A novel two-stage framework to improve the flexibility of grid connected wind-hydro power system in real-time operation

The wind-hydro hybrid power system has been proven to be a viable solution in helping integrate variable wind power into the grid. While few studies consider the joint operation of the wind-hydro power system with the power grid, even fewer extend the research to improve the flexibility of the grid connected wind-hydro power system (WHGS) in real-time operation, aiming to reduce the load shedding in the face of increasing fluctuations and uncertainties from both wind power and demand. To address this gap, a novel two-stage framework is proposed. In the first stage of the framework (F-first stage), a scenario-based two-stage connection node decision model is proposed to improve the topology relationship between the wind power plant, hydropower plant and demands. In the second stage of the framework (F-second stage), a two-stage bilevel flexibility shortage risk averse model is proposed to dynamically decrease the load shedding during the current time period and mitigate flexibility shortage risks for the following time period in real-time operation. Then, a bilevel resource saving model is nested to reschedule the WHGS to conserve resources. Finally, all models are reformulated as MILPs. The case study shows that (1) improving the topology relationship between power plants and demands can decrease the impact of insufficient transmission line capacity and enhance the flexibility of WHGS; (2) the real-time flexibility improvement model can enhance the flexibility of WHGS and ultimately reduce load shedding (by 39.82 %) in real-time operation. It performs effectively even under low power transmission capacity (reducing load shedding by 2.58 %), low generation capacity (reducing load shedding by 7.93 %), and low confidence level (reducing load shedding by 15.82 %); (3) the choice of confidence level depends on the scenario conditions and operational preferences of the system operator.