Angular Acceleration Transient Damping VSG for Paralleled Inverters in Islanded Microgrid With Constrained RoCoF and Suppressed Power Oscillation

Paralleled VSGs can collect resources from multiple devices, forming a large virtual inertia to stabilize an islanded microgrid. This enables an independent way for flexible utilization of renewable energy. Paralleled VSGs often suffer from active power oscillation when countering disturbances. Many efforts have been devoted to solving the problem, however, improved VSG control may have a high rate of change of frequency (RoCoF), leading to load shedding, relay misoperation, and cascaded collapse. Nevertheless, RoCoF constraint is barely discussed in existing literature. This paper proposes an angular acceleration transient damping VSG control for paralleled inverters, to constrain RoCoF and suppress power oscillation simultaneously. This is achieved by adding a negative feedback loop of angular acceleration into existing transient damping VSG, increasing virtual moment of inertia to constrain RoCoF. The side effect of virtual moment increment is a possible enlargement of power oscillation, this is further solved by utilizing an inertial element within the feedback loop to provide an extra damping effect, sustaining good oscillation suppression. Simulation experiments indicate that the proposed method has a much lower RoCoF and slightly better oscillation suppression than transient damping VSG, and holds an overall performance much better than traditional method.