Damping Power System Electromechanical Oscillations Using Time Delays
ABSTARCT :
This paper proposes to utilize intentional time delays as part of controllers to improve the damping of electromechanical oscillations of power systems. Through stability theory, the control parameter settings for which these delays in Power System Stabilizers (PSSs) improve the small signal stability of a power system are systematically identified, including the key parameter settings for which stability regions in the parameter plane remain connected for effective operation. The paper shows that PSSs with two control channels can be effectively designed to achieve best damping characteristics for a wide range of delays. Analytical results are presented on the One-Machine Infinite-Bus (OMIB) electromechanical power system model. To demonstrate the opportunities in more realistic dynamic models, our results are then implemented via numerical analysis on the IEEE standard 14-bus system.
EXISTING SYSTEM :
? The use of a raw measurements from PMUs can lead to ambiguous results due to: 1) possible errors in some of the measured samples, 2) ill conditioned autocovariance matrices in the case of PMUs with high sampling rates (30Hz or more) or 3) existing trends in the signal which do not carry any information about system dynamics .
? Because of these difficulties, before applying any of the spectral estimators, available data must be preprocessed.
? This section analyzes the impact that forced oscillations in PMU data have on damping estimation algorithms, which has been neglected up to now. Several examples are shown where forced oscillations corrupt the accuracy of existing mode meter algorithms.
DISADVANTAGE :
? A remedy to the above issue is to recognize that the characteristic roots of the system vary on the complex plane in a continuum as the delay parameter changes in a continuum .
? These oscillations will show up as narrow band oscillations in PSDs and spectrograms, and if superimposed over a real system mode, they will cause problems to obtain good damping estimates.
? FFTs (Fast Fourier Transforms) is used to examine the data and identify forced oscillations.Different approaches have been proposed to overcome this problem [29]. In this paper, system (15) is transformed to a formally equivalent set of Partial Differential Equations (PDEs), which has infinite dimensions.
PROPOSED SYSTEM :
• In this study, the impact of different feedback input signals on the damping of the two-area test system will be evaluated. Each signal requires different controller (PSS) parameters, as well as different structures.
• The purpose of the design is to achieve a specific damping performanceThe larger in magnitude the modeshape is, the more observable the signal measured (from the dominant path) becomes.
• This will be helpful when selecting feedback signals having high inter-area modal contents for wide-area control. Three algorithm for identification of dominant inter-area oscillation paths are proposed in , each of these algorithms work with different input information: (a) an updated dynamic model, (b) transient responses from PMUs, or (c) ambient data.
ADVANTAGE :
? Measurement and communication delays in local Power System Stabilizers (PSSs) and wide area damping controllers are a potential threat for the overall dynamic performance of power systems .
? While most results in the literature treat delays as undesirable, there is also a large amount of work that has focused on the advantages of having delays in a closed-loop setting.
? A remedy to this was proposed by utilizing some salient features of algebraic geometry on a class of delay systems, and deriving analytical formulae that prescribe how to tune the delays and control gains to achieve a desired performance from these systems
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