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ABSTRACT: In the last decade, distributed generation, with its various technologies, has increased its presence in the energy mix presenting distribution networks with challenges in terms of evaluating the technical impacts that require a wide range of network operational effects to be qualified and quantified. The inherent time-varying behavior of demand and distributed generation (particularly when renewable sources are used), need to be taken into account since considering critical scenarios of loading and generation may mask the impacts. One means of dealing with such complexity is through the use of indices that indicate the benefit or otherwise of connections at a given location and for a given horizon. This paper presents a multiobjective performance index for distribution networks with time-varying distributed generation which consider a number of technical issues. The approach has been applied to a medium voltage distribution network considering hourly demand and wind speeds. Results show that this proposal has a better response to the natural behavior of loads and generation than solely considering a single operation scenario.
IEEE Transactions on Power Delivery 05/2008; · 1.35 Impact Factor
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ABSTRACT: With high levels of variable renewable generation in distribution or transmission systems, the application of demand and generation time series to power flow analysis can be advantageous. Demand data are often available from historic measurements, while renewable generation such as wind turbine output may be recorded or can be derived from resource measurements over the corresponding period of time. Power flow solutions with hourly time steps over a year or more can then be used to produce load duration curves for system components. This paper shows, by example, how utilities can use the method to determine overload conditions or to specify non-firm connection agreements for new generators.
IEEE Transactions on Power Systems 09/2007; · 2.68 Impact Factor
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ABSTRACT: Regulators are aiming to incentivize developers and Distribution Network Operators to connect distributed generation (DG) to improve network environmental performance and efficiency. A key question is whether these incentives will encourage both parties to connect DG. Here, multiobjective optimal power flow is used to simulate how the parties' incentives affect their choice of DG capacity within the limits of the existing network. Using current U.K. incentives as a basis, this paper explores the costs, benefits and tradeoffs associated with DG in terms of connection, losses and, in a simple fashion, network deferral
IEEE Transactions on Power Systems 06/2007; · 2.68 Impact Factor
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ABSTRACT: With the rapid increase in distributed generation (DG), the issue of voltage regulation in the distribution network becomes more significant, and centralized voltage control (or active network management) is one of the proposed methods. Alternative work on intelligent distributed voltage and reactive power control of DG has also demonstrated benefits in terms of the minimization of voltage variation and violations as well as the ability to connect larger generators to the distribution network. This paper uses optimal power flow to compare the two methods and shows that intelligent distributed voltage and reactive power control of the DG gives similar results to those obtained by centralized management in terms of the potential for connecting increased capacities within existing networks
IEEE Transactions on Power Systems 03/2007; · 2.68 Impact Factor
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International Journal of Emerging Electric Power Systems 01/2007; 8 (2):1-13.
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ABSTRACT: Incentives for using wind power and the increasing price of energy might generate in a relatively short time a scenario where low voltage customers opt to install roof-top wind turbines. This paper focuses on evaluating the effects of such situation in terms of energy consumption, loss reduction, reverse power flow and voltage profiles. Various commercially-available roof-top wind turbines are installed in two secondary distribution circuits considering real-life wind speed data and seasonal load demand. Results are presented and discussed
Transmission & Distribution Conference and Exposition: Latin America, 2006. TDC '06. IEEE/PES; 09/2006
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ABSTRACT: Evaluating the technical impacts associated with connecting distributed generation to distribution networks is a complex activity requiring a wide range of network operational and security effects to be qualified and quantified. One means of dealing with such complexity is through the use of indices that indicate the benefit or otherwise of connections at a given location and which could be used to shape the nature of the contract between the utility and distributed generator. This paper presents a multiobjective performance index for distribution networks with distributed generation which considers a wide range of technical issues. Distributed generation is extensively located and sized within the IEEE-34 test feeder, wherein the multiobjective performance index is computed for each configuration. The results are presented and discussed.
IEEE Transactions on Power Delivery 08/2006; · 1.35 Impact Factor
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ABSTRACT: Wave energy will have a key role in meeting renewable energy targets en route to a low carbon economy. However, in common with other renewables, it may be sensitive to changes in climate resulting from rising carbon emissions. Changes in wind patterns are widely anticipated, and this will ultimately alter wave regimes. Indeed, evidence indicates that wave heights have been changing over the last 40 years, although there is no proven link to global warming. Changes in the wave climate will affect wave energy conversion. Where the resource is restricted, there may be reductions in energy exports and, consequently, negative economic impacts. On the other hand, increased storm activity will increase installation survival risks. Here a study is presented that, for the first time, indicates the sensitivity of wave energy production and economics to changes in climate.
IEEE Transactions on Energy Conversion 01/2006; · 2.27 Impact Factor
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ABSTRACT: The aim of this paper is to present a new method for the allocation of new generation capacity, which takes into account fault level constraints imposed by protection equipment such as switchgear. It simulates new generation capacities and connections to other networks using generators with quadratic cost functions. The coefficients of the cost functions express allocation preferences over connection points. The relation between capacity and subtransient reactance of generators is used during the estimation of fault currents. An iterative process allocates new capacity using optimal power flow mechanisms and readjusts capacity to bring fault currents within the specifications of switchgear. The method was tested on a 12-bus LV meshed network with three connection points for new capacity and one connection to an HV network. It resulted in significantly higher new generation capacity than existing first-come-first-served policies.
IEEE Transactions on Power Systems 06/2005; · 2.68 Impact Factor
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ABSTRACT: Distributed generation capacity will increase significantly as a result of UK Government-led targets and incentives. Whereas the technical problems arising from distribution-level connections may be mitigated for individual connections, the anticipated connection volumes imply a potential risk of conflict between connections, in that inappropriately sized or located plant could constrain further development of the network and consequently threaten the achievement of renewable energy targets. One means of addressing this risk is to encourage development at sites that are more suitable and at the same time discouraging those at inappropriate ones. First of all network operators must be able to evaluate the available capacity on the system (i.e. the headroom). A technique is presented that facilitates such an analysis. Termed `reverse load-ability', the approach models fixed-power factor distributed generation as negative loads and uses the optimal power flow to perform negative load shedding that effectively maximises capacity and identifies available headroom. The technique is applied to an extensive distribution and sub-transmission network. It rapidly identifies available headroom within the imposed thermal and voltage constraints. Furthermore, its use is demonstrated in examining the consequences of a sequence of connections in terms of the impact on available headroom and in sterilising the network
IEE Proceedings - Generation Transmission and Distribution 02/2005; · 0.48 Impact Factor
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ABSTRACT: Climate change is expected to lead to changes in ambient temperature, wind speed, humidity, precipitation and cloud cover. As electricity demand is closely influenced by these climatic variables, there is likely to be an impact on demand patterns. The potential impact of future changes in climate on electricity demand can be seen on a daily and seasonal basis through the fluctuation of weather patterns. The magnitude of the impact will depend on the electricity use patterns in the absence of climate change, as well as long-term socio-economic trends. As developing countries improve their standard of living, their use of air conditioning and other weather-dependent consumption may increase their sensitivity to climate change. This paper reviews existing studies on climate impacts on electricity demand and outlines how this is being assessed for the rapidly growing Thailand electricity sector.
Universities Power Engineering Conference, 2004. UPEC 2004. 39th International; 10/2004
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ABSTRACT: This paper presents a novel method of allocating new generation capacity within existing grid using optimal power flow (OPF). New generation capacity and connections to external networks are modelled as generators with quadratic cost functions. This allows preferences to be expressed regarding the location of new capacity and a focus on a specific part of the network whilst, at the same time, considering the technical and economic impact of exports and imports of power on the broader network. Sequential quadratic programming (SQP) is used to solve the OPF as it produces signals that can be used in planning mechanisms for the efficient development of the network.
Universities Power Engineering Conference, 2004. UPEC 2004. 39th International; 10/2004
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ABSTRACT: Limiting the emissions of greenhouse gases from power generation will depend, among other things, on the continuing and increased use of hydroelectric power. However, climate change itself may alter rainfall patterns, adversely affecting the financial viability of existing and potential hydro schemes. Previous work developed a methodology for quantifying the potential impact of climate change on the economics of hydropower schemes. Here, the analysis is extended to examine the potential for changes in project risk. A case study is presented that indicates that the applied climate change scenarios alter not only the mean financial performance of the scheme but also the financial risk facing it. Given that investors must balance project risk and reward, this finding has implications for the future provision of hydropower.
IEEE Transactions on Power Systems 12/2003; · 2.68 Impact Factor
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ABSTRACT: The capacity of distributed generation (DG) is set to increase significantly with much of the plant connecting to distribution networks. This paper briefly reviews the technical problems associated with the connection of DG plant at distribution-level and the mitigation strategies currently available. Further it examines the shortcomings of current connection practice in terms of the potential for inadvertently limiting network capability in absorbing new DG. Finally, it demonstrates the use of optimal power flow with a technique that could facilitate maximisation of renewable generation capacity in the deregulated electricity market.
Transmission and Distribution Conference and Exposition, 2003 IEEE PES; 10/2003
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ABSTRACT: The harnessing of renewable energy sources is key to constraining the extent of climate change. Unfortunately, the very fact that such sources are derived from climatic conditions may leave them vulnerable to changes in climate. In particular, their economic performance may be adversely affecting making them a less attractive prospect to investors. The potential for such changes is examined using hydropower as an example. A methodology is introduced that enables quantification of changes in investment performance following from changes in climate. Results of its use on a planned scheme indicate that investment measures show significant sensitivity to changes in rainfall, implying that, hydropower could become less competitive. Other technologies may show similar impacts and the investigation of them should now be a matter of importance.
Power Engineering Society Summer Meeting, 2002 IEEE; 08/2002
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ABSTRACT: Gaseous emissions from fossil-fuelled electricity generation are
major contributors to climate change. Limiting the extent of such change
will depend, among other things, on the continuing and increased use of
renewable sources, including hydropower. Paradoxically, climate change
itself may alter the availability of this natural resource, adversely
affecting the financial viability of both existing and potential
schemes. A model is described to assess the relationship between changes
in climate and the viability, technical and financial, of hydropower
development. A case study is presented, both to validate the model and
to predict the impact of climate change on a large potential scheme in
Africa
IEE Proceedings - Generation Transmission and Distribution 06/2002; · 0.48 Impact Factor
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ABSTRACT: This paper presents three case studies of risk-based standards from Great Britain: the pre-liberalisation generation planning standard, the present method for deciding operational reserve requirements, and the transmission network planning standard. These illustrate a number of key issues in developing planning and operational standards for wind, including: the ben-efits of risk-based standards in adapting to new circumstances; the importance of considering model assumptions carefully when interpreting risk calculations; consequences of the difficulty in calculating an absolute level (and hence cost) of risk; and the need to account for uncertainty in system background data such as the future plant mix when developing network planning methodologies. Robust standards make a vital contribution in achieving an appropriate balance between system cost and reliability. The transmission network planning standard is studied in particular detail, especially how the present combination of deterministic and probabilistic sections might evolve for use in a future power system with a very high renewable penetration.
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ABSTRACT: Anthropogenic emissions of greenhouse gases are expected to lead to significant changes in climate over the next century. One of the many potential effects is that river catchment runoff may be altered. This could have implications for the design, operation and viability of hydroelectric power stations. This describes attempts to predict and quantify these impacts. It details a methodology for computer based modelling of hydroelectric resources and proposes analysis of the impacts on the electrical system and on the investment performance of hydro.
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ABSTRACT: Climate change is expected to lead to changes in ambient temperature, wind speed, humidity, precipitation and cloud cover. As electricity demand is closely influenced by these climatic variables, there is likely to be an impact on demand patterns. The potential impact of future changes in climate on electricity demand can be seen on a daily and seasonal basis through the fluctuation of weather patterns. The magnitude of the impact will depend on the electricity use patterns in the absence of climate change, as well as long-term socio-economic trends. As developing countries improve their standard of living, their use of air conditioning and other weather-dependent consumption may increase their sensitivity to climate change. This paper reviews existing studies on climate impacts on electricity demand and outlines how this is being assessed for the rapidly growing Thailand electricity sector.
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ABSTRACT: The generation capacity connected in distribution networks is increasing, largely because of the necessity of siting renewable generation where resources are available. If distributed generation is connected in inappropriate parts of a network, it can cause a significant decrease in the total potential of the network for new generation. An optimal power flow-based method has previously been proposed for assessing network generation capacities. As, for a realistic assessment, it is necessary to include as many of the relevant physical and technical constraints as possible, limits on the voltage step changes on loss of a generator are added to the model here. Results on the variation of the network capacity with the generator power factors and the allowed voltage step window are presented.
