Simplified Virtual Synchronous Compensator With Grid-Forming Capability

The Simplified Virtual Synchronous Compensator (S-VSC) is a Virtual Synchronous Machine (VSM) solution available in the literature, which operates as a virtual compensator. Previous works demonstrated that it can provide grid services (e.g., inertial behavior, grid support during faults) only in grid-following operation. However, the grid-forming capability of the S-VSC (and in general of a virtual compensator) has never been investigated in the literature. Therefore, this article proposes an S-VSC model able to operate both in grid-following and in grid-forming configuration. First, the article validates the small-signal stability of the control algorithm both in grid-mode and island operation through an eigenvalue-based stability analysis. Next, the control algorithm is experimentally validated on a 15 kVA inverter connected to a scaled microgrid. The experimental tests demonstrate that the S-VSC can operate both as grid-following and grid-forming. Moreover, it can seamlessly switch from the grid-connected to the island operation without requiring any communication system. Finally, the grid-forming capability of the S-VSC is experimentally validated even in case of a fault occurrence, thus representing a valid solution for the control of a microgrid.