Internatonal Journal of Engneerng Trends and Technology (IJETT) Volume 0 Number 4 Feb 05 ower Loss Reducton and Voltage rofle mprovement by hotovoltac Generaton Seyed Reza Seyednour #, Homayoun Ebrahman *, Aref Jall #3 Department Of Electrcal Engneerng, Ardabl Branch, Islamc Azad Unversty,,, 3 Ardabl, Iran Abstract ower Loss reducton and Voltage rofle mprovement n radal dstrbuton system by mplementaton of hotovoltac Generaton () are the objectves of ths study. The multobjectve functon based on system performance ndces of IL and ILQ, related to real and reactve power es, and IVD, related to voltage profle mprovement, are utlzed n the present wor. The artcle Swarm Optmzaton (SO) has been employed to mnmze the multobjectve functon. Two scenaros have been studded n ths wor. In the frst scenaro, the constrant for unt sze has not been consdered. In the second scenaro, the constrant for unt sze has been consdered and n both scenaro problem has been solved wth one. The studes have been carred out on IEEE 33 bus test. The results show that penetraton has decreased power and mproved voltage profle. Comparson of the results obtaned by the proposed method wth those attaned n other studes shows the effectveness of the proposed method. Keywords photovoltac dstrbuted generator (), radal dstrbuton system, the artcle Swarm Optmzaton (SO), power es, voltage profle. I. INTRODUCTION World net electrcty generaton ncreases by 93 percent, from 0. trllon lowatthours n 00 to 39.0 trllon lowatthours n 040. In many parts of the world, concerns about securty of energy supples and the envronmental consequences of greenhouse gas emssons have spurred government polces that support a projected ncrease n renewable energy sources []. Among the renewable energy sources, photovoltac (V) applcaton has receved a great attenton n research because t appears to be one of the most effcent and effectve solutons to ths envronmental problem. In addton to the above expresson another problem s wth the exstng electrc power system. Most of the dstrbuton networs were desgned n order to operate n radal confguraton wth sngle source. Wth ths nd of networ, the power flows from the substaton to the loads n every pont of the grd [].Ths undrectonal power flow results n power es and voltage reducton along the dstrbuton system. Dstrbuted generaton unts (also called decentralzed generaton, dspersed generaton, and embedded generaton) are small generatng plants connected drectly to the dstrbuton networ or on the customer ste of the meter. In the last decade, the penetraton of renewable and nonrenewable dstrbuted generaton (DG) resources s ncreasng worldwde encouraged by natonal and nternatonal polces amng to ncrease the share of renewable energy sources and hghly effcent mcrocombned heat and power unts n order to reduce greenhouse gas emssons and allevate global warmng [3]. Next to envronmental advantages, DGs contrbute to the techncal benefts. Inapproprate DG placement may ncrease system es and networ captal and operatng costs. On the contrary, optmal DG placement (ODG) can mprove networ performance n terms of voltage profle, reduce flows and system es, and mprove power qualty and relablty of supply. The DG placement problem has therefore attracted the nterest of many research efforts n the last ffteen years [3].In order to maxmze the benefts of usng DGs n power systems, t s crucal to fnd the best locaton and sze of DGs smultaneously [4]. The typcal ODG problem deals wth the determnaton of the optmum locatons and szes of DG unts to be nstalled nto exstng dstrbuton networs, subject to electrcal networ operatng constrants, DG operaton constrants. The objectve functon of the ODG can be sngle or multobjectve. The man sngle-objectve functons are: ) mnmzaton of the total power of the system; ) mnmzaton of energy es; 3) mnmzaton of system average nterrupton duraton ndex (SAIDI); 4) mnmzaton of cost; 5) mnmzaton of voltage devatons; 6) maxmzaton of DG capacty; 7) maxmzaton of proft; 8) maxmzaton of a beneft/cost rato; and 9) maxmzaton of voltage lmt [3]. The objectves of ths wor are to mnmze power es and mprove voltage profle n the radal dstrbuton system by the optmal placement and szng of photovoltac dstrbuted generator (. II. SYSTEM MODELING The IEEE 547 rules that the dstrbuted recourses shall not actvely regulate the voltage at the pont of common couplng [5]. The most commonly used operatonal mode s smply unty F. The nverter wll output actve power based on the nsolaton levels captured by the V arrays. Ths mode comples wth IEEE 547 and s most common. Inverter desgns for both small- and large-scale applcatons typcally sze the nverter to match the dc ratng of the V cells, after applyng deratng factors. Ths s because the nverter does not need to be controlled to manage the reactve power export. For power flow analyss, ths means that the nverters are to be modeled as current source nverters operatng at unty F, or smply negatve actve load. In ths study the has been modeled as negatve actve load [6]. Another reason to operate the at unty F s that t s normally consdered that maxmum beneft can be extracted when DG s are operated on unty power factor because the cost of real power s hgher [7]. ISSN: 3-538 http://www.jettjournal.org age 9
Internatonal Journal of Engneerng Trends and Technology (IJETT) Volume 0 Number 4 Feb 05 III. ROBLEM FORMULATION A. Objectve Functon Formulaton The objectve of ths study s to mnmze the power es and mprove voltage profle by njectng n optmal locaton and sze. The locaton and ts correspondng sze n the dstrbuton feeders can be optmally determned usng the followng functon. level mn f, Q, V (3) In ths wor several ndces wll be computed n order to descrbe the effect of n the power es and voltage mprovement. These ndces are defned as follows: Real ower Loss Index (IL): The real power ndces are defned as: IL (4) wth wthout wth Where s the total real power of the dstrbuton system after ncluson of. And wthout s the total real system wthout n the dstrbuton system. Reactve ower Loss Index (ILQ): The reactve power ndces are defned as: Q (5) ILQ Q wth wthout wth Q Where s the total reactve power of the dstrbuton system after ncluson of. And wthout Q s the total reactve system wthout n the dstrbuton system. Voltage rofle Index (IVD): One of the advantages of proper locaton and sze of the DG s the mprovement n voltage profle. Ths ndex penalzes a sze locaton par whch gves hgher voltage devatons from the nomnal value (V nom ). In ths way, the closer the ndex s to zero better s the networ performance. The IVD can be defned as: IVD n Vnom V max Vnom Where n s the number of buses. The multobjectve performance ndex (IMO) was produced from the gather of these ndces by the weghtng factor assgned to that mpact. (6) IMO w IL w * ILQ w * IVD (7) * 3 The sum of the absolute values of the weghts assgned to all ndces should add up to one as shown n the followng equaton: w w w (8) 3 Ths weghtng factor s chosen by the planner to reflect the relatve mportance of each parameter n the decson mang of sttng and szng the. Table I shows the values for the weghts used n present wor and they are selected guded by the weghts n [7]. However, these values may vary accordng to engneer concerns. B. Constran formulaton TABLE I Indces Weghts ndces weghts IL 0.55 ILQ 0.5 IVD 0. Voltage lmts: The voltage drop lmts depend on the voltage regulaton lmts provded by the dsco V mn V V max (9) Lne Thermal lmts: ower flow through any dstrbuton feeder must comply wth the thermal capacty of the lne S S,max (0) capacty: Ths secton defnes the boundary of power generaton by : mn () max IV. MYTHOLOGY A. Bacward Forward Sweep Load Flow Method Tradtonal load flow methods, whch ncorporate the Gauss Sedel method, the Newton Raphson method, and fast decoupled technques, were prmarly developed for transmsson system analyss. Addtonally, a Bacward Forward Sweep method for radal dstrbuton systems usng basc crcut theores and laws s another well-nown method. Dstrbuton systems usually fall nto the category of llcondtoned power systems havng hgh R/X ratos, due to whch the methods le Newton Raphson and fast decoupled may provde naccurate results and may not converge. Therefore, tradtonal load flow methods cannot be drectly appled to dstrbuton systems snce the assumptons made for transmsson systems are not vald for the unque characterstcs of dstrbuton systems [8]. On the other hand, ISSN: 3-538 http://www.jettjournal.org age 93
Internatonal Journal of Engneerng Trends and Technology (IJETT) Volume 0 Number 4 Feb 05 Bacward Forward Sweep methods are qute sutable for radal networs wth hgh R/X rato [0]. B. artal swarm optmzaton (SO) Kennedy and Eberhart developed SO through smulaton of brd flocng n a two-dmensonal space. The poston of each agent s represented by ts x, y axs poston and also ts velocty s expressed by v x (the velocty of x axs) and v y (the velocty of y axs). Modfcaton of the agent poston s realzed by the poston and velocty nformaton. Brd flocng optmzes a certan objectve functon. Each agent nows ts best value so far (pbest) and ts x, y poston. Ths nformaton s an analogy of the personal experences of each agent. Moreover, each agent nows the best value so far n the group (gbest) among pbests. Ths modfcaton can be represented by the concept of velocty (modfed value for the current postons). Velocty of each agent can be modfed by the followng equaton: v wv c rand c rand gbest s pbest s () frst scenaro, the constrant for unt sze has not been consdered. Scenaro II, on the other hand, represents the stuaton where the constrant for unt sze has been consdered and problem has been solved wth one. 5% of total actve load of dstrbuton system represent the constrant for unt sze n the second scenaro. The substaton voltage n both scenaros was consdered as.0 p.u. the can be can be connected to any buses except the frst bus whch s consdered to be the slac bus. The proposed SO-based algorthm was appled to the IEEE 33-bus test system to determne the optmal sze and ste of DG unts such that the mult-objectve functon gven n (7) s mnmzed. For ths test system, three DG unts were optmally szed and placed. The IEEE 33-bus test system operates at.66 V s shown n Fg.. The networ data can be found n []. Ths test networ has loads connected to all buses except bus. The total demand of the networ s 3.75 MW and.3 MVar. where v s velocty of agent at teraton, w s weghtng functon, c j s weghtng coeffcents, rand s random number between 0 and, s s current poston of agent at teraton, pbest s pbest of agent, and gbest s gbest of the group. The followng weghtng functon s usually utlzed n (): wmax wmn w wmax ter (3) ter max Where wmaxs ntal weght, wmns fnal weght, termaxs maxmum teraton number, and ter s current teraton number []. Sh and Eberhart tred to examne the parameter selecton of the above parameters [9, 0]. Accordng to ther examnaton, the followng parameters are approprate and the values do not depend on problems: c =, c =, w max =0.9, w mn =0.4. The current poston (searchng pont n the soluton space) can be modfed by the followng equaton: s s v (4) The power flow soluton method gven n secton IV s used to calculate the IMO functon whch s the system es and voltage profle. The SO wll be used to mnmze IMO functon whle t s searchng for the optmal ste and szng of the. V. SIMULATION AND RESULTS The studes have been carred out on an IEEE 33-bus test system. The load has been modelled as constantan power. We studed two load scenaros, scenaro I and scenaro II. For the Fg.. Sngle lne dagram of the IEEE 33-bus test system The power es for base case (wthout DG) of the IEEE 33-bus test system are 0.7897W and 74.4 Kvar. A. scenaro I: As dscussed above there sn t the constrant for unt sze n ths scenaro. Table II shows the best results. Table III also shows Voltage and power es for IEEE 33-bus test system for scenaro I. Fg. and 3 llustrate Voltage profles and SO convergence for placement, respectvely. One TABLE II RESULTS FOR IEEE 33-BUS TEST SYSTEM FOR SCENARIO I Impact ndex Ste Sze w w Q var IL 0.5093 ILQ 0.55064 IVD 0.047579 IMO 0.47 6 594.887 0.790 74.464 TABLE III VOLTAGE AND OWER LOSS FOR IEEE 33-BUS TEST SYSTEM FOR SCENARIO I NO One ower Loss As % Of Total Actve Load 5.43.766 power Loss reducton% - 49.06 Mnmum Voltage (pu) 0.934 0.954 ISSN: 3-538 http://www.jettjournal.org age 94
IMO V pu V pu Internatonal Journal of Engneerng Trends and Technology (IJETT) Volume 0 Number 4 Feb 05 0.99 0.98 0.97 0.96 0.95 0.94 0.93 voltage profle wth 0.9 wthout wth one 0.9 5 0 5 0 5 30 bus number Fg.. Voltage profles of the IEEE 33-bus test system for scenaro I 0.99 0.98 0.97 0.96 0.95 0.94 0.93 0.9 wthout wth 5% voltage profle 0.9 5 0 5 0 5 30 bus number Fg. 4. Voltage profles of the IEEE 33-bus test system scenaro II 0.4 0.4 0.38 SO Converge Results on IEEE 33-bus test system for the second scenaro revealed that n the case the unt sze was 5% of total actve load, the power reduced by 36.98% and mnmum voltage mproved to 0.9836 pu. 0.36 0.34 0.3 0.3 0 40 60 80 00 0 40 60 80 00 Iteraton number Fg. 3. The convergence of the SO for placement on IEEE 33-bus test system Table III and Fg. show how cases power reducton and voltage mprovement on IEEE 33-bus test system for the frst scenaro. In the case we penetrated the power reducton was 49.06% and mnmum voltage mproved from 0.934 pu to 0.954 pu. B. scenaro II: Constrant for unt sze has been defned for ths scenaro. Table IV shows the best results. Table V also shows Voltage and power es for IEEE 33-bus test system for scenaro II. Fg. 4 llustrates Voltage profle. ower generaton of 930 KW (5%) TABLE IV RESULTS FOR IEEE 33-BUS TEST SYSTEM FOR SCENARIO II Impact ndex IL 0.6978 ILQ 0.6479 IVD 0.07684 IMO 0.56 Ste Sze w w Q var 30 930 7.49 86.407 TABLE V VOLTAGE AND OWER LOSS FOR IEEE 33-BUS TEST SYSTEM FOR SCENARIO II NO 930 KW (5%) ower Loss As % Of Total Actve Load 5.43 3.45 power Loss reducton% - 36.97 Mnmum Voltage (pu) 0.934 0.9836 VI. COMARATIVE STUDY The comparatve study has been done for valdty of the results. The results of the SO algorthm for IEEE 33-bus test system n the frst scenaro were compared wth the solutons obtaned based on the analytcal method [3], GA method [4] and ABC [5-6]. TABLE VI COMARATIVE STUDY FOR IEEE 33-BUS TEST SYSTEM FOR SCENARIO I roposed [3] [4] [5] [6] approach One DG Ste, sze (w) Loss reducton % 490 47.33 380 44.83 400 48.9 590 46.9 594 49.06 The comparson shows that the methodology s more effectve n determnng the szes and locatons for power reducton. VII. CONCLUSION In ths paper, the SO algorthm has been used to fnd the optmal soluton of s szng and sttng problems. The goal of ths optmzaton was mnmzng the power and mprovng voltage profle by penetratng. Inverter s formulated n form of negatve actve load. The smulaton result demonstrates that n optmum szng and sttng can reduce power and mprove voltage profle. For IEEE 33-bus test system n the frst scenaro power reduced by 49.06% and mnmum voltage mproved from 0.934 pu to 0.954 pu. And n the second scenaro power reduced by 36.98% and mnmum voltage mproved by 0.9836 pu. Results for IEEE 33-bus test system n the frst scenaro were compared by results of other studes and the comparsons show that the methodology s more effectve n determnng the szes and sze for power reducton. ISSN: 3-538 http://www.jettjournal.org age 95
Internatonal Journal of Engneerng Trends and Technology (IJETT) Volume 0 Number 4 Feb 05 REFERENCES [] U.S. Energy Informaton Admnstraton (EIA). July 03. Internatonal Energy Outloo 03 wth rojectons to 040. [] D. Sngh, D. Sngh and K. S. Verma, Electrcal Impact of hotovoltac lantn Dstrbuted Networ, IEEE Transactons on Industry Applcatons, VOL. 45, NO., pp. 47 43 January/February 009. [3].S. Georglas and N. D. Hatzargyrou, Optmal Dstrbuted Generaton lacementn ower Dstrbuton Networs: Models, Methods, and Future Research, IEEE Trans. ower Syst., vol. 8, no. 3, pp. 340 348, August 03. [4] A. Amel, S. Bahram, F. hazael and M.-R. Haghfam, Optmum locaton of resources n dstrbuted plannng, IEEE Trans. ower Delvery., vol. 9, no. 4, pp. 83 840, August 04. [5] A. T. Davda, B. Azzopard, B. R. areh and M. D. Desa, Dspersed Generaton Enable Loss Reductonand Voltage rofle Improvement n Dstrbuton Networ Study, Gujarat, Inda, IEEE Trans. ower Syst., vol. 9, no. 3, pp. 4 49, May 04. [6] IEEE, July. 003. IEEE Standard for Interconnectng Dstrbuted Resources wth Electrc ower Systems, formal specfcatons. IEEE Standard 547TM-003. [7] Shre,G. J and Lasster, A.B., July/August. 03. hotovoltac ower Generaton, IEEE Industry Applcatons Magazne.,pp. 63 7. [8] D. Sngh, D. Sngh and K. S. Verma, Multobjectve Optmzaton for DG lannng wth Load Models, IEEE Trans. ower system. vol. 4, no., pp. 47 43 February. 009. [9] Sh Y, Eberhart R. A modfed partcle swarm optmzer. roceedngs of IEEE Internatonal Conference on Evolutonary Computaton (ICEC 98). Anchorage: IEEE ress; 998. p. 69 73. [0] Sh Y, Eberhart R. arameter selecton n partcle swarm optmzaton. roceedngs of the 998 Annual Conference on Evolutonary rogrammng. San Dego: MIT ress; 998. [] Lee, K. Y and El-Sharaw, M. A., 008. Modern Heurstc Optmzaton Technques. IEEE ress. [] Kashem MA, Ganapathy V, Jasmon GB, Buhar MI. A novel method for mnmzaton n dstrbuton networs. In: roceedngs of nternatonal conference on electrc utlty deregulaton and restructurng and power technologes, 000. p. 5 5. [3] Acharya, N; Mahat, and Mthulananthan, N., Dec. 006.An analytcal approach for DG allocaton n prmary dstrbuton networ, Elect. ower Syst. Res., vol. 8, no. 0, pp. 669 678. [4] Shula, T. N. Sngh, S.. Srnvasarao, V and Na, K. B., 00. Optmal szng of dstrbuted generaton placed on radal dstrbuton systems, Elect. ower Compon. Syst., vol. 38, no. 3, pp. 60 74. [5] F. S. Abu-Mout and M. E. El-Hawary, Optmal Dstrbuted Generaton Allocaton and Szng n Dstrbuton Systems va Artfcal Bee Colony Algorthm, IEEE Transactons on ower Delvery, VOL. NO. 4, pp. 090 0, October 0. [6] Hussan, I and Roy, A.K., March. 0. Optmal Dstrbuted Generaton Allocaton n Dstrbuton Systems Employng Modfed Artfcal Bee Colony Algorthm to Reduce Losses and Improve Voltage rofle, IEEE-Internatonal Conference On Advances In Engneerng, Scence And Management., pp. 565 570. ISSN: 3-538 http://www.jettjournal.org age 96