1. Ronnie Belmans Florence, 5 November 2010
Challenges to Climate Policy: Integrating Network Regulation Meshed DC networks for offshore wind development
Ronnie Belmans
Florence, 5 November 2010
/ November-2010

2. ronnie.belmans@esat.kuleuven.be / November-2010
Overview
Historical development of HVDC
→ can we stretch to ‘supergrids’?
VSC HVDC
Offshore
Wind applications
Multi-terminal
Challenges for offshore Multi-terminal Direct Current (MTDC) systems
Technical
Economic/financial
Political/Sociopolitical
Standardization
How to connect to AC grid
/ November-2010 2

3. ronnie.belmans@esat.kuleuven.be / November-2010
Supergrid: Why?
Supergrid: Why?
Harness RES, crucial role of offshore wind, but also wave, tidal and osmotic energy.
Balancing: wind - hydro - natural gas
Connect remote energy sources
Trading: single market
/ November-2010 3

4. Planning How will the future grid look like?
Can we manage by stretching the current 380 kV grid to its limits?
Or do we need a new overlay grid?
“Stretching” was successful for trains
Be aware of the “sailing ship syndrome”…
We must accept the limits of today’s situation
/ November-2010 4

5. Planning: How will the future grid look like?
A renewed grid vision?
1956
1948
2008
1974 ?
2020
2050 …
/ November-2010 5

6. Supergrid Visions How will the future DC grid look like?
source:
/ November-2010 6

7. Supergrid Visions How will the future DC grid look like?
Hydro power
Solar power
Wind power
DC transmission
99LFC0825
Wind
300 GW
km sq
5000 x 10 km
Hydro
200 GW
Cables (Solar)
140 pairs of
5 GW and
3000 km each
Solar
700 GW
8000 km sq
90 x 90 km
© ABB Group Slide 7 10MP0458
/ November-2010 7

8. Supergrid Visions How will the future DC grid look like?
G. Czisch
/ November-2010 8

9. Supergrid Visions How will the future DC grid look like?
wind-energy-the-facts.org
pepei.pennnet.com
mainstreamrp.com
Statnett
wikipedia/desertec
Desertec-australia.org
Statnett
© ABB Group
Slide 9
10MP0458
/ November-2010 9

10. ronnie.belmans@esat.kuleuven.be / November-2010
CSC: Classical HVDC
Advances in semiconductors led to thyristor valves with many advantages
Simplified converter stations
Overhauls less frequently needed
No risk of mercury poisoning
Easy upscaling by stacking thyristors (increased voltage levels) and parallel-connecting thyristor stacks (increasing current rating)
Gradual replacement of mercury arc valves to thyristor valves. First replacement 1967: Gotland
Today only 1 or 2 HVDC systems with mercury arc valves remain
/ November-2010 10

11. ronnie.belmans@esat.kuleuven.be / November-2010
Highlights
Pinnacle: Itaipu : ±600 kV, 2 x 3150 MW
First multi-terminal: 1987
800 kV Shanghai-Xiangjiaba (2011), LCC HVDC world records:
Voltage (800 kV)
Transmitted power (6400 MW)
Distance (2071 km)
/ November-2010 11

12. ronnie.belmans@esat.kuleuven.be / November-2010
CSC HVDC
Filter requirements result in huge footprint
Not viable for offshore application
/ November-2010 12

13. Multi-terminal Hydro Québec - New England (1992)
Extended to 3-terminal
Originally planned: 5-terminal but cancelled (Des Cantons, Comerford)
Fixed direction of power
/ November-2010 13

14. Multi-terminal Mainland Italy-Corsica-Sardinia
1965: monopolar between mainland and Sardinia
1987: converter added in Corsica
1990: mercury arc replaced by thyristors
1992: second pole added
/ November-2010 14

15. Intermediate Conclusion 1
Footprint too large because of filtering requirements
There is no offshore voltage source, needed for commutation
General multi-terminal operation not feasible, only ‘pseudo-multi-terminal’
CSC for offshore multi-terminal HVDC is a dead end
/ November-2010 15

16. ronnie.belmans@esat.kuleuven.be / November-2010
VSC HVDC
Not new development, but entirely new concept based on switches with turn-off capability
Characteristics:
No voltage source needed to commutate
Very fast
Very flexible: independent active and reactive power control
/ November-2010 16

17. ronnie.belmans@esat.kuleuven.be / November-2010
VSC HVDC
First installation: Gotland (yes, again)
1999
50 MW
±80 kV
Subsequent installations have ever higher ratings, but ratings CSC remain out of reach
/ November-2010 17

18. ronnie.belmans@esat.kuleuven.be / November-2010
State-of-the-art
Existing
VSC HVDC
350 MW
± 150 kV DC
180 km
CSC HVDC
6300 MW
±600 kV DC
785 km km
Currently possible
CSC HVDC
7200 MW
±800 kV DC
2000 km
VSC HVDC
1100 MW
± 320 kV DC
/ November-2010 18

19. ronnie.belmans@esat.kuleuven.be / November-2010
Construction
Less filters → reduced footprint
Only cooling equipment and transformers outside
Valves pre-assembled
/ November-2010 19

20. VSC HVDC for offshore applications
Modified design for offshore applications
Troll (2005)
First offshore HVDC converter
40 MW, 70 km from shore
Oil-platform
/ November-2010 20

21. VSC HVDC for offshore applications
Valhall (2010)
78 MW
292 km
Oil-platform
/ November-2010 21

22. VSC HVDC for offshore applications
Borwin alpha (2010)
First offshore HVDC converter for wind power
400 MW
200 km
Wind collector
/ November-2010 22

23. ronnie.belmans@esat.kuleuven.be / November-2010
Borwin alpha
AC side with transformers, breakers, and filters
AC phase reactors
Valves
DC side with capacitors and cable connections
Cooling equipment
/ November-2010 23

24. VSC HVDC for wind applications
No cable length issues
Wind farms are independent of power system
Do not need to run on main frequency
Do not need to run on fixed frequency
Wind farm topology must be re-evaluated (fixed speed induction machines?)
Multiple wind farms can be connected to offshore grids
This could lead to a ‘supergrid’ connecting different areas with different wind profiles
/ November-2010 24

25. Offering Ancillary Services to the Grid
TSO’s Grid Code: “Wind turbines must have a controllable power factor”
Grid code country-
specific
Demands at PCC
for 300 MW
Minimum PF = 0,95
Required: 98,6 MVAr
Capacitive limit
Inductive limit
/ November-2010 25

26. Offering Ancillary Services to the Grid
Additional equipment needed such as SVC, STATCOM,…
Compensate AC cable capacitance
Be grid compliant
Resonances between cable C and grid L
/ November-2010 26

27. Multi-terminal VSC HVDC
VSC HVDC only developed for point-to-point, but…
…looks very promising for MTDC
Converter’s DC side has constant voltage → converters can be easily connected to DC network.
Extension to ‘pseudo-multi-terminal’ systems straightforward: e.g. star-connections
/ November-2010 27

28. Intermediate Conclusion 2
Footprint can be made small enough for offshore applications because of limited filtering requirements
No offshore voltage source needed
Offshore operation is proven for point-to-point connection
General multi-terminal operation possible because DC side has constant voltage
VSC for offshore multi-terminal HVDC looks promising
/ November-2010 28

29. Challenges for supergrid
Technical
Offshore equipment
Ratings
Losses
Reliability
MTDC Control
Economic/Financial
Political/Sociopolitical
Standardization
/ November-2010 29

30. ronnie.belmans@esat.kuleuven.be / November-2010
Challenges
Losses
Converter losses were very high (> 1.3%) but improvements are made (now 1%)
Special switching techniques
New materials
Cooling
Ratings
Proven power ratings low compared to CSC HVDC
Proven voltage levels low compared to CSC HVDC
/ November-2010 30

31. ronnie.belmans@esat.kuleuven.be / November-2010
Challenges
Reliability
DC Fault leads to complete shutdown
To protect IGBTs from fault current, they are blocked
Anti-parallel diodes keep conducting the fault current
No DC breakers are present
The fault needs to be cleared by opening AC breakers
For MTDC, a DC fault would lead to loss of whole MTDC grid. This is not acceptable. The fault needs to be cleared selectively at DC side.
Problem
DC breaker not commercially available yet, but should come out of the laboratories soon
Current rises extremely fast
Very fast fault detection needed
Very fast and precise fault localisation needed
Very fast breaker needed
/ November-2010 31

32. ronnie.belmans@esat.kuleuven.be / November-2010
Challenges
Reliability
DC voltage needs to remain within small band
Problem:
If only one converter controls DC voltage, DC voltage can become unacceptably low in MTDC grid
What if voltage controlling converter fails?
Other voltage control method needed. Which one?
Grid codes will be needed
/ November-2010 32

33. Technical challenges by auxiliary equipment and maintenance
Pumps, fans, cooling in harsh and remote environment (also valid for windturbine itself)
Maintenance
Training and availability of personnel
Accessability in winter
/ November-2010 33

34. ronnie.belmans@esat.kuleuven.be / November-2010
Challenges
Economical/Financial issues
Different generation and load scenarios
Cost/benefit of scenarios
Electricity prices
Financial demand per scenario
Financing by not directly involved TSO’s
Realization and ownership of the Supergrid
European funding
Potential investors
Source: ENTSO-E, “Ten-year network development plan ”
/ November-2010 34

35. ronnie.belmans@esat.kuleuven.be / November-2010
Challenges
Political/Sociopolitical issues
Legal and regulatory framework
Social acceptance of the Supergrid
Permitting processes, harmonization of national rules
European policy on DSM
New areas to be incorporated: Russia, Norway,…
Political stability of regions
Start up of regulation now for the starting projects for which technology is ready to go:
Point to point
Star connected (Kriegers Flak, Channel area, Dogger Bank)
Source: ENTSO-E, “Ten-year network development plan ”
/ November-2010 35

36. Challenges Standardization
General justification for standards
Reducing variety of technology  competition
Interoperability  avoid lock-in
For HVDC
Competition? Several manufacturers/vendors in the market
 Fairly OK
Interoperability? Not at all!
 Need for standards
/ November-2010 36

37. Challenges Standardization
Interoperability: in a context of meshed DC grids very important
Today different systems are incompatible
/ November-2010 37

38. Challenges Standardization
What should be standardized?
Minimum minimorum to allow integration in a DC grid
Voltage levels
Necessary to avoid excessive integration costs
Cable sizes
Footprints
Cubicle sizes
Voltage control
Optimal interoperability
Power electronics
Filters
Short circuit current
Protection
Communication
EMF-EMC
/ November-2010 38

39. ronnie.belmans@esat.kuleuven.be / November-2010
Challenges
Other
Technical compatibility
Common, long term vision
Planning …
/ November-2010 39

40. ronnie.belmans@esat.kuleuven.be / November-2010
Connection to AC grid
Connection to AC grid
Close to shore
Reinforcement AC grid needed
OHL AC
Underground AC cable
To strong, inland AC bus
Overhead DC
Underground DC
/ November-2010 40

41. ronnie.belmans@esat.kuleuven.be / November-2010
Example: Borwin
128 km DC sea cable
75 km DC land cable (less expensive)
/ November-2010 41

42. ronnie.belmans@esat.kuleuven.be / November-2010
Example: Borwin
/ November-2010 42

43. ronnie.belmans@esat.kuleuven.be / November-2010
Conclusions
CSC HVDC
Stretching not possible
Too large
Grid voltage needed
VSC HVDC
Stretching possible
Small footprint
Passive grid operation
Technical characteristics suited to wind applications
Offshore applications proven
Technical challenges remain…
DC breaker
Fast fault detection and localisation
Losses
Ratings
DC voltage control
…but can be solved
Need to further look into economic and political challenges
Standardization required
/ November-2010 43