Comparative analysis of multi-mode operation for cascade hydropower plants and assessment of carbon reduction benefits

Cascade development is a key approach for modern hydropower utilization. However, differences in ownership and scheduling authority lead to multiple operation modes in cascade hydropower plants, including cooperative scheduling (CSM), game-based scheduling (GSM), and independent scheduling (ISM). These modes influence both operational efficiency and the accommodation of wind and PV, thereby affecting the power system's carbon reduction potential. This study proposes a framework to evaluate carbon reduction benefits under different scheduling modes. A load generalization method is developed to capture daily variability and peak shaving, based on which a multi-energy complementary carbon reduction model (MECR-PS) is established. Using the LYX, LXW, and NN cascade hydropower plant as a case study, the results show: (1) CSM improves carbon reduction benefits by 3.5 % compared to ISM and GSM. (2) GSM benefits upstream plants, while ISM favors downstream plants. (3) Wind generation and hydropower discharge are positively correlated with carbon reduction. (4) Under high-flow conditions, GSM for the upstream, ISM for the midstream, and CSM for the downstream plants yield the highest individual power generation. Under other conditions, CSM consistently delivers the highest generation across all plants. These findings offer valuable insights for cascade hydropower operation and low-carbon power system development worldwide.