An improved voltage compensation approach in a droop-controlled DC power system for the more electric aircraft

This paper proposes an improved voltage regulation method in multi-source based DC electrical power system in the more electric aircraft. The proposed approach, which can be used in terrestrial DC microgrids as well, effectively improves the load sharing accuracy under high droop gain circumstance with consideration of cable impedance. Since no extra communication line and controllers are required, it is easily implemented and also increases the system modularity and reliability. By using the proposed approach the DC transmission losses can be reduced and system stability is not deteriorated for normal and fault scenarios. In this paper optimal droop gain settings are investigated and the selection of individual droop gains as well as the proportional power sharing ratio has been described. Experimental results validate the effectiveness of the proposed method

Analysis and Design of New Harmonic Mitigation Approaches

Numerous approaches have been proposed in order to resolve the problems of current harmonics in electrical distribution systems. The rapid development of power semiconductors along with the revolutionary advances on microprocessors consolidated the motor drives industry and with it a massive proliferation of non-linear loads. It was thought that these very same technological advances would trigger an explosive development of harmonic solutions based on power electronics. Moreover, the introduction of the instantaneous active and reactive power theory or the so-called p, q theory which simplifies and gives more robustness to the control strategies of active filters reinforced this idea. Three decades have passed since the first IGBT was introduced in early 1980s, and active harmonic solutions are not the first choice to solve harmonic pollution in electrical distribution systems, mainly due to the high cost and the perception of low reliability. Given this scenario, in this work two main approaches are explored. First, the combination of an asymmetric 18-pulse rectifier with a reduced KVA active harmonic filter to improve the performance under abnormal utility conditions. Second, an interleaved active harmonic filter using multiple inverters connected in parallel at the ac and dc size, which will allow for higher power ratings and power density increase. The performance issues of the asymmetric 18-pulse rectifier under unbalanced voltage and pre-existing harmonic components are analyzed, as well as the current distortion improvement, achieved when an active power filter is introduced. On the other hand, the high frequency harmonic cancellation when interleaved inverters are used, the circulation of zero-sequence current and the impact of interleaving on dc bus capacitor are analyzed. Finally, some methods to mitigate the low frequency circulating currents based on eliminating the zero-sequence component, and the introduction of common mode inductors to reduce the high frequency circulating current are studied. Without a doubt the search for new cost-effective topologies able to reach broader power levels and voltage ranges will continue emerging giving more alternatives to users. Moreover, extensive research on wide band gap devices such as Silicon Carbide (SiC) and Gallium Nitride (GaN), with which it is possible to reach higher voltage breakdown and at least an order-of-magnitude lower switching losses, makes the future more promising for active solutions

Паралельна робота DC-DC перетворювачів

У ході виконання роботи було розглянуто класифікацію та проведено порівняння різних типів паралельного з’єднання джерел напруги. Детально досліджено роботу та характеристики сонячних елементів. Зважаючи на проведених аналіз існуючих систем було розроблено новий тип системи керування для перетворювача постійної напруги в постійну нижчого рівня. Розраховано параметри та проаналізовано режими роботи. За допомогою моделювання в програмному середовищі Simulink досліджено роботу схеми на необхідне навантаження. Даний проект має високу ступінь актуальності, так як в наш час все частіше виникає питання про екологічно чистих установках, призначених для різних потреб людства.During the execution of the work was investigated different types of parallel connections of voltage sources was performed. The work and characteristics of solar cells are investigated in detail. Taking into account the analysis of existing systems, a new type of control system was developed for the constant voltage converter to a constant lower level. The parameters are calculated and the operating modes analyzed. Simulink simulates the work of the circuit on the required load. This project has a high degree of relevance, as in our time the question of ecologically clean installations intended for different needs of mankind is becoming more and more frequent

Software-based and regionally-oriented traffic management in Networks-on-Chip

Since the introduction of chip-multiprocessor systems, the number of integrated cores has been steady growing and workload applications have been adapted to exploit the increasing parallelism. This changed the importance of efficient on-chip communication significantly and the infrastructure has to keep step with these new requirements. The work at hand makes significant contributions to the state-of-the-art of the latest generation of such solutions, called Networks-on-Chip, to improve the performance, reliability, and flexible management of these on-chip infrastructures

Design and Analysis of Intelligent Fuzzy Tension Controllers for Rolling Mills

This thesis presents a fuzzy logic controller aimed at maintaining constant tension between two adjacent stands in tandem rolling mills. The fuzzy tension controller monitors tension variation by resorting to electric current comparison of different operation modes and sets the reference for speed controller of the upstream stand. Based on modeling the rolling stand as a single input single output linear discrete system, which works in the normal mode and is subject to internal and external noise, the element settings and parameter selections in the design of the fuzzy controller are discussed. To improve the performance of the fuzzy controller, a dynamic fuzzy controller is proposed. By switching the fuzzy controller elements in relation to the step response, both transient and stationary performances are enhanced. To endow the fuzzy controller with intelligence of generalization, flexibility and adaptivity, self-learning techniques are introduced to obtain fuzzy controller parameters. With the inclusion of supervision and concern for conventional control criteria, the parameters of the fuzzy inference system are tuned by a backward propagation algorithm or their optimal values are located by means of a genetic algorithm. In simulations, the neuro-fuzzy tension controller exhibits the real-time applicability, while the genetic fuzzy tension controller reveals an outstanding global optimization ability

Research in structural and solid mechanics, 1982

Advances in structural and solid mechanics, including solution procedures and the physical investigation of structural responses are discussed

Methoden und Beschreibungssprachen zur Modellierung und Verifikation vonSchaltungen und Systemen: MBMV 2015 - Tagungsband, Chemnitz, 03. - 04. März 2015

Der Workshop Methoden und Beschreibungssprachen zur Modellierung und Verifikation von Schaltungen und Systemen (MBMV 2015) findet nun schon zum 18. mal statt. Ausrichter sind in diesem Jahr die Professur Schaltkreis- und Systementwurf der Technischen Universität Chemnitz und das Steinbeis-Forschungszentrum Systementwurf und Test. Der Workshop hat es sich zum Ziel gesetzt, neueste Trends, Ergebnisse und aktuelle Probleme auf dem Gebiet der Methoden zur Modellierung und Verifikation sowie der Beschreibungssprachen digitaler, analoger und Mixed-Signal-Schaltungen zu diskutieren. Er soll somit ein Forum zum Ideenaustausch sein. Weiterhin bietet der Workshop eine Plattform für den Austausch zwischen Forschung und Industrie sowie zur Pflege bestehender und zur Knüpfung neuer Kontakte. Jungen Wissenschaftlern erlaubt er, ihre Ideen und Ansätze einem breiten Publikum aus Wissenschaft und Wirtschaft zu präsentieren und im Rahmen der Veranstaltung auch fundiert zu diskutieren. Sein langjähriges Bestehen hat ihn zu einer festen Größe in vielen Veranstaltungskalendern gemacht. Traditionell sind auch die Treffen der ITGFachgruppen an den Workshop angegliedert. In diesem Jahr nutzen zwei im Rahmen der InnoProfile-Transfer-Initiative durch das Bundesministerium für Bildung und Forschung geförderte Projekte den Workshop, um in zwei eigenen Tracks ihre Forschungsergebnisse einem breiten Publikum zu präsentieren. Vertreter der Projekte Generische Plattform für Systemzuverlässigkeit und Verifikation (GPZV) und GINKO - Generische Infrastruktur zur nahtlosen energetischen Kopplung von Elektrofahrzeugen stellen Teile ihrer gegenwärtigen Arbeiten vor. Dies bereichert denWorkshop durch zusätzliche Themenschwerpunkte und bietet eine wertvolle Ergänzung zu den Beiträgen der Autoren. [... aus dem Vorwort

Development of an in vitro blood flow model to evaluate antimicrobial coatings for blood-contacting devices

Pre-clinical evaluation of novel antimicrobial coatings for blood-contacting devices commonly relies on the performance of animal studies since alternative in vitro models do not adequately represent the interactions between blood, bacteria, and material surfaces as they occur in vivo. To reduce the need of these cost-intensive and controversial animal tests, this project was dedicated to the development of a new model setup that overcomes this limitation and allows in vitro evaluation under in vivo-like conditions. This newly developed model was intended to be directly applied to evaluate recently in-house developed antimicrobial coatings, so-called anchor polymers. Therefore, the project was divided into two parts. The first part of the project focused on the evaluation of the anchor polymer coatings concerning their applicability in blood-contacting devices. For this purpose, the PEGylated styrene-maleic acid copolymers were intensively studied using established laboratory tests. These examinations showed very promising results regarding adsorption and stability on relevant polymer substrates, antimicrobial efficacy, and biological safety of the coatings, thus revealing their great potential for future applications in medical devices. Moreover, this basic characterization was meant to allow a subsequent comparison of the new in vitro model with state-of-the-art in vitro tests. The second part of the thesis focused on the development of the realistic in vitro model. Here, a single-pass flow system realized the implementation of adjustable flow conditions. Furthermore, incubation with freshly drawn human blood provided a physiological nutrient environment and included the influence of an immune response. Staphylococcus aureus were chosen as representative microorganisms, as they are responsible for a majority of device-related blood stream infections. The resulting blood flow model was validated with one anti-adhesive and one contact-killing anchor polymer coating, confirming the model’s ability to differentiate the investigated surfaces. Inflammatory and coagulant blood activation correlated slightly with bacterial coverage, which in turn was strongly dependent on the investigated material surface. Incubation with varying flow conditions demonstrated the model’s capability to reflect the well-documented dependence of bacterial colonization and occurring flow conditions. In contrast to the state-of-the-art in vitro tests, the simultaneous incubation of test surface, bacteria and whole blood allowed the analysis of mutual interactions of the three parameters. Thus, the model represents an excellent method for pre-clinical evaluation of novel antimicrobial coatings for blood-contacting devices