A multi-level isobaric hydrogen-electric coupled energy storage system with a wide-range operational strategy: enhancing efficiency and flexibility in renewable-dominated power grid

Fluctuations in electricity caused by high penetration of renewable energy sources impose greater demands on energy storage systems for flexible absorption and efficient power supply. This paper proposes a novel integration strategy that combines the efficiency of isobaric energy storage technology with the flexibility of hydrogen-electric hybrid energy storage technology. Based on this, a multi-level net-zero emissions isobaric hydrogen-electric coupled energy storage system is developed. The system offers a wide range of power consumption capabilities, and its effectiveness has been validated in real-world scenarios with high renewable energy penetration rates when combined with an adaptive power allocation scheme. The results indicate that the system accommodates five charge modes and four discharge modes, with peak efficiencies achieved in charge mode I (85.17%) and discharge mode II (46.66%). The wide-range coordinated control framework maintains higher compressor isentropic efficiencies while expanding the adjustable power range by 45.28% compared to series configurations using only VS control, operating in a coordination control mode with variable speed and inlet guide vanes below rated power, and switching to variable speed mode above rated power. The adaptive power allocation scheme categorizes the imbalanced power into eight scenarios, keeping the CO2 compressor operates under design conditions during the charging process, while the discharge side consistently utilizes the low-pressure turbine as a stable power source. Compared with the conventional strategy, the proposed approach demonstrates improvements of 3.49% and 5.12% in average charge and discharge efficiencies, respectively, while reducing wind curtailment and mismatch power by 22.85% and 30.69%, respectively. In addition, parameter analysis indicates that the mutual constraints among efficiency and reliability index parameter adjustments must be comprehensively considered to enhance overall performance and effectively suppress unbalanced power in practical applications.