Development of an active power filter based on wide-bandgap semiconductors

Pla de Doctorat Industrial, Generalitat de CatalynuaElectrical and electronic equipment needs sinusoidal currents and voltages to function properly. Equipment such as computers, household appliances, electric vehicle chargers, and LED lights can distort the grid and worsen grid quality. Distorted electrical grids can cause malfunctions, reduce service life, and decrease the performance of connected equipment. Industry commonly solves these problems using active power filters, which can minimise the harmonics of the grid, eliminate undesirable reactive power, and restore balance to unbalanced power grids. This thesis deals with the design and implementation of an active power filter based on wide-bandgap semiconductors, which have properties that are superior to classical silicon devices. An active power filter’s design must take advantage of these benefits to build converters that are smaller, more efficient, and consume fewer resources. However, wide-bandgap semiconductors also present design challenges. Because the most commonly used active power filters in the industry are based on two-level voltage source converters, the research for this doctoral thesis focuses on this converter topology. Moreover, its main objective is to contribute new modulation techniques that are specially designed to work with wide-bandgap semiconductors. The proposed modulations consider different aspects, such as the computational cost of the algorithms, converter losses, and the electromagnetic distortion generated. First, this thesis presents a hexagonal sigma-delta (H-S¿) modulation based on sigma-delta (S¿) modulation. The properties of this modulation are studied, and the technique is compared with other widely used modulations. The comparison considers efficiency, harmonic distortion, the electromagnetic compatibility of the converter, and the type of wideband semiconductor used. In addition, a fast algorithm is mathematically developed to simplify the presented modulation and reduce its computational cost. Secondly, this thesis presents a family of sigma-delta modulations specially designed to improve electromagnetic compatibility: the reduced common-mode voltage sigma-delta (RCMV-S¿) modulations. These modulations avoid using the vectors that generate the maximum common-mode voltage, which significantly reduces the generated electromagnetic distortion without affecting the performance of the converter and its harmonic distortion. Finally, the proposed modulations are applied in a wide-bandgap power converter working as an active filter. Thus, it is verified that the techniques presented in this thesis will obtain satisfactory results when implemented in commercial active power filters.Els equips elèctrics i electrònics necessiten corrents i tensions sinusoïdals per funcionar correctament. Existeixen equips com els ordinadors, els electrodomèstics, els carregadors de vehicle elèctric o les llums LED, que poden distorsionar la xarxa i empitjorar la qualitat d'aquesta. Les xarxes elèctriques distorsionades poden causar el mal funcionament dels equips que s'hi connecten, reduir la seva vida útil i també empitjorar la seva eficiència. A la industria és habitual utilitzar filtres actius per a solucionar aquests problemes. Els filtres actius permeten minimitzar els harmònics presents a la Δxarxa, eliminar la potència reactiva no desitjada i equilibrar xarxes elèctriques desequilibrades. Aquesta tesi tracta sobre el disseny i la implementació d'un filtre actiu basat en semiconductors de banda ampla. Aquests semiconductors presenten propietats superiors als clàssics dispositius de silici. El disseny d'un filtre actiu ha d'aprofitar aquests avantatges per a construir convertidors més petits, eficients i que consumeixin menys recursos. Tanmateix, els semiconductors de banda ampla també presenten problemes que el disseny ha de solucionar. Els filtres actius més utilitzats en la indústria són els basats en convertidors de font de tensió (voltatge source converters) amb dos nivells. La recerca d'aquesta tesi doctoral està focalitzada en aquesta topologia de convertidor, i el seu principal objectiu és l’aportació de noves tècniques de modulació especialment dissenyades per treballar amb semiconductors de banda ampla. Les modulacions proposades tenen en compte diferents aspectes: el cost computacional dels algoritmes, les pèrdues del convertidor i la distorsió electromagnètica generada. En primer lloc, es presenta una modulació sigma-delta hexagonal (H-__) que es basa en la modulació sigma-delta (ΣΔ). S'estudien les propietats d'aquesta modulació i la tècnica es compara amb altres modulacions àmpliament usades. La comparativa realitzada considera l’eficiència, la distorsió harmònica, la compatibilitat electromagnètica del convertidor i el tipus de semiconductor de banda ampla emprat. Addicionalment, es desenvolupa matemàticament un algoritme ràpid per simplificar la modulació presentada i reduir el seu cost computacional. En segon lloc, es presenta una família de modulacions sigma-delta especialment dissenyades per millorar la compatibilitat electromagnètica: les modulacions sigmadelta amb tensió en mode comú reduïda (RCMV-ΣΔ ). Aquestes modulacions eviten fer servir els vectors que generen la màxima tensió en mode comú. D'aquesta manera es redueix significativament la distorsió electromagnètica generada sense afectar de forma notable al rendiment del convertidor ni a la seva distorsió harmònica. Finalment, les modulacions proposades s'apliquen en un convertidor de potència, basat en semiconductors de banda ampla, que treballa com a filtre actiu. Això es verifica que les tècniques presentades en aquesta tesi poden ser implementades en filtres actius comercials obtenint resultats satisfactoris.Postprint (published version

Efficiency analysis of wide band-gap semiconductors for two-level and three-level power 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.Power devices based on wide band-gap materials are emerging as alternatives to silicon-based devices. These new devices allow designing and building converters with fewer power losses, and are thus more highly efficient than traditional power converters. Among the wide band-gap materials in use, silicon carbide (SiC) and gallium nitride (GaN) devices are the most promising because of their excellent properties and commercial availability. This paper compares the losses produced in two-level and three-level power converters that use the aforementioned technologies. In addition, we assess the impact on the converter performance caused by the modulation technique. Simulation results under various operating points are reported and compared.Peer ReviewedPostprint (author's final draft

Comparison and Assessment of Two Emission inventories for the Madrid Region

Emission inventories are databases that aim to describe the polluting activities that occur across a certain geographic domain. According to the spatial scale, the availability of information will vary as well as the applied assumptions, which will strongly influence its quality, accuracy and representativeness. This study compared and contrasted two emission inventories describing the Greater Madrid Region (GMR) under an air quality simulation approach. The chosen inventories were the National Emissions Inventory (NEI) and the Regional Emissions Inventory of the Greater Madrid Region (REI). Both of them were used to feed air quality simulations with the CMAQ modelling system, and the results were compared with observations from the air quality monitoring network in the modelled domain. Through the application of statistical tools, the analysis of emissions at cell level and cell – expansion procedures, it was observed that the National Inventory showed better results for describing on – road traffic activities and agriculture, SNAP07 and SNAP10. The accurate description of activities, the good characterization of the vehicle fleet and the correct use of traffic emission factors were the main causes of such a good correlation. On the other hand, the Regional Inventory showed better descriptions for non – industrial combustion (SNAP02) and industrial activities (SNAP03). It incorporated realistic emission factors, a reasonable fuel mix and it drew upon local information sources to describe these activities, while NEI relied on surrogation and national datasets which leaded to a poorer representation. Off – road transportation (SNAP08) was similarly described by both inventories, while the rest of the SNAP activities showed a marginal contribution to the overall emissions

Modelització, control i simulació de xarxes VSC-HVDC per a la integració de parcs eòlics marins.

El present treball presenta l’anàlisi, la modelització, el control i la simulació de xarxes mallades High Voltage Direct Current (HVDC) utilitzades per transmetre a la xarxa elèctrica l’energia generada a parcs eòlics marins. La xarxa HVDC utilitza convertidors Voltage Source Converters (VSC) per tal de mantenir la tensió constant i per transformar el corrent altern a continu i viceversa. A més, a la xarxa HVDC estudiada, s’ha considerat que un dels convertidors VSC és a la costa, mentre que els altres es troben connectats a parcs eòlics marins. Addicionalment, es realitza un anàlisi, una modelització i un estudi del control de diferents tipologies de current flow controllers (CFC) per gestionar els fluxos de corrent a la xarxa mallada HVDC. També es realitza la modelització i el control d’una turbina eòlica; i s’utilitza un model agregat per tal de treballar amb dos parcs eòlics sencers. Finalment, es duu a terme la simulació de la xarxa mallada HVDC amb els models agregats dels parcs eòlics i amb els diferents tipus de current flow controllers; emprant models ideals per estudiar els VSCs. Tots els models, simulacions i càlculs del present treball s’han realitzat utilitzant el programari MATLAB SIMULINK

Efecto de los cambios en el uso del suelo sobre la materia orgánica edáfica, en masas de bosque seco de la provincia de San Luis (Argentina)

No contiene resumenProducción Vegetal y Recursos forestalesMáster en Ingeniería de Montes2019-09-092019-09-0

Ophrys bombyliflora var. albarranii, var. nov. (Orchidaceae)

Se describe una nueva variedad de Ophrys bombyliflora (Orchidaceae). Esta planta ha sido recolectada en Alcalá de Guadaíra (Sevilla, España). Se aportan determinados datos respecto a su morfología y ecología.A new variety of Ophrys bombyliflora (Orchidaceae) is described. This plant has been collected in Alcalá de Guadaíra (Seville, Spain). Morphological and ecological data are reported

The generalized bode criterion: application to the dc voltage control of a three-phase photovoltaic grid-tied inverter

As renewable energies are becoming more important in the electrical generation system, power electronic converters are facing new design issues related not only to their components but also to their control loops. In this context, the Generalized Bode Criterion (GBC) appears as a good tool to correctly determine stability and to help the controller design. In order to show the potential of the GBC and how it can be applied, this paper studies a dc voltage regulation with compensation of the photovoltaic power in a three-phase photovoltaic grid-tied inverter.info:eu-repo/semantics/embargoedAcces

Novel three-phase topology for cascaded multilevel medium-voltage conversion systems in large-scale PV plants

Solar photovoltaic renewable energy systems are expanding in the power sector thanks to its increasingly competitive prices. Traditionally, large-scale PV plants have reduced their cost by increasing the power ratings of the inverters and the line-frequency transformers. However, cost-reduction limits of large-scale PV plants are being reached. Cascaded converters have appeared as a solution to continue reducing the cost of large PV plants as they reduce the wiring cost. In this paper, a novel three-phase topology for cascaded conversion structures is proposed. It only has 2 conversion steps, one without switching losses. Hence, it increases the efficiency and reduces the cost of the previously proposed cascaded conversion systems. The topology is patent pending.The authors acknowledge the financial and continuous support of INGETEAM POWER TECHNOLOGY

Analysis of Contributions to NO2 Ambient Air Quality Levels in Madrid City (Spain) through Modeling. Implications for the Development of Policies and Air Quality Monitoring

As environmental standards become more stringent (e.g. European Directive 2008/50/EC), more reliable and sophisticated modeling tools are needed to simulate measures and plans that may effectively tackle air quality exceedances, common in large cities across Europe, particularly for NO2. Modeling air quality in urban areas is rather complex since observed concentration values are a consequence of the interaction of multiple sources and processes that involve a wide range of spatial and temporal scales. Besides a consistent and robust multi-scale modeling system, comprehensive and flexible emission inventories are needed. This paper discusses the application of the WRF-SMOKE-CMAQ system to the Madrid city (Spain) to assess the contribution of the main emitting sectors in the region. A detailed emission inventory was compiled for this purpose. This inventory relies on bottom-up methods for the most important sources. It is coupled with the regional traffic model and it makes use of an extensive database of industrial, commercial and residential combustion plants. Less relevant sources are downscaled from national or regional inventories. This paper reports the methodology and main results of the source apportionment study performed to understand the origin of pollution (main sectors and geographical areas) and define clear targets for the abatement strategy. Finally the structure of the air quality monitoring is analyzed and discussed to identify options to improve the monitoring strategy not only in the Madrid city but the whole metropolitan area