Optimized operation of integrated electricity-HCNG systems with distributed hydrogen injecting

Green hydrogen, the cleanest energy carrier, is receiving increased attention in recent years. Transporting hydrogen through a natural gas system (NGS) will significantly promote the use of hydrogen, moreover, hydrogen-enriched compressed natural gas (HCNG) has great potential for renewable energy accommodation. To solve the problem of altered gas flow caused by hydrogen injection into natural gas networks, an optimized operation model of integrated electricity-HCNG systems (IEHCNGS) with distributed hydrogen injecting is proposed in this paper. Firstly, a calculating model of hydrogen volume fraction based on minimum square summation and depth-first search is established to describe the gas flow distribution of NGS accurately. Secondly, a quantitative method of gas supply reliability based on maximum entropy is proposed to ensure the safe operation of the system. Finally, an optimization model of IEHCNGS is established considering the coupling constraints of the integrated system and the reliability of NGS. The case study shows that the hydrogen volume fraction calculation model can correct the heat value of gas in each pipeline in real-time, the maximum entropy model helps to improve the gas supply reliability of NGS, and the distributed hydrogen injecting mode is more capable of accommodating renewable energy.