Contribución a técnicas de modelado y reducción de EMI en sistemas multiconvertidor

This Thesis has been developed in the research group TIEG (Terrassa Industrial Electronics Group). It is focused on the reduction of conducted electromagnetic interferences (EMI) generated by switched power converters. Particularly, it deals with multiphase buck converters. In such kind of systems interleaving is commonly and widely used because of advantages it reports. Among these advantages, it should be mentioned the reduction of the output voltage ripple and conducted disturbances as well. However, interleaving can be combined with other techniques in order to improve the electromagnetic compatibility (EMC) performance. These methods can be classified as filtering or suppression techniques. Filtering methods prevent interferences from propagating through mains, power lines, data lines, etc. Suppression methods directly suppress the noise source. The modulation of the switching pattern of the converter is one of such techniques. These suppression techniques are complementary to the conventional filtering techniques based in passive elements. The aim of this Thesis is to determine the optimum combination of both techniques (interleaving and modulation) in order to achieve the best attenuation of conducted disturbances. The influence of several modulation parameters on the attenuation will be investigated and the undesired side effects produced by these new techniques will be evaluated as well. In order to fulfil this goal, several modulation strategies were considered. Particularly, the switching frequency modulation (SFM), pulse position modulation (PPM) and pulse width modulation (PWM) have been investigated. Finally, three modulation techniques based on the frequency modulation of the switching pattern have been proposed. These techniques are the Constant Delay Tm with switching Frequency Modulation (CDFM-Tm), Constant Delay Tc with switching Frequency Modulation (CDFM-Tc) and Variable Delay with switching Frequency Modulation (VDFM). The experimental validation of these 3 techniques has been conducted on a 4 phases buck converter operated in hard switching regime.Esta tesis se ha desarrollado dentro de una de las líneas de investigación del Grupo de Electrónica Industrial de Terrassa (TIEG). Concretamente, se centra en el área de la reducción de las interferencias electromagnéticas conducidas (EMI), generadas por los convertidores de potencia. Dentro de este campo, se estudia el caso particular de los convertidores buck multifase. En este tipo de sistemas es común el uso de la técnica de interleaving que conlleva una serie de beneficios entre los que destaca la reducción del rizado de la tensión de salida y de las interferencias generadas. No obstante, es posible combinarla con otras técnicas para mejorar los resultados obtenidos desde el punto de vista de la compatibilidad electromagnética (EMC). En la actualidad existen diversos métodos para la reducción de las interferencias conducidas en convertidores de potencia que se pueden aplicar conjuntamente con la técnica de interleaving. Estos métodos se pueden clasificar como métodos de filtrado o supresión. Los primeros actúan evitando que las interferencias generadas se propaguen a través de las líneas de alimentación, datos, etc. Mientras que los segundos actúan directamente sobre las fuentes de ruido, reduciendo en origen las perturbaciones. Dentro de los métodos de supresión se encuentran las técnicas basadas en la modulación de la señal de control del convertidor. Estas técnicas de supresión son alternativas o complementarias a las técnicas de filtrado convencionales, basadas en elementos pasivos. El objetivo de la tesis es determinar la combinación óptima de estas dos técnicas (interleaving y modulación) en relación a la atenuación de las perturbaciones conducidas, cuantificando el efecto de diferentes parámetros de modulación sobre ésta. Por otro lado, también se desea evaluar los efectos no deseados producidos por estas nuevas técnicas. Para lograr este objetivo, se han evaluado diferentes estrategias de modulación que se pueden aplicar sobre la señal de control de los convertidores de potencia. En concreto, se han estudiado la modulación en frecuencia (SFM), la modulación de la posición del pulso (PPM) y la modulación por ancho de pulso (PWM). Por último, se han desarrollado tres técnicas de modulación basadas en la modulación en frecuencia de la señal de control, Constant Delay Tm with switching Frequency Modulation (CDFM-Tm), Constant Delay Tc with switching Frequency Modulation (CDFM-Tc) y Variable Delay with switching Frequency Modulation (VDFM). La validación experimental de las técnicas desarrolladas se ha llevado a cabo sobre un convertidor buck de 4 fases, operando en conmutación forzada

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

Diseño de sistemas digitales

2021/20222n quadrimestr

Decimator filter based on B-splines

The cascaded integrator-comb (CIC) filters are widely used as decimators in many applications, such as in delta sigma AD converters to decimate the sampled signal on its output. One problem with these filters is that by increasing its order to improve the signal attenuation in the stop band, worsens the passband response. In this paper we propose a so-called least-squares filters (LSF) based on B-splines to improve that response, compensating for CIC filter drop and flattening the magnitude response of the pass band. We also study the relationship between the CIC filters, otherwise called moving average, and the B-splines expanded by an integer factor. We show that the least-squares filters based on B-splines can be decomposed in CIC filters, with a higher order than the splines used, plus a compensator filter. Another important contribution of this work are the FIR approximations of anti-causal IIR filters needed to implement LSFs.Peer ReviewedPostprint (published version

Interleaving and switching pattern modulation to conducted EMI reduction

This paper explores new techniques to reduce the conducted EMI generated by switched power converters operating in multiconverter arrangement. These techniques are based in the combined application of interleaving and the modulation of some characteristics of the switching patterns. The effectiveness of such methods in terms of EMI reduction is theoreticaly developed and experimentally validated in a four channel parallel buck converter operating in closed loop. The technique that provides the best attenuation results is identified. Finally, undesired sideeffects produced by these techniques, such as an increase in the output voltage ripple, are evaluated.Peer ReviewedPostprint (published version

Laboratori semipresencial de microprocessadors

L’objectiu final d’aquest projecte és millorar la docència impartida per el Departament d’Enginyeria Electrònica en el Campus de Terrassa en el àrea de microprocessadors. La millora té dos eixos fonamentals, d’una banda coordinar els continguts i els mètodes docents en les assignatures de primer i segon cicle i de l’altre dotar d’un caràcter semipresencial a les assignatures en general i a les pràctiques de laboratori en particular. Les actuacions dutes a terme s’han centrat en l’adequació i ampliació del material de laboratori, en el desenvolupament de nou material docent multimèdia, en el desenvolupament d’una plataforma web d’e-learning i finalment el desenvolupament d’un simulador software d’un dels equips de laboratori. La plataforma web i el simulador son els resultats més innovadors del projecte permeten a l’alumne, si ho desitja, un aprenentatge semipresencial, gràcies a les facilitats de comunicació de la plataforma i a la facilitat de experimentació amb el simulador

A new switching frequency modulation scheme for EMI reduction in multiconverter topology

This paper presents a modulation scheme in order to reduce conducted Electromagnetic Interference (EMI) generated by modular power converters with parallel topology. The proposed scheme is based on a combination of interleaving and Switching Frequency Modulation (SFM) techniques. The objective of this modulation scheme is to cancel certain harmonics of EMI and to reduce the amplitude of the remaining harmonics. The proposed scheme has been implemented in a field programmable gate array and a four channel parallel buck converter has been used in order to verify it. A significant EMI reduction has been obtained in comparison to use the interleaving and Switching Frequency Modulation separately.Peer ReviewedPostprint (published version

Contribution to conducted EMI reduction in multiconverter topology

This paper contributes to the conducted EMI reduction generated by switched power converters operating in multiconverter arrangement. The EMI reduction is achieved by means of the combination of two techniques: interleaving and switching frequency modulation. The effectiveness of such methods in terms of EMI reduction is experimentally validated in a four channel parallel buck converter. The technique that provides the best attenuation results is identified. Finally, special attention has been paid to possible undesired side-effects produced by these techniques. For this reason the converter efficiency and output voltage ripple are evaluated.Peer ReviewedPreprin

Hard-less common mode active EMI filter

Active EMI filters appear as an alternative to classical EMI filters based on passive components. Active EMI filters can provide more compact, cheaper and lighter solutions than passive approach. In this paper we present a theoretical analysis of the 4 possible configurations. Expressions of the transfer function and insertion losses considering impedances of mains and source of noise are presented. The voltage-current topology is identified as the more convenient solution. Finally, preliminary experimental results of a prototype capable to provide attenuation up to 100MHz are shown.Peer ReviewedPostprint (published version

Efficiency comparison of power converters based on SiC and GaN semiconductors at high switching frequencies

© 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.Hard-switching voltage source converters (VSC) based on wide-bandgap (WBG) devices surpass their silicon equivalents in every aspect. Nevertheless, at high switching frequencies, the efficiency significantly differs depending on the WBG semiconductor used. This article presents an extensive comparison between gallium nitride (GaN), and silicon carbide (SiC) devices in terms of efficiency. The impact of the switching frequency is evaluated for each semiconductor using two modulation techniques: the classical space vector pulse width modulation (SVPWM) technique, and the innovative hexagonal sigma-delta modulation (H-S¿). The performance and losses of both WBG technologies are analysed here using Matlab/Simulink and PLECS. Experimental results performed on two VSC converters, one based on SiC devices and the other made using GaN transistors, show the influence of the semiconductor technology and the modulation strategy on the efficiency at high switching frequenciesPeer ReviewedPostprint (published version