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ScienceDirect Procedia Computer Science 70 (2015) 733 – 739

4thInternational Conference on Eco-friendly Computing and Communication Systems

Performance Evaluation and Improvement in Transient Instability of IEEE 9 bus System using exciter and governor control Divya Asijaa, Pallavi Choudekarb*, Ruchirac†, Malvika Chouhand a,b,c,d

Amity University Uttar Pradesh

Abstract In the contemporary world, especially developing countries, the demand for electricity is proliferating continuously and power is not only a criterion for fulfilling the requirement, but it is also the responsibility of engineers to provide the reliable and stable power to the consumers in a satisfactory manner. This paper discusses about the designing and improvement in “Transient Stability of IEEE 9 Bus Test System” using Power World Simulator. The simulation work explain the transients inthe system due to a fault which is an evaluated of the voltage stability, Rotor angle stability, frequency stability, Active power and reactive power. The simulation is done using a GNCLS model in which synchronous machine is represented using classical modelling [3]. This paper used exciter (AC7B) and PSS with AVR for improving transient instability. © 2015 2014 The TheAuthors. Authors.Published PublishedbybyElsevier ElsevierB.V. B.V. © This is an open access article under the CC BY-NC-ND license Peer-review under responsibility of organizing committee of the International Conference on Eco-friendly Computing and (http://creativecommons.org/licenses/by-nc-nd/4.0/). Communication (ICECCS 2015). Peer-review underSystems responsibility of the Organizing Committee of ICECCS 2015 Keywords:Power World Simulator; Power System Stability; Transient Stability; Load Flow Analysis; Power System Stabilizer (PSS);AutomaticVoltage Regulator (AVR).

1. Introduction Transient stability is the ability of a system which maintains the synchronism condition after subjected to the large disturbance in a power system. Tripping of transmission lines, sudden change in load demand and switching

* PallaviChoudekar. Tel.: +91-9891424508. E-mail address: [email protected] †Ruchira. Tel.: +91-9650573232. E-mail address: [email protected]

1877-0509 © 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the Organizing Committee of ICECCS 2015 doi:10.1016/j.procs.2015.10.111

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Divya Asija et al. / Procedia Computer Science 70 (2015) 733 – 739

condiitions are the main m causes of disturbances d [5]. Due to thesee disturbances, any system attaains the discreppancy situattion between thhe mechanical input and electtrical output. Iff these disturbaances cause thee change in rottating frequency of generattor having greatter tendency, theen it will be nott operated with rest of system. It will automatiically disconnect from the rest of the systeem. This condittion is called ouut of step condiition of that discconnected generrator. d of geneerator can prove to be more ex xpensive for thee whole system m[2]. In the casee of failure of ppower Any damage system m, frequency iss real signal whhich will be affeected. Any channges in demandd of power systeem, the speed oof the generrator will be chaanged and it willl further affect the speed of intter-related equippment and devicces of power system. Thus the rate of channge of frequencyy is used as an indicator i [4]. Thhis paper has thhe main objectiv ve which is relatted to oving the transiient stability off a system wheen the system is i subjected to certain types of o disturbance. This impro objecctive has been acchieved using excitation contro ol and AVR therreby improving the stability of the system. 2. Litterature Review w In 1991, it is desscribed about thhe Excitation system, s which consists c of som me components such as Autom matic AVR), Exciter, PSS, Measuring g elements, Protective device aand limiters. Geenerator transferrs the Voltaage Regulator (A mech hanical energy into i electrical energy using th he excitation system. The funnction of excitaation system w which impro oves the transieent stabilityhas been explained d[1].In 1994, it is described how the power system stabilityy has been affected with diisturbances andd the efficient method m for improoving the stabiliity after transien nts [5]. In 1997, it is c of transsformed TEF.T Transformer TEF F follow the priinciple of conseervation [6].In 22005, discussed about the concept o power flow (OPF) whhich is having the transient sttability limitatioon. It it discussed about thhe analysis of optimal he help of potenntial energy bouundary surface method[7].In m 20012 it explaains the evaluatiion of transient stability with th is fou und that the load decrement method m for imp proving the trannsient stabilityiis more beneficcial. In this meethod quanttity to be shed is i reduced as coompared to the load l sheddinginn conventional m method [8]. In 2013, 2 some metthods for im mprovement in the steady-statee stabilityhave been b discussed. It explains impprovement of stteady state stabbility, impro ovement in the positive p dampinng of the system m and removes Low L frequency oscillations witth the help of power system m stabilizer [9]. In 2014, thee combined opeeration of PSS and SVC for Power System m Transient Stabbility Enhanncement has been b studied annd it discuss about the imprrovement of trransient stabilitty using PSS. The enhan ncement the smaall signal stabiliity with the help p of PSS is also considered [100]. 3. Mo odel of IEEE 9 Bus Test Systtem

Fig. 1 IEEE 9 Bus Test System Model usingg Power World Simuulator


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Fig g 1 shows the baasic structure off the IEEE 9 tesst bus system. This T system has the main comp ponents which aare 3 generaators (Gen#1, Gen#5, G Gen#9), 3 transformerrs and 9 buses. The modelingg of IEEE 9 bus test system and simulaation results anaalysis the pre faault condition, during d fault con ndition and withh excitation meethod for improvving the traansient stability y. Generators (11, 5 and 9) generate total pow wer of 323.36 M MW. Three load ds which are joined throug gh bus 3, 6 and 7 consume 313.266 MW. This IEEE 9 Bus Teest System operaates at 50 Hz. 4. Casses for Represeentation of Pow wer System Con ndition 4.1Case 1- Pre Fault Condition of IE EEE 9 Bus Test System Case1 discuss about the pre fault condition c when all the system parameters aree having normaal stabilized vallues. o voltage stability, frequency stability, rotor angle stability, bus Figurees given below shows the quallitative values of voltag ge and speed off the three geneerators which have been execu uted with IEEE 9 bus test systtem and tables also describ be the qualitativve value of the system s parametters for the initiaal condition.

Fig 2. Mechanical Input of Gen#1, G a Gen# 9 vs Tim me Gen#5 and

Fig 3. Reactive power off Gen#1, n#5 and Gen#9 vs Time. T Gen

Fig 4. Rotor Angle of Geen #1, T Gen#5 and Gen# 9 vs Time

Fig 5. Field Voltage of Gen#1, Gen#5, Gen#9 vs Time

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Fig 6. Bus Vo oltage of Gen #1, Gen#5 G and Gen# G 9 vs Time

Fig 7. Frrequency of Gen #1, # Gen#5 and Gen# 9 vs Tim me

TABL LE 1.Pre Fault Valu ues of IEEE 9 Bus Test SystemsTAB BLE 2. Pre Fault Values V of IEEE 9 B Bus Test System

No. of Geen Gen n1 Gen n5 Gen n9

Mech Input 168.2 9 85.00 70.07

Bus B N No

V(PU)

Frequency( Hz)

1 2 3 4 5 6 7 8 9

1.000 0.8863 0.8129 0.7728 0.7661 0.7438 0.7078 0.7453 0.7711

50 50 50 50 50 50 50 50 50

Load (MW)

Loaad (Mvaar)

101.45

35.449

120.70 91.11

48.110 30.336

Mva ar

MW Terminal 168.29

Field Voltage V 1 1.4241

191.9 90

85 70.07

0.7846 0 0 0.8859

-5.16 6 37.00

4.2 Case C 2 – During Fault Condition of IEEE 9 Buss Test System In thiis case the fault is introduced att bus no. 9of th he system and due d to this fault, system is show wing the transiennts in its diffferent parametters.The followiing figures show w the system paarameters durinng the fault cond dition. Field vooltage and mechanical m inpu ut will not be afffected, because it is given to thhe system exterrnally. So it willl be ascommon with case 1. 1

F 8 . Reactive Poower of Fig Geen#1, Gen#5 and Gen#9 G vs. Time

Fig 9. Rotor R Angle of Gen n#1, Gen#5 and Gen# 9 vs. Tim me

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Fig 11. Frequency of Gen#1, G T Gen##5 and Gen#9 vs. Time

Fig 10 0. Bus Voltage of Gen#1, G Gen##5 and Gen#9 vs. Time T

TABLE E3.Generator dataa during fault in poower systemTABL LE 4. Bus Data durring fault condition in Power System m

No of n Gen

Mech Input

MW Terminal

Field V Voltage

Mvarr

Gen 1

168.29

135.64

1 1.4241

135.6 64

Gen 5

85.00

68.48

0 0.7846

68.46 6

Gen 9

70.07

50.25

0 0.8859

56.25 5

Bu us N No 1 2 3 4 5 6 7 8 9

V(PU)

Frequency

0.9535 0.8202 0.7512 0.7126 0.7219 0.6149 0.6032 0.6052 0.5771

57.356 57.354 57.342 57.347 57.343 57.356 57.356 57.356 57.359

Load MW M

Load Mvarr

86.64 8

38.31

82.50 8 66.14 6

32.86 22.05

4.3 Ca ase 3- Post Fault Condition of IEEE I 9 Bus Tesst System This case c employs thhe “Excitation Method” for im mproving the trransient stabilitty. Power systeem Stabilizer (P PSS) Exciteer and Automatiic voltage regulator (AVR) are used in Generaator9 which is coonnected near the faulted line. The resultss are shown in figures f 12-16.

Figg 12. Mvar of Gen n#1, Gen #5 and Gen#9 vs Time

Fig 13. Field Voltage of Geen#1, Gen #5 and Gen#9 G vs Time

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Fig 15. Bus V Voltage of Gen#1, Gen G #5 and Gen#9 vs Time

Fig 14. Rotor Angle of Gen#1, G Gen #5 and Gen#9 vs Time T

F 16. Frequency of Gen#1, Gen 5 and Fig a Gen#9 vs Timee LE 5. Gen data durring the Post FaulttTABLE 6. Bus Data D during the Posst Fault TABL No of Gen

Mech Input

MW Terminal

Field Voltage

Mvar M

Gen1

168.29

167.70

1.2037

83 3.97

Gen 5

85.00

82.39

0.9086

0.87 0

Gen 9

70.07

70.26

1.7825

39 91.87

Bus No

V(PU)

Frequency

1 2 3 4 5 6 7 8 9

0.9535 0.8202 0.7512 0.7126 0.7219 0.6149 0.6032 0.6052 0.5771

49.770 49.770 49.771 49.772 49.773 49.768 49.769 49.767 49.766

Load MW

L Load M Mvar

97.48

334.10

112.83 85.88

444.96 228.62

5. Reesults Obtained d Taable7 describes the condition of o all 3 generato ors during the PreP fault condittion in which alll the parameterrs are in norrmal condition .According to th he table, mechaanical input for generator is 3233.36 and the tottal generating power from the generator is i 323.36 MW and 223.74 Mv var which meanns power generrated is equal to mechanical innput. Field voltage is 3.0317 p.u volts forr all generators. Table 8 showss the condition oof three generattors during the ffault, hanical input is 323.36 as in caase 1 but due to fault, total gennerated power beecomes 254.37 MW in this case the mech The reactive po ower (260.35 Mv var) will be incrreased to maintain the stability y of a system and the from all generators .T meters condition of three generaators during thee post field voltage is also similar to case 1.Table 9 descrribes the param ntrolling the volltage. fault. In this case exccitation system provides the fieeld current to thhe terminal of geenerator for con t mechanical input as 323.36 6 and the total generated g powerr as 320.35 MW W. The generatioon of At thiis time we get the poweer has improved d from the casee 2 and the reacctive power is 476.71 4 Mvar w which is increaseed due to excitation

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system which provides the stability to the system .In this case the field voltage of all generators is also increased to 3.8948 p.u. This is the optimum stability case for the observed test system. TABLE 7. Parameters condition of all generators during Pre-FaultTABLE 8. Parameters condition of all generators during Fault

No. of Gen Gen 1

Mech Input 168.29

Gen 2 Gen 3

85 70.07

MW 168.2 9 85 70.07

Field Volt 1.4241

Mvar 191.90

Rotor Angle 23.623

0.7846 0.8859

-5.16 37.00

22.688 9.5

No.of Gen Gen 1

Mech Input 168.29

Gen 5 Gen 9

85 70.07

MW 135.6 4 68.48 50.25

Field Volt 1.4241

Mvar 135.64

Rotor Angle 23.623

0.7846 0.8859

68.46 56.25

22.688 9.5

TABLE 9. Parameters condition of all generators after Fault

No. of Gen Gen 1 Gen 5 Gen 9

Mech Input 168.29 85 70.07

MW 167.70 82.39 70.26

Field Volt 1.2037 0.9086 1.7825

Mvar 83.97 0.87 391.87

Rotor Angle 27.730 17.819 2.3179

Conclusion In this paper the condition of power system has been compared using three cases that are Pre Fault, During Fault, and After Fault. In the Pre Fault condition, we are getting the power 323.36 MW, which is equal to mechanical input. After introducing fault the generated power decreases from 323.36 to 254.37 MW The power drop, during fault has been improved by using the excitation system which will result in sufficient generated power (320.35MW) which is approximately equal to 323.36 MW which is during a Pre fault condition. So it is concluded that during the fault if we use the excitation system, then we can easily control the voltage and system power and can protect the whole system from transient instability. References 1. Jerkovic, Vedrana; Miklosevic, Kresimir; SpoljaricZeljko”Excitation System Models of SynchronousGenerator” KunsongHaung, Hasan Yee “Improved Tangent Hyperplane Method for Transient Stability Studies” November 1991. 2. Ankit Jha, LalthanglianaRalte “Transient stability analysis using equal area criterion using simulink model” Department of Electrical Engineering National Institute of Technology Rourkela 2009. 3. Komal S. Shetye, Thomas J. Overbye and James F. Gronquist “Validation of Power System Transient Stability Results,” IEEE Transactions on power system, 2012. 4. Swaroop KumarNallagalva, Mukesh Kumar Kirar, Dr.GangaAgnihotrim“Transient Stability Analysis of the IEEE 9-Bus Electric Power System”. 5. P. Kundur, Power System Stability and Control, New York, NY: McGraw-Hill, Inc., 1994. 6. D.Z. Fang, T.S.Chung, A.K. David, “Improved techniques for hybrid method in fast transient stability assessment” IEE Gener.Trunsm.Distrib., Vol. 144, No. 2, March 1997. 7. Yan Xia, Ka Wing Chan and Mingboliu“Improved BFGS Method for Optimal Power Flow Calculation with Transient Stability Constraints”, IEEE transaction on power system, 2005. 8. G. Shahgholian“Review of power system stabilizer: Application, Modelling, Analysis and Control Strategy” Vol. 5, Issue 16, September 2014. 9. Bableshkumarjha, Ramjee Prasad Gupta, Dr.Upendra Prasad “Combined Operation of PSS and SVC For Power System Transient Stability Enhancement” Journal of Engineering and Techonology Research, 2014. 10. V. Vittal, “Transient stability test systems for direct stability methods” IEEE Transactions on Power Systems, vol. 7, February 1992. 11. Gursharan S. Grewal, John W konowalec, Mak Hakim“Optimization of a load shedding scheme”, IEEE July 1998. 12. Minghui Yin, C. Y. Chung, K. P. Wong, YushengXue and Yun Zou “An Improved Iterative Method for Assessment of Multi-Swing Transient Stability Limit” IEEE Transaction on Power systems, Vol. 26, no.4, November 2011. 13. Ehsan Nasr Azadani, Claudio Canizares, Kankar Bhattacharya, “Modeling and Stability Analysis of Distributed Generation” IEEE PES General Meeting, July 2012.