1. System restoration using VSC-hvdc connected offshore wind power plant as black-start unit
Holger Becker

2. agenda
Introduction
Simulation Set-up
Results
Conclusion / Outlook

3. Introduction :: black-out
Large area electrical energy system breakdown (black-out) can occur
1965: North-east USA / Canada
2003: North-east USA / South-east Canada
2003: Denmark / Sweden
2004: Athen
2005: Swiss Railway
2006: Europe
2011: Southwest USA / Northwest Mexico
2012: India (2 X)
2015: Turkey
2016: South Australia
Due to one failure security (n-1) the system is robust and black-outs are rare
100% security is not economic
Plans for System restoration must do exist
Today‘s plans do not incorporate distributed generation
Project Netz:Kraft develops strategies to use distributed renewable generation in a constructive way for system restoration

4. Introduction :: system restoration
Strong neighbouring TSO
No strong neighbouring TSO
Voltage provision from neighbouring TSO
Start Island with power plant
No power plant in houseload
Power Plant switched to houseload
~ hours
Start island from inside the affected grid
Start island with blackstart unit
~ days

5. Introduction :: black-start units
Black-Start units in Germany (2019)
Requirements on Black-Start units
Must be able to start / run without electricity from the grid
Must be able to energize a grid (grid forming)
Active power generation needs to follow load demand and load changes
Black-start units (Germany 2019)
Mostly hydro power plants
Gas turbines
A few hard coal
Oil power plants for peak-demand
Fossile fuel will become less
Only a few BSU to the coast

6. Introduction :: System Restoration
System Restoration can begin, when:
Power plants, that could manage to switch into houseload-island operation
Black-start unitst has been black-started
Critical actions should have been proofed in simulation before
Usually the connection of the largest load. Here: start of a feed-water pump of a conventional power plant.

7. Simulation Set-Up :: Requirements on HVDC-OWPP
Generation (offshore-wind energy converters) need to follow load onshore
Black started
Grid forming
Generation follows load
Need to be black-started
Must be grid forming

8. Simulation :: Control structure
Increase of DC-voltage
will increase active Power
Decrease of DC-Voltage will decrease frequency
Increase of load will
Decrease DC-voltage
Start of pump as largest single load is most critical action
grid forming,
U = const
f = f(UDC)
grid forming,
U,f = const
Grid connected,
P=f(f)

9. Results :: Simulation results onshore

10. Results :: Simulation results HVDC

11. Results :: Simulation results offshore

12. Conclusion / outlook
Offshore Wind Power Plant with VSC-HVDC connection can generally be used as a Black-Start unit to support system restoration of the onshore grid after black-out
Active power generation can follow the load on land dynamically due to appropriate interaction between the two converter stations and the wind energy converters
So control structure for each of the components have do be designed together
Restoration scenario should be extended in a way that further power plants are included within the onshore grid

13. Thank you for your attention!