Analysis and Improvement of Damping Factor Based on Virtual Synchronous Generator Control

In virtual synchronous generator (VSG), constant damping factor control method is often used to reduce the active power oscillation. However, constant damping factor control would result in errors in proportional active power sharing when implemented in islanding microgrid because it changes the equivalent droop coefficient of inverter. In this paper, the small-signal models of inverter based on VSG are built first, for both grid-connected mode and islanded mode, to analyze the oscillation of output active power, in order to understand the effect of damping factor. Then this paper analyzes the problem that the constant damping factor control influences the active power sharing. Furthermore, an improved damping control method based on PI regulator is proposed to solve the active power sharing problem. In addition some root locus for the VSG based on improved damping control method are provided to study the effect of the improved damping control on the system stability and dynamic behavior. Simulation results are presented to validate the improved damping control method.