IJETSE INTERNATIONAL JOURNAL OF EMERGING TECHNOLOGIES IN SCIENCES AND ENGINEERING, VOL.5, NO.3, MARCH 2012 722012 IJETSE A Review of Enhancement of Transient Stability by FACTS Devices Rahul Somalwar and Manish Khemariya Department of Electrical & Electronics Engg. Datta Meghe Institute of Engg. Technology & Research, LNCT Wardh, BhopalAbstract : In recent years, power demand has increased substantially while the expansion of power generation andtransmission has been severely limited due to limited resources and environmental restrictions. As a consequence, sometransmission lines are heavily loaded and the system stability becomes a power transfer-limiting factor. Flexible ACtransmission systems (FACTS) controllers have been mainly used for solving various power system steady state controlproblems. However, recent studies reveal that FACTS controllers could be employed to enhance power system stability inaddition to their main function of power flow control. The literature shows an increasing interest in this subject for thelast three decades, where the enhancement of system stability using FACTS controllers has been extensively investigated.This paper presents a comprehensive review on the research and developments in the power system stability enhancementusing FACTS Devices. In addition, some of the utility experience, real-world installations, and semiconductor technologydevelopment have been reviewed and summarized & suggested a new technology Based on the advancement inSemiconductor device . or to control directly the real and reactive power flow in I Introduction the line . A unified power flow controller (UPFC) is the most Development of effective ways to utilize promising device in the FACTS concept. It has thetransmission system to the maximum thermal ability to adjust the three control parameters, i.e. the buscapabilities has caught much research attention in voltage, transmission line reactance, and phase angleresent year. This is one direct outcome of the concept of between two buses, either simultaneously orflexible A.C. transmission system (FACTS) aspects of independently. A UPFC performs this through thewhich have become possible due to advances in power control of the in-phase voltage, quadrature voltage, andelectronics. shunt compensation.Generally, the main objectives of FACTS are to The basic components of the UPFC are two voltageincrease the useable transmission capacity of lines and source inverters (VSIs) sharing a common dc storagecontrol power flow over designated transmission routes. capacitor, and connected to the power system through There are two generations for realization of coupling transformers. One VSI is connected in shuntpower electronics-based FACTS controllers: the first to the transmission system via a shunt transformer,generation employs conventional thyristor-switched while the other one is connected in series through acapacitors and reactors, and quadrature tap-changing series transformer. A basic UPFC functional scheme istransformers, the second generation employs gate turn- shown in fig 1off (GTO) thyristor-switched converters as voltagesource converters (VSCs).The first generation has resulted in the Static VarCompensator (SVC), the Thyristor- Controlled SeriesCapacitor (TCSC), and the Thyristor-Controlled PhaseShifter (TCPS) [1;2]. The second generation hasproduced the Static Synchronous Compensator(STATCOM), the Static Synchronous SeriesCompensator (SSSC), the Unified Power FlowController (UPFC), and the Interline Power FlowController (IPFC) [3 -5].The two groups of FACTS controllers have distinctlydifferent operating and performance characteristics. For the maximum effectiveness of the controllers, theThe Voltage source converter (VSC) can be used selection of installing locations and feedback signals ofuniformly to control transmission line voltage, FACTS-based stabilizers must be investigated. On theimpedance, and angle by providing reactive shunt other hand, the robustness of the stabilizers to thecompensation, series compensation, and phase shifting, variations of power system operating conditions is
IJETSE INTERNATIONAL JOURNAL OF EMERGING TECHNOLOGIES IN SCIENCES AND ENGINEERING, VOL.5, NO.3, MARCH 2012 732012 IJETSEequally important factor to be considered. Also, the contribute even further to the growth of FACTScoordination among different stabilizers is a vital issue technology. After that A device called the Insulatedto avoid the adverse effects. Additionally, performance Gate Bipolar Transistor (IGBT) has been developedcomparison is an important factor that helps in selection with small gate consumption and small turn-on andof a specific FACTS device. turn-off times.S.V.Ravi kumar  find the effect of UPFC with The IGBT has bi-directional current carryinglocation capabilities. More effective use of pulse width • The effect of UPFC is more pronounced when modulation techniques for control of output magnitude the controller is placed near heavily disturbed and harmonic distortion can be achieved by increasing generator. the switching frequencies to the low kHz range. • The effect of UPFC is more pronounced when However, IGBT has until recently been restricted to the controller is placed near faulted bus rather voltages and currents in the medium power range. than placed at remote locations. Larger devices are now becoming available with typical • UPFC helps in improving transient stability by ratings on the market being 3.3 kV/1.2 kA (Eupec), 4.5 improving critical clearing time. kV/2 kA (Fuji), and 5.2 kV/2 kA (ABB) [9,10]. • The transient stability is improved by The Integrated Gate Commutated thyristor (IGCT) decreasing first swing with UPFC and SVC. combines the excellent forward characteristics of the • SVC helps in improving transient stability by thyristors and the switching performance of a bipolar improving critical clearing time transistor. In addition, IGCT does not require snubber circuits and it has better turn-off characteristics, lowerControl systems for FACTS controllers may have to be conducting and switching loss, and simpler gate controldesigned by using intelligent, adaptive digital compared with GTO and IGBT . The ratings ofcontrollers based on information obtained from wide- IGCT reach 5.5 kV/1.8 kA for reverse conductingarea measurement networks. For systems using FACTS IGCTs and 4.5 kV/4 kA for asymmetrical IGCTs .controllers, aiming for high levels of damping may not Currently, typical ratings of IGCTs on the market arebe a safe design goal for wide-area control. Adequate 10 kV/2.3 kA (ABB) and 6 kV/6 kA (Mitsubishi)damping over the largest realistic range of operating The SSSC is a power electronic -based synchronousconditions may be a more desirable criterion to fulfill Voltage source that generates three phase ac voltages of. The coordination of multiple FACTS controllers in controllable magnitude and phase angle. This voltage,the same system as well as in the adjacent systems must which is injected in series with the transmission line, isbe investigated extensively and implemented to ensure almost in quadrature with the line current and hencethe security of power-system operation. emulates an equivalent inductive or capacitiveNelson et al.  considered four FACTS controllers to reactance in series with the transmissionbe evaluated and compared: the SVC, the STATCOM, line.the TCSC, and the UPFC. The effects of differentcontrollers are expressed in terms of the critical clearingtime (CCT). The controller parameters are selected withonly consideration of maximizing the CCT. The CCTobtained for the different controllers are compared.Among the shunt controllers, the STATCOM performsbetter than SVC. The TCSC is more effective than theshunt controllers, as it offers greater controllability ofthe power flow in the line.The UPFC is by far the best controller, as it providesindependent control over the bus voltage and the linereal and reactive power flows. II Development in FACTS Devices The technology behind thyristor-based FACTS Fig 2 Static synchronous series compensatorcontrollers has been present from several decades and istherefore considered mature. More utilities are likely to When the series injected voltage leads the line current,adopt this technology in the future as more promising it emulates an inductive reactance causing the powerGTO-based FACTS technology is fast emerging. flow and the line current to decrease. When the lineFurther advances in silicon power-switching devices current leads the injected voltage it emulates athat significantly increase their power ratings will capacitive reactance thereby enhancing the power flow
IJETSE INTERNATIONAL JOURNAL OF EMERGING TECHNOLOGIES IN SCIENCES AND ENGINEERING, VOL.5, NO.3, MARCH 2012 742012 IJETSEover the line. The basic schematic diagram of the static The ideal power switch would switch like an IGBT andsynchronous series compensator with its test system is conduct like a GTO thyristor, and it would have the lowshown in Figure 2.  fabrication costs and high yields of the GTO thyristors.High performance and cost effective high power This is exactly what the IGCT achieves The IGCT hasvoltage source inverters (VSI) are a prerequisite for the become the power semiconductor of choice in Mediumrealization of SSSC. Since conventional two-pulse Voltage Industrial Applications. Also in the Energyinverters are not available with higher ratings, multi- Management and the Traction market the versatility ofpulse inverters with higher operating range are used to this power switch has enabled performancecater the need in SSSC.  These multi-pulse improvements and cost savings in a variety ofinverters can be operated at lower switching applications. IGCT are currently being applied tofrequencies, generating symmetrical output voltages such devices as: Medium Voltage Drives (current andhaving very low harmonic components. 48-Pulse voltage source), Circuit Breakers, Super-conductinginverter can be used in high power FACTS controllers, Magnetic Energy Storage Systems (SMES), Dynamicwithout AC filters due to its high performance and low Voltage Restorers , STATCOMs, Dynamicharmonic rate on the AC side. 48-Pulse inverters are Uninterruptible Power Supplies, Power Conditioners,obtained by combining eight 6-Pulse VSIs with an Induction Heaters, Traction inverters and choppers.adequate phase shifts between them. Each of the VSIneeds a coupling transformer of which four of them IV Design Rulesrequire a Y-Y transformer with a turns ratio of 1:1 andthe remaining four require a Delta - Star with a turns A New proposed FACTS control device underratio of 1:√3. The output of the phase shifting testing process the, the most important design steps aretransformers is connected in series to cancel out the • The diode turn-off di/dt capability mostlylower order harmonics.[23,26] determines the size of the di/dt choke.Li ≥ (Vdcmax/(di/dtmax)) III Advance FACTS controller A bigger choke might be chosen in order to limit switching losses of the diode or to limit From the very beginning, the development of the surge current stress during shoot-throughpower semiconductors was nothing more than a search in a phase legfor the ideal switch. The lowest on-state and • The clamp circuit parameters, Ccl, and Rs, cancommutation losses, the highest possible commutation be determined after solving the 2nd orderfrequency and a simple drive circuit. Power silicon differential equation for the damped parallelswitches have increased steadily in complexity and resonance circuit Li, Ccl, Rs and optimisingcapability.[13,14] The first silicon-controlled rectifiers the damping factor to force the diode clampingcould switch power off only at the end of an AC cycle. current to zero as fast as possible withoutFrom the transistor and Darlington to the IGBT, low- succeeding oscillations of significantvoltage applications have benefited all the way along amplitudes, Thereby the influence of the straywhile the medium-voltage user could only look on — inductance, Ls2, of the loop Rs – Ccl– Cdc onGTO’s and more GTO’s, nothing else . The the voltage overshoot has to be accounted for.introduction of IGBTs brought faster switching, but at • Safe operating area and turn-off switchingpresent their switching losses are acceptable only at low losses are valid for a stray inductance valuevoltage levels. GTO thyristors consist of thousands of equal to or less than the data sheet value, Lclindividual switching elements fabricated on a silicon .For applications with higher Lcl values, safewafer. Losses occur in all four conditions of operation operating area and switching losses must be(on, off, switching on, switching off). At medium rechecked.voltage, GTO’s exhibit very low on-state losses andreasonable turn-off losses. However, due to switching V Conclusionbeing non-homogeneous, external snubber circuits arenecessary for the switching operation. These snubbercircuits take up more than half the volume of the final In this review, the current status of power systemequipment and account for much of the design stability enhancement using FACTS controllers wascomplexity, costs and losses.  discussed and scrutinized. The essential features ofThe tendency over the years has been for the designers FACTS controllers and their potential to enhanceof all these devices to concentrate mainly on the power system stability was addressed [15 –18]. The locationswitching itself, so that little attention has been paid to and feedback signals used for design of FACTS-basedthe complexities involved in real-world applications. damping controllers were discussed.
IJETSE INTERNATIONAL JOURNAL OF EMERGING TECHNOLOGIES IN SCIENCES AND ENGINEERING, VOL.5, NO.3, MARCH 2012 752012 IJETSEThe coordination problem among different control 450 O n e - m a c h i n e s y s t e m s w i n g c u r ve . F a u l t c l e a r e d a t 0 . 1 3 sschemes was also considered. Performance comparison 400of different FACTS controllers has been reviewed. The 350likely future direction of FACTS technology, especially 300 Delta, degreein restructured power systems, was discussed as well. In 250addition, utility experience and major real-world 200installations and semiconductor technology 150development have been summarized. 100 50 To investigate the effectiveness of the FACTS 0controller under different fault condition the equal area 0 0 .2 0 .4 0 .6 t, s e c 0 .8 1 1 .2 1 .4criteria is applied and simulation is conducted. System is unstable at Pm = 0.91The result of control algorithm is simple and straight 120 O n e - m a c h in e s y s t e m s w in g c u r ve . F a u lt c le a r e d a t 0 . 1 3forward that 110 • Without FACTS controller the power system 100 loses synchronism at particular shaft power Ps 90 • With FACTS controller the power system is Delta, degree 80 stabilized at particular shaft power Ps. 70Utility of FACTS controller for transmission stability 60 50enhancement and damping of large oscillation has been 40elaborated. 30The stability investigation has been already carried out 0 0.2 0.4 0 .6 0.8 1 1 .2 1.4 t, s ecand the system is found to be stable after introduction System stable by introducing angle Alpha by Staticof phase shift by FACTS controller . The investigation Phase shifter on same critical time.has been done by analytical ,graphical & numericalmethods.The scheme of the introduction of the phase VI Referencesshift after the fault clearance is verified by simulationand the system which was earlier unstable was found to 1. IEEE Power Engineering Society, FACTSbe stable after the phase shift α is introduced by Overview. IEEE Special Publication 95 TP108,FACTS controller. 1995.The new technique is suggested in this paper is 2. IEEE Power Engineering Society, FACTSadvanced FACTS Controller in which new Applications. IEEE Special Publication 96semiconductor IGCT is used instead of GTO or IGBT TP116-0, 1996.for designing the FACTS controller . The paper 3. I. A. Erinmez and A. M. Foss, (eds.), Staticanalyzed the advantages of IGCT over other power Synchronous Compensator (STATCOM).electronics switches. The application of this switch is Working Group 14.19, CIGRE Study Committeestudied by using voltage source inverter. Work is in 14, Document No. 144, August 1999.progress for investigation of comparative study of 4. CIGRE Task Force 14-27, Unified Power FlowFACTS controller using IGBT & IGCT. MATLAB – Controller. CIGRE Technical Brochure, 1998.7.1 simulation software used for observing the wave 5. M. R. M. Mathur and R. S. Basati, Thyristor- Based FACTS Controllers for Electricalforms. The graphs which is shown below is simulated Transmission Systems. IEEE Press Series inby using the existing FACTS control device . Power Engineering, 2002. 6. Yong Hua Song and Allan T. Johns, Flexible AC The system is stable at Pm = 0.833 Transmission Systems (FACTS). London, UK: IEE Press, 1999. 110 O ne-m ac hine s y s tem s w ing c urve. F ault c leared at 0.13s 7. CIGRE Task Force 38.02.16, Impact of 100 Interactions Among Power System Controls. 90 CIGRE Technical Brochure No. 166, Paris, 80 August 2000. 70 8. R. Nelson, J. Bian, D. Ramey, T. A. Lemak, T. Delta, degree 60 Rietman, and J. Hill, “Transient Stability 50 Enhancement with FACTS Controllers”, 40 Proceedings of IEEE Sixth International 30 Conference AC and DC Transmission, London, 20 May 1996. 10 0 0.2 0.4 0.6 0.8 1 1.2 1.4 9. Y. H. Liu, R. H. Zhang, J. Arrillaga, and N. R. t, s ec Watson, “An Overview of Self-Commutating
IJETSE INTERNATIONAL JOURNAL OF EMERGING TECHNOLOGIES IN SCIENCES AND ENGINEERING, VOL.5, NO.3, MARCH 2012 762012 IJETSE Converters and Their Application in International Conference on Power Electronics Transmission and Distribution”, 2005 IEEE/PES and Intelligent Control for Energy, Warsaw 2005 Transmission and Distribution Conference and 21. M. S. El-Moursi and A. M. Sharaf, “Novel Exhibition: Asia and Pacific, Dalian, China, reactive power controllers for STATCOM and 2005, pp. 1 – 7. SSSC,”Electric Power Systems Research, vol. 10. S. Bernet, “Recent Development of High Power 76, pp 228- 241, 2006. Converters for Industry and Traction 22. M.Ricardo Davalos, Juan M. Ramirez and Applications”, IEEE Transactions on Power O.Ruben Tapia, “Three-phase multi-pulse Electronics, 15(6)(2000), pp. 1102–1117. converter StatCom analysis,” Electric Power 11. Q. Yu, P. Li, W. Liu, and X. Xie, “Overview of and Energy Systemsvol. 27, pp. 39-51, 2005. STATCOM Technologies”, Proceedings of the 23. B. Geethalakshmi “ A Fuzzy logic control for 2004 IEEE International Conference on Electric Enhancing the Transient stability of 48 pulse Utility Deregulation, Restructuring and Power inverter based SSSC ” ELECTRIKA vol Technologies, DRPT 2004, 5–8 April 2004, Vol. 10,No.2 , 2008 , Page 53- 58. 2, pp. 647 – 652. 12. P. K. Steimer, H. E. Gruning, J. Werninger, E. 24. S. Tara Kalyani “ Simulation of real & Carroll, S. Klaka, and S. Linder, “IGCT-A New reactive power flow control with UPFC Emerging Technology for High Power, Low Cost connected to transmission line“ Journal of Inverters”, Proceedings of the IEEE 32nd Theoretical & applied infomration Industrial Application Society Annual Meeting, technology-2008. IAS’97, October 5–9, 1997, vol. 2, pp.1592– 25. S.V. Ravikumar , S.Siva Nagaraju “ Transient 1599. stability improvement using UPFC and SVC” 13. P.Steimer, O.Apeldoorn, E.Carroll, “IGCT ARPN ( Asian research publishing network ) Devices - Applications and Future journal of Engineering and applied science Opportunities", IEEE/PES, Seattle 2000 ,Vol 2 No.3, June 2007 . 14. Stefan Linder “Power semiconductors at the 26. Siddharth Panda & Mr. R.N. Patel “Optimal center of a silient revolution“ ABB, Review location of shunt FACTS devices in long 4/2003. transmission lines to improve transient 15. Wayne H. Litzenberger, (ed.), An Annotated stability“ international journal of Electrical Bibliography of High-Voltage Direct-Current Engieneering Education 46/2. Transmission and Flexible AC Transmission (FACTS) Devices, 1991-1993. Portland, OR, USA: Bonneville Power Administration and Western Area Power Administration, 1994. 16. Rajiv K. Kumar, Wayne H. Litzenberger, and Jonathan Berge, “Bibliography of FACTS: 2003- Part I & Part II IEEE Working Group Report”, Proceedings of 2007 IEEE Power Engineering Society General Meeting, Tampa, FL, USA, June 24-28, 2007. 17. Rajiv K. Kumar, Wayne H. Litzenberger, Soubhik Auddy, Jonathan Berge, A. C. Cojocaru, and T. Sidhu “Bibliography of FACTS: 2004- 2005 Part I & Part II & Part III IEEE Working group Report”, Proceedings of 2006 IEEE Power Engineering Society General Meeting, Montreal, Canada, June 2006. 18. Rajiv K. Kumar, Wayne H. Litzenberger, Amir Ostadi, and Soubhik Auddy, “Bibliography of FACTS: 2005-2006 Part I & Part II IEEE Working Group Report”, Proceedings of 2007 IEEE Power Engineering Society General Meeting, Tampa, FL, USA, June 24–28, 2007. 19. M Steffen Bernet Peter Streit “ Design and Characteristics of Reverse Conducting 10 kV IGCTS ”, ABB, Review 3/2009. 20. S. Bernet, State of the Art and Developments of Medium Voltage Converter An Overview,