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Power System Challenges of Increasing Renewables
100% Converter-Based Grids
Damian Flynn
Facilitation of Renewables Studies
Fundamental issues
Loss of
largest infeed
Issues that can be mitigated
Voltage Stability Transient Stability
Network Loading
Fundamental issues that need further analysis
Non-issues according to modelling
Voltage Control
Fault LevelsSmall Signal
Stability
Temporary loss of
wind power due
to network faults
Frequency Stability
Short term
frequency
variations
Power balance
fluctuations
and frequency
regulation
Frequency Stability
Ireland and Northern Ireland
Facilitation of Renewables StudiesIreland and Northern Ireland
Annual System Inertia
0 -4 10-14 20-24 30-34 40-44
5-9 15-19 25-29 35-39 MWs
20
15
2
01
4
20
13
2
01
2
Ireland and Northern Ireland
Operational Capability Outlook
Power System Transition
Before System Split …
… After System Split
4 November 2006 – Norwegian Pearl
4 November 2006 – System Split
4 November 2006 – Area Frequency Sy
stem
Fre
qu
en
cy (
Hz)
4 November 2006 – System Split
100% Converter-Based Grids
• No conventional synchronous generation
• What is meant by system frequency?
• Achieving load balancing with ‘local’ controls?
• Operational rules in a ‘100%’ state?
• Requirement for (new) system services?
• …
• Achievable without ‘smart grid’ communications?
Load Balancing (Frequency Control)
Synchronous generator
(Fixed speed) wind turbine generator
50/60 Hz
+ Solar PV+ (Variable speed) wind+ HVDC interconnection+ Tidal stream+ Ocean wave + …
Grid-Forming Control Strategy
Existing inverters are grid-following
SG
SG
50 Hz
What to follow?
50 Hz
Some / many future inverters need to be
grid-forming
Modelling Environment?
Existence of implicit synchronous machine based assumptions?
Future Transmission Network
Grid-Forming Converter Model
Modelling Complexity?
Reduced order converter modelsFull order converter models
Co
nve
rter
cu
rren
t (p
u)
Time (s)
Control Hierarchy?
0
100
200
300
400
500
1 7 13 19
Win
d P
ow
er
(MW
)
Time (Hours)
Cork Antrim Donegal
0
100
200
300
400
500
1 7 13 19
Sola
r P
ow
er
(MW
)
Time (Hours)
Valentia Belfast Kilkenny
0 6 12 18 0
0 6 12 18 0
Time Series Modelling
Future Plans …
• Power system stability assessment• New technical challenges?
• Robustness to system splits + Blackstart capability
• …
• Transitions between ‘100%’ state or ‘<100%’ state
• Definition of (new & existing) system services?
• Migration path from current to new ‘controls’?
• Equipment requirements and grid code updates?
• …• Telecommunication infrastructure?
Future Plans …
Hardware in the Loop Simulation
Power System Challenges of Increasing Renewables
100% Converter-Based Grids
Damian Flynn
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