Now showing 1 - 10 of 14
  • Publication
    Assessing Power System Flexibility for Variable Renewable Integration: A Flexibility Metric for Long-Term System Planning
    Many countries around the world have instituted policies with the aim of increasing the amount of installed variable generation (VG), such as wind and solar. A consequence of increased penetrations of VG is that changes in their output must be met by the remainder of a system’s resources so that the demand-generation balance is maintained. This paper proposes a highlevel methodology to assess power system flexibility. In this context, flexibility is the ability of a power system to deploy its resources to meet changes in the system demand and that of variable generation. The inclusion of such analysis at the long-term system planning stage will help to ensure that systems are optimally planned and operated with high levels of VG. Two case studies are presented which illustrate the flexibility assessment methodology and highlight some key issues relating to flexibility in the context of long-term planning.
  • Publication
    Managing wind uncertainty and variability in the Irish power system
    This paper summarizes work that has been done to examine the impact of the uncertainty and variability of significant installed wind power on the Irish system. As more and more wind power is installed on the system, the operation of conventional plant on the system will be dramatically different. In this paper, three different aspects of the hour-to-hour operation of the Irish power system are examined. An innovative method to schedule the system is described, together with key results giving the effect of the uncertainty of wind on unit commitment of the system. The increased cycling of traditionally base-load units due to large amounts of wind power is quantified, and the steps to reduce this unwanted behavior are outlined. Finally, the use of intelligent decision tools based on sophisticated wind power forecasts for scheduling and provision of reserve is described.
      499Scopus© Citations 3
  • Publication
    Burning peat in Ireland : an electricity market dispatch perspective
    This paper examines peat power production in Ireland under the three pillars of energy policy—security, competitiveness and environment. Peat contributes to energy security—as an indigenous fuel, it reduces dependency on imports. During a period of low capacity margins, the operation of the peat plants is useful from a system security perspective. Peat generation is being financially supported by consumers through an electricity levy. The fuel also has high carbon intensity. It is not politically viable to consider peat on equal economic criteria to other plant types because of history and location. This paper reviews electricity generation through combustion of peat in Ireland, and quantifies the costs of supporting peat utilising economic dispatch tools, finding the subsidy is not insignificant from a cost or carbon perspective. It shows that while peat is beneficial for one pillar of energy policy (security), the current usage of peat is not optimal from a competitiveness or environmental perspective. By switching from the current ‘must-run’ mode of operation for peat to the ‘dispatched’ mode used for the other generation, significant societal savings (in the range €21m per annum) can be achieved, as well as reducing system emissions by approximately 5% per year.
      6126Scopus© Citations 28
  • Publication
    Impact of wind power on the unit commitment, operating reserves, and market design
    This article highlights and demonstrates the new requirements variable and partly unpredictable wind power will bring to unit commitment and power system operations. Current practice is described and contrasted against the new requirements. Literature specifically addressing questions about wind power and unit commitment related power system operations is surveyed. The scope includes forecast errors, operating reserves, intra-day markets, and sharing reserves across interconnections. The discussion covers the critical issues arising from the research.
      956Scopus© Citations 39
  • Publication
    Unit commitment for systems with significant wind penetration
    The stochastic nature of wind alters the unit commitment and dispatch problem. By accounting for this uncertainty when scheduling the system, more robust schedules are produced, which should, on average, reduce expected costs. In this paper, the effects of stochastic wind and load on the unit commitment and dispatch of power systems with high levels of wind power are examined. By comparing the costs, planned operation and performance of the schedules produced, it is shown that stochastic optimization results in less costly, of the order of 0.25%, and better performing schedules than deterministic optimization. The impact of planning the system more frequently to account for updated wind and load forecasts is then examined. More frequent planning means more up to date forecasts are used, which reduces the need for reserve and increases performance of the schedules. It is shown that mid-merit and peaking units and the interconnection are the most affected parts of the system where uncertainty of wind is concerned.
      3184Scopus© Citations 598
  • Publication
    Rolling unit commitment for systems with significant installed wind capacity
    As wind power penetration grows, the amount of reserve needed on the system also grows, due to the increases in the uncertainty of wind power, which grows larger as forecast horizon increases. By scheduling the system more often the amount of extra reserve to be carried to cater for wind uncertainty decreases, depending on the flexibility of plant on the system. This reduces the costs of operating the system. There is a trade off between reduced costs due to more frequent commitment, the ability of wind forecasts to be made more accurately, and the increased costs of more flexible plant. This paper examines the benefits of committing the system more frequently, and how different factors such as reliability of the system, accuracy of the forecasts and plant mix impact on this.
      692Scopus© Citations 53
  • Publication
    Impact of pumped storage on power systems with increasing wind penetration
    In this paper, the unit commitment and dispatch of a power system with and without a pumped storage unit is examined for increasing levels of installed wind power, from 17% of total energy to 80% of total energy generated by wind 3 (3GW to 15GW of installed wind on the Irish system in 2020). At high levels of installed wind, it is shown that storage reduces curtailment and increases the use the base loaded plant on the system. This reduces system costs. However, when the additional capital costs of storage are taken into account, it is shown that storage is not viable from a system perspective until extremely large levels of wind power are seen on the system. At these levels of installed wind, while the system can operate without storage, it is less costly to do so with storage. The capacity credit of the storage unit is also examined, using a simplified approach, and shown to decrease as larger amounts of intermittent wind power are added to the system.
      2141Scopus© Citations 89
  • 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
    Operating the Irish power system with increased levels of wind power
    This paper summarises some of the main impacts of large amounts of wind power installed in the island of Ireland. Using results from various studies performed on this system, it is shown that wind power will impact on all time frames, from seconds to daily planning of the system operation. Results from studies examining operation of the system with up to approximately 40% of electricity provided by wind show that some of the most important aspects to be considered include the type of wind turbine technology, the provision of reserve to accommodate wind forecasting error and the method used to plan plant schedules.
      844Scopus© Citations 12