9 research outputs found

    Advances in Supercapacitor Technology and Applications

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    Energy storage is a key topic for research, industry, and business, which is gaining increasing interest. Any available energy-storage technology (batteries, fuel cells, flywheels, and so on) can cover a limited part of the power-energy plane and is characterized by some inherent drawback. Supercapacitors (also known as ultracapacitors, electrochemical capacitors, pseudocapacitors, or double-layer capacitors) feature exceptional capacitance values, creating new scenarios and opportunities in both research and industrial applications, partly because the related market is relatively recent. In practice, supercapacitors can offer a trade-off between the high specific energy of batteries and the high specific power of traditional capacitors. Developments in supercapacitor technology and supporting electronics, combined with reductions in costs, may revolutionize everything from large power systems to consumer electronics. The potential benefits of supercapacitors move from the progresses in the technological processes but can be effective by the availability of the proper tools for testing, modeling, diagnosis, sizing, management and technical-economic analyses. This book collects some of the latest developments in the field of supercapacitors, ranging from new materials to practical applications, such as energy storage, uninterruptible power supplies, smart grids, electrical vehicles, advanced transportation and renewable sources

    PV System Design and Performance

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    Photovoltaic solar energy technology (PV) has been developing rapidly in the past decades, leading to a multi-billion-dollar global market. It is of paramount importance that PV systems function properly, which requires the generation of expected energy both for small-scale systems that consist of a few solar modules and for very large-scale systems containing millions of modules. This book increases the understanding of the issues relevant to PV system design and correlated performance; moreover, it contains research from scholars across the globe in the fields of data analysis and data mapping for the optimal performance of PV systems, faults analysis, various causes for energy loss, and design and integration issues. The chapters in this book demonstrate the importance of designing and properly monitoring photovoltaic systems in the field in order to ensure continued good performance

    Single and Dual DC Buses Nanogrids with Decentralized Control

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    The existing power system is based on a centralized approach. Large power plants produce AC electricity that is transmitted over long distances for distribution to the consumers. To meet a higher load demand, the entire system has to be upgraded, which is costly and acquiring rights of way can take decades. Another approach, called distributed generation, is the deployment of smaller generation units closer to the users. This can be based on renewable energy sources (RESs) that mitigate the environmental impact of power generation. However, the stochastic nature of RESs can lead to power quality issues in the distribution system. This can be addressed with the addition of energy storage units and controlling the system as a cluster or a microgrid. This concept can be extended for small buildings and residences, called nanogrids, offering a means for the realization of net-zero energy homes (NZEHs). These can be AC or DC, but the latter looks more promising since most RESs suitable for NZEHs provide a DC output and DC-DC interfaces tend to present a higher efficiency than their DC-AC counterparts. DC nanogrids also favor the integration of electric vehicles (EVs) and are compatible with modern, electronically controlled, appliances. To date, there are no standards concerning the number of buses and voltage levels of DC nanogrids. The control structure of DC micro and nanogrids, can be based on a hierarchical approach where the primary control level relies on locally measured quantities. This allows a decentralized operation of interfaces using the DC bus voltage as a communication means and V vs. I curves, with specific parameters, for coordination of operation, a method known as DC bus signaling (DBS). There are several aspects of DC nanogrids for NZEHs that deserve further investigation and are addressed in this thesis. These include a means for a smooth transition of the modes of operation of RESs, such as photovoltaic (PV), which employ V vs. I curves with three regions. This can minimize the DC bus voltage variations as the system adjusts to variations in load demand and power generation due to varying solar irradiances. The use of supercapacitors (SCs) along with batteries in hybrid energy storage systems (HESSs) can mitigate the impact of high and fast current variations on the losses and lifetime of the battery units. However, by controlling the HESS as a single unit, one forfeits the potential contribution of the SC and its high power capabilities to dynamically improve voltage regulation in a DC nanogrid. This can be achieved by controlling the SC and battery independently without sacrificing the support the battery receives from the SC. Finally, although dual DC bus nanogrids have been advocated by industry associations, they are conceived to have power sources and storage units only in the high voltage (HV) bus. The low voltage (LV) bus is fed through a unidirectional converter, making it vulnerable to a fault in a single element. This thesis proposes the deployment of generation and storage in both buses, with a bidirectional interface for optimizing power balance in both buses. The techniques proposed in this thesis are verified by means of simulation or experimental results

    Synchronization of Grid Connected PV System Using PI Controller

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    Grid connected solar system consists ofconverters Circuits are organized in two differentways one is DC/DC boosters and another is PWMInverter. This combination results decrement ofQuality and efficiency of electric power, this paperreflects the use of a single phase 13- level photovoltaic (PV) inverter in solar system connected togrid with a pulse width-modulated (PWM) controlsystem. The rapid variations in radiation can beremunerated by Digital proportional-integralcontroller. This inverter gives a less harmonicdistortion and significant power factor over fivelevel inverters and is examined and experimentedthrough simulation

    Failure prediction of ultra capacitor stack using fuzzy inference system

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    The failure of the ultracapacitor was significantly accelerated by elevated temperature or increased voltage. Because of the capacitance difference between the capacitor cells, after a number of deep charging/discharging cycles, the voltage difference between cells will be enlarged. This will accelerate the aging of the weak ultracapacitors and affect the output power. So, to improve stack reliability, a correct and timely failure prediction is essential. Based on diverse faults, a fuzzy rule-based inference system, which could approximate human reasoning, was considered. With this method we can reduce uncertainty, inconvenience and inefficiency resulting from the inherent factors. The simulate results under industrial application conditions are given to verify the method

    Concepção, análise e implementação de uma microrrede interligada à rede elétrica para alimentação ininterrupta de cargas CC a partir de fontes renováveis

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    Tese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Elétrica, Florianópolis, 2013.Nesta tese apresentam-se os procedimentos envolvidos na implementação prática de uma microrrede composta por um arranjo fotovoltaico de 1 kW,um aerogerador de 1 kW, uma célula a combustível de 1,2 kW e um banco de supercapacitores de 31,5 F/ 250V. O sistema, concebido de maneira apermitir o suprimento ininterrupto de energia a uma carga crítica cc, é capazde operar em dois modos distintos: interligado à rede ou isolado. Quandooperando no modo interligado, a rede elétrica da concessionária se fazpresente, absorvendo a energia excedente nos momentos em que a geraçãorenovável superar a demanda, ou complementando-a, caso contrário.Ressalta-se que neste modo de operação a célula a combustível, por ser afonte cujo custo de despacho é o mais elevado (cenário brasileiro), jamais éacionada. Em contrapartida, no modo isolado, devido à ausência da rede, aoperação do sistema fica condicionada à potência das fontes renováveis,sendo a célula a combustível acionada apenas em casos críticos, de forma aassegurar a continuidade de energia à carga e a autonomia do sistema,definida, por sua vez, pelo montante de hidrogênio estocado. Além daanálise dos resultados inerentes a oito distintos cenários, oriundos dasvariadas combinações de geração e demanda, o trabalho apresentametodologias de escolha, projeto e dimensionamento e controle dosconversores estáticos que compõem cada um dos estágios de processamentode energia, aprofunda a discussão a respeito da geração descentralizada,propõe uma estratégia de controle do fluxo de potência entre as fontesrenováveis, a rede elétrica e a carga crítica e aborda os efeitos relacionadosao emprego de bancos de supercapacitores na estabilidade de sistemascompostos por múltiplas fontes. Por fim, resultados de simulação eexperimentação são apresentados como forma de validar os conceitos. This work presents the procedures related to the practical implementation of a microgrid composed of 1 kW photovoltaic array, a 1 kW wind generator, a 1.2 kW fuel cell and a supercapacitor bank of 31,5 F/ 250V. The system, designed for allowing the uninterrupted maintenance of critical dc load, is able to operate in two distinct modes: grid-connected or stand alone. When in grid-connected mode, the main grid absorbs the extra generated power or complementing it, depending on the load requirements. In this mode, the fuel cell is never active due its high cost (Brazilian scenario). On the other hand, in standalone mode, the load demand is exclusively supplied by the renewable energy sources. However, the fuel cell is started only if there is not enough power provided by the photovoltaic array and wind turbine generator. Thus, the system autonomy is limited to the amount of stored hydrogen. Besides the analysis concerning the results from eight distinct scenarios, obtained by the combination of power generation and load demand, this work presents the methodologies related to the choice, design, size, and control of the employed power converters, discusses about the concept of decentralized generation, proposes a strategy to control the power flow among the renewable energy source, the main grid and the critical load and describes the effects of supercapacitor banks employment on the microgrid stability. Finally, results from simulation and experimentation are used in order to validate the concepts

    Development of a Supercapacitor based Surge Resistant Uninterruptible Power Supply

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    Uninterruptible Power Supplies (UPSs) provide short-term power back-up to sensitive electronic and electrical equipments, where an unexpected power loss could lead to undesirable outcomes. They usually bridge the connected equipment between the utility mains power and other long term back-up power systems like generators. A UPS also provides a “clean” source of power, meaning they filter the connected equipment from distortions in electrical parameters of the mains power like noise, harmonics, surges, sags and spikes. A surge resistant UPS or SRUPS is one that has the capability to withstand surges, which are momentary or sustained increases in the mains voltage, and react quickly enough to offer protection to the connected equipment from the same. Usually UPSs run off battery power when the utility mains power is absent. But the SRUPS developed in this design project uses super capacitors instead of battery packs. The reason for this is that the high energy-densities and medium power-densities offered by super capacitors allow for it to serve two purposes. One is to provide the DC power to operate the UPS in the absence of mains power, as an alternative to batteries. Secondly, super capacitors can withstand heavy momentary high current/voltage surges due to its high energy-density characteristics. Also as the life-time of super capacitors is much higher than that of conventional batteries and as they do not need regular topping-up or inspection, the end result is a truly maintenance-free UPS. Most commercial UPSs do not have inherent surge protection capabilities. The UPS is one entity while a discrete surge protection module is inserted between the utility mains and the UPS to provide for transient surge suppression. In the proposed SRUPS, the super capacitor, because of their inherent capability to absorb transient surges, forms a protective front end to the actual UPS rather than needing to have the involvement of discrete protection devices

    Sensitivity Study of the Dynamics of Three-Phase Photovoltaic Inverters With an LCL Grid Filter

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    [EN] An accurate small-signal model of three-phase photovoltaic (PV) inverters with a high-order grid filter is derived in this paper. The proposed model takes into account the influence of both the inverter operating point and the PV panel characteristics on the inverter dynamic response. A sensitivity study of the control loops to variations of the dc voltage, PV panel transconductance, supplied power, and grid inductance is performed using the proposed small-signal model. Analytical and experimental results carried out on a 100-kW PV inverter are presented.Figueres Amorós, E.; Garcerá, G.; Sandia Paredes, J.; González Espín, FJ.; Calvo Rubio, J. (2009). Sensitivity Study of the Dynamics of Three-Phase Photovoltaic Inverters With an LCL Grid Filter. IEEE Transactions on Industrial Electronics. 56(3):706-717. doi:10.1109/TIE.2008.2010175S70671756
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