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Large uptake in transmission and distribution connected inverter-based resources (IBR) such as wind farms, solar farms, battery energy storage systems (BESS) and distributed rooftop photo-voltaic systems is changing the power system dynamics. Penetration of IBR in remote and weak parts of the Australian network has resulted in the presence of sub-synchronous oscillations in the grid, often confined within an area of the power system. Recently, power system oscillations in the range of 17–20 Hz have been observed around the same area, although their nature is different from the previously observed 8–10 Hz oscillations. The more recent oscillations, unlike those observed in this area in the past, mostly seem to appear without any noticeable network disturbance or change in the network configuration. This paper outlines key characteristics of the recently observed 17–20 Hz oscillations and discusses the complexities associated with identifying the source of these oscillations through real-time measurements. Further, the paper demonstrates how these oscillations have successfully been simulated using EMT models. Two approaches, using a simplified single-machine infinite bus and large-scale network model, were applied to replicate the oscillations in the simulation environment. Finally, the paper compares the simulation outcome with the observations obtained from real-time measurements.