Now showing 1 - 10 of 10
  • Publication
    System-wide contribution to frequency response from variable speed wind turbines
    (Institute of Electrical and Electronics Engineers, 2012-07) ;
    Due to the differing electromechanical characteristics of modern variable speed wind turbines to conventional generators, the provision of ancillary services from wind generation is likely to change the nature of the frequency response of power systems to contingency events. This paper explores the aggregate contribution from wind turbines to the frequency response of future power systems, considering both emulated inertial and governor controls. In particular, the potential issues that may arise as a result of the changing nature of the system frequency response due to the uncertainty over the distribution of ancillary services from embedded generation on the network, are examined in the context of future power system requirements.
    Scopus© Citations 8  687
  • 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
    The role of power system flexibility in generation planning
    As the penetration of variable renewable generation increases in power systems worldwide, planning for the effects of variability will become more important. Traditional capacity adequacy planning techniques have been supplemented with integration studies, which have been carried out in power systems with high targets for renewable generation. These have highlighted the increased variability that a system may experience in the future. As system planning techniques evolve with the demands from variable generation, the flexibility of a system to manage periods of high variability will need to be assessed. A metric may be required to measure the flexibility of a power system for use in planning studies with multi-year horizons. Compared to generation adequacy metrics, system flexibility assessment is more data intensive and requires more detailed system modeling. An algorithm for scenario development in generation planning with high penetrations of variable generation is presented.
    Scopus© Citations 110  1482
  • Publication
    Impact of voltage dip induced delayed active power recovery on wind integrated power systems
    (Elsevier, 2017-04) ;
    Installed wind power capacity is increasing rapidly in many power systems around the world, with challenging penetration targets set at national, and/or regional level. Wind power, particularly at higher penetration levels, introduces various grid issues, with frequency and voltage stability being particularly critical concerns. Voltage dip induced frequency stability following a network fault in such systems is one potential risk that has so far received limited attention by the research community. With state of the art modelling, the potential impact of a delayed active power recovery from wind generation following a network fault induced voltage dip is investigated. The subsequent voltage oscillations introduced by wind turbines, exacerbating frequency stability, are also examined. Analysis is carried out for a wide range of wind penetration levels and system scenarios, with the results demonstrated on the New England benchmark system.
    Scopus© Citations 26  642
  • 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
    Studying the maximum instantaneous non-synchronous generation in an Island system-frequency stability challenges in Ireland
    Synchronous island power systems, such as the combined Ireland and Northern Ireland power system, are facing increasing penetrations of renewable generation. As part of a wider suite of studies, performed in conjunction with the transmission system operators (TSOs) of the All-Island system (AIS), the frequency stability challenges at high and ultra-high wind penetrations were examined. The impact of both largest infeed loss and network fault induced wind turbine active power dips was examined: the latter contingency potentially representing a fundamental change in frequency stability risk. A system non-synchronous penetration (SNSP) ratio was defined to help identify system operational limits. A wide range of system conditions were studied, with results showing that measures such as altering ROCOF protection and enabling emulated inertia measures were most effective in reducing the frequency stability risk of a future Ireland system. © 2014 IEEE.
      2067Scopus© Citations 247
  • Publication
    Challenges posed by the integration of wave power onto the Irish power system
    In order to gauge the potential impact of wave power in Ireland, the capacity factor of theoretical wave farms deployed at various locations around the Irish coast is compared to the system-wide capacity factor of wind power generation over the same period. It is shown that wave power off the coast of Ireland experiences a very significant seasonal variation, but with a lower daily variation. This paper presents the results of that analysis and examines certain challenges that will face the Irish power system if a large portfolio of wave power devices is deployed. Issues such as system adequacy and the capacity value of wave power are discussed.
      406
  • Publication
    Evolution of operating reserve determination in wind power integration studies
    The growth of wind power as an electrical power generation resource has produced great benefits with reductions in emissions and the supply of zero cost fuel. It also has created challenges for the operation of power systems arising from the increased variability and uncertainty it has introduced. A number of studies have been performed over the past decade to analyze the operational impacts that can occur at high penetrations of wind. One of the most crucial impacts is the amount of incremental operating reserves required due to the variability and uncertainty of wind generation. This paper describes different assumptions and methods utilized to calculate the amount of different types of reserves carried, and how these methods have evolved as more studies have been performed.
      1316Scopus© Citations 116
  • 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.
      1015
  • Publication
    Emulated Inertial Response from Wind Power: Ancillary Service Design and System Scheduling Considerations
    Worldwide, variable-speed wind turbine and solar photovoltaic generation are displacing conventional power plant in market schedules. Committing out-of-merit conventional units to redress system synchronous inertia or primary frequency response shortfalls incurs start-up and production costs, and may also engender additional greenhouse gas emissions and wind/solar curtailment. In order to ensure that future system frequency response requirements are met in a low carbon manner, new sources of frequency stability ancillary services will need to be incentivised or mandated via grid codes. Nonsynchronous devices (batteries, flywheels, variable-speed wind turbines), with appropriate control architectures, can provide a fast frequency response following a system disturbance, i.e. a temporary injection of active power, supplied faster than existing primary frequency response deployment times. Operational considerations relevant to transmission system operators when designing a fast frequency response ancillary service are presented, particularly if sourced from wind power emulated inertial response. It is shown that careful consideration regarding the design of fast frequency response characteristics is required in high wind power systems: the system frequency response behaviour may be degraded if a holistic approach to fast frequency response design is not taken. A method to characterise the system-wide (aggregate) emulated inertial response from wind power is presented, which can be integrated as a form of fast frequency response within unit commitment and economic dispatch. Endogenous incorporation in unit commitment and economic dispatch ensures that non-synchronous fast frequency response sources do not only supplement existing fossil fuel-based spinning reserve provision, but also reduce the need to commit synchronous generators for frequency control reasons. However, given the inherent energy recovery/payback experienced by variable-speed wind turbines providing emulated inertial response when operating below rated output, it is imperative to consider the impact of such negative power trajectories on system primary frequency response requirements.
      530