Switched-mode converters (one quadrant)

Switched-mode converters are DC/DC converters that supply DC loads with a regulated output voltage, and protection against overcurrents and short circuits. These converters are generally fed from an AC network via a transformer and a conventional diode rectifier. Switched-mode converters (one quadrant) are non-reversible converters that allow the feeding of a DC load with unipolar voltage and current. The switched-mode converters presented in this contribution are classified into two families. The first is dedicated to the basic topologies of DC/DC converters, generally used for low- to mid-power applications. As such structures enable only hard commutation processes, the main drawback of such topologies is high commutation losses. A typical multichannel evolution is presented that allows an interesting decrease in these losses. Deduced from this direct DC/DC converter, an evolution is also presented that allows the integration of a transformer into the buck and the buck–boost structure. This enables an interesting voltage adaptation, together with a galvanic isolation directly integrated into the converter. The second family is related to DC/DC converters with an intermediary AC stage. Such structures include middle-frequency transformers as described above, and offer reduced commutation losses thanks to natural soft commutation conditions, sometimes reinforced by the insertion of LC components or active devices. This allows high switching frequencies, and then a reduction of the size and weight of such applications

Passive components used in power converters

In power converters, passive components play an important role, and have in general specific nature and properties. The goal of this tutorial is to give an overview, first on inductive components for power conversion, and second on dedicated power capacitors. In a third part, new components— supercapacitors—will be presented. Generally, inductors for power applications must be custom designed. In this tutorial, the most important effects encountered when realising inductive components will be presented in the first part, without entering into the detailed design of such components. For that purpose, the referenced documents that have served as a base for this tutorial must be consulted [1], [2], and mainly [3]. The second part of this tutorial (Capacitors used in power electronics) is dedicated to power capacitors. Unlike inductors, capacitors cannot be specifically designed, but must be selected from a manufacturer’s list of components. Here, the documentation corresponds to a subset of Ref. [4] that has been translated by Dr. Martin Veenstra. The third part of the tutorial (Supercapacitors and applications) presents supercapacitors, new components that have very high energy density and high power density. Modelling and design rules for several applications are presented. This part of the document uses as a base the study made by Dr. Philippe Barrade [5]. Finally, it must be noted that, even with a correct selection or design of passive elements, there can be parasitic effects caused by interactions between components of the same or different nature. As an example, by designing filters combining several passives like inductors and capacitors, the primary specification may be modified by the interaction of parasitics, typically a mutual coupling between the parasitic inductances of neighbouring capacitors. A good description of such effects can be found in Ref. [6]

Simulation tools for Power Electronics : Teaching and Research

The LEI (Laboratoire d’Electronique Industrielle) is one of the laboratories of the DE (Département Electricité) of the EPFL. Its mission and goal are the research and the teaching in the domains of Industrial and Power Electronics. Simulation tools are used both for research and teaching, to allow a good understanding of the structures that are studied before practical tests. This paper will illustrate the way Simplorer is used regarding four main research themes, and regarding pedagogical tools we are developing

Series Connection of Supercapacitors: Comparative Study of Solutions for the Active equalization of the Voltages

Because of their low voltage level, supercapacitors need arrangement with series connection in order to obtain voltage levels from few dozen to few hunderd of volts. As for batteries, devices have then to be defined to balance the voltages across each series connected components. This paper present the problematic of voltage sharing in a series connection of supercapacitors. It is generally described the way the balancing can be obtained easier with a coherent arrangement of the supercapacitors in their tank. Then, the main solutions for sharing the voltages with active devices are presented, detailed and compared, using a global modeling approach

Energy storage and applications with supercapacitors

Dedicated for energy storage, supercapacitors offer new solutions in various applications. This contribution describes briefly main principles of supercapacitors, basics for the design of a supercapacitive tank, and the needed power electronics developments linked to the use of these new components. Typical applications are presented, where supercapacitors are used for load-levelling or as main energy storage devices

Stockage d'énergie électrique par super-condensateurs, solutions de l'électronique de puissance et applications

A moyen et long terme, l’approvisionnement en énergie électrique sera confronté d’une part à une augmentation de la demande, d’autre part à la diminution des ressources primaires, ainsi qu’aux performances limitées des énergies renouvelables. Dans un tel scénario, certains préconisent l’utilisation de structures de micro-réseaux, avec une production décentralisée, qui est particulièrement sensible vis-à-vis des fluctuations de puissance. Dans ce contexte, le stockage d’énergie électrique est appelé à jouer un rôle important, de même que toutes les technologies qui s’y rapportent. En plus des propriétés des accumulateurs super-capacitifs, cet article décrit trois applications possibles de cette technique. Les aspects de la conversion statique par des moyens d’électronique de puissance sont traités, avec un accent sur le rendement énergétique élevé

Key Developments for Supercapacitive Energy Storage: Power Electronic Converters, Systems and Control

Supercapacitors represent one of the newest innovations in the field of electrical energy storage, and will find their place in many applications where energy storage is needed, or can help to the smoothing of strong and short time power solicitations of a distribution network. Other system developments are going on, opening new fields in engineering sciences, based on new possibilities in the field of electrical energy storage. In comparison with classical capacitors, these new components allow a much more higher energy density, together with a high power density. Even if the energy density is not comparable with that one of electrochemical accumulators, the possible energy amount and storage time is compatible with many industrial requirements. In transportation systems, as a first example, the energy needed to relay two bus-stations can easily be transferred from a fixed supercapacitor storage device to another mobile one placed on a bus during passenger transfer time, allowing so the use of electrical propulsion without trolleys [1]. Other complementary storage systems for better share of energy and instantaneous power amounts have also been described [2], as well as supercapacitor tanks as booster for fuelcell powered passenger cars [3]. This contribution will show some actual research and development projects, running at university level, but in connection with specialists from the corresponding application fields. Innovative and promising solutions and technologies are investigated, which need of course clarification of their actual industrial and economical compatibility. They can also be seen as future solutions for next decades, in relation with the tendency of getting weaker distribution of electrical energy