External System Model Research Articles

External system modeling: An approach to minimizing vibroacoustic model sizes for design evaluation

Numerical vibroacoustical models of dynamic systems can easily become so large that they are impractical when used to analyze alternative system designs. Hence, when evaluating designs for single sub-components of a large system, the analysis is often limited either to that sub-component combined with idealized boundary conditions, or to the sub-component and a small portion of the rest of the system (i.e., the exterior system). In this paper a technique, based on the receptance method, is presented that allows a model of the complete system to be replaced by a complete model of the sub-component combined with a minimal model of the exterior system. Thus the insitu dynamics of a particular sub-component may be evaluated without having to solve the entire system. This approach allows sub-component designs to be assessed quickly so that the merits of many potential designs may be evaluated. The assumptions required by this approach are: steady-state conditions, linearity, and that the forces acting on the external system are unaffected by changes in the sub-component. The external system model may be obtained either numerically or experimentally. The proposed approach is demonstrated here analytically using a system of beam-like elements.

Internal decoupled tracking state estimator using external system equivalents

This paper presents an internal decoupled tracking state estimation of a large interconnected power system when part of a system state has to be tracked using the external system equivalent models. The external system models are identified from the real-time internal measurements being processed by the Kalman filtering technique. Those models identified were then embedded into the internal system constant Jacobian models so as to reflect the reaction of the external system arising in response to the internal system conditions. The resulting modified internal system model is then utilized to develop a weighted least square version of the internal decoupled tracking state estimation algorithm. The proposed algorithm has been tested on a 25-bus test system and the results are presented. It is found that the convergence characteristic of the internal decoupled tracking state estimator is the same as that of an overall system tracking state estimator, with a drastic reduction in computation time and memory requirements.

Dispersive kinetics of nonphotochemical hole burning and spontaneous hole filling: Cresyl Violet in polyvinyl films

The dispersive kinetics of nonphotochemical burning and spontaneous filling of the zero-phonon hole of Cresyl Violet in polyvinyl alcohol at 1.6 K are analyzed in terms of the standard external two-level system (TLSezt) model for probe–glass systems and a distribution function for the tunnel frequency derived from a normal distribution function for the tunnel parameter λ. Average values for the relaxation rates for burning and filling are determined. It is shown that the dominant mechanism for filling is not global spectral diffusion but rather antihole reversion. A high degree of positive correlation between the rates of burning and filling associated with the TLSext is found. A new methodology that permits a more physically reasonable interpretation of spontaneous hole-filling kinetics is described. It is based on the hypothesis that only a fraction of burned sites, on reversion to the ground state, yield sites with resonance frequencies that lie within the hole profile.

On-line power system security analysis

A broad overview of on-line power system security analysis is provided, with the intent of identifying areas needing additional research and development. Current approaches to state estimation are reviewed and areas needing improvement, such as external system modeling, are discussed. On-line contingency selection has become practical, particularly for static security. Additional work is necessary to identify better indices of power system stress to be used in on-line screening filters for both static and dynamic security analysis. Use of optimal power flow schemes to recommend optimal preventive and corrective strategies is presented on a conceptual level. Techniques must be further developed to provide more practical contingency action plans, which include real-world operating considerations and use a reasonably small number of control actions. Techniques must be developed for costing operating variables which are not easily quantified in dollars. Soft or flexible constraints and time variables must be included in the preventive and corrective strategy formulation. Finally, the area of on-line transient and dynamic security analysis is presented. >

Decoupled internal state estimation using external system equivalents

An algorithm for internal state estimation of an interconnected power system is presented using three truly decoupled external system equivalent models. The external system models are identified from the real-time internal measurements being processed by the Kalman filtering technique. These identified models are placed on the boundaries of the internal system so as to reflect the reaction of the external system arising in response to the internal system conditions. The resulting modified internal system model is then utilized to develop a weighted-least-square (WLS) version of the fast decoupled internal state estimation algorithm. The algorithm has been tested on a 25-bus test system and similar convergence characteristics are obtained for all three types of external system models. Moreover, it is found to take the same number of iterations as that of an overall estimator with a drastic reduction in its requirements of computer time and storage.