Operation modes of multi-operator hybrid pumped storage hydropower system with bidirectional hydraulic coupling

The integration of pumped storage (PS) within cascade hydropower plants (HPPs) managed by different entities to form a multi-operator hybrid pumped storage hydropower (MOHPSH) system is a crucial strategy for enhancing energy system flexibility. However, this system faces significant operational challenges from its bidirectional hydraulic coupling and the conflicting interests of multiple operators. Previous research has predominantly modeled such system under a single-entity assumption, overlooking the coordination complexities among diverse operators. To conquer the issue, this study develops a coordinated scheduling framework encompassing independent, partially joint, and complete joint schedule modes. Through this framework, we clarify operator interaction mechanisms within the MOHPSH system, identify key factors limiting system peak regulation performace, and provide strategic guidance for the selection of operation modes. Applied to a MOHPSH system on the Han River, the results reveal that: (1) system power generation benefits show limited sensitivity to the choice of operation modes, whereas peak regulation performance is significantly dependent on it; (2) the MOHPSH system's peak regulation performance is primarily constrained by the downstream XY's limited regulatory capacity and suboptimal inter-operator operational prioritization, leading to a loss of peak regulation water volume at XY, which can be as high as 28.7 %; and (3) a critical threshold is identified at an XY initial water level of 240.8 m. Below this level, system operational flexibility is high (excluding mode M4, the PS-priority mode), but above it, the complete joint schedule mode M5 becomes essential to overcome the XY reservoir capacity bottlenecks.