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The most challenging circumstance of forced oscillations (FOs) is when the power system is forced to oscillate at its natural frequencies. This paper uses a novel PMU data-driven mechanism to pinpoint the source of such phenomena under resonance. Following the detection of FOs, the instantaneous changes in the output power and angular velocity of the rotors are calculated. Accordingly, an energy-driven multilateral interaction pattern is obtained for all synchronous generators. Next, an appropriate positive weighted undirected graph is constructed through these functional patterns based on the spectral graph theory. These quantitative indicators are then analyzed through the eigenvalue spectrum of the normalized Laplacian matrix of the system graph reduced to the internal generator buses. Finally, the smallest value in eigenvectors corresponding to the two largest eigenvalues reveals the location of the source. The proposed methodology's validation and verification studies have been performed on the WECC 3-machine 9-bus and New England 10-machine 39-bus benchmark power systems modeled in the Real-Time Digital Simulator (RTDS) and then analyzed in the MATLAB environment. The proposed methodology revealed to be fast and accurate in locating the source of FOs under challenging resonance situations with promising results while addressing the generator side origins. [ABSTRACT FROM AUTHOR]

Differential protection schemes for busbars, generators or transformers connect multiple current transformers in parallel across a common burden. This paper describes the techniques used to simulate such an arrangement and concentrates particularly on the 3 CT case. Index Terms--B-H loop, hysteresis, current transformers, simulation.

The hysteresis loop of the core material in a test CT is simulated using the Jiles-Atherton theory. Comparisons are made between recorded and simulated waveforms and it is found necessary to replace the modified Langevin function used by Jiles and Atherton. Using an alternative function described in the paper, good agreement is achieved between test and simulated waveforms. Index Terms--B-H loop, current transformers, hysteresis, simulation.

Small signal stability analysis in a power system is typically concerned with electromechanical oscillations. For this purpose, it is adequate to model the transmission system using a constant admittance matrix. For torsional oscillations and HVDC interactions, the frequency of interest is much higher and the constant admittance representation is not sufficient. This paper proposes a hybrid model, which allows the parts of the transmission network in the vicinity of HVDC converters or any other dynamic devices to be modeled with their dynamics and the remaining parts to be modeled as constant admittances. The proposed hybrid methodology for small signal stability assessment is the main contribution of this paper. The proposed methodology is validated against an electromagnetic transient simulation program (PSCADIEMTDC) using time responses. The proposed model and two other small signal models are compared against each other in the frequency domain using modal analysis. [ABSTRACT FROM AUTHOR]

The paper presents a platform system for the incorporation of flexible ac transmission systems (FACTS) devices. The platform permits detailed electromagnetic transients simulation as it is of manageable size. It manifests some of the common problems for which FACTS devices are used such as congestion management, stability improvement, and voltage support. The platform can be valuable for the validation of reduced order models such as small signal or transient stability models. The paper presents details on the development and validation of a small signal based model with the inclusion of a Unified Power Flow Controller. The validated model is then used successfully for the design of a feedback controller for improved damping. [ABSTRACT FROM AUTHOR]

This paper summarizes the work done by the Task Force on Assessing the Need to Include Higher Order Terms for Small-Signal (Modal) Analysis. This Task Force was created by the Power System Dynamic Performance Committee to investigate the need to include higher order terms for small signal (modal) analysis. The focus of the work reported here is on establishing and documenting the practical significance of these terms in stability analysis using the method of Normal Forms. Special emphasis was placed on determining and describing conditions when higher order terms need to be included to accurately describe modal interactions. Test cases were developed on a standard test system to demonstrate the application of appropriate indices to detect the occurrence of nonlinear interaction and hence the need for higher order terms in stability analyzes. The use of the higher order terms in the site selection for a damping controller is also documented. [ABSTRACT FROM AUTHOR]

A hysteresis model based on the Jiles--Atherton theory is incorporated into a power transformer model in an electromagnetic transient program (EMTP)-type program. The eddy current effects are also included in the same model. Comparisons are made between recorded and simulated waveforms using a single-phase distribution transformer. A good agreement is achieved between recorded and simulated data. [ABSTRACT FROM AUTHOR]