Distribution Grids Stability Study, The Importance Of Distributed Active Power Control

The medium voltage alternating current (MVAC) networks are changing with a main driver of reaching sustainable development goals. A main change is that fossil fuel-driven synchronous generators are replaced by distributed renewable inverter-based resources (IBR). As a result of this change, there will be new challenges to keep the stability of the MVAC networks. This paper focuses specifically on small signal stability challenges of MVAC networks. This is done by analyzing a simple MVAC test network with high penetration of grid following converters and a very weeak upstream grid model as a synchronous generator. This paper identifies parameters impacting the system’s stability using the tool G2ELin. The results of this study indicate that small signal stability issues can occur when the proportion of the power supplied by the grid following (GFL) converters is high and synchronous generators run low, the observed unstable mode is related to the synchronous generator. Two factors that showed to decrease the stability of the test network are, first, the distance between the synchronous generator’s location to the GFL converters and loads, and, second, natural line capacitance. To improve the stability a QV-droop control is implemented to the GFL converters; it helps the steady state voltage, but it did not improve the stability of the unstable mode. These findings underscore the need for further studies in this area to understand what parameters are important to consider to avoid small signal stability problems as more IBRs are integrated into the MVAC network.