Revealing the complementary mechanism of hydropower-photovoltaic coordinated operation through peak-shifting coordination and energy production trade-off analysis

The coordinated operation of hydro and PV systems is an effective approach to enhancing PV energy utilization by stabilizing total power output through reservoir operation. The complementary operation mechanisms of hydro-PV remain insufficiently explored. This study establishes a coupled modeling framework to reveal the complementary mechanisms by which hydropower offers peak-shifting coordination to reduce PV energy curtailment. A case study of a high-PV-penetration hydro-PV hybrid energy base in China demonstrates that: (1) Coordinated operation significantly increases total energy production, with hydropower regulation capability being the decisive factor; (2) Complementary benefits essentially represent a trade-off relationship between hydropower energy loss and PV energy increment, and the tradeoff curve exhibits a two-stage variation trend with a distinct turning point during the flood season, whereas it shows a consistent variation in the dry season; (3) The increasein PV energy is affected by the maximum peak-shifting depth and duration of hydropower output, and ideal PV energy production. In both the flood and dry seasons, increases in PV energy are primarily dominated by ideal PV energy production. In addition, during the dry season, PV energy increment shows a positive correlation with hydropower peak-shifting depth; and (4) The complementary operation mechanism exhibits a clear peak-shifting pattern in hydropower output, altering the reservoir water level process. Hydropower energy loss is mainly caused by increased spill during the flood season and by reduced average hydraulic head and efficiency during the dry season. These findings provide theoretical and practical support for guiding the coordinated operation of hydro-PV hybrid energy base.