Application of Pulse Doubling in Star-Connected Autotransformer Based 12-Pulse AC-DC Converter for Power Quality Improvement

Transcription

1 Wrld cademy f Science, Engineering and Technlgy Internatinal Jurnal f Electrical and mputer Engineering l:5, N:8, pplicatin f Pulse Dubling in Star-nnected uttransfrmer ased -Pulse -D nverter fr Pwer Quality Imprvement Rhllah. bdllahi, and lireza. Jalilian Internatinal Science Index, Electrical and mputer Engineering l:5, N:8, waset.rg/publicatin/6 bstract This paper presents a pulse dubling technique in a -pulse ac-dc cnverter which supplies direct trque cntrlled mtr drives (DTIMD s) in rder t have better pwer quality cnditins at the pint f cmmn cupling. The prpsed technique increases the number f rectificatin pulses withut significant changes in the installatins and yields in harmnic reductin in bth ac and dc sides. The -pulse rectified utput vltage is accmplished via tw paralleled six-pulse ac-dc cnverters each f them cnsisting f three-phase dide bridge rectifier. n auttransfrmer is designed t supply the rectifiers. The design prcedure f magnetics is in a way such that makes it suitable fr retrfit applicatins where a six-pulse dide bridge rectifier is being utilized. Independent peratin f paralleled dide-bridge rectifiers, i.e. dc-ripple re-injectin methdlgy, requires a Zer Sequence lcking Transfrmer (ZST). Finally, a tapped interphase reactr is cnnected at the utput f ZST t duble the pulse numbers f utput vltage up t pulses. The afrementined structure imprves pwer quality criteria at ac mains and makes them cnsistent with the IEEE-59 standard requirements fr varying lads. Furthermre, near unity pwer factr is btained fr a wide range f DTIMD peratin. cmparisn is made between 6- pulse, -pulse, and prpsed cnverters frm view pint f pwer quality indices. Results shw that input current ttal harmnic distrtin (THD) is less than 5% fr the prpsed tplgy at varius lads. Keywrds D cnverter, star-cnnected auttransfrmer, pwer quality, pulse rectifier, Pulse Dubling, direct trque cntrlled inductin mtr drive (DTIMD). R I. INTRODUTION EENT advances in slid state cnversin technlgy has led t the prliferatin f variable frequency inductin mtr drives (FIMD s) that are used in several applicatins such as air cnditining, blwers, fans, pumps fr waste water treatment plants, textile mills, rlling mills etc []. The mst practical technique in FIMD s is direct trque cntrlled strategy in that it ffers better perfrmance rather than the ther cntrl techniques. direct trque cntrlled technique is implemented in vltage surce inverter which is mstly fed R. bdllahi is Msc student at the Department f Electrical Engineering, Iran University f Science and Technlgy, Tehran, Iran ( rhllah.abdllahi@yah.cm).. Jalilian is with the Department f Electrical Engineering, entre f Excellence fr Pwer System utmatin and Operatin, Iran University f Science and Technlgy, Tehran, Iran ( jalilian@iust.ac.ir). frm six-pulse dide bridge rectifier, Insulated gate biplar transistrs (IGT s) are emplyed as the SI switches. The mst imprtant drawback f the six-pulse dide-bridge rectifier is its pr pwer factr injectin f current harmnics int ac mains. The circulatin f current harmnics int the surce impedance yields in harmnic plluted vltages at the pint f cmmn cupling (P) and cnsequently resulting in undesired supply vltage cnditins fr cstumers in the vicinity. The value f current harmnic cmpnents which are injected int the grid by nnlinear lads such as DTIMDs shuld be cnfined within the standard limitatins. The mst prminent standards in this field are IEEE standard 59 [] and the Internatinal Electrtechnical mmissin (IE) 6-- []. ccrding t cnsiderable grwth f Static Pwer nverters (SP s) that are the majr surces f harmnic distrtin and as a result their pwer quality prblems, researchers have fcused their attentin n harmnic eliminating slutins. Passive and active filters are cmpensating devices which are utilized in pwer grids t enhance pwer quality. Hwever, they intrduce sme drawbacks. Passive filter installatins are bulky and require extra area. Furthermre, they cause additinal lsses and the variatins in resnance frequency influences their peratin and cnsequently making their design cmplex. Likewise, active filters implementatin is cmplicated and cstly. esides, their ratings shuld be analgus t lad rating. The afrementined prblems and harmnic pllutin culd be nearly reslved using multi-pulse -D cnverters. asically, Harmnic cancellatin in multi-pulse cnverters is accmplished via tw r mre paralleled bridge rectifiers in which their supplying vltages are phase shifted accrding t the desired utput vltage pulse number. arius schematics f -pulse -D cnverters have been prpsed by researchers s far [-8]. lthugh, these tplgies d nt meet the IEEE standard requirements fr permissible harmnic distrtin. Obviusly, mre paralleled bridge rectifiers will result in higher pulse numbers and, cnsequently, better pwer quality cnditins. On the cntrary, the cst and cmplexity f the whle system will increase significantly. Reduced cst and cmplexity f - D cnverters beside the imprved pwer quality indices can be achieved by D ripple re-injectin methd [9-6]. Internatinal Schlarly and Scientific Research & Innvatin 5(8) 98 schlar.waset.rg/7-689/6

2 Wrld cademy f Science, Engineering and Technlgy Internatinal Jurnal f Electrical and mputer Engineering l:5, N:8, star-cnnected auttransfrmer, tw six-pulse dide bridge rectifiers paralleled thrugh tw IPTs, and with a DTIMD lad Fig. is als designed and simulated t cmpare its peratin with the prpsed -pulse ac-dc cnverter. Simulatin results f six-pulse, -pulse and prpsed - pulse ac-dc cnverters feeding a DTIMD lad are scheduled and varius quality criteria such as THD f ac mains current, pwer factr, displacement factr, distrtin factr, and THD f the supply vltage at P are cmpared. Internatinal Science Index, Electrical and mputer Engineering l:5, N:8, waset.rg/publicatin/6 Fig. star-cnnected auttransfrmer cnfiguratin fr -pulse ac dc cnversin [] The zigzag-cnnected auttransfrmer-based -pulse tplgy [6] was designed fr IMD s lads having a THD variatin f 5.7% t 6.8% frm full-lad t lightlad (% f full-lad) respectively. The dc link vltage in this tplgy is higher than that f a 6-pulse dide bridge rectifier, thus making the scheme nn-applicable fr retrfit applicatins. star-cnnected auttransfrmer-based -pulse -D cnverter is reprted in [], which is nt within the IEEE- 59 limits. T imprve the pwer quality, a passive shunt filter has been designed in accrdance with IEEE Standard 5- []. alng with the designed passive filters has THD variatin f.% t 8.8% frm full-lad t light-lad (% f full-lad), but even with this cnfiguratin, the THD f ac mains current at light lad is 8.8%, which is als nt within IEEE Standard 59 limits. In this paper, a -pulse ac-dc cnverter is extracted frm this star-cnnected auttransfrmer-based -pulse ac-dc cnverter thrugh adding a pulse dubling circuit in the D link. The prpsed design methd will be suitable even when the transfrmer utput vltages vary while keeping its - pulse peratin. In the prpsed structure, tw three-leg dide-bridge rectifiers are paralleled via a Zer Sequence lcking Transfrmer (ZST) and fed frm an auttransfrmer. Hence, a -pulse utput vltage is btained. In rder t duble the number f pulses up t, a tapped Inter-Phase Reactr (IPR) with tw additinal dides are included in the rectifiers utput. This pulse multiplicatin wrks n the basis f ripple re-injectin methd, where the pwer f the circulating ripple frequency is fed back t the dc system via an IPR [9]. In ther wrds, the remval f harmnics in -pulse cnverter is accmplished via the dc vltage ripple which is the frequency surce fr the derivatin f adequate vltage and current wavefrms. Ratings f IPR are small versus utput apparent pwer. The number f turns in each IPR taps is such that the peratin f dides prduces a near sinusidal wavefrm in the ac line currents. Detailed design tips f the tapped IPR and ttally the whle structure f -pulse ac-dc cnverter are described in this paper and the prpsed cnverter is mdeled and simulated in MTL t study its behavir and specifically t analyze the pwer quality indices at ac mains. Furthermre, a -pulse ac-dc cnverter cnsisting f a II. -PULSE D ONERTER s mentined previusly, the pulse-dubling technique requires a zer-sequence-blcking transfrmer (ZST) and a dide-tapped inter-phase reactr t multiple the number f a pulses up t. It is knwn that a -pulse rectified vltage can be made with tw paralleled six-pulse three-phase (three-leg) didebridge rectifiers. The phase shift between tw supplying vltages shuld be degrees. Similarly, in rder t implement a -pulse ac-dc cnverter thrugh paralleling tw bridge rectifiers, i.e. tw 6-pulse rectifiers, tw sets f threephase vltages with a phase difference f degrees between the vltages f each grup and degrees between the same vltages f the tw grups are required. ccrdingly, each bridge rectifier cnsists f three cmmnande and three cmmn-cathde dides (tw three-leg rectifiers). star-cnnected auttransfrmer is designed t prduce the three phase vltages which are shwn in Fig.. uttransfrmer cnnectins and its phasr diagram which shws the angular displacement f vltages are illustrated in Fig.. n verall schematic f the prpsed -pulse ac-dc cnverter is shwn in Fig... Design f Prpsed uttransfrmer fr -Pulse D nverter The afrementined tw vltage sets are called as ( a, a, a ) and ( b, b, b ) that are fed t rectifiers I and II, respectively. The same vltages f the tw grups, i.e. ai and bi, are phase displaced f degrees. a and b has a phase shift f +5 and -5 degrees frm the input vltage f phase, respectively. ccrding t phasr diagram, the three-phase vltages are made frm ac main phase and line vltages with fractins f the primary winding turns which are expressed with the fllwing relatinships. nsider three-phase vltages f primary windings as fllws: =, =, =. () s s Where, three-phase vltages are: a = S 5, b = S 5, c = S 5 () a = S 5, b = S 5, c = S 5 () s Internatinal Schlarly and Scientific Research & Innvatin 5(8) 99 schlar.waset.rg/7-689/6

3 Wrld cademy f Science, Engineering and Technlgy Internatinal Jurnal f Electrical and mputer Engineering l:5, N:8, Internatinal Science Index, Electrical and mputer Engineering l:5, N:8, waset.rg/publicatin/6 Fig. star-cnnected auttransfrmer cnfiguratin fr -pulse ac dc cnversin Input vltages fr cnverter I are: a b c a b c = K = K = K Input vltages fr cnverter II are: = K = K = K =, =, =. (6) nstants K -K are calculated using ()-(6) t btain the required windings turn numbers t have the desired phase shift fr the tw vltage sets: =.86, K.98. (7) K = Fig. star cnnectin f prpsed auttransfrmer fr -pulse cnverter and its phasr representatin. Design f uttransfrmer fr Retrfit pplicatins The value f utput vltage in multipulse rectifiers bsts relative t the utput vltage f a six-pulse cnverter making the multipulse rectifier inapprpriate fr retrfit applicatins. Fr instance, with the auttransfrmer arrangement f the prpsed -pulse cnverter, the rectified utput vltage is % higher than that f six-pulse rectifier. () (5) Fig. Phasr diagram f vltages in the prpsed auttransfrmer cnnectin alngwith mdificatins fr retrfit arrangement Fr retrfit applicatins, the abve design prcedure is mdified s that the dc-link vltage becmes equal t that f six-pulse rectifier. This will be accmplished via mdificatins in the tapping psitins n the windings as shwn in Fig.. It shuld be nted that with this apprach, the desired phase shift is still unchanged. Similar t sectin II part, the fllwing equatins can be derived as: S =.97 (8) ccrdingly, the values f cnstants K and K are changed fr retrfit applicatins as: K =.795, K =.979. (9) The values f K and K establish the essential turn numbers f the auttransfrmer windings t have the required Internatinal Schlarly and Scientific Research & Innvatin 5(8) schlar.waset.rg/7-689/6

4 Wrld cademy f Science, Engineering and Technlgy Internatinal Jurnal f Electrical and mputer Engineering l:5, N:8, utput vltages and phase shifts. The kilvltampere rating f the auttransfrmer is calculated as []: k =.5 winding I winding () Where, winding is the vltage acrss each auttransfrmer winding and I winding indicates the full lad current f the winding. pparent pwer ratings f the tapped-interphase reactr and zer-sequence-blcking transfrmer (ZST) are als calculated in a same way. Fig. 5 Tapped Inter-phase Transfrmer circuit Internatinal Science Index, Electrical and mputer Engineering l:5, N:8, waset.rg/publicatin/6. Interphase Transfrmer The thery f pulse multiplicatin has been presented in [9] where a tapped inter-phase reactr alng with tw additinal dides are used t duble the number f pulses in the supply line current resulting in current harmnic reductin. fterwards, tapped interphase reactr was used in [7]-[] t duble the number f pulses in -pulse ac-dc cnverters. Furthermre, this type f multiplier was als served in paralleled thyristr bridge rectifiers []. Likewise, we used a tapped interphase rectr (IPR) t extract a -pulse current frm tw paralleled 6-pulse rectifiers. The IPR and tapped dides are shwn in Fig. 5. Fr the pulse multiplicatin prcess, it is necessary t ensure that the average utput vltages f bridges are equal and phase shifted f degrees. s tw 6-pulse rectifiers are paralleled, the vltage acrss the interphase transfrmer, m, has a frequency 6 times that f the supply system. Therefre, size, weight and vlume f the transfrmer reduce relative t rectifiers with a less pulse number. m is an alternating vltage with bth psitive and negative half cycles. Hence, D cnducts when the m is psitive and, n the ther hand, D cnducts when m is negative. The MMF equivalence between the windings when D is n yields: i N = i N () dc dc Where, N and N are number f turns as shwn fr IPR. We als have: i + i = i () dc dc dc Using () and (), utput current f the tw rectifiers are calculated as fllws: i dc = (.5 + K t )idc () i dc = (.5 )i t dc In the abve equatin, N O =N +N and K t =(N.5N O )/N O. The same relatins can be written when m is in its negative half cycle. Therefre, accrding t MMF equatin, the magnitude f utput currents changes which results in pulse multiplicatin in the supply current. In [], it is prved that K t shuld be equal t.57 t eliminate the harmnic currents up t the st rder which can be applied in this applicatin t. D. Zer Sequence lcking Transfrmer In parallel-rectifier cnfiguratins, the tw cnverters cannt be directly paralleled. ecause, the utput vltages are phase-shifted thereby unwanted cnductin sequence f dides is prbable. Therefre, a zer-sequence-blcking transfrmer is required t ensure the independent peratin f tw paralleled rectifiers. In the prpsed -pulse cnverter, the vltage frequency f ZST is three times that f the supply system and it shws high impedance zer sequence (and its multiples) current harmnics and prevents them t flw. Furthermre, high ripple frequency f the supply vltage in ZST makes it small and light. III. MTL-SED SIMULTION Fig. 6 shws the implemented ac-dc cnverter with DTIMD in MTL sftware using SIMULINK and pwer system blck set (PS) tlbxes. In this mdel, a three-phase 6 and 6 Hz netwrk is utilized as the supply fr the -pulse cnverter. The designed auttransfrmer is mdeled via three multi-winding transfrmers. Multi-winding transfrmer blck is als used t mdel ZST and IPT. t the cnverter utput, a series inductance (L) and a parallel capacitr () as the dc link are cnnected t IGT-based ltage Surce Inverter (SI). SI drives a squirrel cage inductin mtr emplying direct trque cntrlled strategy. The simulated mtr is 5 hp (7. kw), -ple, and Y- cnnected. Detailed data f mtr are listed in ppendix.simulatin results are depicted in Figs. 8-. Pwer quality parameters are als listed in Table I fr 6-pulse, -pulse, and -pulse ac-dc cnverters. I. RESULTS ND DISUSSION Table I lists the pwer quality indices btained frm the simulatin results f the 6-pulse, -pulse, and -pulse cnverters. Matlab blck diagram f -pulse ac dc cnverter system simulatin, as shwn in Fig. 7. Fig. 8 depicts tw grups f three-phase vltage wavefrms with a phase shift f degrees between the same vltages f each grup. The rectifiers utput vltages (tw grups f 6-pulse vltage) with a phase difference f degrees are shwn in Fig. 9. The vltage acrss the interphase transfrmer (shwn in Fig. ) has a frequency equal t 6 times that f the supply which results in a significant reductin in vlume and cst f magnetics. Internatinal Schlarly and Scientific Research & Innvatin 5(8) schlar.waset.rg/7-689/6

5 Three-phase DTIMD Wrld cademy f Science, Engineering and Technlgy Internatinal Jurnal f Electrical and mputer Engineering l:5, N:8, Speed ntrller N Flux* N* Trque* 8 SP Mag trl trl DT Trque* 6 Mag Flux* Gates _abc I_ab m N RadRpm 6 6Hz Ld d raking chpper Meas. L+ nv. + L- - inverter g + - Measures Ta I_ab Tb _abc Mta Tc Mtb _m Mtc Inductin Tm Rate Transitin machine RT Tm m Mtr -Pulse -D nverter <Rtr speed (wm)> <Rtr speed (wm)> Wm - Fig. 6 Matlab mdel f -pulse ac dc cnverter fed DTIMD a Universal ridge Internatinal Science Index, Electrical and mputer Engineering l:5, N:8, waset.rg/publicatin/6 Three-Phase Surce b c Universal ridge Fig. 7 Matlab blck diagram f -pulse ac dc cnverter system simulatin Fig. 8 auttransfrmer utput vltage (tw grups f -phase vltage) ZST IPT Ld d nn nn 8 6 Fig. ltage wavefrm acrss the duble-tap IPR Fig. Dides D and D current wavefrms Fig. -pulse ac dc cnverter utput vltage Fig. 9 Rectifiers utput vltage (tw grups f 6-pulse vltage) The current wavefrms f pulse dubling dides are shwn in Fig.. Dide D cnducts when the vltage acrss the IPT is psitive and, cnversely, D is n when the vltage acrss the IPT is in its negative half-cycle. The magnet mtive frce (MMF) equivalence f the IPT windings are frmulated in equatin () when D is n. This cnductin sequence f the dides is the basis f the pulse dubling technique. Internatinal Schlarly and Scientific Research & Innvatin 5(8) schlar.waset.rg/7-689/6

6 Wrld cademy f Science, Engineering and Technlgy Internatinal Jurnal f Electrical and mputer Engineering l:5, N:8, Sr. N. TLE I OMPRISON OF SIMULTED POWER QULITY PRMETERS OF THE DTIMD FED FROM DIFFERENT D ONERTERS Mains urrent I S () Tplgy % THD f ac % THD f I S, at Distrtin Factr, DF Displacement Factr, DPF Pwer Factr, PF D ltage () 6-pulse pulse pulse Statr current g y ( ) y Internatinal Science Index, Electrical and mputer Engineering l:5, N:8, waset.rg/publicatin/ Rtr speed Electrmagnetic Trque D bus vltage Fig. Wavefrms depicting dynamic respnse f -pulse dide rectifier fed DTIMD with lad perturbatin (surce current i s, speed ω r, develped electrmagnetic trque T e, and dc-link vltage dc ) Statr current Rtr speed Electrmagnetic Trque D bus vltage Fig. Wavefrms depicting dynamic respnse f six-pulse dide rectifier fed DTIMD with lad perturbatin The -pulse cnverter utput vltage (shwn in Fig. ) is almst smth and free f ripples and its average value is 67. vlts which is apprximately equal t the D link vltage f a six-pulse rectifier (67.6 vlts). This makes the -pulse cnverter suitable fr retrfit applicatins (s) 8 6 Fundamental (6Hz) =., THD= 5.5% Fig. 5 Input current wavefrm f six-pulse ac dc cnverter at light lad and its harmnic spectrum (s) 8 6 Fundamental (6Hz) = 5.69, THD= 8.5% THD = 5.5% THD = 8.5% Fig. 6 Input current wavefrm f six-pulse ac dc cnverter at full lad and its harmnic spectrum Internatinal Schlarly and Scientific Research & Innvatin 5(8) schlar.waset.rg/7-689/6

7 Wrld cademy f Science, Engineering and Technlgy Internatinal Jurnal f Electrical and mputer Engineering l:5, N:8, (s) (s) Fundamental (6Hz) =.56, THD=.% Fundamental (6Hz) =.9, THD= 5.9% Mag (% f Fundamental) 8 6 THD =.% Mag (% f Fundamental) 8 6 THD = 5.9% Internatinal Science Index, Electrical and mputer Engineering l:5, N:8, waset.rg/publicatin/ Fig. 7 Input current wavefrm f -pulse ac dc cnverter at light lad and its harmnic spectrum Mag (% f Fundamental) (s) 8 6 Fundamental (6Hz) = 5.6, THD= 7.5% THD = 7.5% Fig. 8 Input current wavefrm f -pulse ac dc cnverter at full lad and its harmnic spectrum Different utput and input characteristics f the prpsed -pulse cnverter feeding DTIMD such as supply current, rtr speed, electrmagnetic trque, and D link vltage are shwn in Fig.. These wavefrms can be cmpared with their equivalent parameters f a six-pulse fed DTIMD that are shwn in Fig.. The dynamic characteristics f the tw cnverters can be used t cmpare their dynamic respnse thrugh cnditins such as starting r lad variatins. Input current wavefrms and its harmnic spectrum f the 6-pulse, -pulse, and -pulse cnverters extracted and shwn in Figs. 5-, respectively t check their cnsistency with the limitatins f the IEEE standard 59. These harmnic spectra are btained when inductin mtr perates under light lad (% f full lad) and full lad cnditins. Hence, input current THD f this cnverter will be relatively a large amunt and is equal t 8.5% and 5.8% fr full lad and light lad cnditins that are nt within the standard margins Fig. 9 Input current wavefrm f -pulse ac dc cnverter at light lad and its harmnic spectrum Mag (% f Fundamental) (s) 8 6 Fundamental (6Hz) = 5., THD=.57% THD =.57% Fig. Input current wavefrm f -pulse ac dc cnverter at full lad and its harmnic spectrum The THD f ac mains current f -pulse ac dc cnverter at full lad is 7.5%, which deterirates t.% at light lad, which is als nt within IEEE Standard 59 limits. On the ther hand, as shwn in Figs. 9-, -pulse cnverter has an acceptable current THD (5.9% fr light lad and.57% fr full lad cnditins). In this cnfiguratin, lw rder harmnics up t st are eliminated in the supply current. In general, the largely imprved perfrmance f the - pulse cnverter makes the pwer quality indices such as THD f supply current and vltage (THDi and THDv), displacement pwer factr (DPF), distrtin factr (DF), and pwer factr (PF) satisfactry fr different lading cnditins. The afrementined criteria are listed in Table I fr the three types f cnverters. Internatinal Schlarly and Scientific Research & Innvatin 5(8) schlar.waset.rg/7-689/6

8 Wrld cademy f Science, Engineering and Technlgy Internatinal Jurnal f Electrical and mputer Engineering l:5, N:8, Internatinal Science Index, Electrical and mputer Engineering l:5, N:8, waset.rg/publicatin/6 TLE II OMPRISON OF POWER QULITY INDIES OF PROPOSED - PULSE -D ONERTER (%) THD (%) I S S F f I S DF DPF TPF RF (%) THD f ac mains current (%) Pwer Factr Pulse -Pulse -Pulse (%) Fig. ariatin f THD with lad n DTIMD in 6-pulse, - pulse and -pulse ac-dc cnverter Pulse -Pulse 6-Pulse (%) Fig. ariatin f pwer factr with lad n DTIMD in 6-pulse, -pulse and -pulse ac-dc cnverter Input current THD and pwer factr variatins are als shwn in Figs. and respectively, fr 6-pulse, -pulse, and -pulse ac-dc cnverters. Results shw that the input current crrespnding t the prpsed cnfiguratin has an almst unity pwer factr. Furthermre, in the wrst case (light lads) the current THD has reached belw 5% fr the prpsed tplgy. dc () Different pwer quality indices f the prpsed tplgy under different lading cnditins are shwn in Table II. Results shw that even under lad variatins, the -pulse cnverter has an imprved perfrmance and the current THD is always less than 5% fr all lading cnditins.. ONLUSION In this paper a star-cnnected auttransfrmer was designed and mdeled t make a -pulse ac-dc cnverter with DTIMD lad. fterwards, the prpsed design prcedure was mdified fr retrfit applicatins. zersequence-blcking transfrmer was added t ensure the independent peratin f paralleled rectifiers and a tapped inter-phase reactr was used t duble the number f pulses in the ac mains currents. The increased number f pulses results in the frequency increase f the supply vltages f ZST and IPR, thereby, decreasing the size and vlume f the transfrmers. Simulatin results prve that, fr the prpsed tplgy, input current distrtin factr is in a gd agreement with IEEE 59 requirements. urrent THD is less than 5% fr varying lads. It was als bserved that the input pwer factr is clse t unity resulting in reduced input current fr DTIMD lad. PPENDIX. Mtr and ntrller Specificatins Three-phase squirrel cage inductin mtr 5 hp (7. kw), three phase, fur ple, Y-cnnected, 6, 6 Hz. R s =.8 Ω; R r =.9 Ω; X ls =.Ω; X lr =. Ω, X Lm =.9 Ω, J =. Kg m. ntrller parameters: PI cntrller Kp = ; Ki =. D link parameters: L d = mh; d = μf. Surce impedance: Z s = j.88 Ω (=%). REFERENES []. K. se, Mdern Pwer Electrnics and Drives. Singapre: Pearsn Educatin, 998. [] IEEE Standard 59-99, IEEE Recmmended Practices and Requirements fr Harmnic ntrl in Electrical Pwer Systems. NewYrk: IEEE Inc., 99. [] IE Standard 6--:, Limits fr harmnic current emissins, Internatinal Electrmechanical mmissin. Geneva,. [] D.. Paice, Pwer Electrnic nverter Harmnics: Multipulse Methds fr lean Pwer. New Yrk: IEEE Press, 996. [5] in Wu, High-Pwer nverters and Drives, IEEE Press, Wiley- Interscience, 6. [6] S. hi, P. N. Enjeti, and I. J. Pitel, Plyphase transfrmer arrangements with reduced k capacities fr harmnic current reductin in rectifier type utility interface, IEEE Trans. n Pwer Electrnics, l., N. 5, pp , September 996. [7] P. W. Hammnd, uttransfrmer, U.S. Patent N. 5697, pril 8, 997. [8]. Singh, G. huvaneswari, and. Garg, Harmnic mitigatin using-pulse ac dc cnverter in vectr-cntrlled inductin mtr drives, IEEE Trans. Pwer Delivery, vl., n., pp. 8 9, Jul. 6. [9] S. hi,. S. Lee, and P. N. Enjeti, New -pulse dide rectifier systems fr utility interface f high pwer ac mtr drives, IEEE Trans. Ind. ppl., vl., n., pp. 5 5, Mar. pr Internatinal Schlarly and Scientific Research & Innvatin 5(8) 5 schlar.waset.rg/7-689/6

9 Wrld cademy f Science, Engineering and Technlgy Internatinal Jurnal f Electrical and mputer Engineering l:5, N:8, Internatinal Science Index, Electrical and mputer Engineering l:5, N:8, waset.rg/publicatin/6 []. Singh, G. huvaneswari,. Garg, and S. Gairla, Pulse multiplicatin in ac dc cnverters fr harmnic mitigatin in vectr cntrlled inductin mtr drives, IEEE Trans. Energy nv., vl., n., pp. 5, Jun. 6. []. Singh,. Garg, and G. huvaneswari, Plygn-nnected uttransfrmer-ased -Pulse D nverter fr ectr- ntrlled Inductin-Mtr Drives IEEE Transactins n Industrial Electrnics, vl. 55, n., pp.97 8, January 8. []. Singh, G. huvaneswari, and. Garg, Harmnic Mitigatin in D nverters fr ectr ntrlled Inductin Mtr Drives IEEE Transactins n Energy nversin, l., n., pp , Sept. 7. []. Singh, G. huvaneswari, and. Garg, Harmnic Mitigatin in D nverters fr ectr ntrlled Inductin Mtr Drives in Prc. IEEE nf. Pwer Electrn. Drives Syst. PEDS, 5. [] []. Singh, G. huvaneswari,. Garg, Pwer-quality imprvements in vectr-cntrlled inductin mtr drive emplying pulse multiplicatin in -D cnverters, IEEE Trans. n Pwer Delivery, vl. n., pp , July 6. [5]. Singh, G. huvaneswari,. Garg, -Pulse -D nverter fr Pwer Quality Imprvement in ectr ntrlled Inductin Mtr Drives, Electric Pwer Systems and mpnents, vl., n., pp , Octber 6. [6]. Singh, and S. Gairla, Pulse Multiplicatin in uttransfrmer ased -D nverters using a Zigzag nnectin, Jurnal f Pwer Electrnics, l. 7, N., July 7. [7] S. Miyairi, S. Iida, K. Nakata, and S. Masukawa, New methd fr reducing harmnics invlved in input and utput f rectifier with interhase transfrmer, IEEE Trans. Ind. ppl., vl., n. 5, pp , Oct. Nv [8] M. E. illablanca and J.. rrilaga, Pulse multiplicatin in parallel cnverters by multi tap cntrl f interphase reactr, in Prc. Inst. Elect. Eng., vl. 9, n., Jan. 99, pp.. [9] S. hi,. S. Lee, and P. N. Enjeti, New -pulse dide rectifier systems fr utility interface f high pwer ac mtr drives, IEEE Trans. Ind. ppl., vl., n., pp. 5 5, Mar. pr [] S. Miyairi, S. Iida, K. Nakata, and S. Masubawa, New methd fr reducing harmnics invlved in input and utput f rectifier with interphase transfrmer, IEEE Trans. Ind. ppl., vl. I-, n. 5, pp , Sep./Oct [] P. Qijun, M. Weiming, L. Dezhi, Z. Zhihua, and M. Jin, New ritical Frmula and Mathematical Mdel f Duble-Tap Interphase Reactr in a Six Phase Tap-hanger Dide Rectifier IEEE Transactins n Industrial Electrnics, vl. 5, n., pp.79 85, February 7. [] F. Meng, S. Yang, W. Yang, and X. Jin, mments and Further Results n New ritical Frmula and Mathematical Mdel f Duble Tap Interphase Reactr in a Six-Phase Tap-hanger Dide Rectifier IEEE Transactins n Industrial Electrnics, vl. 57, n., pp.95 95, March. [] J. rrilaga and M. illablance, -pulse HD cnversin, Prc. Inst. Elect. Eng., vl. 8, n., pp. 57 6, Jan. 99 [] IEEE Guide fr pplicatin and Specificatin f Harmnic Filters, IEEE Std. 57,. Internatinal Schlarly and Scientific Research & Innvatin 5(8) 6 schlar.waset.rg/7-689/6