The Integration of Renewable Energy onto the Existing Grid

Dr Norman MacLeod Technical Director, HVDC

Run of the river schemes use the natural force of the water to turn the turbines • Minimal environmental impact Dams create a head of water which turns the turbines • Significant environmental impact Micro-hydro generation • Diverting water from local streams • Connected to the local community

Hydro-electric Power

On-shore

• wind farms are typically 10 – 50MW • Turbines typically up to 3MW rating • Connected at distribution voltage level

Off-shore

• wind farms are typically up to 600MW (AC connected) and 1200MW (DC connected) • Turbines up to 8MW • Connected at transmission voltage level

Wind Power

Domestic

• Connected to the low voltage distribution grid • Supplies local loads and any excess is fed into the distribution grid

Commercial

• Photovoltaic panels generate electricity at low voltage DC • Conversion from DC to AC is needed for connection to the transmission grid

Solar Power

Renewable Energy Sources

Other sources

• Wave power – in development • Tidal power – barrage schemes in use • Tidal power – submerged turbines in development • Bio-mass – in use as a coal replacement • Electric vehicles – both a load and a generator

The Issues

• Intermittency of power generation • Remoteness of power sources from load centres • Impacts on system stability • Loss of inertia on the network – closure of rotating plant • Harmonic distortion – Irish Grid Code • Low voltage ride-through – Irish grid Code

The Solutions

• Diversity of power sources • Fossil fuels + renewables • Grid enhancement • AC transmission lines and/or HVDC embedded links • HVDC interconnectors to neighbouring grids (UK, France) • Dynamic reactive power devices • SVC or STATCOM • Harmonic filters • Passive and/or active • Advanced power electronic controllers • “Synthetic inertia” • Storage systems

Source : Alstom

Off-shore Wind Farm (AC)

On-shore sub station Submarine cable AC Collector Platform Wind Turbines

• Control of reactive power flow • Low voltage ride through • Harmonic distortion • System stability

Source : Siemens

STATCOM

Greater Gabbard off-shore wind farm, UK

i

Network 1

Iac

Q 1

VSC

I C1 P U C1 U C2

HVDC Transmission

Q 2

VSC

Network 2

Station 1 i DC transmission line Station 2 Idc i t t Iac t

Eirgrid AC S/S AC DC Woodland Converter Station 45km

Source : EirGrid

East West Interconnector (EWIC)

National Grid 181km ±200kV XLPE Cables AC 34km DC Shotton Converter Station AC S/S

Source : EirGrid

Woodland Converter Station

Exterior view of converter station Interior view – converter hall

Existing Interconnectors Future interconnectors Embedded links

Ireland HVDC Schemes

The Existing AC Grid

400 kV AC 110 kV AC 10 kV AC AC AC 400 V AC AC AC 10 kV AC AC 400 V AC AC 110 kV AC 10 kV AC AC AC 400 V

Offshore wind farm 150 kV 150 kV DC AC AC 110 kV AC 400 kV 150 kV DC DC

The Grid of the Future?

320 kV AC DC AC AC 110 kV DC DC 150 kV Bulk power import using HVDC DC DC 50 kV 10 kV 400 V AC AC AC AC AC DC AC AC 10 kV DC DC AC 10 kV AC DC DC 500 V AC DC AC AC AC DC 400 V DC DC 10 kV 50 kV DC DC AC 35 kV AC AC DC 500 V DC DC AC AC 400 V Electric Vehicle Charging Station Battery Energy Storage System Photo Voltaic Power Cells

Conclusions

• High levels of renewable generation can result in significant issues on the existing AC network • Smart grid solutions can be used to support and manage integration of renewable energy sources • Smart Grids = Power Electronics + Automation Systems

Any questions?

Tormoid Mhic Leòid