Experimental Study of the Effect of Thyristor and Transistor-Based Power Converter Topologies on Alkaline Water Electrolyzer Losses

Abstract

Large-scale water electrolyzers have the ability to operate as flexible loads, absorbing power fluctuations in power systems with high or full share of variable renewable energy sources (VRESs). For large-scale industrial applications, alkaline water electrolyzers (AWEs) and thyristor-based power converter topologies are commonly used due to their lower cost compared to proton exchange membrane water electrolyzers (PEMWEs) and transistor-based topologies. However, thyristor-rectifiers have a significant ripple when operated at partial load. A wide operational range is required when electrolyzers operate in a flexible manner, and large current ripples due to the power converter topology increase the power losses in the electrolyzer. Therefore, it is essential to study the impact of the current ripple on AWE performance. This article proposes an evaluation approach to systematically assess the impact of different power converter topologies on AWE losses, including an electrolyzer model for power electronic applications and experimental verification. Realistic current waveforms for industrial applications are obtained from a simulated large-scale electrolyzer system, and these waveforms are tested in a small-scale experimental setup. The experimental results validate the large-scale system simulations and the proposed model and provide quantitative assessment of AWE losses caused by the current ripple. The results also show that the six-pulse thyristor rectifier has the highest current ripples, causing the highest additional losses in the electrolyzer.