Conception et intégration d’un nouveau piezo-generateur et d’un système de stockage hybride batteries-supercondensateurs pour la génération et l’amélioration de la qualité d’énergie électrique

Abstract

A large number of studies have been published in the last decade on the possibility of harvesting vibratory energy using piezoelectricity as a conversion mechanism. Several aspects have been studied ranging from different electromechanical models through harvester forms maximizing performance to electrical circuits allowing an improvement of the harvesting energy. By spreading through the distribution electrical networks, the problem of harmonic pollution is becoming more and more worrying with the increasing use of electronic components and nonlinear loads, which leads to harmful consequences and therefore a malfunction of several devices sensitive to this kind of problems. Active power filtering is one of the most effective solutions to this problem. The contribution that brings this thesis, in the energy harvester and improvement field, consists to design a new optimal wind vibratory energy harvester using piezoelectric elements. The work of this thesis revolves around five objectives: 1. Design and experimental validation of a power generator based on piezoelectric transduction and wind flow. 2. Development of an analytical model to predict the performances and explain the chosen geometry of the piezoelectric wind energy harvester. 3. Development of an energy extraction circuit to maximize the harvested power by the piezoelectric elements and adapt the generated voltages to a high level. 4. Design of a hybrid supercapacitors batteries system to store the harvested energy by the wind piezoelectric generator and provide the power difference when an active power imbalance occurs in the harvester system. 5. Development of an active filter compensation model based on piezoelectric harvester not only to mitigate the harmonic currents and voltages in the distribution electrical networks but also to compensate the reactive power on the source side. In order to meet these objectives, at the beginning, we started with a reminder of the potential sources of harvested energy and the different conversion types including piezoelectric conversion and we have established a state of the art of the energy harvesting from piezoelectric elements. Then we presented theoretical notions of piezoelectricity followed by a detailed study of the piezoelectric phenomenon in order to use it in a vibratory energy harvesting structure and we have exposed a state of the art of piezoelectric generators with a macroscopic structure. Next, we have described bimetallic piezoelectric type structure as an example of application. After that, we presented the design, modeling, and the description of the proposed wind piezoelectric harvester, and we have established a literature review of the different generators models based on piezoelectric transduction and wind flow. In addition, the experimental validation of the piezoelectric generator model constituting our original contribution for that a large space was reserved for the presentation of the design process, fabrication and experimental assembly of the device after having developed a special analytical model. Besides, we showed how the extraction of the harvested energy can be conceived in order to maximize the power and adapt the generated voltages to the different electrical uses and how the storage of energy can be reached by a hybrid supercapacitors batteries system in a piezoelectric transduction mode. In the last step, we presented globally the problem of harmonics and the active filters as an effective solution. In addition, on the one hand, we applied a group of 8 identical PZT generators to the parallel active filter for current harmonics compensation, and on the other hand, we associated a group of 8 GEPZT to the series active filter to react against voltage harmonics and in the target to demonstrate its flexibility with piezoelectric systems.