Aggregated and DLL-Integrated PSCAD Modeling of Multipulse Rectifiers for Hydrogen Electrolyzers

Green hydrogen is crucial for achieving carbon emission targets in most major economies, and electrolysis is currently the most optimal method to produce scales of green hydrogen required. The AC-DC rectifier is a key component in such hydrogen production plants - typically operating at a multi-megawatt scale. Robust and reliable grid connectivity of such hydrogen plant depends largely on the rectifier performance. Detailed simulation models of rectifier systems are needed at various design and commissioning stages to ensure grid code compliance. These models are commonly developed using tools like PSCAD and Power Factory and can be broadly classified as open-source (aggregated) or encrypted (detailed) models. This paper presents both an aggregated modelling approach for thyristor rectifiers (6-pulse, 12-pulse, and 18-pulse) and an external code software-based modelling approach for a 6-pulse thyristor rectifier. The proposed methodology uses dynamically linked libraries (DLL) and Fortran wrapper to enhance PSCAD/EMTDC simulation capabilities, enabling high-fidelity modelling of complex power conversion systems. Results demonstrate the effectiveness of DLL-enhanced PSCAD modelling in power electronic interfaces for electrolysis applications using a 6-pulse thyristor rectifier.