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A new approach for AC state estimation based on a linear network model
, Article ELECO 2013 - 8th International Conference on Electrical and Electronics Engineering ; 2013 , Pages 117-121 ; 9786050105049 (ISBN) ; Fotuhi Firuzabad, M ; Aminifar, F ; Lehtonen, M ; Ozdemir, A ; Sharif University of Technology
Abstract
This paper presents a new and efficient formulation for the state estimation (SE) which can be solved in one single shot of computation. The proposed approach adopts line flows and the square of voltage magnitudes as the problem state variable and considers both active and reactive power quantities. The objective function is to minimize the weighted sum of the least square values of measurement residuals. The nonlinearity associated with line losses is left by assuming these values as slack variables. Numerical studies are conducted through two standard networks. In order to compare the performance of the proposed method, the conventional weighted least square (WLS) state estimation with...
Design and Analysis of a High Voltage Power Supply with Variable Output Voltage
, M.Sc. Thesis Sharif University of Technology ; Kaboli, Shahriyar (Supervisor)
Abstract
High voltage DC/DC converters are widely used in lasers, microwave tubes supplies, X-ray equipment, medical and industrial applications. Each of these applications have special attention to certain parameters such as output voltage ripple, fast stability, repeatability and accuracy. For power modulation in microwave tubes, the anode-cathode supply need to be varied. Generally such variations needs a high voltage DC supply so that, in a certain frequency each point can be controlled in specific voltage. Anode- cathode current flow is too low (in milliamps scale) so, the load of converter output can be assumed to be zero. The goal of this thesis is to design a DC/DC converter for Variable...
Micro helical polymeric structures produced by variable voltage direct electrospinning
, Article Soft Matter ; Volume 7, Issue 22 , 2011 , Pages 10548-10551 ; 1744683X (ISSN) ; Iraji Zad, A ; Abdollahzadeh, I ; Shirsavar, R ; Bonn, D ; Ejtehadi, R ; Sharif University of Technology
2011
Abstract
Direct near field electrospinning is used to produce very long helical polystyrene microfibers in water. The pitch length of helices can be controlled by changing the applied voltage, allowing the production of both microsprings and microchannels. Using a novel high frequency variable voltage electrospinning method we determined the helix formation speed and compared the experimental buckling frequency to theoretical expressions for viscous and elastic buckling. Finally we showed that the new method can be used to produce new periodic micro and nano structures
Modified shuffled-frog-leaping algorithm in company with neural networks for harmonic distortion minimisation in real-time control applications of programmed pulse-width modulation inverters
, Article IET Power Electronics ; Volume 4, Issue 8 , 2011 , Pages 943-950 ; 17554535 (ISSN) ; Mazaheri, B ; Abdi, B ; Hosseinian, S. H ; Sharif University of Technology
Abstract
Harmonic pollution minimisation in voltage-source programmed pulse-width modulation (PPWM) inverters is defined as a time-limited optimisation problem in real-time applications with variable DC sources. In order to obtain minimum total harmonic distortion (THD) as the objective function, shuffled-frog-leaping algorithm (SFLA) is modified and employed to calculate the switching angles and compared with non-linear programming as a traditional optimisation method. In addition, particle swarm optimisation and three of its modified versions as popular evolutionary optimisation algorithms are employed to ensure the capability of the proposed optimisation method. Moreover, modified sinusoidal PWM...