I. arc furnace, Adjustable speeddrive (ASD), Power electronic

I. INTRODUCTION1The vast use of semiconductor devices are the main causesof power distortion. Since from 1970’s inventions ofthyristors has been changed the way of current control 12.These devices control the current with atomic level and theyare called atomic switching power devices. By virtue of thisproperty, these devices give very fast control response.

Veryfast ON and OFF response makes the line current distortedand eventually distorted voltage. These distortion increasesthe harmonics 3 and reduced the power quality. It has beenknown that 5th and 7th order harmonics are more significant inpower system 3.

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Fourier Transformation Theory is veryuseful for analysis of harmonics3 4. One phenomena thatis “harmonic propagation” 1 which is a result of seriesand/or parallel harmonic resonance between line inductorsand shunt capacitors in power system. So ‘harmonicsdamping’ has done with series active filter and otherphenomena ‘harmonic elimination’ 1 has been carried outwith shunt active power filter.Now a day devices like TV, computers, mobile charger,LED bulb, regulator of fan, arc furnace, Adjustable speeddrive (ASD), Power electronic converter etc. are used athomes and private companies.

In early days effect of thesedevices on power quality not properly known. But maloperationof protecting devices such as relays and circuitbreakers open the new search area of power quality.1978-1-5386-1138-8/18/$31.00 ©2018 IEEESo these kind of switching devices generate nonlinearcurrent 3 and is called non-linear load. Before SAPF,passive filters were used. But because of more disadvantages23, usage of active power filter becomes popular.

SinceAfter remarkable work done by Hirofumi Akagi, the new wayof control with SAPF have been opened up. He suggested themethods by which the flow of current can be controlled insuch a way that source current will become near to puresinusoidal 1.There after lots of other methods have been proposed byauthors 125679. These techniques are for reducingharmonics, voltage regulation, correction of power factor etc.New techniques have been developed by engineers usingNeural networks and fuzzy logic10. In this paper weconsidering three different techniques.

And there is wideclassification of SAPF based on different topology, based onsupply type and based on connection 2.In section (II) Basic Operation is given that shows howSAPF generates the compensating current and how to designparameters for SAPF with mathematical equations. Here10%,20%,30% unbalance given from supply side.10%unbalance means 10% of peak value.

For phase A no change.For phase B 10% increased. And for phase C 10% decreased.Same for 20% and 30%.

And same is true for phase angleunbalance Which is given in table2.In section (III), Constant Instantaneous Power (CIP)technique, Sinusoidal Current Control (SCC) technique,Fryze current control technique discussed with mathematicalequations and circuit diagrams. Then in section (IV)simulation results are represented with wave forms, tabulardata, and Total Harmonic Distortion (%THD). In this paperperformance of SAPF under unbalancing conditions havebeen evaluated considering possible occurrence of unbalanceduring the unsymmetrical fault condition.

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