Dynamic characteristics and stability comparisons between virtual synchronous generator and droop control in inverter-based distributed generators

Recent years, to replace current source control methods, voltage source control methods such as virtual synchronous generator (VSG) and droop control have been proposed for grid-connected and/or stand-alone inverters. Both methods imitate the behaviors of synchronous generator. With the presence of swing equation, VSG has a virtual inertia, while droop control does not, and the rest of the two control methods are nearly the same. In this paper, the difference brought by the swing equation is studied. Small signal models for both control methods are built to compare the dynamic response during a small loading transition, and state space models are built to analyze the stability of both control methods. The results are verified by simulation in PSCAD/EMTDC.