Survey on forced oscillations in power system

Abstract

The 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 have caught many researchers' attentions. Techniques are proposed to detect forced oscillations and locate their sources. In addition, forced oscillations may have a 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 a timely manner. The negative impact of forced oscillation can be mitigated when they are detected and located. This paper provides an overview of the analysis technique of forced oscillations in power systems. In addition, some future opportunities are discussed in forced oscillation studies.

A Periodogram-Based Method to Identify Forced and Natural Oscillations Using PMUs

“…The emulated PMU data is obtained from the time-domain simulation of the 14-bus system. Stochastic load fluctuations are considered, which follow Orstein-Uhlenbeck process with σ = 0.01 in (2). Besides, we use exponential recovery loads to model load dynamics, the model of which can be described as:…”

“…One of the major threats to the security and stability of power systems is sustained oscillations [1] [2], which can damage equipment, degrade the power quality and increase the risks of cascading power failure. Oscillations in power systems can be categorized into natural oscillations and forced oscillations.…”

“…Natural oscillations often result from inherent interaction among dynamic devices, which typically can be mitigated by power system stabilizer (PSS), intertie line controls, etc. In contrast, forced oscillations refer to system responses to an external periodic perturbation [2], which cannot be depressed by PSS. The only effective measure is to locate and remove the external driving source.…”

Wide area monitoring of sustained oscillations using double-stage mode decomposition

“…Vanfretti et al, Dagle, Rogers, Wang and Turitsyn, and Liu et al classified electromechanical oscillation into 2 groups: natural oscillations and forced oscillations (FOs). Some authors also refer natural oscillations as “free oscillation” or “electromechanical oscillations” or “system's mode” or “natural electromechanical oscillations.” Further, Wang and Turitsyn have classified sustained oscillations in 3 categories: weakly damped oscillations, limit cycles, and FOs. The FOs are further classified by Liu et al into 2 categories: general FOs and special FOs.…”

“…Some authors called FOs as the type of electromechanical oscillations, while some considered them different from electromechanical oscillations . Study on FOs has been widely reported in literatures, but not as much as of electromechanical oscillations. Forced oscillations are not the characteristic of the system but are the response of the system due to some driving functions .…”