Dominant Inter-area Modes Research Articles

Multi-channel measurement-based identification methods for mode estimation in power systems

Mode identification from post-disturbance ringdown responses is a valuable tool for the analysis of the dynamic performance and the stability margins of power systems. In this aspect, several techniques have been proposed, focusing mainly to single-signal analysis. However, considering large-scale power systems and especially future scenarios with high penetration of distributed energy resources, detailed network analysis at all voltage levels is required. As a result of these concerns, multi-channel mode identification algorithms have been developed. Scope of this paper is to evaluate the applicability and the performance of the most known multi-channel measurement-based identification approaches for the modal analysis of modern power systems incorporating active distribution networks. The algorithmic details and distinct characteristics of each method are briefly discussed. The examined methods are used to identify the dominant inter-area modes contained in ringdown responses at different levels of a combined transmission-distribution network.

Real-Time Damping Estimation on Nonlinear Electromechanical Oscillation

Real-time damping estimation for a dominant inter-area mode is important for situational awareness of potential angular instability in power systems. Electromechanical oscillations energized by large disturbances often manifest obvious nonlinearities in measurements on first several swings. Traditional methods based on linear system theory often discard first several swings intentionally to avoid nonlinearity; if not, the estimated damping ratios often vary with the length and starting point of the measuring window. By identifying a nonlinear oscillator to fit a dominant mode, this paper proposes a new measurement-based approach utilizing complete post-disturbance data for robust damping estimation independent of the measuring window. Case studies on the IEEE 9-bus system and a 48-machine Northeast Power Coordinating Council system validate the proposed approach for providing accurate and robust damping estimation compared with existing methods including the Prony's method. Meanwhile, three factors influencing damping estimation in practical applications are also addressed, including measurement noises, limited coverage of PMU measurements, and existence of multiple dominant modes.

Stability analysis and stabilization of delayed reduced-order model of large electric power system

Summary This paper discusses stability analysis using spectral discretization of time-delayed electric power system. The stability assessment is discussed in terms of influence of time delays on inter-area oscillation modes of the power system models: well-known 4-generator and 14-generator Southeast Australian power system. The three dominant inter-area modes available in full-order power system are retained in its equivalent representation, i.e., reduced-order model, obtained with the input–output variables of the generator that participates actively to low-frequency oscillation modes. The pseudospectrum analysis suggests the most dominant modes to be sensitive against time delay. The rightmost characteristic roots and the robust spectral abscissa are computed over a wide range of time delays in the input-output variables. The approach applied in study computes all the characteristic roots in the right half s-plane with the number of discretization points selected in such a way that rational approximation of the exponential functions remains accurate in this region. The effect of time delays on the computation of spectral abscissa is also investigated. Further, reduced-order time-delayed model is also used to design the wide-area controller by optimizing (minimizing) the robust spectral abscissa. Copyright © 2016 John Wiley & Sons, Ltd.

Robust Damping of Multiple Swing Modes Employing Global Stabilizing Signals With a TCSC

This paper demonstrates a robust damping control design for multiple swing mode damping in a typical power system model using global stabilizing signals. A multiple-input, single-output (MISO) controller is designed for a thyristor-controlled series capacitor (TCSC) to improve the damping of the critical interarea modes. The stabilizing signals are obtained from remote locations based on observability of the critical modes. A H/sub /spl infin// damping control design based on the mixed-sensitivity formulation in a linear matrix inequality (LMI) framework is carried out. It is shown that, with local signal, supplementary damping control through three flexible AC transmission systems (FACTS) devices is necessary to provide damping to the three dominant interarea modes. On the other hand, the use of global signals has been shown to improve the damping of all the critical interarea modes with a single controller for the TCSC only. The damping performance of the centralized controller was examined in the frequency and the time domain for various operating scenarios. The controller was found to be robust against varying power-flow patterns, load characteristics, tie-line strengths, and system nonlinearities, including saturation.

Square Butte HVDC modulation system field tests

Results are presented of field tests which were part of an EPRI-sponsored project to develop advanced control techniques for the design of HVDC modulation systems. The objectives of the tests were to validate the digital control design models for the rectifier and inverter controllers which were developed from a digital large-scale model of the power system and to assess the dynamic environment in which the modulation control system must operate. The field tests and digital model results confirm a dominant interarea mode of oscillation of 0.8 Hz. Field tests also established spurious responses in rectifier and inverter frequency measurements, which appear to be attributable to transducer distortion. >