Short-term peak shaving model of cascade hybrid pumped storage hydropower station retrofitted from conventional hydropower

The integration of pumped storage units with conventional cascade hydropower to form a cascade hybrid pumped storage hydropower station (CHPHPS) is considered one of the effective approaches to expedite the development of pumped storage. However, more complex hydraulic and electrical coupling relationships pose challenges to the operation of these stations. In this study, the typical peak shaving mode of CHPSHS is initially analyzed, and a corresponding peak shaving model is proposed. The objective function of the model is to minimize the peak-valley difference in the remaining load on the grid. In terms of modelling, the refined modelling method using the unit as the scheduling unit is used to successfully reflect the differentiated operating characteristics of different types of units. In terms of model solving, state variables are introduced to facilitate the decoupling and switching of operational states. Furthermore, linearization techniques such as piecewise linear approximation, integration of 0–1 integer variables, and discretization of generation head are utilized to handle nonlinear constraints. The model is converted into a mixed-integer linear programming (MILP) problem and solved using the CPLEX tool with Java programming. A case study conducted in southwest China shows that CHPSHS can enhance the peak shaving ability and reduce the peak-valley difference in the remaining load on the grid, providing valuable reference for retrofitting conventional cascade hydropower stations.