Enhancing the economic benefits of cascade hydropower stations through integrated utilization of electricity and capacity benefits

The rapid growth of renewable energy sources is significantly increasing the demand for power system flexibility. Hydropower can leverage its operational flexibility to stabilize renewable energy fluctuations and create economic benefits. Hydropower's electricity benefits(EB) are widely studied, but its flexibility-driven capacity benefits(CB) remain underexplored, limiting the evaluation of its benefits. Moreover, hydraulic interdependencies among cascade hydropower stations(CHSs) complicate benefits improvement. This study develops an optimal dispatching framework for CHSs that incorporates both EB and CB. EB and CB quantification methods are introduced under the power spot portfolio market, which integrates the electricity energy market and the ancillary service markets. An optimal dispatching model for CHSs that considers both EB and CB is established. Subsequently, sensitivity analysis is conducted across different inflow and price scenarios. The framework is applied to the DG, ZM, and JC CHSs in the Yarlung Zangbo River Basin and is compared with a model that considers only EB. The results show that: (1) The proposed model achieves efficient allocation and utilization of hydropower resources. (2) The integration of EB and CB significantly enhances the economic benefits of CHSs when reservoir inflows decline, with an average increase of 12.75 %. (3) Price variations have a stronger impact on benefits growth than changes in reservoir inflow.