nd WSEAS Int. Conf. on CICUITS, SYSTEMS, SIGNA and TEECOMMUNICATIONS (CISST'8)Aapulo, Mexio, January 5-7, 8 Analysis of Wound otor Self-Exited Indution Generators.S. Sandhu (Professor) & S.P.Jain (Professor) Eletrial Engineering Department National Institute Of Tehnology, urukshetra-369 Haryana, India kjssandhu@yahoo.om, kjssandhu@rediffmail.om Abstrat Self-exited indution generators are found to be to be most suitable mahines for wind energy onversion in remote and windy areas due to several advantages over grid onneted mahines. Suh mahine exhibits poor performane in terms of voltage and frequeny under frequent variations of operating speeds, whih is a ommon feature in wind energy onversion. In this paper an attempt has been made to propose a simple model for the ontrol of wound rotor self-exited indution generator. Simulated results as obtained have been ompared with results on a test mahine and found to be in lose agreement. ey-words Indution Generator, enewable Generation, Steady State Analysis (SSA), Self- Exited Indution Generator, Wind Energy Generation, NOMENCATUE a per unit frequeny b per unit speed stator reatane per phase rotor reatane per phase, referred to stator apaitive reatane due to C at rated frequeny C E E exitation apaitane per phase air gap voltage per phase at rated frequeny rotor emf per phase referred to stator E a air gap voltage per phase= ae f I rated frequeny stator urrent per phase I rotor urrent per phase, referred to stator I load urrent per phase I m magnetizing urrent per phase P out output power ext s V load resistane per phase stator resistane per phase rotor resistane per phase, referred to stator external rotor resistane per phase, referred to stator generator slip terminal voltage per phase m magnetizing reatane per phase at rated frequeny. Introdution Continuous redution of onventional soures of energy as well as growing power demand has diverted the attention of sientists towards the non-onventional soures of energy suh as wind energy, solar energy, tidal energy, geothermal energy and biogas. enewal energy is expeted to reate maximum impat in the prodution of eletriity. Projetions indiate that by the end of the first deade of the new entury, it would be ost effetive to generate and supply renewable eletriity. Besides grid supply augmentation, renewable eletri tehnologies offer possibilities of distributed generation at or near points of use, whih an redue peak loads and save on ostly up gradation and maintenane of transmission and distribution networks. Out of these wind energy is the fastest growing area of all renewable energy resoures and is attrative and viable. Man is utilizing wind power for the last 3 years. Earlier it was used to provide mehanial power to pump water or to grind grains. In early 97s with a sharp rise in oil pries, interest in wind power reemerged. However by the end of 99s, wind power beame as one of the sustainable energy resoure. No other renewable energy based eletriity produing tehnology has attained the same level of maturity as wind power. There are no major tehnial barriers to Page 64 ISBN: 978-96-6766-34-3
nd WSEAS Int. Conf. on CICUITS, SYSTEMS, SIGNA and TEECOMMUNICATIONS (CISST'8)Aapulo, Mexio, January 5-7, 8 large-sale penetration of wind power. It also offers an attrative investment option to the private setor for power generation. It is observed that winds arry enormous amount of energy and ould meet suffiient energy needs of the world. The regions in whih strong winds prevail for a suffiient time during the year may use wind energy profitable for different purposes. It has been found that ost of wind generation is omparable to that of hydro and thermal plants. There is a little doubt that while the ost of wind generation would be even lower in the oming years; the pries of fossil fuels used by thermal plants would definitely go up. In view of high apital onstrutional ost hydel power would be dearer too. In addition to this wind energy generation provides a lean and pollution free environment. It does not lead to global warming and ozone depletion. No hazardous waste is reated. Further a wind turbine generator may be a very worthwhile proposition for an isolated and remote area. Appliation of indution generators is well known to extrat the wind energy through turbines. Self-exited indution generators (SEIG) are found to be most suitable for many appliations inluding wind energy onversion systems. Suh generators may also be used in the remote areas in the absene of grid. SEIG has many advantages suh as brush less onstrution (squirrel-age rotor), redued size, absene of DC power supply for exitation as in onventional generators, redued maintenane ost, self short-iruit protetion apability and no synhronizing problem. Steady state equivalent iruit representation and mathematial modelling is requred to evaluate the steady-state performane of a SEIG feeding a speifi load. In order to estimate the performane of a SEIG, researhers have made use of the onventional equivalent iruit of an indution motor. Some of them [-6] used the impedane model, and a few [7-] used the admittane-based model for suh results. However it has been felt that the old onventional equivalent iruit model, in the absene of an ative soure, does not effetively orrespond to generator operation. Therefore [] suggested a new iruit model for the representation of indution generator. Further it is found that suh mahine exhibits poor performane in terms of voltage and frequeny under frequent variations of operating speeds, whih is a ommon feature in wind energy onversion. However suh variations in operating speeds may be ompensated by proper handling of rotor resistane & it is possible only in ase of wound rotor mahines. Therefore, in this paper an attempt has been made to propose a simple model for the steady state analysis and ontrol of wound rotor self-exited indution generator. Simulated results as obtained have been ompared with results on a test mahine and found to be in lose agreement. e /s I ja E a O ja I m ja m I -j /a Fig.. Per phase equivalent iruit representation for wound rotor self-exited indution generator. e = + ext Analysis of real omponents at node O gives; I real =I real O e s + s e a + After rearrangement it gives; = () e + e + = () Where, = = s( + ) = a = a s = + = a a = a + + I V. Steady State Equivalent Ciruit Model The steady-state operation of wound rotor self-exited generator may be analyzed by using an equivalent iruit representation as shown in Fig.. & b = a (+ s) (3) Page 65 ISBN: 978-96-6766-34-3
nd WSEAS Int. Conf. on CICUITS, SYSTEMS, SIGNA and TEECOMMUNICATIONS (CISST'8)Aapulo, Mexio, January 5-7, 8 Analysis of imaginary omponents at node O gives; I m +I imag +I imag = This gives; m = sa ( ) + (4) + a Equation (), (3) & (4) may be used to determine the rotor resistane to ahieve onstant voltage, onstant frequeny operation for a given operating speed, exitation apaitane and load resistane. m as obtained may be used to determine the value of air gap voltage using Appendix-. 3. esults & disussions Figure & Figure3 shows the omparison of simulated & results on indution mahine (Appendix-). Close agreement between the two, proves the validity of proposed modeling. E voltage/phase(volt) 3 5 5 5 4 6 8 load urrent/phase(amp) Fig. 3 Variation of voltage with load, exitation apaitane=.53 pu rpm 4rpm 5rpm 55 frequeny(hz) 45 35 rpm 4rpm 5rpm 5 4 6 8 load urrent/phase(amp) Fig. Variation of frequeny with load, exitation apaitane=.53 pu Table gives the estimated values of external resistane required in rotor iruit to ontrol the terminal voltage and frequeny for variable speed operation. This gives an opportunity to ontrol the terminal onditions (Voltage=.7pu & Freq.=.pu) under unregulated speed operations for indution generator. Page 66 ISBN: 978-96-6766-34-3
nd WSEAS Int. Conf. on CICUITS, SYSTEMS, SIGNA and TEECOMMUNICATIONS (CISST'8)Aapulo, Mexio, January 5-7, 8 Table Estimation of external rotor resistane to maintain terminal voltage and frequeny C=pu, =pu Speed (pu) ext (pu) Terminal frequeny (pu) Terminal Voltage (pu).4...7.3.7..7.3.3..7.4...7.49.6..7.58.3..7.67.39..7.75.45..7.84.5..7.93.58..7..6..7..7..7.9.77..7.8.83..7.37.9..7 Page 67 ISBN: 978-96-6766-34-3
nd WSEAS Int. Conf. on CICUITS, SYSTEMS, SIGNA and TEECOMMUNICATIONS (CISST'8)Aapulo, Mexio, January 5-7, 8 []. S. Sandhu, Iterative model for the analysis of self-exited indution generators, Eletri Power Components and Systems, vol. 3, no., 3, pp. 95-939. []. S. Sandhu and S.. Jain, Operational aspets of self-exited indution generator using a new model, Eletri Mahines and Power Systems, vol. 7, no.,999, pp. 69-8. 4. Conlusion In this paper an attempt has been made to propose a simple model for the steady state analysis of wound rotor selfexited indution generator. Closeness between simulated and omputed results proves the validity of proposed modelling. Further this modelling gives an opportunity to ontrol the terminal voltage and frequeny by proper handling of external resistane in the rotor iruit. Appendix- 3-phase, 4-pole, 5 Hz, wound rotor indution mahine 7 kw, Stator - 4/3 V, 4.7/5.4 A otor (Y)- V, 9.5 A Parameters =.5 ohm, =.96 ohm, = =.6 ohms Air gap voltage Pieewise segmentation of magnetization harateristis of mahine results in to, m < 5. E =77.53 -.4 m 83.8 > m 5. E =38.7 -.4 m 95. > m 83.8 E =349.44 -.67 m 6.> m 95. E =6.44. m m 6. E = Base values Base voltage=3 volt Base urrent=4.7 A Base impedane=5.7 ohm Base apaitane=.6 µf Base frequeny=5 Hz Base speed=5 rpm eferenes [] S. S. Murthy, O. P. Malik, and A..Tandon, Analysis of self-exited indution generators, Pro. IEE,vol. 9,pt. C, no. 6,98, pp. 6-65. [] G. aina and O. P. Malik, Wind energy onversion using a selfexited indution generator, IEEE Trans. Power Apparatus and Systems, vol. PAS-, no.,983,pp. 3933-3936. [3] A.. Tandon, S. S. Murthy and C. S. Jha, New method of omputing steady-state response of apaitor self-exited indution generator, IE(I) Journal-E, vol. 65,985, pp. 96-. [4] N. H. Malik and S. E. Haque, Steady-state analysis and performane of an isolated self-exited indution generator, IEEE Trans. Energy Conversion,vol.EC-,no.3, 986,pp.34-39. [5] N. H. Malik and A. H. Al-Bahrani, Influene of the terminal apaitor on the performane harateristis of a self-exited indution generator, Pro. IEE, vol.37,pt.c, no., 99, pp.68-73. [6] T. F. Chan, Steady-state analysis of self-exited indution generators, IEEE Trans. Energy Conversion, vol. 9, no.,994, pp.88-96. [7].Quazene and G. MPherson, Analysis of the isolated indution generator, IEEE Trans. Power Apparatus and Systems, vol. PAS-, no. 8, 983, pp. 793-798. [8] T. F. Chan, Analysis of self-exited indution generators using an iterative method, IEEE Trans. Energy Conversion, vol. no. 3,995,pp. 5-57. [9] I. A. M. Abdel-Halim, M. A. Al-Ahmar, and M. Z. El-Sherif, A novel approah for the analysis of self-exited indution generator, Eletri Mahines and Power Systems, vol. 7,999, pp. 879-888. Page 68 ISBN: 978-96-6766-34-3