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In a recent paper, we proposed a system identification method for constructing reduced-order models for the electro-mechanical dynamics of large power systems, divided into multiple coherent clusters, using Synchrophasors. Every cluster in the actual model was represented as an aggregate generator in the reduced-order model. An aggregate network graph connected one aggregate generator to another. In this paper, we extend this identification approach to differential-algebraic (DAE) models. First, every cluster is associated with a unique terminal bus, referred to as the pilot bus, that couples its internal network to the rest of the system. The proposed algorithm uses Synchrophasor measurements from the pilot buses to identify the dynamic model of the aggregate generator for each cluster using nonlinear least squares while retaining the identity of all the pilot buses. The resulting reduced-order model is in the form of a nonlinear electric circuit described by aggregate differential and algebraic equations. We illustrate our results using two case studies, one for the IEEE 9-bus power system and another for the IEEE 39-bus power system. We also discuss how these reduced-order DAE models may be useful for designing shunt controllers at the pilot buses by using Synchrophasor feedback. [ABSTRACT FROM AUTHOR]

This paper discusses the conceptual design and operation of an isolated power system, recognizing the reality that generator or turbine trips will occur. The level of reserve generating capacity must be set with proper balancing of capital expenditures and operating costs against revenue lost in a production shutdown. The way that reserve capacity is provided is as important as the amount of reserve; seemingly adequate reserve can turn out to be badly insufficient if it is not well distributed across the available reserve sources. The dynamic behavior of reserve capacity, as much as the amount of capacity that is ultimately available, is critical in determining how an isolated facility will behave in the wake of a unit trip or the loss of a grid connection. In this paper, experiences with detailed dynamic simulations of a range of isolated systems are described. These are related to test work and operational incidents that have provided practical calibrations. Based on simulation and experience, some guidelines are offered for configuring generation and selecting strategies for maintaining stability in large, isolated continuous-process facilities. [ABSTRACT FROM PUBLISHER]

Isolated microgrid power systems are prone to large frequency and voltage deviations, since they have limited generation and finite inertia and may include pulse power loads and large proportion of dynamic loads. Thus, they require effective power management methods to operate optimally, while satisfying operating and security constraints. In this paper, a novel integrated security-constrained model-based power management approach is proposed for isolated microgrids in all-electric ships during the normal/alert operating state. The new power management method was formulated as a multi-objective optimal control problem. A method based on the Nondominated Sorting Genetic Algorithm II was developed to solve the problem. The developed integrated security-constrained power management approach was applied to a notional all-electric ship computer model. The simulation results, conducted in PSCAD, showed the effectiveness of the new power management method. [ABSTRACT FROM PUBLISHER]

Paper presents an equivalent model of an active distribution network cell (ADNC) with distributed generation for transmission system stability studies. The equivalent model of ADNC comprises a converter-connected generator and a composite load model in parallel. The gray-box approach was chosen as it enables inclusion of prior knowledge about the ADNC structure into the model development, hence making the model more physically relevant and intuitive than a black-box or white-box model. The dynamic equivalent model is presented in a seventh-order nonlinear quasi state space format, developed from the algebraic and differential equations describing assumed typical components of the ADNC. The developed equivalent model of ADNC was validated through small and large disturbance studies using the modified IEEE nine-bus transmission system model. [ABSTRACT FROM PUBLISHER]

The purpose of this paper is to present an improved model-based controller for power turbine generators (PTGs) on a shipboard grid system. Propulsion can be accomplished by means of main diesel engines. One arrangement for the onboard power requirements of merchant ships is the PTG extract part of the exhaust gas from the main diesel engines. The speed control, however, is difficult to keep in place because of fouling conditions and variations across time. The proposed controller is evaluated by comparing it with the conventional controller in a simulation. Furthermore, the proposed controller is evaluated in a prototype. In the simulation result using the proposed controller, the limit speed overshooting as a transient response is improved by more than 25 \%. In the prototype test, the limit frequency overshooting is 0.60\%, and the settling time is 3.8 s. Hence, the proposed controller is confirmed to have an excellent property. [ABSTRACT FROM AUTHOR]

Availability of the synchronous machine angle and speed variables give us an accurate picture of the overall condition of power networks leading therefore to an improved situational awareness by system operators. In addition, they would be essential in developing local and global control schemes aimed at enhancing system stability and reliability. In this paper, the extended Kalman filter (EKF) technique for dynamic state estimation of a synchronous machine using phasor measurement unit (PMU) quantities is developed. The simulation results of the EKF approach show the accuracy of the resulting state estimates. However, the traditional EKF method requires that all externally observed variables, including input signals, be measured or available, which may not always be the case. In synchronous machines, for example, the exciter output voltage Efd may not be available for measuring in all cases. As a result, the extended Kalman filter with unknown inputs, referred to as EKF-UI, is proposed for identifying and estimating the states and the unknown inputs of the synchronous machine simultaneously. Simulation results demonstrate the efficiency and accuracy of the EKF-UI method under noisy or fault conditions, compared to the classic EKF approach and confirms its great potential in cases where there is no access to the input signals of the system. [ABSTRACT FROM PUBLISHER]

This paper presents a new field test to adequately assess the oscillation damping effectiveness of the PSSs in a multigenerator power plant. The test allows estimating the location of the dominant open-loop poles (i.e., in the absence of PSSs at the multigenerator plant) from frequency response measurements of the closed-loop multivariable system. This test was first carried out at the Itaipu 60-Hz power station, which was generating 4000 MW at the time. The test validation was made through comparison of obtained frequency response measurements with computer simulations of a detailed dynamic model of the Brazilian interconnected power system. [ABSTRACT FROM AUTHOR]

This paper presents the application of dynamic phasor analysis to understand the effect of passive phase imbalance schemes on the torsional modes of a turbine-generator system. These schemes have been proposed in the previous literature as subsynchronous resonance (SSR) countermeasures. Dynamic phasor analysis of the unbalanced system yields a linearized and time-invariant model which facilitates eigen-analysis. It is seen that large levels of phase imbalance can cause a significant movement in the subsynchronous network modal frequencies. Therefore, in specific cases, SSR can be avoided due to detuning of the torsional and network modes. However, the analysis also shows that damping torque in a series compensated network is negative at subsynchronous frequencies even with phase imbalance. Therefore, phase imbalance cannot be a general countermeasure to the problem of SSR. [ABSTRACT FROM AUTHOR]

The extensive installation of gas-fired power plants in many parts of the world has led electric systems to depend heavily on reliable gas supplies. The use of gas-fired generators for peak load and reserve provision causes high intraday variability in withdrawals from high-pressure gas transmission systems. Such variability can lead to gas price fluctuations and supply disruptions that affect electric generator dispatch, electricity prices, and threaten the security of power systems and gas pipelines. These infrastructures function on vastly different spatio-temporal scales, which prevents current practices for separate operations and market clearing from being coordinated. In this paper, we apply new techniques for control of dynamic gas flows on pipeline networks to examine day-ahead scheduling of electric generator dispatch and gas compressor operation for different levels of integration, spanning from separate forecasting, and simulation to combined optimal control. We formulate multiple coordination scenarios and develop tractable physically accurate computational implementations. These scenarios are compared using an integrated model of test networks for power and gas systems with 24 nodes and 24 pipes, respectively, which are coupled through gas-fired generators. The analysis quantifies the economic efficiency and security benefits of gas–electric coordination and dynamic gas system operation. [ABSTRACT FROM AUTHOR]

In this paper, we present a new Matlab-based toolbox for power system analysis, called MatDyn. It is open-source software, and available for everyone to download. Its design philosophy is based on the well-known open-source Matlab toolbox MATPOWER , but its focus is transient stability analysis and time-domain simulation of power systems, instead of steady-state calculations. [ABSTRACT FROM AUTHOR]

In this paper, the power system with an excitation controller is represented as a class of large-scale, uncertain, interconnected nonlinear continuous-time system in strict-feedback form. Subsequently, dynamic surface control (DSC)-based adaptive neural network (NN) controller is designed to overcome the repeated differentiation of the control input that is observed in the conventional backstepping approach. The NNs are utilized to approximate the unknown subsystem and the interconnection dynamics. By using novel online NN weight update laws with quadratic error terms, the closed-loop signals are shown to be locally asymptotically stable via Lyapunov stability analysis, even in the presence of NN approximation errors in contrast with other NN techniques where a bounded stability is normally assured. Simulation results on the IEEE 14-bus power system with generator excitation control are provided to show the effectiveness of the approach in damping oscillations that occur after disturbances are removed. The end result is a nonlinear decentralized adaptive state-feedback excitation controller for damping power systems oscillations in the presence of uncertain interconnection terms. [ABSTRACT FROM PUBLISHER]

In the analysis of time series of blackouts, a power law dependency of blackout size with respect to frequency has been observed. It has been hypothesized that this behavior is the result of the power system operating near critical points. Models have been created in order to analyze this type of behavior in power systems. In this paper the effect of conservative versus nonconservative generation dispatch is studied using one such model. Conservative dispatches are ones that are performed in order to minimize stress on the system and therefore attempt to minimize possible outages and blackouts. This dispatch is compared with a nonconservative dispatch that attempts to maximize the stress and therefore increase the immediate risk of outages and blackouts. It is found that the nonconservative dispatch although attempting to maximize the immediate risk reduces the frequency of blackouts of all sizes over the conservative dispatch in the long term. [ABSTRACT FROM AUTHOR]

We perform modal analysis of short-term swing dynamics in multi-machine power systems. The analysis is based on the so-called Koopman operator, a linear, infinite-dimensional operator that is defined for any nonlinear dynamical system and captures full information of the system. Modes derived through spectral analysis of the Koopman operator, called Koopman modes, provide a nonlinear extension of linear oscillatory modes. Computation of the Koopman modes extracts single-frequency, spatial modes embedded in non-stationary data of short-term, nonlinear swing dynamics, and it provides a novel technique for identification of coherent swings and machines. [ABSTRACT FROM PUBLISHER]

The authors present their insights into an article by L. Ding, F. M. Gonzalez-Longatt, P. Wall and V. Terzija about the use of a fast controlled algorithm to split a large-scale power system based on a two-step spectral clustering. They seek clarification on the article's discussion on the spectral clustering controlled islanding (SCCI) algorithms and the determinant of the number of coherent generator groups in the IEEE 39-bus test system.

A new internal STATCOM control based on feedback linearization is proposed. The feedback linearization controller is developed without any simplifying assumptions to the STATCOM model. The proposed control is validated on the IEEE 118-bus system with full-order generator and network models as opposed to a small test system. Furthermore, the proposed control is benchmarked against published results. Lastly controllability issues associated with a singularity in the feedback linearization control (FBLC) coordinate transformation is identified, and a solution is provided to avoid instability. [ABSTRACT FROM AUTHOR]