Short-term Optimal Scheduling Method for Watershed Hydro-Solar-Wind Power Bases under AC-DC Hybrid Transmission Mode

To address the increasingly prominent scheduling challenges of large-scale watershed Hydro-Solar-Wind (HSW) generation bases under multi-terminal AC-DC hybrid transmission scenarios, this study proposes a short-term optimal scheduling method for watershed HSW generation bases oriented toward AC-DC hybrid delivery. This method specifically addresses three core technical bottlenecks in practical operation: the strong uncertainty of wind-solar renewable energy output induced by meteorological factor fluctuations, the intense contradiction in power distribution between AC and DC receiving terminals arising from differences in load characteristics and grid operation constraints, and the complexities in upstream-downstream scheduling coordination caused by the intricate cascade hydrological and hydraulic connections of watershed power stations. With the rapid advancement of renewable energy grid integration and the continuous expansion of cross-regional power transmission projects, the safe and efficient operation of multi-terminal AC-DC hybrid transmission systems has become a key bottleneck restricting the accommodation of large-scale HSW generation bases, rendering the development of targeted optimal scheduling methods an urgent practical need. Temporally, to adapt to significant hydrological and operational discrepancies between flood and dry seasons, the proposed method formulates differentiated objective functions in line with actual scheduling requirements. During the dry season, the core objective is to minimize the sum of squares of residual load in the AC receiving terminal grid, thereby enhancing the stability of the receiving-end power system; during the flood season, the core goal shifts to maximizing the total generated power for better economic benefits of the HSW base. Spatially, the method fully accounts for the strong cascade hydraulic connections between upstream and downstream hydropower stations, incorporating upstream-downstream coordinated operation constraints into the scheduling model. Distinct from the traditional independent scheduling mode where each power station formulates scheduling plans separately, this approach ensures that the scheduling decisions of each power station are mutually compatible and globally optimal, giving full play to the operational benefits of individual power stations through integrated scheduling. In addition, to enhance the practical applicability and reliability of the scheduling model, this study comprehensively incorporates a series of key operational constraints. These include the fixed hydropower allocation ratio between AC and DC transmission channels specified in grid planning, the stepped power constraints of DC systems to guarantee the stable operation of converter stations, and the hydropower reserve constraints designed to cope with sudden fluctuations in renewable energy output and unexpected load variations. These constraints ensure the direct applicability of the optimized generation scheduling curve in engineering practice. An application study was performed on a 10-million-kilowatt-level watershed HSW generation base in Southwest China, which serves as a typical representative of multi-terminal AC-DC hybrid transmission projects. The application results demonstrate that the proposed power distribution method can accurately match the demand characteristics of multiple receiving terminals, flexibly achieve the optimal distribution of power from the HSW generation base between AC and DC receiving terminals, and satisfy the power supply and peak-shaving requirements of multiple receiving terminals. Specifically, during the dry season, the peak-valley difference of residual load in the AC receiving terminal grid is reduced by 36% compared with the original load, effectively mitigating the peak-shaving pressure of the receiving-end grid; during the flood season, the power curtailment of downstream power stations is reduced by 556 million kW·h, significantly improving the utilization efficiency of water resources and renewable energy. Meanwhile, a sensitivity analysis of the power allocation ratio and transmission channels was conducted. These results fully validate the effectiveness and superiority of the proposed method, which can provide important theoretical support and technical references for the efficient scheduling and engineering practice of multi-terminal integrated HSW generation bases under AC-DC hybrid transmission scenarios.