Joint operating rules for large-scale hydro–hydrogen–based hybrid energy systems

Both adjustable hydropower and hydrogen power present viable solutions to address the intermittency and fluctuations of renewables such as wind and photovoltaic power. To complement non-schedulable renewables, previous studies have individually explored the operating strategies of hydropower or hydrogen power. However, the joint operating rules of hydropower and hydrogen power have seldom been investigated, primarily due to the complex reciprocal relationship between multiple adjustable power sources. This study aims to develop the joint operating rules for hydro–hydrogen–wind–photovoltaic hybrid energy systems (HESs). First, a deterministic optimal operation model is built to optimize both the operation benefit and assurance rate. Subsequently, the operation decisions are synthesized to identify reference values of operation rules’ parameters, with cross-correlation analysis aiding in the identification of the proper decision variables. Finally, operating rules’ parameters are optimized through the direct policy search method. Results from a case study using China’s Ertan hydro–hydrogen–wind–photovoltaic HES indicate that the reservoir release emerges as the most influential decision variable for formulating joint operating rules. Notably, the joint operating rules outperform conventional methods, yielding a 16.93% improvement in annual operational benefits and a 7.31% increase in assurance rates. These findings underscore the substantial enhancements in energy use efficiency facilitated by the proposed joint operating rules.