Svetlana V. Poroseva

Automated Graph-Based Methodology for Fault Detection and Location in Power Systems

This study investigates how the model-based fault detection and location approach of structural analysis can be adapted to meet the needs of power systems, where challenges associated with increased system complexity make conventional protection schemes impractical. With a global view of the protected system and the systematic and automated use of the systems analytical redundancy, faults are detected and located by more than one means. This redundancy can be used as a confirmation mechanism within a wide-area protection scheme to avoid unnecessary or false tripping due to protection component failure or disturbance. Furthermore, this redundancy turns the sensor configuration problem into an optimization problem with regard to fault detection and location. The effectiveness of different system topologies can then be compared on the basis of the optimal number of sensors they require. The principle of structural analysis is described in detail and illustrated on a simple power system model. Pertinence of the approach is demonstrated through simulation.

Topology of the generator bus in a warship integrated power system

Future naval platforms will feature an integrated power system (IPS) that provides power for all ship systems, including propulsion, combat systems, ship service loads and, ultimately, weapons. It is naturally a requirement that the power system be highly reliable and one of the benefits of the all-electric concept is that reliability in general and, specifically, survivability in battle are enhanced by the ability to reassign power components and network paths to dynamically reconfigure the system in response to events. Much research is being directed at the question of how best to reconfigure a system when portions are damaged: this includes choosing the optimal reconfiguration possible in the system, evaluating the effect of transients introduced by the damage and the switching in and out of parts of the network, etc. Little attention has been focused, however, on the how much reconfiguration is possible in a given network, particularly in the event of multiple faults. After all, if there is no alternative path available between source and load, there can be no reconfiguration. Alternatively, little attention has been given to the question of how to design the network so as to give maximum survivability. These questions are vital, regardless of what reconfiguration strategy is chosen.

Pressure-strain correlation in homogeneous anisotropic turbulence subject to rapid strain-dominated distortion

Rapid distortion calculations of initially anisotropic turbulence are performed to better understand the physics of the pressure-strain correlation in strain-dominated mean flows. Based on the results of simulations we infer important physical characteristics of the “rapid” pressure-strain correlation Φij(r) in such flows: (i) it vanishes when there is no production of anisotropy, (ii) in the proximity of two-componential state it tends to decrease Reynolds stress anisotropy, and (iii) its magnitude is generally smaller than that of production. The observed characteristics are proposed as criteria that pressure-strain correlation models may be required to satisfy. All of the current popular models violate the above criteria for a sizeable subset of anisotropic initial conditions. Reynolds stress transport model calculations show that unphysical and unrealizable model behavior can be directly attributed to these violations.

Structure-based turbulence model: Application to a rotating pipe flow

A new approach for modeling the one-point turbulence statistics, which takes into account the information on turbulence structure, has been suggested in Kassinos and Reynolds (Report TF-61, Thermosciences Division, Department of Mechanical Engineering, Stanford University, 1994). In the present work, the structure-based model [Int. J. Heat Fluid Flow 21, 599 (2000)] (SBM) based on those ideas, was evaluated in a complex inhomogeneous turbulent flow in a cylindrical pipe rotating around its longitudinal axis. It was found that the SBM is able to predict the flow accurately at various Reynolds numbers and under stronger rotation than what is possible with the Reynolds stress transport models (RSTMs). In a fully developed rotating pipe flow, the SBM, being a linear model, slightly improves the profiles obtained with the nonlinear RSTM [J. Fluid Mech. 227, 245 (1991)]. However, if the standard equation for the dissipation rate is used, the SBM, as do the RSTMs, significantly overpredicts the turbulent kinetic...

On the accuracy of RANS simulations with DNS data

Simulation results conducted for incompressible planar wall-bounded turbulent flows with the Reynolds-Averaged Navier-Stokes (RANS) equations with no modeling involved are presented. Instead, all terms but the molecular diffusion are represented by the data from direct numerical simulation (DNS). In simulations, the transport equations for velocity moments through the second order (and the fourth order where the data are available) are solved in a zero-pressure gradient boundary layer over a flat plate and in a fully-developed channel flow in a wide range of Reynolds numbers using DNS data from Sillero et al. (2013), Lee & Moser (2015), and Jeyapaul et al. (2015). The results obtained demonstrate that DNS data are the significant and dominant source of uncertainty in such simulations (hereafter, RANS-DNS simulations). Effects of the Reynolds number, flow geometry, and the velocity moment order as well as an uncertainty quantification technique used to collect the DNS data on the results of RANS-DNS simulations are analyzed. New criteria for uncertainty quantification in statistical data collected from DNS are proposed to guarantee the data accuracy sufficient for their use in RANS equations and for the turbulence model validation.

Floridian high-voltage power-grid network partitioning and cluster optimization using simulated annealing

Abstract Many partitioning methods may be used to partition a network into smaller clusters while minimizing the number of cuts needed. However, other considerations must also be taken into account when a network represents a real system such as a power grid. In this paper we use a simulated annealing Monte Carlo (MC) method to optimize initial clusters on the Florida highvoltage power-grid network that were formed by associating each load with its “closest” generator. The clusters are optimized to maximize internal connectivity within the individual clusters and minimize the power deficiency or surplus that clusters may otherwise have.

Spectral matrix methods for partitioning power grids: Applications to the Italian and Floridian high-voltage networks

Abstract Intentional islanding is used to limit cascading power failures by isolating highly connected “islands” with local generating capacity. To efficiently isolate an island, one should break as few power lines as possible. This is a graph partitioning problem, and here we give preliminary results on islanding of the Italian and Floridian high-voltage grids by spectral matrix methods.

Algorithm development for evaluating the IPS survivability due to its topology

The paper presents a time-efficient computational algorithm for automated evaluation of the topological survivability of the integrated power system (IPS) in an all-electric ship. Topological survivability is the capacity inherent in the IPS architecture to maintain operations under adverse conditions such as, for example, combat damage. The IPS architecture determines whether power is available to loads after damage occurs and, therefore, is a key factor to consider in the analysis of the IPS survivability. Since survivability of an all-electric ship relies on the IPS survivability, clearly, the resistance of the IPS architecture to multiple faults should be analyzed at the early design stage and incorporated into the ship design. The algorithm proposed enables one to conduct such an analysis in a timely manner.

On the Accuracy of RANS Simulations of 2D Boundary Layers with OpenFOAM

OpenFOAM is an attractive Computational Fluid Dynamics solver for evaluating new turbulence models due to the open-source nature and the suite of existing standard model implementations. Before interpreting results obtained with a new turbulence model, a baseline for performance of the OpenFOAM solver and existing models is required. In the current study, we assess the accuracy of simulation results obtained with standard models for the Reynolds-averaged Navier-Stokes equations implemented in the OpenFOAM incompressible solver. Two planar (two-dimensional mean flow) benchmark cases generated by the AIAA turbulence Model Benchmarking Working Group are considered: the boundary layer on a zero-pressure-gradient flat plate and a bump-in-channel flow. OpenFOAM results are compared with the NASA CFD codes CFL3D and FUN3D. Sensitivity of simulation results to the grid refinement, linear pressure solvers, compressibility effects, and model implementation are analyzed. Testing is conducted using standard Spalart-Allmaras one-equation, Wilcox’s 2006 version of the two-equation k-ω, and SST 1994 turbulence models. Simulations using wall-resolved (low Reynolds number) formulations are considered.

Designing Power System Topologies of Enhanced Survivability

Survivability, or the ability to deliver service in spite of multiple simultaneous faults caused by natural or hostile disruptions, is a desirable feature of any complex system. For some systems such as the integrated power system in an all-electric ship, the ability to withstand massive sudden damage is of vital importance. Although many factors contribute to power system survivability, a key factor is its topology – the number of generators and the connections between generators, between loads, and generators with loads. Previously, we developed a basic mathematical framework and computational tools for analyzing the topological survivability of power systems with multiple generators and a single load. This paper considers a case of multiple generators and multiple loads with application to the topology of a notional medium voltage DC shipboard power system. Possible improvements are suggested.