<p>This study aims to explore the optimal operational strategies for electrolyzers in the ancillary services market of wind–solar–storage–hydrogen hybrid power plants to enhance economic performance. A comprehensive trading strategy model has been developed, which encompasses both day-ahead and real-time markets while integrating the rules of the power ancillary services market. The study proposes a two-stage dispatch framework for hybrid power plants, employing stochastic optimization and uncertainty management techniques to address market and demand uncertainties. Detailed modeling of hydrogen production efficiency at non-rated power levels for electrolyzers has also been conducted. By constructing a simulation case based on China's electricity spot and auxiliary service market, the calculation results show that the participation of electrolyzers in the auxiliary service market can enhance the response ability of hybrid power plants to the frequency regulation markets, improve the economy of hybrid power plants, and reduce the cost of hydrogen production.</p>