Synchronous Machine Representations for Stability Studies of Power Systems with Inverters

Since Power Electronics (PE)-based sources present faster dynamics compared to Synchronous Machines (SMs), questions about system modelling for stability studies are raised: Can the transient associated with the grid still be neglected? Are the simplifications in SM modelling still applicable? Focussing on the latter, the main purpose of this paper is to observe the impacts of SM representations on the stability analysis of a power system with PE-based sources. Here, three different representations of SM have been used. A combination of frequency analysis and time domain simulations has shown that one of the simplified models can be considered to be a good approximation of the reference model for stability studies that do not require high precision analysis. On the contrary, the other model displayed a completely different behaviour, presenting even great dependencies between the SM state variables and the critical eigenvalues of the inverter control.