955 resultados para debt contracts


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Demand response can play a very relevant role in the context of power systems with an intensive use of distributed energy resources, from which renewable intermittent sources are a significant part. More active consumers participation can help improving the system reliability and decrease or defer the required investments. Demand response adequate use and management is even more important in competitive electricity markets. However, experience shows difficulties to make demand response be adequately used in this context, showing the need of research work in this area. The most important difficulties seem to be caused by inadequate business models and by inadequate demand response programs management. This paper contributes to developing methodologies and a computational infrastructure able to provide the involved players with adequate decision support on demand response programs and contracts design and use. The presented work uses DemSi, a demand response simulator that has been developed by the authors to simulate demand response actions and programs, which includes realistic power system simulation. It includes an optimization module for the application of demand response programs and contracts using deterministic and metaheuristic approaches. The proposed methodology is an important improvement in the simulator while providing adequate tools for demand response programs adoption by the involved players. A machine learning method based on clustering and classification techniques, resulting in a rule base concerning DR programs and contracts use, is also used. A case study concerning the use of demand response in an incident situation is presented.

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Dissertação de Mestrado Apresentado ao Instituto de Contabilidade e Administração do Porto para a obtenção do grau de Mestre em Empreendedorismo e Internacionalização, sob orientação do Mestre Adalmiro Álvaro Malheiro de Castro Andrade Pereira

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Dissertação de Mestrado apresentada ao Instituto de Contabilidade e Administração do Porto para a obtenção do grau de Mestre em Contabilidade e Finanças, sob orientação da Professora Doutora Cláudia Maria Ferreira Pereira

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Dissertação de Mestrado apresentada ao Instituto de Contabilidade e Administração do Porto para a obtenção do grau de Mestre em Contabilidade e Finanças, sob orientação de Professora Doutora Ana Maria Alves Bandeira, e Professora Doutora Deolinda Maria Moreira Aparício Meira

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Paper developed for the unit “Innovation Economics and Management” of the PhD programme in Technology Assessment at the Universidade Nova de Lisboa in 2009-10 under the supervision of Prof. Maria Luísa Ferreira

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apresentado ao Instituto de Contabilidade e Administração do Porto para a Dissertação de Mestrado para obtenção do grau de Mestre em Contabilidade e Finanças sob orientação do Mestre Adalmiro Álvaro Malheiro de Castro Andrade Pereira

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Dissertação de Mestrado apresentada ao Instituto de Contabilidade e Administração do Porto para a obtenção do grau de Mestre em Contabilidade e Finanças, sob orientação do Dr. Carlos Mota

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Dissertação de Mestrado apresentado ao Instituto Superior de Contabilidade e Administração do Porto para obtenção de grau de Mestre em Empreendedorismo e Internacionalização, sob a orientação da Professora Doutora Manuela Maria Ribeiro da Silva Patrício

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Dissertação de Mestrado em Solicitadoria

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Dissertação de Mestrado em Solicitadoria

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Este trabalho tem como objetivo verificar os determinantes da estrutura de capital das empresas exportadoras portuguesas, comparando, sempre que possível, os resultados obtidos com outros trabalhos já desenvolvidos sobre o tema. Aplicando o Modelo dos Efeitos Fixos (MEF) a uma amostra de 7.001 empresas no período 2007-2013, concluiu-se que os determinantes com maior significância no nível de endividamento empresarial são: a rendibilidade, a dimensão, o crescimento e ainda os outros benefícos fiscais. Em relação às exportações, verificou-se através da variável dummy “exportar”, que o facto de as empresas terem exportações superiores a 10% das vendas totais, têm uma relação positiva com o endividamento de médio e longo prazo mas negativa com o endividamento de curto prazo. Perante estes resultados admitimos que as empresas exportadoras ao diversificarem (na fase inicial) o seu portfólio de clientes conseguem maiores níveis de cash-flows, o que as dispensa de algum endividamento de curto prazo, mas no médio e longo prazo as necessidades de investimento para fazer face a mercados muito competitivos está associada a um maior nível de endividamento. Relativamente à importância explicativa das variáveis “peso das vendas para o mercado comunitário” e “peso das vendas para o mercado extra comunitário”, curiosamente, apresentam resultados diferentes; o peso das vendas para o mercado extra comunitário não revela relação significativa com o endividamento mas já o peso das vendas para o mercado comunitário tem uma relação positiva com endividamento a curto prazo e negativa com o endividamento de médio e longo prazo.

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Dissertação de Mestrado em Solicitadoria

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The integration of growing amounts of distributed generation in power systems, namely at distribution networks level, has been fostered by energy policies in several countries around the world, including in Europe. This intensive integration of distributed, non-dispatchable, and natural sources based generation (including wind power) has caused several changes in the operation and planning of power systems and of electricity markets. Sometimes the available non-dispatchable generation is higher than the demand. This generation must be used; otherwise it is wasted if not stored or used to supply additional demand. New policies and market rules, as well as new players, are needed in order to competitively integrate all the resources. The methodology proposed in this paper aims at the maximization of the social welfare in a distribution network operated by a virtual power player that aggregates and manages the available energy resources. When facing a situation of excessive non-dispatchable generation, including wind power, real time pricing is applied in order to induce the increase of consumption so that wind curtailment is minimized. This method is especially useful when actual and day-ahead resources forecast differ significantly. The distribution network characteristics and concerns are addressed by including the network constraints in the optimization model. The proposed methodology has been implemented in GAMS optimization tool and its application is illustrated in this paper using a real 937-bus distribution network with 20.310 consumers and 548 distributed generators, some of them non-dispatchable and with must take contracts. The implemented scenario corresponds to a real day in Portuguese power system.

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The intensive use of distributed generation based on renewable resources increases the complexity of power systems management, particularly the short-term scheduling. Demand response, storage units and electric and plug-in hybrid vehicles also pose new challenges to the short-term scheduling. However, these distributed energy resources can contribute significantly to turn the shortterm scheduling more efficient and effective improving the power system reliability. This paper proposes a short-term scheduling methodology based on two distinct time horizons: hour-ahead scheduling, and real-time scheduling considering the point of view of one aggregator agent. In each scheduling process, it is necessary to update the generation and consumption operation, and the storage and electric vehicles status. Besides the new operation condition, more accurate forecast values of wind generation and consumption are available, for the resulting of short-term and very short-term methods. In this paper, the aggregator has the main goal of maximizing his profits while, fulfilling the established contracts with the aggregated and external players.

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Energy resource scheduling is becoming increasingly important, such as the use of more distributed generators and electric vehicles connected to the distribution network. This paper proposes a methodology to be used by Virtual Power Players (VPPs), regarding the energy resource scheduling in smart grids and considering day-ahead, hour-ahead and realtime time horizons. This method considers that energy resources are managed by a VPP which establishes contracts with their owners. The full AC power flow calculation included in the model takes into account network constraints. In this paper, distribution function errors are used to simulate variations between time horizons, and to measure the performance of the proposed methodology. A 33-bus distribution network with large number of distributed resources is used.