Method for calculating water level control interval of leading hydropower station with improved compensation and avoidance ability

The substantial energy storage capacity and regulation reservoir capacity of the leading hydropower station, as well as its regulating effect on the downstream hydropower stations, constitute the core mechanism enabling cascaded hydropower to accommodate the continuous high-output periods and compensate for the continuous low-output periods of renewable energy. The key challenge lies in the effective regulation of reservoir water levels. To address this issue, this study proposes a method for deriving the water level control range of leading hydropower stations to enhance their regulation capacity. Considering the complex operational constraints of hydropower systems and the hydraulic correlations between upstream and downstream stations in the cascade, an algorithm for calculating the lower bound of the water level control range is developed, targeting the extreme scenario of future dry incoming flow coupled with continuous low output of renewable energy. Correspondingly, an algorithm for determining the upper bound of the water level control range is presented, which is tailored to the extreme scenario of future abundant incoming flow combined with continuous high output of renewable energy. Ultimately, the water level control range of the leading hydropower station is defined by the derived upper and lower bounds, which ensures the availability of water resources for power generation and reserved storage capacity for water regulation, thereby enhancing the compensation and accommodation capabilities of hydropower systems. Case application of the Lianghekou hydropower station under massive scenarios demonstrates that maintaining the reservoir water level within the derived control range enables effective response to extreme fluctuation events of renewable energy output and natural inflows.