Multi-objective virtual inertia control of renewable power generator for transient stability improvement in interconnected power system

Abstract

In the power system with high penetration of renewable power generators (RPG), although frequency performance can be improved by introducing virtual inertia control, the swing stability of the rotor angle is likely to be reduced due to the changed inertia distribution. The motion equation of an interconnected power system with RPGs is established firstly, and the transient energy function is then derived to analyse the impacts of virtual inertias on transient energy conversion. In this paper, the transient process of the rotor angle after the disturbances is divided into two periods of first swing and multi-swing, and the effects of virtual inertia on the system stability are then analysed in the two periods, respectively. Under the virtual inertia control, the RPGs are utilized not only to share accelerating energy with synchronous generators (SG), but also to provide additional decelerating energy for the reduction of the rotor angle variation during the first swing period. In addition, based on the eigenvalues analysis, the effects of virtual inertias on system damping are evaluated theoretically, and the virtual energy of RPGs is then regulated to damp the oscillations during the subsequent multi-swing period. Experimental tests on a hardware-in-the-loop platform of a two-area interconnected power system with high wind power penetration are carried out to validate the proposed control strategy. The results demonstrate that in addition to the basic frequency support function, the swing stability of rotor angle is also improved, thus greatly improving the reliability of the virtual inertia support.