Stability analysis of offshore HVDC power systems
Power electronic converters pose new challenges in terms of security of supply: their control dynamics are orders of magnitude faster than those of traditional grid elements (e.g. generators), and as such, they give rise to new types of adverse dynamic interactions that can ultimately give rise to a system shutdown. In the future, this can even lead to potential blackouts for power systems entirely relying on power electronics. Hence, guaranteeing component interoperability will be key in order to ensure reliable operation of offshore power systems, as well as for future power systems as a whole. Since power-electronic converters and their controls are much more complex than conventional installations, this requires developing full understanding of their impact on the system dynamics, starting from a detailed characterization of these components and their degrees of freedom in terms of control, and this over an increased frequency range. Recent international industrial trends also point out that it is to be expected that also the future grid codes will need to specify much more in detail the expected behavior of converters. As such, connecting new converters to future offshore power system will also require a more detailed characterization of the power system itself compared to what has been good engineering practice for several decades. As it is often not feasible and/or desired to model the entire power system, there is a need to develop system equivalents that allow to focus on the subset problems to be expected. Such models can greatly facilitate the connection of new installations to an existing power system. The goal of the work is therefore to fully characterize dynamic converter interactions with the rest of the power systems dominated by power-electronic components in order to understand the impact of design choices on the system stability in the short term. The second goal is to develop active control schemes to solve problems caused by dynamic system interactions in order to avoid unexpected system outages. Solutions will be developed into a proof-of-concepts in commercially-graded offline simulation tools, and ultimately in real-time hardware-in-the-loop studies on the RTDS in EnergyVille in order to move the solutions as close to reality as possible.