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teratoal Joural of Computer Applcatos ( ) Volume 5 No., February Optmal lag of Dstrbuted Geerato for mproved Voltage Stablty ad Loss educto S. Kumar jet Sr. Assstat rofessor Dept. of EEE, Sr C College
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teratoal Joural of Computer Applcatos ( ) Volume 5 No., February Optmal lag of Dstrbuted Geerato for mproved Voltage Stablty ad Loss educto S. Kumar jet Sr. Assstat rofessor Dept. of EEE, Sr C College of Egeerg Eluru, A.., da-5347 Dr. Navur Kumar Assocate rofessor Dept. of EE A.U. College of Egeerg, Adhra Uversty, Vzag, da. ABSTACT The mpedg deregulated evromet facg the electrc utltes the twety frst cetury s both a challege ad a opportuty for a varety of techologes ad operatg scearos. Chagg regulatory ad ecoomc scearos, eergy savgs ad evrometal mpacts are provdg mpetus to the developmet of a Actve Dstrbuto Networs (ADN), whch s predcated to play a creasg role the electrc power system the ear future. Coectg Dstrbuted Geerator () to a passve dstrbuto etwor becomes a actve dstrbuto etwor. Dstrbuted Geerators effectvely reduce the real power losses ad mprove the voltage profle adal Dstrbuto Networs (DN). ths paper plag ad operato of actve dstrbuto etwors, wth respect to placemet ad szg of Dstrbuted Geerators are dscussed wth the help of a ew methodology. ut placemet ad szg were calculated usg fuzzy logc ad ew aalytcal method respectvely. A detaled performace aalyss was carred out o -bus, 33-bus ad 69-bus radal dstrbuto etwors to demostrate the effectveess of the proposed methodology. The obtaed results are preseted graphcal maer. Keywords dstrbuted geerato, radal dstrbuto etwor, szg, placemet, fuzzy, voltage stablty, etc. Nomeclature TL La curret Lr of curret a r X A MW total power loss total power loss due to actve compoet of total power loss due to reactve compoet actve brach curret reactve brach curret resstace of the brach reactace of the brach ampere mega watt Mvar Abbrevatos ADN DN T&D G.A mega volt ampere reactve actve dstrbuto etwor dstrbuted geerator radal dstrbuto etwor trasmsso ad dstrbuto geetc algorthm WO wthout dstrbuted geerator W FS VS L S Δ Subscrpt wth dstrbuted geerator fuzzy ferece system voltage stablty dex power loss dex dstrbuted geerator sutablty dex small chage varable ode. NTODUCTON Utltes are cotuously plag the expaso of ther exstg electrcal etwors order to face the load growth ad to properly supply ther cosumers. Dstrbuto system provdes a fal l betwee the hgh voltage trasmsso system ad the cosumer. Electrcty etwors are the era of major trasto from stable passve dstrbuto etwors wth udrectoal electrcty trasportato to actve dstrbuto etwors wth bdrectoal electrcty trasportato. Dstrbuto etwors wthout ay uts are passve sce the electrcal power s suppled by the atoal grd system to the customers embedded the dstrbuto etwors. t becomes actve whe uts are added to the dstrbuto system leadg to bdrectoal power flows the etwors []. a actve dstrbuto etwor the amout of eergy lost trasmttg electrcty s less as compared to the passve 4 teratoal Joural of Computer Applcatos ( ) Volume 5 No., February dstrbuto etwor, because the electrcty s geerated very ear the load cetre, perhaps eve the same buldg. Actve Dstrbuto Networ has several advatages le reduced le losses, voltage profle mprovemet, reduced emsso of pollutats, creased overall effcecy, mproved power qualty ad releved T&D cogesto. Hece, utltes ad dstrbuto compaes eed tools for proper plag ad operato of Actve Dstrbuto Networs. The most mportat beefts are reducto of le losses ad voltage stablty mprovemet. They are crucally mportat to determe the sze ad locato of ut to be placed. Studes dcate that poor selecto of locato ad sze would lead to hgher losses tha the losses wthout []. [3], a aalytcal approach has bee preseted to detfy approprate locato to place sgle radal as well as loop systems to mmze losses. But, ths approach, optmal szg s ot cosdered. Loss Sestvty Factor method (LSF) [4] s based o the prcple of learzato of the orgal olear equato (loss equato) aroud the tal operatg pot, whch helps to reduce the amout of soluto space. The LSF method has wdely used to solve the capactor allocato problem. Optmal placemet of uts s determed exclusvely for the varous dstrbuted load profles to mmze the total losses. They have teratvely creased the sze of ut at all buses ad the calculated the losses; based o loss calculato they raed the odes. Top raed odes are selected for ut placemet. The Geetc Algorthm (G.A) based method to determe sze ad locato of ut s used [5]. They have addressed the problem terms of cost, cosderg cost fucto may lead to devato of exact sze of the ut at sutable locato. t always gves ear optmal soluto, but they are computatoally demadg ad slow covergece. ths paper, a ew aalytcal expresso to calculate optmum sze ad fuzzy logc to detfy the optmum locato for placemet are proposed. The s cosdered to be located the prmary dstrbuto system ad the objectve of the placemet s to reduce the losses ad mprove the voltage profle. The cost ad other assocated beefts have ot bee cosdered whle solvg the locato ad szg problem. The szg ad placemet of s based o sgle stataeous demad at pea, where the losses maxmum ad voltage s mmum. The proposed methodology s sutable for allocato of sgle a gve radal dstrbuto etwor.. LOAD FLOW STUDY Covetoal Newto_aphso ad Gauss_Sedel methods may become effcet the aalyss of dstrbuto systems, due to the specal features of dstrbuto etwors, that s, radal structure, hgh /X rato ad ubalaced loads, etc. These characterstc features mae the dstrbuto systems power flow computato dfferet ad somewhat dffcult to aalyze as compared to the trasmsso systems whe the covetoal power flow algorthms are employed [6]. Varous methods are avalable the lterature to carry out the aalyss of balaced ad ubalaced radal dstrbuto systems [7-9]. Methods developed for the soluto of ll-codtoed radal dstrbuto systems may be dvded to two categores. The frst type of methods [7-9] s utlzed by proper modfcato of exstg methods such as, Newto_aphso ad Gauss_Sedel. O the other had, the secod group of methods [-9] s based o forward ad/or bacward sweep processes usg Krchhoff s Laws or mag use of the well-ow b-quadratc equato. Due to ts low memory requremets, computatoal effcecy ad robust covergece characterstc, forward/bacward sweep based algorthms have gaed the most popularty for dstrbuto systems load flow aalyss. the preset study, etwor topology based forward/bacward sweep algorthms have bee used for load flow aalyss. 3. METHODOLOGY A ew method s troduced to mmze the losses assocated wth the absolute value of brach currets by optmally placg uts. The problem of ut placemet cossts of determg the sze, locato ad umber of uts to be stalled a dstrbuto system such that maxmum beefts are acheved whle operatoal costrats at dfferet loadg levels are satsfed. The total power loss a dstrbuto system havg umber of braches s gve by TL s the curret magtude ad s the resstace. ca be obtaed from load flow study. The brach curret has two compoets, actve compoet a ad reactve compoet r. The total losses assocated wth these two compoets ca be wrtte as TL La Lr () () TL a r For a gve cofgurato of a sgle source radal dstrbuto etwor, the losses La assocated wth the actve compoet of brach curret ca ot be mmzed because all the actve power must be suppled by the source at the root bus. Ths s ot true f uts are to be placed at dfferet locatos for loss reducto that s real power ca be suppled locally by usg uts of optmum sze to mmze La assocated wth the actve compoet of brach curret. However there s sgfcat chage reactve power loss wth ut dstrbuto system. 3. detfcato of optmal Sze Cosder DN wth braches. Let a ut be placed at bus m ad β be a set of braches coected betwee the source ad ut. f the ut s placed at bus X the β cossts of braches X, X, X. The ut supples real compoet of curret a ad for radal dstrbuto etwor t chages oly the actve compoet of curret of brach set β. The curret of other braches s ot affected by the ut. The ew actve compoet of curret s ew a a (3) (4) 4 teratoal Joural of Computer Applcatos ( ) Volume 5 No., February f otherwse a s the actve compoet of curret of th brach the orgal system obtaed from the load flow soluto. The La com s assocated wth the actve compoet of brach currets the compesated system. For a ut placed at ode, the system losses are com La a a ( ) (5) ut curret Subtractg Eq. (5) from Eq. (3), loss reducto due to the troducto of ut at ode s obtaed. a (6) Assumg o sgfcat chage ode voltage wth ut power that ca be geerated V (7) The dea s to place a ut wth a proper sze ad locato such that the system loss reducto s maxmzed usg Eq. (6). For system loss reducto to be maxmum the ut must be placed at ode. a a By substutg Eq. (9) Eq. (7) The expresso for maxmum loss reducto r (8) (9) max ( a ) () t s oted that the loss reducto s always postve. Ths process ca be repeated for all the buses to get the hghest possble loss savg for a sgly located ut. 3. detfcato of Optmal Locato Fuzzy approach Ths study presets a fuzzy approach to determe the sutable locatos for placemet. Two objectves are cosdered whle desgg a fuzzy logc for detfyg the optmal locatos. They are () to mmze the real power loss ad () to mata voltage wth permssble lmts. Voltage stablty ad power loss dces of dstrbuto system are modeled by fuzzy membershp fuctos. A fuzzy ferece system (FS) cotag a set of rules s the used to determe the placemet sutablty of each ode the dstrbuto system. The ut ca be placed o the odes wth hghest sutablty dex. A set of fuzzy rules has bee used to determe sutable locatos a dstrbuto system. Two put ad oe-output varables are selected. put varable- s Voltage Stablty dex (VS) ad put varable- s the ower Loss dex (L). Output varable s sutablty dex (S). Fve membershp fuctos are selected for VS. They are L, LN, N, HN ad H. These membershp fuctos are trapezodal ad tragular as show Fg.. Fve membershp fuctos are selected for L. They are L, LM, M, HM ad H. All the fve membershp fuctos are tragular as show Fg.. Fve membershp fuctos are selected for S. They are L, LM, M, HM ad H. These fuctos are also tragular as show Fg. 3. For the allocato problem, rules are defed to determe the sutablty of a ode for stallato. Such rules are expressed the followg maer: F premse (atecedet), THEN cocluso (cosequet). For determg the sutablty of placemet at a partcular ode, a set of multple atecedet fuzzy rules have bee establshed. The puts to the rules are the voltage ad Loss dces ad the output s the sutablty of placemet. FS edtor receves puts from the load flow program. Several rules may fre wth some degree of membershps. FS s based o Mamda maxm ad max-prod mplcato methods of ferece. These methods determe the aggregated output from the set of trggered rules. The max-m method volves trucatg the cosequet membershp fucto of each fred rule at the mmum membershp value of all the atecedets. A fal aggregated membershp fucto s acheved by tag the uo of all trucated cosequet membershp fuctos of the fred rules. After calculatg the sutablty membershp fucto, t s 4 Optmal Sze of MW teratoal Joural of Computer Applcatos ( ) Volume 5 No., February to be de-fuzzfed usg the cetrod method order to determe the optmal locato []. Fg : Membershp fucto plot for VS Fg : Membershp fucto plot for L 5. Oce the sequece of buses s ow determe the optmum ut szes ad the correspodg loss savg. Sce the system load s tme varat ad load durato curve of the system ca be approxmated.t s assumed that load level s costat. The above algorthm provdes the optmal szes ad locatos for a gve load level. 5. ESULTS The proposed method s tested o three dfferet test systems wth dfferet szes, to show that t ca be mplemeted dstrbuto systems of varous cofguratos ad szes. The parameters of the frst test system are gve Appedx. The secod test system s 33-bus system [], the total real power ad reactve power loads o ths system are 3.7 MW ad.3 Mvar. The tal real ad reactve power losses the system are. MW ad.43 Mvar. The thrd system s a 69-bus system [], the total real power ad reactve power loads o ths system are 3.8 MW ad.69 Mvar. The tal real ad reactve power losses the system are.5 MW ad. Mvar. Based o the method descrbed prevously, the optmal szes of are calculated at all buses for the three test systems. Fg. 4, Fg. 5 ad Fg. 6 show the optmal szes of Dg ut at all buses for, 33 ad 69 bus dstrbuto test systems, respectvely. Wth the help of FS edtor optmal locato of Dg ut s foud where real power loss s more ad voltage s low. The optmal locatos of ut are bus9, bus6 ad bus 6 for, 33 ad 69 bus dstrbuto test systems where total power losses atta the mmum value. Fg 3: Membershp fucto plot for S 4. STES FOLLOWED N ALGOTHM There are may computatoal steps volved fdg the optmal sze ad locato to mmze losses a radal dstrbuto system are:. u the load flow program. Select the bus where the maxmum loss ad low voltage s usg fuzzy logc tool box. Correspodg sze s calculated usg Eq s, respectvely.. epeat ths for all the buses except the source bus. detfy the bus usg the fuzzy logc that provdes hghest loss savg. 3. Compesate the bus wth the hghest loss wth the correspodg ut foud from Eq. (7). 4. epeat the steps ) ad ) to get the ext sze ad hece sequece of buses to be compesated Fg 4: Optmal ut szes for -bus radal dstrbuto system The real ad reactve power losses for the correspodg optmal ut szes are show Fg. 7, Fg. 8, Fg. 9, Fg., Fg. ad Fg.. mprovemet voltage stablty was observed from Fg. 3, Fg. 4, ad Fg. 5 for, 33 ad 69 bus dstrbuto test systems, respectvely. esults obtaed are tabulated Table. Table, for three dfferet test system, the results of proposed method, total power losses wth ad wthout are tabulated. t s see that the total power losses are sgfcatly reduced for all test systems. 43 eactve ower Le Loss Mvar eactve ower Le Loss Mvar eal ower Le Loss MW eal ower Le Loss MW Sze of MW eactve ower Le Loss Mvar Optmal sze of MW eal ower Le Loss MW teratoal Joural of Computer Applcatos ( ) Volume 5 No., February WO W Fg 5: Optmal ut szes for 33-bus radal dstrbuto system Fg 9: eal power le losses of 33-bus radal dstrbuto system wth ad wthout WO W Fg 6: Optmal ut szes for 69-bus radal dstrbuto system Brach Number Brach Number WO W Fg 7: eal power le losses of -bus radal dstrbuto system wth ad wthout WO W Fg 8: eactve power le losses of -bus radal dstrbuto system wth ad wthout Fg : eactve power le losses of 33-bus radal dstrbuto system wth ad wthout WO W Fg : eal power le losses of 69-bus radal dstrbuto system wth ad wthout WO W Fg : eactve power le losses of 69-bus radal dstrbuto system wth ad wthout 44 Voltage Stablty dex Voltage Stablty dex Voltage Stablty dex teratoal Joural of Computer Applcatos ( ) Volume 5 No., February bus / / WO W 69- bus 6.99 / / Fg 3: Voltage stablty dex of -bus radal dstrbuto system wth ad wthout Table- esults of proposed method for test systems System Type -bus 33-bus 69-bus..8 Optmal locato of 9-bus 6-bus 6-bus.6.4. WO W Optmal sze MW Total real power loss MW (WO) Fg 4: Voltage stablty dex of 33-bus radal dstrbuto system wth ad wthout WO W Total reactve power loss MVar (WO) Total real power loss MW (W) Total reactve power loss MVar (W) Fg 5: Voltage stablty dex of 69-bus radal dstrbuto system wth ad wthout eal power loss reducto % Table esults of crtcal bus aalyss ad comparso of actve brach currets wth ad wthout for test systems Ty pe - bus Bus o. corres pod g to lowest voltag e Voltage p.u. / VS W.O. D.G.9433 /.79 W.D. G.98 3/.93 Actve brach curret brach (A) W.O. D.G W.D.G eactve power loss reducto % CONCLUSONS The sze ad locato of ut are crucal factors the plag ad operato of actve dstrbuto etwors. Ths study presets a ew methodology whch ca be used to determe the optmal sze ad placemet of. Ths method s easy to be mplemeted ad faster for the gve accuracy. t s proved that the proposed method ca save huge amout of 45 teratoal Joural of Computer Applcatos ( ) Volume 5 No., February power ad acheve sgfcat mprovemet voltage stablty. stallato of ut at oe locato at a tme s proved to be a vald assumpto the preset study. However, ths paper does ot cosder the other beefts of as well as ecoomcs of t. 7. EFEENCES [] Chowdhury S, Chowdhury S, Crossley.9. Mcro grds ad Actve Dstrbuto Networs. st ed. Lodo. ET eewable Eergy Seres. [] Wlls H. L,. Aalytcal methods ad rules of thumb for modelg dstrbuto teracto. EEE roc. ES summer meetg, vol.3, pp [3] Wag C, ad Nehrr MH. 4. Aalytcal approach for optmal placemet of dstrbuted geerato sources power systems. EEE Tras. WS, 9(4), pp [4] Grff T, Tomosovc K, Secrest D, ad Law A. lacemet of Dspersed Geerato systems for reduced losses. proceedgs of 33rd Aual Hawa teratoal coferece o systems sceces, Mau, Hawa, pp. -9. [5] Mardaesh M, ad Gharehpatta GB. 4. Stg ad szg of uts usg GA ad OF based techque. EEE ego Coferece, 3: [6] Trpathy SC, rasad GD, Mal O, ad Hope GS. 98. Load flow solutos for ll-codtoed power systems by a Newto-le method, EEE Tras ower Ap Syst AS- pp , D.O.:.49/p-c: [7] Tey WG ad Hart CE ower flow solutos by Newto s method. EEE Tras ower Ap Syst AS-86; [8] Zhag F ad Cheg CS. 997.A modfed Newto method for radal dstrbuto system power flow aalyss. EEE Tras ower Syst ; [9] Teg JH.. A modfed Gauss-Sedel algorthm of three-phase power flow aalyss dstrbuto etwors. Electrc ower ad Eergy Systems 4; 97-. [] Shrmohammad D, Hog HW, Semlye A ad Luo GX A compesato-based power flow method for wealy meshed dstrbuto ad trasmsso etwors. EEE Tras ower Syst 3, [] Thuaram D, Bada HMW ad Jerome J A obust three-phase power flow algorthm for radal dstrbuto systems. Electrc ower System esearch 5, [] aja, Veatesh B, Chaturved A ad Das D. 4. ower flow soluto of three-phase ubalaced radal dstrbuto etwor. Electrc ower Compoet Systems 3; [3] Teg JH. 3. A drect approach for dstrbuto system load flow solutos. EEE Tras ower Delver 8; [4] Kerstg WH.. Dstrbuto system modelg ad aalyss, CC ress, Boca ato, FL. [5] Cespedes G. 99. New method for the aalyss of dstrbuto etwors. EEE Tras ower Delver 5; [6] Haque MH Load flow soluto of dstrbuto systems wth voltage depedet load models. Electrc ower System esearch 36; [7] Emoglu U ad Hocaoglu MH. 5. A ew power flow method for radal dstrbuto systems cludg voltage depedet load models. Electrc ower System esearch; 6-4. [8] Luo GX ad Semlye A. 99. A Effcet load flow for large wealy meshed etwors. EEE Tras ower Syst, 39_36. [9] ajcc D, Acovs ad Tales Voltage correcto power flow. EEE Tras ower Delvery 9; [] Fuzzy Logc Toolbox MATLAB User s Gude, Math wors c. [] Kashem MA, Gaapathy V, Jasmo GB ad Buhar M,. A ovel method for loss mmzato dstrbuto etwors. roc. t. Co. Electr. Utl. Deregulato estruct. ower Techol, Aprl, [] Bara ME ad Wu FF. 989 Optmal szg of capactor placemet o radal dstrbuto system. EEE Trasactos o ower Delvery; 4:
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