Impact on Grid by Rectifiers for Green Hydrogen Production

Abstract

The production of green hydrogen, reliant on renewable energy sources, stands as a sustainable and carbon-neutral alternative in the fuel landscape. A pivotal aspect of this process is the conversion of alternating current (AC) to direct current (DC) to power the electrolyzer. Traditionally executed through thyristor-based converters, this conversion method encounters inherent challenges including reactive power injection into the grid, harmonic distortion of grid current, poor power factor, and escalated complexity and cost of the converter system. Mitigation strategies for these issues, such as harmonic filters, and D-STATCOM or STATCOM, augment the complexity and expense of the traditional solution. Furthermore, constraints imposed by grid operators regarding the permissible limit of harmonic distortion exacerbate the challenges inherent in traditional methodologies.

A comprehensive literature review delved into various converter topologies and technologies to address these challenges. Noteworthy among the examined topologies were the 6-pulse and 12-pulse three-phase thyristor rectifiers, both standalone and coupled individually to a DC-DC Buck converter, along with the Active Front End rectifier and Vienna Rectifier. These topologies were subject to simulation in SIMULINK under diverse load configurations.

The inadequacies associated with thyristor-based rectifiers were elucidated, prompting an exploration into alternative solutions. Comparative analysis revealed that the Active Front End rectifier and Vienna rectifier exhibited superior performance metrics, including power factor approaching unity, substantially reduced reactive power injection into the grid compared to thyristor-based counterparts, and total harmonic distortion below 1.5% within regions of optimal operation.

In conclusion, it was deduced that the Vienna and Active Front End rectifiers offer a streamlined complexity compared to traditional thyristor systems. Their operational efficiencies are underscored by diminished stress on system components owing to reduced reactive power demands and minimized harmonic content.