Small-Signal Modeling and Analysis of Multi-GFM System

As the increasing penetration of inverter-based distributed generations (DG) reduces the inertia of the power system, the stability of the system under small disturbances is threatened. Grid-forming (GFM) inverter, which can simulate inertia, damping and droop characteristics, is one of the most effective solutions. Virtual inertia and damping coefficient have important effects on the performance in primary frequency modulation. This paper presents an explicit and universal small-signal model for multi-GFM system based on the Newton-Raffson power flow algorithm in polar coordinates to realize the optimal design of virtual inertia and damping coefficient. The validity of the proposed model is demonstrated by comparing with the simulation model, and the effect of virtual inertia and damping coefficient on frequency response is analyzed in the end.