Research Article A Novel Unified Power Quality Conditioning System for Power Quality Improvement and Bidirectional Power Flow Control for Windmill

Transcription

1 Research Journal of Apple cences, Engneerng an Technology 7(16): 3-39, 14 DOI:1.196/rjaset IN: ; e-in: Maxwell centfc Publcaton Corp. ubmtte: February 15, 13 Accepte: March 14, 13 Publshe: Aprl 5, 14 Research Artcle A Noel Unfe Power Qualty Contonng ystem for Power Qualty Improement an Brectonal Power Flow Control for Wnmll G.L. Valsala an L. Pamasuresh Department of Electrcal an Electroncs Engneerng, Noorul Islam Unersty, Tamlnau, Ina Abstract: Ths stuy proposes a new approach of unfe power ualty contoner whch s mae up of a matrx conerter to mtgate the current harmoncs, oltage sags an swells an control the power flow wth B rectonal capablty for wnmll. Matrx conerter njects the compensaton oltage on the loa-se, so t s possble to mtgate the oltage sag/swell problems, resultng n an effcent soluton for mtgatng oltage an current relate power ualty problems. Thus, the propose topology can mtgate the oltage fluctuatons an current harmoncs wthout energy storage elements an the total harmonc storton prouce by the system also ery low. Due to the brectonal power flow capablty of matrx conerter the propose unfe power ualty contoner capable to control the power flow of the wnmll more oer t also transfer power b-rectonal. The pace-vector Moulaton (VM) s use to control the matrx conerter. MATLAB/IMULINK base smulaton results are presente to alate the approach. Keywors: Current harmoncs, MATLAB/IMULINK, matrx conerter, non lnear loa, unfe power ualty contoner, oltage sag/swell, wnmll INTRODUCTION Power ualty s the set of lmts of electrcal propertes that allows electrcal system to functon n a proper manner. Power ualty problems prouce by a large ncrease of the loa current, lke startng a motor or transformer energzng. Pal et al. (8) state the Flexble AC Transmsson ystem (FACT), mproe the relablty an ualty of power transmsson system, the custom power eces enhance the ualty an relablty of power that s elere to customer. ahkal (8) state the man causes of a poor power ualty at customer se are harmonc currents, poor power factor, supply oltage aratons, etc. In recent years the eman for the ualty of electrc power has been ncrease raply. Khakkar (1) escrbe Unfe Power Qualty Contoner (UPQC) s one of the best customs Power eces use to compensate both source an loa se problems. It conssts of shunt an seres conerters connecte back to back to a common DC lnk. It can perform the Functons of both D-statcom an DVR. Fgure 1 shows a basc system confguraton of a general UPQC consstng of the combnaton of a seres acte flter an shunt acte flter Fujta an Akag (). The man am of the seress acte flter s harmonc solaton between a strbuton system an a loa. It has the capablty of oltage flcker/mbalance compensaton as well as oltage regulaton an Fg. 1: Basc structure of unfe power ualty contoner harmonc compensaton at the utlty-consumer Pont of Common Couplng (PCC). Muthazhag an Kumar (1) escrbes the shunt acte flter s use to absorb current harmoncs, compensate for reacte power an negate-seuence current an regulate the DC-lnk oltage between both acte power flters. Unfe power ualty contoner conssts the DC bus an ts DC capactor must be esgne. Dec capactor achees two goals,.e., to comply wth the mnmum rpple reurement of the DC bus oltage an to lmt the DC bus oltage araton urng loa transents. But the propose matrx conerter base UPQC there s no nee of DC capactor. The entre seres acte flter s controlle by the oltage source conerter. But oltage source conerter has some raw back present. Due to swtchng loss, Corresponng Author: G.L. Valsala, Department of Electrcal an Electroncs Engneerng, Noorul Islam Unersty, Tamlnau, Ina Ths work s lcense uner a Create Commons Attrbuton 4. Internatonal Lcense (URL: 3

2 Res. J. Appl. c. Eng. Technol., 7(16): 3-39, 14 capactor leakage current, etc., the strbuton source must proe not only the acte power reure by the loa but also the atonal power reure by the VI to mantan the DC-bus oltage constant. Unless these losses are regulate, the DC-bus oltage wll rop stealy. Moreoer VC base conerter prouces more harmoncs an swtchng losses hgh. The wnmll s the most mportant non conentonal energy source. Varous wn turbne generators aalable to conert wn energy to electrcal energy. Partcularly nucton type wn turbne generator s commonly use for ts rugge constructon, long lfe an more power hanlng capacty. Taeusz an Jacek (8) foun ths type of wnmll affecte by power ualty problems lke oltage sag, swell an current harmoncs. Inucton type wn generator ntally rawn current from the gr an eler power through same gr. Here the power s brectonal. Yuaraj et al. (11) foun many FACT are use to sole the power ualty ssues n wnmll. Conentonal unfe power ualty contoner VC base conerter use, whch s unrectonal. o conentonal power unfe ualty contoner not sutable for nucton type wnmll. In ths stuy a matrx conerter base unfe power ualty contoner compensatess oltage sag an swell an current harmoncs compare an brectonal power flow capablty MATRIX CONVERTER In ths stuy proposes a matrx conerter base unfe power ualty contoner for wn mll nstea of VC base unfe power ualty contoner. Although matrx conerter was ntally ntrouce as an AC Drer, ue to ts aantages may be use n oltage compensaton applcatons lke seres acte flter, DVR (Abareh an Ghaz, 1) an shunt acte flter (Hers et al., 1). A matrx conerter can operatee as a four uarature Ac-Ac conerter crcut. The outpu oltage, freuency an ts ampltue an also the nput power factor can be controlle by utlzng the proper moulaton metho (VM). The man rawbacks of ths topology are the nee for fully controlle b-rectonal swtches an complex algorthm to perform commutaton. The nne matrx conerter swtches can be represente as a 3 3 matrx: = (1) The relatonshp between loa an nput oltages can be expresse as: [ ] = [ ] T A B C a b c Input phase currents can be relate to the output phase currents (9), usng the transpose of matrx: T T [ ] = [ ] T a b c A B C () (3) PROPOED UNIFIED POWER QUALITY CONDITIONER FOR WINDMILL The propose unfe power ualty contoner for wn mll s esgne usng a matrx conerter s shown f Fg.. l are the smoothng nuctor. C () s the Fg. : Propose unfe power ualty contoner 33

3 Res. J. Appl. c. Eng. Technol., 7(16): 3-39, 14 low freuency transformaton functon (4) an set a snusoal nput oltage, as follows: cos( ωt+ α ) = V cos( ωt+ α π / 3) cos( ω + + / 3) t α π (4) Fg. 3: Funamental agram of propose unfe power ualty contoner connecte to an nucton wn turbne generator smoothng capactor. One step up transformer s use for step up the matrx conerter nput oltage. o the matrx conerter njects the sgnfcant current to PCC for current harmonc mtgaton. In ths stuy, the step up transformer was smply moele by a current source ( trans ) an the focus to put on the control of the nput current for the acte flterng functon. Because matrx conerter transfer rato s lmte to.876. In seres part a unfe power ualty contoner s esgne usng the same matrx conerter topology. eres flter remoes the oltage rpples. The seres transformer also calle njecton transformer whch njects the approprate oltage to the loa to compensate the oltage an remoes the harmoncs. More oer the seres part control the power flow b rectonally by ajustng the matrx conerter swtchng. Fgure 3 shows the funamental representaton of matrx conerter base unfe power ualty contoner for wnmll. V pcc s the pont of common couplng. V s s the source oltage. I c β Is the njecte current for current harmonc mtgaton? A m α m Is the matrx conerter ampltue an ts phase angle. V nj γ = 9 s the njecton oltage for oltage compensaton. UPQC s seres acte flter work as solators, nstea of generators of harmoncs an, hence, they use fferent control strateges. Now, here UPQC s seres acte flters workng as controllable oltage sources. Wth ths approach, the ealuaton of the reference oltage for the seres flter s an shunt acte flter reure. = ABC V = D = ( ad + ( a 1) D cos( ω t + α ) cos( ω t + α π / 3) cos( ω + + / 3) t α π 1 ) (5) where, ϕ s the output (or loa) angle. Usng E. (5), the MC output currents can be wrtten as follows: T = D ABC = I o cos( ωt+ ϕ ) cos( ωt+ ϕo) a + cos( ωt+ ϕo π /3) (1 a) cos( ωt+ ϕo π /3) cos( ω + ϕ + π /3) cos( ω + ϕ + π /3) t o t o { Assume the esre nput current to be: ABC = I o cos( ω t+ α + ϕ ) cos( ωt+ α + ϕ π / 3) cos( ω / 3) t α ϕ π where s the nput splacement angle: = I cos( ω t + α + ϕ ) cos( ω t + α + ϕ π / 3) cos( ω + α + ϕ + π / 3) t (6) (7) (8) Power flow control: Conserng a symmetrcal an balance three-phase system an applyng Krchhoff laws to the AC lne currents are obtane n coornates: t t R 1 = ω + ( L L L R 1 = ω + ( L L L Ro Ro (9) (1) The acte an reacte power of en generator s gen n coornates by: THE CONTROL YTEM OF MATRIX CONVERTER BAED UNIFIED POWER QUALITY CONDITIONER FOR WINDMILL P = Q (11) eres part control system of UPQC: The output termnal oltage an nput termnal current conser the The acte an reacte power P an Q are gen by E. (1) an (13), respectely: 34

4 Res. J. Appl. c. Eng. Technol., 7(16): 3-39, 14 Fg. 4: Control system of seres part of propose unfe power ualty contoner Fg. 5: Control system of shunt part of propose unfe power ualty contoner Q= (1) P= P (13) = (14) P + = (15).. + Reference currents conerte to a reference oltage as shown n euaton: = = (16) (17) For space ector moulaton alues conerte to αβ coornatesas shown n the Fg hunt part control system of UPQC: The loa current s measure an transforme from the fxe reference frame to the rotatng -reference frame usng the relaton (18) an the angle of the oltage at the Pont of Common Couplng (PCC): = 3 cos snθ π cos( θ ) 3 π sn( θ ) 3 π cos( θ + ) 3 π sn( θ + ) 3 θ (18) Fgure 5 show the control system of shunt part of propose unfe power ualty contoner snce the rotatng -reference frame s base on the angle of the oltage at the PCC, the an loa current components represent respectely the acte an reacte components of the loa current. The control objecte s to compensate all the loa current components except for the funamental acte loa current component. Therefore a Hgh Pass Flter (HPF) s ntrouce to flter out the funamental component of the acte current. Only the harmonc an reacte components reman n the current reference. The acte current that s prouce by the transformer also nees to be ae to the acte current reference as the matrx conerter. Fnally are obtane the references mc, mc a b c

5 Res. J. Appl. c. Eng. Technol., 7(16): 3-39, 14 Table 1: mulaton parameter of matrx conerter base UPQC Parameter Value source 44 L s mh L f.5 mh c f µf R f.1ω C µf Matrx conerter swtchng freuency 1 Hz Power system freuency 6 Hz an whch are proe to the outer current control loop. All enttes marke wth astersk are reference alues as oppose to real/measure alues. To control the current we use E. (19): L f t mc = pcc c When E. () s conerte nto the rotatng appear as shown reference frame, cross-couplng terms n E. (1) whch must be compensate. When transformng to the rotatng reference frame agan cross couplng terms appear: C L f f t t c c mc mc ' = ' = mc, mc, pcc c, c, mc, mc, c, ω C () f c, ωl Table 1 shows the system parameters of the propose matrx conerter base seres acte flter. IMULATION REULT In ths stuy three phase matrx conerter base unfe power ualty contoner use to compensate the oltage sag/swell, current harmoncs an control f mc mc, (19), (1) power flow an transfer power b-rectonal for an nucton wn mll connecte network. The source oltage s 44 Vrms; 6 Hz. Table 1 shows the propose system man parameters. It nclues source mpeance parameters L an C alues for passe branches use system has been smulate. All the smulaton s performe by the MATLAB/IMULINK moel n screte form. The sample tme of the screte alue s sec. Result for propose UPQC base compensaton for current harmoncs: Fgure 6 shows the matrx conerter base shunt acte flter to mtgate the current harmoncs effcency compare to conentonal technues. Fgure 6a shows the supply oltage an the waeform s snusoal. Fgure 6b shows the waeform of current after propose compensaton. The wae form also snusoal an the harmonc content s Low/. Fgure 6c shows the total harmonc storton leel. The total harmonc storton s % only. It s clear from Fg. 6c that the current njecte by the matrx conerter compensates the harmonc of the nonlnear loa. The THD of the source current s reuce from 3 to %. Result n propose UPQC base compensaton for oltage sag/swell conton: Fgure 7 shows the sngle phase representaton of the propose unfe power ualty contoner n another case. The supply oltage s 44 olts an loa also reuce. Fgure 7a shows the supply oltage at sag an swell contons. At.1 to. sec the oltage sag accrue the oltage sag oltage s at 1 olts. Moreoer the oltage sag accrue at.3 to.4 sec of 5 olts. Fgure 7b shows the matrx conerter base compensaton compensate the oltage sag an swell. Fgure 7c shows the output of the matrx conerter total harmonc storton. It contans less than % of harmonc present. Fg. 6: Propose matrx conerter controlle current harmonc mtgaton (a) supply oltage, (b) supply current after propose compensaton, (c) total harmonc storton of supply current 36

6 Res. J. Appl. c. Eng. Technol., 7(16): 3-39, 14 Fg. 7: Propose matrx conerter base UPQC oltage compensaton (sngle phase) (a) loa oltage after propose compensaton, (b) supply oltage, (c) total harmonc storton of loa oltage Fg. 8: Injecte oltage (a) supply oltage, (b) njecte oltage 3 phase (3 phase), (c) njecte oltage (sngle phase) Result for njecte oltage for oltage sag an swell contons: Fgure 8 shown the oltage njecton through propose unfe power ualty contoner. Fgure 8a shows the fluctuate oltage. The Fg. 8b shows the corresponng njecte oltage through the transformer an ts matrx conerter output oltage shown n Fg. 8c. Result for power flow control usng a matrx conerter base UPQC: Fgure 9 shows the power flow control usng the propose matrx conerter base unfe power ualty contoner. Fgure 9a shows the loa oltage. The nomnal loa oltage s 44. Fgure 9b hows the loa current. Fgure 9c shows the real power s controlle at 1 to 1.5 sec. Fgure 9 shows the P ref Value. The P Reference alue set 1/unt. o the full power s allowe to the loa a unfe power 37 ualty contoner. After 1 sec the power s set at.94/unt. Up to 1.5 sec/. The unfe power ualty contoner seres part controls the power as shown the smulaton result. Result for power flow control usng a matrx conerter base UPQC: Fgure 1 shows the brectonal power flow capablty of matrx conerter base unfe power ualty contoner connecte wnmll Fg. 1a shows the wnmll termnal oltage of 44 olts. Fgure 1b shows the wn mll s power s fe to gr from to 1 sec. o the matrx conerter base unfe power ualty contoner transfer power from the loa se to source se hence the power flow s negate. After 1.3 sec the wn mll s sconnecte from the loa se. o the power transfer s stoppe an the loa consumes power from the source se. o the

7 Res. J. Appl. c. Eng. Technol., 7(16): 3-39, 14 Fg. 9: Power flow control usng a matrx conerter base unfe power ualty contoner Fg. 1: B-rectonal power flow usng a matrx conerter base unfe power ualty contoner power flow s another recton as shown n Fg. 1b. Fgure 1c shows the corresponng current from the source. Due to wn mll connecte to loa se the source se loa eman s share by the wn mll power. After sconnectng the wn mll at 1.3 sec the source current s ncrease as shown. CONCLUION In ths stuy nestgate the use of matrx conerter base unfe power ualty contoner to mtgate the oltage sag/swell, current harmoncs an power flow. Ths stuy also analyze the brectonal power capablty Unfe Power Qualty Contons. Ths can be achee by change swtchng of matrx conerter. The propose UPQC s eres acte flter hanles both balance an unbalance tuatons wthout any ffcultes an njects the approprate oltage component to correct any abnormaltes n the supply oltage to keep the loa oltage balance an constant at the nomnal Value. Moreoer ths controls 38 the power to the loa also. The propose unfe power ualty contoner s mplemente to wn mll the power transfer also achee. Moreoer the shunt control system controls the remoe the current harmonc of loa. Base on smulaton results the matrx conerter base UPQC also mtgates the current harmoncs effcently wth low total harmonc storton, oltage sag an swell an control the power flow brectonal. REFERENCE Abareh, M.H. an R. Ghaz, 1. A new confguraton for ynamc oltage restorer baseon matrx conerter. Proceeng of the 45th Internatonal Unerstes Power Engneerng Conference (UPEC). Carff, Wales, pp: 1-6. Fujta, H. an H. Akag,. The unfe power ualty contoner: The ntegraton of seres an shunt-acte flters. IEEE T. Power Electr., 13():

8 Res. J. Appl. c. Eng. Technol., 7(16): 3-39, 14 Hers, A.A., E. Babae an.h.a. Hossen, 1. New shunt acte power flter base on the nrect matrx conerter. Proceeng of the Iranan Conference on Electrcal Engneerng, pp: Khakkar, V., 1. Enhancng electrc power ualty usng UPQC: A comprehense oerew. IEEE T. Power Electr., 7(5): Muthazhag, M. an N.. Kumar, 1. Comparson of controllers for power ualty mproement employng shunt acte flter. Proceeng of the Internatonal Conference on Computng, Electroncs an Electrcal Technologes, pp: Pal, Y., A. warup an B. ngh, 8. A reew of compensatng type custom power eces for power ualty mproement. Proceeng of the IEEE Internatonal Conference on Power ystem Technology, pp: 1-8. ahkal, H., 8. Power ualty nexes for contnue an screte sturbances n a strbuton area. Proceeng of the n IEEE Internatonal Power an Energy Conference, pp: Taeusz, L. an R. Jacek, 8. Power storton ssues n wn turbne power systems uner transent states. J. Electr. Eng., 16(3): 3-4. Yuaraj, V., E. Pratheep Raj, A. Mowlharan an L. Thrugnanamoorthy, 11. Power ualty mproement for gr connecte wn energy system usng FACT ece. Proceeng of the Jont 3r Internatonal Workshop on Nonlnear Dynamcs an ynchronzaton (IND), 16th Internatonal ymposum on Theoretcal Electrcal Engneerng (ITET), pp: