## 2 Methods
### Analysis of Hedging Relationship in Hydropower and Photovoltaic Combined Operation  
The hydropower photovoltaic joint scheduling problem can be described as follows: in the reservoir of water balance and the premise of flood safety, the power system in the short term (within days or more) of electricity power balance, hydropower and photovoltaic of online distribution, water and electricity for photovoltaic power compensation ability, hydro and photovoltaic joint power load ability, and so on needs to be studied and solved. Considering the water storage period, the hydropower and photovoltaic joint operation should not only ensure the peak regulation and power generation demand of the combined system, but also consider the flood control risk of the reservoir and its upstream and downstream. This is a typical multi-objective conflict problem, such as the conflict between hydropower and photovoltaic power station power generation benefits, the conflict between hydropower ownership departments and water use departments, and the conflict between upstream and downstream hydropower goals. From the perspective of time, there is a conflict between the current storage efficiency goal and the flood control risk goal in the future. Figure 2 shows the multi-objective conflict relation diagram in the joint dispatching of hydropower and photovoltaic. Figure 1: Standard operating policy (SOP) and hedging regulation (HR). The hydropower and photovoltaic joint scheduling problem is a complex multi-objective conflict problem, which is analyzed using the hedging mechanism. According to the inflow runoff data, combined with the PV output forecast data, the rapid regulation ability of a hydropower station is used to maximize the profit benefit of the reservoir on the basis of ensuring the safety of flood control. If the inflow runoff in the future period is relatively small, the power generation efficiency of the combined system can also be increased. On the contrary, if there is a large incoming flow forecast in the future, the reservoir capacity can be adjusted by pre-discharge dispatching in the effective forecast period under the condition of guaranteeing the basic planned electricity. If the inflow runoff in the future period is relatively small, the power generation efficiency of the combined system can also be increased. On the contrary, if there is a large incoming flow forecast in the future, the reservoir capacity can be adjusted by pre-discharge dispatching in the effective forecast period under the condition of guaranteeing the basic planned electricity. If the pre-storage is less, the corresponding flood control risk is reduced. However, the hydropower station may not be able to meet the power generation plan issued by the power department because of its low power generation, which brings the risk of power shortage to the power system. Therefore, for the combined hydropower and photovoltaic system, in the decision-making stage, the reservoir should not only reserve enough water storage space to meet the flood control risk demand, but also take into account the maximization of resource utilization and power generation benefits. Dynamic Decision-Making Process of Hydropower and Photovoltaic Joint Operation Based on Hedge Theory  
In actual dispatching, it is necessary to coordinate multi-objective demands such as reservoir pre-storage benefit, flood control risk, and photovoltaic consumption, according to the inflow runoff, photovoltaic output, and load predicted in the face of the time period, and formulate the dispatching plan for the current period and, in the next period, formulate the decision value for this period again according to the latest forecast data. The actual scheduling is the process of combining the forecast information of the current period and the future period to carry out the rolling forecast and decision in turn. The prediction errors of warehouse incoming flow and photovoltaic power increase with the increase in forecast lead time.