With the continuously increasing penetration of renewable energy sources (RES) in modern power systems

the inertia distribution

impedance characteristics and dynamic behaviour of the grid undergo significant changes

which may alter out-of-step oscillation-centre locations and affect the applicability of out-of-step splitting schemes based on fixed splitting sections. Based on a modified two-machine equivalent model incorporating RES integration

this paper investigates the impact of increasing RES penetration on out-of-step oscillation centre migration in large-scale power systems. Theoretical analysis shows that an increase in RES installed capacity reduces the parallel equivalent impedance at the integration point

causing the oscillation centre to migrate in the direction opposite to the RES integration side. Case studies based on an actual regional power grid in China are carried out using the PSD-BPA simulation software. The results show that

as RES penetration increases

the oscillation centre may migrate from the inter-provincial tie-line section into the interior of an adjacent region

accompanied by a change of the out-of-step mode. These findings provide guidance for the configuration of out-of-step splitting schemes in power systems with high RES penetration.