FACTS & HVDC Controllers

by

Issarachai Ngamroo, Ph.D.

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

SirindhornSirindhorn International Institute of TechnologyInternational Institute of TechnologyThammasatThammasat UniversityUniversity

December 16, 2004December 16, 2004

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

Why FACTS & HVDC ?

1. Connection of generation

Some of power plants (large hydro and thermal stations) can be located near the load and can be connected by relatively short AC lines to the grid. But some of them have to be located far from the load, particularly hydro plants and coal plants, and the transmissions often has to be HVDC or AC with FACTS.

FACTS or HVDC

Three Gorges HVDCs, China

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

Why FACTS & HVDC ?

2. Connection of isolated loadsWith isolated loads we mean loads that due to geographical or other conditions are not connected to a major grid but have to rely on (small) localgeneration. Examples are

islands and remote towns and villages. The local generation is often expensive and not environmentally sound. If an isolated load can be connected to a main grid the cost of electricity goes down. The transmissions options are often HVDC/HVDC Light or AC with FACTS.

HVDC or FACTS

The HVDC link to Gotland, Sweden

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

Why FACTS & HVDC ?3. Interconnection

It is increasingly economic to interconnect with neighbouring grids to benefit from the pooling of resources. We have selected to distinguish interconnections within a grid and new interconnections between grids.

3.1 Within a grid (same frequency)By this we mean const ructing or strengthening a circuit between

two points that belongs to the same synchronous grid (or group of grids). If the electrical distance is short or of moderate length, it is often enough to build one or two uncompensated AC-lines or cables. But with increasing distance, the addition of FACTS and utilizing HVDC can be the optimum choice.

HVDC or FACTS

50 Hz 50 Hz

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

Why FACTS & HVDC ?

This means linking two separate networks that are not running in synchronism so that exchange of power can take place. If they are linked by an AC circuit assuming the same nominal frequency, then the combined network becomes one synchronous grid with common frequency control. But if the power transfer is on a HVDC link, the networks can maintain their separate frequencies.

HVDC

Between grids

3.2 Between grids (different frequencies)

50 Hz 60 Hz

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

Why FACTS & HVDC ?4. Increasing existing grid utilization

In many countries new transmission facilities are not permitted and transmission grids world-wide are as a consequence of load growth stressed closer to their power transfer limits. In many cases FACTS solutions appear as an attractive short term means to raise the transfer limit or to more generally enhance the reliability of the existing grid.

FACTS solutions is an attractive means to raise the capability or enhance the reliability of the grid.

new transmission lines are expensive and not permitted

FACTS

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

Flexible AC Transmission Systems (FACTS) are the name given to the application of power electronics devices to control the power flows and other quantities in power systems.

IEEE Definitions

FACTS: AC transmission systems incorporating the power electronic-based and other static controllers to enhance controllability and increase power transfer capability.

FACTS Controllers: A power electronic based system & other static equipment that provide control of one or more AC transmission parameters.

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

FACTS Concepts

( )1 212 1 2sinVVP

xδ δ= −

jx1 1V δ∠ 2 2V δ∠

12 12P jQ+

Bus 1 Bus 2

Active Power Flow

Control Variables1. Phase Difference : δ1-δ2 2. Voltage : V1, V2 3. Line Reactance : x

( )2

1 1 212 1 2cosV VVQ

x xδ δ= − −Reactive Power Flow

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

Objectives of FACTS Controllers1. Solve Power Transfer Limit & Stability Problems

1.1 Thermal Limit1.2 Voltage Limit1.3 Stability Limit

1.3.1Transient Stability Limit 1.3.2 Small Signal Stability Limit1.3.3 Voltage Stability Limit

2. Increase (control) power transfer capability of a line3. Mitigate subsynchronous resonance (SSR)4. Power quality improvement5. Load compensation6. Limit short circuit current7. Increase the loadability of the system

Demerits1. Expensive 2. Controller interactions are possible

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

Types of FACTS Controllers

FACTS

Series-Shunt

Series-Series

• ThyristorControlledSeries Capacitor(TCSC)

• Static Synchronous Series Compensator (SSSC)

Series Shunt• Static Var

Compensator (SVC)

• Static Synchronous Compensator (STATCOM)

• Unified Power Flow Controller(UPFC)

• Interline Power Flow Controller(IPFC)

Thyristor-based FACTS Controllers: TCSC, SVC ect.

VSC-based FACTS ControllersSSSC, STATCOM, UPFC, IPFC

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT Figure: Basic type of FACTS controllers: (a) general symbol

for FACTS controller; (b) Series Controller; (c) Shunt Controller; (d) Unified Series-Series Controller; (e) Coordinated Series and Shunt Controller and (f) Unified Series-Shunt Controller.

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

Series Controllers

1. It could be a variable impedance such as capacitor, reactor, etc or power electronics based variable source of main frequency, sub-synchronous or harmonic frequencies ( or a combination).

2. All series controller inject voltage in series with line.3. If voltage is in phase quadrature with the line

current, it only supplies or absorbs the variablereactive power.

Shunt Controllers

1. It could be a variable impedance, variable source or a combination of these.

2. All shunt controllers inject current into the system at the point of connection.

3. If injected current is in quadrature with the linevoltage, it only supplies or absorbs the variable reactive power.

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

Combined Series-Shunt Controllers

1. It could be a combination of separate shunt and series controllers as coordinated or unified. UPFC is example of this.

2. Combined series and shunt controller injects current into the system with shunt part and voltage in series with series part of controller.

3. When shunt and series controllers are unified there can be a real power exchange between shunt and series controllers via DC power link.

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

Static Var Compensator (SVC)

• Regulate the linevoltage by connecting an inductor or a capacitor in shunt with the transmissionline

• Thyristor Controlled Reactor (TCR)

• Thyristor Switched Capacitor (TSC)

A shunt-connected static var generator or absorber whose outputis adjusted to exchange capacitive or inductive current so as tomaintain or control the bus voltage.

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

Thyristor Controller Reactor (TCR)

LIL

α

V

L

V - ΔV

∆QSVC

A shunt-connected, thyristor-controlled inductor whose effectivereactamce is varied in a continuous manner by partial-conductioncontrol of the thyristor valve.

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

TCR: Bus voltage and current

σ = 2(π-α)

σ : conduction angle

α : firing angle

BTCR (α) = 2(π – α) + sin 2α

πXL

= σ – sin σ

πXL

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

Control Characteristic of the TCR Susceptance, BTCR

• BTCR is maximum at full conduction ( α = 90° or σ = 180° )

BTCR(MAX) = 1/XL

• BTCR is minimum at α = 180 ° or σ = 0°

BTCR(MIN) = 0

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

Thyristor Switched Capacitor (TSC)

CIC

α

V

C

V + ΔV

∆QSVC

A shunt-connected, thyristor-switched capacitor whose effectivereactance is varied in a stepwise manner by full-or zero-Conduction operation of the thyristor valve.

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

SVC Applications1. Damping of power oscillations

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

Voltage Stability Enhancement

thV VI

thX

P jQ+

2. Voltage Stability Enhancement

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

3. Maximum Power Transfer Improvement

No SVC P = (V2/X) sin δ

With SVC P = (2V2/X) sin (δ/2)

QSVC = (4V2/X) (1 - cos (δ/2))

0 5 0 1 0 0 1 5 00

1

2

3

4

5

6

a n g le ( d e g )

P (p

u)

Q s v c ( m a x ) = 4 * P m a x = 5 .3 2

P m a x ( c o m p ) = 2 * P m a x = 2 .6 6

P m a x ( u n c o m p ) = 1 .3 3

jX/2

P + jQV 0V δ

jX/2

SVC

V

QSVC

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

4. Transient Stability Margin Enhancement

0 20 40 60 80 100 120 140 160 1800

0 .5

1

1 .5

2

2 .5

3

A cce lera tin gA rea

D ece lera tin gA rea

D ece lera tin gA rea M arg in(S h u n t C o m p .)

Equal-Area Criterion With SVC, decelerating area margin is larger.

jX/2 jX/2

SVC

V

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

Thyristor Control Series Capacitor (TCSC)

Tunable Parallel LC Circuit

Swedish National Grid TCSC at Stode

A capacitive reactance compensator which consists of a series capacitorbank shunted by a thyristor-controlled reactor in order to provide a smoothly variable series capacitive reactance.

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

TCSC Applications1. Transient Stability Enhancement

( )1 212( ) 1 2sinnc

VVPx

δ δ= −

( )1 212( ) 1 2sinc

c

VVPx x

δ δ= −−

With SC

Without SC

P12(max) with SC > P12(max) without SC

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

2. Voltage Stability Enhancement

Decreasing line reactance increases maximum active power demand

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

3. Damping of Power Oscillations

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

4. Subsynchronous Resonance (SSR) Mitigation

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

Voltage Source Converter (VSC)-based FACTS Controllers : STATCOM, SSSC, UPFC

Voltage Source Converter

Vs Vc

P + jQ

DC Energy Storage

PowerSystem

AC Voltage Source with controllable

Magnitude & PhaseXt

P + jQVc ӨVs 0

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

Active & Reactive Power Control by VSC

Xt

P + jQVs 0° Vc Ө

P = (VsVc/Xt) sin Ө

Q = Vs (Vccos Ө - Vs)/XtVs

Vc

Ө

Control Variables for Power Flow Direction

1. Active Power Flow => Phase difference Ө2. Reactive Power Flow => Voltage magnitude Vc

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

Active & Reactive Power Diagram of VSC

P

QSupplies PSupplies Q

Rectifier Inverter Vs

Vc

Ө

Vs

Vc

ӨӨVc

Vs

VsӨ

Vc

Absorbs PSupplies Q

Absorbs PAbsorbs Q

Supplies PAbsorbs Q

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

Static Synchronous Compensator (STATCOM)

Vc

Vs

IqQ

Vdc

+-Idc

Vs

Vc

Xt

Iq

STATCOM is the voltage-source converter, which converts a DC input voltage into AC output voltage in order to compensate the active and reactive needed by the system.

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

Iq

Vc > Vs

Vc < Vs

Vac

Inductive Mode(absorbs Q)

-Iq

Capacitive Mode(supplies Q)

At AC TerminalVs

Vc

Xt

Iq

Control Modes of STATCOM

Advantages

1. Voltage Stability Enhancement2. Angle Stability Improvement3. Power Quality etc.

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

Static Synchronous Series Compensator (SSSC)

XtIVq

IVq

Q

SSSC is the solid-state synchronous voltage source employing an appropriate DC to AC inverter with gate turn-off thyristor used for series compensation of transmission lines.

I

Vq

Capacitive Mode(supplies Q)

Inductive Mode(absorbs Q)

-Vq

At AC Terminal

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

Control Modes of SSSC

XtIVq VrVs

- Injected voltage (Vq) emulates an inductive or a capacitive in series with the transmission line.

Vs Vr

VL

Vq

δVs Vr

VLVq

δ

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

Unified Power Flow Controller (UPFC)

VV + Vpq

Vpq

• Independent reactive power exchange between shunt/series converters and power system.

• Active power constraint : Pshunt = Pseries

VpqI V V + Vpq

QQP

STATCOM SSSC

UPFC is a combination of STATCOM and SSSC, which are coupled via a common DC link, to allow bi-directional flow of real power between the series output terminals of the SSSC and the shunt output terminals of the STATCOM, and are controlled to provide concurrent real and reactive series line compensation without an external electric energy source.

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

HVDCThe High Voltage Direct Current (HVDC) technology

is used to transmit electricity over long distances by overhead transmission lines or submarine cables. It is also used to interconnect separate power systems, where traditional alternating current (AC) connections can not be used.

Converter Converter

DC line or cableAC AC

Limitations of HVAC Transmission1. Reactive Power Loss 2. Stability 3. Current Carrying Capacity 4. Ferranti Effect

Solve byHVDC

Transmission

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

Advantages of HVDC 1. Total investment cost of HVDC transmission is lower.

Investment Cost

TerminalCost

TransmissionLine Cost Tower Cost Land Cost

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

Terminal Cost & Transmission Line Cost

1.1 A HVDC transmission line costs less than an AC line for the same transmission capacity.

1.2 DC terminal cost is more expensive than AC terminal cost.

1.3 But above a certain distance, the so called "break-even distance",the HVDC alternative will always give the lowest cost.

1.4 Break even distance: 600 ~ 800km

Total DC cost < Total AC cost

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

Tower Cost & Land Cost

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

2. HVDC cable transmissions for long distance water crossing

In a long AC cable transmission, the reactive power flow due to the large cable capacitance will limit the maximum possible transmission distance. With HVDC there is no such limitation, why, for long cable links, HVDC is the only viable technical alternative. The longest HVDC submarine cable presently in operation is the 250 km Baltic Cabletransmission between Sweden and Germany. Several HVDC submarine cables of 500 km or more are currently being planned in Europe and elsewhere.

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

3. HVDC transmission has lower losses.

An optimized HVDC transmission line has lower losses than AC lines for the same power capacity. The losses in the converter stations have of course to be added, but since they are only about 0.6 % of the transmitted power in each station, the total HVDC transmission losses come out lower than the AC losses in practically all cases.HVDC cables also have lower losses than AC cables.The diagram below shows a comparison of the losses for overhead line transmissions of 1200 MW with AC and HVDC.

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

4. HVDC transmission for asynchronous connection

Many HVDC links interconnect incompatible AC systems.Several HVDC links interconnect AC system that are not running in synchronism with each other. System frequencies of both areas may be same or different.

Examples4.1 Interconnected System with same frequency

a) UCTE (Union for the Co-ordination of transmission of Electricity) and Nordel

(websites: www.ucte.org and www.nordel.org)b) US Eastern & Western

4.2 With different frequency: In Japan 50-60 Hz systems

Converter Converter

DC line or cableAC AC

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

Interconnection with Same Frequency

The Nordel power system in Scandinavia is not synchronous with the UCTEgrid in western continental Europe even though the nominal frequencies are the same.

The power system of eastern USA is not synchronous with that of western USA. The reason for this is that it is sometimes difficult or impossible to connect two AC networks due to stability reasons.

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

Interconnection with Different Frequencies

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

Other advantages of HVDC

5. Require less space compared to ac for same voltage rating and size

6. Ground can be used as returned conductor

7. Less corona loss and radio interference

8. No charging current

9. No skin and Ferranti effect

10. No switching transient

11. An HVDC transmission limits short circuit currents

12. HVDC transmission for controllability of power flow

13. Environmental benefits.

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

Disadvantages of HVDC1. High cost of terminal equipments

HVDC transmission system requires converters at both ends and those are very expensive than ac equipments

2. Introduction of harmonicsConverter generate considerable amount of harmonics

both on ac and dc sides. Some harmonics are filtered out but some harmonics still enter into the system and affect the apparatus These harmonics may also interfere with communication system.

3. Blocking of reactive power DC lines block the flow of reactive power from one end

to another end. These reactive powers are required by some load that must be fulfilled by the inverters.

4. Point-to-point transmission not possible.It is not possible to tap dc power at several locations in

the line. Wherever power is to be trapped, a control station is required and coordinated with other terminals. This increases the complexity and cost of the systems.

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

Types of HVDC Links1. Monopolar & Bipolar

Monopolar- Having one

conductor and ground is used as return path.

Bipolar-There are two conductors (Poles). One operates at

+v polarity and other is on –v polarity.

-During fault in one pole, it works as monopolar.

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

2. HVDC back-to-back station : Japan 50/60 Hz systems

2.1 To create an asynchronous interconnection between two AC networks, which could have the same or different

frequencies.

2.2 Both the rectifier and the inverter are located in the same station

2.3 The direct voltage level can be selected without consideration to the optimum values for an overhead line and a cable, and is therefore normally quite low, 150 kV or lower. The only major equipment on the DC-side is a smoothing reactor.

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

3. HVDC multi-terminal system

3.1 A multi-terminal HVDC transmission is an HVDC system with more than two converter stations.

3.2 A multi-terminal HVDC transmission is more complex than an ordinary mono/bi-polars transmission. In particular, the control system is more elaborate and the telecommunicationrequirements between the stations become larger.

3.3 There is only one large-scale multi-terminal HVDC system in operation in the world today. It is the 2000 MW Hydro Québec – New England transmission

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

Main Components of an HVDC System

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

Converter

1. Sending end converter works as rectifier (converts AC power to DC power), however converter at receiving end works as inverter

(converts DC power to AC power).

2. Several thyristors are connected in series/ parallel to form a valve to achieve higher voltage/current ratings.

3. Line-commutated converter: use thyristor as switch Self-commutated converter: use Gate-turn off (GTO) thyristor etc, as switch

3 phase arrangement inside a valve hall (500 kVdc / 825MW).

3 phase converter arrangement(thyristor and arresters):

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

HVDC Converter Transformers

1. Voltage transformation between the AC supply and the HVDC system.

2. Supply of AC voltages in two separate circuits with a relative phase shift of 30electrical degrees for reduction of low order harmonics, especially the 5th and 7th harmonics.

3. Act as a galvanic barrier between the AC and DC systems to prevent the DC potential to enter the AC system.

4. Reactive impedance in the AC supply to reduce short circuit currents and to control the rate of rise in valve current during commutation.

For six-pulse converter, a conventional 3-phase or three single phasetransformers is used. Converter transformers serve several functions.

1 phase / 3 winding /354 MVA

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

DC Smoothing ReactorsA DC reactor is normally connected in series with the converter.

The main objectives of the reactor are:1. To reduce the harmonic currents on the DC side of the converter.2. To reduce the risk of commutation failures by limiting the rate of

rise of the DC line current at transient disturbances in the AC or DC systems.

Air-core smoothing reactor in the FennoSkan HVDC transmission

Oil-insulated smoothing reactorin the Rihand - Dehli HVDC

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

AC/DC Filters1. Harmonics generated by converters are of the order of

np±1 in AC side and np in DC side where p is number of pulses and n is integer.

2. Filters are used to provide low impedance path to the ground for the harmonic currents.

3. They are connected to the converter terminals so that harmonics should not enter to the AC system.

500 kV DC-filter with Suspended capacitor

Two three-phase AC filter banks for 400 kV at the Tjele HVDC converter station, Denmark.

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

Reactive Power SourcesConventional HVDC converters always have a demand for

reactive power. At normal operation, a converter consumes reactive power in an amount that corresponds to approximately 50 % of the transmitted active power. The least costly way to generate reactive power is in shunt connected capacitor banks.

400kV shunt capacitorat the Dannebo HVDC

converter station, Sweden

Capacitor Bank

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

HVDC Light1. HVDC Light unit sizes range from a few tens of MW to presently

350 MW and for DC voltages up to ±150 kV and units can be connected in parallel.

2. HVDC Light consists of two elements: converter stations and a pair of cables. The converter stations are Voltage Source Converters (VSCs) employing state of the art turn on/turn off IGBT power semiconductors. (IGBT = InsulatedGate Bipolar Transistor) => Self-commutated switch

3. VSC => Active Power & Reactive Power are controllable.

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

HVDC Light Applications1. Infeed of small-scale generation e.g. small hydraulic

generators, windmill farms and solar power etc.2. Feed small local loads, isolated load, and island 3. Asynchronous grid connection etc.

Rectifier Inverter

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

Conventional HVDC & HVDC LightHVDC Light main circuit Conventional HVDC

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

Whether HVDC or FACTS ?

1. Both are complementary technologies.

2. The role of HVDC is to interconnect ac systems where a reliable ac interconnection would be too expensive.2.1 Independent frequency and control2.2 Lower line cost2.3 Power control, voltage control and stability control

possible

3. The large market potential for FACTS is within AC system on a value added basis where3.1 The existing steady-state phase angle between bus

node is reasonable3.2 The cost of FACTS solution is lower than the HVDC cost 3.3 The required FACTS controller capacity is lesser than the

transmission rating

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

Costs of HVDC & FACTS

20-30 M120-170 M1000 MW

30-50 M200-300 M2000 MW

10-20 M75-100 M500 MW

$ 5-10 M$ 40-50 M200 MW

FACTSHVDC 2 terminalThroughput

50/kvarUPFC(shunt portion)

50/kvarUPFC(series portion)

50/kvarSTATCOM

40/kvarTCSC

40/kvarSVC

20/kvarSeries Capacitor

8/kvarShunt Capacitor

Cost (US$)FACTS

Trai

ning

Wor

ksho

p on

FA

CTS

App

licat

ion,

En

ergy

, AIT

References1. N.G. Hingorani & L. Gyugyi, Understanding FACTS, IEEE Press.2. Y.H. Song & A.T. John, Flexible AC Transmission Systems

(FACTS), IEE Power and Energy Series.3. R.M. Mathur & R.K. Varma, Thyristor-Based FACTS Controllers

for Electrical Transmission Systems, Wiley.4. E. Acha et al, FACTS Modelling and Simulation in Power

Networks, Wiley.5. P.M. Anderson, Series Compensation of Power System,PBLSH!6. E. Acha et al, Power Electronic Control in Electrical Systems,

Newnes.7. S.N. Singh, Electric Power Generation, Transmission and

Distribution, Prentice-Hall.8. P. Kundur, Power System Stability and Control, McGraw Hill.9. Pardiya, HVDC Power Transmission System, Wiley.10. E.W. Kimbark, Direct Current Transmission, Wiley.11. E.Uhlmann, Power Transmission by Direct Current, Springer.12. J.Arrillaga, High Voltage Direct Current Transmission, IEE.