TITRE PRESENTATION 11

19/04/23

2

TECHNO-ECONOMIC ASPECTS OF POWER SYSTEMS

Ronnie BelmansDirk Van Hertem

Stijn Cole

• Lesson 1: Liberalization• Lesson 2: Players, Functions and Tasks• Lesson 3: Markets• Lesson 4: Present generation park• Lesson 5: Future generation park• Lesson 6: Introduction to power systems• Lesson 7: Power system analysis and control• Lesson 8: Power system dynamics and security• Lesson 9: Future grid technologies: FACTS and

HVDC• Lesson 10: Distributed generation

• Power system control• Why?• How?

• FACTS• Voltage control• Angle control• Impedance control• Combination

• HVDC• Classic• Voltage source converter based

OVERVIEW

POWER TRANSFER THROUGH A LINEHOW?

• Active power transfer:• Phase angle • Problems with long distance transport

• Phase angle differences have to be limited• Power transfer ==> power losses

• Reactive power transfer• Voltage amplitude• Problems:

• Voltage has to remain within limits• Only locally controlled

By changing voltage, impedance or phase angle, the power flow can be altered ==> FACTS

Power transfer through a line:

distanceX ~

1 2

2

1 1 2

P = sin

Q = cos

U Uδ

X

U U Uδ

X X

POWER TRANSFER THROUGH A LINETHEORY

UK

F CH

IE

B

D35 %

A

NL

18 %13 %

8 %

34 %34 %

20 %

10 % 3 %

11 %

EUROPEAN POWER FLOWSTRANSPORT FRANCE ==> GERMANY

OVERVIEW

• Power system control• Why?• How?

• FACTS• Voltage control• Angle control• Impedance control• Combination

• HVDC• Classic• Voltage source converter based

• Application Voltage magnitude

control Phase angle control Impedance Combination of the

above

DIVISIONS WITHIN FACTS

• Implementation • Series • Shunt • Combined• HVDC

• Energy storage• Yes or no

• Switching technology• Mechanical • Thyristor • IGBT/GTO: Voltage Source Converter

APPLICATION DOMAIN FACTS

Transmission level• Power flow control

• Regulation of slow power flow variations

• Voltage regulation• Local control of voltage profile

• Power system stability improvement• Angle stability

• Caused by large and/or small perturbations

• Voltage stability• Short and long term

APPLICATION DOMAIN FACTS

Distribution level• Quality improvement of the delivered voltage to sensitive loads

• Voltage drops• Overvoltages• Harmonic disturbances• Unbalanced 3-phase voltages

• Reduction of power quality interferences• Current harmonics• Unbalanced current flows• High reactive power usage• Flicker caused by power usage fluctuations

• Improvement of distribution system functioning• Power factor improvement, voltage control, soft start,...

1 2

21 1 2

P= sin

Q= cos

U Uδ

X

U U Uδ

X X

VOLTAGE MAGNITUDE ADJUSTMENT

Different configurations: Thyristor Controlled Reactor (TCR) Thyristor Switched Capacitor (TSC) Thyristor Switched Reactor (TSR) Mechanical Switched Capacitor (MSC) Mechanical Switched Reactor (MSR) Often a combination

STATIC VAR COMPENSATION - SVC

• Variable thyristor controlled shunt impedance• Variable reactive power source• Provides ancillary services

• Maintains a smooth voltage profile• Increases transfer capability • Reduces losses

• Mitigates active power oscillations• Controls dynamic voltage swings under various

system conditions

STATIC COMPENSATORSTATCOM

• Shunt voltage injection• Voltage Source Convertor (VSC)• Low harmonic content• Very fast switching• More expensive than SVC• Energy storage? (SMES, supercap)

PRICE COMPARISON VOLTAGE REGULATION

• Cost of voltage regulation capabilities dependent on:• Speed• Continuous or discrete regulation• Control application

• 300 MVAr – 150 kV• Capacitor banks: 6 M€ (min)• SVC: 9 à 17 M€ (# periods)• Statcom: 31 M€ (ms)

1 2

21 1 2

P= sin

Q= cos

U Uδ+α

X

U U Uδ+α

X X

PHASE SHIFTING TRANSFORMER VOLTAGE ANGLE ADJUSTMENT.

1 2 sinPST

U UP= δ+α

X + X

PHASE SHIFTING TRANSFORMER

• Allows for some control over active power flows

• Mechanically switched ==> minutes

U

25 ° ==> 10 % voltage rise ==> 40 kV @ 400 kV

PHASE SHIFTING TRANSFORMER (II)PRINCIPLES

• Injection of a voltage in quadrature of the phase voltage

• One active part or two active parts

Asymmetric Symmetric

2

1'

311

2

32'3'3'

Voltages over coils on the same transformer leg are in phase

PHASE SHIFTING TRANSFORMER (III) ONE ACTIVE PART

• Series voltage injection• In quadrature to the phase voltage• One active part: low power/low voltage (high

shortcircuit currents at low angle)

PHASE SHIFTING TRANSFORMERREGULATING

• Changing injected voltage:• Tap changing transformer• Slow changing of tap position: ½

min• Control of the injected voltage:

• Centrally controlled calculations • Updates every 15 minutes• Often remote controlled• Can be integrated in

WAMS/WACS system

GGGGGGGG

GGG

A B

C

1018 MW

Flow of A to B gets distributed

according to the impedances

173.5 MW 170.4 MW

344.3 MW

800 MW800 MW

500 MW

500 MW

1000 MW

losses: 18 MW

Slack bus

PHASE SHIFTER INFLUENCEBASE CASE

GGGGGGGG

GGG

A B

C

1024.6 MW

Flow of A to B is taken mostly by

line A-B

33 MW32.8 MW

491.8 MW

800 MW800 MW

500 MW

500 MW

1000 MW

losses: 24.6 MW

15 °

PHASE SHIFTER INFLUENCE1 PHASE SHIFTER PLACED

GGGGGGGG

GGG

A B

C

1034 MW

Overcompensation causes a

circulation current

41.4 MW42.3 MW

580 MW

800 MW800 MW

500 MW

500 MW

1000 MW

losses: 34 MW

30 °

PHASE SHIFTER INFLUENCE1 PHASE SHIFTER PLACED: OVERCOMPENSATION

GGGGGGGG

GGG

A B

C

1052.3 MW

The phase shifting transformers can

cancel their effects

238.4 MW221 MW

313.9 MW

800 MW800 MW

500 MW

500 MW

1000 MW

losses: 52.3 MW

15 °

15 °

PHASE SHIFTER INFLUENCE2 PHASE SHIFTERS: CANCELLING

GGGGGGGG

GGG

A B

C

1052.3 MW

238.4 MW221 MW

313.9 MW

800 MW800 MW

500 MW

500 MW

1000 MW

Additional losses: + 34.4 MW

15 °

15 ° -8.8 %

+14.6 %+18.8 %

FLOWS relative to base case (no PS)

When badly controlled, little

influence on flows, more on losses

PHASE SHIFTER INFLUENCE2 PHASE SHIFTERS: CANCELLING

GGGGGGGG

GGG

A B

C

1054 MW

The phase shifting transformers can

`fight'

294.3 MW259.7 MW

259.7 MW

800 MW800 MW

500 MW

500 MW

1000 MW

losses: 54 MW

15 °

30 °

GGGGGGGG

GGG

A B

C

1052.3 MW

238.4 MW221 MW

313.9 MW

800 MW800 MW

500 MW

500 MW

1000 MW

Additional losses: + 34.4 MW

15 °

15 ° -8.8 %

+14.6 %+18.8 %

FLOWS relative to base case (no PS)

When badly controlled, little

influence on flows, more on losses

PHASE SHIFTER INFLUENCE2 PHASE SHIFTERS: FIGHTING

GGGGGGGG

GGG

A B

C

1054 MW

The phase shifting transformers can

`fight'

294.3 MW259.7 MW

259.7 MW

800 MW800 MW

500 MW

500 MW

1000 MW

losses: 54 MW

30 °

15 °

+35 %

-24.5 %

+28 %

FLOWS relative to base case (no PS)

PHASE SHIFTER INFLUENCE2 PHASE SHIFTERS: FIGHTING

PHASE SHIFTERS IN BELGIUM

• Zandvliet – Zandvliet• Meerhout – Maasbracht (NL)• Gramme – Maasbracht (NL)

• 400 kV• +/- 25 ° no load• 1400 MVA• 1.5 ° step (34 steps)

• Chooz (F) – Monceau B• 220/150 kV• +10/-10 * 1.5% V (21 steps)• +10/-10 * 1,2° (21 steps)• 400 MVA

• Power system control• Why?• How?

• FACTS• Voltage control• Angle control• Impedance control• Combination

• HVDC• Classic• Voltage source converter based

OVERVIEW

1 2

21 1 2

P= sin

Q= cos

U Uδ

X

U U Uδ

X X

SERIES COMPENSATIONLINE IMPEDANCE ADJUSTMENT

SERIES COMPENSATION – SC AND TCSC

• Balances the reactance of a power line• Can be thyristor controlled

• TCSC – Thyristor Controlled Series Compensation

• Can be used for power oscillation damping

1 2

21 1 2

P= sin

Q= cos

U Uδ

X

U U Uδ

X X

ΔU

UNIFIED POWER FLOW CONTROLLER ULTIMATE FLOW CONTROL

UPFC - UNIFIED POWER FLOW CONTROLLER

• Voltage source converter-based (no thyristors)

• Superior performance

• Versatility

• Higher cost ~25%

• Concurrent control of

• Line power flows

• Voltage magnitudes

• Voltage phase angles

• Benefits in steady state and emergency situations

• Rapid redirection power flows and/or damping of power oscillations

P shunt=− P series

21

UNIFIED POWER FLOW CONTROLLER (II) ULTIMATE FLOW CONTROL

• Two voltage source converters• Series flow control • Parallel voltage control• Very fast response time

• Power oscillation damper

P series 1=− P series 21

3

2

INTERLINE POWER FLOW CONTROLLER IPFC

• Two voltage source converters• 2 Series flow controllers in separate lines

OVERVIEW

• Power system control• Why?• How?

• FACTS• Voltage control• Angle control• Impedance control• Combination

• HVDC• Classic• Voltage source converter based

DC DCP=U I

• High voltage DC connection• No reactive losses

• No stability distance limitation• No limit to underground cable length• Lower electrical losses

• 2 cables instead of 3• Synchronism is not needed

• Connecting different frequencies• Asynchronous grids (UCTE – UK)• Black start capability? (New types, HVDC light)

• Power flow (injection) can be fully controlled• Renewed attention of the power industry

HIGH VOLTAGE DIRECT CURRENTHVDC

HISTORY OF HVDC

• Back to back

• Multiterminal• Bipolar

• Monopolar

(Sea)

+

-

HVDC CONFIGURATIONS:TRANSMISSION MODES (I)

HVDC CONFIGURATIONS:TRANSMISSION MODES (II)

LCC HVDC

• Thyristor or mercury-arc valves

• Reactive power source needed

• Large harmonic filters needed

VSC HVDC

• IGBT valves• P and Q (or U)

control• Can feed in passive

networks• Smaller footprint• Less filters needed

HVDC EXAMPLENORNED CABLE

HVDC EXAMPLENORNED CABLE: SCHEMA

HVDC EXAMPLENORNED CABLE: SEA CABLE

HVDC EXAMPLEGARABI BACK TO BACK

HVDC EXAMPLEGARABI BACK TO BACK (4X)

• Commissioning year:2002

• Power rating: 220 MW AC

• Voltage:132/220 kV • DC Voltage:+/- 150

kV • DC Current: 739 A• Length of DC

cable:2 x 180 km

VSC HVDCEXAMPLE: MURRAY LINK

VSC HVDCEXAMPLE: TROLL

• Commissioning year: 2005

• Power rating: 2 x 42 MW AC Voltage:132 kV at Kollsnes, 56 kV at Troll

• DC Voltage: +/- 60 kV

• DC Current: 350 A• Length of DC

cable:4 x 70 km

HVDC: CURRENT SIZES

LCC VSC

Voltage (kV) ±600 ±150

Current (kA) 3.93 1.175

Power (MW) 2 x 3150 350

Length (km) 1000 2 x 180

REFERENCES

• Understanding Facts: Concepts and Technology of Flexible AC Transmission Systems, Narain G. Hingorani, Laszlo Gyugyi

• Flexible AC transmission systems, Song & Johns• Thyristor-based FACTS controllers for electrical

transmission systems, Mathur Vama• Power system stability and control, Phraba

Kundur, 1994, EPRI