Modeling and control of a grid-supporting electrolyzer

Abstract

The transition of the fossil fuel based centralized power generation in many countries towards renewable resources based distributed generation enables to reduce greenhouse gas emission as well as energy sources dependency. Besides the positive aspects of increasing the share of renewables in the energy mix, the technical feasibility of integrating variable renewable sources should be considered. This thesis investigates electrolyzers as promising systems to compensate the stochastic and intermittent behavior of renewable sources by storing energy in the form of hydrogen. Moreover, the study mainly covers the potential of the electrolyzers to enhance the robustness and stability of the decentralized power systems which are decreased due to absence of rotating inertia. Thus, to balance generation and consumption, electrolyzers can play a crucial role. The current state of the art is to regard electrolyzers as loads and connect them to the grid mainly using transistor rectifiers. In this thesis the interactions between an electrical grid, represented by a synchronous generator and an electrolyzer as a load are under investigation. Therefore, a model of synchronous generator, electrolyzer and power electronic devices for connection have been built, and a plausible parameterization is implemented. In a second step, the control algorithms for the power electronic devices are synthesized and analyzed regarding their grid supporting properties. Furthermore, a designated grid supporting control algorithm is adapted to ascertain the contribution of the electrolyzer in the frequency and voltage amplitude stability of the power network. To study the impact of electrolysers on power system stability, various Electromagnetic Transient (EMT) simulations have been performed. These simulations show that electrolyzers have a positive effect on frequency stability, as electrolyzers are able to respond for frequency deviations faster than conventional generator governors.