The extensive usage of open communication networks in power system control causes inevitable time delays. This paper studies impacts of such delays on the stability of one-area and two-area load ...frequency control (LFC) systems and proposes an analytical method to determine delay margins, the upper bound on the delay for stability. The proposed method first eliminates transcendental terms in characteristic equation of LFC systems without making any approximation and transforms the transcendental characteristic equation into a regular polynomial. The key result of the elimination process is that real roots of the new polynomial correspond to imaginary roots of the transcendental characteristic equation. With the help of new polynomial, it is also possible to determine the delay-dependency of system stability and root tendency with respect to the time delay. An analytical formula is then developed to compute delay margins in terms of system parameters. For a large set of controller gains, delay margins of LFC systems are computed to investigate the qualitative effect of controller gains on the delay margin. Finally, simulations studies are carried out to verify the effectiveness of the proposed method.
This paper discusses a transmission-line modeling approach that incorporates available ambient temperature information. Several proposed line modeling techniques are studied and include distributed ...and lumped parameter models. In order to capture the nonuniformity of line parameters caused by temperature gradients, a model with multiple nonuniform segments is also proposed. An automated tool has been developed to obtain appropriate line model segmentation and parameter values of each segment, given a set of temperature measurements and their locations along the line.
This paper describes a building electrical-thermal load model that is both suitable for power system analysis as well as retains essential thermodynamic information. The model is developed using ...observations made over multiple time windows to elicit both steady state characteristics, for planning, as well as dynamic behavior, for demand side control applications. Consequently, multiple model evolutions based on data availability are presented. Physically-based parameters are used in the modeling process to describe the influence of building automation systems on the electrical load profile. The end goal is to provide an improved understanding of building temperature-load interactions to facilitate more efficient use of buildings as demand side resources.
This paper presents a transmission-line modeling tool to obtain a desired level of accuracy at non-fundamental frequencies. Specifically, the approach compares finitely segmented models to the ...uniformly distributed model in order to determine the appropriate segmentation of the line model for a desired frequency range. The line model performance is characterized through waveform propagation, including attenuation and phase shift. The software-based modeling tool is validated through hardware tests of different segmentations.
This paper presents a linear approximation method to determine the probability density function (PDF) of the critical clearing time (CCT) and probability of stability for a given disturbance in power ...system transient stability analysis. The CCT is the maximum time interval by which the fault must be cleared in order to preserve the system stability. The CCT depends on the system load level and thus, is modeled as a random variable due to the probabilistic nature of system load demand. The proposed method first determines the sensitivity of the CCT with respect to the system load, and using these sensitivities it computes the PDF of the CCT based on the PDF of the system load. The probability of system being transiently stable for a particular disturbance and for a given fault clearing time is calculated using the PDF of CCT. This approach is verified to be accurate under the condition of small load deviation by Monte Carlo simulations method. Moreover, the proposed method reduces the computational effort significantly in Monte Carlo simulations indicating that it could be used in real-time on-line applications.
This paper develops a model of an electrical power system with its inherent embedded communication system for the purpose of studying the characteristics of power system measurement errors due to ...communication delays. This model is referred to as an "information-embedded power system" to emphasize the inclusion of information variables that represent measurements that have been delivered across the communication system and observed at a control center. These information variables are added to the standard power system model for the energy balance within the power system. A stochastic system model is developed, which is composed of both the physical infrastructure of the power system as well as the embedded computer network communication infrastructure. This type of analysis is an extension of traditional observability approaches, which usually only assume steady-state conditions in the power system and do not consider time delays in delivering measurements. An experimental platform has also been designed to validate the developed model.
This work describes MATLAB/Simulink implementation of three induction motor tests, namely dc, no-load, and blocked-rotor tests performed to identify equivalent circuit parameters. These simulation ...models are developed to support and enhance electric machinery education at the undergraduate level. The proposed tests have been successfully integrated into electric machinery courses at Drexel University, Philadelphia, PA, and Nigde University, Nigde, Turkey.
In this paper, we present an efficient algorithm to compute singular points and singularity-induced bifurcation points of differential-algebraic equations for a multimachine power-system model. Power ...systems are often modeled as a set of differential-algebraic equations (DAE) whose algebraic part brings singularity issues into dynamic stability assessment of power systems. Roughly speaking, the singular points are points that satisfy the algebraic equations, but at which the vector field is not defined. In terms of power-system dynamics, around singular points, the generator angles (the natural states variables) are not defined as a graph of the load bus variables (the algebraic variables). Thus, the causal requirement of the DAE model breaks down and it cannot predict system behavior. Singular points constitute important organizing elements of power-system DAE models. This paper proposes an iterative method to compute singular points at any given parameter value. With a lemma presented in this paper, we are also able to locate singularity induced bifurcation points upon identifying the singular points. The proposed method is implemented into voltage stability toolbox and simulations results are presented for a 5-bus and IEEE 118-bus systems.
In this paper, the authors address computational issues associated with implementation of VLSI technologies-specifically, the utilization of field programmable analog array (FPAA) technology to ...analyze the steady-state as well dynamic behavior of nonlinear, multiscale power systems. Emphasis is placed on the following issues: adaptation of FPAA hardware for power flow analyses, design and construction of physical prototype, optimal hardware scaling, and application of emulation to transient fault analyses.
PDF
