The complementary scheduling of hydropower with wind and photovoltaic (PV) power is an effective way to promote new energy consumption. However, previous studies have disregarded the operational risks of hydropower plants due to their physical constraints when complementing new energy sources. This study proposes a risk control method for a hybrid hydro-PV power system by adding electrochemistry energy storage (EES). A “day ahead–intrada. The complementary scheduling of hydropower with wind and photovoltaic (PV) power is an effective way to promote new energy consumption. However, previous studies have disregarded the operational risks of hydropower plants due to their physical constraints when complementing new energy sources. This study proposes a risk control method for a hybrid hydro-PV power system by adding electrochemistry energy storage (EES). A “day ahead–intraday–real-time” three-layer nested model is developed to guide the joint operation of the hydro-PV-EES hybrid system. The complementary flexibility of hydropower and EES is quantified and utilized to minimize unfavorable operating conditions of hydropower units when regulating PV forecast deviations. A case study of China's Longyangxia hydro-PV complementary project shows that after EES is connected to the system: (1) the total power generation of the system is improved 3.04%, and no power curtailment or shortage occurs; (2) the number of startups and shutdowns, and crossing the vibration zone of hydropower units are reduced by 12.87% and 12.17%, thereby improving the safety and operational stability of the hydropower plant; (3) the regulation flexibility supply of the complementary system is considerably improved; and (4) EES achieves flexible and safe control itself, with over 90% of the scheduling periods being in a healthy SOC range.••••Quantify the comprehensive regulation flexibility of hydropower and energy storage;••Reduce the operation risk of the hydro-PV complementary system by deploying energy storage;••Propose a complementary operation strategy of hydro-PV- energy storage hybrid power system.Photovoltaic powerHydro-PV complementary schedulingEnergy storageFlexibility quantificationWith the continuous development of the global energy pattern, a new paradigm centered on renewable energy is gradually emerging. A green, clean, low-carbon, environmentally friendly, safe, and efficient energy system is gradually being established. Following China's commitment to the “30·60 carbon peak and carbon neutrality” goal, renewable energy sources, such as wind and photovoltaic (PV) power will assume a pivotal role in driving China's energy transition and spearheading its future energy development [2,3]. According to statistics, the installed capacities of wind and PV power reached 370 and 390 million kW by the end of 2022, accounting for 14.24% and 15.33% of the total installed capacity in China, respectively. These figures are expected to increase to 21.00% and 27.00% by 2030. Owing to the strong intermittency, randomness, and volatility of wind and PV power [6,7], direct large-scale grid connection would cause serious curtailment, making it difficult to ensure a reliable power supply and safe grid operation. Therefore, there is an urgent need to efficiently integrate a high proportion of new energy into the grid while ensuring safe and stable grid operation.Hydropower is a traditional high-quality renewable energy source characterized by rapid start-up and shutdown, flexible operation, wide regulation range, and mature technology. It offers the power system a long-term, large-capacity,. The hydro-PV-EES complementary system (Fig. 1) includes at least one hydropower plant, one PV power plant, one load center (power grid), and one EES plant located under the same outgoing cross-section of the power grid. The system is controlled by a control center, which is responsible for the load management and energy distribution of the system. The control center guides the rapidly adjustable hydropower units to track and compensate for the random and intermittent PV output, then the joint power serves as a hybrid power source to be integrated into the power system. Meanwhile, the control center devises optimal charging and discharging strategies for EES, allowing it to cooperate with hydropower units in adjusting the deviation of PV forecast. And in order to improve energy utilization efficiency and reduce costs, EES is shared by all units of the hydropower station. This approach reduces the operational risk of the hydropower plant caused by regulating PV deviation alone.In this system, the PV plant can be seen as a virtual unit of the hydropower station. The control center formulates a day-ahead power generation plan for the hydro-PV-EES system and reports it to the power grid. In real operation, the total day-ahead power generation plan reported from the control center may be revised according to the states of other power sources in the grid and the load demand of the end-user. In this study, we ignore the possibility of revision an.
