26 k. subramanian

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26 k. subramanian

  1. 1. Implementation Of Vernier Mode Operation Using STATCOM For Terminal Voltage Regulation Of a 3-Ø Stand-Alone Self-excited Induction Generator by K. Subramanian, S. P. Sabberwal, M. Arunachalam and D. P. Kothari Over View: of the Presentation Abstract Key words 1. Introduction 2. System Configuration 3. Equivalent Circuit Analysis 4. Modeling of the Proposed System 5. Experimental Work 6. Results and Discussion 7. Conclusion References 12/10/2013 8:15 AM Power Electronics and Drives Division ,VIT University,Vellore,TamilNadu, India 632 014 1
  2. 2. Abstract  This paper describes regulated voltage operation of a 3-Ø self-excited induction generator (SEIG) supplies power to an isolated power system comprises of R and R-L loads.  A wind turbine drives the rotor of SEIG generating voltage with variable magnitude and frequency. Therefore, the problem is to control both voltage and frequency.  For frequency control, an active power balancing technique is applied. A 3-Ø thyristor/triac switched reactor (TSR) with STATCOM is employed to regulate the terminal voltage of SEIG.  Instantaneous reactive power theory based control logic developed and implemented to control the power drawn by the additional load (dump load).   Mathematical model of the proposed system derived using steady state equivalent circuit followed by MATLAB/SIMULINK based simulation is executed. To validate the proposed system, a laboratory model of an isolated wind energy conversion scheme (WECS) is rigged up using conventional induction motor of 3Hp,3-Ø, 415V, 4.9A, and 1440 rpm coupled with a 220V, 20A separately excited d.c motor drive. A 3-Ø, 415 V capacitor bank of 100μF (in each phase) is connected across the stator terminals of the machine for its self-excitation. The results show a good agreement between the simulation and experiment. 12/10/2013 8:15 AM Power Electronics and Drives Division ,VIT University,Vellore,TamilNadu, India 632 014 2
  3. 3. 1. Introduction The power generated mainly through the induction machines has a poor voltage regulation in particular isolated mode [5]-[6]. Different controller is used to control the voltage and frequency of SEIG is presented in detail [7]. Tarek Ahmed et al [8] present terminal voltage regulation of SEIG under different load conditions functioning in three distinct steps with static VAr compensator. However, there is a need for economic operation on a continuous basis. Bhim Singh et al [9] presented a stand-alone generating system using self-excited induction generators in the extraction of petroleum products; costly STATCOM is used for voltage regulation of the generator in full-scale range. The aim of this work is to implement a three-phase Voltage Source converter (VSC) based static reactive volt-ampere (VAr) compensator (STATCOM) employed to act as a Vernier between two steps is presented. Attempt is made to study the performance of SEIG for continuous load variation. The advantages of the proposed scheme are:  Rating and cost of STATCOM is low because it operates in Vernier control mode  If an active energy storage system like battery is connected on d.c side of STATCOM, it is called VSI-STATCOM; it aids to regulate the system voltage by supplying active power partially during low wind velocity. The VSC-STATCOM operating in Vernier mode such that it mitigates the excess VAr generated by the full load capacitance along with switched inductor. As soon as the load reactance varies, the generator operation shifts from resonant condition. In order to maintain resonance, the effective reactance of the load, magnetising reactance and switched reactance has to be altered. A simple control circuit is designed and implemented. 12/10/2013 8:15 AM Power Electronics and Drives Division ,VIT University,Vellore,TamilNadu, India 632 014 3
  4. 4. 2. System Configuration Single line diagram of proposed system is shown in Fig.5.1. It comprises of thyristor/triac switched inductor, VSC-STATCOM and selfexcited induction generator. It supplies power to a three-phase R-L load. The full load excitation capacitor CFC is split into two; one is used to excite the generator at no-load (Cno-load) the other (Cadd.) will supply the leading VAr to mitigate the load lagging VAr. The switched inductor LSR and Cadd are connected in parallel with load. This combination resonates with the system frequency at all load conditions and VSC-STATCOM will operate in Vernier control of SEIG for terminal voltage regulation. Fig.1 Single line diagram of SEIG supplying power to R-L load with switched reactor 12/10/2013 8:15 AM Power Electronics and Drives Division ,VIT University,Vellore,TamilNadu, India 632 014 4
  5. 5. 3. Equivalent circuit Analysis Xceqt Xc X VSC F F F Is [10] &[11] (1) Zs (2) Where, ZS Z1 ZC Zc R eqt Z1 RS Zc R eqt j F XL : XCeqt F Z 2 Zm ; Zm Z2 Z2 Zm Rr jFX L F (3) j FXm P X m , F (A1X m A 2 )F 3 (A 3 X m A 4 )F 2 (A 5 X m A 6 )F A 7 X m A 8 0 Q X m , F (B1X m B 2 )F 2 (B 3 X m B 4 )F B 5 0 Is E g Z c R eqt Z1 Z c R eqt 12/10/2013 8:15 AM Z c R eqt ; Ir IS Z m Z2 Zm ;I L Fig. 2 Single-phase steady state equivalent circuit of SEIG with VSC (4) (5) IS Zc R eqt Zc ; Vt I L R eqt ; Pin 3 I2 R r r F and Pout Vt I L (6) Power Electronics and Drives Division ,VIT University,Vellore,TamilNadu, India 632 014 5
  6. 6. 4. Modeling of the system PT 0.5C p AV 3 ; TT PT / TR V ;C p 116/ 1 0.4 5e 165/ 1 ; 1 1/ 0.089 0.035/ 2 1 (7) (8) T Fig. 3 Simulated wind turbine characteristics 12/10/2013 8:15 AM Power Electronics and Drives Division ,VIT University,Vellore,TamilNadu, India 632 014 6
  7. 7. Modeling of the system cont… R s i qs L ls R r i qr L lr R r i dr L lr Z where V Vcq I dt di qs dt di dr dt di qs Lm Lm 1 di qs dt C dt di qs dt 1 di qr Lm 1 di ds dt C dt di dr 1 di dr dt (9) (10) r dr C dt di dr Lm Vcq C dt Vcd (11) (12) r qr Fig. 4 D-Q Equivalent circuit of SEIG with load V Vcd R s pLls Z dt di qr R s i ds L ls C di qs (13) kq 1 pC 0 pLm r Lm k d 1; I i qs 0 R s pLls r Lm pLm i ds iqr idr 1 ; C pLm 1 pC pLm R r pLr r Lr r Lr R r pLr (14) i qs i qr 2 im Eg 0 0 0 0 0 0 1 (15) i ds i dr 2 (16) Lm im Lm f im (17) (18) Te 3 2 P 2 L m i dr i qs i qr i ds and Tshaft T e J 2 P p r p r P 2J Te Tshaft 12/10/2013 8:15 AM Power Electronics and Drives Division ,VIT University,Vellore,TamilNadu, India 632 014 (19) (20) 7
  8. 8. Modeling of the system cont… 4.3 STATCOM model [9] pVdc i ca SA i cbSB i ccSC C dc e a V dc SA SB e b Vdc SB SC e c V dc SC SA v a r i ca L p i ca ea r i cb L p i cb v b r i cb L p i cb e b r i cc L p i cc i ca i cb i cc 0 v b r i cb pL i cb eb r i ca pL i ca r i cc pL i cc pLi ca pLi cb v a e ab ri ca ri ca pLi ca 2pLi cb v b e bc ri ca 2ri ca pi ca pi cb pi cc v b e bc r 2 v a e ab 3rf i ca 3L f ; v b e bc r 2 v a e ab 3rf i ca 3L f & v b e bc r 2 v a e ab 3rf i ca 3L f 12/10/2013 8:15 AM (24) (25) (26) (27) (28) Fig. 5 VSC based STATCOM (29) Power Electronics and Drives Division ,VIT University,Vellore,TamilNadu, India 632 014 8
  9. 9. STATCOM Control 4.4.3 Total Source Current Vt 2 3 Va 2 Vb 2 Vc 2 (30) u a Va Vt u b Vb Vt u c Vc Vt Wa ua I *sa I *saq I *sad I *sb I *sbq I *sbd I *sc I *scq I *scd (31) 3 uc Wb 3u a 2 Wa 3u a 2 3 ub uc ub 4.4.4 PWM Current Controller 2 3 (32) I saerr I *sa I sa I sberr I *sbr I sb I scerr I *sc I sc uc 2 3 4.4.1 Quadrature Component of Reference Source Current Verr Vtref (39) Vtmea I *smqnew I *smsqold K p Verrnew Verrold (40) 4.4.5 Voltage Magnitude at Point of Common Coupling (PCC) (33) K i Verrnew (34) I *saq I *saqnew Wa ; I *sbq I *sbqnew Wb and ; I *scq I *scqnew Wc (35) pVa i a i lb i sta pVb i a i lc i sta Va Vb Vc 0 i b i lb i sta 3C i b i lc i sta 3C (41) 4.4.2 in Phase Component of Reference Source Current Vdcerr Vdcref Vdcmea I *smdnew I *smsdold K p Vdcerrrnew Vdcerrold (36) K i Vdcerrnew (37) I *sad I *smdnew u a ; I *sbd I *smdnew u b and ; I *scd I *smdnew u c 12/10/2013 8:15 AM (38) Power Electronics and Drives Division ,VIT University,Vellore,TamilNadu, India 632 014 9
  10. 10. 5. Experimental work The induction motor draws inductive current if the load on the generator increases. In order to compensate the lagging VAr required by the induction machine and change in magnetizing reactance, the synchronous motor is excited in an overexcited mode i.e, excitation is greater than the normal excitation thereby yielding the required leading VAr. The corresponding terminal voltage at PCC is measured and noted, Table-1, without and with TSR, VSC-STATCOM. The corresponding characteristics are shown in Fig.7. Fig.6 Photograph of SEIG with rotating STATCOM and load connection 12/10/2013 8:15 AM Power Electronics and Drives Division ,VIT University,Vellore,TamilNadu, India 632 014 10
  11. 11. 6. RESULT AND DISCUSSION using the above cited model of the proposed SEIG-STATCOM is wired using built in libraries of power system toolbox in MATLAB/SIMULINK software version 9.0 and simulated for 10seconds. The simulated results of SEIG are show in Figs.7 (a) and (b) with lagging power factor loads. The loads are divided into ¼, ½, ¾ and full load. It is switched on at 2, 4, 6 and 6 seconds. The STATCOM compensated the SEIG terminal voltage drop (Vdrop) in each step. The experimental and simulated load characteristics of SEIG with and without controller are show in Figs.8 (a) and (b) respectively Fig. 7 Terminal voltage variation of SEIG with time (a) without controller (b) with controller 12/10/2013 8:15 AM Power Electronics and Drives Division ,VIT University,Vellore,TamilNadu, India 632 014 11
  12. 12. Results and Discussion cont… Table 1 Load characteristics (experimental) of SEIG Terminal voltage (volts) with FC =100μF Without With VSC-TATCOM VSC-TATCOM Sl. No. Load Power (Watts) 1 00 240 240 2 300 180 240 3 500 165 239 4 600 136 238 5 700 40 237 The corresponding terminal voltage at PCC is measured and noted, Table-1, without and with TSR, VSC-STATCOM. The corresponding characteristics are shown in Fig.7. 12/10/2013 8:15 AM Power Electronics and Drives Division ,VIT University,Vellore,TamilNadu, India 632 014 12
  13. 13. 7. CONCLUSION Fig. 8 Load characteristics of SEIG with full load excitation capacitor  From Figures 7 and 8, it is observed that load terminal voltage of the self-excited induction generator is drooping with load.  This fact brings out essentiality of external control mechanism for maintaining the load terminal voltage with varying load. The terminal voltage is thus regulated, 8(b). 12/10/2013 8:15 AM Power Electronics and Drives Division ,VIT University,Vellore,TamilNadu, India 632 014 13
  14. 14. REFERENCES [1] [2] [3] [4] [5] [6] [7] [8] Basset E. D and Potter F. M.(1935), “Capacitive Excitation For Induction Generators,” AIEE E committee of Electrical Engineering, pp.535-545. G. Raina and O. P. Malik (1983), “Wind Energy Conversion Using a Self-Excited Induction Generator,” IEEE Trans. Power App. Syst., Vol. PAS- 102,no.12, pp. 3933-3936. R. C. Bansal, T. S. Bhatti and D. P. Kothari (2003), “Bibliography on the application of Induction Generators in non-conventional energy system”, IEEE Trans. on Energy Conversion, Vol. 18, No.3, pp. 433-439. R. C. Bansal (2005), “Three-Phase Self-Excited Induction Generators: Over View,” IEEE Trans. on Energy Conversion, vol. 20, No.2, pp.292–299. N. P. A. Smith (1996), “Induction Generators For Stand Alone Micro-Hydro Systems,” IEEE proceeding of International conference on Power Electronics drives and Energy System For Industrial Growth, pp 669 - 673. S. S. Murthy, B. P. Singh, C. Nagamani and K. V. V. Satynarayana (1988), “Studies of the Conventional Induction Motor as SEIGs”, IEEE Trans. On Energy Conversion, Vol.3, No.4, pp 842 - 848. Yogesh K., Chauhan, Sanjay K. Jain, and Bhim Singh (2010), “A prospective on voltage regu lation of self-excited induction generators for industry applications, IEEE Tran. On Industry Applications, Vol. 46, No.2, pp 720-730. T. Ahmed, O. Noro, E. Hiraki and M. Nakaoka (2004). “Terminal voltage regulation character istics by Static VAr compensator for a 3-Ø SEIG”, IEEE Trans. On Industry Appl., Vol.40, No.4, pp.978 - 988. 12/10/2013 8:15 AM Power Electronics and Drives Division ,VIT University,Vellore,TamilNadu, India 632 014 14
  15. 15. Ref. cont… [9] B. Singh, S. S. Murthy and S. Gupta (2010). “A stand-alone generating system using SEIG s in the extraction of petroleum products”, IEEE Trans. On Industry applications,Vol.46, No .1, pp. 94 - 101 [10] Luiz A.C. Lopres and Rogerio G. Almedia (2006). “Wind-driven self-excited induction generat or and frequency regulated by a reduced rating VSI”, IEEE Trans. On Energy Conversion, Vol.21, No. 2, pp. 297-304. [11] [12] [13] [14] [15] 12/10/2013 8:15 AM Murthy, S.S., B. Singh, S. Gupta and B. M. Gulati (2003). “General steady state analysis of three phase self-excited induction generator feeding three-phase un balanced load / single phase load for stand-alone applications”, Proc., IEE, Gen.Trans. Dist, Vol.150, No.1, pp. 49-55. Murthy, S. S., O. P. Malik and A.K. Tandon (1982). “Analysis of self-excited induction generators”, Proc., IEE, Gen. Trans. Dist., Vol. 123, No. 6, pp. 260-265. D. M. Egglestonnad F.S. Stoddard, “Wind Turbine Engineering Design”, New York:Van Nostrand Reinhold Co. 1987 Andrew miller, Ed. Muljadi, Donald S. Zinger (1997),“A variable speed wind turbine power control”, IEEE Trans. On Energy Conversion, Vol. 12,No. 2, pp. 181-186. Mat lab/Simulink Software Version.9.0 Power Electronics and Drives Division ,VIT University,Vellore,TamilNadu, India 632 014 15
  16. 16. THANK YOU 12/10/2013 8:15 AM Power Electronics and Drives Division ,VIT University,Vellore,TamilNadu, India 632 014 16

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