<p>This thesis focuses on controller design and analysis for induction motor (IM) drives, flux control for electrically excited synchronous motors with damper windings (EESMs), and to enhance voltage sag ride-through ability and analysis for a wind turbine application with a full-power grid-connected active rectifier. The goal is to be able to use the existing equipment, without altering the hardware. Further, design and analysis of the stabilization of DC-link voltage oscillations for DC systems and inverter drives is studied, for example traction drives with voltage sags in focus.</p><p>The proposed IM controller is based on the field-weakening controller of Kim and Sul [31], which is further developed. Applying the proposed controller to voltage sag ride-through gives a cheap and simple ride-through system.</p><p>The EESM controller is based on setpoint adjustment for the field current controller. The analysis also concerns stability for the proposed flux controller.</p><p>The DC-link stabilization algorithm is designed following Mosskull [38], where a component is added to the current controller. The algorithm is further developed.</p><p>Analysis is the main focus, and concerns the impact of the different parameters involved. Proper parameter selection for the controller, switching frequency, and DC-link capacitor is given.</p><p>The impact of voltage sags is investigated for a power-grid-connected rectifier. Here, we analyze the impact of different types of voltage sags and phase-angle jumps. The analysis gives design rules for the DC-link capacitor and the switching frequency.</p><p>Experimental results and simulations verify the theoretical results.</p>

<p>The Reliability-Centred Asset Maintenance (RCAM) is a structured approach to determine maintenance strategies for electric power system which is developed at KTH School of Electrical Engineering. RCAM focus on reliability aspects of the system and one of the main steps in RCAM in to modeling the relationship between reliability and the elect of maintenance for critical components within the system. The transformer has been identified as a critical component within a power system and in spring 2006 the Ph.D project “<i>Life time modeling and management of</i> <i>transformers</i>” was started within the RCAM group. The overall goal for the project is to develop a quantitative model for the lifetime distribution of a transformer with the final goal to implement the developed model into a maintenance planning.</p><p>Dissolved Gas Analysis (DGA) is a widely used technique to estimate the condition of oil-immersed transformers. Incipient faults within the transformer may be detected by analyzing the gases which are dissolved in the transformer-oil. The objective of this thesis is mainly to analyze available data from DGA, and investigate if this kind of data may be useful in quantitative modeling of the transformers reliability.</p><p>One conclusion from this work is that the difficulty in modeling the transformers reliability lies mainly in the limited availability of adequate data. Transformer is a reliable device and since the number of failures in critical in mathematical modeling of a component´s reliability it becomes very difficult to determine such models. Another aspect is the difficulty to draw conclusions about a transformer´s condition only from the DGA results. Although there are standards available for this purpose the DGA interpretation should also be based on other information about the particular transformed such as size, construction and operation circumstance. During this work no sources have been found from which the correlation between DGA data and probability for transformer failures could be estimated. For this reasons the proposed failure rate function in this work is based on several subjective assumptions and has not been possible to verify.</p>

Den här uppsatsen är en C-uppsats för Programmet för Pedagogisk Mjukvaruutveckling, Högskolan i Halmstad, 2004. I denna uppsats undersöker vi vilken navigeringsdesign som kan vara lämplig att applicera på e-papperstidningar. Genom en kvalitativt förhållningssätt har vi genomfört en undersökning där vi har blandat observation med intervju samt kompletterat med en enkät. Vi har även inhämtat information från litteratur samt databaser som IEEE och ACM. En ryggrad i uppsatsen är Ben Shneidermans (1998) åtta gyllene regler för att uppnå en god gränssnittsdesign. Med detta som grund, angriper vi vårt problem. Resultatet av undersökning och teori beskriver hur den tilltänkta navigeringsdesignen kan se ut och vad användaren anser vara viktigt, ur navigeringssyfte, för den framtida e-papperstidningen. Kortfattat fann vi Shneidermans åtta gyllene regler applicerbara även på e-papperstidningen.

This thesis focuses on controller design and analysis for induction motor (IM) drives, flux control for electrically excited synchronous motors with damper windings (EESMs), and to enhance voltage sag ride-through ability and analysis for a wind turbine application with a full-power grid-connected active rectifier. The goal is to be able to use the existing equipment, without altering the hardware. Further, design and analysis of the stabilization of DC-link voltage oscillations for DC systems and inverter drives is studied, for example traction drives with voltage sags in focus. The proposed IM controller is based on the field-weakening controller of Kim and Sul [31], which is further developed. Applying the proposed controller to voltage sag ride-through gives a cheap and simple ride-through system. The EESM controller is based on setpoint adjustment for the field current controller. The analysis also concerns stability for the proposed flux controller. The DC-link stabilization algorithm is designed following Mosskull [38], where a component is added to the current controller. The algorithm is further developed. Analysis is the main focus, and concerns the impact of the different parameters involved. Proper parameter selection for the controller, switching frequency, and DC-link capacitor is given. The impact of voltage sags is investigated for a power-grid-connected rectifier. Here, we analyze the impact of different types of voltage sags and phase-angle jumps. The analysis gives design rules for the DC-link capacitor and the switching frequency. Experimental results and simulations verify the theoretical results. / QC 20101012

Diss. (sammanfattning) Linköping : Univ., 2005. / Härtill 7 uppsatser vilka återfinns i Vol. 2.

Diss. Linköping : Linköpings universitet, 2005.

No description available.

This master’s thesis investigates publishing of Swedish literary classics on the web. The purpose is to find out who is publishing and why, and what practice of publishing is used. The purpose is also to find out what importance the publishers attach to textual quality and proofreading. For these questions the “Guidelines for editors of scholarly editions” by MLA is used. The result gives a very scattered picture. Some of the publishers have professional experience in literature publishing and most of them are active in the literary field in one way or another. All the publishers give the overall impression of a true interest in literature and literature as the main purpose of publishing. All editions examined had all the standard information of printed books, ISBN excluded and all publishers except one also followed a good practice of web publishing with easy navigation and information concerning purpose and responsibility. The questions based on MLA’s guidelines revealed big differences between the publishers, some of which had all the information recommended for scholarly editions and some of which had nothing at all. Many of these publishers had other material in abundance though, such as pictures, recordings, musical notes and interactive material. The conclusion is that MLA’s guidelines are not best fitted to examine non-scholarly electronic publishing. A fair picture of many of the publishers in this study was given with other questions focusing navigation, design and other material. Finally, the different publishers are placed in three groups: “The critical editions” with high textual quality and a main purpose of serving the academic world; “The study editions” with their abundance of material and a main purpose of serving students at different levels and “The reading editions” with hardly any extra material and with a main purpose of serving readers - of telling a story. / Uppsatsnivå: D

No description available.

<p>Elektronisk handel är på väg att bli allt vanligare. Detta examensarbete behandlar en av de två olika typerna av elektronisk handel, nämligen webhandeln. Den andra varianten är EDI. Webhandel är den elektroniska handel som bedrivs mellan företag och privatpersoner, till skillnad från EDI som är handel mellan företag.</p><p>Det har blivit allt vanligare att företag kan erbjuda sina kunder att både beställa och betala via Internet. Det finns några olika sätt att betala för sina inköp, nämligen med betalkort, att vara medlem i ett shoppingtorg eller att använda digital valuta. Det kan dock vara riskfyllt att lämna ut sitt kontokortnummer på Internet, eftersom en skicklig och oärlig person skulle kunna avlyssna transaktionen och sedan använda kortnumret för egna inköp.</p><p>Mitt examensarbete är ett försök att reda ut hur farligt det egentligen är att betala via Internet. De problemställningar som har utretts är:</p><p>Vilka krav finns på säkerhet från de olika aktörerna på marknaden, dvs banker, webbutiker och kunder?</p><p>Vilket av betalningssätten uppfyller säkerhetskraven i störst utsträckning?</p><p>De slutsatser jag kommit fram till är:</p><p>De krav på säkerhet som ställs från de inblandade är att betalningen skall vara säker mot avlyssning, webbutik och kund skall kunna identifiera varandra samt kunden vill känna förtroende för att ingen information om hans köp hamnar i orätta händer.</p><p>Vad gäller säkerheten i de olika betalningssätten så anser jag att samtliga elektroniska betalningssätt uppfyller kraven, men att den allra säkraste metoden är SET - Secure Electronic Transactions.</p>