Unit Commitment of Integrated Electric-Natural Gas-Hydrogen Systems Including FCR Services

The integration of hydrogen production through electrolysis and the injection of hydrogen into natural gas pipelines offer important operating flexibility for accommodating intermittent renewable energy resources. It is of growing interest to analyze the coordination of the power system, natural gas system, and electrolyzers. We develop a scheduling model of power generators and electrolyzers in integrated electric—natural gas—hydrogen systems. Our model incorporates spinning reserve and frequency containment reserve services, which accommodates for operating flexibility provision to balance renewable energy generation. Pursuing computational tractability, a progressive McCormick envelope relaxation approach is developed to convexify nonlinear hydrogen-gas blending flows. Numerical results verify that the proposed model reduces the total operating cost by modeling the ‘standby’ flexibility of electrolyzers. Additionally, the proposed convexification approach results in tighter solutions.