New Controller Design for PMSG Based Wind Generator with LCL-Filter Considered

Transcription

1 Ths s th author's vrson of th papr publshd n ths confrnc. Changs may appar n th publshd vrson. DOI: 1.119/ICElMach Nw Controllr Dsgn for PMSG Basd Wnd Gnrator wth LCL-Fltr Consdrd Marwan Rosyad, S. M. Muyn, Ron Takahash, Junj Tamura Φ Abstract -- In ths papr dsgn and analyss of th grd sd convrtr controllr for Prmannt Magnt Synchronous Gnrator (PMSG) basd varabl spd wnd gnrator connctd to a grd through LCL fltr ar prsntd. Snc utlzaton of th LCL fltr n output of th convrtr can lad to stablty problm du to rsonanc at hgh frquncy, dtrmnaton of th controllr paramtrs should b carfully dsgnd. In ths study, a smpl dynamc modl of th LCL fltr s dvlopd n ordr to analyz th prformanc of th control systm asly. By usng th bod dagram and stp rspons of th systm, th combnaton of gan controllr and dampng rsstanc paramtrs can b slctd. Th proposd mthod has bn mplmntd on th grd sd controllr dsgn for 2.5 MW PMSG basd varabl spd wnd gnrator. Th smulaton rsults show that th proposd mthod s vry usful and good rspons prformanc of th control systm can b achvd. Indx Trms --Varabl spd wnd turbn, PMSG, voltag sourc convrtr, LCL fltr, passv dampng rsstanc I. INTRODUCTION UE to th problm of global warmng, utlzaton of D dstrbutd gnraton systm whch s connctd wth dstrbuton grd systm has bn ntrstd and rcvd consdrabl attnton nowadays. Th dstrbutd gnraton can b locatd clos to load consumrs. It can hav som mrts: ncrasng th avalabl powr, mprovng th ovrall systm rlablty, lowr costs, rducng mssons, and xpandng thr nrgy optons [1]. Th wnd powr s on of th dstrbutd rsourcs. Connctng wnd turbn gnrator to dstrbuton grd systm lads stablty problm. Thrfor, t s vry mportant to analyz a sutabl control dsgn for wnd gnrators connctd to th grd. Ovr rcnt yars mgawatt class of Varabl Spd Wnd Turbns wth Prmannt Magnt Synchronous Gnrator (VSWT-PMSG) hav bn manufacturd and bcom th most popular typ of wnd turbn gnrator. Th VSWT-PMSG systm s dsgnd to achv maxmum arodynamc ffcncy, ncras nrgy captur, and rduc mchancal strss on th wnd turbn [2]. Th gnrator can b drctly drvn by a wnd turbn wthout gar transmsson. In addton, th prmannt magnt machns hav larg ar gaps whch rduc flux lnkag although wth mult magntc pols [3], [4]. Howvr, ths typ of wnd gnrator has mor complcatd controllr systm compard wth othr typs. Thrfor, th analyss mthod to dsgn controllr systm of th gnrator stll nds to b mprovd. Th VSWT-PMSG s, n gnral, connctd to th utlty powr systm through th voltag sourc powr convrtrs. Th convrtr prmts vry flxbl control of actv and Φ Marwan Rosyad, R. Takahash, J. Tamura ar wth th Elctrcal and Elctronc Engnrng Dpartmnt, Ktam Insttut of Tchnology, Ktam 9-857, Japan (-mal: marwanrosyad@yahoo.co.d). S. M. Muyn s wth th Dpartmnt of Elctrcal Engnrng, th Ptrolum Insttut, Abu Dhab, UAE. ractv powr flows to th grd systm. Th full powr convrtr totally dcoupls th PMSG from th grd, and hnc grd dsturbancs hav no drct mpact on th gnrator. Howvr, th convrtr s opratd at hgh swtchng frquncs btwn 2-15 khz rsultng hgh ordr harmoncs whch can dsturb dvcs on th grd and gnrat powr losss [5], [6]. In ordr to rduc harmonc currnts njctd to th grd, LCL fltr s an attractv soluton bcaus of ts many potntal advantags such as hghr harmonc attnuaton and smallr nductancs compard wth L fltr [7]. Howvr, rsonanc at hgh frquncy causd by th fltr can lad stablty problm. Dtrmnaton of controllr paramtrs should b consdrd n dsgn applcaton. To avod th rsonanc problm, a passv dampng rsstanc should b adoptd n th LCL fltr although ths mthod can rduc th fltr ffctvnss and ncras losss [6]. Slcton of a dampng rsstanc valu should also b takn nto account n th controllr dsgn of VSC as wll as th fltr ffctvnss and ts losss. In ths papr dsgn and analyss of th controllr for 2.5 MW class of th VSWT-PMSG connctd to dstrbuton ntwork ar prsntd. Ths study s concrnd wth th nvstgaton of th stablty prformanc of currnt controlld grd sd convrtr connctd to th grd through LCL fltr. Th controllr s dsgnd basd on th synchronous d-q rfrnc fram. A smpl dynamc modl for LCL fltr ncludng dampng rsstanc s proposd as plant systm n whch th confguraton of th fltr can b accuratly rprsntd. Analytcal xprssons and plots ar gvn to show th systm stablty prformanc. Smulaton rsults show that th controllr systm s vry ffctv to control powr dlvrd to th grd wth small total harmoncs dstorton. II. VSWT-PMSG MODEL SYSTEM Th block dagram of control systm for VSWT-PMSG consdrd n ths papr s shown n Fg. 1. Th VSWT- PMSG conssts of th followng componnts: a drct drv PMSG, two lvls back to back convrtrs composd of stator sd convrtr (SSC) and grd sd convrtr (GSC), a DC-lnk crcut wth a capactor (C dc ), stator sd controllr, and grd sd controllr. Th SSC s connctd to th stator of PMSG, and t convrts th thr phas AC voltag gnratd by PMSG to DC voltag. Th thr phas voltag and currnt snsors ar attachd on th stator trmnal of PMSG. Th rotor spd of PMSG s masurd from th rotor of wnd turbn. Th GSC s connctd to th grd systm through LCL fltr and a stp up transformr. Th grd currnt and th grd voltag snsors ar attachd on convrtr sd and grd sd of th LCL fltr, rspctvly. Th DC voltag (V dc ) across th DC capactor s dtctd. Th voltag rfrnc of grd sd voltag sourc convrtr for modulaton s controlld by usng th grd sd controllr /12/$ IEEE 2112

2 r Fg. 1. Modl and control systm of PMSG basd varabl spd wnd turbn Fg. 2. Cp - λ charactrstc for dffrnt ptch angl Fg. 3. Turbn powr charactrstc (β = ) In modulaton tchnqu, Thrd Harmonc Injcton Puls Wav Modulaton (THIPWM) s usd n ths work. Injcton of thrd harmonc n th rfrnc voltag maks t possbl to utlz th voltag rfrnc wthout ovr modulaton. In addton, th THIPWM can maxmz fundamntal componnt of th output voltag [8]. A. Wnd Turbn Modl Th mchancal powr output of wnd turbn capturd from th wnd powr can b calculatd as follows [9]: 2 3 w p P =.5ρπR V C ( λ, β ) (1) w whr P w s th capturd wnd powr (W), ρ s th ar dnsty (Kg/m 3 ), R s th radus of rotor blad (m), V w s wnd spd (m/s), and C p s th powr coffcnt. Th valu of C p s dpndnt on tp spd rato (λ) and blad ptch angl (β) basd on th turbn charactrstcs as follows [9]: c 5 C2 λ C p ( λ, β ) = c1 c3β c4 + c6λ λ wth (2) = (3) λ λ.8β β whr c 1 to c 6 dnot charactrstc coffcnts of wnd turbn (c 1 =.5176, c 2 =116, c 3 =.4, c 4 =5, c 5 =21 and c 6 =.68). Th Cp-λ prformanc charactrstcs for dffrnt valus of β ar shown n Fg. 2. It s sn that th optmum valu of C p (C popt =.48) s achvd at λ = 8.1 wth β =. Ths valu of λ s st as th optmal valu (λ opt ). Fg. 3 dpcts th charactrstc btwn th turbn powr output and th rotor spd for dffrnt wnd spds whr th blad ptch angl s st at dg. Th maxmum powr output (1 pu) of wnd turbn s obtand at 12 m/sc of wnd spd and 1 pu of rotatonal spd. In varabl spd wnd turbn systm, th rotor spd of wnd turbn ( r ) s masurd n ordr to dtrmn th Maxmum Powr Pont Trackng (MPPT). In gnral, t s dfcult to masur th wnd spd accuratly, and hnc th maxmum powr (P mppt ) should b calculatd wthout masurng th wnd spd as xprssd n (4) [1]. Th rfrnc powr (P rf ) s lmtd wthn th ratd powr of gnrator. P mppt 3 rr 2.5 R = ρπ Cp opt (4) λopt B. Dynamc Modl of PMSG Th dynamc modl of PMSG n th d-q rotatng rfrnc fram s xprssd by th followng (5) and (6) [11]. wth dψ dψ = V R I ψ (5) s s = V R I + ψ (6) m ψ = L I + ψ (7) ψ = L I (8) whr V and V ar stator voltags, R s s th stator wndng rsstanc, I and I ar stator currnts, s th gnrator rotatonal spd, ψ and ψ ar th stator flux lnkags, L and L ar nductancs of th stator wndng, and ψ m s th prmannt magnt flux lnkag. By substtutng (7) and (8) nto (5) and (6), th dfrntal quatons of PMSG can b obtand as follows: di L = V RsI LI (9) 2113

3 L di = V R I + L I + ψ (1) s C. Mathmatcal modl of LCL Fltr As prvously mntond, utlzaton of th LCL fltr can lad to stablty problm du to rsonanc. To avod th rsonanc a passv dampng rsstanc should b allocatd n srs wth a fltr capactor n th fltr. Howvr, adoptng a dampng rsstanc can caus powr losss and thn dcras th fltr ffcncy. Thrfor, n dsgnng th voltag sourc convrtr controllr systm, a passv dampng rsstanc should b takn nto account n th plant systm modl. m Fg. 6. Block dagram of LC fltr n th d-q rotatng rfrnc fram Th dynamc block dagram of th grd connctd LC fltr n th d-q rotatng rfrnc fram can b drvd as shown n Fg. 6, whr s dnots a Laplac oprator. III. VSWT-PMSG CONTROLLER SYSTEM Fg. 4. Sngl phas LC fltr quvalnt crcut Sngl phas LCL fltr quvalnt crcut s shown n Fg. 4. Th LCL fltr s composd of an nvrtr sd nductanc (L ) and ts parastc rsstanc (R ), a grd sd nductanc (L g ) and ts parastc rsstanc (R g ), a fltr capactor (C f ), and a dampng rsstanc (R d ). V and I ar voltag and currnt on th convrtr sd of th LCL fltr. V g and I g ar voltag and currnt on th grd sd of th LCL fltr. It should b notd that V cf s a voltag on th fltr capactor (C f ). Th dffrntal quaton of LCL fltr n statonary rfrnc fram can b wrttn as follows: di = V V ( R R )I R d I g (11) di g L g = Vcf Vg ( Rg ) I g I (12) L cf + d + C f dv cf = I I (13) g From (11) to (13) dfrntal quatons n th d-q rotatng rfrnc fram ar obtand: did L = Vd Vcfd ( R ) Id + LI q I gd (14) diq L = Vq Vcfq ( R ) Iq LI d I gq (15) di gd L g = Vcfd Vgd ( Rg ) I gd + LI gq Id (16) di gq L g = Vcfq Vgq ( Rg ) I gq LI gd Iq (17) dvcfd C f = Id I gd + C f Vcfq (18) dvcfq C f = Iq I gq C f Vcfd (19) A. Stator sd Controllr Dtal of th stator sd controllr systm s prsntd n a block dagram shown n Fg. 7. Th am of th stator sd controllr s to control actv and ractv powr output of th PMSG. Th currnt control loop s dsgnd basd on th d-q rotatng rfrnc fram. Th rotor angl poston (θ r ) usd n th transformaton btwn abc and dq varabls s obtand from th rotor spd of gnrator. Th actv powr (P s ) and ractv powr (Q s ) of th gnrator ar controlld by th d-axs currnt (I ) and th q-axs currnt (I ), rspctvly. Th valu of actv powr rfrnc (P rf ) s dtrmnd by MPPT mthod of th wnd turbn charactrstc as shown n Fg. 3. Th ractv powr rfrnc (Q s *) s st to zro for unty powr factor opraton. Th cross couplngs I L and I L should b compnsatd at th output of th currnt controllrs n ordr to mprov trackng capablty. To dsgn controllr paramtrs, th plant transfr functon s rprsntd as 1/(R s +L s s) for d or q currnt loop. By usng th pol placmnt mthod, th gan of th PI controllr can b tund. Fg. 7. Stator sd controllr systm B. Grd sd Controllr Grd sd Controllr s ssntal n dsgn of control systm bcaus t can domnat th prformanc of VSWT- PMSG connctd to a grd systm. Th ams of VSC control ar: 1) to mantan DC lnk crcut voltag; 2) to control th ractv powr xchang wth th grd systm as wll as mantan th powr factor to b unty [12]. 2114

4 TABLE I THE SYSTEM PARAMETERS Fg. 8. Grd sd controllr systm Fg. 8 shows a block dagram of th grd sd control systm. In ths control stratgy, th control systm basd on th d-q rotatng rfrnc fram, whch has sam rotatonal spd as th grd voltag, s mplmntd. By usng th Phas Lockd Loop (PLL) th grd sd phas angl (θ) for th d-q transformaton s obtand. In ths papr PLL block ntroducd n [13] s usd. Whn grd voltags on th statonary rfrnc fram ar transformd nto th d-q rotatng rfrnc fram, V gd bcoms constant and V gq bcoms zro. Thrfor, th actv and ractv powr dlvrd to th grd can b controlld sparatly by th d- axs currnt (I d ) and th q-axs currnt (I q ), rspctvly. In ordr to assur th actv powr xchang btwn PMSG and th grd, th voltag of DC-lnk capactor (V dc ) s mantand constant. Hnc, th d-axs currnt rfrnc sgnal (I d *) s dtrmnd from output of th DC-voltag controllr. For unty powr factor opraton, th q-axs currnt rfrnc sgnal (I q *) s also st to zro. To mprov trackng capablty of control systm, th cross couplng trms could b cancld by addng L tot at th output of th currnt controllrs, whr L tot s total srs nductancs of th fltr and transformr. Th output of currnt controllr (V gd * and V gq *) s transformd nto th statonry rfrnc fram (V ga *, V gb *, V gc *) whch s usd as rfrnc sgnal for puls wav modulaton. C. Ptch Angl Controllr Wnd turbn powr dpnds on th wnd spd, and thus, th output powr of a wnd gnrator always fluctuats du to th wnd spd varatons. In ordr to mantan th output powr of gnrator undr th ratd lvl, a ptch controllr s consdrd as shown n Fg. 9. Th transfr functon of th ptch actuator s rprsntd by a frst-ordr transfr functon wth an actuator tm constant of 5s and th ptch rat lmtr of 15dg/s. A classcal PI controllr s usd to manag trackng rror. In VSWT th ptch controllr s usd to rgulat rotatonal spd of PMSG undr ts ratd valu (1pu). IV. Componnt Paramtr Valu Ratng 2.5 MW Rs.1 (pu) PMSG L 1. (pu) L.7 (pu) AC/DC/AC Powr Convrtr Transformr ψ m H SSC frquncy Swtchng GSC frquncy Swtchng Grd Frquncy DC Lnk capactor DC Lnk voltag Total wndng nductanc(lt) Total wndng rsstanc (Rt ) Convrtr sd voltag Grd sd voltag 1.4 (pu) 3. (sc) 1 khz 4 khz 5 Hz 25 μf 1.75 kv.4 pu.16 pu 1. kv 6.6 kv GRID SIDE CURRENT CONTROL ANALYSIS WITH LCL FILTER CONSIDERED A. LCL Fltr Paramtrs In ordr to obtan th LCL fltr paramtrs, th systm condtons shown n Tabl I ar consdrd. Thr ar many mthods that may b consdrd n dtrmnng th fltr paramtrs. Howvr, n ths papr procdur and lmtatons of LCL fltr paramtrs prsntd n [6] ar consdrd. Accordng to th paramtrs n Tabl I,.4Ω bas mpdanc, 1.3mH bas nductanc, and 8μF bas capactanc ar calculatd. As th nductanc on th nvrtr sd (L ), 5.% of bas nductanc s adoptd. In ordr to calculat th grd sd nductanc (L g ), th transformr nductanc (L t ) should b consdrd. 4% of bas nductanc has bn adoptd as transformr nductanc. Addng a small valu of grd sd nductanc (L g ), total 4.1% of bas nductanc s obtand. Th ntal valu for fltr capactor (C f ) s st to maxmum lmtaton (5%). Th rsonanc frquncy of LCL fltr s around 1.4 khz. B. Dynamc Stablty Analyss of Currnt Controllr In ordr to analyz th dynamc stablty of th control systm, th block dagram of LCL fltr n th d-q rotatng rfrnc fram shown n Fg. 6 s consdrd as a plant systm. In ths study, th d-axs and th q-axs componnts ar assumd dntcal, and hnc th plant systm can b modld by usng on axs componnt only. Fg. 1 shows proposd block dagram of th d-axs componnt, whr th cross couplng and grd voltag ar nglctd. It should b notd that th nductanc (L t ) and ractanc (R t ) of transformr ar ncludd n L g and R g. β Fg. 9. Ptch angl controllr In ths papr 2.5 MVA VSWT-PMSG s consdrd. Tabl 1 prsnts systm paramtrs of th grd connctd VSWT-PMSG. Fg. 1. LCL fltr modl wth d-axs componnt only A block dagram of th currnt control loop s shown n Fg. 11. Th controllr s composd of a PI controllr, a procssng dlay, and a plant systm. Transfr functon of th plant systm (I d /V d ) s smply obtand from Fg. 1. Th transfr functon has th convrtr sd voltag (V d ) as nput 2115

5 and th convrtr sd currnt (I d ) as output. Thr s a tm dlay (T d ) n th control systm for th dgtal procssng. Th tm dlay s composd of on sampl dlay causd by swtchng frquncy (T s =1/f s ) and on half sampl dlay causd by th dad tm of PWM convrtr (T cnv =1/T s ). For PI controllr usually th ntgral tm constant (T ) s st qual to th plant systm tm constant (L tot /R tot ) [7], whr L tot and R tot ar total of srs nductancs and ts parastc rsstancs of th plant systm, rspctvly. Fg. 11. Block dagram of currnt control loop Th dynamc stablty of th controllr systm s analyzd basd on frquncy rsponss n bod dagram and stp rspons. Th ntal gan s obtand by usng optmum modulus crtron [14]. Fg. 12 shows a bod dagram of th currnt control loop for four dffrnt dampng rsstancs. Th bod dagram shows that rducng dampng rsstanc can mak systm dynamc stablty poor. Fg. 13 shows a bod dagram of th currnt control loop for four dffrnt K pd wth R d valu of.9 ohm (around on thrd of mpdanc at frquncy rsonanc). It s sn that ncrasng proportonal gan of PI controllr lads hgh frquncy rspons and dcrasd magntud of th gan margn. Accordng to Fgs.12 and 13, t s concludd that a good stablty prformanc of th control systm can b obtand by slctng a sutabl combnaton btwn R d and K pd. In addton, Fg. 14 shows th stp rspons of currnt controllr for dffrnt K pd, n whch th sttlng tm and ovrshoot of th stp rspons can b analyzd. In ths study, n ordr to stablz th currnt controllr, gan margn (Gm) largr than 6 db and phas margn (Pm) largr than 45 dg ar rqurd for stp rspons lss than or qual 2.5 msc of sttlng tm and 3% maxmum ovrshoot. Wth a mnmum dampng rsstanc of R d =.5 ohm and maxmum gan K pd =.2, stabl loop wth a gan margn of 6.42 db and a phas margn of 73.8 dg s obtand as shown n Fg. 15. Stp rspons of th currnt control loop n dscrt systm s dpctd n Fg. 16. It s sn that th sttlng tm of rspons s 2.41 msc and maxmum ovrshoot s 2.76%. Magntud (db) Phas (dg) Rd= Rd=.9 Rd= Rd= Frquncy (rad/sc) Fg. 12. Bod dagram of currnt controllr for dffrnt R d Magntud (db) Phas (dg) Ampltud (pu) Magntud (db) Phas (dg) Kpd= Kpd= Kpd=.25 Kpd= Frquncy (rad/sc) Fg. 13. Bod dagram of currnt controllr for dffrnt K pd Kpd=.15.2 Kpd=.2 Kpd=.25 Kpd= x 1-3 Fg. 14. Stp rspons of currnt controllr for dffrnt K pd Gm = 6.42 db (at rad/sc), Pm = 73.8 dg (at rad/sc) Frquncy (rad/sc) Fg. 15. Bod dagram of currnt controllr (R d =.5 ohm, K pd =.2). Ampltud (pu) Ovrshoot Sttlng Tm x 1-3 Fg. 16. Closd loop stp rspons of currnt controllr (R d =.5 ohm, K pd =.2). Ampltud (pu) I d I d * Fg. 17. Stp rspons of d-axs currnt obtand by Matlab/Smulnk 2116

6 Ampltud (pu) Fg. 18. Currnt obsrvd on phas A Ia Iga Wnd Spd (m/sc) Fg. 21. Wnd spd data Ampltud (pu) Fg. 19. Voltag obsrvd on phas A Th currnt controllr prformanc and ffctvnss of th LCL fltr hav bn vrfd by usng powr systm blockst of Matlab/Smulnk. Fg 17 shows th stp rspons obsrvd on th I d of controllr systm. It s sn that th stp rspons n Fg. 17 has good agrmnt wth analytcal rspons n Fg 16. Th currnt and voltag rsponss on th convrtr sd and grd sd of th LCL fltr ar shown n Fgs. 18 and 19, rspctvly. It s sn that th fltr attnuats th harmonc dstorton vry ffctvly. Th THD (total harmonc dstorton) s masurd by usng Fast Fourr Transform (FFT) tool n Matlab. Th THD of th grd sd currnt s 1.17%, whl th THD of th grd sd voltag s 2.29%. V. SIMULATION STUDY Valdty of th dsgn and analyss mthod xpland abov has bn valuatd usng th modl systm shown n Fg. 2. A VSWT- PMSG ratd at 2.5 MW s connctd to 6.6 kv dstrbuton systm through convrtrs composd of stator sd and grd sd VSCs, a LCL fltr, a 1./6.6 kv stp up transformr, and a doubl crcut transmsson ln. A local load ratd at 1 MW s nstalld nar th wnd gnrator. In th fgur, mpdancs of th transmsson ln ar shown n th form of R+jX, whr R and X rprsnt th rsstanc and ractanc, rspctvly. Systm bas powr s 1 MVA. Va Vga Ptch Angl (dg) Actv Powr (MW) Ractv Powr (MVar) DC Lnk Voltag (kv) Fg. 22. Ptch angl rspons.5 Prf Ps Pg Fg. 23. Actv powr output -.2 Qs Qg Fg. 24. Ractv powr output Fg. 25. DC lnk voltag zro as shown n Fg 24. Th rspons of th DC lnk voltag s shown n Fg. 25. It s sn that th DC voltag can also b mantand constant at ratd valu (1.75 kv). Fg. 2. Modl systm In ordr to valuat th dynamc prformancs of th proposd systm, th wnd spd data shown n Fg. 21 s consdrd. Smulatons wr prformd by usng PSCAD/EMTDC. Fg. 22 dpcts th ptch angl rspons of th VSWT-PMSG, whch s actvatd whn th wnd spd xcds th ratd valu. Th actv powr rfrnc (P rf ), th actv powr output of PMSG (Ps), and th actv powr dlvrd to th grd (P g ) ar shown n Fg. 23. It s sn that P S and P g follow P rf vry wll. Th ractv powr outputs of th gnrator and th grd sd convrtr ar kpt almost VI. CONCLUSION In ths papr, dsgn and analyss of th control systm for 2.5 MW class of VSWT-PMSG connctd to a dstrbuton grd systm through LCL fltr s prsntd. Dsgn and analyss of th grd sd currnt controlld voltag sourc convrtr s focusd, n whch passv dampng rsstanc of th fltr and gans of PI controllrs of VSC ar slctd basd on frquncy rspons of th bod dagram and dynamc stp rspons. Accordng to th smulaton rsults t s concludd that th controllr systm s ffctv to control actv and ractv powr dlvrd to th grd. Morovr, th LCL fltr s vry ffctv to attnuat th harmonc dstortons. 2117

7 Powrd by TCPDF ( VII. ACKNOWLEDGEMENT Ths study was supportd by a Grant-n-Ad for scntfc Rsarch (B) from Th Mnstry of Educaton, Scnc, Sports and Cultur of Japan. VIII. APPENDIX Tabl II shows PI controllr paramtrs usd n th smulaton analyss. Th paramtrs for PI 1 to PI 4 (PI controllrs for th stator sd controllr) ar slctd by usng th pol placmnt mthod. Th paramtrs for DC lnk voltag controllr of th grd sd controllr (PI 5) can b slctd sam as thos of PI 6 and PI 7. TABLE II PI CONTROLLER GAINS PI Controllr K p T PI PI PI PI PI PI PI IX. REFERENCES [1] T. Ackrmann, G. Andrsson, L. So dr, "Dstrbutd gnraton: a dfnton," Elsvr, Elctrc Powr Systms Rsarch, Vol. 57, pp , 21. [2] Thomas Ackrmann, Wnd powr n powr systm, UK: John Wly & Sons, 25, pp [3] Y. Shankr, "Rvw of wnd turbns drv systms and why Garlss drct drv," RCREEE Wnd Enrgy Buldng Capacty Program Stag 2 Rabat, Tangr 29 March 2nd Apr. 21. [4] P. Vas, Elctrcal machns and Drv S A spac vctor thory approach, Nw York: Oxford Unv. Prss [5] W. A. Hll and S. C. Kapoor, "Effct of two-lvl PWMsourcs on plant powr systm harmoncs," n Conf. Rc. IEEE-IAS Annu. Mtng, pp , 1998,. [6] M. Lsrr, Frd Blaabjrg, Stffan Hansn, "Dsgn and Control of an LCL-fltr basd Thr-phas Actv Rctfr," IEEE Trans, Industry Applcatons Confrnc, Vol. 41, No. 5, pp , Spt/Oct. 25. [7] V. Blasko and V. Kaura, "A novl control to actvly damp rsonanc n nput lc fltr of a thr-phas voltag sourc convrtr," IEEE Trans.Ind. Appl., vol. 33, no. 2, pp , Mar./Apr [8] B. Fard O. Amar, "A Study of Nw Tchnqus of Controlld PWM Invrtrs, " Europan Journal of Scntfc Rsarch, Vol.32 No.1. pp , 29 [9] Sgfrd Hr, Grd ntgraton of wnd nrgy convrson systms, John Wly & Sons Ltd 1998, pp [1] S.M.Muyn, Ahmd Al-Durra, J. Tamura, "Varabl Spd Wnd Turbn Gnrator Systm wth Currnt Controlld Voltag Sourc Invrtr", Enrgy Convrson and Managmnt, Vol. 52, No. 7, pp , Jul [11] Shuhu L, Tmoth A. Haskw, and Lng Xu "Convntonal and novl control dsgn for drct drvrn PMSG wnd turbns," Elsvr, Elctrc Powr Systm rsarch, Vol. 8, pp , 21. [12] L. M. Frnands, C. A. Garca, F. Jurado, "Opratng Capablty as a PQ/PV nod of a Drct-Drv Wnd Turbn basd on a prmannt magnt synchronous gnrator, " Elsvr, Rnwabl Enrgy, Vol. 35, pp , 21. [13] S.M.Muyn, R. Takahash, T.Murata, J. Tamura, "A Varabl Spd Wnd Turbn Control Stratgy to Mt Wnd Farm Grd Cod Rqurmnts, " IEEE Trans, Powr Systms, Vol.25, No. 1, pp , Fb. 21. [14] Cvjn, J, "PI/PID Controllr Dsgn for FOPDT Plants Basd on th Modulus Optmum Crtron," In Procdngs of th 18th Intrnatonal Confrnc on Procss Control, Tatranská Lomnca, Slovaka, Jun 14 17, pp , Jun, 211. X. BIOGRAPHIES Marwan Rosyad rcvd Sarjana Tknk (quvalnt to B.Sc. dgr) from Adh Tama Insttut of Tchnology Surabaya and M. Eng. dgr from Spuluh Nopmbr Insttut of Tchnology, Indonsa, n 24 and 26 rspctvly, all n Elctrcal Engnrng. Prsntly h s workng towards hs Ph.D Dgr at th Ktam Insttut of Tchnology, Ktam, Hokkado, Japan. Hs rsarch ntrsts ar stablty and control of powr systm ncludng wnd gnrator. S. M. Muyn rcvd hs B.Sc. Eng. Dgr from Rajshah Unvrsty of Engnrng and Tchnology (RUET), Bangladsh, formrly known as Rajshah Insttut of Tchnology, n 2, and M. Sc. Eng. and Dr. Eng. Dgrs from Ktam Insttut of Tchnology, Japan, n 25 and 28 rspctvly, all n Elctrcal and Elctronc Engnrng. Aftr compltng hs Ph.D. program h workd as a Postdoctoral Rsarch Fllow undr th vrsatl bannr of Japan Socty for th Promoton of Scnc (JSPS) from at th Ktam Insttut of Tchnology, Japan. Prsntly h s workng as Assstant Profssor n Elctrcal Engnrng dpartmnt at th Ptrolum Insttut, n UAE. Hs rsarch ntrsts ar powr systm stablty and control, lctrcal machn, FACTS, nrgy storag systm (ESS), Rnwabl Enrgy, and HVDC systm. Ron Takahash rcvd hs B.Sc. Eng. and Dr. Eng. Dgrs from Ktam Insttut of Tchnology, Japan, n 1998 and 26 rspctvly, all n Elctrcal and Elctronc Engnrng. Now h s workng as Assocat Profssor n Dpartmnt of Elctrcal and Elctronc Engnrng, Ktam Insttut of Tchnology. Hs major rsarch ntrsts nclud analyss of powr systm transnt, FACTS and wnd nrgy convrson systm. Junj Tamura rcvd hs B. Sc. Eng. Dgr from Muroran Insttut of Tchnology, Japan, n 1979 and M.Sc. Eng. and Dr. Eng. dgrs from Hokkado Unvrsty, Japan, n 1981 and 1984 rspctvly, all n lctrcal ngnrng. H bcam a lcturr n 1984, an Assocat Profssor n 1986, and a Profssor n 1996 at th Ktam Insttut of Tchnology, Japan. Currntly h s a Vc Prsdnt of th Ktam Insttut of Tchnology. Dr. Tamura s a Snor Mmbr of th IEEE Powr Engnrng Socty. 2118