Performance Enhancement of Indirect Matrix Converter Based Variable Speed Doubly-Fed Induction Generator

Transcription

1 1t Power Electronic & Drive Sytem & Technologie Conference Performance Enhancement of Inirect Matrix Converter Bae Variable Spee Doubly-Fe Inuction Generator J. Amini, R. Kazemzahe, H. Maai Kojabai Sahan Univerity of Technology, Tabriz, Iran. Abtract The conventional type of DFIG ytem ha ome rawback mainly ue to large DC link capacitor. Exitence of thi capacitor caue converter average lifetime an reliability of ytem reuction, an maintenance cot proliferation. In thi paper a DFIG bae win turbine generation ytem propoe, in which it common back-toback converter replace with an inirect matrix converter (IMC) that ue Sigma-Delta (ΣΔ) moulator to control witche matrix. In thi ytem DC link capacitor i omitte, o ytem get more reliable performance an it i cot effective. Furthermore by uing ΣΔ moulator IMC performance enhance. Therefore ue to generate current THD reuction, pulative torque of ytem reuce that ha uneniable effect on mechanical ytem lifetime. Beie THD of output current win turbine reuce, that improve power quality of generate power. Keywor: DFIG, Matrix Converter, Sigma-Delta, Win Energy, Power Quality. I. Introuction In many countrie in the worl energy policy i focue on the increae utilization of win energy ue the fact that win energy can provie a conierable fraction of electrical energy eman. Beie, win repreent a natural reource which i renewable, environment frienly an available nearly in every country. Nowaay DFIG bae ytem (Fig. 1) i mot ol technology [1] becaue of it many avantage [2], [3]. Both the tator wining an rotor wining of DFIG are connecte to the power gri. The rotor wining i connecte to upply circuit via power electronic converter. The mot common converter configuration in thi topology i the back to back rectifier-inverter pair tructure. The back to back rectifier-inverter pair i biirectional power converter that conit of two voltage ource converter. Thee two converter are connecte together via a c-link coniting of a capacitor. Thi inirect AC/AC converter ha ome rawback mainly ue to c-link capacitor. The clink capacitor i heavy an bulky, reuce the overall lifetime of ytem [4] an increae the maintenance cot. Since the penetration of thi topology increae continuouly, it reliability, power quality an cot effectivene mut be enhance. Therefore it i eirable to ue a uitable ubtituting intea. A matrix converter (MC) a a irect AC/AC converter ha potential for replacing the rectifier-inverter pair tructure. The MC allow a reliable an compact eign ue to omitting of c-link capacitor for energy torage. Coniering it robutne, reliability an reuce ize, MC are goo caniate to utilize in variable pee win energy ytem. In thi paper an inirect matrix converter i propoe to ubtitute the conventional converter (Rectifier- Inverter pair) in DFIG bae WECS (Fig. 2). ΣΔ moulator i ue to control the IMC. Thi ytem enjoying avantage of MC, which are well ocumente in the literature [5], [6]. Beie ΣΔ moulator improve performance of IMC compare to PWM moulate IMC. Thi caue torque an pee better regulation that ha ameliorating effect on mechanical part lifetime an increae power generation lightly, furthermore reuce converter generate harmonic an improve power quality of WECS. The propoe ytem imulate uing PSCAD/EMTDC an compare with imilar ytem which ue PWM moulate IMC. Fig. 1 Simple iagram of conventional DFIG ytem /10/$ IEEE 450

2 Fig. 2 DFIG with ΣΔ controlle inirect matrix converter II. Active an Reactive Power Control Vector control of a gri connecte DFIG ha alreay been tuie [7], [8]; o only a brief ecription i given here. The DFIG ynamic moel in -q reference i expree a follow [7], [8]: V = R i + ψ + jωψ (, q) (, q) (, q) (, q) t V = R i + ψ + j( ω ω ) ψ t r(, q) r r(, q) r(, q) r r(, q) ψ = L (, q) i (, q) + Lm i r(, q) ψ = L i + L i r (, q) r (, q) (, q) m (1) (2) 3 Te = P. Lm ( iq i i iqr ) (3) 2 where V an i are the tator voltage an current; V r an i r are the rotor voltage an current; R an R r are the tator an rotor reitance repectively; Ψ i tator flux an Ψ r i the rotor flux; ω an ω r are the ynchronou an rotating angular frequencie; L, L m an L r are the tator, magnetizing an rotor inuctance repectively; T e i the electrical torque an P in number of pole. The active an reactive power of tator an rotor are given by: P = V. i + V. i Q = V. i V. i (, r) (, r) (, r) (, r) q (, r) q (, r) (, r) q (, r) (, r) (, r) q (4) To achieve a tator active an reactive power vector control, the machine i controlle uing a irect vector control orientate along the tator flux vector. By etting the flux of tator vector aligne with - axi, an neglecting the tator reitance we have: ψ = ψ ; ψ = 0 q V = 0; V = V = ωψ q ψ = ψ = L I + L I ; ψ = L I + L I m r r r r m ψ = 0 = L I + L I ; ψ = L I + L I q q m rq rq rq m q (5) Form equation (4) an (5) the tator active an reactive power an rotor voltage accoring to the rotor current can be written a: 3 L m P = ) V i V i V i q q rq 2 + = L 0 3 U ψ U L Q = u i u i = i m q q r 2 L L 0 (6) 2 2 L i L V = R i + L m r ω L m i r r r r L t r L rq (7) 2 i 2 L L L V m rq V = R i + L + ω L m i + ω m qr r rq r L t r L r ω L where i lip. The control methoology i bae on igma-elta moulation that applie on IMC. Control chematic of a DFIG i hown in Fig

3 coθa ac = (9) coθc coθb bc = (10) coθc By the ame way correponing uty ratio an witche tate for all circuit conition can be foun. Table 1 how uty ratio while π/6 <θ a < 5π/6. Rectifier' witche tate have to etermine uing thee uty ratio. In the output converter the tate of witche mut control accoring to reference ignal (eire voltage on rotor terminal on DFIG). Fig. 3 Schematic of control ection III. Moelling of the Matrix Converter In Fig. 2 the propoe IMC ha been hown. A it i een the inirect type of IMC i utilize. The baic iea of the inirect moulation technique i to ecouple the control of the gri ie an rotor ie converter. Thi way the IMC can be regare a a back-to-back rectifier-inverter pair without any clink energy torage. The gri ie converter provie the poitive DC voltage by witching the input line voltage, an the output converter generate require voltage acro the rotor circuit. The metho of calculation of witching pattern of rectifier ie i explaine in [9]. Rectifier ie witching equence i ecie referring to input voltage an eire power factor. To maintain unity input power factor, the uty cycle for the witche of input converter are calculating a [9]: 1. if the voltage of phae A i poitive an ha greater abolute value, an phae B an C in then negative: Uner thi conition, witch S ap mut be maintaine in the conucting tate while S bn an S cn are moulate. The uty ratio of S bn an S cn i given by: ba ca coθb = (7) coθ a coθc = (8) coθ a Where θ i phae voltage angel. 2. if the voltage of phae C i negative an ha greater abolute value, an phae A an B in then poitive: Uner thi conition, witch S cn mut be maintaine in the conucting tate, an S ap an S bp are moulate. The uty ratio of S bn an S cn i calculate by: IV. Sigma-Delta moulator In thi ection, we view witching power converter a an analog to igital (A/D) converter in which the analog input are uty cycle of each witch in rectifier ie an reference ignal to be yntheize in inverter ie, an the quantize igital output i the tate of the circuit witche. A/D converion i an inherently non-linear operation an introuce error to the converion [10]. In both communication an power electronic application, the aim i to eign the ytem o that the input ignal i pae through the ytem with minimum noie itortion. Overample technique i one of quantization error reuction metho. Recently overample moulator have receive a many attention for highreolution ata converion application uch a highquality igital auio intrumentation an meaurement an enor application [11]. A icu later thi moulator o not reuce the magnitue of the quantization noie, but intea hape the power enity pectrum of thi error moving the energy towar high frequencie an reuce quantization noie within the ignal ban (Fig.4). Increae noie in the high frequency ban can eaily remove by uing imple low pa filter becaue noie frequency an funamental frequency are eparate. The well-known tructure of thi technique i ΣΔ moulator. ΣΔ moulator achieve the performance of high reolution quantizer by uing low reolution quantizer in a fee back loop with linear filtering. Table 1 Switching pattern of rectifier 452

4 Fig. 4 The Sigma Delta moulator noie haping characteritic (firt-orer) Since witching frequencie of both converter are much higher than the input/output funamental frequencie, to generate witching pule of the high frequency moulate converter, ΣΔ moulation can be ue. Fig. 2 how propoe inirect IMC that it both ie are controlle by ΣΔ moulator. V. Simulation Reult an Dicuion The propoe IMC i utilize in a gri connecte DFIG bae WECS. The parameter value for ytem are inicate in Table 2. In the imulation, DFIG enter to torque control moe in econ 0.6. The reult are obtaine with etting reference of reactive power equal to zero, an by uing contant λ (tip pee ratio) MPPT (Maximum Power Point Tracking) metho [13] to active power control. The active power varie accoring to the win pee. For >0, rotor of DFIG aborb active power. For =0, the rotor active power i mall correponing to the converter an rotor loe. For <0, rotor of DFIG inject active power to gri. In thi paper, in reaon of exceive number of figure, jut figure of operation in over ynchronou conition are hown. The win pee i 12m/ that caue generator work in over ynchronou conition. Generator pee an mechanical an electrical torque in pu are hown in Fig. 5. Rotor, tator an generate active power epicte in Fig. 6. Fig. 7 how the rotor voltage an current waveform. It ha to be note the frequency of thee voltage an current vary accoring to the haft pee. Gri voltage an current i epicte in Fig. 8 alo. Fig. 5 Electrical an mechanical torque, an generator pee in pu of ΣΔ controlle IMC equippe DFIG Fig. 6 Rotor, tator an generate power of ΣΔ controlle IMC equippe DFIG, repectively from above Fig. 7 Rotor voltage an current of ΣΔ controlle IMC equippe DFIG Table 2 Simulate ytem' parameter value Parameter: Gri voltage: Bae VA Synchronou pee: L m : L l : L lr : R : R r : f Value: 13.8kV L-L(RMS) 5MVA 2π60(ra/ec) 4.36pu 0.102pu 0.11pu pu 0.006pu 20kHz Fig. 8 Gri voltage an current of ΣΔ controlle IMC equippe DFIG 453

5 A ytem with ame parameter an conition with PWM moulate IMC i imulate alo, to provie comparion fortunate. Thi ytem imulation reult are hown Fig. 9 to Fig.12. Juging from thee reult, it i clear that DFIG bae WECS, the one which profiting ΣΔ moulate IMC ha better performance. It pee an torque i more regulate, prouce lightly greater average power; in thi tuy cae propoe ytem generate 35kW more power compare to other imulate ytem. Furthermore meauring gri current THD in both ytem how it reuce from 1.99% in conventional ytem to 1.54%, therefore propoe ytem ha better power quality compare to ytem which ue PWM moulation (Fig.8 an Fig.12). Fig. 9 Electrical an mechanical torque, an generator pee in pu of PWM controlle IMC equippe DFIG Fig. 10 Rotor, tator an generate power of PWM controlle IMC equippe DFIG, repectively from above Fig. 11 Rotor voltage an current of PWM controlle IMC equippe DFIG Fig. 12 Gri voltage an current of PWM controlle IMC equippe DFIG VI. Concluion Matrix converter ha many avantage i.e. increaing reliability an ytem average lifetime, all ue to elimination of bulky capacitor of c-link in comparion in conventional back-to-back converter. Inuction machine, which are robut an inexpenive are alo uitable for win energy generation, therefore the propoe WECS in thi work combine both technology. Furthermore, ΣΔ moulation ha been ue to etermine matrix converter witching equence. By uing thi moulation metho THD of input current an output voltage reuce compare to PWM moulate MC. Reucing THD of output voltage of IMC ha uneniable ameliorating effect on torque an pee regulation that caue acoutic noie reuction an mechanical part like gearbox lifetime increaing, an reuction of input It ha to be note propoe ytem generate lightly more active power. It preictable MC ue to it avantage ubtitute the conventional rectifier-inverter pair epecially in win energy application. Uing ΣΔ moulation in their contruction will a more feature to them. Reference [1] BTM Conult internet homepage, Available: March [2] T. Ackermann, Win Power in Power Sytem, John Wiley & Son, [3] F. Blaabjerg an Z. Chen, Power Electronic for MoernWin Turbine, A Publication in the Morgan & Claypool Publiher, Printe in USA, [4] A. Aleina, M. Venturini, Analyi an Deign of Optimum-Amplitue Nine-SwitchDirect AC- AC Converter, IEEE Tran. on Power Electronic, Vol. 4, no. 1, pp , January [5] P. Nielen, The matrix converter for an inuction motor rive, Ph.D. iertation, Int. Energy Technology., Aalborg Univ., Aalborg Eat, Denmark,

6 [6] J. P. W. Wheeler an D. A. Grant, A low lo matrix converter for AC variable-pee rive, in Proc. EPE Conf., vol. 5, 1993, pp [7] F. Poitier, M. Machmoum, R. Le Doeuff, M. E. Zaim, Control of a Doubly-Fe Inuction Generator for Win Energy Converion Sytem, GE44-LARGE, Saint Nazaire, France. [8] D. Aouzellage, K. Gheami, E. M. Berkouk, Network Power Flow Control of Variable Spee Win Turbine, in Proc. POWERENG, April [9] L. Wei, T.A. Lipo, A novel matrix converter topology with imple commutation, Rec. in Conf. Thirty-Sixth IAS 2001, Inutry Application IEEE Conf Annual Meeting, vol. 3, Sept. 2001, pp [10] R. M. Gray Quantization Noie Spectra, IEEE Tran. Inform. Theory vol , pp [11] R. Schreier, J.C. Teme, Unertaning Delta- Sigma Data Converter, Hobokn, New Jery, John Wilely & Son Pre, [12] L. Breem, J.H. Huijing Continuou-Time Sigma Delta Moulation for A/D Converion in Raio Receiver, the Springer International Serie in Engineering an Computer Science, Vol. 634, [13] M. Ermi, H. B. Ertan, E. Akpinar, F. Ulgut, Autonomou Win Energy Converion ytem with a Simple Controller for Matximum-Power Tranfer, IEEE Proc, Vol. 139, Sept. 1992, pp