Forecasts with uncertainties for calculating electricity reserves

Abstract: The continued growth of renewable energy sources modifies the established electricity system. Power generation reserves are a vital part of this system as they are used to balance out the load fluctuations and the natural intermittence of renewables. The management of power reserves is largely impacted by the ongoing trend. Their proper dimensioning becomes more important with time, as the optimal sizing of these reserves could save substantial resources for the electricity system. Therefore, this study presents a method which could be used by Transmission System Operators (TSO) to determine the necessary amount of electricity reserves.  A dynamic approach is used that allows to calculate the required margin at all times of the day for various typical operational strategies in electricity networks. Drivers for typical imbalances such as renewable production forecast errors, load forecast errors and power plant outages are analyzed in order to determine probability density function. In that process, key variables for forecast errors are investigated and statistics on power plants’ outages and delays are calculated.  Finally, these drivers are summed to get a universal probability density function, able to size the required reserve margin by a levelized criterion on forecast security that TSOs and regulatory authorities would choose as a governing factor in their operational strategy.