Different from the energy definition of the above references, defined the total energy of power system based on Hamiltonian realization, and the external disturbance could be located effectively in large-scale power systems containing complicated control devices. Further, proposed the concept of energy flow in the network, based on which the oscillation sources could be located correctly on a generator or a load bus. As for the oscillation source locating, the concept of generator energy was firstly introduced and successfully used to identify the generator where the external disturbance exists in. Reference decomposed the energy supply on port (ESP) and discriminated the oscillation properties according to the features of ESP’s aperiodic component. The oscillation properties were discriminated according to the components of power response in. Reference focused on the initial period of the waveforms, proposing a second order differential method.
In identifying oscillation properties, the characteristics of waveforms in different oscillation period were analyzed in. Recent years, enormous progresses have been made in measurement-based oscillation analysis because of the rapid development of wide-area measurement system (WAMS). Moreover, it is very difficult to ensure computational convergence and accuracy when calculating the modes and mode-shapes of a large system. However, with the expansion of system scales, to obtain parameters of all system devices becomes harder than before. This approach heavily depends on the availability of power system models and parameters. Therefore, it is essential to discriminate oscillation properties when an LFO is detected.Įigen-analysis is a major approach in LFO study. To restrain the WDO, the output power of some strongly correlated generators needs to be decreased temporarily if the oscillation mode is unexpected, and thereafter controllers such as power system stabilizers (PSS) need to be added or retuned whereas to attenuate the FO, the oscillation source needs to be isolated or tripped. However, the corresponding control measures are entirely different.
These two kinds of oscillations have similar appearance. FOs are caused by oscillatory sources with approximate frequency to a system’s inherent mode.
WDOs occur in systems with weak or negative damping so that the oscillation can hardly calm down. The LFOs are generally classified into two categories, the weak damping oscillations (WDO) and the forced oscillations (FO), according to different intrinsic inducements. It is crucial to discover the origin of LFO accurately and to generate corresponding control strategies effectively. It has been a serious problem limiting the transmission power of tie-lines and threatening the security and stability of power systems. Low frequency oscillation (LFO) is a common phenomenon in power systems.
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