In a deregulated power market, customers would have more choices for their power service and the improvement of service quality has become a challenge to power transmission and distribution companies. Distribution system reliability that was traditionally considered within the planning activities, is now incorporated in the operational environment. This dissertation presents study results of a multi-objective feeder operation optimization problem that considers how to balance network efficiency, switching and reliability costs in a distribution network. The proposed method divides annual feeder load curve into multi periods of load levels and optimizes the feeder configurations for different load levels in annual operation planning. Customer load profiles and seasonal varying data of feeder section failure rates and customer interruption costs are considered. Simulations results demonstrate the time varying effects on the optimal distribution feeder reconfiguration and operation costs. A binary particle swarm optimization (BPSO) search is adopted to determine the feeder configuration in each time period. Test results indicate that not considering time varying effects and using only simplified fixed load and reliability parameters could underestimate the total loss to the utility and its customers.

The main focus of this thesis is placed on high frequency PCB signal Integrity Is-sues and RF/Microwave filters using EBG structures. From the signal Integrity aspect, two topics were mainly discussed. On one hand, the effect of increasing frequency on classical design rules for crosstalk reduction in PCBs was investigated experimentally and by full-wave simulations. An emphasis was placed on the 3×W spacing rule and the use of guard traces. Single-ended and differential transmission lines were considered. S-parameter measurements and simu-lations were carried out at high-frequency (up to 20 GHz). The results emphasize the necessity to reevaluate traditional design rules for their suitability in high frequency applications. Also, the impacts of using guard traces for high frequency crosstalk re-duction were clearly pointed out. On the other hand, the effect of high loss PCB ma-terials on the signal transmission characteristics of microstrip lines at high frequency (up to 20 GHz) was treated. Comparative studies were carried out on different micro-strip configurations using standard FR4 substrate and a high frequency dielectric ma-terial from Rogers, Corporation. The experimental results highlight the dramatic im-pact of high dielectric loss materials (FR4 and solder mask) and magnetic plating metal (nickel) on the high frequency signal attenuation and loss of microstrip trans-mission lines. Besides, the epoxy-based SU8 photoresist was characterized at high frequency (up to 50 GHz) using on-wafer conductor-backed coplanar waveguide transmission lines. A relative dielectric constant of 3.2 was obtained at 30 GHz. Some issues related to the processing of this material, such as cracks, hard-skin, etc, were also discussed. Regarding RF/Microwave filters, the concept of Electromagnetic Band Gap (EBG) was used to design and fabricate novel microstrip bandstop filters using periodically modified substrate. The proposed EBG structures, which don’t suffer conductor backing issues, exhibit interesting frequency response characteristics. The limitations of modeling and simulation tools in terms of speed and accuracy are also examined in this thesis. Experiments and simulations were carried out show-ing the inadequacies of the Spice diode model for the simulations in power electronics. Also, an Artificial Neural Network (ANN) model was proposed as an alternative and a complement to full-wave solvers, for a quick and sufficiently accurate simulation of interconnects. A software implementation of this model using Matlab’s ANN toolbox was shown to considerably reduce (by over 800 times) the simulation time of microstrip lines using full-wave solvers such as Ansoft’s HFSS and CST’s MWS. Finally, a novel cooling structure using a double heatsink for high performance electronics was presented. Methods for optimizing this structure were also discussed. / QC 20100809

Forecast and estimation on transmission line losses is a vital task in the daily operation and planning of the Swedish power system. The aim with this thesis is to design a new line loss prediction model at Svenska kraftnät (Svk), which provides a hourly forecast of the transmission line losses the next day for the Swedish bidding areas (SE1-SE4). The final goal is to reduce the additional cost related to inaccurate predictions. The developed model is based on regression analysis on historical line losses and estimated exchange flows between the adjacent bidding areas computed by linear programming. Simulation results for 2015 show that it is, with rather simple estimates and assumptions, possible to increase the prediction accuracy with up to 27% compared with the existing method and to reduce the related costs in a similar way. The study also shows that future modelling has potential to increase the precision even further and recommends a Neural Network approach as the next step. / Prognoser och estimering av stamnätsförluster är en central del i den dagliga driften av det svenska kraftsystemet. Den här uppsatsen har därför syftat till att utveckla en simuleringsmodell som ger en timvisprognos över morgondagens förluster i varje elområde (SE1-SE4). Detta verktyg är senare tänkt att precisera den dagliga upphandlingen av förluster och därmed minska kostnaden kopplad till osäkra prognoser. Den utvecklade modellen bygger på en regressionsanalys av tidigare uppmätta förluster och uppskattade transmissionsflöden mellan de närliggande elområdena beräknad med linjär programmering. Simulerignar för 2015 visar att, det med föhrhållandesvis enkla antaganden och uppskattningar av indata, går att precisera förlusterna med uppemot 27% jämfört med dagens prognos och därmed minska kostnaderna i liknande omfattning. Studien visar också att förbättringspotentialen är stor och rekommende-rar fortsatta studier utifrån en Neurala Nätverk modell.