IEEE-FACTs & HVDC - Modern Countermeasures to Blackouts

8/19/2019 IEEE-FACTs & HVDC - Modern Countermeasures to Blackouts

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IEEE power & energy magazine september/october 20061540-7977/06/$20.00©2006 IEEE36


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september/october 2006 IEEE power & energy magazine

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SOME OF THE COMMON SCENARIOS IN THE EARLY STAGES OF A BLACKOUT ARE PARALLELtransmission paths overloading and tripping in a cascading sequence, system voltage collapsing due to a lack of

reactive power reserves and, thus, a lack of voltage regulation ability, growing power oscillations on the system

(small-signal instability), and transient rotor-angle instability.Many of the modern power-electronic-based transmission technologies can help to alleviate these types of

problems. For example, high-voltage dc (HVDC) can be used to provide the benefits of interconnecting twosystems (i.e., power transfer) while essentially acting as a barrier across which phenomena such as power

oscillations are not propagated. Thus, HVDC can effectively shield one system from electrical distur-bances on the other. In addition, flexible ac transmission systems (FACTS) can provide economic alter-natives to building additional extra-high-voltage (EHV) lines for the purpose of increasing the power

transfer capability across transmission corridors, thereby enhancing system dynamic performance. Inthis article, we discuss some of these technologies together with their potential benefits.

FACTSThe concept of FACTS was first introduced in the mid-1980s. In traditional power systems, atremote locations far from generating plants, network voltage is controlled by either switching

mechanically switched shunt devices (capacitors and reactors) or by changing taps on on-load tap-changing transformers. These methods of voltage control can be sluggish and rathercoarse (i.e., result in step changes in voltage rather than smooth, continuous regulation).

Under severe contingen-cies, particularly thoseoccurring near load cen-ters remote from genera-t io n, such sl ow andcoarse voltage controlcan result in an inabilityto regulate voltage fastenough and may lead tovoltage instability orvoltage collapse. One of

the major causes of such voltage collapse conditions is the use of modern air conditioning. Asair conditioning has become a “necessary” comfort of the typical household, the on-peak

summertime load in many electrical power systems has grown. To further exacerbate the prob-lem, air-conditioning load is characterized by light electrical motors at the heart of the air-con-

ditioning systems. During major system disturbances, these motors have a tendency to stall andbecome a significant drain of reactive current, resulting in local voltage collapse that may lead to

wide-area cascading outages. To address such problems, the solution often tends to be a combina-tion of faster protection systems (that is, an ability to remove the faulted line as quickly as possible

from service) and the addition of fast-acting dynamic reactive power devices. With the advent of modern power electronics, shunt devices, such as static var compensators (SVCs) and static compen-

sators (STATCOMs), can be implemented to provide the necessary fast and smooth dynamic reactive

support. These devices also boast other system performance benefits, such as improving transient stabili-ty and small-signal stability as well as significant operational benefits.Other FACTS controllers include the series devices such as the thyristor-controlled series capacitor (TCSC).

Series FACTS devices can also be used to enhance the damping of interarea modes of oscillation between gener-ating plants while improving transient stability and providing a means of controlling power flow on parallel ac

transmission paths.At the heart of FACTS devices is either the thyristor valve or the gate-turn-off device. The thyristor valve has been

around since the 1970s and is a four-layered junction semiconductor device. The thyristor is line commutated and, while itsturn-on time can be controlled, turn-off occurs only when the line current reverses. This means that thyristor-based devices arecontrolled passive components. That is, through controlled switching of thyristors, the effective impedance of a series or shunt

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device can be quickly and smoothly changed to result in con-trol of a power system parameter. More advanced technolo-gies use gate-turn-off thyristors (GTOs), insulated gate bipolartransistors (IGBTs), or insulated gate-commutated thyristors(IGCTs). These power electronic devices allow controlledswitching both on and off. As such, extremely fast switch-ing frequencies (kilohertz) can be used to fully control theoutput of the device. In this manner, through forced commuta-tion, a truly active voltage-source device can be designed. Inthe following sections, these technologies and their benefits inreducing the risk blackouts are described in more detail.

Shunt FACTS Devices and Voltage ControlShunt FACTS devices such as SVCs or the static compen-sator (STATCOM) can be used to provide significantimprovements in voltage control and stability. Shunt FACTSdevices have been applied at voltages ranging from 35–735kV to improve system dynamic voltage performance.

The SVC is an impedance device that uses thyristorvalves to control the effective impedance applied to the sys-tem. By regulating the device’s impedance as a function of measured system voltage, vernier voltage control can beeffected. In addition, by integrating the control of othernearby mechanically switched capacitor banks (which mayalready exist in the system), a fully integrated static VArsystem (SVS) can be implemented to provide much greaterflexibility and control. Such a design ensures that theswitching of the mechanically switched capacitor (MSC)banks and the SVC is fully coordinated and automated,thereby removing the need for operator action (and possibleoperator error) following a major disturbance.

Another shunt FACTS device is the STATCOM, which isbased on voltage-sourced converter technology. Under cer-

tain system conditions, these devices present additionalbenefits since, once at its reactive limit, a STATCOM is aconstant-current device, while an SVC is a constant-imped-ance device. However, it is possible to build SVC andSTATCOM devices having equal system performance pro-vided that the individual device rating is different. In mostutility transmission applications, the decision for SVC orSTATCOM technology is typically not driven by electricalsystem performance since both devices have similar per-formance. However, while SVCs have generally proven tohave lower equipment costs and lower losses, STATCOMs

figure 1. Building blocks for shunt FACTS devices such as the SVC or STATCOM.

TCRTSR

TSC TCR/FC TCR/TSC VSC

figure 2. A ±100-MVAr STATCOM installed in a U.S. citycenter to provide dynamic voltage support following theretirement of generation adjacent to the STATCOM site.The power electronics are enclosed in a two-story buildingto reduce the footprint and reduce audible noise to thesurrounding area.

IEEE power & energy magazine september/october 200638


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have also been used in transmission where land constraints,audible noise, or visual impact are of concern.

Figure 1 shows the basic power-electronic-based buildingblocks used for the SVC and the voltage source converter—the main building block for the STATCOM. The thyristor-controlled reactor (TCR) provides vernier control throughout

the rating of this building block, but as a nonlinear device,the TCR generates harmonics that must be mitigated withfilters. For this reason, a TCR is always combined with har-monic filters, which also provide part or all of the SVC’scapacitive rating. A thyristor-switched capacitor (TSC) canalso be added to a TCR and filter to increase the operatingrange of an SVC.

A voltage source converter (VSC) has by its nature a sym-metrical output. However, in many cases where reactive sup-port is required, a greater capacitive rating of the device isneeded relative to inductive rating. For this reason, a VSC isoften combined with MSCs.

In recent years, shunt FACTS devices have been increas-

ingly applied at subtransmission levels to facilitate the retire-ment of old or uneconomic generation assets [often calledreliability must-run (RMR) generation]. This application (of both SVC and STATCOM) to facilitate the retirement of uneconomic generation assets is often attributed to electricutility deregulation. Also, some aging generating facilities areretired due to environmental concerns related to emissions.Under market-based generation dispatch, the lowest-cost gen-

eration is the first to come online, except in cases where ahigher-cost generator is required to maintain voltage undernormal or contingency conditions to maintain system reliabil-ity—hence the term “reliability must-run” generation. Multi-ple indpendent system operators (ISOs) and regionaltransmission authorities have reported annual RMR costs in

excess of US$100 million. Given the magnitude of thesecosts and the objective of market operators to constantlyimprove market efficiency, several system operators havetaken specific actions to reduce RMR costs. However, retiringgeneration without consideration for voltage support canadversely impact overall system reliability. Shunt FACTSdevices have been applied in several locations in the UnitedStates since the late 1990s to provide dynamic reactive sup-port as generators are retired for the purpose of reducingRMR costs. Figure 2 shows ±100-MVAr STATCOM appliedfor fast voltage support in a U.S. city center to facilitate theretirement of a generating plant without adversely impactingsystem reliability.

Power plant generators are the most common form of dynamic reactive power. However, as indicated above, theymay not be the most economical. In particular, concentratedareas of load such as city centers have sufficient transmissionavailable to serve the megawatt demand from distant sourcesof low-cost generation. However, if city-center generation isretired, some form of dynamic voltage support must be sup-plied in some alternative variety. Without adequate dynamic

Device Potential Application Potential Benefits as Countermeasures to Blackouts

HVDC (conventional) Transmission of power over Ability to control power on the dc path independently of parallellong distances or between ac paths. Ability to isolate the two interconnected systems,asynchronous systems creating a “firewall” between the two systems. In some cases

the ability to improve damping of power oscillations on parallelac paths through proper application of supplemental controlson the dc converters.

HVDC (voltage Transmission of power over Same benefits as conventional dc with the added advantage ofsource converter) long distances or between being able to control both real and reactive power independently

asynchronous systems at each converter, thereby providing voltage support/regulation.This type of dc link also allows for black-start, that is, load canbe picked up without any other source of power but the dcconverter.

SVC/STATCOM To provide local voltage These shunt devices can provide a number of potential benefits:support in heavy load ✔ Improve/ensure voltage stability and regulationcenters remote from ✔ Improve/ensure transient stability when placed

generation; to improve appropriately on long transmission pathspower transfer on long ✔ Improve small-signal stability through the propertransmission paths, by tuning and application of supplemental dampingproviding fast voltage controls.support midline and, thus,improved transient stabilitymargins

TCSC To allow for control of This technology can mitigate SSR for series capacitorpower flow on parallel applications. In addition, through the application ofac paths. To mitigate supplemental power oscillation damping controls, it can be usedsubsynchronous resonance to enhance small-signal stability. Clearly, the series capacitor(SSR) itself provides significant improvements in transient stability margins.

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Table 1. Summary of transmission technologies.


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reactive support, reliability issues such as voltage collapse orwidespread loss of load (blackout) can arise. The smoothlycontrollable dynamic nature of FACTS devices makes theman increasingly common substitute for dynamic reactive com-pensation, which was formerly supplied by a generator locat-ed close to a load center.

Shunt FACTS devices have also been applied at bulktransmission voltages since the 1980s to improve powertransfer capability by improving transient stability margins,postfault voltage recovery, and damping power oscillations.

In terms of cost per MVAr, MSCs can be an order of

magnitude less costly than FACTS devices. Given theseeconomics and the fact that MSCs work well to controlsteady-state voltage, it is often desirable to automate theoperation of MSCs with an SVC or STATCOM. The vernieroutput of the FACTS device can be used to smooth the volt-age profile between MSC switching steps, while the outputof the SVC or STATCOM is held within a small bandwidthclose to zero to conserve its dynamic range for severeevents. However, when combining shunt FACTS deviceswith mechanically switched devices such as capacitorbanks, it is crucial to confirm that the mix of the smoothlycontrollable reactive support under the control of powerelectronics versus discrete mechanically switched reactivecomponents is appropriate. For example, MSC banks typi-cally must be discharged for several minutes once deener-

gized. Thus, if an MSC is inserted following a contingencyand then taken off line, it cannot be reinserted for severalminutes. The span of a dynamic event can range from mil-liseconds to minutes, reducing the effectiveness of an MSCto actively compensate for typical postcontingency voltageperturbations. An SVC or STATCOM can vary its output ona millisecond basis without limitation.

Another means of reducing the cost of an SVC orSTATCOM is by designing a short-term or “overload” rat-ing. The reason for having a short-term rating is that, insome applications, the FACTS device may only be needed

for a short time following contingencies. However, caremust be taken in applying this approach. Following a criti-cal contingency, it may take operators minutes or hours toestablish the impact on load and generation and redispatchthe system appropriately. While dynamic simulations maydemonstrate that a device rated with short-term rating of seconds is appropriate to recover system voltage immedi-ately following a critical contingency, it is often advanta-geous for system operation to have a fully rated device. Forexample, blocks of load may trip during a fault and thenautomatically reconnect several seconds or minutes follow-ing the contingency. A fully rated FACTS device can beused during this period to stabilize voltage during thesetypes of operations, while a short-term device may be at itslimit due to the initial contingency.

For an SVC, short-term ratingcan range from an additionalfraction of the steady-state ratingto several times the steady-staterating. Depending on the SVCcomponent being thermally over-loaded, the duration of an SVC’sshort-term rating can be on theorder of 5–10 s or 2–4 h. A STAT-COM can also be designed to

have a short-term rating of severaltimes its steady-state rating forseveral seconds.

Series FACTS DevicesThe use of conventional seriescapacitors in helping to improvetransient stability margins on longEHV transmission corridors iswell known. While often not clas-sified as a FACTS device, a


figure 3. Principle of series compensation.

Degree of Compensation: k = X c

X L

Power Transfer WithoutSeries Compensation

Power Transfer withSeries Compensation

P 2 =U 1 U 2

X L

sin Ψ P 2 =U 1 U 2

X L − X c

sin Ψ =U 1 U 2

X L(1−k )sin Ψ

P 1

Q 1

O 1 JX L −JX C O 2 O 1 O 2

P 2

Q 2

Ψ

Shunt FACTS devices such as static VAr compensatorsor the static compensator can be used to provide significantimprovements in voltage control and stability.

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conventional series capacitor reduces the effective reactiveimpedance of a transmission line. Since a capacitor is thedual of an inductor, a series capacitor acts to “cancel” part of the impedance inherent in a transmission line, thereby mak-ing the effective electrical distance between load centers andpower plants appear shorter. In this way, a series capacitorcan improve system stability. The principles behind seriescompensation are illustrated in Figure 3.

Although series capacitors arewidely used in many power sys-tems (such as the Western Electric-

ity Coordinating Council of theNorth American power system),one of the concerns with seriescapacitor application is that of sub-synchronous resonance, which is aresonance between the series-com-pensated electrical network and themechanical shaft of nearby turbine-generators. There are, however,many established means of addressing this issue, includingactive damping controls on thegenerating plant(s) of concern, pas-sive filtering at the generatingplants, and operational strategies.Another effective way to addressthis issue is by implementing partor all of the series capacitor as athryristor-controlled series capaci-tor (TCSC), a series FACTSdevice. One concept of TCSC con-trol is described in Figure 4. Oneof the consequences of the TCSCcontrol strategy is that the apparentimpedance of the device at torsion-

al frequencies (i.e., frequencyrange corresponding to mechanicalmodes of torsional oscillation onturbine generator shafts) is induc-tive. This eliminates any electro-mechanical resonance between thecontrolled series capacitor and thetorsional modes of nearby turbine-generators. Figure 5 shows how theTCSC can effectively mitigate tor-sional instability.

Other benefits of a TCSC are the ability to regulateflows between parallel transmission paths and the ability toimprove small-signal stability. Through dynamic control of the effective impedance of the series device, the impedanceof a transmission path can be varied relative to other paral-lel paths, allowing some control of the power flow. Thiscan be particularly useful after a major disturbance, whenlines become overloaded due to the redistribution of power.

figure 4. General concept of the control of a TCSC. By firing the forward-biasedthyristor just prior to a capacitor voltage zero crossing, an additional current isinjected into the capacitor, causing its voltage to “jump” further when crossingzero. Thus, the effective voltage across the capacitor is increased at fundamentalfrequency, and so its apparent impedance increases. Therefore, throughcontrolled firing of the thyristors, the apparent impedance of the series capacitorcan be varied over a designed range of values.

LR

I V

I L +

u c

−

−0.5

0

0.5

−0.5

0

0.5

−20

−10

0

20

10

i L ( k A )

i v ( k A )

U c

( k V )

2 2.005 2.01 2.015 2.02 2.025

2 2.005 2.01 2.015 2.02 2.025

2 2.005 2.01 2.015 2.02 2.025

Time (s)

F

C

Many of the modern power-electronic-basedtransmission technologies can help to alleviatethese types of problems.

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Following such a disturbance, either by operator action orthrough automated control, the effective impedance of apath compensated by the TCSC can be controlled tochange the power flow on that path to mitigate thermaloverload on that or adjacent paths. Similarly, through fastmodulation of the effective impedance of a TCSC, the

power oscillations on a majortransmission line can be quicklydamped to prevent small-signalinstability following a major dis-turbance. More traditional devices,such as phase-shifting transform-

ers, can also often be applied forcontrolling power flow on parallelpaths. However, these devices donot offer the significantly fasterresponse time associated with thepower electronics employed in aTCSC. Emerging technologiessuch as the unified power flowcontrollers (UPFCs) can also con-trol power flow on parallel trans-mission corridors, while providingall the other benefits of voltagecontrol and stability improve-

ments. However, the UPFC is yetto be established as a commercial-ly viable technology.

HVDCTransmission SystemsHVDC transmission is widelyrecognized as being advantageousfor economic long-distance, bulk-power delivery, asynchronous

interconnections, and long submarine cable crossings.HVDC lines and cables are less expensive and have lowerlosses than those for three-phase ac transmission. Higherpower transfers are possible over longer distances withfewer lines with HVDC transmission than with ac trans-mission. Higher power transfers are possible without

figure 6. Rapid city tie with modular 2 × 100 MW capacitor commutated converters.

++

Ua

UIa

++

Ub

UIb

++

Uc

UIc

Uca I

Ucb I

Ic Ucc

+

+

+

I

1 3 5

264Valve

EnclosuresCommutation

CapacitorConverter

Transformer

figure 5. TCSC application for mitigating torsional oscillations. From 1–5 s, the thyris-tor valves in the TCSC portion of the series capacitor are deliberately blocked. Due toSSR, the 20-Hz torsional mode of the shaft becomes unstable (the machine used is theIEEE first SSR benchmark). Once the TCSC is released, the apparent impedance of theline at subsynchronous frequencies changes dramatically, eliminating the SSR prob-lem near 20 Hz and resulting in damping of the torsional oscillations.

0.98

0.985

0.99

0.995

1

1.005

1.01

1.015

1.02

0 2 4 6 8 10 12 14 16 18 20Time (s)

M a c h i n e M e c h a n i c a l S p e e d ( p u

)

TCSCBlocked

TCSC Released



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distance limitation on HVDC cable systems using fewercables than with ac cable systems, whose capacity dimin-ishes with distance due to their charging current. Becauseof their controllability, HVDC links offer firm capacitywithout limitation due to network congestion or loop flowon parallel paths.

With HVDC transmission systems, interconnections canbe made between asynchronous networks for more eco-nomic or reliable operation. The asynchronous intercon-nection allows interconnections of mutual benefit but

provides a buffer between the two systems. Often theseinterconnections use back-to-back converters with no trans-mission line. The asynchronous links act as an effective“firewall” against propagation of cascading outages fromone network to another. Many asynchronous interconnec-tions exist in North America between the eastern and west-ern interconnected systems, between the ElectricReliability Council of Texas (ERCOT) and its neighborsand between Quebec and its neighbors. The August 2003Northeast blackout provides an example of this “firewall”against cascading outages provided by dc asynchronousinterconnections. As the outage propagated around thelower Great Lakes and through Ontario and New York, it

stopped at the asynchronous interface with Quebec. Que-bec was unaffected. The weak ac interconnections betweenNew York and New England tripped, but the HVDC linksfrom Quebec continued to deliver power to New England.

Conventional HVDC transmission employs line-commutated converters with thyristor valves. These convert-ers require a relatively strong synchronous voltage source tocommutate. The conversion process demands reactivepower, which is supplied by mechanically switched ac fil-ters or shunt capacitor banks that are an integral part of the

converter station. Any surplus or deficit in reactive powermust be accommodated by the ac system. This difference inreactive power must be kept within a given band to keep theac voltage within the desired tolerance. The weaker the sys-tem or the further away the HVDC is from generation, thetighter the reactive power exchange must be to stay withinthe desired voltage tolerance.

Converters with series capacitors connected between thevalves and the transformers were introduced in the late1990s for weak-system back-to-back applications. Theseconverters are referred to as capacitor-commutated convert-ers (CCCs). The series capacitor provides some of the con-verter reactive power requirements automatically with load

figure 7. VSC-based HVDC system control.

acVoltageControl

+ +

dcVoltageControl

InternalCurrentControl

acVoltageControl

q ref1 p ref1 p ref2 q ref2

u ac-ref2

u ac2

i

u dc2u dc1

u ac-ref1

u ac1−

+

i

u dc-ref1 u dc-ref2

− −

dcVoltageControlPWM

InternalCurrentControl

PWM


Other benefits of a TCSC are the abilityto regulate flows between parallel transmission pathsand the ability to improve small-signal stability.

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current and provides part of the commutation voltage,which improves voltage stability. This reduces the need forswitching of shunt compensation with load changes. TheCCC configuration allows higher power ratings in areaswere the ac network is close to its voltage stability limit.

The asynchronous Garabi interconnection between Braziland Argentina consists of four 550-MW parallel CCClinks. The Rapid City Tie between the eastern and westerninterconnected systems consists of two 100-MW parallelCCC links (Figure 6).

HVDC transmission using VSCs with pulse-width modula-tion (PWM) is an new addition to the HVDC family. TheseVSC-based systems are force-commutated with IGBT valvesand solid-dielectric, extruded HVDC cables.

HVDC transmission and reac-tive power compensation with VSCtechnology has certain attributesthat can be beneficial to overallsystem performance. VSC convert-er technology can provide rapid,

independent control of both activeand reactive power. Reactive powercan also be controlled at each ter-minal independent of the dc trans-mission voltage level. This controlcapability gives total flexibility toplace converters anywhere in theac network since there is no

restriction on minimum network short-circuit capacity.Forced commutation with VSC even permits black-start,i.e., the converter can be used to synthesize a balanced setof three-phase voltages like a virtual synchronous genera-tor. The dynamic support of the ac voltage at each con-

verter terminal improves the voltage stabil i ty andincreases the transfer capability of the sending- andreceiving-end ac systems.

Being able to independently control ac voltage magni-tude and phase relative to the system voltage allows the useof separate active and reactive power control loops forHVDC system regulation (Figure 7). The active power con-trol loop can be set to control either the active power or thedc side voltage. In a dc link, one station will be selected to

control the active power while theother must be set to control the dcside voltage. The reactive powercontrol loop can be set to controleither the reactive power or the acside voltage. Either of these twomodes can be selected independ-ently at either end of the dc link.No mechanical switching of reac-tive power compensation elementsis required, unlike in conventionalHVDC. The reactive powerdynamic range, however, can bebiased by a mechanically switchedcapacitor bank, similar to what isdone with SVSs.

Figure 8 shows the reactivepower demand of a conventionalconverter station. In contrast, Figure9 shows the reactive power capabili-ty of a VSC station.

ConclusionsA brief overview of moderntransmission technologies andhow they may be effectively usedto enhance system dynamic per- figure 9. Typical HVDC VSC converter active (P) and reactive (Q) power capability.

figure 8. Reactive power balance conventional HVDC.

Shunt

Banks

Harmonic

Filters

ClassicFilter

Converter

Unbalance1.0

Id

0,13

0,5

Q


−1.25−1.25

−1.25

−1.25

−1

−1

−0.75

−0.75

−0.5

−0.5

−0.25

−0.25

0.25

0.25

0.5

0.5

0.75

0.75

1

1

1.25

1.250

Operating Area

P-Q Diagram (Vchada Volga Range)1.25

D(φ) 1.25

Range Power (Rµ)

Y-axis: Active Power

A c t i v e P o w e r

| P .

U .

|

P ( I )


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formance in response to major system disturbances hasbeen presented (Table 1 provides a brief summary). Inthis way, some of the risks of potential cascading outagesand islanding of the system can be mitigated. Of course,the application of these devices requires proper coordina-tion and tuning of controls to ensure robust performance.

The key benefit is the ability to effect fast and automaticresponse to system disturbances, thereby enhancingdamping in power oscillations, transient stability mar-gins, and smooth voltage recovery and regulation follow-ing major system disturbances.

For Further ReadingN.G. Hingorani, “High power electronics and flexible actransmission system,” IEEE Power Eng. Rev., vol. 8, no. 7,pp. 3–4, July 1988.

N.G. Hingorani, “Flexible AC transmission,” IEEE Spectr., vol. 30, no. 4, pp. 40–45, Apr. 1993.

J.J. Paserba, “How FACTS controllers benefit AC trans-

mission systems,” in Proc. IEEE PES General Meeting, June2004, pp. 1257–1262.

E. John, A. Oskoui, and A. Petersson, “Using a STATCOMto retire urban generation,” in Proc. IEEE PES Power SystemsConf. and Exposition, New York, Oct. 10–13, 2004, pp.693–698.

P. Pourbeik, A. Boström, and B. Ray, “Modeling andapplication studies for a modern static VAr system installa-tion,” IEEE Trans. Power Del ivery , vo l. 21 , no. 1, pp.368–377, Jan. 2006.

P. Pourbeik, D. Wang, and K. Hoang, “Load modeling involtage stability studies,” in Proc. IEEE PES General Meet-ing, San Francisco, June 2005, pp. 1893–1900.

P.M. Anderson and R.G. Farmer, Series Compensation of Power Systems. Encinitas, CA: PBLSH Inc., 1996.

L. Angquist, G. Ingestrom, and H-A. Jonsson, “Dynami-cal performance of TCSC schemes,” in Proc. CIGRE Session,Paris, France, 1996, pp. 14–302.

C. Gama, L. Angquist, G. Ingestrom, and M. Noroozian,“Commissioning and operative experience of TCSC fordamping power oscillation in the Brazilian North-South Inter-connection,” in Proc. CIGRE Session 2000, Paris, France,2000, pp. 14–104.

P. Pourbeik and M.J. Gibbard, “Damping and synchroniz-ing torques induced on generators by FACTS stabilizers in

multimachine power systems,” IEEE Trans. Power Syst., vol.11, no. 4, pp. 1920–1925, Nov. 1996.L. Kirschner, D. Retzmann, and G. Thumm, “Benefits of

FACTS for power system enhancement,” in Proc. 2005 IEEE/PES Transmission and Distribution Conf. and Exhibi-

tion: Asia and Pacific Dalian, China, pp. 1–7.D. McCallum, G. Moreau, J. Primeau, D. Soulier, M.

Bahrman, and B. Ekehov, “Multiterminal integration of thenicolet converter station into the Quebec-New EnglandPhase II HVC transmission system,” in Proc. CIGRE Session1994, Paris, France, pp. 1–7.

M. Bahrman, D. Dickinson, P. Fisher, and M. Stoltz, “TheRapid City Tie—New technology tames the East-West inter-connection,” in Proc. Minnesota Power Systems Conf., Nov.2004, pp. 1–6.

Biographies

Pouyan Pourbeik received his B.E. and Ph.D. degrees inelectrical engineering from the University of Adelaide, Aus-tralia, in 1993 and 1997, respectively, and is a registered pro-fessional engineer in the state of North Carolina. In June2006, he joined EPR Solutions Inc.Before joining EPRI, heworked for ABB and prior to that GE Power Systems.While at ABB, he was heavily involved with studies relatedto the application and modeling of flexible ac transmissionsystems (FACTS) and high-voltage dc (HVDC). He ispresently the chair of the IEEE Power Engineering Society(PES) Power Systems Stability Subcommittee and convenerof the CIGRÉ WG C4.6.01 on Power System SecurityAssessment. He is a Senior Member of the IEEE.

Mike Bahrman is currently the U.S. marketing and salesmanager for high-voltage dc (HVDC) and flexible ac trans-mission systems (FACTS) with ABB, Inc., of Raleigh, NorthCarolina. He has 23 years of experience with ABB PowerSystems. This experience includes system analysis, systemdesign, project engineering, and project management for vari-ous HVDC and FACTS projects in North America. Prior to

joining ABB, he was with Minnesota Power for ten years,where he held positions as transmission planning engineer,HVDC control engineer, and manager of system performanceand dispatch.

Eric John received a bachelor’s degree in electric powerengineering from Rensselaer Polytechnic Institute, NewYork, and and an M.B.A. from Duke University’s FuquaSchool of Business. He is currently the U.S. marketing andsales manager for flexible ac transmission systems (FACTS)with ABB, Inc., of Raleigh, North Carolina. Since joiningABB in 1998, he has held a number of engineering and mar-keting functions related to power quality and FACTS, bothin Sweden and the United States. Prior to joining ABB, heworked with Westinghouse Power Generation on powerquality and FACTS.

Willie Wong received a B.S.E. degree from Northern Ari-zona University, an M.S.E. degree from Arizona State Uni-versity, and an M.B.A. from the University of North

Carolina. He is director of Electric Systems Consulting withABB, Inc., in Raleigh, North Carolina. His area of expertiseis in power system analysis application of advanced tech-nologies such as high-voltage dc (HVDC), static var com-pensator (SVC), and other FACTS devices. Prior to joiningABB in 1984, he was a senior engineer in transmission plan-ning at a major utility company in Phoenix, Arizona. He isactive in the IEEE and is a member of several subcommit-tees under the Power System Dynamic Performance Com-mittee. He has authored/coauthored many papers on powersystem engineering and holds one U.S. patent. p&e

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IEEE-FACTs & HVDC - Modern Countermeasures to Blackouts