Response Coordination of Distributed Generation and Tap Changers for Voltage Support

Transcription

1 Response Coordnaton of Dstrbuted Generaton and Tap Changers for Voltage Support An D.T. Le, Student Member, IEEE, K.M. Muttaq, Senor Member, IEEE, M. Negnevtsky, Member, IEEE,and G. Ledwch, Senor Member, IEEE Abstract-- The recent ntroducton of the compettve electrcty market n many countres has sparked a renew tr n connectng small-sze generators nto dstrbuton networks. Those new generators together wth dfferent other types of equpment such as On-load Tap Changng (OLTC) transformer, shunt capactors, shunt reactors, etc, wll all partcpate nto the voltage regulaton process n the power systems. Poor coordnaton between these devces may cause unnecessary operatons, and consequently unnecessary wear, unnecessary energy consumpton as well as poor voltage qualty. In ths paper, we present an nnovatve strategy to coordnate the voltage control actons n a dstrbuton system wth more than one voltage regulatng devce. The method for voltage control coordnaton s developed based on the prorty level of each regulatng devce and mplemented through communcaton. A senstvty-based technque for determnng the control zones of the regulatng devces has been developed. A practcal system wth tap changers and dstrbuted generator has been chosen to test the developed control method. Smulatons have been carred out extensvely on a practcal dstrbuton system to show the effectveness of the method. Index Terms-- Dstrbuted Generaton, Power Dstrbuton System, Voltage Control, Control Zone, On-load Tap Changng Transformer. O I. INTRODUCTION Ne of the most mportant dutes of a dstrbuton system s to mantan the voltage suppled to customers wthn the acceptable lmts, under any loadng crcumstances. Falure to meet ths responsblty may result n malfunctons or damage of customers equpment. Voltage fluctuatons occurrng n the network s essentally the result of changng loads due to varyng demands of customers at dfferent tmes throughout the day. In order to keep these fluctuatons wthn the statutory lmts, ndrect method wth dstrbuted generatons (), shunt reactors/capactor banks, Statc VArs Compensators Ths research has been fnancally supported by the Australan Research Councl under ARC Lnkage Grant K0043 Integraton of Dstrbuted and Renewable Power Generaton nto Electrcty Grd Systems, collaboraton wth Aurora Energy, Tasmana. Ms. An D.T. Le, Dr. Mohammad A. Kashem, and Prof. Mchael Negnevtsky are wth the School of Engneerng, Unversty of Tasmana, Hobart, Australa, and Prof. Gerard Ledwch s wth the School of Engneerng Systems, Queensland Unversty of Technology, Brsbane, Australa, (emals: M.Kashem@utas.edu.au; dtale@utas.edu.au; Mchael.Negnevtsky@utas.edu.au; g.ledwch@qut.edu.au). (SVC), etc., and drect method wth On-load Tap Changng (OLTC) transformer, regulators, etc. are used []. In ths paper, the voltage regulaton task s accomplshed by usng the OLTC n conjuncton wth the. Whle the OLTC s already avalable n most dstrbuton feeders, the s chosen here as voltage regulatory equpment for the many benefts such as voltage support, lne loss reducton, mprovement of supply relablty and securty. A problem that arses n ths knd of voltage control system, however, s the possblty of excessve operatons of the OLTC and/ or the. Ths mght happen due to nsuffcent voltage control method or a lack of proper coordnaton between the two devces n ther smultaneous operaton. Unnecessary actons of the OLTC (or voltage regulator) and are undesrable because of economc reasons. Changng tap poston of the OLTC causes transents and mechancal wear on the OLTCs themselves []. Operaton of the consumes energy resources (some of them are expensve, such as fuel) and also reduces the operatonal age of the machne. The voltage control coordnaton s therefore necessary n the dstrbuton network and has been a subject of nterest n many research papers. H.M. Ma et al n [3] have used the herarchcal genetc algorthm (HGA) to optmse the power voltage control systems accordng to the number of control actons. In [4], an ntegrated voltage control called Coordnated Secondary Voltage Control (CSVC) has been proposed for controllng the OLTC postons to ensure that voltage and loadng constrants are satsfed durng normal and emergency condtons. Another voltage regulaton method n power dstrbuton systems ncludng systems has been developed n [5] through optmzng sng voltages usng the Least Square method. Authors n [6] have coordnated the operatons of swtched capactors and OLTC n a radal dstrbuton system by approxmatng the problem as a constraned dscrete quadratc optmzaton. In [7], the coordnaton method for the and step voltage regulator operatons for mproved dstrbuton system voltage regulatons has been presented. However, none of these coordnaton methods has consdered the prorty/selectvty of dfferent voltage regulatng devces n the system wth the presence of. Ths concept s ncorporated n ths paper for the purpose of ncreasng the effectveness as well as reducng the operatng cost of the control actons. The am of ths paper s to buld up a complete, suffcent and applcable voltage regulaton method for the OLTC and

2 the n ther smultaneous operaton durng peak load hours. The objectve of the coordnaton controller s to reduce, or elmnate the number of counter-actng operatons between the two devces. II. VOLTAGE REGULATION METHOD Conventonally, the voltage on any dstrbuton feeder s controlled by the OLTC placed at the substaton. The man purpose of ths voltage regulaton s to keep the voltages of all the customers wthn the acceptable lmts, whch s ± 5% for Australa dstrbuton system. However, wth the rapdly ncrease of load, the OLTC can not always guarantee that t wll be able to keep the regulaton requrement satsfed. The recent tr of ntroducng nto the dstrbuton networks has become a potental soluton for solvng voltage problem, especally durng peak hour. In ths secton, we ntroduce a coordnated voltage control technque usng parallel operaton of the OLTC and the wth mnmum level of communcaton system. A. Smple System Model To analyze the operaton of the OLTC and the, as well ther effects on the dstrbuton feeder, a smplfed model has been used as shown n Fg.. ~ OLTC Load Fg. Smplfed model of dstrbuton feeder The dstrbuton feeder s connected to the substaton, whch s modelled as a Thevenn source, at the pont of common couplng. For smplcty, dstrbuton lne of length L s represented as seres resstance and reactance wth load represented by equvalent lumped values at N number of nodes. The network s equpped wth an OLTC at the substaton. The OLTC has provson for correctng the voltage from -5% to +5%, each step represents a.5% change n voltage. A connected to the dstrbuton lne through a load bus d km from the substaton. It s modelled as a current source and able to nject both real and reactve power to the system. B. Voltage Regulaton by OLTC The operaton of the OLTC ncludes fve major steps, whch are descrbed n detals below: Step - Status determnaton: The OLTC recognzes the current voltage condton, whch s represented by the value of voltage error. The voltage error of the OLTC controller, V err deps on two nputs, the actual voltage at the target bus of the OLTC, V t, and the reference voltage V ref. It can be calculated usng (): d L V = V V () err ref t It should be noted that V ref s normally set at.0 p.u. The target bus of the OLTC s referred to as the furthest bus from the substaton whch belongs to the control zone of the OLTC. In other words, the OLTC s meant to regulate the weakest voltage pont wthn ther zone of responsblty. Defnton of control zone wll be dscussed later on n ths paper. Step produces an output called S, whch takes a value of 0, or -, or + depng on how dfference the V err compared to the deadband a s, as shown n (). S 0 = + - for - a V for V for V err err > a < a a err () Value of the deadband defnes the total voltage range, around the voltage settng V ref, whch the OLTC controller wll consder as a satsfed condton. Choce of a small deadband wll result n more tap changes to occur, but wll provde a better regulaton. On the contrary, a larger deadband causes fewer tap changes, but at the expense of a closely regulated lne. Step Comparson of current and prevous voltage status: n ths step, the current status S wll be compared to the prevous status S -. Ths s done to keep track of the changes of voltage status at the target bus. Step 3 Counter settng: A counter s employed to determne the tme duraton of the voltage error exceedng the deadband. The counter bascally starts accumulatng the tme when voltage error s outsde of the deadband. It wll be reset n three cases: the voltage error fluctuates below and above the deadband, the voltage error changes sgn, or the voltage error s currently wthn the deadband. Output of the counter s determned based on the results of the comparson n Step : 0 for S S C = 0 for S = 0 (3) C + t for S = S Where t s the tme step. Step 4 Tme delay settng: In ths step, value of the counter wll be compared to the tme delay settng DT, and the control acton wll take place only f the tme delay s elapsed. The tme delay vares dep on the control coordnaton algorthm, whch has a great mpact on the performance of the system. Selecton of the DT value wll be dscussed n more detals n the secton of Coordnated voltage control. Step 5 Acton of tap changer: f there s a requrement of a tap change and the counter value s equal or greater than the tme delay settng (C DT), a sgnal wll be sent to the tapchanger motor to move the tap up or down. The actual tap rato s: n = n + u( n) (4) f n n n andv V V mn max mn local Where n and n - are the current and prevous actual tap rato, respectvely, n s the tap step, and u s the desred tap rato whch s + for requrement of a tap up, - for requrement of a tap down, and 0 for no requrement of tap acton. n mn and n max max

3 3 represent the workng band of the OLTC, V mn and V max are the lower and upper voltage lmts, respectvely. C. Voltage Regulaton by The controller operates n a much smlar manner wth a sequence of 5 steps. The steps and ther outputs are as followngs: Step - Status determnaton: The status S can be determned by (5); 0 for -b Verr b S = + for Verr > b (5) - for Verr < b and Verr = Vref Vt (6) Where, V err s voltage error of the controller, V t s actual voltage at the target bus of the, b s the voltage deadband of V t. Step Comparson of current and prevous voltage status: S s compared to S -. Step 3 Counter settng: Counter value s calculated as: 0 for S S C = 0 for S = 0 (7) C + t for S = S Step 4 Tme delay settng: Tme delay of the s denoted as TD. Settng for tme delay of the controller wll be descrbed later n secton.4. Step 5 Acton of the : The desred output of the, I, s calculated usng the proportonal controller as n (8): I = K V (8) P err Where K P s the proportonal constant. In ths work, however, the s set to step-by-step update ts output towards to desred value, nstead of makng a substantal change. Ths s done to allow tme for the other regulatng devces (OLTC n ths case) to take part nto the regulatng process. Also, t helps to avod unnecessary extra energy delvered by the n case when the later change of the load demand would possbly elmnate the voltage volaton. By controllng output n ths way, we would be able to reduce the operaton cost of the. However, t causes ncreasng tme of the response to voltage volaton f the current load condton mantans suffcently long. D. Coordnated Voltage Control In order to avod huntng between the unts, proper coordnaton s needed. The coordnaton makes sure that all regulatng devces n the system wll response to any voltage volaton n a correct order. As we have mentoned earler, the task of coordnatng responses of the OLTC and n ths paper s done usng a defnton of control zone. Idea of the control zone s that the area subject to voltage control s dvded nto two zones. Each devce s manly responsble for controllng voltage n one zone, where ts control acton has hgher nfluence to the voltage. The other devce wll act as a supporter n case the acton of the man s not satsfactory or fals. In ths work, we propose a method for determnaton of voltage control zones accordng to the senstvty analyss. From the network equaton Y BUS V BUS = I BUS, for a N+-load bus system wth bus, bus n, and bus n+ represent the substaton, the remote load bus, and the nternal bus whch connects the nto the system, respectvely, we obtan: T = Y ( Y V Y V ) (9) V3 N 3 S + 5 V3 y,3 K y, n Where, V3 N = M, Y = V y,3 K y, n n V S V = V S, and V s voltage at the connecton pont. The relatve changes of V 3-N due to the njecton and the tap operaton can be obtaned wth substtutng V S = 0 nto (9) and examnng ndvdually the response of the system to.0 p.u. voltage at the connecton pont and.0 p.u. voltage at V, whch s the secondary sde of the OLTC, usng the superposton prncple. The results are: Y = Y 3 (0) s 5 T 0 s TX = Y3 Y () If values of (0) & () are graphcally plotted wth respect to the load bus from 3 to N, ther ntersecton pont could be defned as the boundary for control zones of the OLTC and the. Let the ordnate of the ntersecton s C b. The responsblty of each devce s defned by followng rules: - If the voltage senstvty of bus wth respect to voltage s greater than C b ( s C ), bus s belong to the control b zone of. - If the voltage senstvty of bus wth respect to the V s greater than C b ( s C ), bus s belong to the control zone tx b of the OLTC. The man purpose of voltage control zone determnaton s that we wll be able to assgn hgher opportunty to a more effcent devce to operate. Thus, the voltage drop wll be compensated more quckly wth less number of control actons. Let us assume that the boundary bus s bus m. In other words, the control zone of the OLTC s from bus to bus m, whle control zone s from bus (m+) to bus n, whch s the remote bus. Delay tme values of the OLTC and, whch are denoted as DT and DT, respectvely, are not constant, but changng from tme to tme depng on the network condtons. The delay tme could be one of the followng types: - Transent tme (TT for OLTC and TT for ): the tme that has to elapse before any voltage correcton s permtted to take place. Ths settng s to avod voltage correcton to occur due to temporary voltage excursons. - Gradng tme (GT for OLTC and GT for ): the tme n whch a regulatng equpment has to delay ts acton to enable

4 4 the equpment wth hgher prorty to complete ther voltage correcton. In ths paper, snce the operaton cost of the OLTC s less than that of the, we assume that the default Gradng Tme of the s two tmes hgher than the OLTC s Gradng Tme. - Second-acton tme (ST for OLTC and ST for ): the tme delay before any further acton can take place, f requred. The next acton has to be n the same drecton wth the prevous one for the Second-acton tme to apply. Otherwse, the tme delay wth be ether Transent Tme or Gradng Tme. It should be noted that Second-acton Tme s always shorter than Transent Tme. The algorthm for the control coordnaton has been proposed wth a set up of communcaton system as follows: - One way communcaton from the target load buses to ts correspondng controller, whch s depng on the control zones. - Two way communcaton betweens controllers of regulatng devces n the system. The frst part of the communcaton system s bult to provde hghly accurate feedback sgnal to the controller, whch s the voltage status at target buses. The later part of the communcaton system, on the other hand, s used to nform status of one devce to another. Ths would be very helpful n the case that when one devce fals to operate, ther responsblty could then be passed on to other equpment wthn the shortest tme, and thus reduce the duraton of voltage rse/drop. The prorty of controller n ths coordnaton scheme has been determned based on the dea of control duty. Ths means that f more sgnfcant load change occurs n the control zone of one regulatng devce, t then has more prorty to operate than the other. However, takng nto account that operaton of the s more expensve than the OLTC, the, n case of hgher prorty, wll only ssue one step change n ts output then wat untl the Gradng Tme has passed before dong any further voltage correcton. Ths wll allow tme for the OLTC to operate f necessary. Moreover, by usng the communcaton system, a sgnal could be sent from one controller to another to nform ther status. If one devce s exceedng ts capacty or fals to carry out the desred acton, the other one wll operate wth mnmum delay tme, regardless ts prorty. The tme delay of the OLTC and the for ths control coordnaton s calculated as n () & (3) usng IF statements. It should be noted that the equatons appled only f S 0 and S 0, respectvely. V r and V m are used to denote the actual remote voltage and the actual voltage at boundary bus m, respectvely. Tme delay for the OLTC: f S 0 f TD TT then TD = TT f S 0 f VD post VD pre w f TD TT then TD = TT else f the fals to operate f TD TT then TD = TT else f TD TT + TT then TD= TT + TT () Tme delay for the : f VD post VD pre w f the OLTC fals to operate f TD TT then TD = TT else f else f TD TT then TD = TT TT < TD GT then TD = GT else then TD = ST (3) Where, VD pre and VD post are the smulated voltage drops before and after voltage excurson. ω s a threshold value to determne the prorty of the regulatng equpment. In () & (3), the three varables VD pre, VD post, and ω are used to determne the knowledge of where the causes of voltage volaton are. Ths knowledge s used as a crteron to assgn the tme delay values for the OLTC as well as the. When the remote voltage s outsde the deadband, ths s due to one or both of the followng reasons: - A voltage change upstream the - A load change downstream the The dstncton between those two can be found by montorng the local voltage and current at pont, as well as the upstream feeder mpedance. Ths nformaton could provde us a smulated voltage drop, from whch we are able to defne f there s any load change has occurred n the voltage control zone of the [8]. If the dfference between smulated voltage drop before and after voltage excurson s large, then the second cause s more lkely to occur.

5 5 III. CASE STUDY The proposed coordnaton method has been tested on a system, whch s modfed from a dstrbuton feeder of Aurora Energy. The man feeder s 48 km long wth.036 MVA load dstrbuted along the lne. Loads are assumed to be lumped at 69 nodes, n whch node s represented for the substaton and node 69 s denoted for the remote load bus. There are nne laterals attached to the man, whch s shown n Fg.. WOOLNORTH H G Fg. : Smthton - Woolnorth test feeder F E D C In order to properly llustrate how the coordnaton methods work, modfed form of the system has been used. The feeder has an automatc OLTC at the substaton and a 36 km from the substaton. IV. SIMULATION RESULTS Frstly, we demonstrate how to determne the control zones for each regulatng unt by the approach of zone determnaton wth the system offlne load data. The senstvty values of load bus voltages wth respect to voltage at the secondary sde of the OLTC (s TX ) and wth respect to voltage of the connecton pont (s ) have been plotted on the same graph, as shown n Fg.3. The ntersecton of s TX and s dvdes the feeder nto two parts. The upstream part from bus to bus 5 s belong to the OLTC control zone, whle the downstream part from bus 53 to the remote belongs to the control zone. We should note that the senstvty analyss here s carred out for those load buses located on the man feeder only. For the laterals, those attach to the backbone at ponts whch belongs to the OLTC control zone, wll also be the major regulatng duty of the OLTC. Otherwse, the wll be the man responsble regulatng unt. B A SMITHTON Senstvty values Determnaton of control zone Control zone of the OLTC Load bus number Fg. 3: Determnaton of the control zones s s TX Control zone of the The load varaton, as shown n Fg.4, has been used to test the proposed method of voltage control coordnaton. Total smulaton tme s 400 seconds. Durng ths perod of tme, the total load demand ncreases from.0 MVA up to 4.0 MVA. At each second, there are a number of random load buses changng ther load demand wth a random magntude. Ths has been done to mtate the practcal stuaton of load fluctuatons, whch are random and non-unform. Snce undervoltage stuatons are more lkely to occur n the dstrbuton systems, an ncreasng load profle has been used n the smulaton. By dong ths test, we would be able to know how much the maxmum loadng capacty s before the system voltage fals to meet the safety margns. P (MW) and Q(MVars) Real and reactve power of load demand Real power Reactve power Tme (sec) Fg. 4: Dynamc load profle Normally, the tme delay of an automatc OLTC would be around 0 secs for the frst tap and 5 secs for the consequent ones. However, snce our smulaton tme s relatvely short, we assume that the tme delay values are as follows: TT = 0 secs, GT = 0 secs, and TT = secs TT = 3 secs, GT = 0 secs, and TT = sec In all smulatons, the reference voltage V ref s.0 p.u. The varables a and b are set to be 0.05p.u. and p.u., whch

6 6 represent the varaton lmts of bus 5 and bus 69, respectvely. Snce bus 5 s at around two-thrd of the feeder from the substaton, we would lke to keep ts voltage at a reasonable level (±0.05 varaton s chosen here) n order that further voltage drops along the lne wll not cause the remote to fall below 0.95 p.u. The varable b s chosen to be nstead of 0.05 to gve some levels of tolerance to the control system. Fgs.5, 6 and 7 show the results of the coordnaton method usng communcaton system, ncludng the tap response, the response, and the voltage at the remote, respectvely. In Fg.5, we can see that the OLTC alters ts rato accordng to the voltage varaton at bus 5. At frst, t ncreases wth the ncrease of load. After that, at t = 0 seconds, tap rato stops rsng at the value of.063. Even though the capacty of the OLTC has not exceeded yet, further ncrease of tap rato s not allowed because of upper voltage constrant at the secondary sde of the OLTC. Tap rato / Voltage at target bus (p.u.) Tap poston Tap rato Actual voltage at bus Tme (sec) Fg. 5: Tap response and voltage at the target bus bus 5 P (MW) and Q(MVars) Real and reactve power of Real power Reactve power Tme (sec) Fg. 6: response By observng the voltage at the remote (Fg.7), whch s controlled by the, we can see that the voltage drops below the deadband at t = 335 seconds. However, the has not responded at that tme snce the duraton of voltage volaton s not suffcent enough to actvate the controller. When t = 35 seconds, the starts respondng to the excurson at the remote bus. After that, from t = 360 seconds, the output ncreases rapdly to compensate the voltage drop as t detects the saturaton condton of the OLTC. Voltage profle of system shows that the voltage s well regulated most of the smulaton tme. Actons of the OLTC has mantaned the voltage wthn the safety margns, and thus kept the offlne for more than 85% of tme. The only partcpates nto the control process when the voltage drops below the lmt, and the OLTC fals to operate further. Ths can be consdered as a desred soluton for solvng voltage problems n a dstrbuton system, whch maxmses the capacty of the OLTC and utlses the only n real need. Voltage (p.u.) Voltage at the remote Tme (sec) Fg. 7: Remote voltage profle V. CONCLUSION In ths paper, an algorthm for the control acton coordnaton between the OLTC and the has been developed wth the utlzaton of communcaton system. The method works by ncorporatng several concepts, ncludng the control zones, settngs of reference voltage, voltage deadband, as well as tme delay. Selecton of these settngs has been dscussed n detals n the paper, whch makes t easer for the control engneers to desgn ther systems. The coordnaton method offers a reasonable recovery tme for the system voltage. At the same tme, t tres to mnmze the operatng cost of regulatng devces by maxmzng the capacty of the OLTC, whch s cheaper, and mnmzng the control acton of the. Smulatons have been conducted and the results prove that the algorthm works well and also very flexble. The approach can be expanded to be applcable for more complex systems wth more number of regulatng devces, such as voltage regulator. Wth the rapd growth of new technologes and the decrease n ther cost, t s beleved that n the near future, communcaton system wll become popular and affordable for most of utltes. As the result, the proposed method can be used wdely for satsfactory operaton of the dstrbuton networks.

7 7 VI. ACKNOWLEMENT The authors gratefully acknowledge the support and cooperaton of Aurora Energy personnel n provdng data and advce on the operaton of dstrbuton systems. VII. REFERENCES [] M. Larsson, Coordnaton of Cascaded Tap Changers usng a Fuzzy- Rule Based Controller, Fuzzy Sets and Systems, Vol. 0, Issue, pp.3 3. [] G.W. Km, and K.Y. Lee, Coordnaton Control of ULTC Transformer and STATCOM Based on an Artfcal Neural Network, IEEE Transactons on Power Systems, May 005, Vol. 0, Issue, pp [3] H.M. Ma, K.F. Man, and D.J. Hll, Control Strategy for Multobjectve Coordnate Voltage Control Usng Herarchcal Genetc Algorthms, IEEE Internatonal Conference on Industral Technology, ICIT 005, 4-7 Dec. 005, pp [4] F.A.B. Lemos, L.C. Werberch, J.S. Fretas, and M.A. da Rosa, A Strategc for Voltage Coordnated Control to Improve System Operaton, 00 IEEE Porto Power Tech Proceedngs, 0-3 Sept. 00, Vol.. [5] D. Rho, H. Kta, J. Hasegawa, and K. Nshya, A Study on the Optmal Voltage Regulaton Methods n Power Dstrbuton Systems Interconnected wth Dspersed Energy Storage and Generaton Systems, Proceedngs of EMPD '95., 995 Internatonal Conference on Energy Management and Power Delvery, 995, -3 Nov. 995, Vol., pp [6] R. Baldck and F.F. Wu, Effcent Integer Optmzaton Algorthms for Optmal Coordnaton of Capactors and Regulators, IEEE Transactons on Power Systems, Aug. 990, Vol. 5, Issue 3, pp [7] L.A. Kojovc, Coordnaton of Dstrbuted Generaton and Step Voltage Regulator Operatons for Improved Dstrbuton System Voltage Regulaton, 006 IEEE Power Engneerng Socety General Meetng, 8- June 006. [8] C.A. Smth, M.A. Redfern, and S.Potts, Improvement n the Performance of On-Load Tap Changer Transformers Operatng n Seres, IEEE Power Engneerng Socety General Meetng, 3-7 July, 003, Vol. 3. Member of CIGRE AP36 (Electromagnetc Compatblty), Australan Techncal Commttee. Gerard Ledwch (M 73 SM 9) receved the Ph.D. n electrcal engneerng from the Unversty of Newcastle, Australa, n 976. He has been Char Professor n Electrcal Asset Management at Queensland Unversty of Technology, Australa, snce 998. He was Head of electrcal engneerng at the Unversty of Newcastle from 997 to 998. Prevously, he was assocated wth the Unversty of Queensland from 976 to 994. Hs nterests are n the areas of power systems, power electroncs, and controls. Prof. Ledwch s a Fellow of the Insttuton of Engneers Australa. VIII. BIOGRAPHIES An D.T. Le receved the B.E. (Hons.) from the Unversty of Tasmana, Australa, n 004. She s currently pursung the PhD degree at the Unversty of Tasmana. Her specal felds of nterests are power system analyss, renewable energy, dstrbuted generaton, power system control and protecton. K.M. Muttaq (A 00 SM 05) receved the Ph.D. degree from Multmeda Unversty, Malaysa, n 00. Currently, he s a Senor Lecturer at the School of Engneerng, Unversty of Tasmana, Australa. He was assocated wth the Queensland Unversty of Technology, Australa as a Postdoctoral Research Fellow from 000 to 00. Prevously, he also worked for Multmeda Unversty as a Lecturer for three years. Hs specal felds of nterests nclude dstrbuted generaton, renewable energy, dstrbuton system automaton, power system plannng, and artfcal ntellgence. He has publshed more than 50 techncal papers n these areas. Mchael Negnevtsky (M 95) receved the B.S.E.E. (Hons.) and Ph.D. degrees from Byelorussan Unversty of Technology, Mnsk, Belarus, n 978 and 983, respectvely. Currently, he s Professor, Char n Power Engneerng and Computatonal Intellgence, n the School of Engneerng at the Unversty of Tasmana, Hobart, Australa. From 984 to 99, he was a Senor Research Fellow and Senor Lecturer n the Department of Electrcal Engneerng, Byelorussan Unversty of Technology. After arrvng n Australa, he was wth Monash Unversty, Melbourne, Australa. Hs nterests are power system analyss, power qualty, and ntellgent systems applcatons n power systems. Dr. Negnevtsky s a Chartered Professonal Engneer, a Senor Member of the Insttuton of Engneers Australa, and a