Haute tension | EPFL Graph Search

La haute tension est un terme qui caractérise, selon des normes européennes, les valeurs de la tension électrique supérieures à en courant alternatif et en courant continu. France En France, on distingue deux domaines de hautes tensions :

le domaine haute tension A (ou HTA)), concerne les installations électriques dans lesquelles la tension : ** excède sans dépasser en courant alternatif, ** ou excède sans dépasser en courant continu ;
le domaine haute tension B (ou HTB) concerne les installations électriques dans lesquelles la tension : ** excède en courant alternatif, ** ou excède en courant continu.

, on utilisait couramment les termes :

extra-haute tension, pour désigner les tensions alternatives de 300 à ;
ultra-haute tension, dans les années 1990, .

L'appellation très haute tension (THT) est quant à elle une dénomination de la classe des tensions utilisées dans les anciens téléviseurs à tube cathodique. Jargon u

Ultra-high voltage, low power and energy recovering electronics for dielectric elastomer actuators

Raphaël Johannes Charles Mottet

Heart failure is a cardiovascular disease affecting between 1 and 2% of the population of developed countries alone - more than 10 million people - with this number bound to increase due to the ageing of the population. This condition starts to develop itself when the heart is not capable to properly pump the blood in the circulatory system anymore, and it can be due to other cardiovascular diseases, hypertension, heart attacks, etc. When cases become very severe, surgical procedures are then necessary to install cardiac assist devices to help reduce the stress experienced by the heart and allow it to potentially heal itself. However, the devices currently used are bulky and very invasive with risks of infections and rejections.As such, the Center for Artificial Muscles (CAM) was tasked to investigate and develop a new kind of cardiac assist devices which would be much less invasive to install. To do so, the idea envisioned consisted of working with Dielectric Elastomer Actuators (DEAs) which are often nicknamed artificial muscles due to their close resemblance with the natural ones as they, amongst other things, light, thin and can deform themselves significantly. One of the main challenges of working with this technology comes from the fact that DEAs have very uncommon needs concerning the driving electronics. Indeed, to operate to the maximum of their abilities, DEAs require voltages of several thousands of volts - between 5 and 20 kV depending on the actuator - to be applied to them. Currently, these actuators are powered using extremely large and impractical laboratory power supplies which is unacceptable for portable and medical applications. It was therefore critical to investigate and uncover a solution for the electronics so that the DEAs' needs could be met with a system as compact and efficient as possible.Thus, this thesis presents the investigating process followed to obtain in the end an electronics system capable of supplying at least 8 kV to a DEA and recover unused electrical energy stored in the actuator. Process which consisted at first of an investigation of power electronics topologies capable of amplifying a given input voltage to a higher level in order to determine the most suitable one. It was concluded that the DC/DC flyback converter was the best candidate for the job.This was followed by an in depth analysis of the working principle of this converter topology to determine the limiting factors regarding the supply of high voltages. This analysis was confirmed through the development of an analytical model depicting the behavior of the converter when it charges the actuator to the required voltage. Thanks to this a list of solutions to overcome these factors could be given.Then, due to the voltage levels worked with and the necessity to recover the unused electrical energy stored in the actuator, it was revealed that commercially available solutions were scarce to nonexistent to properly control the electronics. As such, control strategies and custom devices were ultimately conceived to resolve this problem.In the end, the final ultra-high voltage bidirectional flyback converter prototype was used to operate a DEA pump placed in a test bench recreating the pressure conditions and blood flow which are expected to be found in a living body. These tests showed that the electronics performed very well and managed to operate without major issues the new cardiac assist device created by the CAM.

EPFL2022

Etude formelle pour la synthèse de convertisseurs multiniveaux asymétriques

Jean-Sébastien Mariéthoz

The multilevel converters allow generating a voltage waveform whose magnitude and quality are higher than those of conventional converters. They are devoted to medium and high-voltage, high-switching-frequency applications. Among the series connected cell inverters, the symmetrical multilevel inverters are made of identical cells, which topology is generally the H-bridge inverter. This dissertation deals with asymmetrical multilevel converters, which combine high-voltage cells — made of low conduction loss switches — with low-voltage cells — made of low switching loss switches. The different cells play different roles. The goal is to design a converter that has both better energetic efficiency and higher resolution with the same number of cells. This dissertation develops a set of tools that allows synthesizing an asymmetrical multilevel converter. It develops the cell combination rules, which allow defining several cell association classes. The inverter step uniformity condition determines the finesse that can be reached. The optimized modulation condition allows to reduce the highvoltage cell switching frequency without changing the low-voltage cell switching frequency. This property is essential to derive benefit from combining switches of different characteristics. The power balance condition determine how to control the power sharing between the cells. These association classes are different for the single-phase converters and the three-phase converters — without neutral wire. They allow to select a configuration suitable for a given application. Furthermore, several ways that allow improving the inverter resolution are investigated. The modulation is essential to associate a high-quality signal (which will really be delivered to the load by means of the inverter levels) to the reference signal (which should ideally be applied to the load). The modulator evaluation methods are assessed. An approach—based on the modulated signal decomposition in elementary frames—is proposed. The main modulator drawbacks are highlighted. A modulator—which arrange the frames in order—allows to reduce the modulated signal distortion and number of transitions. The specific control methods that allow to minimize the inverter number of switchings are developed. The active power cell supply implies several conversion stages, which decrease the converter energetic efficiency. Some solutions that allow to reduce these losses are proposed. Finally, this dissertation attempts to determine, which are the more interesting solutions, depending on the application.

EPFL2005

Ultra-High-Voltage (7-kV) Bidirectional Flyback Converter Used to Drive Capacitive Actuators

Morgan Almanza, Alexis Boegli, Raphaël Johannes Charles Mottet, Yves Perriard, Lucas Pniak

Dielectric elastomer actuators (DEAs) have extremely advantageous characteristics such as lightness, compactness, flexibility, and large displacements. However, in order to operate, they can require voltages in the order of several thousands of volts. Thus, to unleash the full potential of DEAs, it becomes essential to be able to generate and manipulate such voltages with an electronics as compact and efficient as possible. While previous works showed that it was possible to implement a system capable of supplying voltages of up to 2.5 kV and recovering part of the energy stored in DEAs (due to their capacitive nature), no work managed to go over that threshold for two main reasons: first, due to the absence of switches capable of withstanding more than 4.5 kV, and, second, due to parasitic capacitances of the flyback's coupled inductor, which steal an increasingly large part of the energy destined for the load when the output voltage is higher. This article, therefore, proposes a global design, where the factors limiting the increase in the output voltage have been mastered. Through a careful design of the coupled inductor combined with the use of MOSFETs put in series, thanks to the pulsed transformer gate drive topology to handle the high voltages, this work goes beyond the current state of the art. Indeed, here, we present various strategies undertaken, which led to the manufacture of a bidirectional flyback converter capable of amplifying an input voltage of 12 V to more than 7 kV across a capacitive load and recuperating parts of the energy stored. A preliminary study of the efficiency shows an approximate 58% efficiency during the charge phase from 0 V to 7 kV and a 54% efficiency during the discharge phase.

IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC2021