The Compensator Approach: Solving the Transient Stability Issues of Virtual Synchronous Machines

The continuous integration of renewable energy sources (RES) into the grid through power electronics impacts the power system stability, posing new challenges for control techniques implemented on power converters. The virtual synchronous machine (VSM) represents a viable power converter control solution for the RES integration, providing natural grid support capability resulting from the emulation of the synchronous machine behavior. However, the VSM control faces transient stability issues under large voltage sags due to the significant acceleration of the virtual rotor. The literature reports numerous transient stability analyses, proposing different control solutions to improve the transient response of virtual synchronous generators (VSGs). However, they increase the complexity of the control algorithm, requiring additional tuning. Furthermore, they often mitigate rather than eliminate the transient stability issues. Therefore, this article provides a new perspective on VSM implementation, proposing the virtual synchronous compensator (VSC) concept as a straightforward and definitive solution to eliminate the VSM's transient instability. The VSC maintains its synchronism under large and prolonged voltage sags, overcoming the transient stability issues implied by conventional VSG algorithms without additional control modules. The VSC's transient response is verified theoretically and experimentally, proving the claimed benefits.