Now showing 1 - 10 of 88
  • Publication
    Stochastic analysis of the impact of electric vehicles on distribution networks
    Advances in the development of electric vehicles, along with policy incentives, will see a wider uptake of this technology in the transport sector in future years. However, large penetrations of EVs could lead to adverse effects on power system networks, especially at the residential distribution network level. These effects could include excessive voltage drop and thermal loading of network components. A stochastic method is developed to take account of the uncertainties associated with EV charging and the technique is implemented on a residential test network using power system simulation software. The results show how voltage levels, component loading network losses are impacted from EV charging, taking into account the probabilistic behaviour of the EV owners.
  • Publication
    Effect of energy harvesting network reactive support on transmission system voltage performance
    It is common to operate distributed generators (DGs) at fixed inductive power factors to overcome voltage rise constraints on distribution networks. This approach increases distribution system reactive power demand, which may strain transmission system reactive power resources at times of system-wide high DG output, particularly if such output displaces synchronous generators. If a number of adjacent DGs are connected to a transmission node in a clustered fashion via a dedicated energy harvesting network (EHN), it is possible to characterise their aggregated reactive power capability as a form of virtual power plant. Such a characterisation will be provided in this paper. The aggregated capability may readily be included in transmission system models. This work will explicitly compare the transmission system voltage-control performance of EHN reactive capability with that of traditional synchronous plant.
  • Publication
    Unit Commitment Considering Regional Synchronous Reactive Power Requirements : Costs and Effects
    Highly renewable power systems may have to impose regional minima on the number of online synchronous units to ensure appropriate availability of controllable reactive power. Given the declining net loads associated with increasing wind penetration levels, these regional constraints are anticipated to come into effect with greater frequency. Such constraints have a tangible effect on the total cost of unit commitment schedules, with out-of-merit units being committed solely to preserve secure voltage regimes. The use of novel reactive power resources may make regional constraints less necessary, and the voltage-control capabilities of distribution-connected wind farms will be examined in this role. Harnessing these resources may not require any roll-out of new technology, but would be an operational change to utilise the pre-existing voltage-control capabilities implicit in the power electronic topology of modern wind turbine generators. Given the capital costs of new dedicated VAr sources, and the generating costs associated with using synchronous plant for voltage control, it appears vital to derive the greatest possible value from existing assets.
  • Publication
    A sustainability strategy for Ireland’s electricity network
    (Risø National Laboratory for Sustainable Energy, 2009-09) ; ; ; ;
    The electricity system of Ireland is unique as it has no synchronous connections to other systems, while the existing non-synchronous connection provides limited flexibility. When coupled with a target of 40% electricity from renewables by 2020, exceeding any other country, the challenge is truly striking. However, this challenge also gives Ireland the opportunity to be the world leader in this area. The unique experience in solving this problem will provide the technology and knowledge to harness renewable energy sources globally and limit the dependency on petrochemicals. The continued development of the electricity distribution network as a smart network is a critical element of this process which spans electricity generation, transportation and energy end use. This paper described the various elements of ESB Networks’ sustainability strategy and the associated research themes being jointly pursued by ESB Networks, the Electric Power Research Institute (EPRI) and the Electricity Research Centre, University College Dublin.
  • Publication
    Application of wind generation capacity credits in the Great Britain and Irish systems
    The concept of capacity credit is widely used to quantify the contribution of renewable technologies to securing demand. This may be quantified in a number of ways; this paper recommends the use of Effective Load Carrying Capability (ELCC, the additional demand which the new generation can support without increasing system risk), with system risk being measured using Loss of Load Expectation (LOLE, this is calculated through direct use of historic time series for demand and wind load factor). The key benefit of this approach is that it automatically incorporates the available statistical information on the relationship between wind availability and demand during the hours of very high demand which are most relevant in assessing system adequacy risk. The underlying assumptions are discussed in detail, and a comparison is made with alternative calculation approaches; a theme running through the paper is the need to consider the assumptions carefully when presenting or interpreting risk assessment results. A range of applications of capacity credits from Great Britain and Ireland are presented; this includes presentation of effective plant margin, ensuring that the optimal plant mix secures peak demand in economic projection models, and the Irish capacity payments system. Finally, new results comparing capacity credit results from the Great Britain and Irish systems using the same wind data are presented. This allows the various factors which influence capacity credit results to be identified clearly. It is well known that increasing the wind load factor or demand level typically increases the calculated capacity credit, while increasing the installed wind capacity typically decreases its capacity credit (as a percentage of rated capacity). The new results also show that the width of the probability distribution for available conventional generating capacity, relative to the peak demand level, also has a strong influence on the results. This emphasises further that detailed understanding of risk model structures is vitally important in practical application.
  • Publication
    Electrical and Thermal Characteristics of Household Appliances: Voltage Dependency, Harmonics and Thermal RC Parameters
    Detailed bottom-up load modelling of the residential sector has become increasingly important to examine the network impacts of both changing load composition due to the introduction of sustainable technologies, and changing load behaviour with increased levels of demand response. An important aspect of these models is the electrical and thermal behaviour of household loads. This paper examines the fundamental electrical and thermal characteristics of common household appliances. Methods to obtain the voltage de endency and equivalent resistive-capacitive (RC) circuit parameters for mode ling thermostatically controlled appliances (TCAs) are presented. The paper also presents the results of laboratory experimental determination of voltage dep endency coefficients, subjecting common appliances to a range of voltages within +/- 10% of the standard supply voltage. The thermal behaviour of TCAs are examined by use of thermocouples and plug-load monitoring devices. Appliances are grouped into into five distinct categories; lighting, motor, power electronic, resistive and wet appliance loads, and both their characteristics and operational behaviour is presented.
  • Publication
    Minimum cost curtailment for distributed generation voltage management
    The penetration of DG is increasing on distribution networks across the world. As a result, networks are being pushed closer to their operating limits. In particular, voltage rise has been identified as a key barrier to further DG capacity. Active management of the voltage constraint may be possible, leading to a form of constraint management at distribution level for the first time. Here a novel method is proposed, which minimises the cost of curtailment. It takes advantage of the dispatchable capability of certain forms of DG, such as biomass, hydro or landfill gas. There are a number of well established methods for congestion management on the transmission network. A number of these are applied to voltage management on the distribution network and used for comparison with the new minimum cost method. The variability of voltage sensitivities andmarket prices is also investigated, with their impact on the cost of curtailment quantified.
  • Publication
    Impact of high penetrations of micro-generation on low voltage distribution networks
    Due to rising fossil fuel and electricity prices and the overall need to reduce carbon emissions, there is a growing interest in the utilisation of micro-generation amongst electricity consumers and governments alike. Electricity consumers are installing small scale generators on their premises, which are also being connected to existing low voltage (LV) electricity supply networks. High penetrations of micro-generation may present challenges to the planning and operation of LV electricity networks. This is due to LV distribution networks being designed for delivery of electricity from sub-stations to the consumers and not for accommodating generation. The aim of the work presented in this paper is to examine the effect of high penetrations of micro-generation on the voltage levels of a section of existing Irish LV distribution network.
  • Publication
    A small - signal stability analysis of DFIG wind generation
    This paper examines the small-signal stability impacts of high penetrations of doubly-fed induction generator (DFIG) wind turbines on power systems. It provides a basic overview of small-signal stability concepts and then examines the response of DFIG generation to two local contingency event. Using the New England 39 bus test system, this paper will demonstrate the stability implications of DFIG turbines utilizing terminal voltage control and fixed power factor control in response to reactive and active power loss events. By implementing terminal voltage control strategies in DFIG wind turbines, system stability is improved and allows for increased levels of wind penetration levels while maintaining a high level of system security.