Small-Signal Stability Analysis of Parallel Grid-Connected System with Grid-Forming Converter and Grid-Following Converter

In order to guarantee the stable operation of new energy sources when connected to the power system through converters, it is of paramount importance to conduct thorough research the small-signal stability of parallel grid-connected system with grid-forming converter (GFM) and grid-following converter (GFL). Initially, the state-space small-signal model of the parallel grid-connected system with GFM and GFL are derived. Subsequently, the impact of the phase-locked loop (PLL) bandwidth, virtual inertia, and reactive power loop integral coefficient on system stability is assessed using the eigenvalue locus method. Moreover, the participation factor analysis method is employed to identify the dominant state variables of the oscillatory mode. Finally, the correctness of the theoretical analysis is validated using PLECS.