Studies on Sensor-Less Hysteretic Multi-Scalar Control of Doubly Fed Machine for Wind Power Generators

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1 Available online at Enegy Pocedia 2 (20) ICSGCE 20: Septebe 20, Chengdu, China Studie on Seno-e Hyteetic Multi-Scala Contol of Doubly Fed Machine fo Wind Powe Geneato Yang Zhang *, Zijing Wang, Zhaohong Bie, Jing Chen Hennan Electic Powe Suvey & Deign Intitute, Zhenghou, Henan, China Abtact A one of the advanced technologie, the vaiable peed contant fequency doubly-fed induction geneato (VSCF- DFIG) ha been widely ued nowaday. The ulti-cala contol chee of DFIG i fitly intoduced in thi pape, the cuent hyteei PWM technology i then intoduced to iplify the contol yte. An open-loop peed obeve i deigned accoding to the ulti-cala contol yte. By uing the oto cuent efeence coponent intead of the eal cuent coponent, the obeve deign i iplified and obeve effect i evidently ipoved. The dynaic epond pefoance i bette in ulti-cala contol yte and the whole contol poce doe not depend on any electic achine paaete. The popoed peed obeve can ovecoe oe of the diadvantage of the taditional open-loop peed obeve. PSCAD/EMTDC iulation oftwae i ued to tet the popoed chee. Teting eult have deontated the efficiency of the contol chee a well a the peed obeve. 20 Publihed by Elevie td. Open acce unde CC BY-NC-ND licene. Selection and/o pee-eview unde eponibility of Univeity of Electonic Science and Technology of China (UESTC) Keywod: DFIG; Multi-cala contol; Cuent hyteei PWM; Open-loop peed obeve. Intoduction Wind powe, a an enoou, enewable and non-polluting enegy, ha ecently gained oe and oe woldwide attention. Wind powe geneation technology ha enteed a fatet-gowing peiod. In ode to educe the geneation cot and inceae the utiliation efficiency of wind powe, the capacity of the wind geneato i tuning lage and vaiable pitch a well a vaiable peed contant fequency (VSCF) technology i applied to the geneato. The VSCF-DFIG i accodingly becoing the aintea of lage capacity wind geneato [-2]. The eeach on contol technology of DIFG i theefoe of geat neceity. At peent, vecto contol technology i widely ued in the VSCF-DFIG contol field. Howeve, oe inheent defect have to be noticed. It pefoance i exteely affected by the peciion of vecto * Coeponding autho. Tel.: E-ail adde: yang.84@gail.co Publihed by Elevie td. Selection and/o pee-eview unde eponibility of Univeity of Electonic Science and Technology of China (UESTC). Open acce unde CC BY-NC-ND licene. doi:0.06/j.egypo

2 742 Yang Zhang et al. / Enegy Pocedia 2 (20) oientation. And lot of coodinate tanfoation ut be applied to contol yte in the coputation [3-5]. On account of all thee diadvantage, a new ethod ulti-cala contol technology i popoed in thi pape [6-8]. In contat with vecto contol, the pinciple of ulti-cala technology i to intoduce 4 cala a tate vaiable. The non-linea feedback function i adopted to lineaie DFIG odel which i a non-linea, tong coupling yte. Then, the DIFG odel can be divided into 2 linea ubyte which ae echanical and electoagnetic ubyte. In thi way, ulti-cala inne-loop contol yte can be foed [6]. And the 4 cala ae oto peed, quae of tato flux aplitude, vecto poduct of tato flux and oto cuent, and finally cala poduct of tato flux and oto cuent. Copaed with vecto contol, the pefoance of ulti-cala technology ipove ignificantly. Coodinate tanfoation fequency i deceaed obviouly. Coodinate oientation in t equied anyoe, o that the pobability of eo i anaged effectively. Moeove, iulation tet eult how that ulti-cala technology povide a good pefoance in the low voltage ide though (VRT) [8]. A fo taditional ulti-cala contol technology, it i deeply dependent on oto paaete, which i a ignificant dawback. A we known, thee paaete will vay with the agnetic atuation and tepeatue inceaing in the opeation poce, conequently contol effect will be influenced oewhat. To begin with, the DFIG ulti-cala contol odel i intoduced in thi pape, afte that cuent hyteetic technology i added to ipove the taditional ulti-cala technology to deceae the influence bought by the oto paaete. Finally PSCAD/EMTDC iulation oftwae i ued to deontate the feaibility and effectivene of the popoed chee. The oto poition and peed infoation ae eential in the DFIG contol yte. The photoelectic encode and othe taditional peed obeve ae widely ued nowaday in DIFG contolle, wheea high peciion peed obeve bing about high cot and difficultie in intallation and aintenance [2]. Becaue of which, oe attention i ecently paid on the eno-le contol technology. Thee ae two kind of peed obeve, the open loop and the cloe loop peed obeve. In [9-] cloe loop peed obeve ae deigned, which not only i elf coecting but alo ha tong obutne to achine paaete, while at the ae tie i oe inticate in deigning, and highly coupled to contol yte. A copact open loop peed obeve chee i popoed in thi pape baed on the chaacteitic of the hyteetic ulti-cala contol yte, iulation eult have appoved the feaibility of thi deign. 2. The DFIG Multi-cala Contol Schee 2.. The atheatical odel of DIFG To tat with, DIFG atheatical odel in the vecto equation fo i given in ynchonouly otating fae. The DIFG tato and oto ide voltage equation i expeed a: U = RI + py + jωy () U = RI + py + j( ω ω ) y { The DIFG otion equation i expeed a: * Jpω = I( yi) T0 (2 ) whee y, y ae tato and oto flux vecto, U, U ae tato and oto voltage vecto, ω i DIFG ynchonou angula velocity, ω i DIFG oto velocity, R, R ae tato and oto ide eitance, J i oent of inetia. T0 i load toque.

3 Yang Zhang et al. / Enegy Pocedia 2 (20) The DIFG tato and oto ide flux equation i a follow: I = y I I = y I (3) whee I, I ae tato and oto cuent vecto, i the equivalent utual inductance in d-q efeence fae, i equivalent tato winding elf-inductance, i equivalent oto winding elf-inductance in d-q coodinate. Accoding to the atheatical odel, the diffeential equation can be deived a follow: R pyxs = yxs + R IxS + UxS (4) ys ys ys ys R py = y + R I + U (5) pi R + R R = xr IxR y xr w w ωy + U U w w w yr yr xr pi R + R R = yr IyR y yr w w ωy + U U w w w xr yr yr (6) (7) pω = ( yxs IyS yys IxS ) T0 (8) J J whee 2 w = (9) And ubcipt S ean quantitie in the coodinate yte which i tationay elative to tato; ubcipt R ean quantitie in the coodinate yte which i tationay elative to oto The contol tategy baed on ulti-cala odel The ain pinciple of ulti-cala technology i to intoduce 4 cala a tate vaiable. The nonlinea feedback function i adopted to lineaie the DFIG odel. Afte that, the DIFG odel can be divided into echanical linea ubyte and electoagnetic linea ubyte. Accoding to all thee above, the ulti-cala inne-loop contol yte i foed. Conideing the elationhip between tato ide active & eactive powe and the tate vaiable entioned above, the powe oute-loop decoupled contol yte i acquied, which i a double cloed-loop contol yte [7]. In thi pat, the taditional DIFG ulti-cala contol chee baed on voltage SPWM technology i eviewed. And the fundaental i illutated a below: In ode to do nonlinea tanfoation fo DFIG odel, fou cala ae defined a tate vaiable, they

4 744 Yang Zhang et al. / Enegy Pocedia 2 (20) ae = ω (0) = y I y I () 2 x y y x = y (2) 2 2 = y I + y I (3) 22 x x y y whee oto peed; 2 vecto poduct of tato flux and oto cuent; 2 quae of tato flux aplitude; 22 cala poduct of tato flux and oto cuent. In new tate vaiable, DFIG odel linea ubyte ae depicted a follow: Mechanical ubyte: p = 2 T0 J J (4) p = ( + ) (5) 2 2 Tv whee i an inteediate contol vaiable to contol 2. Electoagnetic ubyte: R R p uf 2 (6) p = ( + ) (7) Tv in which uf 2 = uxyx + uyyy, and 2 i an inteediate contol vaiable to contol 22. Since the voltage dopped on tato eitance can be neglected in teady tate, the tato eitance i oitted in thi eeach to iplify the odel. And the tato ide active and eactive powe expeion i: P = 2 (8) Q = 22 (9) It can be een fo (8), (9) that, the tato active and eactive powe i epectively linealy elated to the tate vaiable 2 and 22. By odulating the two tate vaiable we can achieve the DIFG tato ide active-eactive decoupling contol. It i eential to etablih the elationhip between 2 & 22 and oto voltage in ode to accoplih contol chee in SPWM technology. And it i jut the point to intoduce inteediate vaiable and 2. Following it, the tak i to build the elation between & 2 and oto voltage. And the oto voltage can be decibed a:

5 Yang Zhang et al. / Enegy Pocedia 2 (20) u y + u y ux = 2 u y u y uy = 2 y 2 x 2 y y (20) whee w u = uf ui + w w Tv u w = R R + i w u u + f 2 i2 + 2 w Tv 2 w = u = u y u y f y x x y u = u i u i i x y y x u = u i + u i i2 x x y y Now, a ulti-cala DFIG contol yte baed on SPWM technology i built accoding to the atheatical odel deivation popoed above The cuent hyteei ulti-cala contol chee In contat with vecto contol, the advantage of ulti-cala contol chee ae to deceae the coodinate tanfoation fequency and it doen t equie coodinate oientation any oe. But fo the theoetical deivation popoed above, it can be een that the opeation poce of ulti-cala contol chee i tediou and lot of oto paaete ae enolled. Thee paaete will vay with the agnetic atuation and tepeatue inceaing in the opeation poce, theefoe contol peciion will be influenced oewhat. In thi pape, cuent hyteei tacking technology i applied to DFIG ulti-cala contol yte to iplify the contol odel and ipove the contol effect. Cuent hyteei contol technology i killed at dynaic epone and voltage utiliation. And the fundaental can be illutated a below. Fo the ake of keeping cuent to be ine, contol pule i obtained, that i to ay contol cicuit geneate a inuoidal efeence cuent with given aplitude and fequency to copae with the actual cuent. And the tate of convete bidge leg i deteined accoding to the eult. When the actual cuent i ove the given hyteei belt uppe liit, the uppe bidge leg of the conveto tun off and unde bidge leg tun on, the phae cuent deceae, in the ae way when the actual cuent eache the lowe liit, the conveto unde bidge tun off, uppe bidge on, leading to phae cuent inceaing. The futhe fundaental explanation of cuent hyteei ulti-cala contol technology i depicted a follow: in the oto ide convete, cuent hyteei technology i applied to ake the actual cuent * * in the oto ide tace the efeence cuent coponent i x, iy diectly. Unlike the taditional way of intoducing exta contol vaiable to etablih the elationhip between tate vaiable and oto voltage u, u.theefoe the iplification of contol yte i ealied. * d * q

6 746 Yang Zhang et al. / Enegy Pocedia 2 (20) Fo () and (3), the elationhip between oto cuent and tate vaiable 2 & 22 can be deived diectly. 22yx 2yy ix = 2 (2 2yx + 22y y iy = 2 ) * * Thu, the oto efeence cuent coponent i x, iy can be calculated diectly by the tate vaiable and obeved tato flux. The application of popoed cuent hyteei technology can ipleent the actual oto cuent tacking the efeence cuent. Afte that the total contol poce i ealied. Applying popotional-integal egulato PI contol to active and eactive powe, tate vaiable 2 and * * 22 ae acquied. A fo oto efeence cuent coponent i x, iy ae calculated by (2). Baed on the analyi, the odel of hyteetic ulti-cala contol yte i hown a below: Fig. The chee of odel of hyteetic ulti-cala contol yte fo the DFIG In Fig., the application of cuent hyteei can iplify the contol yte a well a tengthen the obutne pefoance ince the whole contol chee didn't involve any oto paaete. 3. An Open-loop Speed Obeve Schee The DIFG peed obeve deign i of two kind, the open loop and cloe loop peed obeving technique. In open loop peed obeve the oto poition angle i calculated diectly fo actual tato and oto ide electical quantitie accoding to the DIFG atheatical odel. The open loop chee i copact and intuitionitic copaed with the cloe loop chee, while lack of elf coecting ability, oe enitive to the oto paaete and haonic cuent ae it defect. Accoding to the chaacteitic of hyteei vecto contol yte, a copact open loop peed obeve i deigned. The baic pinciple i a below.

7 Yang Zhang et al. / Enegy Pocedia 2 (20) Fig. 2 The pinciple of open loop peed obeve In Fig.2 I i the oto cuent vecto, αβ i the tato tatic efeence fae, αβ i oto ynchonouly efeence, dq i the ynchonouly otating efeence fae. θ i the angle between oto cuent vecto and d axi, θ2 i the angle between oto cuent vecto and α axi, θ3 i the angle between d and α axi, which i apopo the tato flux poition angle in tato flux oiented contol chee. The oto poition angle to be obtained in Fig.2 i angle θ. Accoding to Fig.2 the oto poition angle θ can be calculated by θ, θ2 and θ3 fo the equation: θ = θ + θ θ (22) 3 2 Thu the iue coe down to obtaining θ and θ 2. To obeve the angle θ 2, only need to eaue the thee-phae oto cuent i a ib ic in oto ynchonouly efeence abc, and calculate the two oto cuent coponent in αβ coodinate though 3 /2 tanfo. The angle θ 2 i obtained iply though the following calculation: i β θ2 = tan ( ) (23) i α A to angle θ, due to the cuent hyteei PWM technology, the actual cuent can tack the efeence value in high peciion, o that the two actual cuent coponent in dq coodinate ae vey cloe to the efeence value. Theefoe the angle θ can be obtained though the two efeence cuent * * coponent i d, iq in dq coodinate without any actual cuent eaueent o conveion. * i q θ = tan ( ) (24) * i d The oto poition angle can be acquied though (22), (23) and (24). The PSCAD odel of the open loop peed obeve accoding to thi pinciple i hown in Fig.3. Fig. 3 The PSCAD iulation odel of open loop peed obeve

8 748 Yang Zhang et al. / Enegy Pocedia 2 (20) By uing the cuent efeence in vecto contol yte intead of the actual cuent, thi appoach not only iplified the obeve deign but alo educed the ipact of electical haonic. Since electical calculation i not involved in the obeve deign, none achine paaete i needed, the influence of vaiational oto paaete i well avoided. Baed on the above thi deign can to a cetain extent ovecoe the diadvantage of the taditional obeve. 4. Siulation and Analyi A gid connected DIFG iulation odel wa built a i hown in Fig.4, uing PSCAD/EMTDC oftwae to tet the popoed contol yte and peed obeve. Fig. 4 Wind powe geneation yte with DFIG The achine paaete ae: ated capacity =0.4Mva, tato ated voltage 0.69kV, tato eitance pu, oto eitance pu, the utual inductance 4.362pu, tato leakage inductance 0.02pu, oto leakage inductance 0.pu. To initialie the oto excitation and peed, the geneato i in peed contol ode in the fit 0.3 duing the iulation tie, and then tun into the toque contol ode. The wind peed etting i hown in Fig.5, whee the ean wind peed i 8/, a gut wind appea when t 7, with a gut peak velocity of 5/, o the axial wind peed i 3/. The efeence oto peed i calculated by the cuent wind peed accoding to optiu peed theoy. The total iulation tie i 0; the tato efeence eactive i 0.3Mva. Siulation eult i hown below: Fig.5 The wind peed

9 Yang Zhang et al. / Enegy Pocedia 2 (20) Fig.6 Geneato otation peed tacking the efeence value Fig.7 Stato eactive powe Accoding to Fig.6, to aintain the optiu blade top peed atio, the efeence oto peed ut be linealy elated to wind peed. Afte the oto ente toque contol ode at 0.3, it take appoxiate.2 fo the actual oto peed to tack the efeence value. In Fig.7 the tato eactive powe ie fo 0Mva to the efeence value 0.3Mva in 0.8 and then eain table. Accoding to Fig.6 and 7, the tato eactive powe can accuately tack the efeence value, duing the change of oto peed, thu the decoupling contol i achieved. (a) Roto phae efeence cuent (b) Roto phae actual cuent Fig 8 Roto phae cuent tacking the efeence value The oto efeence phae cuent wa calculated though foula (2) and changed with otation peed. The copaion of (a) and (b) in Fig.8 how that, by uing cuent hyteei PWM technology the oto cuent tacking eo can be etained in a hyteei band, the width of which i eticted by witch fequency, in thi iulation the eo wa liited in 0.2kA.

10 750 Yang Zhang et al. / Enegy Pocedia 2 (20) The oto poition angle obeving iulation eult ae hown a follow: (a) The actual oto poition angle (b) The obeving poition angle (c) The obevation eo cuve Fig.9 The iulation eult of oto poition angle eaueent The obeving oto poition angle in Fig.9 (b) i vey cloe to the actual value in Fig.9 (a). The eo cuve in Fig.9 (c) ha eached a inial a 0-5 degee agnitude ode. The obeve output i ooth and baely influenced by electical haonic, which can take the place of photoelectic encode to achieve DIFG eno-le contol. 5. Concluion In thi pape, the cuent hyteei PWM technology i intoduced to iplify the taditional DIFG ulti-cala contol yte. The contol epone peed i inceaed and obutne pefoance againt the achine paaete geatly tengthened. An open-loop oto poition angle obeve i deigned accoding to the ulti-cala contol yte, which i oe iplified and effective than the taditional chee. By uing the cuent efeence intead of the actual cuent, the influence of vaiational oto paaete and lectical haonic i well avoided, the obeving effect i evidently ipoved. The iulation eult have deontated the efficiency of the cuent hyteei contol chee a well a the accuacy of the popoed peed obeve, thu the DIFG eno-le decoupling contol i achieved. Refeence [] Baihi Chen. Electicity Pull Autoation Contol Syte[M]. China Machine Pe, 2003(in Chinee). [2] Shuying Yang. Convete and Contol fo Double Fed Induction Geneato-Baed Wind Powe Geneation[D]. Powe Electonic and Dive, Ming Yi,

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