  Malfunctioning equipment, erroneous operating conditions or periodic load
variations can cause periodic disturbances that would persist over time,
creating an undesirable transfer of energy across the system -- an effect
referred to as forced oscillations. Wide-area oscillations may damage assets,
trigger inadvertent tripping or control actions, and be the cause of equipment
failure. Unfortunately, for wide-area oscillations, the location, frequency,
and amplitude of these forced oscillations may be hard to determine. Recently,
a data-driven maximum-likelihood-based method was proposed to perform source
localization in transmission grids under wide-area response scenarios. However,
this method relies on full PMU coverage and all buses having inertia and
damping. Here, we extend this method to realistic scenarios which includes
buses without inertia or dumping, such as passive loads and inverter-based
generators. Incorporating Kron reduction directly into the maximum likelihood
estimator, we are able to identify the location and frequency of forcing
applied at both traditional generators and loads.
