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.