Day-Ahead Economic Dispatch Optimization for Cascade Hydro–Photovoltaic Complementary Power Generation Systems Based on Dual-Layer Decoupling (DP-MAPPO)

To address the deep coupling of unit commitment and load allocation, nonlinear unit characteristics, and non-convex feasible regions caused by vibration zones in intraday dispatching of cascade hydropower under high photovoltaic penetration, this paper proposes a dual-layer decoupled DP-MAPPO method for hydro-photovoltaic complementary systems, aiming to minimize total water consumption. The upper layer uses dynamic programming to optimize unit commitment, while the lower layer employs Multi-Agent Proximal Policy Optimization (MAPPO) for continuous load allocation. A case study is conducted on a hydro–photovoltaic power system comprising five cascaded hydropower plants and two photovoltaic plants, with a 24-h scheduling horizon and a 15-min time step. The results show that MAPPO exhibits stable convergence under fixed evaluation scenarios. For a typical day scenario, the objective function value obtained by DP-MAPPO is essentially consistent with the benchmark optimal value. Compared with the actual dispatch schedules, DP-MAPPO reduces total water consumption by 9.15%, 3.42%, and 0.65% across the three typical days analysed, respectively, with no violations of turbine vibration-zone constraints in any scenario. These results demonstrate that the proposed method achieves optimized scheduling that balances water conservation with safe and stable operation.