Optimisation Operation Strategy for Cascaded Small Hydropower Aggregation Virtual Power Plants Considering Hydro‐Logical Processes

ABSTRACT Unlike large‐scale hydropower plants, small hydropower stations typically have limited or even no reservoir capacity, making their flexibility in regulation highly sensitive to meteorological variability. The hydrological dynamic propagation across cascaded small hydropower stations significantly affects their output and inter‐station coordination, which has often been overlooked in existing scheduling models. To address this gap, this paper proposes an optimised dispatch strategy for a virtual power plant (VPP) that aggregates cascaded small hydropower units with explicit modelling of hydrological processes. First, a flexibility quantification framework is developed by integrating reservoir and river channel storage capacities through the Xin'anjiang rainfall–runoff model and the Muskingum flow routing method, capturing the rainfall runoff and hydrological coupling within cascaded systems. Then, considering multiple uncertainties—precipitation, wind and solar power—the net load is used to represent their joint influence, and a Wasserstein distance‐based distributionally robust stochastic optimisation model is established to manage these uncertainties. Finally, a case study based on a real river basin demonstrates that the proposed method significantly enhances operational performance: the VPP's total operating cost is reduced by 22.6%, net revenue increases by 57.1%, curtailment and load‐shedding costs decrease by 9.5% and flexibility deficit costs are reduced by 68.0% compared with conventional scheduling. These results confirm that the proposed framework effectively leverages the unique flexibility of cascaded small hydropower and provides a robust and tractable solution for VPP operation under uncertainty.