Synchronous frequency resonance of virtual synchronous generators and damping control

The Virtual Synchronous Generator (VSG) is an effective solution for high-penetration renewable energy sources integrated into the power system. Although the VSG has a similar behavior as the conventional synchronous generator, the fast and flexible control capability of converters may give rise to some specific characteristics. In this paper, it is explained that flux dynamics may induce synchronous frequency resonance in VSGs, which possibly leads to power-angle oscillations. A precise small-signal model is established to investigate the synchronous frequency resonance phenomenon. Based on this model, two damping control methods are proposed, which suppress the resonance through increasing the virtual mechanical inertia or adding virtual electrical resistance. The effectiveness of the theoretical conclusions is verified by simulation and experimental results.