DVR Transient Analysis with Saturated Iron-Core Superconducting Fault Current Limiter

The saturated iron-core super conducting fault current limiter exceeds all other fault current limiters in terms of technical performance. Based on the real structure, magnetic structures have been proposed. Simulated current limiting inductance was calculated using the Newton iteration method and the fundamental magnetization curve. Sagging and soaring current levels occurred frequently during the faulting process. Short circuits and voltage fluctuations are two of the most typical grid-related issues.. The use of the SISFCL and DVR in this project resulted in a reduction in the amount of fault current and voltage variation. With the help of Matlab/Simulink and theoretical insights from previous research, we were able to construct an electromagnetic transient simulation model. The transient behavior of these devices during simulation tests demonstrates the accuracy and validity of the suggested strategy. Keywords: Analysis of transient electromagnetic waves in a saturated iron core using a Newton iteration method. Fault current limiter (SISFCL), dynamic voltage restorer (DVR), pulse width modulation (PWM)

Adaptive preconditioning for a stream of SLAEs

The paper considers the way of reducing the time consumed to solve SLAEs with iterative methods by reusing the data structures obtained in the solution of a previous SLAE, or selecting a preconditioner from the available set of preconditioners to minimize the time of solving the next SLAEs. Such adaptive preconditioning is used to solve time-dependent nonlinear problems. SLAEs generated at the Newton iteration n-1 of every computation step are solved using the SLAE structure of the first Newton iteration and the selection of a preconditioner from the given set allows reducing the time of solving SLAEs of a varying complexity at different time steps. The adaptive preconditioning idea and its application are demonstrated for a stream of SLAEs in some RFNC-VNIIEF’s codes.

Local Equilibrium Mechanistic Simulation of CO2-Foam Flooding

Mechanistic modeling of the non-Newtonian CO2-foam flow in porous media is a challenging task that is computationally expensive due to abrupt gas mobility changes. The objective of this paper is to present a local equilibrium (LE) CO2-foam mechanistic model, which could alleviate some of the computational cost, and its implementation in the Matlab Reservoir Simulation Tool (MRST). Interweaving the LE-foam model into MRST enables users quick prototyping and testing of new ideas and/or mechanistic expressions. We use MRST, the open source tool available from SINTEF, to implement our LE-foam model. The model utilizes MRST automatic differentiation capability to compute the fluxes as well as the saturations of the aqueous and the gaseous phases at each Newton iteration. These computed variables and fluxes are then fed into the LE-foam model that estimates the bubble density (number of bubbles per unit volume of gas) in each grid block. Finally, the estimated bubble density at each grid block is used to readjust the gaseous phase mobility until convergence is achieved. Unlike the full-physics model, the LE-foam model does not add a population balance equation for the flowing bubbles. The developed LE-foam model, therefore, does not add much computational cost to solving a black oil system of equations as it uses the information from each Newton iteration to adjust the gas mobility. Our model is able to match experimental transient foam flooding results from the literature. The chosen flowing foam fraction (Xf) formula dictates to a large extent the behavior of the solution. An appropriate formula for Xf needs to be chosen such that our simulations are more predictive. The work described in this paper could help in prototyping various ideas about generation and coalescence of bubbles as well as any other correlations used in any population balance model. The chosen model can then be used to predict foam flow and estimate economic value of any foam pilot project.

A Galerkin–Newton Algorithm for Solution of a Kirchhoff-Type Static Equation

In this paper, an algorithm is proposed to find an approximate solution for the Kirchhoff -type nonlinear differential equation, which describes the static state of a beam. The solution of the problem consists of two parts. First, we apply the Galerkin method. Next, to solve the obtained discrete system of equations, we use the Newton iteration method. The algorithm total error is estimated. The results of the numerical experiment are given.

Free (rational) derivation

By representing elements in free fields (over a commutative field and a finite alphabet) using Cohn and Reutenauer’s linear representations, we provide an algorithmic construction for the (partial) non-commutative (or Hausdorff-) derivative and show how it can be applied to the non-commutative version of the Newton iteration to find roots of matrix-valued rational equations.