Accentuating of the Resulting Effects after Connecting Power Active Filters on Supplying Line of the Electric Traction System

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1 Aentting of the Reslting Effets fter Conneting Power Ative Filters on Spplying Line of the Eletri Trtion System Ion Bi, Corin Dniel Cntn, Rl Ro, Cis Pnoi Astrt This pper nlyzes the effets tht re otined fter onneting n tive filter in trtion ssttion. The tive filter ommnd is mde in fntion of the tive nd retive power otined sing Clrke trnsformtion. The tive filter simlted in PSCAD is onneted t 0kV three phse system sing power trnsformers. The thors present in this pper the rrents nd voltges vrition wveforms for the mono phsed n three phsed irits of DC trtion loomotive Keywords Ative filter, tive power, hrmoni distortion ftor. retive power, voltge nd rrent hrmonis, I. INTRODUCTION Ative filters re power stti onverters tht n omplish vrios fntions. Present filtering shemes permit the synthesizing of ny rrent wveform tht ontins hrmoni omponents of high orders t high power levels []. The eletri energy onsmer n hoose in priniple for one of the following soltions: ndons the eqipments tht sor distorted rrent nd invests in new eqipments tht ontins irits tht mkes the power system rrents sinsoidl or invests in eletri devies tht keep the distortion level etween imposed limits: tive, pssive or hyrid filters. Term tive power filter is pplying to mny tegories of eletri power irits tht ontin power semiondtors nd pssive elements for energy stokge indtivities or pitors. The filters fntions n e vrios, depending on the pplition []. There re two possile onfigrtions: lned nd non lned lods. For lned lods there re sed three phse Ion Bi - Eletril Engineering nd Indstril Informtis Deprtment, Timisor Polytehnil University, Flty of Engineering Hnedor, (emil: ion.i@fih.pt.ro) Corin Dniel Cntn - Eletril Engineering nd Indstril Informtis Deprtment, Timisor Polytehnil University, Flty of Engineering Hnedor, (e-mil: orin.ntn@fih.pt.ro) Rl Ro - Eletril Engineering nd Indstril Informtis Deprtment, Timisor Polytehnil University, Flty of Engineering Hnedor, (e-mil: rl.ro@fih.pt.ro) Cis Pnoi - Eletril Engineering nd Indstril Informtis Deprtment, Timisor Polytehnil University, Flty of Engineering Hnedor, (e-mil: is.pnoi@fih.pt.ro) filter for hrmoni elimintion. For non lned lods, there re sed three mono phsed ompenstor, t there re for rms strtres (three phses nd nll). The disdvntge onsists in the following: nll rm loding is hrder the other three. II. THEORETHICAL ISSUE In order to solve the prolems of the prolifertion of the hrmoni genertion eqipments, the eletri energy delers tries to stimlte the importnt indstrils onsmers to t in onformity with the present stndrds. The tendeny is strong enogh to determine some eqipment proders to inlde tive filters in hrmonis genertion instlltions in order to improve power qlity genertion []. Prllel strtre, presented in figre, of the filter onnetion hs the lrgest distrition [4]. The tive filter ompenstes the lod hrmoni rrents tht in other wy wold e injeted in power system. Shnt tive filter Figre. Ative filter in prllel onnetion. Nonliner lod Depending on the strtre nd the ommnd system, this topology hs the possiility to ompenste the retive power nd to eqilirte the power system. The filter ondts only the ompenstion rrent. This is n importnt dvntge of prllel onnetion. In the sme time there n e onneted more filter nities in order to inrese the system power. These types of filters re ontining voltge inverters in rrent ommnd. In some modern tioning systems when the lod vrites Isse 5, Volme 5, 0 505

2 etween zero nd nominl lod, there re generted hrmonis nd rel order hrmonis whih mplitdes nd drtions re vrile in energy trnsmission lines. In order to ensre sinsoidl rrents nd in phse with the spplying voltge, it mst e determined the vrge vles for the rrent, nd not to ont the vritions of the lod rrent in fndmentl freqeny period [5][6]. These impose the neessity of elortion of new theory to led to instnteos tretment of the sittion. This is the p-q theory of the instntneos rel nd imginry powers tht offers the possiility to determine the tive nd fitive omponents for eh phse rrent of three phse lod. This leds to rel time ontrol for the fitive power ompenstors. In p-q theory domin, Akgy defines the instntneos rel power nd lso the instntneos imginry power []. The verge period vle of these led to tive nd retive powers. The expression of retive power in non sinsoidl regime is different from the lssil expression. More then this, eh of instntneos power ontins n lterntive power term. It is reslting tht the distorted power ppers s n expression of the eletromgneti energy osilltions etween sore nd lod, the oth instntneos powers ontining prts of this. Definition of the α, β, 0 omponents: In order to define these powers the thors se Clrke trnsformtion from,, omponents to α,β, omponents. α β or sing mtrix: α β () () Using mtrix inverting, there n e otined voltges,, 0 α β () ( t ), ( t ), ( t ) If re phse voltges of three phse lod whih trnsformted omponents re α ( t ),β ( t ), ( t ) nd these voltges spply the lod i ( t ),i ( t ),i ( t ) with rrents whih trnsformted i ( t ),i ( t ),i ( t ) omponents re α β, then instntneos rel power is defined like in lssil theory [7]. p( t) i + i + i p + p + p (4) This instntneos power n e rewritten s the following: p( t) i + i + i α α β β pα + pβ + p pr + p (5) where: p r ( t ) p α ( t ) + p β ( t ) (6) is instntneos rel power withot homopolr omponents nd: p ( t ) ( t )i ( t ) (7) is homopolr power. As it n e oserved from reltions (6) nd (7), one of the dvntges of α, β, 0 trnsformtion is the seprtion of the instntneos homopolr omponent from instntneos rel power expression. Akgi sggested the defining of new vrile nmed instntneos imginry power q(t) (or p i ( t ) ) tht will not e inflened y the homopolr seqene omponents: q( t ) pi( t ) β ( t )iα ( t ) α ( t )i β ( t ) (8) The thors proposed new mesrement nit for its verge vle: imginry volt-mper [VAI]. This new power n e expressed in fntion of line voltges nd phse rrents [],[7]: q [ i + i + i ] (9) p (t) In these onditions, i nd q(t) n e expressed in mtrix form: p r ( t ) α ( t ) β ( t ) iα ( t ) q( t ) β ( t ) α ( t ) iβ ( t ) (0) Using nottion: α ( t ) + β ( t ) () from reltion () n e written the vles of the α nd β Isse 5, Volme 5, 0 506

3 rrents omponents: iα ( t ) α ( t ) β ( t ) p r ( t ) iβ ( t ) β ( t ) α ( t ) q( t ) () The oth of these instntneos powers ontin n verge term nd vrile term: p ( t ) p + p~ ( t ) q ( t ) q + q ~ ( t ) () (4) From reltion (4) n e oserved the differene from the lssil theory in wy tht the retive power is presented like n verge vle of instntneos imginry power. In lssil theory retive power expresses the mximm vle of the osilltion from sore nd lod tht determines power loss in eletri lines, eing prt of this. p~ ( t ) q ~ ( t ) Prtilly, the lterntive terms nd determine power osilltions tht pper etween sore nd lod. They ontrite in ppering of vrile power whih rms vle is distorted power: D P ~ + Q ~ (5) where: P ~ is rms vle of p~ ( t ) ; Q ~ is rms vle of q ~ ( t ). In other words, the distorted power is diretly responsle for eletromgneti energy osilltions etween sore nd lod. Using this ide, retive power exists prtilly in eh phse, like retive rrrents [8]. Rel nd imginry instntneos powers t the lod tht fntions in distorted regime. In the followings, the thors write the rel nd imginry instntneos powers in se when the oth spplying voltges nd the lod rrents re non sinsoidl, eh of these systems dmits Forier deomposition. -for voltges: (t ) Uk sin(kωt ) ( k ) (t ) Uk sin(kωt k π / ) ( k ) (t ) Uk sin(kωt + k π / ) ( k ) (6) - for rrents: i( t ) Il sin( lωt ) ( l ) i ( t ) Il sin( lωt l π / ) ( l ) i ( t ) Il sin( lωt + l π / ) ( l ) (7) Tking into onsidertion the reltions (), α,β,0 omponents of the spplying voltges nd lod rrents re: α(t ) U k sin(kωt )[ os(k π/ )] ( k ) β (t ) Uk os(kωt )sin(k π/ ) ( k ) 6 (t ) U k sin( kωt + α k ) ( k ) (8) iα (t ) I l sin(kωt )[ os(l π / )] ( l ) iβ (t ) Il os(kωt )sin(l π / ) ( l ) 6 i(t ) I l sin( lωt + β l ) (l ) (9) The expression of rel instntneos power depends on the α,β,0 omponents of the voltge nd rrent. Tking into onsidertion reltion (6), for llting the rel instntneos power will e find: p ( t ) p + p~ ( t ) (0) where: p U k I k os ϕk, ( k ) ϕk α k βk () represents the verge vle of the instntneos rel power, eql with tive power in power system Some oservtions n e mde onerning the imginry instntneos power [], [], []: The verge vle of this one, q, does not ontin the mltiple rrent hrmonis. It is ler tht q expression is different of lssil retive power.. The retive power, s the verge vle of the imginry instntneos power is not the one tht is responsile of the eletromgneti energy etween sore nd lod. Responsile ~ elements re p ( t ) nd q ~ ( t ).. In the expression of retive power pper with hnged sign q U I sinϕ U I sinϕ + U I sinϕ U I sinϕ + U I sinϕ () This my e n explntion for the reson tht t the three phse lods tht fntion in non sinsoidl regime, the lod n e dmged in trying to ompenste the powers on one sperior hrmoni. The verge vles of the rel nd imginry instntneos powers remin onstnt in stile sttes (inlding the periodi ones) tht led to freqent ltertion of the rrent, et). [], [4]. III. SIMULATION RESULTS Using PSCAD-EMTDC simltion tool, the thors stdied the vrition of the eletril prmeters t the interfe with the power distrition for two eletri loomotives. Simlting sheme ontins the following elements (figre4): 4 Isse 5, Volme 5, 0 507

4 - voltge sore with nominl voltge Un0kV nd prent power Sn00MVA with three phse power trnsformer 0/0kV, 0MVA for the simltion of the eletri trnsformtion sttion Peştiş. - two power trnsformers 0/7,5kV, 6MVA for simltion of the trnsformtion sttion 0/7,5kV. Eh loomotive hs 6 d motors with seril exittion. The loomotives re spplied throgh two feeders onneted t 7,5kV voltge. Motors spplying (Un0,77kV) is mde sing diode ridge retifiers. The ontinos rrent motor model demnds n inpt signl wm -the rotor rottion speed. Te is n otpt signl nd represents the eletri field generted y motor. For simlting the rottion movement of the motor, it is relised model tht genertes the wm signls (figre ). In order to ssign the hrmoni distortion level tht is introded y this onsmer in power distrition, sing Fst Forier Trnsformer nd hrmoni distortion lltor, the thors llte THD generted y Is, Is, Is rrents on 0kV level in 0/7,5kV eletri sttion. In order to rede THD llted in this wy, shnt tive filter (SAF) instlltion is onneted to 0kV level in 0/7,5kV eletri sttion. The instlltion ontins two power trnsformers in seril onnetion: 0/7,5kV, MVA şi 7,5/kV, MVA. The tive filter with six GTO thyristors is spplying fom the seondry winding of the seond trnsformer. SAF instlltion ontins three phse inverter nd 0kV onnetion trnsformers, s in figre. Figre. Shnt tive filter relized with thyristors. Figre. Model for generting the rottion speed Isse 5, Volme 5, 0 508

5 Figre 4. PSCAD simltion of the stdied instlltion. Isse 5, Volme 5, 0 509

6 Figre 5. Control lgorithm for rrent ompenstion sed on p-q theory. Figre 6. Model for tive filter ommnd sing p-q theory. Figre 7. Three phse voltges nd rrents vritions. Isse 5, Volme 5, 0 50

7 Figre 8. Model for GTO thyristor plse ommnd. Figre 9. Mono phse voltges nd rrents, powers nd THD vritions. Isse 5, Volme 5, 0 5

8 SAF is modeled to injet rrent eql in mgnitde t in opposite phse to hrmoni rrent to hieve sinsoidl rrent wve in phse with the spply voltge [9],[0],[]. Using instntneos power theory introded y prof. Hirofmi Akgi, it ws reted model for llting the referene rrents for tive filter, presented in figre 5 [7]. GTO thyristors re ommnded y firing ontrol devie tht genertes the firing plses signls g, g, g, g4, g5 nd g6. The differene etween filter rrents nd the referene rrents genertes the ontrol signls of the firing ontrol devie.(figre 8) PSCAD model for llting the ompenstion rrents permitts to determine instntneos tive nd retive powers (figre 6). Model of ontrol signls of the firing ontrol devie for GTO ses referene signls tht re determined in previos prgrph. After rnning the simlting progrm t onstnt lod of trtion motors, there re otined the line voltges nd rrents wveforms for three phse irits, downstrem nd pstrem to the SAF onnetion, s in figre 7. It n e oserved tht one phse rrent vle is the dole vle of the rrents on the other two phses. The explntion is tht were onneted two loomotive on two different phses. For mono phse spplying, see figre 9, re presented the vritions for the retified voltge, d motor rrent, tive nd retive powers (efore nd fter filtering) nd THD. IV. CONCLUSION Pssive filters represent the simplest method of hrmoni reding, t in order to rede the distortion regime introded y eletri trtion eqipments, there re neessry mny pssive devies, one for eh hrmoni. This onlsion mkes lmost impossile the exlsive sing of pssive filters, so this method mst e jointed with other power ompenstion devies. Using tive filters spposes THD reding y onneting the filter t 0kV level with dpttion trnsformers. It n e oserved the inresing of the onsmed tive power ese of the dpttion trnsformer. Also n e oserved the inresing of the retive power with the sme vle (in modls) ese of the indtive hrter introded y the dpttion trnsformer. Using tive filters onneted t 0kV voltges demnds high osts nd importnt filtering powers. Reding the instlltion power on the tive filter imposes sing pssive filters for low hrmonis (, 5, 7 rnk) nd dimensioning the tive filter for the rest of hrmonis. This method imposes n dditionl stdy regrding the lotion of the pssive filter, ese i tis diffilt to relize the onnetion to the 0kV rs. From nlyzing the fntioning of the shnt tive filter, there n e oserved n improvement of the non sinsoidl regime, t the instlltion re very expensive, so there mst e mde n nlyzing of dvntges nd disdvntges. REFERENCES [] Bhtthry S., Frnk T., Divn D., Bnerjee B., Prllel tive filter system implementtion nd design isses for tility interfe of djstle speed drive systems, Pro. IEEE IAS Ann. Meeting Conf. Re., pp. 0-09, 996. [] Akgi H., Tskmoto Y., Ne A., Anlysis nd design of n tive power filter sing qdseries voltge-sore PWM onverters, IEEE Trns. Ind. Appl. 6 (), pp.9 98, 990 []Akgi H., Generlised Theory of the Instntneos Retive Power in Three-Phse Cirits, Interntionl Conferenes on Power Eletronis, Tokyo, 98. [4]Adrin Bt, Adrin Pnă, Symmetriztion of the Eletri Distrition Grids Lod, University Horizons, Timişor, 000. [5] Akgi H., New trends in tive filters for power onditioning, IEEE Trns. Ind. Appl., pp., 996. [6] Steimel A., Eletri Trtion Motive-Power nd Enrgy Spply. Bsis nd Prtil Experiene, Oldenorg Indstrie Gmh, 008. [7] Akgi H., Generlised Theory of the Instntneos Retive Power in Three-Phse Cirits, Interntionl Conferenes on Power Eletronis, Tokyo, 98 [8] Zho J., Di W., Wng K., Shnt Ative Power Filter nd Its Applition, 00 Interntionl Conferene on Chllenges in Environmentl Siene nd Compter Engineering, vol., 00, pp. 7 76, Chin. [9] Ali H., Lmhih M.T., Rofi M., Shnt Power Ative Filter Control nder Non Idel Voltges Conditions, Interntionl Jornl of Informtion Tehnology, pp.64-69, 006. [0] Popes M., Bitolen Al., Dorien M., Cse Stdy Srvey of Hrmoni Polltion Generted y Rilwy Systems nd Filtering Soltions, th WSEAS Interntionl Conferene on Systems, Herklion, Greee, Jly, -4, 008, pp. 0 5, ISBN , ISSN [] Popes M., Bitolen A., Dorien M., Hrmoni Crrent Redtion in Rilwy Systems, WSEAS Trnstions on Systems, Isse 7, Vol. 7, ilie 008, ISSN: , pp [] Niole P.M., Clitte energiei eletrie in sisteme eletroenrgetie de ptere limitt, Editr Tehni, Bresti,998 Isse 5, Volme 5, 0 5