Advanced Simulink Modelling of PV–PEM Electrolyser Coupling

Sammanfattning

A higher production rate of green hydrogen is needed to meet climate change targets. This thesis investigates the behaviour of four photovoltaic (PV) and proton exchange membrane (PEM) electrolyser coupling configurations in MATLAB Simulink. Direct and indirect coupling are simulated, and systems are created with PV reconfiguration, with and without a battery, to investigate the behaviour of systems producing green hydrogen. The systems are built with components available in Simscape an electrical library of Simulink. The core of the models is a validated equivalent electrical circuit (EEC) model of the PEM electrolyser. The models show that direct coupling is the simplest system with the lowest energy transfer losses, but it can suffer from higher mismatch losses, depending on the local irradiance profile. An optimised indirectly coupled system could reduce those mismatch losses at the cost of increased energy transfer losses. The indirectly coupled system highlights the importance of optimising its control strategy to be able to reduce mismatch losses. With the reconfiguration of the PV modules, the mismatch losses of the direct coupling are reduced, and the overall solar-to-hydrogen (STH) efficiency is improved. To utilise the disconnected PV modules, a battery is added to the directly coupled system with reconfiguration. The addition of the battery lowered the STH efficiency due to increased energy transfer losses inside the battery converter. This is likely due to the simplified control logic of the battery, which leads to low PV and energy transfer efficiencies. The additional battery enables nighttime hydrogen production, which increases the hydrogen availability. Three of the four cases are simulated with a two-day irradiance profile, leading to an STH efficiency of 12.89% for the direct coupling, 15.39% for the direct coupling with reconfiguration and 10.79% for the direct coupling with reconfiguration and storage. The results demonstrate that the system with PV reconfiguration has the highest STH efficiency, but that the utilisation of the disconnected PV panels needs improvement. Overall, this thesis can be seen as a foundational framework for building circuit level PV-PEM systems using discrete electrical components from the MATLAB Simulink Simscape library. The modelled systems provide a platform for future optimisation and research on component interactions.