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At least 145 records · Page 8

Nominal and adversarial synthetic PMU data for standard IEEE test systems

GridSTAGE (Spatio-Temporal Adversarial scenario GEneration) is a framework for the simulation of adversarial scenarios and the generation of multivariate spatio-temporal data in cyber-physical systems. GridSTAGE is developed based on Matlab and leverages Power System Toolbox (PST) where the evolution of the power network is governed by nonlinear differential equations. Using GridSTAGE, one can create several event scenarios that correspond to several operating states of the power network by enabling or disabling any of the following: faults, AGC control, PSS control, exciter control, load changes, generation changes, and different types of cyber-attacks. Standard IEEE bus system data is used to define the power system environment. GridSTAGE emulates the data from PMU and SCADA sensors. The rate of frequency and location of the sensors can be adjusted as well. Detailed instructions on generating data scenarios with different system topologies, attack characteristics, load characteristics, sensor configuration, control parameters are available in the Github repository - https://github.com/pnnl/GridSTAGE. There is no existing adversarial data-generation framework that can incorporate several attack characteristics and yield adversarial PMU data. The GridSTAGE framework currently supports simulation of False Data Injection attacks (such as a ramp, step, random, trapezoidal, multiplicative, replay, freezing) and Denial of Service attacks (such as time-delay, packet-loss) on PMU data. Furthermore, it supports generating spatio-temporal time-series data corresponding to several random load changes across the network or corresponding to several generation changes. A Koopman mode decomposition (KMD) based algorithm to detect and identify the false data attacks in real-time is proposed in https://ieeexplore.ieee.org/document/9303022. Machine learning-based predictive models are developed to capture the dynamics of the underlying power system with a high level of accuracy under various operating conditions for IEEE 68 bus system. The corresponding machine learning models are available at https://github.com/pnnl/grid_prediction.

99 GENERAL AND MISCELLANEOUS↗

Damping characteristics of a liquid squeeze film.

Consideration of the damping characteristics of a liquid film located between two nearly parallel plane surfaces in relative normal motion which are always closely spaced compared to the dimensions describing the area of the two like surfaces. It was found that if the motion is slow enough (about 3 centipoise or less), the fluid inertia can be neglected and the resulting fluid flow conforms to Reynold's lubrication theory. Experiments were also carried out to determine how the damping factor of a liquid squeeze film varies with film viscosity, film thickness, amplitude, and frequency under free vibration of a single-degree-of-freedom system. The data are compared to computer solutions of the nonlinear differential equation of motion. With other variables held constant, the damping factor was found to decrease as the plate spacing is increased, decrease as the viscosity is decreased, and increase as the initial spacing is decreased.

Yabe, T.↗

Calculation of free fall trajectories based on numerical optimization techniques

The development of a means of computing free-fall (nonthrusting) trajectories from one specified point in the solar system to another specified point in the solar system in a given amount of time was studied. The problem is that of solving a two-point boundary value problem for which the initial slope is unknown. Two standard methods of attack exist for solving two-point boundary value problems. The first method is known as the initial value or shooting method. The second method of attack for two-point boundary value problems is to approximate the nonlinear differential equations by an appropriate linearized set. Parts of both boundary value problem solution techniques described above are used. A complete velocity history is guessed such that the corresponding position history satisfies the given boundary conditions at the appropriate times. An iterative procedure is then followed until the last guessed velocity history and the velocity history obtained from integrating the acceleration history agree to some specified tolerance everywhere along the trajectory.

Source record↗

Prior to failure extension of flaws in a rate sensitive Tresca solid.

Theoretical analysis shows that the amount of slow growth occurring prior to fracture in a plane stress tension specimen subjected to a subcritical stress intensity level is affected by the ductility and rheological sensitivity of the material, the rate of loading, the initial crack size, and the geometrical configuration of the test. These parameters enter the governing nonlinear differential equation which describes the quasi-static crack extension in a rate-sensitive Tresca solid. Examples of numerical integration are given and employed to predict the maximum fracture toughness attained in a plane stress tension test.

Wnuk, M. P.↗