Unit commitment in a hybrid diesel/wind/pumped-storage isolated power system considering the net demand intra-hourly variability

This paper presents a novel two-stage stochastic mixed-integer linear programming model for the generation scheduling of a hybrid diesel/wind/pumped-storage power system that considers the intra-hourly net demand variability during the first stage. The model aims to minimise the scheduling cost, calculates the power system storage opportunity cost and considers that the start-up cost of thermal units depends on the time passed since the previous shutdown in a detailed manner for the first stage (i.e. using integer variables) and in an approximate manner (relaxing the integrality constraints) for the second stage. To increase the model's computational efficiency, a solution approach based on the Benders decomposition technique is applied. The model is implemented in the real power system of El Hierro island, an isolated hybrid diesel/wind/pumped-storage power system with a closed-loop pumped-storage plant and high wind power installed capacity. The schedules provided by the proposed model are compared to the ones provided by a similar model that does not consider the intra-hourly net demand variability, resulting in generation schedules with a significantly lower wind energy curtailment. The results demonstrate the importance of considering the intra-hourly net demand variability in order to integrate more wind energy at a moderate extra cost.