Complementary operation rules of hydropower-photovoltaic systems to prevent power curtailment

The complementary operation of photovoltaic (PV) power with hydropower effectively promotes its integration into the power grid, but it also intensifies the competition for transmission channels, potentially leading to severe power curtailment issues. This study introduces complementary operation rules for hydro-photovoltaic (hydro-PV) systems aimed at preventing power curtailment for the first time. The rules are presented by an operation chart, which is divided into four zones: storage zone (Zone I), no curtailment zone (Zone II), PV curtailment zone (Zone III), and PV and hydro curtailment zone (Zone IV), based on three critical power curtailment states. Then, day-ahead and real-time operation strategies for hydro-PV complementary systems, derived from the operation chart, are proposed. Finally, the sensitivity of the operation chart to various PV output scenarios is analyzed, and the performance under different forecast accuracy levels is evaluated. A case study in China demonstrates that (1) the operation chart provides preventive operation rules for the hydro-PV complementary system and identifies warning inflow thresholds for both PV and hydro curtailment; (2) by increasing power output in advance and strategically lowering the reservoir water level, the complementary systems can effectively reduce power curtailment caused by reservoir capacity constraints during periods of high PV generation; and (3) the operation chart varies with PV scenarios, and operational schemes should be adapted flexibly to guide complementary operations based on PV prediction accuracy.