Modular platform for research in microgrids

The present Ph.D. thesis has been developed following an Industrial Ph.D. program and verses on developing a commercial piece of equipment for teknoCEA, a spin-off company from CITCEA-UPC. The thesis is centered on developing power electronics-based emulation systems for research in microgrids. Lately, the use of power electronics-based emulation systems is drawing substantial attention in the field of microgrids because their characteristics substantially facilitate research in laboratory facilities. First, the suitability of different topologies for implementing an emulation platform is analyzed. The focus is set on the topologies adjustability to implement various types of emulation systems. The analysis determines the most appropriate number of legs for the platform. A comparative analysis is done between two-level and multi-level topologies to determine their suitability based on different aspects. Moreover, the analysis confirms the usefulness of wide-bandgap semiconductors for this type of application. Next, a control structure is proposed together with its implementation in a low-cost microcontroller based on a modular software architecture. The control strategy based on fractional proportional resonant controllers for AC emulation systems provides a control system with high control bandwidth while keeping a low computational cost. The control strategy for DC emulation systems is provided to reach a fast transient response and immunity to external disturbances, which is key for good emulation of electric systems. The modular software architecture provides a software framework easily adjustable to the needs of multiple emulation systems. That allows the implementation of the multiple control strategies with minimum changes. Additionally provides a graphical representation of the software architecture from a static and dynamic point of view. Last, the reliability of the proposed platform is assessed based on the reliability curves provided in the literature. The reliability analysis is centered on the semiconductors and capacitors. It provides evidence that emulation systems typical currents and voltages clearly affect their reliability. For the capacitors reliability assessment, a thermal modeling methodology is proposed to overcome the limitations of standard approximations. The methodology is based on anisotropic modeling of the capacitor winding. Finally, the reliability analysis establishes the guidelines to assess the platform reliability if a given mission profile is provided.La present tesi doctoral s'ha dut a terme seguint un programa de doctorat industrial. La tesi exposa el desenvolupament d'un equip comercial per a teknoCEA, una spin-off del CITCEA-UPC. La tesi es centra en el desenvolupament d'emuladors basats en electrònica de potència per recerca en el camp de les microxarxes. Darrerament, l'ús d'emuladors s'ha estès ja que les seves característiques faciliten molt la recerca en laboratoris. En primer lloc, s'analitza la idoneïtat de diferents topologies per implementar una plataforma d'emulació. El focus recau en la capacitat de diferents topologies per ajustar-se a la implementació de múltiples sistemes d'emulació. L'anàlisi determina el número òptim de branques. Un anàlisi comparatiu entre topologies dos nivells i multinivell permet determinar-ne la idoneïtat en funció de diferents aspectes. A continuació, es proposa una estructura de control juntament amb la seva implementació en un microcontrolador de baix cost a partir d'una arquitectura de programari modular. L'estratègia de control basada en controladors FPR (fractional proportional resonant) per a emuladors de corrent altern, proporciona un sistema de control amb un gran ample de banda amb un baix cost computacional. L'estratègia de control proposada per emuladors de corrent continu proporciona una resposta transitòria ràpida i elevada immunitat a pertorbacions, aspecte clau per a una bona emulació de sistemes elèctrics. L'arquitectura de programari modular proporciona un marc de programari fàcilment ajustable a les necessitats de múltiples emuladors. Això permet la implementació de les múltiples estratègies de control amb canvis mínims. A més, ofereix una representació gràfica de l'arquitectura del programari tant des d'un punt de vista estàtic com dinàmic. Finalment, s'avalua la fiabilitat de la plataforma a partir de les corbes de fiabilitat disponibles a la bibliografia científica. L'anàlisi es centra en els semiconductors i condensadors i proporciona evidència que els corrents i les tensions típics en emuladors afecten la seva fiabilitat. Per a l'avaluació de la fiabilitat dels condensadors, es proposa una metodologia de modelització tèrmica que permet superar les limitacions de les metodologies emprades típicament en la bibliografia científica. La metodologia es basa en el modelatge del bobinat del condensador com un element anisòtrop. Per últim, l'anàlisi de fiabilitat estableix les pautes per avaluar la fiabilitat de la plataforma en el cas que es proporcioni un perfil d'operació determinat.Postprint (published version

Design, control and testing of a modular multilevel converter with a single cell per arm in grid-forming and grid-following operations for scaled-down experimental platforms

Modular multilevel converters (MMC) can be used in several applications, especially (but not only) in high-voltage direct current (HVDC) and STATCOM. In order to develop experimental scaled-down test benches for lab validation, several projects have developed MMCs with a limited number of cells, but they need to use pulse width modulation (PWM) techniques to achieve acceptable power quality (because nearest level modulation (NLM), common in HVDC applications with hundreds of levels, cannot achieve sufficient power quality unless the number of cells is high enough). The present paper proposes a new concept which is based on designing arms with a single cell. This allows to have the simplest possible converter that maintains the structure of an MMC. While all the inner controllers of large-scale HVDC MMCs are included, the only remarkable difference is that PWM is used and NLM cannot be implemented. As this is also a limitation for other low voltage MMC, the proposed concept is suggested for scaled-down low voltage applications. The paper includes the design and construction of the converter, the definition and implementation of the converter controllers, and the converter testing, with detailed dynamic simulations and an experimental setup.Peer ReviewedPostprint (published version

Semiconductores de banda de prohibición ancha

En los últimos años han aparecido nuevos materiales semiconductores que mejoran las propiedades de los empleados hasta la actualidad. Este artículo reflexiona sobre las ventajas e inconvenientes que estos nuevos materiales pueden aportar al campo de la electrónica de potencia y cuáles serán las consecuencias para los usuarios

Semiconductores de banda de prohibición ancha

En los últimos años han aparecido nuevos materiales semiconductores que mejoran las propiedades de los empleados hasta la actualidad. Este artículo reflexiona sobre las ventajas e inconvenientes que estos nuevos materiales pueden aportar al campo de la electrónica de potencia y cuáles serán las consecuencias para los usuarios

Multipurpose emulation platform for research in microgrids

This paper proposes the outline design of a platform that can be used to implement multiple emulators to replicate the behaviour of different energetic resources, storage systems, loads or electric grids. This platform can be used to test control algorithms of microgrids with different elements connected into it.Postprint (author's final draft

Multipurpose emulation platform for research in microgrids

This paper proposes the outline design of a platform that can be used to implement multiple emulators to replicate the behaviour of different energetic resources, storage systems, loads or electric grids. This platform can be used to test control algorithms of microgrids with different elements connected into it

Resonant load emulator for distributed energy resources to test anti-islanding algorithms

A resonant load emulator for distributed energy resource inverters to test anti-islanding algo- rithms is presented. This emulator allows to change the operation conditions that can be applied during development, test and certification of an inverter under resonant loads. It is based on a three-phase three-wire inverter that exchanges the required currents imitating the behavior of real resonant loadsPostprint (published version

Resonant load emulator for distributed energy resources to test anti-islanding algorithms

A resonant load emulator for distributed energy resource inverters to test anti-islanding algo- rithms is presented. This emulator allows to change the operation conditions that can be applied during development, test and certification of an inverter under resonant loads. It is based on a three-phase three-wire inverter that exchanges the required currents imitating the behavior of real resonant load

Impact absorbing surfaces for children's playgrounds

SIGLEAvailable from British Library Document Supply Centre-DSC:q97/16307 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Development and implementation of a dynamic PV emulator with HMI interface for high power inverters

In this paper a 10 kVA photovoltaic emulator is presented. The system implemented generates photovoltaic V-I characteristic curves to analyse and test maximum power point tracking algorithms of real photovoltaic inverters according to the standard EN50530. The power converter used includes a threephase ac-dc active rectifier. The power stage selected allows to minimize the harmonic current content and permits to be closed to the unity power factor with a fast response. The emulator is controlled by a digital signal processor that communicates with a human-machine-interface. It allows to emulate static and dynamic responses. Furthermore, the interface is also capable of simulating weather evolution and situations under shaded conditions