Design-Oriented Analysis and Transient Stability Enhancement Control for a Virtual Synchronous Generator

Under fault conditions, virtual synchronous generators (VSGs) are prone to lose transient stability, similar to synchronous generators. However, the existing studies on VSG transient stability are not comprehensive. The transient characteristics of VSGs are highly affected by control parameters, but the transient models of VSGs in existing studies are overly simplified. In addition, the critical clearing angle (CCA) and critical clearing time (CCT) are two indices used to measure the transient stability of a system, but there are few studies that consider both CCA and CCT. In this article, we analyze the CCA and CCT quantitatively to describe the transient stability boundary of a VSG under different control parameters and fault conditions. Then, an equal proportional area criterion is proposed to provide guidance for the control of virtual inertia in the VSG. Based on a theoretical analysis, a transient control method for a VSG is proposed, which can improve the transient stability of the VSG in terms of both CCA and CCT. Finally, simulation and experimental tests are performed to validate the correctness of the theoretical analysis and the proposed method.