A NOVEL APPROACH FOR MITIGATION OF HARMONICS AND INTERHARMONICS IN VARIABLE FREQUENCY DRIVES

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1 Joural of Theoretcal ad Aled formato Techology JATT & LLS. All rghts reserved. SSN: E-SSN: A NOVEL APPROACH FOR MTGATON OF HARMONCS AND NTERHARMONCS N VARABLE FREQUENCY DRVES PROF.VJAYAKUMAR.A, 2 DR.MAHENDRA BABU. T.K Faculty of Electrcal ad Electrocs Egeerg, AAM Egeerg College, Kovlve 2 Professor ad Former Faculty, KLN College of Egeerg, Madura E-mal: vjme@gmal.com 2 babutkm2004@yahoo.com ABSTRACT terhmocs e o-teger multles of the fudametal frequecy that causes several udesrable effects. Vable frequecy drves e ma sources of terhmocs. Also terhmocs e geerated whe the verter load s ubalaced or the verter s oeratg overmodulato. ths study, adjustable seed drve emloyg dode brdge fer ad voltage source verter wth load ubalace s cosdered. Proogato of terhmocs the suly sde due to load ubalace s aalysed ad a ovel method for mtatg terhmocs s roosed. The roosed method emloys a actve flter suly sde whch s smulated usg PSM. Wth the roosed actve flter the comesato effectveess s sgfcatly mroved ad allows the elmato of assve flters thereby reducg t ad sace requred. Keywords: terhmocs, Power Qualty, Adjustable Seed Drve, Actve Flter, terhmocs Mtgato.. NTRODUCTON Wth the advacemet of ower electroc techologes, voltage source verter (VS fed drves e wdely emloyed dustres geerate hmocs ad terhmocs resultg serous ower le olluto. Power qualty s thus aggravated. The dstorted curret due to olluted ower suly causes some udesrable effects o the ower system equmets ad load[7]. Hmocs e sectral comoets that e teger multles of the fudametal frequecy. Hmocs result overheatg of trasformer that leads to deratg of the trasformer. Also t results ulsatg torque vable frequecy drve (VFD whch reduces the effcecy of the drve. terhmocs e comoets that e ot a tegral multle of the fudametal frequecy[2]. At from roblems related wth hmocs, terhmocs result vous other roblems such as low frequecy oscllato of mechacal system, telecommucato terferece, voltage flcker, saturato of curret trasformer, reduced lfe of ducto motor[5]. terhmocs e geerated by loads oeratg traset state ad also whe the suly ad the load oeratg frequeces e dfferet.[4] AC-DC-AC coverso systems ad cyclocoverters e ma sources of terhmocs. VFD geerates terhmocs whe the verter s oeratg overmodulato or the load s ubalaced. As terhmoc frequecy s ot costat ad ves wth the load oeratg frequecy, t s dffcult to elmate t usg assve flters whch e tued at tcul frequecy. By usg actve flters, terhmocs ca be elmated effectvely. ths work, VFD wth load ubalace s cosdered ad ts effect o utlty s dscussed. A sutable shut actve flter s desged ad ts effectveess elmatg hmocs ad terhmocs s justfed usg PSM smulato. Also SAF mroves the suly sde ower factor as t comesates the reactve ower the le[8]. 2. DETALED MODEL OF VARABLE FREQUENCY DRVE 2. Dode-Brdge Rectfer Three hase sx ulse dode brdge fer s most commoly used VFD as a frot ed coverter whch s show Fg.. A lge dc lk caactor s used to reduce rles the fed outut. 360

2 Joural of Theoretcal ad Aled formato Techology JATT & LLS. All rghts reserved. SSN: E-SSN: hmoc currets that e ooste hase to that roduced by VFD. Therefore whe t s coected the ut sde of the VFD, almost all the hmocs ad terhmocs e elmated from the suly. A sgle le dagram of shut actve flter s show Fg.3. Fg.: Dode Brdge Rectfer The three hase suly voltages e exressed as V V V a b c = V = V = V m m m sωt s( ωt 20 s( ωt Pulse Wdth Modulato verter Three hase two level PWM verter s the commoly used verter VFD alcatos. Hgh seed swtchg devces lke GBT ad MOSFET e emloyed for vable frequecy drves. two level verter dodes e coected atallel wth the ma swtches. Susodal PWM techque s used whch the outut ulse tra s roduced by dly comg susodal referece sgal wth the tragul crer sgal at hgh frequecy[3]. Fg.2 shows the PWM verter emloyed for ducto motor cotrol. Fg.3:Sgle Le Dagram Of SAF 3. NTERHARMONC ANALYSS To aalyse motor curret ubalace, a ducor s coected seres wth oe of the stator hase wdgs of the motor[]. 3. Hmoc Trasfer From The verter To The Dc Lk As the motor curret s ubalaced, addto to the ostve sequece comoets, egatve sequece comoets e also reset the motor currets[]. The motor ut curret s gve by u = sqrt.2( ( ωt + ϕ ( + sqrt.2 t + ( ( ω ϕ curret - ostve sequece comoet of curret - egatve sequece comoet of Fg.2: PWM verter 2.3 Shut Actve Flter Shut actve flter (SAF acts as a curret source. Whe t s roerly cotrolled, t roduces These comoets of currets have hase shft of ϕ ad ϕ Smlly motor ut curret equatos ca be wrtte for the remag two hases. 36

3 Joural of Theoretcal ad Aled formato Techology JATT & LLS. All rghts reserved. SSN: E-SSN: The verter ut curret s gve by = S + S + S (2 v u u v v w w ( 2ω + ϕ (3 v = dc + 2 v out 3 = 2 ϕ (4 ad 4 dc m S u, S v, S w e verter swtchg fuctos. dc comoet results actve ower trasfer. The comoet v s resosble for the chage of the verter dc lk curret wth two tmes the outut frequecy 3.2 Hmoc Trasfer Through Dc Lk The dsturbace the verter sde dc lk s trasferred to the dc lk of fer. The dsturbed curret at the dc lk of the fer s gve by ( 2ω t φ (5 = dc + sqrt.2 out + follows S S S br cr = A ( ω t 2π = A ωt 3 2π = A ωt + 3 (8 A s the amltude of the fudametal hmoc comoet ad t s gve by = 2sqrt.3 π A (9 Thus the derved ut curret of the fer for hase A s + + = H H ( ωt + ϕ (( 2ω outt + ω t + φ (( 2ω t ω t + φ out (0 = k dclk v (6 = A H dc = A 2 ( (2 k dclk s the dc lk curret magfcato factor. Ths magfcato occurs at the dc lk due to allel resoace []. As the motor outut frequecy s ved from 0 to f out the fer sde dc lk curret fluctuates wth the frequecy ragg from 0 to 2 f out. 3.3 Hmoc Trasfer Through The Rectfer For ths aalyss, the fer swtchg fuctos e cosdered. The fer s assumed to coduct cotuously. The ut currets of the fer cosderg the swtchg fucto e gve by br cr = S = S = S br cr (7 The swtchg fuctos of the fer e oxmated to ther fudametal comoets as Thus the ubalace the motor curret s roagated to the suly wth two comoets whch e symmetrcal at 2f out ± f. 4..SYSTEM CONFGURATON OF SAF The ma objectve of SAF s to elmate hmocs ad terhmocs. The actve flter curret s cotrolled so that t jects a curret the le ooste to that of the hmoc currets roduced by the load.[6] Fg.4 shows the VFD wth SAF. The block dagram of SAF cotrol scheme s show Fg.6 whch s mlemeted PSM. The referece susodal curret s subtracted from the suly curret ad the flter curret s subtracted from the resultg sgal ad s comed wth the hgh frequecy referece sgal 362

Joural of Theoretcal ad Aled formato Techology 2005-204 JATT & LLS. All rghts reserved. SSN: 992-8645 www.jatt.org E-SSN: 87-395 to geerate trggerg ulses for the devces the SAF. Fg.

4 Joural of Theoretcal ad Aled formato Techology JATT & LLS. All rghts reserved. SSN: E-SSN: to geerate trggerg ulses for the devces the SAF. Fg.5 : Block Dagram Of Cotrol Scheme Of SAF 4.. Smulato Results For the smulato of load ubalace, a ductor of 0.25mH s coected seres wth oe of the hase wdgs. The ducto motor cosdered for smulato s 20kW ad 6 ole ad the motor oeratg frequecy s 40Hz. To demostrate the suerorty of shut actve flter, measuremets e made at the ut sde wth ad wthout SAF. Smulato s cred out usg the ameters lsted Table 4.. Smulato results wthout SAF Measuremets e made at the suly sde wthout actve flter ad e show Fg.6. Fg.7 : Sectrum Of Utlty Curret Accordg to the aalyss made secto 3, for the motor oeratg frequecy of 40Hz, terhmocs wll occur at frequeces of (2f out +f ad (2f out -f e. At 30Hz ad 30Hz resectvely the utlty curret. The magtude of these terhmocs e measured ad tabulated Table. Also hmocs e measured ad tabulated Table. terhmoc s calculated as show below. terhmo corder= terhmoc terhmocfreque cy Fudameta lfrequecy TABLE terhmoc frequecy terhmoc magtude as % of fudametal Hz Hz 4.2 Hmoc Hmoc frequecy Table Hmoc magtude as % of fudametal 5 250Hz Hz 7.7 Fg.6: Utlty Curret The sectrum of the utlty curret obtaed usg FFT s show Fg.7. Power factor s also measured the suly sde ad s calculated to be The relato betwee utlty voltage ad curret waveform s as show Fg

Joural of Theoretcal ad Aled formato Techology 2005-204 JATT & LLS. All rghts reserved. SSN: 992-8645 www.jatt.org E-SSN: 87-395 Fg.8 : Relato Betwee Utlty Voltage Ad Curret 4.

5 Joural of Theoretcal ad Aled formato Techology JATT & LLS. All rghts reserved. SSN: E-SSN: Fg.8 : Relato Betwee Utlty Voltage Ad Curret 4..2Smulato results wth SAF Crcut show Fg.4 s smulated usg PSM. The utlty curret, hase a curret ad actve flter curret of VFD e measured ad e show Fg.9. The utlty curret s susodal ad the magtude of the terhmoc comoet e measured at the utlty sde ad e tabulated Table V. Hmoc comoets e measured ad tabulated table V. Table V terhmoc terhmoc frequecy terhmoc magtude as % of fudametal Hz Hz 0.3 Hmoc Table V Hmoc frequecy Hmoc magtude as % of fudametal 5 250Hz Hz.69 For comso, the results e tabulated Table V. Fg.9: Utlty Curret, Phase A Curret Of VFD Ad Actve Flter Curret The sectrum of utlty curret obtaed usg FFT s show Fg.0. Fg.0 : Sectrum Of Utlty Curret Hmoc ad terhmoc frequecy of suly curret Table V Wthout SAF Wth SAF 30Hz Hz Hz Hz From the results obtaed, t s observed that usg actve flter ffth hmoc comoet s reduced from 26.7% to.27%. ad seveth hmoc comoet s reduced from 7.7% to.69% whch shows cosderable reducto hmocs. The magtude of the terhmoc comoet at (2f out +f e. At 30Hz s reduced from 4.2% to 0.3%. The results show that the SAF s very effectve mtgatg both hmocs ad terhmocs. At from hmoc ad terhmoc elmato, SAF mroves the suly ower factor by reactve ower comesato. Wth SAF ower factor s calculate at the suly sde whch s equal to The utlty curret ad voltage waveforms e show Fg.. 364

Joural of Theoretcal ad Aled formato Techology 2005-204 JATT & LLS. All rghts reserved. SSN: 992-8645 www.jatt.org E-SSN: 87-395 By usg SAF, the utlty ower factor s mroved from 0.69 to 0.93. Fg.

6 Joural of Theoretcal ad Aled formato Techology JATT & LLS. All rghts reserved. SSN: E-SSN: By usg SAF, the utlty ower factor s mroved from 0.69 to Fg. : Utlty Voltage Ad Curret Wth SAF 5. CONCLUSON ths work, a sutable shut actve flter s roosed to mtgate hmocs ad terhmocs from the suly le of vable frequecy drve to mrove the qualty of ower suly system. VFD wth SAF s smulated PSM. The results e comed wth those obtaed for VFD wthout SAF. O comso of the results t ca be cocluded that the roosed system s effectve reducg both hmoc ad terhmoc comoets. At from elmatg hmocs ad terhmocs, SAF mroves the utlty ower factor. Ths shows the suerorty of SAF mrovg qualty of the ower suly system. [4] R.Yacam, Power System Hmocs, t 4 terhmocs, Power Eg. J.,.85-93, Aug. 996, Tutoral. [5] F. De Rosa, R. Lagella, A. Sollazzo, ad A. Testa, O the terhmoc Comoets Geerated by Adjustable Seed Drves, EEE Trasactos o Power Delvery, Vol. 20. No.4, , Oct [6] M.B. Rfa T.H. Otmeyer ad W.J. McQulla, Evaluato of Curret terhmocs from AC drves, EEE Trasactos o Power Delvery, Vol. 5. No.3, , July 2000 [7] Lorezo Mco, Fabo Roch, Adrea Tll, Robust ole cotrol of shut actve flters for hmoc curret comesato, Scece D, Automatca 43 ( , 2006 [8] Murat Kale, Eg O zdemr, Hmoc ad reactve ower comesato wth shut actve ower flter uder o-deal mas voltage, Scece D, Electrc Power Systems Resech 74 ( , Mch 2005 REFERENCES: [] Duro Basc, ut Curret terhmocs of Vable-Seed Drves due to Motor Curret mbalace, EEE Tras. Power Del. Vol.25, o. 4, Oct.200. [2] EEE terhmoc Task Force, terhmocs: theory ad modelg, EEE Tras. Power Del.,vol. 22, o. 4, , Oct [3] S.K.Che, H.J.Su ad G.W.Chag, Modellg VS - fed ASDs by Matlab/Smulk for Hmoc ad terhmoc Assessmet, EEE Xlore Dgtal Lbry,

7 Joural of Theoretcal ad Aled formato Techology JATT & LLS. All rghts reserved. SSN: E-SSN: Fg.4: VFD wth actve flter Table AC Source ducto Motor Voltage 400V Rated Power 20kW Frequecy 50Hz Rated Voltage 400V Resstace 8mΩ Stator Resstace 0.294Ω ductace 0.5mH Stator Leakage ductace H DC Lk Rotor Resstace 0.56Ω Resstace 3.5mΩ Rotor Leakage ductace H ductace 0.00H Ps of Poles 3 Caactace F Motor Oeratg Frequecy 40Hz to 50Hz 366

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