais (Buck; Boost; etc); O mesmo alcanÃou um rendimento mÃdio de 94%; Quanto ao processamento de energia elÃtrica a partir de fontes renovÃveis; foram testados dois mÃtodos heurÃsticos: Pertube e Observe (P&O) e CondutÃncia Incremental (IC); A eficiÃncia mÃdia do protÃtipo usando a tÃcnica P&O no rastreamento da mÃxima potÃncia foi de 79;9%; enquanto usando a segunda tÃcnica alcanÃou-se uma eficiÃncia de 82;5% ;

The needs to the sustainable development of electricity, energy efficiency improvement, and environment pollution reduction have favored the development of distributed generation (DG). But the problems come with increasing DG penetration in distribution networks. This thesis presents the Solar Energy Grid Integration System (SEGIS) Stage III project done by Portland General Electric (PGE), Advanced Energy, Sandia National Lab on a PGE selected distribution feeder. The feeder has six monitored commercial solar PV systems connected. The total power output from the PV systems has the potential to reach 30% of the feeder load. The author analyzes the performance of the solar feeder on both generation and voltage effects. As a project report, it introduced a new islanding detection done by other team members to give an islanding solution of future high penetration distribution networks. At last, the author describes micro-grid and grid support concepts in a SEGIS concept paper with some examples.

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.

The global market for photovoltaics (PV) has increased rapidly: during 2014, 44 times more was installed than in 2004, partly due to a price reduction of 60-70% during the same time period. Economic support schemes that were needed to make PV competitive on the electricity market have gradually decreased and self-consumption of PV electricity is becoming more interesting internationally from an economic perspective. This licentiate thesis investigates self-consumption of residential PV electricity and how more PV power can be allowed in and injected into a distribution grid. A model was developed for PV panels in various orientations and showed a better relative load matching with east-west-oriented compared to south-oriented PV panels. However, the yearly electricity production for the east-west-system decreased, which resulted in less self-consumed electricity. Alternatives for self-consumption of PV electricity and reduced feed-in power in a community of detached houses were investigated. The self-consumption increased more with shared batteries than with individual batteries with identical total storage capacity. A 50% reduction in feed-in power leads to losses below 10% due to PV power curtailment. Methodologies for overvoltage prevention in a distribution grid with a high share of PV power production were developed. Simulations with a case with 42% of the yearly electricity demand from PV showed promising results for preventing overvoltage using centralized battery storage and PV power curtailment. These results show potential for increasing the self-consumption of residential PV electricity with storage and to reduce stress on a distribution grid with storage and power curtailment. Increased self-consumption with storage is however not profitable in Sweden today, and 42% of the electricity from PV is far more than the actual contribution of 0.06% to the total electricity production in Sweden in 2014.

The United Nations (UN) project "Sustainable energy for all" sets three ambitious objectives to favor a sustainable development and to limit climate change: - Universal access to modern energy services. Electricity is currently not available for 1.3 billion people and the global energy demand is expected to grow of about 35% within 2040, due to the increasing world population and the expanding economies - Double the global rate of improvement in energy efficiency - Double the share of renewable energy sources (RESs) in the global energy mix In addition, according to the climate scenario assessed in the fifth assessment report (AR5) of the International Panel on Climate Change (IPCC), the prevention of undesirable climate effects requires a 40-70% reduction of greenhouse gas (GHG) emissions, compared with 2010 levels, by mid-century, and to near-zero by the end of this century (IPCC, 2014). The achievement of such objectives requires and encourages the spread of RESs in the global energy mix, gradually replacing depleting and polluting energy sources based on fossil fuels, which still have the main incidence on the energy sector. RESs already play a major role in several countries, due to the technological development and the increasing market competitiveness, and the world renewable power capacity reached 22.1% in 2013, showing an increasing trend in 2014 (REN, 2014). However, supporting policies, robust investments from the private sector and efforts from the scientific community are still crucial to demonstrate the technical and economic sustainability and effectiveness of RESs, helping their large-scale diffusion. Starting from such a background, this Ph.D dissertation focuses on the study, design and development of methods and tools for the optimization and enhancement of renewable energy technologies and their effective integration with energy storage solutions and traditional energy sources powered by fossil fuels (hybrid energy systems). The analysis of the major literature and the different scenarios and perspectives of RESs in the national and international contexts have shown that their economic sustainability, and then their diffusion, is closely connected to a number of technical, economic/financial and geographical parameters. Such parameters are the input of the analytic models developed for the techno-economic design of photovoltaic (PV) plants and small wind turbines (SWTs) and applied to the economic feasibility study, through multi-scenario analysis, of such systems in some of the main European Union (EU) Countries. Among the obtained results, the self-consumption of the produced energy plays a crucial role in the economic viability of SWTs and PV plants and, particularly, after the partial or total cut of incentives and uncertainties related to supporting policies within the EU context. The study of the energy demand profile of a specific user and the adoption of battery energy storage (BES) systems have been identified as effective strategies to increase the energy self-consumption contribution. Such aspects have led to the development of an analytic model for the techno-economic design of a grid connected hybrid energy system (HES), integrating a PV plant and a BES system (grid connected PV-BES HES). The economic profitability of the grid connected PV-BES HES, evaluated for a real case study, is comparable with PV plants without storage in case of a significant gap between the cost of energy purchased from the grid and the price of energy sold to the grid, but high BES system costs due to the initial investment and the maintenance activities and the eventual presence of incentives for the energy sold to the grid can make the investment not particularly attractive. Thus, the focus has shifted to the techno-economic analysis of off-grid HES to meet the energy demand of users in remote areas. In this context, BES systems have a significant role in the operation and management of the system, in addition to the storage of exceeding energy produced by the intermittent and variable RESs. The analysis has also been strengthened by an industrial application with the aim to configure, test and install two off-grid HESs to meet the energy demand of a remote village and a telecommunication system. In parallel, two experimental activities in the context of solar concentrating technology, a promising and not fully developed technology, have been carried out. The former activity deals with the design, development and field test of a Fresnel lens pilot-scale solar concentrating prototype for the PV energy distributed generation, through multi-junction solar cells, and the parallel low temperature heat recovery (micro-cogeneration CPV/T system). The latter activity deals with the development of a low cost thermal energy (TES) storage prototype for concentrating solar power (CSP) plants. TES systems show a great potential in the CSP plants profitability since they can overcome the intermittent nature of sunlight and increase the capacity factor of the solar thermal power plant. Concluding, the present Ph.D dissertation describes effective methods and tools for the optimization and enhancement of RESs. The obtained results, showing their critical issues and potential, aim to contribute to their diffusion and favor a sustainable development<br>Il progetto delle Nazioni Unite "Sustainable energy for all" ha fissato tre obiettivi ambiziosi per favorire uno sviluppo sostenibile e limitare l'impatto del cambiamento climatico: - Accesso universale a moderni servizi elettrici. Tali servizi sono attualmente indisponibili per circa 1.3 miliardi di persone ed è previsto un aumento del 40% della domanda globale di energia elettrica entro il 2040, a causa dell'incremento della popolazione mondiale e delle economie in crescita nei paesi in via di sviluppo - Raddoppio del tasso globale di miglioramento dell'efficienza energetica - Raddoppio del contributo di fonti di tipo rinnovabile nel mix energetico globale Inoltre, lo scenario climatico proposto nel "fifth assessment report (AR5)" redatto da "International Panel on Climate Change (IPCC)" stabilisce la necessità di ridurre l'emissione di gas ad effetto serra del 40-70%, rispetto ai valori registrati nel 2010, entro il 2050 ed eliminarli in modo quasi definitivo entro la fine del secolo con lo scopo di evitare effetti climatici indesiderati. Il raggiungimento di tali obiettivi richiede e incoraggia la diffusione di fonti energetiche rinnovabili (FER) all'interno del mix energetico globale, rimpiazzando gradualmente le fonti di energia convenzionali basate su combustibili fossili, inquinanti e in via di esaurimento, che hanno ancora l'incidenza principale nel settore energetico. A seguito nel loro sviluppo tecnologico e la crescente competitività nel mercato, le FER rivestono già un ruolo fondamentale nel mix energetico di numerose Nazioni ricoprendo il 22.1% del fabbisogno globale di energia nel 2013 e mostrando un andamento in rialzo nel 2014 (REN, 2014). Tuttavia, sono ancora cruciali politiche di supporto, ingenti investimenti privati e contributi della comunità scientifica per dimostrare l'efficacia e la sostenibilità tecnica ed economica delle FER e favorire, quindi, una loro diffusione in larga scala. In questo contesto, la seguente tesi di dottorato è rivolta allo studio, progettazione e sviluppo di metodi e strumenti per l'ottimizzazione e la valorizzazione di tecnologie energetiche rinnovabili e la loro integrazione efficace con fonti di produzione di energia convenzionali alimentate da combustibili fossili e sistemi di accumulo di energia (Sistemi energetici di tipo ibrido). I contributi scientifici disponibili in letteratura e l'analisi dei diversi scenari e delle prospettive delle FER nei vari contesti nazionali ed internazionali hanno dimostrato che la loro sostenibilità economica, e quindi la loro diffusione, è strettamente legata ad una serie di parametri tecnici, economico / finanziari e geografici. Tali parametri sono stati impiegati come input in due modelli analitici sviluppati per la progettazione tecnico-economica di impianti fotovoltaici (FV) e micro turbine eoliche e applicati per lo studio della loro fattibilità economica, attraverso analisi multi-scenario, in alcuni dei maggiori Paesi Europei. I risultati ottenuti hanno mostrato come l'autoconsumo dell'energia prodotta rivesta un ruolo fondamentale nella redditività economica dei citati impianti ed, in particolare, a seguito del taglio parziale o totale dei sistemi di incentivazione e l'incertezza attorno alle politiche di supporto all'interno del panorama Europeo. Lo studio specifico del profilo di domanda elettrica delle utenze e l'impiego di sistemi di accumulo di energia sono stati identificati come strategie efficaci al fine di incrementare la quota di autoconsumo. Tali considerazioni hanno portato allo sviluppo di un modello analitico utile alla progettazione tecnico-economica un sistema energetico ibrido connesso alla rete Nazionale integrante un impianto FV e un sistema di accumulo a batterie. La redditività del sistema, valutata su un caso reale, risulta comparabile a un impianto fotovoltaico privo di batterie in caso di un gap significativo tra il costo dell'energia elettrica acquistata dalla rete e il prezzo di vendita dell'energia elettrica ceduta in rete. Tuttavia, gli elevati costi dovuti all'acquisto iniziale e alle attività di manutenzione, e l'eventuale incentivazione sulla vendita dell'energia in rete, non rendono l'investimento particolarmente attrattivo per impianti connessi alla rete. L'attenzione si è quindi rivolta all'analisi tecnico-economica di sistemi energetici ibridi non connessi alla rete, comunemente definiti in isola o off-grid, per soddisfare il fabbisogno energetico di utenti in area remote e quindi prive di allaccio a una rete elettrica. In tali sistemi, i sistemi di accumulo a batterie, oltre alla capacità di accumulo dell'energia prodotta in eccesso variabili e intermittenti FER, hanno funzioni fondamentali nella gestione del sistema stesso. L'attività è stata anche rafforzata da un'applicazione industriale per la configurazione, test e installazione di due sistemi energetici ibridi in isola impiegati per soddisfare il fabbisogno energetico di un villaggio e di un sistema di telecomunicazione situati in aree remote. In parallelo, sono state svolte due attività sperimentali applicate alla promettente, ma non ancora completamente sviluppata a livello industriale, tecnologia solare a concentrazione. La prima attività riguarda la progettazione, sviluppo e test sperimentali di un prototipo in scala ridotta di concentratore solare a lenti di Fresnel per la produzione distribuita di energia elettrica, mediante l'uso di celle fotovoltaiche multi giunzione, ed energia termica a bassa temperatura, tramite un sistema di recupero termico. La seconda attività concerne lo sviluppo e test sperimentali di un prototipo di sistema di accumulo termico per impianti termodinamici alimentati da sistemi a concentrazione solare. Il sistema di accumulo consente di compensare la natura intermittente e variabile della fonte solare incrementando le ore di funzionamento dell'impianto termodinamico con i conseguenti benefici economici. Concludendo, la presente tesi di dottorato include la descrizione di metodi e strumenti per l'ottimizzazione e valorizzazione delle FER. I risultati evidenziano le criticità e potenzialità dei sistemi studiati con lo scopo di contribuire a una loro diffusione e favorire uno sviluppo sostenibile

With the increased penetration of intermittent renewable energy sources (RESs) in future grids (FGs), balancing between supply and demand will become more dependent on demand response (DR) and energy storage. So far, FG feasibility studies, especially those claiming a long-term view, typically do not model the electrical network and/or the effect of DR. Thus, in this thesis, we first present a simulation platform for performance and stability assessment of FG scenarios. The platform considers market simulation, load flow calculation and stability assessment together. Using the platform, we illustrate how displacing conventional generators with RESs, especially inverter-based and intermittent RESs, could have significant impacts on performance and stability of FGs, confirming the importance of stability assessment for FG feasibility studies. Second, to carry out accurate stability analysis of FG scenarios, we need a representation of the aggregate demand including the effect of emerging demand-side technologies (distributed generation (DG), DR and storage). In this research, we propose generic demand models including the aggregated impact of price-responsive users equipped with emerging demand-side technologies (prosumers). The proposed models capture essential behaviour of the prosumers without giving lots of detail which is costly in repeated use for applications such as scenario comparisons. So, such models demand some simplifications, just as conventional generic load modelling did. The proposed frameworks are based on the unit commitment (UC) problem aiming to minimise the system cost. The conventional demand model in the associated optimisation formulations are augmented by including the aggregated influences of prosumers equipped with rooftop photovoltaics (PV)-battery systems. It is noted that as the frameworks are generic, they are capable of easy integration of other demand-side technologies as well. The developed frameworks are intended specifically for modelling net demand by including the impact of prosumers in FG scenario studies. Nevertheless, they do not assume any particular market structure. As such, they are not suitable for modelling of existing electricity markets, but rather their aim are to capture the behaviour of future electricity markets provided a suitable market structure is adopted. Finally, the impact of prosumers on performance and voltage stability of the Australian National Electricity Market (NEM) is studied with the increased penetration of RESs in the grid. We have considered different penetrations of RESs, and assessed the influence of different penetrations of prosumers on the balancing, loadability and voltage stability of the NEM.

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

Microgrids containing photovoltaic (PV) cells and wind power gain more and more interest. These microgrids may work in stand-alone mode ("islanding") or be conncted to the main grid. In both modes of operation, power quality must be monitored and controlled. This report focuses on microgrids and aims to implement a monitoring system based on FPGA. In the monitoring system, two applications can be achieved, firstly a PAS-MPPT algorithm in a DC-DC boost converter to improve the maximun power point tracking of a PV unit, and secondly a detection and switching system of the grid mode - stand-alone or connected to the main grid. Simulation results prove the Verilog programs in FPGA are suitable to be used in microgrids.

Ces dernières années, un intérêt croissant pour les systèmes électroniques de puissance a été motivé par l'émergence de sources d'énergie distribuées et renouvelables raccordées aux réseaux électriques. Dans ce contexte, la nécessité de topologies de faibles puissances alimentées par quelques modules photovoltaïques, en évitant l'utilisation de transformateurs, a ouvert l'étude de convertisseurs spéciaux et l’étude des stratégies de commande associées afin d’assurer la stabilité, la fiabilité et un rendement élevé du dispositif. Une possible solution est d’utiliser un dispositif générique connu dans la littérature scientifique et commerciale comme « micro-onduleur » ou «convertisseur intégré au module » qui avec le module photovoltaïque définit un produit « plug and play » appelé "module AC".Ce travail est consacré à l'étude d'un micro-onduleur monophasé avec deux étapes sans transformateur raccordée au réseau. La topologie proposée est composé d’un convertisseur DC-DC non isolé élévateur avec un gain quadratique et un onduleur réducteur lié au réseau connectés en cascade. Le convertisseur DC-DC extrait en permanence la puissance maximale du module photovoltaïque malgré les changements dans les conditions environnementales. L'étape DC-AC injecte la puissance extraite par l'étape DC-DC dans le réseau et assure un niveau élevé de qualité de l’énergie. Les efforts de recherche de ce travail sont concentrés sur la mise au point de commandes utilisant comment base, la théorie de contrôle par mode de glissement, qui conduit à une mise en œuvre simple avec une description théorique complète validée á partir de simulations et expérimentations.Après avoir décrit l'état de l’art dans le premier chapitre, le manuscrit est divisé en quatre chapitres, qui sont dédiés respectivement à l’algorithme de recherche du point de puissance maximale (MPPT), á l’étape de conversion DC-DC, á l'étape de conversion DC-AC et finalement au micro-onduleur complet. Un nouvel algorithme de recherche extrémal du point de puissance maximale est développé (SM-ESC). Pour la étape DC-DC, le convertisseur élévateur quadratique avec seulement un interrupteur contrôlé est étudié utilisant le concept de résistance sans perte par mode de glissement (de l’acronyme anglais : Sliding-Mode Loss-Free-Resistor – SM-LFR) afin d’obtenir un gain de tension élevé avec un fonctionnement sûr et compatible avec l’algorithme MPPT. Pour la étape DC-AC, le convertisseur de pont complet est contrôlé comme un onduleur de source de puissance (de l’acronyme anglais : Power Source Inverter - PSI) en utilisant une commande par mode de glissement qui poursuit une référence sinusoïdale de courant de sortie. Cette commande est complétée par une boucle de régulation de la tension du bus DC qui assure une haute qualité d’énergie injectée dans le réseau. Enfin, les trois étapes constitutives sont fusionnées pour obtenir un micro-onduleur complètement contrôlé par la technique de mode de glissement, ce qui constitue le principal résultat et contribution de cette thèse<br>These last years, a growing interest in power electronic systems has been motivated by the emergence of distributed renewable energy resources and their interconnection with the grid. In this context, the need of low power topologies fed by a few photovoltaic modules avoiding the use of transformers opens the study of special converters and the associated control strategies ensuring stability, reliability and high efficiency. A resulted generic device known in the commercial and scientific literature as “microinverter” or “module integrated converter” performs a plug and play product together with the PV module called an “AC module”.This work is devoted to the study of a transformer-less single-phase double-stage grid-connected microinverter. The proposed topology has a non-isolated high-gain boost type DC-DC converter and a non-isolated buck type DC-AC converter connected in cascade through a DC bus. The DC-DC converter permanently extracts the maximum power of the PV module ensuring at the same time a good performance coping with power changes introduced by the change in the environmental conditions. The DC-AC stage injects the power extracted by the DC-DC stage into the grid ensuring a high level of power quality. The research efforts focus on the involved control functions based on the sliding mode control theory, which leads to a simple implementation with a comprehensive theoretical description validated through simulation and experimental results.After giving the state-of-the-art in the first chapter, the manuscript is divided into four chapters, which are dedicated to the Maximum Power Point Tracking (MPPT), the DC-DC stage and its control, the DC-AC stage and its control and the complete microinverter. A new Extremum Seeking Control (ESC) MPPT algorithm is proposed. The single-switch quadratic boost converter is studied operating as a Loss-Free-Resistor (LFR) obtaining a high DC output voltage level with a safe operation. The full-bridge converter is controlled as a Power Source Inverter (PSI) using a simple sliding-mode based tracking law, regulating the voltage of the DC bus and then ensuring a high power quality level in the grid connection. Finally, the three building blocks are merged to obtain a sliding mode controlled microinverter constituting the main result and contribution of the work

Submitted by Renata Lopes (renatasil82@gmail.com) on 2016-09-21T17:33:46Z No. of bitstreams: 1 viniciussobreiralacerda.pdf: 3531215 bytes, checksum: 422eca8f67f53625eceb5e46317386f9 (MD5)<br>Approved for entry into archive by Diamantino Mayra (mayra.diamantino@ufjf.edu.br) on 2016-09-26T20:27:18Z (GMT) No. of bitstreams: 1 viniciussobreiralacerda.pdf: 3531215 bytes, checksum: 422eca8f67f53625eceb5e46317386f9 (MD5)<br>Made available in DSpace on 2016-09-26T20:27:18Z (GMT). No. of bitstreams: 1 viniciussobreiralacerda.pdf: 3531215 bytes, checksum: 422eca8f67f53625eceb5e46317386f9 (MD5) Previous issue date: 2010-08-30<br>FAPEMIG - Fundação de Amparo à Pesquisa do Estado de Minas Gerais<br>Este trabalho aborda a análise, a modelagem matemática, o projeto e a simulação computacional de um sistema monofásico de aproveitamento fotovoltaico (PV) nãoisolado conectado à rede elétrica, em que se pretende sintetizar uma corrente de baixa distorção harmônica mantendo-se o ponto de máxima potência dos painéis. São avaliadas duas estruturas conversoras equivalentes, uma com dois estágios de processamento de energia e outra com apenas um estágio. Ambas as estruturas desempenham o papel de converter a energia CC dos painéis fotovoltaicos em energia CA, sob a forma de corrente elétrica de baixa distorção injetada na rede. Uma revisão sucinta dos modelos matemáticos de representação do comportamento termo-fotoelétrico do painel fotovoltaico (ou conjunto de painéis) é realizada, resultando na adaptação de uma das alternativas na forma de modelo numérico adaptado à ferramenta computacional PSIM. Algumas alternativas monofásicas de conversão CC-CA são elencadas neste trabalho, com destaque para o número de estágios de conversores, característica de isolamento e qualidade da energia injetada. Como base nesta análise, propõe-se um sistema composto por um conversor CCCC tipo buck operando em modo de condução contínua em alta frequência, em cascata com um inversor fonte de corrente (CSI) acionado na frequência da rede, para realização do aproveitamento fotovoltaico desejado. Amparado por ferramentas de integração de estágios de conversores, percebe-se que o conjunto de dois estágios pode ser arranjado em uma única etapa conversora baseada no inversor fonte de tensão (VSI). Ambas as propostas são modeladas, projetadas e simuladas no PSIM. A descrição teórico-matemática da planta PV, incluindo suas malhas de controle, é realizada. Com propósito de validação das concepções teóricas, tais sistemas são simulados, inicialmente, empregando-se elementos idealizadores e, em segundo momento, adotando-se um arranjo que inclui alguns componentes parasitas, sensores em escala real e o subcircuito do integrado UC3854. Os resultados numéricos, realizados para variações da irradiação solar e perturbações na tensão da rede, confirmam que o conceito proposto é factível, resultando em uma alternativa simples, compacta e possivelmente de baixo custo.<br>This work deals with the analysis, mathematical modeling, design and computer simulation of a single phase non-isolated photovoltaic (PV) system, which is connected to the electrical grid and is controlled to synthesize a low harmonic current while keeps the maximum power point of the panels. Two structures are evaluated, one with two stages of processing power and another with a single stage. Both structures converts DC power from solar panels into AC power, in the form of a low distortion electrical current to be injected into the grid. A brief review of PV panel mathematical models is performed, resulting in the adaptation of one alternative in the form of a numerical model oriented to the computational tool PSIM. Moreover, some alternatives to single-phase DC-AC conversion are listed in this work, highlighting the number of stages of inverters, isolation characteristic and quality of the power injected. To support this analysis, a two-stage system has been firstly studied, which is constituted of a buck converter operating in continuous conduction mode at high frequency, cascaded with a current source inverter (CSI) which works in the frequency of the grid. Using the integration of stages theory, the two stage system can be arranged into a single stage converter based on a voltage source inverter (VSI). Both proposals are modeled, designed and simulated in PSIM program. The theoretical and mathematical description of the PV plant, including its control loops, is presented. With the purpose of validation of the theoretical concepts, such systems are simulated, initially, using idealized elements, and then, adopting an arrangement that includes some parasitic components, sensors and full-scale integrated subcircuit of UC3854. The numerical results carried out for changes in solar radiation and mains voltage sags/swells, confirm that the proposed concept is feasible, resulting in a simple, compact and potentially low cost.

Mauritius is an isolated island with ambitious targets for renewable energy generation and plans to invest in more solar power. The aim of this study is to assess how the implementation of photovoltaic technologies might affect the frequency stability in Mauritius and thus assess whether solar power can help the country obtain their targets for green energy generation. The research question is answered by conducting a literature study and simulating relevant scenarios in Matlab and Simulink. By simulating the frequency response for a production disturbance with different values for system inertia and PV capacity, the inertia requirements for frequency stability is assessed. Mauritius appears to have a high potential for increasing solar power generation. Based on the simulations, their electrical grid seems to be able to maintain frequency stability with PV capacity corresponding to the generation targets for 2020, 2025 and 2030, even for low amounts of system inertia. However, the significance of these results are called into question because of the varying quality of input data. With more accurate, specific data, the applicability of the results can be improved. Nevertheless, the study can be used as a guideline on how to use the given model to evaluate frequency stability in isolated power systems in island states. Ways to further this study is to evaluate other stability challenges related to PV production such as the reactive power in the system, voltage stability and rotor angle stability.<br>Mauritius är en isolerad ö som har sett en stor ekonomisk växt de sista åren. För att möta en ökande efterfrågan på el på ett hållbart sätt har Mauritius satt ambitiösa mål för förnybar energiproduktion som bland annat innebär betydande investeringar i solkraft. Målet med denna studie är att utvärdera hur implementeringen av utökad solcellskapacitet skulle kunna påverka frekvensstabiliteten i nätet på Mauritius och således fastställa ifall solenergin kan bidra till deras mål om ökad grön energiproduktion, utan att öka risken för strömavbrott. Frågeställningen besvaras genom att först utföra en litteraturstudie och sedan använda en matematisk modell, utvecklad av Danilo Obradovic från KTH, för att simulera relevanta scenarier i Matlab och Simulink. Simuleringarna visar frekvenssvaret vid produktionsbortfall som relateras till den mängd svängmassa som behövs för att säkerställa frekvensstabilitet vid olika mängder solceller. Litteraturstudien visar att Mauritius har god tillgång på solinstrålning och solceller verkar vara en lämplig teknologi för att utnyttja denna energin. Enligt de simuleringar som genomförts verkar Mauritius kunna bibehålla frekvensensstabilitet om den installerade solcellskapaciteten ökas till de planerade nivåerna i 2020, 2025 och 2030, även för låga värden på systemets svängmassa. Slutsatserna bör dock analyseras kritiskt då indatan som används för simuleringarna är av varierande kvalitet. Med bättre och mer specifik indata kan den föreslagna metodiken och modellen användas för att dra mer relevanta slutsatser för Mauritius. Metodiken som använts i denna studie kan därav ses på som en riktlinje för hur frekvensstabiliteten i isolerade elnät kan undersökas. Vidare kan studien utökas genom att utvärdera sociala och ekonomiska aspekter och även andra stabilitetsfrågor relaterade till en ökad mängd solceller, så som den reaktiva effekten i systemet, spänningsstabilitet och rotorvinkelstabilitet.

Submitted by Marlene Santos (marlene.bc.ufg@gmail.com) on 2017-12-18T16:25:14Z No. of bitstreams: 2 Dissertação - Ciliana Karine Dias Lima - 2017.pdf: 23149224 bytes, checksum: c070892c298f576da2daf6724723a45b (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5)<br>Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2017-12-19T12:03:47Z (GMT) No. of bitstreams: 2 Dissertação - Ciliana Karine Dias Lima - 2017.pdf: 23149224 bytes, checksum: c070892c298f576da2daf6724723a45b (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5)<br>Made available in DSpace on 2017-12-19T12:03:47Z (GMT). No. of bitstreams: 2 Dissertação - Ciliana Karine Dias Lima - 2017.pdf: 23149224 bytes, checksum: c070892c298f576da2daf6724723a45b (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-12-11<br>Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq<br>Sustainable development is a present issue in world society and it is also a strategic challenge for Cape Verde’s energy policy in coming years because the large fragilities in the electrical system in Cape Verde such as, dependence on imports of fuels, geographical dispersion, the high costs associated with managing energy systems and the great energy waste. The bet on photovoltaic systems may be one of the alternatives to reducing these fragilities. In this context, the present work highlights the great existent potential for use of renewable energy focused on solar energy. The text describes incentives for the production of electric energy based on renewable sources and presents analyses on the implementation of two grid-connected photovoltaic systems in the island of São Vicente. One of the systems is a photovoltaic rooftop 19.8 kWp plant installed in a public secondary school building and the other system is 3 MWp photovoltaic power plant connected to electrical utility grid in São Vicente Island. The study included design, operation simulation of São Vicente Island distribution network in the presence and absence of photovoltaic systems and financial analyses in order to determine payback time, actual present value, intern return rate of investment and financial sensibility analyses to assess the influence of Wp cost and interest rate on the financial figures. The results show that the implementation of photovoltaic systems is attractive in financial and technical terms, the microgeneration system causes a large reduction in energy acquired by the network, and the large power plant has not worsened the appropriate operating voltage levels and decreased the system's active losses.<br>O desenvolvimento sustentável é uma questão presente na sociedade mundial e é também um desafio para a política energética de Cabo Verde nos próximos anos, devido às grandes fragilidades do sistema elétrico do arquipélago, tais como a forte dependência da importação dos combustíveis fosseis, a dispersão geográfica, os elevados custos associados à gestão dos sistemas energéticos e o grande desperdício energético. A aposta em sistemas fotovoltaicos é uma das alternativas para a redução dessas fragilidades. Neste contexto, o presente trabalho destaca o grande potencial existente em Cabo Verde para utilização de energia renovável com o foco na fonte solar. O trabalho descreve os incentivos legais locais para a produção de energia elétrica com base em fontes de origem renovável e apresenta a análise da implantação de dois sistemas fotovoltaicos conectados à rede elétrica na ilha de São Vicente. Um deles é um sistema de microgeração fotovoltaica de 19,8 kWp instalado em um edifício público de ensino e o outro é uma usina fotovoltaica de grande porte de 3 MWp, ligada à rede elétrica e também localizada na ilha de São Vicente. O estudo inclui o dimensionamento, a simulação de operação da rede de distribuição da ilha de São Vicente na ausência e na presença de sistemas fotovoltaicos. São feitas análises financeiras a fim de determinar o tempo de retorno dos investimentos, o valor atual líquido e a taxa interna de retorno dos investimentos. Também é feito uma análise de sensibilidade financeira para avaliar a influência do custo do Wp instalado e da taxa de juros do financiamento sobre os parâmetros financeiros. Os resultados mostram que a implementação dos sistemas fotovoltaicos é atrativa em termos financeiros e técnicos. A instalação do sistema de microgeração provoca uma grande redução da energia adquirida junto à rede pela unidade consumidora. É mostrado também que a usina de grande porte notadamente não alterou os níveis de tensão de funcionamento da rede e proporcionou uma diminuição das perdas ativas do sistema.

Este trabalho apresenta um estudo sobre a corrente de fuga de modo comum em inversores monofásicos sem transformador utilizados para a conexão de sistemas fotovoltaicos (FV) à rede de distribuição de energia elétrica. O estudo se concentra em inversores do tipo fonte de tensão que empregam a topologia em ponte completa. A partir da adequada modelagem do sistema (rede, conversor e módulo fotovoltaico) identifica-se e quantifica-se a contribuição das tensões de modo comum e modo diferencial para a corrente de fuga. Conclui-se que a tensão de modo comum de alta frequência produzida pelo inversor, que depende da estratégia de modulação por largura de pulso (PWM Pulse Width Modulation) empregada, fornece a maior contribuição para produção da corrente de fuga. Esse estudo mostra que os inversores sem transformador, com topologia em ponte completa e modulação que produz tensão de saída com três níveis, necessitam de medidas adicionais para a minimização da corrente fuga quando aplicados em sistemas fotovoltaicos conectados à rede. Algumas soluções propostas na literatura para a minimização da corrente de fuga baseadas em topologias modificadas e filtros de modo comum são listadas e discutidas. Neste trabalho é proposto um filtro integrado de modo comum e modo diferencial com amortecimento passivo de baixas perdas, para minimizar a corrente de fuga produzida por um inversor monofásico sem transformador. Um exemplo de aplicação do filtro proposto é apresentado juntamente com seu procedimento de projeto, resultados de simulação e experimentais que validam a proposta. Além disso, a influência da variação da indutância da rede elétrica e da capacitância parasita do sistema fotovoltaico no comportamento do filtro proposto é analisada. A influência da variação da indutância da rede no comportamento do sistema de controle e o impacto da corrente de modo comum no projeto dos indutores do lado do conversor também são analisados.<br>This paper presents a study on the common mode leakage current in single-phase transformerless inverters for grid-connected photovoltaic (PV) systems. The study focuses on voltage source inverters (VSI) employing the full-bridge topology. The common mode and differential mode voltages that contribute to the leakage current are identified and quantified from the analysis of the system model (utility grid, converter and PV module). The system model analysis shows that the high frequency common mode voltage produced by the inverter, which depends on the Pulse Width Modulation (PWM) strategy, is the main source contributing to the leakage current. This work shows that transformerless inverters employing the full-bridge topology and a modulation strategy that produces a three-level output voltage require some leakage current minimization strategy when they are employed in grid-connected PV systems. Some solutions proposed in the literature for leakage current minimization based on modified topologies and common mode filters are listed and discussed. In this dissertation an integrated common and differential filter with low loss passive damping is proposed to minimize the leakage current produced by a single-phase transformerless PV inverter. An application example of the proposed filter is presented with design procedure, simulation and experimental results validating the proposal. Additionally, the influence of grid inductance and PV module parasitic capacitance variations on the behavior of the proposed filter is analyzed. The behavior of the control system considering the grid inductance variation and the impact of the common mode current on the converter side inductors design are also analyzed.

博士<br>國立高雄應用科技大學<br>電機工程系<br>97<br>Power converter interface is one of the key technologies for the solar power generation system. The topology of power converter, islanding detection and the maximum power point tracking are the key technologies for power converter interface of the photovoltaic generation system. In this thesis, the grid-connected current-mode power converter and the grid-connected voltage-mode power converter for the photovoltaic generation system are studied. Besides, a novel islanding detection method and an maximum power point tracking method are proposed and incorporated into the controller of the power converter for the photovoltaic generation system. The prototype of the grid-connected current-mode power converter and the grid-connected voltage-mode power converter for the photovoltaic generation system are developed and tested to verify the performance of the proposed methods. The experimental results show that the performance of the proposed photovoltaic generation system is as expected.

碩士<br>國立高雄應用科技大學<br>電機工程系<br>98<br>A three-phase multi-level power converter for grid-connected photovoltaic generation system is in this thesis. This three-phase multi-level power converter includes a non-isolated DC/DC power converter, a three-phase multi-level DC/AC power converter. The DC/DC power converter is controlled to trace the maximum power point of the solar cell array and regulate the voltage generated by the solar cell array to match the specified DC voltage of the DC/AC power converter. The three-phase multi-level DC/AC power converter is controlled to regulate the output voltage of DC/DC power converter and generate a fundamental real power injected into the utility. The computer simulation results show that the performance of this three-phase multi-level power converter for grid-connected photovoltaic generation system is as expected.

碩士<br>雲林科技大學<br>電機工程系碩士班<br>98<br>This paper develops a grid-connected photovoltaic generation system. Considering the costs of photovoltaic modules and the output voltage of photovoltaic modules not directly for dc/ac conversion. The power circuits of the system are composed of the dc/dc boost and the single-phase full-bridge inverter. The pulse-width modulation is used for dc/dc boost, the unipolar voltage switching by sinusoidal pulse width modulation and a maximum power point tracking algorithm is used to control the single-phase full-bridge inverter, and that is connected to utility by using the synchronous technology of grid zero-crossing signal. A hybrid tracking algorithm is presented for maximum power point tracking in photovoltaic. For the utility side, the system also makes use of islanding detection algorithms to effectively prevent the island phenomenon. A digital signal processor (TMS320LF2407A) is used for the system control that can reduce hardware components. Finally, develop an output voltage 110V/60Hz, 350W maximum output power of grid connected photovoltaic generation systems, it not only using renewable energy fully, but also reducing electricity expenditure.

碩士<br>國立高雄應用科技大學<br>電機工程系博碩士班<br>101<br>A photovoltaic power generation system consists of a dual output DC-DC power converter and a multi-level DC-AC power converter is developed in this thesis. A dual output DC-DC power converter with the functions of output voltage into a multiple relationship and maximum power point tracking is required. The multi-level DC-AC power converter includes a dual buck power converter and a full-bridge power converter. The dual buck power converter generate a four-level DC voltage. The full-bridge power converter is switched in low frequency and synchronously with the utility voltage and it convert this four-level DC voltage to a seven-level AC voltage inject into grid; it can also operate to an active power filter to compensate harmonic current.Computer simulation and 1.2kW hardware prototype are developed to verify the performance of the propose novel seven-level grid-connect photovoltaic power generation system. Both simulation and experimental results show that the performance of the propose novel seven-level grid-connect photovoltaic power generation system has the expected results.

碩士<br>國立臺灣科技大學<br>電機工程系<br>95<br>This thesis presents the development of a photovoltaic power generation system. The dc-dc boost converter and perturbation & observation algorithm are employed to achieve maximum power output. In this thesis, the three leg voltage-fed inverter mathematical model and controller design are built and simulated by using MATLAB/Simulink. Finally, The system can be operated in a grid connected mode or stand-alone mode to supply sinusoidal voltage to the loads.

碩士<br>國立清華大學<br>電機工程學系<br>92<br>Wind energy and solar energy, due to their inexhaustible supply and environmentally clean characteristic, are probably two kinds of most potential renewable energy for recent development. In Taiwan area, the solar energy is quite rich during the day while the wind energy is usually available during the night. Hence, it is the main objective of this thesis to focus on the implementation of a photovoltaic (PV) and wind power hybrid generating system to enhance the utilization rate and efficiency of the system. Also, in order to reduce the installation cost, the concerned hybrid system is supposed to be connected to the grid system. Basically, the contributions of thesis may be summarized as follows. First, a new configuration of a grid connected PV and wind power hybrid generating system is proposed. Only two three-phase Insulated Gate Bipolar Transistor (IGBT) modules are required for implementing the ten active switches to achieve more compact volume and higher reliability. Second, the dc link voltage is stabilized by controlling the reactive power from the grid system and served as a basis for integrating the control of different renewable energy source. Third, by using the concept of conservation of energy, a dynamic model of the proposed hybrid generating system is derived and four control modes are defined to achieve the corresponding d-axis current commands for integrating into a total input command of the hybrid system. Since the real power control is independent of the reactive power control of the dc link voltage, fast response together with better power quality control can be achieved. Fourth, as far as the operation of the hybrid system is concerned, five operation modes, namely, the starting mode, normal operation mode, emergent control mode, power quality control mode and the shut down mode, are defined for convenient control and maintenance of the hybrid system. Finally, a prototype is constructed and experimental results are presented for verifying the feasibility of the proposed hybrid system.

The solar energy become a popular and environmental friendly solution for meeting demand of the increasing demand for electric power. The photovoltaic system has now become grid connected system from stand-alone system as it was previously. Now feed in tariff (FIT) has made it a distributed energy (DG) sources in many countries around the world. The power quality of the grid is being degenerated by the injection of the current by the grid connected PV system with the converters used for DC to AC conversion or the inverter functioning unaware of the harmonics injected by it. Additionally the voltage harmonics is also introduced by the current injected with filtering. Especially the increasing penetration of the DGs in low voltage networks which uses the PV energy as source has had worsened the situation. The rising use of non-linear load has resulted in excessive harmonic pollution resulting in losing of reliability and power quality of the system. Active power filtering can be performed by following various theories one such popular theory is the one using instantaneous power theory proposed and cross vector theory. Other theories like power balance theory and Synchronous reference frame is also effective in APF for distorted and unbalanced supply along with power injection from PV source. Combining the PV system and APF through a single three phase voltage sourced inverter (VSI) thus making the full utilization of the switching devices at all times is the objective achieved. The PV power is used for the DC voltage regulation and the surplus power from the PV source is also fed through the voltage source inverter (VSI) to the load or the grid. For improving the efficiency single stage conversion is used. Current control is used with reference current generated for both the filtering of harmonics and the MPPT of PV panel and the DC voltage regulation. P&O algorithm with variable perturbation size was used for the efficient tracking of the MPP.

碩士<br>清雲科技大學<br>電機工程所<br>100<br>This thesis is concerned with the development and simulation of a grid-connected photovoltaic generation system. First, we observed the output characteristics of solar cell. The perturb-and-observe method was adopted to control the DC/DC boost converter to achieve maximum power point tracking control for improving the output power of the photovoltaic generation system. Finally, the voltage-Fed current-controlled method was used to control the full-bridge inverter to convert DC/AC power and connect to the grid using the smart power module. The Powersim (Psim) package software was adopted to simulate a grid-connected photovoltaic generation system. First, the single-crystal silicon solar cells and PV module mathematical model was built to establish the characteristics of I-V and P-V curves, the perturb-and-observe method was used to control the boost DC chopper for maximum power point tracking. Finally, a full-bridge inverter was used to convert DC/AC power and connect to the grid to accomplish system simulation for system design and digital control. A digital signal processor (DSP, TMS320LF2812) was applied to implement 1kW prototype digitized control grid-connected photovoltaic generation system. Experiment was then conducted to verify the theory.

At present scenario, renewable energy sources have emerged as best alternative0source of energy for0future and to alleviate the environment pollution0problems. Renewable energy sources like solar energy, wind energy system etc. when connected to grid, termed as micro grid, uses0power electronics converters so as to interface between renewable energy system0and utility grid. Although solar energy conversion efficiency is very low, it has been preferred widely due to its abundant nature. An attempt has been taken to develop an improved MPPT which uses d-axis grid current and dc link voltage as reference. It not only tracks the maximum power effectively but also provides a dynamic response to the fast changing atmospheric condition. The converters used for interfacing, are basically a voltage source0inverter (VSI) connected to the source0network, operated in order to achieve0objectives such as to control the power0flow and also to have operate at unity0power factor. The grid is required to have independent0control of active & reactive power, proper grid0synchronization, improved power0quality and good transient response0during any fault conditions etc. The voltage0oriented control (VOC) implemented on the grid0side converter is universally adapted for independent control of the active and reactive power0of a grid as it is controlled in0synchronous rotating frame. However, the dynamic response0of grid, during abnormal condition, is very0sluggish and poor0power quality. In order to design a0controller for robust performance and0to know its control characteristics, 0VSI needs to be modeled accurately. This project0has taken an attempt to derive the small0signal analysis of a three phase0grid connected VSI and further, relevant0transfer functions have been0obtained from the model in order0to analyze the system performance, to0be used for designing a0controller by utilizing bode plots. The studied system is0then modeled and simulated in the0MATLAB-Simulink environment.

The world has been traditionally dependent on non-renewable sources of energy for industrial applications and other daily domestic applications. The modern world is moving fast towards greener sources. Various ongoing research works are dedicated towards meeting the demands of local loads with help of green energy. Solar energy is one of the most abundantly available forms of renewable energy. But extracting power from solar photovoltaic arrays according to the demand of the load under changing grid conditions and environmental conditions has been a challenge. In this work, active/reactive power control and maximum power point tracking control strategies are investigated. First a working model of solar array is developed and simulated using MATLAB/Simulink. This model is further used for our control strategies investigation purposes. The developed solar array is investigated under varying solar irradiation and varying temperatures. The effect of these factors on voltage, current and consequently on power is observed. A solar photovoltaic array of 100KW is used for simultaneous testing of active/reactive control and MPPT control. The active and reactive power control of photovoltaic array is implemented usually when the available solar power is sufficient, the active and reactive power is controlled in such a way that it follows the load‘s demand characteristics. The photovoltaic array acting as generator should be able to mitigate the sudden change in load demands successfully which is tested by simulating the load change conditions in MATLAB. This active/reactive power control is relatively simpler as it is a single stage configuration with an inverter. The inverter is responsible for controlling, processing and delivering the solar power to the load side efficiently. The MPPT control is investigated under changing solar irradiation from 800W/m2 to 1000W/m2 .The sudden injection in power due to increase in irradiation is seen. The solar photovoltaic array tracks the maximum power and delivers it to the load efficiently. The power at AC and DC sides of the inverter is verified. This two stage configuration is more complex in nature with three control loops. One loop is exclusively for MPPT control. The other two loops are for inverter power control and indirect control of solar photovoltaic voltage and inverter voltage. The ability to deliver maximum power under changing irradiation of the solar photovoltaic generator is simulated with help of MATLAB/Simulink.

碩士<br>清雲科技大學<br>電機工程研究所<br>96<br>This thesis presents the analysis and implementation of a digitized grid-connected photovoltaic generation system. The power circuit of the photovoltaic generation system is composed of the dc/dc boost chopper and the single-phase full-bridge inverter. The short current method, hill-climb method and perturb-and-observe method were adopted to achieve the maximum power point tracking for comparing their advantages and defects. The current control method was used to control the single-phase full-bridge inverter for connecting to utility. All the control methods were achieved by digital control to enhance conversion efficiency of photovoltaic generation system. This thesis used the Matlab software to simulate characteristic curves of the solar modules, and used Powersim software to simulate output characteristics of the single-phase full-bridge inverter. The control circuit is based on a digital signal processor (DSP) TMS320LF2407A to control the dc-link voltage and the single-phase AC source to implement a 1.65kW prototype of digitized grid-connected photovoltaic generation system. The system efficiency is 82.66%. Simulation and experimental results are provided for verification.

碩士<br>國立高雄第一科技大學<br>綠色能源及IC設計產業碩士專班<br>103<br>This thesis presents the design and implementation of a 2kW wind-power grid-connected inverter system. Wind power is generated by wind turbine, of which output voltage is a varying-frequency varying-amplitude sinusoidal waveform. In low power application, a full-bridge rectifier is adopted for ac-to-dc transform. However, the rectified dc voltage level is not enough to inject wind power into utility. Therefore, a voltage step-up converter is needed for grid connection. In this thesis, a double-boost converter and a full-bridge inverter, which are in cascade connection, are incorporated for dc/dc and dc/ac conversion, respectively. The control core of the wind-power system is implemented on a DsPIC30F4011 Microcontroller unit (MCU). All the power controlling and system protection, such as feedback signal detection, phase displacement controlling, voltage regulation, SPWM controlling, and maximum power tracking, are fulfilled by the MCU-based controller. Simulations by Caspoc are carried out to aid parameter design. Hardware measurements also have validated the feasibility of the wind-power grid-connected inverter system.

The demand of energy is increasing rapidly year by year worldwide & the whole world is looking for the alternative source of energy. The most populous alternative source of energy is renewable energy. Among, various available renewable energy sources, solar photovoltaic (SPV) energy is considered to be most reliable, environment friendly, pollution free and it’s unlimited amount of availability in nature. The solar energy is directly converted into electrical energy by solar cell/ module. The characteristics of PV depend upon irradiation and temperature. The temperature and the irradiation of the solar cell depend on the atmospheric conditions. Hence, it is essential to track the MPP in any conditions to assure that the maximum available power is obtained from the PV panel. In stand-alone mode PV can feed power to fixed loads & lower power rating loads only and the storage support is also required for stand-alone mode. The grid interconnected mode of PV operation offers infinite storage. When PV is interfaced to the grid power quality problems arises due to use of power electronic devices. Solar PV is modelled using single diode electrical equivalent circuit of solar cell and the characteristics of PV module are generated. The different maximum power point tracking (MPPT) algorithm is studied. Incremental conductance and perturbation and observation (P&O) is modelled and implemented. The maximum power point (MPP) is obtained using MPPT and dc-dc boost converter. The complete evacuation of generated and tracked maximum power is need of the entire system to improve the efficiency. The model of Solar PV system connected to the utility grid is modelled and simulated in MATLAB/Simulink environment. Solar PV system is controlled and synchronised to grid using synchronous reference frame theory (SRFT) algorithm and power balance theory (PBT) algorithm. To handle the power quality problems the system is run under unity power factor (UPF) and zero voltage regulation mode (ZVR). UPF is obtained on the ac mains/grid side for grid voltage and grid current and zero voltage regulation is obtained for the terminal voltage of point of common coupling (PCC) voltage.

Solar renewable energy harvesting is the demand of the century because of the huge energy requirement of the world today. India being a home to a huge population witnesses high Incident Solar radiations throughout the year. Planning has been made to produce at least 20 Gigawatts of high quality solar power by the year 2020. Energy harvested from the sun is a necessarily a valuable source but still most it part goes unutilised in Indian subcontinent although being a tropical region. The main obstacle for the wide usage of solar Photovoltaic systems is their efficiency which is very low (20-25% for single crystal 10-15% for polycrystalline and 3-5% for amorphous silicon solar cells) and high cost of manufacturing. In main objective behind the work in this thesis lies in extracting maximum harvestable power from a Photovoltaic module and use the energy for a DC application as well as the grid connection of the generated power so that the surplus power unutilised in the load can be transferred to the grid. Maximum Power Point Tracking (MPPT), use of Boost converter and the importance of bridge inverter have been the main investigation in this project. Also the grid connection along with supply to a three phase load using bridge inverter and PWM has been shown. First SIMULINK software is used to model the photovoltaic cell. Then MPPT interfacing is done with a boost converter and resistive load and finally through an inverter connected to the 3 phase grid. All simulations have been done in SIMULINK software of MATLAB

In view of supplementing power generation to meet increasing load demand while minimizing environmental pollution, more attention is currently given to use renewable power extraction for Photovoltaic (PV) and Wind energy conversion system. Amongst all the renewable power generation options, PV power generation is being considered as the most suitable one owing to the abundant availability of solar irradiance with pollution¬free operation. A PV system can be operated as standalone or grid connected modes. The thesis focuses on design, development, and practical realization of robust and adaptive control schemes for effective synchronization of a two¬stage three¬phase Grid Connected Photovoltaic System (GCPVS) to the utility grid. The PV power varies continuously during the day, and PV current and voltage characteristics depend upon the irradiation and ambient temperature, respectively. Therefore, to track this random variation in the Maximum Power Point Tracker (MPPT), adaptive MPPT algorithms is necessary on the PV side. On the grid side, the grid voltage distortions, corrupts the grid synchronization controllers. To resolve these issues, a robust controller needs to be designed. The thesis first designs a Adaptive MPPT controller to improve the Maximum Power Point (MPP) tracking performance. The classical MPPT controllers such as P&O has fixed step size, and its MPP tracking performance is influenced by predefined parameters such as perturbation size, sampling time and initial duty ratio. Therefore, fast tracking of the MPP through these MPPT algorithms is difficult. To resolve these issues, a PI controller is employed to generate a variable step size duty ratio, to improve the tracking performance of this proposed Improved Adaptive Perturbed and Observed (IAPO) MPPT algorithm. In this algorithm, the step size is varied based on the PV power variation, which is embedded as an adaptive feature to a PI controller. This adaptive feature results in fast tracking of the MPP even during transients, less oscillations of DC link voltage during steady state, and least dependence on predefined parameters such as initial duty ratio. Subsequently, to achieve current control for synchronization, an Integral Sliding Mode Controller (ISMC) is designed in which issues regarding the harmonics in the grid injected current is reduced. The classical PI current controller performance deteriorates due to grid voltage distortions and hence there is a need to employ harmonic suppression schemes. But, this slows down the current controller dynamics. Whereas, the ISMC aids in achieving faster dynamics in face of modeling and parametric uncertainties. It also suppresses the harmonics in the injected grid current despite the presence of high Total Harmonic Distrotion (THD) vii content in the grid voltage. It is also found to have excellent decoupling of the cross coupling terms and provide independent control of active and reactive current. The ISMC based current controller is then integrated with the IAPO MPPT algorithm for a two stage GCPVS. Its performance is then compared with other control schemes, namely, SMC¬IAPO and PI¬IAPO control schemes. The comparison envisages that with ISMC¬IAPO control approach, the performance of the overall system improves, and this control strategy does provide faster dynamics despite rapid variations in the PV power, uncertainties owing to modeling and parametric variations in the PV system and grid disturbances. It is also found that this ISMC¬IAPO approach gives the best quality current in comparison to ISMC¬P&O, SMC¬IAPO, and PI¬IAPO. The robust performance of the ISMC is then evaluated in grid fault situations where a Vector Current Control with Feedforward (VCCF) control strategy is employed in the control of two stage GCPVS to deliver balanced three phase currents to the gird. The control of two stage GCPVS in the Low Voltage Ride Through (LVRT) situation becomes a real challenge. It is because the control operation needs to regulate the DC link voltage at its nominal value. Therefore, to transfer the reactive power, the PV panel is operated in the de¬rated mode of operation. This is only possible if MPPT operation is halted and boost converter is operated in constant duty ratio mode. This new duty ratio and reactive current reference are calculated based on the percentage of voltage dips. The ISMC based VCCF strategy is evaluated in the three phase symmetrical and two phase unsymmetrical fault. The ISMC provides both active and reactive current to the grid. The ISMC is compared with a PI controller based VCCF strategy and found to have good performance in damping the inrush currents that arise in the event of fault occurrence and fault clearance. All these control algorithms are simulated in MATLAB/Simulink environment followed real-time implementations on a prototype PV system. A prototype of 2 kW PV system is developed in the laboratory. The aforesaid grid synchronization algorithms were then implemented and verified in real-time on the prototype GCPVS, and results obtained are analyzed.

We are going to study the operational principle and the structure of the present grid-connected photovoltaic system. It describes the two inverter control methods. a) voltage source inverter control method b) power type PWM inverter control method On the basis of above two kinds of inverter control methods, we will present an improved PWM inverter control system that can be applied in grid-connected PV generation and uses MATLAB/Simulink software to simulate and analyze. The result of the simulation shows that the improved inverter control system can effectively control the grid current waveform which tends to sine wave, meanwhile it can achieve the maximum power point tracking, besides it is able to put the arbitrary power out to the load or to the grid, while the control system has a good stability.

碩士<br>國立高雄應用科技大學<br>電機工程系<br>99<br>The fossil fuel was used widely, and it has resulted in the problem of global warming. Thus, the interest in the renewable energy has been aroused. Wind energy is one of the important renewable energies due to the cost. The diode rectifier is used to convert the AC power into DC power for saving the cost of AC-DC converter. However, it results in the harmonic current in the AC side of rectifier, and then it causes a pulsation torque in the permanent synchronous wind power generator. Thus, the output capacity is reduced, and the life span of the permanent synchronous wind power generator is shortened. In this paper, an AC-DC power converter for small permanent synchronous wind power generator is developed. The AC-DC power converter is regarded as virtual resistor so as to control the output current of wind generator to be sinusoidal and in phase with the output voltage of wind generator. Moreover, the efficiency of the developed wind power generation system will compared with the conventional wind power generation system using diode rectifier. To verify the performance of the developed wind power generation system, a prototype is developed and tested. The experimental results show the performance of developed system is as expected.

碩士<br>健行科技大學<br>電機工程系碩士班<br>103<br>This thesis focuses on design and implementation of a single-phase transformerless grid-connected photovoltaic generation system. A 1.14kW photovoltaic generation system model was built by Powersim (PSIM) software. The simulation and analysis results were used to design the control algorithms and programs for system testing. First,we observed the output characteristics of solar cell, the perturb-and-observe method was adopted to control the boost DC chopper for maximum power point tracking. Finally, the current control method was adopted to control a new single-phase full-bridge inverter for grid connected control to convert DC/AC power and connect to the grid. A digital signal processor (DSP, TMS320F28335) was applied to implement 1kW prototype single-phase transformerless grid-connected photovoltaic generation system. Experiment was then conducted to verify the theory.

Synchronizing PV system with grid encounters a number of control challenges for maintaining the grid codes. These include various power quality problems such as voltage and current harmonics, voltage sag and swell, and grid frequency fluctuation. In this thesis it is intended to design suitable grid synchronization control scheme for a three-phase single stage grid connected PV system (TPSSGCPVS) considering power quality disturbances. The proposed control schemes are implemented both by simulation in MATLAB/Simulink followed by experimentation on a prototype TPSSGCPVS developed in the laboratory. Firstly, the thesis focuses on the design of a Self-Tuning Filter-Proportional Integral (STF-PI) grid synchronization control scheme for TPSSGCPVS. The Self-Tuning Filter (STF) extracts the fundamental voltage of the distorted Point of Common Coupling (PCC) voltage and load current without any change in phase and amplitude of the fundamental component. To verify the effectiveness of the proposed STF-PI control scheme, a comparative analysis on its performance with that of the Improved Linear Sinusoidal Tracer-PI (ILST-PI) control scheme is pursued. Form the stability analysis, it is observed that the STF-PI control scheme has a wider range of stability region as compared to the ILST-PI control scheme. Simulations are performed by implementing these control schemes on a PV system considering the power quality disturbances. Subsequently, the proposed STF-PI control scheme is implemented in real-time on a prototype TPSSGCPVS developed in the laboratory. From both the simulation and experimental results obtained, it is verified that the proposed STF-PI control scheme provides effective grid synchronization of the PV system. Along with maximum PV power injection into the grid, the proposed STF-PI control scheme provides efficient harmonics compensation under PCC voltage distortion, load current distortion, load fault, PCC voltage sag and swell. From the obtained results, it is observed that using STF-PI control scheme, the grid current is maintained sinusoidal by reducing the harmonics as compared to ILST-PI control scheme. The current is injected into the grid at Unit Power Factor (UPF) by reducing the reactive current component to almost zero. The grid currents are maintained balanced and sinusoidal with reduced distortion despite load fault. The THD of the grid current is reduced from 26.7% to 4 % using the above STF-PI control scheme, satisfying the limits prescribed by the IEEE 519 grid code. The THD of the grid current is reduced to 4 % using STF-PI control scheme even under PCC voltage sag and swell conditions. It is observed that, with a fixed cut-off frequency of STF, the THD of the grid current varies in real time as grid frequency varies. In order to further reduce the THD and reduce the THD variation, Extended Kalman Filtering (EKF) and Iterated EKF (IEKF) algorithms are employed for grid synchronization of a PV system. EKF and IEKF are used to estimate the fundamental sinusoidal component of the PCC voltage. IEKF uses an iterative loop to reduce the mean square error and increases the convergence speed of the grid current. From the simulation results it is observed that the grid current reaches the steady state faster using IEKF-PI control scheme than using EKF-PI and STF-PI control schemes. The THD of the grid current in real-time is reduced to the lowest value of 3.5% using the proposed IEKF-PI control scheme than the corresponding values of 3.6% and 4% respectively yielded in case of EKF-PI and STF-PI control schemes. Even by changing the grid frequency, the grid current is maintained sinusoidal using IEKF-PI control scheme. THD variation is minimized using IEKF and EKF-PI control schemes than STF-PI control scheme. As IEKF uses the Jacobin matrix for linearization, the estimation accuracy is limited to first order approximation of the Taylor series. Unscented transformation is a nonlinear transformation, which propagates the mean and covariance through a nonlinear function. A set of sigma points is chosen to preserve the nonlinear nature of the system. Firstly, an Unscented Kalman (UKF) is proposed to further reduce the THD of the grid current and reduce the THD variation. In UKF, the sigma points are determined by finding the square root of the error covariance, obtained using Cholesky decomposition. In order to apply Cholesky decomposition, the error covariance matrix must be positive semi definite. The loss of the positive definiteness may result in stopping the UKF to run continuously or even cause divergence. To resolve the difficulties encountered in UKF, a Square Root Cubature Kalman Filter (SRCKF)-PI grid synchronization control scheme is proposed. From the obtained results, it is observed that the variation in THD of the grid current is minimized by both UKF-PI and SRCKF-PI control schemes as compared to IEKF-PI control scheme. The THD of the grid current is reduced to a lowest value to 3.2 % using SRCKF-PI control scheme than the corresponding values of 3.3% yielded by UKF-PI control scheme. Form the obtained results with all the proposed control schemes for grid synchronization of the PV system, it is observed that these are able to maintain the grid codes by reducing the THD below 5%. However, the SRCKF algorithm essentially transmits the square root factors of the predictive and posterior error covariance in order to eliminate the square root operation thus providing the best convergence speed which minimizes the settling time. The estimation of the fundamental component of the PCC voltage using the cubature points in SRCKF algorithm provides increased estimation accuracy. As a result, the THD of the grid current is thus minimized to a value of 3.2 % using SRCKF-PI control scheme. It is thus concluded that amongst all the proposed controllers, SRCKF-PI control scheme exhibits the superior grid synchronization control performance with power quality disturbances.

In view of meeting increasing power demand while minimizing carbon emission, more emphasis is being given to generate the power from renewable energy sources. Due to availability of abundant solar radiation, and low operational cost, the installation of PV based renewable power generation is increasing rapidly as compared to other renewable sources. The PV power generation can be operated either in standalone mode or grid connected mode. The control of grid connected PV power generation is challenging due to intermittent solar irradiance, and nonlinear environment dependent characteristics of PV source. The maximum power of a PV source depends upon the environmental parameters such as ambient temperature and irradiance. A Maximum Power Point Tracking (MPPT) algorithm is employed in PV control system to extract the maximum power from solar PV panels. The MPPT algorithm generates the reference PV voltage for PVVC. For single stage Grid Connected PV System (GCPVS), a PV Voltage Controller (PVVC) is employed to track the reference PV voltage, and simultaneously generates the reference grid current. Further, Grid Current Controller (GCC) tracks that reference grid current by controlling the switching of the inverter. To reduce the PV voltage ripple in single-stage GCPVS, DC-link capacitor is connected at the input of inverter. Also, coupling filters (such as Resistive Inductive (RL) filter) are used at the output of inverter to reduce the switching ripple in inverter output current. The performances of the PVVC and GCC depend upon the parameters of PV module, DC-link capacitor and RL filter. The internal resistance of PV module varies with its operating point resulting uncertainties in PV side. The DC-link capacitor varies due to aging. Coupling filter impedance varies with age, temperature and operating conditions. Further, grid current quality at low irradiance is an integral issue of GCPVS as all the passive components are designed at nominal power rating. To handle parametric uncertainties and intermittency in irradiance, it is necessary to design efficient adaptive controllers for GCPVS. The thesis focusses on design, development, and practical realization of different adaptive control schemes for achieving effective grid integration of single-stage three phase GCPVS. The thesis first develops an aging linked model of PV model by considering aging in PV parameters. Subsequently, a Quadrature Axis Small Signal Model (QASSM) of Grid Connected Inverter (GCI) with DC battery by considering the internal resistances, such as Equivalent Series Resistance (ESR) of DC link capacitor, internal resistance of PV cell, and internal resistance of coupling filter, is developed. This model is used to analyze the eigenvalues of the GCI. Subsequently, a QASSM of GCPVS is developed by considering GCI with PV source. From the eigenvalue analysis of the GCPVS , it is observed that internal resistance of the PV causes instability in GCPVS. Then the performances of GCPVS are evaluated at different aging periods. From this performance analysis, it is observed that PV voltage ripple, MPPT tracking efficiency and THD of grid current are deteriorated with increase in aging of GCPVS. Subsequently, the thesis develops different adaptive control schemes for GCPVS to handle the parametric uncertainties in GCPVS. First, a real-time parameter estimation based adaptive controller scheme, called as Self-tuning Sinusoidal Recursive Controller (STSRC), for GCPVS has been developed to handle the parametric uncertainties. The STSRC scheme employed an Improved Linear Sinusoidal Tracer (ILST) based Recursive Least Square (RLS) estimation called as IRLS. The IRLS estimates the GCPVS parameters effectively under distorted grid voltage profiles, and under low speed sampled data. The STSRC employed for both PVVC and GCCs. Efficacies of the proposed STSRC scheme are compared with Proportional Integral (PI) controller, Integral Sliding Mode Controller (ISMC) and Robust Nonlinear Adaptive Backsteeping Controller (RNBC). The comparison envisages that STSRC provides improved performance of GCPVS in terms of achieving low PV voltage ripple and low grid current THD. Then, a Lyapunov Based adaptive Voltage Controller (LBAC) is developed to control the PV voltage. The Total Harmonics Distortion (THD) of grid current increases at low irradiation. The THD of grid current not only depends upon the GCC but also depends upon the accurate tracking of PV voltage. Oscillation in PV voltage causes the distortion in grid current. This further degrades the grid power quality. Thus, tracking performance of PVVC plays an important role in better power extraction and in overall grid power quality. The LBAC is designed to provides critically damped PV voltage tracking with desired settling time despite the different disturbances in GCPVS. Efficacies of the proposed LBAC are compared with PI controller and RNBC. The comparison envisages that LBAC provides smooth critically damped PV voltage tracking with low voltage ripple as compared to PI controller and RNBC. The improved PV voltage tracking, yielded by LBAC, improves the THD of grid current in both high and low irradiance as compared to PI controller and RNBC. Finally, a cascaded Model Reference Adaptive Controller (MRAC) scheme is developed for GCPVS to handle the parametric uncertainties and disturbances. Apart from uncertainties, measurement noise affects the performances of the controller in GCPVS. However, use of additional filtering of feedback signals reduces the stability margins of controller. A cascaded MRACs are designed for both PVVC and GCC to achieve improved performances even under measurement noise. The proposed control scheme comprises of a reference model, and a Lyapunov based parameter adaptation scheme which provides the nominal tracking performance despite uncertainties in the GCPVS dynamics. Two separate reference models are chosen respectively for PVVC and GCC to define the critically damped desired tracking characteristics. The efficacies of the designed MRAC scheme are compared with PI controller, RNBC, LBAC and ISMC. Due to cascaded MRAC, the designed MRAC scheme is more noise resistant as compared to other controllers. Further, the MRAC scheme provides critically damped PV voltage response with reduced PV voltage ripple, and low grid current THD as compared to PI controller, ISMC, RNBC and LBAC. All the adaptive control schemes are first verified through simulation studies in MATLAB/SIMULINK environment. Then, efficacies of the different proposed adaptive control schemes are verified through real-time implementation using the 2.25 kW GCPVS prototype, developed in our laboratory. From the comparative analysis, it is observed that both LBAC and MRAC schemes exhibit critically damped PV voltage response with less ripple, and less grid current THD. However, MRAC scheme provides improved performance in robust PV voltage tracking with reduced grid current THD under the measurement noise as compared to PI controller, ISMC, RNBC and LBAC.

碩士<br>國立成功大學<br>電機工程學系專班<br>98<br>The design and implementation of grid-connected type inverter for tidal current power generation system is presented in this thesis. The output voltage would be stable in the default variation of input voltage. Because the input voltage will be varied in certain range, so a control procedure is made to reduce the influence to output voltage. Under stand-alone mode, the voltage feedback control is used to adjust the duty of pulse-width modulation and maintain output voltage in the default range. Under grid-connected mode, the current feedback control is used to limit output current for the purpose of output power control. Finally, the experimental result and PSIM simulation are presented to verify the control theorem and design procedure of inverter, and efficiency of inverter could be more the 91% under stand-alone mode.

碩士<br>國立中正大學<br>電機工程研究所<br>107<br>This thesis uses fuzzy control to design a grid-connected solar power optimized management system. This grid-connected solar power optimized management system is divided into renewable energy part, load part, grid part, energy storage part and energy management part. The renewable energy part includes solar panels and a maximum power tracker. The solar panels are operated at the maximum power point through perturb and observe method. The load part is a DC load that is connected to the DC bus. The grid part buys and sells power to the grid through a single-phase bidirectional inverter which can also stabilize the DC bus voltage. The energy storage part contains a lithium-iron battery and a bidirectional converter which performs charging and discharging through perturb method. The energy management part is used to decide the system buys and sells power or charging and discharging based on the power required by the load, the power of the battery, the power of solar power generation, and the state of charge of the lithium-iron battery, and is implemented by a microprocessor. This thesis uses genetic algorithm to do optimized design of fuzzy controller. Use reproduction, crossover, mutation and elitism strategy in genetic algorithm to search gains of input variables and output variables of the fuzzy controller amd make the system response best. Finally, computer simulations and experimental results demonstrate that the energy management designed in this thesis is feasible and effective for the grid-connected solar power generation optimized management system.

As we know unconventional resources are most,used to resources in all over the world. These resources include coal, natural oil, fossil fuels, etc. these all unconventional resources are in the verge of exhaust level.Therefore,to fulfill all the load demand,we have to think for the different alternative solution. Renewable resources or we can say that conventional resources are the incredible match for the same, it includes several conventional resources such as solar, wind, tidal, geothermal etc. in our setup, surplus energy generated by the panel can be store in BSS or either be sold back to utility grid to prevent from energy loss at the same time our load demand must be fulfill in all condition. In this setup, our first priority is to fulfill the requirement of the load demand, and if surplus energy is there then this whole surplus energy we have to use for BSS or to make money from the electricity board by providing the excess power to utility grid. On the other hand, our second task is, energy give to grid when there is having high price, similarly energy take from the grid when price related to energy is low, but in all condition our first priority is to keep the load demand full.For that we have to choose the BSS such that it can provide energy whenever there is requirement,doesn’t matter for making money or to provide uninterrupted power supply to load. At the same time also,we have to keep minimum cost associated with BSS.

High output electrical energy is obtained from photovoltaic (PV) systems subject to high irradiance. However, at high irradiance, the efficiency of PV systems drops due to increase of the temperature of the systems. In order to improve the efficiency of photovoltaic systems, much effort has been spent on developing hybrid photovoltaic thermal (PVT) systems using water as a coolant to withdraw heat from solar modules. This research is focused on the study of the behavior of hybrid PVT collectors using rectangular channel profiles which provide a large surface for heat exchange between PV panels and thermal collectors unlike the circular channel profile used in conventional PV systems. In hybrid PVT systems, coolant water circulates in a closed circuit by means of the thermosyphon phenomenon and the heat from this water is extracted from a storage tank and can be used in hot water systems instead of an electric geyser. Numerical models of water velocity in channels due to the thermosyphon phenomenon and the temperature of solar modules was developed and a system was designed for modest Durban household demand. A simulation was run for specific summer and winter days comparing a conventional PV system and a hybrid PVT system. The results were very encouraging, and demonstrated that the equipment is capable of extending the PVT application potential in the domestic sector where more than 40% of electricity cost is heating water.<br>Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2012.

In electric distribution system Power control of a hybrid generation system that is wind and solar system for interconnection operation is presented in this paper. Renewable resources offer clean, abundant energy. As the power demand increases power failure also increases so the renewable energy can be used to provide constant loads. To converting the basic circuit equation of solar cell into simplified form a model developed including the effects of changing solar irradiation and temperature. This paper consists of PMSG as a wind generator, solar array, dc-dc converter and grid interface inverter. Maximum power point tracker (MPPT) control is essential to ensure the output of photovoltaic power generation system at the maximum power output as possible. There are many MPPT technique. In this paper perturbation & observation (P&O) method and incremental conductance (IncCond) method are used and simulated in Mat lab/Simulink. P&O method is simple in operation and hard ware requirement is less, but it has some power loss. IncCond method has more precise control and faster response, but it has higher hardware requirement. in order to achieve maximum efficiency of photovoltaic power generation, an efficient control methods that is (P&O) should be chosen. The voltage source inverter interface with grid transfers the energy drawn from the wind turbine and PV array to the grid by keeping common dc voltage constant. The simulation results show the control performance and dynamic behavior of the hybrid wind-PV system.