Current Issue : July - September Volume : 2014 Issue Number : 3 Articles : 7 Articles
To protect humans, devices and maintain high reliability of electrical equipments, efficient\nearthing system has to be provided for residential and commercial buildings. The use of chemical\nelements around the electrode of earthing systems reduces the earth resistance which improves\nthe efficiency of these systems. However, the use of these elements can�t achieve very small earth\nresistance especially in the case of dry clay. In addition, they are expensive and not available all\nthe time. This paper presents a method that treats the soil with adding the Dead Sea water instead\nof the chemical elements to further reduce the earth resistance and to avoid the expenses of these\nelements. In our approach, the Dead Sea water is added to a hole around the electrode with a distance\nnot exceeding 10 cm to avoid the corrosion layer on the electrode. Practical measurements\nare demonstrated to show the efficiency of the proposed approach....
Grid connected voltage source inverters (VSIs) are essential for the integration of the distributed energy resources.\nHysteresis current control (HCC) is a commonly employed method for power control of VSIs. This control\nmethod, in contrast with voltage control, provides good dynamics, good stability and implicit over current\nprotection. However, the most important concern of digital implementation of HCC is related with the sampling\nperiod of the measured currents. This paper presents a predictive hysteresis current control (HCC) for grid\nconnected voltage source inverter and its FPGA implementation. Simulation and experimental results are provided\nto verify the validity of the proposed implementation....
This study presents a method based on the experimental measurement of the short-circuit current\n(Icc) and the open circuit voltage (Vco) of the solar cell. It permits the determination of recombination\nparameters such as: diffusion length (L), back surface recombination velocity (Sb), intrinsic\njunction recombination velocity (Sjo), and macroscopic parameters in particular, the shunt and\nseries resistances of a bifacial solar cell for various illumination levels (n). Illumination level effects\non macroscopic parameters are highlighted....
Absorption enhancement has been considered as an effective way of improving coefficient of performance\n(COP) of refrigeration systems and magnetic enhancement is one of these methods. A\nmodel of magnetic field enhancement in ammonia-water absorption systems is presented in this\npaper. A numerical model using finite difference scheme was developed based on the conservation\nequations and mass transport relationship. Macroscopic magnetic field force was introduced in\nthe momentum equation. The model was validated using data obtained from the literature. Changes\nin the physical properties of ammonia solution while absorbing both in the direction of falling\nfilm and across its thickness were investigated. The magnetic field was found to have some positive\neffect on the ammonia-water falling film absorption. The results indicate that absorption performance\nenhancement increased with magnetic intensity. The COP of simple ammonia solution\nabsorption refrigeration system increased by 1.9% and 3.6% for magnetic induction of 1.4 and 3.0\nTesla respectively....
New method for determination of optimal placement and value of installed capacity of renewable\nsource of energy (RES) by the criterion of minimum losses of active power, that allows taking into\nconsideration the dependence of RES on natural conditions of region, schedule of energy supply,\nparameters and configuration of distribution network is suggested in the paper. Results of computations\nof test scheme confirm the efficiency of the proposed method and its simplicity as compared\nwith the methods considered in literature sources....
In this paper, we present the concept of transmitting power without using wires i.e., transmitting power as microwaves from one place to another is in order to reduce the transmission and distribution losses. This concept is known as microwave power transmission. This paper focuses on the past and future possible advancements in WPT and explaining why it has still not come into practical utility. Wireless energy transfer has been around for about a century, but not yet familiar and viable technology....
HVDC (High Voltage Direct Current) systems are increasingly being applied to improve power system operation\nand controllability. However, inappropriate setting of HVDC controller may have a detriment effect on the system\nperformance. Generally, PSS (Power System Stabilizer) is known as a simple concept, easy to perform, and\ncomputationally effective to enhance damping of power system oscillations through excitation control of synchronous\ngenerator. This paper examines the effectiveness of the PSS to enhance the dynamic performance of\nAC-DC power systems and to compensate the negative damping of HVDC system. The dynamic performance is\nevaluated by examining the system response to various disturbances. In order to ensure the reliability of the simulation\ntest results as well as the performance of the PSS, detailed HVDC modeling is adopted using SimPowerSystems\ntoolbox in the MATLAB, and some important conclusions are drawn....
Loading....