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Neutral-point-clamped multilevel converters are a suitable solution to the implementation of low–medium voltage and power applications at present, thanks to their intrinsic superior voltage and current quality. The conventional configurations of these converters present uneven power loss distribution, causing thermal stress in some power semiconductors, which weakens the power converter reliability. To overcome this, an implementation of the neutral-point-clamped multilevel converter based on a switching-cell array is introduced, adding redundant conduction paths on one side and more options to distribute the switching losses on the other side. An active thermal control is proposed to balance the temperature distribution in the converter. A four-level converter has been implemented to evaluate the proposed solution. The experimental results show that the proposed implementation and active thermal control presents an enhanced temperature distribution in the converter and, therefore, reduced thermal stress and better reliability., Peer Reviewed, Postprint (published version)

Nowadays, the internal combustion engine in vehicles is being replaced by electric motors, giving way to the electric vehicle, which results in reduced environmental impact, higher efficiency and lower emission of greenhouse gases. The powertrain of an electric vehicle is its most prominent subsystem, with the batteries and traction inverter being key components. Thus, due to their relevance, advances in the design of both components are of paramount importance. In this paper, the potential benefits achieved through a powertrain design approach based on combining a modular battery bank with multilevel NPC traction inverter topologies were analyzed, in comparison to a conventional two-level powertrain design. Several aspects were analyzed: modularity, complexity, battery-pack state-of-charge balancing, inverter loss, motor ac voltage harmonic distortion, motor common-mode voltage and reliability. Particularly, from the comparison study developed under the selected design scenario, the proposed design approach, based on modular battery packs and multilevel technology, shows a potential reduction of up to 55% in inverter losses, up to 65% in motor ac-voltage total harmonic distortion, and up to 75% in rms common-mode voltage., 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)

© 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 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., 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)

© 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 article proposes a novel device designated as an intelligent electronic fuse (iFuse) intended to be connected in series with any current-bidirectional voltage-unidirectional active switch present in a power converter. The iFuse duty is to selectively isolate its series-associated switch from the rest of the converter circuit immediately after detecting that this switch has failed in short circuit. Nonetheless, it maintains the reverse (free-wheeling) current path originally offered by the failed switch. The failure detection is typically performed when the failed switch causes a shoot-through event. Therefore, the iFuse is able to block large currents. The iFuse allows increasing the power-converter fault tolerance and reliability with regard to switch short-circuit failures (SCFs), as in converters featuring switches in parallel, redundant legs, and multilevel neutral-point-clamped topologies. The reliability model analysis of a two-level converter leg with two parallel switches per position reveals that its reliability can be increased up to four times when an iFuse is implemented in series with each switch. The iFuse device feasibility and good performance are verified through experimental tests, proving that it can detect and isolate the associated-switch failure in 6 µs , while stopping short-circuit currents of up to 1 kA without incurring in harmful di / dt values., Peer Reviewed, Postprint (author's final draft)

This article explores the thermal and reliability benefits of configuring the power semiconductor block of power converters with several small standard power semiconductor devices instead of a few larger ones at a fixed total chip area. The effectiveness of a finer power semiconductor device granularity is analyzed in the context of a synchronous buck converter design under different operating conditions and employing a recently proposed component, the switching-cell array, to implement the semiconductor-component block of the converter. Comparative evalua tions are undertaken under different degrees of granularity and in terms of semiconductor loss distribution, semiconductor temperature distribution, and converter mean time to failure. The article also discusses the thermo-electrical and reliability models employed, and the assumptions made for a fair and straightforward comparison in a generic case. The comparison results reveal that a finer granularity can potentially provide remarkable benefits, although the incremental improvements decrease as the granularity becomes finer. A tradeoff solution must be sought in each specific case balancing the benefits achieved with the added complexity, Postprint (author's final draft)

© 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 Reviewed, Postprint (published version)

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 works

This paper studies a multilevel multiphase dc-ac conversion system configured by a neutral-point-clamped converter fed by multiple battery packs connected in series. A virtual-vector modulation is selected and a state-of-charge (SoC) balancing control is designed to be able to employ the full battery bank capacity, even under different battery initial SoC values or different battery nominal capacities. The SoC balancing among battery packs is accomplished through the multilevel converter operation in a lossless manner, by simply distributing the dc-to-ac power flow among the batteries according to their SoC. A simple average system model is also presented, which allows performing very fast system simulations over long periods of time and serves as a convenient tool to tune the compensator parameters. The satisfactory performance of the proposed system configuration and control, which can be applied with any number of levels and phases, has been verified through simulations and experiments in a four-level three-phase dc-ac converter fed by three lithium-ion battery packs. The results prove the feasibility and advantages of the proposed system configuration, which can be used to implement conversion systems with different specifications combining several instances of a standard battery pack and a standard power semiconductor device, Peer Reviewed, Postprint (updated version)

© 2017 IEEE. Personal use of this ma terial is permitted. Permission from IEEE must be obtained for al l other uses, in any current or future media, including reprinting /republishing this material for advertising or promotional purposes, creating new collective works, f or resale or redistribution to se rvers or lists, or reuse of any copyrighted compone nt of this work in other works, This paper proposes a modulation strategy for multilevel multiphase diode-clamped dc–ac converters (also applicable to other functionally equivalent topologies) able to keep the dc-link capacitor voltages balanced under passive front ends, low frequency modulation indices (i.e., low number of switching transitions per fundamental cycle), any value of the amplitude modulation index, and any ac-side displacement power factor. A suitable phase voltage pattern with minimum number of switching transitions is presented for the n-level three-phase case. Subsequently, it is extended to higher number of switching transitions per fundamental cycle and to higher number of phases. Simulation results with three, four, and five levels; three and five phases; and several frequency-modulation-index values are presented to validate the proposed modulation strategy. Experimental results obtained with a four-level three-phase dc–ac converter prototype are also provided. The proposed modulation strategy enables the use of this type of converters in applications where the ac fundamental frequency may be close to the switching frequency, such as in high-power systems and variable-speed motor drives., Peer Reviewed, Postprint (author's final draft)

This paper presents a model of a bidirectional MV/LV solid-state transformer (SST) for distribution system studies. A modular multilevel converter configuration is used in the MV side of the STT. The LV side uses a three-phase four-wire configuration that can be connected to both load and generation. The model developed for this work has been implemented in MATLAB/Simulink, and its behavior has been tested by carrying out several case studies under different operating conditions. The simulation results support the feasibility of the SST and its advantages in comparison to the conventional transformer. The paper also includes a discussion of the main model limitations and the future work., Postprint (published version)

© 2016 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, As wind power technology points to increase power ratings, the implementation based on a permanent-magnet synchronous generator (PMSG) with a full-power converter is expanding its market share. Multilevel converters, as for example, neutral-point clamped (NPC) converters, are therefore well suited for this application. Predictive current control presents similar dynamic response and reference tracking than other well-established control methods, but working at lower switching frequencies, and providing extensive flexibility to apply either online or offline different control laws to the same plant. In this work, the predictive current control is applied to both sides of the back-to-back NPC converter connecting a permanent-magnet synchronous wind power generator to the grid. DC-link neutral-point balance is achieved by means of the predictive control algorithm, which considers the redundant switching states of the back-to-back NPC converter. Reduced number of commutations, current spectrum control, and compliance with the low-voltage ride-through (LVRT) requirement are carried out with the predictive control. The obtained experimental results confirm the suitability of the proposed control approach., Peer Reviewed, Postprint (author's final draft)

El present projecte consisteix en la millora de rendiment i funcions d’un projecte antecedent. El projecte anterior presenta un convertidor CC/CA controlat per control predictiu que quan es sotmet a simulació funciona de forma molt eficient i efectiva però al fer-ho experimentalment apareixen diferències notables entre el senyal de referència i el real. Per a solucionar aquests errors es prenen les mesures possibles per a reduir el temps de resposta. Com a millora funcional s’aplica el circuit a la xarxa elèctrica com a generador elèctric fent servir el control predictiu i un PLL per a la sincronització.

En aquest projecte es realitza la programació d’un llaç de control a les corrents de les bobines del motor de reluctància lineal del tren Telmag. Amb aquesta implementació es pretén millorar la velocitat de resposta i el comportament del motor de reluctància lineal quan el tren està en règim dinàmic. Primer s’estudia tota l’electrònica implementada al tren, per després realitzar un mòdul de lectura de corrents i, finalment, un mòdul de control. Es validen els resultats amb instrumentació de laboratori, simulant escrupolosament les senyals provinents de l’electrònica del tren segons documentació tècnica facilitada.

The low-voltage ride through (LVRT) requirement demands the wind power plants to remain connected to the grid in the presence of grid voltage dips, actively helping the network overall control to keep network voltage and frequency stable. Wind power technology points to increase power ratings. Hence, multilevel converters, as for example, neutral-point-clamped (NPC) converters, are well suited for this application. Predictive current control presents similar dynamic response and reference tracking than other well-established control methods, but working at lower switching frequencies. In this paper, the predictive current control is applied to the grid-side NPC converter as part of a wind energy conversion system, in order to fulfill the LVRT requirements. DC-link neutral-point balance is also achieved by means of the predictive control algorithm, which considers the redundant switching states of the NPC converter. Simulation and experimental results confirm the validity of the proposed control approach., Postprint (author’s final draft)

In this paper, a predictive control scheme is proposed for the low-voltage ride-through (LVRT) enhancement of direct-driven permanent-magnet-synchronous-generator-based megawatt-level wind turbines. The proposed method uses the turbine-generator rotor inertia to store the surplus energy during the grid voltage dips. The power conversion system is realized using a three-phase diode-bridge rectifier, a three-level-boost converter, and a neutral-point-clamped (NPC) inverter. The wind turbine requirements, such as maximum power point tracking, net dc-bus voltage control, balancing of the dc capacitor voltages, and reactive power generation, are modeled as the reference control variables. The generator-and grid-side cost functions are defined to deal with these control objectives. During each sampling interval, the control goals are achieved based on the minimization of cost functions. The coordination of boost and NPC converters and the exchange of reference control variables during normal and LVRT operation are formulated such that the power converters operate in a safe mode while meeting the grid code requirements. Simulation and experimental results are presented to validate the proposed strategy., Postprint (published version)

Detailed switching models of power electronics devices often lead to long computing times, limiting the size of the system to be simulated. This drawback is especially important when the goal is to implement the model in a real-time simulation platform. An alternative is to use dynamic average models (DAM) for analyzing the dynamic behavior of power electronic devices. This paper presents the development of a DAM for a bidirectional solid-state transformer and its implementation in a real-time simulation platform. Several case studies have been carried out in order to evaluate the behavior of the model under different operating conditions, check its feasibility for power quality improvements and explore the implementation in a real-time simulation platform. (C) 2014 Elsevier B.V. All rights reserved., Postprint (published version)

L’objectiu d’aquest treball és dissenyar una instal·lació solar fotovoltaica per autoconsum per a una nau industrial en funcionament. Hi ha moltes alternatives de disseny i dimensionament, però s’ha de cercar la opció més adient a la realitat de la instal·lació. Per a trobar la millor alternativa s’han de valorar diferents escenaris de producció i compararlos amb el consum anual típic de la instal·lació elèctrica. Una vegada escollit l’escenari, s’ha de dimensionar la instal·lació solar fotovoltaica i definir exactament els components necessaris i les seves característiques. El resultat és un projecte que permet realitzar una instal·lació solar fotovoltaica per autoconsum amb la millor rendibilitat econòmica.

This paper presents a generalized multilevel direct power control (ML-DPC) scheme for grid-connected multilevel power converters. The proposed method extends the original DPC operating principle by considering only the closest subset of two-level voltage vectors to the present switching state. The implementation of this principle requires the power derivatives for feedback, which can present numerical problems when applied experimentally, mainly due to high measurement noise sensitivity. Therefore, a derivative estimator is proposed based on the converter-grid model in the synchronous reference frame. In addition, a virtual flux observer is developed to achieve synchronization and improve robustness in the presence of grid voltage harmonics. The proposed method is applicable to any multilevel converter topology of any number of levels. In this paper, simulations and experimental results are presented for a seven-level cascaded H-bridge converter., Postprint (published version)

Predictive current control is applied to a wind energy conversion system implemented with a permanent-magnet synchronous generator connected to the grid through a back-toback neutral-point-clamped converter. This control approach allows to work in steady-state and to fulfill the low-voltage ride through requirements demanded by the power system operators.Dc-link neutral point voltage balance is also achieved by means of the predictive control algorithm., Postprint (published version)

The solid state transformer is an emerging technology which aims at replacing the conventional lowfrequency power transformer by means of a high-frequency transformer driven by a proper AC/AC power electronics conversion system, at both transformer sides. In comparison with the conventional power transformer, the solid state transformer provides extended and enhanced operating capabilities that can be achieved with an appropriate controller design for the power electronics converters. In this work, the interaction of the solid state transformer with a distribution system is analyzed under different operating conditions. Bidirectional active power flow, full reactive power control, low-voltage side current unbalance management and high-voltage side low-voltage ride-through are achieved with the proposed control approach., Postprint (published version)

This paper presents an efficiency analysis of a recently-published topology, the multilevel-active-clamped (MAC) topology. In order to assess the MAC topology, an efficiency comparison between a four-level MAC leg and a conventional two-level leg operating in low voltage is carried out. First, overall losses of both topologies are estimated. Then, experimental tests to measure their overall losses and their efficiency are presented. Finally, obtained results from the experimental tests are compared with the estimations to substantiate the analysis. The efficiency of the MAC topology is higher in all the switching-frequency range., Postprint (published version)

Thanks to the inherent redundancy to generate the different output voltage levels, the multilevel active-clamped (MAC) topology presents an important fault-tolerance ability which makes it interesting for several applications. This paper presents an analysis of the fault-tolerance capacity of the MAC converter. Both open-circuit and short-circuit faults are considered, and the analysis is carried out under single-device and two simultaneous device faults. Switching strategies and different hardware modifications to overcome the limitations caused by faults are proposed. Experimental tests with a four-level MAC prototype are presented to validate the analysis., Postprint (published version)

A partir del control predictiu d’un inversor de tres nivells programat sobre Matlab- Simulink, s’ha traduït el programa a llenguatge de programació C per tal de millorar la seva velocitat d’execució. S’han ofert dos programes diferents amb la mateixa finalitat i s’ha demostrat, mitjançant les simulacions, el correcte funcionament de tots dos, amb una considerable millora del segon programa presentat respecte del primer.

Aquest estudi pretén donar a conèixer un procediment genèric per realitzar diversos projectes tècnics, els passos que cal seguir davant de l’administració pública per tal de legalitzar les activitats i instal·lacions i la descripció dels requisits mínims que han d’incloure. També s’han inclòs casos pràctics reals mitjançant el procediment genèric descrit. Finalment, aquests casos pràctics reals, s’han adequat tecnològicament a la normativa vigent d’aplicació.

Aquest treball consisteix en realitzar l’estudi , el disseny i la construcció d’un circuit de protecció per a un interruptor bidireccional, per evitar les sobretensions generades en la seva commutació. S’estudien aquestes sobretensions, que poden arribar a ser més de dues o tres vegades la tensió de bloqueig del semiconductor en condicions normals, per tant poden arribar a destruir el component. Es proposen diferents tipus de circuits de proteccio, i es realitza una comparativa dels resultats obtinguts amb cada un d’ells. Finalment en aquest treball es construeix una combinació de dos circuits, amb el que es comprova la reducció de les sobretensions.

Este proyecto consiste en estudiar, diseñar y montar un sistema de transmisión de datos con fibra óptica, para señales de carácter TTL, y será aplicado a un inversor trifásico de tres niveles.

Thanks to the inherent redundancy to generate the different output voltage levels, the multilevel active clamped (MAC) topology presents an important fault-tolerance ability which makes it interesting for several applications. This paper presents an analysis of the fault-tolerance capacity of the MAC converter. Both open-circuit and short-circuit faults are considered and the analysis is carried out under single-device and two-simultaneous-device faults. Switching strategies to overcome the limitations caused by faults are proposed. Experimental tests with a four-level MAC prototype are presented to validate the analysis., Postprint (published version)

El proyecto desarrollado consiste en poner en marcha un interruptor bidireccional de potencia que permita conmutar entre dos entradas de potencia sobre una salida, de manera que la corriente no sufra ningún tipo de discontinuidad. Este interruptor bidireccional debe considerar el sentido de la corriente. Más específicamente, en el proyecto se ha realizado todo el cableado relacionado con el circuito de potencia (hardware) y el circuito de control del sistema (software), que se realiza mediante la tarjeta DS1102 de dSPACE. La conmutación entre las dos entradas de potencia se realizará mediante la conmutación de cuatro MOSFETs. Toda la programación para el correcto funcionamiento del proceso de conmutación de los MOSFETs y del control del proyecto se realiza desde el PC con el programa MATLAB-Simulink.

The increasing influence of wind power in the power system operation has caused the power system operators to include wind power plants in the control of the overall power system, both in steady-state and transient operation. Therefore, the grid connection requirements of the power system operators involve wind power systems. Low voltage ride-through requirement is probably the most demanding grid connection requirement to meet, at least from the point of view of the wind energy conversion system. In presence of grid voltage dips, the low voltage ride-through compliance produces a mismatch between the generated active power and the active power delivered to the grid. The management of this mismatch supposes a challenge for the wind energy conversion system. In this work, a control scheme for the back-to-back neutral-pointclamped converter is proposed. Under grid voltage dip, the controllers for generator-side and grid-side converters work concurrently to meet the low voltage ride-through requirement by storing the active power surplus in the inertia of the generator and keeping constant the dc-link voltage. Simulation results verify the proposed control scheme., Peer Reviewed, Postprint (published version)

This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder, A novel noninverting boost-buck dc-dc converter topology is presented, applicable when both sides of the converter need to have the same grounding. It is based on the back-to-back connection of two n-level diode-clamped converter legs, and allows bidirectional power flow. A simplified topology is proposed for unidirectional power flow applications. Two new pulse width modulation strategies with different advantages are proposed to operate the converter guaranteeing dc-link capacitor voltage balance in every switching cycle for all possible operating conditions and using small capacitance values. The semiconductor device losses are analytically compared to the losses in a conventional two-level boost-buck converter. The analysis yields a higher efficiency for the multilevel converter, especially as the number of levels increases. Experimental results are presented to validate the good converter performance in a five-level converter prototype., Peer Reviewed, Postprint (published version)

Resumen: El proyecto desarrollado contiene dos objetivos principales: 1. Guía para emplear las herramientas de programación del DSC TMS320F28335. 2. Realización de una aplicación en tiempo real Para conseguir el primer objetivo se ha realizado un estudio de las herramientas de programación contenidas en el software CCStudio v3.3, desarrollado por Texas Instruments. En el proyecto se ha utilizado un kit de evaluación eZdsp F28335, el cual contiene el Controlador de Señales Digitales (DSC) TMS320F28335, una tarjeta de evaluación con los conectores necesarios para su conexión al ordenador, y un CD con el software y drivers necesarios. Además se ha desarrollado una aplicación en tiempo real con la tarjeta de evaluación. La aplicación desarrollada realiza el control predictivo de un inversor de tres niveles. Para desarrollar dicha aplicación se ha tenido que realizar la puesta en marcha de la tarjeta de evaluación y crear el hardware necesario para acondicionar las señales de entrada y salida del DSC al inversor de tres niveles.

In the previous literature, the introduction of the virtual space vector concept for the three-level three-leg neutral-point-clamped converter has led to the definition of pulsewidth modulation (PWM) strategies guaranteeing the dc-link capacitor voltage balance under any type of load, with the only requirement being that the addition of the three phase currents equals zero. This paper presents the definition of the virtual space vectors for the general case of an n-level converter, suggests guidelines for designing virtual-space-vector PWM strategies, and provides the expressions of the phase duty-ratio waveforms corresponding to this family of PWMs. Modulations defined upon these vectors enable the use of diode-clamped topologies with passive front-ends. The performance of these converters operated with the proposed PWMs is compared to the performance of alternative designs through analysis,simulation and experiments., Postprint (published version)

This paper presents a three-level three-phase neutral-point-clamped back-to-back converter applied to a wind emulator, where a wind power generator is connected to the grid through the back-to-back converter. The converter regulates the power extracted from the generator and controls how this power is injected to the grid with the desired power factor. Two phase locked loops are in charge of synchronizing the generator-side and the grid-side converters, regardless of the rotor speed of the generator. DC-link neutral point voltage balance is performed by the modulation strategy of the back-to- back converter. Simulation and experimental results are provided to verify the correct performance of the system., Peer Reviewed, Postprint (published version)

This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder., In presence of grid voltage dips, Low Voltage Ride-Through (LVRT) requirements demand the wind power plant to remain connected to the grid, helping the network to keep voltage and frequency stable. Neutral-Point-Clamped (NPC) converters are appropriate for wind power systems, because the current trend of increasing voltage levels. Predictive current control presents as fast dynamic response and accurate reference tracking as other well established control methods, while providing more flexibility. In this work, three different control strategies are applied to the grid-side NPC converter, in order to fulfil LVRT requirements, which are implemented with the predictive current control technique. Dc-link neutral point voltage is kept balanced by the predictive control algorithm, using the redundant switching states of the NPC converter. Simulation results confirm the validity of the proposed control approach., Peer Reviewed, Postprint (published version)

In the previous literature, the introduction of the virtual space vector concept for the three-level three-leg neutral-point-clamped converter has led to the definition of pulsewidth modulation (PWM) strategies guaranteeing the dc-link capacitor voltage balance under any type of load, with the only requirement being that the addition of the three phase currents equals zero. This paper presents the definition of the virtual space vectors for the general case of an n-level converter, suggests guidelines for designing virtual-space-vector PWM strategies, and provides the expressions of the phase duty-ratio waveforms corresponding to this family of PWMs. Modulations defined upon these vectors enable the use of diode-clamped topologies with passive front-ends. The performance of these converters operated with the proposed PWMs is compared to the performance of alternative designs through analysis, simulation and experiments., Peer Reviewed, Postprint (published version)

El proyecto consiste en el diseño de un parque solar fotovoltaico de 100 kW con conexión a red utilizando una estructura soporte de inclinación variable, entre 20º y 55º. El parque solar se ha situado en una parcela de 2.000 m², que pertenece al término municipal de Xerta, en la provincia de Tarragona. La dimensión del parque permite generar 115.500 Wp de potencia, y está constituido por 700 paneles de 165 Wp de potencia nominal unitaria, conectándose 20 paneles en serie y un total de 35 filas en paralelo. Los valores de tensión y corriente continua de entrada en el inversor son 860 V y 178,85 A, respectivamente. Un inversor con una potencia nominal de 100 kW convertirá la tensión y corriente generada de continua a alterna. El centro transformador trabajará con la relación 420V/36kV para inyectarla a la red de distribución. La viabilidad económica vendrá determinada por los 193.447 kW/h generados anualmente. El estudio de viabilidad económica se determina a una vida útil de la instalación de 25 y 30 años, considerando una financiación bancaria del 80% de la inversión inicial. La inversión inicial asciende a 464.888 €, siendo el tiempo de retorno de 9 años para una inversión de 25 años, un VAN de 380.499,11 € y una TIR del 18,13%. En el caso de optar por una inversión a 30 años, se consigue la misma tasa de tiempo de retorno en 9 años, un VAN de 418.674,68 € y una TIR del 18,27%. Tras el estudio de viabilidad económica, se concluye como un proyecto viable.

This paper presents a new Power Electronic Building Block (PEBB) designed to facilitate the implementation of different power converter topologies. The proposed PEBB consists of two diodes and two transistors and it can be used to implement the most relevant power converter topologies, due to its modularity. The addition of the two diodes is an exclusive feature of the new PEBB, which permits to implement neutral point clamped (NPC) multilevel converters. The application of the PEBB to build a three-level NPC converter and a dc-dc push-pull converter is presented and detailed in the paper, and demonstrate that the presented PEBB can be useful to shorten converter development times., Peer Reviewed, Postprint (published version)

Low-voltage ride-through (LVRT) requirements demand wind-power plants to remain connected to the network in presence of grid-voltage dips. Most dips present positive-, negative-, and zero-sequence components. Hence, regulators based on symmetrical components are well suited to control gridconnected converters. A neutral-point-clamped topology has been considered as an active front end of a distributed power-generation system, following the trend of increasing power and voltage levels in wind-power systems. Three different current controllers based on symmetrical components and linear quadratic regulator have been considered. The performance of each controller is evaluated on LVRT requirement fulfillment, grid-current balancing, maximum grid-current value control, and oscillating power flow. Simulation and experimental results show that all three controllers meet LVRT requirements, although different system performance is found for each control approach. Therefore, controller selection depends on the system constraints and the type of preferred performance features., Peer Reviewed, Postprint (published version)

La presente tesis estudia, propone y realiza sus principales aportaciones en el campo del control para el convertidor CC/CA de tres niveles, sobre la topología denominada Neutral-Point-Clamped, aunque se puede extender a otras topologías y/o número de niveles. Se presenta una metodología de modelado que emplea funciones de conmutación de fase, el operador de promediado y la transformación D-Q, tal que los modelos obtenidos en el dominio D-Q contienen una información completa sobre la dinámica del sistema. La estrategia de conmutación se puede entender como una extensión de la estrategia PWM senoidal de dos a tres niveles. Esta estrategia es simple y no realiza el control de ninguna de las variables del sistema. En esta tesis, el controlador se encarga de regular todas las variables del sistema, incluido el equilibrio del bus de continua. Este es un enfoque diferente del convencional, donde el equilibrio del bus de continua se consigue mediante la elección adecuada de los estados redundantes del convertidor en la estrategia de conmutación, mientras que el resto de variables se regulan a través del controlador. Para la realización del controlador, se propone la técnica de control lineal multivariable LQR (Linear Quadratic Regulator), complementada con la técnica de control no lineal adaptativo denominada programación de ganancia (Gain Scheduling). Se presenta, además, una metodología de cálculo del controlador. Este control es versátil, abierto y adaptable. En cualquier caso, el controlador se puede adaptar a las necesidades concretas de cada aplicación. El cálculo del controlador se realiza mediante simulación con MatLab-Simulink. Los modelos matemáticos que emplean las funciones de conmutación del convertidor son aquellos que ofrecen un mejor compromiso entre velocidad de simulación y precisión. Para validar el control propuesto, se ha diseñado y construido un equipo experimental donde el controlador se ha mostrado aplicable, útil y eficaz en la regulación de las di, This dissertation study, propose and carry out the main contributions in the field of three-level inverter control, using the topology Neutral-Point-Clamped, although results can be extended to other topologies and/or number of levels. A procedure for modelling is presented, based on line-switching functions, moving average operator and D-Q transformation. Then, the obtained models in D-Q frame contain complete information about system dynamics. Switching strategy is simple and can be considered as an extension of two-level sinusoidal PWM to three level. The system variables are not controlled by the switching strategy. In this work, all the system variables are controlled by the regulator, including DC-link balance. This control approach is different than the conventional one, where DC-link balance is achieved by means of a proper selection of redundant states in the switching strategy, and the other variables are controlled by the regulator. The regulator is based on the multivariable linear control technique LQR (Linear Quadratic Regulator), in combination with the non-linear adaptive control technique Gain Scheduling. Moreover, a methodology for the calculation of the controller is presented. This controller is versatile, open and adaptable. However, the controller can be built depending on the concrete specifications of each application. The controller is calculated by means of simulation using MatLab-Simulink. The mathematical models based on the switching functions of the converter give the best trade-off between simulation speed and precision. In order to validate the proposed controller, an experimental prototype has been designed and implemented. Experimental results show that the controller is useful and effective for the regulation of different loads and applications, even with non-linear loads, different operation points and variables to control, in steady-state and transitory operation. Dynamic response speed and quality are similar to other control sy, Postprint (published version)