AC-DC converters for electrolyzer applications: State of the art and future challenges

The main objective of the article is to provide a thorough review of currently used AC-DC converters for alkaline and proton exchange membrane (PEM) electrolyzers in power grid or wind energy conversion systems. Based on the current literature, this article aims at emphasizing the advantages and drawbacks of AC-DC converters mainly based on thyristor rectifier bridges and chopper-rectifiers. The analysis is mainly focused on the current issues for these converters in terms of specific energy consumption, current ripple, reliability, efficiency, and power quality. From this analysis, it is shown that thyristors-based rectifiers are particularly fit for high-power applications but require the use of active and passive filters to enhance the power quality. By comparison, the association combination of the chopper-rectifier can avoid the use of bulky active and passive filters since it can improve power quality. However, the use of a basic chopper (i.e., buck converter) presents several disadvantages from the reliability, energy efficiency, voltage ratio, and current ripple point of view. For this reason, new emerging DC-DC converters must be employed to meet these important issues according to the availability of new power switching devices. Finally, based on the authors' experience in power conversion for PEM electrolyzers, a discussion is provided regarding the future challenges that must face power electronics for green hydrogen production based on renewable energy sources.