Combined optimization and flexible reserve of electricity–hydrogen coupled integrated energy systems based on three-state start–stop technology

To address the challenges of grid stability and uncertainty arising from the large-scale grid integration of renewable energy, this paper investigates the optimization of unit combinations within electricity–hydrogen coupling systems to enhance system flexibility and economic efficiency. Based on three-state start-stop characteristics, a scheduling model for electrolytic hydrogen production systems was established. A mixed-integer nonlinear model was constructed, employing a Gaussian mixture model to analyze renewable energy forecasting errors and quantify the impact of flexible reserve requirements on scheduling. Findings indicate that transitioning between flexible reserve and thermal reserve states significantly reduces reserve costs and increases renewable energy absorption rates. Concurrently, the study examines the impact of renewable energy penetration rates, unit start-stop characteristics, and the three-state model on scheduling costs. Simulation results demonstrate that at 40.5% renewable energy penetration, system operating costs decrease by 1.1%; rising to 6.3% when penetration reaches 80%. Concurrently, system carbon intensity decreased by 62.8%, reducing annual carbon emissions by 126 000 tonnes. This research provides theoretical and practical support for the economic optimization of electricity–hydrogen coupled integrated energy systems. As hydrogen technologies mature, this system holds promise as a key enabler for energy transition.