Search

International audience

International audience

International audience; The Pulsed Field Magnetization (PFM) is a compact and fast method to magnetize superconducting bulks compared to the field cooling method. However, the heat generation induced by the strong applied variable magnetic field during the PFM makes high trapped magnetic field harder to achieve. In order to make the REBaCuO bulks easier to magnetize by PFM, superconducting bulks including a superconducting weld are studied taking into account the thermal and electromagnetic properties of the weld different from those of the bulk body. This artificial grain boundary obtained by superconducting welding method might increase the trapped magnetic flux without increasing the applied magnetic field. In this paper, we are modelling the superconducting weld behavior during PFM using a 3D finite element model with the software COMSOL Multiphysics. The simulations are based on an H-formulation from Maxwell's equations and the heat diffusion equation. We analyse the impact of the critical current Jc of the weld on the trapped magnetic field.

International audience

International audience; This paper presents a validation of the hybrid method using the H and A formulations for Pulsed Field Magnetization (PFM). This hybrid method can help for simulating more complex problems involving superconductors, electric circuit and/or ferromagnetic materials. In some cases, the hybrid method can even speed up the simulation compare to the model that is based on H formulation only. A 2D axisymmetric model of PFM coupled with electrical circuit is first considered. To validate our concept, we simulated the same model governed by the hybrid method and the H formulation. The comparison of the final trapped magnetic flux density is then performed. The hybrid method was faster around 46 %. In the final paper, the validation and comparison will also be made on a 3D problem.

This paper presents an optimised model dedicated to design integrated systems for piezoelectric energy harvesting. Such systems implement a Full Active Rectifier (FAR) circuit whose efficiency depends on the architecture and switching strategy. In order to replace heavy transistor-level simulations, the proposed highly-configurable Matlab-Simulink® model offers the possibility to study the behaviour and assess the performance of any operation mode. The comparisons between simulations and experimental results performed on a CMOS integrated prototype of our FAR confirm the reliability and robustness of our model. The model thus enables large time scale system-level transient analysis with low computational resources and simulation time.

International audience

International audience; Sensorless control theory is considered as one of the most important keys to reduce the cost of manufacturing and maintenance in automotive applications. This article presents a current sensorless control algorithm of a wound rotor synchronous machine using a model-free-adaptive control (MFAC). The only controlled variable in this method is the rotor speed, and no observation or estimation will be performed on the phase currents. The presented controller is also compared with a current sensorless control method that uses a Lyapunov-based observation of phase currents in the control algorithm. The developed control algorithm is first tested in simulation under several operating conditions, such as starting, tracking, parameter variation, and load step. Then, experimental tests validated the effective performance of MFAC in a current sensorless control algorithm. According to these results, the control of phase currents is guaranteed with a small error but without using any current sensors.

Based on a multidisciplinary and configurable modeling approach, this work deals with the optimal choice and the design of a hybrid propulsion with the associated power management strategy to replace a conventional propulsion in a low tonnage river ferry operating on short cycles, with the aim of reducing its environmental impact and the costs over its entire lifetime. The considered ferry is used for the transport of people and vehicles crossing the Seine river, with an installed propulsive power of 330 KW. The operating cycle of the ferry and the energy consumption of its classical propulsion have been determined experimentally and then used as references in simulations for validation and comparison purposes. Two hybrid structures involving the use of batteries and supercapacitors were proposed and compared. It is shown that the hybridization leads to a substantial reduction in CO2 emissions. The supercapacitor- and battery-based hybrid structures lead respectively to 18% and 29.7% CO2 reduction compared to classical propulsion, representing, respectively, about 382 and 626 tons of CO2 reduction over 20 years of operation. Despite the fact that the use of batteries leads to a more significant reduction in CO2 emissions, the solution using supercapacitors is chosen following a technical-economic study over 20 years of operation.

High-Temperature Superconductors (HTS) considerably accelerate the development of superconducting machines for electrical engineering applications such as fully electrical aircraft. This present contribution is an overview of different superconducting materials that can be used as magnetic screens for the inductor of high specific power electrical machines. The impact of the material properties, such as the critical temperature (Tc) and the critical current density (Jc), on the machine performances is evaluated. In addition, the relevance to flux modulation machines of different HTS bulk synthesis methods are addressed.

International audience; The self-discharge phenomenon results in a decrease of the open-circuit voltage (OCV), which occurs when an electrochemical device is disconnected from the power source. Although the self-discharge phenomenon has widely been investigated for energy storage devices such as batteries and supercapacitors, no previous works have been reported in the literature about this phenomenon for electrolyzers. For this reason, this work is mainly focused on investigating the self-discharge voltage that occurs in a proton exchange membrane (PEM) electrolyzer. To investigate this voltage drop for modeling purposes, experiments have been performed on a commercial PEM electrolyzer to analyze the decrease in the OCV. One model was developed based on different tests carried out on a commercial-400 W PEM electrolyzer for the self-discharge voltage. The proposed model has been compared with the experimental data to assess its effectiveness in modeling the self-discharge phenomenon. Thus, by taking into account this voltage drop in the modeling, simulations with a higher degree of reliability were obtained when predicting the behavior of PEM electrolyzers.

This paper presents the design, modeling, and the experimental build of a 1.5 kW relatively low-cost wind turbine emulator (WTE), based on the variable speed wind power system concept with partly rated power converters. The turbine simulator is composed of a controlled DC motor (DCM) in order to manage the static-dynamic behavior of a real wind turbine, including an ideal gearbox. This emulator is integrated into a connected wind energy conversion system chain (WECS), based on the double fed induction generator (DFIG) configuration. The latter ensures the electromechanical conversion. It allows the transfer of active and reactive power to the power grid during hypo and hyper synchronous modes. The aerodynamic emulation principle requires controlling the DC armature current with a PI controller. This leads to an electrical drive that applies a shaft torque identical to the wind turbine transmission drive train. The current reference is calculated as function of the static settings of the wind turbine and real wind speed data gives different operating points. In addition, this paper also proposes to test the TSR (Tip Speed Ratio) based MPPT algorithm to extract the maximum available power on the emulator by adjusting the rotational speed according to the actual given wind speed data. The MPPT, the DC motor control and the DFIG power control algorithms are implanted in C language, using dSPACE DS1104 control board, meanwhile simulations are done using MATLAB/Simulink. The experimental and simulation results show the effectiveness of using the controlled DC motor to emulate the wind turbine and also the great performances of the proposed MPPT structure to achieve the extraction of the maximum instantaneous power available on the drive shaft.

International audience

International audience; In this paper, we present a simplified magneto-thermal modeling strategy for switched reluctance electrical machines (SRM) operating at high temperatures. In addition to the magnetic non-linearity, the variations of the electromagnetic and thermal properties of materials with the temperature are taken also into account. The rapidity of the proposed approach makes it compatible with a CAD approach.

International audience; This article aims to develop a proton exchange membrane (PEM) electrolyzer emulator. This emulator is realized through an equivalent electrical scheme. It allows taking into consideration the dynamic operation of PEM electrolyzers, which is generally neglected in the literature. PEM electrolyzer dynamics are reproduced by the use of supercapacitors, due to the high value of the equivalent double-layer capacitance value. Steady-state and dynamics operations are investigated in this work. The design criteria are addressed. The PEM electrolyzer emulator is validated by using a 400-W commercial PEM electrolyzer. This emulator is conceived to test new DC-DC converters to supply the PEM ELs and their control as well, avoiding the risk to damage a real electrolyzer for experiment purposes. The proposed approach is valid both for a single cell and for the whole stack emulation.

International audience; High-temperature superconducting (HTS) bulks can be used in electrical applications. Experimental characterization of large-size HTS bulks is a tricky issue. The relevant parameters for their application were directly measured in this study. This paper has three main aims. Firstly, features of YBaCuO bulks are presented. Secondly, an electrical motor application is developed using magnetic field shielding and trapping. Thirdly, the HTS bulks are characterized. Several classical methods were used, which are mainly magnetic methods only available for small samples. The complete penetration magnetic field and the critical current density were found to be the main parameters relevant for applications. An innovative entire HTS bulk characterization method is presented. This characterization method is useful for end users and engineers to better implement HTS bulks.

L'auteur a souhaité limiter l'accès aux membres de l'Enseignement supérieur français jusqu'au 1er septembre 2022.; Ensuring service continuity in safety-critical applications is indispensable. In some of these applications, the multilevel inverters play a vital role. Hence, employing a multilevel converter with fault tolerant feature is of great importance. In this regard, a fault tolerant five-level Neutral Point Clamped (NPC) inverter is proposed in this research work. The proposed fault diagnosis algorithm is based on failure mode analysis, which is a logic based approach. The realization of this strategy does not require any component modeling and complicated calculations. Although switches are more fragile than clamping diodes, clamping diodes are also subjected to breakdown. Hence, identification of a defective clamping diode is also studied in this research work. Moreover, for fault detection procedure, a voltage quantifier is proposed to avoid any misdiagnosis arising from measurement errors and voltage drop in the circuit. Following to the fault diagnosis, the proposed fault tolerant strategy aims to restore the rated voltage and current at the inverter terminal in the presence of an open-circuit fault in a switch or in a clamping or anti-parallel diode. Compared with healthy operation, harmonic content of the terminal voltage and current is not increased. The proposed fault tolerant structure does not include any contactor or bidirectional switch, which allows fast triggering of fault tolerant operation. The simulation and experimental results are presented to validate the effectiveness of the proposed approaches. A fault is detected in 20 µs and localized between 20 and 60 µs after occurrence, depending on the faulty semiconductor (switch or clamping diode).; La sûreté de fonctionnement de la conversion d’énergie est indispensable pour un grand nombre d’applications, en particulier lors de la mise en œuvre de convertisseurs multiniveaux. Par conséquent, il est important d’assurer la continuité de service de ces convertisseurs, lors de la défaillance d’un des semi-conducteurs. Dans cet objectif, ce mémoire propose un onduleur monophasé multiniveaux à tolérance de pannes, de structure Neutral Point Clamped (NPC) en pont en H, à cinq niveaux. L’algorithme de diagnostic de défaut est basé sur une étude préliminaire des modes de défaillance et repose donc sur analyse des conséquences d’un défaut, basée sur de la logique. Il ne nécessite ni modélisation des composants de l’onduleur, ni calculs complexes. Bien que moins sujettes à défaillance que les interrupteurs actifs, les diodes de clamp peuvent également être en défaut. Dans ce mémoire, l’identification d’une diode de clamp défaillante est également étudiée. De plus, un quantificateur de tension est mis en œuvre lors du diagnostic, afin d’éviter toute fausse détection en raison des erreurs de mesure et des chutes de tension dans le circuit. Suite au diagnostic d’un défaut, des mesures correctives sont appliquées afin de pouvoir assurer la tension et le courant de sortie à leurs valeurs nominales, lors de la défaillance en circuit ouvert d’un interrupteur actif, d’une diode de clamp ou d’une diode de roue libre. Le contenu harmonique des grandeurs électriques de sortie de l’onduleur n’est donc pas affecté par le défaut. La structure proposée pour l’onduleur à tolérance de pannes ne comporte ni contacteur, ni interrupteurs bidirectionnels ; les mesures correctives peuvent donc être appliquées très rapidement. Une sélection de résultats de simulation et de résultats expérimentaux illustre et démontre l’efficacité et la validité de l’approche proposée. Un défaut est détecté en 20 µs et localisé entre 20 et 60 µs après son apparition, selon le semi-conducteur défaillant (interrupteur actif ou diode de clamp).

The storage of electrical energy is now booming as it seems to be one of the necessary conditions to support the development of intermittent renewable energies in electrical networks. It competes, among other things, with historical sources of flexibility such as pumping stations or gas-fired power plants. The work of this thesis consists in the hybridization of two sources, namely the storage of energy in electrical form (lithium-ion battery) and a combined cycle (gas-steam cogeneration plant), in order to improve the stability of the networks and the operability of the plant. The main objectives are to specify the system specifications (functions, storage technology, pre-sizing), to create a configurable lithium-ion battery model based on the manufacturer's data and to define the control strategy for the hybrid. The pre-sizing methodology draws on both the similar work done by Gauthier Delille and the experience of General Electric, a manufacturer of combined cycles, to guide these systems towards suitable solutions. During the detailed dimensioning phase, the work led to the creation of a "system-oriented" lithium-ion battery model that can be implemented in GE's real-time software. This model, validated by tests in the GREEN laboratory, achieves a correct accuracy of about 95% (on cell voltage and energy). Finally, the energy management of this hybrid system is achieved by integrating a new controller in the power plant that provides instructions to the storage systems by processing both the internal data of the power plant and the data measured at the storage terminals. The choice was oriented towards simple commands (droop, PI, etc.) coupled with a fuzzy logic algorithm. This was configured using genetic optimization on data from an existing power plant. Despite several encouraging contacts with potential customers who showed interest in such a system, no prototype could be built., Le stockage de l'énergie électrique est aujourd'hui en plein essor car il semble être l'une des conditions nécessaires pour soutenir le développement des énergies renouvelables intermittentes dans les réseaux électriques. Il est en concurrence, entre autres, avec des sources de flexibilité historiques telles que les stations de pompage ou les centrales électriques à gaz. Les travaux de cette thèse consistent en l'hybridation de deux sources, à savoir le stockage de l'énergie sous forme électrique (batterie lithium-ion) et un cycle combiné (centrale de cogénération gaz-vapeur), afin d'améliorer la stabilité des réseaux et l'exploitabilité de la centrale. Les principaux objectifs sont de préciser les spécifications du système (fonctions, technologie de stockage, pré-dimensionnement), de créer un modèle de batterie lithium-ion configurable à partir des données du fabricant et de définir la stratégie de contrôle de l'hybride. La méthodologie de pré-dimensionnement s'inspire à la fois des travaux similaires réalisés par Gauthier Delille, et de l'expérience de General Electric, constructeur de cycles combinés, pour orienter ces systèmes vers des solutions adaptées. Au cours de la phase de dimensionnement détaillé, les travaux ont abouti à la création d'un modèle de batterie lithium-ion orienté "système" qui peut être mis en œuvre dans le logiciel temps réel de GE. Ce modèle, validé par des tests dans le laboratoire GREEN, obtient une précision correcte d'environ 95% (sur la tension et l'énergie des cellules). Enfin, la gestion de l'énergie de ce système hybride est réalisée en intégrant un nouveau contrôleur dans la centrale électrique qui fournit les instructions aux systèmes de stockage en traitant à la fois les données internes de la centrale et celles mesurées aux bornes du stockage. Le choix a été orienté vers des commandes simples (statisme, PI, etc.) couplées à un algorithme de logique floue. Celui-ci a été configuré en utilisant l'optimisation génétique sur des données provenant d'une centrale électrique existante. Malgré plusieurs contacts encourageants avec des clients potentiels qui se sont montrés intéressés par un tel système, aucun prototype n'a pu être construit.

A 2-D analytical model is proposed to calculate the magnetic field distribution in axial magnetic coupler with disk magnets. The 2-D simplification is possible by assuming an infinite radius of the ferromagnetic yokes. Then, an analytical solution is obtained for a single magnet. This solution allows the determination of the magnetic field due to all the magnets so the total magnetic field is obtained by superposition. To demonstrate the validity of the model, the analytical results are compared with those obtained from 3-D finite-element (FE) simulations and from experimental tests carried out on a magnetic coupler equipped with disk magnets and high temperature superconducting (HTS) pancake coils.

Rapid developments in hydrogen fuel cell (FC) energy and DC microgrid systems have extended the applications of multiphase parallel interleaved step-up converters for stabilizing DC bus voltages. DC microgrid applications include vehicle systems, shipboard power systems, and more electric aircraft, which generate power at low voltage levels. The cascade architecture of a power converter in a DC microgrid may cause large oscillations and imbalance given that converters considered as loads have constant power load characteristics. In this work, output DC bus voltage stabilization and current sharing of a multiphase parallel-interleaved-FC boost converter is presented. The proposed robust controller with added integrator action is based on the Hamiltonian–Lyapunov function. The efficacy and robustness of the designed controller were successfully authenticated by experimental results obtained using a 2.5 kW prototype FC converter (via four-phase parallel-interleaved boost converters) and the dSPACE MicroLabBox platform. The main source of the FC is based on a fuel reformer engine that converts fuel methanol and water into H2 gas in a polymer-electrolyte-membrane-FC stack (50 V, 2.5 kW).

International audience; It is well known that the interaction between cascaded individually designed power conversion systems can cause instability. To overcome this issue, a Hamiltonian energy control scheme is proposed, which is based on passivity control theory and port-controlled Hamiltonian framework. A complementary PI adjustment term is also included in the control algorithm to eliminate the steady-state output voltage error caused by the parameter uncertainty. The proposed control approach is applied to three different cascade structures. First, the cascade structure between dc/dc converters is considered, and the detailed controller design is given. Second, the cascade connection of a single converter and its LC filter is studied. By placing the LC filter into the Hamiltonian model of the controlled converter system, the dynamic and potential instability caused by the filter can be adjusted. Finally, the cascade structure between subsystems including filters and converters, which are common in microgrids, is studied. By using the Hamiltonian function (storage function) as the Lyapunov function candidate, the large-signal stability of each controlled converter system is proved. When the cascade structure contains multiple controlled converter systems, the stability of the entire cascaded system is guaranteed by the superposition of multiple Lyapunov functions. A 3.5 kW 220-270-350 V test bench is built in the laboratory to demonstrate the application of the proposed control approach to these three cascade structures.

International audience; Dynamic rating is an approach which implies to operate an electrical network closer to its thermal limits. This approach may be very beneficial for wave farms, as they are expected to present a highly fluctuating electrical current profile while benefiting from the large thermal inertia of the soil where their export cable will be buried. However, as the implementation of this approach is still in its infancy for offshore wind farms, it may be expected that the first wave farms, under the form of small-scale test sites, will be sized with respect to electrical current limits at a first stage. This sizing may be upgraded at a second stage when design methods will have included dynamic rating. However, this raises the question of the economic feasibility of this two-step approach, which is studied in this paper. Also, performing such a techno-economic analysis requires developing an electrothermal model of the export cable able to represent its transient response in a sufficiently precise manner while requiring also a reasonable computing time. In this perspective, a comparative analysis between several electrothermal modelling methods is also described in this paper.

International audience; This paper presents the utilization of differential flatness techniques from nonlinear control theory to permanent magnet assisted (PMa) synchronous reluctance motor (SynRM). The significant advantage of the proposed control approach is the potentiality to establish the behavior of the state variable system during the steady-state and transients operations as well. The mathematical models of PMa-SynRM are initially proved by the nonlinear case to show the flatness property. Then, the intelligent proportional-integral (iPI) is utilized as a control law to deal with some inevitable modeling errors and uncertainties for the torque and speed of the motor. Finally, a MicroLab Box dSPACE has been employed to implement the proposed control scheme. A small-scale test bench 1-KW relying on the PMa-SynRM has been designed and developed in the laboratory to approve the proposed control algorithm. The experimental results reflect that the proposed control effectively performs high performance during dynamic operating conditions for the inner torque loop control and outer speed loop control of the motor drive compared to the traditional PI control.

International audience; The use of High Temperature Superconducting (HTS) cables in power systems increases transmission capacity while reducing the volume of the installation. In addition, when transmission currents exceed a few kA, HTS DC cables significantly reduce power losses, rights-of-way and total system mass. This summary describes the various studies to be carried out in order to correctly dimension DC HTS cables for the new railway network envisaged by the French company SNCF, which has to take into account the ultra-urban needs. The process used to design DC cables for different operating current values between 5 kA and 20 kA at 1 750 V using commercial (RE)BaCuO tapes is presented. In this design stage, the dependence of the critical current density Jc(B, θ, T) of the superconducting tapes, the thermal properties of the materials used, and the different cooling modes as a function of the cable length were taken into account. Finally, we are discussing a cryogenic solution to protect the cable in case of short-circuit or overload.

International audience; The cascaded connection of power converters in a DC microgrid may cause instabilities. Indeed, power converters operating as external loads exhibit constant power load (CPL) behaviors. In this study, the design of the feedback controller of a multi–cell interleaved fuel cell (FC) step–up power circuit is based on the adaptive Hamiltonian control law. It includes two integral terms to confirm that there is no steady-state error in the DC bus voltage, and to guarantee the current balancing of each input inductor current. The design confirms that the desired equilibrium point is (locally) asymptotically stable by using the Lyapunov stability proof. The control approach is validated via digital simulations and experimental tests performed with a 2500 W FC converter supplied by an FC/reformer size of 2500 W and 50 V.

International audience; Electrical machines are important parts of different power systems. The application of high temperature superconductors (HTS) in electrical machines is very promising due to high transport currents. This paper reviews various topologies of superconducting motors and generators using HTS published in the literature in recent time. It begins with a brief presentation of the HTS material used in electrical machines. The description of AC losses and cryogenic systems is done afterwards. Then we offer a striking description of the various realizations of HTS electrical machines such as half HTS synchronous machines, fully HTS synchronous machine, machines with HTS bulks and stacks. Some of these machines are totally innovative compared to conventional ones and their operating principle is strictly related to the presence of HTS materials.

Purpose The purpose of this paper is to study the high-frequency impacts of fast switching wide-bandgap transistors on electronic and motor designs. The high-frequency power converters, dedicated to driving high-speed motors, require specific models to design predictively electronic and motors. Design/methodology/approach From magnetic and electric models, the high-frequency parasitic elements for both electronics and motor are determined. Then, high-frequency circuit models accounting for of parasitic element extractions are built to study the wide bandgap transistors commutations and their impacts on motor windings. Findings The results of the models, for electronics and motors, are promising. The high-frequency commutation cell study is used to optimize the layouts and to improve the commutation behaviours and performances. The impact of the switching speed is highlighted on the winding voltage susceptibility. Then, the switching frequency and commutation rapidity can be both optimized to increase the performance of motor and electronics. The electronic model is validated by experimentations. Research limitations/implications The method can be only applied to the existing motor and electronic designs. It is not taken into account in an automized global high-frequency optimizer. Originality/value Helped by magnetic and electric FEA calculations where the parasitic element extractions are performed. The switching frequency and commutation rapidity can be both optimized to increase the performance of motor and electronics.

International audience; This paper presents the design, modeling and the experimental build of a 1.5 kW relatively low-cost wind turbine emulator (WTE) equipped by a DC motor (DCM) in order to simulate the static-dynamic behavior of a real wind turbine, including the gearbox. This emulator is integrated into a connected wind energy conversion system chain (WECS), based on the double fed induction generator (DFIG) configuration. The latter ensures the electromechanical conversion. It allows the transfer of active and reactive power with the power grid during hypo and hyper synchronous modes. The aerodynamic emulation principle requires controlling the DC armature current with a PI regulator. This leads to an electrical drive that applies a shaft torque identical to the wind turbine. The current reference is calculated as function of the static settings of the wind turbine and real wind speed data give different operating points. In addition, this paper also proposes to test the Tip Speed Ratio (TSR) based MPPT algorithm to extract the maximum available power on the emulator. The MPPT, the dc motor control and the DFIG power control algorithms are implemented in C, using dSPACE DS1104 control board. The experimental results confirm the effectiveness of the controlled dc motor to emulate the wind turbine with great performances of the proposed MPPT structure.

International audience; This article proposes a modified interconnection and damping assignment passivity-based control (IDA-PBC) for dc/dc converter cascaded with an LC filter. The plant is modeled using the port-controlled Hamiltonian (PCH) form. The main objective is to stabilize the cascaded system in case the system supplies constant power load (CPL). To solve the instability issues caused by tightly controlled cascaded systems, the IDA-PBC based on an overall PCH model, including LC input filter and dc/dc converter, is established. Moreover, to ensure that the proposed IDA-PBC admits one unique solution, an adaptive interconnection matrix is designed to build the internal links in the PCH model. Furthermore, in order to improve the implementation on an onboard dc microgrid application with time-varying CPLs, a modified IDA-PBC algorithm is proposed based on the error between the state vector and the desired operating point, which might be variable. The closed-loop Hamiltonian function is chosen as the Lyapunov candidate function to guarantee that the system operates in a stable manner. The virtual damping assignment technique is addressed to tune the dynamic characteristic of the closed-loop system. Simulation and experimental results are carried out to illustrate the proposed method’s effectiveness.

Submitted for publication at IEEE Transactions on Control Systems Technology

International audience; The transition to electric propulsion aircraft requires electrical motors or generators with high power density. The "zero resistivity" of the superconducting materials could be used in electrical machines to produce high magnetic fields and reduce the use of heavy components such as the ferromagnetic parts. The discovery and recent developments in High Temperature Superconductors (HTS) technology make the superconducting machine a serious candidate in the future of aircraft. The design of a superconducting machine is strongly dependent on its electromagnetic and thermal behavior. In this paper, the design of a 50 kW superconducting aircraft generator is presented. The mass of the cryogenic cooling system is included into the design in order to optimize the entire superconducting system. The study shows that the choice of the cooling temperature to reduce the mass of the superconducting machine and its cooling system will depends on the input power of the machine.

The presented work focuses on the study of the architecture of a hybrid electric system (HES) made of different sources. First, we studied a configuration consisting of photovoltaic, wind, PEM fuel cell as sources and batteries, electrolyser and hydrogen tank as storage elements. Then in a second phase, only hydrogen storage is considered to ensure the electrical autonomy of a rural area in Comoros.The coupling of these different sources aims to improve the performance, the availability of the resulting electrical network, the supply of electricity over much longer periods and, above all, the satisfaction of the uses by operating each source in a reasoned way. First, we have analysed the main components of our system.Then, we established the mathematical models that describe the behaviour of the different parts of our hybrid energy system which is here the formalism used for the modelling. The modelling and simulation of the PV and wind systems use a MPPT control to maximize the delivered power.In the first configuration, the battery charge/discharge process is controlled to stabilize the DC bus voltage. The fuel cell makes the system more durable. It also helps to stabilize the DC bus voltage, in case of too much battery discharge.Thus, the use of a harmonic filter reduces the rate of harmonic distortion. Harmonics are compensated as well than the reactive current component in normal or unbalanced operating conditions. The presented simulation results have illustrated the behaviour of the different components of the HES in transient and steady states.Finally, the proposed system, analysed with the help of HOMER, would be able to provide a solution to the demand of a rural area in the Comoros or in any place suffering of a weak grid by using only hydrogen storage., Le travail présenté est axé sur l’étude de l’architecture d’un système électrique hybride (SEH) constitué de différentes sources. Dans un premier temps, nous avons étudié une configuration constituée de sources, photovoltaïque, éolienne, pile à combustible de type PEM et de systèmes de stockage, batteries, électrolyseur et réservoir d’hydrogène. Puis dans un second temps, nous avons conservé de la configuration présentée uniquement le stockage par hydrogène afin d’assurer l’autonomie électrique d’une zone rurale aux Comores.Le couplage de ces différentes sources a pour but d’améliorer les performances, la disponibilité du réseau électrique résultant, la fourniture d’électricité sur des périodes beaucoup plus longues et surtout la satisfaction des besoins en utilisant chaque source de façon raisonnée. Nous avons d’abord effectué une étude détaillée des principaux composants de notre système.Ensuite, nous avons établi les modèles mathématiques qui décrivent le comportement des différentes parties de notre système d’énergie hybride, modèles utiles pour la modélisation de l’ensemble. Les systèmes PV et éolien sont contrôlés par l’application d’une commande MPPT pour maximiser la puissance délivrée.Dans la première configuration, le processus de charge/décharge de la batterie contribue à la stabilisation de la tension du bus continu. La pile à combustible est utilisée pour rendre le système plus durable. Elle contribue également à la stabilisation de la tension du bus continu, en cas de trop forte décharge des batteries.Nous montrons ensuite que l’utilisation d’un filtre d’harmonique constitue une technique efficace pour réduire le taux de distorsion harmonique. Ce qui montre que le système proposé est bien compensé aux niveaux des harmoniques et du réactif quel que soit le mode de fonctionnement, normal ou déséquilibré. Les résultats de simulation présentés ont illustré le fonctionnement des différents composants du SEH en régimes transitoires et permanents. La solution proposée, analysée avec le logiciel HOMER, permet d’envisager une solution aux problèmes d’alimentation d’une zone rurale située aux Comores ou dans des endroits soufrant de surcharge ou même d’affaiblissement de la tension en ayant uniquement recours au stockage de dihydrogène.

International audience; Financial growth, clean environment, global peace, mitigating climate change, and future development of the world require new materials that improve the quality of life. Superconductivity, in general, allows perfect current transmission without losses. This makes it a valuable resource for sustainability in several aspects. High-temperature superconducting (HTSC) materials will be crucial for sustainable everyday applications and more attractive for the United Nations’ SDGs. Superconducting magnets can be used as high-field magnets in magnetic resonance imaging, nuclear magnetic resonance, water purification, magnetic drug delivery, etc. Hunger can be partly avoided if there is sustainability in agriculture. In future, DC electric energy from solar plants in Africa could be transported worldwide, especially to cold countries, using superconducting cables. Superconducting technology is an efficient way to create sustainability as well as reduce greenhouse gases. This book presents the latest global achievements in the processing and applications of high-Tc superconductors and discusses the usefulness of the SDGs. It summarizes the related advances in materials science and developments with respect to the SDGs. The book also covers large-scale applications of HTSC materials, which will be connected to the SDGs.

Présentation orale; National audience; L'azote solide (SN2) est capable de fournir un environnement cryogénique uniforme et stable pour des systèmes à base de supraconducteurs à haute température (HTS) tels que des échantillons massifs durant leur aimantation et/ou pour leur caractérisation.Un système de refroidissement utilisant de l’azote solide a été dimensionné, conçu et testé.Un réseau de résistances thermiques non-linéaires a été développé afin d'estimer le temps de refroidissement de cette installation. Nous avons estimé que 50 L d'azote liquide (LN2) peuvent être refroidis à 30 K en 36 h à l’aide d’un cryoréfrigérateur Sumitomo CH-110 et d’un échangeur approprié dans le bain de LN2.Durant ce spot, nous détaillerons les différents éléments du système, les résultats expérimentaux issus du premier refroidissement ainsi qu’une comparaison avec les résultats obtenus par notre modélisation numérique.

The aim of this thesis is to optimize the process of magnetization of superconducting pellets at high critical temperature (SHTC) by pulsed field magnetization (PFM) in order to use them in applications in the field of electrical engineering. In the design phase of the inductor necessary to magnetize these SHTC pellets, modeling and simulation are strongly recommended to perform the necessary calculations of the various electrical characteristics of the magnetization system. Therefore, we have developed an analytical model to study the influence of the presence of a superconducting bulk on the value of the inductance of an induction coil in a ferromagnetic circuit. The aim is to solve the Laplace and Poisson equations in different regions of interest through the magnetic vector potential. The analytical resolution was performed (carried out) using a computer code developed under MATLAB where the results obtained were in good agreement with those obtained by numerical simulation under COMSOL. The inhomogeneity of YBaCuO type SHTC pellets in terms of critical current density Jc was also investigated. To do this, we carried out experiments on the magnetization of these bulks by the PFM method. We have shown that the flat surface containing the crystallization germ (seed) of these pellets is characterized by a higher Jc than the other surface. Also, we studied the influence of the position of the seed crystallization in the two-pellet characterization method.; L’objectif de ce travail de thèse est d’optimiser le processus d’aimantation des pastilles supraconductrices à haute température critique (SHTC) par un champ magnétique impulsionnel ou PFM (Pulsed Field Magnetization) afin de les mettre en œuvre dans des applications dans le domaine de l’électrotechnique. Dans l’étape de conception de l’inducteur nécessaire pour magnétiser ces pastilles SHTC, la modélisation et la simulation sont fortement recommandées pour effectuer les calculs nécessaires des différentes caractéristiques électriques du système d’aimantation. De ce fait, nous avons développé un modèle analytique pour étudier l’influence de la présence d’une pastille supraconductrice dans un circuit ferromagnétique sur la valeur de l’inductance d’une bobine inductrice. Il s’agit de résoudre les équations de Laplace et de Poisson dans différentes régions d’intérêt à travers le potentiel vecteur magnétique. La résolution analytique a été effectuée à l’aide d’un code de calcul développé sous MATLAB où les résultats obtenus ont été en bonne concordances avec ceux obtenus par simulation numérique sous COMSOL. L’inhomogénéité des pastilles SHTC de type YBaCuO en termes de la densité de courant critique Jc a été également étudiée. Pour cela, nous avons réalisé des expériences de l’aimantation des ces pastilles par la méthode PFM. Nous avons montré que la surface plane contenant le germe de cristallisation (seed) de ces pastilles est caractérisée par une Jc plus élevée que l’autre surface. Ainsi, nous avons étudié l’influence de la position du germe de cristallisation dans la méthode de caractérisation à deux pastilles.

Purpose On-time fault diagnosis in electrical machines is a critical issue, as it can prevent the development of fault and also reduce the repairing time and cost. In brushless synchronous generators, the significance of the fault diagnosis is even more because they are widely used to generate electrical power all around the world. Therefore, this study aims to propose a fault detection approach for the brushless synchronous generator. In this approach, a novel extension of Relief feature selection method is developed. Design/methodology/approach In this paper, by taking the advantages of the finite element method (FEM), a brushless synchronous machine is modeled to evaluate the machine performance under two conditions. These conditions include the normal condition of the machine and one diode open-circuit of the rotating rectifier. Therefore, the harmonic behavior of the terminal voltage of the machine is obtained under these situations. Then, the harmonic components are ranked by using the extension of Relief to extract the most appropriate components for fault detection. Therefore, a fault detection approach is proposed based on the ranked harmonic components and support vector machine classifier. Findings The proposed diagnosis approach is verified by using an experimental test. Results show that by this approach open-circuit fault on the diode rectifier can effectively be detected by the accuracy of 98.5% and by using five harmonic components of the terminal voltage [1]. Originality/value In this paper, a novel feature selection method is proposed to select the most effective FFT components based on an extension of Relief method, and besides, FEM modeling of a brushless synchronous generator for normal and one diode open-circuit fault.

Purpose This paper aims to propose a new 3D electromagnetic model to compute translational motion eddy current in the conducting plate of a novel linear permanent magnet (PM) induction heater. The movement of the plate in a DC magnetic field created by a PM inductor generates induced currents that are at the origin of a heating power by Joule effect. These topologies have strong magnetic end effects. The analytical model developed in this work takes into account the finite length extremity effects of the conducting plate and the reaction field because of induced currents. Design/methodology/approach The developed model is based on the combination of the sub-domain’s method and the image’s theory. First, the magnetic field expressions because of the PMs are obtained by solving the three-dimensional Maxwell equations by the method of separation of variables, using a magnetic scalar potential formulation and a magnetic field strength formulation. Then, the motional eddy currents are computed using the Ampere law, and the finite length extremity effects of the conducting plate are taken into account using the image’s method. To analyze the accuracy of the proposed model, the obtained results are compared to those obtained from 3D finite element model (FEM) and from experimental tests performed on a prototype. Findings The results show that the developed analytical model is very accurate, even for geometries where the edge effects are very strong. It allows directly taking into account the finite length extremity effects (the transverse edge effects) of the conducting plate and the reaction field because of induced currents without the need of any correction factor. The proposed model also presents an important reduction in computation time compared to 3D finite element simulation, allowing fast analysis of linear PM induction heater. Practical implications The proposed electromagnetic analytical model can be used as a quick and accurate design tool for translational motion PM induction heater devices. Originality/value A new 3D analytical electromagnetic model, to find the induced power in the conducting plate of a novel translational motion induction heater has been developed. The studied heating device has a finite length and a finite width, which create edge effects that are not easily considered in calculation. The novelty of the presented method is the accurate 3D analytical model, which allows finding the real power heating and real distribution of the induced currents in the conducting plate without the need to use correction factor. The proposed model also takes into account the reaction field because of induced currents. In addition, the developed model improves an important reduction in the computation time compared with 3D FEM simulation.

International audience

Purpose This paper aims to propose a novel direct method for indefinite algebraic linear systems. It is well adapted for sparse linear systems, such as those of two-dimensional (2-D) finite elements problems, especially for coupled systems. Design/methodology/approach The proposed method is developed on an example of an indefinite symmetric matrix. The algorithm of the method is given next, and a comparison between the numbers of operations required by the method and the Cholesky method is also given. Finally, an application on a magnetostatic problem for classical methods (Gauss and Cholesky) shows the relative efficiency of the proposed method. Findings The proposed method can be used advantageously for 2-D finite elements in stepping methods without using a block decomposition of matrices. Research limitations/implications This method is advantageous for direct linear solving for 2-D problems, but it is not recommended at this time for three-dimensional problems. Originality/value The proposed method is the first direct solver for algebraic linear systems proposed since more than a half century. It is not limited for symmetric positive systems such as many of direct and iterative methods.

Purpose The purpose of this paper is to investigate the transient performance of an induction machine coupled with a magnetic gear for industrial applications with low speed and high torque requirements. This new solution increases mechanical reliability and does not require maintenance and lubrication. The main objective is to study the direct-on-line starting ability of the electrical machine and its stability regarding a sudden change for the load torque. Design/methodology/approach A nonlinear analytical model for the induction machine and the magnetic gear is first developed. The model is then linearized around an operating point to obtain the transfer function between the load angle and the electromagnetic torque from which an analytical expression for the mechanical resonant frequency is obtained. Findings It is shown that the direct on-line starting is possible, if the moment of inertia of the load is not greater than a maximum value. Moreover, it is demonstrated that this new system present inherent overload protection. Originality/value A new high-performance direct-on-line starting electrical machine is proposed to achieve high torque at low speed without mechanical gear to improve reliability and reduce maintenance.

The performance of proton exchange membrane fuel cells (PEMFC) is partly governed by complex, coupled transport processes at high polarization which usually occur in the low frequency region. Electrochemical impedance spectroscopy (EIS) is a powerful tool to extract valuable information about ohmic, charge and mass transport processes but fails marginally below 1 Hz as limited information on mass transport can be extracted. In this work, electrochemical pressure impedance spectroscopy (EPIS) was performed by applying fluctuations of the gas pressure at the fuel cell cathode outlet in the frequency range 1 mHz to 1 Hz to peek into transport processes. An experimental bench was designed and setup for reliable EPIS measurements on a single 100 cm2 FC. Conditions of pressure modulation in the test bench were thoroughly examined, leading to a standard protocol of operation. Two cases were studied in an attempt to better understand and differentiate the various transport phenomena occurring in fuel cell operation. Sensitivity of impedance modulus to mass transport control by the presence of liquid water could be shown for frequency below 0.1 Hz. Moreover, EPIS spectra exhibit striking profile differences in both modules and phases, with variations of the oxygen mole fraction in the cathode gas fed, evidencing gas diffusion phenomena in particular over 0.1 Hz. EPIS has been shown here to become an attractive complementary technique to EIS, even if further work is required for full beneficiation of this promising tool.

International audience; In this paper, it is aimed to use the cogging torque of PM machines for providing the load torque in the valve positioning applications. The policy is to use the machine cogging torque to overcome the load torque at the steady-state condition (fixed valve position). Therefore, there is no excitation, and no armature Joule losses at the steady-state condition and consequently lower thermal stress for the machine. To have a more compact actuator, it is tried to increase the machine cogging torque. Two well-known types of PM machines, i.e. Surface-mounted PM (SPM) and Flux-Switching PM (FSPM) machines are studied to be applied in this application. Some techniques such as applying auxiliary slots and PM segmentation (for the SPM machine), and two-part rotor topology (for both SPM and FSPM machines) are proposed to increase the machine cogging torque. The impact of each technique on the developed cogging torque is studied by means of Finite Element Analysis (FEA). Finally, the SPM and FSPM machines are compared together in the terms of the torque density. The validity of the proposed concept of providing the load torque by the cogging torque is investigated by experimental tests.

International audience; The use of electric motors or generators for aircraft application requires fewer prime movers and auxiliary equipment than conventional propulsion systems. Thus, the performance in terms of efficiency, reliability is improved. However, the dynamic behaviour of an aircraft required motor which transmit high torque on the propellers. The challenge is to develop an axial-field superconducting motor or a generator with high power density, up to 20 kW/kgThe inductor is composed of several YBCO bulks located inside a YBCO solenoid. The solenoid is fed by a direct current and produce a magnetic field in the axial direction. The diamagnetic behaviour of a superconducting bulk cooled under zero-field is used to obtain a variation of the magnetic flux density in the air-gap. The YBCO bulks is one of the critical parts of this electrical machine. It is therefore important to know their characteristic. In this paper, we present experimental tests for the YBCO bulk at several temperature in order to evaluate their performance in terms of screening.

International audience; Mg-B superconducting bulk materials are characterized as simple and uniform metallic compounds, and capable of trapping homogeneous field with beautiful conical shapes. Although pulsed-field magnetization technique (PFM) is expected as a cheap and an easy way to activate them, the heat generation due to magnetic flux motion in bulk magnets causes serious degradation of captured fields. It is important to suppress the flux motions during PFM to decrease the heat generation. In this study, authors precisely estimated the flux trapping to the bulk samples, found that the flux-shielding effect related to the sample dimensions. Moreover, the Ti-addition to the bulk sample affected the frequency of flux jump happenings. The magnetic field capturing of 5.0wt%Ti-added samples reached the highest value of 0.76 T, while the starting point of magnetic field invasion into the sample centre shifted from 1.0 T to 1.2 T with increasing sample thickness from 3.67 mm to 5.80 mm. The occurrence of flux jumps was suppressed in 5.0wt%Ti-dopped sample, which means that the heat capacity of the compounds shifted with varying Ti addition, effectively prevented the flux jumps.

International audience; Turbo-electric propulsion is seen as a potential solution for reducing greenhouse gas emissions from the aircraft industry. However, electrical machines must achieve high power to mass ratios (PtM) to meet aviation requirements. Superconducting technologies are a promising option for creating compact and efficient machines. Indeed, superconductors make it possible to generate large magnetic fields while reducing the need for ferromagnetic materials. In previous works, a 50 kW partially superconducting flux modulation machine has been realised [1]. The flux modulation machine is an unconventional topology where the inductor is composed by a large static superconducting coil and rotating superconducting bulks acting as magnetic field shields. This topology allows controlling the inductor excitation while being brushless. In this paper, we design a 500 kW flux modulation machine considering the results of the 50 kW prototype and the constraints dues to the structure change of scale.

National audience

The work in this thesis deals with the study of an axial flux claw pole machine for automotive traction. In an industrial context, the objective is not the absolute search for precision but to develop tools to obtain as quickly as possible useful information for design and decision making. The choice was made on free and open softwares, Gmsh/GetDP for the finite element part and NOMAD for the optimization in order to adapt these tools specifically to the engine sizing of this thesis with a control of the geometry, the mesh, the solved formulations and the optimization problem. An API was developed in order to automatize the setting up of models and the dialogue between the different softwares. In addition, the use of free software with the control of the solved formulations has allowed the implementation of practical methods to facilitate modeling. The obtained results are never an exact image of reality and must be used with care. In an industrial context, several questions arise so as not to waste time calculating non-exploitable quantities. Which quantities can be calculated with confidence ? To what extent can the mesh be expanded in order to find the compromise between speed and precision ? To answer these questions, a methodology based on the comparison of results from two formulations has been developed. Finally, the use of models solved by the finite element method in an optimization process, allowed the design of several innovative structures satisfying the specifications. A search for simplification of the inductor has allowed to obtain unconventional structures that could be interesting in a search for cost reduction., Les travaux présentés dans cette thèse portent sur l’étude de machines à griffes et flux axial pour traction automobile. Dans un contexte industriel, l’objectif n’est pas la recherche absolue de précision mais la mise au point des outils permettant d’obtenir le plus rapidement possible des informations utiles au dimensionnement et à la prise de décision. Le choix s’est porté sur des logiciels libres et ouverts, Gmsh/GetDP pour la partie éléments finis et NOMAD pour l’optimisation afin d’adapter des outils spécifiques avec un contrôle de la géométrie, du maillage, des formulations variationnelles et du problème d’optimisation. Une API a été développée afin d’automatiser la mise en place des modèles et le dialogue entre les différents logiciels. De plus, l’utilisation de logiciels libres avec le contrôle des formulations variationnelles a permis la mise en place d’astuces permettant de faciliter la modélisation. Les résultats obtenus ne sont jamais une image exacte de la réalité et doivent être exploités avec précautions. Dans un contexte industriel, plusieurs questions se posent alors pour ne pas perdre de temps à calculer des grandeurs non-exploitables. Quelles grandeurs peuvent être calculées avec confiance ? Comment trouver le compromis entre rapidité et précision ? Pour répondre à ces questions, une méthodologie reposant sur la comparaison de résultats issus de deux formulations a été développée. Enfin, ces outils ont permis le dimensionnement de plusieurs structures innovantes répondant au cahier des charges. Une recherche de simplification de l’inducteur a permis d’obtenir des structures non-conventionnelles pouvant être intéressantes dans une recherche de réduction de coût.

The work in this thesis deals with the study of an axial flux claw pole machine for automotive traction. In an industrial context, the objective is not the absolute search for precision but to develop tools to obtain as quickly as possible useful information for design and decision making. The choice was made on free and open softwares, Gmsh/GetDP for the finite element part and NOMAD for the optimization in order to adapt these tools specifically to the engine sizing of this thesis with a control of the geometry, the mesh, the solved formulations and the optimization problem. An API was developed in order to automatize the setting up of models and the dialogue between the different softwares. In addition, the use of free software with the control of the solved formulations has allowed the implementation of practical methods to facilitate modeling. The obtained results are never an exact image of reality and must be used with care. In an industrial context, several questions arise so as not to waste time calculating non-exploitable quantities. Which quantities can be calculated with confidence ? To what extent can the mesh be expanded in order to find the compromise between speed and precision ? To answer these questions, a methodology based on the comparison of results from two formulations has been developed. Finally, the use of models solved by the finite element method in an optimization process, allowed the design of several innovative structures satisfying the specifications. A search for simplification of the inductor has allowed to obtain unconventional structures that could be interesting in a search for cost reduction.; Les travaux présentés dans cette thèse portent sur l’étude de machines à griffes et flux axial pour traction automobile. Dans un contexte industriel, l’objectif n’est pas la recherche absolue de précision mais la mise au point des outils permettant d’obtenir le plus rapidement possible des informations utiles au dimensionnement et à la prise de décision. Le choix s’est porté sur des logiciels libres et ouverts, Gmsh/GetDP pour la partie éléments finis et NOMAD pour l’optimisation afin d’adapter des outils spécifiques avec un contrôle de la géométrie, du maillage, des formulations variationnelles et du problème d’optimisation. Une API a été développée afin d’automatiser la mise en place des modèles et le dialogue entre les différents logiciels. De plus, l’utilisation de logiciels libres avec le contrôle des formulations variationnelles a permis la mise en place d’astuces permettant de faciliter la modélisation. Les résultats obtenus ne sont jamais une image exacte de la réalité et doivent être exploités avec précautions. Dans un contexte industriel, plusieurs questions se posent alors pour ne pas perdre de temps à calculer des grandeurs non-exploitables. Quelles grandeurs peuvent être calculées avec confiance ? Comment trouver le compromis entre rapidité et précision ? Pour répondre à ces questions, une méthodologie reposant sur la comparaison de résultats issus de deux formulations a été développée. Enfin, ces outils ont permis le dimensionnement de plusieurs structures innovantes répondant au cahier des charges. Une recherche de simplification de l’inducteur a permis d’obtenir des structures non-conventionnelles pouvant être intéressantes dans une recherche de réduction de coût.