Grid Connected Renewable Energy Sources with Four Leg Inverter for Power Quality Improvement

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1 Proeedngs of tonl onferene on omputng, Eletrl, Eletrons nd Sustnle Energy Systems Grd onneted Renewle Energy Soures wth Four Leg verter for Power Qulty Improvement Y.nthonmm 1.Tejsr 2 1PG Sholr, Deprtment of EEE, Godvr sttute of Engneerng nd Tehnology, Rjhmundry, ndhr Prdesh, d. 2ssstnt Professor, Deprtment of EEE, Godvr sttute of Engneerng nd Tehnology, Rjhmundry, ndhr Prdesh, d. STRT Tody, rese the demnd of Renewle energy resoures (RES) n dstruton systems euse totl energy demnd s suppled y the urnng of fossl fuels nd t s lmted. ths projet presents hysteress ontrol strtegy of three phse four wre grd nterfng nverter to effetvely utlze the renewle energy Soure wth grd. ontrollng of nverter n suh wy tht to utlze the followng funton 1) ompenste lod urrent (.e. redue hrmons), 2) ompenste lod voltge (.e. redue hrmons), 3) ompenste lod retve power nd lod neutrl urrent. The Renewle Energy Soure my e Solr or Wnd depends on dstruton system voltge level. ll these works of the nverter s done ether ndvdully or omned to overome the unlned effets of ll types of lner, nonlner, lne or unlne lods t dstruton level. Ths new ontrol onept s demonstrted wth extensve MTL/Smulnk smulton to vldted result. KEYWORDS: Three phse four wre nverter, Grd nteronneton, dstruton genertor, dstruton system, ttery storge Energy, power qulty. opyrght 216 terntonl Journl for Modern Trends n Sene nd Tehnology ll rghts reserved. I. ITRODUTIO The nresng numer of renewle energy soures nd dstruted genertors requres new strteges for the operton nd mngement of the eletrty grd n order to mntn or even to mprove the powersupply rellty nd qulty. ddton, lerlzton of the grds leds to new mngement strutures, n whh trdng of energy nd power s eomng nresngly mportnt. The powereletron tehnology plys n mportnt role n dstruted generton nd n ntegrton of renewle energy soures nto the eletrl grd, nd t s wdely used nd rpdly expndng s these ppltons eome more ntegrted wth the grdsed systems. Durng the lst few yers, power eletrons hs undergone fst evoluton, whh s mnly due to two ftors. The frst one s the development of fst semondutor swthes tht re ple of swthng qukly nd hndlng hgh powers. The seond ftor s the ntroduton of reltme omputer ontrollers tht n mplement dvned nd omplex ontrol lgorthms. These ftors together hve led to the development of osteffetve nd grdfrendly onverters. Renewle energy soure (RES) ntegrted t dstruton level s termed s dstruted generton (DG). The utlty s onerned due to the hgh penetrton level of ntermttent RES n dstruton systems s t my pose thret to network n terms of stlty, voltge regulton nd powerqulty () ssues. Therefore, the DG systems re requred to omply wth strt tehnl nd regultory frmeworks to ensure sfe, relle nd effent operton of overll network. Wth the dvnement n power eletrons nd dgtl Volume 2 Spel Issue 1 Otoer 216 ISS:

2 Proeedngs of tonl onferene on omputng, Eletrl, Eletrons nd Sustnle Energy Systems ontrol tehnology, the DG systems n now e tvely ontrolled to enhne the system operton wth mproved t P. However, the extensve use of power eletrons sed equpment nd nonlner lods t P generte hrmon urrents, whh my deterorte the qulty of power [1], [2]. Generlly, urrent ontrolled voltge soure nverters re used to nterfe the ntermttent RES n dstruted system. Reently, few ontrol strteges for grd onneted nverters norportng soluton hve een proposed. [3] n nverter opertes s tve ndutor t ertn frequeny to sor the hrmon urrent. ut the ext lulton of network ndutne n reltme s dffult nd my deterorte the ontrol performne. smlr pproh n whh shunt tve flter ts s tve ondutne to dmp out the hrmons n dstruton network s proposed n [4]. [5], ontrol strtegy for renewle nterfng nverter sed on theory s proposed. ths strtegy oth lod nd nverter urrent sensng s requred to ompenste the lod urrent hrmons. The nonlner lod urrent hrmons my result n voltge hrmons nd n rete serous prolem n the power system network. tve power flters (PF) re extensvely used to ompenste the lod urrent hrmons nd lod unlne t dstruton level. Ths results n n ddtonl hrdwre ost. However, n ths pper uthors hve norported the fetures of PF n the, onventonl nverter nterfng renewle wth the grd, wthout ny ddtonl hrdwre ost. Here, the mn de s the mxmum utlzton of nverter rtng whh s most of the tme underutlzed due to ntermttent nture of RES. It s shown n ths pper tht the grdnterfng nverter n effetvely e utlzed to perform followng mportnt funtons: 1) Trnsfer of tve power hrvested from the renewle resoures (wnd, solr, et.). 2) Lod retve power demnd support. 3) urrent hrmons ompenston t P nd 4) urrent unlne nd neutrl urrent ompenston n se of 3phse 4wre system. Moreover, wth dequte ontrol of grdnterfng nverter, ll the four ojetves n e omplshed ether ndvdully or smultneously. The onstrnts t the P n therefore e strtly mntned wthn the utlty stndrds wthout ddtonl hrdwre ost. The pper s rrnged s follows: Seton II desres the system under onsderton nd the ontroller for grdnterfng nverter. Hysteress ontrol s presented n Seton III. Smulton Results re dsussed n Seton IV nd fnlly, Seton V onludes the pper. Fg.1 Shemt of proposed renewle sed dstruted generton II. DESRIPTIO OF THE SYSTEM. Topology n tve power flters re power eletron deves tht nel out unwnted hrmon urrents y njetng ompenston urrent whh nels hrmons n the lne urrent. Shunt tve power flters ompenste lod urrent hrmons y njetng equlut opposte hrmon ompenstng urrent. Generlly, fourwre PFs hve een oneved usng four leg onverters [5]. Ths topology hs proved etter ontrolllty [6] thn the Volume 2 Spel Issue 1 Otoer 216 ISS:

3 Proeedngs of tonl onferene on omputng, Eletrl, Eletrons nd Sustnle Energy Systems lssl threeleg fourwre. ths pper, t s shown tht usng n dequte ontrol strtegy, even wth three phse fourwre system, The topology of the nvestgted PF nd ts nteronneton wth the grd s presented n Fg. 1. It onssts of threeleg fourwre voltge soure nverter. ths type of ppltons, the VSI opertes s urrent ontrolled voltge soure. The proposed system s Three Phse Four wre whh onssts of wnd turne system onneted to the dlnk of grd nterfng nverter s shown n Fg. 1. The voltge soure nverter s key element of wnd system s t nterfes the renewle energy soure to the grd nd delvers the generted power. The Wnd Turne system s onneted to grd wth n nverter oupled to dlnk. The dptor deouples the Wnd Turne system from grd nd lso llows ndependent ontrol of onverters on ether sde of dlnk.. Wnd Turne Wnd turnes re used to onvert the wnd power nto eletr power. Eletr genertor nsde the turne onverts the mehnl power nto the eletr power. Wnd turne systems re vlle rngng from 5W to 23 MW. The energy produton y wnd turnes depends on the wnd veloty tng on the turne. Wnd power s used to feed oth energy produton nd onsumpton demnd, nd trnsmsson lnes n the rurl res. Wnd turnes n e lssfed wth respet to the physl fetures (dmensons, xes, numer of lde), generted power nd so on. For exmple, wnd turnes wth respet to xs struture: horzontl rotor plne loted turnes, turnes wth vertl or horzontl spnnng dretons wth respet to the wnd. Turnes wth lde numers: 3lde, 2lde nd 1 lde turnes. On the other hnd, power produton pty sed lssfton hs four sulsses. Smll Power Systems Moderte Power Systems g Power Systems Megwtt Turnes. Voltge Soure onverter (VS). Voltge Soure onverter (VS) s power eletron deve tht onneted n shunt or prllel to the system. It n generte snusodl voltge wth ny requred mgntude, frequeny nd phse ngle. It lso onverts the D voltge ross storge deves nto set of three phse output voltges. It s lso ple to generte or sors retve power. If the output voltge of the VS s greter thn us termnl voltges, s sd to e n ptve mode. So, t wll ompenste the retve power through system. The type of power swth used s n IGT n ntprllel wth dode. The three phse four leg VSI s modelled n Smulnk y usng IGT. D. ontroller for tve Power Flter The d lnk voltge, Vd s sensed t regulr ntervl nd s ompred wth ts referene ounterprt Vd*.The error sgnl s proessed n PIontroller. The output of the p ontroller s denoted s Im. The referene urrent templtes (I*,I*,nd I*) re otned y multplyng ths pek vlue (Im) y the threeunt sne vetors (U, U nd U) n phse wth the three soure voltges. These unt sne vetors re otned from the three sensed lne to neutrl voltges. The referene grd neutrl urrent (*) s set to zero, eng the nstntneous sum of lned grd urrents. Multplton of mgntude Im wth phses (U,U, nd U) results n the three phse referene supply urrents (I*,I*,nd I*). The grd synhronzng ngle (Ѳ) otned from phse loked loop (PLL) s used to generte unty vetor templte s Fg.2. ontrol Sheme The nstntneous vlues of referene three phse grd urrents re ompute s Volume 2 Spel Issue 1 Otoer 216 ISS:

4 Dsrete, Ts = 5e5 s powergu lod From4 lod From5 Igrd From13 sgnl THD Sope2 Sope9 renewle energy soures Sope13 n Dsply Vgrd From6 p From8 From16 lod From7 nv From2 nv From17 Vd From14 Sope5 Sope7 Sope6 Sope1 Sope ont6roller 4 5 verter Sope12 Step Vgrd From1 Igrd From3 T From9 T From nv From12 nv From11 om nv Vd Sope3 Sope4 Sope8 From15 LODS Sope11 Proeedngs of tonl onferene on omputng, Eletrl, Eletrons nd Sustnle Energy Systems The neutrl urrent s onsdered s dfferene etween the desred urrent nd the urrent eng njeted y the nverter. If the error exeeds the upper lmt of the hysteress nd, the upper swth of the nverter rm s turned off nd the lower swth s turned on. s result, the urrent strts deyng. I n * = (7) The referene grd urrents(i*, I*, I*nd *) re ompred wth tul grd urrents(i, I,Ind ) to ompute the urrent errors s These error sgnls re gven to hysteress urrent ontroller then genertes the swthng pulses for sx IGTs of the grd nterfng nverter. E. DSTTOM DSTTOM s lso ple to generte or sors retve power. If the output voltge of the VS s greter thn us termnl voltges, DSTTOM s sd to e n ptve mode. So, t wll ompenste the retve power through system nd regultes mssng voltges. These voltges re n phse nd oupled wth the system through the retne of ouplng trnsformers. Sutle djustment of the phse nd mgntude of the DSTTOM output voltges llows effetves ontrol of tve nd retve power exhnges etween DSTTOM nd system. ddton, the onverter s normlly sed on some knd of energy storge, whh wll supply the onverter wth D voltge. III. HYSTERESIS URRET OTROL The hysteress urrent ontrol (H) s the esest ontrol method to mplement; t ws developed y rod nd ovotny n The shunt PF s mplemented wth three phse urrent ontrolled VSI nd s onneted to the mns for ompenstng the urrent hrmons. The VSI gte ontrol sgnls re rought out from hysteress nd urrent ontroller. hysteress urrent ontroller s mplemented wth losed loop ontrol system nd wveforms re shown n Fg.3. n error sgnl s used to ontrol the swthes n voltge soure nverter. Ths error s the Fg. 3.Wveform of Hysteress urrent ontroller If the error rosses the lower lmt of the hysteress nd, the lower swth of the nverter rm s turned off nd the upper swth s turned on. s result, the urrent gets k nto the hysteress nd. The mnmum nd mxmum vlues of the error sgnl re e mnnd e mx respetvely. The rnge of the error sgnl e mx e mn dretly ontrols the mount of rpple n the output urrent from the VSI. GRID IV. SIMULTIO IRUIT D RESULTS Totl Hrmon Dstorton ThreePh 3phse tve & Retve Power 3phse tve & Retve Power1 3phse tve & Retve Power2 Fg.4: Trdtonl MTL Smulton rut Dgrm Volume 2 Spel Issue 1 Otoer 216 ISS:

5 Mg (% of Fundmentl) Dsrete, Ts = 5e5 s powergu GRID lod From4 lod From5 Igrd From13 Pv model1 Sope2 Sope9 ThreePh n2 _ renewle energy soures Vgrd From6 p From8 From16 lod From7 nv From2 nv From17 DD2 Vd From14 1 _1 Sope5 Sope7 Sope6 Sope1 Sope 4 5 verter Sope12 Step om nv Vgrd From1 Igrd From3 nv From12 nv LODS ont6roller 3phse tve & Retve Power From 3phse tve & Retve Power1 From11 3phse tve & Retve Power2 Vd Sope3 Sope4 Sope8 From15 Sope11 Proeedngs of tonl onferene on omputng, Eletrl, Eletrons nd Sustnle Energy Systems Fg.5: Smulton results: () Grd voltges, () Grd urrents () Unlned lod urrents, (d) verter urrents Produt1 Gn3 1 Ppv1 Goto 4 s 1 T From9 T Kv Vpv Tmer Goto1 Ipv Goto K s Fg.6: Smulton results: () Grd, () Lod, () verter, (d) dlnk voltge Fg. 9: Equvlent rut of PV ell 1 Seleted sgnl: 48 yles. FFT wndow (n red): 3 yles m Seres RL rnh v Voltge Mesurement2 Sope Tme (s) Wnd Frm Unversl rdge 2 Fundmentl (6Hz) = 17.88, THD= 13.29% Fg. : Modelng of Wnd Energy System Frequeny (Hz) Fg. 7: THD of the rut s 13.29% Fg. 11: Smulton results: () Grd voltges, () Grd urrents () Unlned lod urrents, (d) verter urrents Fg. 8: Proposed MTL smulton rut Dgrm wth Solr nd Wnd System Fg. 12:Smulton results: () Grd, () Lod, () verter, (d) dlnk voltge Volume 2 Spel Issue 1 Otoer 216 ISS:

6 Mg (% of Fundmentl) Proeedngs of tonl onferene on omputng, Eletrl, Eletrons nd Sustnle Energy Systems Seleted sgnl: 48 yles. FFT wndow (n red): 3 yles Tme (s) Replng the duton Genertor wth Douly fed duton genertor s preferred for etter results. future the offshore wnd turnes wll e well mplemented due to ts dvntges of produng hgh power Fundmentl (6Hz) = 2.4, THD= 1.17% Frequeny (Hz) Fg. 14:THD of the rut s 1.17% TLE 3 omprson of THD for Trdtonl nd Modfed rut Models Trdtonl rut Model Modfed rut Model THD % V. OLUSIO D FUTURE SOPE Ths Projet hs presented novel ontrol of n exstng grd nterfng nverter to mprove the qulty of power t P for 3phse 4 wre DG system, flters nd DSTTOM. It hs een shown tht the grdnterfng nverter n e effetvely utlzed for power ondtonng wthout ffetng ts norml operton of rel power trnsfer. The flters n mtgte the hrmons n the output of the nverter nd the DSTTOM n ompenste the voltge t the dstruton level. The grdnterfng nverter wth the proposed pproh n e utlzed to: ) jet rel power generted from RES to the grd, nd/or, ) Operte s shunt tve Power Flter (PF). Ths pproh thus elmntes the need for ddtonl power ondtonng equpment to mprove the qulty of power t P. Extensve MTL/Smulnk smulton s well s the DSP sed expermentl results hve vldted the proposed pproh nd hve shown tht the grdnterfng nverter n e utlzed s multfunton deve. The uthors n onlude on the top dsussed nd proposed. Future enhnement n lso e refed here. Future Sope: STTOM n e repled wth U for etter power ontrol. REFEREES [1] J. M. Guerrero, L. G. de Vun, J. Mts, M. stll, nd J. Mret, wreless ontroller to enhne dynm performne of prllel nverters n dstruted generton systems, IEEE Trns. Power Eletron., vol. 19, no. 5, pp , Sep. 24. [2] J. H. R. Ensln nd P. J. M. Heskes, Hrmon nterton etween lrge numer of dstruted power nverters nd the dstruton network, IEEE Trns. Power Eletron., vol. 19, no. 6, pp , ov. 24. [3] U. orup, F. ljerg, nd P.. Enjet, Shrng of nonlner lod n prllelonneted threephse onverters, IEEE Trns. d. ppl., vol. 37, no. 6, pp , ov./de. 21. [4] P. Jntkosonwt, H. Fujt, H. kg, nd S. Ogswr, Implementton nd performne of oopertve ontrol of shunt tve flters for hrmon dmpng throughout power dstruton system, IEEE Trns. d. ppl., vol. 39, no. 2, pp , Mr./pr. 23. [5] J. P. Pnto, R. Pregtzer, L. F.. Montero, nd J. L. fonso, 3phse 4wre shunt tve power flter wth renewle energy nterfe, presented t the onf. IEEE Renewle Energy & Power Qulty, Sevlle, Spn, 27. [6] F. ljerg, R. Teodoresu, M. Lserre, nd. V. Tmus, Overvew of ontrol nd grd synhronzton for dstruted power generton systems, IEEE Trns. d. Eletron., vol. 53, no. 5, pp , Ot. 26. [7] J. M. rrso, L. G. Frnquelo, J. T. lsewz, E. Glván, R.. P. Gusdo, M. Á. M. Prts, J. I. León, nd. M. lfonso, Power eletron systems for the grd ntegrton of renewle energy soures: survey, IEEE Trns. d. Eletron., vol. 53, no. 4, pp. 2 16, ug. 26. [8]. Renders, K. De Gusseme, W. R. Rykert, K. Stokmn, L. Vndevelde, nd M. H. J. ollen, Dstruted generton for mtgtng voltge dps n lowvoltge dstruton grds, IEEE Trns. Power. Del., vol. 23, no. 3, pp , Jul. 28. [9] V. Khdkkr,. hndr,. O. rry, nd T. D. guyen, pplton of U to protet senstve lod on polluted dstruton network, n Pro. nnu. onf. IEEE Power Eng. So. Gen. Meetng, 26, pp [] M. Sngh nd. hndr, Power mxmzton nd voltge sg/swell rdethrough plty of PMSG sed vrle speed wnd energy onverson system, n Pro. IEEE 34th nnu. onf. dus. Eletron. So., 28, pp Volume 2 Spel Issue 1 Otoer 216 ISS: