ABSTRACT Social networks have become one of our daily life activities not only in socializing but in e-commerce, e-learning, and politics. However, they have more effect on the youth generation all over the world, specifically in the Middle East. Arabic slang language is widely used on social networks more than classical Arabic since most of the users of social networks are young-mid age. However, Arabic slang language suffers from the new expressive (opinion) words and idioms as well as the unstructured format. Mining ...

ABSTRACT Social networks have become one of our daily life activities not only in socializing but in e-commerce, e-learning, and politics. However, they have more effect on the youth generation all over the world, specifically in the Middle East. Arabic slang language is widely used on social networks more than classical Arabic since most of the users of social networks are young-mid age. However, Arabic slang language suffers from the new expressive (opinion) words and idioms as well as the unstructured format. Mining ...

In this article, network reconfiguration and distributed generation allocation in distribution networks are dealt with simultaneously while imposing an objective of minimizing energy loss. The proposed method, which is based on a genetic algorithm, takes into consideration the uncertainty related to renewable distributed generation output power and the load variability. Three scenarios are assessed to analyze the superiority of the proposed method. In the first scenario, distributed generation units are allocated using the base configuration, followed by network reconfiguration. In the second scenario, distributed generations are allocated after network reconfiguration. In the third scenario, distributed generations are allocated simultaneously with network reconfiguration. The constraints involved include voltage limits, line current limits, and radial topology. Both balanced and unbalanced distribution systems are used as case studies.

Micro Energy Grid (MEG) represents a natural step in the evolution to smart grids. In future, distribution system will operate according to interconnected micro energy grids. In MEG, both operational cost and emissions are, mainly, dependent on the types of distributed energy resources (DERs) used. Using DERs with multiple fuel options can reduce the generation costs and increase the reliability in power systems. This paper presents an approach to interconnected MEGs generation scheduling with multiple fuel options. The scheduling approach determines the optimal outputs of DERs on the basis of multi-objective genetic algorithm (GA) optimization compromising between the operational cost and emission of the entire interconnected MEGs system. DERs operate within their respective capacity limits and economically satisfy both electrical and heat demands. The global economic scheduling scheme coordinates power transactions among MEGs and between each MEG and the main electrical grid. Results show that power sharing among MEGs and between each MEG and the main electrical grid can reduce the total operational cost and emissions of the entire interconnected MEGs system.

ThelowfaultcurrentphenomenainthestandaloneMicro-Grid(MG)isaresultofelectronicinterfacingof theMGDistributedGenerators(DGs).DuetolowfaultcurrentphenomenaonthestandaloneMG,thereis a difficultyindifferentiatingbetweenthefaultdisturbanceandtheoverloadconditions.Thispaperpre- sentsacomprehensivesurveyaboutthestandaloneMGprotectionissuesandschemes.Allnewtrendsand schemesavailableandsuggestedforMGprotectionduringboththegridconnectedandthestandalone modesaredescribedindetails.Also,thispaperpresentsasimpletechniqueforsolvingtheproblemsdueto lowfaultcurrentphenomenainthestandaloneMG.Theproposedtechniqueisimplementedbycon- nectingallMGloadsneutralpointswiththeMGearthingsystemneutralline.Theproposedtechnique suppressesthetouchvoltagesatallMGbuses.Also,theproposedschemeresultsindoublingtheMGfault currentinthestandalonemode.Consequently,theMGprotectiondevicescaneasilydetectanddiffer- entiatebetweenthefaultdisturbancesandtheoverloadconditions.Also,theproposedtechniquedamps andsuppressesthetouchvoltagenotonlyatfaultlocationbutalsothroughalltheMGnetworkbuses.The mostcommonfaulttypes(singlephasetogroundanddoublephasetoground)areanalyzedindetails. Resultsprovedthat,employingtheproposedtechniqueabletosolvethelowfaultcurrentandthetouch voltagesproblemsfromtheirroots.Noadditionalhardwareisrequiredforimplementingthenewscheme. Theproposedtechniqueisverysimpleandhighlyeconomicalattractive.

Low rating and individual characteristics of the Distributed Generators (DGs) make the standalone Micro Grid (MG) weak power system. When the standalone MG contains wind generation system, special care should be taken during the starting process of the wind generation system to avoid the MG instability. This study proposes a new soft starting controller to improve the starting process of the wind generation system. In the proposed controller, both the wind turbine blade pitch angle (mechanical) and the thyristor switches firing angles (electrical) are coordinated, and controlled simultaneously. The coordination aims to minimize and suppress the undesirable effects and consequences of the wind generation system starting on the standalone MG performance. With employing the proposed hybrid and coordinated controller, the wind generator starting current grows very slowly until it reaches its rated value. On the other side, without employing the proposed controller, the wind generator starting current suddenly jumps and exceeds 400% of its rated value. Also, without employing the proposed controller, the MG frequency drops to less than 49.3 Hz. In addition, the voltage at MG buses drops to 0.9 p.u. in absence of the proposed controller compared with 0.95 p.u. if the controller is employed. The novelty on the proposed controller is the coordination between the thyristor valve firing angle (electronic) and the wind turbine blade pitch angle (mechanical) to achieve the desired performance. The overall performance and the power quality of the standaloneMGhave been highly improved after employing the proposed coordinated hybrid soft starting controller.

StandaloneMicroGrid(MG)suffersfromhighvoltageunbalancingduetobothsinglephaseandunba- lanced loads.Thispaperpresentsacomprehensivesurveyabouttheavailabletechniquesandcontrollers for MGpowerqualityimprovement.RecenttrendsandschemesforthestandaloneMGpowerquality improvementarereportedindetail.ThetechniqueswhichconcernwiththeMGvoltageunbalancing issue arehighlighted.Inaddition,thispaperdevelopsasimpleschemeforbalancingtheMGphase voltages.Theproposedschemeemploysanewinterfacinginvertertopologyandcontrol.Thethreephase compact unitinterfacinginverteroftheDistributedGenerators(DGs)hasbeenrebuiltinformofthree single phaseinverterunits.EachsinglephaseinverterunitiscontrolledindependentlytoachieveMG phase voltagebalancing.Atdifferentloadoperatingconditions,thethreesinglephaseinverterunitsrun at differentvaluesandtypes(leadingorlagging)powerfactors(PF).Employingtheproposedinverter control achievesperfectphasevoltagesbalancingatthemostMGbuses.Beforeemployingtheproposed invertercontrol,thevoltageunbalancingratioatsomebusesexceedsthan6%.Thisratioapproximately shrinks tozeroafterincludingtheproposedinvertercontrol.Theperformanceoftheproposedinverter control hasbeentestedunderdifferentloadconditions.Inaddition,theperformanceoftheproposed invertercontroliscomparedwithboththeoldinvertercontrol(unitypowerfactorinverter)andthe conventionalinvertercontrol(constantpowerfactorinverter)performance.Only,asimplemodification to theoldinvertercontrolissufficient toimplementthenewinvertercontrol.Theproposedinverter control isverysimpleandhighlyeconomicalattractive

This paper studies the influence of the load type on the fault performance of the standalone Micro Grid (MG). Different load types (static and dynamic) are considered to show their effects on the standalone MG fault behavior. Specifically, the effects of constant power static loads, constant impedance static loads, and constant current static loads are analyzed. Also, effects of dynamic (rotating) loads are highlighted. Results show, that the rotating loads have dominant effects on the fault performance of the MG during the standalone (islanded) mode. Furthermore, rotating loads cause fault currents and touch voltages three times the values associated with the static loads. Consequently, the employed protective devices with the rotating loads MG must be rated three times larger than the employed protective devices with the static loads MG. Also, the time settings of the MG protection devices are highly influenced with the load type. For static load MG, it is equal to 250% of the rotating loads MG protection devices time settings. The three types of static load show different impacts on islanded MG fault performance. Constant power static load has the highest effect compared to the other two static load types (namely, constant impedance and constant current static loads). The results obtained in this study provide a guide for the MG protection designers and planners to consider the effects of load type on the MG protection devices rating and setting.

This paper proposes two controllers for employing part of variable speed wind generation systems kinetic energy in supporting the standalone MG frequency. The first controller acts similar to the frequency droop control, while the second controller emulates both the inertia response and the frequency droop control simultaneously. The MG frequency dropped only to 49.9 Hz with employing the proposed controllers compared with 49.68 Hz without employing the proposed controllers. Also, the injected active power from the storage device dropped from 20 kW to only 3 kW after employing the proposed controllers. In addition, the reactive power capability of the Double Fed Induction Generator (DFIG) wind generation system has been employed to maintain the standalone MG bus voltage at acceptable level. If there are fixed speed wind generation systems in the standalone MG, this paper proposed using the pitch angle controller to employ a suitable wind turbine power reserve in MG frequency supporting during the standalone mode. Results proved the effectiveness of the proposed controllers in improvement the MG overall performance during and subsequent the islanding occurrence.

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