Mitigation of Harmonics by Shunt Active Power Filter using Synchronous Detection Method

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1 Interntonl Journl of Engneerng Trends nd Technology (IJETT Volume 4 Issue 6- June 013 Mtgton of Hrmoncs y Shunt Acte Power Flter usng Synchronous Detecton Method A.Surmny S #1, M.Bhn * # Electrcl nd Electroncs Engneerng, Ann Unersty Chenn/Ann Unersty Regonl Centre Mdur/PG Scholr, Mdur, Tmlndu, Ind # Electrcl nd Electroncs Engneerng, Ann Unersty Chenn/Ann Unersty Regonl Centre Mdur/Assstnt Professor, Mdur, Tmlndu, Ind Astrct In recent dys the usge of non-lner lods re ecomng enormous whch ges n lrmng sgnl to power system nd power engneers. Ths pper dels wth desgn, smulton expermentton of shunt cte power flter (SAPF to mproe power qulty. Due to lrge mount of non-lner power electronc equpments, nd fluctutng lods (such s tht of rc furnce, hey merchnt mll etc, prolems of power qulty he ecome more nd more serous wth ech pssng dy. The usge of cte flter mtgtes the hrmoncs present n the current sgnl resultng n mntnng the qulty of the power supply n the system. It s known from the fct tht Hrmonc Dstorton s one of the mn power qulty prolems frequently encountered y the utltes. As result Shunt Acte power flter (SAPF gns much more ttenton due to excellent hrmonc compenston. Here Synchronous Detecton Method (SDM s used to tune the Shunt cte power flter. On owng SDM method ges wy n outstndng performnce under ny oltge condtons (lnced, un-lnced, lnced non snusodl nd lnced snusodl. Extense smultons were crred out; Smulton results ldte the superor performnce of Synchronous Detecton method (SDM. Smulton s done n Mtl/smulnk softwre nd the results shows tht Totl Hrmonc Dstorton (THD s reduced sgnfcntly when compred wth other methods. Index Terms Hrmonc compenston, Shunt Acte power flter, hysteress controller, IGBT, SDM control strtegy. I.INTRODUCTION Mny socl nd economc cttes depend on electrcl energy qulty nd effcency. Both ndustrl nd commercl users re nterested n gurnteeng the electrcl weform qulty, whch supples ther dfferent systems. The nonlner lod cn generte current hrmoncs nd/or oltge hrmoncs, whch mkes worse the power qulty. Therefore, these hrmoncs must e mtgtng. In order to chee ths, seres or prllel confgurtons or comntons of cte nd psse flters he een proposed dependng on the pplcton type. Trdtonlly, psse LC power flter s used to elmnte current hrmoncs when t s connected n prllel wth the lod. Ths compenston equpment hs some drwcks mnly relted to the ppernce of seres or prllel resonnces ecuse of whch the psse flter cnnot prode complete soluton. In recent yers, sngle-phse electronc equpments he een wdely used n domestc, eductonl nd commercl pplnces. These equpments nclude computers, communcton equpments, electronc lghtng llsts etc. Also, lrge numer of computers re turned on t the sme tme. Ech computer nd ts relted deces he dode rectfer to conert AC electrcty to DC one. In other words, those equpments drw non-snusodl currents whch pollute the utlty lne due to the current hrmoncs generted y the nonlner lods. [1] [5] Snce the egnnng of the 1980s, cte power flters (APFs he ecome one of the most htul compenston methods. The APF cn e connected ether n prllel or n seres wth the lod. The shunt connecton APF s the most studed topology. Howeer, the costs of shunt cte flters re reltely hgh for lrge-scle system nd re dffcult to use n hgh-oltge grds.[7] In ddton, ther compenstng performnce s etter n the hrmonc current source lod type thn n the hrmonc oltge source lod type. The frst of these proposed y Akg lso known s Instntneous P-Qtheory cn e effecte only when the supply oltges re lnced. [9] Two mn ctegores of APFs exst: shunt flters, lso clled prllel flters, nd seres flters. [][3] The former re effecte for those nonlner lods, whch cn e consdered s current hrmonc sources (e.g., phse-controlled rectfers wth lrge dc nductnce. Shunt flters re therefore used to generte hrmonc currents to compenste lod hrmonc currents. Seres flters re effecte to generte hrmonc oltges to compenste lod hrmonc oltges. Ths pper dels wth shunt flters. [11] Three-phse APFs he hstorclly drwn more ttenton. In ths cse, three optml compenston trgets cn e ISSN: Pge 584

2 Interntonl Journl of Engneerng Trends nd Technology (IJETT Volume 4 Issue 6- June 013 ddressed y the APF controller, from whch three control strteges dere: 1 Constnt nstntneous source power control; Snusodl current control; 3 Generlzed Fryze current control. Ths pper descres the prncple of synchronous detecton method (SDM. Ths technque s sutle only for three-phse system nd ts operton reles n the fct tht the three-phse currents re lnced. [4] [6] It s sed on the de tht the APF forces the source current to e snusodl nd n phse wth the source oltge despte the lod rtons. [8][10] Ths mproed method s smulted, nd the rel-tme nd ccurcy of ths method s proed. II. OVERVIEW OF ACTIVE POWER FILTER To cncel the hrmoncs nd compenste the recte power APF s the sutle soluton. The APF concept s to use n nerter to nject currents or oltges hrmonc components to cncel the lod hrmonc components. The more usul confgurton s shunt APF to nject current hrmoncs nto the pont of common couplng (PCC. The APF cn e nstlled n low oltge power system to compenste one or more lods; thus, t ods the propgton of current hrmoncs n the system. The deelopments of dfferent control strteges ge APF to new locton. As APF compenste the recte power nd cncel the hrmoncs, t s lso clled s cte power lne condtoners (APLC. The three mn spects of n cte power condtoner re: The confgurton of power conerter (the scheme nd the topology of conerter nd the electroncs dece used The control strtegy (the clculton of APLC control reference sgnls The control method used (how the power nerter follows the control reference. The topology of cte power flter s clssfed nto three types. Seres cte power flters Shunt cte power flters Hyrd cte power flters. through couplng trnsformer. The compenston oltge s used to cncel the oltge hrmoncs of lod. Fg. Shunt APLC scheme The three-phse shunt cte power flter s three-phse current controlled oltge source nerter (CC-VSI wth md-pont erthed, splt cpctor n the dc us nd nductors n the c output. Conentonlly, shunt APF s controlled n such wy s to nject hrmonc nd recte compenston currents sed on clculted reference currents. The njected currents re ment to cncel the hrmonc nd recte currents drwn y the non-lner lods. Howeer, the reference or desred current to e njected must e determned y extense clcultons wth nherent delys, errors nd slow trnsent response. A key component of ths system s the dded seres nductnce X L whch s comprle n sze to the effecte grd mpednce, Z S. Wthout ths nductnce (or seres cte flter, lod hrmonc oltge sources would produce hrmonc currents through the grd mpednce, whch could not e compensted y shunt APF. Currents from the APF do not sgnfcntly chnge the hrmonc oltge t the lods. Therefore, there re stll hrmonc oltges cross the grd mpednce, whch contnue to produce hrmonc currents. The grd current s sensed nd drectly controlled to follow symmetrcl snusodl reference sgnls n phse wth the grd oltge. Hence, y puttng the current sensors on the grd sde, the grd current s forced to ehe s snusodl current source nd the grd ppers s hgh-mpednce crcut for hrmoncs. By forcng the grd current to e snusodl, the APF utomtclly prodes the hrmonc, recte, negte nd zero sequence currents for the lod, followng the sc current summton rule: GRID (1 APF LOAD The snusodl grd current reference sgnl s gen y: fg 1 Seres APLC scheme The connecton scheme of seres APLC s s shown n the followng dgrm. It s connected to the power system. REF k GRID 1 ( where grd -1 s the fundmentl component of the grd oltge, nd k s otned from n outer control loop regultng the CC-VSI dc-us oltge. III. ACTIVE FILTER DESIGN USING SDM METHOD ISSN: Pge 585

3 Interntonl Journl of Engneerng Trends nd Technology (IJETT Volume 4 Issue 6- June 013 Ths pper presents new detecton method clled Synchronous Detecton Method (SDM. It hs een ppled to shunt cte power flter the followng ssumptons re mde n clcultng the three phse compenstng currents usng equl current dstruton method of synchronous detecton lgorthm. The sc de s formng rottng coordnte y usng rtul symmetrcl three-phse system synthetc oltge ector system. Ths method does not need PLL, so t elmntes the derse effects generted y PLL. Here we ssume tht Voltge s not dstorted. Loss n the neutrl lne s neglgle. The three phse mn currents re ssumed to e lnced fter compenston n ths method nd lso try to determne the requred mpltude of the source currents. Let the nstntneous lod currents e (t,(t,c(t nd ther correspondng phse oltge e (t,(t,c(t re shown n the fg1.the rel power P(t s clculted s elow. P( t [ ( t ( t ( t] [ ( t ( ( c] (3 c Therefore the erge lue Pdc cn e determned y pplyng P(t to low pss flter. Thus, the rel power s splt nto three phses, they re P P (4 dc m [ m m cm] P P (5 c dc m [ m m cm] P P (6 dc cm [ m m cm] Where m, m nd cm re the mpltudes of (t,(t nd c(t respectely. Thus the lnced current cn e determned s, (P s (7 m ( P s (8 m (cpc sc (9 cm The compenston current references re thus, c c s s (11 (10 The compenston currents c*, c*, cc* re fed to the CSI whch supples the exct replc of hrmonc currents so tht they re cncelled out nd pure snusodl current re fed to the source. Snce the CSI s ssumed to e nstntneous to trck the compenston currents, t s modeled s current mplfer wth unty gn. Ths method cn e extensely used for compenston of recte power, current mlnce nd mtgton of current hrmoncs. It s the smplest method s t requres mnmum clcultons. Source SDM lgorthm Hysteress SDM FILTER BLOCK Fg.3 SAPF tuned wth SDM method Non lner lod IGBT Ths method cn e extensely used for compenston of recte power, current mlnce nd mtgton of current hrmoncs. It s the smplest method s t requres mnmum clcultons. The SDM method s desgned n such wy tht t conssts of three phse source connected to the three phse nonlner lod (unersl rdge rectfer wth RL crcut. In etween these components, the erge power determnton (needed for the functon of SDM nd shunt cte power flter s connected. Ths erge power determnton nd flter s re dfferent s whch ncorported to perform dfferent opertons nd fnlly produce compenston current nd nject t nto the trnsmsson lne. The three phse current nd oltge re llowed nto Aerge power determnton. At frst the nstntneous rel power P(T (3 consumed y the lod s clculted nd from the product of correspondng nstntneous oltges nd lod currents of ech phse re summng up y the lues of ll the three phses. Then t s pssed to the zero order hold nd men lue detector so tht the erge power Pdc s clculted for ech phse. Then the erge power otned s fed nto the flter crcutry for the generton of compenston currents. The flter crcutry conssts of followng s shown n fg 3: SDM lgorthm. Hysteress control lgorthm. IGBT gtng pulse crcut. Then the correspondng rel power (P, P, Pc for ech phse s stted n the equtons 4, 5, 6 s segregted. From such rel power of ech phse, the reference lne currents for ech phse s determned whch s clculted from the ISSN: Pge 586

4 Current (A Current (A Voltge (V Voltge (V Current (A Voltge (V Interntonl Journl of Engneerng Trends nd Technology (IJETT Volume 4 Issue 6- June 013 equton 7, 8, 9. Then the dfference etween the reference lne currents for ech phse (I*s, I*s, I*sc nd Lod currents (I, I, Ic s clculted whch yelds the compenston current whch s gong to e njected n the lne. The compenston current thus otned s fed nto the hysteress control Thus the currents (*f, f, (*f, f,(*fc, fc re compred wth comprtor efore whch the currents *f, *f, *fc re dded wth constnt lue of 1 nd IGBT currents of f, f, fc re sutrcted from the sme constnt lue of 1. The compred lue s llowed to process through SR flp-flop whose ntl condton tht s the stte of Q s ssgned wth lue of 1.The processed output of ech SR flp-flop of ech phse (Q, s llowed for the unt dely whch produces the Pulstng sgnls (G1,G,G3,G4,G5,G6 for trggerng the GTO present n the IGBT gtng pulse crcut. Fg.6 Source Voltge Weform efore Flterng IV. SIMULATION RESULTS The shunt cte power flter whch s connected to oltge source type non-lner lod s smulted y usng MATLAB/SIMULINK enronment. The scheme s frst smulted wthout ny flter to fnd out the THD of the supply current. Then t s smulted wth the flter tuned wth SDM method to osere the dfference n THD of supply current. Smulton s lso crred out wth hysteress controller nd to fnd out the comprte study of the THD of the supply current. Fg.7 Lod Current Weform efore Flterng Fg.8 Lod Voltge Weform efore Flterng Fg 4 Nonlner lod oltge weform Fg.9 Source Current Weform fter Flterng Fg.5 Source Current Weform efore flterng ISSN: Pge 587

5 Current (A Interntonl Journl of Engneerng Trends nd Technology (IJETT Volume 4 Issue 6- June 013. Murzo Crrncone, Memer IEEE, Mrcello Pucc,Memer IEEE, Gnpolo Vtle, Memer IEEE, & Adelltf Mrou, Memer, IEEE, Current Hrmonc Compenston y Sngle-Phse Shunt Acte Power Flter Controlled By Adpte Neurl Flterng IEEE Trns on Industrl Electroncs, Vol,56.NO.8, AUG Md. Ashfnoor Kr nd Upl Mhu Synchronous Detecton nd Dgtl control of Shunt Acte Power Flter n Power Qulty Improement Bngldesh Unersty of Engneerng IEEE Trnsctons 011. Fg.10 Generted Compenstng Current Weform 4. Ptrco Slmeron & Reyes S. Herrer Dstorted & Unlnced System Compenston Wthn Instntneous Recte Power Frmework IEEE Trns. On Power Delery.Vol.1,NO. 5. Izzeldn Idrs dll, K.S.Rm Ro, N.Peruml Three Phse Four- Leg Shunt Acte Power Flter to Compenste hrmoncs & Recte Power 011 IEEE Symposum on Computer & Informtcs. 6. Chenn Slm & Benchou Mohmed Toufk IEEE Memer Intellgent Controllers for Shunt Acte Flter to Compenste Current Hrmoncs Bsed on SRF nd SCR Control Strteges Interntonl Journel on Electrcl Engg & Informtcs Vol 3, 011. Fg.11 THD on Source Sde V. CONCLUSION In ths work Synchronous Detecton Method (SDM control strteges s deeloped nd erfed wth three phse four wre system. It s osered tht SDM method ges lwys etter results under un-lnced & non-snusodl oltge condtons oer other methods. In ths method, ngle θ s clculted drectly from mn oltges & thus enles the method to e frequency ndependent. Thus lrge numer of synchronzton prolems wth un-lnced nd non-snusodl oltges s lso oded. By usng ths method the source sde THD s reduced from 9% to 0.91%. VI. REFERENCES 1. Y Tng, Student Memer, IEEE, Poh Chng Loh, IEEE,Peng Wng, Memer,IEEE, Fook Hoong Choo, Feng Go, Memer, IEEE, & Frede Bljerg, Fellow, IEEE Generlsed Desgn Of Hgh Performnce Shunt Acte Power Flter Wth Output LCL Flter IEEE Trns on Industrl Electroncs, Vol.59,NO.3,Mrch Hrofum Akg, Yoshhr Knzw nd Akr Ne, Instntneous recte power compenstor comprsng swtchng power deces wthout energy storge components, IEEE Trnsctons on Industry Applctons, Vol. 1A-0, My/June 1984, pp. 8. M. F. Shoush*, Student Memer, IEEE, S. A. Zd*, nd O. A. Mhgou*, Memer, IEEE Better Performnce for Shunt Acte Power Flters Electrcl Power nd Mchnes Deprtment, Cro Unersty, (Egypt IEEE Trnsctons Ptrco Slmeron nd Sldor P. Ltrn A Control Strtegy for Hyrd Power Flter to Compenste Four- Wres Three-Phse Systems IEEE Trnsctons on Power Electroncs, ol. 5, no. 7, july Hu Yong-jun,Fn L-l, Hu Y-jng A Recte nd Hrmonc Current Detecton Method of Three-phse Asymmetrc System 010 Interntonl Conference on Computtonl nd Informton Scences. 11. Moleykutty George nd Krtk Prsd Bsu Performnce Comprson of Three-Phse Shunt Acte Power Flter Algorthms Amercn Journl of Appled Scences 5 (11: , 008 ISSN Scence Pulctons ISSN: Pge 588