Converter-Driven Small Signal Stability and Interaction Analysis for Grid-Following Converters in Weak and Strong Grids

Increased penetration of converter interfaced generation influences the overall power system dynamics and therefore requires new stability analysis. To this end, we present a small signal stability and interaction analysis in the sense of converter-driven stability for grid-following (GFL) converters. Since interaction can occur between control loops of several converters as well as between the control loops and passive grid elements, we use a 2-bus system containing two GFL converters, two loads, a line, and a Thévenin equivalent. Modular state space component models allow the implementation of the linearized state space model of the whole considered power system that we further use for the small signal stability and interaction analysis via eigenvalue, participation factor, and indices analysis. We furthermore outline the influence of the grid strength on interactions and show that in the case of a weak grid, which can be equated with a high proportion of converter interfaced generation, interactions and the risk of instabilities may increase. EMT simulations for validation purposes as well as the analyses are performed in Matlab Simulink.