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College of Engineering and Applied Science

    Back to SeminarsAdd Seminar

Presenter: Urmila Agrawal
Date: 3/23/2018
Time: 3:10 pm
Location: EN1045
Contact Email:

Topic: Analysis of low-frequency oscillations in power systems
Abstract: Oscillations in power systems are a continuously occurring phenomenon and can be broadly classified into electromechanical and forced oscillations (FO). Electromechanical oscillations are an inherent response of a system to disturbances such as random load variations, generator-trip, etc. and are associated with system modes. FOs, on the other hand, are the portion of the response associated with a rogue input and often caused by an ill--operating piece of equipment in the system, such as an excitation system, control valve, etc. These FOs can have some undesirable effects such as reducing the amount of power that can transferred through transmission lines and biasing the system mode estimates obtained by using mode-meter algorithms. Any bias in the mode estimates, which give critical information on the system small-signal stability margin, is not desired. Thus, it becomes necessary to detect the presence of FOs in the system so that the source of the FOs can be located and some action can be taken to repair the malfunctioning piece of equipment to eliminate these oscillations. Also needed is a method that can accurately estimate system modes in the presence of FOs. This presentation will address these issues concerning FOs and modal analysis.

The first part of the presentation will focus on the detection and the estimation of frequencies of FOs by incorporating the harmonic information of the FOs in the detection algorithm of a periodogram detector. FOs are usually periodic in nature and often contain harmonic components. The detection performance of a periodogram detector can be significantly improved by including these harmonics information enabling the detection of one or more low-amplitude components of FOs. Next, a method will be presented to estimate system modes in the presence of the FOs using an ARMAX system model. Unlike other existing methods, the proposed method do not require any time related information of FOs. Results obtained using both simulated and real--world measured data will be presented for both the proposed methods.

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