the integration of renewable energy onto the existing grid dr norman macleod technical director,...

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

Wind Power

Off-shore

• wind farms are typically up to 600MW (AC connected) and 1200MW (DC connected)

• Turbines up to 8MW

• Connected at transmission voltage level

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

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

Renewable Energy Sources

• 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 Issues

• 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

The Solutions

Off-shore Wind Farm (AC)Source : Alstom

Wind Turbines

AC Collector Platform

On-shore sub-station

Submarine cable

STATCOMSource : Siemens

Greater Gabbard off-shore wind farm, UK

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

HVDC Transmission

DC transmissionline

Q1 Q2P

VSC VSC

Station 1 Station 2

UC1 UC2

IC1

Network1

Network2

t

i

Iact

i

Iact

Idci

East West Interconnector (EWIC)Source : EirGrid

AC

DC

AC

DC

AC S/S

AC S/S

Woodland Converter Station

Shotton Converter Station

45km 181km 34km

Eirgrid National Grid

±200kV XLPE Cables

Woodland Converter StationSource : EirGrid

Exterior view of converter station Interior view – converter hall

Ireland HVDC Schemes

Existing Interconnectors

Future interconnectors

Embedded links

The Existing AC Grid

ACAC

110 kV 110 kV

400 V 400 V

10 kV

400 kV

400 V

10 kV

10 kV

AC

AC

AC

AC

AC

AC

AC

AC

AC

AC

AC

AC

AC

AC

AC

AC

The Grid of the Future?

ACAC

DCDC

110 kV 110 kV

400 V 400 V

10 kV

400 kV

400 V

10 kV

35 kV

Offshore wind farm

150 kV 150 kV 150 kV150 kV

Bulk power import using HVDC

320 kV

ACDC

DC

DC

AC

DC

AC

DC

50 kV 50 kV

DC

DC

DC

DC

AC

AC

AC

AC

AC

AC

AC

AC

AC

AC

AC

AC

AC

AC

AC

DC

DC

DC

DC

DC

DC

DC

DC

DC500 V

Electric VehicleCharging Stationstation

AC

DC

AC

AC

10 kV 10 kV

AC

DC

AC

AC

500 V

BatteryEnergyStorageSystem

Photo Voltaic

DC

DC

Power Cells

• 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

Conclusions

Any questions?

Tormoid Mhic Leòid