Derivation of operating rule curves for cascade hydropower reservoirs considering the spot market: A case study of the China's Qing River cascade-reservoir system

The spot price varies in deregulated markets, and is important for the revenue of cascade hydropower reservoirs. However, the conventional operating rules maximize hydropower generation without considering the spot price. To address this issue, this study focuses on deriving operating rule curves to maximize revenue by integrating reservoir operations and a spot market. Spot prices are simulated by aggregating supply bids and estimating demand. A parameter-simulation-optimization approach is then used to maximize the hydropower revenue and reliability, and minimize spill water simultaneously. With China's Hubei province as the market boundary, the Qing River cascade-reservoir system was selected as the case study. The spot price is significantly affected when the Qing River cascade-reservoir system participates, compared with the market without the cascade system. The spill water reduction (1.33%) and average water head increase (0.56%) contributes to the 1.74% hydropower generation increment of the derived rule curves compared with the conventional operating rules, resulting in hydropower revenue increase by 2.25% with the mean spot price raised by 0.36%. The firm-output operational zone is expanded during the refill period, compared with that derived in an independent pricing scenario. The derived operating rule curves are effective to maximize hydropower revenue for long-term operation.