Diseño y realización de un convertidor multinivel cc-cc-ca en cascada para la conexión a red eléctrica de sistemas fotovoltaicos

El presente proyecto nace con la idea de mejorar el diseño la primera generación de PEBBs (Power Electronic Building Blocks o bloques constitutivos electrónicos de potencia) realizados en el PFC de Elena Argüelles. Un PEBB consiste en un módulo integrado y compuesto por una serie de elementos utilizados en los sistemas electrónicos de potencia, como pueden ser dispositivos semiconductores, circuitos integrados de potencia, circuitos drivers, fuentes de alimentación, circuitos de protección, sensores de temperatura, corriente o tensión, etc. Estos módulos se interconectan de la manera conveniente para la realización de diferentes topologías de convertidores electrónicos de potencia. Los enfoques de mejora de los módulos están destinados a aumentar la potencia que pueden procesar, mejorar su constructibilidad, mejorar el acceso a la toma de medidas y mejorar su diseño mecánico. El correcto funcionamiento de los nuevos módulos funcionales se prueba con la realización de un doble convertidor cc-cc-ca en cascada, cuyo diseño se basa en que pueda servir para conectar a red eléctrica la instalación fotovoltaica que se encuentra en la cubierta de la ETSEIB. El doble convertidor a realizar consiste primeramente en un Push-Pull, el cual tiene la finalidad de aumentar la tensión del bus de continua y permite introducir un transformador de aislamiento de alta frecuencia. Seguidamente se conecta un inversor trifásico de 3 niveles de la topología NPC (Neutral Point Clamped), que permite generar la tensión trifásica que posteriormente se conectaría a la red eléctrica. Después de la realización de los nuevos módulos funcionales, se puede decir que se ha logrado el objetivo previsto, ya que la nueva generación de PEBBs permite procesar casi 5 veces más de potencia, además de haber mejorado significativamente su constructibilidad, su medibilidad y su diseño mecánico. Se han realizado los dos convertidores con la utilización de estos PEBBs y se ha probado experimentalmente cada uno por separado. Los resultados han sido correctos, aunque el inversor trifásico de 3 niveles no se pudo probar a muy alta potencia porque alguno de los drivers daba señal de error. En un futuro inmediato se intentará solucionar el problema del inversor para que pueda ser probado a elevadas potencias. Como propuesta futura se plantea verificar experimentalmente la modulación simulada por ordenador en el PFC de Mónica Pietzsch basado en el inversor de 3 niveles NPC. Del mismo modo se propone realizar las pruebas experimentales con la conexión del doble convertidor a la instalación fotovoltaica y a la red eléctrica

Design and analysis of a novel multilevel active-clamped power-converter

Multilevel converter technology has been receiving increasing attention during the last years due to its important advantages compared to conventional two-level conversion. Multilevel converters reduce the voltage across each semiconductor. These converters also synthesize waveforms with better harmonic spectrum, and in most cases, increasing the efficiency of the power conversion system. However, a larger quantity of semiconductors is needed and the modulation strategy to control them becomes more complex. There are three basic multilevel converter topologies: diode clamped, flying capacitor, and cascaded H-bridge with separate dc sources. Numerous hybrid configurations combining them and other multilevel topologies have also been presented in the literature. A novel multilevel active-clamped (MAC) topology is the subject of study of the present thesis. This topology is derived from the generalized multilevel topology by simply removing all flying capacitors. The topology can also be seen as an extension into an arbitrary number of levels of the three-level active neutral-point-clamped (ANPC) topology. The novel converter is controlled using a proper set of switching states and a switching state transition strategy, which permits to obtain the maximum benefits from the converter. In this thesis, the performance and operating capabilities of the MAC topology are studied through comprehensive efficiency and fault-tolerance analyses. The efficiency analysis comprises a study of power-device conduction and switching losses in the topology, followed by analytical and experimental efficiency comparisons between the MAC converter and conventional two-level converters. In the analysis of the fault-tolerance capacity of the MAC topology both open- 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 and topology variations to increment the fault-tolerance ability of the MAC converter are proposed. The thesis also proposes guidelines to guarantee a proper MAC converter design and improve its performance

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

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

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

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

Decoupled DC-Link capacitor voltage control of DC-AC multilevel multileg converters

© 2015 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 worksThis paper studies the coupling between the capacitor voltage control loops of diode-clamped (or functionally equivalent) multilevel multileg (multiphase) dc-ac converters. From a complete model of the plant revealing the coupling, a simple approach consisting in multiplying the vector of control commands by a constant matrix is proposed to decouple the control problem and achieve a better controller performance. Simulation and experimental results are presented to prove the superior performance of the proposed decoupled control.Postprint (author's final draft

Entrepreneurship Education: Creating A Positive Adrenaline

A method to develop Entrepreneurship Education in any regular Engineering course is presented. The method is based in a team of students working on the description of the idea for the development of a real start-up using a structured approach trained by a business advisor and by the teacher. The team analyses the problem, the potential market, the solution, the development and the financing challenges of the start-up. The team works the Case development along an Engineering Course related with the technology of the start-up. The dedication of each student to the Case development is 25 hours, working along the different phases of the analysis and synthesis, mentored by the business advisor and the teacher. The added value of the experience is based on: first, the preparation and development of a 1 hour interview of the student team with one of the founders of the company, usually the CEO; second, a weekly validation of the technological value proposition with the business advisor, as part of the analysis. Along with the interview, the student team will consolidate their findings and debate with the CEO about their own ideas, being a process full of positive adrenaline and creating a very significant engagement along the whole course. The approach has been tested in two academic years, working 4 cases with the collaboration of 4 start-ups of EIT InnoEnergy. The results of the student surveys demonstrate the validity and engagement level of the approach

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

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

2 transistors + 2 diodes-based PEBB designed for general applications in power electronics

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 ReviewedPostprint (published version

A novel pulsewidth modulation to operate a bidirectional two-stage dc-ac converter with high-frequency isolation in discontinuous conduction mode for photovoltaic applications

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 holderPeer ReviewedPostprint (author’s final draft

Model predictive current control of grid-connected neutral-point-clamped converters to meet low-voltage ride-through requirements

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