Enhancement of Transient Performance of a Single Machine Infinite Bus System Using Thyristor Controlled Braking Resistor

Transcription

1 6th NATONAL OWR SYSTMS CONFRNC, 5th-7th DCMBR, 766 nhancement of Transient erformance of a Sine Machine nfinite Bus System Usin Thyristor Controe Brakin Resistor B.Yaairi Department of ectrica nineerin University Coee of nineerin Osmania University, Hyeraba-7 e-mai:iri357@mai.com A.V.R.S.Sarma Department of ectrica nineerin University Coee of nineerin Osmania University, Hyeraba-7 e-mai:avrs@yahoo.com Abstract Transient Stabiity stuies of a power systems are necessary for the pannin an reiabe operation. Severa techniues ike hvc, fact controer s etc. are use to enhance the transient performance of the system. n a these techniues the eectrica enerator output is improve urin an post isturbance conition. n this paper Thyristor Controe Brakin Resistor (TCBR is use to enhance the transient performance of Sine Machine connecte to nfinite Bus (SMB. The effect of TCBR is stuie over ifferent ine reactances an operatin conitions. The system is simuate usin MATLAB an resuts are presente. Resuts ceary inicate the effect of TCBR in improvin the transient performance of SMB uner a conitions. of TCBR is teste uner various ine parameters an operation conitions.. MODL FOR TH SNGL MACHN CONNCTD TO NFNT BUS (SMB. Moe for sine machine connecte to infinite bus without TCBR Keywors-TCBR, SMB. NTRODUCTON System stabiity stuies are important for reiabe operation. Growths in interconnection, use of new techniues an contro strateies have increase the importance of transient stabiity. The system operates in a continuousy chanin environment i.e oa variation. The system stabiity epens upon initia operatin conitions, type of isturbance an ocation isturbance. A major isturbance wi ca upon interaction of various controers in the system to eveop forces to remain in synchronism. naeuacy in system pannin an ineffective controers action wi resut in the system backout. Hence propery esine power system, an effective controers wi operate the system in synchronism, which is otherwise threatene. A are isturbance may ea to structura chanes ue to the isoation of the faute eements. At an euiibrium set, a power system may be stabe for a iven (are physica isturbance, an unstabe for another. t is impractica an uneconomica to esin power systems to be stabe for every possibe isturbance []. n this paper TCBR is use to enhance the transient performance of the system foowin a suen an are isturbance. The rotor spee eviation is use in firin the thyristor of the TCBR in orer to obtain reuire brakin resistor for stabiity, thus contro action is continuous ti the enerator spee euas to synchronous spee. The performance Fi.. Fi.. SMB ower system moe without TCBR.A Steay state phasor iaram for ower-orer synchronous enerator Department of ectrica nineerin, Univ. Coee of n., Osmania University, Hyeraba, A., NDA.

2 6th NATONAL OWR SYSTMS CONFRNC, 5th-7th DCMBR, 767. Steay State uations Aebraicay the machine currents an bus votaes are reate by: Rotor ane at enerator termina i δ sin b * Loa current an power factor ane are + b * X i θ cos b * -axis votae is * b * cos ( δ ( X + X + * * *( X X *sin( θ b + * * b + nitia rotor ane cos( θ * ( + X δ o sin -axis component of oa current is * cos( δ o + θ -axis component of oa current is * sin( δ o + θ -axis component of infinite bus votae is b b *cos( δ o -axis component of infinite bus votae is b b *sin( δ o -axis component of enerator termina votae is b + -axis component of enerator termina votae is b nterna votae of enerator is o + Votae proportiona to the fie eakaes is b + * ( X + X Manitue of enerator termina votae an ane are + δ tan Reference votae is o ref + K r.3 Moe for Synchronous Generator The thir orer synchronous machine moe is consiere in this stuy. Swin euation ω o t M δ ωo ω t i * ( Fie ecrement uation ( X X f * Δ * Δt T o AVR uation K r * Δt f Δ f Δt T * r Durin Short circuit -axis component of oa current is X The enerator eectrica power output is o ost faut uations -axis component of oa current is b * cosδ ( + X -axis component of oa current is b * sinδ ( + X -axis component of enerator termina votae is b * sin δ * -axis component of enerator termina votae is -axis component of infinite bus votae is b b * cosδ -axis component of infinite bus votae is b b *sinδ The enerator eectrica power output o * + * Δ t ref Department of ectrica nineerin, Univ. Coee of n., Osmania University, Hyeraba, A., NDA.

3 6th NATONAL OWR SYSTMS CONFRNC, 5th-7th DCMBR, AVR Moe Fi. 3. AVR moein The bock after summer represents the transfer function of a votae reuator. The reuator has time constant T A. an a ain K A 5. The inear proportionaity an the ceiin votaes V Rmax 3. an V Rmin -3. are aso shown in above bock iaram.. MODLNG OF TCBR The power system moe aon with thyristor switchin circuit use for the simuation is shown in fi.4. t consists of a enerator suppyin power to an infinite bus over a oubecircuit ine. The initia operatin conitions an enerator parameters use for the simuation are shown in Tabes an respectivey. t has been consiere that a three-phase faut occurs at sec at enerator bus bar as shown in fi.4. n the next step, a controer is empoye aon with the TCBR. The bock iaram of the contro scheme use is shown in Fi 5. TABL. NTAL CONDTONS Mechanica power input, i (pu.5 Generator termina votae, (pu.5 nfinite bus bar votae, b (pu hase anes of enerator termina votae, δ (e nitia rotor anes, δo (e. Time interva, Δt (sec. Line reactance, X L (pu. TABL. GNRATOR ARAMTRS nertia constant, H (sec 4 -axis synchronous reactance, X (pu. -axis synchronous reactance, X (pu.7 Generator transient reactance, X (pu. - axis open circuit transient fie time const, To (sec 5 Reuator ain constant, K r 5 Reuator time constant, T r (sec. ntera controer ain, K i 5 roportiona controer ain, K p Conuctance of brakin resistor, GTCBR (pu System freuency (Hz Fi. 4. SMB ower system moe Fi.5(a shows the propose circuit of two reverse paraeconnecte thyristors, T an T aon with the brakin resistor. Foowin a faut, current fows throuh BR if thyristor T or T is in ON state, an it ecreases the acceerate power by consumin excessive transient enery. n this way, urin are isturbances, the brakin resistor can contro the spee eviation an acceeratin power in enerators, an thereby makes the power system stabe by brinin spee eviation an acceeratin power near the euiibrium point. The typica waveforms of votae an current throuh BR are shown in Fi.5 (b. Therefore, when the firin ane for the thyristor switch is α as shown in Fi.5 (b, averae power, TCBR, consume by the brakin resistor is iven by: TCBR Vi V G R TCBR ( ωt ( α +.5sin α Firin-ane (α for the thyristor switch is cacuate from the output of the controer (i.e., Gout. The esire power consumption etermine by Gout an the rea power consumption etermine by G TCBR are eua an hence firinane, α, can be cacuate from the foowin power euation. V TCBR out GTCBR ( α +.5sin α V Where V is the rms vaue of the enerator termina bus votae an G TCBR is specifie to. pu. G out Department of ectrica nineerin, Univ. Coee of n., Osmania University, Hyeraba, A., NDA.

4 6th NATONAL OWR SYSTMS CONFRNC, 5th-7th DCMBR, 769 Therefore, it can be concue that the improvement in the transient stabiity conition of the system is much more with the TCBR-controer combination. These resuts hihiht the effectiveness of the appication of a TCBR aon with a controer in improvin the transient stabiity of a power system. V. FLOW CHART AND RSULTS (a TCBR Fi. 5. (b Votae an current waveforms Thyristor switchin circuit for BR an waveforms. (a TCBR. (b Votae an current waveforms. The Contro Scheme As shown in fi.6 the enerator spee eviation,, an the esire conuctance vaue of BR, G out, are seecte as the input an output respectivey. Foowin a faut in power system, the rotor spee eviation,, of the enerator is measure, an then the esire conuctance vaue, G out, is etermine by controer. For the fast contro of the enerator isturbances, we have tune the controer parameters by tria an error metho. Fi. 6. controer moe The enerator rotor speeω is taken as the contro variabe. t is compare with the reference vaue of spee ωref an the error is fe to a controer. The output of the is the firin ane of the TCBR, α. This is passe throuh a imiter to keep it within the output of the imiter is suppie to the firin circuit of TCBR. The effect of the TCBR on the transient stabiity of the system epens arey on the proper functionin of the controer. Therefore, choice of suitabe vaues of controer constants K an K. Department of ectrica nineerin, Univ. Coee of n., Osmania University, Hyeraba, A., NDA.

5 X:.58 Y: 45 6th NATONAL OWR SYSTMS CONFRNC, 5th-7th DCMBR, 7 One-machine system swin curve. Faut ceare at.39s i.5,xl. Deta, eree, Fi. 9. Rotor ane response Case (: Without Brakin Resistor, Mechanica power input i.5, p.u ine reactance X L.4 p.u faut cearin time t c.8sec Here faut is at enerator terminas an faut cearin time is t c.8sec, with Brakin Resistor in the system such that rotor ane is increases to maximum, then ecreases an osciates with ecreasin ampitue an reaches steay state as shown in fiures. The rotor ane (δ Vs time (t, pot is shown. One-machine system swin curve. Faut ceare at.8s 9 Deta, eree, Fi. 7. Fow chart for sine machine connecte to infinite bus system Transient stabiity resuts for sine machine connecte to infinite bus system: Case (: Without Brakin Resistor, Mechanica power input i.5, p.u ine reactance X L., p.u faut cearin time t c.39sec Here faut is at enerator terminas an faut cearin time is t c.39sec, without Brakin Resistor in the system such that rotor ane increases continuousy unti synchronism is ost an the system becomes unstabe as shown in fiure 8. The rotor ane (δ, Vs time (t pot is shown Deta, eree, 9 One-machine system swin curve. Faut ceare at.9s Fi.. Rotor ane response without TCBR With Brakin Resistor, Mechanica power input i.5, p.u ine reactance X L.4, p.u faut cearin time t c.8sec: Here faut is at enerator terminas an faut cearin time is t c.8sec, with Brakin Resistor in the system such that rotor ane is increases to maximum, then ecreases an osciates with ecreasin ampitue an reaches steay state as shown in fiures. The rotor ane (δ Vs time (t, pot is shown. Deta, eree, One-machine system swin curve. Faut ceare at.8s X:.56 Y: 3.4 i.5,xl Fi. 8. Rotor ane response without TCBR With Brakin Resistor, Mechanica power input i.5, p.u ine reactance X L., p.u faut Cearin time t c.39sec: Here faut is at enerator terminas an faut cearin time is t c.39sec, with Brakin Resistor in the system such that rotor ane is increases to maximum, then ecreases an osciates with ecreasin ampitue an reaches steay state as shown in fiures 9. The rotor ane (δ Vs time (t, pot is shown Fi... Rotor ane response Case (3: Without Brakin Resistor, Mechanica power input i, p.u ine reactance X L., p.u faut cearin time t c.9sec Here faut is at enerator terminas an faut cearin time is t c.9sec, without Brakin Resistor in the system such that rotor ane increases continuousy unti synchronism is ost an the system becomes unstabe as shown in fiure.. The rotor ane (δ, Vs time (t pot is shown. Department of ectrica nineerin, Univ. Coee of n., Osmania University, Hyeraba, A., NDA.

6 X:.38 Y: 8.9 6th NATONAL OWR SYSTMS CONFRNC, 5th-7th DCMBR, 77 One-machine system swin curve. Faut ceare at.9s with ecreasin ampitue an reaches steay state as shown in fiures.5. The rotor ane (δ Vs time (t, pot is shown. Deta, eree, One-machine system swin curve. Faut ceare at.5s i,xl.4 X:.56 Y: Deta, eree, Fi... Rotor ane response without TCBR With Brakin Resistor, Mechanica power input i, p.u ine reactance X L., p.u faut cearin time t c.9sec: Here faut is at enerator terminas an faut cearin time is t c.39sec, with Brakin Resistor in the system such that rotor ane is increases to maximum, then ecreases an osciates with ecreasin ampitue an reaches steay state as shown in fiures.3 The rotor ane (δ Vs time (t, pot is shown. Deta, eree, One-machine system swin curve. Faut ceare at.9s i,xl Fi. 3. Rotor ane response Case (4: Without Brakin Resistor, Mechanica power input i, p.u ine reactance X L.4, p.u faut cearin time t c.5sec Here faut is at enerator terminas an faut cearin time is tc.5sec, with Brakin Resistor in the system such that rotor ane is increases to maximum, then ecreases an osciates with ecreasin ampitue an reaches steay state as shown in fiures.4 The rotor ane (δ Vs time (t, pot is shown. Deta, eree, One-machine system swin curve. Faut ceare at.5s Fi. 4. Rotor ane response without TCBR With Brakin Resistor, Mechanica power input i, p.u ine reactance X L.4, p.u faut cearin time t c.5sec: Here faut is at enerator terminas an faut cearin time is t c.5sec, with Brakin Resistor in the system such that rotor ane is increases to maximum, then ecreases an osciates Fi. 5.. Rotor ane response By observin the above four cases, we can say that by proviin brakin resistor to the system the osciations wi ie out an they wi sette to a fina steay state vaue with in a very short time uration. V. CONCLUSONS n this paper, the transient stabiity assessment of a sine machine connecte to infinite bus system is carrie out for three phase faut at enerator terminas usin R.K. fourth orer metho. A TCBR controer has been moee an impemente on a sine machine connecte to infinite bus system controer etermines the firin ane, α, which is input to the Thyristor Controe Brakin Resistor (TCBR which contros the acceeratin power in enerator an makes the system transienty stabe. Without TCBR the rotor ane increases continuousy unti synchronism is ost an system becomes unstabe as shown in the fiures 8,,,4. Usin the TCBR the rotor ane increases to a maximum, then ecreases an osciates with ecreasin ampitue an reaches steay state as shown in the fiures 9,,3,5. RFRRNCS [] rabha Kunur, John aserba, Definition an Cassification of ower System Stabiity, Trans. on ower Systems., Vo. 9, No., pp 387-, May 4. [] D..Kothari an.j Narath, Moern ower System Anaysis, 3r ition, Aut. 6. [3].W.Kimbark, ower System Stabiity, Vo.,Wiey,New York,4. [4] Masaki Yaami,Junji Tamura nhancement of Transient Stabiity Usin Faut Current Limiter an Thyristor Controe Brakin Resistor, proceeins, owertech 7, pp.38-43,7. [5] M.H.Ai, T.Murata, an J.Tamura, An anaysis of the fuzzy oic controe brakin resistor for transient stabiity improvement in mutimachine power system, J Trans.. vo.4, no.4, pp.553-5, 4. [6] H.Jian, J.Dorsey, an T.Habeter, A cost effective enerator brake for improve enerator transient response, Trans. ower Systems, vo.9, no.4, pp.8-846, 994. [7] A.H.M.A. Rahim an A..J. A-Sammak, Optima Switchin of Dynamic Brakin Resistor, Reactor or Capacitor for Transient Stabiity of ower Systems, roceeins, art C, Vo. 38, No., pp.89-93, January 99. Department of ectrica nineerin, Univ. Coee of n., Osmania University, Hyeraba, A., NDA.