Analysis of the Impact of the Increasing Inverter-based Resources on Inter-area Modes of the U.S. Eastern Interconnection

The retirement of conventional synchronous generators and the integration of inverter-based renewable energy sources (RES) are transforming power systems in unprecedented ways. Understanding the impact and consequences of this resource mix transition is crucial to maintaining reliable grid operation. In this regard, this paper examines the impact of increased renewable energy sources on the oscillatory behavior of the U.S. Eastern Interconnection. From our analysis, we found that no single trend could be used to correlate the impact of increased RES penetration levels on the damping ratio of system modes. In fact, the impact of the increased RES penetration levels on a system mode was influenced by the group of synchronous machine models that were replaced with RES machine models. For example, replacing the synchronous generators in Florida significantly increased the damping ratio of the 0.21 Hz mode, whereas the impact was relatively small on the mode when synchronous machines were replaced in the North-eastern areas of the EI.