Addressing future power system stability challenges as distribution system operators - current status and priorities

Distribution system operators (DSOs) are increasingly required to address future power system stability challenges. In Germany, policy makers and experts analysed these challenges and defined processes and responsibilities in the System Stability Roadmap. E.ON and its DSOs analysed these and prioritized the topics of integrating grid-forming converters (GFCs), future grid and supply restoration concepts, short-circuit current levels in inverter dominated grids, and reactive power provision for voltage regulation. For each of these, open questions and milestones are defined. These are and will be addressed with methods ranging from theoretical analyses to field testing. We exemplary show our current progress in the GFC integration topic by presenting selected results of a simulation study on the impact of GFCs integration at MV and LV on unintended islanding. These results show that even relatively small shares of GFCs (even below 25%) can cause unintended islanding and prevent established active islanding detection methods from ensuring a secure shutdown of the grid segments. This shows that before mass integration of GFCs at MV and LV level, further investigations of interdependencies and further development of the operating principles are required. This highlights the necessity for a stepwise approach to solve these challenges.