Christian A. Hans

Ujjwal Pratap, Steffen Hofmann, Christian A. Hans

This paper studies robust optimal operation control problems for microgrids with a high share of renewable energy sources. The main goal is to ensure an optimal operation in the presence of a wide range of scenarios of uncertain infeed of renewable sources and uncertain load demand. We formally state a minimum-regret robust model predictive control (MPC) problem and address it by making effective use of a hierarchical microgrid control structure. In detail, we consider an enhanced primary control layer composed of droop control and an autonomous limitation of power and energy. We prove that this enables us to use constant power setpoints to achieve an optimal operation under certain conditions. To obtain a tractable controller, we then combine the abovementioned constant saturation-aware setpoints with an energy management system, which solves a robust unit commitment problem within a model predictive control framework. In a case study, we finally demonstrate the viability of the control design.

Hannes M. H. Wolf, Christian A. Hans

With the shift towards decentralized energy generation, the increasing complexity of power systems renders physics-based modeling challenging. At the same time the growing amount of available measurement data opens the door for obtaining models in a data-driven manner. A modern method to do so are neural ordinary differential equations (NODEs), offering a framework for continuous time system identification. Recent extensions, so called graph NODEs impose a structural inductive bias that has the potential to improve generalization of the learned representation. In this work, we employ graph NODEs and extend them with novel ideas to develop message-passing graph NODEs (MPG-NODEs) for identification of coupled systems with heterogeneous node dynamics and edge couplings. This encompasses state-of-the-art machine learning architectures to infer latent representations of unmeasured states from past measurements, local node and edge embeddings to account for heterogeneity as well as an autoregressive scheme to allow for piecewise constant control inputs. We apply MPG-NODEs to identify voltage and frequency dynamics of power systems and compare them to a monolith NODE under identical measurement assumptions. Our case study on the IEEE 9-bus system indicates that the proposed MPG-NODE offers a much more flexible framework with transfer learning options that allow to add or remove powerlines and units with little to no retraining.