Now showing 1 - 10 of 80
  • Publication
    The relationship between base-load generation, start-up costs and generation cycling
    (International Association for Energy Economics, 2008-12) ; ;
    Developments in the electricity sector such as the integration of increasing levels of renewable power, mainly wind, and the deregulation of electricity markets have resulted in some unconventional operation of base-load units. These units, which were originally designed for continuous operation, are now being forced into more flexible or cycling operation. This cycling operation results in serious physical degeneration of the unit’s components and hence incurs substantial costs to the plant operator. Using a planning tool of the Irish electricity system, the impact of increasing wind penetration on the operation of the base-load units is modelled. The results show that as wind penetration on the system increased, the base-load units were required to start up and shut down more often. However the units found to be cycled the most were not those with the cheapest start-up cost, but in fact those units with the shortest synchronisation time1. On the basis that the resulting cycling costs would increase the start-up costs of the base-load unit to some degree, the effect of increasing start-up costs on the operation of the base-load units was also examined. The results show that by increasing the start-up costs of base-load units, those units will be scheduled to operate in a more conventional base-loaded manner, the extent of which depends on the amount of wind power present.
      2678
  • Publication
    Varying penetration ratios of wind turbine technologies for voltage and frequency stability
    This paper examines the ability of a power system to accommodate wind generation with varying ratios of doubly fed induction generator and fixed speed induction generator turbines from both static and dynamic aspects. By controlling the ratio between the two types of turbines, voltage stability is maintained for steady-state conditions for a large range of varying wind speeds. Using the ratio determined from the static analysis, the dynamic analysis explores the voltage and frequency characteristics of the system under contingency conditions. An initial analysis was carried out on the IEEE 30 bus test system. The results of this analysis are presented in this paper and detail how by varying the ratio of the turbine types the frequency stability and voltage stability can be improved.
    Scopus© Citations 38  1447
  • Publication
    Multi-mode operation of combined-cycle gas turbines with increasing wind penetration
    As power systems evolve to incorporate greater penetrations of variable renewables, the demand for flexibility within the system is increased. Combined-cycle gas turbines are traditionally considered as relatively inflexible units, but those which incorporate a steam bypass stack are capable of opencycle operation. Facilitating these units to also operate in opencycle mode can benefit the power system via improved system reliability, while reducing the production needed from dedicated peaking units. The utilization of the multi-mode functionality is shown to be dependent on the flexibility inherent in the system and the manner in which the system is operated.
      1084Scopus© Citations 39
  • Publication
      567
  • Publication
    Optimal firm wind capacity allocation to power systems with security constraints
    Many countries have declared future renewable energy penetration targets. Wind power connection to power systems is delayed by limited transmission system capacity as attractive wind sites are often located in weakly designed transmission areas. Optimal use of existing transmission system resources should be made in the allocation of capacity connection permits. The volume of wind power connection applications and their power production statistical inter-dependencies suggest that they should be assessed in a collective probabilistic manner. This paper uses a sequential probabilistic load flow method in tandem with a linear programming computational geometry constraint redundancy approach to optimally allocate wind capacities given the transmission system capacity that is securely available.
    Scopus© Citations 17  1987
  • Publication
    Improved system operations with high penetration of wind power : a dialog between academia and industry - Ireland
    This is a submission to a panel session at the 2010 IEEE PES General Meeting. It discusses effective collaboration between academia and industry.
      392
  • Publication
    Assessment of power system flexibility: A high-level approach
    (Institute of Electrical and Electronics Engineers, 2012-07) ; ;
    The targeted growth of variable generation capacity in many power systems has led to concern that future systems may have insufficient flexibility to meet ramps in variable generation (VG) production and system demand. This paper introduces a high-level flexibility assessment methodology for use by those involved in planning, and with little experience of the integration of large quantities of variable generation. This is proposed as a first step in assessing the future needs of a system. Comparison is drawn between the proposed high-level flexibility assessment and a more detailed flexibility assessment. The insufficient ramp resource expectation (IRRE) highlights those time horizons in which the system may have insufficient flexibility to meet changes in the net load. The methodology is demonstrated on a test system from which high-level conclusions may be drawn. A number of other insights are also offered by the proposed methodology, including the distributions of the size of the deficit, and surplus, of ramping capability.
    Scopus© Citations 51  1015
  • Publication
    Pumped storage in systems with very high wind penetration
    (Elsevier, 2011-04) ;
    This paper examines the operation of the Irish power system with very high levels of wind energy, with and without pumped storage. A unit commitment model which accounts for the uncertainty in wind power is used. It is shown that as wind penetration increases, the optimal operation of storage depends on wind output as well as load. The main benefit from storage is shown to be a decrease in wind curtailment. The economics of the system are examined to find the level at which storage justifies its capital costs and inefficiencies. It is shown that the uncertainty of wind makes the option of storage more attractive. The size of the energy store has an impact on results. At lower levels of installed wind (up to approximately 50% of energy from wind in Ireland), the reduction in curtailment is insufficient to justify building storage. At greater levels of wind, storage reduces curtailment sufficiently to justify the additional capital costs. It can be seen that if storage replaces OCGTs in the plant mix instead of CCGTs, then the level at which it justifies itself is lower. Storage increases the level of carbon emissions at wind penetration below 60%.
    Scopus© Citations 169  667
  • Publication
    Power system flexibility assessment — State of the art
    (Institute of Electrical and Electronics Engineers, 2012-07) ; ;
    Recent research has led to the development of a number of metrics for the assessment of flexibility in a power system. This paper presents an overview of the tools currently available to those involved in planning and operations to directly incorporate the assessment of the requirements for flexibility, the flexibility resource available in each system and methodologies to assess the overall flexibility of a system including operational and transmission constraints. Current challenges and areas for future development are also highlighted.
    Scopus© Citations 44  1931
  • Publication
    Effect of generator flow control strategies on the long term dynamics of a model for power systems
    Cascading component failure can cause system-wide blackouts in power systems. Complex system analysis of the long term dynamics suggests that power transmission systems operate near a critical point. Here the effect of generator operation in a model for power systems is investigated. Two opposing methods of dispatching generators are compared. These two methods are to minimize and maximize the line flows with respect to their limits across the system. These methods are also compared to an economic dispatch. It is shown that the generator dispatch method used affects the frequency distributions and other statistics of blackouts. Dispatching using the maximization method causes a reduction in the frequencies of all blackouts as measured by the amount of load shed. This reduction is concurrent with an increase in the investment in the transmission system. These observations suggest that economic dispatch, while attempting to increase reliability, actually decreases the robustness of the system.
      552Scopus© Citations 1