On the impact of high-power grid-connected thyristor rectifiers on the efficiency of hydrogen electrolyzers

This paper investigates the impact of power supply and dc current ripple on the efficiency of water electrolyzers and demonstrates that optimally sized thyristor rectifiers meeting grid power quality regulations can effectively supply high-power electrolyzers with minimal impact on electrolyzer efficiency. Firstly, an equivalent electrical model for the electrolyzer is developed, and the efficiency reduction caused by dc current ripple is analyzed. This is validated by means of experimental data from a 5-kW alkaline electrolyzer operated with both thyristor- and IGBT-based rectifiers. Next, the paper explores the operation of high-power electrolyzers supplied by 6- and 12-pulse thyristor rectifiers complying with grid power quality standards. Results show that with optimal sizing of ac-side source voltage and filtering inductances, these solutions exhibit negligible dc current ripple impact on electrolyzer efficiency. These findings, validated through simulation of a 5.5 MW electrolyzer, highlight the viability of thyristor rectifiers in high-power electrolysis applications, and emphasize the importance of an optimal power supply design and sizing for enhancing water electrolyzers' performance.