L2EP Logo


Recherche, Développement et Innovation en Génie Electrique

Seminar in OMN TEAM

The research team OMN works on different numerical methods associated to electromagnetic field computation. We organize regularly the internal seminar in LILLIAD Learning center innovation by our Ph.D. students, as well as our postdocs. Moreover, the external researchers are welcome to give us a talk about their work. If you would like to give us a talk or have some collaboration ideas about our work, please contact Zuqi TANG who is in charge of the seminar, we can invite you to Lille.
The seminar can be held in English (or French) as you like. There is no limit for the duration of the seminar.

Upcoming seminars:

August 31, 2018: Invited seminar, Salle 2S53, Lilliad

Pr. Chijie ZHUANG (Tsinghua University)

Chijie Zhuang received the B.Eng. and Ph.D. degrees from the Department of Electrical Engineering, Tsinghua University, Beijing, China, in 2006 and 2011, respectively. After a 2-year post-doc program, he became an assistant professor in Tsinghua University, where he was promoted to be an associate professor in 2015. His research interest includes air gap discharge and lightning protection, as well as numerical simulations for problems in electrical engineering.
He has published about 30 papers in international peer-reviewed journals. He was the secretory of CIGRE C4.26 working group (WG), and is the secretory of C4.45 WG, a member of IEEE P2426 WG. He also serves as an associate editor of High Voltage published by IET and CSEE Journal of Power and Energy Systems published by IEEE.

Shock Wave in Atmospheric Air Gap Leader Discharge: Observation and Simulation Results

A leader is an electric discharge mechanism in long-air-gap discharges, which is generally described by a set of convection-diffusion equations, Poisson’s equation and Navier-Stokes equations. We report the shockwave phenomenon in an air-gap leader discharge observed using a Mach-Zehnder interferometer with a time resolution of several microseconds. The continuous temporal evolution of the shock wave and the plasma channel was recorded and reproduced with a thermo-hydrodynamic model discretized by MUSCL and TVDRK schemes, with the measured current as the model input. The simulation results for the shock wave front positions and the plasma channel radius showed good consistency with the experimental measurements. Detailed thermal parameters obtained through the simulation showed that continuous energy injection by the current results in a temporary over-pressure process in the plasma channel and produces the shock wave.



Past seminars:


July 2, 2018, invited seminar

Pr. Anouar BELAHCEN (Aalto University)

Anouar Belahcen (M’13-SM’15) received the M.Sc. (Tech.) and Doctor (Tech.) degrees from Helsinki University of Technology, Finland, in 1998, and 2004, respectively. He is now Professor of Energy and Power at Aalto University, Finland and Visiting Professor of electrical machines at Tallinn University of Technology, Estonia. His research interest are numerical modelling of electrical machines, magnetic materials, coupled magnetomechanical problems, magnetic forces, magnetostriction, and fault diagnostics of electrical machines.

Research at Aalto University, with an emphasis on the magnetomechanical coupling

The first part of the presentation introduces some of the research subjects at Aalto University, Department of Electrical Engineering and Automation. The second part focuses on the research related to the magnetomechanical coupling in electrical steel. Here a measurement setup for rotational magnetic field and arbitrary mechanical stress will be presented together with the results of measurements on a non-oriented electrical sheet. Further, a model for the magnetomechanical coupling will be presented and discussed. The magnetic properties of electrical steel sheets are known to be highly stress dependent. During the manufacturing processes and operation of these devices, multi-axial stresses are exerted on the core laminations. The performance of the electrical machines is then significantly affected by these multi-axial loadings. In order to be able to design efficient devices and analyze the existing ones with better accuracy, the dependency of the core losses on the multi-axial stresses should be studied comprehensively. Yet another important issue is the effect of these loading on the noise and vibrations of electrical machines.



Juin 21, 2018, seminar


Reda El Bechari was born in Taza, Morocco, in 1993. He received his Master degree from ENSAM Lille, in 2016. Jointly, he has got an engineering degree (Industrial Engineering) from ENSAM Casablanca, Morocco.
He is currently a Ph.D. student with L2EP in Centrale Lille. His research fields include numerical methods of electromagnetic fields, robust design and reliability based design optimization for electromagnetic devices.

Approaches to Design Optimization of Electromagnetic Devices using Finite Element Method

The increasing constraints on the design of electromagnetic devices require numerical tools that are able to finely model the electromagnetic fields in the studied domain. Finite Element Method (FEM) is the most used tool to satisfy such a requirement. However, it may turn out that this tool is very expensive in computational time due to nonlinear behavior, 3D geometries, and time dependency. Thus, its usage for optimization, i.e. iterative process, should be made with caution since only a limited number of evaluations of the simulation tool are possible. Thus, the use of some specific algorithms may not be possible in a limited time, e.g. genetic algorithms, that require many evaluations of the FEM code. On the other hand, gradient-based algorithms cannot be used to their full potential due to the re-meshing error that may appear when computing the gradient using finite difference.
There exist two approaches. A non-intrusive approach that considers the FEM simulation as a black-box and constructs cheap meta-models to reduce the computational burden while refining only in promising regions. And a second approach aims to exploit the derivative of quantities of interest computed from the finite element code by using the adjoint method to be able to use gradient-based algorithms.


Juin 1, 2018


Kévin Darques was born in Neufchâteau, Vosges, France in 1990. He received his Master of Electrical Engineering from Lorraine University in 2014. During is degree, he had the opportunity to work with the Jeumont Electric company to study the permanent magnet losses in electrical machines with concentrated windings. After that, he started a Ph.D. at the University of Lille and EDF R&D (CIFRE). His work focused on the analysis of the shaft voltage of high-power turbogenerators. His research topic focuses toward His research topic focuses toward the finite element analysis of electrical machines.

Contribution to the shaft voltage modeling of high-power generators

In large turbo-generators, shaft voltage exists due to the inherent minor imperfections in the construction of the machine or material imperfections but also to defects such as eccentricities or rotor shorts circuits. Therefore, its analysis can constitute a variable to be used to diagnosis some machine defects. A first step consists in determining in an accurate way the effect of these defects on the shaft voltage. In this aim, a didactic analysis is carried out with the help of numerical model based on 2D FEM.
Two high-power non-salient pole synchronous generators of 2 and 4 poles are studied. The study is carried out gradually, first on a simplified structure and then introducing the effect of the stator slots, the parallel coupling, the load or eddy currents in the damper bars have been investigated. The obtained results are analysed in order to clearly determine the impact of each variable.


May 23, 2018, invited seminar

Antonio Wendell de Oliveira Rodrigues (IFCE)

Antonio Wendell de Oliveira Rodrigues a soutenu une thèse de l’Université des Sciences et Technologies de Lille (France) sur un sujet relatif à l’informatique haute performance utilisant les GPU avec une approche IDM pour la simulation des machines électriques, cofinancée par le Ministère de l’Éducation Française et la société VALEO. Il a fait un stage postdoctoral en gestion de l’innovation au Collège Lambton (Canada) et est titulaire d’un diplôme en ingénierie électrique avec spécialisation en informatique de l’Université Fédérale de Ceará. Enseignant-chercheur à l’IFCE (Brésil) dans les domaines de recherche suivants : ingénierie logicielle, calcul haute performance, réseaux informatiques et systèmes distribués. Il travaille dans divers projets de RD&I en utilisant le traitement d’images pour l’identification des patterns, l’utilisation de drones pour l’inspection par imagerie thermique, SmartGrid, IoT, l’apprentissage de machine…

RD&I et projets appliqués au secteur électrique au Brésil

Antonio Wendell de Oliveira Rodrigues nous fera un panorama des projets de RD&I pour le secteur de la génération, la transmission et la distribution d’énergie au Brésil via une approche calcul scientifique, basée sur des techniques de traitement d’images pour la reconnaissance d’objets, le calcul haute performance, l’intelligence artificielle, IoT et autres.


April 26, 2018, invited seminar

Brijesh Upadhaya (Aalto University)

Brijesh Upadhaya was born in a small town of Saptari district, Nepal, in 1986. He received his Bachelor of Engineering (Electrical Engineering) degree from Kathmandu University, in 2008. After receiving the B.Eng. degree he joined the alternative energy promotion center (AEPC, Ministry of Environment), and worked as a technical officer for the rural energy development program in the hilly and mountaineous districts of Nepal. In year 2010 he participated for the Fredkorpset Norway (:fK) south-south exchange program as an electrical engineer for the development of the micro-hydro power, in Laos. During his assignment in Laos he was hosted by the Sunlabob Renewable Energy Ltd. Brijesh had an opportunity to work for the energy demand forcast in southern Laos, detail feasibility study of the micro and pico hydro systems in Northern Laos, design of the solar home systems for the projects in Cambodia and Marshall Islands. After completion of the project in Laos, Brijesh started his Master of Science degree in electrical engineering at Aalto University, Finland, in 2012. He received his M.Sc. (Tech) degree in 2014 with a major in electrical systems and minor in electrical drives. Brijesh enrolled as a doctoral student in the research group of electromechanics at the Aalto University and he is currently working towards his doctor of science degree in electrical engineering. His research topic focuses toward the development of a vector hysteresis model that take into account the magnetic anisotropy. The anisotropic model should be suitable for the magnetic field analysis of the mangetic devices.

Modeling of the magnetic anisotropy in a soft magnetic material

A non-oriented (NO) electrical steel sheet present a certain level of magnetic anisotropy. Unlike a grain oriented (GO) electrical steel, the degree of magnetic anisotropy found in the NO electrical steels vary considerably, between low-to-medium levels. A large percentage of the electrical applications utilize the NO electrical steel sheet, such as the rotating electrical machines. Thus, for an efficent design of the electrical applications, an accurate magnetic material model have become increasingly important. For this reason, the magnetic material model capable of describing a weakly anisotropic NO electrical steel sample has been studied in this work. This studied model is an extension of the phenomenological Jiles-Atherton hysteresis model. Furthermore, the extended model of the magnetic anisotropy is analysized, and the simulation results from this model has been compared with the measured magnetic charecteristic. Moreover, the numerical challanges has been studied, regarding the implementation of the vector Jiles-Atherton hysteresis model in a 2D finite element analysis.


April 20, 2018, C2EI seminar

Moustafa AL EIT

Moustafa Al Eit was born in Baalbeck, Lebanon in 1990. He received the graduate degree in electrical engineering from the faculty of engineering at the Lebanese university, Beirut, Lebanon in 2013. Within an international exchange program, he received a master’s degree in Physics and engineering in the electrical energy from the École Superieure d’Électricité (SUPELEC) and achieved his final study internship at the Électricté de France (EDF) in 2013. In 2016, he received the Ph. D. degree in Physics for electrical engineering applications from the University of Paris-Saclay. Actually, he is a post-doctoral researcher at the laboratory L2EP in the École Nationale Supérieure d’Arts et Métiers (ENSAM). His research topic is axed on the numerical modeling of electrical systems and the integration of efficient model reduction techniques (POD, DEIM, Perturbation/Zooming techniques, Exploitation of geometrical periodicity, …).

Exploitation of the geometrical periodicity of electrical machines in the FE modeling


April 20, 2018, C2EI seminar


Jian Zhang received his Ph.D. degree in electrical engineering from University of Nantes, France, in 2015. Then, he worked as a post-doctor researcher at Lille Laboratory of Electrical Engineering and Power Electronics (L2EP). His research interest included in electrical machine optimization and design, fault diagnosis and electric power systems control for renewable energy application.

modeling and experiment validation of squirrel cage asynchronous machine with and without faults


April 20, 2018, C2EI seminar


Emna Jaïem obtained a PhD degree in Applied Mathematics from Tunis El Manar University, Tunis, Tunisia in July 2016. During her PhD thesis, she investigated the geometrical inverse problem related to the identification of defects in mechanical structures from, on the one hand overdetermined boundary data and on the other hand sub-Cauchy data. Indeed, her research fields include shape optimization (shape derivative, topological derivative, level set method, …). In September 2017, her work was recognized with the TWMA (Tunisian Women Mathematicians’ Association) award for the best PhD thesis in Applied Mathematics for Tunisian women (https://tunwma.com/twma-awards/twma-awards/). She is currently a postdoctoral research at L2EP working on the numerical analysis of electromagnetic field and more precisely on spectral methods (Harmonic Balance Method).

Spectral finite element method to solve magnetostatic problem taking into account the movement


March 8, 2018, seminar

Sylvain Babicz

Sylvain Babicz was born in the city of Beuvry, Nord-Pas de Calais, France in 1989. He received his Master of Science in Electrical Engineering in 2013. He then began doctoral studies at Université d’Artois (Béthune) on the possibility of using anodized aluminum strip in the design of electrical machines running on high temperatures (above 300 °C). Sylvain obtained his Ph.D degree in december 2016. He had the opportunity to continue, during the academic year 2016-2017, his study about high temperature materials. The aim of the work was to develop an original insulation to improve the dielectric performance of ceramic wires. This work was concluent and lead to a paper on an IEEE journal, currently under reviewing process. He is currently assistant professor in the laboratory L2EP of the University of Lille.

Characterizations of Electrical Engineering Materials: Application to Dielectric Materials submitted to High Temperatures (>300°C)

A part of the evolution in the field of electrical engineering concerns the increase of device temperature class. Concerning magnet wire organic insulations, the temperature class seemed to reach a limit. As a consequence, laboratories start to explore inorganic insulations. These are principally composed of alumina and must be characterized as they will be used in electrical devices. High temperatures, above 300°C, are becoming of high interest whether it is for aeronautical equipment, near the turbines, or in the case of the increase of the power-to-weight ratio for new transport applications as electric vehicles. All the components of a classic electric motor must be re-thought and studied in the case of high temperatures. This presentation will discuss the problem for dielectric purposes, and will be extended to magnetic materials.


April 19, 2018, seminar

Sylvain SHIHAB

Sylvain Shihab receive his Master and Phd in condensated matter physics at the Pierre and Marie Curie University in 2012 and 2015. He worked mainly on the magnetization dynamics in the diluted magnetic semiconductor (Ga,Mn)(As,P). He is currently research engineer at the L2EP laboratory. His main researches are on the study and the characterization of soft magnetic steel alloys used in electrical machine to improve models describing magnetization behavior law.

Characterization and modeling of magnetic steels alloys used in electrical machines

Magnetic materials are the heart of electrical machine for mechanical to electrical energy conversion. Thus, an improvement of magnetic materials performance lead to an improvement of the electrical machine. To better understand all relevant materials parameters which have an impact on the magnetic properties, it is necessary to characterize materials in various experimental conditions. Then, starting from our observations, we can propose and improve models of magnetic behavior laws.
During this seminar, I’ll present you our work on the magnetic characterization of non-oriented sheets and bulk magnetic steel alloys, on the conductivity measurement and on the improvement of magnetic losses model.


February 15, 2018, invited seminar

Ruohan GONG (Wuhan University)

Ph.D. candidate of Electrical Engineering School of Wuhan University. Graduated from Physics and Technology School of Wuhan University with BE degree at 2012. Worked as an associated researcher in High voltage and Insulation Center of Wuhan University form 2012 to 2018. Major in Lightning-protection and Grounding, Electrical Engineering Materials, Multi-Physics Coupling Simulation of electrical devices and Inversion problem.

Study on Hot-spot Temperature Calculation and Inversion Detection Method of Oil-immersed Transformer

Power transformers are one of the most important equipment of the electrical power system. The operating reliability of transformers has a close influence on security and stability of power systems. The end of the life span of power transformers is most due to the loss of their normal insulation, which is very much dependent on the highest temperature occurred in any part of a winding insulation system, as known as hot spot temperature (HST). Thus, getting the values and location of HST is significant to meet the goals of maximizing the load ability, improving the effective lifetime and lowering the total cost associated with transformer operation and maintenance. Some works focused on this topic has been developed as follows:
(1) Considering the complicated and special solid-liquid-gas structure of oil-immersed transformer, the heat dissipation process inside transformer including heat conduction and convection is investigated by multi-physics coupling analysis. The validity and accuracy of calculation model is verified by temperature rise test.
(2) According to the temperature and velocity distribution analysis of inner transformer, an inverse detection method of HST based on support vector regression(SVR) is put forward. This method takes load and tank temperatures as input characteristics. The relative error of HST steady state temperature inversion is less than 3%.
(3) On the basis of steady inversion, an improved HST transient calculation method based on thermal-electrical analogy and IEC standard is proposed. The thermodynamic parameters of this model are estimated by Levenberg-Marquardt(LM) method. This model has been successfully applied to transformers with different voltage classes, capacities and structures. The maximum temperature difference is less than 3℃.


November 13, 2017, invited seminar

Pr. Shuhong WANG (Xi’an Jiaotong University)

Shuhong Wang (M’11–SM’13) received the B.E., M.E., and Ph.D. degrees in electrical engineering from Xi’an Jiaotong University, Xi’an, China, in 1990, 1993, and 2002, respectively. He is currently a Professor with the school of Electrical Engineering, Xi’an Jiaotong University. His research fields include numerical analysis of electromagnetic field and multiphysics problems, design and optimization of electromagnetic devices, measurement and modeling of properties of novel magnetic materials, the analysis and application for high temperature superconductivity.

Extended Finite Element Method in Electromagnetic Fields

In some situations, the classic finite-element method (CFEM) uses the shape functions for interpolation and does not account easily for regions of discontinuity and singularity in electromagnetic problems, such as the magnetic field and eddy current distribution in one silicon sheet of magnetic core, the electric field distribution near the crack tip in the electrical insulation material. The extended finite element method (XFEM) is able to incorporate the local enrichment into the approximation space within the framework of CFEM, the resulting enriched space is then capable of capturing the non-smooth and singularity solutions. The interface between two materials, which may cross through the element, can be described by using level-set functions and Guass integration is applied to construct the stiffness matrix of XFEM. Two numerical examples demonstrate that XFEM has some advantages for electromagnetic field analysis of discontinuous and singular solutions comparing with CFEM. The XFEM can not only improve the computational accuracy, but also save computation memory and time.