Techno-economic aspects of power systems

1. Techno-economic aspects of power systems • Ronnie Belmans • Dirk Van Hertem • Stijn Cole

2. 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. Overview • Power system control • Why? • How? • FACTS • Voltage control • Angle control • Impedance control • Combination • HVDC • Classic • Voltage source converter based

4. 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

5. Power transfer through a lineTheory Power transfer through a line:

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

7. Overview • Power system control • Why? • How? • FACTS • Voltage control • Angle control • Impedance control • Combination • HVDC • Classic • Voltage source converter based

8. 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. 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

10. 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. Voltage magnitude adjustment

12. 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

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

14. 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. Phase shifting transformer Voltage angle adjustment.

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

17. D 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. 3' 1' 2' 3 3' 1 2 1 2 3 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) Voltages over coils on the same transformer leg are in phase

19. 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

20. 1018 MW 500 MW A B G G G G G G G G 1000 MW 500 MW Slack bus 344.3 MW 173.5 MW 170.4 MW Flow of A to B gets distributed according to the impedances C G G G 800 MW 800 MW losses: 18 MW Phase shifter influenceBase case

21. 1024.6 MW 500 MW A B G G G G G G G G 1000 MW 500 MW 491.8 MW 15 ° 32.8 MW 33 MW Flow of A to B is taken mostly by line A-B C G G G 800 MW 800 MW losses: 24.6 MW Phase shifter influence1 phase shifter placed

22. 1034 MW 500 MW A B G G G G G G G G 1000 MW 500 MW 580 MW 30 ° 42.3 MW 41.4 MW Overcompensation causes a circulation current C G G G 800 MW 800 MW losses: 34 MW Phase shifter influence1 phase shifter placed: overcompensation

23. 1052.3 MW 500 MW A B G G G G G G G G 1000 MW 500 MW 15 ° 313.9 MW 15 ° 221 MW 238.4 MW The phase shifting transformers can cancel their effects C G G G 800 MW 800 MW losses: 52.3 MW Phase shifter influence2 phase shifters: cancelling

24. 1052.3 MW FLOWS relative to base case (no PS) 500 MW A B G G G G G G G G 1000 MW 500 MW -8.8 % 15 ° 313.9 MW 15 ° 221 MW +14.6 % 238.4 MW +18.8 % When badly controlled, little influence on flows, more on losses C G G G 800 MW Additional losses: + 34.4 MW 800 MW Phase shifter influence2 phase shifters: cancelling

25. 1052.3 MW 1054 MW FLOWS relative to base case (no PS) 500 MW 500 MW A A B B G G G G G G G G G G G G G G G G 1000 MW 1000 MW 500 MW 500 MW -8.8 % 30 ° 15 ° 313.9 MW 259.7 MW 15 ° 15 ° 259.7 MW 221 MW +14.6 % 294.3 MW 238.4 MW +18.8 % When badly controlled, little influence on flows, more on losses The phase shifting transformers can `fight' C C G G G G G G 800 MW 800 MW Additional losses: + 34.4 MW 800 MW 800 MW losses: 54 MW Phase shifter influence2 phase shifters: fighting

26. 1054 MW FLOWS relative to base case (no PS) 500 MW A B G G G G G G G G 1000 MW 500 MW -24.5 % 15 ° 259.7 MW 30 ° 259.7 MW 294.3 MW +28 % +35 % The phase shifting transformers can `fight' C G G G 800 MW 800 MW losses: 54 MW Phase shifter influence2 phase shifters: fighting

27. 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. Overview • Power system control • Why? • How? • FACTS • Voltage control • Angle control • Impedance control • Combination • HVDC • Classic • Voltage source converter based

29. Series compensationLine impedance adjustment

30. 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

31. Unified Power Flow Controller Ultimate flow control ΔU

32. 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

33. 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. 1 2 3 Interline Power Flow ControllerIPFC • Two voltage source converters • 2 Series flow controllers in separate lines

35. Overview • Power system control • Why? • How? • FACTS • Voltage control • Angle control • Impedance control • Combination • HVDC • Classic • Voltage source converter based

36. High Voltage Direct CurrentHVDC • 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

37. History of HVDC

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

39. HVDC Configurations:Transmission modes (II)

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

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

42. HVDC ExampleNorned cable

43. HVDC ExampleNorned cable: schema

44. HVDC ExampleNorned cable: sea cable

45. HVDC ExampleGarabi back to back

46. HVDC ExampleGarabi back to back (4x)

47. VSC HVDCexample: Murray link • 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

48. 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

49. HVDC: Current sizes

50. 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