Comparison of thyristor and insulated-gate bipolar transistor -based power supply topologies in industrial water electrolysis applications

Abstract The demand for green hydrogen is growing as the increasing production of pure hydrogen can no longer be based on fossil hydrocarbons. As water electrolysis would move from niche to a significant consumer of emission-free electricity, the efficiency of electrolytic gas production, lifetime of water electrolysis systems, and balance in the electricity grid become essential. The operational and investment costs of an industrial-scale alkaline water electrolyzer with four practical rectifier topologies are investigated. The results show thyristor-based rectifiers provide poor quality for the AC and DC sides, which leads to nonoptimal specific energy consumption (SEC) of the water electrolyzer and a notable reactive power component. Transistor-based topologies may offer up to 4.5% lower SEC of the electrolyzer than the conventional 6-pulse thyristor bridge. The reactive power results in additional costs in either investments in compensation equipment or regular allowance costs. An additional DC/DC converter can be installed to improve the power quality for the electrolyzer, but the second conversion stage adds to the system complexity and cost without eliminating reactive power. A modular single-stage rectifier based on insulated-gate bipolar transistor (IGBT) bridges is suggested as an alternative to provide improved power quality for both the electrolyzer and the electricity grid.