EPECentre: Reports

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  • ItemOpen Access
    Quantifying benefits of wind power diversity in New Zealand
    (IET Renewable Power Generation, 2019) McQueen, Dougal; Wood, Alan
    Wind integration studies often focus on the capacity value of wind power without considering Unit Commitment and Economic Dispatch or resolving requirements for ancillary services. Here, a novel method for simulating wind power time series with sufficient temporal span to support capacity studies and temporal resolution to support UCED studies is developed. Wind speed time series (WSTS), with 6 h temporal and 0.7 × 0.7 degree spatial resolutions, are extracted from the ECMWF-interim reanalysis, interpolated, scaled, and imputed so that they are representative of a point wind speed measurement with a 5 min temporal resolution. Imputation is made using a wavelet multi-resolution analysis approach that ensures temporally consistent correlations while accounting for heteroskedasticity. WSTS are transformed to power using wind power plant power curves, lowpass filters, and a Markov Chain model of operational efficiencies. The wind power model is validated using a set of measurements made at wind power plants (WPPs) in New Zealand and used to simulate power time series for 2 GW portfolios of WPPs representing compact, disperse, diverse, and business-as-usual portfolios. Metrics for dependability, variability, and predictability are applied to quantify the benefits of spatial diversification.
  • ItemOpen Access
    Recommendations for Ancillary Service Markets under High Penetrations of Wind Generation in New Zealand
    (2019) Schipper J; Wood A; Edwards C; Miller A
    This report analyses the demand for reserves, including Ancillary Services Frequency Keeping (FK) and Instantaneous Reserves (IR), under higher penetrations of wind generation in the New Zealand power system. Recommendations are made for the development of the Ancillary Service (AS) markets to ensure security of the power system under high wind penetrations, while achieving economic efficiency. The analysis centers around anticipating the dispatch of generation under eight scenarios of increasing wind generation. These scenarios are 500 MW to 4000 MW of extra wind generation in 500 MW steps above the current 690 MW of wind capacity. The scenarios were chosen in order to achieve 100% electricity generation from renewable resources, the maximum foreseeable installation of wind farms under current demand for electricity. Simulating the dispatch is modelled on historical data from 2013 to 2015 inclusive, which has sufficient data to accurately model the impacts, and a basis on which to compare the results of each scenario. The new dispatch determines the changes in the contingency risk, and the impact wind generation has on the inertia of the power system, and hence the demand for IR. This report focuses on wind generation without consideration of other forms of renewable generation, such as Hydro, Geothermal, Solar, and Biomass. This is for the express purpose of isolating the impacts of wind generation. It is expected wind generation is going to have the greatest impact on demand for reserve as New Zealand approaches 100% renewable generation. Future demand scenarios were not considered, again for the purpose of isolating the impacts of wind generation, and the understanding that the power system is most susceptible to frequency instability under lightly loaded conditions.