abstract: Modular multilevel converters (MMCs) have become an attractive technology for high power applications. One of the main challenges associated with control and operation of the MMC-based systems is to smoothly precharge submodule (SM) capacitors to the nominal voltage during the startup process. The existing closed-loop methods require additional effort to analyze the small-signal model of MMC and tune control parameters. The existing open-loop methods require auxiliary voltage sources to charge SM capacitors, which add to the system complexity and cost. A generalized precharging strategy is proposed in this thesis. For large-scale MMC-embedded power systems, it is required to investigate dynamic performance, fault characteristics, and stability. Modeling of the MMC is one of the challenges associated with the study of large-scale MMC-based power systems. The existing models of MMC did not consider the various configurations of SMs and different operating conditions. An improved equivalent circuit model is proposed in this thesis. The solid state transformer (SST) has been investigated for the distribution systems to reduce the volume and weight of power transformer. Recently, the MMC is employed into the SST due to its salient features. For design and control of the MMC-based SST, its operational principles are comprehensively analyzed. Based on the analysis, its mathematical model is developed for evaluating steady-state performances. For optimal design of the MMC-based SST, the mathematical model is modified by considering circuit parameters. One of the challenges of the MMC-based SST is the balancing of capacitor voltages. The performances of various voltage balancing algorithms and different modulation methods have not been comprehensively evaluated. In this thesis, the performances of different voltage-balancing algorithms and modulation methods are analyzed and evaluated. Based on the analysis, two improved voltage-balancing algorithms are proposed in this thesis. For design of the MMC-based SST, existing references only focus on optimal design of medium-frequency transformer (MFT). In this thesis, an optimal design procedure is developed for the MMC under medium-frequency operation based on the mathematical model of the MMC-based SST. The design performance of MMC is comprehensively evaluated based on free system parameters. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2020

Doctor en Ingeniería Eléctrica / Hoy en día, la construcción de maquinaria y plantas industriales exigen soluciones de accionamiento con un diseño flexible y escalable. En sectores industriales como la petroquímica, la minería, la generación de energía, etc., existe una demanda de soluciones con alta eficiencia, seguridad integrada y respaldo de las compañías proveedoras. En este contexto, el Convertidor Multinivel Modular (MMC) ha aparecido como una opción prometedora para accionamientos de media tensión de alta potencia debido a sus características, como modularidad total, flexibilidad de control, niveles de media tensión, calidad de potencia y posible operación sin transformador. Por lo tanto, esta tesis discute la aplicación del MMC para accionamientos de máquinas. El modelado del MMC y sus sistemas de control asociados para esta aplicación son analizados ampliamente en este documento. Específicamente, se ha propuesto un nuevo modelado basado en coordenadas dq y su sistema correspondiente sistema de control para regular el valor instantáneo de las tensiones de los condensadores del MMC. Además, se ha propuesto la integración de los sistemas de control de la máquina y del MMC para mejorar el rendimiento general del sistema. Por ejemplo, se demostró que las corrientes circulantes requeridas durante bajas frecuencias ac se reducen al considerar la interacción de ambos sistemas de control. La efectividad de las estrategias de control propuestas se validó a través de extensos resultados experimentales, que se han publicado en dos artículos (IEEE Transactions on Industrial Electronics) y seis artículos de conferencia (indexados en la base de datos Scopus), así como contribuciones importantes en otros proyectos relacionados con el control de convertidores multinivel modulares. El prototipo utilizado se compone de 18 celdas de potencia. El sistema se controla utilizando un procesador de señales digitales y dos FPGAs. Un segundo MMC con 12 celdas de potencia también se usó para algunas pruebas, conformando una unidad Back-to-Back MMC. Se probó el rendimiento dinámico y en estado estable de las metodologías de control propuestas, considerando el arranque del MMC, cambios escalón tanto en el par y las corrientes de magnetización, rampas de velocidad, pruebas de cruce por velocidad cero, operación de rotor bloqueado, operación con flujo debilitado, diferentes condiciones de carga, manipulación de la tensión dc del MMC, etc. En todos los casos, el rendimiento alcanzado es consistente con los resultados esperados. Nowadays, machinery and plant construction are demanding drive solutions with flexible and scalable design. In industrial sectors such as petrochemical, mining, power generation, etc., there is a demand for solutions with high efficiency, integrated safety and support from the supplier companies. In this context, the Modular Multilevel Converter (MMC) has appeared as a promising option for high-power medium-voltage drives due to their characteristics, such as full modularity, control flexibility, medium-voltage levels, power quality and possible transformer-less operation. Thereby, this thesis discusses the application of the MMC as a machine drive. The modelling and control systems required for this application are extensively analysed and discussed in this document. Specifically, a novel dq-based modelling of the MMC and its associated control system has been proposed to regulate the instantaneous value of the MMC capacitor voltages. Additionally, the integration of the machine and MMC control systems has been proposed to enhance the performance of the overall system. For example, it was demonstrated that the required circulating currents during low-ac frequencies are reduced by considering the interaction of both control systems. The effectiveness of the proposed control strategies is validated through extensive experimental results, which have been published in two journal papers (IEEE Transaction on Industrial Electronics) and six conference papers (indexed in the Scopus database), as well as important contributions in other projects related to the control of modular multilevel converters. The downscaled prototype utilised is composed of 18 power cells. The system is controlled using a Digital Signal Processor and two Field Programmable Gate Arrays (FPGAs). A second MMC with 12 power cells was also used for some tests, conforming a Back-to-Back MMC-based drive. The dynamic and steady-state performance of the proposed control methodologies were tested, considering the MMC starting-up, step changes in both the torque and magnetising currents, speed-ramps, zero-speed crossing test, rotor-locked operation, flux-weakening operation, different loading conditions, manipulation of the input voltage of the MMC, etc. In all cases, the achieved performance is consistent with the expected results.

This PhD thesis addresses the development of novel computational methods for designing modular structures i.e. structures composed of the assembly of identical components called modules. Current methodologies tackle this challenge by implementing topology optimization of the module but their efficiency is limited by the performance deterioration when numerous modules are used in the structure. In this work, the design of lightweight modular structures is addressed by simultaneously optimizing the topology of the modules and their respective position in the structure. This contribution also includes a novel strategy that reconciles lightness, structural performance, and constructability (i.e. fabrication and erection phases) by incorporating module rotations as additional design variables. To ensure the practical applicability of the proposed approach, stability is included to provide meaningful solutions that are globally stable and resist local buckling. For this purpose, global stability constraints using linear prebuckling are adopted, while local stability is formulated based on Euler buckling and properties of standard profiles obtained from commercial catalogues. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished

In a 2005 paper, Yang constructed families of Hilbert Eisenstein series, which when restricted to the diagonal are conjecturedto span the underlying space of elliptic modular forms. Oneapproach to these conjectures is to show the non-vanishing of an innerproduct of elliptic eigenforms with the restrictions of Eisensteinseries. In this paper, we compute this inner product locally by usingexplicit values of new vectors in the Waldspurger model.

Indiana University-Purdue University Indianapolis (IUPUI) / Nanoparticles (NPs) are an emerging technology in biomedical engineering with opportunities in diagnostics, imaging, and drug delivery. NPs can be prepared from a wide range of organic and/or inorganic materials. They can be fabricated to exhibit different characteristics for biomedical applications. The goal of this thesis was to develop NPs with tunable surface properties for selective cell targeting. Specifically, polyelectrolyte complexes composed of heparin (Hep, a growth factor binding glycosaminoglycan) and poly-L-lysine (PLL, a homopolymeric lysine) were prepared via a pulse sonication method. The Hep/PLL core NPs were further layered with additional Hep, tetrazine (Tz) modified Hep, or dextran sulfate (DS). The addition of Tz handle on Hep backbone permitted easy modification of NP surface with norbornene (NB) modified motifs/ligands, including inert poly(ethylene glycol) (PEG), cell adhesive peptides (e.g., RGD), and/or fluorescent marker. Both Hep and DS coated NPs could be readily internalized by J774A.1 monocytes/macrophages, whereas PEGylated NPs effectively reduced cellular uptake/recognition. The versatility of this NP system was further demonstrated by laying DS on the Hep/PLL NP surface. DS-coated NPs were recognized by J774A.1 cells more effectively. Furthermore, DS-layered NPs seemed to reduce IL-10 production on a per cell basis, suggesting that these NPs could be used to alter polarization of macrophages.

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In this thesis project, I have explored ways to reach spatial complexity through the use of a simple system of volumetric building elements. The ambition has been to draw an apartment building with emphasis on a variety in the apartment layouts as well as to let the functions of circulation, which I define as both shared and private functions such as stairs, elevators and passages, become an integrated part of the architectural expression. The volumetric building element, with proportions derived from our infrastructural norms as it requires transformation on a truck, is today an ubiquitous object or even an architectural typology of its own. When they are assembled, it can both become a system of similar parts or one new, larger object. The project has then also been a search for an architectural ambivalence between hiding and exposing the fact that a building is the outcome of a system.

Den här studien avser undersöka behovet av modularitet inom mjukvaruutveckling, dess implikationer på utvecklingsprocessen samt dess affärsnytta, men berör också tekniker för att uppnå modularitet. Detta är en fallstudie kring utvecklingen av Control Center, en flexibel och konfigurerbar plattform för data-management. Control Center har utvecklats för, och tillsammans med, Tuzame AB. Control Center är kundens interface för att hantera sin data och sin digitala plattform. Möjligheten att skapa en flexibel plattform för att snabbt kunna skapa olika typer av kundlösningar genom att välja komponenter från en testad kodbas kommer att undersökas. Rapporten har två huvudsakliga målsättningar; dels att beskriva hur utvecklingsarbetet kring en modulär plattform kan gå till, och dels att undersöka vilken påverkan en modulär plattform kan ha på utvecklingsprocessen av ett data management-verktyg på ett litet företag.  “CC is highly configurable and flexible data management tool which gives an easy and reliable way to access and modify data” - Pavel Getta, utvecklare på Tuzame AB / This study aims at investigating the need for modularity in software development, what implications it might have on the development process, what business value it might hold and touches on some techniques for achieving modularity. The study was done as a case study regarding the development of Control Center, a highly configurable and flexible data management tool. Control Center has been developed for, and in collaboration with, Tuzame AB. Control Center is the customer interface for handling their data and digital platform. The possibility to create a flexible platform to quickly create different types of customer solutions by selecting components from a tested code base will be investigated. The report has two main objectives; to describe how software development based on  a modular platform can improve the workflow, and to investigate the extent to which a modular platform can affect the development process of a data management tool in a small business. “CC is highly configurable and flexible data management tool which gives an easy and reliable way to access and modify data” - Pavel Getta, developer at Tuzame AB.

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