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Power electronic components are becoming essential for the present and future grids, giving useful services apart from integrating electrical vehicles (EV), renewable energies or batteries. Voltage Source Converters (VSCs) are a good option to ensure the stability of the grid when there is a fault, which is known as Fault-Ride Through (FRT). In most cases the fault is unbal- anced, which affects directly the control of the power electronic device, having to add a positive and negative sequence control. Despite the wide use of the symmetrical components in the lit- erature, their explanation is not clear in the literature. This thesis aims to explain what are these components and how they can be calculated. Furthermore, the analysis of the symmetrical se- quences is used to try to obtain a small-signal model of a VSC with positive and negative control directly from the sequences. The objective is to use the linear model to analyse the stability and design the controls taking into account the effect of the asymmetry. This thesis also explains the limitations of the presented methodology due to the coupling between positive and negative se- quence components at 0 Hz and 100 Hz. Finally, the obtained model is analysed to identify the differences in the dynamics with respect to a model with positive sequence control.

The scope of this project is to comprehend, analyze and model on-chain-link based multiport converters able to connect High Voltage Direct Current (from now on HVDC) and Medium Voltage Direct Current (from now on MVDC) to Alternating current networks Firstly, there is a theoretical study where multiple types of converters are exposed. It’s explained how do they work, how they classify and their functionality. It starts from the mostsimple converters and it reaches complex structure converters, which are going to be in the scope for the results. Following on, models studied have been analyzed and represented using MATLAB [2] software, which helps to analyze and faithfully study the behavior of our converter or electrical system. Finally, this knowledge is being put together into creating a MMC converter simulating its behavior in the AC network. Models have been made through MATLAB’s Simulink add-on, which makes it easier to view and schematize the converters and network, meaning that, for the explanations and for the obtention of results, MATLAB is going to be used. Results are going to be broken down and conclusions will be made regarding the results of all the study, leaving a follow-up path for the interest of the reader.

© 2024 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., Impedance/admittance transfer matrix characterization of voltage source converters is an important issue in frequency domain stability studies. Several approaches in the dq- and pn-frame are proposed to obtain this matrix with either experimental or numerical simulation measurements. Although these are well-established approaches, various issues require further study. The paper presents a detailed review and discussion on the dq- and pn-frame approaches for converter impedance/admittance transfer matrix measurements and contributes to clarifying the influence of the mirror frequency effect and the starting point of the FFT window on these measurements. Index The contributions are validated by PSCAD/EMTDC simulation with a VSC model containing PLL and outer controls., Objectius de Desenvolupament Sostenible::7 - Energia Assequible i No Contaminant, Objectius de Desenvolupament Sostenible::7 - Energia Assequible i No Contaminant::7.1 - Per a 2030, garantir l’accés universal a serveis d’energia assequibles, confiables i moderns, Objectius de Desenvolupament Sostenible::7 - Energia Assequible i No Contaminant::7.2 - Per a 2030, augmentar substancialment el percentatge d’energia renovable en el con­junt de fonts d’energia, Objectius de Desenvolupament Sostenible::7 - Energia Assequible i No Contaminant::7.a - Per a 2030, augmentar la cooperació internacional per tal de facilitar l’accés a la investigació i a les tecnolo­gies energètiques no contaminants, incloses les fonts d’energia renovables, l’eficiència energètica i les tecnologies de combustibles fòssils avançades i menys contaminants, i promoure la inversió en infraestructures energètiques i tecnologies d’energia no contaminant, Objectius de Desenvolupament Sostenible::7 - Energia Assequible i No Contaminant::7.b - Per a 2030, ampliar la infraestructura i millorar la tecnologia per tal d’oferir serveis d’energia moderns i sos­tenibles per a tots els països en desenvolupament, en particular els països menys avançats, els petits estats insulars en desenvolupament i els països en desenvolupament sense litoral, d’acord amb els programes de suport respectius, Postprint (author's final draft)

This paper discusses that the existing grid codes on the fault ride-through (FRT) opera-tion have certain complications to be implemented in the grid-forming (GFM) converters.In particular, they do not provide a clear guidelines on the suitable prioritization of thepositive- and negative-sequence currents needed for a desired voltage profile during FRToperation. To address this challenge, two FRT controls which are based on (i) voltagebalancing priority, and (ii) voltage magnitude priority are investigated for GFM convert-ers. The former gives priority to the elimination of negative-sequence voltage, while theremaining converter’s capacity is used to increase the positive-sequence voltage. On thecontrary, the latter prioritizes the increase of positive-sequence voltage, while it tries toreduce negative-sequence voltage by using the remaining converter’s capacity. The dynamicperformances of these two FRT controls are thoroughly discussed, and the simulationresults show that depending on the desired voltage profile during fault, one of them canbe implemented., Peer Reviewed, Postprint (published version)

Títol diferent a la intranet docent de l'EPSEVG: "Control de convertidores en microrredes aisladas durante cortocircuitos", Este documento propone nuevas estrategias de limitación de corriente para proteger a inversores trifásicos en modo “grid-feeding” ante sobrecorrientes causadas por fallos en la red eléctrica. A diferencia de estrategias ya existentes para estas situaciones, estos controles alternativos no requieren reducir, a priori, todas las corrientes del convertidor simultáneamente para limitar la corriente máxima del convertidor. Esto permite que se pueda dar prioridad a una consigna de funcionamiento del inversor específica por encima del resto al aplicar la estrategia correcta. Se estudian dos tipos de condiciones anormales de red distintas: tensión entre fases Vabc simétrica y asimétrica. Para cada una se propone un funcionamiento del inversor coherente acorde al fallo producido. El diseño de las estrategias alternativas se acompaña de un gran número de explicaciones sobre el fundamento teórico de las mismas. Además, se presentan los resultados experimentales obtenidos tras implementar cada una de las estrategias en un entorno práctico para corroborar la validez del estudio., This document presents new current limitation strategies to protect three-phase inverters in grid-feeding mode against overcurrent produced by grid faults. Unlike already existing strategies for these situations, these alternative control methods do not require, in most cases, to lower all converter’s currents simultaneously to limit the maximum current. This allows one to prioritize one of the inverter's operating references ahead of others by applying the correct strategy. Two different types of abnormal grid conditions are studied: symmetric and asymmetric phase-to-phase voltages Vabc. For each case, a coherent inverter operation is proposed. The design of alternative strategies is presented along with a large number of explanations regarding the theoretical base of each strategy. Moreover, experimental results obtained after implementing each strategy in a practical environment have been included to corroborate the validity of the study.

En el present Treball de Fi de Grau s’explica el procés de disseny, construcció i prova d’una cel·la de commutació de 600 V, un dispositiu innovador en el camp dels convertidors electrònics de potència multinivell, enfocat sobretot al sector de l’automoció. El treball s’emmarca dins d’un projecte amb l’objectiu final de crear diferents convertidors de potència utilitzant un únic tipus de cel·la de commutació. A l’inici del treball es disposava del prototip d’una cel·la de commutació de 100 V, de la qual s’ha partit com a base pel nou disseny. El treball realitzat comença en aquest punt i es tracta de diferents tasques que s’han anat realitzant en el transcurs de totes les etapes del projecte. El primer objectiu és donar suport al GREP en el procés de disseny del nou prototip, ajudant en la projecció de l’esquemàtic i en la cerca i simulació de nous components. Per això, la primera tasca realitzada ha estat l’estudi i comprensió de la cel·la de commutació i les seves parts, la qual està explicada en el present treball. El segon objectiu és el de dissenyar i construir nous dispositius auxiliars necessaris per a les proves del prototip. En total s’han projectat i fabricat dues plaques de circuit imprès (PCB) que han estat usades en les proves al laboratori. Aquest punt cobreix gran part del cos del treball on s’explica la funcionalitat, esquemàtic, disseny PCB, prova i verificació de les dues plaques. El tercer objectiu, és el de donar suport al GREP en el procés de proves experimentals del prototip, participant en el muntatge i recollida de resultats, cosa que també ha servit per verificar el funcionament de les plaques auxiliars dissenyades. Finalment, com a objectiu addicional s’ha aprofundit en el circuit de processat lògic del prototip, dissenyant una alternativa que permet estalviar espai en el disseny final, així com abaratir costos de fabricació, millorar l’eficiència del prototip i tenir millor control dels senyals dins de la placa. Al finalitzar el treball, t, En el presente Trabajo de Fin de Grado se explica el proceso de diseño, construcción y prueba de una celda de conmutación de 600 V, un dispositivo innovador en el campo de los convertidores electrónicos de potencia multinivel, enfocado principalmente al sector de la automoción. El trabajo se enmarca dentro de un proyecto con el objetivo final de crear diferentes convertidores de potencia utilizando un único tipo de celda de conmutación. Al inicio del trabajo se disponía de un prototipo de celda de conmutación de 100 V, del cual se ha partido como base para el nuevo diseño. El trabajo realizado comienza en este punto y consta de diferentes tareas que se han ido realizando en el transcurso de las etapas del proyecto. El primer objetivo es dar apoyo al GREP en el proceso de diseño del nuevo prototipo, ayudando en la proyección del esquemático y en la búsqueda y simulación de nuevos componentes. Para ello, la primera tarea realizada ha sido el estudio y comprensión de la celda de conmutación y sus partes, la cual está explicada en el presente trabajo. El segundo objetivo es el de diseñar y construir nuevos dispositivos auxiliares necesarios para las pruebas del prototipo. En total se han proyectado y fabricado dos placas de circuito impreso (PCB) que han sido usadas en las pruebas en el laboratorio. Este punto cubre gran parte del cuerpo del trabajo donde se explica la funcionalidad, esquemático, diseño PCB, prueba y verificación de las dos placas. El tercer objetivo es el de dar apoyo al GREP en el proceso de pruebas experimentales del prototipo, participando en el montaje y recopilación de resultados, lo que ha servido para verificar el funcionamiento de las placas auxiliares diseñadas. Finalmente, se ha profundizado en el circuito de procesamiento lógico del prototipo, diseñando una alternativa que permite ahorrar espacio en el diseño final, así como abaratar costes de fabricación, mejorar la eficiencia del prototipo y tener mejor control de las señales dentro de la, In this Final Degree Project, the process of designing, constructing, and testing a 600 V switching cell is explained. It is an innovative device in the field of multilevel power electronic converters, primarily focused on the automotive sector. The work is part of a project with the ultimate goal of creating different types of power convertors using only one type of switching cell. A 100 V switching cell prototype has served as the basis for the new design. The work done begins at this point and consists of different tasks that have been performed throughout the stages of the project. The first objective is to support GREP in the design process of the new prototype, assisting in schematic projection and the search and simulation of new components. Therefore, the first task has been the study and understanding of the switching cell and its parts, which is explained in this paper. The second objective is to design and build new auxiliary devices necessary for the prototype testing. A total of two printed circuit boards (PCBs) have been designed and manufactured, which have been used in the laboratory tests. This section covers a significant part of the work, explaining the functionality, schematic, PCB design, testing, and verification of the two boards. The third objective is to support GREP in the experimental testing process of the prototype, participating in the assembly and data collection, which has also served to verify the operation of the designed auxiliary boards. Finally, an in-depth study has been conducted on the logical processing circuit of the prototype, designing an alternative that allows for space savings in the final design, as well as reducing manufacturing costs, improving the prototype's efficiency, and providing better signal control within the board. This proposal has been simulated to ensure compliance with the specifications. Upon completion of the work, all proposed objectives have been successfully achieved: the design of the new switchin

Recently, multilevel converters have become popular because of their advantages over two-level converters, although they are implemented with a much larger number of semiconductor devices. Modularity and compactness are key features to address the efficient multilevel converters implementation. The multilevel converters can be implemented by the interconnection of smart power modules, made of a power transistor with its anti-parallel diode, a gate driver, a floating gate driver power supply (GDPS), and auxiliary circuitry. This master?s thesis studied some existing GDPS solutions, their benefits and drawbacks. Then, this work proposed two new solutions improving GDPS issues, one mainly for high-voltage applications (IRGDPS) and the other for low-voltage applications (NP-IRGDPS). Both proposed solutions were analyzed and compared by simulation and experimental tests. The IRGDPS improves the efficiency and robustness of the GDPS at the expense of increasing the cost and area compared with the existing self-powered solutions. On the other hand, comparing it with an isolated DC-DC, which is the typical GDPS implementation, there is a considerable reduction in cost and volume. Moreover, the NP-IRGDPS is the first self-powered gate driver power supply implemented with discrete components that can operate from battery voltages around 1.5V to 3.7V, and there are no commercially available isolated DC-DC converters with such an input voltage range.

In the XFLEX HYDRO Vogelgrun demonstrator, a run-of-river hydropower plant, the hybridization of one turbine-generator unit with a battery energy storage system is being investigated. This paper describes the integration methodology of the hybrid control algorithm without replacing the existing speed governor of the unit. Furthermore, the comparison of the performances of a non-hybrid and hybrid unit is discussed, and first experiences gained during the operation and monitoring of the hybrid operating mode are presented., This work has been realized with the participation of INES.2S. David Valentín and Alexandre Presas acknowledge the Serra Húnter program. The corresponding author would like to express his gratitude to Nicolas Ruchonnet for his contributions during the revision., Postprint (published version)

This short communication addresses the risk of synchronisation loss during frequency excursions for droop-based grid-forming converters when active power limitations are considered. The synchronising capability of this control approach is based on the converter’s active power exchange, which is used to generate the internal frequency of the converter control. The power available in the resource or converter ratings can impact the synchronising capability during frequency deviations. The analysis is restricted to droop-based grid-forming converters, but it could be extended to other active-power-based synchronising methods. A droop-based control is proposed to extend the operation frequency range of grid-forming converters. The performance of the suggested method is also compared to alternative ones presented in the literature. Finally, the proposed control is validated in the IEEE 9-bus system with different VSC penetration levels through EMT simulations developed in PSCAD., This work was supported by the European Union’s Horizon 2020 Research and Innovation Program (POSYTYF Project) under Grant 883985. This work was also supported by Ministerio de Ciencia e Innovación (MCIN/AEI/10.13039/501100011033) and by the European Union's Next Generation PRTR program (FAIR project), with reference TED2021-129796B-C22. Marc Cheah-Mane and Eduardo Prieto-Araujo are lecturers of the Serra Húnter programme. The work of Oriol Gomis-Bellmunt was supported by the Institució Catalana de Recerca i Estudis Avançats (ICREA) Academia Program., Peer Reviewed, Postprint (published version)

This paper proposes the use of linear-assisted switching power converters in the context of single-inductor dual-output (SIDO) for microgrids (MG) applications. By combining a DC/DC ripple-controlled switching power converter with the respective voltage linear regulators at each output, improved performance in terms of load and line regulations is obtained. To achieve that aim, a current-steering switching policy is proposed, together with a resource-aware circuit implementation. The ripple-based hysteretic control results in variable switching frequency to guarantee critical conduction mode (boundary of CCM and DCM)., Peer Reviewed, Postprint (published version)

En el presente estudio se simula y analiza el comportamiento y desempeño de un convertidor DAB resonante para diversas topologías de tanques resonantes considerando modulaciones de frecuencia fija del tipo phase-shift. Además, se estudia el transformador presente en el tanque resonante que lo provee de aislamiento galvánica; sus propiedades, se simula mediante el método elementos finitos y se implementa. Respecto a las topologías resonantes se ha estudiado cómo se comportan las corrientes y tensiones en el tanque resonante, qué diferencia tiene este comportamiento con el de un DAB convencional y se obtiene la eficiencia considerando dos tipos de modulación phase-shift. El convertidor DAB resonante simulado consta de dos puentes completos con transistores de Nitruro de Galio (GaN). Para las simulaciones se han considerado dos fuentes de tensión en la entrada y la salida del convertidor. Para la realización del presente estudio se ha utilizado Matlab-Simulink-PLECS. Mediante este programa se ha podido obtener además de las simulaciones y el comportamiento del circuito, el cálculo directo de las pérdidas de conducción, conmutación y resistivas. Esto último ha permitido realizar un estudio en detalle de cómo se comporta la eficiencia para distintas modulaciones y topologías, así como ver cómo varía el aporte que realiza cada una a la disminución en el desempeño del convertidor. Para el caso del transformador se ha obtenido una aproximación para las pérdidas magnéticas a partir de simulaciones de elementos finitos y las curvas provistas por el fabricante, para luego proceder a su implementación real y la obtención experimental de los valores de sus parámetros

A fully normalized algorithm to implement the optimal triple-phase-shift (TPS) modulation strategy of the dual active bridge (DAB) converter is proposed in this article. The algorithm evaluates three simple expressions that fit the optimal solutions obtained in recent works, which allows the algorithm to be implemented in real-time and valid for the whole operating range. As a result, the converter operates under zero voltage switching (ZVS) conditions and minimizes conduction losses. In addition, the algorithm considers the minimum current required to guarantee the ZVS condition that faces the undesired dead-band of switching devices effect. The proposal achieves a soft transition between any operation region and a fast closedloop response with no stability concern, presenting robustness under leakage inductance deviation. Finally, the algorithm presented in this article is verified with a 4-kW experimental prototype. Experimental results show that the algorithm proposed can be evaluated with less than 2.8 µs and allows soft transition between any operation region to be achieved. Besides, fast closedloop changes of 750 µs through all the operating ranges, keeping minimum rms current under ZVS, are shown, Peer Reviewed, Postprint (published version)

This paper introduces semi-explicit multilinear modeling to ac power systems, including voltage source converters. Firstly, the novel semi-explicit multilinear modeling class is explained. Then this class is applied to a small example of PV inverter connected to an infinite bus. Some part of the nonlinear current reference calculation is expressed as a multilinear algebraic constraint. The formulation of this multilinear algebraic constraint allowed modeling the whole nonlinear inverter as a semi-explicit multilinear model. The novel modeling approach is compared with common nonlinear time-based simulation in Simulink. The results show a good approximation of the nonlinear model by its semi-explicit multilinear model where the relative error is below . This low error motivates the further usage of the semi-explicit multilinear modeling class for power system analysis., Peer Reviewed, Postprint (published version)

L'energia elèctrica es pot generar de diverses maneres i, per poder-la emprar en diferents aplicacions domèstiques i industrials actuals, és imprescindible disposar d'equips de conversió que permetin transformar-la entre els diferents formats amb el màxim rendiment possible. Els dissenys dels convertidors han de donar resposta als nous reptes i requeriments, per això s'ha investigat ininterrompudament el desenvolupament tant de noves topologies com de nous materials semiconductors. Aquest article presenta el disseny d'un convertidor estàtic Phase-Shifted Full-Bridge, caracteritzat per posseir un rendiment elevat gràcies a ser capaç de commutar a voltatge nul al primari del convertidor, reduint les pèrdues de l'equip. En aquest TFG es procedirà a realitzar les simulacions pertinents per comprovar el funcionament correcte de la topologia. També es presentarà el llistat de components que intervindran en la implementació del convertidor., La energía eléctrica se puede generar de diversas formas y, para poder emplearla en distintas aplicaciones domésticas e industriales actuales, es imprescindible disponer de equipos de conversión que permitan transformarla entre los diferentes formatos con el máximo rendimiento posible. Los diseños de los convertidores deben dar respuesta a los nuevos retos y requerimientos, por eso se ha investigado ininterrumpidamente en el desarrollo tanto de nuevas topologías como de nuevos materiales semiconductores. Este artículo presenta el diseño de un convertidor estático Phase-Shifted Full-Bridge, caracterizado por poseer un rendimiento elevado gracias a ser capaz de conmutar a voltaje nulo en el primario del convertidor, reduciendo las pérdidas del equipo. En el presente TFG se procederá a realizar las simulaciones pertinentes para comprobar el correcto funcionamiento de la topología. También se presentará el listado de componentes que intervendrán en la implementación del convertidor., Electrical energy can be generated in multiple ways. Having conversion equipment that can transform energy between different formats – at its highest performance – is crucial so that this energy can be used in domestic and industrial applications. Converter designs must satisfy new challenges and requirements, therefore there has been constant research in the development of both new topologies and new semiconductor materials. This article carries out the design of a Phase-Shifted Full-Bridge converter. This converter presents a very high performance since it can switch to zero voltage in the primary side of the converter, reducing the losses of the equipment. The correct performance of the topology will be verified through simulations and a list of components needed to implement the converter will be presented.

This paper presents a model predictive control (MPC) for a grid-connected voltage source inverter (VSI) with current limitation. The control algorithm is performed in the dq frame to obtain the amplitude of the inverter currents. First, a state observer with a reduced model of the converter is used to estimate the inverter current and perform active damping. Then, an MPC algorithm is used to regulate the currents to a desired reference but with the advantage that these currents can be limited to a maximum value by introducing a constraint in the cost function instead of clipping the current of the inverter above a maximum current. This controller has been tested experimentally under a current reference step change and without a physical damping resistor., This publication is part of the project I+D+i PID2021-122835OB-C21, financed by MCIN/AEI/10.13039/501000011033 and FEDER “Una manera de hacer Europa”., Peer Reviewed, Postprint (author's final draft)

Superconducting electromagnets are key components in modern scientific particle accelerators. For example, among other tasks, they are used to focus particle beams in the collision points. Their magnetic field needs to be precisely controlled by regulating the power electronics that feed such magnets. This work discusses the most relevant aspects regarding the digital implementation of an FPGA-based Rapid Control Prototyping (RCP) platform intended to regulate a high-current low-voltage two-quadrant Series Capacitor (SC) DC/DC power converter prototype. This converter has been developed to study the powering of the Inner Triplet (IT) superconducting electromagnets of the High Luminosity (HL) upgrade of the Large Hadron Collider (LHC) at CERN. The design guidelines, based on the well-known Model Based Design (MBD) approach, are highlighted, and implementation details are provided. Experimental results that show the correct operation of the RCP platform are finally presented., Peer Reviewed, Postprint (published version)

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 Reviewed, Postprint (published version)

El present treball consisteix en la modelització dels diferents elements que intervenen en el funcionament d'un aerogenerador de tipologia direct-drive PMSG (Permanent Magnet Synchronous Generator), és a dir, amb generador síncron d’imants permanents (GSIP) de transmissió directe (sense caixa de transmissió). Concretament es descriuen diferents models per: la velocitat del vent, la turbina eòlica, el generador síncron d’imants permanents, el convertidor back-to-back i la xarxa elèctrica. Amb aquests elements es simula el comportament d'un aerogenerador connectat a la xarxa. Una altra part important del projecte és la implementació d'estratègies de control que permeten la regulació de les diferents variables del sistema, com poden ser els voltatges, intensitats i potències involucrades en el sistema. Les principals estratègies que s’estudien són; el control de la potència òptima, el control de l’angle de Pitch i el control davant de sots de tensió. Un cop descrit tot el model i el sistema de control es simularà el model complet de la turbina eòlica enfront de diferents situacions, com poden ser augments sobtats de la velocitat del vent, sots de tensió a la xarxa, etc. Analitzant els resultats d’aquestes simulacions s’extrauran conclusions sobre el funcionament dels aerogeneradors. Finalment, també s’inclou un anàlisi de l'impacte ambiental que pot produir la instal·lació d'un parc eòlic al mar (offshore) i també un estudi econòmic valorant el cost real que podria suposar la seva instal·lació, Objectius de Desenvolupament Sostenible::7 - Energia Assequible i No Contaminant::7.2 - Per a 2030, augmentar substancialment el percentatge d’energia renovable en el con­junt de fonts d’energia, Objectius de Desenvolupament Sostenible::9 - Indústria, Innovació i Infraestructura::9.2 - Promoure una industrialització inclusiva i sostenible i, a tot tardar el 2030, augmentar de manera significativa la contribució de la indústria a l’ocupació i al producte interior brut, d’acord amb les circumstàncies nacionals, i duplicar aquesta contribució als països menys avançats

The current climate emergency situation has lead to a need for an energetic transition in which the renewable-based energy is playing an indispensable role. Far from the technical constraints the increase of passive Renewable Energy Sources (RES) connections to the grid might cause, the performance of a proper control on the raising integration can play in favor of the develop- ment of a more efficient, flexible and reliable operation of the grid. This project focuses on the analysis of the integration of distributed RES in an islanded mi- crogrid and the contribution to the microgrid voltage and frequency regulation by means of grid-following voltage-sourced converters in grid-supporting mode. The modeling of grid-following voltage-sourced converters operating in grid-supporting mode is detailed. Also, the modelling of a MV isolated microgrid and a controlled synchronous gener- ator, being this element the forming element of the microgrid, is carried out. Finally, the mod- elled voltage-sourced converters are connected to different points of the modelled microgrid representing RES constant distributed generation. Three different disturbances during the operation of the microgrid are simulated with MAT- LAB SIMULINK to analyse the frequency and voltage of the microgrid under this conditions: connection of additional load, three-phase fault, reduction of generation in one of the RES units.

En els últims anys, la indústria de les energies renovables ha experimentat un fort creixement i una implantació amb tendència a l’augment en la societat. Concretament, el sector de les energies solars ha desenvolupat una forta evolució, fent-se servir cada cop més en múltiples aplicacions. Molts governs aposten, promouen i inciten a l’explotació de recursos renovables com a fonts d’energia per al col·lectiu de la societat. Un exemple en són els anomenats fons Next Generation que han impulsat, entre altres coses, la implantació d’una gran quantitat de noves instal·lacions d’autoconsum fotovoltaic. L’augment del pes que representen les tecnologies renovables en el total de producció energètica respecte de les centrals convencionals planteja un repte pel que fa a la robustesa de la xarxa. D’a- questa manera existeix la necessitat de dur a terme investigacions amb la finalitat d’aconseguir millores en el rendiment de les tecnologies actuals tant pel que fa a les tecnologies generadores com al disseny control i optimització de xarxes i microxarxes elèctriques. Així doncs, aquest projecte neix de la necessitat de disposar d’una plataforma que permeti emu- lar diferents sistemes elèctrics que componen les microxarxes elèctriques, per exemple mòduls fotovoltaics, inversors, bateries entre d’altres, sense haver de recórrer a l’ús d’equips reals. El principal desavantatge d’aquesta opció resideix en la dependència de les condicions atmosfèri- ques o en el desgast dels equips en funció del sistema. D’aquesta forma l’estudi realitzat es basa la implementació d’un programari que permeti emu- lar el comportament d’una bateria fent ús d’un convertidor de potència desenvolupat en pro- jectes anteriors per CITCEA-UPC. El programari proposat té una arquitectura modular i està dissenyat amb l’objectiu que sigui escalable. S’ha desenvolupat una HMI fent ús de la tecno- logia web, i les comunicacions industrials amb el convertidor s’han implementat mitjançant el protocol CAN. En la pri

The paper analyzes grid strength and grid impedance for systems with significant penetration of power electronics. The work shows that the traditionally employed Thévenin equivalent cannot capture the different saturation states of power converters and therefore some classical definitions of grid strength based on short-circuit power at the point of connection fail to describe the system behavior. The paper proposes to map the impedance for all the different possible voltages at the point of connection and analyzes how the impedance depend on the voltage and angle of derivation for different possible simplified systems (grid-following converter in parallel with a Thévenin equivalent and grid-forming converter) considering the different saturation states of the converter. Numerical results and case studies are included as examples of the conducted analysis., Peer Reviewed, Postprint (author's final draft)

As penetration of photovoltaic (PV) and wind generation systems driven by grid-connected power converters monotonously increases, unusual interactions between innovative and legacy generation systems become more concerning, since they threaten the system stability and reliability. These undesirable interactions are mainly due to the fact that power converters and conventional electromechanical generators currently work under different physical and control principles and rules. This gives rise to some incompatibilities in terms of dynamic response and physical limits, which has become evident once the share of power converters connected to the grid has become relevant enough. In order to address this issue, this chapter presents some relevant concepts for implementing grid-following and grid-forming power converters. In this way, after reviewing some basis on PV and wind generation, this chapter discusses about the operation principle of such power converters, reviewing some fundamentals on grid synchronization strategies and current controllers. After that, some control schemes for gird-forming converters will be presented, paying particular attention to the role of droop control loops and the virtual impedance control. Finally, a general introduction of the synchronous power controller is provided as a preferred implementation of a grid-forming converter based on the virtual synchronous machine concept., Peer Reviewed, Postprint (published version)

© 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., With the aim to increase standardization, reduce the cost, and obtain advanced performance features, the design of voltage-source power converter legs can be undertaken by combining several instances of a standard switching cell, properly connected in active neutral-point-clamped structures to reach the desired voltage and current ratings. These switching cells can be organized into switching-cell arrays. This design approach introduces several degrees of freedom into the design. Namely, the different options to interconnect the cells and the distribution of switching losses among these cells. This article aims to define an optimization problem to explore this design space. The design problem is formulated in different scenarios, involving different conversion configurations (dc-dc and dc-ac), different leg number of levels (two and three), and different types of available cells (standard and conduction-optimized in combination with switching-optimized). A weighted objective function is then defined in terms of leg simplicity, efficiency, and reliability. The value of the design variables that minimize the objective function with different sets of weighting factors are obtained under selected scenarios and operating conditions, to illustrate the flexibility of the converter design approach under study. The solution of the optimization problem is obtained using a surrogate optimization algorithm in MATLAB, well suited to quickly solve optimization problems involving a combination of integer design variables (the number of parallel switching cells in each converter leg position) and continuous design variables (the proportion of switching losses taken by each cell), together with linear and nonlinear constraints., Postprint (author's final draft)

En aquest projecte es desenvolupa un model de Flux de Potència Òptim (OPF - Optimal Power Flow) aplicat a xarxes híbrides AC/DC. Per fer-ho, primerament s'haurà de modelitzar la xarxa, distingint el sistema AC, el sistema HVDC i les estacions convertidores que els interconnecten. A partir de la formulació extreta de la modelització, es podrà definir el model d'optimització OPF. Per tal de comprovar el correcte funcionament del model OPF desenvolupat, es portarà a terme l'anàlisi d'un sistema test conformat per una xarxa híbrida., En este proyecto se desarrolla un modelo de Flujo de Potencia Óptimo (OPF - Optimal Power Flow) aplicado a redes híbridas AC/DC. Para ello, primeramente deberá modelizarse la red, distinguiendo el sistema AC, el sistema HVDC y las estaciones convertidoras que los interconectan. A partir de la formulación extraída de la modelización, podrá definirse el modelo de optimización OPF. Para comprobar el correcto funcionamiento del modelo OPF desarrollado, se llevará a cabo el análisis de un sistema test conformado por una red híbrida., In this thesis, an OPF calculation model applied to AC/DC hybrid grids is presented, with the aim of developing an extension of MatPower that allows this type of calculation. With this tool, the OPF is studied for a test system defined by a hybrid grid. First, an introduction to HVDC transmission systems is given. After this, the modelling of hybrid AC/DC grids is developed, adding converters and HVDC lines to the model for AC. Then, the OPF mathematical model is defined, whose objective function, variables and constraints associated with the hybrid AC/DC model are presented. From here, the test system to be studied is introduced and results are shown from the developed MatPower extension. These results allow comparing different scenarios for the test system, each one having an HVDC system with different levels of meshing., Outgoing

Dada la gran electrificación que se está viviendo en el mundo, los convertidores de potencia son esenciales en el desarrollo de las actividades de la vida moderna. Son fundamentales para asegurar el buen flujo energético entre los agentes del sistema eléctrico. Su utilidad se asemeja a la del corazón en el ser humano, este bombea sangre con la cantidad requerida de nutrientes y oxígeno a las distintas partes del cuerpo. Los convertidores, transforman la energía eléctrica en la forma y cantidad requerida por los distintos aparatos eléctricos conectados. Se encuentran prácticamente en todos los sectores: movilidad, energía, telecomunicaciones, sanidad... A su vez, se considera que los procedimientos más utilizados para realizar esta tarea se encuentran en un estado consolidado de la tecnología. Sin embargo, aún existe una gran ventana para el progreso hacia una mayor versatilidad, modularidad y estandarización, con el propósito de poder aplicar la misma tecnología, dispositivos, diseño y fabricación en cualquier aplicación. Una forma de conseguir esto último es el desarrollo de los convertidores multinivel. El objetivo principal del proyecto es probar una rama de un convertidor multinivel que utiliza una tecnología desarrollada por el Grup de Recerca en Electrònica de Potència (GREP) durante más de 20 años para realizar conversiones de cualquier tipo. Una de sus últimas estrategias de diseño, fundamentada en las Switching-Cell Array (SCA), consiste en construir el convertidor usando unas celdas de conmutación optimizadas. La implementación multinivel es de tipo enclavamiento a punto neutro y se comprueba su buen funcionamiento para el caso de tres niveles operando como regulador de continua. Además, incorpora un modo de control nuevo de tipo jerárquico, dividido en dos etapas, que simplifica la operación del convertidor y permite su estandarización. Entre otras cosas, el control permite poder distribuir una parte de las pérdidas de conmutación de los dispositivos semi, Donada la gran electrificació que s'està vivint en el món, els convertidors de potència són essencials en el desenvolupament de les activitats de la vida moderna. Són fonamentals per a assegurar el bon flux energètic entre els agents del sistema elèctric. La seva utilitat s'assembla a la del cor en l'ésser humà, que bomba sang amb la quantitat requerida de nutrients i oxigen a les diferents parts del cos. Els convertidors transformen l'energia elèctrica en la forma i quantitat requerida pels diferents aparells elèctrics connectats. Es troben pràcticament en tots els sectors: mobilitat, energia, telecomunicacions, sanitat... Actualment, es considera que els procediments més utilitzats per a fer aquesta tasca es troben en un estat consolidat de la tecnologia. No obstant això, encara existeix una gran finestra per al progrés cap a una major versatilitat, modularitat i estandardització, amb el propòsit de poder aplicar la mateixa tecnologia, dispositius, disseny i fabricació en diferents aplicacions. Una manera d'aconseguir això últim és el desenvolupament dels convertidors multinivell. L'objectiu principal del projecte és provar una branca d'un convertidor multinivell que utilitza una tecnologia desenvolupada pel Grup de Recerca en Electrònica de Potència (GREP) durant més de 20 anys per a realitzar conversions de qualsevol tipus. Una de les seves darreres estratègies de disseny, fonamentada en les Switching-Cell Array (SCA), consisteix en construir el convertidor fent ús d'unes cel·les de commutació optimitzades. La implementació multinivell és de tipus enclavament a punt neutre i es comprova el seu bon funcionament per al cas de tres nivells operant com a regulador de contínua. A més, incorpora una mode de control nou de tipus jeràrquic, dividit en dues etapes, que augmenta la facilitat d'interacció amb l’usuari per configurar el mode de treball. Entre altres coses, el control permet distribuir una part de les pèrdues de commutació dels dispositius semiconductors. Pe, Given the great electrification that is taking place in the world, power converters are essential in the development of modern life activities. As they are fundamental to ensure a good energy flow between the different constituents of the electrical system. Their operation principle is similar to that of the human heart, which pumps blood with the required amount of nutrients and oxygen to the different parts of the body. Converters transform electrical energy into the form and quantity required by the electrical devices connected. They are used practically everywhere: in mobility, energy, telecommunications, healthcare... At the same time, the most commonly used procedures to perform this task are considered to be a consolidated technology. However, there is still a large window for progress towards greater ersatility, modularity and standardization, with the purpose of being able to apply the same technology, devices, design and manufacturing in any application. One way to achieve that is the development of multilevel converters. The main objective of the project is to test a branch of a multilevel converter using the technology developed by the Power Electronics Research Group (GREP) for more than 20 years to perform any conversion. One of their latest design strategies, based on Switching-Cell Array (SCA), consists on building the converter using optimized switching cells. Multilevel neutral-point clamped topology is used and its performance is tested as a three-level direct current (DC) regulator. In addition, it uses a new hierarchical control, divided into two stages, which simplifies the operation of the converter and allows its standardization. Among other things, the control enables to distribute part of the switching losses of the semiconductor devices. In order to comply with the above, the control board, the power board and the SCAs have been assembled, verified and connected to each other to constitute the branch. The first stage controller has been pr

The power calculation is an indispensable element in droop-controlled inverters because the bandwidth of the measured power has a direct impact on the controller performance. This paper proposes a fast and accurate power calculation algorithm based on the combined Second Order Generalized Integrator (SOGI) filters in stationary coordinates for a three-phase system, which takes into consideration the use of nonlinear loads. The power calculation scheme is formed by the two-stage SOGI filters that are employed for obtaining the active and reactive powers required to perform a droop-based inverter operation, respectively. From the two-stage structure, the first SOGI is used as a band-pass filter (BPF) for filtering harmonics and obtaining the fundamental current of the nonlinear load; The second SOGI is used as a low-pass filter (LPF) for extracting the DC-component, which corresponds with the average power. A small-signal model of a two droop-controlled inverters system is built to obtain the dynamical response and stability margin of the system. And compared it with the dynamical behaviour of a standard droop-control method. Next, the proposed power calculation system is designed in order to achieve the same ripple amplitude voltage as that obtained with the standard droop-control method by adjusting the bandwidth gains. Through simulation and hardware in the loop (HIL) validation, the proposed approach presents a faster and more accurate performance when sharing nonlinear loads, and also drives the inverters’ output voltage with lower distortion., Peer Reviewed, Postprint (published version)

This paper compares four sliding-mode control strategies for a dual active bridge. The proposed control algorithms define different switching functions resulting in first-and second-order controllers, and using both discontinuous and continuous sliding-mode algorithms. The paper details the design stage and includes simulation and experimental tests to better compare the performance for each control scheme., Peer Reviewed, Postprint (published version)

Se realiza una adaptación de una placa antigua a una nueva de mejores y mayores prestaciones

© 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 proposes a new sliding mode control based on a non-linear switching surface that provides a suboptimal current-limited start-up response in step-down converters. The main idea behind the design consists in combining different switching surfaces. The first one forces the system trajectories to track a constant current path until the output voltage error is small. A non-singular terminal switching surface then drives the trajectories to the vicinity of the steady state operating point. Finally, a first order switching surface regulates the steady state providing very good rates of load and line regulation. The paper presents the design guidelines of the suboptimal sliding mode control and the experimental evaluation that confirms the effectiveness of the proposal., This work was partially supported by the Government of Spain through the Agencia Estatal de Investigacion´ Project DPI2017-85404-P and by the Generalitat de Catalunya through the Project 2017 SGR 872., Peer Reviewed, Postprint (author's final draft)

© 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, The grid-forming converter is an important unit in the future power system with more inverter-interfaced generators. However, improving its performance is still a key challenge. This paper proposes a generalized architecture of the grid-forming converter from the view of multivariable feedback control. As a result, many of the existing popular control strategies, i.e., droop control, power synchronization control, virtual synchronous generator control, matching control, dispatchable virtual oscillator control, and their improved forms are unified into a multivariable feedback control transfer matrix working on several linear and nonlinear error signals. Meanwhile, unlike the traditional assumptions of decoupling between AC and DC control, active power and reactive power control, the proposed configuration simultaneously takes all of them into consideration, which therefore can provide better performance. As an example, a new multi-input-multi-output-based grid-forming (MIMO-GFM) control is proposed based on the generalized configuration. To cope with the multivariable feedback, an optimal and structured H8 synthesis is used to design the control parameters. At last, simulation and experimental results show superior performance and robustness of the proposed configuration and control, Peer Reviewed, Postprint (author's final draft)

This paper deals with the short-circuit analysis of distribution systems dominated by Voltage Source Converters (VSCs). A novel methodology has been proposed in this paper for short-circuit calculation of power systems populated with VSCs where the control modes and potential current-saturated operation of power converters are considered. The studied distribution system has been modeled using an element-based steady-state formulation that includes the converter equations in both normal operation and fault scenarios. Then, equilibrium points of the studied distribution system are identified by solving the established systems of equations for different potential current-saturation states of the VSCs. The methodology identifies possible solutions involving different saturation states of different converters. The proposed methodology is applied to a specific case study of a distribution system penetrated with VSCs in both grid-forming and grid-following control. The short-circuit analysis results indicate that VSCs operation shows a significant impact on the short-circuit equilibrium points of the studied system. In addition, multiple equilibrium points may exist depending on whether the grid-forming converter is saturated or not. The existence of multiple equilibrium points is validated through dynamic simulations., Peer Reviewed, Postprint (author's final draft)

In this paper, it has been implemented a code able to provide the optimal energy generation of an isolated power system, which for this study case it is represented by Tenerife, an island situated in Spain. The optimization algorithm has been developed using CVXPY, which is an open-source-based on Python capable of modeling a language for convex optimization problems. Tenerife power system can be represented as a Dynamic Virtual Power Plant (DVPP) which includes conventional and renewable power plants. In the first scenario, it has been assumed that the electricity needed to satisfy the demand in Tenerife has been produced using three power sources, coal, wind, and PV. In the second scenario, in addition, it has been included a battery energy storage system (BESS) and it has been chosen the lithium-ion technology for the battery. The aim of this study is to obtain the renewable capacity, BESS size, and hourly renewable generation which minimize the total cost of the DVPP. Several different possibilities have been discussed, in particular focusing on the influence of renewable penetration on the solution. This has been done considering the European environmental policies and targets for 2030 and 2050 that the European Union has developed to tackle the climate change. Furthermore, it has been discussed the influence of the BESS capital expenditures (CAPEX) on the solution, considering that the battery cost is strongly decreasing over the years. Finally, the ramp-rate control for coal, wind, and PV power plants has been implemented, which limits how quickly a plant can change its output. This has been done because power quality and network stability can be harmed by a short-term fluctuation in the power generated by grid-connected power plants with a significant size., Objectius de Desenvolupament Sostenible::7 - Energia Assequible i No Contaminant

© 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, The effective fault current limiting is very significant for the dc distribution system. However, the traditional dc fault current limiting method, i.e., directly installing dc reactor, may trigger negative impacts the system normal operation and fast isolation of the circuit breaker. Therefore, an improved hybrid dc circuit breaker with self-adaptive fault current limiting capability is proposed in this article. Not only can it realize fault current limitation in a quick and efficient manner, but also ensures the continuous operation of the converter and the fault ride-through of the healthy network after the dc fault. In this sense, the requirements on the protection and arrester capacity are reduced. Compared with other types of fault current limiting methods, the proposed topology has the merit of few negative effects on system stability and transient response. It can effectively perform fault current limiting and fault isolation, with low conduction loss and low implementation difficulty. The working principle and advantages of the proposed topology are verified by experimental tests and simulation cases., Peer Reviewed, Postprint (author's final draft)

This paper analyses the capabilities of the Open-Modelica environment to perform electromagnetic transient (EMT) type simulations of power transmission systems with grid-connected converters. A power transmission system has been modelled and simulated in OpenModelica and Simulink to compare both tools in terms of accuracy, robustness, flexibility and computational performance. Power system transient studies such as faults and switching of capacitor banks have been performed. The results confirmed an excellent overall agreement between both software and demonstrated a remarkable potential for using OpenModelica for EMT-type modelling and simulation of future power electronic dominated grids., This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 883985 (POSYTYF project). The work of Oriol Gomis-Bellmunt is supported by the ICREA Academia program. Eduardo Prieto-Araujo is a Serra Húnter Lecturer., Postprint (published version)