The Integration of Renewable Energy
onto the Existing Grid
Dr Norman MacLeod
Technical Director, HVDC
Hydro-electric Power
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
Wind 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
Solar 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
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 substation
Submarine cable
AC Collector Wind
Platform
Turbines
Source : Siemens
STATCOM
Greater Gabbard
off-shore wind
farm, UK
•
•
•
•
Control of reactive power flow
Low voltage ride through
Harmonic distortion
System stability
HVDC Transmission
Q1
Q2
P
IC1
Network
1
UC1
VSC
DC transmission
line
Station 1
i
i
UC2
Network
2
VSC
Station 2
Idc
i
Iac
Iac
t
t
t
Source : EirGrid
East West Interconnector (EWIC)
Eirgrid
AC
S/S
National Grid
AC
AC
45km
181km
DC
Woodland
Converter Station
34km
DC
±200kV XLPE Cables
Shotton Converter
Station
AC
S/S
Source : EirGrid
Woodland Converter Station
Exterior view of converter station
Interior view – converter hall
Ireland HVDC Schemes
Existing Interconnectors
Future interconnectors
Embedded links
The Existing AC Grid
400 kV
AC
110 kV
AC
AC
AC
AC
AC
AC
AC
AC
110 kV
AC
10 kV AC
10 kV
10 kV
400 V
AC
AC
AC
AC
AC
AC
400 V
400 V
The Grid of the Future?
320 kV
DC
AC
400 kV
Bulk power import using HVDC
DC
DC
Offshore
wind farm
150 kV
150 kV
150 kV
DC
AC
110 kV
AC
DC
150 kV
AC
DC
AC
AC
DC
AC
DC
110 kV
DC
50 kV
50 kV
AC
AC
AC
AC
AC
DC
10 kV
DC
10 kV
AC
DC
DC
AC
DC
AC
AC
AC
DC
AC
DC
DC
DC
DC
10 kV
AC
500 V
AC
DC
10 kV
400 V
35 kV AC
DC
Electric Vehicle
Charging
Station
station
AC
DC
AC
DC
400 V
500 V
Battery
Energy
Storage
System
Photo
Voltaic Power
Cells
AC
AC
400 V
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