Accurate State Space grid-following inverter model for small signal stability analysis in converter based power systems

The future grid is expected to be mostly based on renewable energy plants, such as wind farms or solar plants, as well as hybrid power plants combining both technologies. As these technologies need a power inverter coupling, new dynamic interactions produced between each other arise, affecting the current stability of the grid. For that reason, there is an urgent need of developing simulation models, capable of analyzing these stability challenges, with a compromise between computational cost and accuracy. Previous studies validate the fidelity in terms of stability of a traditional grid-following inverter using nonlinear Averaged Electromagnetic Transient models with low simulation time, compared to nonlinear Switching Electromagnetic Transient models with high accuracy and high computational cost. This paper proposes a further implementation of the Averaged model, linearizing its behaviour by a State Space representation and using the same validation procedure focused on small signal stability, ensuring the high-fidelity approach of the State Space model. Additionally, it is shown how the State Space representation provides new insights in modal analysis, being able to study analytically the stability of the system in the frequency domain, understanding how the control variables are affecting the system stability and reducing the complexity of simulating multiple inverters. Therefore, the grid-following State Space model becomes the best choice for this type of stability studies.