Now showing 1 - 7 of 7
  • Publication
    Real-time System-wide Inertia Estimation in Power Systems with High Wind Penetration Levels
    Knowledge of on-line inertia in power systems with high and increasing levels of wind penetration is becoming more important for power system operators. In this paper, the basis of a real-time stored energy estimator is developed, which accounts for the inertia contribution from loads as well as generators in the system. By creating a simplified first order model of the system, power and frequency signals recorded are utilized to estimate real-time feeder stored energy by use of a linear least-squares estimator. The capability of the proposed estimator is investigated by application on a test system. The estimation error is analysed in respect of data resolution and feeder contributions to stored energy. Discussion on the requirements for applications within power systems and the communication configuration are also presented.
  • Publication
    System-wide inertial response from fixed speed and variable speed wind turbines
    (IEEE, 2011-07-24) ;
    As wind penetration levels on power systems increase worldwide, the dynamic characteristics of these systems are changing due to the displacement of synchronous generation. One issue, of particular concern, is the resulting reduction in system inertia. Modern, variable speed wind turbines are controlled by power electronics and so do not inherently contribute to the inertial response of the system. Such devices can however be fitted with a control loop which provides an active power response to significant frequency deviations, similar to the inertial response of fixed speed wind turbines and synchronous generation. However, the response of variable speed turbines is dependent on local wind speeds and so cannot be quantified deterministically by system operators. This paper examines the potential for wind generation to contribute to system inertial response and considers the aggregated inertial response capabilities of fixed speed and variable speed wind generation.
      1117Scopus© Citations 33
  • 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.
      691Scopus© Citations 8
  • Publication
    Load inertia estimation using white and grey-box estimators for power systems with high wind penetration
    (Elsevier - International Federation of Automatic Control (IFAC), 2012-09-02) ; ; ;
    The increasing penetration of wind farms in power systems has increased concerns over the frequency behaviour and control of synchronous power systems due to a low contribution from modern wind turbines to overall system inertia. With this trend of conventional generators being displaced by variable speed wind turbines, the contribution from load inertia becomes more significant. The need for greater consideration towards load inertia estimation, or even on-line tracking of load inertia, seems to be required. A white-box method for estimation of load inertia is examined using system frequency and generator output power signals from previous generator forced outages. A grey-box identification method is also applied to estimate the inertia of synchronous generators. The impact of sampling rates, time shifting and signal averaging on parameter estimation is also considered. The method is shown to be robust enough to be applied for load inertia estimation in control centres.
      979Scopus© Citations 24
  • Publication
    Quantifying the Aggregate Frequency Response from Wind Generation with Synthetic Inertial Response Capability
    (Energynautics GmbH, 2013-10-24) ;
    Modern variable-speed wind turbines, although decoupled from the system frequency, can respond to significant power imbalances through power electronic controls as synthetic inertial or governor-like droop responses. However, frequency response capabilities from wind power plant cannot be considered a direct replacement for traditional frequency responsive services. Before such capabilities should be in- corporated into systems, their most effective implementation should be considered and a methodology for system operation under high synthetic inertia technology penetration should be identified. This paper considers a possible system frequency response requirement from wind generation and investigates issues surrounding quantification and scheduling of the future system resource, taking the combined Ireland and Northern Ireland system as an example. The distribution of local wind speeds, the variation in the response provided by different control structures, as well as the uncertainty associated with the aggregated capability at any one time, and the implications for the development of ancillary service market incentives or grid code requirements are considered. The impact of uncertainty over the aggregate wind response available is assessed and a strategy for the forecasting, management and coordination of such a resource on future power systems is proposed.
  • Publication
    Emulated Inertial Response from Wind Turbines: The Case for Bespoke Power System Optimisation
    (Energynautics GmbH, 2012-11-15) ;
    The dynamic characteristics of power systems with increasing wind penetration levels are changing rapidly as the nature of the frequency response capability of these systems develop with the evolving plant mix. Consequently, the protocols for how these systems are operated are changing. While modern variable speed wind turbines do not inherently contribute to the inertial response of the system, they can offer a controlled response to system frequency imbalances, which harnesses the stored rotational energy of the blades. Unlike conventional machines, however, the tunable emulated inertial response of a variable speed wind turbine is dependent on the operating condition of the wind turbine and provides a distinct response to conventional generators. In some cases it is possible that inappropriate tuning of such a response could hinder the recovery of the system frequency following an imbalance. In this paper the emulated inertial response from wind generation on power systems of varying size is optimised, and the impact of system conditions on the response required is examined.
  • 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.