Conference Agenda

Domain decomposition is a strategy designed to be used on parallel machines. This strategy leads to hybrid methods between direct and iterative solvers and allows users to benefit from the advantages of both. Lately, the growing size of simulations in electromagnetics brought to light the interest of using domain decomposition. Nonlinearity is also one of the problems specificities where the need for an efficient solver is high. This paper provides a comparison between two techniques of domain decomposition for solving 3D nonlinear magnetostatic problems. A test case illustrates the results that can be expected.

Choosing a limited set of sensor locations to characterize or control a high-dimensional system is an important challenge in electrical machines. The reliability, efficiency, performance and operational safety are always critical issues, which implies that the monitoring and analysis during the operation of the equipment need to be strengthened. In general, more sensors can give higher accuracy of the estimated physical quantity, but bring a more expensive cost. In this paper, two algorithms are presented and adopted to optimize the location of sensors, the first one principally is based on the parameterized background data-weak (PBDW) approach, where the second based on the Maxvol technique. To further investigate the performance of these algorithms, a prototype concerning an anisotropic magnetostatic problem is studied.

In the effective medium theory, a material parameter of a heterogeneous structure is replaced by an effective material. This effective material is based on physically observable values like losses or powers and is calculated a priori in a cell problem representing a meaningfull part of the heterogeneous structure. In this work, the magnetic permeability of a laminated ferromagnetic iron core is modelled by the scalar Preisach model. Additionally to eddy current losses and magnetic reactive energies, the introduced effective material copes with hysteretic losses. The high accuracy of the novel approach is demonstrated on a basic numerical example.

History-dependent hysteresis models have potential to accurately describe magnetization curves of all orders. This property is indispensable when modeling magnetization dynamics and power loss inside magnetic components subjected to distorted excitations. Ones of the most accepted history-dependent hysteresis models are the Zirka-Moroz models. This paper gives insight into the identification procedure of the basic history-dependent Zirka-Moroz hysteresis model. A two stage parameter identification procedure based on measured first-order reversal curves was employed and analyzed. A significant change in the reversal curve’s shapes at high ΔB_rev was discovered, which influenced the overall accuracy of the identified model.

In the ground return mode of high-voltage direct current (HVDC) transmissions, a direct current is injected into the soil through a grounded electrode, resulting in a ground potential rise in the soil. Consequently, it is essential to develop a methodology to calculate ESPs for the site determination of the grounded electrode and the operation analysis of the transmission system. The earth surface potential (ESP) is closely related to the soil structure, and its solution involves an extremely largely computational domain. However, a few studies have been devoted to solve 3D soil potential problems, and the efficient computation of 3D earth surface potentials is still demanding. In this article, a novel numerical methodology based on coupled boundary elemen-finite element method (BEM-FEM) is developed for the calculation of 3D ESP, taking the complex soil structure into account. An iterative solution approach is proposed to allow shallow and deep soil subdomains to be analyzed separately by FEM and BEM. Numerical examples are presented, illustrating the performance of the proposed method and its potentialities in engineering applications.

We propose an innovative technique for dealing with optimal shape design problems characterised by curved boundaries between ferromagnetic and dielectric sub-regions. The proposed approach relies on the ability of the Virtual Element Method in handling meshes with polygonal elements having curved edges. The shape synthesis of an electromagnet is considered as the case study.

The dielectric properties of cartilage are essential for the development of reliable numerical models of electrical stimulation devices intended for the regeneration of cartilage. They are, however, not widely known. To determine the dielectric properties of cartilage, we propose a numerical workflow that incorporates detailed tissue-specific 3D geometries based on fluorescent microscopic images and describes how different parameters can affect the results. At low frequencies, there was no frequency-dependent conductivity. By including the pericellular matrix and nucleus of the cells, the γ-dispersion could be modelled. Because the internal layers of the cartilage tissue differ from the external layers, the simple model cannot be used to analyze the dielectric properties of such tissue.

In this work, an adaptive nonlinear iteration method for both 2D and 3D finite element analysis of electric fields is proposed for either electrostatic, DC conduction or electroquasistatic problems. Since pure fixed point iteration or pure Newton iteration is not always efficient and convergent ensuring good nonlinear convergence rate. A solution technique to enhance the stability of nonlinear iteration is proposed by combining both nonlinear iteration methods in an adaptive manner from extensive numerical tests. This adaptive iteration method is better in convergence rate based on our numerical tests. Benchmark examples is solved using the proposed method.

One observes when simulating RC circuit or electroquasistatic problems where conductors and non conductors are present, that large time steps or low frequencies lead to numerical instabilities. This can be easily related to the condition number of the system matrix. Here we propose multiple stable formulations by scaling and preconditioning the equation systems. This allow the reliable calculation of solutions even for very low frequencies, or large time steps. Numerical experiments underline the findings.

In this study, we numerically analyzed the conduction mechanism of polymeric insulators under HVDC environments. Based on the Space-charge limited current theory, various representative theoretical research has been investigated for a few decades. The space charge dynamics inside the polymeric insulators consist of the electrode and bulk-limited conduction. Under a high electric field, a noticeable conduction current of a measurable size can pass through the polymeric insulator even though it is an insulator. These current changes depend on the electric field strength and temperature. Various theories could not be well-matched with a wide range of current-electric field-temperature relationships. In this study, we numerically evaluated the various theories to clarify the space charge dynamics inside the polymeric insulators. Herein, we suggested well-matched simple approaches to describe the current phenomena and space charge packets following the broad range of environmental conditions: field strength and temperatures.

Noise suppression sheets (NSSs) are often applied on conducting surfaces to eliminate surface currents on them and thus reduce the unwanted noise coupling in near-field region.

In this work, a test method for properly evaluating the intra-decoupling characteristics of NSS on a conductive plane using two loop probes is proposed. Compared to the standard test method for NSS presented in IEC 62333-2, the suitability and superiority of the proposed method was discussed through 3D electromagnetic-field simulation and measurement. In addition, through the analysis using the Design of Experiment (DoE), a test setup for measuring the intra-decoupling of NSS used at the frequency range below 100 MHz is presented.