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

agenda Introduction Simulation Set-up Results Conclusion / Outlook

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

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

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

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.

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

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)

Results :: Simulation results onshore

Results :: Simulation results HVDC

Results :: Simulation results offshore

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

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