Sliding mode Control of Chopper Connecting Wind Turbine with Grid based on synchronous generator

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1 Proceedngs o the 4 Internatonal onerence on Power Systems, Energy, Envronment Sldng mode ontrol o hopper onnectng Wnd Turbne wth Grd based on synchronous generator Ahmed TAHOUR, Abdel Ghan AISSAOUI, Mohamed ABID, Najb ESSOUNBOULI, Ferc NOLLET Abstract: In ths chapter we propose to desgn a robust control usng sldng mode or chopper control o synchronous generator. The purpose s thereore to make the voltage and the current control resst to speed varatons, because the varaton o speed degrades the perormance o the voltage pruducted to the networks. The use o the nonlnear sldng mode method provdes very satsactory perormance or chopper control o synchronous generator, and the chatterng eect s also elmnated by the uncton sat. Smulaton results show that the mplementaton o the sldng mode controllers lea to robustness and dynamc perormance satsacton. onclusons are summarzed n the last secton. Keys wor: synchrone generator, wnd turbne, sldng mode control and voltage control. I. INTRODUTION Global consumpton o energy has ncreased n recent years because o massve ndustralzaton whch ten to grow more and more, speccally n certan geographc areas as Asan countres []. The rsk o shortages o ossl uels and ther eects on clmate change, nate once agan the mportance o renewable energy. Followng ths awareness, economc development that takes care o the envronment becomes absolutely necessary []. Several sources o renewable energy are object o advanced researches, whch am to develop technques or extractng power wth hgh relablty, lower cost and ncrease energy ecency [-3]. In ths paper, we ocus on the converson o wnd energy nto electrcal energy that has became compettve due to three man actors [4]: Wnd energy s clean, renewable and naturally replenshed by nature, The development o the wnd turbne ndustry, The evoluton o semconductor technology, and new methodologes or control o varable speed turbnes. However, several problems, related n part to the complexty o wnd converson systems as the need or speed multpler between the turbne and generator, and the nstablty o wnd speed on the other hand [5]. The use o wnd turbne structures wth synchronous generator o hgh poles number make o wnd converson systems wth varable speed more attractve than those wth xed speed, because o the possblty o extractng the optmal energy or derent wnd speed, ucng mechancal stresses by elmnatng the multpler whch Unversty o Mascara, 9, Algera orrespondng author e-mal: tahourahmed@yahoo.r IREOM Laboratory, Unversty o Sd Bel Abbes,, Algera, mproves system relablty, and uce the mantenance costs [, 6]. Ths paper deals wth a varable-speed system consstng o synchronous generator, dode recter and thyrstor nverter. The advantages o the synchronous generator and a dode recter are the hgh ecency o the recter and the low prce. There are two dsadvantages that can be mportant n wnd turbne generator systems. Motor start o the turbne s not possble wthout auxlary equpment and the torque control s normally not aster. The am o ths report s to descrbe an ecent varablespeed system and to model the generator and converter losses []. In ths context, the present study ocuses on wnd energy, whch seems to be one o the most promsng. The am o ths paper s to present a comprehensve model o a synchronous generator based on a proposed structure and control strateges to optmze power output, to regulate the D bus voltage, and to control voltage transmtted to the network [, 7]. To control the Wnd Energy onverson System (WES) we need robust controller. Sldng Mode ontrol (SM) s a nonlnear control technque derved rom varable structure control system theory and developed by Vladm UTKIN. Such control soluton has several advantages such as smple mplementaton, robustness and good dynamcal response. Moreover, such control comples wth the nonlnear characterstc o the swtch mode power supples [4,, ]. The organzaton o ths chapter s as ollow: n the rst secton, we establsh the model o the turbne. The second secton s devoted to modelng the synchronous machne wth ther equvalent electrcal model. Global model o the chan o wnd converson devce and assocated controller are developed n an equvalent contnuous model that takes nto account relevant parts o the voltages at the generator, the D bus and the network s started at thrd Secton. The last secton s devoted to the smulaton results. All models developed n ths study are smulated by the Matlab-smulnk. II. WIND ONVERSION SYSTEM MODEL The WES descrbed n ths artcle ncludes the wnd turbne, synchronous generator, a transormer, a dode recter, a lter and an nverter. In ths system, the wnd energy s transmtted through the turbne to the threephase synchronous machne and generated n electrcal orm. Ths energy s transmtted drectly through a transormer, a brdge recter and nverter to the electrcal ISBN:

2 Proceedngs o the 4 Internatonal onerence on Power Systems, Energy, Envronment network (Fgure ). We consder n ths study that the transormer s perect. The man assumpton n ths smpled study s that the currents are snusodal and semconductors are deal [6-7]. Fgure () shows the equvalent dagram o the WES. Recter hopper Inverter Electrcal Network SG Fg.3. Power coecent p as a uncton o and Fg.. Wnd electrcal converson system based on synchronous machne A. Turbne Model The turbne model s to present the power and the torque developed by the turbne, and whch can be dened by the ollowng equatons [-3, 8]: Pm R v 3 p ( ) () Pm 3 Tm R v p () Whch presents the rato between the turbne angular speed and the wnd speed. Ths rato called the tp speed raton and s dened as: R (3) v Where: s the ar densty, R s the blade length, v s the wnd speed, p s the power coecent, s the turbne angular speed. The power coecent ( ) presents the aerodynamc ecency o the turbne and depen on the specc speed and the angle o the blades. It s derent rom a turbne to another, and s usually provded by the manuacturer and can be used to dene a mathematcal approxmaton. A model o wnd s developed and t s presented on gure (). Fg.. Model o Wnd Fgure (3) represents the power coecent uncton o and. p p as a Fgure (4) shows the mechancal power as a uncton o rotor speed o the turbne or derent values o wnd speed [4]. Fg.4. The characterstcs o the mechancal power as uncton o the turbne speed. B. Generator Model The generator chosen or the converson o wnd energy s the synchronous generator [6, 9-]. The dynamc model o synchronous generator n d-q rame can be represented by the ollowng equatons: Electrcal equatons: d V Rs qs d qs Vqs Rsqs (4) d V R The lux lnkage equatons are: qs L d L L q qs M M The dynamc behavor o synchronous generator can be dened by: d Tm Tem J (6) Where R s stator resstance, (5) R s the eld résstance, L, L qs respectvely drect and quadrature stator nductances, L s eld nductance, T W Wnd torque ISBN:

3 Proceedngs o the 4 Internatonal onerence on Power Systems, Energy, Envronment appled to SG rotor, T em electromagnetc torque, p par number o poles, s the dampng coecent, J s the moment o nerta, electrcal angular speed o motor. SG Recter hopper Inverter Electrcal Network III. Sldng Mode ontroller A. Sldng mode prncple Sldng modes s phenomenon may appear n a dynamc system governed by ordnary derental equatons wth dscontnuous rght-hand sdes. It may happen that the control as a uncton o the system state swtches at hgh requency, ths moton s called sldng mode. It may be enorced n the smplest trackng relay system wth the state varable x(t) [7, 8]: x ( x) u (7) Wth the bounded uncton (x) x) cons tan t and the control as a ( relay uncton (gure(5)) o the trackng error x e r( t) r(t) by : s the reerence nput and u s gven u e u or u e u usgn( e) u cons tan t Fg. 5 relay control e r The values o e and ( x) usgn( e) have r derent sgns u. B. ONTROL STRATEGY It s possble to control the load voltage, by the control o the converter assocated. The all system s shown n Fgure (6). The control o the system s based on the control o the PWM nverter and the chopper [5-6]. The D-Lnk s made by usng buck D/D converter. SM Fg.6. ontrol o the WES. For the Buck converter we consder the ollowng sldng surace S : SM Vdre S ( e ). (8) where k s the sldng coecent and e s the output voltage error dened as ollows : e (9) V re V By consderng the mathematcal model o the Buck converter, the surace can be expressed by the ollowng expresson (Tan, et al, 6; Ben Saad et al 8): Vre S. l.( Vre V) () and ts dervatve s gven by : S V V re re.. L ( ). V V ( ). u () The next step s to desgn the control nput so that the state trajectores are drven and attracted toward the sldng surace and then reman sldng on t or all subsequent tme. The SM sgnal u conssts o two components a nonlnear component us and an equvalent component ueq, [3].. Vre Vre L u eq... L ( ). V () V V V V Let us consder the postve dente Lyapunov uncton V dened as ollows: S V. (3) The tme dervatve V V o V must be negatve dente to nsure the stablty o the system and to make the surace S attractve. Such condton lea to the ollowng nequalty: S V. S.(. us ) S (4) To satsy such condton, the nonlnear control component can be dened as ollows: u s sgn(s) ISBN:

4 speed (m/s) Proceedngs o the 4 Internatonal onerence on Power Systems, Energy, Envronment Where V output voltage o chopper, V ntput voltage o chopper, V dre reerence voltage, L and s the nductance and capactance o chopper.. SIMULATION DES RESULTATS In ths part we have smulated, the system descrbed n Fgure (6), takng nto account o the real waveorms. The wnd speed taken s 3m/s and that change to 6m/s at t=s (Fg. 7). The reerence D-lnk voltage taken s V re 58v and whch correspon to the voltage appled n the network wth a value o v and a requency o5 Hz. Fgures 8.a and 8.b present the smulaton results usng a sldng mode controller voltage. It can be shown that the voltage generated wll nluence the energy consumpton gure (8.a). In gure (8.b), the voltage gven by the chopper ollows the reerence voltage needed or the voltage requested by the network. Fg. 8. The voltages n the output o: a- Recter, b- hopper In the grd sde, we have smulated the WES n two cases: wthout usng controllers and wth usng controllers. In the rst case, the voltages n the grd phases vary wth the varaton o wnd speed (Fgure 9.a). In the second case, the voltages n the grd phases are constant n derent varatons o wnd speed (gure 9.b). Fgure () shows the voltages n three grd phases. The use o SM gves good result n control o voltages transmtted to the grd Fg. 7. The curve o wnd speed a a b ISBN:

5 Proceedngs o the 4 Internatonal onerence on Power Systems, Energy, Envronment b- Fg. 9. The voltage n the grd phase A : a- Wthout controller, b- In the presence o controller Fg.. The voltages n the three phases grd consstng o a synchronous generator, a three-phase dode recter, a Buck chopper and a PWM Inverter. We have subsequently bult a devce or controllng the chan o the proposed converson. The all system s smulated n two derent wnd speed. The smulaton results show the possblty o extractng the maxmal o wnd power, and the control o the chopper output voltage and the nverter n order to regulate the grd voltages to the des values. REFERENES [] A. MIREKI, Etude comparatve de chaînes de converson d énerge dédées à une éolenne de pette pussance, Thèse de doctorat de L nsttut natonal polytechnque de Toulouse le 5 avrl 5. [] F. Poters "Etude et ommande de Génératrce Asynchrone pour L utlsaton de L énerge Eolenne ", Thèse de Doctorat de l Unversté de Nantes, 9 décembre 3. [3] G. A. Smth, K.A. Ngm, Wnd-energy Recovery by a Statc Scherbus Inducton Generator", Proc. IEE, 98, 8, pp [4] Nguyen, V.M. & Lee,.Q. (996). Indrect mplementatons o sldng-mode control law n buck-type converters, Proceedngs o the IEEE Appled Power Electroncs onerence and Exposton, pp. 5, Vol., March, 996. [5] A. Rachd, Systèmes de régulaton, Masson, pars, 996. [6] huntng M, Marano Flppa, Johan Shen and Narashm Natarajan, Modelng and ontrol o Varable Speed onstant Frequency Synchronous Generator Wth brushless Excter, IEEE Transactons on ndustry applcaton, vol, 4, No,, pp , March/aprl 4. [7] E. S. Abdn, W. Xu, ontrol desgn and Dynamc Perormance Analyss o a Wnd Turbne- Inducton Generator Unt, IEEE Trans. on Energy converson, vol.5, No, March. [8] H. amblong, Mnmsaton de l mpact des perturbatons d orgne éolenne dans la Génératon d électrcté par des aérogénérateurs à vtesse varable, Thèse de doctorat, ENSAM Bordeaux, 3. [9] Reou, B.A.T. Al Zahaw, A.G. Jack "Analyss and modellng o the steady state behavor o the statc Kramer nducton generator", IEEE Transactons on Energy onverson,volume 4, Issue 3, 999, pp [] S. El Aman, Modélsaton de dérentes technologes d éolennes ntégrées dans un réseau de moyenne tenson», Thèse de doctorat de l Ecole entrale de Llle (EL) ohablté avec L unversté des scences et technologes de Llle (USTL), 6 décembre 4. [] Tan, S..; La, Y.M.; heung, M.K.H. & Tse.K. (5). On the practcal desgn o a sldng mode voltage controlled buck converters, IEEE Transactons on Power Electroncs, Vol., No., pp , March 5, ISBN [] Tan, S..; La, Y.M. & Tse,.K. (6). An evaluaton o the practcalty o sldng mode controllers n D-D onverters and ther general desgn ssues, Proceedngs o the IEEE Power Electroncs Specalsts onerence, pp.87-93, June 6. [3] Ben Saad, K.; Sahban, A. & Benrejeb M. Desgn Procedure and Implementaton o a Robust Fuzzy Sldng Mode ontroller or Buck onverters, Internatonal Revew o Automatc ontrol, Vol., No.3, pp. 33-3, September 8, ISSN [4] S.R.Guda, «Modelng and power management o a hybrd wndmcroturbne power generaton». thèse de master de l unversté de Bozeman, Monata. Jullet 5. [5] A.D. Hansen,.Jauch, P.Sørensen, F.Iov, F. Blaabjergm, Dynamc wnd turbne models n power system smulaton tool DIgSILENT, projet de recherche, laboratore natonal de Rso, Rosklde. Décembre 3. [6] K. Ame, Y. Igkayasu, T. Ohj, M. Saku, A Maxmum Power ontrol o Wnd Generator System Usng a Permanent Magnet synchronous Generator and a Boost hopper rcut, D. ONLUSION In ths chapter, we have descrbed the derent structures o wnd turbnes based on the synchronous generator; we have establshed a model o the wnd converson chan, ISBN: