Localização e preço de contrato ótimo da geração distribuída em sistemas de distribuição radiais de energia elétrica

Pós-graduação em Engenharia Elétrica - FEIS

Estudo sobre o panorama da energia elétrica no Brasil e tendências futuras

Pós-graduação em Engenharia Elétrica - FEB

Making the case for grid-connected photovoltaics in Brazil

In the developed world, grid-connected photovoltaics (PVs) are the fastest-growing segment of the energy market. From 1999 to 2009, this industry had a 42% compound annual growth-rate. From 2009 to 2013, it is expected to grow to 45%, and in 2013 the achievement of grid parity - when the cost of solar electricity becomes competitive with conventional retail (including taxes and charges) grid-supplied electricity - is expected in many places worldwide. Grid-connected PV is usually perceived as an energy technology for developed countries, whereas isolated, stand-alone PV is considered as more suited for applications in developing nations, where so many individuals still lack access to electricity. This rationale is based on the still high costs of PV when compared with conventional electricity. We make the case for grid-connected PV generation in Brazil, showing that with the declining costs of PV and the rising prices of conventional electricity, urban populations in Brazil will also enjoy grid parity in the present decade. We argue that governments in developing nations should act promptly and establish the mandates and necessary conditions for their energy industry to accumulate experience in grid-connected PV, and make the most of this benign technology in the near future. (C) 2010 Elsevier Ltd. All rights reserved.

Development and characterization of a distributed measurement system for the evaluation of voltage quality in electric power networks

The research activity carried out during the PhD course in Electrical Engineering belongs to the branch of electric and electronic measurements. The main subject of the present thesis is a distributed measurement system to be installed in Medium Voltage power networks, as well as the method developed to analyze data acquired by the measurement system itself and to monitor power quality. In chapter 2 the increasing interest towards power quality in electrical systems is illustrated, by reporting the international research activity inherent to the problem and the relevant standards and guidelines emitted. The aspect of the quality of voltage provided by utilities and influenced by customers in the various points of a network came out only in recent years, in particular as a consequence of the energy market liberalization. Usually, the concept of quality of the delivered energy has been associated mostly to its continuity. Hence the reliability was the main characteristic to be ensured for power systems. Nowadays, the number and duration of interruptions are the “quality indicators” commonly perceived by most customers; for this reason, a short section is dedicated also to network reliability and its regulation. In this contest it should be noted that although the measurement system developed during the research activity belongs to the field of power quality evaluation systems, the information registered in real time by its remote stations can be used to improve the system reliability too. Given the vast scenario of power quality degrading phenomena that usually can occur in distribution networks, the study has been focused on electromagnetic transients affecting line voltages. The outcome of such a study has been the design and realization of a distributed measurement system which continuously monitor the phase signals in different points of a network, detect the occurrence of transients superposed to the fundamental steady state component and register the time of occurrence of such events. The data set is finally used to locate the source of the transient disturbance propagating along the network lines. Most of the oscillatory transients affecting line voltages are due to faults occurring in any point of the distribution system and have to be seen before protection equipment intervention. An important conclusion is that the method can improve the monitored network reliability, since the knowledge of the location of a fault allows the energy manager to reduce as much as possible both the area of the network to be disconnected for protection purposes and the time spent by technical staff to recover the abnormal condition and/or the damage. The part of the thesis presenting the results of such a study and activity is structured as follows: chapter 3 deals with the propagation of electromagnetic transients in power systems by defining characteristics and causes of the phenomena and briefly reporting the theory and approaches used to study transients propagation. Then the state of the art concerning methods to detect and locate faults in distribution networks is presented. Finally the attention is paid on the particular technique adopted for the same purpose during the thesis, and the methods developed on the basis of such approach. Chapter 4 reports the configuration of the distribution networks on which the fault location method has been applied by means of simulations as well as the results obtained case by case. In this way the performance featured by the location procedure firstly in ideal then in realistic operating conditions are tested. In chapter 5 the measurement system designed to implement the transients detection and fault location method is presented. The hardware belonging to the measurement chain of every acquisition channel in remote stations is described. Then, the global measurement system is characterized by considering the non ideal aspects of each device that can concur to the final combined uncertainty on the estimated position of the fault in the network under test. Finally, such parameter is computed according to the Guide to the Expression of Uncertainty in Measurements, by means of a numeric procedure. In the last chapter a device is described that has been designed and realized during the PhD activity aiming at substituting the commercial capacitive voltage divider belonging to the conditioning block of the measurement chain. Such a study has been carried out aiming at providing an alternative to the used transducer that could feature equivalent performance and lower cost. In this way, the economical impact of the investment associated to the whole measurement system would be significantly reduced, making the method application much more feasible.

La Previsione dei Consumi Elettrici nel Mercato Energetico Italiano : un nuovo modello empirico con struttura triangolare

L'obiettivo principale della tesi è lo sviluppo di un modello empirico previsivo di breve periodo che sia in grado di offrire previsioni precise ed affidabili dei consumi di energia elettrica su base oraria del mercato italiano. Questo modello riassume le conoscenze acquisite e l'esperienza fatta durante la mia attuale attività lavorativa presso il Romagna Energia S.C.p.A., uno dei maggiori player italiani del mercato energetico. Durante l'ultimo ventennio vi sono stati drastici cambiamenti alla struttura del mercato elettrico in tutto il mondo. Nella maggior parte dei paesi industrializzati il settore dell'energia elettrica ha modificato la sua originale conformazione di monopolio in mercato competitivo liberalizzato, dove i consumatori hanno la libertà di scegliere il proprio fornitore. La modellazione e la previsione della serie storica dei consumi di energia elettrica hanno quindi assunto un ruolo molto importante nel mercato, sia per i policy makers che per gli operatori. Basandosi sulla letteratura già esistente, sfruttando le conoscenze acquisite 'sul campo' ed alcune intuizioni, si è analizzata e sviluppata una struttura modellistica di tipo triangolare, del tutto innovativa in questo ambito di ricerca, suggerita proprio dal meccanismo fisico attraverso il quale l'energia elettrica viene prodotta e consumata nell'arco delle 24 ore. Questo schema triangolare può essere visto come un particolare modello VARMA e possiede una duplice utilità, dal punto di vista interpretativo del fenomeno da una parte, e previsivo dall'altra. Vengono inoltre introdotti nuovi leading indicators legati a fattori meteorologici, con l'intento di migliorare le performance previsive dello stesso. Utilizzando quindi la serie storica dei consumi di energia elettrica italiana, dall'1 Marzo 2010 al 30 Marzo 2012, sono stati stimati i parametri del modello dello schema previsivo proposto e valutati i risultati previsivi per il periodo dall'1 Aprile 2012 al 30 Aprile 2012, confrontandoli con quelli forniti da fonti ufficiali.

Integrating structured and unstructured data in a business-intelligence-system

The recent liberalization of the German energy market has forced the energy industry to develop and install new information systems to support agents on the energy trading floors in their analytical tasks. Besides classical approaches of building a data warehouse giving insight into the time series to understand market and pricing mechanisms, it is crucial to provide a variety of external data from the web. Weather information as well as political news or market rumors are relevant to give the appropriate interpretation to the variables of a volatile energy market. Starting from a multidimensional data model and a collection of buy and sell transactions a data warehouse is built that gives analytical support to the agents. Following the idea of web farming we harvest the web, match the external information sources after a filtering and evaluation process to the data warehouse objects, and present this qualified information on a user interface where market values are correlated with those external sources over the time axis.

A dynamic factor model for mid-term forecasting of wind power generation

The main objective of this paper is the development and application of multivariate time series models for forecasting aggregated wind power production in a country or region. Nowadays, in Spain, Denmark or Germany there is an increasing penetration of this kind of renewable energy, somehow to reduce energy dependence on the exterior, but always linked with the increaseand uncertainty affecting the prices of fossil fuels. The disposal of accurate predictions of wind power generation is a crucial task both for the System Operator as well as for all the agents of the Market. However, the vast majority of works rarely onsider forecasting horizons longer than 48 hours, although they are of interest for the system planning and operation. In this paper we use Dynamic Factor Analysis, adapting and modifying it conveniently, to reach our aim: the computation of accurate forecasts for the aggregated wind power production in a country for a forecasting horizon as long as possible, particularly up to 60 days (2 months). We illustrate this methodology and the results obtained for real data in the leading country in wind power production: Denmark

Integrated plant monitoring to improve plant operation strategy and results

The more and more demanding conditions in the power generation sector requires to apply all the available technologies to optimize processes and reduce costs. An integrated asset management strategy, combining technical analysis and operation and maintenance management can help to improve plant performance, flexibility and reliability. In order to deploy such a model it is necessary to combine plant data and specific equipment condition information, with different systems devoted to analyze performance and equipment condition, and take advantage of the results to support operation and maintenance decisions. This model that has been dealt in certain detail for electricity transmission and distribution networks, is not yet broadly extended in the power generation sector, as proposed in this study for the case of a combined power plant. Its application would turn in direct benefit for the operation and maintenance and for the interaction to the energy market

A integração da indústria de energia elétrica na América do Sul: análise dos modelos técnicos e de regulamentação.

Os recursos energéticos naturais não estão distribuídos uniformemente pelo globo terrestre, e são raros os países que os têm na quantidade e na qualidade que necessitam para atender as suas necessidades. Ante a essa realidade, o comércio de energéticos tem sido a forma principal de acesso dos países que não os dispõem em relação as suas necessidades. Esse comércio, que muitas vezes é regido por tratados ou acordos firmados entre países ou blocos econômicos regionais, diversificou-se, traspassou fronteiras e, atualmente, tornou-se um item significativo nas pautas de exportações de vários países. A evolução desse comércio tem a favor a alternativa de integração por meio de interconexões estratégicas de redes e da constituição de mercados comuns, que viabilizam a exploração do potencial de complementariedade energética de forma mais racional. Diante desse contexto, esta dissertação apresenta um estudo exploratório que avalia o estado da arte da integração energética sul-americana e faz análises dos modelos técnicos, das regulamentações, das regulações regionais e multilaterais estabelecidas pelos blocos econômicos sul-americanos e pela Organização Mundial do Comércio. De forma complementar, o estudo verifica e apresenta os fatores que podem comprometer o avanço e a instituição de um futuro mercado comum de energia no continente, conclui pela viabilidade do prosseguimento de ações em prol da ampliação da integração da indústria de energia elétrica na América do Sul e tece recomendações. Os resultados e as recomendações deste trabalho oferecem um embasamento procedimental para a gestão e a atuação institucional dos envolvidos no processo de integração energética da indústria de energia elétrica da região sul americana.

Formação do preço da energia convencional nas transações entre agentes no mercado de curto prazo brasileiro.

Hoje no mercado brasileiro de eletricidade, o preço da energia convencional é composto pela soma do valor do Preço de Liquidação das Diferenças (PLD) divulgado pela Câmara de Comercialização de Energia Elétrica (CCEE) semanalmente com o valor do Spread negociado bilateralmente no mercado à vista (mercado de curto prazo), resultante do equilíbrio entre oferta e demanda. Em alguns momentos, o valor do Spread chega a representar mais de 100% do custo total da energia. Este trabalho faz uma análise do mercado brasileiro, bem como, de alguns mercados no exterior de energia elétrica e destaca os pontos que tem influência direta, na formação do Spread da energia convencional e como isso afeta a decisão de contratação dos agentes. Além disso, o trabalho busca encontrar correlações entre dados divulgados, como carga e oferta de energia, com o ágio negociado no mercado de curto prazo, buscando entender o real impacto de cada um desses fatores e explicar as grandes variações já observadas. Sugere-se também um modelo de regressão linear múltipla para a projeção de valores do ágio. Para tanto, foram utilizadas informações proveniente de um banco de dados de cotações de negócios efetivamente realizados no curto prazo desde janeiro de 2011 até julho de 2014, bem como informações retiradas da CCEE e Operador Nacional do Sistema (ONS).

Abolishing Oil Indexation in Gas Contracts: Is it the cure-all? CEPS Commentaries, 3 March 2014

Recently, the EU energy debate has been dominated by the discussion on energy prices and the competitiveness of the European industry. According to the latest estimates of the International Energy Agency, gas prices in the US are one-quarter of those in Europe. Moreover, prices of imported gas vary across the EU member states. Some EU policy-makers hope that the completion of the internal energy market and the transition to hub-based pricing will solve these discrepancies. Julian Wieczorkiewicz asks in this Commentary whether the abolition of oil-indexation will constitute a cure-all for the above-mentioned problems.

German companies strengthen their cooperation with Russian gas suppliers. OSW Commentary No. 64, 2011-10-24

Germany’s decision to give up the use of nuclear energy will force it to find a conventional low-carbon energy source as a replacement; in the short term, in addition to coal, this is likely to be gas. Due to their continued high debt and the losses associated with the end of atomic power, German companies will not be able to spend large funds on investing in conventional energy. First of all, they will aim to raise capital and repay their debts. The money for this will come from selling off their less profitable assets; this will include sales on the gas market. This will create opportunities for natural gas exporters and extraction companies such as Gazprom to buy back some of the German companies’ assets (electricity companies, for example). The German companies will probably continue to seek to recover the costs incurred in the investment projects already underway, such as Nord Stream, the importance of which will grow after Russian gas imports increase. At the same time, because of their debts, the German companies will seek to minimise their investment costs by selling some shares on the conventional energy market, to Russian corporations among others; the latter would thus be able to increase their stake in the gas market in both Western (Germany, Great Britain, the Benelux countries) and Central Europe (Poland, the Czech Republic). It is possible that while establishing the details of cooperation between the Russian and German companies, Russia will try to put pressure on Germany to give up competing projects such as Nabucco. However, a well-diversified German energy market should be able to defend itself against attempts to increase German dependence on Russian gas supplies and the dictates of high prices.

Energising the TTIP: Political economy of the trade policy rationale. Paper No. 9 in the CEPS-CTR project “TTIP in the Balance’’and CEPS Special Report No. 113/July 2015

Despite accounting for a significant share of global trade and the resulting interdependencies from it, energy governance remains largely fragmented and there is no global framework or agreement defining the rules of energy trade. This paper, after presenting the main global and regional energy market developments, discusses the opportunities to ‘energise the TTIP’, i.e. to include a chapter dedicated to trade and cooperation in the sphere of energy. The shale revolution in the US, the ever-rising interconnectedness of energy markets (recently proven by the disappearance of the ‘Asian gas premium’) and the EU’s quest to diversify its energy supplies generally sets favourable conditions to reinforce energy relations between the EU and the US. The question, as is often the case, is whether there is sufficient political will to tighten relations in a strategic sphere with connotations for national security and sovereignty.

Rethinking the security of the European Union’s gas supply. Bruegel Policy Contribution, Issue 2016/01 January 2016

Highlights: • The security of the European Union’s gas supplies is crucial to ensuring that supplies to households are not disrupted in freezing winters, that industry can flourish and that the EU cannot be blackmailed in vital foreign policy questions. • Gas supply security should be addressed at EU level because a joint solution would be cheaper, national approaches could undermine the internal energy market and have adverse effects on other countries, and the EU Treaty explicitly calls for energy solidarity. • The current focus on supply diversification and reduction of dependence on imported gas is expensive and does not constitute a systemic response. • Instead of doing everything to reduce gas supplies from key suppliers, gas supply security could more effectively be safeguarded by ensuring that unused alternatives are maintained so that they can be tapped into for an indefinite period in case of supply disruption from a key supplier.This Policy Contribution outlines a market approach that could safeguard gas supply security at very low cost.

Variational inference for Student-t MLP models

This paper presents a novel methodology to infer parameters of probabilistic models whose output noise is a Student-t distribution. The method is an extension of earlier work for models that are linear in parameters to nonlinear multi-layer perceptrons (MLPs). We used an EM algorithm combined with variational approximation, the evidence procedure, and an optimisation algorithm. The technique was tested on two regression applications. The first one is a synthetic dataset and the second is gas forward contract prices data from the UK energy market. The results showed that forecasting accuracy is significantly improved by using Student-t noise models.