Anti-Islanding Protection Using Histogram Analysis in Self Excited Generations Wind Turbines

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1 Inernaonal Research Journal of Appled and Basc Scences 03 Avalable onlne a ISSN 5-838X / Vol, 4 (0): Scence Explorer Publcaons An-Islandng Proecon Usng Hsogra Analyss n Self Exced Generaons Wnd Turbnes Mehd Nooshyar, Behrooz Sobhan *. Techncal Engneerng Deparen, Unversy of Mohaghegh Ardabl, Ardabl, Iran Correspondng auhor eal :b.sobhany@gal.co ABSTRACT: Increasng dsrbued resources creae any probles n power syses. One of hese probles s unwaned slandng phenoenon. Due o several reasons concernng such as personnel and equpen safey, hs condon should be deec n he fases possble e. Ths paper s proposed a novel passve slandng deecon algorh based on volage hsogra analyss for wnd urbnes. The proposed ehod easures he volage sgnal of wnd urbne and deecs slandng condon based on s ean square error. In order o relable and fas deecon, he saplng wndow s seleced fro syse e consan n slandng ode. The presened sudes are based on e-doan sulaons usng MATAB, The resuls evaluaon confr ha he proposed slandng deecon ehod succeeds n deecng slandng ode fro oher swchng condons. Oher conrbued of proposed ehod s nondeecon zone reducon of he syse and also he relably and fasness of deecon process s ncreased. Keywords: Islandng Deecon, Wnd Turbne, Hsogra algorh, Dsrbued Generaon, MSE INTRODUCTION DGs generally refer o Dsrbued Energy Resources (DERs), ncludng phoovolac, fuel cells, cro urbnes, sall wnd urbnes, and addonal equpen. In recen years, he ncrease of dsrbued resources n he elecrc uly syses wh ongong echnologcal, socal, econocal and envronenal aspecs shows hgh deph of peneraon of Dsrbued Generaons (DGs). Wh provng n DGs echnologes and power elecroncs, DG uns have becoe ore copeve agans he convenonal cenralzed syse. Hence, aracs any cusoers fro ndusral, coercal, and resdenal secors (Zeneldn e al., 006; Chang e al., 0; Jay e al., 008) Many ules around he world already have sgnfcan peneraon of DGs n her syse. Annually, he oal global nsalled wnd capacy a he end of 00 was.5% of he oal global deand. Based on he curren growh raes, World Wde Energy Assocaon (WWEA) predcs ha, n end of he year 00, a leas 500 GW can be expeced o be nsalled globally ( When he dsrbued generaon syses are operaed n parallel wh uly power syses, especally wh reverse power flow, he power qualy probles becoe sgnfcan. Power qualy probles nclude frequency devaon, volage flucuaon, haroncs and relably of he power syse. In addon, one of he echncal ssues creaed by DG nerconnecon s nadveren slandng (Dash e al., 0; Zeneldn e al., 006). Islandng occurs when a DG and s local load becoe elecrcally solaed fro he uly; eanwhle, he DG produces elecrcal energy and supples he local load (Jayaweera e al., 007). Islandng condon causes abnoral operaon n he power syse and also causes negave pacs on proecon, operaon, and anageen of dsrbuon syses. Therefore, s necessary o effecvely deec he slandng condons and swfly dsconnec DG fro he nework. Exsng sandard hus do no per DGs o be ulzed n slandng ode (Zeneldn e al., 007) because Islandng creaes any probles (Zeneldn e al., 007; Swsher e al., 00) n power syses such as: Safey hazards for personnel, Power qualy probles for cusoers load, overload condons of DG, ou-of-phase recloser connecons. In order o avod he above probles occurrng, slandng condons should be deeced whn less han s (Wlsun e al., 004). Orgnally, he ehods of slandng deecon were dvded no wo caegores: councaon and local. ocal ehods were classfed as acve and passve echnques, n whch acve echnques are based on drec neracon wh he ongong power syse operaon (Zeneldn e al., 007). Soe poran acve echnques are pedance easureen, frequency shf and acve frequency drf (Chowdhury e al., 009), curren njecon

2 (González and Iravan., 006), Sanda frequency shf and Sanda volage shf (John and Kolwalkar., 004), and negave phase sequence curren njecon (Kar e al., 008). Acve ehods usually used n converer based dsrbued generaor. Passve echnques ha used n nducon wnd urbne generaor are based on easureens and nforaon a he local se. Over/under volage and frequency (Kaze and Sobhan., 0) s one of he sples passve ehods used n slandng deecon. Unforunaely, f he load and he generaon on he sland are closely ached, he change n volage and frequency gh be very sall and whn he hresholds, hus leadng o an undeeced slandng suaon. Oher passve echnques have been proposed based on onorng rae of change of frequency (ROCOF)(El-Arroud e al., 007) and Rae of change of phase angle drf (ROCOPAD), phase angle dsplaceen, rae of change of generaor power oupu (Chowdhury e al.,009), pedance onorng, he THD echnque, non deecon zone concep (Zhhong e al.,004), vecor surge and phase dsplaceen onorng (Kune and Gao.,008) and he wavele ransfor funcon (Hseh e al., 008). Ths paper nroduces a novel approach for slandng deecng based on volage hsogra sgnal ha reduce he NDZ. Hgh dsoron n volage sgnal easureen s caused he Mean Absolue Error (MAE) of slandng ode volage becoe very hgher han grd conneced ode. In order o deec slandng condon of wnd urbnes, we use of hs MAE sgnal of volage n hs paper. The resuls n several condons of local loads can be provng hs preense and llusrae s robus perforance for slandng deecon. Ths approach easures he volage sgnal a he arge dsrbued generaon locaon and feeds o he proposed hsogra based algorh n order o deec he slandng condon fro oher condons. The proposed echnque, whch s suable for asynchronous DGs, s explaned n Secon. In Secon 3 he sulaon es syse ha used o verfy he effecveness of he proposed ehod s presen. Secon 4 explores he aheacal odel and Non-Deecon Zones conceps. Effecveness and robusness of he proposed algorh appled o he sulaon es syses s presen n secon 5 and Secon 6 concludes he paper. The sulaon es syses were sulaed n MATAB/SIMUINK. The sulaon resuls show ha he proposed slandng deecon echnque can successfully deec slandng operaons whn accepable e duraon. Proposed Algorh Noralzed Hsogra e { 0,,,..., M } denoe he M dsnc values n a dscree sgnal of sze N saples, and le n denoe he nuber of saples wh value. The oal nuber, N, of saples s N = n0 + n nm. The noralzed n hsogra has coponens (saples) p =, fro whch follows ha: N M p = () = 0 Iner Hsogra Mean Square Error (IHMSE) We nroduce a easure for calculang he dfference beween wo hsogras and call Iner Hsogra Mean Square Error (IHMSE). Consder wo hsogras H and H. If he oal nuber of dsnc values (M) for wo hsogras are he sae and ph j shows he h noralzed coponen (=,,M) of jh (j=,) hsogra, he IHMSE beween H and H s calculaed as follows: K IHMSE ( H, H ) = ( n n ) () K = 0 For each possble pars of he hsogras of slandng cases he IHMSE values are calculaed and repored. Slarly for each possble pars of he hsogras of non-slandng cases he IHMSE values are calculaed and repored. These IHMSE values are called Auo IHMSE (AIHMSE) because hey represen dfference beween wo hsogras whch relaed o he slar condons. An IHMSE value, whch s calculaed beween an slandng case hsogra and a non-slandng case hsogra, s called Cross IHMSE (CIHMSE) (Nobuyuk Osu.,979). The average value of CIHMSE s greaer han he average value of AIHMSE. Ths dfference beween CIHMSE and AIHMSE values s ovaed us o nroduce an approach o classfy an unknown condon, based on he calculaon of IHMSE (beween and known slandng or non-slandng cases), no slandng cases or nonslandng cases. 898

3 Suppose ha we have NI known slandng cases and NN known non-slandng cases, These cases are he ranng cases of he proposed ehod, hen we can calculae (NI + NN ) and (NI NN) possble AIHMSE and CIHMSE values respecvely. All of he AIHMSE and CIHMSE values (The nuber of he s: NI + NN + NI NN) are sored and he hsogra of he s consdered. Ths hsogra s called IHMSE hsogra. I s expeced ha he IHMSE hsogra wll be a bpare hsogra n whch he CIHMSE values are placed n one par and he AIHMSE values are placed n anoher par. Thus, a proper hreshold value, we call k*, separae he IHMSE hsogra no wo groups. The value of k* can be found by an approprae hresholdng ehod such as Osu ehod (Nobuyuk Osu.,979). For an unknown case f s volage hsogra s accessble, he IHMSE values beween and known slandng cases are calculaed. The average value of hese IHMSEs s called as k. Slarly he IHMSE values beween and known non-slandng cases are calculaed and he average value of hese IHMSEs s called as k. By Coparng of he value of k* wh k and k we can deerne he condon of he unknown case. Case Sudy Sngle lne dagra of sudy syse n hs research, s shown n Fg. The DG un s a wnd urbne nducon generaor whch s raed volage s 0.69 kv and s conneced o a Pon of Coon Couplng (PCC) wh a sep-up ransforer ha s raed power s.5mva. The local load s a hree-phase parallel R before he crcu breaker (CB), n whch r sands for he seres ressance nducance and R s he parallel load ha conneced o syse n Y connecon. In order o correcon he power facor a capacor bank s used. ocal load and syse paraeers are gven n Table. In he grd-conneced condon, he slandng ode occurs when SW s open. For he evaluaon of slandng deecon echnques he parallel R s radonally adoped as he local load when he load nducance s adjused o he syse frequency. The aoun of local load and capacor should be se o allowable aoun, ha n slandng condon he volage, curren and frequency rean n allowable value. I should be noed ha he frequency and volage of DG should have adssble values n boh grd-conneced and slanded odes. In he grd-conneced condon, he volage agnude and frequency of he local load a he PCC are regulaed by he grd. Fgure. Sngle lne dagra of sudy syse Table. Paraeers of es syse DG nonal power 660KVA Volage rs (-) 0.69kV r s s 7.H Nonal freguency 50HZ R H C.59F 899

4 Maheacal Model Syse odelng Sae-space aheacal odel for he slanded syse have been provde n hs secon. In he slandng ode, he crcu odel of wnd urbne wh fxed wnd speed has shown n Fg. a. and he sple odel shown n Fg. b. I s assued ha he DG un and he local load are balanced hree-phase subsyses whn he sland. The sae space equaons of he poenal sland of Fg. n he sandard sae space for are. X = y( ) = CX u = AX + Bu v d In balanced hree-phase subsyses whn he sland, he sae-space odel s: abc d abc g abc abc v g = s + rs g + v d abc abc abc dv abc g = + C + v d R abc abc d abc v = + r d (3) (4) r s ls ' lr R r C R r s + V R r c C r s s g V g Fgure. Model of case sudy a) orgnal odel b) sple odel v g v In he -frae, dynac odel of syse s g = = g d = s d + C d d + r dv d s g + r + v + v R Wh ransfer o roang reference frae ( condon and V as reference frae: x = x dq e (5) jθ ) and assung of consan frequency n slanded 900

5 d gd r = v s + ω d gd gd gq s s d gq = ω ω + v d gd gd q s dv d = v gd d d d C C CR d d r = v + ω d ( ) q ( ) d ( ) d d r q = ω d d q ωcv = d gd q v d s Fnally he sae-space equaon can be wren as follow: rs ω0 0 - s s gd r CRω rs 0 ω0 ω 0 ω0 gq R = r d 0 ω0 ω0c v d 0 C C CR [ v v ] T gd gq d q gd gq d v q s [ v ] x = (8) [ y] [ 0 0 0]x = (9) The ransfer funcon of sae-space odel s gven by Y ( s) = C.( SI A). B (0) ( s) Y (s) V d = () (.5s s ) e4 V d ( s) = () 4 3 (4.0e 4) s +.359s +.54e4s e5s + 57e6 The sep response of oupu volage s ploed n Fg. 3. gd (6) (7) 90

6 Fgure 3. Sep response of V d (s) of case sudy Fro of Fg. 3, he ransen response e s abou 0.5 seconds, we consder 0.5 second for analyss e o acheve relable deecon fro of sep response. Non Deecon Zone (NDZ) In order o deerne he perforance of slandng deecon ehod Non deecon Zone (NDZ) s one of he poran characerscs. NDZ s defned as an operang regon where slandng condons canno be deeced n a ely anner. In hs regon power sach beween producon and consupon have a sall value. In hs par of sudy, NDZ based on OVP/UVP and OFP/UVP s deerned. Ths ehod s pleened for consan curren conrolled nverers. In order o deerne he aoun of sach for whch he OVP/UVP and OFP/UFP wll fal o deec slandng, he aoun of acve power sach n ers of load ressance can be expressed as follows: P = 3 V I 3 ( V + V ) I = 3 V I (3) Whch V and I show he raed volage and curren, respecvely. Accepable volage range n dsrbuon nework s beween 0.88 pu and. pu. These volage levels are equvalen o V pu = 0. and V pu = 0., respecvely. The calculaed balance aoun by he Eq. (3) for our es nework (he oupu power n ach condon s 50 kw), are 8 kw and -5 kw, respecvely. Frequency and volage of an RC load has he acve and reacve power as follows: P Q V R = (4) = V ωc ω Where,, P and Q are he load frequency, acve and reacve power, respecvely. In grd conneced condon, he volage of PCCC s dcaed by he an grd. Once he sland s occurred, he devaon of PCC volage leads o acve power balance fro he nonal values. Snce he oupu power of he nverer s n uny power facor, before slandng reacve power of load s suppled jus by nework and afer slandng he aoun of reacve power balance s equal o he consued load before slandng, hence we have: V ( ) ω n ω C = 3 ω n ω r V = 3 ω n Q (6) (5) 90

7 Where ω n and ω r are raed frequency and resonance frequency of load, respecvely. resonance frequency generae fro balance power, hen he frequency changes afer he slandng occurrence s equal o he dfference beween nework frequency and load resonance frequency. ω r = ω n ± ω, ω r = (7) C Thus, he reacve power balance needed for ceran changes n frequency can be obaned by, V f n Q = 3 ω ( f f ) (8) n n In hs sudy, he accepable frequency range consder beween 49.7 and 50.3Hz whch are equal o f = 0. 3 and f = 0. 3 Hz. hereupon, he aouns of reacve power balances are 6.393kVAr and -6.5kVAr, respecvely. Fgure 4.NDZ for he sudy es syse SIMUATION RESUTS In hs secon, he es syse shown n Fg. has been sulaed by MATAB/Sulnk. The raed paraeers of syse, DG, and load are lsed n Table.. The proposed slandng deecon ehod has been also esed for varous condons. Islandng Mode Tes In order o shows he perforance of he proposed echnque, he varous load condons s analyzed n slandng ode. When he balance of reacve power value s equal o zero and acve power value s n NDZ range, n hs condons he slandng deecon s ore dffcul o denfy. The deals of he es load condons are presened n Table.. Addon, he load qualy facor s equal o.8 whch s he axu recoended aoun n sandards. Power (kw) R (k) (H) C(F) Table. varous loads for slandng ode es Case Case Case3 Case Case Case For esed load condons ha are presened n Table.. Crcu breaker of wnd urbne opens a =3 sec and wnd urbne wh s local loads solaed fro power grd and slandng ode s occurred. Effecve value of volage and frequency of he PCC for each case s ploed n Fg.5. and Fg. 6, respecvely. Hsogra of volage sgnal for 903

8 Islandng condon s llusraed n Fg. 7. The ean square error of volage hsogras beween hese sudes s represened n able (3). I can be seen, ha he value of MSE n hs condons beween each wo slandng condons s varan n range. Fgure 5. Effecve volage wavefor of he syse n slandng odes Fgure 6. he frequency of syse for slandng condons Fgure 7. Hsogra sgnal of volage for slandng ode es 904

9 Islandng Condon Islandng Condon Islandng Condon 3 Islandng Condon 4 Islandng Condon 5 Islandng Condon 6 Table 3. MSE beween each wo Islandng condons (IHMSE values) Islandng Condon Islandng Condon Islandng Condon 3 Islandng Condon 4 Islandng Condon 5 Islandng Condon Swchng Condon In hs secon, he oher swchng condons such as load, oor and capacor bank ha deals s presen n Table.4 a he e = 3sec, slandng condons s appled o he syse. Effecve volage wavefor and s frequency are represened n Fg.8 and Fg.9 respecvely. Hsogra of volage sgnal n hese condons s llusraed n Fg. 0. MSE value of volage hsogra sgnals beween each wo swchng condon are shown n Table 5. Power (kw) R (k) (H) C(F) Table 4. Paraeers of varous load n swchng condon Case Case Case3 (oad swchng) (oad swchng) (oor sarng) 75kW (Ou) kW (IN) kW Power facor=0.78 lag (In) Case4 (Capacor swchng) 40kVAr Fgure 8. Effecve volage wavefor of he syse n swchng condons Fgure 9. he frequency of syse for swchng condons 905

10 Fgure0. Hsogra sgnal of volage for swchng ode Non Islandng Condon Non Islandng Condon Non Islandng Condon 3 Non Islandng Condon 4 Table 5. MSE beween each wo swchng es condons (IHMSE values) Non Islandng Condon Non Islandng Condon Non Islandng Condon 3 Non Islandng Condon Proposed Algorh for he case under sudy Fgure 7 and Fg. 0 show hsogras for volage sgnals of sx dfferen cases of slandng condons and hsogras for volage sgnals of four dfferen cases of non-slandng condons, respecvely. For each possble pars of he hsogras of slandng cases (Fg.7) he IHMSE values are calculaed and repored n Table 3. Slarly for each possble pars of he hsogras of non-slandng cases (Fg.0) he IHMSE values are calculaed and repored n Table 5. Table 6 shows all 4 possble values of CIHMSE values for he hsogras of Fgs. Obvously he average value of CIHMSE s greaer han he average value of AIHMSE. Fro of hese values ha her nu s greaer han axu IHMSE values for each group (slandng and non-slandng), slandng condon can be classfed fro oher condon. Table 6. MSE beween each swchng and slandng es condons (CIHMSE values) Non Islandng Condon Non Islandng Condon Non Islandng Condon 3 Non Islandng Condon 4 Islandng Islandng Islandng Islandng Islandng Islandng Condon Condon Condon 3 Condon 4 Condon 5 Condon

11 CONCUSION Increasng of dsrbued generang uns and enlarged sze of he n a odern power syse s caused he proecon agans slandng has becoe exreely challengng nowadays. The slandng condon of dsrbued generaon should be deeced due o safey reasons and o anan qualy of power suppled o he cusoers. Volage hsogra based analyss s proposed for slandng deecon of wnd urbnes n hs paper. Reducng he NDZ o as close as possble and fas deecon are he an conrbue of he proposed echnque n hs paper. In order o show he perforance of he proposed ehod, he es wnd urbne syse sulaed n MATAB sofware. Sx slandng condon n NDZ and four swchng condon n es syse are sulaed and proposed slandng deecon appled o hese condons. The resuls show he suable relably of he proposed ehod under dfferen load condons, such as load and capacor bank swchng and oor sarng ha slandng deecon under hese condons s dffcul. The ehod was able o deec he slandng condon of an nducon generaor ype of a wnd urbne whn less han 0.5 s. REFERENCES Zeneldn H H., Saadany E F E, Salaa M M A Islandng Deecon of Inverer Based dsrbued Generaon, IEE Proc.Gener.Trans.Dsrb. 53: Chang W J, Jou H, Wu J C. 0. Acve slandng deecon ehod for nverer-based dsrbuon generaon power. Inernaonal Journal of Elecrcal Power & Energy Syses. 4: Jay H, Chuanwen J, Rong X A revew on dsrbued energy resources and cro-grd, Renew, Sus Energ Rev: hp:// Dash P K, Padhee M, Bark S K. 0. Esaon of power qualy ndces n dsrbued generaon syses durng power slandng condons, Inernaonal Journal of Elecrcal Power & Energy Syses. 36: 8-30 Zeneldn H H, El-Saadany Ehab F, Salaa MMA Ipac of DG nerface conrol on slandng deecon and non-deecon zones, IEEE Trans Power Delvery. :55 3. Jayaweera D, Galloway S, Bur G, McDonald JR A saplng approach for nenonal slandng of dsrbued generaon, IEEE Trans. on Power Sys. : 54-. Zeneldn HH, Abdel-Gall T, El-Saadany EF, Salaa MMA Islandng deecon of grd conneced dsrbued generaors usng TS- ESPRIT, Elecr. Power Sys Res, 77: Wlsun X, Konrad M, Sylvan M An assessen of DG slandng deecon ehods and ssues for Canada, CETC-Varennes. 074: -6. Swsher R, De Azua CR, Clendenn J. 00. Srong wnds on he horzon: wnd power coes of age, Proceedngs of he IEEE. 89: Chowdhury SP, Chowdhury S, Crossley PA Islandng proecon of acve dsrbuon neworks wh renewable dsrbued generaors: a coprehensve survey. Elecr Power Sys Res. 79: -9. Hernández-González G, Iravan R Curren njecon for acve slandng deecon of Elecroncally-Inerfaced dsrbued resources. IEEE Trans On Power Delv. : John V, Ye Z, Kolwalkar A Invesgaon of an slandng proecon of power converer based dsrbued generaors usng frequency doan analyss, IEEE Trans on Power Elecronc. 9(5): Kar H, Yazdan A, Iravan R Negave-sequence curren njecon for fas slandng deecon of dsrbued resource un, IEEE Trans on Power Delv. 3(): Kaze Karegar H, Sobhan B. 0. Wavele ransfor ehod for slandng deecon of wnd urbnes, Renewable Energy. 38 : El-Arroud K, Joós G, Kawa I, McGlls DT Inellgen based approach o slandng deecon n dsrbued generaon, IEEE Trans on Power Delv. : Zhhong Y, Kolwalkar A, Zhang Y, Du P, Wallng R Evaluaon of an-slandng schees based on non deecon zone concep, IEEE Trans of Power Elecronc. 9: Kune SR, Gao W. (008). Coparson and revew of slandng deecon echnques for dsrbued energy resources, IEEE 40h Norh Aercan Power Syposu, 8-30 Sep: -8. Hseh CT, n JM, Huang SJ Enhanceen of slandng-deecon of dsrbued generaon syses va wavele ransfor-based approaches, Inernaonal Journal of Elecrcal Power & Energy Syses 30(0): Nobuyuk Osu, "A Threshold Selecon Mehod fro Gray-evel Hsogras," IEEE rans. on syses, Vol SMC-9, No.,