1. Master in Advanced Power Electrical Engineering © Copyright 2005 Techno-economic aspects of power systems Ronnie Belmans Dirk Van Hertem Stijn Cole

2. © Copyright 2005 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

3. © Copyright 2005 Power system control  Why?  How? FACTS  Voltage control  Angle control  Impedance control  Combination HVDC  Classic  Voltage source converter based Overview

4. © Copyright 2005 Power transfer through a line How? Active power transfer:  Phase angle  Problems with long distance transport o Phase angle differences have to be limited o Power transfer ==> power losses Reactive power transfer  Voltage amplitude  Problems: o Voltage has to remain within limits o Only locally controlled By changing voltage, impedance or phase angle, the power flow can be altered ==> FACTS

5. © Copyright 2005 Power transfer through a line: Power transfer through a line Theory

6. © Copyright 2005 UK F CH I E B D 35 % A NL 18 % 13 % 8%8% 34 % 20 % 10 %3 % 11 % European power flows transport France ==> Germany

7. © Copyright 2005 Overview Power system control  Why?  How? FACTS  Voltage control  Angle control  Impedance control  Combination HVDC  Classic  Voltage source converter based

8. © Copyright 2005 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

9. © Copyright 2005 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 o Caused by large and/or small perturbations  Voltage stability o Short and long term

10. © Copyright 2005 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,...

11. © Copyright 2005 Voltage magnitude adjustment

12. © Copyright 2005 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 o Maintains a smooth voltage profile o Increases transfer capability o Reduces losses  Mitigates active power oscillations  Controls dynamic voltage swings under various system conditions

13. © Copyright 2005 STATic COMpensator STATCOM Shunt voltage injection  Voltage Source Convertor (VSC)  Low harmonic content  Very fast switching  More expensive than SVC  Energy storage? (SMES, supercap)

14. © Copyright 2005 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)

15. © Copyright 2005 Phase shifting transformer Voltage angle adjustment.

16. © Copyright 2005 Phase shifting transformer Allows for some control over active power flows Mechanically switched ==> minutes

17. © Copyright 2005  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

18. © Copyright 2005 2 1' 3 1 1 2 3 2'3' 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)

19. © Copyright 2005 Phase shifting transformer Regulating 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

20. © Copyright 2005 GGGG GGGG GGG A B C 1018 MW Flow of A to B gets distributed according to the impedances 173.5 MW170.4 MW 344.3 MW 800 MW 500 MW 1000 MW losses: 18 MW Slack bus Phase shifter influence Base case

21. © Copyright 2005 GGGG GGGG GGG A B C 1024.6 MW Flow of A to B is taken mostly by line A-B 33 MW 32.8 MW 491.8 MW 800 MW 500 MW 1000 MW losses: 24.6 MW 15 ° Phase shifter influence 1 phase shifter placed

22. © Copyright 2005 GGGG GGGG GGG A B C 1034 MW Overcompensation causes a circulation current 41.4 MW 42.3 MW 580 MW 800 MW 500 MW 1000 MW losses: 34 MW 30 ° Phase shifter influence 1 phase shifter placed: overcompensation

23. © Copyright 2005 GGGG GGGG GGG A B C 1052.3 MW The phase shifting transformers can cancel their effects 238.4 MW 221 MW 313.9 MW 800 MW 500 MW 1000 MW losses: 52.3 MW 15 ° Phase shifter influence 2 phase shifters: cancelling

24. © Copyright 2005 GGGG GGGG GGG A B C 1052.3 MW 238.4 MW 221 MW 313.9 MW 800 MW 500 MW 1000 MW Additional losses: + 34.4 MW 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 influence 2 phase shifters: cancelling

25. © Copyright 2005 GGGG GGGG GGG A B C 1054 MW The phase shifting transformers can `fight' 294.3 MW 259.7 MW 800 MW 500 MW 1000 MW losses: 54 MW 15 ° 30 ° GGGG GGGG GGG A B C 1052.3 MW 238.4 MW 221 MW 313.9 MW 800 MW 500 MW 1000 MW Additional losses: + 34.4 MW 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 influence 2 phase shifters: fighting

26. © Copyright 2005 GGGG GGGG GGG A B C 1054 MW The phase shifting transformers can `fight' 294.3 MW 259.7 MW 800 MW 500 MW 1000 MW losses: 54 MW 30 ° 15 ° +35 % -24.5 % +28 % FLOWS relative to base case (no PS) Phase shifter influence 2 phase shifters: fighting

27. © Copyright 2005 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

28. © Copyright 2005 Power system control  Why?  How? FACTS  Voltage control  Angle control  Impedance control  Combination HVDC  Classic  Voltage source converter based Overview

29. © Copyright 2005 Series compensation Line impedance adjustment

30. © Copyright 2005 Series Compensation – SC and TCSC Balances the reactance of a power line  Can be thyristor controlled o TCSC – Thyristor Controlled Series Compensation  Can be used for power oscillation damping

31. © Copyright 2005 ΔU Unified Power Flow Controller Ultimate flow control

32. © Copyright 2005 UPFC - Unified Power Flow Controller  Voltage source converter-based (no thyristors) o Superior performance o Versatility o Higher cost ~25%  Concurrent control of o Line power flows o Voltage magnitudes o Voltage phase angles  Benefits in steady state and emergency situations o Rapid redirection power flows and/or damping of power oscillations

33. © Copyright 2005 2 1 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

34. © Copyright 2005 1 3 2 Interline Power Flow Controller IPFC Two voltage source converters 2 Series flow controllers in separate lines

35. © Copyright 2005 Overview Power system control  Why?  How? FACTS  Voltage control  Angle control  Impedance control  Combination HVDC  Classic  Voltage source converter based

36. © Copyright 2005 High voltage DC connection  No reactive losses o No stability distance limitation o No limit to underground cable length o Lower electrical losses  2 cables instead of 3  Synchronism is not needed o Connecting different frequencies o Asynchronous grids (UCTE – UK) o Black start capability? (New types, HVDC light)  Power flow (injection) can be fully controlled Renewed attention of the power industry High Voltage Direct Current HVDC

37. © Copyright 2005 History of HVDC

38. © Copyright 2005 Back to back Multiterminal Bipolar Monopolar (Sea) + - HVDC Configurations: Transmission modes (I)

39. © Copyright 2005 HVDC Configurations: Transmission modes (II)

40. © Copyright 2005 LCC HVDC Thyristor or mercury-arc valves Reactive power source needed Large harmonic filters needed

41. © Copyright 2005 VSC HVDC IGBT valves P and Q (or U) control Can feed in passive networks Smaller footprint Less filters needed

42. © Copyright 2005 HVDC Example Norned cable

43. © Copyright 2005 HVDC Example Norned cable: schema

44. © Copyright 2005 HVDC Example Norned cable: sea cable

45. © Copyright 2005 HVDC Example Garabi back to back

46. © Copyright 2005 HVDC Example Garabi back to back (4x)

47. © Copyright 2005 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 HVDC example: Murray link

48. © Copyright 2005 VSC HVDC example: 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

49. © Copyright 2005 HVDC: Current sizes LCCVSC Voltage (kV)±600±150 Current (kA)3.931.175 Power (MW)2 x 3150350 Length (km)10002 x 180

50. © Copyright 2005 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