Impact of Modelling Assumptions on the Voltage Stability Assessment of Active Distribution Grids

Renewable energy sources (RES) penetrate power grids at all voltage levels. A large number of RES units are connected to medium-voltage (MV) and low-voltage (LV) levels resulting in a significant share of overall generation. Therefore, the dynamic behavior of such distribution grids should be thoroughly examined. The goal of this paper is to show how various changes in the composition of the dynamic power flows interact with Low-Voltage Ride Through (LVRT) requirements, and how they affect the very important aspect of the RES-penetrated grids – voltage stability. The analysis is performed on a selected network, which is modeled with real grid data. The concluding concepts, however, are applicable for any distribution grid topology with a large number of distributed energy resources (DER). The results show essential grid details that should be modeled more precisely. This paper also addresses the level of complexity needed to obtain accurate results. Models are generally always imperfect and therefore, having more detailed data for a specific study is of the uttermost importance.