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Experimental dynamical encircling of an exceptional point in coupled pendulums
No full textInternational audienceExceptional points (EPs) correspond to specific values of the system parameters that yield defective eigenvalues. The concept is demonstrated experimentally in the case of a simple mechanical system consisting of two coupled linearized pendulums. The latter is designed and instrumented in order to allow the encircling of an EP: the modulation of both the mass and stiffness matrices is achieved by controlling the length of one pendulum, whereas the damping is controlled by using eddy current brake mechanisms. The time evolution of the state vector, identified with the help of the extended Kalman filter, is described using the instantaneous modal basis. This allows one to quantify and observe mode coupling mechanisms, non-adiabatic effects and chiral behaviour. The paper ends with a numerical study, via the analysis of the monodromy matrix and the multiple-scale approach, which illustrates both the effect on chirality of the period of encircling and the presence of an EP in the loop
3D hepatic spheroids and liver‐organ on chip models displayed maintenance of hepatic functions and maturation profile in a long‐term culture of the humanized HepaSH cells, a human cell population harvested from chimeric mice
No full textInternational audienceLong‐term functional hepatocyte and reproducible cultures are required in pharmaceutical industries to model chronic liver disorders and to perform associated drug testing. In this frame, we have investigated the behavior of the HepaSH cells when cultivated in liver biochips, in 3D spheroids, and in petri for 20 days. HepaSH is a newly developed humanized hepatocyte harvested from chimeric mice. After the cell's harvesting and inoculation, the HepaSH were successfully maintained in cultures in petri dishes, spheroids, and biochips for 20 days. The immunostaining confirmed the expressions of albumin, CYP1A2, and CYP3A4 in all conditions. Furthermore, the CYP1A2, CYP2A6, CYP2B6, CYP2C9, CYP2D6, and CYP3A4 activities were successfully detected in all conditions after 20 days of cultures. Continuous production of albumin and biliary acids was detected in biochips, spheroids, and petri, among which biochip culture showed the highest albumin secretion level. The RNA sequencing analysis revealed that biochips and spheroids cultures enriched hepatic maturation, xenobiotic, lipid, small molecule, steroid, and alcohol metabolisms compared to petri cultures. Overall, our data demonstrated the feasibility of cultivating the HepaSH cells in petri, biochips, and spheroids for 20 days in the presented protocol, while keeping important liver functions. biochip and spheroids cultures show advantages in hepatic maturation, drug metabolism‐related gene expression, and albumin secretion (in biochips) compared with conventional petri culture
Accelerated SOH Balancing in Lithium-ion Battery Packs Using Finite Set MPC
No full textInternational audienceState of Health (SOH) balancing is crucial for extending lithium-ion battery life. This paper introduces a Finite Control Set Model Predictive Control (FCS-MPC) method for an 8-cell pack, achieving faster SOH uniformity than traditional methods by dynamically adjusting control actions and optimizing cell usage to reduce degradation
Development of Medium-Frequency Molded Transformer for SST with Simultaneous Insulation and Forced Air-Cooling capabilities
No full textInternational audienceThis paper proposes a new plastic moldstructure for medium-frequency moldedtransformers used in solid-state transformers(SSTs), aiming to enhance both the coolingperformance of windings and insulationcapabilities. In medium-frequency transformersfor 6.6-kV SST, high-voltage insulationperformance is required between the primary andsecondary windings. Therefore, insulation shouldbe provided by molding around the windings. Incontrast, an effective cooling method forwindings is necessary because copper losses inthe windings also increase as the operatingfrequency rises.In this paper, temperature rise in the windings,which is a problem in medium-frequency moldedtransformers, is addressed by applying plasticmolding only to the high electric field generatingpart in a structure that allows efficient cooling.Experimental results show that the developedtransformer, which has a power density of 12.6kW/L, continuously transmit 37.5 kW with amaximum transmission efficiency of 99.2%. Inaddition, partial discharge tests of the developedtransformer show that it has sufficient insulationperformance for SST with a 6.6-kV input
Multi-objective Optimization based Design of 3-L Inverters Considering an Extensive WBG Semiconductors Library
No full textInternational audienceThis paper presents a comparative analysis of the performance of 3-Level DC/AC inverter topologies in terms of price, loss, and volume. An extensive library of commercially available SiC and GaN semiconductors was implemented to create performance maps for the 3-L topologies across various power levels, aiding power electronics engineers in making informed design decisions. The analysis employs a highly precise design-byoptimization methodology to derive the optimal Pareto front for each topology. To ensure a fair comparison and minimize expert bias, all degrees of freedom were retained, and no design rules were imposed during the design flow. The optimization results provide quantitative insights into the enhanced capabilities of 3-L inverters utilizing WBG technology
Efficiency and Cost Comparison of GaN/Si and SiC/Si Hybrid ANPC Three-phase Inverter
No full textInternational audienceThis paper evaluates the benefits of a hybrid Active Neutral Point Clamped (ANPC) topology that combines Wide Band Gap (WBG) materials, Gallium Nitride (GaN) or Silicon Carbide (SiC), with Silicon (Si) technologies. The proposed topology enables the integration of GaN semiconductors, typically rated up to 650 V, into 800 V bus applications-an input voltage that the automotive market tends to reach. Using hybridization of semiconductor technologies, the system achieves substantial cost reduction without compromising efficiency. The concept is experimentally validated using a 15 kW threephase prototype
Development of Integrated Functions in GaN
No full textInternational audienceThis paper takes advantages of Gallium Nitride (GaN) as an ideal material in the development of electronic devices for high power and frequency applications. The paper details the circuit design and implementation of logic and analogue gates using a GaN-on-SI, non isolated proprietary technology to create a gate driver circuit for driving and instrumenting wide-gap power transistors
Comprehensive model of a synchronous generator for single-node studies
No full textInternational audienceAs power electronics increasingly replace Synchronous Generators (SGs), the focus on system frequency stability has grown. To study frequency dynamics during disturbances, time-domain models, such as the simple single-node model, are used. The commonly used single-node models lack sufficient representation of electric power dynamics, simplifying converter-interfaced generation (CIG) behavior as reduced system inertia. However, control strategies, such as Power System Stabilizers (PSS) on SGs or Power Oscillation Dampers (POD) on CIG, can modify the system-wide frequency response. This paper presents a comprehensive state-space model of a SG for single-node studies, offering flexibility to analyze electrical interactions involving the Automatic Voltage Regulator (AVR) and PSS, while facilitating the inclusion of power electronics. Additionally, the model provides a mathematical framework for understanding the relationships between system parameters through statespace representation and could be used to explore other critical interactions
Magnetic field measurement for contactless current sensing in power electronic converters
No full textInternational audienceCurrent sensing plays an important role in power electronics for both protection and control of power electronic converters. This paper proposes an approach for detecting short-circuit (SC) events through the measurement of the magnetic field radiated by power converters. Two magnetic field sensor technologies (AMR and induction coils) were evaluated. The magnetic field mapping over the PCB is carried out to estimate favorable positions for detecting SC events. The obtained results show that the induction coil is a promising candidate, not only for detecting a SC event but also for performing contactless current measurement in power converters. This work plans to develop the integration of contactless current sensors for power converters, or for intelligent drivers integrating protection against SC event (or over-currents), especially dedicated to wide band gap devices such as GaN and SiC materials which could have lower SC robustness compared to silicon
Carrier Synchronization Method using High-Speed Sampling for Parallel Inverters without Communication
No full textInternational audienceThis paper proposes a novel carriersynchronized control method for the parallel operation of two inverters using high-speed sampling. The proposed method focuses on the active power component at the switching frequency. When carrier synchronization is achieved, the active power at the switching frequency becomes zero for inverters connected in parallel. The proposed method calculates the active power at the switching frequency using high-speed sampling, switching states, and the fast Fourier transform (FFT). The proposed method requires only DC voltage and inductor current measurement without additional sensors. Furthermore, the proposed method is implemented in a single-phase inverter and does not need communication between units. Experimental results demonstrate that the circulating current is successfully suppressed to less than 66% of the rated current, thereby, validating the efficacy of the proposed control method