A Survey on Forced Oscillations in Power System
  Oscillations in a power system can be categorized into free oscillations and forced oscillations. Many algorithms have been developed to estimate the modes of free oscillations in a power system. Recently, forced oscillations caught many attentions. Techniques are proposed to detect forced oscillations and locate their sources. In addition, forced oscillations may have negative impact on the estimation of mode and mode-shape if they are not properly accounted for. To improve the power system reliability and dynamic properties, it is important to first distinguish forced oscillations from free oscillations and then locate the sources of forced oscillations in timely manner. The negative impact of forced oscillation can be mitigated when they are detected and located. This paper provides an overview on the analysis technique of forced oscillations in power systems. In addition, some future opportunities are discussed on forced oscillation studies. 
Mohammadreza Ghorbaniparvar
cs.SY