Virtual Voltage Control of VSG for Overcurrent Suppression Under Symmetrical and Asymmetrical Voltage Dips

This article proposes a novel and easily implementable overcurrent suppression control for voltage-controlled virtual synchronous generators (VSGs). The VSG is vulnerable to grid voltage disturbances, such as voltage dip/recovery, because it consists of voltage source inverters (VSIs). In the worst case, the overcurrent caused by the voltage disturbance damages the VSI. The proposed VSG control can suppress the overcurrent caused by not only symmetrical but also asymmetrical voltage dip/recovery. The key idea is to use novel virtual grid voltages for the VSG reference output voltage. The proposed VSG control requires no complicated analysis/tuning for the implementation and no additional equipment, such as a fault-current limiter. Because of these advantages, the overcurrent in the VSG can be suppressed without increasing the cost and the tuning effort. The effectiveness of the proposed method is verified through simulations and experiments.