Analysis of operation reserves in a hydrothermal electric system with high wind power share under demand and wind power uncertainties

The paper analyses the amount of operation reserves procured in a hydrothermal system to deal with wind power and demand uncertainty. The operation planning of the system is formulated as a detailed hourly unit commitment (UC) solved as an MIP optimization problem. This model takes into account the startup and shutdown power trajectories of thermal units, up and down secondary reserves, up and down power ramps, minimum up and down times. Besides, hydro power plants are represented in the model in an aggregated mode but still capturing their capability to provide operation reserves. The operation cost determined by the UC is re-evaluated through 5-min economic dispatch (ED) simulation under hundreds of wind generation and demand scenarios. This combination of optimization and simulation models allows to analyze: • On the one hand, the effect in the operation reserve usage of the hourly energy-block operation planning versus the 5-min economic dispatch and • On the other hand, the impact of the wind power and demand uncertainty in the use of the operation reserves procured Additionally, alternative time periods for market clearance different from one hour are analyzed and their impact on the operation reserves usage, e.g., a half an hour or a quarter of an hour. The previous analysis is done for the Spanish electric system to see the effects of the current operation reserve procurement.