"an overview on facts and power quality issues: technical challenges, research opportunities

1P. Ribeiro June, 2002

"An Overview on FACTS and Power Quality Issues:Technical Challenges, Research Opportunities

and Cost Considerations."

Paulo F. Ribeiro, BSEE, MBA, PHD, PE

CALVIN COLLEGEEngineering DepartmentGrand Rapids, MI 49546

http://engr.calvin.edu/PRibeiro_WEBPAGE/[email protected]

10 5 0 5 102

0

2


FACTS

• The Concept• History / Background - Origin of FACTS, Opportunities, Trends• System Architectures and Limitations• Power Flow Control on AC Systems• Application Studies and Implementation• Basic Switching Devices• Systems Studies• AC Transmission Fundamentals• Voltage Source vs. Current Source• Voltage Sources• Static Var Compensator (SVC), STATCOM, TCSC, UPFC, SMES• System Studies (by EMTP, ATP, Saber, EDSA, EMTDC)• Systems Integration, Specification, Cost Considerations and Technology Trends• Impact of FACTS in interconnected networks• Market Assessment, Deregulation and Predictions


Power Quality

Objectives - Motivation - Background

Limitation of Traditional Tools

Advanced Techniques:· Wavelet Theory Making Waves· Expert Systems To Sag or Not to Sag: This is The ?· Fuzzy Logic Not Really a Harmonic Distortion· Neural Networks Remembering Wave Signatures· Genetic Algorithms Evolutionary Distortions· Combining Techniques Power Quality Diagnostic System• Power Electronics Implementing Advanced Power

Concepts


The reason, therefore, that some intuitive minds are not mathematical is that they cannot at all turn their attention to the principles of mathematics. But the reason that mathematicians are not intuitive is that they do not see what is before them, and that, accustomed to the exact and plain principles of mathematics, and not reasoning till they have well inspected and arranged their principles, they are lost in matters of intuition where the principles do not allow of such arrangement. They are scarcely seen; they are felt rather than seen; there is the greatest difficulty in making them felt by those who do not of themselves perceive them. These principles are so fine and so numerous that a very delicate and very clear sense is needed to perceive them, and to judge rightly and justly when they are perceived, without for the most part being able to demonstrate them in order as in mathematics, because the principles are not known to us in the same way, and because it would be an endless matter to undertake it. We must see the matter at once, at one glance, and not by a process of reasoning, at least to a certain degree.

1660 PENSEES by Blaise Pascal


Ptg

PV

VP

X

XP

The Concept


A transmission system can carry power up to its thermal loading limits. But in practice the system has the following constraints:

-Transmission stability limits-Voltage limits-Loop flows

Transmission stability limits: limits of transmittable power with which a transmission system can ride through major faults in the system with its power transmission capability intact.

Voltage limits: limits of power transmission where the system voltage can be kept within permitted deviations from nominal. Voltage is governed by reactive power (Q). Q in its turn depends of the physical length of the transmission circuit as well as from the flow of active power. The longer the line and/or the heavier the flow of active power, the stronger will be the flow of reactive power, as a consequence of which the voltage will drop, until, at some critical level, the voltage collapses altogether.

Loop flows can be a problem as they are governed by the laws of nature which may not be coincident with the contracted path. This means that power which is to be sent from point ”A” to point ”B” in a grid will not necessarily take the shortest, direct route, but will go uncontrolled and fan out to take unwanted paths available in the grid.

The Concept


FACTS devices

FACTS are designed to remove such constraints and to meet planners´, investors´ and operators´ goals without their having to undertake major system additions. This offers ways of attaining an increase of power transmission capacity at optimum conditions, i.e. at maximum availability, minimum transmission losses, and minimum environmental impact. Plus, of course, at minimum investment cost and time expenditure.

The term ”FACTS” covers several power electronics based systems used for AC power transmission. Given the nature of power electronics equipment, FACTS solutions will be particularly justifiable in applications requiring one or more of the following qualities:

-Rapid dynamic response-Ability for frequent variations in output-Smoothly adjustable output.

Important applications in power transmission involving FACTS and Power Quality devices:SVC (Static Var Compensators), Fixed * as well as Thyristor-Controlled Series Capacitors (TCSC) and Statcom. Still others are PST (Phase-shifting Transformers), IPC (Interphase Power Controllers), UPFC (Universal Power Flow Controllers), and DVR (Dynamic Voltage Restorers).

The Concept


History, Concepts, Background, and Issues

Origin of FACTS-Oil Embargo of 1974 and 1979-Environmental Movement-Magnetic Field Concerns-Permit to build new transmission lines-HVDC and SVCs-EPRI FACTS Initiative (1988)-Increase AC Power Transfer (GE and DOE Papers)-The Need for Power semiconductors

Why we need transmission interconnection-Pool power plants and load centers to minimize generation cost-Important in a deregulated environment

Opportunities for FACTSIncrease power transfer capacitySVC (Nebraska GE 1974, Minnesota Westinghouse 1975, Brazil Siemens 1985)TCSC, UPFC AEP 1999

Trends-Generation is not being built-Power sales/purchases are being


System ArchitectureRadial, interconnected areas, complex network

Power Flow in an AC SystemPower Flow in Parallel and Meshed Paths

Transmission LimitationsSteady-State (angular stability, thermal limits, voltage limits)Stability Issues (transient, dynamic, voltage and SSR)System Issues (Post contingency conditions, loop flows, short-circuit levels)

Power Flow and Dynamic Stability Considerations

Controllable Parameters

Basic FACTS Devices - Impact of Energy Storage

System Architectures and Limitations


The relative importance of transmission interconnection

Interconnections in a European type system are not very important because the system is built by providing generation close to the loads and therefore, transmission is mainly for emergency conditions.

In the US,very large power plants far from the load centers were built to bring "coal or water by wire". Large plants provided the best solution - economy of scale. Also, seasonal power exchanges have been used to the economic advantage of the consumers.

Newer generation technologies favor smaller plants which can be located close to the loads and therefore, reduces the need for transmission. Also, if distributed generation takes off, then generation will be much closer to the loads which would lessen the need for transmission even further.

However, for major market players, once the plant is built, the transmission system is the only way to bring power to the consumer that is willing to pay the most for the power. That is, without transmission, we will not get a well functioning competitive market for power.

System Architectures and Limitations


Power Flow Control on AC Systems

RadialParallel

Meshed

Power Flow in Parallel PathsPower Flow in a Meshed SystemsWhat limits the loading capability?

Power Flow and Dynamic Considerations


Power Flow Control on AC Systems

Relative Importance of Controllable Parameters

Control of X can provide current controlWhen angle is large X can provide power controlInjecting voltage in series and perpendicular to the current flow, can increase or decrease

50% Series Compensation


Transmission Transfer Capacity Enhancement

Advanced Solutions

Transmission Link

Enhanced Power Transfer

and Stability

Line Reconfiguration

Fixed Compensation

FACTS

Energy Storage

Better Protection

Increased Inertia

Breaking Resistors Load

Shedding

FACTS

Devices

Traditional Solutions

SVCSTATCOMTCSC, SSSCUPFC

Steady StateIssues

Voltage LimitsThermal Limits

Angular Stability LimitsLoop Flows

DynamicIssues

Transient StabilityDamping Power Swings

Post-Contingency Voltage ControlVoltage Stability

Subsynchronous Res.

FACTS Applications and Implementations


FACTS DevicesShunt Connected

Static VAR Compensator (SVC)Static Synchronous Compensator (STATCOM)Static Synchronous Generator - SSGBattery Energy Storage System (BESS)Superconducting Magnetic Energy Storage (SMES)

Combined Series and Series-Shunt ConnectedStatic Synchronous Series Controllers (SSSC)Thyristor Controlled Phase-Shifting Transformer orPhase Angle Regulator (PAR)Interline Power Flow Controller (IPFC)Thyristor Controlled Series Capacitor (TCSC)Unified Power Flow Controller (UPFC)

Relative Importance of Different Types of ControllersShunt, Shunt-Serie Energy Storage

Energy Storage


DevicesDiode (pn Junction)Silicon Controlled Rectifier (SCR)Gate Turn-Off Thyristor (GTO) GEMOS Turn-Off Thyristor (MTO) SPCOEmitter Turn-Off Thyristor (ETO) Virginia TechIntegrated Gate-Commutated Thyristor (IGCT) Mitsubishi, ABBMOS-Controlled Thyristor (MCT) Victor TempleInsulated Gate Bipolar Transistor (IGBT)

Power Electronics - Semiconductor Devices

DiodesTransistors

IGBTThyristors

SCR, GTO, MTO, ETO, GCT, IGCT, MCT


Power Electronics - Semiconductor DevicesPrincipal Characteristics

Voltage and CurrentLosses and Speed of Switching

Speed of SwitchingSwitching Losses

Gate-driver power and energy requirements

Parameter Trade-offPower requirements for the gatedi/dt and dv/dt capabilityturn-on and turn-off timeUniformityQuality of silicon wafers

IGBT has pushed out the conventional GTO as IGBTs ratings go up.IGBTs - Low-switching losses, fast switching, current-limiting capabilityGTOs - large gate-drive requirements, slow-switching, high-switching lossesIGBTs (higher forward voltage drop)


VSI CSI

Natural Forced

Synchronous PWM

Hard Soft

Two-Level Multi-Level

SCR GTO IGBT MCT MTO

System

CommutationApproach

SwitchingTechnology

TransitionApproach

CircuitTopology

DeviceType

Power Electronics - Semiconductor DevicesDecision-Making Matrix


Planing StudiesEvaluate the technical and economic benefits of a range of FACTS alternative solutions which may allow enhancement of power transfer across weak transmission links. Part I of this effort should concentrate on preliminary feasibility studies to assess the technical merits of alternative solutions to correct real and reactive power transfer ratings, system voltage profiles, operational effects on the network, equipment configurations, etc.

A - Load flow studies will be performed to establish steady-state ratings, and identify the appropriate locations for connection of alternative compensation devices. Load flow studies will be used to address the following:

•System Criteria (maximum steady-state power transfers, short-term operating limits, etc.)•Controller Enhancements (controller types, ratings, sensitivities, etc.)•Controller Losses (based on operating points and duration)•System Losses (system losses base on controller operating point and duration)•Overvoltsages ((steady-state and short-term voltage insulation requirements)•Compare technical and economic benefits of alternatives•Identify interconnection points •Identify critical system contingencies•Establish power transfer capability of the transmission system•Confirm that reliability criteria can be met•Identify the cost of capital of equipment and losses•Identify steady-state and dynamic characteristics of FACTS controllers

Stability Studies

IEEE


System Studies

System data and configuration

Outages and load transfer

Load Flow(P,Q, V, )

Transient Stability

(P,Q, V, , time)

Dynamic Stability

(P,Q, V, , , time)

Generator data

Voltage Reg. Data

(AVR)

Governor data

Relay data

System operat. limits

Induction motor data

Fault data

System changes

Load Shedding

Identify Transmission

Systems - Provide System data and Configuration

Outages and load transfer

Perform Load Flow

(P,Q, V, )

System operat. limits

Identify and Size Transfer

Enhancement Solutions Devices

Perform Economic Analysis

IEEE


E2 / 2

X

E1 / 1 I

P&Q

E1

E2

E1 . sin ()

E2 . cos()

(E1 - E2 . cos()E2 . sin()

I

(E2 - E1 . cos()Iq1 = (E1 - E2 . cos() / X

E1 . Cos ()

Ip1 = E2 sin() / X

E1 - E2P1 = E1 . Ip1

AC Transmission Fundamentals


Active component of the current flow at E1

Ip1 = (E2 . sin ()) / X

Reactive component of the current flow at E1

Iq1 = (E1 - E2 . cos ())/X

Active Power at the E1 end

P1 = E1 (E2 . sin ())/X

Reactive Power at the E1 end

Q1 = E1(E1 - E2 . cos ()) / X

AC Transmission Fundamentals


E2 / 2

P1 = E1 (E2 . sin ())/X

I

X

E1

E2

E1 - E2

Regulating end bus voltage mostly change reactive power - Compensating at an intermediate point between buses can significantly impact power flow

E1 / 1 I

P&Q

Q / VP1 = k1.E1 (E2 . sin (/k2))/X

AC Transmission Fundamentals (Voltage - Shunt Control)


E1

E2

I

X

E1 - E2

Injected Voltage

Injecting Voltage in series with the line mostly change real power

E1 / 1 E2 / 2I

P&Q

Vinj

P1 = E1 . E2 . sin () / (X - Vinj / I)

AC Transmission Fundamentals (Voltage-Series Injection)


X

E1 / 1 E2 / 2I

P&Q

0 0.5 1 1.5 2 2.5 3 3.50

1

22

0

P1 x delta V1( )

3.140 delta

Real Power Angle Curve

Changes in X will increase or decrease real power flow for a fixed angle or change angle for a fixed power flow. Alternatively, the reactive power flow will change with the change of X. Adjustments on the bus voltage have little impact on the real power flow.

Vx

I

Vxo

Vs

I

Xeff = X - Xc

Vx

Vr

Vc

Vseff = Vs + Vc

VrVc

Vseff

P1 = E1 . E2 . sin () / (X - Xc)

Vs

Phase Angle

Pow

er T

rans

f er

AC Transmission Fundamentals (Series Compensation)


X

E1 / 1 E2 / 2

IP&Q

P

E1

E2

I

E1 - E2

Injected Voltage

Integrated voltage series injection and bus voltage regulation (unified) will directly increase or decrease real and reactive power flow.

AC Transmission Fundamentals (Voltage-Series and Shunt Comp.)


1 - prior to fault

2 - fault cleared

3 - equal area

3 >crit - loss of synchronism

Improvement of Transient Stability With FACTS CompensationEqual Area Criteria

1 2 3 crit

A1

A2

Amargin

Max

imum

Po w

e r T

ran s

f er

Phase Angle

no compensation

with VAR compensation (ideal midpoint)

A1 = Acceleration EnergyA2 = Deceleration Energy

Therefore, FACTS compensation can increase

power transfer without reducing the stability margin

Q / V

AC Transmission Fundamentals (Stability Margin)


Voltage Source Vs. Current Source Converters

CSC Adv/Dis

VSC

Adv/Dis

Device Type

Thyristor Self-Commutation

Thyristor Self-Commutation

Device Characteristic Symmetry

Symmetrical Asymmetrical +

Short-Circuit Current

Lower

+ Higher

Rate of Rise of Fault Current

Limited by DC Reactor + Fast Rise (Due to capacitor discharge)

Losses

Higher - Lower +

AC Capacitors

Required Not Required +

DC Capacitors

Not Required + Required

Valves dv/dt

Lower (AC Capacitors)

+ Higher

Interface with AC System

More Complex Less Complex +

Reactive Power Generation

Depends on Current Flowing through Energy Storage

Independent of Energy Storage

+

Performance

Harmonics

AC capacitors may produce resonances near the characteristic harmonics – may cause overvoltages on valves and transformer.

-


System bus

ConverterSwitching

DC-AC

C+

Vdc

s

Shunt Compensation

System busV

Transformer leakageinductance

Transformer

o

X

V

I

Coupling

C+

Vdc

s

ConverterSwitching

DC-AC

Transformer leakageinductance

TransformerCoupling

Series Compensation

o

X

V

I

VV

Voltage Source Converters


Basic 6-Pulse, 2-level, Voltage-Source Converter

cec

Ta2 a2D Tb2

a

b

e

e

ai a1T

ib

i

a1 b1D T

D Tb2 c2 Dc2

dc2

V

b1 c1D T c1D

dc+Cs

V

dci

dcV

Hypotheticalneutral point

2



2, 3, 5-level, VSC Waveforms

vdc2

vdc2 +

vdc2

vdc2

eout

vdc+

Neutral(mid-) point

dc+v

eout

- v dc

+ v dc

+vdc

dc+

v

Neutral(mid-) point

+vdc

dc+

v

1

2

eout

2 dcv

dcv



Voltage-Source Converter Bridges

Three-phase, two-level six-pulse bridge

Single-phase,two-level H-bridge

CC

vdc

C

vdc

voa vvoa obvoc

Three-phase, three-level 12-pulse bridge

C/2C

dcV dcV

C/2

vvoa obvoc



Output voltage control of a two-level VSC

v

oFv (

ov ( )

ov ( )

*=

=) V(+ sin t)

V=oF ( ) sin(+ )

=

*

v sinV t

t

=

=

dc

t

v dc

dci

CC

t(v+v)dc

dc nominalvdcv)(v-

t

v

1dci dt

f C

dci

t (V=vo o )

0io

Vv=



Output voltage control of a three-level VSC

=

= *

omaxv

< <

ov

)(

dcV

max = 23

oF= ,v f ( = -) sin(t

sin

*

v=V t

t

const Vdc

tC/2

)

t

Vdc

C/2

t)oo v =V (

Vio

v= 0



Multi-pulse VSC with wave-forming magnetic circuits

Magnetic structurefor multi-pulse waveform synthesis

Converter 1 Converter 2

System Busbar

Converter n

TransformerCoupling

Interface Magnetics

138kV Bus

CouplingTransformer



FACTS Technology - Possible Benefits

• Control of power flow as ordered. Increase the loading capability of lines to their thermal capabilities, including short term and seasonal.

• Increase the system security through raising the transient stability limit, limiting short-circuit currents and overloads, managing cascading blackouts and damping electromechanical oscillations of power systems and machines.

• Provide secure tie lines connections to neighboring utilities and regions thereby decreasing overall generation reserve requirements on both sides.

• Provide greater flexibility in siting new generation.

• Reduce reactive power flows, thus allowing the lines to carry more active power.

• Reduce loop flows.

• Increase utilization of lowest cost generation.


FACTS and HVDC: Complimentary SolutionsHVDCIndependent frequency and controlLower line costsPower control, voltage control,stability control

FACTSPower control, voltage control,stability control

Installed Costs (millions of dollars)

Throughput MW HVDC 2 Terminals FACTS

2000 MW $ 40-50 M $ 5-10 M 500 MW $ 75-100M $ 10-20M1000 MW $120-170M $ 20-30M2000 MW $200-300M $ 30-50M

(*)Hingorani/Gyugyi


FACTS and HVDC: Complimentary Solutions

Large market potential for FACTS is within the ac system on a value-added basis, where:

• The existing steady-state phase angle between bus nodes is reasonable• The cost of a FACTS device solution is lower than HVDC or other alternatives• The required FACTS controller capacity is less than 100% of the transmission throughput rating

HVDC Projects: Applications

Submarine cable

Long distance overhead transmission

Underground Transmission

Connecting AC systems of different or incompatible frequencies


FACTS Attributes for Different ControllersFACTS Controller Control Attributes

Static Synchronous Compensator(STATCOM without storage)

Voltage control, VAR compensation, damping oscillations, voltagestability

Static Synchronous Compensator(STATCOM with storage, BESS, SMES,large dc capacitor)

Voltage control, VAR compensation, damping oscillations, transientand dynamic stability, voltage stability, AGC

Static VAR Compensator (SVC, TCR,TCS, TRS

Voltage control, VAR compensation, damping oscillations, transientand dynamic stability, voltage stability

Thyristor-Controlled Braking Resistor(TCBR)

Damping oscillations, transient and dynamic stability

Static Synchronous Series Compensator(SSSC without storage)

Current control, damping oscillations, transient and dynamic stability,voltage stability, fault current limiting

Static Synchronous Series Compensator(SSSC with storage)

Current control, damping oscillations, transient and dynamic stability,voltage stability

Thrystor-Controlled Series Capacitor(TCSC, TSSC)


Thyristor-Controlled Series Reactor(TCSR, TSSR)


Thyristor-Controlled Phase-ShiftingTransformer (TCPST or TCPR)

Active power control, damping oscillations, transient and dynamicstability, voltage stability

Unified Power Flow Controller (UPFC) Active and reactive power control, voltage control, VARcompensation, damping oscillations, transient and dynamic stability,voltage stability, fault current limiting

Thyristor-Controlled Voltage Limiter(TCVL)

Transient and dynamic voltage limit

Thyristor-Controlled Voltage Regulator(TCVR)

Reactive power control, voltage control, damping oscillations,transient and dynamic stability, voltage stability

Interline Power Flow Controller (IPFC) Reactive power control, voltage control, damping oscillations,transient and dynamic stability, voltage stability


X

Regulating Bus VoltageCan Affect Power Flow Indirectly / Dynamically

E1 / 1 E2 / 2I P&Q

P1 = E1 (E2 . sin ())/X

FACTS Implementation - STATCOM


Line Impedance CompensationCan Control Power Flow Continuously

E1 / 1 E2 / 2P&Q

P1 = E1 (E2 . sin ()) / Xeff

X

FACTS Implementation - TCSC

Xeff = X- Xc

The alternative solutions need to be distributed; often series compensation has to be installed in several places along a line but many of the other alternatives would put both voltage support and power flow control in the same location. This may not be useful. For instance, if voltage support were needed at the midpoint of a line, an IPFC would not be very useful at that spot. TCSC for damping oscillations ...


X

Breaker

Slatt TCSC

TCSC module #1

MOV

TCSC

#2

TCSC

#5

TCSC

#3

TCSC

#6

TCSC

#4



X X

Damping Circuit

Damping Circuit

Breaker

Kayenta TCSC

TCSC 15 to 60 Ω

MOV

Breaker

MOV MOV

40 Ω 55 Ω



X

E1 / 1 E2 / 2I

P&Q

FACTS Implementation - SSSC

P1 = E1 (E2 . sin ()) / Xeff

Xeff = X - Vinj/I


X

E1 / 1 E2 / 2I

P&Q

Regulating Bus Voltage and Injecting Voltage In Series With the LineCan Control Power Flow

P1 = E1 (E2 . sin ()) / Xeff

Xeff = X - Vinj / I

FACTS Implementation - UPFC

Q1 = E1(E2 - E2 . cos ()) / X


Shunt Inverter Series Inverter

Unified Power Flow Controller

Series Transformer

Shunt

Transformer

FACTS Implementation - UPFC


X

Regulating Bus Voltage Plus Energy StorageCan Affect Power Flow Directly / Dynamically

E1 / 1 E2 / 2I

P&Q

Plus Energy Storage

FACTS Implementation - STATCOM + Energy Storage


X

E1 / 1 E2 / 2I

P&Q

FACTS Implementation - SSSC + Energy Storage

Plus Energy Storage

Voltage Injection in Series Plus Energy StorageCan Affect Power Flow Directly / Dynamicallyand sustain operation under fault conditions


X

E1 / 1 E2 / 2

IP&Q

Plus Energy Storage

Regulating Bus Voltage + Injected Voltage + Energy StorageCan Control Power Flow Continuously, and Support Operation Under Severe Fault Conditions (enhanced performance)

FACTS Implementation - UPFC + Energy Storage


Shunt Inverter

Series Inverter

Unified Power Flow Controller - SMES Interface

SMES Chopper and Coil

1000μF

1000μF

1000μF

1000μF



SMES Chopper and Coil - Overvoltage Protection

UPFC Grounding

MOV



$

Regulating Bus Voltage + Energy Storage + Line Impedance CompensationCan Control Power Flow Continuously, and Support Operation Under Severe Fault Conditions (enhanced performance)

FACTS Implementation - TCSC + STACOM + Energy Storage


E1 / 1 E3 / 3

FACTS Implementation - IPFC

P12 = E1 (E2 . sin (1- 2)) / X

E2 / 2

P13 = E1 (E2 . sin (1- 3)) / X


Series Inverter #1 Series Inverter #2

Interline Power Flow Controller

Series Transformer, Line 2

Series Transformer, Line 1

FACTS Implementation - IPFC


Increased Power Transfer

Enhanced Power Transfer and Stability:Technologies’ Perspective

FastReal Power Injection

and Absorption

FastReactive Power Injection

and Absorption

FastReactive Power Injection and

Absorption

CompensationDevices

FACTS DevicesEnergy Storage

Electric Grid Electric Grid

P

QQ

P AdditionalStability Margin

PTSSCSSSCUPFC

SMES

0 0.5 1 1.5 2 2.5 30

0.5

1

1.5

2

Phase Angle

Pow

er T

ransf

er

AccelerationArea

DecelerationArea

StabilityMargin

STATCOM STATCOM

TSSCSSSCUPFC


STATCOMReactive Power OnlyOperates in the vertical axis only

STATCOM + SMESReal and Reactive PowerOperates anywhere within thePQ Plane / Circle (4-Quadrant)

P

Q

The Combination or Real and Reactive Power will typically reduce the Rating of the Power Electronics front end interface.Real Power takes care of power oscillation, whereas reactive power controls voltage.

The Role of Energy Storage: real power compensation can increase operating control and reduce capital costs

P - Active PowerQ - Reactive Power

MVA Reduction

FACTS + Energy Storage


SMES Power (MW)

Add

itio

nal P

ower

Tra

nsfe

r(M

W)

Closer to generation

Closer to load centers

FACTS + Energy Storage - Location Sensitivity


2 STATCOMs 1 STATCOM + SMES

Voltage and Stability Control Enhanced Voltage and Stability Control

Syst

em F

requ

ency

(H

z)

60.8

59.2

time (sec) time (sec)

(2 x 80 MVA Inverters) ( 80 MVA Inverter + 100Mjs SMES)

Syst

em F

requ

ency

(H

z)

60.8

59.2

Syst

em F

requ

ency

(H

z)

60.8

59.2

time (sec)

No Compensation

Enhanced Power Transfer and Stability:Location and Configuration Type Sensitivity


FACTS For Optimizing Grid Investments

FACTS Devices Can Delay Transmission Lines ConstructionBy considering series compensation from the very beginning, power transmission between regions can be planned with a minimum of transmission circuits, thus minimizing costs as well as environmental impact from the start.

The Way to Proceed

· Planners, investors and financiers should issue functional specifications for the transmission system to qualified contractors, as opposed to the practice of issuing technical specifications, which are often inflexible, and many times include older technologies and techniques) while inviting bids for a transmission system.

· Functional specifications could lay down the power capacity, distance, availability and reliabilityrequirements; and last but not least, the environmental conditions.

· Manufacturers should be allowed to bid either a FACTS solution or a solution involving the building of (a) new line(s) and/or generation; and the best option chosen.


Specifications

(Functional rather than Technical )

Transformer ConnectionsHigher-Pulse OperationHigher-Level OperationPWM ConverterPay Attention to Interface Issues and Controls

ConverterIncrease Pulse NumberHigher LevelDouble the Number of Phase-Legs and Connect them in ParallelConnect Converter Groups in ParallelUse A Combination of several options listed to achieve required rating and performance


Technology Transmission LineTransfer Enhancement

Cost Range Operating principle ProcurementAvailability

Reconductor lines Increase thermal capacity $50K to $200K permile

Increases thermal limit for line Competitive

Fixed or Switched ShuntReactors

Voltage reduction – LightLoad Management

$8-$12 kVAR Compensates for capacitive var-load

Competitive

Fixed or Switched ShuntCapacitors

Voltage support andstability

$8-$10 kVAR Compensates for inductive var-load

Competitive

Fixed or Switched SeriesCapacitors

Power flow control,Voltage support andStability

$12-$16 kVAR Reduces inductive lineimpedance

Competitive

Static VAR Compensators Voltage support andstability

$20-$45 kVAR Compensates for inductiveand/or capacitive var-load

Competitive

Thyristor Controlled SeriesCompensation (TCSC)

Power flow control,Voltage support andstability

$25-$50 kVAR Reduces or increases inductiveline impedance

Limitedcompetition

STATCOM Voltage support andstability

$80-$100 kVAR Compensates for inductive andcapacitive var-load

Limitedcompetition

STATCOM w/SMES Voltage support andstability

$150-$300 kW Compensates for inductiveand/or capacitive var-load plusenergy storage for active power

Limited

Unified Power FlowController (UPFC)

Power flow control,Voltage support, andStability

$150-$200 kW SVC and TCSC functions plusphase angle control

Sole source

Unified Power FlowController (UPFC) w/SMES

Power flow controlVoltage support andStability,

$250-$350 kW SVC and TCSC functions plusvoltage regulator, phase anglecontroller and energy storage

Sole source

Shaded area indicates technologies that are either permanently connected or switched on or off with mechanical switches. (i.e. these arenot continuously controllable)

Cost Considerations


Hardware

Eng & Project Mgmt.

Installation

Civil Works

Commissioning

Insurance

Cost Considerations

Cost structure

The cost of a FACTS installation depends on many factors, such as power rating, type of device, system voltage, system requirements, environmental conditions, regulatory requirements etc. On top of this, the variety of options available for optimum design renders it impossible to give a cost figure for a FACTS installation. It is strongly recommended that contact is taken with a manufacturer in order to get a first idea of costs andalternatives. The manufacturers should be able to give a budgetary price based on a brief description of thetransmission system along with the problem(s) needing to be solved and the improvement(s) needing to beattained.

(*) Joint World Bank / ABB Power Systems PaperImproving the efficiency and quality of AC transmission systems


Technology & Cost Trends

I

$$$

$

I

additional cost savings possible

$


Concerns About FACTS

CostLosses

Reliability


Economics of Power Electronics

Sometimes a mix of conventional and FACTS systems has the lowest costLosses will increase with higher loading and FACTS equipment more lossy than conventional onesReliability and security issues - when system loaded beyond the limits of experienceDemonstration projects required

Cost of SystemCost of System

100% Power 100% Power Electronics Electronics

100% 100% ConventionalConventional

Delta-PDelta-P11

Delta-PDelta-P22 Delta-PDelta-P33

Delta-PDelta-P44

Stig Nilson’s paper


Operation and Maintenance

Operation of FACTS in power systems is coordinated with operation of other items in the same system, for smooth and optimum function of the system. This is achieved in a natural way through the Central Power System Control, with which the FACTS device(s) is (are) communicating via system SCADA. This means that each FACTS device in the system can be operated from a central control point in the grid, where the operator will have skilled human resources available for the task. The FACTS device itself is normally unmanned, and there is normally no need for local presence in conjunction with FACTS operation, although the device itself may be located far out in the grid.

Maintenance is usually done in conjunction with regular system maintenance, i.e. normally once a year. It will require a planned standstill of typically a couple of days. Tasks normally to be done are cleaning of structures and porcelains, exchanging of mechanical seals in pump motors, checking through of capacitors, checking of control and protective settings, and similar. It can normally be done by a crew of 2-3 people with engineer´s skill.

Joint World Bank / ABB Power Systems PaperImproving the efficiency and quality of AC transmission systems


Impact of FACTS in interconnected networksThe benefits of power system interconnection are well established. It enables the participating parties to share the benefits of large power systems, such as optimization of power generation, utilization of differences in load profiles and pooling of reserve capacity. From this follows not only technical and economical benefits, but also environmental, when for example surplus of clean hydro resources from one region can help to replace polluting fossil-fuelled generation in another.

For interconnections to serve their purpose, however, available transmission links must be powerful enough to safely transmit the amounts of power intended. If this is not the case, from a purely technical point of view it can always be remedied by building additional lines in parallel with the existing, or by uprating the existing system(s) to a higher voltage. This, however, is expensive, time-consuming, and calls for elaborate procedures for gaining the necessary permits. Also, in many cases, environmental considerations, popular opinion or other impediments will render the building of new lines as well as uprating to ultrahigh system voltages impossible inpractice. This is where FACTS comes in.

Examples of successful implementation of FACTS for power system interconnection can be found among others between the Nordic Countries, and between Canada and the United States. In such cases, FACTS helps to enable mutually beneficial trade of electric energy between the countries.Other regions in the world where FACTS is emerging as a means for AC bulk power interchange between regions can be found in South Asia as well as in Africa and Latin America. In fact, AC power corridors equipped with SVC and/or SC transmitting bulk power over distances of more than 1.000 km are a reality today.

Joint World Bank / ABB Power Systems PaperImproving the efficiency and quality of AC transmission systems


Power Quality Issues

1 – Background (Power Quality – Trade Mark)2 – The Need For An Integrated Perspective of PQ3 – Harmonics4 – Imbalance5 – Voltage Fluctuations6 – Voltage Sags 7 – Standards, Limits, Diagnostics, and Recommendations

Flexibility, Compatibility, Probabilistic Nature, Alternative Indices8 – Combined effects9 – Power Quality Economics10 – Measurement Protocols11 – Probabilistic Approach12 – Modeling & Simulation13 – Advanced Techniques

(Wavelet, Fuzzy Logic, Neural Net, Genetic Algorithms)14 – Power Quality Programs


Compatibility: The Key Approach


kUref

kUrefkUkRTL ,0max

Relative Trespass Level (RTL)

Uk - measured or calculated harmonic voltage

Uref - harmonic voltage limit (standard or particular equipment)

k - harmonic order

2 4 6 8 10 12 140

2

4

6

88

0

RTL k

132 k

0 0.05 0.10

2

4

6

88

0

RTL k

.10 Uk


Possible Problems

Caution SevereDistortions

DangerousLevels

NormalLevels

A B C D E F G RTL0

1

Norm

alB

elowN

ormal

Over

Heating

Very

Hot

Below

Norm

alab

cd

e

Equ

ipm

ent

Mal

fun c

t io n

Mag

nitu

de $

Ph a

se

Ang

le

Individual Harmonics (Vh)Equipment Malfunction

Fuzzy - Color Code CriteriaNo Problem

Caution

Possible Problems

Imminent Problems

Harmonic Distortion Diagnostic Index Applying Fuzzy Logic Comparisons

Alternative Approach


HarmonicsDefinition of harmonics

Sources of harmonics

Effects of harmonics

Mitigation methods

Considerations on the extra costs due to harmonic pollution

Measurement results

Voltage fluctuations/FlickerDefinitions

Sources of voltage fluctuations/flicker

Effects of voltage fluctuations/flicker

Mitigation methods

Measurement results


Voltage DipsDefinition

Sources of voltage dips

Effects of voltage dips

Mitigation methods

Measurement results

Conclusions

UnbalanceDefinition

Sources of unbalance

Effects of unbalance

Mitigation methods

Measurement results

Transient Overvoltages


How To Interpret This?


Generation Delivery Conversion Processing

CentralStation

T&D AC-ACSupplies

Motion

Environmental Maintainability Availability Safety Efficiency Reliability Performance PricePower Quality

Power System Value Chain

Power Electronics Systems and Components

SMESBatteries

FACTSSMESPQ Parks

UPS Appliances

INPUTS OUTPUTS

Val

ue D

imen

sion

s

Energy Power Communication

Light / Motion

Utility User

The Total Quality Environment


Benefits of a Power Quality Program

Offer options to customers with PQ concerns

Attract new business to area (regional development)

Facilitate load retention of current customers

Meet changing needs of customer's new technology

Discourage co-generation or self-generation as solutions of PQ Problems

Enhance and public image - as customers hold utility accountable for both PQ and reliability

Add value to service

Serve customers' best interests and save customers money

Support utility mission


Suggested Topics for Investigation

FACTS

Inclusion of Energy Storage

Topology Combination

Power Quality

Effects of Power Quality on Relaying Equipment

Cost/Benefit Analysis of PQ

Application of Advanced Techniques


Conclusions

• Future systems can be expected to operate at higher stress levels• FACTS could provide means to control and alleviate stress• Reliability of the existing systems minimize risks (but not risk-free)• Interaction between FACTS devices needs to be studied• Existing Projects - Met Expectations• More Demonstrations Needed• R&D needed on avoiding security problems (with and w/o FACTS)• Energy storage can significantly enhance FACTS controllers performance


ConclusionsPower supply industry is undergoing dramatic change as a result of deregulation and political and economical maneuvers. This new market environment puts demands for flexibility and power quality into focus. Also, trade between companies and countries of electric power is gaining momentum, to the benefit of all involved. This calls for the right solutions as far as power transmission facilities between countries as well as between regions within countries are concerned.

FACTS Benefits included:-An increase of synchronous stability of the grid;-An increased voltage stability in the grid;-Decreased power wheeling between different power systems;-Improved load sharing between parallel circuits;-Decreased overall system transmission losses;-Improved power quality in grids.

•The choice of FACTS device is simple and needs to be made the subject of detailed system studies, taking all relevant requirements and prerequisites of the system into consideration, so as to arrive at the optimum technical and economical solution. In fact, the best solution may often be lying in a combination of devices.


From an economical point of view, more power can be transmitted over existing or new transmission grids with unimpeded availability at an investment cost and time expenditure lower, or in cases even far lower than it would cost to achieve the same with more extensive grids. Also, in many cases, money can be saved on a decrease ofpower transmission losses.

From an environmental point of view, FACTS enables the transmission of power over vast distances with less or much less right-of-way impact than would otherwise be possible. Furthermore, the saving in transmission losses may well bring a corresponding decrease in need for generation, with so much less toll on the environment.

All these things help to enable active, useful power to reach out in growing quantities to growing populations under safe and favorable conditions all over the world. Also, individual countries´ own border lines no longer constitute any limit to power industry. With FACTS, power trade to the benefit of many can be established to a growing extent across borders, by making more efficient use of interconnections between countries, new as well as existing.

Conclusions


Conclusions

A Balanced and Cautious Application

The acceptance of the new tools and technologies will take time, due to the computational requirements and educational barriers.

The flexibility and adaptability of these new techniques indicate that they will become part of the tools for solving power quality problems in this increasingly complex electrical environment.

The implementation and use of these advanced techniques needs to be done with much care and sensitivity. They should not replace the engineering understanding of the electromagnetic nature of the problems that need to be solved.


Questions and Open Discussions


Appendix

"an overview on facts and power quality issues: technical challenges, research opportunities

Documents