Improvemed Power Quality Using Photovoltaic Unified Static Compensation Techniques

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1 Improeme Power Qalty Usng Photooltac Une Statc ompensaton Technes Narayanappa K. Thanshko 2 Astract - Ths paper escres the esgn an smlaton o cstom power controller photooltac ase power electronc ece se or mtgatons n oltage sag, swells an reacte power compensaton an also controlle crrent harmoncs. Ths system ncreases ecency when compare to the conentonal power strton system. A new PWM ase control scheme s perorme y sng gtal smlator PSAD/EMTD.4.2 an the smlaton was carre ot. The smlaton reslts proe the capalty o the photooltac ase system n mtgatng oltage sag, lcker recton an oltage nalance mtgaton n a power strton system. Keywors - oltage sag, cstom power, PU, PSAD/EMD, photooltac cells. I. INTRODUTION The shnt conerter s se to proe acte power emane y the seres conerter throgh a common D lnk. The seres conerter proes the man ncton o the PU y njectng an A oltage wth controllale magnte an phase angle. To the Dstrton system throgh seres conerter an t exchanges the acte an reacte power wth the A system. Snce the conerters are connecte to a common D lnk, they exchange only acte power an there s no reacte power etween them. It means that reacte power can e controlle nepenently at oth conerters. The Fg. enales oltage control y the shnt nerter an the seres nerter controls acte an reacte power. In recent years power alty sses hae ecome more an more mportant oth n practce an n research. Power alty can e consere to e the proper characterstcs o spply oltage an also a relale an eecte process or elerng electrcal energy to consmers. Bnng stanars an reglatons mpose on spplers an consmers, the olgaton to keep rere power alty parameters at the pont o common coplng (P). Interest n power alty sses reslts not only rom the legal reglatons t also rom growng consmer emans. Owng to ncrease senstty o apple receers an process controls, many cstomers may experence seere techncal an economcal conseences o poor power alty. Dstrances sch as oltage lctatons, lcker, or malance can preent applances rom operatng properly an make some nstral processes sht own. On the other han, sch phenomena now appear more reently n the power system ecase o systematc growth n the nmer an power o nonlnear an reently tme arale loas. When goo power alty s necessary or techncal an economcal reasons, some kn o strance compensaton s neee an that s why applcatons o power alty epment hae een ncreasng. 59 II. OPERATION OF PHOTOOTAI UNIFIED OMPENSATION (PU) The general strctre o the Photooltac Une ompensaton (PU) contans two "ack to ack" oltage sorce conerters sng Inslate-Gate-Bpolar Transstor (IGBT) wth a common D lnk n Fg.. Shnt conerter s connecte as parallel an another conerter s seres wth strton system. The paper rst recee 9 No2009 an n rese orm 8 Mar 200. Dgtal Re: Dgtal Re: A Department o Electrcal Engneerng, Ahyamaan college o Engneerng, Anna Unersty, Emal:narayansn@yahoo.co.n 2 Drector n AET, Anna Unersty, omatore, Emal: thansh_r@remal.com Fg.: Dagram o the photooltac ne compensator. In the shnt ranch o PU the controlle y the phase angle o the conerter an otpt oltage. In the seres ranch o PU the acte an reacte power n the transmsson lne are nlence y the amplte as well as phase angle o the njecte oltage. Thereore the acte power controller ncate wth the reacte power an ce ersa. In orer to mproe the nteracton etween the acte an reacte power control, y ecople control algorthm ase on - axs theory was se [8,9]. Photooltac moels hae een presente y seeral athors [8, 6]. The PU moel conssts o a controllale oltage sorce connecte n seres wth the Dstrton system an two crrent sorces ae n shnt. The present moel s connecte n seres an shnt wth Dstrton system. III. ONTRO STRATEGY OF PU The control system o PU has two parts an s escre n the ollowng ssectons. A. ontrol system o shnt Inerter The controllng magnte an phase o lne oltage an power low can e controlle. By the P array spples the oltage an nerter njecte oltage to the strton system shown Fg 2. The esgn o controllers or shnt an seres nerter as ollows.

2 Asan Power Electroncs Jornal, ol. 4 No.2 Agst 200 The nerter otpt oltage represente y n three phase system as ollows. k= a,, c () an kn an kn nn nn smlarly an c phases. Each phase oltage can e wrtten as: (2) k kn Sk c In a three phase, three wre system oltage represent wth respect netral: nn an N cn 3 (3) Sstttng nn n eaton () 2 (4) n an N cn Smlar eaton can e wrtten or phase an c. The phase oltage can e also wrtten as: an T 2 n T cn T (5) The arales T k represent the states o nerter swtches operaton. T k s 0 or open the Swtches an or close the Swtches. Denng the k swtchng state ncton. a 2 Ta (6) 2 T 3 c 2 T c onerter eces oltage represents. c (7) T aat T cc The system moel s complete n the ac reerence eaton (8) n Fg 3. Fg. 2: Shnt Inerter PSAD/EMTD smlaton crct. Fg. 3: ontrol lock agram o shnt Inerter. a 0 0 a a S (8) a 0 0 S 2 c 0 2a a 2 0 a,, c - three phase conerter crrent, c - nctance o the transormer, a,,c - three phase swtchng state nctons, - apactance o D lnk, sa,s,sc- three phase spply oltages. In e(8), the steay state namental components are snsoal to rece control complexty an rame n e (9) rotatng at the spply reency can e se. Wth ths rame, the poste seence components at namental reency ecome constant. c coswt cos( wt2 /3) cos( wt2 /3) ca (9) 2 sn wt sn( wt 2 / 3) sn( wt 2 / 3) c 3 c co / 2 / 2 / 2 cc c, c --axs -axs conerter crrents, co - Zero seence conerter crrent, w - Spply anglar reency, Takng nto accont the asence o the zero-seence components n the crrents n a three wre system, the smple transormaton matrx can e se. cos( wt / 6) sn wt 2 sn cos( wt / 6) cos wt The moel o - rame eaton () s: 0 w S w 0 S c 0 0, -axs an -axs swtchng state nctons, a (0) () 60

3 s, s --axs an -axs spply oltages. The eaton () changes n to the crrent eaton moels. Dene c c. w... w.. S S (2) (3). w.. S (4). w.. (5) an conserng that the crrent control s realze y sng PI controller, the eatons (6) an (7) sng n Fg. 3. S. w. (6) S. w. (7) The oltage eaton n the moel (3) can e wrtten as: (8). p.. (9) An conserng that oltage control s realze y sng a PI controller, the eaton (20) sng n Fg. 3 s: 2 (20) cr p 3 sp B. ontrol system o seres nerter The oltage compensator s a system ase on power electroncs nerter njecte oltage an compensate the oltage sags, an keepng the loa oltage aron ts rate ale Fg 4. Uner alance conton the seres nerter otpt oltage The arales T k 2 represent the states o seres nerter operaton o swtches. T k 2 s 0 or open the Swtches an or the closng the Swtches. Denng the k as swtches state ncton. a2 2 Ta2 (2) 2 2 T 2 3 c2 2 T c2 The lter otpt oltage s (22) ko k k The complete moel o the system as shown Fg (23) 0 w 0 2 w 0 0 o o 0 0 w l o o 0 w 0 a,, c three phase conerter crrents S c - nctance o the transormer, a,, c - three phase swtchng state nctons, - apactance o D lnk, sa, s, sc - three phase spply oltages. The steay state namental component s snsoal to rece control complexty n the rame when rotatng at the spply reency can e se. Wth ths ame the poste seence components at namental reency ecomes constant. The crrent eaton n the moels can e wrtten as: (24) (25) onserng that the crrent control s realze y sng PI compensators the eatons (26) an (27) sng n Fg. 5. o 2 (26) 2 o 2 (27) 2 The oltage eaton n the moel (23) can e wrtten as: (28)... (29) p an conserng that oltage control s realze y sng a PI compensator, the eatons (26) an (27). 2 (30) cr p 3 sp Fgs 3 an 5 shows the gate plse generator crct o the seres an shnt nerters ase on SPWM techne. In the presente SPWM techne, the error sgnal s apple to a PI controller an the otpt sgnal o PI controller s the reerence sgnal o the SPWM techne. oltage sag compensate eaton s per-sag - per(p) (3) %Sag = * 00 per-sag (p ) I. SIMUATION RESUTS The schematcs agrams Fgs. 2 an 4 are smlate y sng PSAD/ EMTD, The PU s place n a k strton system wth statc loa o 2.7 MA. The smlatons are carre ot an llstrate the eecteness o the PU as a ne compensator or oltage reglaton, oltage sag compensaton, oltage lcker recton, an oltage nalance mtgaton. oa s ncrease rom 0.5 to.0 per nt as shown n Fg 6. The loa oltage ecreases an retrns to ts rate oltage e to the oltage sag compensaton capalty o PU system. Fg 7 (a).shows the lne oltage sag wthot PU an the Fg 7 () shows that lne oltage sag compensaton wth PU. The smlaton pero 300ms-600ms, the loa s ncrease y closng swtch. In ths case, the oltage rops y almost 34% wth respect to the reerence ale. 6

4 Asan Power Electroncs Jornal, ol. 4 No.2 Agst 200 At 600ms. The swtch s opene an remans so throghot the rest o the smlaton the loa oltage s ery close to the reerence ale. In ths same nteral A s close an the PU starts operatng to mtgate the oltage sag an restore the oltage ack to the reerence ale. The smlaton also carre ntally an nalance oltage e to two phase to gron alts that are phase A an phase at tme t = 300ms to t = 600ms. As shown n Fg 8. a) P oltage wthot oost conerter a) Wthot PU. ) P oltage wth oost conerter ) Wth PU. Fg.6: Per nt oltage rms at the loa pont. Tme n sec a) Wthot PU a) Wthot PU. Tme n sec ) Wth PU ) Wth PU. Fg 7: ne oltage a at the loa pont. Tme n sec c) Wth spply oltage o PU Fg. 8: Phase alts 62

5 . ONUSION The se o compter programs n smlaton o cstom power controllers nclng photo oltac s extremely mportant or the eelopment an nerstanng o the power electroncs ase technology. The reslt s achee throgh gtal smlaton whch clearly shows the capalty o the PU to mtgate the oltage sags prong a contnosly arale leel o shnt compensaton o oltage sages an reglates the oltage a new PU esgn whch ncorporates P mole as a D oltage sorce to mtgate oltage sags n a strton system has een presente. The PU s moele wth a new eeack controller scheme to control the IGBT swtches o the nerter. The otpt s ltere n orer to mtgate the harmoncs generate rom swtchng. The P s connecte to a oost conerter so as to achee a hgher otpt oltage or chargng the capactor ecently. Smlaton reslts proe that the P s a sel alternate D sorce or the PU. I. REFERENES [] Z.A. Zakara, B..hen M.O. Hassan an J.X Yan Dstrton statc compensator se as cstom power Epment an ts smlaton Usng PSAD Inormaton Technology Jornal, ol 7, No. 8, pp [2] Introcton to PSAD/EMTD, Mantoa HD Research centre, March [3] Anaya. ar, E. Acha, Moelng an analyss o cstom power systems y PSAD/EMTD IEEE Trans Power elery, ol. 7, No., Janary 2002, pp [4] Math.H.J. Bollen nerstanng power alty prolems-oltage sags an nterrpton IEEE Press, 2000, pp [5] S. Km, Gwonjongyoo. Jnsoo Song A Bnctonal Utlty connecte Photooltac system wth power actor correcton an UPS aclty IEEE,PS ol. 25, May 996, pp [6] Y. hen an O. Boon-Teck STATOM Base an mltmoel s o mltleel conerters ner mltple reglaton eeack control IEEE Trans, Power Electroncs, ol. 4, Sept 999, pp [7] Km Hyosng an K Sl Seng ompensaton oltage control n ynamc oltage restorer y se o ee orwar an state eeack scheme IEEE Transacton on Power Electroncs, ol. 20, No. 5, 2005, pp [8] B. Sawr, M.R. Ghan, A. A.Zn, A.H. Yatn an H. Shaon oltagesag Malaysa Expernence, IEEE, ol. 2, Ag 998, pp [9] Bhm Sngh, Alka Aya, AP. Mttal an J.R.P. Gpta Moellng o DSTATOM or strton system Internatonal Jornals o Eenrgy an Technology Polcy, ol. 4, No. /2, 2006, pp [0] M.A. Hannan an AzahMohame PSAD /EMTD smlaton o ne seres- shnt compensator or power alty mproement. IEEE Trancaton on Power Delery, ol. 20, No. 2, Aprl 2005, pp [] D.G. ho, E.Ho. Song, A Smple UPF control algorthm an smlaton on statonary reerence rame, ISIE onerence, Psan, Korea, 200, pp [2] J. Jng, M. Da an A. Keyhan Moelng an control o a el ell Base Z-sorce conerter, IEE Apple Power Electroncs onerence, APE 05, ol. 2, March 6-0, 2005, pp BIOGRAPHIES Narayanappa recee ME, Degree n power electroncs n UE an at presently workng as Asst. Proessor, Ahyamaancollege o Engneerng, Hosr. K. Thanshko BE. MSc (Engg), Ph. D. He Sere as Prncpal n Goernment Engneerng olleges an also as memer o Research Boar Anna Unersty, presently workng as Drector n AET, omator. 63