Evaluation of 1-phase, 3-phase and Lightning Faults on Wind Farms using EMTP-RV

Transcription

1 Majlesi Journal of Elecrical Engineering Vol. 8, No., March Ealuaion of -phase, 3-phase and Lighning Fauls on Wind Farms using EMTP-RV Saber Arabi Nowdeh, Mohsen Chisaz, Saheb Khanabdal Deparmen of Elecrical Engineering, Urmia Uniersiy, Urmia, Iran Receied Noember Reised Sepember 3 Acceped Noember 3 ABSTRACT: Since he deelopmen of wind power plans insallaion is growing, problems which are relaed o nework connecing, sabiliy and olage effecs become more imporan. On he oher hand, wind farms are ofen open o lighning because of heir long heigh and specific appearance. In his paper, modeling and simulaion of -phase, 3- phase and lighning fauls in a wind farm consising of wind urbines and fauls impac on wind farm and he nework is inesigaed in EMTP-RV enironmen. In his field, i s necessary o deelop a precise modeling ou of wind power plan in order o ealuae he effecs of hese power plans on dynamical behaior of he power sysem. These models can be used in designing new proecion sysems, new proecion algorihms, and new sraegies for power plans exploiaion improemen. Each wind uni in he farm is conneced o he whole unis ha are conneced o he nework using a doubly fed inducion generaor (DFIG). KEYWORDS: Wind Farm, Transien Sae, 3-phase Faul, Lighning, EMTP-RV. INTRODUCTION Wind farms hae some adanages compared o oher ypes of power plans: No using waer for cooling, no emiing carbon, being locaed near he producion and local loads, no using ransmission lines capaciy. Since he deelopmen of wind power plans is daily increasing he problems relaed o nework connecing, sabiliy and olage effecs are becoming more imporan []. Hence, seeral ransmission sysem operaors hae defined cerain characerisics and circumsances in which a wind power plan can be conneced o he nework []-[] Topology of wind farm neworks has major difference wih oher ransmission and disribuion sysems. In order o reduce array losses he urbines are usually separaed by a leas 5 blade diameers which needs expensie cable sysems and a number of deices like circui breakers and sep-up ransformers [5]. Combinaion of hese deices in large offshore wind farms has been idenified as a poenial source of ransien oer olages [6]. In addiion, faul exisence in any of he wind farm ransformers cause o high coss of fixing. Regarding ransien sabiliy, some Elra consrains are needed which occur beween wind power plan and power nework and hey are inesigaed in he nework by simulaion when fauls occur [7]. One of he mos efficien ways o increase he urbine oupu power is increasing he heigh in order o exploi more wind. Nowadays, wind urbines are on aerage 5 meers, heigh and some urbines wih nearly meers heigh. The more he heigh of a ower, he more he chance of being sruck by he lighing which can cause he following damages: Increasing poenial of wind farms. Volage drop along he cable. Heaing of blades and ball-bearings which can cause hem o mel. In his field, i seems necessary o deelop a precise model of wind power plans o ealuae effecs of hese power plans on sysem dynamical behaior [8]. Such models can suppor designing new proecion sysems, new proecion algorihms and new sraegies for power plan exploiaion improemen. Transien saes in large wind farms are sudied in PSCAD/EMTDC enironmen [9], dynamical model of wind farms and power sysem is sudied in DigSilen including boh normal operaion and ransien sae []. Also, inesigaing he effecs of arious aspecs of wind farms such as generaor s echnology, disribued generaion and so forh are inesigaed in DigSilen enironmen []. In [] he effecs of lighning on wind farms were sudied using a curren source o simulae he lighning. 53

2 Majlesi Journal of Elecrical Engineering Vol. 8, No., March In his paper, he -phase, 3-phase and lighning faul s impac are inesigaed on a wind farm consis of wind urbine using is modeling and simulaion in EMTP-RV enironmen. The impacs of fauls are analyzed on wind farm- fauled bus and he bus of nework conneced o wind farm.. BASIC CONCEPTS.. DFIG concep DFIG is an abbreiaion for Double Fed Inducion Generaor, a generaing principle widely used in wind urbines. I is based on an inducion generaor wih a muliphase wound roor and a muliphase slip ring assembly wih brushes for access o he roor windings. The roor winding is conneced o he main grid by self commuaed AC/DC conerers allowing o conroll he slip ring olage of he inducion machine in magniude and phase angle. Doubly-fed inducion generaor sysem is illusraed in Fig.. 3 P R λβ R p w = ρπ C (, ) V () Where, P : R V w : Roor power Wind speed C ( λβ, p ) : Characerisic power coefficien λ : β : ρ : R : Tip speed raio Pich angle Air densiy Blade radius The ip speed raio is defined by (): ω R R λ = () V w Where ω refers o he angular speed of roor blades. R.3.Inducion generaor The inducion generaor is represened using he wind orque model, applied o he shaf of he inducion machine model as shown in Fig.. The model also incorporaes a pich conrol block, which changes he angle of he blades of he machine a high wind speeds in order o modify he orque characerisic and hus limi he oupu power o he raing of he machine [5]. Fig.. Doubly-fed inducion generaor sysem In conras o a conenional, singly-fed inducion generaor, he elecrical power of a doubly-fed inducion machine is independen from he speed [3]. I is possible o undersand a ariable speed wind generaor allows oadjus he mechanical speed o he wind speed and hence operaing he urbine a he aerodynamically opimal poin for a cerain wind speed range... Wind model The power exracion of wind urbine is being known o be a funcion of hree main parameers: he wind power aailable, he power cure of he machine and he abiliy of he machine o respond o wind flucuaions []. The wind urbine aerodynamic is modeled wih an algebraic equaion as gien by: Fig.. Direc conneced inducion generaor model in EMTP-RV.. EMTP-RV soler The ransien analysis sofware program used in his paper allows for he represenaion of ery large sysems and produces ery accurae resuls, enabling simulaion of numerous cycles o een muliple seconds, wih relaiely shor execuion imes [6]. The abiliy of he sofware o model large sysems wih muliple machines, power elecronics, and conrol 5

3 Majlesi Journal of Elecrical Engineering Vol. 8, No., March makes i ideal for modeling wind energy sysems and sudying he inerconnecion characerisics. 3. SYSTEM SIMULATION ANDFAULTS STUDY 3.. The nework under Sudy Fig. 3 shows he sudied nework which comprises wind unis which each one of hem are conneced o he wind farm sysem and nework by a DFIG. Each Turbine is conneced o he corresponden bus by a YΔ ransformer and a capacior. The unis sar working in each radial row each wih. seconds of delay. Therefore, he firs urbine is placed in he nework from he beginning of simulaion and he las uni in each radial row is placed in he circui a =.s. Capaciy of each power plan uni is MVA, series capaciy is MVA (acie power of each uni is 3 S r = 3 = MW and reacie power is.5s r = 5MVAR. Ineria consan of each generaor is.3s and ha of each urbine is considered 3s. WIND DFIG_ Fig.. Schemaic illusraion of a wind power plan Table. Required Parameers for Simulaion Parameer Value Vbase.69 kv rms H_Gen.3 Generaor Ineria in s H_Tur 3. Turbine Ineria in s Sbase 5 MVAr Droop 5 % Fs 6 Hz Qraing.5*SbaseMVAr P poles Rs.66 pu Lls.85 pu Llr. pu Lm 3. pu Rr. pu WIND block consiss of daa relaing o he wind speed in 3 ime periods namely -,, s. inernal schema of his block is shown in Fig. 5. f(u) f(u) Fb3 sel ec sel ec Gain3.9 Fm f(u) Fb Fb Fig. 3. The nework under sudy Nominal olage of each generaor is.69 kv and number of poles is. Three loads are conneced o he nework. Load : ( P = 77 MW, Q = MVAR ), Load : ( P = MW, Q = 6MVAR ) and Load 3: ( P = 5 MW, Q = MVAR ). Each wind unis is modeled as in Fig. which includes equaions relaing o urbine and DFIG. The required parameers for simulaion are gien in Table. Fig. 5.Inernal schema of WIND block. 3-PHASE FAULT STUDY In his secion, we sudy 3-phase fauls simulaion on a wind farm wih wind urbine. The urbines in 5 rows are conneced o a bus as radial so ha he bus connecs o a 5 KV low olage nework hrough a ransformer. This nework is illusraed in Fig

4 Q P Majlesi Journal of Elecrical Engineering Vol. 8, No., March m8 MPLOT A?i m9 prms3 BUS6 P Q Load3 5MW MVAR scp3 scope BUS3 a Vrms m? 5kVR M SLL /_?/?/? P Q Load MW 6MVAR 77M W M VAR Load?/?/? Faul VM m3 Locaion 69/5 DYg_ prms scp scope Vrms m? a. SW m m9?? a prms Vrms scope scp DEV DEV DEV DEV3 DEV6 DEV5 DEV8 DEV7 DEV DEV9 DEV DEV DEV DEV3 DEV6 DEV5 DEV8 DEV7 DEV Delay DEV Delay DEV Delay DEV6 Delay DEV8 Delay DEV3 Delay DEV3 Delay m7 A?i A?i m m5? DEV9 DEV DEV3 DEV5 DEV7 DEV9 DEV3 DEV3 DEV33 DEV35 DEV8 DEV37 DEV36 DEV39 DEV38 DEV DEV DEV3 DEV DEV5 DEV DEV7 DEV6 DEV9 DEV8 DEV5 DEV5 DEV53 DEV5 BUS DEV55 DEV5 BUS DEV57 DEV56 BUS DEV59 DEV58 DEV6 DEV6 BUS DEV63 DEV6 m6? DEV67 DEV69 DEV7 DEV73 DEV75 DEV77 DEV79 DEV65 DEV6 DEV66 DEV68 DEV7 DEV7 DEV7 DEV76 DEV78 Fig. 6. Faul locaion in a wind farm simulaed in EMTP-RV A 3-phase faul in =6s occurs on wind power plan uni which is shown in Fig. 5 and iremains in he nework unil =7s. The curesare relaed o heolage, amoun of effecie olage in differen buses, speed and orques of DFIG generaors are shown in Fig. 7-. T e [N.m ] x - Elecromagneic Torque 6 x fauled Bus 6 x 6 Oupu Power V [V] - P e [ W ] - V [V] 6 x - main Bus N [rpm ] Generaor Speed 85 Fig.7. Fauled bus olage cure and he main bus of he wind farm 8 Fig. 8. Torque, oupu power and speed of generaor 56

5 Majlesi Journal of Elecrical Engineering Vol. 8, No., March P o [W ] x 6 - Oupu Acie Power of One Turbine As he generaor orque drops, he speed of generaor acceleraes since he orque gien o he urbine by he wind is nearly consan and ice ersa. Fig. 9 shows acie and reacie power of wind urbine uni is decreased in faul ime. Also in Fig. he effecie olage alue of fauled bus dropped o.5 pu when faul occurred bu effecie olage of bus from he nework (high olage) remained consan. In order o compensae speed flucuaions and preen nework collapse due o seere olage drops, using FACTS deices such as STATCOM and SVC seems necessary. Q [Var] x 6 - Oupu Reacie Power of One Turbine 5. -PHASE FAULT STUDY In his secion, a -phase faul occurs in he same place as he preious 3-phase faul from =6s o =7s for second. Cures of olage, effecie olage in differen busses, along wih speed and orques of DFIG generaors are nex. 6 x fauled Bus - Fig. 9. Acie power cure and urbine reacie of a wind uni x 3 fauled Bus V a [V ] - 6 x fauled Bus V [V] V b [ V ] - x one Bus of grid side 5 x fauled Bus 8 V [V] 6 V c [ V ] Fig.. Effecie olage cure of he fauled bus and a bus from he nework -5 Fig.. 3-phase fauled bus olage cure According o Fig. 7, Fauled bus olage and he main bus of he wind farm drops o.5 pu in spie of danger which is ery dangerous and can cause olage and he nework o collapse. Fig. 8 shows he flucuaion in he generaor orque, oupu power and speed due o faul. 57

6 Majlesi Journal of Elecrical Engineering Vol. 8, No., March x Elecromagneic Torque x fauled Bus 3 T e [N.m ] - Vrms [V] 6 x 6 Oupu Power Pe [W] - x 8 one Bus of Grid Side N [rpm ] Generaor Speed 85 Fig.. Torque cure, speed and oupu power of he generaor Po [W] Qo [Var] x 6 - Oupu Acie Power of one Turbine x 6 - Oupu Reacie Power of one Turbine Vrms [V] 6 Fig.. Effecie olage cure of fauled bus and ha of a bus from nework Fig. shows he fauled bus olage declined o.5 pu in phase a and in oher phases iis inariable. Also according o Fig., elecromagneic orque and generaor s speed and power during fauling cause inensie flucuaions. In Fig. 3, acie and reacie powers of wind urbine uni are decreased in faul ime as hey are shown in he picure. Since no enough reacie power is injeced (because here are no FACTS deices) during he faul, speed shows a sligh increase afer faul eliminaion. Also fauled bus effecie olage alue decreases o ( / 3 )*.57 pu in he momen of faul and he bus olage from nework is inariable as i s shown in Fig.. 6. LIGHTENING STRIKES STUDY This secion is deal wih lighening srikes o a wind farm. To simulae lighening, a curren source is employed which generaes a maximum curren of KA and a pre-wae ime of 3 ms. Lighening block and is inernal schema are depiced in Fig Fig. 3. Acie and reacie power cure of a urbine in a wind farm 58

7 Majlesi Journal of Elecrical Engineering Vol. 8, No., March Ligh_ou ka/3us k R Icigre?i A B C Fig. 5. A) Lighning block B) inernal schema C) curren wae diagram for modeling he lighning( Imax = KA, f = 3ms ) The cures of curren, effecie olage in differen buses, speed and orques of DFIG generaors are shown in Fig Ia [A ] Ib [A ] Ic [A ] - - fauled bus -3 fauled bus fauled bus Te [N.m ] Po [W] N [rpm] 5 x Elecromagneic Torque -5 x Oupu Power Generaor Speed Fig. 7. Torque cure, oupu power and speed of he generaor -5 Fig phase curren cure of fauled bus 59

8 Majlesi Journal of Elecrical Engineering Vol. 8, No., March Po [W] Qo [Var] x 6 - Fig. 8. Acie and reacie power cures of a urbine in a wind farm. Vrms [V] Vrms [V] x 7 Oupu Acie Power of one Turbine - x 3 Oupu Reacie Power of one Turbine x 8 6 fauled Bus one bus of Grid Side Fig. 9. Effecie olage of fauled bus, and ha of he main bus of wind farm and a bus from nework Fig. 6 shows cures of 3-phase fauled bus curren which has a seer peak when lighning srikes and his inense currens can damage proecion deices and ransformers. Inensie flucuaions in elecromagneic orque and generaor oupu power, along wih grea speed changes can be clearly obsered in Fig. 7. Also according o Fig. 8, acie and reacie power of wind urbine uni is decreased in faul ime. Fig. 9 shows a decrease in effecie olage alue of fauled bus and he effecie olage of bus from nework is inariable. 7. CONCLUSION In his paper we inesigaed -phase, 3-phase and lighning fauls impac on a wind farm consising of wind urbines in EMTP-RV enironmen. Resuls of he experimens were presened and i was obsered ha in each of 3 cases, fauled bus olage and he main bus of he wind farm was declined o.5 Pu, which was ery dangerous and can cause olage and he nework o collapse bu he bus olage of nework conneced o wind farm was inariable during fauling. The generaor orque, speed and oupu power flucuaion due o faul was concluded. Also he acie and reacie power of fauled bus was decreased. According o obained resuls, if here was no deice o supply nework wih more reacie power during he faul, we will ineiably face seere olage loss in arious poins of he nework which can possibly cause i o collapse. In he nex sudy, he effec of using FACTS deicesuch as SVC and STSTCOM for decreasing seere flucuaions of orque, speed and olage drops will be proposed. REFERENCES [] S. Heier, Grid Inegraion of Wind Energy Conersion Sysems, New York, John Wiley & Sons, 998. [] T. Ahmed, K. Nishida, and M. Nakaoka, Adanced conrol of PWM conerer wih ariable-speed inducion generaor, IEEE Trans. Indusry Applicaions, Vol., pp , 6. [3] Y. Coughlan, P. Smih, A. Mullane, and M. O Malley, Wind urbine modeling for power sysem sabiliy analysis - A sysem operaor perspecie, IEEE Trans. Power Sysems, Vol., pp , 7. [] N. R. Ullah and T. Thiringer. Variable speed wind urbines for power sysem sabiliy enhancemen, IEEE Trans. Energy Conersion, Vol., pp. 5, 7. [5] Elra, Technical Regulaion for he Properies and he Regulaion of WindTurbines, Tech. rep, Elransmission.dk A/S, Fredericia, Denmark,. [6] R. King and N. Jenkins, Swiching Transiens in Large Offshore Wind Farms, 7h Inernaional Workshop on Large Scale Inegraion of Wind Power and on Transmission Nework for Offshore Wind Farms, 8. [7] V. Akhmao, H. Knudsen, and A. H. Nielsen, Adanced simulaion of windmills in he elecric power supply, In. Journal of Elecr. Power Energy Sys., Vol., pp. 3,. [8] I. Zubia, X. Osolaza, A. Susperregui, G. Tapia, Complee wind farm elecromagneic ransien 6

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