Modelling active distribution grids in power systems frequency stability studies

Due to the urgency of the energy transition, a lot of changes are made on the grid. The main goal is to keep stable and reliable energy provisioning while reducing its carbon footprint. While renewable generators like PV panels are more and more connected to the grid, the stability of the latter is impacted. In order to improve that stability, battery energy storage system (BESS) are connected onto the grid. The objective of this work is to propose a simplified model which has the same behavior in case of frequency deviations, than a real grid with active components. First, the BESS and its connection to the grid as well as its control will be explained. Then, an equivalent model of a distribution grid with active components (PV panel and BESS) is designed, using the Monte-Carlo methodology on a "grey box" approach. The main elements leading to the equivalent model will be analysed and described. Among others, a partial tripping is added to the equivalent active components in order to react to the variance of tolerance to frequency deviation of the different active components present on the distribution grid. Analysis demonstrates that the best calculation error in the methodology corresponds to the mean of the absolute value. It is also shown that the parameters with a small influence on the power response as well as the ones for which the initial value is fairly accurate can be discarded from the methodology, in order to decrease the computation time by approx. 38 %. It's also noticed that the voltage stays inside acceptable range even if some powers are exchanged between active components and the grid, so there is no need to control it. Finally, the suggested equivalent model continues to work well against more complex distribution grids and associated models as well as with load's dependency to frequency. As a result of this work, we obtain a methodology that can design the equivalent model to active distribution grids, so that they all have the same reaction to frequency issues.