Desenvolupament de la modulació SHE en un inversor NPC de 3 nivells

En el present projecte final de carrera s’ha treballat en l’aplicació de la modulació Selective Harmonic Elimination en inversors de tres nivells de la topologia Neutral Point Clamped. La modulació Selective Harmonic Elimination s’empra en convertidors que processen altes potències, això limita la freqüència de commutació dels transistors per evitar al màxim possible les pèrdues per commutació, mantenint, a la vegada, el compromís d’obtenir una ona de tensió alterna a la sortida de l’inversor amb un baix contingut harmònic. El quid de la modulació rau en generar una ona semi-quadrada a la sortida de l’inversor on els instants de commutació d’aquesta permeten eliminar els harmònics desitjats, que normalment són els de més baix ordre, per facilitar el disseny del filtre de sortida del convertidor. La implementació de la modulació s’ha dut a terme sobre una plataforma experimental present en els laboratoris del Grup de Recerca en Electrònica de Potència, usada en anteriors projectes. Aquesta es composa de dos convertidors de tres nivells de la topologia Neutral-Point-Clamped en configuració back-to-back, dels quals només s’utilitza l’etapa inversora d’aquests, juntament amb els equips necessaris per al control dels convertidors i monitoratge dels senyals elèctrics desitjats. L’objectiu principal proposat és l’obtenció d’una ona de tensió a la sortida de l’inversor on els harmònics 5, 7, 11 i 13 s’hagin eliminat mitjançant aquesta modulació. El projecte es desglossa en les següents parts. Inicialment es realitza un estudi matemàtic de la modulació Selective Harmonic Elimination, adaptada al cas particular de l’inversor utilitzat, trobant-se diferents conjunts de solucions (angles de commutació) per a assolir la cancel·lació de els harmònics prèviament seleccionats. Es realitzen simulacions per estudiar el comportament teòric de les tensions a la sortida de l’inversor. Com a pas previ a la realització de les proves experimentals s’ha adaptat la plataforma experimental a les necessitats del projecte. Finalment, s’han realitzat proves experimentals que ens permeten comparar el comportament teòric de les tensions amb el seu comportament real. Comparant els resultats experimentals amb les simulacions realitzades es pot concloure que la modulació funciona correctament sobre l’inversor, acomplint-se l’objectiu principal del projecte

Modulation and capacitor voltage balancing control of multilevel NPC dual active bridge DC-DC Converters

© 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.The present paper provides a solution to operate multilevel dual active bridge (ML-DAB) converters built upon neutral point clamped switching legs in a full-bridge disposition and with any number of levels on either side of the converter. The main issue of such converters is addressing the inherent unbalance of the dc-link capacitor voltages, which hinders the proper operation and optimum utilization of the converter. The proposed solution comprises a generalized to N levels modulation and control scheme that allows operating these converters, while guaranteeing the proper balance of the dc-link capacitor voltages. The suitability of the proposed solution is verified through simulation and experimental tests performed in five different converter configurations, three of them with an asymmetric number of voltage levels, proving that capacitor voltage balance is achievable in a wide range of operation conditions. Moreover, the efficiency of the ML-DAB converters is demonstrated to be superior to the conventional two-level DAB case.Postprint (author's final draft

Self-powered bipolar gate-driver power supply circuit for neutral-point-clamped converters

© 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting /republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other worksThe design of gate-driver power supply (GDPS) circuits for multilevel neutral-point-clamped converters is a challenge due to the large number of power switches required and the fact that each device presents a different GDPS reference node. This paper presents a compact self-powered bipolar GDPS circuit, consisting of two subcircuits connected across the power switches, which altogether produce all the positive and negative supply voltages required by the GDs. As these subcircuits essentially contain semiconductor components, they can be integrated with the power switch and gate driver, to produce a compact cell from which obta in a compact converter leg implementation. Overall, this BGDP S design is suitable for all types of NPC multilevel topol ogies with any type of power transistor, although it is most suitable for moderate device voltage ratings. The good perfor mance of the proposed BGDPS circuit has been confirmed through experiments on a conventional two-level leg, and on three-level and four-level active-clamped converter legs.Peer ReviewedPostprint (author's final draft

Disseny i implementació d'un RDS basat en software lliure

En aquest TFG veurem el desenvolupament d'un projecte per a crear un cloud de PostgreSQL basat en dues capes. Els avantatges d'aquest tipus d'implementacions front una instal·lació típica son molts, entre ells, tenir les dades centralitzades i la possibilitat d'un escalat horitzontal

Combining Dictionary-and Corpus-Based Concept Extraction

Abstract. Concept extraction is an increasingly popular topic in deep text analysis. Concepts are individual content elements. Their extraction offers thus an overview of the content of the material from which they were extracted. In the case of domain-specific material, concept extraction boils down to term identification. The most straightforward strategy for term identification is a look up in existing terminological resources. In recent research, this strategy has a poor reputation because it is prone to scaling limitations due to neologisms, lexical variation, synonymy, etc., which make the terminology to be submitted to a constant change. For this reason, many works developed statistical techniques to extract concepts. But the existence of a crowdsourced resource such as Wikipedia is changing the landscape. We present a hybrid approach that combines state-of-the-art statistical techniques with the use of the large scale term acquisition tool BabelFy to perform concept extraction. The combination of both allows us to boost the performance, compared to approaches that use these techniques separately

Operating Principle and Performance Optimization of a Three-Level NPC Dual-Active-Bridge DC-DC Converter

© 1982-2012 IEEE. Aiming to improve the performance features of conventional two-level dual-active-bridge (DAB) converters, this paper presents a three-level neutral-point-clamped (NPC) DAB dc-dc converter. A general modulation pattern is initially defined, the dc-link capacitor voltage balancing is analyzed in detail, and a proper balancing control is designed. Then, a set of decoupled optimization problems is formulated as a function of the available modulation degrees of freedom to minimize the predominant converter losses. Finally, a simple and practical specific modulation strategy is provided, resembling the optimum solutions. The good performance of the proposed three-level NPC DAB converter operated with the proposed modulation strategy and voltage balancing control is verified through simulation and experiments. The capacitor voltage balancing can be guaranteed for all operating conditions. In addition, it is concluded that the multilevel topology provides benefits compared with the conventional two-level DAB converter.Postprint (published version

Comparison of modulations and dc-link balance control strategies for a multibattery charger system based on a three-level dual-active-bridge power converter,

© 2022 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.This paper focuses on the study of a charger for two batteries connected in series. From the three-phase grid, the batteries are charged through a three-level neutral-point-clamped (NPC) ac-dc converter in cascade with a three-level NPC dualactive-bridge converter. The system provides galvanic isolation and allows bidirectional power flow. A simple control strategy to charge the batteries is considered, based on the regulation of the common- and differential-mode components of the batteries charging currents. In addition, the proposed control system regulates the total dc-link voltage and the dc-link voltage balance in the two systems dc-links. This work is particularly focused on the comparison of the charger performance under two competitive ac-dc converter modulations, in terms of the ac-side voltage harmonic content, the number of switching transitions, the dc-link voltage balance, and the charging current control capacity. Simulation results with the performance comparison are provided and the merits and demerits of each option are highlighted.This publication is part of Grant DPI2017-89153-P, funded by MCIN/AEI/10.13039/501100011033 and by ERDF A way of making Europe.Peer ReviewedPostprint (author's final draft

Multibattery charger system based on a three-level dual-active-bridge power converter

© 2021 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.A charger for two batteries connected in series is presented in this work. From the three-phase grid, the batteries are charged through a three-level neutral-point-clamped ac-dc converter in cascade with a three-level dual active bridge converter. The system provides galvanic isolation and allows bidirectional power flow. A simple control strategy to charge the batteries is presented, based on the regulation of the commonand differential-mode components of the batteries’ charging currents. With this control approach, each battery bank can be charged independently, allowing it to reach full battery bank capacity, even under different battery initial state-of-charge values or different battery nominal capacities. Moreover, the proposed control system also regulates the total dc-link voltage and the dc-link voltage balance in both dc-links of the system. The simulation results verify the feasibility of the proposed implementation and control system approach.This work was supported by the Ministerio de Economía, Competitividad, Spain, under Grant DPI2017-89153-P (AEI/FEDER, UE).Peer ReviewedPostprint (published version

Fast Reliability Assessment of Neutral-Point-Clamped Topologies through Markov Models

This article presents detailed Markov models for the reliability assessment of multilevel neutral-point-clamped (NPC) converter leg topologies, incorporating their inherent fault-tolerance under open-circuit switch faults. The Markov models are generated and discussed in detail for the three-level and four-level active NPC (ANPC) cases, while the presented methodology can be applied to easily generate the models for a higher number of levels and other topology variants. In addition, this article also proposes an extremely fast calculation method to obtain the precise value of the system's mean time to failure from any given formulated system Markov model. This method is then applied to quantitatively compare the reliability of two-level, three-level, and four-level ANPC legs under switch open-circuit-guaranteed faults and varying degrees of device paralleling. The comparison reveals that multilevel ANPC leg topologies inherently present a potential for higher reliability than the conventional two-level leg, questioning the suitability of the traditional search for topologies with the minimum number of devices in order to improve reliability. Experimental results are presented to validate the fault-tolerance assumptions upon which the presented reliability models for the three-level and four-level ANPC legs are based. This article is accompanied by supplementary MATLAB scripts.Peer Reviewed© 2022 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other work

A survey on capacitor voltage control in neutral-point-clamped multilevel converters

Neutral-point-clamped multilevel converters are currently a suitable solution for a wide range of applications. It is well known that the capacitor voltage balance is a major issue for this topology. In this paper, a brief summary of the basic topologies, modulations, and features of neutral-point-clamped multilevel converters is presented, prior to a detailed description and analysis of the capacitor voltage balance behavior. Then, the most relevant methods to manage the capacitor voltage balance are presented and discussed, including operation in the overmodulation region, at low frequency-modulation indexes, with different numbers of AC phases, and with different numbers of levels. Both open- and closed-loop methods are discussed. Some methods based on adding external circuitry are also presented and analyzed. Although the focus of the paper is mainly DC–AC conversion, the techniques for capacitor voltage balance in DC–DC conversion are discussed as well. Finally, the paper concludes with some application examples benefiting from the presented techniques.Peer ReviewedPostprint (published version