A Control Strategy for Unified Power Quality Conditioner

Transcription

1 A Control Strtegy for Unfed Power Qulty Condtoner Luís FC Montero, Student memer, IEEE, Murío Aredes, Memer, IEEE, nd João A Moor Neto COPPE/UFJ, Eletrl Engneerng Progrm POox 68504, o de Jnero, rzl E-ml: lfm@oeufrjr Astrt Ths pper presents ontrol strtegy for Unfed Power Qulty Condtoner Ths ontrol strtegy s used n three-phse three-wre systems The UPQC dee omnes shunt-te flter together wth seres-te flter n kto-k onfgurton, to smultneously ompenste the supply oltge nd the lod urrent Preous works presented ontrol strtegy for shunt-te flter tht gurntees snusodl, lned nd mnmzed soure urrents een f under unlned nd / or dstorted system oltges, lso known s Snusodl Fryze Currents Then, ths ontrol strtegy ws extended to deelop dul ontrol strtegy for seres-te flter Now, ths pper deelops the ntegrton prnples of shunt urrent ompenston nd seres oltges ompenston, oth sed on nstntneous te nd non-te powers, dretly lulted from -- phse oltges nd lne urrents Smulton results re presented to ldte the proposed UPQC ontrol strtegy Index Terms Ate Flters, Ate Power Lne Condtoners, Instntneous Ate nd ete Power, Snusodl Fryze Currents, Snusodl Fryze Voltges O I INTODUCTION NE of the serous prolems n eletrl systems s the nresng numer of eletron omponents of dees tht re used y ndustry s well s resdenes These dees, whh need hgh-qulty energy to work properly, t the sme tme, re the most responsle ones for njetons of hrmons n the dstruton system Therefore, dees tht soften ths drwk he een deeloped One of them s the unfed power qulty ondtoner UPQC, s shown n Fg It onssts of shunt-te flter together wth seres-te flter Ths omnton llows smultneous ompenston of the lod urrents nd the supply oltges, so tht ompensted urrent drwn from the network nd the ompensted supply oltge delered to the lod re snusodl, lned nd mnmzed The seresnd shunt-te flters re onneted n k-to-k onfgurton, n whh the shunt onerter s responsle for regultng the ommon DC-lnk oltge In the 0 s of the lst entury, Fryze [] proposed set of te nd non-te rete power defntons n the tme domn From these onepts, Tent et l [] deeloped ontrol strtegy for shunt-te flters tht gurntees ompensted urrents n the network tht re snusodl een f the system oltge t the pont of ommon ouplng PCC lredy ontns hrmons Howeer, ths ontrol strtegy does not gurntee lned ompensted urrents f the system oltge tself s unlned e t ontns fundmentl negte-sequene omponent In [], ths drwk ws oerome, y the ddton of postesequene oltge detetor n the shunt-te flter ontroller Ths ontrol rut determnes the phse ngle, frequeny nd mgntude of the fundmentl postesequene oltge omponent Ths new ontrol strtegy hs een denomnted s the Snusodl Fryze Currents on- S C S L C L C L V d f PWM oltge ontrol C * C * PWM urrent ontrol f S S UPQC ontroller L Fg enerl onfgurton of the Unfed Power Qulty Condtoner UPQC

2 trol strtegy Ths work explots the use of tht poste-sequene oltge detetor to deelop new ontrol strtegy for seres-te flter It s sed on dul mnmzton method for oltge ompenston, together wth synhronzng rut PLL rut The synhronzng rut s responsle to detet the fundmentl frequeny, s well s the phse ngle of the poste-sequene oltge omponent The dul mnmzton method s responsle to urtely determne the mgntude of ths oltge omponent Ths ontrol strtegy s denomnted here s the Snusodl Fryze Voltges ontrol strtegy Further, ths pper presents the ntegrton the Snusodl Fryze Currents nd the Snusodl Fryze Voltges ontrol strteges nto n UPQC ontroller Addtonlly, the proposed UPQC ontroller nludes n lgorthm tht prodes dmpng n hrmon oltge propgton nd hnders lod hrmon urrents to flow nto the network A omplete model of the UPQC pproh s mplemented n dgtl smultor nd results s presented to ldte the proposed ontrol strtegy II THE UPQC CONTOLLE Fg shows the omplete funtonl lok dgrm of the UPQC ontroller The prt shown n Fg s responsle to determne the ompenstng urrent referenes for PWM ontrol of the UPQC shunt onerter, wheres the other prt shown n Fg genertes the ompenstng oltge referenes for PWM seres onerter Next, eh funtonl lok of Fg wll e detled s s s DC V Voltge Detetor DC Voltge egultor 4 loss s s s 5 Dmpng h h Controller h l l l Current Mnmzton s s s Compenstng Voltges lulton Fg The funtonl lok dgrm of the UPQC ontroller for shunt UPQC onerter nd seres UPQC onerter A The Poste-Sequene Voltge Detetor V A poste-sequene oltge detetor [V oltgedetetor lok n Fg ] n terms of "mnmzed oltges" s deeloped A dul prnple for oltge mnmzton s employed, together wth phse-lokedloop rut PLL rut, s shown n Fg The used PLL rut s detled n the next seton In ft, ths dul prnple of oltge mnmzton s used here for extrtng "nstntneously" the fundmentl poste-sequene omponent V n phsor notton, or,, s nstntneous lues, s the outputs of Fg from gener three-phse oltge The dstorted nd unlned oltges s, s, s of the power supply re mesured nd gen s nputs to the PLL rut As shown n the next seton, t determnes the sgnls,,, whh re n phse wth the fundmentl poste-sequene omponent V ontned n s, s, s Thus, only the mgntude of V s mssng The fundmentl hrterst of the used PLL llows the use of dul expresson for determnng te oltges n the form p p p s s s s n rtfe to extrt the V omponent from s, s, s The reson s tht the sgnls,, re three symmetr snus funtons wth unty mpltude, whh orrespond to n uxlry fundmentl poste-sequene urrent I tht s n phse wth V Hene, the erge lue of the "three-phse nstntneous power", V I osφ, s mxmum would e zero f V nd I re orthogonl, nd the erge sgnl r n Fg omprses the totl mpltude of V Therefore, t s possle to gurntee tht the sgnls,, re snusodl nd he the sme mgntude nd phse ngle of the fundmentl poste-sequene omponent of the mesured system oltge s s s s PLL Synhronzng Crut s s r r r Low Pss Flter 5 th Order Cut freq 50 Hz r Fg The V oltge detetor dgrm lok

3 The PLL Crut The used PLL rut Fg 4 n operte stsftorly under hgh dstorted nd unlned system oltges The nputs re s s nd s s The outputs of the PLL rut re,, The lgorthm s sed on the nstntneous te three-phse power expresson p φ The urrent feedk sgnls wt snwt nd wt snwt π/ re ult up y the PLL rut, just usng the tme ntegrl of output ω of the PI-Controller Note tht they he unty mpltude nd wt leds 0 o wt Thus, they represent feedk from postesequene omponent t frequenyω The PLL rut n reh stle pont of operton only f the nput p φ of the PI-Controller hs zero erge lue p 0 nd hs φ mnmzed low-frequeny oslltng portons n ~ p φ p φ p ~ φ p φ One the rut s stlzed, the erge lue of p φ s zero nd, wth ths, the phse ngle of the poste-sequene system oltge t fundmentl frequeny s rehed At ths ondton, the uxlry urrents ωt nd ωt snωt π/, eomes orthogonl to the fundmentl poste-sequene omponent of the mesured oltges s, s respetely Therefore, ωt snωt π/ s n phse wth the fundmentl poste-sequene omponent ontned n s The DC oltge regultor The d oltge regultor s used to generte ontrol sgnl loss, s shown n Fg Ths sgnl fores the shunt te flter to drw ddtonl te urrent from the network, to ompenste for losses n the power rut of the UPQC Addtonlly, t orrets d oltge rtons used y norml operton nd trnsent ompenston errors Ths pont s lrfed lter, where smulton results re dsussed Fg 5 shows the d oltge regultor rut It onssts only of PI-Controller [s K p K I /s], where, for normlzed nputs, K p 050 nd K I 80 ω t snω t X p φ ω Σ PI-Controller X V DC_ref ω t snω t π/ ω t s snω t π/ snω t π/ π/ snω t π/ π/ Fg 4: The Synhronzng Crut PLL Crut Σ low-pss flter PI ontroller loss C Current Mnmzton Fg 6 shows n detls tht funtonl lok nmed "Current Mnmzton" n Fg It determnes the nstntneous ompenstng urrent referenes, whh should e syntheszed y the shunt PWM onerter of the UPQC It hs the sme kernel s the enerlzed Fryze Currents methods wdely used, lke n [4], [5] nd [6] The nputs of the ontroller re the lod urrents,,, the ontrol oltges,, determned y the V detetor, nd the DC oltge regultor sgnl loss The ondutne s determned n Fg 6 orresponds to the te urrent of the lod In other words, t omprses ll urrent omponents tht n produe te power wth the oltges,, A low-pss ffth order flter s used to extrt the erge lue of, whh s denomnted s r Now, sne,, omprses only the VD omponent, r must orrespond to the te porton of the fundmentl poste-sequene omponent I of the lod urrent The ontrol sgnl ontrol s the sum of r nd loss, whh, together wth the ontrol oltges,,, re used to determne the urrents w, w, w These ontrol sgnls re pure snusodl wes n phse wth,, nd nlude the mgntude of the poste-sequene lod urrent proportonl to r nd the te urrent proportonl to loss tht s neessry to ompenste for losses n the UPQC Sne the shunt te flter of the UPQC ompenstes the dfferene etween the lulted te urrent nd the mesured lod urrent, t s possle to gurntee tht the l l l l l l w w w ontrol ontrol ontrol r ontrol Low Pss Flter 5 th Order Cut freq 50 Hz Σ w w w l loss l w w w l l l l DC Fg 5: The DC oltge regultor Fg 6 The Current Mnmzton ontrol lgorthm

4 ompensted urrents s, s, s drwn from the network re lwys snusodl, lned nd n phse wth the postesequene system oltges Ths hrterst represents gret mproement done t the enerlzed Fryze Currents ontrol strtegy D The Dmpng Control Algorthm In UPQC onfgurton, nstlty prolems due to resonne phenomen my our In order to enhne the oerll system stlty, n uxlry rut n e dded to the ontroller of the seres te flter The s de onssts n nresng hrmon dmpng, s seres resstne, ut effete only n hrmon frequenes, others thn the fundmentl one Ths dmpng prnple ws frst proposed y Peng [7], n terms of omponents defned n the pq Theory nd used y Aredes [8] nd Fujt [9] The dmpng ontrol lgorthm, now deeloped n terms of rles n the phse mode, n e seen n Fg 7 The nputs to the dmpng rut re the soure urrents s, s, s ompensted urrents, whh re flowng through the seres trnsformers of the UPQC, nd the oltges determned y the V oltge detetor,, The te nd non-te nstntneous powers re determned y usng the equtons nd ; P s s s Q omp 7 omp 8 q s q / q / q / q q q p p p q q q 6 q q q s s s s q s q q s q q s s 4 omp omp omp omp q omp q omp q q s 6 q s q s h h h p p p q q q Hgh Pss Flter 5 th order Cut off freq 50 Hz Hgh Pss Flter 5 th order Cut off freq 50 Hz 5 h h h h ; h h h omp 7 omp h 8 K K K h h n K Fg 7 Dmpng ontrol lgorthm n terms of rles h h where, q q q / / / ; Note tht the oltges q, q, q re heed from the fundmentl poste-sequene oltges,, Therefore, t s possle to gurntee tht the oltges q, q, q re stll snusodl nd lg 90º the oltges,,, respetely A ondutne nd suseptne re determned from the lulted te nd non-te nstntneous powers, s shown n Fg 7 Then, hgh-pss, ffth order flters re used to extrt the oslltng prts of tht ondutne nd suseptne The uxlry urrents p, p, p nd q, q, q, re determned s follows: p os p os ; 4 p os q os q q os q 5 q os q Dmpng sgnls hrmon omponents stll present n the soure urrents re determned s desred n 6 h q p h q p 6 h q p Fnlly, the multplton etween the dmpng sgnls h, h, h nd gn K determnes the dmpng oltges h, h, h tht wll e dded to the ompenstng oltge referenes of the seres te flter of the UPQC, s wll e explned n the next seton Thus, the gn K ts s hrmon resstne to dmp resonne phenomen E Compenstng Voltges Clulton The lok dgrm tht determnes the ompenstng oltges,, [Fg ], whh s syntheszed y the seres PWM onerter, s shown n Fg 8 The nputs re the ontrol oltges determned y the V oltge detetor:,,, the soure oltges: s, s, s, nd the dmpng oltges: h, h, h The ompenstng oltge re: s s s h h h 7 Idelly, the ompensted oltges delered to the rtl lod wll omprse only the fundmentl poste-sequene omponent,, of the supply oltge S The dmpng oltges wll mproe stlty nd prode hrmon solton

5 h 5 h h l s s s h h h s s s s Fg 9: Lod urrent, urrent of the shunt te flter nd soure urrent Fg 8 Compenstng oltges lulton As onluson, the proposed UPQC ontrol strtegy prodes ompensted oltges nd urrents tht re snusodl, lned nd mnmzed n phse Therefore, the power ftor s del, the oltges delered to the lod re snusodl nd lned, nd t s possle to gurntee tht the soure urrents wll e snusodl, lned nd mnmzed een f under unlned nd / or dstorted system oltges III SIMULATION ESULTS A test se ws mounted to nestgte the performne of the UPQC flter through dgtl smultons, n the Ser Desgner TM Per unt pu qunttes nnot e used dretly n ths smultor Thus, V phse to ground nd A lne urrent were used s the ss of the system A lned, V, three-phse, oltge soure s used A three-phse sxpulse thyrstor retfer, wth 0 A DC-urrent 0%, s used s non-lner lod The shunt-te flter nd the seres-te flter strt ts operton n 0s The totl smulton tme s 08s The thyrstor retfer s onneted t t 0s An ndutor nd resstor, whose lues orrespond to 0 % of the system se mpedne, ompose the soure mpedne In ths se, the short-rut power t the lod termnl s equl to 0 pu The smll hgh-pss flters to mtgte swthng frequeny hrmons t the seres nd shunt PWM onerters re 06 Ω nd C 70 µf Although t sems hgh ptor, t orresponds to 5% of the system sempedne A ptor of 400µF s used t the DC lnk of the UPQC The referene oltge s equl to 45 V To ge n de of the ptor s dmenson, the unt ptor onstnt UCC s lulted, y the followng equton: C V 400µ 45 UCC 8 8 ms P Fg 9 shows the lod, shunt nd soure urrents l,, s, efore, nd fter the strt of the shunt-te flter After the strt of the shunt te flter, the soure urrent eomes lmost snusodl It my e noted, tht the tme tht the soure urrents tke to reh the stedy stte s pretty smll Ths demonstrtes tht the proportonl nd ntegrl gns of the DC oltge regultor re well dmensoned Fg 0 shows the supply oltge s unompensted, left sde of the UPQC, the ompenstng oltge of the UPQC, nd ompensted oltge w, delered to the rtl lod, efore nd fter the strt of the seres te flter The soure oltge hs 0% of negte-sequene omponent t the fundmentl frequeny, plus 5% of 5 th hrmon nd 5% of 7 th hrmon The w oltge, fter the strt of the seres te flter, eomes lmost snusodl Fg shows the DC Lnk Voltge DC nd the losses n the UPQC, represented y the loss sgnl The referene lue t the termnls of the DC-lnk s equl to 45 olts It my e noted, tht the rpple t the DC-lnk oltge s ery smll, n the order of 04% of the referene lue durng short trnsent perod, fter the strt of the UPQC, nd less thn 0 %, n stedy-stte operton The swthng losses of the nerters my not represent the relty, sne del models of swthes n the dgtl smultor re used Ths ondton s needed n the proposed system, euse ss of V nd A ws hosen Fg shows the soure urrents s, s, s, the ompensted oltges w, w, w, nd the urrent s together wth oltge w repeted n seprted grph, efore nd fter s w Fg 0 Supply oltge, ompenstng oltge, nd the ompensted oltge delered to the rtl lod

6 the UPQC energzton It my e seen tht, when the UPQC strt ts operton the soure urrents, s well the ompensted oltges eome lmost snusodl nd lned The soure urrent s nd the ompensted oltge w re lmost n phse fter the strt of the UPQC It onfrms tht the ontrol strtegy proposed s useful n threephse three-wre system, where the system oltges re unlned nd dstorted nd the lod urrents wth hgh ontents of hrmons IV CONCLUSIONS DC loss A ontrol strtegy for Unfed Power Qulty Condtoner the UPQC s proposed Smulton results he ldted the proposed ontrol strtegy, for the use n three-phse three-wre systems In se of usng n threephse four-wre systems, there s the neessty of ompenstng the neutrl urrent In ths se, three-phse fourwre PWM onerter s neessry The omputtonl efforts to deelop the proposed ontrol strtegy s redued, f ompred wth pq-theory-sed ontrollers, sne the α-β-0 trnsformton s oded For three-phse three-wre systems, the performne of the proposed pproh s omprle wth those sed on the pq Theory, wthout loss of roustness een f opertng under dstorted nd unlned system oltge ondtons Presently, the uthors re workng on the posslty of extendng the proposed ontrol strtegy for the use n threephse four-wre systems Fg DC lnk oltge sgnl DC nd DC oltge regultor sgnl loss s w w s w s s w Fg Soure urrents, ompensted oltges nd the ompensted oltge w together wth the soure urrent s V EFEENCES [] S Fryze, Wrk-, lnd- und Shenlestung n elektrshen Stromknsen mt nht-snusfömgen Verluf on Strom und Spnnung, ETZ-Arh Elektroteh, ol 5, 9, pp , 65-67, [] L Mlesn, L osseto, P Tent, Ate Flter for ete Power nd Hrmons Compenston, IEEE PESC 986, pp -0 [] Luís FC Montero, M Aredes, A Comprte Anlyss Among Dfferent Control Strteges for Shunt Ate Flters, Pro CDOM of the V INDUSCON - Conferên de Aplções Industrs, Sldor, rzl, July 00, pp45-50 [4] T Furuhsh, S Okum, Y Uhkw, "A Study on the Theory of Instntneous ete Power," IEEE Trns on Industrl Eletrons, ol 7, no, pp 86-90, Fe 990 [5] L ossetto, P Tent, "Eluton of Instntneous Power Terms n Mult-Phse Systems: Tehnques nd Applton to Power- Condtonng Equpments," ETEP Eur Trns Elet Power Eng, ol 4, no 6, pp , No/De 994 [6] M Depenrok, D A Mrshll, J D n Wyk, "Formultng equrements for Unerslly Applle Power Theory s Control Algorthm n Power Compenstors," ETEP Eur Trns Elet Power Eng, ol 4, no 6, pp , No/De 994 [7] FZ Peng, H Akg, A Ne, A New Approh to Hrmon Compenston n Power Systems A Comned System of Shunt Psse nd Seres Ate Flters, IEEE Trns Ind Appl, ol6, no6, No/De 990, pp [8] M Aredes, J Häfner, K Heumnn, A Comned Seres nd Shunt Ate Power Flter, IEEE/KTH Stokholm Power Teh Conf, ol Power Eletrons, pp 7-4, Stokholm, Sweden, June 995 [9] H Fujt, H Akg, The Unfed Power Qulty Condtoner: The Integrton of Seres nd Shunt Ate Flters, IEEE Trns on Power Eletrons, ol, No, Mrh 998 VI IOAPHIES Luís Fernndo Corrê Montero ws orn n o de Jnero Stte on Mrh 975 He reeed the S Degree from Federl Unersty of o de Jnero n 00 He s enrolled n MS t COPPE/UFJ n Power Eletrons where s deelopng ontrol strteges for te flters nd dees to mproe the power qulty n the eletrl system Hs Mn reserh res of nterest re Custom Power nd FACTS The engneer Luís F C Montero s student memer of the rzln Power Eletrons Soety SOAEP, Interntonl Eletrl nd Eletrons Engneerng IEEE, nd Counl on Lrge Eletr Systems CIE Murío Aredes S 94, M 97 ws orn n São Pulo Stte, rzl, on August 4, 96 He reeed the S degree from Flumnense Federl Unersty, o de Jnero Stte n 984, the MS degree n Eletrl Engneerng from Federl Unersty of o de Jnero n 99, nd the Dr-Ing Degree mgn um lude from Tehnshe Unerstät erln n 996 From 985 to 988 he worked t the Itpu HVDC Trnsmsson System nd from 988 to 99 n the SCADA Projet of Itpu Power Plnt From 996 to 997 he worked wthn CEPEL Centro de Pesquss de Energ Elétr, o de Jnero, s &D Engneer In 997, he eme n Assote Professor t the Federl Unersty of o de Jnero, where he tehes Power Eletrons Hs mn reserh re nludes HVDC nd FACTS systems, te flters, Custom Power nd Power Qulty Issues Dr Aredes s memer of the rzln Soety for Automt Control nd the rzln Power Eletrons Soety João A Moor Neto ws orn n o de Jnero Stte on 965 He reeed the S Degree from UCP-J n 99, nd MS from Federl Unersty of Itjuá n 995 He s enrolled n DS t COPPE/UFJ n Power Eletrons sne 00 In 995 he eme Professor t UNIJUI-S, where he tehes Power System Hs mn reserh res of nterest re FACTS nd Custom Power